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1

Magnetic Properties of Fe-Al-Si\\/Fe Multilayer Films  

Microsoft Academic Search

This paper reports on the magnetic properties of Fe-Al-Si\\/Fe multilayer films prepared by rf sputtering. As-deposited Fe-Al-Si\\/Fe multilayer films have a high saturation flux density of 16 kG and an initial permeability of more than 1000, even though the initial permeability of single-layer Fe-Al-Si film is less than 500. As-deposited Fe and Fe-Al-Si single-layer films of thickness less than 1000

A. Gyotoku; H. Tomiyasu; F. Kobayashi

1991-01-01

2

Soft Magnetic Characteristics of Multilayered Films with Fe-Al-Si Layers  

Microsoft Academic Search

The magnetic properties of Fe-Al-Si\\/Fe, Fe-Al-Si\\/Fe-Si and Fe-Al-Si\\/Ni-Fe multilayer films prepared using rf sputtering equipment were investigated. These multilayer films had an initial permeability of more than 1000 prior to annealing; the Fe-Al-Si\\/Fe and Fe-Al-Si\\/Fe-Si multilayer films in particular had a high saturation flux density Bs of more than 14 kG. The magnetic properties of Fe-Al-Si\\/Ni-Fe multilayer film were nearly

A. Gyoutoku; H. Tomiyasu; F. Kobayashi

1992-01-01

3

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

Microsoft Academic Search

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

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

2005-01-01

4

Assessment of different techniques for quantification of ?-Al(FeMn)Si and ?-AlFeSi intermetallics in AA 6 xxx alloys  

Microsoft Academic Search

During homogenisation of AA 6xxx aluminium alloys, the platelike ?-AlFeSi intermetallic phase will transform to a less Si-rich and more spheroidised ?-Al(FeMn)Si phase which is more favourable for extrusion. In this study, several quantitative methods, which determine the relative volume fraction of ?-Al(FeMn)Si and ?-AlFeSi, are compared and an assessment of each method is made. The methods used are optical

N. C. W. Kuijpers; W. H. Kool; P. T. G. Koenis; K. E. Nilsen; I. Todd; S. van der Zwaag

2002-01-01

5

Precipitation of ?-Al5FeSi Phase Platelets in Al-Si Based Casting Alloys  

NASA Astrophysics Data System (ADS)

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

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

2009-10-01

6

27Al and 29Si NMR spectroscopy of MgSiO3 perovskite: mechanisms of Al and Fe incorporation  

NASA Astrophysics Data System (ADS)

The boundary between the Earth's upper and lower mantle is generally attributed to the decomposition of (Mg,Fe)2SiO4 ringwoodite into ferropericlase and perovskite-structured (Mg,Fe)SiO3, hereafter perovskite. Concomitant with this phase change is the more gradual disappearance of a separate Al-bearing phase (majoritic garnet) and dissolution of Al into perovskite. The mechanism of Al incorporation is strongly affected by the presence of Fe due to the co-substitution of Al3+ and Fe3+ for Si4+ and Mg2+, respectively. However, questions about specific substitution mechanisms, site occupancy, and long- and short-range ordering of Fe and Al are still not fully understood. These are questions that NMR is particularly suited to address. We are applying Mossbauer, and 27Al and 29Si MAS-NMR spectroscopy to a series of Al- and Fe-bearing MgSiO3 perovskites of nominal composition Mg1-xFexSi1-xAlxO3 (x = 0.01, 0.025, 0.05). These were synthesized in a multi-anvil cell press at 26 GPa and 1900°C from either glassy starting material or Fe-bearing, aluminous pyroxene synthesized at 8-10 GPa and 1200°C. 29Si spectra show the presence of only a narrow perovskite peak at -191.7 ppm and a broad peak at -81 ppm from an amorphous phase likely formed when crushing the multi-anvil run products. 27Al spectra contain one narrow peak at 6.4 ppm and one broad peak at -14.6 ppm, matching those seen in previous NMR studies of aluminous perovskite and corresponding to Al3+ substituting for Si4+ and Mg2+ respectively. The ratio of observable Al3+ in Si4+ vs. that in Mg2+ sites ranges from 5.5 to 6.3 when the signal to noise of the -14.6 ppm peak is sufficient for quantitation. NMR spectra of materials containing paramagnetic species (i.e. Fe2+ or Fe3+) are often complicated and difficult to interpret due to line broadening, signal loss, "contact" shifts, etc. However, with an understanding of paramagnetic interactions in NMR spectroscopy, valuable information can be gained about some Fe-bearing geological materials. For the pyroxene starting materials used here, NMR signal loss increases linearly with increasing Fe content, an expected result given the likely uncoupled substitution of Fe2+ and Al3+ in these materials. However, 27Al signal loss for the perovskite samples is non-linear with a nearly constant value going from Fe/(Fe + Mg) = 0.01 to 0.025 indicating strong ordering of Fe3+ and Al3+ onto adjacent crystallographic sites. Complete signal loss at Fe/(Fe + Mg) = 0.05 suggests the upper limit of Fe2+ and Fe3+ concentration at which useful NMR data can be obtained for this system. The results of this study are a start to a better understanding of the mechanism of solution of Fe and Al in perovskite and continued work on this problem could provide valuable information on this important lower mantle phase. In addition, this study has potential to give us more general insights into paramagnetic interactions in NMR spectroscopy of geological materials.

Palke, A.; Stebbins, J. F.; Frost, D. J.; McCammon, C. A.

2011-12-01

7

Pseudo Output and Magnetic Properties of Fe-Al-Si Film in MIG Head  

Microsoft Academic Search

In Fe-Al-Si film deposited on ferrite material, there is a layer near the film-ferrite interface with inferior magnetic properties. This layer, which acts as a pseudo-gap in MIG heads, is caused by the nonuniform structure of the Fe-Al-Si film and by interdiffusion between film and ferrite. Improvement of the properties of these Fe-Al-Si films requires better crystal orientation, smaller grain

A. Gyotoku; H. Tomiyasu; N. Koga; F. Kobayashi

1990-01-01

8

Microstructure and mechanical properties of RSP\\/M Al-Fe-V-Si and Al-Fe-Ce alloys  

Microsoft Academic Search

Two aluminium alloys with nominal compositions of Al-8Fe-4Ce and Al-8Fe-1V-2Si (all compositions in wt?%) were rapidly solidified by ultrasonic gas atomization. The atomized powders with an average particle size (d50) of 30 µm were vacuum hot pressed and subsequently hot extruded. The P\\/M extrusion exhibited similar microstructure and elevated temperature tensile properties. The tensile and stress rupture samples of both

U. Prakash; T. Raghu; A. A. Gokhale; S. V. Kamat

1999-01-01

9

Effect of Strontium and Phosphorus on Eutectic Al-Si Nucleation and Formation of ? Al 5 FeSi in Hypoeutectic Al-Si Foundry Alloys  

Microsoft Academic Search

The present investigation was carried out on hypoeutectic Al-Si alloys containing two levels of Fe, 0.5 and 1.1 wt pct, and\\u000a Sr in the range of 30 to 500 ppm. The addition of Sr in excess of 100 ppm significantly reduced the number of eutectic grains\\u000a and also resulted in the formation of polygonal-shaped Al2Si2Sr intermetallics. Transmission electron microscopy studies revealed that the

Y. H. Cho; H.-C. Lee; K. H. Oh; A. K. Dahle

2008-01-01

10

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

Microsoft Academic Search

The purpose of this paper is to investigate the isothermal behavior of Fe–27.3Mn–7.6Al–C–6.5Cr–0.25Si–0.88Mo (Mo(0)) and Fe–27.3Mn–7.6Al–1.0C–6.5Cr–0.25Si\\u000a (Mo(1)) alloys and compare it against Fe–9Cr–1Mo (FCR) commercial alloy. The experiments were carried out at 600°C, 700°C,\\u000a 750°C and 850°C, each one during 72 h in static air. The oxidation kinetics was measured as a function of time using a Thermogravimetry\\u000a analyzer (TGA). The

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

2008-01-01

11

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

Microsoft Academic Search

The purpose of this paper is to investigate the isothermal behavior of Fe–27.3Mn–7.6Al–C–6.5Cr–0.25Si–0.88Mo (Mo(0)) and Fe–27.3Mn–7.6Al–1.0C–6.5Cr–0.25Si\\u000a (Mo(1)) alloys and compare it against Fe–9Cr–1Mo (FCR) commercial alloy. The experiments were carried out at 600°C, 700°C,\\u000a 750°C and 850°C, each one during 72 h in static air. The oxidation kinetics was measured as a function of time using a Thermogravimetry\\u000a analyzer (TGA). The

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

12

(Fe,Si,Al)-based nanocrystalline soft magnetic alloys for cryogenic applications  

NASA Astrophysics Data System (ADS)

In this work Al and Si are substituted for Fe in a (Fe,Si,Al)-Nb-B-Cu alloy with the goal of improving its magnetic properties at 77 K. The x-ray diffraction patterns for a series of five alloys annealed at 823 K shows a Fe3(Si,Al) ordered phase with some residual amorphous phase. The lowest coercivity at room temperature was observed for the alloy with composition Fe68Si15.5Al3.5Nb3B9Cu1. At cryogenic temperatures, the saturation magnetization of 99.3 A m2/kg, coercivity of 0.45 A/m, and resistivity of 122 ?? cm for the Fe63Si17.5Al6Nb3B9Cu1 alloy, compare favorably to commercial alloys at 77 K.

Daniil, Maria; Osofsky, Michael S.; Gubser, Donald U.; Willard, Matthew A.

2010-04-01

13

The Morphology and Chemistry Evolution of Inclusions in Fe-Si-Al-O Melts  

NASA Astrophysics Data System (ADS)

This study aims to elucidate the process of inclusion precipitation in Fe-Si and Fe-Si-Al melts. Deoxidation experiments were carried out in a vacuum induction furnace (VIF) at 1873 K (1600 °C). In the Si-deoxidation experiments, spherical SiO2 of 1~2 ?m diameter was dominant. When 3 wt pct Si and 300 ppm Al were added, such that Al2O3 and mullite were thermodynamically stable, the resulting inclusions depended on the addition sequence. When aluminum was added before silicon, spherical aluminum oxides were dominant after the Al addition, but after the Si addition, the number and size of alumina decreased and Al-Si oxides and mullite appeared with increasing time. When silicon was added before aluminum, spherical SiO2 was dominant after the Si addition, but after the Al addition, spherical and polygonal alumina inclusions were dominant. When Al/Si was added simultaneously, polygonal alumina inclusions were dominant initially, but with time, Al-Si oxide and mullite inclusions increased in numbers. If the Al amount in the Al/Si addition was increased to 600 ppm, only alumina was found. This study shows how, under similar thermodynamic conditions, the transient evolution of inclusions in iron melts in the Si-Al-O system differ depending on the alloy addition sequence.

Kwon, Youjong; Choi, Juhan; Sridhar, Seetharaman

2011-08-01

14

The Morphology and Chemistry Evolution of Inclusions in Fe-Si-Al-O Melts  

Microsoft Academic Search

This study aims to elucidate the process of inclusion precipitation in Fe-Si and Fe-Si-Al melts. Deoxidation experiments were\\u000a carried out in a vacuum induction furnace (VIF) at 1873 K (1600 °C). In the Si-deoxidation experiments, spherical SiO2 of 1~2 ?m diameter was dominant. When 3 wt pct Si and 300 ppm Al were added, such that Al2O3 and mullite were thermodynamically stable, the resulting inclusions depended

Youjong Kwon; Juhan Choi; Seetharaman Sridhar

2011-01-01

15

Phase analysis of iron rich superalloys within the multicomponent system Fe-Mn-Cr-Mo-(Nb)-Al-Si-C  

Microsoft Academic Search

This investigation deals with developing low cost in Fe-base superalloys with duplex microstructure, in which MâCâ carbide fibers reinforced the ..gamma..-Fe matrix. These alloys are sought to be substitutes for currently existing Ni- and Co-base superalloys for high temperature applications. To accomplish this, a systematic study of Fe-base ternary Fe-Mo-C, quaternary Fe-Al-Si-C, quinaries Fe-Mn-Al-Si-C and Fe-Cr-Al-Si-C, six component Fe-Mn-Cr-Al-Si-C, and

1986-01-01

16

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

NASA Astrophysics Data System (ADS)

5Cr-0.5Mo steel was coated by hot-dipping in a molten Al-10 wt.% Si bath at 700 °C for 10, 60, 120 or 180 s. The identification of the phases in the Fe-Al-Si intermetallic phases formed in the aluminide layers during hot-dipping was carried out by using a combination of scanning electron microscope (SEM) with energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and electron backscatter diffraction (EBSD). The EDS results show a ? 5(H)-Al 7Fe 2Si phase, which exhibited 2 distinct morphologies, small particles widely dispersed and a continuous layer. Also revealed by EDS were ? 6-Al 4FeSi and ? 4-Al 3FeSi 2 phases, which showed plate-shaped morphology, in an Al-Si topcoat. However, the XRD results show the intermetallic phases in the aluminide layer were composed of outer cubic ? 5(C)-Al 7(Fe,Cr) 2Si and inner hexagonal ? 5(H)-Al 7Fe 2Si. EBSPs and mapping functions in EBSD helped to clarify the confused phase identifications yielded by EDS and XRD. In this way, the small intermetallic particles and the continuous intermetallic layer were identified as cubic ? 5(C)-Al 7(Fe,Cr) 2Si and hexagonal ? 5(H)-Al 7Fe 2Si, respectively, and the plate-shaped intermetallic phase was identified as monoclinic ? 6-Al 4FeSi and tetragonal ? 4-Al 3FeSi 2 with the same metallographic morphology. EBSD proved to be a very effective technique for local phase identification of aluminide layers with complicated multiphase morphologies.

Cheng, Wei-Jen; Wang, Chaur-Jeng

2011-03-01

17

Rapidly solidified Al-Fe-Mo-Si alloys for high temperatures applications  

Microsoft Academic Search

Iron solubility in aluminium can be extended through the rapid solidification route, allowing the precipitation of a high volume fraction of intermetallic phases. In the ternary Al-Fe-Si system, the observed metastable hardening phase Al13Fe3Si is sensitive to ripening. Thermal stability can be improved by modification of the surface energy of the precipitate, i.e. by lattice parameter variation, through addition of

M. C. S. DE MACEDO; G. MICHOT

1993-01-01

18

Oxidation behavior of Fe-Si-Al alloys at 1173–1373 K  

Microsoft Academic Search

The oxidation behavior of Fe-Al-Si alloys prepared by ingot metallurgy (IM) and powder metallurgy (PM) in air and oxygen was investigated in the temperature range 1173–1373 K. A fine dispersion of TiB2 in the PM alloys stabilized a fine grain size (2O3-scale-forming Fe-Al-Si PM alloys makes them strong candidates for use below 1273 K; the IM alloys, in comparison, showed

S. Guruswamy; J. P. Hirth; G. W. Powell

1983-01-01

19

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

NASA Astrophysics Data System (ADS)

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

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

2012-05-01

20

Study on Fe-Al-Si in situ composite coating fabricated by laser cladding  

NASA Astrophysics Data System (ADS)

Fe-Al-Si in situ composite coating was fabricated on the surface of ASTM A283Gr.D steel by laser cladding with the preplaced powder. The influence of powder composition, laser power and scanning speed on microstructure, microhardness and wear resistance were investigated in this paper. The results show that Fe-Al-Si in situ composite coating with the good metallurgical bond mainly consists of Fe, SiO2 and Al2Fe3Si4 intermetallic compound. With the increase of laser power and scanning speed, the grain size of coating gets the minimum value. With the increase of laser power and scanning speed, microhardness and wear resistance both get the peak vaule, and their value are three times and 3.5 times those of substrate, respectively. The optimum parameters are followed as: the ratio of the preplaced composite powder: 8:1:1, laser power: 1600 W and scanning speed: 400 mm/min.

Zhao, Long-zhi; Zhao, Ming-Juan; Li, De-Ying; Zhang, Jian; Xiong, Guang-Yao

2012-02-01

21

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.

2012-12-01

22

Electromagnetic wave absorption properties of flaky Fe-Ti-Si-Al nanocrystalline composites  

NASA Astrophysics Data System (ADS)

Nanocrystalline Fe-Ti-Si-Al flaky powders with large aspect ratio have been fabricated by high-energy planetary milling melt-spun ribbons. Magnetic composites made of thermally annealed Fe-Ti-Si-Al flaky powders embedded in epoxy resin exhibit excellent electromagnetic wave absorption properties in a wide frequency range from 100 MHz to 2.65 GHz. Ti additions can enhance the electrical resistivity of Fe-Si-Al alloy without changing the crystallographic structure, resulting in the reduction of eddy current loss at high frequencies. Moreover, the substitution of Ti for Fe enhances the cut-off frequency of flaky powder-polymer composites. Meanwhile, compared to the Ti-free composites, reflection loss of the Ti-doped composites (3 mm in thickness) is lower than -10 dB in the frequency range from 593 MHz to 1.83 GHz, indicating that the composites can effectively work in a wider frequency bandwidth.

Liu, Junhu; Ma, Tianyu; Tong, Hui; Luo, Wei; Yan, Mi

2010-04-01

23

Diffusion in intermetallic phases of the Fe–Al and Fe–Si systems  

Microsoft Academic Search

Self-diffusion of Fe and impurity diffusion of In in Fe–aluminides of 26.5, 34 and 50 at.% aluminium have been investigated over wide temperature ranges. For Fe diffusion in Fe3Al an influence of A2–B2 and B2–D03 transitions has been observed. The activation enthalpy increases with increasing order. Diffusion in alloys with higher Al content shows linear Arrhenius behaviour. Impurity diffusion of

H Mehrer; M Eggersmann; A Gude; M Salamon; B Sepiol

1997-01-01

24

Electrical resistivity of nanocrystals in Fe-Al-Ga-P-B-Si-Cu alloy  

NASA Astrophysics Data System (ADS)

In new supercooled Fe74Al4Ga2P11B4Si4Cu1 alloy the 10nm size ?-Fe(Si) nanocrystals are precipitated. Thermal stability is analyzed by the electron transport and magnetization measurements. Temperature variation of electrical resistivity of nanocrystals is determined and discussed for alloys with different initial crystalline fraction. Possible mechanism inhibiting the grain growth is presented.

Pekala, K.; K.; Ja?kiewicz, P.; Nowi?ski, J. L.; Pekala, M.

2003-05-01

25

Microwave absorption capability of microcapsules by coating FeSiAlCr with SiO2  

NASA Astrophysics Data System (ADS)

Electromagnetic wave absorption of microcapsules by coating FeSiAlCr with SiO2 is investigated. The absorption amplitude of the microcapsules is found to increase significantly in the lower frequency of microwave compared with the corpuscles of FeSiAlCr alloy. Reflection loss (RL) exceeding -10 dB can be obtained for all frequencies within 2.6-7.3 GHz, covering half of the S-band, and the whole C-band when the absorber layer thickness is 2 mm. The maximum RL can exceed -18 dB at 4.3 GHz, while the RL is only -4 dB with the corpuscles of FeSiAlCr alloy. The reason is that the microcapsules's conductance is decreased and the absorption of electromagnetic wave in the microcapsule materials is easier.

Huang, Weirong; Zhang, Penghua; Yan, Wenjing; Zhou, Liang; Xu, Hui

2012-10-01

26

Influence of Grain-Refiner Addition on the Morphology of Fe-Bearing Intermetallics in a Semi-Solid Processed Al-Mg-Si Alloy  

NASA Astrophysics Data System (ADS)

The three-dimensional morphologies of the Fe-bearing intermetallics in a semisolid-processed Al-Mg-Si alloy were examined after extracting the intermetallics. ? c-AlFeSi and ?-AlFeSi are the major Fe-bearing intermetallics. Addition of Al-Ti-B grain refiner typically promotes ?-AlFeSi formation. ?-AlFeSi was observed with a flat, plate-like morphology with angular edges in the alloy with and without grain refiner, whereas ? c-AlFeSi was observed as "flower"-like morphology in the alloy with grain refiner.

Smith, Tahsina; O'Reilly, Keyna; Kumar, Sundaram; Stone, Ian

2013-11-01

27

Viscosity of SiO2-"FeO"-Al2O3 System in Equilibrium with Metallic Fe  

NASA Astrophysics Data System (ADS)

The present study delivered the measurements of viscosities in SiO2-"FeO"-Al2O3 system in equilibrium with metallic Fe. The rotational spindle technique was used in the measurements at the temperature range of 1473 K to 1773 K (1200 °C to 1500 °C). Molybdenum crucibles and spindles were employed in all measurements. The Fe saturation condition was maintained by an iron plate placed at the bottom of the crucible. The equilibrium compositions of the slags were measured by EPMA after the viscosity measurements. The effect of up to 20 mol. pct Al2O3 on the viscosity of the SiO2-"FeO" slag was investigated. The "charge compensation effect" of the Al2O3 and FeO association has been discussed. The modified quasi-chemical viscosity model has been optimized in the SiO2-"FeO"-Al2O3 system in equilibrium with metallic Fe to describe the viscosity measurements of the present study.

Chen, Mao; Raghunath, Sreekanth; Zhao, Baojun

2013-08-01

28

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

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

29

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

30

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

31

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

NASA Astrophysics Data System (ADS)

Heterojunction solar cells with Al-alloyed polycrystalline p-type ?-phase iron disilicide [p-?-FeSi2(Al)] on n-Si(100) were investigated. The p-?-FeSi2(Al) was grown by sputter deposition and rapid-thermal annealing. Photocurrent of ~1.8 mA/cm2 and open-circuit voltage of ~63 mV were obtained for p-?-FeSi2(Al)/n-Si(100)/Ti/Al control cells with indium-tin-oxide (ITO) top electrode. Open-circuit voltage increased considerably once thin Al layer was deposited before amorphous-FeSi2(Al) deposition. Furthermore, device performances were found to improve significantly (~5.3 mA/cm2 and ~450 mV) by introducing germanium-nitride electron-blocking layer between ITO and p-?-FeSi2(Al). The improvement is attributed to the formation of epitaxial Al-containing p+-Si at p-?-FeSi2(Al)/n-Si(100) interface and suppressed back-diffusion of photogenerated electrons into ITO.

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

2011-01-01

32

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

NASA Astrophysics Data System (ADS)

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

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

2011-05-01

33

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

Microsoft Academic Search

5Cr–0.5Mo steel was coated by hot-dipping in a molten Al–10wt.% Si bath at 700°C for 10, 60, 120 or 180s. The identification of the phases in the Fe–Al–Si intermetallic phases formed in the aluminide layers during hot-dipping was carried out by using a combination of scanning electron microscope (SEM) with energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) and electron

Wei-Jen Cheng; Chaur-Jeng Wang

2011-01-01

34

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

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

35

Magnetism and crystal structure of Fe\\/Al\\/Si films prepared by dual-ion-beam sputtering  

Microsoft Academic Search

Fe\\/Al\\/Si multilayered films have been deposited using an ion-beam sputtering apparatus. The effects of ion bombardment onto growing film surfaces and the effects of annealing after deposition on their crystal structure and magnetic properties have been investigated. The thicknesses of Fe, Al, and Si layers were adjusted at the value corresponding to the Sendust composition. Then the Fe layer thickness

K. Kubota; M. Nagakubo; M. Naoe

1990-01-01

36

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

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

37

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

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

38

High-pressure elasticity of perovskite and post-perovskite (Mg,Fe,Al)(Al,Si)O3  

NASA Astrophysics Data System (ADS)

We determine the effect of chemistry on the elasticity and seismic wave velocities of perovskite and post-perovskite using first-principles calculations. The elastic constants tensor in perovskite is more isotropic than in post-perovskite. The pure shear elastic constants are comparable between perovskite and post-perovskite; for post-perovskite, MgSiO3 has the largest values, and both Al2O3 and FeSiO3 show elastic instability at low pressures. The shear modulus of post-perovskite is larger than of perovskite at high pressures in all three cases. The difference in bulk modulus between the perovskite and post-perovskite structures, for MgSiO3 and FeSiO3 is on the order of about 15-20 GPa. The post-perovskite phase of Al2O3 shows the smallest bulk modulus at high pressures. The Vp values for FeSiO3 and Al2O3 post-perovskite are respectively about 2.0 and 1.6 km/s below the values for MgSiO3 post-perovskite. V_s shows similar trends for all the three compositions: at low pressures post-perovskite is softer than perovskite and has lower V_s values, while at higher pressure post-perovskite has larger values than perovskite. At 120 GPa MgSiO3 post-perovskite has V_s higher than FeSiO3 post-perovskite by about 1.7 km/s and higher than Al2O3 by about 0.9 km/s. For a pyrolitic mantle the effect of chemistry is relatively small, decreases on the order of up to 2% for Vp and up to 1.5% for V_s. Due to the perovskite to post-perovskite transition in Fe- and Al- bearing MgSiO3, Vp increases by 0.7% (about 0.1 km/s) and Vs by 2.5% (about 0.2 km/s) at 120 GPa.

Caracas, R.; Cohen, R. E.

2005-12-01

39

Structural chemistry of uranium associated with Si, Al, Fe gels in a granitic uranium mine  

Microsoft Academic Search

The structure of natural uranium-bearing, recently formed products arising from oxidative weathering of a U deposit (Peny, Massif Central, France) was studied to determine mechanisms of U-trapping by natural gels. Sampled waters are close to saturation with respect to amorphous silica and crystalline-hydrated U-hydroxides and silicates. All products are U-bearing Si\\/Al- and Fe-rich gels with minor Ca, Mg and water.

Thierry Allard; Philippe Ildefonse; Catherine Beaucaire; Georges Calas

1999-01-01

40

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

SciTech Connect

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

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

2010-07-15

41

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

42

The effect of iron concentration on the compressibility of (Fe,Mg)(Al,Si)O3 perovskite.  

NASA Astrophysics Data System (ADS)

Recent studies have indicated that the substitution of Al into (Mg,Fe)(Al,Si)O3 perovskite is coupled to ferric Fe and that a significant portion of the Fe in the lower mantle perovskite is, therefore, likely to be in the ferric state. The substitution of trivalent cations into silicate perovskite can occur either by coupled substitution onto both Mg and Si sites or by substitution onto the Si site charge balanced by the creation of an oxygen vacancy. The results of previous studies are inconclusive as to the effect of these substitutions on elastic properties. To resolve these issues we have investigated the effect of bulk iron concentration on equation of state properties of Al bearing magnesium silicate perovskite using single crystal x-ray diffraction in a diamond anvil cell. Three single crystals with the compositions, (Mg2+0.93,Fe3+0.034,Fe2+0.035,Al3+0.012)(Si4+0.89,Al3 +0.096)O2.96 (Mg2+0.872,Fe3+0.088,Fe2+0.042,Al3+0.007)(Si4+0.892,Al 3+0.108)O3 (Mg2+0.782,Fe3+0.192,Fe2+0.048,Al3+0.031)(Si4+0.863,Al {3+}0.137)O2.95 were synthesized using a multianvil apparatus at 25 GPa and 2000°C. Ferric iron concentrations were determined using Mössbauer and Electron energy loss spectroscopic techniques. The single crystals were compressed to 9 GPa at ambient temperature. The compression data were fitted to a third order Birch Murnaghan equation of state. The bulk modulii of the three crystals decreases with increasing Fe content from 243(3) GPa to 240(2) GPa to 234(2) GPa. In addition, increasing the Fe content raises the K'.

Saikia, A.; Boffa Ballaran, T.; Frost, D. J.; Rubie, D. C.

2007-12-01

43

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

SciTech Connect

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

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

1996-05-15

44

Study of Al–Cu–Fe–Ti–Cr–Si powders for thermal spraying produced by mechanochemical synthesis and subsequent annealing  

Microsoft Academic Search

The paper examines the phase transformations of composite powders based on Al63Cu25Fe12 that contain alloying elements (Ti, Cr, Si in the ratio AlCuFe : TiCrSi = 75 : 25). The powders are produced by mechanochemical\\u000a synthesis and subsequent thermal treatment. Amorphous and crystalline powder mixtures form during synthesis; their annealing\\u000a results in multiphase structures consisting of ?, ?1, and ?2

A. L. Borisova; L. I. Adeeva; A. Yu. Tunik; M. V. Karpets; V. L. Rupchev; A. N. Burlachenko

2009-01-01

45

The Viscous Behavior of FeO t Al 2 O 3 SiO 2 Copper Smelting Slags  

Microsoft Academic Search

Understanding the viscous behavior of copper smelting slags is essential in increasing the process efficiency and obtaining\\u000a the discrete separation between the matte and the slag. The viscosity of the FeOt-SiO2-Al2O3 copper smelting slags was measured in the current study using the rotating spindle method. The viscosity at a fixed Al2O3 concentration decreased with increasing Fe\\/SiO2 ratio because of the

Hyun-Shik Park; Su Sang Park; Il Sohn

2011-01-01

46

Laser cladding of quasi-crystal-forming Al-Cu-Fe-Bi on an Al-Si alloy substrate  

NASA Astrophysics Data System (ADS)

We report here the results of an investigation aimed at producing coatings containing phases closely related to the quasi-crystalline phase with dispersions of soft Bi particles using an Al-Cu-Fe-Bi elemental powder mixture on Al-10.5 at. pct Si 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. The basic reason for choosing Bi lies in the fact that it is immiscible with each of the constituent elements. Therefore, it is expected that Bi will solidify in the form of dispersoids during the rapid solidification. A detailed microstructural analysis has been carried out by using the backscattered imaging mode in a scanning electron microscope (SEM) and transmission electron microscope (TEM). The microstructural features are described in terms of layers of different phases. Contrary to our expectation, the quasi-crystalline phase could not form on the Al-Si substrate. The bottom of the clad and remelted layers shows the regrowth of aluminum. The formation of phases such as blocky hexagonal Al-Fe-Si and a ternary eutectic (Al + CuAl2 + Si) have been found in this layer. The middle layer shows the formation of long plate-shaped Al13Fe4 along with hexagonal Al-Fe-Si phase growing at the periphery of the former. The formation of metastable Al-Al6Fe eutectic has also been found in this layer. The top layer, in the case of the as-clad track, shows the presence of plate-shaped Al13Fe4 along with a 1/1 cubic rational approximant of a quasi-crystal. The top layer of the remelted track shows the presence of a significant amount of a 1/1 cubic rational approximant. In addition, the as-clad and remelted microstructures show a fine-scale dispersion of Bi particles of different sizes formed during monotectic solidification. The remelting is found to have a strong effect on the size and distribution of Bi particles. The dry-sliding wear properties of the samples show the improvement of wear properties for Bi-containing clads. The best tribological properties are observed in the as-clad state, and remelting deteriorates the wear properties. The low coefficient of friction of the as-clad and remelted track is due to the presence of approximant phases. There is evidence of severe subsurface deformation during the wear process leading to cracking of hard phases and a change in the size and shape of soft Bi particles. Using these observations, we have rationalized possible wear mechanisms in the Bi-containing surface-alloyed layers.

Biswas, Krishanu; Chattopadhyay, Kamanio; Galun, Rolf; Mordike, Barry L.

2005-07-01

47

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

NASA Astrophysics Data System (ADS)

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

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

2001-12-01

48

Study of Microstructural Changes in an Fe-Mn-Al-Si-C Alloy  

NASA Astrophysics Data System (ADS)

The microstructural changes in a 0.05C-26.3Mn-4.88Si-4.13Al-Fe alloy were studied. The two constituting phases were austenite and ordered DO3. The morphology of austenite phase was found to be different under various conditions. The DO3 phase had a modulated microstructure, and secondary austenite flakes precipitated within the DO3 matrix when both cast and hot-rolled alloys were heat treated at 1073 K (800 °C). An attempt was made to explain the secondary austenite precipitation in view of a schematic phase diagram.

Bhattacharya, Basudev

2012-06-01

49

The Mössbauer effect in natural almandine: Fe3Al2(SiO4)3  

NASA Astrophysics Data System (ADS)

A natural sample of Almandine, Fe3Al2 (SiO4)3, was studied by 57Fe Mössbauer Spectroscopy at various temperatures. The values for the Electric Field Gradient tensor components have been determined from the lowest temperature (2K) spectrum to be: Vzz = -1.75 × 10-18 V/cm2, Vxx = 0.82 × 10-18 V/cm2 and Vyy = 0.92 × 10-18 V/cm2. The separation between the two electronic lower levels is inferred from a simple model for the quadrupolar interaction. The lower level is a dz2-one and is 872 cm-1 (similar 1250K) below the first excited state which is a dxy-state. Both constitute the 5Eg-doublet.

de Oliveira, J. C. P.; Kunrath, J. I.; Vasquez, A.

1987-09-01

50

Giant magnetoimpedance effect in ultrasoft FeAlSiBCuNb nanocomposites for sensor applications  

SciTech Connect

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

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

2005-07-01

51

As-spray-deposited structure of an Al20Si5Fe Osprey preform and its development during subsequent processing  

Microsoft Academic Search

The application of the Osprey process to the fabrication of newly developed Al-20Si-X alloys is at present a subject of considerable interest. This paper reports the results of a study on the as-spray deposited structural characteristics of an Al-20Si-5Fe alloy preform and their development during subsequent hot extrusion and high-temperature exposure, by means of X-ray diffraction, differential scanning calorimetry and

J. Zhou; J. Duszczyk; B. M. Korevaar

1991-01-01

52

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

Microsoft Academic Search

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

Samuel S. Shinozaki; Anthony Arrott

1966-01-01

53

Structural and magnetic properties and tunnel magnetoresistance for Co2(Cr,Fe)Al and Co2FeSi full-Heusler alloys  

Microsoft Academic Search

We have investigated the structure and magnetization of Co2(Cr1-xFex)Al (0 <= x <= 1) and Co2FeSi full-Heusler alloy films deposited on thermally oxidized Si (SiO2) and MgO (001) single crystal substrates by ultra-high vacuum sputtering at various temperatures. The films were also post-annealed after deposition at room temperature (RT). Magnetic tunnel junctions with a full-Huesler alloy electrode were fabricated with

K. Inomata; S. Okamura; A. Miyazaki; M. Kikuchi; N. Tezuka; M. Wojcik; E. Jedryka

2006-01-01

54

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

Microsoft Academic Search

After the nucleation and sedimentation of primary Fe-rich phases, the microstructures of Al-11.5Si-0.4Mg cast alloys with\\u000a 0.35–1.03Fe and 0.18–0.59Mn have been studied to investigate the solidification characteristics of Fe-rich phases. Depending\\u000a on the iron and manganese contents as well as cooling rates, Fe-rich phases may solidify as predendritic (primary), pre-eutectic,\\u000a coeutectic, and posteutectic intermetallics at the different stages of solidification

X. Cao; J. Campbell

2004-01-01

55

Untersuchungen der Konstitution und zum Verformungsverhalten von intermetallischen Phasen auf der Basis von Fe(sub 3)(AlSi). (Constitution and deformation of Fe(sub 3)(AlSi)-based intermetallic phases).  

National Technical Information Service (NTIS)

The constitution of Fe(sub 3)(AlSi)-based alloys was examined by means of transmission electron microscopy and X-ray powder diffraction on quenched samples. Critical temperatures for DO(sub 3)-order as well as the ranges of the several miscibility gaps be...

H. Bosse

1992-01-01

56

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

SciTech Connect

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

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

2009-11-15

57

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

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

58

Analysis of the Fe–Zn interface of galvanized high Al–low Si TRIP steels  

Microsoft Academic Search

TRIP-assisted steels are ideal for lightweight automotive applications due to their high strength and ductility. The selective oxidation of the alloying elements Mn, Al and Si during annealing prior to galvanizing can cause poor reactive wetting during galvanizing, resulting in bare spot defects. Despite the selective oxidation of alloying elements two high Al–low Si TRIP steels were successfully galvanized. It

E. M. Bellhouse; J. R. McDermid

2008-01-01

59

A study of damage under tensile loading in a new Al-Si-Fe alloy processed by the Osprey route  

Microsoft Academic Search

The mode of damage in tension of a new Al-Si-Fe alloy made by spray deposition was studied. This alloy has a composite type structure composed of silicon and intermetallic particles in an aluminium matrix. In situ tensile tests in the SEM, with gold microgrids deposited on the surface of the specimen as an indicator of local plastic strains, provide us

A. Mocellin; R. Fougeres; P. F. Gobin

1993-01-01

60

Effect of impurity on the elasticity of perovskite and postperovskite: Velocity contrast across the postperovskite transition in (Mg,Fe,Al)(Si,Al)O3  

NASA Astrophysics Data System (ADS)

We calculated the acoustic velocity contrasts between perovskite and postperovskite in MgSiO3, FeSiO3 and Al2O3 compounds, using the planewave pseudopotential method for a pressure range of the Earth's lower mantle. Both FeSiO3 and Al2O3 pv and ppv have about 20% smaller shear moduli than Mg-phases at deep mantle pressures, though the bulk moduli are comparable, consistent with previous studies. For the relative variations of shear to compressional velocities, bulk to shear velocities and density to shear velocity at constant pressure due to variations in Fe and Al content up to 20 mol%, we find RS/P of 1.5~2.2, R?/S of 0.1~0.4 and R?/S of -1.0~-0.2. Both Fe and Al influence elasticity of ppv more than that of pv. Therefore velocity contrasts across the postperovskite phase change would decrease with increasing Fe and Al content. We find that positive velocity variations are hardly produced in pv with the MORB composition.

Tsuchiya, Taku; Tsuchiya, Jun

2006-05-01

61

Site preference and magnetism of Fe3-xCrxAl0.5Si0.5  

NASA Astrophysics Data System (ADS)

In order to gain better insight into the origin of the observed differences between Fe3-xCrxAl and Fe3-xCrxSi, alloys of Fe3-xCrxAl0.5Si0.5 (x=0, 0.125, 0.250, 0.375 and 0.5) were prepared and studied by means of X-ray and neutron diffraction as well as by magnetization measurements. Electronic structure calculations of these alloys have been performed by means of TB-LMTO-ASA method. It was expected, and experimentally verified, that the presence of silicon and aluminum atoms in 1:1 proportion will result in the independence of the lattice parameter on the iron/chromium concentration. All samples have been proved to be a single phase of the DO3-type of structure. Theoretical and experimental results indicate that chromium atoms locate preferentially in B sublattice. Cr magnetic moments are oriented antiparallel to Fe magnetic moments. Neutron measurements show a linear dependence of the magnetic moments of Fe(A,C), Fe(B) and Cr(B) as a function of Cr concentration. However the calculated total magnetic moment decreases faster with chromium content than indicated by the experiment.

Go, A.; Re?ko, K.; Dobrzy?ski, L.; Milczarek, J. J.; Biernacka, M.

2012-08-01

62

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

Microsoft Academic Search

The alternating current induced remagnetization process in FeCuNbSiB\\/Al\\/FeCuNbSiB films is studied. The frequency spectra of the voltage arising in the pick-up coil wound around the sample are measured as a function of an external dc magnetic field. It is shown that the frequency spectra differ substantially for the transverse and longitudinal external magnetic field directions. For the transverse field, several

N A Buznikov; A S Antonov; A L Dyachkov; A A Rakhmanov

2004-01-01

63

Magnetic properties of spray-formed Fe–6.5%Si and Fe–6.5%Si–1.0%Al after rolling and heat treatment  

Microsoft Academic Search

The maximum silicon content in commercial Fe–Si steels is limited to about 3.5wt%Si, since the ductility declines sharply as this maximum is exceeded, hindering the production of thin sheets by cold\\/hot rolling. However, the best magnetic properties are attained at about 6.5wt%Si, a silicon content that renders magnetostriction practically null and minimizes magnetic losses. Using spray-forming, our research group has

Claudemiro Bolfarini; Mário Cézar Alves Silva; Alberto Moreira Jorge; Claudio Shyinti Kiminami; Walter José Botta

2008-01-01

64

Magnetic properties of spray-formed Fe 6.5%Si and Fe 6.5%Si 1.0%Al after rolling and heat treatment  

Microsoft Academic Search

The maximum silicon content in commercial Fe Si steels is limited to about 3.5 wt%Si, since the ductility declines sharply as this maximum is exceeded, hindering the production of thin sheets by cold\\/hot rolling. However, the best magnetic properties are attained at about 6.5 wt%Si, a silicon content that renders magnetostriction practically null and minimizes magnetic losses. Using spray-forming, our

Claudemiro Bolfarini; Mário Cézar Alves Silva; Alberto Moreira Jorge; Claudio Shyinti Kiminami; Walter José Botta

2008-01-01

65

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

Microsoft Academic Search

The aim of this work is to study the effect of cooling rate and subsequent hot consolidation on the microstructural features and mechanical strength of Al–20Si–5Fe–2X (X=Cu, Ni and Cr) alloys. Powder and ribbons were produced by gas atomization and melt spinning processes at two different cooling rates of 1×105K\\/s and 5×107K\\/s. The microstructure of the products was examined using

M. Rajabi; M. Vahidi; A. Simchi; P. Davami

2009-01-01

66

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

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

67

Effect of particle size on the microstructure of rapidly solidified Al–20Si–5Fe–2 X ( X = Cu, Ni, Cr) powder  

Microsoft Academic Search

The effects of particle size and alloying elements on the size and morphology of secondary\\/intermetallic phases in gas atomized Al–20Si–5Fe–2X (X=Cu, Ni, Cr) powders were studied. The microstructure composed of particle-like primary Si with average diameter of 0.5–2.7?m, ?-Al4FeSi2 intermetallic compound containing small amount of dissolved alloying elements with the size of 1.4–7.7?m, and fine Al–Si eutectic matrix with 0.25–0.4?m

M. Rajabi; A. Simchi; M. Vahidi; P. Davami

2008-01-01

68

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

NASA Astrophysics Data System (ADS)

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

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

2013-02-01

69

Magnetocrystalline anisotropy constants, rotational hysteresis energy and magnetic domain structure in UFe 6Al 6, UFe 9AlSi 2 and ScFe 10Si 2 intermetallic compounds  

Microsoft Academic Search

The magnetic torque, T, was applied to determine the anisotropy constants K1 and K2 of the UFe6Al6, UFe9AlSi2 and ScFe10Si2 compounds. The mechanism of magnetization reversal processes in these compounds was investigated on the basis of the analysis of the rotational hysteresis energy, Wr and rotational hysteresis integral, R, calculated from the magnetic torque curves. Applying the powder pattern method,

J. J. Wyslocki; W. Suski; P. Pawlik; K. Wochowski; B. Kotur; O. I. Bodak

1996-01-01

70

Photovoltaic and phototransient interface states properties of nanocomposite Fe3O4–graphene/n-Si/Al photodiode  

NASA Astrophysics Data System (ADS)

A photodiode based on Fe3O4–graphene/n-Si/Al diode was fabricated. The electrical and capacitance properties of the diode were investigated by transient current and capacitance measurements. Ag/Fe3O4–graphene/n-Si photovoltaic device gives Isc of 0.111 mA and Voc of 375 mV under 1.5 A.M. The maximum electrical power Pmax value of the device was found to be 7.567 ?V. This suggests that the studied photovoltaic device can be used as a microvoltage generator. The capacitance of the device increases with illumination. This indicates that the device exhibits a photocapacitance behavior. This behavior was analyzed by transient photocapacitance measurements. The transient interface states density plots of the diode were obtained. The photocapacitance mechanism was explained with the change in the interface states.

Alahmed, Z. A.; Phan, D.-T.; Chung, G.-S.; Yakuphanoglu, F.

2013-11-01

71

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

Microsoft Academic Search

Properties of the interface between the epitaxial layer of heavily doped Al0.48In0.52As:Si and the InP(Fe) substrate are investigated by photoluminescence in AlInAs:Si\\/InP(Fe) heteroestructures grown by molecular beam epitaxy. The effect on heterostructure optical properties of including a thin Al0.22Ga0.26In0.52As:Si layer at the interface is investigated as well. To explain the different interface emission energies observed, the results are analyzed by

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

2002-01-01

72

Thermodynamic modelling of phase equilibria in melts of Fe-Ca-Al-Si-Mn-V-Nb-Ni-Mo-P-C-O system  

NASA Astrophysics Data System (ADS)

A thermodynamic analysis of the phase equilibria in the Fe-Ca-Al-Si-Mn-V-Nb-Ni-Mo-P-C-O system at fixed concentrations of silicon, manganese, vanadium, niobium, nickel, molybdenum, phosphorus and carbon was performed. The formation of nonmetallic phases at 1873 K in liquid metal solutions of various compositions was studied. It has been established that, depending on the concentrations of calcium and aluminum, the metal melt can be in equilibrium with (FeO, CaO, Al2O3, SiO2, MnO) liquid solutions, |FeO, CaO, MnO| and |Al2O3, V2O3| solid solutions, individual compounds 3Al2O3·SiO2, CaO·2Al2O3, CaO·6Al2O3 and {Ca} gas.

Tanklevskaya, N. M.; Chernova, L. A.; Mikhailov, G. G.

2008-02-01

73

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

74

Fracture of an Osprey{trademark} AlSiFe alloy: A microstructure based model for fracture of microheterogeneous materials  

SciTech Connect

This paper is concerned with the failure in tension of an AlSiFe alloy with a particular composite type microstructure. The experimental observations allow to distinguish three main steps in the damage process: nucleation by the cracking of some big silicon particles, increasing of the number of cracked particles with macroscopic plastic strain and final failure by joining of the microcracks thus created. This schematization is the basis of the modelization which requires Eshelby type calculations and energetic balances. This model is in good agreement with experiment for the studied alloy and makes the microstructural parameters of the material clearly appear.

Mocellin, A.; Fougeres, R. [INSA Lyon, Villeurbanne (France); Brechet, Y. [ENSEEG, Saint Martin d`Heres (France)

1995-03-01

75

Influence of Co addition on the magnetocaloric effect of FeCoSiAlGaPCB amorphous alloys  

SciTech Connect

The FeCoSiAlGaPCB alloys can be prepared as bulk amorphous materials, with outstanding mechanical properties and increased electrical resistivity. These features can be beneficial for their application as a magnetic refrigerant. The influence of Co addition on the magnetic entropy change of the alloy has been studied. This compositional modification displaces the temperature of the peak entropy change closer to room temperature, but reduces the refrigerant capacity of the material. For the Co-free alloy, the peak entropy change is increased with respect to a Finemet alloy containing Mo, but its refrigerant capacity is not enhanced.

Franco, V.; Borrego, J.M.; Conde, A.; Roth, S. [Dpto. Fisica de la Materia Condensada, ICMSE-CSIC, Universidad de Sevilla, P.O. Box 1065, 41080 Sevilla (Spain); Leibniz Institut fuer Metallische Werkstoffe, IFW Dresden, Postfach 270016, D 01171 Dresden (Germany)

2006-03-27

76

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

77

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

78

Structural asymmetry of Si/Fe and Fe/Si interface in Fe/Si multilayers  

NASA Astrophysics Data System (ADS)

We have investigated silicon on iron (Si-on-Fe) and iron on silicon (Fe-on-Si) interfaces in Fe/Si multilayer(ML) structures. Fe/Si MLs of various Fe and Si layer thicknesses are deposited by the ion beam deposition technique. Structural information on the interfaces is obtained using grazing incidence x-ray reflectivity, x-ray standing wave and cross-sectional transmission electron microscopy measurements. Interdiffusion is greater at the Si-on-Fe interface compared with the Fe-on-Si interface. Silicide interlayer formation is observed at both interfaces. FeSi is the main component of interfacial silicide. The presence of crystalline FeSi and Fe2Si is observed.

Naik, S. R.; Rai, S.; Tiwari, M. K.; Lodha, G. S.

2008-06-01

79

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

NASA Astrophysics Data System (ADS)

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

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

2012-02-01

80

Glass formation and magnetic properties of Fe-C-Si-B-P-(Cr-Al-Co) bulk metallic glasses fabricated using industrial raw materials  

NASA Astrophysics Data System (ADS)

Formation of Fe-C-Si-B-P-(Cr-Al-Co) bulk metallic glasses with enhanced glass-forming ability (GFA) and magnetic properties fabricated using industrial pig-iron and Fe-P alloys as raw materials has been studied. It was found that GFA of the pig-iron (Fe79.5C18.0Si2.3P0.2, at%) could be improved by proper additions of only metalloids C, Si, P and B, and fully glassy structure was obtained in the Fe75.5C7.0Si3.3B5.5P8.7 alloy with a critical diameter of 1 mm. With suitable additions of metallic elements Cr, Co and Al, the GFA is further increased and fully amorphous rods in 4 mm diameter can be prepared for the Fe68.2C7.0Si3.3B5.5P8.7Cr2.3Al2.0Co3.0 alloy that shows a unique combination of good soft-magnetic properties (Ms=1.03 T, Hc=9.39 A/m), high GFA and high fracture strength. These low-cost Fe-based bulk metallic glasses fabricated using industrial raw materials have a potential to be utilized as engineering materials.

Li, H. X.; Wang, S. L.; Yi, S.; Jiao, Z. B.; Wu, Y.; Lu, Z. P.

2009-09-01

81

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

82

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

2010-11-01

83

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

84

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

Microsoft Academic Search

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

Harumi Yokokawa; Masao Fujishige; Seiichi Ujiie; Masayuki Dokiya

1987-01-01

85

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

NASA Astrophysics Data System (ADS)

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 ˜1.7 pct for the gravity die cast LM25 alloy to ˜8.0 pct for the direct squeeze cast LM25 alloy in the T6 heat-treated condition. 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 ˜6.5 pct, compared to that of ˜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.

1999-05-01

86

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

Microsoft Academic Search

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

X. Cao; J. Campbell

2003-01-01

87

Effects of Si and Al concentrations in Fe–Cr alloy on the formation of oxide scales in H 2–H 2O  

Microsoft Academic Search

Effects of silicon and aluminum concentrations in Fe–Cr alloys on the formation of oxide scales were examined in H2–H2O atmosphere for interconnects of solid oxide fuel cells (SOFCs). The morphology and oxide scale growth rates were compared between conventional and modified Fe–Cr alloys (Si and Al concentration reduced). The formed oxide scales were characterized by surface and depth profile analyses.

Teruhisa Horita; Katsuhiko Yamaji; Harumi Yokokawa; Akihiro Toji; Toshihiro Uehara; Kei Ogasawara; Harukuni Kameda; Yoshio Matsuzaki; Satoshi Yamashita

2008-01-01

88

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

PubMed

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

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

2011-09-07

89

Effect of Thermal Exposure, Forming, and Welding on High-Temperature, Dispersion-Strengthened Aluminum Alloy: Al-8Fe-1V-2Si.  

National Technical Information Service (NTIS)

The feasibility of applying conventional hot forming and welding methods to high temperature aluminum alloy, Al-8Fe-1V-2Si (FVS812), for structural applications and the effect of thermal exposure on mechanical properties were determined. FVS812 (AA8009) s...

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

1991-01-01

90

Oxidation of Fe8Cr14Ni-Al-Si-Mn from 700 to 1000°C  

Microsoft Academic Search

This paper reports an investigation into reducing the Cr concentration in commercial-grade stainless steels while maintaining oxidation protection at elevated temperatures. Aluminum and Si were added as partial substitute alloy elements to enhance the reduced operation protection resulting from Cr concentration reduced by approximately 50 pct of that found in stainless steels. The goal of this study was to determine

James C. Rawers; Darrell E. Larsont

1987-01-01

91

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

Microsoft Academic Search

Low-pressure proportional counters (LPPCs) with walls made from the elements C, Mg, Al, Si, Fe and Zr and from the chemical compounds A-150 plastic, AlN, Al2 O3 , SiO2 and ZrO2 were used to measure neutron fluence-to-kerma conversion coefficients at energies up to 66 MeV. The LPPCs served to measure the absorbed dose deposited in the gas of a cavity

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

2000-01-01

92

Preheated shock experiments in the molten CaAl2Si2O8-CaFeSi2O6-CaMgSi2O6 ternary: A test for linear mixing of liquid volumes at high pressure and temperature  

NASA Astrophysics Data System (ADS)

We performed 17 new shock wave experiments on preheated (1673 K) hedenbergite liquid (CaFeSi2O6) and two model basalt liquids (an equimolar binary mix of CaAl2Si2O8 + CaFeSi2O6 and an equimolar ternary mix of CaAl2Si2O8 + CaFeSi2O6 +CaMgSi2O6) in order to determine their equations of state (EOS). Ambient pressure density measurements on these and other Fe-bearing silicate liquids indicate that FeO has a partial molar volume that is highly dependent on composition, which leads to large errors in estimates of the densities of Fe-bearing liquids at ambient pressure based on an ideal mixing of any fixed set of end-member liquids. We formulated a series of mixing tests using the EOS determined in this study to examine whether ideal mixing of volumes might nevertheless suffice to describe the ternary system CaAl2Si2O8-CaFeSi2O6-CaMgSi2O6 at high temperature and pressure. The ideal mixing null hypothesis is rejected; compositional variations in partial molar volume of FeO appear to extend to high pressure. Only densities of Fe-bearing liquid mixtures with oxide mole fraction of FeO less than 0.06 can be adequately approximated using an ideal solution.

Thomas, Claire W.; Asimow, Paul D.

2013-07-01

93

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

NASA Astrophysics Data System (ADS)

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

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

2011-04-01

94

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

PubMed

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

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

2012-07-04

95

Computational Modeling of Uranium Corrosion and the role of Impurities(Fe, Cr, Al, C and Si)  

SciTech Connect

My talk will focus on our recent computational modeling results of uranium corrosion and the impact of impurities on uranium corrosion, which occurs primarily through hydriding Uranium hydriding is one of the most important processes that has received considerable attention over many years. Although significant number of experimental and modeling studies have been carried out concerning thermo chemistry, diffusion kinetics and mechanisms of U-hydriding, very little is known about the electronic structure and electronic features that govern the U-hydriding process. Our modeling efforts focus the electronic feature that controls the activation barrier and thus the rate of hydriding. Our recent efforts have been focused on the role of impurities such as Fe, Cr, Si, C, Al and so on. Moreover the role of impurities and the role of the product UH{sub 3} on hydriding rating have not been fully understood. Condon's diffusion model was found to be in excellent agreement with the experimental reaction rates. From the slopes of the Arrhenius plot the activation energy was calculated as 6.35 kcal/mole. Bloch and Mintz have discussed two models, one, which considers hydrogen diffusion through a protective UH{sub 3} product layer, and the second where hydride growth occurs at the hydride-metal interface. These authors obtained two-dimensional fits of experimental data to the pressure-temperature reactions. Powell et al. have studied U-hydriding in ultrahigh vacuum and obtained the linear rate data over a wide range of temperatures and pressures. They found reversible hydrogen sorption on the UH{sub 3} reaction product from kinetic effects at 21 C. This demonstrates restarting of the hydriding process in the presence of UH{sub 3} reaction product. DeMint and Leckey have shown that Si impurities dramatically accelerate the U-hydriding rates. We report our recent results of relativistic computations that vary from complete active space multi-configuration interaction (CAS-MCSCF) followed by multi-reference configuration interaction (MRSDCI) computations that included up to 60 million configurations for modeling of uranium-hydriding with cluster models will be presented. Our computed potential energy surface for the insertion of a U site into H{sub 2} reveals that pure U site has to surpass a barrier of 20.9 kcal/mole for the U-hydriding. Once the barrier is surpassed a stable product is formed which is 22.4 kcal/mole more stable than the reactants. We have also developed a computational model to study the role of the UH{sub 3} product and other impurities such as Fe, Cr, Si, C, Al, etc., on the uranium hydriding reaction. Our model reveals that the product UH{sub 3} is highly ionic and thus U transfers electron density to the three hydrogens resulting in a U{sup +3} state. U{sup +3} is shown to insert into H{sub 2} spontaneously thus demonstrating the U-site in the product UH{sub 3} binds to H{sub 2} spontaneously forming a complex in which H{sub 2} is separated far enough so as to cause liberation of H atoms in the presence of U. Our computed potential energy surfaces reveal a 21 kcal/mole activation energy barrier for pure U reaction with H{sub 2}. However, the presence of the product UH{sub 3} catalyzes the U-hydriding. We have also modeled the presence of Si impurities for the U-hydriding reaction to show that the activation barrier is lowered by the presence of Si. However carbon impurity does not influence the hydriding process. Our computations reveal an electron donor-acceptor model for the U-hydriding, where H{sub 2} exchanges electronic density from its occupied 1{sigma}{sub g} orbital to the U(6d {sigma}) orbital and back donation from the U(6d {pi}) orbital back to H{sub 2} 1{sigma}{sub u} antibonding orbital. As seen from the figures shown below our recent works show that elemental impurities such as Al do not have impact on hydriding, elements such as Fe and Cr have small impact while the elemental carbon inhibits corrosion through the formation of ionic uranium carbide species.

Balasubramanian, K; Sikehaus, W; Balazs, B; Mclean II, W

2005-10-31

96

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

NASA Astrophysics Data System (ADS)

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

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

2012-08-01

97

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

98

The effects of Cr and Zr addition on the microstructure and mechanical properties of rapidly solidified Al20Si5Fe alloys  

Microsoft Academic Search

The effects of Cr and Zr addition on mechanical properties of Al-20Si-5Fe alloys, manufactured by gas atomization followed by degassing and hot extrusion, were studied by a combination of scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray microanalysis, X-ray diffractometry, tensile testing and wear testing. The microstructure of extruded bars showed a homogeneous distribution of two different sizes of

S. J. Hong; T. S. Kim; W. T. Kim; B. S. Chun

1997-01-01

99

Effect of annealing on the microstructure and mechanical properties of cold rolled Fe–24Mn–3Al–2Si–1Ni–0.06C TWIP steel  

Microsoft Academic Search

Fe–24Mn–3Al–2Si–1Ni–0.06C TWinning Induced Plasticity (TWIP) steel was 42% cold-rolled and isochronally annealed at temperatures between 600 and 850°C. Optical, secondary and transmission electron microscopy found that a majority of as cold-rolled grains contain a large fraction of primary twin densities and a smaller fraction of secondary twins. Partially recrystallised microstructures comprise a mix of recrystallised grains and annealing twins as

Dagoberto B. Santos; Ahmed A. Saleh; Azdiar A. Gazder; Andrew Carman; Dayanna M. Duarte; Érica A. S. Ribeiro; Berenice M. Gonzalez; Elena V. Pereloma

2011-01-01

100

Catalytic cracking of isobutane over HZSM-5, FeHZSM-5 and CrHZSM-5 catalysts with different SiO 2 \\/Al 2 O 3 ratios  

Microsoft Academic Search

Several systems of HZSM-5, FeHZSM-5 and CrHZSM-5 zeolite catalysts with different ratios of SiO2\\/Al2O3 (25,38,50,80, and 150) were prepared and they were characterized by means of X-ray diffraction (XRD), UV–Vis, NH3-TPD and BET techniques. The results indicated that, compared with uncalcined HZSM-5 zeolites, the total acid amounts, acidic\\u000a site density and acidic strength of HZSM-5, FeHZSM-5 and CrHZSM-5 zeolite catalysts

Jiangyin Lu; Zhen Zhao; Chunming Xu; Aijun Duan; Xiaoning Wang; Pu Zhang

2008-01-01

101

Thermostability and magnetic properties of Sm2(Fe,M)17(C,N)y (M=Ga, Al and Si)  

NASA Astrophysics Data System (ADS)

The effect of heat treatments on the interstitial nitrides and carbides prepared from Sm2(Fe,M)17 and Sm2Fe15Ga2C2 by gas-solid reaction (GSR) was investigated in order to understand more about the influence of the substitutions M=Ga, Al and Si on the thermostability of these compounds. X-ray diffraction measurements of the heat-treated samples have shown that all of these substitutions improve the thermostability of the Th2Zn17-type interstitial structure, with Al having the smallest influence and Si and Ga having a stronger influence on the thermostability. Contrary to the nitrides, the carbides prepared by GSR can be significantly stabilized with an increasing amount of the stabilizing elements. Already for a small amount of the substitution element, e.g. Sm2Fe16.5Ga0.5, the 2 : 17-type interstitial phase was stabilized up to 750 degC. Carburization at temperatures above 500 degC was possible for the stabilized 2 : 17 compounds making possible much shorter carburization times for high C contents. Investigations on Sm2Fe15Ga2Cy have revealed a dependence of the thermostability on the amount of absorbed C and on the processing route for the interstitial modification by GSR. A coercivity ?0JHc up to about 2.8 T was obtained for Sm2Fe15Ga2C2N showing the magnetic potential of these modified compounds.

Handstein, A.; Kubis, M.; Cao, L.; Gebel, B.; Müller, K.-H.

1999-02-01

102

Shear modulus, heat capacity, viscosity and structural relaxation time of Na2O-Al2O3-SiO2 and Na2O-Fe2O3-Al2O3-SiO2 melts  

NASA Astrophysics Data System (ADS)

The configurational heat capacity, shear modulus and shear viscosity of a series of Na2O-Fe2O3-Al2O3-SiO2 melts have been determined as a function of composition. A change in composition dependence of each of the physical properties is observed as Na2O/(Na2O + Al2O3) is decreased, and the peralkaline melts become peraluminous and a new charge-balanced Al-structure appears in the melts. Of special interest are the frequency dependent (1 mHz-1 Hz) measurements of the shear modulus. These forced oscillation measurements determine the lifetimes of Si-O bonds and Na-O bonds in the melt. The lifetime of the Al-O bonds could not, however, be resolved from the mechanical spectrum. Therefore, it appears that the lifetime of Al-O bonds in these melts is similar to that of Si-O bonds with the Al-O relaxation peak being subsumed by the Si-O relaxation peak. The appearance of a new Al-structure in the peraluminous melts also cannot be resolved from the mechanical spectra, although a change in elastic shear modulus is determined as a function of composition. The structural shear-relaxation time of some of these melts is not that which is predicted by the Maxwell equation, but up to 1.5 orders of magnitude faster. Although the configurational heat capacity, density and shear modulus of the melts show a change in trend as a function of composition at the boundary between peralkaline and peraluminous, the deviation in relaxation time from the Maxwell equation occurs in the peralkaline regime. The measured relaxation times for both the very peralkaline melts and the peraluminous melts are identical with the calculated Maxwell relaxation time. As the Maxwell equation was created to describe the timescale of flow of a mono-structure material, a deviation from the prediction would indicate that the structure of the melt is too complex to be described by this simple flow equation. One possibility is that Al-rich channels form and then disappear with decreasing Si/Al, and that the flow is dominated by the lifetime of Si-O bonds in the Al-poor peralkaline melts, and by the lifetime of Al-O bonds in the relatively Si-poor peralkaline and peraluminous melts with a complex flow mechanism occurring in the mid-compositions. This anomalous deviation from the calculated relaxation time appears to be independent of the change in structure expected to occur at the peralkaline/peraluminous boundary due to the lack of charge-balancing cations for the Al-tetrahedra.

Falenty, Katarzyna; Webb, Sharon L.

2010-10-01

103

Synthesis and equation of state of perovskite with almandine composition (Fe3Al2Si3O12) to 149 GPa  

NASA Astrophysics Data System (ADS)

Fe and Al are important elements in Earth’s mantle and they may be concentrated in lower mantle chemical heterogeneities associated with subducting slabs, mantle plumes, or core-mantle reaction products. We studied an almandine garnet composition to explore the stability and physical properties of phases in this system at high P-T. Previous multi-anvil and diamond cell studies (Akaogi et al. 1998, Kesson et al. 1995) reported that end-member almandine dissociated to oxides, but no previous work has examined almandine in situ at lower mantle pressures and temperatures. Synthetic Fe3Al2Si3O12 glass powder was mixed with 10-15 wt% Au as pressure calibrant and loaded with NaCl or Ne as thermal insulator and pressure medium. X-ray diffraction experiments were performed in the laser-heated diamond anvil cell at the GSECARS (13-ID-D) and HPCAT (16-ID-B) sectors of the Advanced Photon Source. Heating to 2500K at 43 GPa produced a mixture of orthorhombic perovskite, stishovite, and wüstite. However, by heating at 80-90 GPa, we synthesized single-phase orthorhombic GdFeO3-type perovskite, (Fe0.75Al0.25)(Si0.75Al0.25)O3. We examined this perovskite phase under both compression and decompression from 5-149 GPa as calibrated by the Au pressure scale of Fei et al. (2007). Perovskite volume data were fit to a Birch-Murnaghan equation of state with V0 of 170.3 (0.9) Å3, K0 of 257 (13) GPa and K0’ of 3.95 (0.14). This represents a significant volume increase, but the bulk modulus is comparable to that of MgSiO3 perovskite (Lundin et al. 2008, Nishio-Hamane et al. 2008). At 100 GPa, we find a 4.5% volume increase and 1.6% bulk modulus decrease for our sample compared with MgSiO3 perovskite at this pressure.

Dorfman, S. M.; Shieh, S. R.; Meng, Y.; Prakapenka, V.; Duffy, T. S.

2009-12-01

104

On the Formation of non-metallic inclusions in fe-50 pct Ni type alloys by deoxidation with Mn, Si, and Al  

NASA Astrophysics Data System (ADS)

This investigation deals with deoxidation experiments in 30 g lab melts of Fe-50 pct Ni alloys. After deoxidation with different amounts of Mn, Si and Al and their combinations the samples were quenched into water at different times. Metallographic studies comprising light microscopy, scanning electron microscopy, electron microprobe and image analysis were performed. Classical nucleation theory was used for computation of the different supersaturation with oxygen or the deoxidant necessary for homogeneous nucleation. The different deoxidation reactions and the transformation of inclusions due to diffusion of oxygen, or the deoxidant, from or into the inclusions was treated for the different cases of deoxidation. Most deoxidation reactions take place within some seconds. The experimental results were to be used to estimate the pertinent interfacial tensions between the oxides and the melt and the values obtained for the different oxides seemed to be reasonable. The diffusional computations were successfully used for predicting the different transformations taking place. For example, in deoxidation with 0.03 pct Si the oxygen solubility is controlled by the equilibrium with liquid FeO ? SiO2. The time taken to reach equilibrium is determined by the number of inclusions and the particle size. In deoxidation with 0.1 pct Si or more, the equilibrium is controlled by SiO2 inclusions and the time taken to reach equilibrium, less than 1 s, is much shorter compared to the samples with 0.03 pct Si. The deoxidation reactions with aluminum were treated in the same way, and it was shown that the number of particles determined the time elapsing before equilibrium with respect to the formation of FeOAl2O3 or A12O3. It was further shown that transformation of primary liquid FeOAl2O3 with high contents of FeO into solid FeOAl2O3 was expected to occur within one second. However, the experiments showed that it took somewhat longer, due to formation of solid FeOAl2O3 around the liquid FeOAl2O3 inclusions, thereby preventing the diffusion of aluminum into the particles.

Fredriksson, Hasse; Hammar, Örjan

1980-09-01

105

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

SciTech Connect

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

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

2010-03-15

106

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

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

107

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

NASA Astrophysics Data System (ADS)

The phase equilibria and the liquidus temperatures in the system ZnO-“FeO”-Al2O3-CaO-SiO2 have been determined experimentally in equilibrium with metallic iron. Specifically, the effects of Al2O3 concentrations in Imperial Smelting Furnace slags are identified, and the results are presented in the form of pseudo-ternary sections ZnO-“FeO”-(Al2O3 + CaO + SiO2) in which CaO/SiO2 = 0.93 and (CaO + SiO2)/Al2O3 = 5.0 and 3.5, respectively. It was found that, in the presence of Al2O3, the spinel phase is formed, the spinel primary phase field expands, and the wustite and melilite primary phase fields are reduced in size with an increasing Al2O3 concentration. The implications of the findings to industrial practice are discussed.

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

2010-04-01

108

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

109

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

PubMed

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

Koshy, V J; Garg, V N

1987-11-01

110

Spin Dynamics of B2 and L21-Ordered Co2FeAl0.5Si0.5 Heusler Alloy Films  

NASA Astrophysics Data System (ADS)

Measurements of magnetization precession are performed for L21 and B2-ordered Co2FeAl0.5Si0.5 full Heusler alloy films using the time-resolved magneto-optical Kerr effect technique in the out-of-plan configuration. Dependence of the precession frequency on the external magnetic field can be fitted by the Landau-Lifshitz-Gilbert equation. The chirp parameters are close to each other for the L21 and B2 structures, and decrease with the external magnetic field increasing. The relaxation rate of the B2-ordered film is smaller than that of the L21 one.

Yi, Ming; Chen, Zhi-Feng; Chen, Da-Xin; Sukegawa, Hiroaki; Inomata, Koichiro; Lai, Tian-Shu; Zhou, Shi-Ming

2011-06-01

111

Physicochemical modeling and experimental study of the interaction in the Si-Al-Ca-Mg-Fe-Na-K-V-Cl-H-O system  

Microsoft Academic Search

Physicochemical modeling is used to study the interaction in the SiO2-Al2O3-CaO-MgO-Fe3O4-Na2O-V2O3(V2O5)-HCl-H2O system. The regions of formation of calcium (magnesium, iron) vanadates and various vanadium oxides are determined. The\\u000a conditions for the most complete extraction of vanadium into hydrochloric acid solutions are estimated. The data obtained\\u000a can be used to develop the procedure a the extraction of vanadium during the leaching

N. V. Kochetkova; N. P. Dergacheva; S. V. Fomichev; V. A. Krenev

2009-01-01

112

The effect of Sr and Fe additions on the microstructure and mechanical properties of a direct squeeze cast Al7Si0.3Mg alloy  

Microsoft Academic Search

This article describes the results of an investigation into the microstructure and mechanical properties of a gravity die\\u000a cast and direct squeeze cast LM25 alloy (Al-7Si-0.3Mg-0.3Fe). The direct squeeze cast LM25 alloy has superior mechanical properties\\u000a compared to the gravity die cast LM25 alloy, especially with regard to ductility, which is increased from ?1.7 pct for the\\u000a gravity die cast

J. X. Dong; P. A. Karnezis; G. Durrant; B. Cantor

1999-01-01

113

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

114

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

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

115

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

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

116

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

NASA Astrophysics Data System (ADS)

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

Zimova, M.; Webb, S.

2004-12-01

117

Aluminum and silicon diffusion in Fe-Cr-Al alloys  

Microsoft Academic Search

Foils of Fe-Cr-Al alloys containing about 20 wt% Cr, 5 wt% Al and additions of Si and reactive elements like Ce, La, Y, Hf, Zr or Ti are widely used as a substrate in metal-supported automotive catalytic converters. In the present paper the authors report on measurements of Al and Si diffusion in Fe-Cr-Al alloys. Due to a lack of

A. Heesemann; E. Schmidtke; F. Faupel; A. Kolb-Telieps; J. Kloewer

1999-01-01

118

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

NASA Astrophysics Data System (ADS)

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

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

2011-03-01

119

Ascast morphology of iron-intermetallics in Al–Si foundry alloys  

Microsoft Academic Search

The “as-cast” three-dimensional morphologies of ?-Al15(Fe,Mn)3Si2 and ?-Al5FeSi intermetallics were investigated by serial sectioning. Large ?-Al5FeSi intermetallics were observed to grow around pre-existing dendrite arms. The ?-Al15(Fe,Mn)3Si2 intermetallic particle was observed to have a central polyhedral particle and an external highly convoluted three-dimensional structure.

Cameron M. Dinnis; John A. Taylor; Arne K. Dahle

2005-01-01

120

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

NASA Astrophysics Data System (ADS)

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

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

1983-03-01

121

The Perovskite to Post-Perovskite phase transition in Al-bearing (Mg,Fe)SiO3: A XANES in-situ analysis at the Fe K-edge  

NASA Astrophysics Data System (ADS)

Phase transition from perovskite (Pv) to Post-Pv (PPv) phase in MgSiO3 has been studied by many groups since its discovery in 2004 (1,2) and the different studies find similar transition pressures. The effect of Al and Fe on the phase transition remains more controversial. The most recent studies suggest an increase of the transition pressure with increasing Fe-content (3,4), but other experimental work (5) as well as ab-initio calculations (6) show the opposite effect. The effect of Al was reported to increase slightly the pressure transition to the CaIrO3 form (4,7), but its influence on the Fe3+ content in the PPv phase has not been documented yet. By means of in situ study of the Fe K-edge fine structures (XANES), we investigated the phase relations between Pv and PPv phases for three different Al-(Mg,Fe)SiO3 compositions. For this, we synthesized various Pv and PPv mixtures using laser-heated diamond anvil cell (DAC) for pressures between 60 and 170 GPa. The sample's mineralogy, i.e. the Pv and PPv phase fractions, was determined using in-situ X-ray diffraction at the ID27 beamline of the ESRF (8,9). Then, we probed the Fe speciation, i.e. the Fe concentration in each phases, in-situ in the DAC using the µ-XANES mapping technique available at the ID24 beamline (10,11). Both pieces of information were combined to retrieve the Fe partitioning coefficient between the two high-pressure phases. Our results show that Fe partitions strongly into the PPv phase, which implies a very large binary loop of coexistence of the two phases. Thus, at the core-mantle boundary pressure (135 GPa), the Pv and PPv phase always coexist for all geophysically relevant Al-(Mg,Fe)SiO3 compositions, and the Fe-content in the PPv-phase is only a few percent. References: 1. M. Murakami, K. Hirose, K. Kawamura, N. Sata, Y. Ohishi, Science 304, 855 (2004). 2. A. R. Oganov, S. Ono, Nature 430, 445 (2004). 3. S. Tateno, K. Hirose, N. Sata, Y. Ohishi, Phys. Earth Planet. Inter. 160, 319 (2007). 4. D. Nishio-Hamane, T. Nagai, K. Fujino, Y. Seto, N. Takafuji, Geophys. Res. Lett. 32, L16306 (2005). 5. W. L. Mao et al., PNAS 101, 15867 (2004). 6. J. P. Brodholt, A. R. Oganov, personal communication. 7. S. Ono, A. R. Oganov, T. Koyama, H. Shimizu, Earth Planet. Sci. 246, 326 (2006). 8. N. Guignot, D. Andrault, G. Morard, M. Mezouar, Earth Planet. Sci. 256, 162 (2007). 9. E. Schultz et al., High Press. Res. 25, 71 (2005). 10. S. Pascarelli, O. Mathon, M. Muñoz, T. Mairs, J. Susini, J. Synch. Rad. 13, 351 (2006). 11. M. Muñoz et al., Geochemistry Geophysics Geosystems 7, Q11020 (2006).

Andrault, D.; Munoz, M.; Bolfan-Casanova, N.; Guignot, N.; Perrillat, J.; Aquilanti, G.; Pascarelli, S.

2008-12-01

122

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

NASA Astrophysics Data System (ADS)

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

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

2011-04-01

123

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

124

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

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

125

Enhancement of anomalous Hall effect in Si/Fe multilayers  

NASA Astrophysics Data System (ADS)

Anomalous Hall effect (AHE) studies were performed at 300 K on Si/Fe multilayers prepared by dc magnetron sputtering. About 60 times enhancement in the saturation Hall resistance and 80 times enhancement in anomalous Hall coefficient were obtained in [Si(50 Å)/Fe(tFe)]20 multilayers when decreasing the Fe layer thickness from 100 to 20 Å. The largest anomalous Hall coefficient (Rs) of 1.4 × 10-7 ? m T-1 was found for tFe = 20 Å, which is about three orders of magnitude larger than that of pure Fe and Fe/Cr, Al/Fe, Cu/Fe, SiO2/FePt/SiO2 multilayers. The ordinary Hall coefficient R0 was about two orders of magnitude larger than that of pure Fe. The Rs was found to vary with the longitudinal electronic resistivity, ? as Rs??2.2, indicating the role of interfaces for the enhancement of the AHE in the multilayers. An increase of Hall sensitivity from 9 m? T-1 to 1.2 ? T-1 was observed on decreasing tFe from 100 to 10 Å. The high Hall sensitivity obtained was about three orders of magnitude larger than that of Al/Fe and Cu/Fe multilayers, showing it as an emerging candidate for Hall element for potential applications.

Das, S. S.; Senthil Kumar, M.

2013-09-01

126

Effects of Annealing on the Microstructure and Properties of 6FeNiCoCrAlTiSi High-Entropy Alloy Coating Prepared by Laser Cladding  

NASA Astrophysics Data System (ADS)

The content of each constituent element in the newly developed high-entropy alloys is always restricted in equimolar or near-equimolar ratios to avoid the formation of complex brittle phases during the solidification process. In this article, a high-entropy alloy coating of 6FeNiCoCrAlTiSi has been prepared by laser cladding and subsequently annealed at 500, 750, 1000, and 1150 °C for 5 h. Surprisingly, the coating has a simple BCC solid solution phase with high microhardness, good resistance to softening, and high electrical resistivity properties. After annealing <750 °C, the coating shows high thermal stability, the electrical resistivity decreases slightly and the microhardness almost remains unchanged. After annealing above 750 °C, the microhardness of the coating slowly decreases with the decomposition of the supersaturated BCC solid solution.

Zhang, Hui; Pan, Ye; He, Yizhu

2011-09-01

127

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

128

Magnetism of MnSi and FeSi.  

National Technical Information Service (NTIS)

A review is presented of neutron scattering studies of isostructural MnSi and FeSi. MnSi exhibits typical characteristics of an itinerant electron ferromagnet. On the other hand, FeSi is a unique example of temperature-induced magnetism through a narrow b...

G. Shirane

1987-01-01

129

Magnetism of MnSi and FeSi  

SciTech Connect

A review is presented of neutron scattering studies of isostructural MnSi and FeSi. MnSi exhibits typical characteristics of an itinerant electron ferromagnet. On the other hand, FeSi is a unique example of temperature-induced magnetism through a narrow band gap.

Shirane, G.

1987-05-01

130

Electrical peculiarities in Al\\/Si\\/Ge\\/…\\/Ge\\/Si and Al\\/SiGe\\/Si structures  

Microsoft Academic Search

The current–voltage (I–V) and capacitance–voltage (C–V) behaviour of different Si\\/Ge multilayers and SiGe single layers prepared on p-type Si substrates by magnetron sputtering and annealing, has been studied in the temperature range of 80–320K by using Al Schottky contacts as test structures. Although a significant influence of the microstructure of the Si\\/Ge multilayers and SiGe layers was obtained on the

Zs. J. Horváth; K. Jarrendähl; M. Ádám; I. Szabó; Vo Van Tuyen; Zs. Czigány

2002-01-01

131

Effect of Fe 2O 3 concentration on the structure of the SiO 2–Na 2O–Al 2O 3–B 2O 3 glass system  

Microsoft Academic Search

The structural properties of the glass matrix 40SiO2·30Na2O·1Al2O3·(29?x)B2O3·xFe2O3 (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 Fe3O4 crystal formation for Fe2O3 concentrations of 29.0mol%. DTA showed that glass transition and crystallization temperatures changed as a function of Fe2O3 concentration and that these alterations were related to structural change

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

2011-01-01

132

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

NASA Astrophysics Data System (ADS)

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

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

2010-04-01

133

Pressure effect on the electronic structure of iron in Mg,Fe Si, Al O{sub 3} perovskite : a combined synchrotron Mossbauer and x-ray emission spectroscopy study up to 100 GPa.  

SciTech Connect

We investigated the valence state and spin state of iron in an Al-bearing ferromagnesian silicate perovskite sample with the composition (Mg0.88Fe0.09)(Si0.94Al0.10)O3 between 1 bar and 100 GPa and at 300 K, using diamond cells and synchrotron M{umlt o}ssbauer spectroscopy techniques. At pressures below 12 GPa, our Mossbauer spectra can be sufficiently fitted by a ''two-doublet'' model, which assumes one ferrous Fe2+-like site and one ferric Fe3+-like site with distinct hyperfine parameters. The simplest interpretation that is consistent with both the M{umlt o}ssbauer data and previous X-ray emission data on the same sample is that the Fe2+-like site is high-spin Fe2+, and the Fe3+-like site is high-spin Fe3+. At 12 GPa and higher pressures, a ''three-doublet'' model is necessary and sufficient to fit the Mossbauer spectra. This model assumes two Fe2+-like sites and one Fe3+-like site distinguished by their hyperfine parameters. Between 12 and 20 GPa, the fraction of the Fe3+-like site, Fe3+/{Sigma}Fe, changes abruptly from about 50 to 70%, possibly due to a spin crossover in six-coordinate Fe2+. At pressures above 20 GPa, the fractions of all three sites remain unchanged to the highest pressure, indicating a fixed valence state of iron within this pressure range. From 20 to 100 GPa, the isomer shift between the Fe3+-like and Fe2+-like sites increases slightly, while the values and widths of the quadruple splitting of all three sites remain essentially constant. In conjunction with the previous X-ray emission data, the Mossbauer data suggest that Fe2+ alone, or concurrently with Fe3+, undergoes pressure-induced spin crossover between 20 and 100 GPa.

Li, J.; Sturhahn, W.; Jackson, J.M.; Struzhkin, V.V.; Lin, J.F.; Zhao, J.; Mao, H.K.; Shen, G.; X-Ray Science Division; Univ. of Illinois; Carnegie Inst. of Washington; LLNL

2006-11-01

134

Structure and properties of nitrided body-centered cubic Fe-base alloys alloyed with Al, Si, Ge, or Sn  

Microsoft Academic Search

The intercrystalline brittleness of bcc Fe-base alloys may be eliminated or decreased by additional alloying with surface-active elements, tin or germanium, adsorbed on the interphase and intergranular boundaries, which prevents the formation of brittle nitride phases.

V. A. Fedchun; N. V. Silina

1988-01-01

135

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

Microsoft Academic Search

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

Francesco S. Interesse; Francesco Lamparelli; Vincenzo Alloggio

1984-01-01

136

Transition Metal Ions and Heterogeneous Nucleation in Glass. Technical Report No. 3. Magnetic and Morphological Study of Fe2O3 Catalysed Crystallisation in a CaO-MgO-Al2O3-SiO2 Glass.  

National Technical Information Service (NTIS)

A CaO-MgO-Al2O3-SiO2 glass containing the nucleating catalyst Fe2O3 was subject to a series of nucleating heat treatments. Magnetic susceptibility measurements from room temperature to 50mK have been made on these samples, and the paramagnetic resonance d...

D. W. Moon J. C. Williams R. K. MacCrone

1975-01-01

137

Creep Behavior of Al-Rich Fe-Al Intermetallics.  

National Technical Information Service (NTIS)

The compression creep behavior of two dual-phase intermetallic alloys (FeAl2-Fe2Al5 and FeAl3-Fe2Al5) was investigated over the temperature range 600-1000 deg C. A normal primary creep stage, stress exponent between 4 and 5, and normal creep transient aft...

Y. L. Jeng E. J. Lavernia R. M. Hayes J. Wolfenstine

1995-01-01

138

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); Kim, S.J. [Korea Inst. of Machinery and Materials, Changwon (Korea, Republic of)

1998-10-05

139

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

140

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

Microsoft Academic Search

A high-temperature solution calorimetric method suitable for thermochemical studies of anhydrous minerals containing Fe 2+ ions has been developed. The method is based on an oxide melt solvent with 52 wt% LiBO 2 and 48 wt% NaBO 2 maintained at a temperature of 750°C. In a first application of this method the enthalpies of solution of synthetic almandine, fayalite, a

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

1983-01-01

141

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

Microsoft Academic Search

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

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

2006-01-01

142

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); Kaprzyk, S. [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)]|[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)

1999-11-01

143

Surface segregation in FeSi alloys  

NASA Astrophysics Data System (ADS)

The surface segregation of a Fe94Si6 and Fe76Si24 alloys was studied using high resolution photoemission spectroscopy with synchrotron radiation at 150 166 eV photon beam energy. During Ar+ ion sputtering and following heat treatment, a SiO2 layer and segregation of Si atoms in three clearly resolved phases occurred. This indicates formation of silicides, mainly Fe3Si and cubic FeSi superstructures. The photoemission measurements were complemented by 57Fe Mössbauer spectroscopy in different modes which gave information about deeper surface layers (approximately 10 30 000 nm) of the samples. The results derived from the Mössbauer spectra support the conclusions concerning phase composition of the surface deduced from photoemission spectroscopy.

Vondrá?ek, M.; Dudr, V.; Tsud, N.; Lej?ek, P.; Cháb, V.; Prince, K. C.; Matolín, V.; Schneeweiss, O.

2006-09-01

144

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

NASA Astrophysics Data System (ADS)

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

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

1994-11-01

145

Multilayer FeBSi\\/Si\\/FeBSi films - FMR experiment  

Microsoft Academic Search

Multilayer thin films of metallic glasses of FeBSi\\/Si\\/FeBSi alloys have been investigated by means of the ferromagnetic resonance technique. Here we measure the resonance at the x-band and in a magnetic field rotating from perpendicular orientation to the parallel case.FeBSi layers were from L=200 to 1500 Å thick. The thickness t of the intermediate Si film varied in the range

L. J. Maksymowicz; A. Z. Maksymowicz; H. Jankowski

1988-01-01

146

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

USGS Publications Warehouse

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

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

1977-01-01

147

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

148

Diffusion in ordered Fe-Si alloys  

Microsoft Academic Search

The measurement of the diffusional Mössbauer line broadening in single crystalline samples at high temperatures provides microscopic information about atomic jumps. We can separate jumps of iron atoms between the various sublattices of Fe-Si intermetallic alloys (D03 structure) and measure their frequencies. The diffusion of iron in Fe-Si samples with Fe concentrations between 75 and 82 at% shows a drastic

B. Sepiol; G. Vogl

1995-01-01

149

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

150

Effect of alloying elements and degassing pressure on the structure and mechanical properties of rapidly solidified Al–20Si–5Fe–2X (X=Cr, Zr, or Ni) alloys  

Microsoft Academic Search

Rapidly solidified Al–20Si–5Fe–2X (X=Cr, Zr, or Ni) alloys produced by gas atomization were degassed under different vacuum levels before consolidating them by hot extrusion. The microstructure and mechanical properties of the as-solidified and extruded alloys were evaluated. It was shown that the addition of a quaternary element resulted in the formation of very fine particles that contributed to the improved

Taek-Soo Kim; C. Suryanarayana; Byong-Sun Chun

2000-01-01

151

Constitution of the Moon: 1. Assessment of thermodynamic properties and reliability of phase relation calculations in the FeO-MgO-Al2O3SiO2 system  

Microsoft Academic Search

The thermodynamic functions of minerals in the FeO-MgO-Al2O3-SiO2 (FMAS) system have been assessed using phase equilibria, equations of state and calorimetric data. Phase equilibria in this system have been calculated using ideal, symmetric and asymmetric models of solid solution for minerals to obtain KD of exchange reactions consistent with experimental data. A symmetric model for olivine (Wol = 10 800

O. B. Fabrichnaya; O. L. Kuskov

1994-01-01

152

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

NASA Astrophysics Data System (ADS)

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.

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

2008-04-01

153

Transition Metal Ions and Heterogeneous Nucleation in Glass. Technical Report No. 2. A Magnetic Study of the Catalysed Crystallisation of a CaO-MgO-Al2O3-SiO2 Glass Using Fe2O3.  

National Technical Information Service (NTIS)

Magnetization measurements have been made on (mole %) 28.9 CaO14.3 MgO-11.4 Al2O3-40.4 SiO2 glass containing 5 mole % Fe2O3 from 300 K to 50 mK. Electron paramagnetic resonance measurements were also made on these specimens at 300K. A qualitative elucidat...

D. W. Moon J. C. Williams R. K. MacCrone K. J. Kim

1975-01-01

154

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

155

Extreme Ultraviolet Photoemission of MnSi, FeSi and CoSi  

Microsoft Academic Search

The valence band photoemission has been observed on MnSi, FeSi and CoSi over the excitation energy range from 40 to 130 eV. In MnSi, the spectral profile is consistent with the reported energy band calculation. The width of the main band decreases in the order of MnSi, FeSi and CoSi, indicating that the 3d electrons tend to localize more as

Akito Kakizaki; Hidenao Sugawara; Ichiro Nagakura; Yoshikazu Ishikawa; Takemi Komatsubara; Takehiko Ishii

1982-01-01

156

Creep resistance in a new alloy based on Fe[sub 3]Al. [Fe-28Al-5Cr-1. 0Nb-1. 33Ti-1. 0Si-3. 13B-0. 03C-0. 01Zr  

SciTech Connect

Iron aluminide alloys based on the composition Fe[sub 3]Al are receiving considerable attention as structural materials for applications at high temperatures in view of their excellent resistance to oxidation and corrosion as well as reasonable mechanical properties. Recently, problems associated with poor ductility at room temperature have been alleviated by small additions of Cr and by microstructure control, as well by as the realization that the low ductility is, in part, extrinsic behavior due to environmental attack. These materials suffer also from a loss of their good strength at temperatures above about 600 C, and recent attention has led also to the development of creep resistant alloys. The present report considers a new alloy developed for improved creep resistance which shows also good oxidation and erosion resistance. Effort has been devoted to an examination of the dislocation structures that characterize deformation, both cold and hot, during fast tensile straining as well as during creep testing.

Morris, D.G. (Univ. of Neuchatel (Switzerland). Institute of Structural Metallurgy); Nazmy, M.; Noseda, C. (ABB Power Generation Ltd., Baden (Switzerland))

1994-07-15

157

Effect of thermomechanical treatment on the properties of Fe11Al and Fe14Al alloys  

Microsoft Academic Search

Fe-Al alloys have the potential to be relatively inexpensive soft magnetic materials if their formability could be improved. An investigation has been made on the effect of thermomechanical treatment on the properties of Fe-11 wt%Al and Fe-14 wt%Al alloys (designated Fe-11Al and Fe-14Al respectively). For the former the room temperature mechanical properties were found to be determined principally by the

Syahril; R. D. Rawlings

2002-01-01

158

Influence of low temperature working on microstructure and mechanical properties of AI7Si(Fe) alloys  

Microsoft Academic Search

Changes in the microstructure and mechanical properties of Al-7Si-(Fe) alloys by low temperature working have been investigated.\\u000a The size and shape of eutectic Si and intermetallic AlSiFe compound were controlled by the low temperature working process.\\u000a This process consisted of repeated cold working at 77 K and recovery treatment at 793 K. By applying this process to the Al-7Si-1Fe\\u000a alloy,

Cha-Yong Lim; Osa mu Umezawa; Kotobu Nagai

1998-01-01

159

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

NASA Astrophysics Data System (ADS)

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

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

2013-07-01

160

High-temperature mass spectrometric study of the vaporization processes in the system CaO-MgO-Al2O3-Cr2O3-FeO-SiO2.  

PubMed

Knudsen effusion mass spectrometry was used to study vaporization processes and thermodynamic properties of twenty samples of chromium-containing slags in the CaO-MgO-Al2O3-Cr2O3-FeO-SiO2 system in the temperature range 1850-2750 K. Tungsten cells were used and Cr2O3 solid was used as a reference material. The system was calibrated using liquid gold. As FeO was the first emanating vapor species, monitoring of the chromium-containing species could be carried out only after the complete vaporization of FeO. This, however, was found to have very little impact on the concentration of the slags investigated. During the measurements, the ion current intensities of CrO+ and CrO2+ species in the mass spectra of the vapor over the CaO-MgO-Al2O3-Cr2O3-FeO-SiO2 samples were monitored and compared with those corresponding to solid Cr2O3. Data on the partial pressures of vapor species as well as the activities of Cr2O3 as a function of temperature were obtained. The results are expected to be valuable in the optimization of slag composition in high alloy steelmaking processes. PMID:19530146

Wang, L J; Stolyarova, V L; Lopatin, S I; Seetharaman, S

2009-07-01

161

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

SciTech Connect

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

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

2009-02-15

162

Microstructure of hot dip coated Fe–Si steels  

Microsoft Academic Search

Hot dipping is a coating technique pre-eminently used in industry to galvanize machine parts or steel sheets for constructional applications. However, other hot dipping applications have been developed in order to have a positive effect on specific material properties. For instance, in Fe–Si electrical steels, a Si\\/Al rich top layer is applied and followed by diffusion annealing to increase the

I. Infante Danzo; K. Verbeken; Y. Houbaert

163

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

164

Relative ion yields for SIMS analysis of trace elements in metallic Fe, Fe-Si alloy, and FeSi  

Microsoft Academic Search

The ion yields of a number of siderophile trace elements dissolved in Fe, Fe-Si alloy, and FeSi have been measured using secondary ion mass spectroscopy. Ion yields are a complex function of ionisation potential, energy distribution, oxide bond strength, and matrix material. The exact nature of secondary ion yield is poorly understood, yet there are regular trends throughout the ion

Matt R. Kilburn; Richard W. Hinton

2001-01-01

165

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

National Technical Information Service (NTIS)

The crack growth resistance and yield strength of the B2 iron aluminides Fe-40Al, Fe-45Al, are Fe-10Ni-40Al (at. %) have been investigated at room temperature laboratory air. After fast cooling from 1273 K, Fe-45Al and Fe-10Ni-40Al are much stronger than ...

J. H. Schneibel P. J. Maziasz

1994-01-01

166

Epitaxial Growth of (100)-Oriented ?-FeSi2 Thin Films on Insulating Substrates  

NASA Astrophysics Data System (ADS)

Epitaxial ?-FeSi2 thin films were grown on insulating substrates by rf magnetron sputtering. (100)-Oriented ?-FeSi2 films were epitaxially grown on (100) yttria-stabilized zirconia (YSZ) and (001) Al2O3 substrates. The epitaxial relationship of the ?-FeSi2 film with the (100) YSZ substrate was the same as that with the (100) Si substrate. On the (001) Al2O3 substrate, the epitxial film had a threefold symmetry domain structure, which has not been reported on a film grown on a Si substrate. Epitaxial growth of (100)-oriented ?-FeSi2 film was affected by not only lattice mismatch but also atomic or ionic matching between ?-FeSi2 and substrate and requires substrates consisting of either a single element or only cations.

Akiyama, Kensuke; Kaneko, Satoru; Kimura, Takeshi; Funakubo, Hiroshi

2005-04-01

167

Vibrational dynamics of Fe in amorphous Fe-Sc and Fe-Al alloy thin films  

NASA Astrophysics Data System (ADS)

The atomic vibrational dynamics of 57Fe in 800-Å thick amorphous (a-) 57Fe0.25Sc0.75, a-57Fe0.67Sc0.33 and a-57Fe0.14Al0.86 alloy thin films has been investigated at room temperature by nuclear resonant inelastic X-ray scattering (NRIXS) of synchrotron radiation. The amorphous phase has been successfully stabilized by codeposition of Fe and Sc or Al in ultrahigh vacuum onto substrates held at -140 °C during deposition. The amorphous structure of the samples was confirmed by X-ray diffraction and conversion electron Mössbauer spectroscopy. The 57Fe-projected partial vibrational density of states, geE), has been obtained from the measured NRIXS vibrational excitation probability, together with thermodynamic quantities such as the probability of recoilless absorption (f-factor), the average kinetic energy per Fe atom, the average force constant, and the vibrational entropy per Fe atom. A plot of the reduced density of states, g(E)/E2, versus excitation energy E proves the existence of non-Debye-like vibrational modes (boson peak) with a peak energy, E bp , in the range of 3-7 meV. Both, the boson peak height Hbp and E bp were found to depend on the composition. Above the boson peak, g(E)/E2 exhibits an exponential decrease. Our results demonstrates that the features of the boson peak depend on the amount and type of element M (M = Al, Si, Mg, Sc).

Sahoo, B.; Keune, W.; Schuster, E.; Sturhahn, W.; Zhao, J.; Toellner, T. S.; Alp, E. E.

168

A Thermodynamic Description of the Al-Cr-Si System  

Microsoft Academic Search

The Al-Cr-Si system was critically assessed using the CALPHAD technique. The solution phases (liquid, bcc, fcc, and diamond)\\u000a were described by a substitutional solution model. The compounds CrSi2, Cr3Si, AlCr2, ?Al8Cr5, ?Al8Cr5, Al4Cr, and Al11Cr2 in the Al-Cr-Si system were treated with sublattice models (Cr, Si)(Al, Cr, Si)2, (Cr, Si)3(Al, Cr, Si), (Al, Cr, Si)(Al, Cr)2, ?(Al, Cr, Si)8(Al, Cr,

Yu Liang; Cuiping Guo; Changrong Li; Zhenmin Du

2009-01-01

169

Magnetic properties of FeAl2 and Fe2Al5  

NASA Astrophysics Data System (ADS)

We have investigated magnetic properties of the FeAl2 and Fe2Al5 intermetallic compounds. By measuring the zero-field-cooled and field-cooled static (dc) magnetic susceptibilities in low and high magnetic fields, the frequency-dependent (ac) susceptibility, the magnetization versus the magnetic field, and the thermoremanent magnetization time decay, we found that the magnetic structures of FeAl2 and Fe2Al5 are richer than those published so far in the literature. FeAl2 undergoes complex two-step magnetic ordering. At T ? 32 K, a magnetic phase transition (not yet specified) takes place in which a small fraction of the Fe spins participate, whereas at Tf2 ? 12 K, the majority spin fraction undergoes a spin-freezing transition to a spin glass phase. Fe2Al5 undergoes a transition to a spin glass phase at the spin freezing temperature Tf ? 3 K, which was not reported previously. The spin glass phase in Fe2Al5 is “soft” and fragile with respect to the external magnetic field and can only be observed in low magnetic fields below ˜100 Oe. The origins of the spin glass ordering in the FeAl2 and Fe2Al5 phases are randomness and frustration that are present on the Fe sublattices of both compounds. In FeAl2, the Fe spins are positioned randomly on the three mixed-occupation Al/Fe sites of the unit cell, whereas in Fe2Al5, partial occupation of the Fe-neighboring Al2 and Al3 atomic sites imposes different degrees of Fe moment screening by the electron cloud, resulting in a random distribution of the magnetic moment sizes. Geometric frustration because of positioning of the antiferromagnetically coupled Fe spins on triangles is present in both compounds as well.

Jagli?i?, Z.; Vrtnik, S.; Feuerbacher, M.; Dolinšek, J.

2011-06-01

170

Chimie d'interface du couple fer/alliage Al-Si (13,5 % Si) : aspects théoriques et appliqués  

NASA Astrophysics Data System (ADS)

The interface chemistry of the Fe/Al-13,5 wt% Si couple has been investigated at temperatures ranging from 600 to 800 °C. New data have been acquired on the phase equilibria in the Al-Fe-Si ternary system and on the kinetics of the interface reactions. A push out test has been developed to examine the relationships between the extent, thickness or composition of the insert/alloy reaction zone and the mechanical properties of the Fe/Al-Si joint.

Pontevichi, S.; Bosselet, F.; Dezellus, O.; Peronnet, M.; Rouby, D.; Viala, J. C.

2004-12-01

171

High-coercivity iron-rich rare-earth permanent magnet material based on (Fe, Co)3B-Nd-M (M=Al, Si, Cu, Ga, Ag, Au)  

Microsoft Academic Search

High-coercivity, high-remanence permanent magnet materials have been obtained via a crystallization treatment of amorphous (Nd,Dy)xFe80.5?x?yCoyB18.5M1 alloys for 3?x?5 and 0?y?5, where M represent the additives Al, Si, Cu, Ga, Ag, and Au. It has been found that addition of Co and M results in a significant reduction of the crystal grain size and leads to significant improvements both in the

Satoshi Hirosawa; Hirokazu Kanekiyo; Minoru Uehara

1993-01-01

172

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

173

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

SciTech Connect

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

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

2012-02-15

174

Aluminum and silicon diffusion in Fe-Cr-Al alloys  

SciTech Connect

Foils of Fe-Cr-Al alloys containing about 20 wt% Cr, 5 wt% Al and additions of Si and reactive elements like Ce, La, Y, Hf, Zr or Ti are widely used as a substrate in metal-supported automotive catalytic converters. In the present paper the authors report on measurements of Al and Si diffusion in Fe-Cr-Al alloys. Due to a lack of suitable radiotracers concentration profiles were obtained by means of electron microprobe analysis. In connection with data evaluation they present numerical calculations assessing the accuracy of the Matano analysis and the thin-film solution of Fick`s 2nd law as function of the thickness of the initial diffusant layer. The results are of general interest, particularly for the evaluation of diffusion measurements involving industrial specimens with given geometry.

Heesemann, A.; Schmidtke, E.; Faupel, F. [Technische Fakultaet der Univ. Kiel (Germany). Lehrstuhl fuer Materialverbunde; Kolb-Telieps, A.; Kloewer, J. [Krupp VDM GmbH, Werdohl (Germany)

1999-02-05

175

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

176

Thermoelectric properties of ?-FeSi2  

NASA Astrophysics Data System (ADS)

We investigate the thermoelectric properties of ?-FeSi2 using first principles electronic structure and Boltzmann transport calculations. We report a high thermopower for both p- and n-type ?-FeSi2 over a wide range of carrier concentration 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 to 2 × 1021 cm-3 may optimize the thermoelectric performance.

Pandey, Tribhuwan; Singh, David J.; Parker, David; Singh, Abhishek K.

2013-10-01

177

Spin accumulation in Fe/MgO/Si heterostructures  

NASA Astrophysics Data System (ADS)

We report on spin injection experiments at Fe/MgO/Si interfaces using all electrical injection and detection. MgO is a promising magnetic tunnel junction material, and its incorporation with Si-based spintronics has only recently been reported in degenerately doped Si (n ˜10^20 cm-3) [1]. We focus here on spin accumulation under the injecting contact for much lower n-doping levels by measuring the Hanle effect in a standard 3-terminal scheme where injection and detection are done using the same contact. The Fe/MgO spin injector was sputter deposited onto various n-doped Si bulk substrates using a variety of different substrate temperatures. The best tunnel barriers were obtained when the MgO was deposited at 70^oC and annealed in-situ before Fe deposition. Fits to Hanle curves using the drift-diffusion model for Si samples with n=4x10^18 cm-3 yield spin lifetimes ?s = 0.28 ns up to 30 K and a spin diffusion length Ls=?D?s of 0.65 ?m (the diffusion constant D is obtained from the mobility assuming degenerate statistics). We determine the dependence on n, and comment on the potential differences between SOI and bulk Si wafer transport channels. [1] T. Sasaki, et al., Appl. Phys. Exp. 2 (2009).

Hanbicki, A. T.; van't Erve, O. M. J.; Cheng, S.-F.; Goswami, R.; Li, C. H.; Kioseoglou, G.; Thompson, P. E.; Jonker, B. T.

2011-03-01

178

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

Microsoft Academic Search

This article describes an evaluation of contamination by Al, As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Se and Zn in the surroundings of a FeSi smelter, by measurement of tissue levels of the elements in terrestrial mosses growing in the area. The total concentrations of As, Cu and Fe were modelled by surface response fitting. Use of

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

2004-01-01

179

Dry sliding wear behaviour of Al–12Si and Al–12Si–3Cu cast alloys  

Microsoft Academic Search

This paper attempts to investigate the influence of the microstructural changes on the dry sliding wear behaviour of Al–12Si and Al–12Si–3Cu cast alloys by grain refinement (Al–1Ti–3B), modification (Al–10Sr) and combined action of both (Al–1Ti–3B+Al–10Sr). Results indicate that combined grain refined and modified Al–12Si–3Cu cast alloys have microstructures consisting of uniformly distributed ?-Al grains, eutectic Al–silicon and fine CuAl2 particles

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

2009-01-01

180

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

Microsoft Academic Search

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

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

2011-01-01

181

Effect of thickness on secondary recrystallization of Fe3%Si  

Microsoft Academic Search

A study was made on the effect of the final thickness on the secondary recrystallization of Fe-3%Si using MnS and AlN as inhibitors. When heated in hydrogen during final annealing, the 0.60 mm thick specimen underwent a complete secondary recrystallization, but the 0.36 mm and thinner specimens did an incomplete secondary recrystallization. When heated in a mixture gas of hydrogen

S. Nakashima; K. Takashima; J. Harase

1994-01-01

182

Annealing effects on Al and Al-Si contacts with 3C-SiC  

NASA Astrophysics Data System (ADS)

Annealing effects on the current-voltage characteristics of Al and Al-Si contacts with n-type and p-type 3C-SiC films, epitaxially grown on Si by chemical vapor deposition, have been investigated. Al electrodes on n-type 3C-SiC show ohmic characteristics stable up to 400 C, but show distinct rectifying characteristics with annealing at 900 C. To the contrary, Al on p-type 3C-SiC clearly changes from non-ohmic into ohmic with annealing at 900 C. Al-Si alloys, which are usually used as ohmic electrodes for p-type SiC, show the same behavior as Al on n-type 3C-SiC. These results suggest the diffused Al atoms to yield a certain p-type layer.

Daimon, H.; Yamanaka, M.; Sakuma, E.; Misawa, S.; Yoshida, S.

1986-07-01

183

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

NASA Astrophysics Data System (ADS)

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

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

2002-01-01

184

Enhanced ductility in Al-Si-Cu-Mg foundry alloys with high Si content  

NASA Astrophysics Data System (ADS)

It has recently been suggested that the ?-Al5FeSi and ?-Al2Cu intermetallic particles are refined and dispersed in the presence of high silicon, thereby improving the ductility of Al-Si-Cu-Mg alloys. However, limited metallographic evidence was presented to support these claims. Therefore, a study of the effect of Si content in the range of 4.5 to 9 pct on the morphology and distribution of Fe-rich and Cu-rich intermetallic phases has now been conducted. It is shown that Si, indeed, exerts a refining effect on the iron-containing particles ( ? and ?) and disperses clusters of intermetallics (including the Cu-rich particles). In alloys with low Si content, the Fe- and Cu-rich particles form long and closely intertwined clusters. Microcracks originating from cracked intermetallic particles extend and propagate along the clusters with little plasticity, resulting in the low ductility of the alloys. At a high Si content, the intermetallic phases appear more dispersed and the clusters of particles are small and isolated from each other. Microcracks resulting from the cracked intermetallics are short and are isolated, as well, thereby increasing the ductility of the alloys. The mechanisms by which the refinement and dispersion of intermetallic phases occur are discussed.

Cáceres, C. H.; Taylor, J. A.

2006-12-01

185

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

SciTech Connect

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

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

2010-10-15

186

Uniaxial anisotropy induced in 57Fe/Co/Al multilayers  

NASA Astrophysics Data System (ADS)

The magnetic properties of 57Fe/Co/Al multilayers with 20 and 40 trilayers, deposited on Si (100) substrate using ion beam sputtering, are reported here. X-ray reflectivity and X-ray diffraction studies indicate the formation of good quality films with preferential growth along the (110) direction. Conversion electron Mössbauer spectra show considerable inter-mixing between the layers and the formation of Fe-Al/Fe-Co-Al phases. The samples are extremely soft with coercivities <=0.48 × 103 A/m, exhibit strong in-plane uniaxial anisotropy and calculations show that they possess a high ferromagnetic resonance frequency of ~2 GHz. The saturation magnetization value of 1.80 × 106 A/m is comparable with that obtained in multilayer samples with much higher content of Co. The combination of magnetic properties in these multilayers thus makes them ideal candidates for high frequency device applications.

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

2013-06-01

187

Powder Metallurgy Processing of Dual Phase Al Rich Fe-Al Intermetallics.  

National Technical Information Service (NTIS)

A powder metallurgy technique was used to fabricate two different dual-phase Al-rich Fe-Al intermetallics, namely, FeAl2-Fe2Al5 and FeAl3-Fe2Al5. Powders were first produced by inert gas atomization, and then subsequently consolidated by hot pressing at 1...

Y. L. Jeng R. Hayes J. Wolfenstine E. J. Lavernia

1995-01-01

188

Magnetism in Fe4Al13 and related FeAl intermetallics  

NASA Astrophysics Data System (ADS)

We report the results of an experimental study of FeAl alloys, including Fe4Al13, FeAl2 and Fe2Al5. By using NMR, dc magnetic susceptibility, and specific heat, we found that Fe4Al13 and Fe2Al5 are non-magnetic with some dilute magnetic moments, while FeAl2 can be characterized as a concentrated local moment system. Fe4Al13 is a decagonal quasicrystal approximant with 102 atoms in its unit cell. The ^27Al NMR spin-lattice relaxation indicates a very narrow pseudogap in the electronic density of states [g(E)] in the vicinity of the Fermi energy. The observations could be fit assuming a parabolic variation of g(E), consistent with observations in other quasicrystals and approximants. NMR lineshape measurements also agree with this analysis, and show that the system is dilute-magnetic, in strong contrast to the FeAl2 ordered intermetallic. We use specific heat to analyze the dilute moment density. This work was supported by the Robert A. Welch Foundation, Grant No. A-1526, by the National Science Foundation (DMR-0103455), and by Texas A&M University through the Telecommunications and Informatics Task Force.

Chi, Ji; Li, Yang; Gou, Weiping; Goruganti, V.; Rathnayaka, K. D. D.; Ross, Joseph H., Jr.

2006-03-01

189

Annealing effects on Al and Al-Si contacts with 3C-SiC  

Microsoft Academic Search

Annealing effects on the current-voltage characteristics of Al and Al-Si contacts with n-type and p-type 3C-SiC films, epitaxially grown on Si by chemical vapor deposition, have been investigated. Al electrodes on n-type 3C-SiC show ohmic characteristics stable up to 400 C, but show distinct rectifying characteristics with annealing at 900 C. To the contrary, Al on p-type 3C-SiC clearly changes

Hiroshi Daimon; Mitsugu Yamanaka; Eiichiro Sakuma; Shunji Misawa; Sadafumi Yoshida

1986-01-01

190

FePt-Si Nanoparticles With Perpendicular Anisotropy  

NASA Astrophysics Data System (ADS)

FePt Nanoparticles are attractive for applications in magnetic recording media because of their high magnetocrystalline anisotropy. In this work, FePt-Si nanoparticles were fabricated by sputtering an FePt-Si target onto heated MgO substrates. The deposition temperature varied from 350^o to 500^oC. The ratio of FePt to Si in the films was changed by varying the amount of Si in the target. XRD results show that the lattice parameters of L10 phase changed in the FePt-Si nanoparticles from 3.71 to 3.61 å for the c parameter and from 3.85 to 3.87 å for the a parameter. Higher amounts of Si led to a larger change in lattice parameters. The change of lattice parameters in FePt nanoparticles affected the magnetic properties as indicated by the decrease of the coercivity in the FePt-Si samples. TEM images show that the FePt/Si nanoparticles have a better size distribution than the FePt/C nanoparticles. Selected area electron diffraction patterns show that the FePt-Si nanoparticles deposited on MgO have a (001) texture due to the lattice matching between FePt and MgO. The FePt-Si nanoparticles have properties that can be tailored for applications in magnetic recording media.

Wan, J.; Zhang, Y.; Huang, Y.; Bonder, M.; Hadjipanayis, G. C.; Ni, C.; Weller, D.

2006-03-01

191

Elastic properties of FeSi  

SciTech Connect

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

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

2010-09-15

192

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

193

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

NASA Astrophysics Data System (ADS)

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

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

2013-03-01

194

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

195

Effects of temperature and pressure on phonons in FeSi1?xAlx  

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

196

Disorder-induced reversal of spin polarization in the Heusler alloy Co2FeSi  

NASA Astrophysics Data System (ADS)

We study the spin polarization in the conduction band of Co2FeSi layers with a different degree of structural order. The injected spin polarization in Co2FeSi/(Al,Ga)As spin light-emitting diodes as well as the planar Hall effect measured for the Co2FeSi injectors exhibit a sign reversal between injectors crystallized in the ordered L21 phase and the Fe-Si disordered B2 phase. These results are explained by a disorder-induced change in the spin polarization at the Fermi energy of Co2FeSi. Support for the occurrence of such a striking change in the electronic band structure is obtained by first principles calculations.

Bruski, P.; Erwin, S. C.; Ramsteiner, M.; Brandt, O.; Friedland, K.-J.; Farshchi, R.; Herfort, J.; Riechert, H.

2011-04-01

197

High temperature oxidation of mechanically alloyed NiAl–Fe–AlN–Al 2O 3  

Microsoft Academic Search

A new NiAl–Fe alloy containing uniformly distributed ultra-fine AlN and Al2O3 dispersoids was produced by mechanical alloying in a controlled atmosphere and by subsequent hot extrusion process. The new NiAl–Fe–AlN–Al2O3 alloy was oxidized in the temperature range between 1073 and 1473 K in air. The alloy displayed similar oxidation behavior with conventional NiAl alloys. As the oxidation temperature increased, the

D. B. Lee; G. Y. Kim; S. W. Park; S. C. Ur

2002-01-01

198

Electronic and magnetic properties of ring-like Fe 6 and Fe 6@Si 12 clusters  

Microsoft Academic Search

Novel structures based on Fe atoms encapsulated within a Si12 cluster are studied. Electronic and magnetic properties of ring-like Fe6 and Fe6@Si12 were investigated using the frame work of density functional theory (DFT). We have demonstrated that Si12 cluster can be stabilized by encapsulating transition metal atoms (TMAs), Fe atoms. The magnetic moment of free Fe6 cluster is of 3.67?B,

M. Samah; M. A. Belkhir

2005-01-01

199

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

200

Magnetic decoupling in sputtered Fe/Si superlattices and multilayers  

SciTech Connect

A series of sputtered Fe/Si superlattices was grown to study the magnetic coupling between ferromagnetic Fe layers (30{Angstrom} thick) for Si spacer-layer thicknesses (t{sub Si}) between 10 and 40{Angstrom}. The material is ferromagnetically coupled for t{sub Si}<13{Angstrom} and antiferromagneticly coupled for 13{Angstrom}Si}<17{Angstrom}. For t{sub Si}>17{Angstrom} the magnetic Fe layers are uncoupled. X-ray analysis indicates that the system is well layered, but that the crystal structure remains coherent only for t{sub Si}<17{Angstrom}. These results, along with our Moessbauer investigation, strongly suggest that the Si layer is crystalline for t{sub Si}<17{Angstrom}, and is iron silicide in nature. For thicker spacers, Si becomes amorphous. We propose a model of the layering that is consistent with the known properties of Fe-silicide.

Fullerton, E.E.; Mattson, J.E.; Lee, S.R.; Sowers, C.H.; Huang, Y.Y.; Felcher, G.; Bader, S.D. [Argonne National Lab., IL (United States); Parker, F.T. [University of California, San Diego, La Jolla, CA (United States) Center for Magnetic Recording Research.

1992-09-01

201

Magnetic decoupling in sputtered Fe/Si superlattices and multilayers  

SciTech Connect

A series of sputtered Fe/Si superlattices was grown to study the magnetic coupling between ferromagnetic Fe layers (30[Angstrom] thick) for Si spacer-layer thicknesses (t[sub Si]) between 10 and 40[Angstrom]. The material is ferromagnetically coupled for t[sub Si]<13[Angstrom] and antiferromagneticly coupled for 13[Angstrom]Si]<17[Angstrom]. For t[sub Si]>17[Angstrom] the magnetic Fe layers are uncoupled. X-ray analysis indicates that the system is well layered, but that the crystal structure remains coherent only for t[sub Si]<17[Angstrom]. These results, along with our Moessbauer investigation, strongly suggest that the Si layer is crystalline for t[sub Si]<17[Angstrom], and is iron silicide in nature. For thicker spacers, Si becomes amorphous. We propose a model of the layering that is consistent with the known properties of Fe-silicide.

Fullerton, E.E.; Mattson, J.E.; Lee, S.R.; Sowers, C.H.; Huang, Y.Y.; Felcher, G.; Bader, S.D. (Argonne National Lab., IL (United States)); Parker, F.T. (University of California, San Diego, La Jolla, CA (United States) Center for Magnetic Recording Research.)

1992-09-01

202

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

NASA Astrophysics Data System (ADS)

In this work we have studied the giant magnetoimpedance (GMI) effect and its field sensitivity (?) in Co69Fe4.5X1.5Si10B15 (X = Ni, Al, Cr) amorphous ribbons in the frequency (f) range of 0.1 to 10 MHz. We find that at f < 5 MHz, the GMI effect and ? reach the largest values for the Al-containing sample and the smallest values for the Ni-containing sample, while an opposite trend is observed at f > 5 MHz. Magnetization and atomic force microscopy (AFM) experiments reveal that the largest values of the low-frequency GMI effect and ? for the Al-containing sample result from the largest value of magnetic permeability, while the largest values of the high-frequency GMI effect and ? for the Ni-containing sample are attributed to the smallest surface roughness of this sample. These results point to the importance of the sample surface in determining high-frequency GMI behavior. A correlation between the sample surface and high-frequency GMI is established in the investigated ribbons.

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

2011-03-01

203

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

SciTech Connect

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

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

1987-08-01

204

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

205

Moessbauer effect and X-ray distribution function analysis in complex Na{sub 2}O-CaO-ZnO-Fe{sub 2}O{sub 3}-Al{sub 2}O{sub 3}-SiO{sub 2} glasses and glass-ceramics  

SciTech Connect

Moessbauer spectroscopy at room temperature was carried out to determine the state of iron ions in complex glasses and glass-ceramics in the SiO{sub 2}-CaO-ZnO-Na{sub 2}O-Fe{sub 2}O{sub 3}-Al{sub 2}O{sub 3} system. Isomer shift values of the glasses suggest that Fe{sup 3+} and Fe{sup 2+} are in tetrahedral and octahedral coordination, respectively. The spectrum of the glass-ceramic shows that about 60 wt% total iron is in the magnetite phase. The Fe{sup +3}/Fe{sup +2} ratio varies with the total iron oxide content of the glasses, indicating that the vitreous network is more distorted when the iron content is greater. X-ray diffraction measurements were carried out to obtain the radial distribution function (RDF). The interatomic distances for Si-Si and Si-O have been determined. The complex composition of these glasses does not allow the estimation of Al-O and Fe-O distances.

Romero, M.; Rincon, J.M.; Musik, S.; Kozhukharov, V.

1999-05-01

206

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

SciTech Connect

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

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

1994-09-01

207

Impurities Removal from Metallurgical-Grade Silicon by Combined Sn-Si and Al-Si Refining Processes  

NASA Astrophysics Data System (ADS)

The purification of metallurgical-grade silicon (MG-Si) by combined solvent refining processes has been studied. The final high-purity silicon was recovered through Sn-Si refining and Al-Si refining processes in sequence after acid leaching, and the removal mechanism of impurities was explored. Inductively coupled plasma (ICP) chemical analysis revealed the concentrations of main impurities including B and P, and typical metallic impurities except for solvents Sn and Al were reduced to below 1 ppmw. The final removal efficiencies of B and P were 97.7 pct and 99.8 pct, respectively, and those of most metallic impurities were above 99.9 pct. SEM analysis showed that P-containing phases (Al-Ca-Mg-Si-P and Al-Si-P) formed on the surface of refined Si after Sn-Si refining and Al-Si refining, which was confirmed to be the main approach for P removal. It was also found that the formation of binary silicide such as Fe3Si7 and Mn11Si19 or multicomponent phases such as Ca-Mg-Si phase occurred during the solvent refining process, and they segregated on the grain boundaries in Si or attached to the surface of Si, which led to high removal efficiency of metallic impurities by the solvent refining process.

Hu, Lei; Wang, Zhi; Gong, Xuzhong; Guo, Zhancheng; Zhang, Hu

2013-04-01

208

Effects of annealing conditions and thickness ratio of Si\\/Al films on the Hall carrier mobility, Al carrier concentration, and nanovoids formed in the metal-induced Si crystallization of Si\\/Al\\/Si\\/SiO2\\/glass specimens  

Microsoft Academic Search

In the present study, a-Si\\/?c-Al\\/a-Si\\/SiO2\\/glass specimens were prepared with various combinations of thicknesses of the ?c-Al layer and the two a-Si layers. The effects of ?c-Al film thickness, a-Si film thickness, the thickness ratio of Al film to Si films, and the annealing temperature on the metal-induced Si crystallization and void defects formed in the sandwich composite specimens were investigated.

Cheng Chang Peng; Chen Kuei Chung; Bo Hsiung Wu; Min Hang Weng; Chil Chieh Huang; Jen Fin Lin

2011-01-01

209

Al-induced faceting of Si(113)  

NASA Astrophysics Data System (ADS)

Adsorption of Al on a Si(113) substrate at elevated temperatures causes a faceting transition of the initially flat surface. The (113) surface decomposes into a quasi-periodic sequence of Al terminated (115)- and (112)-facets. The resulting surface morphology is characterized in-situ by reciprocal space maps obtained with in-situ spot profile analyzing low-energy electron diffraction and ex-situ atomic force microscopy. The periodicity length of the faceted surface increases with adsorption temperature from 7 nm at 650 °C to 80 nm at 800 °C. The stability of the Al terminated Si(112) surface is the driving force for the faceting transition.

Klein, Claudius; Heidmann, Inga; Nabbefeld, Tobias; Speckmann, Moritz; Schmidt, Thomas; Meyer zu Heringdorf, Frank-J.; Falta, Jens; Horn-von Hoegen, Michael

2013-12-01

210

Reaction between amorphous Si and crystalline Al in Al\\/Si and Si\\/Al bilayers: microstructural and thermodynamic analysis of layer exchange  

Microsoft Academic Search

Aluminium-induced crystallization of amorphous silicon (a-Si) in Al\\/Si and Si\\/Al bilayers was studied upon annealing at 250 °C by X-ray diffraction and Auger electron spectroscopy. The Al\\/a-Si bilayers and a-Si\\/Al bilayers were prepared by sputter deposition on single-crystal silicon wafers with a silicon-oxide film on top. During the isothermal annealing a layer-exchange process occurred in both types of bilayers. A

D. He; J. Y. Wang; E. J. Mittemeijer

2005-01-01

211

Reaction between amorphous Si and crystalline Al in Al\\/Si and Si\\/Al bilayers: microstructural and thermodynamic analysis of layer exchange  

Microsoft Academic Search

Aluminium-induced crystallization of amorphous silicon (a-Si) in Al\\/Si and Si\\/Al bilayers was studied upon annealing at 250 °C by X-ray diffraction and Auger electron spectroscopy. The Al\\/a-Si bilayers and a-Si\\/Al bilayers were prepared by sputter deposition on single-crystal silicon wafers with a silicon-oxide film on top. During the isothermal annealing a layer-exchange process occurred in both types of bilayers. A continuous

D. He; J. Y. Wang; E. J. Mittemeijer

2005-01-01

212

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

2011-12-01

213

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

214

An evaluation of weldments joined by Fe-Mn-Al and Fe-Cr-Ni consumables  

SciTech Connect

Stainless steel plates were joined using Fe-Mn-Al and Fe-Cr-Ni consumables to evaluate the strength and corrosion resistance of the weldments. The Fe-Mn-Al consumables successfully joined austenitic stainless steel plates. However, the corrosion performance of the Fe-Mn-Al weld metals was poor. As a result, at room temperature, Fe-Mn-Al consumables cannot replace Fe-Cr-Ni consumables in an acidic chloride-bearing environment.

Aidun, D.K.; Makhamreh, K.M.; Morrison, D.J. (Clarkson Univ., Potsdam, NY (United States)); Olszewski, J. (Aluminum Co. of America, Massena, NY (United States))

1994-03-01

215

Investigation of magnetic properties in 57Fe/Al multilayers  

NASA Astrophysics Data System (ADS)

Fe/Al multilayer thin films prepared by ion beam sputtering, with an overall atomic concentration ratio of Fe/Al = 1:2 have been studied by x-ray diffraction spectroscopy (XRD), X-ray reflectivity (XRR) and D.C. Magnetization. These studies show the formation of Fe Al intermetallic layers. Two magnetic regions and transition temperatures of 473 and 533 K are evident from magnetization studies. Conversion Electron Mössbauer Spectroscopy (CEMS) shows formation of off-stoichiometric Fe3Al like phase and phases consisting of pure Fe and Fe-rich extended Fe Al solutions.

Jani, Snehal; Sebastian, Varkey; Lakshmi, N.; Reddy, V. R.; Venugopalan, K.; Gupta, Ajay

2008-07-01

216

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

217

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

NASA Astrophysics Data System (ADS)

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.

Jang, Pyungwoo; Shin, Seungchan; Jung, Chip-Sup; Kim, Kwang-Ho; Seomoon, Kyu

2013-04-01

218

Microstructure characterization of a pressureless infiltrating oxidized SiCp preform by Al-8Mg  

NASA Astrophysics Data System (ADS)

The microstructure of a pressureless infiltrating 55vol% oxidized SiC preform by Al-8Mg alloy was characterized by transmission electron microscopy (TEM), high resolution TEM (HRTEM), field emission scanning electron microscopy (FE-SEM), and X-ray diffraction. The TEM image of the interface between Al and SiC shows that the surface of SiC is covered by a rough nanocrystal layer of MgAl2O4, Al2O3, and Si, produced by the interfacial reaction of Al, Mg, and SiO2 on the surface of SiC. The Al-SiC interface is also examined by HRTEM to be better understood how MgAl2O4 and Al2O3 are produced. Dendritic Al2O3 crystals are embedded in the pores of the composite generated from the mutual bonding of SiO2 on the surface of SiC. Columnar AlN crystals of about 250 nm in length are bunched vertically on the SiC particle surface.

Ren, Shu-Bin; Shen, Xiao-Yu; He, Xin-Bo; Qu, Xuan-Hui

2011-04-01

219

Dissimilar metal joining of aluminum alloy to galvanized steel with Al–Si, Al–Cu, Al–Si–Cu and Zn–Al filler wires  

Microsoft Academic Search

Aluminum alloy sheets were lap joined to galvanized steel sheets by gas tungsten arc welding (GTAW) with Al–5% Si, Al–12% Si, Al–6% Cu, Al–10% Si–4% Cu and Zn–15% Al filler wires. Different amounts of Si, Cu and Zn were introduced into the weld through different filler wires. The effects of alloying elements on the microstructure in the weld and tensile

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

220

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

NASA Astrophysics Data System (ADS)

We present the results of thermodynamic modeling of fluid-rock interaction in the system Si-Al-Fe-Mg-Ca-Na-H-O-Cl using the GEM-Selektor Gibbs free energy minimization code. Combination of non-ideal mixing properties in solids with multicomponent aqueous fluids represents a substantial improvement and it provides increased accuracy over existing modeling strategies. Application to the 10-component system allows us to link fluid composition and speciation with whole-rock mineralogy, mass and volume changes. We have simulated granite-fluid interaction over a wide range of conditions (200-600 °C, 100 MPa, 0-5 m Cl and fluid/rock ratios of 10 -2-10 4) in order to explore composition of magmatic fluids of variable salinity, temperature effects on fluid composition and speciation and to simulate several paths of alteration zoning. At low fluid/rock ratios ( f/ r) the fluid composition is buffered by the silicate-oxide assemblage and remains close to invariant. This behavior extends to a f/ r of 0.1 which exceeds the amount of exsolved magmatic fluids controlled by water solubility in silicate melts. With increasing peraluminosity of the parental granite, the Na-, K- and Fe-bearing fluids become more acidic and the oxidation state increases as a consequence of hydrogen and ferrous iron transfer to the fluid. With decreasing temperature, saline fluids become more Ca- and Na-rich, change from weakly acidic to alkaline, and become significantly more oxidizing. Large variations in Ca/Fe and Ca/Mg ratios in the fluid are a potential geothermometer. The mineral assemblage changes from cordierite-biotite granites through two-mica granites to chlorite-, epidote- and zeolite-bearing rocks. We have carried out three rock-titration simulations: (1) reaction with the 2 m NaCl fluid leads to albitization, chloritization and desilication, reproducing essential features observed in episyenites, (2) infiltration of a high-temperature fluid into the granite at 400 °C leads to hydrolytic alteration commencing with alkali-feldspar breakdown and leading to potassic, phyllic and argillic assemblages; this is associated with reduction and iron metasomatism as observed in nature and (3) interaction with a multicomponent fluid at 600 °C produces sodic-calcic metasomatism. Na, Ca and Fe are the most mobile elements whereas immobility of Al is limited by f/ r ˜ 400. All simulations predict a volume decrease by 3.4-5.4%, i.e., porosity formation at f/ r < 30. At higher fluid/rock ratios simulation (2) produces a substantial volume increase (59%) due to mineral precipitation, whereas simulation (3) predicts a volume decrease by 49% at the advanced albitization-desilication stage. Volume changes closely correlate with mass changes of SiO 2 and are related to silica solubility in fluids. The combined effects of oxygen fugacity, fluid acidity and pH for breakdown of aqueous metal complexes and precipitation of ore minerals were evaluated by means of reduced activity products. Sharp increases in saturation indexes for oxidative breakdown occur at each alteration zone whereas reductive breakdown or involvement of other chloride complexes favor precipitation at high fluid/rock ratios only. Calculations of multicomponent aqueous-solid equilibria at high temperatures and pressures are able to accurately predict rock mineralogy and fluid chemistry and are applicable to diverse reactive flow processes in the Earth's crust.

Dolejš, David; Wagner, Thomas

2008-01-01

221

Photoluminescence Properties from ?-FeSi2 Film Epitaxially Grown on Si, YSZ and Si//YSZ  

NASA Astrophysics Data System (ADS)

We have succeeded in expitaxial growth of (101) and (110)-oriented ?-FeSi2 films on (111)Si, (111)Si-buffered (111)YSZ and (111)YSZ substrates by metal organic chemical vapor deposition (MOCVD). All the films showed highly perfection in orientation irrespective of the substrate. After annealing at 900°C in Ar atmosphere, their photoluminescences (PL) around 1.54 ?m were observed in the ?-FeSi2 films grown on (111)Si and (111)Si-buffered (111)YSZ substrates, except for the film on (111)YSZ substrates. This suggests that the ?-FeSi2/Si interface is a crucial structure for enhancement of PL and that the Si atom diffuses into ?-FeSi2 is important factor to 1.54-?m PL.

Akiyama, Kensuke; Kaneko, Satoru; Terai, Yoshikazu; Maeda, Yoshihito; Funakubo, Hiroshi

2005-02-01

222

Forging of FeAl intermetallic compounds  

SciTech Connect

Much activity has been concentrated on the development of intermetallic compounds with the aim of improving tensile ductility, fracture toughness and high notch sensitivity in order to develop an attractive combination of properties for high and low temperature applications. This paper reports experience in processing and forging of FeAl intermetallic of B2 type. During the experiments two different temperatures were employed, and the specimens were forged after annealing in air, 10{sup {minus}2} torr vacuum and argon. From the results it was learned that annealing FeAl in argon atmosphere prior to forging resulted in better deformation behavior than for the other two environments. For the higher forging temperature used in the experiments (700C), the as-cast microstructure becomes partially recrystallized.

Flores, O.; Juarez, J.; Campillo, B.; Martinez, L. [UNAM, Cuernavaca (Mexico). Lab. de Cuernavaca; Schneibel, J.H. [Oak Ridge National Lab., TN (United States)

1994-09-01

223

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

224

Photoluminescence Properties from beta-FeSi2 Film Epitaxially Grown on Si, YSZ and Si\\/\\/YSZ  

Microsoft Academic Search

We have succeeded in expitaxial growth of (101) and (110)-oriented beta-FeSi2 films on (111)Si, (111)Si-buffered (111)YSZ and (111)YSZ substrates by metal organic chemical vapor deposition (MOCVD). All the films showed highly perfection in orientation irrespective of the substrate. After annealing at 900°C in Ar atmosphere, their photoluminescences (PL) around 1.54 mum were observed in the beta-FeSi2 films grown on (111)Si

Kensuke Akiyama; Satoru Kaneko; Yoshikazu Terai; Yoshihito Maeda; Hiroshi Funakubo

2005-01-01

225

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

Microsoft Academic Search

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

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

2010-01-01

226

Hydrogen embrittlement of Fe 3Al alloys  

Microsoft Academic Search

The tensile and fatigue crack growth behavior of two Fe?Al alloys, FA-129 and FAP-Y, are described. FA-129 is an ordered intermetallic while FAP-Y is disordered. The intermetallic is embrittled by both laboratory air and by hydrogen gas, while FAP-Y is embrittled only by hydrogen gas. Fractographic features as well as dislocation substructures for both alloys are described. Oxygen is found

A. Castagna; N. S. Stoloff

1995-01-01

227

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

NASA Astrophysics Data System (ADS)

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

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

1997-07-01

228

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

NASA Astrophysics Data System (ADS)

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

Yilmaz, G.

2012-07-01

229

Oxidation Behavior of FeAl+Hf,Zr,B.  

National Technical Information Service (NTIS)

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 gr...

J. L. Smialek J. Doychak

1988-01-01

230

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

231

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

Microsoft Academic Search

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,

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

2008-01-01

232

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

Microsoft Academic Search

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,

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

2008-01-01

233

Characterization of (Fe,Al)FER synthesized in presence of ethylene glycol and ethylene diamine  

Microsoft Academic Search

(Fe,Al)Ferrierite type zeolite was hydrothermally crystallized in a gel system of sodium aluminosilicate with ethylene glycol a nitrogen-free organic compound, as well as, ethylene diamine. The zeolite crystals obtained were characterized by X-ray diffractometry (XRD), thermal analysis (TGA–DTA), electron scanning microscopy (SEM), chemical analysis, N2 adsorption\\/desorption at 77K and 29Si–, 27Al–, 13C–, and 1H NMR spectroscopy. Fe atoms essentially occupy

S. Candamano; P. Frontera; T. I. Kora´nyi; A. Macario; F. Crea; J. B. Nagy

2010-01-01

234

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

SciTech Connect

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

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

2012-07-15

235

Roll Casting of Al-25%Si  

SciTech Connect

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

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

2011-05-04

236

Thermal equation of state of Fe(III) and Al-bearing magnesium silicate perovskite  

NASA Astrophysics Data System (ADS)

Recent work indicates that Fe3+ may be an important cation in lower mantle perovskite, but very few studies have examined the impact of oxidized iron on the mechanical properties of magnesium silicate perovskite in the absence of Fe2+. In order to examine the properties of (Mg,Fe3+)(Si,Al)O3 type perovskites, samples were synthesized from an oxide mixture using a multi-anvil apparatus at 1700 oC and 25 GPa, with Fe2O3 as the exclusive source of Fe. A layer of Fe2O3 was also placed between the Pt capsule and Re heater in order to maintain high oxygen fugacity within the capsule. Perovskites with and without Al were synthesized, and yielded microprobe compositions of Mg0.975Fe3+0.050Si0.975O3 and Mg0.947Fe3+0.040Si0.956Al0.054O3. Mossbauer spectroscopy revealed that Fe2+ was absent in the run product. The thermal equations of state of the Fe3+-bearing perovskite (up to 65 GPa) and the (Fe3++Al)-bearing perovskite (up to 40 GPa) were measured using in situ synchrotron X-ray diffraction in a laser-heated diamond anvil cell, with Au as the pressure calibrant and Ne as the pressure medium. Equations of state are compared with those of Fe2+-bearing perovskite and Fe-free perovskite. The effect of trivalent cations on equation of state parameters is discussed, as well as implications for elastic properties of the lower mantle.

Hummer, D. R.; Fei, Y.; Seagle, C. T.

2011-12-01

237

Magnetomechanical hysteresis damping in FeAl alloys  

Microsoft Academic Search

The magnetomechanical hysteresis damping of Fe-Al alloys has been investigated using a computer-controlled automatic inverted torsion pendulum. It has been shown that Al content and heat treatment have a significant effect on the magnetomechanical hysteresis damping of the alloys. The Fe-10.5 (at.%)Al alloy has an optimal damping capacity after it was air-cooled from 900°C and the Fe-Al alloys with 29(at.)%Al

Z. C. Zhou; Z. C. Shen; Z. Jiang; F. S. Han

2005-01-01

238

Interaction between Al-Si-Cu alloys and MoSi sub 2  

Microsoft Academic Search

The interaction at the metal-metal interface of the Al-Si-Cu\\/MoSiâ bilayer system has been investigated as a function of the Cu concentration. The Al in the Al-Si-Cu alloy reacts with the MoSiâ at temperatures above 400C. Al atoms diffuse into the MoSiâ and the excess Si diffuses into the Al layer. After the reaction, the amorphous MoSiâ becomes crystalline Mo(Al, Si)â.

Shinichi Fukada; Motoo Suwa; Yasushi Koubuchi; Jin Onuki

2008-01-01

239

Elasticity of AlFeO3 and FeAlO3 perovskite and post-perovskite from first-principles calculations  

NASA Astrophysics Data System (ADS)

We use state-of-the-art ab initio calculations based on the generalized gradient approximation of the density functional theory in the planar augmented wavefunction formalism to determine the elastic constants tensor of perovskite and post-perovskite with formulas AlFeO3 and FeAlO3 in which Fe or Al respectively occupy only octahedral sites, for the stable magnetic configurations. The phase transition between perovskite and post-perovskite is associated with a site exchange, during which Fe from the inter-octahedral site in perovskite moves into the octahedral site in post-perovskite. Following this transition path the elastic moduli show positive jumps, considerably larger than for MgSiO3. The phase transition is marked by a positive jump of 0.04 km/s (0.33%) in the velocity of the compressional waves and by a negative jump of -0.15 km/s (-1.87%) in shear wave velocity. We find that the effects of the Mg + Si <=> Al + Fe substitution on the seismic properties of MgSiO3 perovskite and post-perovskite depend on the crystallography of the substitution, namely the position the exchanged cations take in the structure.

Caracas, R.

2010-10-01

240

High-temperature tribological properties of CrAlN, CrAlSiN and AlCrSiN coatings  

Microsoft Academic Search

Cr–Al–Si–N coatings with high and low Cr\\/Al ratios (CrAlSiN and AlCrSiN, respectively) were deposited on WC substrates by cathodic arc and compared with a reference Cr–Al–N coating. The silicon content was close to 3at.%. X-ray diffraction analysis showed that CrAlN and CrAlSiN coatings exhibited the cubic Cr(Al)N structure, whereas in AlCrSiN a mixture of cubic Cr(Al)N and wurtzite-type AlN was

Tomas Polcar; Albano Cavaleiro

2011-01-01

241

Anomalous phonon properties in the silicide superconductors CaAlSi and SrAlSi  

NASA Astrophysics Data System (ADS)

Lattice-dynamical properties of CaAlSi and SrAlSi with a similar layer structure to MgB2 have been first investigated by both Raman-scattering and ab initio calculations. All Raman-active phonons with E' symmetry have been clearly observed for both compounds. Their line shapes are asymmetric but their linewidths are ˜10cm-1 , which is very narrower than that of MgB2 . In addition to the Raman-active modes, several extra peaks have been observed below 160cm-1 . These low-energy extra modes can be assigned to the out-of-plane vibrations of Al perpendicular to Al-Si basal plane. Since these peak intensities are strongly affected by the incident energy (resonance Raman process), the electronic state is important for them. Moreover, in both crystals of CaAlSi and SrAlSi, we point out the energy difference for the different propagation directions along the c axis and the c plane, in spite of the very close wave vector to the Brillouin-zone center. This energy difference cannot be explained by a usual Raman-scattering scenario at this stage.

Kuroiwa, S.; Hasegawa, T.; Kondo, T.; Ogita, N.; Udagawa, M.; Akimitsu, J.

2008-11-01

242

Porous silicon based beta-FeSi2 and photoluminescence  

Microsoft Academic Search

Highly-pure iron powder was covered on porous silicon for fabricating semiconducting beta-FeSi2 structures. X-ray diffraction and Raman scattering results confirm the formation of pure-phase beta-FeSi2 after high-temperature annealing at 1100°C and then long-time persistence at 900°C. Scanning electron microscope observations reveal that large-size (>mum) beta-FeSi2 grains mainly form in the pores of porous silicon and some nanocrystals grow on local

H. T. Chen; X. L. Wu; Y. Y. Zhang; W. N. Su

2009-01-01

243

Porous silicon based ? -FeSi 2 and photoluminescence  

Microsoft Academic Search

Highly-pure iron powder was covered on porous silicon for fabricating semiconducting ?-FeSi2 structures. X-ray diffraction and Raman scattering results confirm the formation of pure-phase ?-FeSi2 after high-temperature annealing at 1100°C and then long-time persistence at 900°C. Scanning electron microscope observations\\u000a reveal that large-size (>?m) ?-FeSi2 grains mainly form in the pores of porous silicon and some nanocrystals grow on local

H. T. Chen; X. L. Wu; Y. Y. Zhang; W. N. Su

2009-01-01

244

Properties of Sintered Al Substituted NdFeB Magnets  

NASA Astrophysics Data System (ADS)

The effect of partial substitution of Fe by Al (Al, Al2O3) on the magnetic properties and the corrosion resistance of the sintered NdFeB magnet has been investigated. With the increasing amount of Al, the anisotropy field and the saturation magnetization decrease, but the coercivity increases up to 4 at.% Al and further alloying of Al leads to a decrease of the coercivity. Different substances like Al (metallic Al or Al2O3) modify the microstructure to different increase in the coercivity and especially to changes in the remanence. Alloying Al via metallic Al decreases the remanence, whereas via Al2O3) up to 4 at.%0 Al increases it. The Al additions inhibit atmospheric corrosion of the magnet. We have found that Al2O3 in sintered NdFeB magnet substantially improves the coercivity and the corrosion resistance with the improved remanence.

Szymura, S.; Bala, H.; Rabinovich, Yu. M.; Wiechu?a, J.

245

The effect of Si in Al-alloy on electromigration performance in Al filled vias  

NASA Astrophysics Data System (ADS)

Electromigration performance of vias filled with Al-Si-Cu alloys on Ti glue layers was investigated in comparison with W-stud vias. In Al-Si-Cu filled vias, voids were formed at only a few locations in the test structure, while voids were formed at every via in W-stud via chains. It is supposed that Al moves through the Al-Si-Cu via during electromigration in spite of the existence of a glue layer at the via bottom. This phenomenon was observed only in the vias filled with Al-Si-Cu alloy. Al movement was prohibited in Al-Cu filled vias. In Al-Si-Cu filled vias, an Al-Ti-Si alloy was formed at the via bottom while Al3Ti was formed at Al-Cu filled vias. Al is speculated to move through this Al-Ti-Si alloy during electromigration.

Kageyama, Makiko; Hashimoto, Keiichi; Onoda, Hiroshi

1998-01-01

246

Thermodynamics of the FCC FeMc-C and Fe-Si-C Alloys.  

National Technical Information Service (NTIS)

The activity of carbon in austenitic Fe-Mn-C and Fe-Si-C alloys was studied by equilibration with controlled CH4-H2 atmospheres at temperatures in the range 848 to 1147C and for composition up to about 60 pct Mn and 7 pct Si. The activity coefficient of c...

T. Wada H. Wada J. F. Elliott J. Chipman

1971-01-01

247

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.

2013-08-01

248

High temperature properties of CrAlN, CrAlSiN and AlCrSiN coatings – Structure and oxidation  

Microsoft Academic Search

CrAlN, CrAlSiN and AlCrSiN coatings were deposited by cathodic arc deposition technique from composite targets. Three targets were used: (i) Cr\\/Al ratio close to 1, (ii) Cr\\/Al ratio close to 1 with Si addition, and (iii) Cr\\/Al ratio close to 1\\/2 and Si addition. Nitrogen flow was kept constant during the depositions. The Cr\\/Al ratio of the films, measured by

Tomas Polcar; Albano Cavaleiro

2011-01-01

249

Formation of buried aSi\\/Al\\/Si, aSi\\/Sb\\/Si and aSi\\/B\\/Si interfaces and their electrical properties  

Microsoft Academic Search

Si:Al, Si:Sb and Si:B surface phases capped by amorphous Si layers were grown by MBE. The formation of the buried interfaces was studied by low-energy electron diffraction and Auger electron spectroscopy which revealed that, except for the stable Si(111)?3 × ?3 -B, the majority of the surface phases suffer either from in-plane redistribution (i.e. break-up of surface reconstruction) or surface

A. V. Zotov; F. Wittmann; J. Lechner; S. V. Ryzhkov; V. G. Lifshits; I. Eisele

1995-01-01

250

Interface mixing of Al/Fe and Fe/Al bilayer systems and the role of Ti as a stabilizing interlayer using Rutherford backscattering spectrometry and x-ray reflectometry  

SciTech Connect

Al/Fe and Fe/Al bilayer films with and without a Ti stabilizing interlayer at the interface have been grown on Si wafers using dc magnetron sputtering. X-ray reflectometry and Rutherford backscattering spectrometry were used to probe individual layer thicknesses and intermixing lengths. It is observed that the intermixing length is always higher when the Fe layer is on top of the Al layer. The samples with the Ti stabilizing layer, particularly when the Al layer is on top of the Fe, show that the Ti layer promotes the formation of abrupt interfaces.

Priyantha, Weerasinghe A.; Chen, Hui; Kopczyk, M.; Smith, Richard J.; Kayani, Asghar N.; Comouth, Andreas; Finsterbusch, M.; Nachimuthu, Ponnusamy; Mccready, David E.

2008-01-01

251

Effect of thickness on secondary recrystallization of Fe-3%Si  

SciTech Connect

A study was made on the effect of the final thickness on the secondary recrystallization of Fe-3%Si using MnS and AlN as inhibitors. When heated in hydrogen during final annealing, the 0.60 mm thick specimen underwent a complete secondary recrystallization, but the 0.36 mm and thinner specimens did an incomplete secondary recrystallization. When heated in a mixture gas of hydrogen and nitrogen during final annealing, all specimens underwent a complete secondary recrystallization, but the thinner the specimen, the lower the magnetic flux densities were. The reduction of final thickness makes the specimen too sensitive to the atmosphere during final annealing to get a precisely Goss-oriented secondary-recrystallized texture.

Nakashima, S. [Kyushu Kyoritsu Univ., Kitakyushu (Japan); Takashima, K.; Harase, J. [Nippon Steel Corp., Shintomi Futtsu (Japan)

1994-02-01

252

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

253

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

SciTech Connect

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

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

1996-04-01

254

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

SciTech Connect

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

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

2011-04-01

255

Criteria for the formation of protective Al 2O 3 scales on Fe–Al and Fe–Cr–Al alloys  

Microsoft Academic Search

The conditions for the formation of external alumina scales on binary Fe–Al alloys and the nature of the third-element effect due to chromium additions have been investigated by studying the oxidation at 1000°C in 1atm O2 of a binary Fe–10at.% Al alloy (Fe–10Al) and of two ternary Fe–Cr–10at.% Al alloys containing 5 and 10at.% chromium (Fe–5Cr–10Al and Fe–10Cr–10Al, respectively). An

Z. G. Zhang; F. Gesmundo; P. Y. Hou; Y. Niu

2006-01-01

256

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

SciTech Connect

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

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

2004-12-01

257

A thin-film solar cell of high-quality ? -FeSi 2\\/Si heterojunction prepared by sputtering  

Microsoft Academic Search

High-quality (110)\\/(101)-oriented epitaxial ?-FeSi2 films were fabricated on Si (111) substrate by the sputtering method. The critical feature was the formation of a high-quality thin ?-FeSi2 template buffer layer on Si (111) substrate at low temperature. It was demonstrated that the template is very important for the epitaxial growth of thick ?-FeSi2 films and for the blocking of Fe diffusion

Zhengxin Liu; Shinan Wang; Naotaka Otogawa; Yasuhito Suzuki; Masato Osamura; Yasuhiro Fukuzawa; Teruhisa Ootsuka; Yasuhiko Nakayama; Hisao Tanoue; Yunosuke Makita

2006-01-01

258

Skyrmion Lattice Domains in Fe1-xCoxSi  

Microsoft Academic Search

The strongly doped semiconductor Fe1-xCoxSi displays a dome of helimagnetic order for 0.05 <= x <= 0.7. We report small angle neutron scattering of the magnetic structure in the skyrmion lattice phase of Fe1-xCoxSi for x = 0.2 and magnetic field parallel to a crystallographic (100) direction. We observe twelve equally spaced maxima of scattering intensity on a ring, with

T. Adams; S. Mühlbauer; A. Neubauer; W. Münzer; F. Jonietz; R. Georgii; B. Pedersen; P. Böni; A. Rosch; C. Pfleiderer

2010-01-01

259

Phase equilibria in the Nb–Fe–Cr–Si System  

Microsoft Academic Search

Efforts to improve the CVD process used to elaborate protective coatings against oxidation for niobium alloys have needed a good knowledge of the quaternary Nb–Fe–Cr–Si phase diagram. Many phase equilibria have been established at 1473 K and a new quaternary, Nb6.6Fe1.4Cr4Si8, phase has been identified and studied using single X-ray diffraction data. The crystal structure is of a new type,

M. Vilasi; M. Francois; H. Brequel; R. Podor; G. Venturini; J. Steinmetz

1998-01-01

260

Compressive behavior of SiC p\\/AlSi 9Mg composite foams  

Microsoft Academic Search

Closed-cell AlSi9Mg foams and SiCp\\/AlSi9Mg composite foams with different SiCp volume fractions were prepared successfully by means of direct foaming of melt using CaCO3 blowing agent in this paper. The compressive behaviors of these foams were studied. In comparison with the compressive stress–strain curve of AlSi9Mg foams that of SiCp\\/AlSi9Mg composite foams is not smooth and exhibits some serrations. At

Yanru Luo; Sirong Yu; Wen Li; Jiaan Liu; Ming Wei

2008-01-01

261

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

PubMed

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

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

2010-03-01

262

Microstructure and properties of Si p\\/Al–Si surface composites prepared by ultrasonic method  

Microsoft Academic Search

Primary Si particles reinforced Al–Si surface composites (Sip\\/Al–Si surface composites) were prepared by means of ultrasonic equipment with a special horn crucible. The microstructure and properties of the surface composites were investigated using optical microscope, scanning electron microscopy (SEM), hardness meter and friction and wear tester. The results show that when Al–12%Si alloy was treated by ultrasonic, Si element was

H. K. Feng; S. R. Yu; Y. L. Li; L. Y. Gong

2009-01-01

263

Structures and superparamagnetic properties of overaged Fe-Al-Mn-C alloys  

SciTech Connect

Microstructures and superparamagnetic properties in aged-hardened Fe-9%Al-30%Mn-(x)C,Si alloys, resulting from overaging at a temperature of 823 K for 48 h to 313 days, have been investigated by transmission electron microscopy (TEM), X-ray diffraction patterns, and vibrating sample magnetometry (VSM). The results reveal that the precipitate {kappa}-phase [(Fe,Mn){sub 3}AlC] decomposition in this alloy, overaged at 823 K for one week, resulted from two separate mechanisms: (1) wetting of the 1/2 a{prime}{sub 0}{l{underscore}angle}100{r{underscore}angle} antiphase boundary segment (APBs) of D0{sub 3} [(Fe/Mn){sub 3}Al] domains by the B2 [(Fe/Mn)Al] phase; and (2) precipitation of the B2 [(Fe/Mn)Al] phase within the domain. A superparamagnetic behavior was discovered when the alloy was overaged at 823 K for {approx}120--313 days. The super-soft magnetic property was mainly attributable to the ferromagnetic spinel-ordered (B2 [(Fe/Mn)Al] + D0{sub 3} [(Fe/Mn){sub 3}Al]) phases and ordered B2 with monoclinic {alpha}{prime}Mn structures.

Lin, Y.C.

1999-12-10

264

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

NASA Astrophysics Data System (ADS)

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

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

2008-08-01

265

Magnetic and structural properties of Co2FeAl1-xSix thin films  

NASA Astrophysics Data System (ADS)

We investigate different types of disorder which are predicted to influence the spin polarization by x-ray and electron diffraction (RHEED). We observe that the compound Co2FeAl grows in the B2 ordered structure. However, for Co2FeAl0.3Si0.7 the analysis revealed with increasing annealing temperature a crossover from B2 to L21 order. The magnetization of the samples is investigated by SQUID magnetometry and x-ray magnetic circular dichroism (XMCD) experiments in bulk sensitive transmission and surface sensitive total electron yield (TEY) mode. The results reveal the same surface and bulk moments of Co2FeAl. However, with increasing annealing temperature the Co2FeAl0.3Si0.7 thin films display a small decrease of the surface moment in contrast to a not changing bulk moment. This observation is relevant concerning potential device applications of Co2FeAl0.3Si0.7.

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

2010-01-01

266

Reaction between amorphous Si and crystalline Al in Al/Si and Si/Al bilayers: microstructural and thermodynamic analysis of layer exchange  

NASA Astrophysics Data System (ADS)

Aluminium-induced crystallization of amorphous silicon (a-Si) in Al/Si and Si/Al bilayers was studied upon annealing at 250 °C by X-ray diffraction and Auger electron spectroscopy. The Al/a-Si bilayers and a-Si/Al bilayers were prepared by sputter deposition on single-crystal silicon wafers with a silicon-oxide film on top. During the isothermal annealing a layer-exchange process occurred in both types of bilayers. A continuous polycrystalline silicon (poly-Si) film was formed within, and thereby gradually replacing, the initial Al metal layer. The sublayer sequence in the original bilayer influenced the speed of the poly-Si formation and the layer-exchange process. After annealing, the Al fiber texture in the as-deposited bilayers had become stronger, the Al crystallites had grown laterally, and the macrostress in the Al layer had been released. The amorphous Si layer had crystallized into an aggregate of nanocrystals with {111} planes parallel to the surface, with a crystallite size of about 15 25 nm. An extensive analysis of the Gibbs energy change due to annealing showed that the layer exchange may be promoted by the release of elastic energy and grain growth for the Al phase.

He, D.; Wang, J. Y.; Mittemeijer, E. J.

2005-02-01

267

Tribological properties of FeAl intermetallics under dry sliding  

Microsoft Academic Search

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

Jun Yang; Peiqing La; Weimin Liu; Qunji Xue

2004-01-01

268

Magnetic Properties on Ferromagnetic FeAlO  

Microsoft Academic Search

FeAlO3 polycrystalline sample was fabricated by the sol-gel method. The crystallographic and magnetic properties of the sample were measured using X-ray diffractometer, Mossbauer spectroscopy, and vibrating sample magnetometer (VSM). The crystal structure was found to be an orthorhombic with the space group Pna21, which has four cation sites labeled Fe1, Fe2, Al2(octahedral sites), and Al1(tetrahedral site). Magnetic hysteresis curves of

Jee Hoon We; Sam Jin Kim; Chul Sung Kim

2006-01-01

269

Natural Occurrence of Fe2SiO4 - in Shocked Umbarger l6 Chondrite  

NASA Astrophysics Data System (ADS)

Fe2SiO4 with the spinel structure was synthesized by Ringwood [1] and inferred to be important in Earth's upper mantle [1,2], but it has not previously been found in nature. Umbarger is an L6 chondrite, which contains a series of high-pressure phases: ring-woodite, akimotoite, augite and hollandite-structured plagioclase [3-6]. Transmission electron microscopy also revealed a Fe2SiO4-spinel and stishovite assem-blage in a Fe-rich zone of a melt pocket. Phyllosili-cates and glass are also associated with the Fe2SiO4-spinel, indicating post-shock aqueous glass alteration. The Fe2SiO4-spinel grains are equant to irregular, with sizes from 100 to 400 nm. Diffraction patterns can only be indexed as a spinel structure, but the unit cell is a little large (a= 8.46 Å) relative to synthetic Fe2SiO4-spinel (a=8.234 Å [1]). EDS analyses show that the spinel has a fayalite compositon with Fe/(Fe+Mg) ratio ranging from 62% to 97%. Stishovite occurs as elongated prismatic crystals up to 1 mm long and up to 100 mm wide. The alteration products in Umbarger are phyllosilicates rich in Fe and Si, with a basal layer spacing of about 9.7 Å. Crystallization of melt veins began with akimotoite and ringwoodite at pressures up to 25 GPa and ended with augite at pressure less than 18 GPa [3, 4]. Mg2SiO4-spinel and stishovite are stable in the pres-sure range from 15 GPa to 25 GPa in the enstatite-forsterite system [7], while Fe2SiO4-spinel and stishovite is stable at lower pressure. Fe2SiO4-spinel and stishovite assemblage, like that of Akimotoite plus ringwoodite, is a sub-solidus assemblage, indicating crystallization of a supercooled liquid during rapid cooling and decompression associated with shock pres-sure release. Reference: [1] Ringwood A.E. (1958) GCA,15, 18-29. [2] Irifune T. (1993) The Island Arc, 2, 55-71. [3] Xie Z. and Sharp T. G. (2000a) LPS XXXI, 2065.pdf. [4] Xie Z. and Sharp T. G. (2000b) MAPS, 35 A172. [5] Xie Z. et al.(2001) LPS XXXII, 1805.pdf. [6] Sharp T.G. (2001) LPS XXXII, 2159.pdf. [7] Gasparik T. (1992) JGR, 97, 15181-15188.

Xie, Z.; Sharp, T. G.

2001-12-01

270

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

SciTech Connect

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

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

2012-05-15

271

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

NASA Astrophysics Data System (ADS)

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

2008-09-01

272

Ultrasonic nanowelding of SiC microparticles on Al surface  

NASA Astrophysics Data System (ADS)

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

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

2012-05-01

273

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

274

Ion implantation and diffusion of Al in a SiO2/Si system  

NASA Astrophysics Data System (ADS)

The diffusion and segregation of ion implanted Al in SiO2 and Si layers were studied for several experimental conditions. Al ions were implanted into SiO2, Si and through a SiO2 layer into Si substrates at several energies (80, 300, 650 and 6000 keV) and doses (3.4 × 1014 - 1 × 1015 cm-2). The Al diffusion coefficient in SiO2 was measured at 1200°C for times up to 5 days, and it results five orders of magnitude lower than in Si. The experiments show that the Al atoms implanted into Si do not out-diffuse during thermal treatments from the SiO2 capping layer, but segregate at the SiO2/Si interface. The high segregation coefficient gives rise to a trapping of Al into the oxide layer comparable to the out-diffusion of Al from uncapped Si substrates. The determined parameters for Al diffusion and segregation in the SiO2/Si system were introduced in a simulation code to calculate the Al diffusion profiles which result in agreement with the experimental data.

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

1996-08-01

275

Crystal structure of the orthorhombic Al4(Cr,Fe) approximant of the Al Cr Fe decagonal quasicrystal  

Microsoft Academic Search

The crystal structure of the orthorhombic phase Al4(Cr,Fe) with a composition of Al80.6Cr10.7Fe8.7 has been determined by single-crystal x-ray diffraction (table 2). There are 11 crystallographically independent Cr\\/Fe sites, of which 10 are icosahedrally coordinated. Of the 28 crystallographically independent Al sites 5 are icosahedrally coordinated. However, owing to the presence of many partial occupancies, caused by split atoms, some

D. W. Deng; Z. M. Mo; K. H. Kuo

2004-01-01

276

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

Microsoft Academic Search

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

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

1975-01-01

277

Thermodynamics of Al-substitution in Fe-oxyhydroxides  

NASA Astrophysics Data System (ADS)

Ab initio simulation results are presented for dilute Al-substitution in the common Fe-(oxyhydr)oxide materials hematite, goethite, lepidocrocite and ferrihydrite. Experimental evidence from the literature suggests that Al-substitution in these materials may influence particle stability and phase transformation behavior, typically stabilizing the oxyhydroxide phases relative to the oxide, hematite. We find that all the alloyed phases studied are unstable with respect to phase separation into their unalloyed Fe/Al-(oxyhydr)oxide end members. Among the phases studied, ferrihydrite is predicted to allow Al-substitution with the lowest energy cost, while hematite appears to have the strongest tendency for phase separation. Considering the effect on thermodynamic stability relative to the stable Fe-oxide hematite, the three Fe-oxyhydroxide materials (goethite, lepidocrocite, ferrihydrite) are shown to be stabilized relative to doped Al-hematite as Al content is increased. Interactions between Al dopant atoms on neighboring Fe sites are simulated and are shown to have minimal influence on Fe-Al alloying thermodynamics in each of the materials simulated within the range of Al-dopant concentrations calculated. Simulations of Al-substitutions at the goethite (1 0 1) surface indicate that surface segregation of Al dopants is energetically favored for low Al concentrations, however this tendency diminishes when Al dopants form a full monolayer at the mineral surface.

Pinney, Nathan; Morgan, Dane

2013-11-01

278

Influence of disorder on electronic structure and magnetic properties in Fe-rich Fe–Si alloys  

Microsoft Academic Search

We present the results of ab initio calculations of the spin-polarized electronic structure of disordered bcc and fcc Fe1?xSix alloys from dilute solid solutions of Si on iron up to FeSi intermetallic compound composition (x=0.01..0.5) and ordered intermetallic phases FeSi in B20 structure and Fe3Si in DO3 structure. The self-consistent calculations were performed with the coherent potential approximation within the

N. I Kulikov; D Fristot; A Postnikov; J Hugel

2000-01-01

279

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

SciTech Connect

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, A.K.

1989-05-01

280

Investigation of optical properties of interfaces between heavily doped Al0.48In0.52As:Si and InP (Fe) substrates by photoreflectance analysis  

Microsoft Academic Search

A set of heavily doped Al0.48In0.52As samples grown by molecular beam epitaxy on InP (Fe) substrates was investigated using the photoreflectance (PR) technique. The spectra at 300 K are characterized by a transition in the vicinity of the InP energy gap, followed by strongly damped Franz–Keldysh oscillations (FKOs) which do not appear when the spectra are obtained at 77 K.

E. Laureto; I. F. L. Dias; J. L. Duarte; E. Di Mauro; H. Iwamoto; M. T. P. Freitas; D. O. Toginho Filho; J. C. Harmand

1999-01-01

281

Investigation of optical properties of interfaces between heavily doped Al0.48In0.52As:Si and InP (Fe) substrates by photoreflectance analysis  

Microsoft Academic Search

A set of heavily doped Al0.48In0.52As samples grown by molecular beam epitaxy on InP (Fe) substrates was investigated using the photoreflectance (PR) technique. The spectra at 300 K are characterized by a transition in the vicinity of the InP energy gap, followed by strongly damped Franz-Keldysh oscillations (FKOs) which do not appear when the spectra are obtained at 77 K.

E. Laureto; I. F. L. Dias; J. L. Duarte; E. di Mauro; H. Iwamoto; M. T. P. Freitas; S. A. Lourenço; D. O. Toginho Filho; J. C. Harmand

1999-01-01

282

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

Microsoft Academic Search

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

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

1999-01-01

283

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.; Morris, D.G. [Univ. of Neuchatel (Switzerland). Inst. of Structural Metallurgy

1998-05-01

284

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.

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

2012-01-01

285

Thermal expansion, Debye temperature and Grüneisen parameter of synthetic (Fe, Mg)SiO3 orthopyroxenes  

NASA Astrophysics Data System (ADS)

Thermal expansion properties of synthetic orthopyroxenes (Fe0.20Mg0.80)SiO3, (Fe0.40Mg0.60)SiO3, (Fe0.50Mg0.50)SiO3, (Fe0.75Mg0.25)SiO3 and (Fe0.83Mg0.17)SiO3 were systematically studied by means of single-crystal x-ray diffraction in the temperature range from 296 to 1300 K. The measurements of unit cell dimensions as a function of temperature reveal that the a and c dimensions and the unit cell volume V increase nonlinearly with a positive curvature with rising temperature, whereas the b dimension behaves differently, depending on the total Fe content. For Mg-rich orthopyroxenes (Fe/(Fe+Mg)<30%), the b dimension expands similarly as the a and c dimensions, but it exhibits a nonlinear increase with a negative curvature for orthopyroxenes with Fe/(Fe+Mg)>30%. Together with the high temperature neutron diffraction data on enstatite (MgSiO3) (McMullan, Haga and Ghose, unpublished) and x-ray diffraction data on ferrosilite (FeSiO3) (Sueno et al. 1976), the measured unit cell dimensions were analyzed in terms of the Grüneisen theory of thermal expansion. The linear thermal expansion coefficients ? a and ? c both increase as temperature is elevated, with ? c increasing faster, while ? b changes gradually from increasing for Mg-rich orthopyroxenes to decreasing for Fe-rich orthopyroxenes. The relative magnitudes of linear thermal expansion coefficients are always in the order ? b >? c >? a between 300 and 500 K, but at higher temperatures, the order changes to ? c >? b >? a for Mg-rich orthopyroxenes and ? c >? a >? b for Fe-rich ones. The linear thermal expansion behavior is interpreted on the basis of the structural mechanical model of Weidner and Vaughan (1982). The anomalous behavior of ? b is mainly attributed to the changes in the Fe2+ population at the M2 site and the relative stiffness of the M2(Fe2+)-O bonds compared to the M2(Mg2+)-O bonds. The volume thermal expansion coefficients are nonlinear functions of temperature and lie between 23 and 49×10-6/K. The previously reported results of mean volume thermal expansion coefficients appear to represent the ? V values characteristic of higher temperatures compared to our results. The thermal Debye temperatures are composition-dependent, decreasing linearly from 812 (MgSiO3) to 561 K (FeSiO3), and are systematically higher than the corresponding acoustic Debye temperatures. The Grüneisen parameters range from 0.85 to 0.89 and do not seem to vary with composition. The linear compressibilities derived from thermal expansion and elastic moduli data agree very well. The pressure derivatives of the isothermal bulk modulus (dK0/dP) are also composition-dependent and decrease from 11.2 (MgSiO3) to 8.77 (FeSiO3). Such large values indicate possible anomalous elastic behavior of orthopyroxenes at high pressures in the Earth's upper mantle.

Yang, Hexiong; Ghose, Subrata

1994-05-01

286

Rapidly solidified powder metallurgy of Al-Ti-Fe-X alloys  

SciTech Connect

Mechanical properties of powder metallurgy (P/M) aluminum alloys have been improved through a rapid solidification (RS) technique. High-strength RS P/M aluminum alloys were recently developed in Al-Ni-(Y or Ce)-(Co, Ti or Zr) systems containing from 89 to 91 at% Al. The alloy systems have a glass-forming ability, resulting in easy attainment of nanocrystalline structure. Recently, the authors have reported that Al{sub 93}Ti{sub 3.5}Fe{sub 3.5}RS P/M alloys exhibited tensile strength of 786 MPa, plastic elongation of 3.2%, high thermal stability up to 600 K, low density of 2.90 gcm{sup {minus}3}, high Young`s modulus of 91 GPa and low coefficient of thermal expansion of 20.2 {times} 10{sup {minus}6} K{sup {minus}1}. The Al-Ti-Fe P/M alloys are expected to be applied as elevated-temperature materials such as Al-Fe-Ce, Al-Fe-Mo, Al-Fe-V-Si and Al-Cr-Zr RS P/M alloys, because the Ti and Fe elements exhibit limited solid solubility and low diffusivity in aluminum. The transition metals of V, Cr, Mo and Zr have low diffusivity in aluminum. The addition of these elements to the Al-Ti-Fe alloys is expected to improve its thermal stability and elevated-temperature strength. The purpose of this paper is to report the synthesis of elevated-temperature Al-Ti-Fe-X (X = V, Cr, Mo and Zr) RS P/M alloys.

Kawamura, Yoshihito; Inoue, Akihisa [Tohoku Univ., Sendai (Japan). Inst. for Materials Research; Takagi, Makoto; Ohta, Hidenobu; Imura, Toru [Aichi Inst. of Tech., Toyota (Japan); Masumoto, Tsuyoshi [Research Inst. for Electric and Magnetic Materials, Sendai (Japan)

1999-04-23

287

Evidence for {open_quotes}loose spins{close_quotes} in epitaxial Al/Fe/Al  

SciTech Connect

Polarization-dependent Fe K-edge x-ray absorption fine structure measurements of an Al/Fe/Al(001) trilayer reveal a small tetragonal distortion of the Fe sites with c=2.863 {Angstrom} (normal to the film plane) and a=2.874 {Angstrom} (in the film plane). This tetragonal distortion is consistent with the formation of Fe{sub 1{minus}x}Al{sub x} alloys in the vicinity of the roughened Fe{endash}Al trilayer interfaces, and agrees with grazing incidence x-ray reflectivity and magnetometry measurements of the trilayer. The deduced alloyed/roughened interfacial regions are the likely source of Fe {open_quotes}loose spins{close_quotes} as recently suggested by Slonczewki{close_quote}s biquadratic coupling model for the epitaxial Fe/Al/Fe system. {copyright} {ital 1997 American Institute of Physics.}

Gutierrez, C.J.; Selestino, R. [Department of Physics, Southwest Texas State University, San Marcos, Texas 78666 (United States); Mayanovic, R.A. [Department of Physics and Astronomy, Southwest Missouri State University, Springfield, Missouri 65804 (United States); Prinz, G.A. [Naval Research Laboratory, Washington, DC 20375 (United States)

1997-04-01

288

Analysis of depth redistribution of implanted Fe near SiO2/Si interface  

NASA Astrophysics Data System (ADS)

We have studied diffusion and clustering processes of room-temperature (RT)-implanted Fe ions in a SiO2/Si structure during annealing at 600 and 800 °C temperatures. The depth profile of implanted Fe was analyzed by Rutherford backscattering spectroscopy (RBS). In the previous study, we found that the hot-implanted Fe ions near the SiO2/Si interface at high substrate temperatures of 600 and 800 °C were distributed significantly different from the result predicted in the TRIM simulation. We think that the diffusion phenomena during the ion implantation at such elevated temperatures are recognized to be strongly enhanced by ion-beam-irradiation effect. In this study, to simplify the diffusion phenomenon, we particularly treat thermal diffusion process of RT-Fe implantation around the SiO2/Si interface in the post annealing at high temperatures. It is clearly seen that Fe atoms post-annealed at 800 °C are preferably gathered at a definitive depth in the SiO2 layer around 15 nm distances from the interface. We finally compare the Fe depth distribution for hot-implanted samples to that for the post-annealed ones by RBS analysis quantitatively.

Hoshino, Y.; Yokoyama, A.; Yachida, G.; Nakata, J.

2013-11-01

289

Electrical conductivity of FeSi under pressure  

NASA Astrophysics Data System (ADS)

Chemical arguments suggest that FeSi can result from the reaction of the Fe-rich perovskite and post-perovskite in the D" layer with the Fe of the liquid core [1]. FeSi could thus accumulate in the lower parts of D", in particular the ultra-low velocity zones (ULVZ). Physical arguments (high density) and seismological arguments (low velocities) plead for its existence in these regions [2]. We compute the temperature-dependent electronic conductivity of FeSi from density-functional perturbation theory. From the phonons and electron-phonon coupling we solve the Boltzmann transport equations to the lowest order to give the electrical and thermal conductivities [3]. We find that the electrical resistivity of FeSi at lower mantle and outer core conditions is on the order of 3.5-4.0 micro Ohm m at 2500-3000K. This is about twice the resistivity of Fe in the same conditions, which is similar to the assumed resistivity of the outer core. If present in significant amounts, then the large values of the conductivity computed here suggest FeSi as the major conducting phase in the D" and ULVZ, and the mineral that would ensure the electromagnetic coupling between the mantle and the core. [1] E. Knittle and R. Jeanloz, Science, 251, 1438 (1991). [2] R. Caracas and R.M. Wentzcovitch, Geophys. Res. Lett. 31, No. 20, 10.1029/2004GL020601 (2004) [3] S.Y. Savrasov and D.Y. Savrasov, Phys. Rev. B, 54, 16487 (1996).

Verstraete, M.; Caracas, R.

2007-12-01

290

Thermodynamics of the fcc Fe-Mn-C and Fe-Si-C alloys  

Microsoft Academic Search

The activity of carbon in austenitic Fe-Mn-C and Fe-Si-C alloys has been studied by equilibration with controlled CH4-H2 atmospheres at temperatures in the range 848 to 1147C and for composition up to about 60 pct Mn and 7 pct Si. The activity\\u000a coefficient of carbon is diminished by manganese and is increased by silicon. Activity coefficients and derived values of

Tsuguyasu Wada; Harue Wada; John F. Elliott; John Chipman

1972-01-01

291

Solid Solubility of Si in Al under High Pressure  

Microsoft Academic Search

By making use of a 15 mm cubic anvil apparatus, Al-Si alloys of Si-concentration up to 15 at% were studied at a pressure of 54 kbar. The liquidus, solidus and solvus of the Al-rich alloys were determined by means of the 4-probe electric resistance measurement. The solubility limit of Si in Al was extended beyond 15 at% at 54 kbar

Hisao Mii; Masafumi Senoo; Ikuya Fujishiro

1976-01-01

292

Potential limitations of Al-Si bonded fuel elements  

Microsoft Academic Search

Tests in which aluminum-jacketed, Al-Si bonded uranium fuel elements were baked at various temperatures have shown there is a time-temperature relationship for Al-Si layer decomposition. For heat transfer and secondary coolant barrier considerations, the extent of bonding layer deterioration during fuel element irradiation is important. Under present reactor operating conditions, Al-Si bonded fuel elements show evidence of internal bond deterioration,

1960-01-01

293

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

PubMed

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

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

2012-03-28

294

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.

2013-04-01

295

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

296

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.

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

2012-01-01

297

Activities in CaO-SiO2-Al2O3 slags and deoxidation equilibria of Si and Al  

NASA Astrophysics Data System (ADS)

By using the data in previous and present slag-metal equilibrium experiments, the activities of SiO2 along the liquidus lines in CaO-SiO2-Al2O3 slags were determined at 1823 and 1873 K from the reaction Si+2 O=SiO2 (s), in which the oxygen activities were estimated from the measured oxygen contents or from the combination of nitrogen distribution ratios ( L N) and nitride capacities ( C N). The activities of Al2O3 were also determined from the reaction 2 Al+3 O=Al2O3 (s), in which the oxygen activities were estimated from the values for L N and C N, or from the reaction 3SiO2 (s)+4 Al=2Al2O3 (s)+3 Si, in which the activities of SiO2 and the contents of Al and Si along with the respective interaction coefficients were used. The activities of Al2O3 and CaO in the entire liquid region were estimated from the Rein and Chipman’s activities of SiO2 by using the method of Schuhmann. On the basis of these activities, the deoxidation equilibria of Si and Al in steels were discussed.

Ohta, Hiroki; Suito, Hideaki

1996-12-01

298

Oxidation of {gamma}{prime}-Ni{sub 3}Al and {gamma}{prime}-Ni{sub 3}Al(Si) intermetallic compounds at low-oxygen pressures  

SciTech Connect

The oxidation behavior of {gamma}{prime}-Ni{sub 3}Al and {gamma}{prime}-Ni{sub 3}Al(Si) (Ni{sub 75}Al{sub 20}Si{sub 5}) intermetallic compounds was studied at 1073 K and oxygen partial pressures of 5 {approximately} 9 x 10{sup {minus}6} atm, 1.2 x 10{sup {minus}14} atm, and 1.2 x 10{sup {minus}19} atm by means of a manometric apparatus, and Rhines packs of NiO/Ni and FeO/Fe, respectively. Oxidation kinetics were determined either by recording weight gains or by measuring the internal-oxidation-zone depths. The structures and morphologies of oxides were also studied. Relatively low oxidation rates occurred for both compounds when oxidized in the manometric apparatus, while fast internal oxidation was observed for both compounds in the NiO/Ni pack. The fastest oxidation occurred in the {gamma}{prime}-Ni{sub 3}Al compound in the FeO/Fe pack. A healing Al{sub 2}O{sub 3} layer was formed on the surface of {gamma}{prime}-Ni{sub 3}Al(Si) compound in the FeO/Fe pack, indicating a synergistic effect between the solute elements in the compound at the oxygen pressures corresponding to the dissociation of FeO. The oxidation rate was found to depend on the volume expansion associated with solute-atom oxidation.

Yi, H.C. [Guigne International, Newfoundland (Canada); Smeltzer, W.W.; Petric, A. [McMaster Univ., Hamilton, Ontario (Canada)

1996-04-01

299

Coadsorption of potassium and oxygen on thin ?-FeSi2 overlayers on Si(111)  

NASA Astrophysics Data System (ADS)

We report UPS, AES and WF measurements on the interaction of K and O2 on thin semiconducting epitaxial layers of ?-FeSi2 on Si(111). Oxygen was adsorbed on clean and K-covered ?-FeSi2 at 300 K and the system was heated up to 900 K with the suicide remaining stable. A correlation of the experimental results indicates that at RT on clean ?-FeSi2 oxygen chemisorbs dissociatively on silicon sites and does not interact with iron. In the presence of K oxygen chemisorbs on iron and on silicon sites with an increased sticking coefficient. No potassium oxide was formed. Upon heating up to 800 K SiO2 is formed on the suicide film under conditions in which the suicide remains stable.

Kennou, S.; Tan, T. A. Nguyen

1991-07-01

300

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

NASA Astrophysics Data System (ADS)

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

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

2008-12-01

301

Effect of Transition-Metal Substitution for Fe in Superconducting Lu2Fe3Si5.  

National Technical Information Service (NTIS)

The effect of transition-metal substitution for Fe on the superconducting transition temperature, T/sub c/, of compounds Lu/sub 2/(Fe/sub 1-x/T/sub x/)/sub 3/Si/sub 5/, where T = Cr, Mn, Co, Ni, Ru, is reported. In every instance, T/sub c/ of the host com...

Y. Xu R. N. Shelton

1987-01-01

302

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

PubMed

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

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

2012-11-29

303

Abrasive wear behavior and mechanical properties of Al–Si\\/SiC composites  

Microsoft Academic Search

In this study, the effect of Si addition up to 8% Si on the abrasive wear and mechanical properties of Al–Si\\/60vol.% SiC composites produced by pressure infiltration technique has been investigated. Optimum properties in terms of improved strength and abrasion resistance without significant loss in toughness were obtained when the matrix alloy contained 1% Si. At Si contents higher than

Hayrettin Ahlatci; Ercan Candan

2004-01-01

304

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

National Technical Information Service (NTIS)

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 ...

R. Subramanian J. H. Schneibel

1997-01-01

305

Investigation of the role of Al/CoFe interface in proximity effect of Nb/Al/CoFe  

NASA Astrophysics Data System (ADS)

When a few nm-thick Al layer is inserted between Nb and ferromagnetic (F) layers such as CoFe, Ni, or CuNi, the superconducting critical temperature of the trilayers increase rapidly almost to a level of Nb/Al bilayers. In order to understand the role of Al/CoFe interface in the proximity effect of Nb/Al/CoFe, we have added Mg and Au scattering centers and found different behavior. The Mg scattering center did not change the critical temperature behavior of Nb/Al/CoFe, while the Au scattering centers reduced the critical temperature. The results point toward the importance of spin-orbit scattering. In addition, tunneling spectroscopy data on Nb/Al/F vs. on Nb/F will be presented in order to further characterize the role of Al/F interfaces.

Char, K.; Kwon, Junhyung; Lu, Wenjian

2008-03-01

306

Mechanical alloying characteristics and thermal stability of Ti–Al–Si and Ti–Al–Si–C powders  

Microsoft Academic Search

Several stoichiometric ternary Ti–Al–Si and quaternary Ti–Al–Si–C alloys have been prepared by mechanical alloying of elemental powder blends. The structural and morphological evolutions in these powders are characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). XRD results have shown that the elemental powders Ti–Al–Si are progressively transformed into a nanocrystalline solid solution and amorphous phase during mechanical alloying.

A. Vyas; K. P. Rao; Y. V. R. K. Prasad

2009-01-01

307

Cyclic Oxidation of FeCrAlY/Al2O3 Composites.  

National Technical Information Service (NTIS)

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 ...

J. A. Nesbitt S. L. Draper C. A. Barrett

1999-01-01

308

Thermal formation of vacancies in Fe3Si  

Microsoft Academic Search

The formation of thermal vacancies in the intermetallic compound Fe3Si was studied below and at the ferromagnetic-paramagnetic phase transition by means of positron-lifetime spectroscopy. Low values of the vacancy formation enthalpies HFV,f=0.77 eV in the ferromagnetic state and HFV,p=0.74 eV in the paramagnetic state are derived in the case of stoichiometric Fe75Si25. These values substantially increase to HFV,f=1.11 eV and

E. A. Kümmerle; K. Badura; B. Sepiol; H. Mehrer; H.-E. Schaefer

1995-01-01

309

Magnetic texture in SiFe sheets and ribbons  

Microsoft Academic Search

The magnetic texture of grain oriented and non-oriented electrical steel sheets and rapidly solidified Fe?6.5 Si and Fe?6.5\\u000a Si?0.08 Sb ribbons was investigated by means of Mssbauer spectroscopy. For the grain oriented sheets the most simple and\\u000a fastest method using scattering geometry was applied. The non-oriented sheet was investigated more exactly and the distribution\\u000a of the magnetic moments in the

O. Schneeweiss; A. Sólyom; P. Marko; V. Fric

1989-01-01

310

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

311

Al-Fe-Ni (Aluminum-Iron-Nickel)  

Microsoft Academic Search

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

V. Raghavan

1994-01-01

312

A Thermodynamic Model of Sulfur Distribution Ratio between CaO–SiO 2 –MgO–FeO–MnO–Al 2 O 3 Slags and Molten Steel during LF Refining Process Based on the Ion and Molecule Coexistence Theory  

Microsoft Academic Search

A thermodynamic model for calculating the sulfur distribution ratio between ladle furnace (LF) refining slags and molten steel\\u000a has been developed by coupling with a developed thermodynamic model for calculating the mass action concentrations of structural\\u000a units in LF refining slags, i.e., CaO–SiO2–MgO–FeO–MnO–Al2O3 hexabasic slags, based on the ion and molecule coexistence theory (IMCT). The calculated mass action concentrations of

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

313

The assessment of thermodynamic parameters in the Fe-O and Fe-Si-O systems  

NASA Astrophysics Data System (ADS)

Thermodynamic data for phases in the Fe-Si-O system have been assessed using experimental information on phase equilibria, electrochemical measurements of oxygen activity, calorimetry, and elastic property measurements. The sublattice model was applied to magnetite, wustite, and liquid phase. To get consistency between two sets of experimental data on subsolidus phase equilibria in the Fe-O system at 1 bar and in the Fe-Si-O system at pressures up to 20 GPa and temperatures up to 2000 K, the thermodynamic data for solid phases has been optimized (the volumetric properties for fayalite, magnetite, and ferrosilite, enthalpy and heat capacity for fayalite, enthalpy, and entropy for ferrosilite and -spinel). Thermodynamic properties of liquid phase (Gibbs free energy of Fe 2 SiO 4 endmember and mixing parameters) have been reassessed to reach consistency with experimental data. Parameters in the Fe-FeO system have been evaluated up to 16 GPa. The assessment of liquid mixing parameters in the Fe-Si-O system has been made only at 1 bar, due to the lack of experimental data at high pressures.

Fabrichnaya, O. B.; Sundman, B.

1997-11-01

314

Phase diagrams of the ternary systems Mn, Fe, Co, Ni-Si-N  

SciTech Connect

Phase equilibria in the ternary systems Mn, Fe, Co, and Ni-Si-N are investigated and isothermal sections at 900/sup 0/C (Fe-Si-N, Ni-Si-N), at 1000/sup 0/C (Mn-Si-N, Co-Si-N) and at 1150/sup 0/C (Fe-Si-N) are presented. In the system N-Si-N, Si/sub 3/N/sub 4/ coexists with MnSiN/sub 2/, Mn/sub 3/Si, Mn/sub 5/Si/sub 3/, MnSi, and MnSi/sub 2-x/. In the systems Fe, Co, Ni-Si-N, Si/sub 3/N/sub 4/ coexists with all binary silicides but reacts rapidly with iron above 1120 +/- 10/sup 0/C, and cobalt and nickel above 1170 +/- 10/sup 0/C to form binary silicides and nitrogen gas.

Weitzer, F.; Schuster, J.C.

1987-10-01

315

Refinement of Eutectic Si Phase in Al-5Si Alloys with Yb Additions  

NASA Astrophysics Data System (ADS)

A series of Al-5 wt pct Si alloys with Yb additions (up to 6100 ppm) have been investigated using thermal analysis and multiscale microstructure characterization techniques. The addition of Yb was found to cause no modification effect to a fibrous morphology involving Si twinning; however, a refined plate-like eutectic structure was observed. The Al2Si2Yb phase was observed with Yb addition level of more than 1000 ppm. Within the eutectic Al and Si phases, the Al2Si2Yb phase was also found as a precipitation from the remained liquid. No Yb was detected in the ?-Al matrix or plate-like Si particle, even with Yb addition up to 6100 ppm. The absence of Yb inside the eutectic Si particle may partly explain why no significant Si twinning was observed along {111}Si planes in the eutectic Si particle. In addition, the formation of the thermodynamic stable YbP phases is also proposed to deteriorate the potency of AlP phase in Al alloys. This investigation highlights to distinguish the modification associated with the ever present P in Al alloys. We define modification as a transition from faceted to fibrous morphology, while a reduction of the Si size is termed refinement.

Li, J. H.; Suetsugu, S.; Tsunekawa, Y.; Schumacher, P.

2013-02-01

316

Strength anomaly in B2 FeAl single crystals  

SciTech Connect

Strength and deformation microstructure of B2 Fe-39 and 48%Al single crystals (composition given in atomic percent), which were fully annealed to remove frozen-in vacancies, have been investigated at temperatures between room temperature and 1073K. The hardness of as-homogenized Fe-48Al is higher than that of as-homogenized Fe-39Al while after additional annealing at 698K the hardness of Fe-48Al becomes lower than that of Fe-39Al. Fe-39Al single crystals slowly cooled after homogenizing at a high temperature were deformed in compression as a function of temperature and crystal orientation. A peak of yield strength appears around 0.5T{sub m} (T{sub m} = melting temperature). The orientation dependence of the critical resolved shear stress does not obey Schmid`s law even at room temperature and is quite different from that of b.c.c. metals and B2 intermetallics at low temperatures. At the peak temperature slip transition from <111>-type to <001>-type is found to occur macroscopically and microscopically, while it is observed in TEM that some of the [111] dislocations decompose into [101] and [010] on the (1096I) plane below the peak temperature. The physical sources for the positive temperature dependence of yield stress of B2 FeAl are discussed based on the obtained results.

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

1994-12-31

317

Eutectic nucleation in hypoeutectic Al-Si alloys  

SciTech Connect

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

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

2008-10-15

318

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

SciTech Connect

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

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

2012-04-15

319

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

NASA Astrophysics Data System (ADS)

Applying density functional theory in the framework of the full-potential linearized augmented plane-wave (FLAPW) method [1], we investigated electronic structure of potential future photovoltaic materials, ?-FeSi2 and FeS2, for selected surface orientations and terminations. The most stable orientations are determined by comparing their surface energy. Detailed electronic structure calculations show that surface states originating from Fe play an important role and might determine photovoltaic properties. Our results show that anti-ferrimagnetic ordering exists for Fe-terminated surface. Furthermore, we also studied how electronic structure and photovoltaic efficiency are affected by the recently observed structural defects such as stacking fault in ?-FeSi2. [4pt] [1] www.flapw.de

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

2013-03-01

320

Low-Temperature Fabrication of Polycrystalline Si Thin Film Using Al-Induced Crystallization without Native Al Oxide at Amorphous Si/Al Interface  

NASA Astrophysics Data System (ADS)

Low-temperature fabrication of polycrystalline silicon (poly-Si) thin film has been performed by Al-induced crystallization (AIC), and the structural properties have been investigated. In our experiments, to prevent native oxidation of Al film, an amorphous silicon (a-Si)/Al bilayer was formed on the SiO2/Si substrate by electron beam evaporation without breaking the vacuum. The a-Si/Al/SiO2/Si structure was then heated at a low temperature of 400°C to induce AIC. It was confirmed that layer exchange of the a-Si/Al bilayer is induced even though there is no native oxidation of Al film, which was demonstrated by scanning transmission electron microscopy and energy dispersive X-ray analysis. The mechanism for layer exchange of the a-Si/Al bilayer has been discussed. Furthermore, it was verified by scanning electron microscopy and spectroscopic ellipsometry that the a-Si/Al thickness ratio of roughly 1:1 is suitable to achieve a flat surface morphology of poly-Si. In addition, it was found, by X-ray diffraction and orientation imaging microscopy, that the Si(111)-oriented grain becomes dominant with decreasing thickness of the a-Si/Al bilayer.

Sugimoto, Youhei; Takata, Naoki; Hirota, Takeshi; Ikeda, Ken-ichi; Yoshida, Fuyuki; Nakashima, Hideharu; Nakashima, Hiroshi

2005-07-01

321

Fabric cutting application of FeAl-based alloys  

SciTech Connect

Four intermetallic-based alloys were evaluated for cutting blade applications. These alloys included Fe{sub 3}Al-based (FAS-II and FA-129), FeAl-based (PM-60), and Ni{sub 3}Al-based (IC-50). These alloys were of interest because of their much higher work-hardening rates than the conventionally used carbon and stainless steels. The FeAl-based PM-60 alloy was of further interest because of its hardening possibility through retention of vacancies. The vacancy retention treatment is much simpler than the heat treatments used for hardening of steel blades. Blades of four intermetallic alloys and commercially used M2 tool steel blades were evaluated under identical conditions to cut two-ply heavy paper. Comparative results under identical conditions revealed that the FeAl-based alloy PM-60 outperformed the other intermetallic alloys and was equal to or somewhat better than the commercially used M2 tool steel.

Sikka, V.K.; Blue, C.A. [Oak Ridge National Lab., TN (United States). Metals and Ceramics Div.; Sklad, S.P. [Univ. of Virginia, Charlottesville, VA (United States); Deevi, S.C. [Philip Morris U.S.A., Richmond, VA (United States); Shih, H.R. [Jackson State Univ., MS (United States)

1998-11-01

322

Wetting behaviour in the Al-Si\\/SiC system: interface reactions and solubility effects  

Microsoft Academic Search

The sessile drop technique was used to study the wetting behaviour of Al-Si alloys on SiC sintered ceramic substrates under vacuum in the 700–1100°C temperature interval. Al-Si alloys with Si concentrations up to 50% were tested. An expected non-wetting\\/wetting transition was observed at 900–1000°C due to the presence of an alumina film surrounding the molten alloy. At higher temperatures wetting

A. C. Ferro; B. Derby

1995-01-01

323

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

Microsoft Academic Search

The sessile drop technique was used to study the wetting behavior of Al-Si alloys on SiC sintered ceramic substrates under vacuum in the 700--1,100 C temperature interval. Al-Si alloys with Si concentrations up to 50% were tested. An expected non-wetting\\/wetting transition was observed at 900--1,000 C due to the presence of an alumina film surrounding the molten alloy. At higher

A. C. Ferro; B. Derby

1995-01-01

324

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

325

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

NASA Astrophysics Data System (ADS)

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

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

2010-01-01

326

Si self-diffusion in cubic B20-structured FeSi  

NASA Astrophysics Data System (ADS)

Self-diffusion of implanted 31Si in the ?-phase FeSi (cubic B20-structure) has been determined in the temperature range 660-810 °C using the modified radiotracer technique. With an activation enthalpy of 2.30 eV and a pre-exponential factor of 15×10-8 m2 s-1 the silicon diffusivity was found to be slightly slower than Ge impurity diffusion in FeSi. This difference is proposed to originate from attractive elastic interactions prevailing between the slightly oversized Ge atoms and the Si sublattice vacancies. The results confirm the argument that 71Ge radioisotopes may be used to substitute the short-lived 31Si radiotracers when estimating self-diffusion in silicides.

Riihimäki, I.; Virtanen, A.; Pusa, P.; Salamon, M.; Mehrer, H.; Räisänen, J.

2008-06-01

327

First-principles electronic structure of ?-FeSi2 and FeS2  

NASA Astrophysics Data System (ADS)

Applying density functional theory in the framework of the full-potential linearized augmented plane-wave (FLAPW) method [1], we investigated electronic structure of potential future photovoltaic materials -?-FeSi2 and FeS2 in their bulk phases and for selected surface orientations and terminations. Their band gaps are examined using hybrid functionals as well as many-body perturbation theory in the GW-approximation to get insight of their photovoltaic performance. The gap nature in ?-FeSi2 changes from direct to indirect as suitable stain field is induced in the structure by epitaxially matching with Si substrate. Furthermore, we also studied the atomic and electronic structure of ?-FeSi2 and FeS2 thin films for different orientations with different terminations. The most stable orientations are determined by comparing their cohesive energy. Detailed electronic structure calculations show that surface states originating from Fe play an important role and might determine their photovoltaic properties. [4pt] [1] www.flapw.de

Xu, Pengxiang; Schena, Timo; Blügel, Stefan; Bihlmayer, Gustav

2012-02-01

328

Al-Si crystallographic-orientation transition in Al-Si/TiN layered structures and electromigration performance as interconnects  

NASA Astrophysics Data System (ADS)

Formation of aluminum-silicon (Al-Si) alloy/titanium nitride (TiN) layered structures and their electromigration (EM) performance have been investigated. The crystallographic structure of the TiN film changes with the sputter-deposition conditions. A large negative substrate bias in reactive sputtering induces a structural transition in the TiN film. The crystal orientation normal to the film surface is easily controlled from the zone axis group 111 to the zone axis group 200 direction. The crystallographic orientation of the Al-Si alloy film has been successfully controlled by the film deposition on an orientation controlled barrier TiN film. The Al-Si alloy film grows epitaxially on TiN at the initial stage of deposition and this causes the Al-Si alloy's preferred orientation to the underlying TiN film. These layered structures with different levels of Al-Si alloy preferred orientation have been subjected to EM tests, and the Al-Si alloy film with stronger zone axis group 111 orientation was found to have a longer EM lifetime. The best EM resistance has been obtained on Al-Si alloy film with the strongest zone axis group 111 orientation, which is achieved on a TiN film formed by the nitridation of a titanium (Ti) film. Thus, highly reliable interconnects can be obtained by improving the preferred orientation of Al-Si alloy film using texture improved TiN film.

Onoda, Hiroshi; Kageyama, Makiko; Hashimoto, Keiichi

1995-01-01

329

Adsorption of carbon dioxide on Al/Fe oxyhydroxide.  

PubMed

The structure and reactivity of 0-70mol% Al/Fe iron oxyhydroxides (ferrihydrite in the absence and presence of Al) toward gaseous CO2 were investigated with X-ray photoelectron spectroscopy (XPS), atomic absorption (AA), scanning transmission electron microscopy with electron dispersive X-ray spectroscopy (STEM/EDS), X-ray diffraction (XRD), and attenuated total reflectance Fourier transform Infrared spectroscopy (ATR-FTIR) combined with density functional theory (DFT) calculations. Results showed that Al/Fe oxyhydroxide particles containing more than 20 mol% Al consisted at least in part of Fe-oxyhydroxide with incorporated Al and a discrete AlOOH phase. Results from ATR-FTIR experiments and DFT calculations suggested that the bicarbonate complex formed by passing CO2 over the particles was accommodated on at least three distinct binding sites. At the lowest Al concentrations bicarbonate was bound to individual sites with primarily Fe or Al character. At the highest concentrations of Al (>20 mol%) bicarbonate bound to discrete AlOOH phases became apparent. Results also suggested that the amount of CO2 adsorption for a given particle mass increased as the Al concentration was increased from 0 to 30%. This increase was likely due in large part to differences in the morphology of the particle aggregates that formed in the dry state, which would be expected to affect the amount of surface that was available to adsorb CO2. PMID:23561821

Pierre-Louis, Andro-Marc; Hausner, Douglas B; Bhandari, Narayan; Li, Wei; Kim, Jongsik; Kubicki, James D; Strongin, Daniel

2013-02-06

330

Formation and properties of Al composites reinforced by quasicrystalline AlCuFeB particles  

Microsoft Academic Search

Al-based composites reinforced by icosahedral (i-) Al59Cu25.5Fe12.5B3 quasicrystalline particles were prepared by solid-state sintering. It was found that Al diffusion from the matrix to the quasicrystalline particles induces phase transformation into the ?-Al7Cu2Fe tetragonal phase. In order to preserve the i phase, we used an oxidation pre-treatment of the particles and studied its influence on the kinetics of the phase

S. Kenzari; P. Weisbecker; M. Curulla; G. Geandier; V. Fournee; J. M. Dubois

2008-01-01

331

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

PubMed

Pyrosmalite-(Fe), ideally Fe(II) (8)Si(6)O(15)(OH,Cl)(10) [refined composition in this study: Fe(8)Si(6)O(15)(OH(0.814)Cl(0.186))(10)·0.45H(2)O, octa-iron(II) hexa-silicate deca-(chloride/hydroxide) 0.45-hydrate], is a phyllosilicate mineral and a member of the pyrosmalite series (Fe,Mn)(8)Si(6)O(15)(OH,Cl)(10), which includes pyrosmalite-(Mn), as well as friedelite and mcgillite, two polytypes of pyrosmalite-(Mn). This study presents the first structure determination of pyrosmalite-(Fe) based on single-crystal X-ray diffraction data from a natural sample from Burguillos del Cerro, Badajos, Spain. Pyrosmalite-(Fe) is isotypic with pyrosmalite-(Mn) and its structure is characterized by a stacking of brucite-type layers of FeO(6)-octa-hedra alternating with sheets of SiO(4) tetra-hedra along [001]. These sheets consist of 12-, six- and four-membered rings of tetra-hedra in a 1:2:3 ratio. In contrast to previous studies on pyrosmalite-(Mn), which all assumed that Cl and one of the four OH-groups occupy the same site, our data on pyrosmalite-(Fe) revealed a split-site structure model with Cl and OH occupying distinct sites. Furthermore, our study appears to suggest the presence of disordered structural water in pyrosmalite-(Fe), consistent with infrared spectroscopic data measured from the same sample. Weak hydrogen bonding between the ordered OH-groups that are part of the brucite-type layers and the terminal silicate O atoms is present. PMID:22259315

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

2011-12-14

332

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

PubMed Central

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

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

2012-01-01

333

Synthesis and oxidation resistance of TiAlSiN and multilayer TiAlSiN\\/CrAlN coating  

Microsoft Academic Search

Oxidation resistant is one main factor to investigate for protective coatings of cutting tool application. In addition the formation of multilayer structure can be an alternative in improving the oxidation resistance. The monolayer TiAlSiN and multilayer TiAlSiN\\/CrAlN coating was deposited by cathodic arc ion-plating (AIP) method and oxidation resistance was studied in the range of 800 to 1000 °C. TiAlSiN with

N. Fukumoto; H. Ezura; T. Suzuki

2009-01-01

334

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

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

335

Radiation effects in bulk nanocrystalline FeAl alloy  

Microsoft Academic Search

Bulk-ordered nanocrystalline FeAl intermetallic compound with a grain size of 35 nm was prepared using severe plastic deformation. Nanocrystalline and coarse-grained counterparts with a grain size of 160 nm were subjected to 1.5 MeV Ar ion irradiation at room temperature. Enhanced irradiation resistance of nanocrystalline FeAl has clearly been identified by means of grazing-incidence X-ray diffraction and Mössbauer spectroscopy. At the identical damage

A. Kilmametov; A. Balogh; M. Ghafari; C. Gammer; C. Mangler; C. Rentenberger; R. Valiev; H. Hahn

2012-01-01

336

Melting and casting of FeAl-based cast alloy  

Microsoft Academic Search

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

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

1998-01-01

337

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

NASA Astrophysics Data System (ADS)

The inverted pyramid array textured Si substrate was used as an antireflection technology for ?-FeSi 2 solar cell application. ?-FeSi 2 thin film was deposited on the textured Si substrate by magnetron sputtering. The ?-FeSi 2 thin film remained as the inverted pyramid array and the average reflectance reduced to 4.33% in the wavelength range from 200 nm to 1500 nm. The prototype ?-FeSi 2 /textured-Si heterojunction showed a rectifying ratio of 2.89 × 10 5 and a built-in voltage of 0.58 V.

Xu, Jiaxiong; Yao, Ruohe; Liu, Yurong

2011-09-01

338

U–Mo\\/Al–Si interaction: Influence of Si concentration  

Microsoft Academic Search

Within the framework of the development of low enriched nuclear fuels for research reactors, U–Mo\\/Al is the most promising option that has however to be optimised. Indeed at the U–Mo\\/Al interfaces between U–Mo particles and the Al matrix, an interaction layer grows under irradiation inducing an unacceptable fuel swelling.Adding silicon in limited content into the Al matrix has clearly improved

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

2010-01-01

339

FeAl2O4 nano-rod array structures on Fe(Al) solid solution fabricated by internal oxidation process  

NASA Astrophysics Data System (ADS)

Nano-rod array structure consisting of FeAl2O4 was successfully prepared on Fe-5 mol% Al solid solution. The internal oxidation of Fe-5 mol%Al was carried out at 1000°C for 12 h in Fe/FeO buffer. The nano-rod array structure was obtained by removing Fe in internal oxidation zone with electropolishing. The diameter of nano-rod was ranged from 500 to 800 nm.

Do, D. T. M.; Nanko, M.

2011-03-01

340

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

341

Fabrication, phase transformation studies and characterization of SiC-AlN-Al2OC ceramics. Progress report.  

National Technical Information Service (NTIS)

The research effort conducted to date had two specific objectives: (1) to determine phase relations and phase transformations in SiC-AlN, AlN-Al(sub 2)OC, and SiC-Al(sub 2)OC pseudobinary systems and in SiC-AlN-Al(sub 2)OC pseudoternary system, and (2) to...

A. V. Virkar

1990-01-01

342

Alloy development and processing of FeAl: An overview  

SciTech Connect

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

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

1997-03-01

343

Optical and magneto-optical properties of nanocrystalline Fe-rich Fe-Si alloy films  

Microsoft Academic Search

A set of nanocrystalline and amorphous Fe_1-xSix alloy films with 0 < x < 1 were prepared by DC magnetron sputtering, and their magnetic, optical and magneto-optical (MO) properties were investigated for the 0 < x < 0.5 compositional range. The optical-conductivity (OC) spectrum of amorphous Fe_0.51Si_0.49 alloy film shows a great resemblance with the OC spectrum of crystalline ?

Youngpak Lee; Yuri Kudryavtsev; Janusz Dubowik; Joo Yull Rhee

2003-01-01

344

Surface Microstructure of Fe3Al After Severe Plastic Deformation  

NASA Astrophysics Data System (ADS)

Nanocrystals were produced on the surface of Fe3Al intermetallic compound by a severe plastic deformation technology—surface mechanical attrition. The phase and grain evolutions were characterized through x-ray diffraction technology, transmission electron microscopy, and Mossbauer spectroscopy. The results show that surface grains are refined to 15 nm in average size after 60 min of attrition. The surface grains present inhomogeneity due to the nonuniform plastic deformation when the attrition time is less than 15 min. Large quantities of dislocations and tangles of dislocations are observed in those larger grains. Al8Cr5 phase forms on the surface of Fe3Al samples which have undergone attrition for less than 15 min. When the attrition time increases, the Al8Cr5 phase becomes disordered and dissolves into the matrix. In addition, disordering of Fe3Al occurs only in a very thin area during severe plastic deformation.

Ren, Jiangwei; Li, Dong; Xu, Peiquan

2013-10-01

345

?-FeSi2 Continuous Films Prepared on Corning 7059 Glass by RF-Magnetron Sputtering  

NASA Astrophysics Data System (ADS)

More than 1-?m-thick single-phase ?-FeSi2 continuous films on Corning 7059 glass and quartz have been obtained by an easy method. We controlled the Si/Fe composition ratio of Fe-Si precursor using a Si target with sectorial Fe plates placed on it. Both surface flatness of the film and ?-FeSi2/substrate interface were satisfactory, and cracks were not observed by secondary ion microscopy. Suitable electric properties of ?-FeSi2 for solar cell absorption layers ( p-type, 5 ?\\cdotcm, 40 cm/(V \\cdot s), and 1 × 1017 cm-3) were obtained from a Si/Fe=1.7 Fe-rich precursor.

Okuda, Yukiko; Momose, Noritaka; Takahashi, Masashi; Hashimoto, Yoshio; Ito, Kentaro

2005-09-01

346

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

NASA Astrophysics Data System (ADS)

The current study delivered the measurements of viscosities in the system "FeO"-SiO2 in equilibrium with metallic Fe in the composition range between 15 and 40 wt pct SiO2. The experiments were carried out in the temperature range of 1473 K to 1773 K (1200 °C to 1500 °C) using a rotational spindle technique. An analysis of the quenched sample by electron probe X-ray microanalysis (EPMA) after the viscosity measurement enables the composition and microstructure of the slag to be directly linked with the viscosity. The current results are compared with available literature data. The significant discrepancies of the viscosity measurements in this system have been clarified. The possible reasons affecting the accuracy of the viscosity measurement have been discussed. The activation energies derived from the experimental data have a sharp increase at about 33 wt pct SiO2, which corresponds to the composition of fayalite (Fe2SiO4). The modified quasi-chemical model was constructed in the system "FeO"-SiO2 to describe the current viscosity data.

Chen, Mao; Raghunath, Sreekanth; Zhao, Baojun

2013-06-01

347

Tunnel Magnetoresistance Effect in CoFeB\\/MgO\\/Co FeSi and Co MnSi Tunnel Junctions  

Microsoft Academic Search

We have fabricated MgO-based magnetic tunnel junctions (MTJs) with the CoFeB bottom electrode and top electrodes of poly crystalline Co2FeSi and Co2MnSi Heusler alloys. We have measured temperature dependence of the TMR ratio and TMR-V characteristics at 6 K. We have achieved a high TMR ratio of 90% at RT for the MTJ with Co2FeSi electrode after annealing at 325degC.

T. Daibou; M. Shinano; M. Hattori; Y. Sakuraba; M. Oogane; Y. Ando; T. Miyazaki

2006-01-01

348

Tribological properties of Fe 3Al–Fe 3AlC 0.5 composites under dry sliding  

Microsoft Academic Search

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

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

2005-01-01

349

Oxidation of Fe25Cr4Al-Pd and Fe25Cr4Al-Ru alloys  

Microsoft Academic Search

Fe-25Cr-4Al alloys containing Pd and Ru additions were oxidized in air at 1090C. Scanning electron microscopy, dispersive x-ray analyses, and x-ray mapping were used to characterize the morphologies of the scales formed on these alloys. The results showed that Pd tended to segregate at the oxide-alloy interface as discrete and platelike particles during elevated temperature oxidation of the Pd-containing Fe-Cr-Al

Tjong

1993-01-01

350

NMR and Mössbauer study of FeAl_2  

NASA Astrophysics Data System (ADS)

The ordered alloy FeAl2 was recently recognized as a spin glass, with an anomalously large magnetic moment per Fe, while most of the low-Fe aluminides are non-magnetic. A spin glass is a magnetic system in which the spins freeze in a disordered configuration at low temperatures. NMR and Mössbauer spectroscopy are particularly useful for probing the inhomogeneous local magnetic properties of such materials. We observed a large increase in ^57Fe Mössbauer magnetic hyperfine field at the 35 K spin freezing temperature (T_f). ^27Al NMR linewidths and shifts exhibit Curie-Weiss behavior consistent with a direct, negative transfer hyperfine coupling between the ^27Al and neighboring Fe local moments. The NMR spin-lattice relaxation rates exhibit a peak at T_f, and temperature-independent behavior at high temperatures, which is characteristic of local-moment systems. A detailed model is in excellent agreement with the observed rates, confirming that stable local Fe moments, rather than band magnetism, are the source of the magnetism in FeAl2 contrary to expectations for this material. This work was supported by the Robert A. Welch Foundation, Grant No. A-1526, by the National Science Foundation (DMR-0103455).

Chi, Ji; Li, Yang; Vagizov, Farit; Goruganti Ross, Venkateshwarlu, Jr.

2004-10-01

351

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

SciTech Connect

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

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

2007-02-12

352

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

NASA Astrophysics Data System (ADS)

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

Garcés, Jorge E.; Bozzolo, Guillermo; Hofman, Gerard; Rest, Jeffrey

2007-02-01

353

Mössbauer and SEM study of Fe-Al film  

NASA Astrophysics Data System (ADS)

Fe-Al alloy with Fe/Al ratio of 3:1 was first prepared by argon arc melting. It was subsequently coated on glass slide and cellophane tape using an electron beam gun system to have a thickness of 2,000 Å. X-ray diffraction spectrum of the coated sample indicates a definite texture for the film with a preferential growth along the Fe(110) plane. SEM micrographs of the film showed the presence of nano islands of nearly 3 x 1012/m2 surface density. Composition of different parts of the film was determined using EDAX. Room temperature Fe-57 Mössbauer spectrum of coated sample showed the presence a quadrupole doublet with a splitting of 0.46 mm/s, which is typical of Al-rich iron compounds. MOKE study shows an in-plane magnetic moment.

Sebastian, Varkey; Sharma, Ram Kripal; Lakshmi, N.; Venugopalan, K.

354

Mössbauer and SEM study of Fe Al film  

NASA Astrophysics Data System (ADS)

Fe Al alloy with Fe/Al ratio of 3:1 was first prepared by argon arc melting. It was subsequently coated on glass slide and cellophane tape using an electron beam gun system to have a thickness of 2,000 Å. X-ray diffraction spectrum of the coated sample indicates a definite texture for the film with a preferential growth along the Fe(110) plane. SEM micrographs of the film showed the presence of nano islands of nearly 3 × 1012/m2 surface density. Composition of different parts of the film was determined using EDAX. Room temperature Fe-57 Mössbauer spectrum of coated sample showed the presence a quadrupole doublet with a splitting of 0.46 mm/s, which is typical of Al-rich iron compounds. MOKE study shows an in-plane magnetic moment.

Sebastian, Varkey; Sharma, Ram Kripal; Lakshmi, N.; Venugopalan, K.

2006-04-01

355

Magnetization of ultra thin Fe deposits on Si(111) and Si(100)  

Microsoft Academic Search

We report in-situ SMOKE of ultra-thin Fe deposits on Si(111) and Si(100). Perpendicular magnetisation is observed for growth at 100 K on both substrates but not for growth at 300 K. We correlate the structural and magnetic phase diagrams and we suggest that growth at the lower temperature leads to deposits of more uniform thickness. We attribute the observation of

M. Hardiman; Z. H. Nazir; C.-K. Lo

1996-01-01

356

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

357

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

358

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

359

Chronoamperometric studies of pitting corrosion of Al and (Al–Si) alloys by halide ions in neutral sulphate solutions  

Microsoft Academic Search

The pitting corrosion of Al, (Al+6%Si), and (Al+18%Si) alloys in neutral 0.50 M Na2SO4 solution in the absence and presence of NaCl, NaBr and NaI under the influence of various experimental variables has been studied by using potentiodynamic and chronoamperometric techniques. The results showed that the pitting corrosion resistance of the three Al samples decreases in the order: (Al+18%Si)>(Al+6%Si)>Al. The

Sayed S Abdel Rehim; Hamdi H Hassan; Mohammed A Amin

2004-01-01

360

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

361

Surface acoustic wave devices on AlN/3C-SiC/Si multilayer structures  

NASA Astrophysics Data System (ADS)

Surface acoustic wave (SAW) propagation characteristics in a multilayer structure including a piezoelectric aluminum nitride (AlN) thin film and an epitaxial cubic silicon carbide (3C-SiC) layer on a silicon (Si) substrate are investigated by theoretical calculation in this work. Alternating current (ac) reactive magnetron sputtering was used to deposit highly c-axis-oriented AlN thin films, showing the full width at half maximum (FWHM) of the rocking curve of 1.36° on epitaxial 3C-SiC layers on Si substrates. In addition, conventional two-port SAW devices were fabricated on the AlN/3C-SiC/Si multilayer structure and SAW propagation properties in the multilayer structure were experimentally investigated. The surface wave in the AlN/3C-SiC/Si multilayer structure exhibits a phase velocity of 5528 m s-1 and an electromechanical coupling coefficient of 0.42%. The results demonstrate the potential of AlN thin films grown on epitaxial 3C-SiC layers to create layered SAW devices with higher phase velocities and larger electromechanical coupling coefficients than SAW devices on an AlN/Si multilayer structure. Moreover, the FWHM values of rocking curves of the AlN thin film and 3C-SiC layer remained constant after annealing for 500 h at 540 °C in air atmosphere. Accordingly, the layered SAW devices based on AlN thin films and 3C-SiC layers are applicable to timing and sensing applications in harsh environments.

Lin, Chih-Ming; Chen, Yung-Yu; Felmetsger, Valery V.; Lien, Wei-Cheng; Riekkinen, Tommi; Senesky, Debbie G.; Pisano, Albert P.

2013-02-01

362

Domain wall resistance in AlFe nanocontact  

NASA Astrophysics Data System (ADS)

In spin electronic devices, passing a spin-polarized current through the device is a better way to switch the magnetic configuration than applying an external magnetic field with an external current line, because there are several drawbacks associated with the use of external magnetic fields in terms of energy consumption and the risk of crosstalk. One good method is using a current to induce domain wall motion from a constriction in a spin-valve structure, which generates much interest in the case of spin-dependent electron transport across a nanocontact or a nanoconstriction. The samples are fabricated on a SiO2/Si substrate using electron beam lithography and a lift-off technique. Electron beam lithography was used to define the nanocontact structure and radio frequency magnetic sputtering with pure Ar was used to deposit an Al50Fe50 alloy layer about 30 nm thick and an Au cap-layer about 2 nm thick. Ultrasonic assisted lift-off in acetone is used to obtain the wire and the constriction. The I-V measurement is performed at room temperature without applied magnetic field. A sharp drop in resistance was observed in the 50-nm-wide nanocontact, which is attributed to the removal of the domain wall from the contact by the reflection of spin polarized electron. In the low resistance state, no domain wall is pinned at the contact, while in the high resistance state the presence of a domain wall must be responsible for the additional resistance, which is the domain wall resistance.

Xu, Peng; San, Haisheng; Chen, Xuyuan

2008-05-01

363

Improvement of environmental degradation resistance of Fe–Al-based alloys by surface modification treatments  

Microsoft Academic Search

The influence of surface modifications on the resistance of environmental degradation of an Fe–18Al–0.1Nb–2Si alloy was investigated. A variety of surface modification techniques including electroplating, electroless plating, magnetron sputtering, fluidized bed and pack cementation were applied to the alloy to produce various protective coatings. The result of electrochemical hydrogen permeation tests showed that the specimens with a Ni-coating by a

Pee-Yew Lee; Liu-Ho Chiu; Chih-Fu Yang; Wei-Der Chen; Wu Kai; Jinn P. Chu

1997-01-01

364

Optical properties of amorphous and crystalline FeSi2, TaSi2, MoSi2 and CrSi2 films  

Microsoft Academic Search

The optical properties and the peculiarities of the electron energy spectra of polycrystalline and amorphous TaSi2 FeSi 2, MoSi2 and CrSi2 films were investigated by means of ellipsometric technique. Polycrystalline state in these disilicides was produced by the annealing of as deposited amorphous films at different temperatures and various gas media. The peculiarities of the experimental optical conductivity and imaginary

Yu. V. Kudryavtsev; M. V. Belous; Yu. N. Makogon; S. I. Sidorenko; T. T. Silakova

1997-01-01

365

{beta}-SiAlON-silicon nitride multilayered composites  

SciTech Connect

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

Shigegaki, Yasuhiro [Fine Ceramics Research Association, Nagoya (Japan). Synergy Ceramics Lab.; Brito, M.E.; Hirao, Kiyoshi; Toriyama, Motohiro; Kanzaki, Shuzo [National Industrial Research Inst. of Nagoya (Japan)

1997-10-01

366

Importance of considerations of mixing properties in establishing an internally consistent thermodynamic database: thermochemistry of minerals in the system Mg2SiO4-Fe2SiO4-SiO2  

NASA Astrophysics Data System (ADS)

A thermodynamic solution model is developed for minerals whose compositions lie in the two binary systems Mg2SiO4-Fe2SiO4 and Mg2Si2O6-Fe2Si2O6. The formulation makes explicit provision for nonconvergent ordering of Fe2+ and Mg2+ between M1 and M2 sites in orthopyroxenes and non-zero Gibbs energies of reciprocal ordering reactions in both olivine and orthopyroxene. The calibration is consistent with (1) constraints provided by available experimental and natural data on the Fe-Mg exchange reaction between olivine and orthopyroxene ± quartz, (2) site occupancy data on orthopyroxenes including both crystallographic refinements and Mössbauer spectroscopy, (3) enthalpy of solution data on olivines and orthopyroxenes and enthalpy of disordering data on orthopyroxene, (4) available data on the temperature and ordering dependence of the excess volume of orthopyroxene solid solutions, and (5) direct activity-composition determinations of orthopyroxene and olivine solid solutions at elevated temperatures. Our analysis suggests that the entropies of the exchange [Mg(M2)Fe(M1)?Fe(M2)Mg(M1)] and reciprocal ordering reactions [Mg(M2)Mg(M1)+ Fe(M2)Fe(M1)?Fe(M2)Mg(M1)+Mg(M2)Fe(M1)] cannot differ significantly (± 1 cal/K) from zero over the temperature range of calibration (400° 1300° C). Consideration of the mixing properties of olivine-orthopyroxene solid solutions places tight constraints on the standard state thermodynamic quantities describing Fe-Mg exchange reactions involving olivine, orthopyroxene, pyralspite garnets, aluminate spinels, ferrite spinels and biotite. These constraints are entirely consistent with the standard state properties for the phases ?-quartz, ?-quartz, orthoenstatite, clinoenstatite, protoenstatite, fayalite, ferrosilite and forsterite which were deduced by Berman (1988) from an independent analysis of phase equilibria and calorimetric data. In conjunction with these standard state properties, the solution model presented in this paper provides a means of evaluating an internally consistent set of Gibbs energies of mineral solid solutions in the system Mg2SiO4-Fe2SiO4-SiO2 over the temperature range 0 1300° C and pressure interval 0.001 50 kbars. As a consequence of our analysis, we find that the excess Gibbs energies associated with mixing of Fe and Mg in (Fe, Mg)2SiO4 olivines, (Fe, Mg)3Al2Si3O12 garnets, (Fe, Mg)Al2O4 and (Fe, Mg)Fe2O4 spinels, and K(Mg, Fe)3AlSi3O10(OH)2 biotites may be satisfactory described, on a macroscopic basis, with symmetric regular solution type parameters having values of 4.86±0.12 (olivine), 3.85±0.09 (garnet), 1.96±0.13 (spinel), and 3.21±0.29 kcals/gfw (biotite). Applications of the proposed solution model demonstrate the sensitivity of petrologic modeling to activity-composition relations of olivine-orthopyroxene solutions. We explore the consequences of estimating the activity of silica in melts forming in the mantle and we develop a graphical geothermometer/geobarometer for metamorphic assemblages of olivine+orthopyroxene+quartz. Quantitative evaluation of these results suggests that accurate and realistic estimates of silica activity in melts derived from mantle source regions, P-T paths of metamorphism and other intensive variables of petrologic interest await further refinements involving the addition of “trace” elements (Al3+ and Fe3+) to the thermodynamic formulation for orthopyroxenes.

Sack, Richard O.; Ghiorso, Mark S.

1989-03-01

367

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

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

368

Isothermal Transformation Studies on the Effect of Alloying Elements (Mo, Ni, Cr, Mn, Al, Si, CO) in Steels on the Kinetics of the Austenite to Bainite Transformation.  

National Technical Information Service (NTIS)

Thermodilatomeric experiments were performed on seven Fe-C-X ternary systems (where X = Mo, Ni, Cr, Mn, Al, Si, Co) at different alloy concentrations. TTT diagrams for the isothermal decomposition of austenite in the bainite range were obtained. Extension...

A. M. Llopis

1976-01-01

369

SiAlON ceramic compositions and methods of fabrication  

Microsoft Academic Search

A method of fabricating a SiAlON ceramic body includes: (a) combining quantities of Si[sub 3]N[sub 4], Al[sub 2]O[sub 3] and CeO[sub 2] to produce a mixture; (b) forming the mixture into a desired body shape; (c) heating the body to a densification temperature of from about 1,550 C to about 1,850 C; (d) maintaining the body at the densification temperature

M. H. OBrien; B. H. Park

1994-01-01

370

On the theory of Al, Si ordering in albite  

Microsoft Academic Search

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

E. E. Senderov

1980-01-01

371

Modelling electrical behaviour of nonuniform Al-Si Schottky diodes  

Microsoft Academic Search

The heat-treated Al-Si contacts show large nonuniformities and cannot be described by a one-dimensional theory. The authors partially succeed in describing circular Al\\/n-Si contacts by a crude model: two diodes in parallel (the first central and circular, the second peripheral and annular). It was shown that only a part of the contact area is effective for samples treated at lower

D. Dascalu; G. Brezeanu; P. A. Dan; C. Dima

1981-01-01

372

Dry sliding wear of eutectic Al–Si  

Microsoft Academic Search

The wear of as-cast eutectic Al–Si was studied using pin-on-disk tribotests in two different environments, air and dry argon.\\u000a The counterface in all tests was yttria-stabilized zirconia. It was found that wear of the Al–Si was reduced by about 60%\\u000a by the removal of oxygen from the test environment. The zirconia counterfaces showed measurable wear after tests performed\\u000a in air,

I. BakerY; Y. Sun; F. E. Kennedy; P. R. Munroe

2010-01-01

373

AlSiC composite materials in IGBT power modules  

Microsoft Academic Search

The reliability of IGBT modules is limited by thermal fatigue of soft solder layers due to different coefficients of thermal expansion. A thermally matching conducting material can be produced from Al matrix composites containing high volume fractions of SiC particulates. Variously processed prototypes of AlSiC baseplates were investigated with a view to their suitability for IGBT power modules. The volume

G. Mitic; H. P. Degischer; G. Lefranc; T. Licht

2000-01-01

374

Some effects of unidirectional stress in Si-Fe sheets  

NASA Astrophysics Data System (ADS)

The longitudinal stress effect on magnetic properties of Si-Fe sheet materials is considered. Polish sheet materials (grain oriented ET-5 grade and non-oriented EP-20 grade) were tested. Core losses and permeability were determined using a single sheet tester with a device for exerting tensile and compressive stress. Considerable changes of specific core loss, permeability and the shape of hysteresis loop of specimens subjected to stress were observed.

Dabrowski, M.; Zgodzinski, T.

1989-10-01

375

Adhesive wear behaviour of B 4C and SiC reinforced 4147 Al matrix composites (Al\\/B 4C–Al\\/SiC)  

Microsoft Academic Search

Adhesive wear characteristics of 4147Al\\/B4C, 10, 15 and 20wt.% B4C particle and Al\\/SiC metal matrix composites 20wt.% SiC contain produced by liquid metallurgy have been investigated under the dry sliding conditions and their wear behaviours are compared with 4147 Al\\/SiC-reinforced 20wt.% SiC. The results showed that the wear resistance of Al\\/B4C matrix increases considerably with increasing wt.% B4C particle content

R. Ipek

2005-01-01

376

Structure and magnetic properties of Sm-Fe-Si nitrides with SmFe5 phase  

NASA Astrophysics Data System (ADS)

A study on the structure and magnetic properties of Sm10Fe79Si11Nx has been performed. The Curie temperature was found to reach 641 K. There are also substantial increases in magnetization and magnetocrystalline anisotropy, showing suitable intrinsic magnetic properties for permanent magnet applications.

Fu-Ming, Yang; Qing-An, Li; Yi, Lu; Tang, N.; Tegus, O.; Ming-Jun, Yu; Ru-Wen, Zhao; Bao-Gen, Shen; Lin-Yuan, Yang

1992-08-01

377

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

Microsoft Academic Search

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

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

2008-01-01

378

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

379

Effects of Fe-Enrichment on the Equation of State and Stability of (Mg,Fe)SiO3 Perovskite and Post-Perovskite  

NASA Astrophysics Data System (ADS)

Fe-enrichment in the deep lower mantle has been proposed as an explanation for seismic anomalies such as large low shear velocity provinces (LLSVPs) and ultralow velocity zones (ULVZs). In order to resolve the effect of Fe on the stability and equation of state of the lower mantle’s dominant constituent, (Mg,Fe)SiO3 perovskite, we have studied Fe-rich natural orthopyroxenes, (Mg0.61Fe0.37Ca0.02)SiO3 and (Mg0.25Fe0.70Ca0.05)SiO3 (compositions determined by microprobe analysis), at lower mantle P-T conditions. Pyroxene starting materials were mixed with Au (pressure calibrant and laser absorber) and loaded with NaCl or Ne (pressure medium and thermal insulator) in a symmetric diamond anvil cell. X-ray diffraction experiments at pressures up to 122 GPa with in-situ laser heating were performed at the GSECARS (13-ID-D) and HPCAT (16-ID-B) sectors of the Advanced Photon Source. Heating samples to 2000 K produced single-phase orthorhombic GdFeO3-type perovskite at 63 GPa for the Mg# 61 composition and at 72 GPa for the Mg# 25 composition. At lower pressures (56 GPa for Mg# 61, 67 GPa for Mg# 25), heating both compositions resulted in a mixture of perovskite, SiO2 and (Mg,Fe)O. These measurements provide new constraints on the dependence of (Mg,Fe)SiO3 perovskite stability on pressure and composition. Upon further compression to 93 GPa and higher pressures with laser heating, Mg# 25 perovskite transformed to a two-phase mixture of perovskite and post-perovskite. This is consistent with previous findings that Fe substitution destabilizes (Mg,Fe)SiO3 perovskite relative to (Mg,Fe)SiO3 post-perovskite (Mao et al. 2004, Caracas and Cohen 2005). The bulk modulus at 80 GPa (K80) is ~550 GPa for both Fe-rich perovskites, comparable to values measured for MgSiO3 perovskite (Lundin et al. 2008). However, the volume of Fe-rich perovskites increases linearly with Fe-content. The (Mg0.25Fe0.70Ca0.05)SiO3 perovskite is 3% greater at 80 GPa than V80 for the Mg end-member, corresponding to a 20% density difference. This volume difference arises from variations in the a (2% larger than Fe-free perovskite) and c (1% larger) lattice parameters. Volumes under compression show no evidence of a discontinuity in the range measured; any magnetic spin transition in the Fe is either gradual or has too weak an effect on volume to be observed.

Dorfman, S. M.; Holl, C. M.; Meng, Y.; Prakapenka, V.; Duffy, T. S.

2010-12-01

380

Atomic model for GP-zones in a 6082 Al–Mg–Si system  

Microsoft Academic Search

Heat treatments of 6082 Al-alloy with 0.6 wt% Mg, 0.9 wt% Si, 0.5 wt% Mn and 0.2 wt% Fe can lead to a considerable increase in hardness. This increase is due to the presence of several metastable phases (in particular ??). To determine the structure of the phase formed before the ?? phase, a detailed high resolution electron microscopy (HREM)

C. D. Marioara; S. J. Andersen; J. Jansen; H. W. Zandbergen

2001-01-01

381

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

382

Oxidation behavior of Si-doped nanocomposite CrAlSiN coatings  

Microsoft Academic Search

Recently more and more hard coatings greatly emphasize the importance of oxidation characteristics. This study attempts to dope Si into conventional CrAlN to form the CrAlSixN coatings by RF magnetron sputtering on silicon wafers to investigate how Si content affects oxidation behavior. The oxidation resistance of the CrAlSixN coatings was evaluated after annealing at temperatures ranging from 800 to 1000°C.

Hsien-Wei Chen; Yu-Chen Chan; Jyh-Wei Lee; Jenq-Gong Duh

2010-01-01

383

Investigation of Ti Addition Effects on the Thickness of 55 pct Al-Zn-1.6 pct Si Coating by First-Principles Calculation  

NASA Astrophysics Data System (ADS)

First-principles method was performed to predict the effect of Ti addition on thickness and adhesion of 55 pct Al-Zn-1.6 pct Si coating. The results of optimized geometric configurations, total energy, and charge distributions for the Ti substitution in Fe2Al5 and FeAl3 phases indicated Ti will grab electronic charges from Al atoms, form bonds with neighboring Al, which will reduce the growth of Fe-Al intermetallic layers, and finally enhance the adhesion of the coating/substrate. Furthermore, experiments were performed to validate the prediction results of first-principles successfully.

Wu, Guangxin; Zhang, Jieyu; Ren, Yuling; Li, Guoyang; Wu, Xiaochun; Li, Qian; Chou, Kuochih

2012-06-01

384

Structural characterization by electronic transport properties on Fe3Si films  

NASA Astrophysics Data System (ADS)

We have investigated the electronic transport properties of resistivity, magnetoresistance and the Hall effect on epitaxial and polycrystalline Fe3Si thin films. The electrical transport measurements reveal the microstructure which has not been clarified from x-ray diffraction and/or scanning electron microscopy. We show that (1 0 0)-oriented epitaxial film 36 nm thick on MgO(1 1 1) exhibits ferromagnetic-tunnelling conduction, (1 1 0)-oriented epitaxial film 36 nm thick on yttria stabilized zirconia [YSZ(1 1 1)] is in a percolated region, and polycrystalline film 36 nm thick on Al2O3(1 1 0) and (1 0 0)-oriented epitaxial film 150 nm thick on MgAl2O4(1 0 0) have metallic conduction. These results imply that the electrical transport measurements are a powerful tool for evaluating the microstructure of the samples. The coefficients of the skew and the side-jump scatterings in the extraordinary Hall effect, and the quadratic temperature coefficient of resistivity observed on (1 0 0)-oriented epitaxial film 150 nm thick on MgAl2O4 show that Fe3Si is a ferromagnetic metal where the effective electron mass is slightly enhanced compared with Fe, Co and Ni due to the electron-electron correlation.

Kobayashi, Y.; Kaneko, T.; Kamogawa, M.; Asai, K.; Akiyama, K.; Funakubo, H.

2007-11-01

385

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

386

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

NASA Astrophysics Data System (ADS)

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

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

2012-09-01

387

Precise Measurements of Lattice Compression of Al, Si and Al-Si Alloys by High Pressure X-Ray Diffractometry  

Microsoft Academic Search

By making use of a cubic anvil press equipped with a rotating-target type X-ray generator and a goniometer, lattice compression in Al, Si and Al-Si alloys was precisely measured up to 90 kbar. The experimental precision was greatly improved by newly-devised treatments such as correctioning for off-centering of a sample and for peak shifts due to stacking faults, and the

Masafumi Senoo; Hisao Mii; Ikuya Fujishiro; Takao Fujikawa

1976-01-01

388

Study of magnetization dynamics in Fe\\/FeSi\\/Fe-trilayes using Nuclear Resonant Scattering of Synchrotron Radiation  

Microsoft Academic Search

The difierent spectra were analyzed by means of the fltting program CONUSS (3). The FeSi spacer showed four difierent hyperflne flelds, which are frozen in at low temperatures. At higher temperatures, timespectra could be analyzed by allowing these hyperflne flelds to ?uc- tuate between difierent directions, and accurate values of the ?uctuation frequencies for each hyperflne fleld could be obtained.

N. Planckaert; A. Vantomme; J. Meersschaut

389

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

390

Fine structures in Fe 3 Al alloy layer of a new hot dip aluminized steel  

Microsoft Academic Search

The fine structure in the Fe-Al alloy layer of a new hot dip aluminized steel (HDA) was examined by means of X-ray diffractometry\\u000a (XRD), electron diffraction technique, etc. The test results indicated that the Fe-Al alloy layer of the new aluminized steel\\u000a mainly composed of Fe3Al, FeAl and ?-Fe (Al) solid solution. There was no brittle phase containing higher aluminum

LI Yajiang; Wang Juan; Zhang Yonglan; X. Holly

2002-01-01

391

57Fe Mossbauer spectra in splat quenched Al0.5, 1, 3 and 5 at% Fe alloys  

Microsoft Academic Search

57Fe Mossbauer spectra of highly supersaturated Al-Fe alloys containing 0.5, 1, 3 and 5 at % Fe were obtained. The spectra were interpreted as a superposition of a single line due to isolated Fe atoms and broad quadrupole split lines due to Fe associations and precipitations. From the area ratio between single line and doublet, it was found that the

S. Nasu; U. Gonser; P. H. Shingu; Y. Marakami

1974-01-01

392

Preparation of AlFe nanoparticles by mechanical alloyed technique.  

PubMed

Small metallic particles (1-3 nm) have been obtained using mechanical alloying techniques. Analytical techniques such as scanning electron microscopy have been used for the morphological and chemical characterization of the AlFe alloyed powders. B, Ni and Ti have been explored as reinforced elements to the initial AlFe mixture. X-ray diffraction patterns and transmission electron microscopy (TEM) techniques have been employed for the structural characterization of the small metallic particles. Theoretical simulations based on molecular dynamics have been used to interpret some of the experimental structural results. Furthermore, theoretical simulations of HREM images based on the dynamical theory of electron diffraction have also been obtained and comparisons with the experimental results have been carried out. The complementary analyses determined that the produced clusters are basically AlFe alloyed nanoparticles immersed in a matrix and with multiple defected structures. PMID:16430152

Rosas, G; Esparza, R; Liu, H B; Ascencio, J A; Pérez, R

2005-12-01

393

Interpenetrating Hybrid Reinforcement in Al2O3 Short Fiber Preforms Infiltrated by Al-Si Alloys  

Microsoft Academic Search

In this work, the effect of the Si content and its morphological features on the mechanical properties of different short fiber-reinforced Al-Si matrices is studied. Al-Si alloys with Si contents of 7 wt pct and more contain a percolating Si network in the as-cast condition. The addition of alumina fibers into these Al-Si matrices increases the mechanical properties by forming

Fernando Lasagni; Jorge Antonio Acuña; Hans Peter Degischer

2008-01-01

394

Electron energy loss spectroscopy characterization of TANOS (TaN/Al?O?/Si?N?/SiO?/Si) stacks.  

PubMed

The interfacial layer between the Al?O? layer and the Si?N? layer formed after postdeposition annealing (PDA) of TaN/Al?O?/Si?N?/SiO?/Si (TANOS) stacks was investigated using transmission electron microscopy (TEM), scanning transmission electron microscopy, and electron energy loss spectroscopy (EELS). From the result of the TEM analysis, it was found that the 2-nm-thick interface layer between Al?O? and Si?N? layers was amorphous. The high-loss EELS analysis showed that the phases of the interfacial layer weakly bound together instead of the substoichiometric silicon oxide and amorphous Al?O? near the bottom interface of the crystalline Al?O?. The low-loss EELS analysis showed that aluminum existed in metallic state at the interface. Therefore, we speculated that SiO(x)N(y) could be formed by oxidation of Si?N? during PDA and that metallic aluminum could be formed by the decomposition of weakly bound amorphous Al?O? during electron irradiation. These complicated reactions near the interface could induce oxygen deficiency in the Al?O? layer and finally degrade the retention properties of TANOS stacks. PMID:23920186

Park, Jucheol; Heo, Sung; Chung, JaeGwan; Park, Gyeong-Su

2013-08-01

395

Experimental studies on the ignition of single Ni\\/Al, Fe\\/Al, and Ti particles  

Microsoft Academic Search

The work presented here focuses on the ignition of single Ni- and Fe-coated Al particles in pure CO2 and Ar atmospheres and Ti particles in O2\\/N2 and O2\\/Ar environments. The importance of studying Ni- and Fe-coated Al particles is related to their potential use in propulsion and materials synthesis applications. Meanwhile, Ti combustion may be utilized to eliminate hazardous chemical

Timothy Al Andrzejak

2007-01-01

396

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

SciTech Connect

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

de Farias, Robson F.; Airoldi, Claudio

2001-05-01

397

Oxidation of Fe-25Cr-4Al-Pd and Fe-25Cr-4Al-Ru alloys  

SciTech Connect

Fe-25Cr-4Al alloys containing Pd and Ru additions were oxidized in air at 1090C. Scanning electron microscopy, dispersive x-ray analyses, and x-ray mapping were used to characterize the morphologies of the scales formed on these alloys. The results showed that Pd tended to segregate at the oxide-alloy interface as discrete and platelike particles during elevated temperature oxidation of the Pd-containing Fe-Cr-Al alloys. These Pd particles appeared to improve the adherence of the alumina scale. However, no improvement of the scale adherence of Ru-containing Fe-Cr-Al alloys was observed as outward diffusion of Ru cations to the external alumina scale led to the formation of RuO[sub 2] within this scale.

Tjong, S.C. (City Polytechnic of Hong Kong, Kowloon (Hong Kong))

1993-06-01

398

Interfacial reactions in the SiO2\\/Ru and SiO2\\/Ru\\/Al-Si structures  

Microsoft Academic Search

The interfacial reactions in the structures of Si\\/SiO2 (500 nm)\\/Ru (65 nm) (up to 950 °C) and Si\\/SiO2 (500 nm)\\/Ru (72 nm)\\/Al-0.8 wt % Si (630 nm) (up to 700 °C), were studied by Rutherford backscattering spectrometry, Auger electron spectroscopy, x-ray diffractometry, selected-area electron diffraction, energy-dispersive x-ray spectroscopy, scanning electron microscopy, and transmission electron microscopy. A thin film of Ru

Shi-Qing Wang; Stella Hong; Allen White; Carolyn Hoener; J. W. Mayer

1995-01-01

399

Structural Investigation of Fe-Ni-S and Fe-Ni-Si Melts by High-temperature Fluorescence XAFS Measurements  

SciTech Connect

Iron-nickel (Fe-Ni) alloy is regarded as the most abundant constituent of Earth's core, with an amount of 5.5 wt% Ni in the core based on geochemical and cosmochemical models. The structural role of nickel in liquid Fe-Ni alloys with light elements such as S or Si is poorly understood, largely because of the experimental difficulties of high-temperature melts. Recently, we have succeeded in acquiring Ni K-edge fluorescence x-ray absorption fine structure (XAFS) spectra of Fe-Ni-S and Fe-Ni-Si melts and alloys. Different structural environment of Ni atoms in Fe-Ni-S and Fe-Ni-Si melts is observed, supporting the effect of light elements in Fe-Ni melts.

Manghnani, M.; Hong, X.; Newville, M.; Balogh, J. (Hawaii); (UC)

2007-03-01

400

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

401

Microstructure and mechanical properties of nanoscale SiC\\/Ca ?-SiAlON composites  

Microsoft Academic Search

Ceramic composites comprising nanoscale (less than 200 nm) silicon carbide particles distributed in a matrix of calcium a-SiAlON (a') have been prepared by uniaxial hot pressing, and the reaction sequence, during densification of a sample containing 20 wt% SiC, has been investigated in the temperature range 1400–1800°C. Samples containing up to 20 wt% SiC were produced to near full density

H Wang; Y.-B Cheng; B. C Muddle; L Gao; T. S Yen

1997-01-01

402

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

NASA Astrophysics Data System (ADS)

Self-assembled ?-FeSi2 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 ?-FeSi2 island phase, in an ?-FeSi2{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 ?-FeSi2 phase, and may open new pathways to high-density magnetic memory storage devices.

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

2012-12-01

403

Effect of Antimony on the Interfaces of Cast AlSi-SiC Composites.  

National Technical Information Service (NTIS)

When the matrix alloy of an AlSi7Mg - SiC composite has been modified with antimony, the wetting properties deteriorate. By transmission electron microscopy and microanalysis it is found that this is probably related to the formation of a film-like amorph...

A. Bardal

1991-01-01

404

Current-voltage characteristics of Al&sngbnd;SiO2&sngbnd;Si structures  

Microsoft Academic Search

Experimental results are presented on conduction, breakdown, and switching in Al&sngbnd;SiO2&sngbnd;Si MOS dots. Transitions from the low-conduction state are found to terminate in self-healing breakdowns. There also exists a higher-conduction state in which destructive breakdowns do not occur.

M. Av-Ron; M. Shatzkes

1972-01-01

405

Superconductivity in Al-substituted Ba8Si46 clathrates  

NASA Astrophysics Data System (ADS)

There is a great deal of interest vested in the superconductivity of Si clathrate compounds with sp3 network, in which the structure is dominated by strong covalent bonds among silicon atoms, rather than the metallic bonding that is more typical of traditional superconductors. A joint experimental and theoretical investigation of superconductivity in Al-substituted type-I silicon clathrates is reported. Samples of the general formula Ba8Si46-xAlx, with different values of x were prepared. With an increase in the Al composition, the superconducting transition temperature TC was observed to decrease systematically. The resistivity measurement revealed that Ba8Si42Al4 is superconductive with transition temperature at TC = 5.5 K. The magnetic measurements showed that the bulk superconducting Ba8Si42Al4 is a type II superconductor. For x = 6 sample Ba8Si40Al6, the superconducting transition was observed down to TC = 4.7 K which pointed to a strong suppression of superconductivity with increasing Al content as compared with TC = 8 K for Ba8Si46. Suppression of superconductivity can be attributed primarily to a decrease in the density of states at the Fermi level, caused by reduced integrity of the sp3 hybridized networks as well as the lowering of carrier concentration. These results corroborated by first-principles calculations showed that Al substitution results in a large decrease of the electronic density of states at the Fermi level, which also explains the decreased superconducting critical temperature within the BCS framework. The work provided a comprehensive understanding of the doping effect on superconductivity of clathrates.

Li, Yang; Garcia, Jose; Chen, Ning; Liu, Lihua; Li, Feng; Wei, Yuping; Bi, Shanli; Cao, Guohui; Feng, Z. S.

2013-05-01

406

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

SciTech Connect

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

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

2012-01-09

407

(Si)5-2y(AlP)y alloys assembled on Si(100) from Al-P-Si3 building units  

NASA Astrophysics Data System (ADS)

An original class of IV/III-V hybrid (Si)5-2y(AlP)y/Si(100) semiconductors have been produced via tailored interactions of molecular P(SiH3)3 and atomic Al yielding tetrahedral ``Al-P-Si3'' building blocks. Extensive structural, optical, and vibrational characterization corroborates that these units condense to assemble single-phase, monocrystalline alloys containing 60%-90% Si (y = 0.3-1.0) as nearly defect-free layers lattice-matched to Si. Spectroscopic ellipsometry and density functional theory band structure calculations indicate mild compositional bowing of the band gaps, suggesting that the tuning needed for optoelectronic applications should be feasible.

Watkins, T.; Jiang, L.; Xu, C.; Chizmeshya, A. V. G.; Smith, D. J.; Menéndez, J.; Kouvetakis, J.

2012-01-01

408

Al2Ti precipitation in Al64Fe8Ti28 alloy  

NASA Astrophysics Data System (ADS)

Precipitates of Al2Ti with three different stacking sequences have been observed in Fe-modified Ll2-type ordered Al3Ti specimens. Two of the stacking sequences have been observed previously. The third type of Al2Ti, Al2TiIII, is identified in this study using conventional and highresolution transmission electron microscopy (TEM). The Al2Ti precipitates form as plates along {100} planes and compression tests performed at liquid N temperature show microcracks occurring along those {100} planes. The Al2Ti phase is believed to be responsible for the low cleavage strength that is observed.

Yang, T. Y.; Goo, E.

1994-04-01

409

The effect of Si and microstructure evolution on the thermal expansion properties of Fe–42Ni–Si alloy strips  

Microsoft Academic Search

An alloying element of 0–1.5 wt.% Si was added to an Fe–42%Ni system, and alloy strips were fabricated using a melt drag casting\\u000a process. The effects of the Si and annealing treatments on the thermal expansion properties of Fe–42Ni alloy were investigated.\\u000a The addition of Si enlarged the coexisting temperature region of the solid–liquid phase and reduced the melting point, which

M. K. Kim; J. Namkung; Y. S. Ahn

2008-01-01

410

Deposition and characterization of Al–Si metallic TBC precursor on Mo–Si–B turbine materials  

Microsoft Academic Search

The interfacial reactions of Mo–Si–B with Al–Si metallic coatings during processing to achieve high-temperature corrosion protective mullite coating for advanced turbine materials are discussed. Al–Si is being deposited on the Mo–Si–B substrate material by immersion in liquid Al–Si alloy, molten salt cathodic deposition, and organic electrolysis, to achieve adhesion and compositional gradients across the interfacial region. The interfacial region during

J. E. Jackson; D. L. Olson; B. Mishra; A. N. Lasseigne-Jackson

2007-01-01

411

Synthesis and characterization of Fe 2O 3\\/SiO 2 nanocomposites  

Microsoft Academic Search

Fe2O3\\/SiO2 nanocomposites based on fumed silica A-300 (SBET=337m2\\/g) with iron oxide deposits at different content were synthesized using Fe(III) acetylacetonate (Fe(acac)3) dissolved in isopropyl alcohol or carbon tetrachloride for impregnation of the nanosilica powder at different amounts of Fe(acac)3 then oxidized in air at 400–900°C. Samples with Fe(acac)3 adsorbed onto nanosilica and samples with Fe2O3\\/SiO2 including 6–17wt% of Fe2O3 were

V. M. Bogatyrev; V. M. Gun’ko; M. V. Galaburda; M. V. Borysenko; V. A. Pokrovskiy; O. I. Oranska; E. V. Polshin; O. M. Korduban; R. Leboda; J. Skubiszewska-Zi?ba

2009-01-01

412

Thermal Stress Calculation and Fabrication of 6063 Al\\/60SiC35Al5Si Graded Materials by Spark Plasma Sintering  

Microsoft Academic Search

The high intensity of thermal stress was generated during fabrication of 6063 aluminum\\/60SiC-35Al-5Si double-layer material. In order to decrease the thermal stress, graded materials of Al\\/60SiC-35Al-5Si was fabricated by spark plasma sintering. The CTE in the graded layer was controlled by SiC fraction and particle sizes. The calculation results indicate that the net stress of more than 800 MPa was

Zhang Dongming; Zhang Lianmeng; Gu Xiaofeng; Chen Fei

2008-01-01

413

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

414

Understanding the magnetic anisotropy in Fe-Si amorphous alloys  

SciTech Connect

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

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

2002-08-01

415

The precipitation sequence in Al–Mg–Si alloys  

Microsoft Academic Search

Fine-scale precipitation that occurs during age hardening of Al alloy 6061 has been studied using differential scanning calorimetry (DSC), atom probe field ion microscopy (APFIM) and transmission electron microscopy (TEM). It was found that the precipitation sequence is: independent clusters of Mg and Si atoms?co-clusters that contain Mg and Si atoms?small precipitates of unknown structure??? needle-shaped precipitates?B? lath-shaped precipitates and

G. A. Edwards; K. Stiller; G. L. Dunlop; M. J. Couper

1998-01-01

416

Irradiation mixing of Al into U{sub 3}Si  

SciTech Connect

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

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

1995-11-01

417

Hydrogenation of sulfur dioxide to hydrogen sulfide on chromium promoted Fe\\/SiO 2 catalysts  

Microsoft Academic Search

The hydrogenation of sulfur dioxide to hydrogen sulfide was studied over a series of Fe-Si-Cr catalysts in a flow reactor. These catalysts were prepared by co-precipitation of iron nitrate, sodium silicate and chromium nitrate, which had Cr\\/Fe atomic ratios of 0–0.04 and Si\\/Fe atomic ratios of 0–1.2. The addition of Cr and Si dramatically improved the SO2 hydrogenation activity of

Kuo-Tseng Li; Yao-Chun Hung; Tien-Ting Ko

2003-01-01

418

Mechanical properties of Ni{sub 3}Al and FeAl: Recent developments  

SciTech Connect

Recent developments in the understanding of the ductility and fracture behavior of Ni{sub 3}Al and FeAl are reviewed. Both intrinsic factors (e.g., alloy stoichiometry), and extrinsic factors (e.g., environment) have been shown to affect their mechanical properties. Of all the recent developments, perhaps the most significant is the realization that Ni{sub 3}Al and FeAl are intrinsically ductile (at least on the Al-deficient side of stoichiometry); their brittleness when tested in ambient air is due mainly to environmental embrittlement. Another intriguing discovery is that boron embrittles Ni{sub 3}Al in gaseous hydrogen (until recently, B was though to have only beneficial, or at most neutral, effects). The authors review these and other recent discoveries and discuss, wherever possible, the underlying physical mechanisms giving rise to the observed mechanical behavior.

George, E.P.; Liu, C.T. [Oak Ridge National Lab., TN (United States). Metals and Ceramics Div.

1997-08-01

419

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

420

Microindentation of Al-Cu-Fe icosahedral quasicrystal  

SciTech Connect

Many different microindentation experiments have been performed at ambient temperature on icosahedral quasicrystals (QCs). They have shown that icosahedral QCs, such as Al-Cu-Fe, Al-Pd-Mn, Al-Li-Cu, Al-Ru-Cu and Mg-Zn-Y are rather hard and exhibit a low fracture toughness. In other respects, compression experiments have shown that these materials exhibit a brittle-to-ductile transition temperature (BDTT) at about 0.7 T{sub m} where T{sub m} is the melting temperature. Few results have been reported concerning microindentation experiments performed at high temperatures, either in the brittle or in the ductile regime. The hardness behavior of icosahedral QCs as a function of temperature has been presented in two cases, however: Al-Li-Cu and Al-Pd-Mn. This paper is aimed at providing information about microindentation measurements performed on an icosahedral Al-Cu-Fe alloy over an extended temperature range. The results are analyzed within the frame used for previous results obtained in the same alloy by means of compression experiments.

Giacometti, E.; Baluc, N.; Bonneville, J.; Rabier, J.

1999-10-08

421

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

SciTech Connect

Fe-Si and Co-Si thin films were studied with different Si concentrations by x-ray absorption spectroscopy (XAFS), and the analysis was confronted