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1

Interactions between solute atoms in Fe–Si–Al–C alloys as studied by mechanical spectroscopy  

Microsoft Academic Search

In Fe–Si–Al–C alloys, point-defect relaxation includes both the interstitial carbon Snoek-type relaxation, split into a “pure iron” (Fe–C–Fe) Snoek peak and an “interstitial–substitutional” (Fe–C–Me; Me=Al, Si) peak, and the substitutional Zener relaxation. The influence of Al and Si, with varying Al\\/Si ratio, on these effects is used to study the qualitative characteristics of substitutional–interstitial (Si–C, Al–C) and substitutional–substitutional (Al–Al, Si–Si,

H.-R. Sinning; I. S. Golovin; A. Strahl; O. A. Sokolova; T. Sazonova

2009-01-01

2

-CaO Slags by Al in Fe-Al(-Si) Melts  

NASA Astrophysics Data System (ADS)

Kinetic models considering mass transport in, (i) metal phase only and (ii) both metal and slag phases (mixed control or two-phase mass transfer) were developed for the reduction of SiO2 in a SiO2-Al2O3-CaO slag by Al in an Al-Fe melt. The models were validated with experiments of the reaction with Fe-Al melt and SiO2-Al2O3-CaO-MgOsat slags at 1873 K (1600 °C). The models predict that the rate of reaction is slower in the mixed control model because of the added resistance of slag phase mass transport. The mixed control becomes applicable when the slag contains low amounts of SiO2. In this case, when the initial Al content in the metal increases, the normalized rate of reaction decreases. The increased Al content in the metal retards the reaction due to the limited SiO2 provided to the reaction interface in the mixed control model. Sensitivity analyses were done using the models for the ratios of mass transfer coefficients of Si to Al, and Al2O3 to Si, along with slag density, which did not impose a significant effect.

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

2014-08-01

3

Microwave power absorption of magnetic composites filled with surface coated Fe-Al-Si flakes  

NASA Astrophysics Data System (ADS)

The Al2O3 coated Fe-Al-Si flakes were employed as a magnetic filler in 150 ?m-thick dielectric matrix. The saturation magnetizations of the coated Fe-Al-Si flakes were decreased down to 98 emu/g with the increment of the coating thickness (170 nm, 250 nm, 350 nm) in comparison with that of uncoated Fe-Al-Si flakes (130 emu/g). The power absorptions for Al2O3 coated Fe-Al-Si flakes composites were decreased from 62.7% to 57.4% (at 5 GHz) with the increment of coating thickness in comparison with that of uncoated Fe-Al-Si flakes composite (80% at 5 GHz). The thermal conductivities of Al2O3 coated composites were increased up to 0.249 W/m K in comparison with that of uncoated composite of 0.096 W/m K.

Lee, Joonsik; Ho Cho, Sang; Yoon, Sanghoon; Hyeon Kim, Ki

2014-05-01

4

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

5

Microstructural study of laser-clad FeAl bronze on Al-Si alloy  

Microsoft Academic Search

Microstructure studies of laser-clad Fe-Al bronze on an Al-Si alloy were carried out by OM(optical microscope), SEM(scanning electron microscope), TEM(transmission electron microscope) and XRD(X ray diffraction) analyses. The cross-section of the laser-cladding was divided into clad region and transitional region. The clad region composes a matrix with a twin structure of needle-like and feathery appearance and a second phase of

A. H. Wang; C. S. Xie

2001-01-01

6

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

NASA Astrophysics Data System (ADS)

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

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

2006-05-01

7

Evaluation of bulk ?-FeSi2 crystal as a solar cell semiconductor through the photo-response measurements of Al/n-?-FeSi2 Schottky diodes  

NASA Astrophysics Data System (ADS)

?-FeSi2 has many attracting properties as a semiconductor not consisting of toxic chemical elements and is an ideal semiconductor as a thin film solar cell owing to its extremely high optical absorption coefficient. To evaluate ?-FeSi2 as a solar cell, photo-response measurement is critically important and useful. Since ?-FeSi2 thin films are normally deposited on Si substrates, intrinsic photo-response of ?-FeSi2 is usually difficult to be collected due to the strong contribution from Si substrates. We here present the photo-response from bulk ?-FeSi2 crystals, expecting that we can eliminate the contributions coming from the Si substrates and the crystallographic defects existing at the ?-FeSi2/Si interfaces when we use ?-FeSi2 thin films. We prepared bulk specimens by chemical vapor transport method (CVT) in which needle-like and plate-like ?-FeSi2 crystals were obtained. We chose the former specimens for the formation of Al/n-?-FeSi2 Schottky contacts to measure their photo-responses. These contacts were found to form Schottky diodes even though there are large series resistances and leakage currents. Under laser light illumination of 1.31 ?m through optical fiber, the positive voltage was observed between the Al contact and the In solder glued to the back-surface of ?-FeSi2 bulk specimen. Two-dimensional distribution of photo-responses were measured by scanning the above optical fiber with the spot size of 50 ?m. The highest photo-response was obtained in the vicinity of Al wire, and was 7.7 mA/W for the as-grown sample, and 31 mA/W for the annealing one, respectively. These observations state that ?-FeSi2 holds appropriate optical features to be used as a solar cell.

Fukuzawa, Yasuhiro; Ootsuka, Teruhisa; Nakayama, Yasuhiko; Makita, Yunosuke

2008-04-01

8

Hot Tear Susceptibility of Al-Mg-Si-Fe Alloys with Varying Iron Contents  

NASA Astrophysics Data System (ADS)

Hot tear susceptibility in cast Al-0.52Si-0.34Mg- xFe 6060 aluminum alloys was investigated using a hot tearing test apparatus to simulate hot tearing in DC casting. The test apparatus has two cast bars, one that is used to measure the load response and one which is fixed at both ends to restrain thermal contraction so that hot tearing can be observed and rated where it occurred. The iron (Fe) content, ranging from 0.02 to 0.5 wt pct, was seen to have a major influence on the load response during solidification and the tear rating of these alloys. The findings are discussed in terms of Rappaz-Drezet-Gremaud (RDG) model sensitivity analysis and related to the effect of Fe content on the morphology and prevalence of the ?-Al5FeSi and ?-AlFeSi intermetallic phases and their influence on the coherency and coalescence of the microstructure.

Sweet, Lisa; Easton, Mark A.; Taylor, John A.; Grandfield, John F.; Davidson, Cameron J.; Lu, Liming; Couper, Malcolm J.; StJohn, David H.

2013-12-01

9

Plasma Nitriding Behavior of Fe-C-M (M = Al, Cr, Mn, Si) Ternary Martensitic Steels  

NASA Astrophysics Data System (ADS)

Change in surface hardness and nitrides precipitated in Fe-0.6C binary and Fe-0.6 mass pct C-1 mass pct M (M = Al, Cr, Mn, Si) ternary martensitic alloys during plasma nitriding were investigated. Surface hardness was hardly increased in the Fe-0.6C binary alloy and slightly increased in Fe-0.6C-1Mn and Fe-0.6C-1Si alloys. On the other hand, it was largely increased in Fe-0.6C-1Al and Fe-0.6C-1Cr alloys. In all the Fe-0.6C-1M alloys except for the Si-added alloy, fine platelet alloy nitrides precipitated inside martensite laths. In the Fe-0.6C-1Si alloy, Si-enriched film was observed mainly at a grain boundary and an interface between cementite and matrix. Crystal structure of nitrides observed in the martensitic alloys was similar to those in Fe-M binary ferritic alloys reported previously. However, there was a difference in hardening behavior between ferrite and martensite due to a high density of dislocations acting as a nucleation site of the nitrides and partitioning of an alloying element between martensite and cementite changing the driving force of precipitation of the nitrides.

Tomio, Yusaku; Kitsuya, Shigeki; Oh-ishi, Keilchiro; Hono, Kazuhiro; Miyamoto, Goro; Furuhara, Tadashi

2014-01-01

10

[Release of Si, Al and Fe in red soil under simulated acid rain].  

PubMed

bstract:A laboratory leaching experiment on simulated acid rain was carried out using soil columns. The release of Si, Al and Fe from soils and pH values of eluates were investigated. The results showed that under the given leaching volume, the release amounts of cations were influenced by the pH value of simulated acid rain, while their response to acid rain was different. Acid rain led to Si release, nearly none of Fe. Within the range from pH 3.0 to 5.6, a little Al release but mass Al only release at the pH below 3.0, both Si and Al had a declining release ability with the undergoing eluviation. At pH 2.5, the release amounts of Si and Al, especially Al, increased significantly with the strengthened weathering process of soil mineral. With an increase of the leaching amount of acid rain, the release of Si and Al increased, but acceleration of Si was slower than Al which was slower and slower. When the soil pH falling down to a certain grade, there are negative correlation between pH and both Al and DOC concentration of eluate. released, but most of Al derived from the aluminosilicates dissolved. Acid deposition can result in solid-phase alumino-organics broken and Al released, but most of Al derived from the aluminosilicates dissolved. PMID:18269008

Liu, Li; Song, Cun-yi; Li, Fa-sheng

2007-10-01

11

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

E-print Network

Laser Cladding of Quasi-Crystal-Forming Al-Cu-Fe-Bi on an Al-Si Alloy Substrate KRISHANU BISWAS substrates. A two-step process of cladding followed by remelting is used to fine-tune the alloying, phase distribution, and microstructure. A powder mix of Al64Cu22.3Fe11.7Bi2 has been used to form the clads

Srivastava, Kumar Vaibhav

12

Mössbauer study of mechanical deformation induced order-disorder transition in Fe75AlSi alloys  

NASA Astrophysics Data System (ADS)

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

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

2012-03-01

13

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

NASA Astrophysics Data System (ADS)

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

Jain, Syadwad

14

A Preliminary Study of the Phase Transformations in Rolled Al-Fe-Si Alloy  

NASA Astrophysics Data System (ADS)

The precipitation of phases in the Al-Fe-Si system has been studied using differential scanning calorimetry (DSC) and thermoelectric power (?S) in homogenized and deformed by rolling samples. Two predominant associated effects being observed on homogenized samples: the first one, after precipitation of Fe and Si at temperatures lower than 673 K (400 °C) and the second, the Al3Fe phase, at a temperature close to 773 K (500 °C). In DSC, the effect of severe deformation by rolling is manifest in two ways: (1) displacing the peaks reported in homogenized samples and (2) introducing two new exothermic transformations associated with the processes of recovery and recrystallization. In ?S, the two transformations are maintained, although displaced and magnified by the effect of a faster and more abundant Fe precipitation. The isoconversional method is used to calculate the activation of precipitated phases.

Luiggi A., Ney J.

2010-12-01

15

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

16

Electrical and Magnetic Study of Bulk Amorphous Alloys Fe-Al-Ga-P-B-Si  

NASA Astrophysics Data System (ADS)

Bulk amorphous alloys Fe-Al-Ga-P-B-Si were prepared by a single-roller melt spinning method. Electrical resistivity of alloys is of the order of 200 cm. The structural and magnetic components of resistivity are separated. The anomalous rise of resistivity during crystallization observed in Fe-Al-Ga-P-B-Si alloys with higher Si content is related to the precipitation of high resistivity crystalline phases. The strong exchange interaction is revealed by the Curie temperatures reaching 640 K. The room temperature values of the effective magnetic moment vary between 1.79 and 1.83 B depending weakly on alloy composition. The AC hysteresis loops were recorded in magnetic fields up to 50 A/cm and frequencies between 10 Hz to 400 kHz. The frequency variation of power losses shows that high resistivity reduces eddy current losses.

P?ka?a, K.; Ja?kiewicz, P.; Grabski, J.; Latuch, J.; P?ka?a, M.

2002-02-01

17

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

18

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

19

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

20

Discussion of ``Effect of Strontium and Phosphorus on Eutectic Al-Si Nucleation and Formation of ?-Al5FeSi in Hypoeutectic Al-Si Foundry Alloys''*  

NASA Astrophysics Data System (ADS)

The nucleation of Si during the solidification of Al-Si hypoeutectic alloys appears to result from a hierarchy of nucleating substrates operating at progressively lower temperatures: (1) AlP, whose generally particulate morphology can initiate the formation of compact Si particles as seen in hypereutectic alloys; (2) oxide bifilms alone, whose planar form creates platelike Si morphologies; and (3) a currently unknown nucleant that initiates the coral eutectic growth morphology. The consequential growth forms are particulate when initiated on particles and coarse (unmodified) plates when initiated on oxide films. However, when oxide films are deactivated by Sr, eutectic is forced to grow at a lower formation temperature with a consequently fine coral morphology known as “modified” Si. Increasing Sr additions progressively eliminate each substrate in turn to effect the change from the “unmodified” to the modified structure.

Campbell, John

2009-05-01

21

Glass formation by first-order transition in Al-Fe-Si system  

NASA Astrophysics Data System (ADS)

There are two quite different views of metallic glasses. One, that a glass forms when an undercooled melt becomes kinetically frozen. This mechanism is quite universal and in principle occurs for all melts if they can be cooled rapidly enough. Usually such glasses tolerate wide compositional variations and occur at deep eutectics. The other view looks for efficient high-density low-energy packing of atoms in an aperiodic isotropic structure. These glasses, which we dubbed q-glasses, are expected to be less tolerant of composition variations and do not require deep eutectic. In our earlier publications we presented evidence of the existence of a q-glass in Al-Fe-Si. The glass was found to form from the melt as a primary phase by a nucleation and growth reaction before there is any crystallization was found to occur in. Here we present detailed study of formation of the Al-Fe-Si q-glass in a wide range of compositions. It was found that the glass behaves as a stoichiometric compound, with a concentration near 15 a/o Fe, 20 a/o Si. For other compositions formation of complex intermetallic compounds and an icosahedral phase were observed

Bendersky, Leonid A.

2005-03-01

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

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

NASA Astrophysics Data System (ADS)

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

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

2005-08-01

24

Surface modification of 5083 Al alloy by electrical discharge alloying processing with a 75 mass% Si-Fe alloy electrode  

NASA Astrophysics Data System (ADS)

This study experimentally investigates the surface modification of 5083 Al alloy by the electrical discharge alloying (EDA) process with a Si-Fe alloy as an electrode. Samples were analyzed by transmission electron microscopy (TEM), scanning electron microscopy (SEM), micro-hardness and corrosion resistance tests. The micro-hardness of EDA alloyed layer was evidently higher than that of the base metal (5083 Al alloy). The TEM results show that the matrix of the alloyed layer has an amorphous-like structure; the matrix contains fine needle-like Si particles, block-like Si particles and nano-size Al4.5FeSi and Al13Fe4 particles. The TEM results support experimental results for the high hardness of the alloyed layer. Moreover, the EDA alloyed layer with composite microstructures has good corrosion resistance in NaCl aqueous solution.

Stambekova, Kuralay; Lin, Hung-Mao; Uan, Jun-Yen

2012-03-01

25

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

Microsoft Academic Search

In the course of studies on the iron-rich multicomponent system Fe-Mn-Cr-Mo-Nb-Al-Si-C, work was concentrated on pertinent quinary and six-component combinations namely Fe-Mn-Al-Si-C, Fe-Cr-Al-Si-C and Fe-Mn-Cr-Al-Si-C which had been elaborated at 65, 72, and 80wt% Fe. From these systems the following conclusions are obvious. Manganese acts as a strong stabilizer for the cementite carbide. Chromium and silicon, when present together prefer

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

1988-01-01

26

Crystal structure and microwave permeability of very thin Fe-Si-Al flakes produced by microforging  

NASA Astrophysics Data System (ADS)

Fine flakes of Fe-Si-Al produced by long-duration microforging exhibit a peculiar dual-peak dispersion in their frequency characteristics of the imaginary part of the permeability. This dual dispersion has a high potential to be a electromagnetic noise suppressor, works effectively in the microwave band. In a previous report we clarified that one of the dispersions (D II), which appears in the lower frequency range, is correlated to a shape anisotropy of the flakes. In this article, the origin of another dispersion (D III) is studied by analyses of crystalline structure changes during forging (100-180 h) and annealing processes. X-ray diffraction and Mössbauer spectra strongly suggest that the annealed flakes have a composition gradient structure consisting of an Fe-rich mother phase and a Si/Al-rich surface layer. The fact that dispersion D III is enhanced with development of this phase separation leads to the conclusion that dispersion D III is caused by a magnetoelastic anisotropy near the flake surface.

Yoshida, Shigeyoshi; Ando, Shinsuke; Shimada, Yutaka; Suzuki, Kei; Nomura, Kiyoshi; Fukamichi, Kazuaki

2003-05-01

27

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

SciTech Connect

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

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

2004-07-15

28

Atomic structure of the (Al,Si)CuFe cubic approximant phase.  

PubMed

The structure of the alpha-(Al,Si)CuFe approximant phase is determined by a single-crystal X-ray diffraction study and compared to the ideal structure obtained by the perpendicular shear method of the parent icosahedral phase. It is shown that the local environments (typical atomic clusters) of the two phases are similar and expand significantly farther than the size of the unit cell of the approximant. The orbit Al(2) issuing from the theoretical icosahedral model corresponding to the inner dodecahedron of the Mackay-type cluster is not found in the approximant and is replaced by a partially occupied inner icosahedron with an unusually large Debye-Waller factor. PMID:12089462

Puyraimond, Frédéric; Quiquandon, Marianne; Gratias, Denis; Tillard, Monique; Belin, Claude; Quivy, Annick; Calvayrac, Yvonne

2002-07-01

29

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

SciTech Connect

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

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

2014-04-24

30

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

31

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

NASA Astrophysics Data System (ADS)

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

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

2010-01-01

32

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

33

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

NASA Astrophysics Data System (ADS)

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

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

2005-09-01

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

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

NASA Astrophysics Data System (ADS)

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

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

2015-02-01

39

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

Microsoft Academic Search

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

M. Akaogi; S. Akimoto

1977-01-01

40

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

NASA Astrophysics Data System (ADS)

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

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

2008-04-01

41

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

NASA Astrophysics Data System (ADS)

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

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

2010-06-01

42

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

Microsoft Academic Search

The temperature variation of the electrical resistivity rho and the Seebeck coefficient S of Heusler-type Fe2VAl1-xSix (0<=x<=1) alloys has been investigated. We have shown that the transport parameters are very sensitive to doping. For the x = 0 sample, high values of rho and negative temperature coefficient of resistivity (TCR) have been observed. As the Si concentration increases, rho decreases

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

2005-01-01

43

Heat capacity and phase equilibria of almandine, Fe3Al2Si3O12  

USGS Publications Warehouse

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

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

1993-01-01

44

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.

2015-01-01

45

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

NASA Astrophysics Data System (ADS)

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

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

2012-07-01

46

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

E-print Network

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

Jacobsen, Steven D.

47

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

48

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

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

49

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

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

50

Micro- and nanocomposite Ti-Al-N/Ni-Cr-B-Si-Fe-based protective coatings: Structure and properties  

NASA Astrophysics Data System (ADS)

A new type of nanocomposite Ti-Al-N/Ni-Cr-B-Si-Fe-based coatings 70-90 ?m thick produced by combined magnetron sputtering and a plasma detonation technology is created and studied. Phases Ti3AlN + Ti3Al2N2 and the phases caused by the interaction of plasma with a thick Al3Ti + Ni3Ti coating are detected in the coatings. The TiAlN phase has a grain size of 18-24 nm, and other phases has a grain size of 35-90 nm. The elastic modulus of the Ti-Al-N coating is E = 342 ± 1 GPa and its average hardness is H = 20.8 ± 1.8 GPa. The corrosion rate of this coating is very low, 4.8 ?g/year, which is about three orders of magnitude lower than that of stainless steel (substrate). Wear tests performed according to the cylinder-surface scheme demonstrate high wear resistance and high adhesion between the thick and thin coatings.

Pogrebnyak, A. D.; Drobyshevskaya, A. A.; Beresnev, V. M.; Kylyshkanov, M. K.; Kirik, T. V.; Dub, S. N.; Komarov, F. F.; Shipilenko, A. P.; Tuleushev, Yu. Zh.

2011-07-01

51

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

NASA Astrophysics Data System (ADS)

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

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

2013-02-01

52

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

NASA Astrophysics Data System (ADS)

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

Mikolajczak, Piotr; Ratke, Lorenz

2014-12-01

53

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

NASA Astrophysics Data System (ADS)

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

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

2011-02-01

54

Giant Tunnel Magnetoresistance at Room Temperature for Junctions using Full-Heusler Co2FeAl0.5Si0.5 Electrodes  

Microsoft Academic Search

The authors have investigated the tunnel magnetoresistance (TMR) effect of magnetic tunnel junctions (MTJs) with Co2FeAl0.5Si0.5 full-Heusler electrodes and a MgO barrier in the thickness range of 1.5-2.5 nm. A cross-sectional transmission electron micrograph showed the epitaxial growth of both the upper and lower Co2FeAl0.5Si0.5 layers and a MgO barrier and some distortion in the MgO barrier after annealing above

Nobuki Tezuka; Naomichi Ikeda; Satoshi Sugimoto; Koichiro Inomata

2007-01-01

55

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

NASA Astrophysics Data System (ADS)

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

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

2009-01-01

56

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

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

57

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

58

Thermodynamic properties of Fe- and Al-bearing MgSiO3 perovskite: an internally consistent LSDA+U study  

NASA Astrophysics Data System (ADS)

To better understand the Earth's lower mantle (LM), thermodynamic properties (TDPs) of LM minerals with Fe and Al dopant should be illustrated more clearly. We have so far reported the TDPs of Fe-bearing MgO, MgSiO3 perovskite (Pv) and post perovskite. [1-4] We furthermore study the TDPs of Fe- and Al-bearing Pv, where the internally consistent LSDA+U method and the lattice dynamics method are applied. Two spin states, high (HS) and low spin state, two substitution sites, Mg and Si site, and several possible distribution configurations are considered. In the LM pressure range, HS Fe3+ substituted at the Mg site with Al3+ at the adjacent Si site (Fe-Al pair) is the most stable configuration and tends to distribute homogeneously in LM. Furthermore, negative frequency cannot be observed in the Fe-Al pair-bearing Pv, and Al contributes to middle frequency while Fe mainly to low part due to its heavy mass. This indicates that the Fe-Al pair is vibrationally stable. Incorporation of the pair for geophysically relevant concentrations can increase volume of Pv a little and has marginal effects on the TDPs of Pv except for thermal expansivity and Grüneisen parameter. Simulated bulk sound velocities and densities show that a composition close to pyrolite is accountable for the reference Earth model. References: [1] A. Metsue, and T. Tsuchiya, J. Geophys. Res. 116, B08207 (2011). [2] A. Metsue, and T. Tsuchiya, Geophys. J. Int. 190, 310 (2012). [3] H. Fukui, T. Tsuchiya, and A. Q. R. Baron, J. Geophys. Res. 117, B12202 (2012). [4] T. Tsuchiya, and X. Wang, J. Geophys. 118, 83 (2013).

Wang, X.; Tsuchiya, T.

2013-12-01

59

Electrochemical corrosion of an Al?Mg?Cr?Mn alloy containing Fe and Si in inhibited alkaline solutions  

NASA Astrophysics Data System (ADS)

The electrochemical corrosion of Al?2.7%Mg?0.19%Cr?0.04%Mn alloy containing 0.27% Fe and 0.14% Si, using open-circuit potential measurements, corrosion rate determinants, potentiodynamic and galvanostatic transients and anode efficiency experiments together with optical microscopy, scanning electron microscopy, transmission electron microscopy and energy dispersion X-ray has been studied to ascertain the effect of Cr and Mn. The experiments were performed at 25 and 50 °C in non-deaerated and stirred 4 M KOH containing K 2MnO 4 and combinations of NaVO 3, NaBiO 3, NaMoO 4, ZnO and Al 2O 3. The open-circuit potentials were rapidly stabilized in values in the range between -1.4 and -1.6 V versus Hg/HgO/OH - (4 M KOH). The alloy dissolution at open circuit and also in the galvanostatic and potentiodynamic experiments were shown to be uniform, this being correlated with the homogeneous distribution of Mg in the material. The anodic oxidation took place with the formation and dissolution of a conducting aluminium oxide film. However, limiting values were found over which the anode became passivated. The limiting values depended on the temperature, being about 125 and 500 mA cm -2 at 25 and 50 °C, respectively. The anode efficiencies were sufficiently high, that is over 90%, only at current densities approaching the limiting value at the corresponding temperature. The anode passivation was related to an excess of Cr and the anode corrosion to an excess of Mg together with the presence of Fe and Si.

Adam, A. M. M. M.; Borràs, N.; Pérez, E.; Cabot, P. L.

60

Fe speciation in geopolymers with Si\\/Al molar ratio of ?2  

Microsoft Academic Search

The speciation of Fe was studied in metakaolin-based geopolymers to which Fe was added as ferric nitrate solution or freshly precipitated ferric hydroxide. From Mössbauer and near-edge X-ray absorption spectroscopies, coupled with X-ray diffraction and electron microscopy, it was concluded that in as-cured geopolymers the Fe was present in octahedral sites, either as isolated ions in the geopolymer matrix or

Dan S. Perera; John D. Cashion; Mark G. Blackford; Zhaoming Zhang; Eric R. Vance

2007-01-01

61

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

62

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

SciTech Connect

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

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

2014-09-15

63

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

SciTech Connect

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

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

2014-05-07

64

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

65

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

NASA Astrophysics Data System (ADS)

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

Kumar, Arvind; Srivastava, P. C.

2014-02-01

66

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

NASA Astrophysics Data System (ADS)

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

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

2015-02-01

67

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

68

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

NASA Astrophysics Data System (ADS)

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

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

2012-03-01

69

Thermodynamic modelling of the system Al 2O 3?SiO 2?CaO?FeO?Fe 2O 3 to predict the flux requirements for coal ash slags  

Microsoft Academic Search

Slags are formed during coal combustion processes as a result of the melting and reaction of the mineral matter. Predicting the outcome of these complex chemical reactions has long been a problem. Improvements in chemical thermodynamic models of oxide systems and computational methods now make these predictions possible. In this paper a model of the system Al2O3?SiO2?CaO?FeO?Fe2O3, developed using the

Evgueni Jak; Sergei Degterov; Peter C. Hayes; Arthur D. Pelton

1998-01-01

70

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

SciTech Connect

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

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

1996-09-01

71

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

72

Characterization of Fe/C catalysts supported on Al2O3, SiO2 and TiO2  

NASA Astrophysics Data System (ADS)

Structural and magnetic properties of Fe/C catalysts synthesized by ball milling and deposited onto Al2O3, SiO2 and TiO2 supports are reported. Ball milling ?-Fe and C in the presence of these supports produced peculiar solid solutions in which antiferromagnetic and ferrimagnetic iron phases doped with Al, Si and Ti coexist. Mössbauer spectroscopy and powder X-ray diffraction data show no evidence of any FexC phase. Instead, oxidation took place even though carbon (graphite) was present. All the catalysts were found to exhibit strong metal-support interactions, with the strongest interactions found in the TiO2 supported catalyst.

Lodya, J. A. L.; Seda, T.; Strydom, A. M.; Manzini, S. S.

2010-01-01

73

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

PubMed

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

Redhammer, Günther J; Roth, G

2004-04-01

74

A containerless study of short-range order in high-temperature Fe-Si-Al-Ca-Mg-Cr-Cu-Ni oxide systems  

NASA Astrophysics Data System (ADS)

The short-range order of a composite Fe-Si-Al-Ca-Mg-Cr-Cu-Ni oxide system in the liquid state (1500 °C) during aerodynamic levitation was studied by high-energy X-ray diffraction and subsequent Reverse Monte Carlo simulations. Structural analysis of the resulting supercells revealed the presence a sialate network consisting of SiO4 tetrahedra chains terminated by AlO4 units. Network modifying Fe and Mg atoms within the sialate cavities provided the necessary charge neutrality. Ca atoms were largely uncoordinated, while Cr, although not assuming a network forming role, maintained a 4-fold coordination, effectively reducing the amount of bridging O atoms in the melt. Due to their low concentration, the Cu and Ni species were not included in the analysis. The stereochemistry of the most probable atomic cluster, characteristic of short-range coordination, was derived.

Antipas, G. S. E.; Temleitner, L.; Karalis, K.; Kohara, S.; Pusztai, L.; Xenidis, A.

2012-07-01

75

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

76

Microstructure and properties of 6FeNiCoSiCrAlTi high-entropy alloy coating prepared by laser cladding  

Microsoft Academic Search

The content of each constituent element in the newly developed high-entropy alloys (HEAs) is always restricted in equimolar or near-equimolar ratio in order to avoid the formation of complex brittle phases during the solidification process. In this study, a 6FeNiCoSiCrAlTi high-entropy alloy coating with simple BCC solid solution phase has been prepared by laser cladding on a low carbon steel

Hui Zhang; Ye Pan; Yizhu He; Huisheng Jiao

2011-01-01

77

Basalt evolution at low pressure: implications from an experimental study in the system CaO-FeO-MgO-Al 2 O 3 SiO 2  

Microsoft Academic Search

New experiments have been performed in the system CaO+MgO+Al2O3+SiO2 (CMAS)+FeO at atmospheric pressure. Most of the experiments were conducted on Fe-rich compositions, in the low-temperature field of the assemblage liq(liquid)+an(anorthite) +aug(augite)+ol(olivine), and mostly along five isotherms. Others were located on, or nearby the assemblage boundaries. These experiments, together with the previously reported high temperature experiments (Shi and Libourel 1991; Libourel

Ping Shi; Universitfit Bayreuth

1992-01-01

78

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

Microsoft Academic Search

We report the structure and transport properties of current-perpendicular-to-plane spin valves (CPP SVs) with Co2FeAl0.5Si0.5 (CFAS) or Co2MnSi (CMS) Heusler alloy magnetic layers and an Ag or Cu spacer layer. A multilayer stack of sub\\/Cr\\/Ag\\/Heusler\\/(Ag or Cu)\\/ Heusler\\/Co75Fe25\\/Ir22Mn78\\/Ru was deposited on a MgO(001) single crystalline substrate by magnetron sputtering. Transmission electron microscopy observations showed epitaxial growth from the substrate to

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

2010-01-01

79

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

PubMed

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

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

2009-06-19

80

Magnetoimpedance studies in as quenched Fe73.5Si13.5B8CuV3-xAlNbx nanocrystalline ribbons  

NASA Astrophysics Data System (ADS)

Ribbons of Fe73.5Si13.5B8CuV3-xAlNbx (x = 0, 1.0, 1.5) alloys were prepared by melt-spun technique at the speed of 37 m/s. Crystalline phase derived from Fe3Si, in an amorphous matrix was observed in all the ribbons. As cast nanocrystalline ribbons were obtained by controlling cooling rates while quenching. The average crystallite sizes was calculated using the Scherrer's equation to be 44 nm, 39 nm, and 35 nm in x = 0, x = 1.0, and x = 1.5 ribbons, respectively. Magnetoimpedance measurements were carried out using an LCR meter. Among the investigated samples (x = 0, 1.0, 1.5), the largest magnetoimpedance of 61% was obtained for x = 1 ribbon annealed at 100 °C for 15 min, at 4 MHz.

Chunchu, Venkatrao; Markandeyulu, G.

2013-05-01

81

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

82

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

NASA Astrophysics Data System (ADS)

A new mineral, ferroindialite, a Fe2+-dominant analog of indialite, has been found in a pyrometamorphosed xenolith of pelitic rock hosted in alkaline basalts. Associated minerals are phlogopite, sanidine, sillimanite, pyroxenes of the enstatite-ferrosilite series, wagnerite, fluorapatite, tridymite, zircon and almandine. Ferroindialite forms brown-purple to gray with a violet-blue tint short prismatic or thick tabular hexagonal crystals up to 1.5 mm in size. The new mineral is brittle, with a Mohs' hardness of 7. Cleavage is not observed. D meas = 2.66(1), D calc = 2.667 g/cm3. IR spectrum shows neither H2O nor OH groups. Ferroindialite is anomalously biaxial (-), ? = 1.539(2), ? = 1.552(2), ? = 1.554(2), 2 V meas = 30(10)°. The mineral is weakly pleochroic, ranging from colorless on X to pale violet on Z. Dispersion is weak, r < v. The chemical composition (electron microprobe, mean of five point analyses, wt %) is as follows: 0.14 Na2O, 0.46 K2O, 4.95 MgO, 1.13 MnO, 12.66 FeO, 2.64 Fe2O3, 30.45 Al2O3, 47.22 SiO2, total is 99.65. The distribution of total iron content between Fe2+ and Fe3+ was carried out according to structural data. The empirical formula of ferroindialite is: (K0.06Na0.03)(Fe{1.12/2+}Mg0.78Mn0.10)?2.00(Al3.79Fe{0.21/3+})?4.00Si4.98O18. The simplified formula is: (Fe2+,Mg)2Al4Si5O18. The crystal structure has been refined on a single crystal, R = 0.049. Ferroindialite is hexagonal, space group P6/ mcc; a = 9.8759(3), c = 9.3102(3) Å, V = 786.40(3) Å3, Z = 2. The strongest lines in the X-ray powder diffraction pattern [ d, Å ( I, %) ( hkl)] are: 8.59 (100) (100), 4.094 (27) (102), 3.390 (35) (112), 3.147 (19) (202), 3.055 (31) (211), 2.657 (12) (212), 1.695 (9) (224). The type specimen of ferroindialite is deposited in the Fersman Mineralogical Museum, Russian Academy of Sciences, Moscow, registration number 4400/1.

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

2014-12-01

83

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

NASA Technical Reports Server (NTRS)

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

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

2001-01-01

84

Mössbauer studies of the magnetic phase transition in La(Fe0.88Si x Al0.12 - x )13 compounds  

NASA Astrophysics Data System (ADS)

Spectra of the nuclear gamma resonance for La(Fe0.88Si x Al0.12 - x )13 compounds with different x values have been measured at 100 K. The compounds exhibit an antiferromagnetic ordering in the range of silicon concentrations x ? 0.024 and a ferromagnetic ordering at x > 0.024. Analysis of the spectra has been carried out with the use of a two-core distribution of quadrupole shifts. It has been demonstrated that upon a transition from antiferromagnetic to ferromagnetic ordering, the average hyperfine field at the Fe nuclei increases by almost 40 kOe. It has been found that antiferromagnetic compounds are mainly characterized by a positive quadrupole shift, and ferromagnetic ones by a negative quadrupole shift. A model of the formation of a magnetic structure that explains the appearance of a layered antiferromagnetic ordering in La(Fe0.88Si x Al0.12 - x )13 compounds has been proposed.

Serikov, V. V.; Kleinerman, N. M.; Vershinin, A. V.; Mushnikov, N. V.

2012-09-01

85

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

86

Spin-polarized tunneling spectroscopy of fully epitaxial magnetic tunnel junctions using Co2FeAl0.5Si0.5 Heusler alloy electrodes  

Microsoft Academic Search

Spin-dependent tunneling spectroscopy has been studied in fully epitaxial magnetic tunnel junctions with full-Heusler Co2FeAl0.5Si0.5 (CFAS) alloys. We fabricated CFAS\\/MgO\\/CFAS structures with L21 - and B2 -ordered CFAS layers and measured the bias voltage dependence of differential conductance G . We found for L21-CFAS\\/MgO\\/L21-CFAS structure symmetrical conductance curves with respect to polarity of the bias voltage for parallel (P) and

Hiroaki Sukegawa; Wenhong Wang; Rong Shan; Tomoya Nakatani; Koichiro Inomata; Kazuhiro Hono

2009-01-01

87

Electronic, structural, and magnetic properties of the half-metallic ferromagnetic quaternary Heusler compounds CoFeMnZ (Z=Al, Ga, Si, Ge)  

NASA Astrophysics Data System (ADS)

The quaternary intermetallic Heusler compounds CoFeMnZ (Z=Al, Ga, Si, or Ge) with 1:1:1:1 stoichiometry were predicted to exhibit half-metallic ferromagnetism by ab initio electronic structure calculations. The compounds were synthesized using an arc-melting technique and the crystal structures were analyzed using x-ray powder diffraction. The electronic properties were investigated using hard x-ray photoelectron spectroscopy. The low-temperature magnetic moments, as determined from magnetization measurements, follow the Slater-Pauling rule, confirming the proposed high spin polarizations. All compounds have high Curie temperatures, allowing for applications at room temperature and above.

Alijani, Vajiheh; Ouardi, Siham; Fecher, Gerhard H.; Winterlik, Jürgen; Naghavi, S. Shahab; Kozina, Xeniya; Stryganyuk, Gregory; Felser, Claudia; Ikenaga, Eiji; Yamashita, Yoshiyuki; Ueda, Shigenori; Kobayashi, Keisuke

2011-12-01

88

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

SciTech Connect

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

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

2014-04-01

89

Experimental Determination of Phase Relations in SiO2-Al2O3-Fe2O3-MgO at Lower Mantle Conditions: Synthesis Results  

NASA Astrophysics Data System (ADS)

We made synthesis experiments in the system SiO2-Al2O3-Fe2O3-MgO (SAFM) using the laser-heated diamond anvil cell at conditions approximating the upper portion of Earth`s lower mantle. Eleven starting compositions spanning five compositional joins were investigated. Starting mixtures are composed of glass, glass+oxide(s), or glass+crystalline materials. Fine Pt black was added to iron-free mixtures for a laser absorber. Seventeen experiments on finely powdered samples were made at pressures of 25-60 GPa and at temperatures of 2000-3000 K. Samples were heated in a double-sided geometry with a diode-pumped YLF laser operating in TEM01 mode. The laser spot was ~ 30 ?m in diameter, and sample areas ~ 70 ?m in diameter were heated by slow and repeated scanning for 15 to 20 minutes. Pressure and temperature quenched samples were analyzed for phase identification using wavelength-dispersive X-ray diffraction at station 12.2.2 of the Advanced Light Source. Multiple spectra spanning the heated regions of the samples were collected using a monochromatic (?=0.62) X-ray beam focused to a spot ~ 30 ?m in diameter. The salient findings are as follows: 1. SAM system: Al2O3 is highly soluble in Mg-perovskite (MPv=MgSiO3), possibly exceeding 50 wt% Al2O3. This shows that coupled substitution of Al3+ on both the six- and eight-coordinated sites is energetically favorable, as predicted in ab initio calculations. 2. Results along MPv-MgAlO2.5 indicate a considerable solution of Al3+ into MgPv via a vacancy forming reaction. 3. SFM system: Fe2O3 has low solubility in MPv, indicating that coupled substitution of 2Fe3+ onto six- and eight-fold sites is generally not energetically favorable. Experiments indicate that Fe3+ enters the six-fold site via an oxygen-vacancy forming reaction. 4. Results within SAFM along the join MPv-FeAlO3 show an extensive region within which MPv, a ferrite-structered Mg(Fex,Al1-x)2O4, and stishovite coexist. Phase relations indicate that as Al3+ is added to the system SFM, coupled substitution of Fe3+ (8-fold) and Al3+ (6-fold) increases over vacancy-forming substitution of Fe3+. Based on a self-consistent set of quaternary phase relations in SAFM, we predict that at conditions of the upper part of the lower mantle (e.g. 25-50 GPa), model mantle peridotite compositions should yield an oxide phase (Mg,Fe)O coexisting with Mg-perovskite dominated by defect substitution mechanisms. This is because in the quaternary system, peridotite composition is confined between the MgO apex and a plane of defect perovskite.

Walter, M.; Tronnes, R.; Caldwell, S.

2005-12-01

90

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

NASA Astrophysics Data System (ADS)

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

Flesch, Frank

91

Element-specific magnetic moments and spin-resolved density of states in CoFeMnZ (Z=Al, Ga; Si, Ge)  

NASA Astrophysics Data System (ADS)

Using circular dichroism in x-ray-absorption spectroscopy (XAS/XMCD), we determined element-specific magnetic moments and spin-resolved unoccupied densities of states (DOS) for Co, Fe, and Mn in the quaternary Heusler compounds CoFeMnZ (Z=Al, Ga; Si, Ge). These compounds belong to a class of highly spin-polarized materials with cubic LiMgPdSn-type structure. Different structure models for the sublattice occupation leading to similar average magnetization values can be distinguished by comparison of element-specific moments with theory. We find that the compounds form similar structures, where Co, Fe, Mn, and Z occupy the X, X', Y, and Z sublattice of the related X2YZ L21-Heusler structure, for which half-metallic behavior was predicted. The unoccupied partial DOS as derived from the XAS/XMCD spectra for Co, Fe, and Mn are compared to theoretical results. A good agreement is found for Co and Fe, while Mn spectra reveal additional final-state effects (multiplets).

Klaer, P.; Balke, B.; Alijani, V.; Winterlik, J.; Fecher, G. H.; Felser, C.; Elmers, H. J.

2011-10-01

92

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

93

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

PubMed

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

Kumar, Manish; Nautiyal, Tashi; Auluck, Sushil

2009-05-13

94

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

95

Effect of Fe2O3 concentration on the structure of the SiO2-Na2O-Al2O3-B2O3 glass system.  

PubMed

The structural properties of the glass matrix 40SiO(2)·30Na(2)O·1Al(2)O(3)·(29-x)B(2)O(3)·xFe(2)O(3) (mol%), 0.0?x?29.0 were studied by X-ray diffraction (XRD), differential thermal analysis (DTA) and Raman and infrared spectroscopy (FT-IR). XRD demonstrated Fe(3)O(4) crystal formation for Fe(2)O(3) concentrations of 29.0 mol%. DTA showed that glass transition and crystallization temperatures changed as a function of Fe(2)O(3) concentration and that these alterations were related to structural change in the glass system. Interesting aspects of Raman and FT-IR spectra were found, and this gives information about of the structure changes in Si-O-Si units of these glasses as a function of Fe(2)O(3) concentration. PMID:21763184

Dantas, Noelio O; Ayta, Walter E F; Silva, Anielle C A; Cano, Nilo F; Silva, Sebastião W; Morais, Paulo C

2011-10-15

96

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

SciTech Connect

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

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

2006-04-15

97

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

98

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

SciTech Connect

10?nm and 50?nm Co{sub 2}FeAl (CFA) thin films have been deposited on MgO(001) and Si(001) substrates by magnetron sputtering and annealed at different temperatures. X-rays diffraction revealed polycrystalline or epitaxial growth (according to CFA(001)[110]//MgO(001)[100] epitaxial relation) for CFA films grown on a Si and on a MgO substrate, respectively. For these later, the chemical order varies from the A2 phase to the B2 phase when increasing the annealing temperature (T{sub a}), while only the A2 disorder type has been observed for CFA grown on Si. Microstrip ferromagnetic resonance (MS-FMR) measurements revealed that the in-plane anisotropy results from the superposition of a uniaxial and a fourfold symmetry term for CFA grown on MgO substrates. This fourfold anisotropy, which disappears completely for samples grown on Si, is in accord with the crystal structure of the samples. The fourfold anisotropy field decreases when increasing T{sub a}, while the uniaxial anisotropy field is nearly unaffected by T{sub a} within the investigated range. The MS-FMR data also allow for concluding that the gyromagnetic factor remains constant and that the exchange stiffness constant increases with T{sub a}. Finally, the FMR linewidth decreases when increasing T{sub a}, due to the enhancement of the chemical order. We derive a very low intrinsic damping parameter (1.1×10{sup ?3} and 1.3×10{sup ?3} for films of 50?nm thickness annealed at 615?°C grown on MgO and on Si, respectively)

Belmeguenai, M., E-mail: belmeguenai.mohamed@univ-paris13.fr; Tuzcuoglu, H.; Zighem, F.; Chérif, S. M.; Moch, P. [LSPM (CNRS-UPR 3407), 99 avenue Jean-Baptiste Clément, Université Paris 13, 93430 Villetaneuse (France); Gabor, M. S., E-mail: mihai.gabor@phys.utcluj.ro; Petrisor, T. [Center for Superconductivity, Spintronics and Surface Science, Technical University of Cluj-Napoca, Str. Memorandumului No. 28 RO-400114 Cluj-Napoca (Romania); Tiusan, C. [Center for Superconductivity, Spintronics and Surface Science, Technical University of Cluj-Napoca, Str. Memorandumului No. 28 RO-400114 Cluj-Napoca (Romania); Institut Jean Lamour, CNRS, Université de Nancy, BP 70239, F–54506 Vandoeuvre (France)

2014-01-28

99

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

NASA Astrophysics Data System (ADS)

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

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

2013-01-01

100

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

NASA Technical Reports Server (NTRS)

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

Herbert, F.

1985-01-01

101

Effect of MgO on Liquidus Temperatures in the ZnO-"FeO"-Al2O3-CaO-SiO2-MgO System in Equilibrium with Metallic Iron  

NASA Astrophysics Data System (ADS)

The phase equilibria in the ZnO-"FeO"-Al2O3-CaO-SiO2-MgO system have been determined experimentally in equilibrium with metallic iron. Synthetic slags were equilibrated at a high temperature, quenched, and then the compositions of the phases in equilibrium were measured using electron probe X-ray microanalysis. Pseudoternary sections of the form ZnO-"FeO"-(Al2O3 + CaO + SiO2) for CaO/SiO2 = 0.71, (CaO + SiO2)/Al2O3 = 5 and fixed MgO concentrations of 2, 4, and 6 wt pct have been constructed. Wustite (Fe2+,Mg,Zn)O and spinel (Fe2+,Mg,Zn)O·(Al,Fe3+)2O3 are the major primary phases in the temperature and composition ranges investigated. The liquidus temperatures are increased by 140 K in the wustite primary phase field and by 70 K in the spinel primary phase field with the addition of 6 wt pct MgO in the slag. The partitioning of MgO and ZnO between the solid and liquid phases has been discussed.

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

2011-06-01

102

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

103

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

104

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

SciTech Connect

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

Hagiwara, M.; Emura, S. [National Research Inst. for Metals, Tsukuba, Ibaraki (Japan)] [National Research Inst. for Metals, Tsukuba, Ibaraki (Japan); Kim, S.J. [Korea Inst. of Machinery and Materials, Changwon (Korea, Republic of)] [Korea Inst. of Machinery and Materials, Changwon (Korea, Republic of)

1998-10-05

105

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

106

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

NASA Astrophysics Data System (ADS)

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

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

2010-06-01

107

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

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

108

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 Al Fe 0.5 nm1 mm Al 700 CVD Al Al2O3 Al2O3 SiO2Fe CNT 750 850 820 CNT G/D 850 m H2 200

Maruyama, Shigeo

109

Electronic structure and magnetism of Fe{sub 3{minus}x}V{sub x}X (X=Si, Ga, and Al) alloys by the KKR-CPA method  

SciTech Connect

We present first-principles charge- and spin-self-consistent electronic structure computations on the Heusler-type disordered alloys Fe{sub 3{minus}x}V{sub x}X for three different metalloids X=(Si,thinspGa, and Al). In these calculations we use the methodology based on the Korringa-Kohn-Rostoker formalism and the coherent-potential approximation generalized to treat disorder in multicomponent complex alloys. Exchange correlation effects are incorporated within the local spin density approximation. Total energy calculations for Fe{sub 3{minus}x}V{sub x}Si show that V substitutes preferentially on the Fe(B) site, not on the Fe(A,C) site, in agreement with experiment. Furthermore, calculations have been carried out for Fe{sub 3{minus}x}V{sub x}X alloys (with x=0.25, 0.50, and 0.75), together with the end compounds Fe{sub 3}X and Fe{sub 2}VX, and the limiting cases of a single V impurity in Fe{sub 3}X and a single Fe(B) impurity in Fe{sub 2}VX. We delineate clearly how the electronic states and magnetic moments at various sites in Fe{sub 3{minus}x}V{sub x}X evolve as a function of the V content and the metalloid valence. Notably, the spectrum of Fe{sub 3{minus}x}V{sub x}X (X=Al and Ga) develops a pseudogap for the majority as well as minority spin states around the Fermi energy in the V-rich regime, which, together with local moments of Fe(B) impurities, may play a role in the anomalous behavior of the transport properties. The total magnetic moment in Fe{sub 3{minus}x}V{sub x}Si is found to decrease {ital nonlinearly}, and the Fe(B) moment to {ital increase} with increasing {ital x}; this is in contrast to expectations of the {open_quotes}local environment{close_quotes} model, which holds that the total moment should vary linearly while the Fe(B) moment should remain constant. The common-band model, which describes the formation of bonding and antibonding states with different weights on the different atoms, however, provides insight into the electronic structure of this class of compounds. {copyright} {ital 1999} {ital The American Physical Society}

Bansil, A. [Department of Physics, Northeastern University, Boston, Massachusetts 02115 (United States)] [Department of Physics, Northeastern University, Boston, Massachusetts 02115 (United States); Kaprzyk, S. [Department of Physics, Northeastern University, Boston, Massachusetts 02115 (United States)] [Department of Physics, Northeastern University, Boston, Massachusetts 02115 (United States); [Faculty of Physics and Nuclear Techniques, Academy of Mining and Metallurgy, al. Mickiewicza 30, 30-073 Krakow (Poland); Mijnarends, P.E. [Interfaculty Reactor Institute, Delft University of Technology, Mekelweg 15, 2629 JB Delft (The Netherlands)] [Interfaculty Reactor Institute, Delft University of Technology, Mekelweg 15, 2629 JB Delft (The Netherlands); [Department of Physics, Northeastern University, Boston, Massachusetts 02115 (United States); Tobola, J. [Faculty of Physics and Nuclear Techniques, Academy of Mining and Metallurgy, al. Mickiewicza 30, 30-073 Krakow (Poland)] [Faculty of Physics and Nuclear Techniques, Academy of Mining and Metallurgy, al. Mickiewicza 30, 30-073 Krakow (Poland)

1999-11-01

110

Spin-polarized tunneling spectroscopy of fully epitaxial magnetic tunnel junctions using Co2FeAl0.5Si0.5 Heusler alloy electrodes  

NASA Astrophysics Data System (ADS)

Spin-dependent tunneling spectroscopy has been studied in fully epitaxial magnetic tunnel junctions with full-Heusler Co2FeAl0.5Si0.5 (CFAS) alloys. We fabricated CFAS/MgO/CFAS structures with L21 - and B2 -ordered CFAS layers and measured the bias voltage dependence of differential conductance G . We found for L21-CFAS/MgO/L21-CFAS structure symmetrical conductance curves with respect to polarity of the bias voltage for parallel (P) and antiparallel (AP) magnetization configurations and two characteristic crossovers in G between P and AP accompanied with a flat feature within ±0.6V in G (P). On the other hand, only one crossover was observed at a negative-bias voltage for L21-CFAS/MgO/B2-CFAS structure. The direct tunneling that reflects the specific spin-dependent density of states of the half-metallic L21-CFAS is proposed as a possible transport mechanism leading to the notable crossovers.

Sukegawa, Hiroaki; Wang, Wenhong; Shan, Rong; Nakatani, Tomoya; Inomata, Koichiro; Hono, Kazuhiro

2009-05-01

111

Phase separation in Fe2CrSi thin films  

NASA Astrophysics Data System (ADS)

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

Meinert, Markus; Hübner, Torsten; Schmalhorst, Jan; Reiss, Günter; Arenholz, Elke

2013-09-01

112

Effect of Sulfur on Liquidus Temperatures in the ZnO-"FeO"-Al2O3-CaO-SiO2-S System in Equilibrium with Metallic Iron  

NASA Astrophysics Data System (ADS)

The phase equilibria in the ZnO-"FeO"-Al2O3-CaO-SiO2-S system have been determined experimentally in equilibrium with metallic iron. A pseudoternary section of the form ZnO-"FeO"-(Al2O3+CaO+SiO2) for CaO/SiO2 = 0.71 (weight), (CaO+SiO2)/Al2O3 = 5.0 (weight), and fixed 2.0 wt pct S concentration has been constructed. It was found that the addition of 2.0 wt pct S to the liquid extends the spinel primary phase field significantly and decreases the size of the wustite primary phase field. The liquidus temperature in the wustite primary phase field is decreased by approximately 80 K and the liquidus temperature in the spinel primary phase field is decreased by approximately 10 K with addition of 2.0 wt pct S in the composition range investigated. It was also found that iron-zinc sulfides are present in some samples in the spinel primary phase field, which are matte appearing at low zinc concentrations and sphalerite (Zn,Fe)S at higher zinc concentrations. The presence of sulfur in the slag has a minor effect on the partitioning of ZnO between the wustite and liquid phases but no effect on the partitioning of ZnO between the spinel and liquid phases.

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

2011-10-01

113

Exchange biasing in NiFe\\/FeMn\\/NiFe with Si seed and capping layers  

Microsoft Academic Search

NiFe\\/FeMn\\/NiFe multilayers with Si (Ta) seed and capping layers were prepared through ion beam deposition. The exchange biasing field (Hex) of the multilayer with Si increased more than that of Ta, with the crystalline (111) texture dominant. The Hex of the Si layer doubled at 200°C, although it disappeared at 250°C due to silicide formation at the Si\\/NiFe interface. To

D. G. Hwang; S. W. Kim; B. K. Kim; J. Y. Lee; J. K. Kim; J. R. Rhee; S. S. Lee

2004-01-01

114

Studies of Acid Properties of FeSiMCM-41 and LaSiMCM-41 by NH 3 -microcalorimetric and NH 3 TPD Measurements  

Microsoft Academic Search

The acidity of mesoporous materials FeSiMCM-41, LaSiMCM-41, SiMCM-41, AlSiMCM-41 and HAlSiMCM-41 has been investigated by microcalorimetric studies of the adsorption of ammonia and temperature programmed ammonia desorption method. In the initial stage, the acid strength sequence is SiMCM-41>HAlSiMCM-41>AlSiMCM-41>FeSiMCM-41>LaSiMCM-41, in agreement with that found for microporous molecular sieves materials. A small number of strong acid sites of SiMCM-41 may result from

N. He; D. Li; M. Tu; J. Shen; S. Bao; Q. Xu

1999-01-01

115

Improved tunnel magnetoresistance of magnetic tunnel junctions with Heusler Co{sub 2}FeAl{sub 0.5}Si{sub 0.5} electrodes fabricated by molecular beam epitaxy  

SciTech Connect

The authors have developed a magnetic tunnel junction of Co{sub 2}FeAl{sub 0.5}Si{sub 0.5} electrodes and a MgO barrier fabricated by molecular beam epitaxy and observed that this device had a tunnel magnetoresistance ratio of 386% at approximately 300 K and 832% at 9 K. The lower Co{sub 2}FeAl{sub 0.5}Si{sub 0.5} electrode was annealed during and after deposition resulting in a highly ordered structure with small roughness. This highly ordered structure could be obtained by annealing treatment even at low temperatures. Furthermore, a weak temperature dependence of the tunnel magnetoresistance ratio was observed for the developed magnetic tunnel junction.

Tezuka, N.; Ikeda, N.; Mitsuhashi, F.; Sugimoto, S. [Department of Materials Science, Graduate School of Engineering, Tohoku University, Aobayama 6-6-02, Sendai 980-8579 (Japan)

2009-04-20

116

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

SciTech Connect

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

Huang, H. B.; Ma, X. Q.; Liu, Z. H.; Meng, F. Y.; Xiao, Z. H.; Wu, P. P. [Department of Physics, University of Science and Technology Beijing, Beijing, 100083 (China); Shi, S. Q. [Department of Mechanical Engineering, Hong Kong Polytechnic University, Hung Hom, Kowloon (Hong Kong); Chen, L. Q. [Department of Materials Science and Engineering, Pennsylvania State University, University Park, Pennsylvania 16802 (United States)

2011-08-01

117

Bulk and interfacial scatterings in current-perpendicular-to-plane giant magnetoresistance with Co2Fe(Al0.5Si0.5) Heusler alloy layers and Ag spacer  

Microsoft Academic Search

We report the transport properties of a current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) device with Co2Fe(Al0.5Si0.5) (CFAS) Heusler alloy ferromagnetic layers and a Ag spacer layer. The CPP-GMR devices showed relatively high DeltaRA values and MR ratios up to 17 m Omega mum2 and 80% at 14 K, and 8 m Omega mum2 and 34% at 290 K. The spin diffusion length

T. M. Nakatani; T. Furubayashi; S. Kasai; H. Sukegawa; Y. K. Takahashi; S. Mitani; K. Hono

2010-01-01

118

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

Microsoft Academic Search

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

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

2008-01-01

119

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

120

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

121

AlN/Fe/AlN nanostructures for magnetooptic magnetometry  

SciTech Connect

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

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

2014-05-07

122

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

123

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

124

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

E-print Network

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

Grossman, Lawrence

125

The sulfide capacities of CaO-SiO 2 melts containing MgO, FeO, TiO 2 , and Al 2 O 3  

Microsoft Academic Search

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\\u000a 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: \\u000a \\u000a \\u000a \\u000a \\u000a $$C_{{\\\\text{S(}}j{\\\\text{)}}} =

Arturo Bronson; George R. St. Pierre

1981-01-01

126

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

127

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

NASA Astrophysics Data System (ADS)

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

Nowacki, Jerzy; Moraniec, Kacper

2015-01-01

128

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

SciTech Connect

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

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

2012-02-06

129

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

130

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

131

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

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

132

Bulk and interfacial scatterings in current-perpendicular-to-plane giant magnetoresistance with Co2Fe(Al0.5Si0.5) Heusler alloy layers and Ag spacer  

NASA Astrophysics Data System (ADS)

We report the transport properties of a current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) device with Co2Fe(Al0.5Si0.5) (CFAS) Heusler alloy ferromagnetic layers and a Ag spacer layer. The CPP-GMR devices showed relatively high ?RA values and MR ratios up to 17 m ? ?m2 and 80% at 14 K, and 8 m ? ?m2 and 34% at 290 K. The spin diffusion length ˜3 nm and the bulk spin asymmetry ˜0.77 for the CFAS alloy at 14 K were estimated by the Valet-Fert model, indicating a large contribution of the interfacial scattering.

Nakatani, T. M.; Furubayashi, T.; Kasai, S.; Sukegawa, H.; Takahashi, Y. K.; Mitani, S.; Hono, K.

2010-05-01

133

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

SciTech Connect

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

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

2014-06-09

134

Effect of FeO on the formation of spinel phases and chromium distribution in the CaO-SiO2-MgO-Al2O3-Cr2O3 system  

NASA Astrophysics Data System (ADS)

Synthetic slag samples of the CaO-SiO2-MgO-Al2O3-Cr2O3 system were obtained to clarify the effect of FeO on the formation of spinel phases and Cr distribution. X-ray diffraction (XRD) and scanning electron microscopy (SEM) equipped with energy-dispersive spectroscopy (EDS), as well as the thermodynamic software FactSage 6.2, were used for sample characterization. The results show that the addition of FeO can decrease the viscosity of molten slag and the precipitation temperatures of melilite and merwinite. The solidus temperature significantly decreases from 1400 to 1250°C with the increase of FeO content from 0wt% to 6wt%. The addition of FeO could enhance the content of Cr in spinel phases and reduce the content of Cr in soluble minerals, such as merwinite, melilite, and dicalcium silicate. Hence, the addition of FeO is conducive to decreasing Cr leaching.

Li, Jian-li; Xu, An-jun; He, Dong-feng; Yang, Qi-xing; Tian, Nai-yuan

2013-03-01

135

Magnetic and Mössbauer spectroscopy studies of NiAl0.2Fe1.8O4/SiO2 nanocomposites synthesized by sol-gel method  

NASA Astrophysics Data System (ADS)

The structural and magnetic properties of NiAl0.2Fe1.8O4/SiO2 nanocomposites prepared with the sol-gel method were studied by using X-ray diffraction, transmission electron microscopy, vibrating sample magnetometer, and Mössbauer spectroscopy. The average grain size of NiAl0.2Fe1.8O4 in the nanocomposites was found to increase from 5 to 37 nm with increasing the annealing temperature from 800 to 1200 °C while the lattice constant was almost kept a constant of ~0.833 nm. The saturation magnetization of the nanocomposites was shown to increase with increasing the grain size. The thickness of the dead layer on the surface of the ferrite grain was obtained to about (0.61±0.02) nm. The Mössbauer spectra indicated the evolution of magnetic properties of NiAl0.2Fe1.8O4 nanoparticles in the nanocomposites from superparamagnetic to magnetically ordered character with increasing the size of nanoparticles.

Li, Jiaming; Wang, Li; Bai, Zhaohui; Li, Ji; Lu, Jingbin; Li, Haibo

2014-03-01

136

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

137

Elasticity of AlFeO3 and FeAlO3 perovskite and postperovskite from firstprinciples calculations  

E-print Network

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

Paris-Sud XI, Université de

138

Mossbauer study of FeSi2 and FeSe thin films  

NASA Technical Reports Server (NTRS)

Structural studies of FeSi2 and FeSe thin films have been conducted via Mossbauer spectroscopy as continuation of earlier investigation of FeTe films. Results discuss structures of bulk and thin-film FeSi2 and bulk and thin-film FeSe.

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

1980-01-01

139

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

140

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

PubMed

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

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

2000-03-01

141

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

142

Spectroscopic characterization of ?-FeSi2 single crystals and homoepitaxial ?-FeSi2 films by XPS and XAS  

NASA Astrophysics Data System (ADS)

Chemical state analysis by a combination of X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) using synchrotron radiation is performed for ?-FeSi2 single crystals and homoepitaxial ?-FeSi2 films. The Si 2p XPS and Fe L-edge XAS spectra imply that the annealing at 1173 K to remove native oxide layers on the crystal induces the formation of FeSi in the surface. The formation of FeSi is also confirmed by Si K-edge XAS analysis. For the homoepitaxial ?-FeSi2 films grown on the crystals, the Si K-edge XAS spectra indicate that structurally homogeneous ?-FeSi2 films can be grown on the ?-FeSi2 single crystals when the substrate temperatures of 973 and 1073 K are applied for molecular beam epitaxy (MBE). Consequently, it is indicated that the combination of XPS and XAS using synchrotron radiation is a useful tool to clarify chemical states of ?-FeSi2 single crystals and homoepitaxial ?-FeSi2 films, which is important to reveal optimized growth conditions of homoepitaxial films.

Esaka, F.; Yamamoto, H.; Udono, H.; Matsubayashi, N.; Yamaguchi, K.; Shamoto, S.; Magara, M.; Kimura, T.

2011-01-01

143

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

144

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

145

Optimization of Solution Treatment of Cast Al-7Si-0.3Mg and Al-8Si-3Cu-0.5Mg Alloys  

NASA Astrophysics Data System (ADS)

The influence of solidification rate on the solution-treatment response has been investigated for an Al-7Si-0.3Mg alloy and an Al-8Si-3Cu-0.5Mg alloy. The concentrations of Mg, Cu, and Si in the matrix after different solution-treatment times were measured using a wavelength dispersive spectrometer. All Mg dissolves into the matrix for the Al-Si-Mg alloy when solution treated at 803 K (530 °C) because the ?-Fe phase is unstable and transforms into short ?-Fe plates which release Mg. The Q-Al5Mg8Cu2Si6 phase do not dissolve completely at 768 K (495 °C) in the Al-Si-Cu-Mg alloy and the concentration in the matrix reached 0.22 to 0.25 wt pct Mg. The distance between ?-Fe phases and Al2Cu phases was found to determine the solution-treatment time needed for dissolution and homogenization for the Al-Si-Mg alloy and Al-Si-Cu-Mg alloy, respectively. From the distance between the phases, a dimensionless diffusion time was calculated which can be used to estimate the solution-treatment times needed for different coarsenesses of the microstructure. A model was developed to describe the dissolution and homogenization processes.

Sjölander, Emma; Seifeddine, Salem

2014-04-01

146

Al(Fe,Ti,Si)-mobility and secondary mineralization implications: A case study of the karst unconformity diasporite-type bauxite horizons in Milas (Mu?la), Turkey  

NASA Astrophysics Data System (ADS)

The Paleogene aged metabauxite deposit in the Upper Cretaceous-Early Paleogene aged marble sequence within the southwestern Menderes Massif in the ?lbir Mountains of the Milas (Mu?la) region of SW Turkey comprises many initially karst unconformity-type bauxite horizons with unusual Al-mobility. Thus, it displays singular geochemical and mineralogical implications. The settling down of these horizons was syngenetic with limestone sedimentation, as evidenced by their lithologic associations. In the region, they are mainly found as karst unconformity diasporite-type upper bauxite horizons due to lower-graded burial metamorphism in the Küçükçaml?k and Büyükçaml?k hills, and also found as emery type lower bauxite horizons due to higher-graded burial metamorphism in the Menevi? and Kure streams. The main focus of this study was the upper bauxite horizons because they contain significant secondary Al- and Fe(Ti)-rich mineralization in the structurally-controlled open spaces (fracture zones) crosscutting the brittle bauxite horizons. This secondary mineralization is unique worldwide because the fracture zones contain coarse crystals of secondary minerals, such as gem-quality diaspore, muscovite, specular hematite, ilmenite, goethite, and chloritoid. These secondary metamorphic minerals were formed by high-temperature hydrothermal activity involving metamorphic remobilized reactions of extraction, mobilization, migration and re-crystallization, from the primary metamorphic mineral constituents in the metabauxite ore bodies. Thus, within the well known Mediterranean Bauxite Belt (MBB) in southern Europe trending from Portugal through Turkey, the metabauxite deposit in the ?lbir Mountains is noteworthy for the coexistence of two serial phases of metamorphic mineralization which occurred when the metabauxite deposit was modified by late-stage Alpine tectono-metamorphism in the Menderes Massif. This study is mainly focused on the original primary metamorphic submicroscopic mineralization, including polycrystalline (overlapped) occurrences, and uses the comparative matching technique on X-ray diffraction patterns to confirm that the main constituents of the karst unconformity-type diasporic metabauxite (diasporite) ore were the main source for secondary metamorphic mineralization in the fracture zones. It was found that the submicroscopic mineral constituents in the original primary diasporite ore are diaspore, gibbsite, corundum, specular hematite, ilmenite, donbassite and chloritoid as major constituents, with goethite, ferroalluaudite and Fe-Mg-rich muscovite as minor constituents. It was concluded that the composition of the primary fine-grained mineralization in the unaltered (original) bauxite ore was adequate to serve as a source for the much coarser later mineralization in the fracture zones.

Hatipo?lu, Murat

2011-05-01

147

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

NASA Astrophysics Data System (ADS)

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

Go, Anna

2015-02-01

148

Spin-transfer switching in an epitaxial spin-valve nanopillar with a full-Heusler Co2FeAl0.5Si0.5 alloy  

NASA Astrophysics Data System (ADS)

We report magnetization switching by spin-transfer torque in an epitaxial spin-valve nanopillar made with a half-metallic full-Heusler Co2FeAl0.5Si0.5 (CFAS) alloy. The CFAS/Ag/CFAS spin valves showed a magnetoresistance ratio of 7%-9%, and spin-transfer switching was clearly observed in the nanopillar by applying a relatively small dc current (˜106 A/cm2 in current density). Statistical analysis based on a thermal activation model revealed an averaged critical current density (Jc0) of 9.3×106 A/cm2 with a thermal stability factor (KV /kBT) of ˜40.

Sukegawa, Hiroaki; Kasai, Shinya; Furubayashi, Takao; Mitani, Seiji; Inomata, Koichiro

2010-01-01

149

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

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

150

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

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

151

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

SciTech Connect

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

Wang Wenhong; Sukegawa, Hiroaki; Shan Rong; Furubayashi, Takao; Inomata, Koichiro [Magnetic Materials Center, National Institute for Materials Science (NIMS), 1-2-1 Sengen, Tsukuba 305-0047 (Japan)

2008-06-02

152

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

NASA Astrophysics Data System (ADS)

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

Kim, Dong Jin; Park, Joo Hyun

2012-08-01

153

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

154

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

155

Oxidation of NiAl and FeAl  

Microsoft Academic Search

Recent studies on the oxidation of the ?-phases NiAl and FeAl are reviewed. Generally, these aluminides form an alumina layer which should be protective, however, certain special features render the pure phases rather susceptible to accelerated oxidation and corrosion. At 1000°C fast growing metastable modifications ?-, ?- and ?-Al2O3 are formed, which are undergrown by ?-Al2O3 and transform to that

H. J Grabke

1999-01-01

156

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

NASA Astrophysics Data System (ADS)

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

Yang, Mao; Shi, Jun-jie

2010-07-01

157

The electrochemical behavior of the Al{sub 3}Fe intermetallic compound and localized corrosion of impure 1100 Al  

SciTech Connect

Pitting of 1100 Al(Al-1.0(Fe,Cu,Si)) due to Al{sub 3}Fe constituent particles has been studied by examining a variety of intrinsic, extrinsic, and environmental factors that contribute to localized corrosion. Consistent with results from other studies, Al{sub 3}Fe is noble with respect to its microstructural surroundings and pitting is localized to the particle periphery. Polarization curves indicate that cathodic electron transfer reactions are supported on Al{sub 3}Fe at high rates, however, a anodic electron transfer reactions are not. Interparticle spacing appears to play a strong role in determining where pitting will occur, while Al{sub 3}Fe particle area plays a lesser role. Solution pH, applied potential, and exposure time each have measurable effects on the electrochemical behavior of Al{sub 3}Fe and the {alpha}-Al matrix phase which can impact either the galvanic potential of the Al{sub 3}Fe/{alpha}-Al couple, or charge transfer processes on Al{sub 3}Fe particles.

Buchheit, R.G.; Maestas, L.M.; Sorensen, N.R.

1993-11-01

158

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

159

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

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

160

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

161

The mechanical properties of FeAl  

SciTech Connect

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

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

1996-12-31

162

Magnetization switching and tunneling magnetoresistance effects of synthetic antiferromagnet free layers consisting of amorphous NiFeSiB  

NASA Astrophysics Data System (ADS)

A synthetic antiferromagnet (SAF) structure comprising of ferromagnetic amorphous Ni16Fe62Si8B14 layers has been devised and employed as a free layer of magnetic tunnel junctions (MTJs) to enhance cell switching performance. We observed -0.03erg/cm2 of exchange coupling energy (Jex) by inserting a 0.5 nm Ru layer in between NiFeSiB layers. In Si /SiO2/Ta 45/Ru 9.5/IrMn 10/CoFe 7/AlOx1.5/(single NiFeSiB 7) or [NiFeSiB(t )/Ru 0.5/NiFeSiB(7-t)]/Ru 60(nm) MTJ structures, we found size dependence of the switching field originating from the lower Jex both experimentally and by simulation. The NiFeSiB SAF structure showed lower switching field than traditional CoFe and CoFeB SAF structures. This is because NiFeSiB possesses low saturation magnetization (Ms=800emu/cm3) and high anisotropy constant (Ku=2,700erg/cm3). These properties were proven beneficial for the switching characteristics such as reducing the coercivity (Hc) and increasing the sensitivity in micrometer to submicrometer sized elements.

Chun, Byong Sun; Yoo, Ilsang; Kim, Young Keun; Hwang, Jae Youn; Rhee, Jang Roh; Kim, Taewan; Park, Wanjun

2005-08-01

163

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

164

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

165

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

166

Magnetic properties of Al/57Fe/Cr multilayers  

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

167

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

168

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

169

Boron strengthening in FeAl  

SciTech Connect

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

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

1998-11-01

170

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

NASA Astrophysics Data System (ADS)

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

Kim, Yeon Soo; Hofman, Gerard L.

2011-03-01

171

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

172

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

173

(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

174

The Sequence of Intermetallics Formation during the Solidification of an Al-Mg-Si Alloy Containing La  

NASA Astrophysics Data System (ADS)

A mechanism by which La modifies the Fe-bearing intermetallics in a 6xxx series Al alloy is examined using calorimetry. Thermal events accompanying the formation of various phases are identified by establishing a correspondence between them and microstructures of as-cast alloys. It is concluded that a previously suggested surface adsorption mechanism is unlikely to be operative. During solidification, the addition of lanthanum results in the formation of the La(Al,Si)2 phase and the depletion of the remaining melt of Si. It is hypothesized that the decreased Si/Fe ratio in the melt caused by the presence of La favors the formation of the ?-AlFeSi phase, which is less detrimental to the formability of the alloy than the ?-AlFeSi phase.

Hosseinifar, Mehdi; Malakhov, Dmitri V.

2011-03-01

175

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

176

A re-assessment of phase equilibria involving two liquids in the system K2O-Al2O3-FeO-SiO2  

NASA Astrophysics Data System (ADS)

In previously published papers the presentation of experimental results involving two liquids has not adequately addressed the quaternary aspects of the phase equilibria. A theoretical examination of the types of quaternary and pseudo-ternary phase diagrams to be expected is prestend here. When applied to much of the previous data, such quaternary diagrams cope with the variation in the K2O?Al2O3 ratio of coexisting liquids, and all the previous data are shown to be in agreement with the existence of the assemblage tridymite-fayalite-two liquids for a limited temperature range along the field boundary between primary tridymite and primary fayalite. The absolute values of temperature in the different investigations are not easily reconciled without appealing to differences in experimental techniques, to differences in oxygen pressure, or to differences in K2O loss during the experiments, as possible explanations of temperature differences greater than reasonable interlaboratory variations.

Biggar, G. M.

1983-06-01

177

The electron metallography of ordering reactions in FeAl alloys  

Microsoft Academic Search

The microstructural changes during the ?? FeAl, FeAl ? Fe3Al, and ?? Fe3Al transitions were studied by transmission electron microscopy. The ordering of ferromagnetic ? was observed to occur in\\u000a a classical manner by the nucleation and growth of particles of the FeAl or Fe3Al type phases. However, the ordering of paramagnetic ? to FeAl and paramagnetic FeAl to Fe3Al

P. R. Swann; W. R. Duff; R. M. Fisher

1972-01-01

178

Sliding wear behavior of plasma sprayed Fe 3Al–Al 2O 3 graded coatings  

Microsoft Academic Search

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

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

2008-01-01

179

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

NASA Astrophysics Data System (ADS)

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

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

2010-05-01

180

Thermodynamic and physical properties of FeAl and Fe3Al: an atomistic study by EAM simulation  

NASA Astrophysics Data System (ADS)

With this work we present a newly developed potential for the Fe-Al system, which is based on the analytical embedded atom method (EAM) with long range atomic interactions. The potential yields for the two most relevant phases B2-FeAl and D03-Fe3Al lattice constants, elastic constants, as well as bulk and point defect formation enthalpies, which are in good agreement with experimental and other theoretical data. In addition, the phonon dispersions for B2-FeAl and D03-Fe3Al show a good agreement with available experiments. The calculated lattice constants and formation enthalpy for disordered Fe-Al alloys are in good agreement with experimental data or other theoretical calculations. This indicates that the present EAM potentials of Fe-Al system is suitable for atomistic simulations of structural and kinetic properties for the Fe-Al system.

Ouyang, Yifang; Tong, Xiaofeng; Li, Chang; Chen, Hongmei; Tao, Xiaoma; Hickel, Tilmann; Du, Yong

2012-12-01

181

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

182

Equations of state in the Fe-FeSi system at high pressures and temperatures  

NASA Astrophysics Data System (ADS)

core is an iron-rich alloy containing several weight percent of light element(s), possibly including silicon. Therefore, the high pressure-temperature equations of state of iron-silicon alloys can provide understanding of the properties of Earth's core. We performed X-ray diffraction experiments using laser-heated diamond anvil cells to achieve simultaneous high pressures and temperatures, up to ~200 GPa for Fe-9 wt % Si alloy and ~145 GPa for stoichiometric FeSi. We determined equations of state of the D03, hcp + B2, and hcp phases of Fe-9Si, and the B20 and B2 phases of FeSi. We also calculated equations of state of Fe, Fe11Si, Fe5Si, Fe3Si, and FeSi using ab initio methods, finding that iron and silicon atoms have similar volumes at high pressures. By comparing our experimentally determined equations of state to the observed core density deficit, we find that the maximum amount of silicon in the outer core is ~11 wt %, while the maximum amount in the inner core is 6-8 wt %, for a purely Fe-Si-Ni core. Bulk sound speeds predicted from our equations of state also match those of the inner and outer core for similar ranges of compositions. We find a compositional contrast between the inner and outer core of 3.5-5.6 wt % silicon, depending on the seismological model used. Theoretical and experimental equations of state agree at high pressures. We find a good match to the observed density, density profile, and sound speed of the Earth's core, suggesting that silicon is a viable candidate for the dominant light element.

Fischer, Rebecca A.; Campbell, Andrew J.; Caracas, Razvan; Reaman, Daniel M.; Heinz, Dion L.; Dera, Przemyslaw; Prakapenka, Vitali B.

2014-04-01

183

Magnetic properties of ultrathin Fe Si films on GaAs(001)  

E-print Network

to an interdiffusion at the Fe3Si/GaAs interface. 1. Introduction The Heusler-like binary compound Fe3Si has entered structure and can be regarded as a quasi Heusler compound (FeA)2(FeB)Si with two inequivalent Fe sites [2, 3

Entel, P.

184

Structural, magnetic, and transport properties of Fe3O4/Si(111) and Fe3O4/Si(001)  

NASA Astrophysics Data System (ADS)

Carrier transport across Fe3O4/Si interfaces has been studied for two different Si substrate orientations. The Fe3O4 films exhibit a (111) texture on both (111)- and (001)-oriented substrates and field-cooling experiments show the characteristic step in film magnetization at the Verwey transition temperature of magnetite. Current-voltage measurements indicate the formation of high-quality Schottky barriers with an ideality factor of about n =1.06. Fits to the transport data using the thermionic emission/diffusion model yield Schottky barrier heights of 0.52 and 0.65eV for Fe3O4/Si(111) and Fe3O4/Si(001) structures, respectively. The interface between the magnetite films and silicon substrates consists of a crystalline iron silicide/amorphous oxide bilayer with reduced magnetic moment.

Boothman, Catherine; Sánchez, Ana M.; van Dijken, Sebastiaan

2007-06-01

185

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

186

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

187

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

SciTech Connect

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

Tao, L. L.; Liang, S. H.; Liu, D. P.; Wei, H. X.; Han, X. F., E-mail: xfhan@iphy.ac.cn [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100190 (China); Wang, Jian [Department of Physics and the Center of Theoretical and Computational Physics, The University of Hong Kong, Hong Kong (China)

2014-04-28

188

Thermal behavior of Al, AlFe- and AlCu-pillared interlayered clays  

Microsoft Academic Search

The purified bentonite parent clay, fraction ?; 2 mm of montmorillonite type, has been pillared by various polyhydroxy cations,\\u000a Al, AlFe and AlCu, using conventional pillaring methods. The thermal behavior of PILCs was investigated by combination of\\u000a X-ray diffraction (XRD), thermal analysis (DTA, TG) and low temperature N2 adsorption\\/desorption (LTNA). Thermal stability\\u000a of Al-, AlFe- and AlCu-PILC samples was estimated

R. P. Marinkovic-Neducin; E. E. Kiss; T. Z. Cukic; D. Z. Obadovic

2004-01-01

189

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

SciTech Connect

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

Naik, S. R.; Rai, S.; Lodha, G. S. [Synchrotron Utilization and Material Research Division, Raja Ramanna Centre for Advanced Technology, Indore 452 013 (India); Chattopadhyay, M. K.; Sharma, V. K. [Magnetic and Superconducting Materials Section, Raja Ramanna Centre for Advanced Technology, Indore 452 013 (India); Majumdar, S. [Department of Physics, Indian Association for Cultivation of Science, Kolkata 700 032 (India)

2008-09-15

190

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

NASA Astrophysics Data System (ADS)

A new mineral, günterblassite, has been found in the basaltic quarry at Mount Rother Kopf near Gerolstein, Rheinland-Pfalz, Germany as a constituent of the late assemblage of nepheline, leucite, augite, phlogopite, åkermanite, magnetite, perovskite, a lamprophyllite-group mineral, götzenite, chabazite-K, chabazite-Ca, phillipsite-K, and calcite. Günterblassite occurs as colorless lamellar crystals up to 0.2 × 1 × 1.5 mm in size and their clusters. The mineral is brittle, with perfect cleavage parallel to (001) and less perfect cleavage parallel to (100) and (010). The Mohs hardness is 4. The calculated and measured density is 2.17 and 2.18(1) g/cm3, respectively. The IR spectrum is given. The new mineral is optically biaxial and positive as follows: ? = 1.488(2), ? = 1.490(2), ? = 1.493(2), 2 V meas = 80(5)°. The chemical composition (electron microprobe, average of seven point analyses, H2O is determined by gas chromatography, wt %) is as follows: 0.40 Na2O, 5.18 K2O, 0.58 MgO, 3.58 CaO, 4.08 BaO, 3.06 FeO, 13.98 Al2O3, 52.94 SiO2, 15.2 H2O, and the total is 98.99. The empirical formula is Na0.15K1.24Ba0.30Ca0.72Mg0.16F{0.48/2+}[Si9.91Al3.09O25.25(OH)3.75] · 7.29H2O. The crystal structure has been determined from a single crystal, R = 0.049. Günterblassite is orthorhombic, space group Pnm21; the unit-cell dimensions are a = 6.528(1), b = 6.970(1), c = 37.216(5) Å, V = 1693.3(4) Å3, Z = 2. Günterblassite is a member of a new structural type; its structure is based on three-layer block [Si13O25(OH,O)4]. The strong reflections in the X-ray powder diffraction pattern [ d Å ( I, %) are as follows: 6.532 (100), 6.263 (67), 3.244 (49), 3.062 (91), 2.996 (66), 2.955 (63), and 2.763 (60). The mineral was named in honor of Günter Blass (born in 1943), a well-known amateur mineralogist and specialist in electron microprobe and X-ray diffraction. The type specimen of günterblassite is deposited in the collections of the Fersman Mineralogical Museum of the Russian Academy of Sciences, Moscow, Russia, with the registration number 4107/1.

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

2012-12-01

191

Study of the crystallization of amorphous Fe 78Si 9B 13 and Fe 76Si 8B 16 by means of magnetic measurements  

Microsoft Academic Search

Measurements of the saturation magnetization of amorphous Fe78Si9B13 and Fe76Si8B16 as a function of temperature and also as a function of the duration of heating the materials at selected temperatures were made. The results suggest that the crystallization of Fe78Si9B13 takes place in two stages, whereas the one of Fe76Si8B16 in three. Since, during the initial stage of crystallization, regions

K. G. Efthimiadis; C. A. Achilleos; S. C. Chadjivasiliou; I. A. Tsoukalas

1997-01-01

192

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

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

193

Microstructure of the Al-La-Ni-Fe system  

NASA Astrophysics Data System (ADS)

The microstructure of alloys based on the Al-La-Ni-Fe system, which are characterized by a unique ability to form metal glasses and nanoscale composites in a wide range of compositions, has been investigated. Al85Ni7Fe4La4 and Al85Ni9Fe2La4 alloys have been analyzed by electron microscopy (including high-resolution scanning transmission electron microscopy), energy-dispersive X-ray microanalysis, electron diffraction (ED), and X-ray diffraction (XRD). It is found that, along with fcc Al and Al4La (Al11La3) particles, these alloys contain a ternary phase Al3Ni1 - x Fe x (sp. gr. Pnma) isostructural to the Al3Ni phase and a quaternary phase Al8Fe2 - x Ni x La isostructural to the Al8Fe2Eu phase (sp. gr. Pbam). The unit-cell parameters of the Al3Ni1 - x Fe x and Al8Fe2 - x Ni x La compounds, determined by ED and refined by XRD, are a = 0.664(1) nm, b = 0.734(1) nm, and c = 0.490(1) nm for Al3Ni1 - x Fe x and a = 1.258(3) nm, b = 1.448(3) nm, and c = 0.405(8) nm for Al8Fe2 - x Ni x La. In both cases Ni and Fe atoms are statistically arranged, and no ordering is found. Al8Fe2 - x Ni x La particles contain inclusions in the form of Al3Fe ? layers.

Vasil'ev, A. L.; Ivanova, A. G.; Bakhteeva, N. D.; Kolobylina, N. N.; Orekhov, A. S.; Presnyakov, M. Yu.; Todorova, E. V.

2015-01-01

194

Comments on ``Electronic and thermodynamic properties of B2-FeSi from first principles'' [Physica B 406 (2011) 363-367  

Microsoft Academic Search

Iron monosilicides (FeSi) is an important material with very interesting properties that can be harnessed for technological applications. Our attention has been drawn to the so-called first principle study of the electronic and thermodynamic properties of B2-FeSi by Zhao et al. (Physica B 406 (2011) 363-367) using pseudopotential plane wave method. They reported that FeSi in B2 phase is a

E. C. Ekuma

2011-01-01

195

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

196

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

197

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

NASA Astrophysics Data System (ADS)

We have studied in situ structures and magnetic properties for several iron silicides grown on Si(111)7×7 clean surfaces by the solid phase epitaxy (SPE) method: deposition of Fe at 40 K and subsequently annealing, and summarized almost all silicide phases depending on the deposition thickness and the annealing temperature as a “schematic magnetic phase diagram”. In the SPE growth, bcc-Fe(111)1×1, c-FeSi(111)1×1, 2×2, and c(4×8), ?-FeSi2(112)2×2, ?-FeSi(111)?3 ×? 3-R30°, ?-FeSi2(101)/(110) and polycrystalline phases are formed on Si(111)7×7 surfaces depending on Fe coverage (0.15-10.0 nm) and annealing temperature (470-1070 K). The structures and magnetic properties of all the above Fe silicide phases have been characterized by using in situ reflection high-energy electron diffraction, scanning tunneling microscopy, and surface magneto-optical Kerr effect. Bulk-unstable c-FeSi phases showed ferromagnetic property at 40 K and this ferromagnetism remained even after air exposure. For the c-FeSi(111)/Si(111) system, the large spin polarization was proposed at the Fe interface atoms in the B5-type interface structure between the c-FeSi(111) ultra-thin film and the Si(111) substrate by first-principle calculations.

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

2014-08-01

198

Magnetoresistance Effect in Co2MnSi/semimetallic-Fe2VAl/CoFe Junctions  

NASA Astrophysics Data System (ADS)

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

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

2011-01-01

199

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

NASA Astrophysics Data System (ADS)

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 FeAl2.5Bx 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 HNO3 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 °C for 10 min for a ˜ 2 ?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.

Qin, C.-D.; Li, A. S. K.; Ng, D. H. L.

1996-04-01

200

Depletion Study of Si And Fe with Mid and Far-Infrared Imaging Spectroscopy with SPICA  

Microsoft Academic Search

Ionic emission lines, such as [Si II] 35 mum, [Fe II] 26 mum, and [Fe III] 23 mum, can be used to investigate the gas-phase abundance of Si and Fe, which are key elements of the constituents of interstellar dust grains. The depletion study of Si and Fe provides crucial information on the chemical composition of dust. The investigation of

Y. Okada; T. Onaka; H. Kaneda; I. Sakon

2009-01-01

201

Magnetocaloric effect in MnFe(P,Si,Ge) compounds  

NASA Astrophysics Data System (ADS)

We have studied the magnetocaloric effect in MnFe(P,Si,Ge) compounds. The structural properties of the compounds were determined by x-ray diffraction. The homogeneity and the stoichiometry of the compounds were checked by electron probe microanalysis. The Curie temperature is found to be near room temperature. Specific-heat measurements made on these compounds show a first-order ferromagnetic-paramagnetic phase transition. The magnetocaloric effect derived from magnetization data shows that this effect in the MnFe(P,Si,Ge) compounds is as large as that in Gd-based compounds and MnFeP1-xAsx compounds. This means that we have succeeded in totally replacing As by (Ge,Si) in the latter compounds without losing the favorable magnetic properties. The upshot is that we have found relatively low cost and nontoxic materials for room-temperature cooling applications.

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

2006-04-01

202

Moessbauer study in thin films of FeSi2 and FeSe systems  

NASA Technical Reports Server (NTRS)

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

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

1978-01-01

203

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

NASA Astrophysics Data System (ADS)

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

Shyni, P. C.; Alagarsamy, Perumal

2014-09-01

204

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

205

Inhomogeneity of rolling texture in Fe28Al2Cr alloy  

Microsoft Academic Search

Inhomogeneity of rolling texture in metal sheets has been investigated, which should be avoided if the normal rolling texture is expected, or promoted if a certain special property could be thus obtained (e.g. in Fe-3%Si sheet). On the other hand, the investigation could also help in revealing the detailed deformation mechanism in metal sheets. Iron aluminides based on Fe[sub 3]Al

W. Mao; Z. Sun

1993-01-01

206

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

SciTech Connect

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

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

1997-10-01

207

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

NASA Astrophysics Data System (ADS)

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

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

2006-04-01

208

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

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

209

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

PubMed

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

Shanableh, Abdallah M; Elsergany, Moetaz M

2013-01-01

210

Large tunnel magnetoresistance at room temperature with a Co{sub 2}FeAl full-Heusler alloy electrode  

SciTech Connect

Magnetic tunnel junctions (MTJs) with a Co{sub 2}FeAl 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 Co{sub 2}FeAl/Al-O{sub x}/Co{sub 75}Fe{sub 25} magnetic tunnel junction (MTJ) fabricated on a thermally oxidized Si substrate despite the A2 type atomic site disorder for Co{sub 2}FeAl. There is no increase of TMR in MTJs with the B2 type Co{sub 2}FeAl, which is prepared by the deposition on a heated substrate. X-ray photoelectron spectroscopy (XPS) depth profiles in Co{sub 2}FeAl single layer films reveal that Al atoms in Co{sub 2}FeAl are oxidized preferentially at the surfaces. On the other hand, at the interfaces in Co{sub 2}FeAl/Al-O{sub x}/Co{sub 75}Fe{sub 25} 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. [Department of Materials Science, Graduate School of Engineering, Tohoku University, Aoba-yama 6-6-02, Sendai 980-8579 (Japan); Department of Materials Science, Graduate School of Engineering, Tohoku University, Aoba-yama 6-6-02, Sendai 980-8579 (Japan); CREST, Japan Science and Technology Agency, 4-1-8 Honcho Kawaguchi, Saitama 332-0012 (Japan)

2005-06-06

211

In situ synchrotron tomographic investigation of the solidification of an AlMg4.7Si8 alloy  

PubMed Central

The solidification sequence of an AlMg4.7Si8 alloy is imaged in situ by synchrotron microtomography. Tomograms with (1.4 ?m)3/voxel have been recorded every minute while cooling the melt from 600 °C at a cooling rate of 5 K min?1 to 540 °C in the solid state. The solidification process starts with the three-dimensional evolution of the ?-Al dendritic structure at 590 °C. The growth of the ?-Al dendrites is described by curvature parameters that represent the coarsening quantitatively, and ends in droplet-like shapes of the secondary dendrite arms at 577 °C. There, the eutectic valley of ?-Al/Mg2Si is reached, forming initially octahedral Mg2Si particles preferentially at the bases of the secondary dendrite arms. The eutectic grows with seaweed-like Mg2Si structures, with increasing connectivity. During this solidification stage Fe-aluminides form and expand as thin objects within the interdendritic liquid. Finally, the remaining liquid freezes as ternary ?-Al/Mg2Si/Si eutectic at 558 °C, increasing further the connectivity of the intermetallic phases. The frozen alloy consists of four phases exhibiting morphologies characteristic of their mode of solidification: ?-Al dendrites, eutectic ?-Al/Mg2Si “Chinese script” with Fe-aluminides, and interpenetrating ?-Al/Mg2Si/Si ternary eutectic. PMID:23470958

Tolnai, D.; Townsend, P.; Requena, G.; Salvo, L.; Lendvai, J.; Degischer, H.P.

2012-01-01

212

In situ synchrotron tomographic investigation of the solidification of an AlMg4.7Si8 alloy.  

PubMed

The solidification sequence of an AlMg4.7Si8 alloy is imaged in situ by synchrotron microtomography. Tomograms with (1.4 ?m)(3)/voxel have been recorded every minute while cooling the melt from 600 °C at a cooling rate of 5 K min(-1) to 540 °C in the solid state. The solidification process starts with the three-dimensional evolution of the ?-Al dendritic structure at 590 °C. The growth of the ?-Al dendrites is described by curvature parameters that represent the coarsening quantitatively, and ends in droplet-like shapes of the secondary dendrite arms at 577 °C. There, the eutectic valley of ?-Al/Mg2Si is reached, forming initially octahedral Mg2Si particles preferentially at the bases of the secondary dendrite arms. The eutectic grows with seaweed-like Mg2Si structures, with increasing connectivity. During this solidification stage Fe-aluminides form and expand as thin objects within the interdendritic liquid. Finally, the remaining liquid freezes as ternary ?-Al/Mg2Si/Si eutectic at 558 °C, increasing further the connectivity of the intermetallic phases. The frozen alloy consists of four phases exhibiting morphologies characteristic of their mode of solidification: ?-Al dendrites, eutectic ?-Al/Mg2Si "Chinese script" with Fe-aluminides, and interpenetrating ?-Al/Mg2Si/Si ternary eutectic. PMID:23470958

Tolnai, D; Townsend, P; Requena, G; Salvo, L; Lendvai, J; Degischer, H P

2012-04-01

213

Signatures of Correlation Effects and Thermopower in FeSi  

NASA Astrophysics Data System (ADS)

Correlated semiconductors have been studied intensively over the years, because they exhibit an unusual metalization process which is poorly understood. At low temperatures FeSi behaves as an ordinary semiconductor, while at high temperatures the system is a bad metal with a Curie like susceptibility. Analogies with heavy fermion Kondo insulators and mixed valence compounds, and anomalous electron phonon coupling have been invoked to account for this behavior, but lacking quantitative methodologies applied to this problem, a consensus remained elusive to date. Here, we use realistic many-body methods to elucidate the metalization of FeSi. Our methodology accounts for all substantial anomalies observed in FeSi : lack of conservation of spectral weight in optics, Curie susceptibility and an anomalous thermoelectric power. Having quantitatively validated our approach, we propose a new scenario. In correlated insulators such as FeSi the metalization is induced by the emergence of non-quasiparticle incoherent states in the gap. This coherence-incoherence crossover is accompanied by a massive reorganization of the spin excitations. Besides the fundamental interest of our theory, our work is relevant to the design of thermoelectric materials based on correlated insulators.

Tomczak, Jan; Haule, Kristjan; Kotliar, Gabriel

2012-02-01

214

Manufacturing of cellular ?-SiAlON\\/?-SiC composite ceramics from cardboard  

Microsoft Academic Search

Light-weight, cellular ?-SiAlON\\/SiC ceramics were produced via dip-coating of an Al\\/Si-powder containing preceramic polymer\\u000a slurry into corrugated cardboard. The coated cardboard preforms were pyrolyzed in Ar-atmosphere at 1200°C, where the cellulose\\u000a fibres decomposed into carbon. Simultaneously the Al\\/Si melt infiltrated into the porous carbon and formed ?-SiC. Subsequent\\u000a nitridation at temperatures between 1200–1530°C resulted in the formation of a ?-SiC-containing

C. R. Rambo; H. Sieber

2006-01-01

215

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

216

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

NASA Astrophysics Data System (ADS)

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

Harada, Noriyuki; Takai, Hiroshi

2003-05-01

217

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

218

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

SciTech Connect

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

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

1998-05-01

219

Does the quasicrystal AlCuFe follow Ohm's law\\?  

NASA Astrophysics Data System (ADS)

We present the first measurements of the electrical I-V characteristics of AlCuFe quasicrystalline thin films processed by solid state interdiffusion of magnetron sputtered Al, Cu, and Fe layers. Despite the peculiar electronic properties of quasicrystals, our results show that those samples follow perfectly Ohm's law for bias voltages which vary by 7 orders of magnitude.

Klein, T.; Symko, O. G.

1994-10-01

220

Does the quasicrystal AlCuFe follow Ohm's law\\\\?  

Microsoft Academic Search

We present the first measurements of the electrical I-V characteristics of AlCuFe quasicrystalline thin films processed by solid state interdiffusion of magnetron sputtered Al, Cu, and Fe layers. Despite the peculiar electronic properties of quasicrystals, our results show that those samples follow perfectly Ohm's law for bias voltages which vary by 7 orders of magnitude.

T. Klein; O. G. Symko

1994-01-01

221

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

NASA Astrophysics Data System (ADS)

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

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

2003-05-01

222

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

NASA Astrophysics Data System (ADS)

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

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

2010-03-01

223

Microstructural and mechanical characterization of Al–Zn–Si nanocomposites  

SciTech Connect

In this paper the addition of silicon nanoparticles into Al–Zn alloys to form metallic matrix nanocomposites by mechanical alloying process was investigated. The influence of various process parameters such as milling time and Si concentration in the Al–Zn matrix has an interesting effect on the microstructure and mechanical properties of the synthesized nanocomposites. The microstructural characterization of the nanocomposites was evaluated by transmission electron microscopy and energy dispersive X-ray spectroscopy (TEM–EDXS) and the mechanical properties were measured by nanoindentation and micro-hardness tests. The results showed that during mechanical milling Si is added to the Al–Zn matrix achieving a uniform and homogeneous dispersion. After solidification, it forms small particles of AlZnSi with blocky morphology in interdendritic regions. The nanoindentation profiles showed that the elastic modulus and hardness properties increase with increasing milling time. However, a high concentration of Si (> 1.2 wt.%) results in a saturation of Si in the Al–Zn matrix, which adversely affects the mechanical properties. Thus, it is important to tune the milling time and concentration of Si added to the Al–Zn alloys to control the growth of brittle phases that result in reduction of the mechanical properties of the material. - Highlights: • A novel technique for addition of Si nanocomposites into Al–Zn liquid alloy is reported. • Good dispersion and homogeneity of Si in the Al–Zn matrix are obtained. • Increasing Si content above 1.2 wt.% decreases the mechanical properties of Al–Zn alloy. • The saturation point of Si in 1.2 wt.% differs from Galvalume® composition. • The Al–Zn–1.5Si alloy with addition of nanocomposite shows 5.7 GPa of hardness.

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

2013-09-15

224

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

SciTech Connect

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

Lal, Chhagan, E-mail: clsaini52@gmail.com [Centre for Non-Conventional Energy Resources, 14-Vigyan Bhavan, University of Rajasthan, Jaipur-302004 (India); Synchrotron S.C.p.A., SS-14 km, 163.5, in Area Science Park, 34149, Basovizza, Trieste (Italy); International Centre for Theoretical Physics (Italy); Di Santo, G.; Caputo, M.; Panighel, M.; Goldoni, A. [Synchrotron S.C.p.A., SS-14 km, 163.5, in Area Science Park, 34149, Basovizza, Trieste (Italy); Taleatu, B. A. [Department of Physics, Obafemi Awolowo University Ile-Ife (Nigeria); Jain, I. P. [Centre for Non-Conventional Energy Resources, 14-Vigyan Bhavan, University of Rajasthan, Jaipur-302004 (India)

2014-04-24

225

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

226

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

227

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

NASA Astrophysics Data System (ADS)

Phonon-drag effect usually occurs in single crystals at very low temperatures (10-200 K). Strong phonon-drag effect is observed in ultra-thin ?-FeSi2 films at around room temperature. The Seebeck coefficient of a 23 nm-thick ?-FeSi2 film can reach -1.375 mV/K at 343 K. However, the thermoelectric power factor of the film is still small, only 0.42×10-3 W/m-K2, due to its large electrical resistivity. When a 27 nm-thick MnSi1.7 film with low electrical resistivity is grown on it, the thermoelectric power factor of the MnSi1.7 film can reach 1.5×10-3 W/m-K2 at around room temperature. This value is larger than that of bulk MnSi1.7 material in the same temperature range.

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

228

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

229

Single-crystal Al-catalyzed Si nanowires grown via hedgehog-shaped Al-Si aggregates  

NASA Astrophysics Data System (ADS)

Single-crystal, Al-catalyzed Si nanowires (SiNWs) were grown under atmospheric pressure using the dimpled feature of Al metal that remained after the removal of an anodic aluminum oxide (AAO) template directly formed on a Si substrate. During the H 2 preannealing prior to growth, the dimpled surface morphology of the remaining Al changed as the Al formed agglomerations with each other and subsequently formed Al-Si alloy islands on the silicon surface. Silicon nanowires were found to only grow on these islands, resulting in the final hedgehog-shaped morphology. The amount of Al agglomeration which controlled the overall size of the alloy islands was determined by varying the H 2/Ar flow ratio during preannealing. High-density growth of SiNWs was observed at a lower ratio of the H 2/Ar flow rates.

Jung, Jin-Young; Jee, Sang-Won; Lee, Jung-Ho

2010-01-01

230

Surface characterization of homoepitaxial ?- FeSi 2 film on ?- FeSi 2 (111) substrate by X-ray photoelectron and absorption spectroscopy  

NASA Astrophysics Data System (ADS)

Surface characterization of a homoepitaxial ?- FeSi2 film grown on a ?- FeSi2 single crystal synthesized with a temperaturegradient solution method was performed by X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS). The annealing to remove native oxide layers on the crystal before homoepitaxial growth induced the formation of Fe-rich silicide in the surface. The XAS spectra confirm that the homoepitaxial ?- FeSi2 film can be grown on the crystal, while Fe-rich silicide is partially formed. The control of the surface chemical state is important to obtain homoepitaxial films with excellent quality.

Esaka, F.; Yamamoto, H.; Udono, H.; Matsubayashi, N.; Yamaguchi, K.; Shamoto, S.; Magara, M.; Kimura, T.

231

Dielectric properties of spark plasma sintered AlN/SiC composite ceramics  

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

232

Mechanisms of linear anelasticity in Fe- M and Fe-Al- M ( M = Ga, Ge) alloys  

NASA Astrophysics Data System (ADS)

Linear anelastic effects in binary and ternary alloys of iron with 13 and 17 at % Ga, 12 at % Ge, and 4-8 at % Al (Fe-13Ga, Fe-17Ga, Fe-12Ge, Fe-8Al-3Ga, Fe-8Al-4Ge, and Fe-4Al-8Ge) have been investigated. In all of these alloys, thermally activated effects of linear anelasticity have been found and identified that are caused by point defects in interstitial (Snoek-type relaxation) and substitutional (Zener relaxation) solid solutions, as well as by dislocations (Hasiguti effect), and by grain boundaries. The effects of the alloy composition on the activation parameters of the above-mentioned relaxation mechanisms have been determined. In addition, frequency-independent effects related to processes of structural rearrangement, such as ordering and disordering of the alloys have been revealed due to the specific features in the curves of the temperature dependences of internal friction for almost all compositions.

Golovin, I. S.

2013-12-01

233

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

SciTech Connect

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 E{sub c}-0.6-0.7 eV. Si doping to (5-7)x10{sup 17} cm{sup -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 {approx}1 eV. Doping with Fe to a concentration of {approx}10{sup 17} cm{sup -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)x10{sup 17} cm{sup -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. [Institute of Rare Metals, Moscow 119017, B. Tolmachevsky 5 (Russian Federation); Dabiran, A. M.; Chow, P. P.; Wowchak, A. M. [SVT Associates Inc., Eden Prairie, Minnesota 55344 (United States); Pearton, S. J. [Department of Material Science and Engineering, University of Florida, Gainesville, Florida 32611 (United States)

2010-01-15

234

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

NASA Astrophysics Data System (ADS)

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

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

2007-11-01

235

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

NASA Astrophysics Data System (ADS)

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

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

2015-02-01

236

CV Shift Characteristics of Metal-Al2O3Si and Metal-Al2O3SiO2Si Structures  

Microsoft Academic Search

C-V shift characteristics of MAS(Metal\\/Al2O3\\/Si) structure with Al2O3 prepared by the hydrolysis of AlCl3 are investigated as a function of the Al2O3 thickness, the temperature and the applied pulse width. Using also MAOS(Metal\\/Al2O3\\/SiO2\\/Si) structure the critical voltage required to shift the C-V curve is given as a function of the SiO2 thickness. The results show that the critical voltage of

Tohru Tsujide

1972-01-01

237

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

238

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

239

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

240

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

PubMed

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

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

2014-09-01

241

A polarized neutron study of the magnetization distribution in Co?FeSi.  

PubMed

The magnetization distribution in Co2FeSi which has the largest moment per formula unit ?6 ?B of all Heusler alloys, has been determined using polarized neutron diffraction. The experimentally determined magnetization has been integrated over spheres centred on the three sites of the L12 structure giving ? Fe = 3.10(3) ?B and ? Co = 1.43(2) ?B, results which are slightly lower than the moments in atomic spheres of similar radii obtained in recent LDA + U band structure calculations (Li et al 2010 Chin. Phys. B 19 097102). Approximately 50% of the magnetic carriers at the Fe sites were found to be in orbitals with eg symmetry. This was higher, ?65%, at the Co sites. Both Fe and Co were found to have orbital moments that are larger than those predicted. Comparison with similar results obtained for related alloys suggests that there must be a finite density of states in both spin bands at the Fermi energy indicating that Co2FeSi is not a perfect half-metallic ferromagnet. PMID:23612471

Brown, P J; Kainuma, R; Kanomata, T; Neumann, K-U; Okubo, A; Umetsu, R Y; Ziebeck, K R A

2013-05-22

242

Removal of arsenite by Fe(VI), Fe(VI)\\/Fe(III), and Fe(VI)\\/Al(III) salts: Effect of pH and anions  

Microsoft Academic Search

The removal of arsenate and arsenite from drinking water poses challenges, especially when arsenite is present in a significant amount. The removal of arsenite by K2FeO4, K2FeO4\\/FeCl3, and K2FeO4\\/AlCl3 salts was studied at pH 6.5 and at an initial As concentration of 500?g As(III)L?1. The arsenite removal in Fe(VI)\\/Fe(III) and Fe(VI)\\/Al(III) systems was also examined as a function of pH

Amita Jain; Virender K. Sharma; Odemari S. Mbuya

2009-01-01

243

Vacancy-induced hardening in Fe-Al alloys  

NASA Astrophysics Data System (ADS)

Hardness of Fe-Al alloys shows a non-trivial dependence on chemical composition and thermal treatment of samples and cannot be fully explained by consideration of intermetallic phases formed according to the equilibrium phase diagram of Fe-Al system. Hardening in Fe-Al alloys caused by quenched-in non-equilibrium vacancies was studied in this work. Non-equilibrium vacancies introduced into the alloys by quenching from 1000 °C were detected by means of positron annihilation spectroscopy. The concentration of quenched-in vacancies was found to strongly increase with increasing Al content from ? 10-5 at.-1 in the alloy with cAl = 18 at. % up to ? 10-1 at.-1 in the alloy with cAl = 45 at. %. Comparison of the vacancy concentration and the Vickers microhardness revealed that hardening is proportional to square root of concentration of quenched-in vacancies.

Luká?, F.; ?ížek, J.; Procházka, I.; Jirásková, Y.; Jani?kovi?, D.; Anwand, W.; Brauer, G.

2013-06-01

244

Work of Adhesion in Al/SiC Composites with Alloying Element Addition  

NASA Astrophysics Data System (ADS)

In the current work, a general methodology was proposed to demonstrate how to calculate the work of adhesion in a reactive multicomponent alloy/ceramic system. Applying this methodology, the work of adhesion of Al alloy/SiC systems and the influence of different alloying elements were predicted. Based on the thermodynamics of interfacial reaction and calculation models for component activities, the equilibrium compositions of the melts in Al alloy/SiC systems were calculated. Combining the work of adhesion models for reactive metal/ceramic systems, the work of adhesion in Al alloy/SiC systems both before and after the reaction was calculated. The results showed that the addition of most alloying elements, such as Mg, Si, and Mn, could increase the initial work of adhesion, while Fe had a slightly decreasing effect. As for the equilibrium state, the additions of Cu, Fe, Mn, Ni, Ti, and La could increase the equilibrium work of adhesion, but the additions of Mg and Zn had an opposite effect. Si was emphasized due to its suppressing effect on the interfacial reaction.

Fang, Xin; Fan, Tongxiang; Zhang, Di

2013-11-01

245

Texture development in SiC-seeded AlN  

SciTech Connect

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

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

1997-01-01

246

Thermal stability of TiAlN and nanocomposite TiAlSiN thin films.  

PubMed

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

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

2009-02-01

247

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

248

The cavitation erosion of Fe?Mn?Al alloys  

Microsoft Academic Search

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

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

1995-01-01

249

Effects of energetic heavy ion irradiation on hardness of Al-Mg-Si alloys  

NASA Astrophysics Data System (ADS)

Al-Mg-Si alloys were irradiated with 5.4 MeV Al ions, 7.3 MeV Fe ions, 10 MeV I ions, and 16 MeV Au ions at room temperature and the Vickers microhardness was measured. The hardness of Al-Mg-Si alloys increases with increasing the ion fluence. In a viewpoint of ion fluence, hardness change of the Al alloys is different by the kind of irradiating ions. But, in a viewpoint of the density of elastically deposited energy, the effect of the four kinds of them on hardness is almost the same. This result means that the effect of irradiation on hardness of Al-Mg-Si alloys is dominated by the elastically deposited energy. The microstructure of the ion-irradiated specimens were investigated by means of three-dimensional atom probe (3DAP). The experimental result was compared with the microstructure and the hardness for thermally aged specimens. We also discuss the difference in ion-irradiation induced change in hardness between Al-Mg-Si alloys and Al-Cu-Mg alloys (duralumin).

Ueyama, D.; Saitoh, Y.; Hori, F.; Kaneno, Y.; Nishida, K.; Dohi, K.; Soneda, N.; Semboshi, S.; Iwase, A.

2013-11-01

250

Dependence of BiFeO3 thickness on exchange bias in BiFeO3/ Co2FeAl multiferroic structures  

NASA Astrophysics Data System (ADS)

We have grown BiFeO3 (BFO) thin films with different thickness on Si/SiO2/Ti/Pt(111) substrates by pulsed laser deposition. Half-metallic Co2FeAl (CFA) films with a thickness of 5 nm were then grown on the BFO films by magnetron sputtering. Through the magnetic hysteresis loops of the BFO/CFA heterostructure, we observe a direct correlation between the thickness of the BFO film and exchange bias (EB) field. The EB field exhibits fluctuation behavior with a cyclical BFO thickness of 60 nm, which is close to the spiral modulation wavelength (62 nm) of BFO. It indicates the influence of spiral modulation on the EB in the BFO/CFA multiferroic structure.

Zhang, X.; Zhang, D. L.; Wang, Y. H.; Miao, J.; Xu, X. G.; Jiang, Y.

2011-01-01

251

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

E-print Network

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

Duffy, Thomas S.

252

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

PubMed

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

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

2012-12-14

253

Amplification of magnetoresistance of magnetite in an Fe3O4SiO2Si structure  

Microsoft Academic Search

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

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

2008-01-01

254

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

NASA Technical Reports Server (NTRS)

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

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

1996-01-01

255

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

256

Investigation of mechanosynthesized Fe50Ni40Al10 powders  

NASA Astrophysics Data System (ADS)

The synthesis of Fe50Ni40Al10 powder mixture has been performed in a high-energy planetary ball mill. The phase transformations and structural changes occurring during mechanical alloying were investigated by X-ray diffraction (XRD) and Mössbauer spectroscopy. XRD analysis and Rietveld method revealed the formation of a single nanocrystalline fcc ?-Ni(Fe,Al) solid solution with a lattice parameter close to a?-Ni(Fe,Al)=0.3612 nm, after 4 h of milling. The final powder is characterized by an average crystallite size of 14 nm accompanied by the introduction of a lattice strain of order of 1.37%. These values are markedly higher than those reported for mechanically alloyed Fe50Ni50 powders. It was found that the formation of the bcc phase, which coexisted with the fcc structure in the Fe-Ni phase diagram, was inhibited. However, mechanical alloying process gives rise to the Ni3Al intermetallic phase, at the early stages of milling. Mössbauer spectroscopy showed that all powders exhibited a ferromagnetic behavior and no paramagnetic phase was detected. The addition of low aluminium content caused more broadening of hyperfine field distributions and lower magnetic field due to the diffusion of Al atoms into ?-FeNi lattice.

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

2013-10-01

257

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

Microsoft Academic Search

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

Moon Suk Kim; Eui Hong Min; Jae Gui Koh

2009-01-01

258

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

Microsoft Academic Search

The raw materials of FeSiCr were processed in the ball mill for 30h 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

Moon Suk Kim; Eui Hong Min; Jae Gui Koh

2009-01-01

259

Interference enhanced magnetic Kerr rotation in compositionally modulated TbFe/SiO films  

SciTech Connect

Magnetic Kerr rotation in compositionally modulated TbFe/SiO films is reported. The spectrum of Kerr rotation angle is tailored with an appropriate choice of the ratio of the thickness of TbFe layer to that of SiO layer, without any change of composition. As the thickness of both the TbFe layers and the SiO layers are small compared to the wavelength of light, the dielectric constant averaged over a compositionally modulated TbFe/SiO film is regarded as an effective dielectric constant of the film. The Kerr rotation angle is enhanced to 25 degrees.

Sato, R.; Saito, N.; Morishita, T.

1988-11-01

260

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

PubMed

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

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

2006-05-25

261

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

NASA Astrophysics Data System (ADS)

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

Miko?ajczak, P.; Ratke, L.

2012-01-01

262

Interdiffusion in Diffusion Couples: U-Mo v. Al and Al-Si  

SciTech Connect

Interdiffusion and microstructural development in the U-Mo-Al system was examined using solid-tosolid diffusion couples consisting of U-7wt.%Mo, U-10wt.%Mo and U-12wt.%Mo vs. pure Al, annealed at 600°C for 24 hours. The influence of Si alloying addition (up to 5 wt.%) in Al on the interdiffusion microstructural development was also examined using solid-to-solid diffusion couples consisting of U-7wt.%Mo, U-10wt.%Mo and U-12wt.%Mo vs. pure Al, Al-2wt.%Si, and Al-5wt.%Si annealed at 550°C up to 20 hours. Scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electron probe microanalysis (EPMA) were employed to examine the development of a very fine multiphase intermetallic layer. In ternary U-Mo-Al diffusion couples annealed at 600°C for 24 hours, interdiffusion microstructure varied of finely dispersed UAl3, UAl4, U6Mo4Al43, and UMo2Al20 phases while the average composition throughout the interdiffusion zone remained constant at approximately 80 at.% Al. Interdiffusion microstructure observed by SEM/TEM analyses and diffusion paths drawn from concentration profiles determined by EPMA appear to deviate from the assumption of “local thermodynamic equilibrium,” and suggest that interdiffusion occurs via supersaturated UAl4 followed by equilibrium transformation into UAl3, U6Mo4Al43, UAl4 and UMo2Al20 phases. Similar observation was made for U-Mo vs. Al diffusion couples annealed at 550°C. The addition of Si (up to 5 wt.%) in Al significantly reduced the thickness of the intermetallic layer by changing the constituent phases of the interdiffusion zone developed in U-Mo vs. Al-Si diffusion couples. Specifically, the formation of (U,Mo)(Al,Si)3 with relatively large solubility for Mo and Si, along with UMo2Al20 phases was observed along with disappearance of U6Mo4Al43 and UAl4 phases. Simplified understanding based on U-Al, U-Si, and Mo-Si binary phase diagrams is discussed in the light of the beneficial effect of Si alloying addition.

D. D. Keiser, Jr.; E. Perez; B. Yao; Y. H. Sohn

2009-11-01

263

Self-Separation of Sublimation-Grown AlN with AlSiN Buffer Layer  

NASA Astrophysics Data System (ADS)

AlN was grown by a sublimation method on 6H-SiC. We found the grown AlN layer is easily separated from the substrate when Si powder is added to the AlN source powder. The formation of AlSiN layer with the Si content of 15% at the AlN/6H-SiC interface was confirmed by energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). This AlSiN layer causes the separation of AlN.

Nishino, Katsushi; Nakauchi, Jun; Hayashi, Kotaro; Tsukihara, Masashi

2013-08-01

264

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

265

/Al-Si Composites Fabricated by Reaction Hot Pressing  

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

266

Crystal structure of the compound Lu/sub 3/FeSi/sub 6/  

SciTech Connect

The crystal structure of Lu/sub 3/FeSi/sub 6/ was determined by the powder method. The filling coefficient and thermal and atomic parameters are given for the title structure. The results of calculation and experimental diffraction pattern of the title structure are given. Also shown are the atomic parameters of structural types CeNiSi/sub 2/ and ZrSi/sub 2/ and compound Lu/sub 3/FeSi/sub 6/. The parameters and volume of the unit cell of R/sub 3/FeSi/sub 6/ (R = Y, Tb, Ho, Er, Tm, Lu) are listed.

Krivulya, L.V.; Bodak, O.I.; Gorelenko, Yu.K.

1987-04-01

267

Mossbauer spectroscopic and x-ray diffraction studies of FeSiO2 nanocomposite soft magnetic materials  

E-print Network

Mo¨ssbauer spectroscopic and x-ray diffraction studies of Fe�SiO2 nanocomposite soft magnetic Nanocomposite high resistive soft magnetic materials Fe/SiO2 Fe volume fraction 50% have been synthesized using a wet chemical reaction method. A series of metal-ceramic Fe/SiO2 nanocomposite powder samples were

Yang, De-Ping

268

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

269

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

270

Dissolution of Si in Molten Al with Gas Injection  

NASA Astrophysics Data System (ADS)

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

Seyed Ahmadi, Mehran

271

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

272

Mechanical properties of in situ Al 2O 3 formed Al–Si composite coating via atmospheric plasma spraying  

Microsoft Academic Search

In this study, mechanically alloyed Al–12Si\\/SiO2 composite powder was deposited onto an aluminum substrate by atmospheric plasma spraying. The composite coating consisting of in situ formed Al2O3 reinforced hypereutectic Al–18Si matrix alloy was achieved. The produced coatings were extensively analyzed with respect to X-ray diffraction (XRD). The XRD patterns of the coatings include Al, Si and Al2O3 phase formation. Mechanical

O. Culha; C. Tekmen; M. Toparli; Y. Tsunekawa

2010-01-01

273

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

274

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

275

Abnormal acoustic wave velocities in basaltic and (Fe,Al)-bearing silicate glasses at high pressures  

NASA Astrophysics Data System (ADS)

have measured acoustic VP and VS velocities of (Fe,Al)-bearing MgSiO3 silicate glasses and an Icelandic basalt glass up to 25 GPa. The velocity profiles of the (Fe,Al)-bearing and basaltic silicate glasses display decreased VP and VS with minima at approximately 5 and 2 GPa, respectively, which could be explained by the mode softening in the aluminosilicate networks. Our results represent the first observation of such velocity softening extending into the chemically complex basaltic glass at a relatively low transition pressure, which is likely due to its degree of polymerization, while the Fe and Al substitutions reduce sound velocities in MgSiO3 glass. If the velocity softening in the basaltic and silicate glasses can be used as analogs for understanding melts in Earth's interior, these observations suggest that the melt fraction needed to account for the velocity reduction in the upper mantle low-velocity zone may be smaller than previously thought.

Liu, Jin; Lin, Jung-Fu

2014-12-01

276

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

277

Amplification of magnetoresistance and Hall effect of Fe3O4SiO2Si structure  

Microsoft Academic Search

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

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

2009-01-01

278

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

279

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

NASA Astrophysics Data System (ADS)

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

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

2009-04-01

280

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

281

Electron spin resonance studies in ?-FeSi2 crystals  

NASA Astrophysics Data System (ADS)

The electron spin resonance studies have been carried out in the temperature range 130-300 K on semiconducting ?-FeSi2 single crystals grown by a chemical vapor transport technique. Two anisotropic doublets with apparent g factors in the range 2.025-2.05 and 1.98-2.03, as well as one complex signal having an isotropic g factor of 2.0195 and exhibiting a five-line hyperfine structure, have been detected. The doublet signals are believed to arise from spin triplet (S=1) states of, presumably, substitutional Ni2+ transition ions, whereas the signal exhibiting the hyperfine structure has been attributed to the spin of a hole, captured by silicon vacancy and interacting with nuclear spins of four iron atoms in the first shell surrounding of the silicon vacancy.

Aksenov, I.; Katsumata, H.; Makita, Y.; Kimura, Y.; Shinzato, T.; Sato, K.

1996-08-01

282

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

283

A facile synthesis of monodisperse CoFe 2O 4/SiO 2 nanoparticles  

NASA Astrophysics Data System (ADS)

Aminated-CoFe 2O 4/SiO 2 magnetic nanoparticles (NPs) were prepared from primary silica particles using modified StÖber method. By optimizing the preparation conditions, monodisperse CoFe 2O 4/SiO 2 NPs with high amino groups' density were obtained, which is necessary for enzyme immobilization. TEM confirm that the sample is a core/shell structure. These aminated-CoFe 2O 4/SiO 2 NPs have narrow size distributions with a mean size of about 60 nm. Moreover, the aminated-CoFe 2O 4/SiO 2 NPs can be easily dispersed in aqueous medium. The experimental results also show that the NPs have superparamagnetism, indicating that the aminated-CoFe 2O 4/SiO 2 NPs can be used as an effective carrier for the enzyme immobilization.

Wang, Hai; Huang, Jun; Ding, Liyun; Li, DaPeng; Han, Yun

2011-06-01

284

Diffusion-driven crystal structure transformation: synthesis of Heusler alloy Fe3Si nanowires.  

PubMed

We report fabrication of Heusler alloy Fe(3)Si nanowires by a diffusion-driven crystal structure transformation method from paramagnetic FeSi nanowires. Magnetic measurements of the Fe(3)Si nanowire ensemble show high-temperature ferromagnetic properties with T(c) > 370 K. This methodology is also successfully applied to Co(2)Si nanowires in order to obtain metal-rich nanowires (Co) as another evidence of the structural transformation process. Our newly developed nanowire crystal transformation method would be valuable as a general method to fabricate metal-rich silicide nanowires that are otherwise difficult to synthesize. PMID:20677783

Seo, Kwanyong; Bagkar, Nitin; Kim, Si-in; In, Juneho; Yoon, Hana; Jo, Younghun; Kim, Bongsoo

2010-09-01

285

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

PubMed

Four novel intermetallic silicides, RE5Mn4Al(23-x)Si(x) (x = 7.9(9), RE = Ho, Er, Yb) and Er44Mn55(AlSi)237, have been prepared by reaction in aluminum flux. Three RE5Mn4Al(23-x)Si(x) compounds crystallize in the tetragonal space group P4/mmm with the relatively rare Gd5Mg5Fe4Al(18-x)Si(x) structure type. Refinement of single-crystal X-ray diffraction data yielded unit cell parameters of a = 11.3834(9)-11.4171(10) Å and c = 4.0297(2)-4.0575(4) Å with volumes ranging from 522.41(5) to 528.90(8) Å(3). Structure refinements on single-crystal diffraction data show that Er44Mn55(AlSi)237 adopts a new cubic structure type in the space group Pm3n with a very large unit cell edge of a = 21.815(3) Å. This new structure is best understood when viewed as two sets of nested polyhedra centered on a main group atom and a manganese atom. These polyhedral clusters describe the majority of the atomic positions in the structure and form a perovskite-type network. We also report the electrical and magnetic properties of the title compounds. All compounds except the Ho analogue behave as normal paramagnetic metals without any observed magnetic transitions above 5 K and exhibit antiferromagnetic correlations deduced from the value of their Curie constants. Ho5Mn4Al(23-x)Si(x) exhibits a ferromagnetic transition at 20 K and an additional metamagnetic transition at 10 K, suggesting independent ordering temperatures for two distinct magnetic sublattices. PMID:23931551

Calta, Nicholas P; Kanatzidis, Mercouri G

2013-09-01

286

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

287

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

288

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

289

Spin glass behavior in FeAl2  

E-print Network

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

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

2001-01-01

290

Effects of magnetic fields on Fe-Si composite electrodeposition  

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

291

Giant magnetic tunneling effect in Fe\\/Al2O3\\/Fe junction  

Microsoft Academic Search

A giant magnetoresistance ratio of 30% at 4.2 K and 18% at 300 K was observed for the first time in an Fe\\/Al2O3\\/Fe junction. The conductance at room temperature was expressed well by G=96.2 (1 + 0.09 cos theta)(Omega-1), where theta is the angle between the magnetizations of two iron electrodes. The dependence of the magnetoresistance ratio, saturated resistance and

T. Miyazaki; N. Tezuka

1995-01-01

292

Development of a Cast Al-Mg2Si-Si In Situ Composite: Microstructure, Heat Treatment, and Mechanical Properties  

NASA Astrophysics Data System (ADS)

An Al-11Mg2Si-Si in situ composite was prepared by a modified investment casting technique that employs sub-pressure for castability improvement and immersion of ceramic shell molds in fluidized beds of silica sand and iron particles for heat extraction improvement. The microstructure of the as-cast composite is explained according to the pseudoeutectic Al-Mg2Si phase diagram. The positive effect of a decreased number of mold investment layers and cooling assisted by immersion of the mold in a metallic bed on the tensile strength and hardness of the heat treated composite is noted. A minor presence of Fe in the master alloys constitutes an essential factor for the brittleness of the composite. Solution treatment notably improves the tensile strength of the composite; however, prolonged treatment deteriorates its ductility. The effect of time and temperature of the aging treatment on the hardness of the composite is investigated. The positive influence of cooling assisted by a metallic fluidized bed on the effectiveness of the aging treatment is noticed.

Georgatis, E.; Lekatou, A.; Karantzalis, A. E.; Petropoulos, H.; Katsamakis, S.; Poulia, A.

2013-03-01

293

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

294

Chemical reactions during submerged arc welding with FeO-MnO-SiO 2 fluxes  

Microsoft Academic Search

Measurements have been made of the compositional changes of fluxes and weld metal during submerged arc flux welding with a\\u000a series of synthetic MnO-FeO-SiO2 model fluxes containing 40 wt pct SiO2 and different ratios of MnO to FeO. Mechanisms for the transfer of Mn, O, Si, C, S, and P are discussed in terms of the thermodynamic\\u000a driving forces and

J. Ernesto Indacochea; Milton Blander; Nils Christensen; David L. Olson

1985-01-01

295

Temperature dependence of ?-phase transformation in Cu added Fe 2Si 5 thermoelectric material  

Microsoft Academic Search

The time–temperature–transformation diagrams for the eutectoid decomposition (???+Si) in slowly solidified Fe2Si5 alloys with small amounts of Mn and Cu were obtained in the temperature range 873 and 1173 K. The shape of the diagrams can typically be described by the character C. The nose temperature in a binary Fe2Si5 alloy was about 1023 K and increased by about 50

Isamu Yamauchi; Takeshi Nagase; Itsuo Ohnaka

1999-01-01

296

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

SciTech Connect

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

Natesan, K. [Argonne National Lab., IL (United States); Johnson, R.N. [Pacific Northwest Lab., Richland, WA (United States)

1995-05-01

297

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

NASA Astrophysics Data System (ADS)

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

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

2005-11-01

298

Chemical structures of AlGaN\\/AlN\\/Si [111] by MOCVD using AES and XPS  

Microsoft Academic Search

In this paper X-ray photoelectron spectrum and Auger electron spectrum were used to study the microstructure of AlGaN\\/AlN\\/Si [111] grown by metal organic chemical vapor deposition. The results indicated that a broad transition region, composed of AlN, Si3N4, SiNx (x<4\\/3) and Si was present at the interface of AlN\\/Si. At the interface of AlGaN\\/AlN, the main incorporation of N shifted

Dongjuan Xi; Youdou Zheng; Peng Chen; Zuoming Zhao; Ping Chen; Shiyong Xie; Bo Shen; Shulin Gu; Rong Zhang

2001-01-01

299

Optical investigations of AlSi-SiC composites subjected to laser CO 2 annealing  

NASA Astrophysics Data System (ADS)

The optical study of the AlSi/SiC composite materials before and after laser annealing has been performed. They concerned total and diffuse reflectance measurements obtained by the means of integrating sphere in the spectral range 250-2500 nm, measurements of intensity of scattered light as a function of scattering angle ( BRDF method) and ellipsometric measurements performed in the range 190-1700 nm. For determination of optical constants, the Kramers-Krönig dispersion relation has been applied. Obtained results had great differences of optical properties alloys before and after laser annealing. For investigated composites roughness and correlation lengths of studied surfaces have been determined. Moreover, optical measurements allowed concluding the light scattering being a result of interaction of light with surface topography and material scattering appeared due to variation of optical constants on surfaces of AlSi/SiC composites.

Jaglarz, Janusz; Grabowski, Andrzej

2010-10-01

300

Correlation between microstructure evolution and high temperature properties of TiAlSiN hard coatings with different Si and Al content  

NASA Astrophysics Data System (ADS)

TiAlSiN coatings with different Si and Al content are synthesized by multi-plasma immersion ion implantation and deposition (MPIIID). The microstructure, oxidation resistance and wear resistance of as-deposited coatings are characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), x-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), nano-indentation, thermo gravimetric analysis (TGA) and friction tests. Studies show that TiAlSiN coating has nc-TiAlN/a-Si3N4 structure. The grain size of nc-TiAlN decreases gradually and the volume fraction of the interfacial a-Si3N4 increases with the increased Si level. The obvious reduction in grain size together with the increase in interfacial a-Si3N4 eventually leads to the superior oxidation resistance of TiAlSiN coating. In addition, TiAlSiN coating with low Si and Al content exhibits poor oxidation stability and thermal stability, which results in its unsatisfied wear resistance at 800 ?C. However, TiAlSiN coating with higher Si and Al content possesses better oxidation stability and thermal stability, and this coating shows excellent wear resistance both at RT and 800 ?C. The correlation between microstructure evolution and oxidation resistance and wear resistance of as-deposited coatings are systematically discussed.

Chen, Tian; Xie, Zhiwen; Gong, Feng; Luo, Zhuangzhu; Yang, Zhi

2014-09-01

301

Site preference of ternary alloying additions in FeAl and NiAl by first-principles calculations  

SciTech Connect

First-principles calculations have been performed to investigate the site preference of ternary alloying additions in FeAl and NiAl. In FeAl, Cr and Ti are found to occupy the Al sublattice whereas Ni has a distinct preference for the Fe sublattice. The site substitutional behavior of 3d ternary elements in FeAl can be explained in terms of the trends in the heat-of-formation. In Al-rich NiAl, Fe atoms occupy exclusively the Ni sublattice. In Ni-rich NiAl, because of the small enthalpy difference between Fe occupying Al and Ni sublattices (i.e. less than 0.1 eV with a preference of Fe for Al sites at 0 K), the site distributions of Fe in these alloys are found to vary with alloy composition and temperature. Due to the large difference in the local magnetic moments between Fe atoms occupying Al and Ni sublattices (with values of 2.4 {micro}{sub B} and less than 0.1 {micro}{sub B}, respectively) in NiAl, magnetic susceptibility measurement should be the most effective way to measure the site distributions of Fe in NiAl.

Fu, C.L.; Zou, J. [Oak Ridge National Lab., TN (United States). Metals and Ceramics Div.] [Oak Ridge National Lab., TN (United States). Metals and Ceramics Div.

1996-04-01

302

Poole-Frenkel conduction in Al\\/ZrO 2 \\/SiO 2 \\/Si structures  

Microsoft Academic Search

Leakage currents through Al\\/ZrO2<\\/Subscript>\\/SiO2<\\/Subscript>\\/n-Si metal-insulator-semiconductor (MIS) capacitors were studied. Thin SiO2<\\/Subscript> films were chemically grown on monocrystalline phosphorous doped silicon wafers. Zirconia films with thicknesses of 15 and 50 nm were deposited by radio frequency (rf) magnetron sputtering and, then, annealed in oxygen ambient at 850 ?<\\/Superscript>C, for 1 h. The dielectric constant of the sputtered and annealed ZrO2<\\/Subscript> layer

P. V. Aleskandrova; V. K. Gueorguiev; Tz. E. Ivanov; J. B. Koprinarova

2006-01-01

303

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

304

Magnetic properties of Fe films and Fe/Si/Fe trilayers grown on GaAs(001) and MgO(001) by ion-beam sputter epitaxy  

SciTech Connect

We grow monocrystalline Fe(001) films and Fe/Si/Fe(001) trilayers by ion-beam sputter epitaxy on GaAs(001) and MgO(001) substrates. Ion-beam sputtering parameters such as substrate presputtering time, substrate temperature, beam voltage, and target angle are optimized for 10-nm-thick Fe(001) films with respect to epitaxial growth and magnetic properties. In situ low-energy electron diffraction patterns confirm the epitaxial and monocrystalline nature of the sputtered films, surprisingly even on untreated and thus oxidized substrates. The magneto-optical Kerr effect and ferromagnetic resonance are employed to investigate the magnetic properties, and the structural properties are characterized by atomic force microscopy and x-ray reflectivity measurements. Using the optimized set of parameters that yields the best magnetic properties for single Fe films on GaAs, we deposit epitaxial Fe/Si/Fe(001) structures and observe antiferromagnetic interlayer exchange coupling for epitaxially sputtered Fe/Si/Fe(001) trilayers on GaAs(001). The total coupling strength reaches values of up to 2 mJ/m{sup 2} at a Si thickness of 15 A.

Damm, Thorsten; Buchmeier, Matthias; Schindler, Alexandra; Buergler, Daniel E.; Gruenberg, Peter; Schneider, Claus M. [Institut fuer Festkoerperfoschung, Forschungszentrum Juelich GmbH, D-52425 Juelich (Germany) and Center of Nanoelectronic Systems for Information Technology (CNI), Forschungszentrum Juelich GmbH, D-52425 Juelich (Germany)

2006-05-01

305

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

SciTech Connect

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

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

2014-04-21

306

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

NASA Astrophysics Data System (ADS)

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

Cassidy, Cathal; Kioseoglou, Joseph; Singh, Vidyadhar; Grammatikopoulos, Panagiotis; Lal, Chhagan; Sowwan, Mukhles

2014-04-01

307

Laser cutting of AlSi-alloy/SiC p composite: modelling of the cut kerf geometry  

NASA Astrophysics Data System (ADS)

This paper presents a physical model characterizing the geometry of gas-assisted laser cutting of the AlSi-alloy/SiCp composite. In the model, a lot of relevant parameters that describe the inhomogeneous optical and thermophysical properties of AlSi-alloy/SiC p have been used. Numerical evaluations of this model give some explanations of "double slope" formation mechanism during laser cutting of the AlSi-alloy/SiC p. The theoretical results are compared with experimental data. It is found that increasing laser beam scanning speed increases the slope of cutting front.

Grabowski, Andrzej; Sleziona, Józef; Nowak, Marian

2007-02-01

308

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

309

Mechanical properties and microstructure of SiC-reinforced Mg(2,4)Al1Si nanocomposites fabricated by ultrasonic cavitation based solidification processing  

Microsoft Academic Search

Nano-sized SiC enhanced magnesium matrix nanocomposites, Mg-2Al-1SiC with 2% SiC and Mg-4Al-1Si with 2% SiC, were successfully fabricated by ultrasonic cavitation based dispersion of SiC nanoparticles in Mg-(2,4)Al-1Si magnesium alloy melts. As compared to the magnesium alloy matrixes, the mechanical properties including tensile strength and yield strength of the Mg-2Al-1Si\\/2% SiC and Mg-4Al-1Si\\/2% SiC nanocomposites were improved significantly, while the

G. Cao; H. Konishi; X. Li

2008-01-01

310

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

311

Current Transport in Al-Diffused ZnO/Si Heterostructures  

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

312

Refinement performance and mechanism of an Al-50Si alloy  

SciTech Connect

The microstructure and melt structure of primary silicon particles in an Al-50%Si (wt.%) alloy have been investigated by optical microscopy, scanning electron microscopy, electron probe micro-analysis and a high temperature X-ray diffractometer. The results show that the Al-50Si alloy can be effectively refined by a newly developed Si-20P master alloy, and the melting temperature is crucial to the refinement process. The minimal overheating degree {delta}T{sub min} ({delta}T{sub min} is the difference between the minimal overheating temperature T{sub min} and the liquidus temperature T{sub L}) for good refinement is about 260 deg. C. Primary silicon particles can be refined after adding 0.2 wt.% phosphorus amount at sufficient temperature, and their average size transforms from 2-4 mm to about 30 {mu}m. The X-ray diffraction data of the Al-50Si melt demonstrate that structural change occurs when the melting temperature varies from 1100 deg. C to 1300 deg. C. Additionally, the relationship between the refinement mechanism and the melt structure is discussed.

Dai, H.S. [Key Laboratory of Liquid Structure and Heredity of Materials, Ministry of Education, Shandong University, 73 Jingshi Road, Jinan 250061 (China); Liu, X.F. [Key Laboratory of Liquid Structure and Heredity of Materials, Ministry of Education, Shandong University, 73 Jingshi Road, Jinan 250061 (China)], E-mail: xfliu@sdu.edu.cn

2008-11-15

313

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

SciTech Connect

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

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

2013-11-15

314

Structural modifications upon deposition of Fe on the icosahedral quasicrystal Al–Pd–Mn  

Microsoft Academic Search

We have deposited Fe on a clean pentagonal surface of an Al–Pd–Mn quasicrystal kept at ?340K. For low coverages, Fe diffuses into the bulk and destroys the quasicrystalline atomic order. At coverages higher than ?0.8nm, some Al is present in the film, which shows magnetic ordering. This is characteristic of only AlFe3 or Fe diluted with Al. This surface consists

Y. Weisskopf; R. Lüscher; M. Erbudak

2005-01-01

315

Investigation of the fracture toughness of radio frequency magnetron sputtered Al–Cu–Fe films via white-beam synchrotron radiography\\/topography  

Microsoft Academic Search

A novel white-beam synchrotron radiography\\/topography substrate curvature technique has been used to study stress development in situ during annealing of Al–Cu–Fe quasicrystalline and approximant coatings, as well as to image their failure modes in real time. Single crystal Si and sapphire substrates were coated with a 2.55 m precursor coating by RF sputtering from an Al65Cu23Fe12 powder composite target and

B L French; M J Daniels; J C Bilello

2005-01-01

316

Investigation of the fracture toughness of radio frequency magnetron sputtered Al Cu Fe films via white-beam synchrotron radiography\\/topography  

Microsoft Academic Search

A novel white-beam synchrotron radiography\\/topography substrate curvature technique has been used to study stress development in situ during annealing of Al Cu Fe quasicrystalline and approximant coatings, as well as to image their failure modes in real time. Single crystal Si and sapphire substrates were coated with a 2.55 µm precursor coating by RF sputtering from an Al65Cu23Fe12 powder composite

B. L. French; M. J. Daniels; J. C. Bilello

2005-01-01

317

Microstructure and electrochemical behavior of laser treated Fe?Cr and Fe?Cr?Si?N surface alloyed layers on carbon steel  

Microsoft Academic Search

Laser surface alloyed Fe?Cr and Fe?Cr?Si?N layers on carbon steel were produced by laser irradiation involving preplaced Fe\\/Cr and Fe\\/Cr\\/Si3N4 powders, respectively. The effects of Cr content (13–25 wt.%) and microstructure on the corrosion behavior of the laser treated Fe?Cr and Fe?Cr?Si?N alloys in deaerated neutral 3.5 wt.% NaCl solution were studied. Potentiodynamic polarization tests and electrochemical impedance spectroscopy measurements

Chong-Cheng Huang; Wen-Ta Tsai; Ju-Tung Lee

1995-01-01

318

Magnetotransport Properties of Co2FeAl Nanowires  

NASA Astrophysics Data System (ADS)

Co2FeAl (CFA) nanowire (NW) exhibit interesting magnetic behavior with temperature, which arises from the granular structure.footnotetextKeshab R Sapkota et.al, J. Appl. Phys. Vol. 111, Issue 12, 123906 (2012); http://dx.doi.org/10.1063/1.4729807 To understand the magnetotransport properties, single CFA NW devices were fabricated using standard electron beam lithography. The magnetoresistance measurements of single CFA NW device were carried out at different temperatures. The magnetoresistance measurements show oscillations as a function of applied external magnetic field.

Sapkota, Keshab R.; Gyawali, P.; Dahal, Bishnu; Dulal, R.; Pegg, I. L.; Philip, John

2013-03-01

319

Missing superconductivity in BaAlSi with the AlB 2 type structure  

NASA Astrophysics Data System (ADS)

The solid solutions BaAl 1- xSi 1+ x (0 ? x ? 0.5) were prepared. The compound with the stoichiometric composition ( x = 0) did not show superconductivity as reported by other investigators, but the solid solutions with x > 0 became superconductors with a transition temperature Tc = 2.8 K. The comparison of the lattice parameters with those of the other isotypic ternary superconductors MAlSi (M = Ca, Sr) suggested that the superconductivity could be related to the lattice parameter within the (AlSi) plane rather than the interlayer spacing. The band structures near the Fermi level of MAlSi (M = Ca, Sr, Ba) were measured using soft X-ray photoelectron spectroscopy, which were in good agreement with the calculated ones, confirming that the contribution of the d orbitals of the alkaline-earth metals were predominant in the conduction bands.

Yamanaka, Shoji; Otsuki, Teruyoshi; Ide, Takayuki; Fukuoka, Hiroshi; Kumashiro, Ryotaro; Rachi, Takeshi; Tanigaki, Katsumi; Guo, FangZhun; Kobayashi, Keisuke

2007-01-01

320

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

321

Corrosion behaviour and biocompatibility of a novel Ni-free intermetallic coating growth on austenitic steel by hot dipping in an Al–12.6%Si alloy  

Microsoft Academic Search

Commercial 316 LVM austenitic stainless steel samples have been coated by immersion in a bath of molten Al–12.6%Si alloy for\\u000a 120 s. The coating consists of the Al12(Fe,Cr)3Si2 intermetallic. In vitro corrosion behaviour has been evaluated in the Ringer’s solution by means of potentiodynamic curves\\u000a and electrochemical impedance spectroscopy. The results reveal that the coated specimens exhibit lower susceptibility to localised

M. A. Arenas; E. Frutos; L. Saldaña; A. Conde; L. Labajos-Broncano; M. L. González-Martín; J. L. González-Carrasco; N. Vilaboa

2011-01-01

322

Combustion synthesis of rod-like ?-SiAlON seed crystals  

Microsoft Academic Search

Rod-like single-phase crystals of Y-?-SiAlON were synthesized by combustion of Si, Al, ?-Si3N4, SiO2 and Y2O3 powders. SEM observation of crystals, separated by chemical etching (HNO3\\/HF=2:1) followed by ultrasonic agitation in ethanol showed rod-like crystals, assigned to almost pure and well crystallized ?-SiAlON.

Renli Fu; Kexin Chen; Xin Xu; José M. F. Ferreira

2004-01-01

323

XRD and TEM analysis on the Fe 3Al\\/18-8 stainless steel diffusion bonded interface  

Microsoft Academic Search

Fe3Al intermetallic and 18-8 stainless steel were diffusion-bonded at 1040 °C for 60 min. The reacted phase in the Fe3Al\\/18-8 diffusion-bonded interface was determined via X-ray diffractometry (XRD) and the lattice orientation relation between constituent phases was analyzed by transmission electron microscope (TEM). The results indicated that there were Fe3Al, Ni3 Al, FeAl, ?-Fe (Al) solid solution and Fe3C in

Juan Wang; Yajiang Li; Peng Liu

2003-01-01

324

Templated fabrication and characterization of SiO{sub 2} nanotube covered Fe nanowires  

SciTech Connect

In this study, Fe nanowires coated with SiO{sub 2} nanotubes have been synthesized by electrodeposition method using anodic alumina oxide template. Before growing Fe nanowires, 6–8?nm thick SiO{sub 2} nanotubes are grown inside the template using a “surface sol-gel” technique. The nanotube structures were characterized by field emission scanning electron microscopy and energy dispersive x-ray spectroscopy. Magnetic properties of the SiO{sub 2} insulated Fe nanowires inside the membrane are characterized by superconducting quantum interference device. Coercivities of around 120?Oe with field parallel to the nanowire axis and 240?Oe with field perpendicular the nanowire axis are observed at room temperature. These values are comparable to Fe nanowires without insulating layer in membrane. The magnetic hysteresis loop suggests that the SiO{sub 2} insulated nanowires have uniaxial magnetic anisotropy with the easy axis magnetization direction along the nanowire arrays due to their large shape anisotropy.

Dastagir, Tawab; Yu, Hongbin, E-mail: yuhb@asu.edu [Ira A. Fulton Schools of Engineering, School of Electrical, Computer and Energy Engineering, Arizona State University, Tempe, Arizona, 85287 (United States)

2014-05-07

325

Templated fabrication and characterization of SiO2 nanotube covered Fe nanowires  

NASA Astrophysics Data System (ADS)

In this study, Fe nanowires coated with SiO2 nanotubes have been synthesized by electrodeposition method using anodic alumina oxide template. Before growing Fe nanowires, 6-8 nm thick SiO2 nanotubes are grown inside the template using a "surface sol-gel" technique. The nanotube structures were characterized by field emission scanning electron microscopy and energy dispersive x-ray spectroscopy. Magnetic properties of the SiO2 insulated Fe nanowires inside the membrane are characterized by superconducting quantum interference device. Coercivities of around 120 Oe with field parallel to the nanowire axis and 240 Oe with field perpendicular the nanowire axis are observed at room temperature. These values are comparable to Fe nanowires without insulating layer in membrane. The magnetic hysteresis loop suggests that the SiO2 insulated nanowires have uniaxial magnetic anisotropy with the easy axis magnetization direction along the nanowire arrays due to their large shape anisotropy.

Dastagir, Tawab; Yu, Hongbin

2014-05-01

326

Electromagnetic dissociation of relativistic 28Si into p+27Al  

NASA Astrophysics Data System (ADS)

We report a direct measurement of the final-state energy spectrum in the electromagnetic dissociation of 28Si into p+ 27Al at an energy of 14.6 GeV/nucleon. The final-state energy is obtained through a calculation of the p-27Al invariant mass in kinematically reconstructed events. The final-state energy spectrum for all targets is peaked near the isovector giant-dipole resonance in 28Si and the dependence of the magnitude of the cross section on target charge confirms that the excitation is largely electromagnetic. By exploiting the expected scaling behavior on target Z and A, the background from nuclear interactions is evaluated and subtracted, leaving a pure electromagnetic dissociation final-state energy distribution. This distribution is well reproduced by simulated events, in which the photon spectrum calculated in the Weiszäcker-Williams approximation is combined with experimental data on the photonuclear reaction 28Si(?,p) 27Al, and slight differences are observed only at low final-state energy.

Barrette, J.; Bellwied, R.; Braun-Munzinger, P.; Cleland, W. E.; David, G.; Dee, J.; Dietzsch, O.; Duek, E.; Fatyga, M.; Fox, D.; Greene, S. V.; Hall, J. R.; Hemmick, T. K.; Herrmann, N.; Hogue, R. W.; Hong, B.; Jayananda, K.; Kraus, D.; Shiva Kumar, B.; Lacasse, R.; Lissauer, D.; Llope, W. J.; Ludlam, T.; Majka, R.; Makowiecki, D.; Mark, S. K.; McCorkle, S.; Mitchell, J. T.; Muthuswamy, M.; O'brien, E.; Polychronakos, V.; Pruneau, C.; Rotondo, F. S.; Sandweiss, J.; Simon-Gillo, J.; Sonnadara, U.; Stachel, J.; Takai, H.; Takagui, E. M.; Throwe, T. G.; Waters, L.; Willis, W. J.; Winter, C.; Wolf, K.; Wolfe, D.; Woody, C. L.; Xu, N.; Zhang, Y.; Zhang, Z.; Zou, Z.

1992-05-01

327

Role of Si/Al Ratio on Immobilization and Stability of Rhodium Complexes on ZSM-5  

E-print Network

Rhodium complexes within the pores of zeolite ZSM-5 with varying Si/Al ratios (Si/Al 23, Si/Al 50, and Si/Al 280) were prepared from Rh1+(CO)2(C5H7O2), Rh22+(CO2CH3)4, and Rh3+(C5H7O2)3 followed by thermal treatment in He. IR results indicate...

Long, Brandon

2009-01-01

328

Mechanism of Catalytic Ozonation in Fe2O3/Al2O3@SBA-15 Aqueous Suspension for Destruction of Ibuprofen.  

PubMed

Fe2O3 and/or Al2O3 were supported on mesoporous SBA-15 by wet impregnation and calcinations with AlCl3 and FeCl3 as the metal precursor and were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectra (FTIR) of adsorbed pyridine. Fe2O3/Al2O3@SBA-15 was found to be highly effective for the mineralization of ibuprofen aqueous solution with ozone. The characterization studies showed that Al-O-Si was formed by the substitution of Al(3+) for the hydrogen of surface Si-OH groups, not only resulting in high dispersion of Al2O3 and Fe2O3 on SBA-15, but also inducing the greatest amount of surface Lewis acid sites. By studies of in situ attenuated total reflection FTIR (ATR-FTIR), in situ Raman, and electron spin resonance (ESR) spectra, the chemisorbed ozone was decomposed into surface atomic oxygen species at the Lewis acid sites of Al(3+) while it was converted into surface adsorbed (•)OHads and O2(•-) radicals at the Lewis acid sites of Fe(3+). The combination of both Lewis acid sites of iron and aluminum onto Fe2O3/Al2O3@SBA-15 enhanced the formation of (•)OHads and O2(•-) radicals, leading to highest reactivity. Mechanisms of catalytic ozonation were proposed for the tested catalysts on the basis of all the experimental information. PMID:25564945

Bing, Jishuai; Hu, Chun; Nie, Yulun; Yang, Min; Qu, Jiuhui

2015-02-01

329

Effect of copper addition on the ?-phase formation rate in FeSi2 thermoelectric materials  

Microsoft Academic Search

The transformation kinetics of the ?-phase from an as-solidified structure composed of ? and ? in the Fe–Si system was investigated\\u000a by using rapidly, unidirectionally or conventionally solidified FeSi2 alloys containing a small amount of Cu (0.1–1 at%). The addition of Cu decreased the size of primary ? and slightly changed\\u000a the solidified eutectic morphology. The solubility of Cu in

I YAMAUCHI; A. SUGANUMA; T OKAMOTO; I OHNAKA

1997-01-01

330

Frequency dependence of core loss in rapidly quenched Fe6.5 wt. %Si  

Microsoft Academic Search

The frequency, field, and temperature dependencies of core loss in rapidly quenched Fe-6.5 wt. %Si ribbons are reported. The annealed material exhibits (001)?uv0? fiber texture, resulting in isotropic properties in plane; equivalent losses and B-H loops are seen in tape-wound toroids and in annuli punched from ribbon. Hysteresis losses predominate in the present Fe-6.5%Si up to about 1 kHz, as

G. E. Fish; C.-F. Chang; R. Bye

1988-01-01

331

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

332

Surface structures of Al-Pd-Mn and Al-Cu-Fe icosahedral quasicrystals  

Microsoft Academic Search

In this dissertation, the author reports on the surface structure of i-Al-Pd-Mn twofold, threefold, fivefold and i-Al-Cu-Fe fivefold surfaces. The LEED studies indicate the existence of two distinct stages in the regrowth of all four surfaces after Ar{sup +} sputtering. In the first stage, upon annealing at relatively low temperature: 500K--800K (depending on different surfaces), a cubic phase appears. The

Shen

1999-01-01

333

Uniaxial magnetic anisotropy of quasi-one-dimensional Fe chains on Pb/Si  

SciTech Connect

We fabricated quasi-one-dimensional Fe chains on a 4{sup o} miscut Si (111) substrate with a Pb film as a buffer layer. The magnetic properties and morphology of Fe chains were investigated by means of scanning tunneling microscope (STM) and surface magneto-optical Kerr effect (SMOKE). STM images show that Fe chains are formed by Fe random islands along the steps of the Pb film due to step decoration. SMOKE data indicate that the Fe chains exhibit in-plane uniaxial magnetic anisotropy along the step direction. The effective in-plane uniaxial anisotropy constant at room temperature was determined by means of electron spin resonance.

Sun, Da-li [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics; Wang, De-yong [Material Science and Technology Division, Oak Ridge National Laboratory; Du, Hai-Feng [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics; Ning, Wei [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics; Gao, Jian-Hua [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics; Fang, Ya-Peng [Institute of High Energy Physics, Chinese Academy of Sciences, China; Zhang, Xiang-Qun [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics; Sun, Young [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics; Cheng, Zhao-Hua [ORNL; Shen, Jian [ORNL

2009-01-01

334

Competitive segregation of Si and P on Fe 96.5 Si 3.5 (100) and (110)  

Microsoft Academic Search

Annealing an Fe96.5Si3.5 (100)\\/(110) bicrystal, containing 90 ppm P, leads immediately to a strong segregation of silicon. The Si atoms, however, desegregate subsequently and are displaced by P, whose segregation enthalpy is larger than that of silicon. The corresponding surface structures formed on both faces have been studied using complementary methods: Scanning tunneling microscopy (STM) to obtain atomically resolved geometrical

A. Biedermann; M. Schmid; B. M. Reichl; P. Varga

1995-01-01

335

The Olivine-Spinel Transition in Fe2SiO4 and Ni2SiO4  

Microsoft Academic Search

The olivine-spinel transition curve has been determined over the temperature range 700 to 1200øC in the pressure range 40 to 70 kb for Fe2SiOand 700 to 1500øC in the pressure range 20 to 40 kb for Ni2SiOby means of a tetrahedral-anvil type of high-pressure apparatus. For both silicates the transition has proved to be reversible within the precision of pressure

Syun-Iti Akimoto; Hideyuki Fujisawa; Takashi Katsura

1965-01-01

336

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

337

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

338

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

339

Enhanced photoconductivity of 3C-SiC by Al/N codoping  

NASA Astrophysics Data System (ADS)

In order to enhance the photoconductivity of 3C-SiC by high Al doping, the Al/N codoping has been investigated using the first principles calculation. Several structural models were constructed, i.e., Al1/N, Al2/N, Al3/N, and Al4/N. Structural stability and electronic property of Al/N codoped 3C-SiC with different models were studied. It is found that the adjacent pair of Al and N in 3C-SiC is energetically favorable, and the structure of Al/N codoped 3C-SiC is more stable than that of the mono Al doped 3C-SiC. The results indicate that the N incorporation facilitates the substitution of Al for Si in 3C-SiC. The mono doping of Al can cause the band gap decrease by 82 meV. However, the codoping of Al and N can further narrow the band gap by 167 meV. Photoconductivity calculation shows the photoconductivity of the Al/N codoped 3C-SiC is higher in the range from near infrared to ultraviolet wavelength in comparison with the intrinsic 3C-SiC. The calculated intrinsic absorption edge of Al/N codoped 3C-SiC shows a red-shift in ultraviolet region with respect to that of Al doped 3C-SiC. The electron density difference of Al/N codoped 3C-SiC indicates the bond between Al and C has stronger covalent characteristics than that between Al and N. The calculations suggest the Al/N codoped 3C-SiC semiconductor as a promising material for device applications in modern electronics.

Dou, Yan-Kun; Li, Jing-Bo; Jin, Hai-Bo; Fang, Xiao-Yong; Cao, Mao-Sheng

2013-09-01

340

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

341

Interaction of Fe(III) and Al(III) during hydroxylation by forced hydrolysis: the nature of Al-Fe oxyhydroxy co-precipitates.  

PubMed

Al-Fe oxyhydroxy co-precipitates were synthesised by forced hydrolysis of Fe(NO3)3·9H2O and Al(NO3)3·9H2O solutions. Solids containing 0, 1, 10, 25, 50, 75, 90 mol% Al were characterised for composition, texture, mineral structure and local atomic environment. Cation substitution in the hydrous oxides was not observed. The solids consisted of hydrous ferric oxide (HFO) nuclei surrounded by Al-hydroxide. Below 50 mol% Al, unit particle size, high specific surface area and microporosity of HFO were preserved. Al-K-edge XANES showed ordered arrangements of Al-octahedra suggesting that some Al bound specifically to HFO surface sites. Above 50 mol%, Al precipitated in multiple layers around the nuclei and also as individual entities. The HFO nuclei exhibited the general characteristics of a 2-line ferrihydrite. However, as Al increased, the structure was slightly modified. While the symmetry of the FeO6 octahedra improved, the number of Fe-Fe linkages decreased, suggesting less polymerisation. An organisation of the Fe-octahedra, faintly resembling akaganeite, was expressed in Raman spectra. These changes in HFO structure were attributed to hindrance in the progressive olation/oxolation of the primary Fe-hydroxypolymers, caused by Al bound to the surface of nuclei. The presence of nitrate is suspected to have favoured the structural changes. PMID:23866199

Hofmann, Annette; Vantelon, Delphine; Montargès-Pelletier, Emmanuelle; Villain, Françoise; Gardoll, Olivier; Razafitianamaharavo, Angelina; Ghanbaja, Jaafar

2013-10-01

342

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

343

Si and Fe depletion in Galactic star-forming regions observed by the Spitzer Space Telescope  

NASA Astrophysics Data System (ADS)

We report the results of the mid-infrared spectroscopy of 14 Galactic star-forming regions with the high-resolution modules of the Infrared Spectrograph (IRS) on board the Spitzer Space Telescope. We detected Si II 35 micron, Fe II 26 micron, and Fe III 23 micron as well as S III 33 micron and H_2 S(0) 28 um emission lines. Based on photodissociation and H II region models the gas-phase Si and Fe abundance are suggested to be 3-100% and <22% of the solar abundance, respectively. Since the Fe II 26 micron, and Fe III 23 micron emissions are weak, the high sensitivity of the IRS enables to derive the gas-phase Fe abundance widely in star-forming regions. The derived gas-phase Si abundance is much larger than that in cool interstellar clouds and that of Fe. The present study indicates that 3-100% of Si atoms and <22% of Fe atoms are included in dust grains which are destroyed easily in H II regions, probably by the UV radiation. We discuss possible mechanisms to account for the observed trend: mantles which are photodesorbed by UV photons, organometallic complexes, or small grains.

Okada, Y.; Onaka, T.; Miyata, T.; Okamoto, Y. K.; Sakon, I.; Shibai, H.; Takahashi, H.

2009-01-01

344

Diffusion in single crystal of melilite: interdiffusion of Al + Al vs. Mg + Si  

Microsoft Academic Search

Interdiffusion coefficients of Al + Al vs. Mg + Si in the gehlenite–åkermanite system of melilite were determined by coupled\\u000a annealing of synthesized end-member single crystals. The observed diffusion coefficients for a couple-annealed sample vary\\u000a for about 2 orders of magnitude, showing strong dependence on the gehlenite–åkermanite composition: diffusion coefficient\\u000a observed at 1350 °C, for example, is 3 × 10?13

H. Nagasawa; T. Suzuki; M. Ito; M. Morioka

2001-01-01

345

Development of dispersion U(Mo)/Al-Si miniplates fabricated at 500 °C with Al 6061 as cladding  

NASA Astrophysics Data System (ADS)

In the frame of U(Mo) dispersion fuel elements qualification, Si additions to Al matrix arose as a promising solution to the unacceptable failures found when pure Al is used. Analysis of as-fabricated fuel plates made with Al-Si matrices demonstrated that good irradiation behavior is correlated with the formation during fabrication of a Si-containing interaction layer around the U(Mo) particles. Thus, the analysis of the influence of fabrication parameters becomes important. Studies on Al-Si dispersion miniplates fabricated in CNEA, Argentina, have been initiated to determine how to obtain the better interaction layer characteristics with the lesser modifications to the fabrication process and the smaller amount of Si in the matrix. In this work results for miniplates made of atomized U-7 wt%Mo particles dispersed in Al-2 wt%Si and Al-4 wt%Si matrices, obtained by mixing pure Al and Si powders, and Al 6061 as cladding are presented. Interaction layer grown during fabrication process (500 °C) consists of Si-containing phases being U(Al, Si)3 its principal component. Its uniformity is not satisfactory due to the formation of an oxide layer.

Mirandou, M. I.; Aricó, S. F.; Balart, S. N.; Fabro, J. O.

2015-02-01

346

A comparative wear study on Al-Li and Al-Li/SiC composite  

SciTech Connect

Aluminum-lithium based unreinforced (Al-8090) alloy and Al-8090/SiCp/17 vol.% metal matrix composite produced by extrusion after spray co-deposition. A dry ball-on disk wear test was carried out for both alloy and composite. The tests were performed against an Al{sub 2}O{sub 3} ball, 10 mm in diameter, at room temperature and in laboratory air conditions with a relative humidity of 40-60%. Sliding speed was chosen as 1.0 ms{sup ?1} and normal loads of 1.0, 3.0 and 5.0 N were employed at a constant sliding distance of 1000 m. The wear damage on the specimens was evaluated via measurement of wear depth and diameter. Microstructural and wear characterization was carried out via scanning electron microscopy (SEM). The results showed that wear loss of the Al-8090/SiC composite was less than that of the Al-8090 matrix alloy. Plastic deformation observed on the wear surface of the composite and the matrix alloy, and the higher the applied load the greater the plastic deformation. Scanning electron microscopy examinations of wear tracks also reveal that delamination fracture was the dominant wear mechanism during the wear progression. Friction coefficient was maximum at the low applied load in the case of the Al-8090/SiC composite while a gradual increase was observed with applied load for the matrix alloy.

Okumus, S. Cem, E-mail: cokumus@sakarya.edu.tr; Karslioglu, Ramazan, E-mail: cokumus@sakarya.edu.tr; Akbulut, Hatem, E-mail: cokumus@sakarya.edu.tr [Sakarya University Engineering Faculty, Department of Metallurgical and Materials Engineering, Esentepe Campus, 54187, Sakarya (Turkey)

2013-12-16

347

A comparative wear study on Al-Li and Al-Li/SiC composite  

NASA Astrophysics Data System (ADS)

Aluminum-lithium based unreinforced (Al-8090) alloy and Al-8090/SiCp/17 vol.% metal matrix composite produced by extrusion after spray co-deposition. A dry ball-on disk wear test was carried out for both alloy and composite. The tests were performed against an Al2O3 ball, 10 mm in diameter, at room temperature and in laboratory air conditions with a relative humidity of 40-60%. Sliding speed was chosen as 1.0 ms-1 and normal loads of 1.0, 3.0 and 5.0 N were employed at a constant sliding distance of 1000 m. The wear damage on the specimens was evaluated via measurement of wear depth and diameter. Microstructural and wear characterization was carried out via scanning electron microscopy (SEM). The results showed that wear loss of the Al-8090/SiC composite was less than that of the Al-8090 matrix alloy. Plastic deformation observed on the wear surface of the composite and the matrix alloy, and the higher the applied load the greater the plastic deformation. Scanning electron microscopy examinations of wear tracks also reveal that delamination fracture was the dominant wear mechanism during the wear progression. Friction coefficient was maximum at the low applied load in the case of the Al-8090/SiC composite while a gradual increase was observed with applied load for the matrix alloy.

Okumus, S. Cem; Karslioglu, Ramazan; Akbulut, Hatem

2013-12-01

348

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

349

Structural, Optical, and Electrical Characterization of Al/n-ZnO/p-Si/Al Heterostructures  

NASA Astrophysics Data System (ADS)

For heterojunction fabrication, zinc oxide thin films were grown on p-Si by pulsed laser deposition. X-ray diffraction patterns were used to study the grain size and morphology of the films. The optical properties of the films were studied by UV-visible and photoluminescence spectroscopy. Experimental observations confirmed that the deposited films have potential for sharp emission in the visible region. High-purity (99.999%) vacuum evaporated aluminium metal was used to make contacts to the n-ZnO and p-Si. The current-voltage characteristics of the Al/n-ZnO/p-Si(100)/Al heterostructure measured over the temperature range 60-300 K were studied on the basis of the thermionic emission diffusion mechanism. The equivalent Schottky barrier height and the diode ideality factor were determined by fitting measured current-voltage data to the thermionic emission diffusion equation. It was observed that the barrier height decreased and the ideality factor increased with decreasing temperature, and that the activation energy plot was non-linear at low temperature. These characteristics are attributed to the Gaussian distribution of barrier heights. The capacitance-voltage characteristics of the Al/n-ZnO/p-Si(100)/Al heterostructure diode were studied over a wide temperature range. The impurity concentration in deposited n-type ZnO films was estimated from measured capacitance-voltage data.

Kumar, Rajender; Chand, Subhash

2014-11-01

350

Structural, Optical, and Electrical Characterization of Al/ n-ZnO/ p-Si/Al Heterostructures  

NASA Astrophysics Data System (ADS)

For heterojunction fabrication, zinc oxide thin films were grown on p-Si by pulsed laser deposition. X-ray diffraction patterns were used to study the grain size and morphology of the films. The optical properties of the films were studied by UV-visible and photoluminescence spectroscopy. Experimental observations confirmed that the deposited films have potential for sharp emission in the visible region. High-purity (99.999%) vacuum evaporated aluminium metal was used to make contacts to the n-ZnO and p-Si. The current-voltage characteristics of the Al/ n-ZnO/ p-Si(100)/Al heterostructure measured over the temperature range 60-300 K were studied on the basis of the thermionic emission diffusion mechanism. The equivalent Schottky barrier height and the diode ideality factor were determined by fitting measured current-voltage data to the thermionic emission diffusion equation. It was observed that the barrier height decreased and the ideality factor increased with decreasing temperature, and that the activation energy plot was non-linear at low temperature. These characteristics are attributed to the Gaussian distribution of barrier heights. The capacitance-voltage characteristics of the Al/ n-ZnO/ p-Si(100)/Al heterostructure diode were studied over a wide temperature range. The impurity concentration in deposited n-type ZnO films was estimated from measured capacitance-voltage data.

Kumar, Rajender; Chand, Subhash

2015-01-01

351

Wear resistance of TiAlSiN thin coatings.  

PubMed

In the last decades TiAIN coatings deposited by PVD techniques have been extensively investigated but, nowadays, their potential development for tribological applications is relatively low. However, new coatings are emerging based on them, trying to improve wear behavior. TiAlSiN thin coatings are now investigated, analyzing if Si introduction increases the wear resistance of PVD films. Attending to the application, several wear test configurations has been recently used by some researchers. In this work, TiAISiN thin coatings were produced by PVD Unbalanced Magnetron Sputtering technique and they were conveniently characterized using Scanning Electron Microscopy (SEM) provided with Energy Dispersive Spectroscopy (EDS), Atomic Force Microscopy (AFM), Electron Probe Micro-Analyzer (EPMA), Micro Hardness (MH) and Scratch Test Analysis. Properties as morphology, thickness, roughness, chemical composition and structure, hardness and film adhesion to the substrate were investigated. Concerning to wear characterization, two very different ways were chosen: micro-abrasion with ball-on-flat configuration and industrial non-standardized tests based on samples inserted in a feed channel of a selected plastic injection mould working with 30% (wt.) glass fiber reinforced polypropylene. TiAISiN coatings with a small amount of about 5% (wt.) Si showed a similar wear behavior when compared with TiAIN reported performances, denoting that Si addition does not improve the wear performance of the TiAIN coatings in these wear test conditions. PMID:23447962

Silva, F J G; Martinho, R P; Alexandre, R J D; Baptista, A P M

2012-12-01

352

Structural and magneto-transport characterization of Co2CrxFe1-xAl Heusler alloy films  

Microsoft Academic Search

We investigate the structure and magneto-transport properties of thin films of the Co2Cr0.6Fe0.4Al full-Heusler compound, which is predicted to be a half-metal by first-principles theoretical calculations. Thin films are deposited by magnetron sputtering at room temperature on various substrates in order to tune the growth from polycrystalline on thermally oxidized Si substrates to highly textured and even epitaxial on MgO(001)

A. D. Rata; H. Braak; D. E. Bürgler; S. Cramm; C. M. Schneider

2006-01-01

353

Investigation of the {Fe}/{Si} interface and its phase transformations  

NASA Astrophysics Data System (ADS)

Thin 57Fe films (3-10 Å) have been grown by molecular beam epitaxy (MBE) on (7 × 7) reconstructed Si(111) and (2 × 1) reconstructed Si(001) surfaces and by e-gun evaporation on an H-terminated Si(111) surface. Conversion electron Mössbauer spectroscopy (CEMS) with high statistical accuracy and resolution allowed a detailed microscopic investigation of the silicide formation mechanism and of the structural phase transformations upon annealing.

Fanciulli, M.; Degroote, S.; Weyer, G.; Langouche, G.

1997-04-01

354

MOKE Study of Fe/Co/Al Multilayers  

SciTech Connect

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

Jani, Snehal; Lakshmi, N.; Venugopalan, K. [Department of Physics, Mohanlal Sukhadia University, Udaipur 313 001 (India); Rajput, Parasmani; Zajaoc, M.; Rueffer, R. [European Synchrotron Radiation Facility, 6 rue Jules Horowitz, BP 220 F-38043 Grenoble Cedex (France); Reddy, V. R.; Gupta, Ajay [UGC-DAE Consortium for Scientific Research, Khandwa Road, Indore 452 001 (India)

2011-07-15

355

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

356

Local formation of a Heusler structure in CoFe-Al alloys  

NASA Astrophysics Data System (ADS)

We systematically study the changes in the local atomic environments of Co in CoFe-Al alloys as a function of Al content by means of nuclear magnetic resonance. We find that a Co2FeAl Heusler type structure is formed on a local scale. The observed formation of a highly spin-polarized Heusler compound may explain the improved magnetotransport properties in CoFe-Al based current-perpendicular-to-the-plane spin-valves.

Wurmehl, S.; Jacobs, P. J.; Kohlhepp, J. T.; Swagten, H. J. M.; Koopmans, B.; Maat, S.; Carey, M. J.; Childress, J. R.

2011-01-01

357

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

358

Nondestructive depth profile of the chemical state of ultrathin Al2O3 Si interface  

E-print Network

Nondestructive depth profile of the chemical state of ultrathin Al2O3 Ã?Si interface Jong Cheol Leea 2004 We investigated a depth profile of the chemical states of an Al2O3 /Si interface usingV as the OIL region closer to Al2O3 layer was sampled, while the Al 2p binding energy remains the same

Oh, Se-Jung

359

Growth mechanisms of silicon in Al-Si alloys  

NASA Astrophysics Data System (ADS)

Eutectic silicon in Al-Si alloy has been examined by optical, SEM and TEM methods. Normal flake silicon grows anisotropically and has a low twin density; quench modified fibrous silicon is essentially twin free and grows isotropically (non-faceted); sodium modified silicon contains a very high twin density and the fibers are somewhat faceted. It is concluded that in the absence of sodium, molecular attachment by the TPRE mechanism is incidental but in the presence of sodium this is the dominant growth mechanism. Various aspects of the modification mechanism are discussed.

Lu, Shu-Zu; Hellawell, Angus

1985-11-01

360

Cyclic Oxidation of FeCrAlY/Al2O3 Composites  

NASA Technical Reports Server (NTRS)

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

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

1999-01-01

361

Site location of Co in {beta}-FeSi{sub 2}  

SciTech Connect

In order to reveal cationic site preference in {beta}-FeSi{sub 2}, Co-substituted samples synthesized by various techniques such as molecular beam epitaxy, ion implantation, and chemical vapor transport were investigated by {sup 57}Fe conversion electron Moessbauer (CEM) as well as {sup 57}Co Moessbauer emission (ME) spectroscopy. Literature on the structure of {beta}-FeSi{sub 2} is somewhat contradictory, especially on the point of the population of the two iron sites in the orthorhombic structure. {sup 57}Co ME and {sup 57}Fe CEM spectra both showed two quadrupole split spectral components in the crystalline phase. Hyperfine parameters indicate that Co atoms substitute Fe in both Fe positions in the orthorhombic lattice. The aim of the present study was to get reliable results on the relative population of the two iron sites and determine the substitution of the iron sites by Co atoms in the {beta}-FeSi{sub 2} lattice. The relative intensities of the two components in the absorption and emission Moessbauer spectra were found to be very similar for the samples prepared by different techniques, indicating a homogeneous distribution of Co on both Fe sites.

Dezsi, I.; Fetzer, Cs.; Kiss, M.; Degroote, S.; Vantomme, A. [KFKI Research Institute for Particle and Nuclear Physics, 114 P.O. Box 49, H-1525 Budapest (Hungary); Instituut voor Kern- en Stralingsfysika, Katholieke Universiteit Leuven, Celestijnenlaan 200D, B-3001 Leuven (Belgium)

2005-10-01

362

Electrolyte effects in Li(Si)/FeS2 thermal batteries  

NASA Astrophysics Data System (ADS)

The most common electrochemical couple for thermally activated ('thermal') batteries is the Li-alloy/FeS2 system. The most common Li-alloys used for anodes are 20% Li-80% Al and 44% Li-56% Si (by weight); liquid Li immobilized with iron powder has also been used. The standard electrolyte that has been used in thermal batteries over the years is the LiCl-KCl eutectic that melts at 352 C. The LiCl-LiBr-LiF eutectic had the best rate and power characteristics. This electrolyte melts at 436(degrees)C and shows very low polarization because of the absence of Li(+) gradients common with the LiCl-KCl eutectic. The low-melting electrolytes examined included a KBr-LiBr-LiCl eutectic (melting at 321 C), a LiBr-KBr-LiF eutectic (melting at 313 C), and a CsBr-LiBr-KBr eutectic (melting at 238 C). The CsBr-based salt had poor conductivity and was not studied further. The LiBr-KBr-LiF eutectic outperformed the KBr-LiBr-LiCl eutectic and was selected for more extensive testing. Because of their lower melting points and larger liquidi relative to the LiCl-KCl eutectic, the low-melting electrolytes are prime candidates for long-life applications (i.e., for activated lives of one hour or more). This paper will detail the relative performance of the Li(Si)/FeS2 couple using primarily the LiCl-KCl (standard) eutectic, the LiCl-LiBr-LiF (all-Li) eutectic, and the LiBr-KBr-LiF (low-melting) eutectic electrolytes. Most of the tests were conducted with 5-cell batteries; validation tests were also carried out with appropriate full-sized batteries.

Guidotti, Ronald A.; Reinhardt, Frederick W.

363

Deformation texture studies in Fe{sub 3}Al alloys  

SciTech Connect

Fe{sub 3}Al alloys currently targeted for commercial manufacture are generally thermo-mechanically processed in a 600--1000 C. In this temperature range, large scale strains are produced, either solely or by a combination of <111>[110], <100>[011], and <100>[001] slip systems. The texture is derived from the dominant slip system operating under a specific set of processing variables (i.e., deformation temperature, rate, etc.). In this report, numerical means have been employed to predict deformation textures in Fe{sub 3}Al alloys produced entirely by crystallographic shears on the <111>[110], <100>[011], and <100>[001] slip systems. It is shown that both <111>[110] and <100>[011] slip systems produce a reasonably strong texture, while <100>[001] induces no texture over the initial random configuration. Experimental texture measurements, for samples deformed {approx}70% by rolling at 650 K, agree well with the predictions for the <111>[110]slip system activation. These results appear to be in disagreement with transmission electron microscopy observations reported in the literature. Possible sources of discrepancies are discussed.

Kad, B.K.; Schoenfeld, S.E.; Asaro, R.J. [California Univ., San Diego, La Jolla, CA (United States). Dept. of Applied Mechanics and Engineering Sciences; McKamey, C.G. [Oak Ridge National Lab., TN (United States)

1994-09-01

364

Structural and magnetic stability of Fe{sub 2}NiSi  

SciTech Connect

Full-potential ab-initio calculations in the stable F-43m phase have been performed to investigate the structural and magnetic properties of Fe{sub 2}NiSi inverse Heusler alloys. The spin magnetic moment distributions show that present material is ferromagnetic in stable F-43m phase. Further, spin resolved electronic structure calculations show that the discrepancy in magnetic moments of Fe-I and Fe-II depend upon the hybridization of Fe with the main group element. It is found that the main group electron concentration is predominantly responsible in establishing the magnetic properties, formation of magnetic moments and the magnetic order for present alloy.

Gupta, Dinesh C., E-mail: idu.idris@gmail.com; Bhat, Idris Hamid, E-mail: idu.idris@gmail.com; Chauhan, Mamta, E-mail: idu.idris@gmail.com [Condensed Matter Theory Group, School of Studies in Physics, Jiwaji University, Gwalior - 474011 (India)

2014-04-24

365

Competitive segregation of Si and P on Fe(96.5)Si(3.5) (100) and (110).  

PubMed

Annealing an Fe(96.5)Si(3.5) (100)/(110) bicrystal, containing 90 ppm P, leads immediately to a strong segregation of silicon. The Si atoms, however, desegregate subsequently and are displaced by P, whose segregation enthalpy is larger than that of silicon. The corresponding surface structures formed on both faces have been studied using complementary methods: Scanning tunneling microscopy (STM) to obtain atomically resolved geometrical information and Auger electron spectroscopy (AES) for the determination of the surface composition. Si substitutes surface Fe atoms on both faces and forms ordered surface alloys, whereas P occupies hollow sites on the surface. Si and P form c(2 x 2) superstructures on the (100) surface, whereby each segregated phosphorus atom blocks in the average one silicon segregation site. The (110) surface, on the other hand, is characterized by a c(1 x 3) Si superstructure. Due to the anisotropy of this surface the P/Si exchange proceeds by the formation of silicon coverage decreasing domain boundaries within the silicon structure, which are simultaneously occupied by P atoms. Furthermore the comparison of the AES and STM derived phosphorus coverages indicates a P multilayer segregation on the (110) surface. PMID:15048478

Biedermann, A; Schmid, M; Reichl, B M; Varga, P

1995-10-01

366

Frequency-dependent magnetotransport phenomena in a hybrid Fe/SiO2/p-Si structure  

NASA Astrophysics Data System (ADS)

We report the large magnetoimpedance effect in a hybrid Fe/SiO2/p-Si structure with the Schottky barrier. The pronounced effect of magnetic field on the real and imaginary parts of the impedance has been found at temperatures 25-100 K in two relatively narrow frequency ranges around 1 kHz and 100 MHz. The observed frequency-dependent magnetotransport effect is related to the presence of localized "magnetic" states near the SiO2/p-Si interface. In these states, two different recharging processes with different relaxation times are implemented. One process is capture-emission of carriers that involves the interface levels and the valence band; the other is the electron tunneling between the ferromagnetic electrode and the interface states through SiO2 potential barrier. In the first case, the applied magnetic field shifts energy levels of the surface states relative to the valence band, which changes recharging characteristic times. In the second case, the magnetic field governs the spin-dependent tunneling of carriers through the potential barrier. The "magnetic" interface states originate, most likely, from the formation of the centers that contain Fe ions, which can easily diffuse through the SiO2 layer.

Volkov, N. V.; Tarasov, A. S.; Eremin, E. V.; Eremin, A. V.; Varnakov, S. N.; Ovchinnikov, S. G.

2012-12-01

367

Study of diffusion bonding of Fe28Al alloy with austenitic stainless steel in vacuum  

Microsoft Academic Search

Diffusion bonding of Fe-28Al alloy with Cr18–Ni8 austenitic stainless steel was carried out in vacuum of 10?4Pa and a diffusion-bonded Fe-28Al\\/Cr18–Ni8 joint with diffusion reaction layer was formed. Microstructure and reacted phases in the joint were investigated by means of scanning electron microscope (SEM) and X-ray diffractometry (XRD). The reacted phases in the diffusion reaction layer are FeAl, Fe3Al, Ni3Al

Wang Juan; Li Yajiang; Ma Haijun

2005-01-01

368

Non-magnetic and magnetic impurity effects on superconductivity in the ternary iron-silicide Lu2FeSi  

NASA Astrophysics Data System (ADS)

We studied effect of non-magnetic and magnetic impurities on superconductivity in LuFeSi by investigating superconducting properties of (LuFeSi (R=Sc,Y, and Dy). The rapid depression of Tc by non-magnetic impurities reveals strong pair breaking by disorder, providing compelling evidence for the sign reversal of the superconducting order parameter in LuFeSi.

Watanabe, Tadataka; Okuyama, Hiroaki; Takase, Kouichi; Takano, Yoshiki

2010-12-01

369

Non-magnetic and magnetic impurity effects on superconductivity in the ternary iron-silicide LuFeSi  

NASA Astrophysics Data System (ADS)

We studied effect of non-magnetic and magnetic impurities on superconductivity in LuFeSi by investigating superconducting properties of (LuFeSi ( R=Sc,Y, and Dy). The rapid depression of Tc by non-magnetic impurities reveals strong pair breaking by disorder, providing compelling evidence for the sign reversal of the superconducting order parameter in LuFeSi.

Watanabe, Tadataka; Okuyama, Hiroaki; Takase, Kouichi; Takano, Yoshiki

370

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

371

On the theory of Al, Si ordering in albite  

NASA Astrophysics Data System (ADS)

Calculations of the equilibrium distribution of Al, Si in the albite framework based on quasi-chemical theories of order, disorder transformations (Yang 1945; Yang and Li 1947; Li 1949) were made for a two-dimensional framework model. The ordering is caused by the energy of Al, Si interchange between sites of different crystal-chemical types and the energy of nearest neighbour interaction. By taking into account the decrease in the energy of interchange between sites with increasing disordering and with increasing temperature, and by examining different relationships for site-to-site interchange energy and the nearest neighbour interaction, it is possible to understand the basic characteristics of the transformation from low (essentially ordered) to high (essentially disordered) albite as revealed by experiment. These characteristics are: (1) abrupt variation of the equilibrium degree of order within a narrow temperature range and possible first order phase transformation for the transition from low-albite to high-albite, (2) hysteresis of the synthetic high albite transformation path and of the low albite hydrothermal “annealing” path, (3) presence of a temperature range where high albite is stable and has a continually changing equilibrium degree of order.

Senderov, E. E.

1980-12-01

372

In situ Ultrasonic Velocity Measurements Across the Olivine-spinel Transformation in Fe2Si04  

SciTech Connect

Compressional (P) and shear (S) wave velocities across the olivine-spinel transformation in Fe{sub 2}SiO{sub 4} were investigated in situ using combined synchrotron X-ray diffraction, X-ray imaging, and ultrasonic interferometry up to 5.5 GPa along the 1173 K isotherm. The onset of the spinel to olivine transformation at 4.5 GPa and olivine to spinel transition for Fe{sub 2}SiO{sub 4} at 4.8 GPa was concurrently observed from X-ray diffraction, the amplitude of the ultrasonic signals, the calculated velocities, and the ratio of P and S wave velocities (v{sub P}/v{sub S}). No velocity softening was observed prior to the fayalite to spinel transition. The velocity contrasts across the Fe{sub 2}SiO{sub 4} spinel to fayalite phase transition are derived directly from the measured velocities, which are 13 and 12% for P and S waves, respectively, together with a density contrast of 9.4%. A comparison with literature data indicates that the changes in compressional-wave velocity and density across the olivine-spinel transformation in Fe{sub 2}SiO{sub 4} are comparable to those with different iron concentrations in the (Mg,Fe){sub 2}SiO{sub 4} solid solution, whereas the shear wave velocity contrast decreases slightly with increasing iron concentration.

Liu, Q.; Liu, W; Whitaker, M; Wang, L; Li, B

2010-01-01

373

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

374

Magnetic assembles of FePt (001) nanoparticles with SiO2 addition  

NASA Astrophysics Data System (ADS)

Isolated FePt (001) nanoparticles surrounded with amorphous SiO2 have been fabricated by electron beam evaporation onto MgO (001) single-crystal substrates via the introduction of a SiO2 intermediate layer into the FePt film structures. The formation of two-dimensional magnetic assemblies of ordered FePt (001) nanoparticles with an average size of about 6nm was directly obtained with this process at only 400°C due to the interpenetration of SiO2, which has a lower surface energy. Studies of angular dependent coercivity show a tendency of a domain-wall motion to weaken toward rotation of reverse-domain type upon thickness of SiO2 additive layer into the FePt film structures. On the other hand, the exchange coupling between neighboring particles in the FePt nanostructures could be reduced with ultrathin SiO2 addition, which is confirmed from the Kelly-Henkel (?M) plot.

Wei, D. H.

2009-04-01

375

Magnetic damping constant of Co{sub 2}FeSi Heusler alloy thin film  

SciTech Connect

Co{sub 2}FeSi films were prepared using magnetron sputtering technique on Cr buffer layers and MgO(001) substrates at various annealing temperatures. We investigated the crystal structures, magnetic properties (M{sub s} and H{sub c}), surface roughness, and magnetic damping constants ({alpha}) of the prepared Co{sub 2}FeSi films. Out-of-plane angular dependences of the resonance field and the linewidth of the ferromagnetic resonance spectra were measured and fitted using the Landau-Lifshitz-Gilbert equation to determine the damping constant. The as-deposited Co{sub 2}FeSi film exhibited an amorphous and disordered structure; the {alpha} value was 0.008. In contrast, the Co{sub 2}FeSi films annealed over 300 degree sign C showed epitaxial growth and had a (001)-oriented and L2{sub 1} ordered structure. Both disordered and L2{sub 1} ordered Co{sub 2}FeSi films showed similar {alpha} values.

Oogane, Mikihiko; Yilgin, Resul; Shinano, Masatsugu; Yakata, Satoshi; Sakuraba, Yuya; Ando, Yasuo; Miyazaki, Terunobu [Department of Applied Physics, Graduate School of Engineering, Tohoku University, Aoba-yama 05, Sendai 980-8579 (Japan)

2007-05-01

376

Application of Central Composite Design to process optimization of Fe3O4\\/SiO2 composited aerogel nanoparticle  

Microsoft Academic Search

The 23 full-factorial Central Composite Design (CCD) and response surface methodology (RSM) was applied to explain the effect and interaction of three factors in the process of Fe3O4\\/SiO2 nanoparticle: NaOH dosage, Fe3O4\\/SiO2 ratio and Fe2+\\/Fe3+ ratio. For the CCD optimization purposes, the canonical parameters was employed where the predicted average size of the nanoparticles was 115.39 nm, and the experiment

Xi-bin Yi; Xiao-dong Shen; Sheng Cui; Yong-mei Li

2010-01-01

377

Inhomogeneous elastic deformation of nanofilms and nanowires of NiAl and FeAl alloys  

NASA Astrophysics Data System (ADS)

The molecular dynamics study of the uniaxial tension of nanofilms and nanowires of NiAl and FeAl intermetallide alloys has been performed. It has been shown that such samples are elastically deformed until failure at a strain of ? xx ? 0.35. There is an ? xx interval where the homogeneous deformation is thermodynamically unstable, leading to the formation of domains with different strains. The strain-stress dependence in the thermodynamically unstable region is almost linear, but has different slopes for a nanofilm and a nanowire because of the difference in the dynamics of domain walls.

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

2013-09-01

378

Electrical investigation of the Al/porous Si/p+-Si heterojunction  

NASA Astrophysics Data System (ADS)

Porous silicon based Al/porous Si/p+-Si heterojunction with porous silicon layer was fabricated on low-resistivity crystalline silicon substrate by electrochemical anodisation. Measurements of the current-voltage I(V) characteristics and capacitance-voltage C(V) at various frequencies were used for the investigation of the electrical properties of this heterojunction. The forward bias I(V) dependencies exhibited a high value of the quality factor close to 7. This was attributed to the existence of interfacial layer and interface states which cause the forward I(V) characteristic not to obey the ideal Schottky diode characteristic. Therefore, it was demonstrated that the current has a square root dependence on the forward bias and it was governed by the Richardson-Schottky conduction mechanism. Furthermore, an ideality factor near the unity has been obtained in the reverse current and the I(V) characteristics were governed by the porous Si/Si heterojunction. The C(V) measurement was performed at different frequencies and revealed that the capacitance behavior was typical of material with interface states. The density of interface states was found to vary from 2×1010 eV-1cm-2 to 1.1×1011 eV-1cm-2 as a function of the interface states energy level position in the band gap of the porous silicon.

Cherif, A.; Jomni, S.; Hannachi, R.; Beji, L.

2013-01-01

379

Fine structure at the diffusion welded interface of Fe 3 Al\\/Q235 dissimilar materials  

Microsoft Academic Search

The interface of Fe\\u000a \\u000a 3\\u000a \\u000a Al\\/Q235 dissimilar materials joint, which was made by vacuum diffusion welding, combines excellently. There are Fe\\u000a \\u000a 3\\u000a \\u000a Al, FeAl phases and ?-Fe (Al) solid solution at the interface of Fe\\u000a \\u000a 3\\u000a \\u000a Al\\/Q235. Aluminum content decreases from 28% to 1.5% and corresponding phase changes from Fe\\u000a \\u000a 3\\u000a \\u000a Al with DO\\u000a \\u000a 3\\u000a \\u000a type body centred cubic\\u000a bcc

Wang Juan; Li Yajiang; Wu Huiqiang

2001-01-01

380

The formation and crystallization for amorphous AlFeZr 4 prepared by mechanical alloying  

NASA Astrophysics Data System (ADS)

Amorphous AlFeZr 4 alloy has been prepared from elemental mixture powders by mechanical alloying. The microstructure, thermal stability and morphology of as-milled mixture powders were analyzed by XRD and DTA respectively. Two sequential exothermal peaks exist during the procedure of crystallization. The effective activation energies for crystallization were evaluated according to Kissinger's plot. The crystallization products of as-milled powders annealed at temperature over the crystallization temperature were studied, and the structural characteristic analysis of annealed sample was performed in an X-ray diffractometer. The crystallized phases are composed of FeZr 2, AlZr 2 and AlFeZr intermetallic compounds. The formation enthalpies for FeZr 2, AlZr 2 and AlFeZr are calculated from first-principles and Miedema's theory. Based on the calculated formation enthalpies, the products of crystallization for amorphous AlFeZr 4 alloy are explained from thermodynamic point of view.

Chen, Hongmei; Ouyang, Yifang; Guo, Debo; Liao, Shuzhi; Zhong, Xiaping; Du, Yong; Liu, Yong

2010-04-01

381

Correlation between crystal structures of CaAlSi with and without superlattice and superconducting properties  

NASA Astrophysics Data System (ADS)

We have succeeded in growing a phase in CaAlSi with Al and Si atoms being distributed regularly in the AlSi layer corresponding to the B2 plane in the AlB2 -type structure without a superlattice along the c axis. The field-induced magnetic response in a phase exhibits an almost isotropic characteristic for the respective crystal axis. Moreover, the 2?(0)/kBTc and ?Cel/?NTc estimated by heat capacity measurements are ˜3.5 and ˜1.4 , respectively, indicating a BCS superconductor with a weak coupling. Although CaAlSi has a two-dimensional layered structure, these results strongly suggest that the superconductivity of the phase in CaAlSi is derived from a three-dimensional electronic ground state such as a conventional s -wave superconductor, which is markedly different from those of superstructured CaAlSi .

Kuroiwa, S.; Sagayama, H.; Kakiuchi, T.; Sawa, H.; Noda, Y.; Akimitsu, J.

2006-07-01

382

Refinement of Eutectic Si in High Purity Al-5Si Alloys with Combined Ca and P Additions  

NASA Astrophysics Data System (ADS)

The effects of combined additions of Ca and P on the eutectic Si in a series of high purity Al-5 wt pct Si alloys have been investigated with the entrained droplet technique and complementary sets of conventional castings. Differential scanning calorimetry (DSC) and thermal analysis were used to investigate the eutectic droplet undercooling and the recalescence undercooling, respectively. Optical microscopy, SEM, EPMA, and TEM were employed to characterize the resultant microstructures. It was found that 250 ppm Ca addition to Al-5Si wt pct alloys with higher P contents leads to a significant increase of the eutectic droplet undercooling. For low or moderate cooling rates, the TEM results underline that Ca additions do not promote Si twinning. Thus, a higher twin density cannot be expected in Ca containing Al-Si alloys after, e.g., sand casting. Consequently, a refinement of the eutectic Si from coarse flake-like to fine plate-like structure, rather than a modification of the eutectic Si to a fibrous morphology, was achieved. This strongly indicates that the main purpose of Ca additions is to counteract the coarsening effect of the eutectic Si imposed by higher P concentrations. Significant multiple Si twinning was observed in melt-spun condition; however, this can be attributed to the higher cooling rate. After DSC heating (slow cooling), most of Si twins disappeared. Thus, the well-accepted impurity-induced twinning mechanism may be not valid in the case of Ca addition. The possible refinement mechanisms were discussed in terms of nucleation and growth of eutectic Si. We propose that the pre-eutectic Al2Si2Ca phase and preferential formation of Ca3P2 deactivate impurity particles, most likely AlP, poisoning the nucleation sites for eutectic Si.

Ludwig, Thomas Hartmut; Li, Jiehua; Schaffer, Paul Louis; Schumacher, Peter; Arnberg, Lars

2015-01-01

383

Nucleation of ordered Fe islands on Al2O3/Ni3Al(111) A. Lehnert a  

E-print Network

Nucleation of ordered Fe islands on Al2O3/Ni3Al(111) A. Lehnert a , A. Krupski b,c,*, S. Degen b the nucleation and stability of iron clusters on the Al2O3/ Ni3Al(111) surface as a function of coverage, it was also shown that metal deposition on Al2O3/Ni3Al(111) may lead to ordered cluster arrays [16

Brune, Harald

384

Al/SiOx/Al single and multiband metamaterial absorbers for terahertz sensor applications  

NASA Astrophysics Data System (ADS)

To increase the sensitivity of uncooled thermal sensors in the terahertz (THz) spectral range (1 to 10 THz), we investigated thin metamaterial layers exhibiting resonant absorption in this region. These metamaterial films are comprised of periodic arrays of aluminum (Al) squares and an Al ground plane separated by a thin silicon-rich silicon oxide (SiOx) dielectric film. These standard MEMS materials are also suitable for fabrication of bi-material and microbolometer thermal sensors. Using SiOx instead of SiO2 reduced the residual stress of the metamaterial film. Finite element simulations were performed to establish the design criteria for very thin films with high absorption and spectral tunability. Single-band structures with varying SiOx thicknesses, square size, and periodicity were fabricated and found to absorb nearly 100% at the designed frequencies between three and eight THz. Multiband absorbing structures were fabricated with two or three distinct peaks or a single-broad absorption band. Experimental results indicate that is possible to design very efficient thin THz absorbing films to match specific applications.

Kearney, Brian; Alves, Fabio; Grbovic, Dragoslav; Karunasiri, Gamani

2013-01-01

385

Multifunctional Fe?O?@nSiO?@mSiO?-Fe core-shell microspheres for highly efficient removal of 1,1,1-trichloro-2,2-bis(4-chlorophenyl)ethane (DDT) from aqueous media.  

PubMed

A novel multifunctional microsphere with an iron oxide-improved mesoporous silica shell and a Fe3O4@SiO2 core has been successfully prepared by a hydrothermal method and impregnation process. The resulting Fe3O4@nSiO2@mSiO2-Fe core-shell microspheres are utilized as a catalyst for the removal of 1,1,1-trichloro-2,2-bis(4-chlorophenyl) ethane (DDT) and its derivatives, i.e., 1,1-dichloro-2,2-bis(4-chlorophenyl) ethane (DDD) and 1,1-dichloro-2,2-bis(4-chlorophenyl) ethylene (DDE). The results indicated that the iron oxide nanoparticles were well dispersed on the mesoporous silica shell of Fe3O4@nSiO2@mSiO2. DDT, DDD and DDE could be quickly and effectively removed from aqueous media in 60 min, and completely dechlorinated at 350°C by Fe3O4@nSiO2@mSiO2-Fe. More importantly, the Fe3O4@nSiO2@mSiO2-Fe microspheres were superparamagnetic and could be separated and collected easily and rapidly using a magnet. PMID:24992299

Tian, Hua; Liu, Feng; He, Junhui

2014-10-01

386

Low-temperature brittleness of Fe-Cr-5% Al alloys  

Microsoft Academic Search

1.A reduction in grain size (by different methods) makes it possible to lower significantly the cold-shortness temperature of high-chromium alloys of the Fe-Cr-5% Al system.2.The increase in the cold-shortness temperature of Fe-Cr-5% Al alloys with increasing grain size is described by a type of Holl-Petch relationship.3.The tendency of alloys of the Fe-Cr-5% Al system to embrittlement as grain size increases

Yu. A. Kurapov; V. N. Minakov; N. D. Rudyk

1991-01-01

387

A new Heusler compound Cu2FeAl: electronic structure, magnetism and transport properties  

Microsoft Academic Search

The new ferromagnetic Heusler alloy of Cu2FeAl has been prepared by melt spinning. The band-structure calculations on this alloy predict a ferromagnetic ground state and the crystal structure not to be stable. The intrinsic properties of Cu2FeAl ribbons are described from magnetic and transport measurements. The electronic structure calculations show that the magnetic moment of Cu2FeAl is not localized, which

Ming Zhang; Yuting Cui; Zhuhong Liu; Guodong Liu; Jinglan Chen; Guangheng Wu; Yu Sui; Yuqiang Liu; Zhengnan Qian; E. H. Brück; F. R. de Boer

2004-01-01

388

Structure of 5Fold Surface of Icosohedral Al-Cu-Fe Quasicrystal as Determined by LEED  

Microsoft Academic Search

Low-Energy Electron Diffraction (LEED) is used to investigate the structure of a fivefold surface of the icosohedral Al-Cu-Fe quasicrystal, with bulk composition Al_63Cu_25Fe_12. Two distinct patterns are observed as a function of temperature and composition. At 550 K a pseudo tenfold (true twofold) LEED pattern is observed. The composition of the surface at this point measured with AES is Al_64Cu_18Fe

P. J. Pinhero; Z. Shen; C. J. Jenks; D. W. Delaney; T. A. Lograsso; P. A. Thiel; A. I. Goldman

1997-01-01

389

SILICON SURFACE PASSIVATION BY ULTRATHIN Al2O3 FILMS AND Al2O3/SiNx STACKS  

E-print Network

SILICON SURFACE PASSIVATION BY ULTRATHIN Al2O3 FILMS AND Al2O3/SiNx STACKS Jan Schmidt, Boris Veith Ohrberg 1, 31860 Emmerthal, Germany ABSTRACT We show that aluminum oxide (Al2O3) layers depo- sited thickness if the Al2O3 films are

390

Letter Report Documenting Progress of Second Generation ATF FeCrAl Alloy Fabrication  

SciTech Connect

Development of the 2nd generation ATF FeCrAl alloy has been initiated, and a candidate alloy was selected for trial tube fabrication through hot-extrusion and gun-drilling processes. Four alloys based on Fe-13Cr-4.5Al-0.15Y in weight percent were newly cast with minor alloying additions of Mo, Si, Nb, and C to promote solid-solution and second-phase precipitate strengthening. The alloy compositions were selected with guidance from computational thermodynamic tools. The lab-scale heats of ~ 600g were arc-melted and drop-cast, homogenized, hot-forged and -rolled, and then annealed producing plate shape samples. An alloy with Mo and Nb additions (C35MN) processed at 800°C exhibits very fine sub-grain structure with the sub-grain size of 1-3?m which exhibited more than 25% better yield and tensile strengths together with decent ductility compared to the other FeCrAl alloys at room temperature. It was found that the Nb addition was key to improving thermal stability of the fine sub-grain structure. Optimally, grains of less than 30 microns are desired, with grains up to and order of magnitude in desired produced through Nb addition. Scale-up effort of the C35MN alloy was made in collaboration with a commercial cast company who has a capability of vacuum induction melting. A 39lb columnar ingot with ~81mm diameter and ~305mm height (with hot-top) was commercially cast, homogenized, hot-extruded, and annealed providing 10mm-diameter bar-shape samples with the fine sub-grain structure. This commercial heat proved consistent with materials produced at ORNL at the lab-scale. Tubes and end caps were machined from the bar sample and provided to another work package for the ATF-1 irradiation campaign in the milestone M3FT-14OR0202251.

Yamamoto,, Y. [ORNL] [ORNL; Yang, Y. [ORNL] [ORNL; Field, K. G. [ORNL] [ORNL; Terrani, K. [ORNL] [ORNL; Pint, B. A. [ORNL] [ORNL; Snead, L. L. [ORNL] [ORNL

2014-06-10

391

Spin crossover in Fe2SiO4 liquid at high pressure  

NASA Astrophysics Data System (ADS)

We combine spin-polarized density functional theory with first principle molecular dynamics (FPMD) to study the spin crossover in liquid Fe2SiO4, up to 300 GPa and 6000 K. In contrast to the much sharper transition seen in crystals, we find that the high- to low-spin transition occurs over a very broad pressure interval (>200 GPa) due to structural disorder in the liquid. We find excellent agreement with the experimental Hugoniot. We combine our results with previous FPMD calculations to derive the partial molar volumes of the oxide components MgO, FeO, and SiO2. We find that eutectic melts in the MgO-FeO-SiO2 system are denser than coexisting solids in the bottom 600 km of Earth's mantle.

Ramo, David Muñoz; Stixrude, Lars

2014-07-01

392

Interface characteristics in diffusion bonding of Fe 3Al with Cr18Ni8 stainless steel  

Microsoft Academic Search

Fe3Al and Cr18-Ni8 stainless steel were diffusion-bonded in vacuum and a Fe3Al\\/Cr18-Ni8 interface with reaction layer was formed. Microstructure in the reaction layer at Fe3Al\\/Cr18-Ni8 interface was analyzed by means of scanning electron microscope (SEM) and electron probe micro-analyzer (EPMA). The growth of reaction layer with heating temperature (T) and holding time (t) was researched. The results indicate that FeAl,

Juan Wang; Yajiang Li; Yansheng Yin

2005-01-01

393

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

SciTech Connect

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

Jiao, Z. [State Key Laboratory of Advanced Welding Production Technology, Harbin Institute of Technology, Harbin 150001 (China); Centre for Advanced Materials Joining, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada); Huang, H.; Zhou, Y., E-mail: hepeng@hit.edu.cn, E-mail: nzhou@uwaterloo.ca [Centre for Advanced Materials Joining, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada); Department of Mechanical and Mechatronics Engineering, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada); Liu, L. [Department of Mechanical and Mechatronics Engineering, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada); Department of Mechanical Engineering, Tsinghua University, Beijing 100084 (China); Hu, A. [Department of Mechanical and Mechatronics Engineering, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada); Department of Mechanical, Aerospace, and Biomedical Engineering, University of Tennessee, Knoxville, Tennessee 37916 (United States); Duley, W. [Centre for Advanced Materials Joining, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada); Department of Physics and Astronomy, University of Waterloo, Waterloo, Ontario N2L 3G1 (Canada); He, P., E-mail: hepeng@hit.edu.cn, E-mail: nzhou@uwaterloo.ca [State Key Laboratory of Advanced Welding Production Technology, Harbin Institute of Technology, Harbin 150001 (China)

2014-04-07

394

The effects of amorphous Al2O3 underlayer on the microstructure and magnetic properties of BaFe12O19 thin films  

NASA Astrophysics Data System (ADS)

Single phase nanostructured BaFe12O19 thin films have been deposited on Si(110) substrate and Si(110) substrate with amorphous Al2O3 underlayer by a sol-gel method. The effects of the amorphous Al2O3 underlayer on the composition, microstructure and magnetic properties were explored by X-ray diffraction, scanning electron microscopy and vibrating sample magnetometery techniques. The results revealed that the amorphous Al2O3 underlayer promoted some perpendicular c-axis orientation with ?Hc=Hc?-Hc?=300 Oe.

Salemizadeh, S.; Seyyed Ebrahimi, S. A.; Masoudpanah, S. M.

2013-10-01

395

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

396

Novel synthetic pathways to wide bandgap semiconductors in the Si–C–Al–N system  

Microsoft Academic Search

Epitaxial SiCAlN films with single-phase wurtzite structures were grown by molecular beam epitaxy via reactions of a specifically designed molecular precursor H3SiCN and Al atoms at 750°C, considerably below the miscibility gap of SiC and AlN at 1900°C. The film growth was conducted directly on Si(111) despite the 19% lattice mismatch between the two materials. Commensurate heteroepitaxy was facilitated by

John Tolle; Radek Roucka; Andrew V. G. Chizmeshya; Peter A. Crozier; David. J. Smith; Ignatius S. T. Tsong; John Kouvetakis

2002-01-01

397

Behcet brain tissue identified with increased levels of Si and Al  

NASA Astrophysics Data System (ADS)

Behcet disease is a multi-system disorder with still uncertain chemical causality. Chemical composition of molecules and elements in a human brain tissue of Behcet diseased patient is of interest. Time-of-flight secondary ion mass spectrometry is used to provide complex composition in Behcet disease and control tissues. Determined organic compounds are represented by fragments of carbohydrates, phospholipids, amino acids, and peptides in both samples without any qualitative differences. Trace heavy elements as Fe, Zn, and Cu are identified in Behcet disease tissue with increased intensities by only an averaged factor of 2.2 in comparison to the control. The significant differences between the control and Behcet disease tissues are in the presence of Si and Al. These two elements have significantly higher intensities by an averaged factor of 10.0 in Behcet disease tissue. The origin of Al and Si occurrence and the chronology of their accumulation are not clear, moreover this observation supports a significance of chemical characterization in an early stage of disease.

Aranyosiova, Monika; Kopani, Martin; Rychly, Boris; Jakubovsky, Jan; Velic, Dusan

2008-12-01

398

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

399

Dissolution of iron intermetallics in Al-Si Alloys through nonequilibrium heat treatment  

NASA Astrophysics Data System (ADS)

Conventional heat treatment techniques in Al-Si alloys to achieve optimum mechanical properties are limited to precipitation strengthening processes due to the presence of second-phase particles and spheroidization of silicon particles. The iron intermetallic compounds present in the microstructure of these alloys are reported to be stable, and they do not dissolve during conventional (equilibrium) heat treatments. The dissolution behavior of iron intermetallics on nonequilibrium heat treatment has been investigated by means of microstructure and mechanical property studies. The dissolution of iron intermetallics improves with increasing solution temperature. The addition of manganese to the alloy hinders the dissolution of iron intermetallics. Nonequilibrium heat treatment increases the strength properties of high iron alloys until a critical solution temperature is exceeded. Above this temperature, a large amount of liquid phase is formed as a result of interdendritic and grain boundary melting. The optimum solution treatment temperature for Al-6Si-3.5Cu-0.3Mg-lFe alloys is found to be between 515 °C and 520 °C.

Narayanan, L. Anantha; Samuel, F. H.; Gruzleski, J. E.

1995-08-01

400

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

401

Electromagnetic wave absorbing properties and hyperfine interactions of Fe—Cu—Nb—Si—B nanocomposites  

NASA Astrophysics Data System (ADS)

The Fe—Cu—Nb—Si—B alloy nanocomposite containing two ferromagnetic phases (amorphous phase and nanophase phase) is obtained by properly annealing the as-prepared alloys. High resolution transmission electron microscopy (HR-TEM) images show the coexistence of these two phases. It is found that Fe—Si nanograins are surrounded by the retained amorphous ferromagnetic phase. Mössbauer spectroscopy measurements show that the nanophase is the D03-type Fe—Si phase, which is employed to find the atomic fractions of resonant 57Fe atoms in these two phases. The microwave permittivity and permeability spectra of Fe—Cu—Nb—Si—B nanocomposite are measured in the frequency range of 0.5 GHz-10 GHz. Large relative microwave permeability values are obtained. The results show that the absorber containing the nanocomposite flakes with a volume fraction of 28.59% exhibits good microwave absorption properties. The reflection loss of the absorber is less than -10 dB in a frequency band of 1.93 GHz-3.20 GHz.

Han, Man-Gui; Guo, Wei; Wu, Yan-Hui; Liu, Min; Magundappa, L. Hadimani

2014-08-01

402

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

403

Distribution of Si, Fe, and Ni in the Intracluster Medium of the Coma Cluster  

NASA Astrophysics Data System (ADS)

We studied the distributions of Si, Fe, and Ni in the intracluster medium (ICM) of the Coma cluster, one of the largest clusters in the nearby universe, using XMM-Newton data up to 0.5 r180 and Suzaku data of the central region up to 0.16 r180. Using the flux ratios of the Ly? line of H-like Si and the 7.8 keV line blend to the K? line of He-like Fe, the abundance ratios of Si to Fe and Ni to Fe of the ICM were derived using APEC model v2.0.1. The Si / Fe ratio in the ICM of the Coma cluster shows no radial gradient. The emission-weighted averages of the Si / Fe ratio in the ICM within 0.0-0.2 r180, 0.2-0.5 r180, and 0.0-0.5 r180 are 0.97±0.11, 1.05±0.36, and 0.99±0.13, respectively, in solar units using the solar abundance table by Lodders (2003, ApJ, 591, 1220). These values are close to those of smaller clusters and groups of galaxies. Using the Suzaku data of the central region, the derived Ni/Fe ratio of the ICM is 0.6-1.5 in solar units, according to the same solar abundance table. The systematic difference in the derived abundance ratios by different plasma codes are about 10%. Therefore, for the ICM in the Coma cluster, the abundance pattern of Si, Fe, and Ni is consistent with the same mixture of the yields of supernova (SN) II and SN Ia in our Galaxy. Within 0.5 r180, the cumulative iron mass-to-light ratio increases with radius, and its radial profile is similar to those of relaxed smaller clusters with cD galaxies at their center. Using the observed Si/Fe ratio, the cumulative metal mass-to-light ratios at 0.5r180 are compared with theoretical expectations.

Matsushita, Kyoko; Sato, Takuya; Sakuma, Eri; Sato, Kosuke

2013-02-01

404

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-Cu