These are representative sample records from Science.gov related to your search topic.
For comprehensive and current results, perform a real-time search at Science.gov.
1

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

2

Hot Extrusion of A356 Aluminum Metal Matrix Composite with Carbon Nanotube/Al2O3 Hybrid Reinforcement  

NASA Astrophysics Data System (ADS)

Over the years, the attention of material scientists and engineers has shifted from conventional composite materials to nanocomposite materials for the development of light weight and high-performance devices. Since the discovery of carbon nanotubes (CNTs), many researchers have tried to fabricate metal matrix composites (MMCs) with CNT reinforcements. However, CNTs exhibit low dispersibility in metal melts owing to their poor wettability and large surface-to-volume ratio. The use of an array of short fibers or hybrid reinforcements in a preform could overcome this problem and enhance the dispersion of CNTs in the matrix. In this study, multi-walled CNT/Al2O3 preform-based aluminum hybrid composites were fabricated using the infiltration method. Then, the composites were extruded to evaluate changes in its mechanical properties. In addition, the dispersion of reinforcements was investigated using a hardness test. The required extrusion pressure of hybrid MMCs increased as the Al2O3/CNT fraction increased. The deformation resistance of hybrid material was over two times that of the original A356 aluminum alloy material due to strengthening by the Al2O3/CNTs reinforcements. In addition, an unusual trend was detected; primary transition was induced by the hybrid reinforcements, as can be observed in the pressure-displacement curve. Increasing temperature of the material can help increase formability. In particular, temperatures under 623 K (350 C) and over-incorporating reinforcements (Al2O3 20 pct, CNTs 3 pct) are not recommended owing to a significant increase in the brittleness of the hybrid material.

Kim, H. H.; Babu, J. S. S.; Kang, C. G.

2014-05-01

3

Spark plasma sintering of aluminum matrix composites  

NASA Astrophysics Data System (ADS)

Aluminum matrix composites make a distinct category of advanced engineering materials having superior properties over conventional aluminum alloys. Aluminum matrix composites exhibit high hardness, yield strength, and excellent wear and corrosion resistance. Due to these attractive properties, aluminum matrix composites materials have many structural applications in the automotive and the aerospace industries. In this thesis, efforts are made to process high strength aluminum matrix composites which can be useful in the applications of light weight and strong materials. Spark Plasma Sintering (SPS) is a relatively novel process where powder mixture is consolidated under the simultaneous influence of uniaxial pressure and pulsed direct current. In this work, SPS was used to process aluminum matrix composites having three different reinforcements: multi-wall carbon nanotubes (MWCNTs), silicon carbide (SiC), and iron-based metallic glass (MG). In Al-CNT composites, significant improvement in micro-hardness, nano-hardness, and compressive yield strength was observed. The Al-CNT composites further exhibited improved wear resistance and lower friction coefficient due to strengthening and self-lubricating effects of CNTs. In Al-SiC and Al-MG composites, microstructure, densification, and tribological behaviors were also studied. Reinforcing MG and SiC also resulted in increase in micro-hardness and wear resistance.

Yadav, Vineet

2011-12-01

4

Coating of 6028 Aluminum Alloy Using Aluminum Piston Alloy and Al-Si Alloy-Based Nanocomposites Produced by the Addition of Al-Ti5-B1 to the Matrix Melt  

NASA Astrophysics Data System (ADS)

The Al-12 pctSi alloy and aluminum-based composites reinforced with TiB2 and Al3Ti intermetallics exhibit good wear resistance, strength-to-weight ratio, and strength-to-cost ratio when compared to equivalent other commercial Al alloys, which make them good candidates as coating materials. In this study, structural AA 6028 alloy is used as the base material. Four different coating materials were used. The first one is Al-Si alloy that has Si content near eutectic composition. The second, third, and fourth ones are Al-6 pctSi-based reinforced with TiB2 and Al3Ti nano-particles produced by addition of Al-Ti5-B1 master alloy with different weight percentages (1, 2, and 3 pct). The coating treatment was carried out with the aid of GTAW process. The microstructures of the base and coated materials were investigated using optical microscope and scanning electron microscope equipped with EDX analyzer. Microhardness of the base material and the coated layer were evaluated using a microhardness tester. GTAW process results in almost sound coated layer on 6028 aluminum alloy with the used four coating materials. The coating materials of Al-12 pct Si alloy resulted in very fine dendritic Al-Si eutectic structure. The interface between the coated layer and the base metal was very clean. The coated layer was almost free from porosities or other defects. The coating materials of Al-6 pct Si-based mixed with Al-Ti5-B1 master alloy with different percentages (1, 2, and 3 pct), results in coated layer consisted of matrix of fine dendrite eutectic morphology structure inside ?-Al grains. Many fine in situ TiAl3 and TiB2 intermetallics were precipitated almost at the grain boundary of ?-Al grains. The amounts of these precipitates are increased by increasing the addition of Al-Ti5-B1 master alloy. The surface hardness of the 6028 aluminum alloy base metal was improved with the entire four used surface coating materials. The improvement reached to about 85 pct by the first type of coating material (Al-12 pctSi alloy), while it reached to 77, 83, and 89 pct by the coating materials of Al-6 pct Si-based mixed with Al-Ti5-B1 master alloy with different percentages 1, 2, and 3 pct, respectively.

El-Labban, Hashem F.; Abdelaziz, M.; Mahmoud, Essam R. I.

2014-10-01

5

The dynamic mechanical response of Al 2O 3 and TiB 2 particulate reinforced aluminum matrix composites produced by in-situ reaction  

Microsoft Academic Search

The dynamic mechanical responses of three aluminum matrix composites reinforced with in-situ Al2O3 and TiB2 particulates were investigated in compression at strain rates ranging from 1.710?3 s?1 to 1.5103 s?1. The results showed that these composites exhibit a high strain-rate sensitivity. The strength and initial strain hardening rate of the composites tended to increase with increasing strain rate. And increasing

S. C. Tjong; Z. Y. Ma; R. K. Y. Li

1999-01-01

6

Joining of 6061 Aluminum Matrix-Ceramic Particle Reinforced Composites  

E-print Network

) ) Joining of 6061 Aluminum Matrix-Ceramic Particle Reinforced Composites by R. Kiehn and T. W................... .. ....... ... ... 3 Literature Review ......... ...... ..... ... . . 3 Conventional Aluminum Brazing ........ 4 Aluminum Composite Joining ........... 5 Aluminum Joining by Unconventional Methods

Eagar, Thomas W.

7

Pathways to a family of low-cost, high-performance, metal matrix composites based on aluminum diboride in aluminum  

Microsoft Academic Search

The continued development of a new family of metal matrix composites based on the in-situ formation of AlB2 flakes in liquid aluminum is described. First, a new synthesis technique for the preparation of high aspect ratio AlB2 is demonstrated. Borax and B2O 3 were reacted with molten aluminum to prepare high aspect ratio AlB 2. The focus then shifts to

Aaron Christopher Hall

1999-01-01

8

Spin Forming of Aluminum Metal Matrix Composites  

NASA Technical Reports Server (NTRS)

An exploratory effort between NASA-Marshall Space Flight Center (MSFC) and SpinCraft, Inc., to experimentally spin form cylinders and concentric parts from small and thin sheets of aluminum Metal Matrix Composites (MMC), successfully yielded good microstructure data and forming parameters. MSFC and SpinCraft will collaborate on the recent technical findings and develop strategy to implement this technology for NASA's advanced propulsion and airframe applications such as pressure bulkheads, combustion liner assemblies, propellant tank domes, and nose cone assemblies.

Lee, Jonathan A.; Munafo, Paul M. (Technical Monitor)

2001-01-01

9

A new discontinuously reinforced aluminum MMC: Al+AlB flakes  

Microsoft Academic Search

Development of a novel metal matrix composite based on the Al-B alloy system has been undertaken. Preparation of this discontinuously reinforced material is based on the precipitation of high aspect ratio AlB from an Al-B alloy. This paper describes a number of efforts forced on preparing high volume fractions (> 30 v%) of AlB in aluminum. New insights into the

AARON C. HALL; J. ECONOMY

2000-01-01

10

Formation of aluminum nitride during cryomilling of NiAl  

SciTech Connect

Prealloyed NiAl powders were milled in liquid nitrogen, a process known as cryomilling. The materials, formed by extrusion or hot isostatic pressing the cryomilled powders, exhibit higher creep strengths than unreinforced NiAl during slow strain rate compression testing. The increased strength was attributed to the presence of approximately 10 volume percent AlN particles which were dispersed along the NiAl prior particle boundaries. The presence of AlN particles within a NiAl matrix was not expected based on previous cryomilling work with oxide dispersion strengthened (ODS) nickel and iron alloys by Petkovic-Luton and Vallone. The experiments of Luton, et al. on ODS aluminum alloys indicated that reactions between liquid nitrogen and aluminum were possible and led to Al(O,N) particles. The hypothesis of Lutton, et al. for the formation of the aluminum oxy-nitrides and the absence of AlN x-ray diffraction peaks in the spectra from as-cryomilled NiAl powders convinced researchers that: (1) the nitrogen exists as an interstitial or solid solution element in NiAl after cryomilling, and (2) AlN precipitates during subsequent thermomechanical processing of the powders. Recent work suggests that this hypothesis is not correct. In an effort to establish the nature of nitrogen in cryomilled NiAl, cryomilled powder particles have been subject to bulk chemical analyses, x-ray diffraction analyses, x-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). Evidence supporting the existence of AlN formation on the surface of cryomilled NiAl powders is presented in this paper.

Aikin, B.J.M.; Dickerson, R.M.; Jayne, D.T. (Case Western Reserve Univ., Cleveland, OH (United States)); Farmer, S.; Whittenberger, J.D. (NASA, Cleveland, OH (United States).)

1994-01-01

11

Characterization of tribological behaviour of graphitic aluminum matrix composites, grey cast iron, and aluminum silicon alloys  

NASA Astrophysics Data System (ADS)

In recent years a number of aluminum-silicon alloys and some graphitic aluminum matrix composites have been fabricated for potential tribological applications in the automotive industry, in particular for lightweight high efficiency internal combustion engines to replace conventional uses of cast iron. This study provides a systematic investigation for wear mechanisms in dry sliding of the graphitic aluminum-matrix composites (A356 Al-10%SiC-4%Gr and A356 Al-5%Al2O3-3%Gr) developed for cylinder liner applications. Two eutectic Al-Si alloys (modified with rare earth elements) developed for wear resistant engine blocks were also studied. The tribological behavior of grey cast iron (ASTM A30), which is a traditional material for engine components, was also investigated as reference. For graphitic aluminum matrix composites, a wear mapping approach has been adopted. Three main regimes: ultra mild, mild and severe wear regions were determined in the maps; additionally, a scuffing region was observed. In the ultra mild wear regime the wear resistance was primarily due to the hard particles supporting the load. It was shown that the onset of severe wear in graphitic composites occurred at considerably higher loads compared to A356 aluminum alloy and A356 Al-20% SiC composite. At the onset of severe wear, the surface temperatures and coefficient of friction of the graphitic composites was lower than that of A356 Al-20% SiC. At all testing conditions in the mild wear regime, a protective tribo-layer was formed, which by increasing the speed and load became more continuous, more compact, smoother, and harder. The tribo-layers were removed at the onset of severe wear. An experimental wear map of grey cast iron was constructed; it consisted of three wear regimes: ultra mild, mild and severe wear. In the ultra mild regime a compacted fine iron oxide powder formed on the contact. The onset of severe wear was started with local material transfer to the steel counterface, and continued by increasing the roughness of the counterface. In the mild wear regime the oxide layers on the contact surface controlled the wear. Because of the microstructure of grey cast iron, large size debris formed in the mild regimes, which could promote a transition from mild to severe wear at loading conditions close to the upper limit of the mild regime. The effects of size and morphology of hard phases in eutectic Al-Si alloys on their scuffing and wear resistance was investigated using etching techniques. Scratch tests and sliding wear tests were performed on the Al-Si samples etched to different times. At low loads, the wear rates and scuffing resistance of Al-Si alloys were a strong function of the etching time, surface roughness before etching, and the morphology of the hard phases. In the etched condition, fracture of the hard phases from the roots of the protruded portions of particles caused scuffing; while fracture of the trailing edges of the hard phases controlled the wear rate of the Al-Si alloys.

Riahi, Ahmad Reza

12

Corrosion control of cement-matrix and aluminum-matrix composites  

NASA Astrophysics Data System (ADS)

Corrosion control of composite materials, particularly aluminum-matrix and cement-matrix composites, was addressed by surface treatment, composite formulation and cathodic protection. Surface treatment methods studied include anodization in the case of aluminum-matrix composites and oxidation treatment (using water) in the case of steel rebar for reinforcing concrete. The effects of reinforcement species (aluminum nitride (AIN) versus silicon carbide (SiC) particles) in the aluminum-matrix composites and of admixtures (carbon fibers, silica fume, latex and methylcellulose) in concrete on the corrosion resistance of composites were addressed. Moreover, the effect of admixtures in concrete and of admixtures in mortar overlay (as anode on concrete) on the efficiency of cathodic protection of steel reinforced concrete was studied. For SiC particle filled aluminum, anodization was performed successfully in an acid electrolyte, as for most aluminum alloys. However, for AlN particle filled aluminum, anodization needs to be performed in an alkaline (0.7 N NaOH) electrolyte instead. The concentration of NaOH in the electrolyte was critical. It was found that both silica fume and latex improved the corrosion resistance of rebar in concrete in both Ca(OH)sb2 and NaCl solutions, mainly because these admixtures decreased the water absorptivity. Silica fume was more effective than latex. Methylcellulose improved the corrosion resistance of rebar in concrete a little in Ca(OH)sb2 solution. Carbon fibers decreased the corrosion resistance of rebar in concrete, but this effect could be made up for by either silica fume or latex, such that silica fume was more effective than latex. Surface treatment in the form of water immersion for two days was found to improve the corrosion resistance of rebar in concrete. This treatment resulted in a thin uniform layer of black iron oxide (containing Fesp{2+}) on the entire rebar surface except on the cross-sectional surface. Prior to the treatment, the surface was non-uniform due to rusting. Sand blasting also made the surface uniform, but is an expensive process, compared to the water immersion method. For cathodic protection of steel rebar reinforced concrete, mortar overlay containing carbon fibers and latex needed 11% less driving voltage to protect the rebar in concrete than plain mortar overlay. However, multiple titanium electrical contacts were necessary, whether the overlay contained carbon fibers or not. For the same overlay (containing carbon fibers and latex), admixtures in the concrete also made a significant difference on the effect of cathodic protection; concrete with carbon fibers and silica fume needed 18% less driving voltage than plain concrete and 28% less than concrete containing silica fume.

Hou, Jiangyuan

13

Cathodoluminescent properties of an Am3+ ion in a matrix of yttrium-aluminum garnet Y3Al5O12  

NASA Astrophysics Data System (ADS)

The luminescent properties of an americium ion are studied. Luminescence spectra of americium in yttrium-aluminum garnet are recorded for the first time. The luminescence bands are identified, and the levels responsible for the observed optical transitions are determined.

Kuznetsova, Ya. V.; Usacheva, V. P.; Zamoryanskaya, M. V.

2014-03-01

14

A new discontinuously reinforced aluminum MMC: Al+AlB{sub 2} flakes  

SciTech Connect

Development of a novel metal matrix composite based on the Al-B alloy system has been undertaken. Preparation of this discontinuously reinforced material is based on the precipitation of high aspect ratio AlB{sub 2} from an Al-B alloy. This paper describes a number of efforts forced on preparing high volume fractions (> 30 v%) of AlB{sub 2} in aluminum. New insights into the behavior of the Al-B alloys system allowed this effort to be successful.

HALL,AARON C.; ECONOMY,J.

2000-06-08

15

Mechanisms of fatigue crack initiation and growth in particulate-reinforced aluminum metal matrix composites. Ph.D. Thesis  

Microsoft Academic Search

The high cycle fatigue crack initiation and small crack growth processes of a particulate-reinforced aluminum alloy metal matrix composite (MMC) system have been evaluated. The research is based on a model Al-Si-Mg system in which Si particles are dispersed within an age-hardenable aluminum alloy matrix. The resulting microstructure is systematically controlled with regard to matrix flow behavior, particulate volume fraction

Lukasak

1993-01-01

16

Pathways to a family of low-cost, high-performance, metal matrix composites based on aluminum diboride in aluminum  

NASA Astrophysics Data System (ADS)

The continued development of a new family of metal matrix composites based on the in-situ formation of AlB2 flakes in liquid aluminum is described. First, a new synthesis technique for the preparation of high aspect ratio AlB2 is demonstrated. Borax and B2O 3 were reacted with molten aluminum to prepare high aspect ratio AlB 2. The focus then shifts to further understanding the Al-B alloy system. Work on the Al-B alloy system concentrated on the Al(L) + AlB 2 ? Al(L) + AlB12 peritectic transformation and the growth of AlB2 in aluminum. The equilibrium peritectic transformation temperature was redetermined and found to be 950 +/- 5C. The kinetics of the peritectic transformation were measured and reported for the first time. Cu, Fe, and Si additions were made to the alloy, and their effect on the peritectic reaction was investigated. All three elements shorten the time required for the peritectic reaction to occur. The effect of these three elements on flake growth was also investigated. They each caused a reduction in the size of growing AlB2 flakes. Finally two samples containing more than 30v% AlB2 in aluminum were prepared. Their properties were measured. The sample containing 40v% AlB2 exhibited a flexural strength of 200 MPa. The 35v% sample exhibited a flexural strength of 150 MPa. When the 35v% sample was tested in compression, it exhibited an ultimate strength close to 200 MPa. Its modulus varied from 200--300 GPa depending on the orientation of the loading axis with respect to the flake reinforcement.

Hall, Aaron Christopher

17

Development and compatibility of magnesium matrix fuel plates clad with 6061 aluminum alloy.  

SciTech Connect

Aluminum (Al) is a commonly used matrix for research reactor fuel plates. It has been found that a reaction between the fuel and the aluminum matrix may reduce or increase the irradiation stability of the fuel. To further understand the contribution of the reaction to the irradiation stability, experiments to develop a non-reacting matrix were performed. The work focused on magnesium (Mg), which is an excellent non-reacting matrix candidate and has a neutron absorption coefficient similar to Al. To avoid the formation of a liquid Al/Mg phase, improvements were made to the roll bonding process to achieve acceptable bonding at 415 C. After these methods were developed, fuel plates were produced with two fuels, uranium (U)-2 w/o molybdenum (Mo) and U-10-w/o Mo with two matrices, Al and Mg. A reaction between the magnesium and the 6061 Al cladding was discovered to take place during the processing at 415 C. To minimize the amount of reaction, methods were successfully developed to roll bond the fuel plates at 275 C. No reaction zone was observed in fuel plates processed at 275 C. Using this method, fuel plates with a Mg matrix are planned to be fabricated and included in the next irradiation matrix for the RERTR high density fuel development program.

Wiencek, T. C.

1998-10-22

18

Thermally conducting aluminum nitride polymer-matrix composites  

Microsoft Academic Search

Thermally conducting, but electrically insulating, polymer-matrix composites that exhibit low values of the dielectric constant and the coefficient of thermal expansion (CTE) are needed for electronic packaging. For developing such composites, this work used aluminum nitride whiskers (and\\/or particles) and\\/or silicon carbide whiskers as fillers(s) and polyvinylidene fluoride (PVDF) or epoxy as matrix. The highest thermal conductivity of 11.5W\\/(mK) was

Yunsheng Xu; D. D. L Chung; Cathleen Mroz

2001-01-01

19

Evaluation of Johnson-Cook model constants for aluminum based particulate metal matrix composites  

Microsoft Academic Search

High strain rate and high temperature response of three types of aluminum based particulate metal matrix ceramic composites is investigated by performing split Hopkinson pressure bar (SHPB) experiments. The composites are: NGP-2014 (15% SiC), NGT-6061 (15% SiC), and NGU-6061 (15% Al2O3), in which all the reinforcement materials are percentage by volume. Johnson-Cook constitutive model constants are evaluated from the high

H. Hilfi; N. S. Brar

1996-01-01

20

Aluminum localization in bone from hemodialyzed patients: Relationship to matrix mineralization  

Microsoft Academic Search

Aluminum localization in bone from hemodialyzed patients: Relationship to matrix mineralization. It has been suggested that in uremic bone, aluminum interferes with normal mineralization. Aluminum content and aluminum localization were studied in iliac crest biopsies of two groups of patients on regular hemodialysis; one group had histologic osteomalacia, and little or no bone resorption (group 1); the other, osteitis fibrosa

Giulia Cournot-Witmer; Johanna Zingraff; Jean Jacques Plachot; Franoise Escaig; Roger Lefvre; Pierre Boumati; Agns Bourdeau; Michle Garabdian; Pierre Galle; Raymond Bourdon; Tilman Dreke; Sonia Balsan

1981-01-01

21

Aluminum (Al) Etch Instructions The CEPSR cleanroom stores Aluminum Etchant Type A, a pre-made product used for  

E-print Network

Aluminum (Al) Etch Instructions The CEPSR cleanroom stores Aluminum Etchant Type A, a pre-made product used for removing or etching away aluminum. This etchant is stored inside the acid or corrosive a specific thickness of aluminum that is desired. Note: Once the bottle is empty or you find that it's etch

Kim, Philip

22

Strengthening behavior of chopped multi-walled carbon nanotube reinforced aluminum matrix composites  

SciTech Connect

Strengthening behavior of the aluminum composites reinforced with chopped multi-walled carbon nanotubes (MWCNTs) or aluminum carbide formed during annealing at 500 C has been investigated. The composites were fabricated by hot-rolling the powders which were ball-milled under various conditions. During the early annealing process, aluminum atoms can cluster inside the tube due to the diffusional flow of aluminum atoms into the tube, providing an increase of the strength of the composite. Further annealing induces the formation of the aluminum carbide phase, leading to an overall drop in the strength of the composites. While the strength of the composites can be evaluated according to the rule of mixture, a particle spacing effect can be additionally imparted on the strength of the composites reinforced with the chopped MWCNTs or the corresponding carbides since the reinforcing agents are smaller than the submicron matrix grains. - Highlights: Strengthening behavior of chopped CNT reinforced Al-based composites is investigated. Chopped CNTs have influenced the strength and microstructures of the composites. Chopped CNTs are created under Ar- 3% H2 atmosphere during mechanical milling. Strength can be evaluated by the rule of the mixture and a particle spacing effect.

Shin, S.E.; Bae, D.H., E-mail: donghyun@yonsei.ac.kr

2013-09-15

23

Self-lubricating aluminum metal-matrix composites dispersed with tungsten disulfide and silicon carbide  

SciTech Connect

This paper describes the synthesis and tribological behavior of self-lubricating aluminum alloy metal-matrix composites (MMCs). The formulations of MMCs comprised of tungsten disulfide (WS{sub 2}) and silicon carbide (SiC) particles dispersed in a commercial aluminum alloy (Al-0.40Si-0.75Mg) matrix. Composites were fabricated by a conventional powder metallurgy route involving blending, compacting and sintering. Friction and wear tests (up to a duration of one million cycles) were performed in a ball-on-disk configuration against a steel counterface. Wear scars on MMC disks and steel balls were analyzed in SEM/EDXS. In a dry nitrogen environment, the steady state friction coefficient of an Al-0.10SiC-0.03WS{sub 2}MMC was 0.05, whereas in laboratory air with relative humidity at approximately 65 percent it was 0.10. In both environments, transfer of aluminum to the steel counterface was absent. 20 refs., 12 figs., 2 tabs.

Prasad, S.V. [Systran Corporation, Dayton, OH (United States); Mecklenburg, K.R.

1994-07-01

24

Aluminum sulfate (alum; Al2 O) is used as a  

E-print Network

, and pelletizing, the use of chemical amendments, primarily aluminum sulfate (alum, Al2 (SO4 )3 ·14H2 O), alter of total phosphorus in poultry wastes is in the organic form, with four main types of organic P compounds to inorganic P (Toor et al., 2006). Other minor organic P compounds commonly found in poultry waste include

Sparks, Donald L.

25

Effects of thermal cycling on density, elastic modulus, and vibrational damping in an alumina particulate reinforced aluminum metal matrix composite (Al{sub 2}O{sub 3p}/2014 Al)  

SciTech Connect

The effects of thermal cycling on the mechanical and physical properties, namely, the density, dynamic elastic modulus and vibrational damping, were measured for a particular reinforced metal matrix composite (MMC). The material was made by Duralcan. Specimens were exposed to up thermal cycles from room temperature to 300 C. The density of the material was measured by the Archimedes technique. The dynamic Young`s Modulus and vibrational damping of the material were determined by the piezoelectric ultrasonic composite oscillator technique (PUCOT). The results showed that the density and elastic modulus of the material increased only slightly due to the thermal cycling while the damping increased significantly. An increase in dislocation concentration near the particle/matrix interfaces caused by the thermal cycling could account for the measured results.

Wolfenden, A.; Tang, H.H. [Texas A and M Univ., College Station, TX (United States). Mechanical Engineering Dept.; Chawla, K. [Univ. of Alabama, Birmingham, AL (United States). Dept. of Materials and Mechanical Engineering; Hermel, T. [Univ. of Minnesota, Minneapolis, MN (United States). Dept. of Chemical Engineering and Materials Science

1999-07-01

26

Activation energy for superplastic flow in aluminum matrix composites exhibiting high-strain-rate superplasticity  

SciTech Connect

It is recognized that the activation energy for superplastic flow in metals is in agreement with the activation energy for lattice self-diffusion or for grain boundary diffusion. Moreover, Mishra et al. showed that the activation energy for superplastic flow in a high strain rate superplastic SiC{sub w}/2124Al composite was 313 KJ/mol and they noted that the activation energy was higher than the activation energy for lattice self-diffusion of aluminum (=142 KJ/mol). Very recently, Higashi et al. revealed that an apparent value of the activation energy for superplastic flow was increased by the presence of a liquid phase for mechanically-alloyed materials exhibiting high-strain-rate superplasticity. The same trend was reported in the high-strain-rate superplastic Si{sub 3}N{sub 4w}/Al-Zn-Mg composite. However, there are a few works describing the activation energy for superplastic flow in metal matrix composites from the viewpoint of effects of a liquid phase. In this paper, the activation energies for superplastic flow in a variety of high-strain-rate superplastic Al-Mg(5052), Al-Mg-Si(6061), Al-Zn-Mg(7064) and Al-Cu-Mg(2124) alloy matrix composites have been analyzed.

Mabuchi, M. [National Industrial Research Inst. of Nagoya (Japan)] [National Industrial Research Inst. of Nagoya (Japan); Higashi, K. [Osaka Prefecture Univ., Sakai (Japan)] [Osaka Prefecture Univ., Sakai (Japan)

1996-06-15

27

High Temperature Sliding Wear of Spray-Formed Solid-Lubricated Aluminum Matrix Composites  

NASA Astrophysics Data System (ADS)

The present work describes the tribological study of the aluminum metal matrix composite manufactured by the spray atomization and deposition technique. The immiscible element Sn is added in the Al-Si alloy in different proportion to see its effect on wear behavior. The economical mineral zircon sand (8 vol.%) of size range 63-90 ?m has been used as ceramic reinforcement. The microstructural features showed that Sn and reinforced particles were homogeneously dispersed in the matrix phase. The wear experiments were conducted at high temperature on pin-on-disk wear testing machine. The wear debris and worn surfaces are analyzed with the help of scanning electron microscope equipped with energy-dispersive spectroscopy facility. The Al-Si-10Sn/ZrSiO4 composite offers higher wear resistance as compared to base alloy and other composites irrespective of the high temperature conditions of wear tests.

Kaur, Kamalpreet; Pandey, O. P.

2013-10-01

28

Specific features of the electronic and atomic structures of silicon single crystals in the aluminum matrix  

NASA Astrophysics Data System (ADS)

Films of Al-Si nanocomposites produced by magnetron evaporation of a complex target onto a silicon substrate have been investigated using scanning electron microscopy, X-ray diffraction, ultrasoft X-ray emission spectroscopy, and X-ray absorption near edge structure spectroscopy. It has been found that silicon inclusions are nanocrystals with the mean size of 20-25 nm, with the surface covered by an amorphous silicon layer. The presence of the aluminum matrix in the initial films changes their band structures, in particular, near the bottom of the valence band. After the removal of aluminum, the structure of the valence band becomes identical to that in the bulk material and the structure of the conduction band indicates the presence of a disordered surface layer with a thickness of 5 nm.

Terekhov, V. A.; Lazaruk, S. K.; Usol'tseva, D. S.; Leshok, A. A.; Katsuba, P. S.; Zanin, I. E.; Spirin, D. E.; Stepanova, A. A.; Turishchev, S. Yu.

2014-12-01

29

The processing and characterization of sintered metal-reinforced aluminum matrix composites  

Microsoft Academic Search

Aluminum metal matrix composites are often reinforced with costly ceramic materials. However, porous sintered metal compacts can provide a low-cost alternative. The objective of this investigation was to produce and characterize sintered ferrous metal reinforced 380 aluminum alloy matrix composites, fabricated through a high-pressure casting technique. Tensile, compressive, and rolling contact fatigue tests were used to evaluate the composite properties.

Richard Paul Baron

1998-01-01

30

Severe plastic deformation processing and high strain rate superplasticity in an aluminum matrix composite  

Microsoft Academic Search

Metal matrix composites possess an attractive set of properties for structural applications. For example, reinforcement of conventional aluminum alloys with second phase ceramic particulates increases the stiffness, high temperature strength, etc. A drawback of ceramic phase reinforcement is that it makes machining of components difficult. Superplastic forming is quite attractive for hard-to-machine materials like composites. A number of aluminum matrix

R. S. Mishra; R. Z Valiev; S. X McFadden; R. K Islamgaliev; A. K Mukherjee

1999-01-01

31

A calorimetric investigation of fiber\\/matrix reactions in fiber-reinforced aluminum alloy 339  

Microsoft Academic Search

The fiber\\/matrix reaction in aluminum composites reinforced with discontinuous ceramic fibers is critical to the formation of a strong interfacial bond. The reactions at ?500C in Kaowool- and Saffil-reinforced 339 aluminum casting alloys were measured by differential isothermal calorimetry. The reaction exotherm is superimposed upon an endotherm associated with dissolution of magnesium-containing precipitates in the aluminum matrix. The time constants

George W. Smith; William J. Baxter; Anil K. Sachdev

2000-01-01

32

Modulus, strength and thermal exposure studies of FP-Al2O3/aluminum and FP-Al2O3/magnesium composites  

NASA Technical Reports Server (NTRS)

The mechanical properties of FP-Al2O3 fiber reinforced composites prepared by liquid infiltration techniques are improved. A strengthening addition, magnesium, was incorporated with the aluminum-lithium matrix alloy usually selected for these composites because of its good wetting characteristics. This ternary composite, FP-Al2O3/Al-(2-3)Li-(3-5)Mg, showed improved transverse strength compared with FP-Al2O3/Al-(2-3)Li composites. The lower axial strengths found for the FP-Al2O3/Al-(2-3)Li-(3-5)Mg composites were attributed to fabrication related defects. Another technique was the use of Ti/B coated FP-Al2O3 fibers in the composites. This coating is readily wet by molten aluminum and permitted the use of more conventional aluminum alloys in the composites. However, the anticipated improvements in the axial and transverse strengths were not obtained due to poor bonding between the fiber coating and the matrix. A third approach studied to improve the strengths of FP-Al2O3 reinforced composites was the use of magnesium alloys as matrix materials. While these alloys wet fibers satisfactorily, the result indicated that the magnesium alloy composites used offered no axial strength or modulus advantage over FP-Al2O3/Al-(2-3)Li composites.

Bhatt, R. T.

1981-01-01

33

Corrosion and wear resistance of titanium- and aluminum-based metal matrix composites fabricated by direct metal laser deposition  

NASA Astrophysics Data System (ADS)

Titanium- and Aluminum-based metal matrix composites (MMC) have shown favorable properties for aerospace applications such as airframes, reinforcement materials and joining elements. In this research, such coatings were developed by direct metal laser deposition with a powder-fed fiber coupled diode laser. The MMC formulations consisted of pure titanium and aluminum matrices with reinforcing powder blends of chromium carbide and tungsten carbide nickel alloy. Two powder formulations were investigated for each matrix material (Ti1, Ti2, Al1 and Al2). Titanium based composites were deposited onto a Ti6Al4V plate while aluminum composites were deposited onto AA 7075 and AA 5083 for Al1 and Al2, respectively. Microstructures of the MMCs were studied by optical and scanning electron microscopy. The hardness and reduced Young's modulus (Er) were assessed through depth-sensing instrumented nanoindentation. microhardness (Vickers) was also analyzed for each composite. The corrosion resistance of the MMCs were compared by monitoring open circuit potential (OCP), polarization resistance (Rp) and potentiodynamic polarization in 0.5 M NaCl to simulate exposure to seawater. The Ti-MMCs demonstrated improvements in hardness between 205% and 350% over Ti6Al4V. Al-MMCs showed improvements between 47% and 79% over AA 7075 and AA 5083. The MMCs showed an increase in anodic current density indicating the formation of a less protective surface oxide than the base metals.

Waldera, Benjamin L.

34

49 CFR 178.46 - Specification 3AL seamless aluminum cylinders.  

Code of Federal Regulations, 2014 CFR

...Cylinders 178.46 Specification 3AL seamless aluminum cylinders. (a) Size and service pressure. A DOT 3AL cylinder is a seamless aluminum cylinder with a maximum water...following: (A) American Standard Pipe Thread (NPT) type, conforming to...

2014-10-01

35

Mechanical characterization of copper coated carbon nanotubes reinforced aluminum matrix composites  

SciTech Connect

In this investigation, carbon nanotube (CNT) reinforced aluminum composites were prepared by the molecular-level mixing process using copper coated CNTs. The mixing of CNTs was accomplished by ultrasonic mixing and ball milling. Electroless Cu-coated CNTs were used to enhance the interfacial bonding between CNTs and aluminum. Scanning electron microscope analysis revealed the homogenous dispersion of Cu-coated CNTs in the composite samples compared with the uncoated CNTs. The samples were pressureless sintered under vacuum followed by hot rolling to promote the uniform microstructure and dispersion of CNTs. In 1.0 wt.% uncoated and Cu-coated CNT/Al composites, compared to pure Al, the microhardness increased by 44% and 103%, respectively. As compared to the pure Al, for 1.0 wt.% uncoated CNT/Al composite, increase in yield strength and ultimate tensile strength was estimated about 58% and 62%, respectively. However, in case of 1.0 wt.% Cu-coated CNT/Al composite, yield strength and ultimate tensile strength were increased significantly about 121% and 107%, respectively. - Graphical Abstract: Copper coated CNTs were synthesized by the electroless plating process. Optimizing the plating bath to (1:1) by wt CNTs with Cu, thickness of Cu-coated CNTs has been reduced to 100 nm. Cu-coated CNTs developed the stronger interfacial bonding with the Al matrix which resulted in the efficient transfer of load. Highlights: Copper coated CNTs were synthesized by the electroless plating process. Thickness of Cu-coated CNTs has been reduced to 100 nm by optimized plating bath. In 1.0 wt.% Cu-coated CNT/Al composite, microhardness increased by 103%. Cu-coated CNTs transfer load efficiently with stronger interfacial bonding. In 1.0 wt.% Cu-coated CNT/Al composite, Y.S and UTS increased by 126% and 105%.

Maqbool, Adnan, E-mail: adnanmaqbool247@gmail.com [Faculty of Materials Science and Engineering, GIK Institute of Engineering Sciences and Technology, Topi 23640, KP (Pakistan); School of Nano and Advanced Material Engineering, Changwon National University, Gyeongnam 641-773 (Korea, Republic of); Hussain, M. Asif; Khalid, F. Ahmad; Bakhsh, Nabi [Faculty of Materials Science and Engineering, GIK Institute of Engineering Sciences and Technology, Topi 23640, KP (Pakistan); Hussain, Ali; Kim, Myong Ho [School of Nano and Advanced Material Engineering, Changwon National University, Gyeongnam 641-773 (Korea, Republic of)

2013-12-15

36

Tailoring Microstructure and Properties of Hierarchical Aluminum Metal Matrix Composites Through Friction Stir Processing  

NASA Astrophysics Data System (ADS)

The fabrication of hierarchical aluminum metal matrix composites (MMCs) begins with the cryomilling of inert gas-atomized AA5083 Al powders with B4C particles, which yields agglomerates of nanocrystalline (NC) Al grains containing a uniform dispersion of solidly bonded, submicron B4C particles. The cryomilled agglomerates are size classified, blended with coarse-grain Al (CG-Al) powders, vacuum degassed at an elevated temperature, and consolidated to form the bulk composite. This hierarchical Al MMCs have low weight and high strength/stiffness attributable to the (A) Hall-Petch strengthening from NC-Al (5083) grains, (B) Zener pinning effects from B4C particulate reinforcement and dispersoids in both the NC-Al and CG-Al, (C) the interface characteristics between the three constituents, and (D) a high dislocation density. The hierarchical Al MMCs exhibit good thermal stability and microstructural characteristics that deflect or blunt crack propagation. A significant change in the microstructure of the composite was observed after friction stir processing (FSP) in the thermomechanically affected zone (TMAZ) due to the mechanical mixing, particularly in the advancing side of the stir zone (SZ). The NC-Al grains in the TMAZ grew during FSP. Evidence of CG-Al size reduction was also documented since CG-Al domain was absent by optical observation. Given the proper control of the microstructure, FSP has demonstrated its potential to increase both strength and ductility, and to create functionally tailored hierarchical MMCs through surface modification, graded structures, and other hybrid microstructural design.

Sohn, Y. H.; Patterson, T.; Hofmeister, C.; Kammerer, C.; Mohr, W.; van den Bergh, M.; Shaeffer, M.; Seaman, J.; Cho, K.

2012-02-01

37

X-ray studies of aluminum alloy of the Al-Mg-Si system subjected to SPD processing  

NASA Astrophysics Data System (ADS)

Recently it has been established that during high pressure torsion dynamic aging takes place in aluminum Al-Mg-Si alloys resulting in formation of nanosized particles of strengthening phases in the aluminum matrix, which greatly improves the electrical conductivity and strength properties. In the present paper structural characterization of ultrafine-grained (UFG) samples of aluminum 6201 alloy produced by severe plastic deformation (SPD) was performed using X-ray diffraction analysis. As a result, structure features (lattice parameter, size of coherent scattering domains) after dynamic aging of UFG samples were determined. The size and distribution of second- phase particles in the Al matrix were assessed with regard to HPT regimes. Impact of the size and distribution of the formed secondary phases on the strength, ductility and electrical conductivity is discussed.

Sitdikov, V. D.; Murashkin, M. Yu; Khasanov, M. R.; Kasatkin, I. A.; Chizhov, P. S.; Bobruk, E. V.

2014-08-01

38

Aluminum-matrix composite materials with shungite rock fillers  

NASA Astrophysics Data System (ADS)

A method is proposed for the introduction of shungite rocks into aluminum melts by mechanical mixing with carriers, namely, aluminum granules and reactive titanium powders taking part in exothermic in situ reactions. The structures of composite materials with shungite rock additions are studied, and a stabilizing effect of these additions on dry sliding friction is revealed.

Kalashnikov, I. E.; Kovalevski, V. V.; Chernyshova, T. A.; Bolotova, L. K.

2010-11-01

39

Corrosion of Continuous Fiber Reinforced Aluminum Metal Matrix Composites (CF-AMCs)  

NASA Astrophysics Data System (ADS)

The first objective of this research is to study the atmospheric corrosion behavior of continuous reinforced aluminum matrix composites (CF-AMCs). The materials used for this research were alumina (Al2O3) and nickel (Ni) coated carbon (C) fibers reinforced AMCs. The major focus is to identify the correlation between atmospheric parameters and the corrosion rates of CF-AMCs in the multitude of microclimates and environments in Hawai'i. The micro-structures of CF-AMCs were obtained to correlate the microstructures with their corrosion performances. Also electrochemical polarization experiments were conducted in the laboratory to explain the corrosion mechanism of CF-AMCs. In addition, CF-AMCs were exposed to seven different test sites for three exposure periods. The various climatic conditions like temperature (T), relative humidity (RH), rainfall (RF), time of wetness (TOW), chloride (Cl- ) and sulfate (SO42-) deposition rate, and pH were monitored for three exposure period. Likewise, mass losses of CF-AMCs at each test site for three exposure periods were determined. The microstructure of the CF-AMCS showed that Al/C/50f MMCs contained a Ni-rich phase in the matrix, indicating that the Ni coating on the C fiber dissolved in the matrix. The intermetallic phases obtained in Al-2wt% Cu/Al 2O3/50f-T6 MMC and Al-2wt%-T6 monolith were rich in Cu and Fe. The intermetallic phases obtained in Al 7075/Al2O3/50f-T6 MMC and Al 7075-T6 monolith also contained traces of Mg, Zn, Ni, and Si. Electrochemical polarization experiment indicated that the Al/Al 2O3/50f Al-2wt% Cu/Al2O3/50f-T6 and Al 7075/Al2O3/50f-T6 MMC showed similar corrosion trends as their respective monoliths pure Al, Al-2wt%-T6 and Al 7075-T6 in both aerated and deaerated condition. Al2O3 fiber, being an insulator, did not have a great effect on the polarization behavior of the composites. Al/C/50f MMCs corroded at a much faster rate as compared to pure Al monolith due to the galvanic effect between C and Al. According to the mass loss data of Al/C/50f MMCs, corrosion rate was high at marine environments (high Cl-) when compared to a tropical rainforest microclimate and low in a test site with a high SO2 and acid rain. Due to presence of conductive C fiber, the galvanic corrosion was a dominating corrosion mechanism. Due to high volume fraction of C, the corrosion phenomenon was cathodically controlled. The galvanic corrosion between C fiber and Al matrix showed a strong positive correlation with Cl - deposition rate. Lower corrosion rate at volcanic test site was attributed to dissolution of Ni rich phase, a potential cathodic site that promotes corrosion of Al/C/50f MMCs. Based on the mass loss data of Al2O3 based CF-AMCs and the monoliths showed maximum corrosion at volcanic test site when compared to any other test site. Due to the small volume fraction of intermetallic phases, the corrosion was anodically controlled. And hence the maximum anodic dissolution was found at volcanic test site (high SO2 and acid rain). The second objective of this thesis is to study the effect localized deformation on the corrosion of CF-AMCs. Corrosion initiation on Al (2 wt% Cu)/Al2O3/60f (60% fiber), Al 6061/Al2O 3/60f, and Al/Al2O3/60f CF-AMCs was studied in an aqueous environment The CF-AMCs and their monolithic alloys were deformed locally using a 1/16" diameter silicon nitride ball and 15-60 Kg load in a Rockwell hardness testing machine. Corrosion initiated at the deformed sites, and after longer exposures, spread over the entire region. Localized mechanical deformation resulted in micro-crevice formations at the fiber matrix interface. When deformed material is exposed to a corrosive solution, the crevices at the fiber matrix interface likely increased the hydrogen ion concentration lowering the pH at those regions, a process that leads to premature corrosion. The copper (Cu) rich CF-AMCs in aqueous solution resulted in dissolution of Cu rich phase and their subsequent deposition and redistribution as Cu over the deformed CF-AMCs surface. The corrosion rates of deformed C

Tiwari, Shruti

40

Fluid cracking catalyst process using a zeolite dispersed in a magnesia-alumina-aluminum phosphate matrix  

Microsoft Academic Search

In a process for cracking gasoline feedstock with superior relectivity to gasoline production and greater metals tolerance, the gasoline feedstock is brought into contact with a fluid cracking catalyst comprising a zeolite dispersed in a magnesia-alumina-aluminum phosphate matrix in which the matrix has outstanding thermal stability.

H. E. Swift; J. J. Stanulonis; E. H. Reynolds

1979-01-01

41

Kinetic energy distributions of sputtered neutral aluminum clusters: Al--Al[sub 6  

SciTech Connect

Neutral aluminum clusters sputtered from polycrystalline aluminum were analyzed by laser postionization time-of-flight (TOF) mass spectrometry. The kinetic energy distributions of Al through Al[sub 6] were measured by a neutrals time-of-flight technique. The interpretation of laser postionization TOF data to extract velocity and energy distributions is presented. The aluminum cluster distributions are qualitatively similar to previous copper cluster distribution measurements from our laboratory. In contrast to the steep high energy tails predicted by the single- or multiple- collision models, the measured cluster distributions have high energy power law dependences in the range of E[sup [minus]3] to E[sup [minus]4.5]. Correlated collision models may explain the substantial abundance of energetic clusters that are observed in these experiments. Possible influences of cluster fragmentation on the distributions are discussed.

Coon, S.R.; Calaway, W.F.; Pellin, M.J. (Argonne National Lab., IL (United States)); Curlee, G.A. (Trinity Univ., San Antonio, TX (United States). Dept. of Physics); White, J.M. (Texas Univ., Austin, TX (United States). Dept. of Chemistry and Biochemistry)

1992-01-01

42

Kinetic energy distributions of sputtered neutral aluminum clusters: Al--Al{sub 6}  

SciTech Connect

Neutral aluminum clusters sputtered from polycrystalline aluminum were analyzed by laser postionization time-of-flight (TOF) mass spectrometry. The kinetic energy distributions of Al through Al{sub 6} were measured by a neutrals time-of-flight technique. The interpretation of laser postionization TOF data to extract velocity and energy distributions is presented. The aluminum cluster distributions are qualitatively similar to previous copper cluster distribution measurements from our laboratory. In contrast to the steep high energy tails predicted by the single- or multiple- collision models, the measured cluster distributions have high energy power law dependences in the range of E{sup {minus}3} to E{sup {minus}4.5}. Correlated collision models may explain the substantial abundance of energetic clusters that are observed in these experiments. Possible influences of cluster fragmentation on the distributions are discussed.

Coon, S.R.; Calaway, W.F.; Pellin, M.J. [Argonne National Lab., IL (United States); Curlee, G.A. [Trinity Univ., San Antonio, TX (United States). Dept. of Physics; White, J.M. [Texas Univ., Austin, TX (United States). Dept. of Chemistry and Biochemistry

1992-12-01

43

Carbide coated fibers in graphites-aluminum composites. [(fabrication of metal matrix composites)  

NASA Technical Reports Server (NTRS)

Research activities are described for a NASA-supported program at the Los Alamos Scientific Laboratory to develop graphite fiber-aluminum matrix composites. A chemical vapor deposition apparatus was constructed for continuously coating graphite fibers with TiC. As much as 150 meters of continuously coated fibers were produced. Deposition temperatures were varied from 1365 K to about 1750 K, and deposition time from 6 to 150 seconds. The 6 sec deposition time corresponded to a fiber feed rate of 2.54 m/min through the coater. Thin, uniform, adherent TiC coats, with thicknesses up to approximately 0.1 micrometer were produced on the individual fibers of Thornel 50 graphite yarns without affecting fiber strength. Although coat properties were fairly uniform throughout a given batch, more work is needed to improve the batch-to-batch reproducibility. Samples of TiC-coated Thornel 50 fibers were infiltrated with an aluminum alloy and hot-pressed in vacuum to produce small composite bars for flexure testing. Strengths as high as 90% of the rule-of-mixtures strength were achieved. Results of the examination of the fracture surfaces indicate that the bonding between the aluminum and the TiC-coated fibers is better than that achieved in a similar, commercially infiltrated material made with fibers having no observable surface coats. Several samples of Al-infiltrated, TiC-coated Thornel 50 graphite yarns, together with samples of the commercially infiltrated, uncoated fibers, were heated for 100 hours at temperatures near the alloy solidus. The TiC-coated samples appear to undergo less reaction than do the uncoated samples. Photomicrographs are shown.

Imprescia, R. J.; Levinson, L. S.; Reiswig, R. D.; Wallace, T. C.; Williams, J. M.

1976-01-01

44

Wear characteristic of in situ synthetic TiB 2 particulate-reinforced Al matrix composite formed by laser cladding  

Microsoft Academic Search

In order to improve the wear resistance of an aluminum alloy, an in situ synthesized TiB2 particulate-reinforced metal matrix composite coating was formed on a 2024 aluminum alloy by laser cladding with a powder mixture of Fe-coated boron, Ti and Al was successfully achieved using a 3-kW CW CO2 laser. The chemical composition, microstructure and phase structure of the composite

Jiang Xu; Wenjin Liu

2006-01-01

45

Manufacturing of nanostructured Al/WCp metal- matrix composites by accumulative press bonding  

NASA Astrophysics Data System (ADS)

The accumulative press bonding (APB) process used as a novel technique in this study provides an effective alternative method for manufacturing Al/10 vol.% WCp metal matrix composites (MMCs). The results revealed that by increasing the number of APB cycles (a) the uniformity of WC particles in aluminum matrix improved, (b) the porosity of the composite eliminated, (c) the particle free zones decreased. The X-ray diffraction results also showed that nanostructured Al/WCp composite with the average crystallite size of 58.4 nm was successfully achieved by employing 14 cycles of APB technique. The tensile strength of the composites enhanced by increasing the number of APB cycles, and reached to a maximum value of 216 MPa at the end of 14th cycle, which is 2.45 and 1.2 times higher than obtained values for annealed (raw material, 88 MPa) and 14 cycles APB-ed monolithic aluminum (180 MPa), respectively

Amirkhanlou, Sajjad; Ketabchi, Mostafa; Parvin, Nader; Khorsand, Shohreh; Carreo, Fernando

2014-08-01

46

The study of in-situ formed alumina and aluminide intermetallic reinforced aluminum-based metal matrix composites  

NASA Astrophysics Data System (ADS)

Aluminum-based metal matrix composites (MMCs) have been widely used as structural materials in the automobile and aerospace industry due to their specific properties. In this thesis, we report the fabrication of in-situ formed alumina and aluminide intermetallic reinforced aluminum-based metal matrix composites by the displacement reactions between Al and selected metal oxides (NiO, CuO and ZnO). These MMCs were produced when the Al-20wt% NiO, Al-20wt% CuO and Al-10wt% ZnO green compacts were reaction sintered in the tube furnaces. In this work, differential thermal analysis (DTA) was performed on the green samples. The green samples were then sintered separately in different tube furnaces for 30 minutes. In order to study the reaction mechanisms, the x-ray diffractometry (XRD) was used to obtain diffraction patterns of these sintered samples, the scanning electron microscope (SEM) and transmission electron microscope (TEM) were used to study the microstructures of these samples. The elemental quantitative compositions of samples were determined by the energy dispersive x-ray spectrometry (EDX). In order to study the effect of cooling rate on the samples, the green samples were further sintered to 1000C and cooled down to room temperature in different conditions: by furnace-cooling, air-quenching, oil-quenching or NaCl-solution-quenching. The SEM, TEM and atomic force microscopy (AFM) were conducted to investigate their microstructures. A microhardness tester was used to measure the hardness values of these samples. It was found that during sintering of the Al-20wt% NiO green sample, displacement reaction between Al and NiO initially occurred in solid-solid form and was soon halted by its products that separated the NiO particles from the Al matrix. The reaction then resumed in solid-liquid form as the temperature increased to the eutectic temperature of Al3Ni-Al when liquid (Al, Ni) phase appeared in the sample. After cooling, Al2O 3 particles, Al3Ni proeutectic phase and fiber-like Al 3Ni-Al eutectic were found in the sintered Al-MMC sample. (Abstract shortened by UMI.)

Yu, Peng

47

Fracture toughness of SiC/Al metal matrix composite  

NASA Technical Reports Server (NTRS)

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

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

1989-01-01

48

The crystallization and growth of AlB2 single crystal flakes in aluminum  

Microsoft Academic Search

An {ital in situ} high temperature heat treatment was used to investigate the crystallization and growth behavior of AlB flakes in aluminum. Aluminum samples containing 1.8% boron were heated above the liquidus and then rapidly cooled through the Al{sub (L)}+AlB region to avoid the formation of AlB crystals. Subsequently, a homogeneous distribution of high aspect ratio AlB flakes crystallized upon

C. Deppisch; G. Liu; A. Hall; Y. Xu; A. Zangvil; J. K. Shang; J. Economy

1998-01-01

49

Al-toxicity studies in yeast using gallium as an aluminum analogue  

Microsoft Academic Search

Aluminum (Al) is normally present in soils as the insoluble, harmless Al2O3. The highly toxic Al3+ and AlOH2+ monomeric cations are formed in acid soils but there is little consensus on the physiological basis of Al toxicity in plants.\\u000a A major factor that has retarded progress in understanding aluminum toxicity in vascular plants is the lack of a convenient radioisotope

Raymond J. Ritchie; Shyam Sundar Raghupathi

2008-01-01

50

Comparing addition of ZrO II particles in micron and nano scale on microstructure and mechanical behavior of aluminum-matrix composites produced by vortex route  

NASA Astrophysics Data System (ADS)

Aluminum matrix composites are important engineering materials in automotive, aerospace and other applications because of their low weight, high specific strength and better physical and mechanical properties compared to pure aluminum. ZrO II particles as reinforcement were selected to add aluminum with micron and nano size. Al/ZrO II composites were produced by direct incorporation (vortex method) in different temperatures and 5 volume percents of ZrO II particles. Microstructure of the samples was studied by scanning electron microscopy (SEM). Chemical composition of the phases was studied by XRD. Hardness, and density of these composites were also measured. The microstructure and mechanical properties tests of composites and study the effect of particle size, resulted the better properties compared to matrix aluminum. Homogeneous dispersion of the reinforcement particles in the matrix aluminum was observed. The results show enhancing the composites properties for all samples compared to the monolithic alloy. However there are some differences in results because of particle size of ceramics and therefore differences between particles surface area. Maximum volume percent that can be added to A356 aluminum alloy is 5 vol.%, for nano ZrO II particles, but it seems that is more than 5 vol.% for micron particles. Increasing of viscosity, porosities and much more defects are caused by increasing volume percents and using smaller particles. The casting processing is difficult in these conditions. Furthermore, optimum temperatures of casting for micron and nano zirconia particles are not the same.

Baghchesara, M. A.; Karimi, M.; Abdizadeh, H.; Baharvandi, H. R.

2007-07-01

51

Applicability of ultrasonic testing for the determination of volume fraction of particulates in alumina-reinforced aluminum matrix composites  

SciTech Connect

An ultrasonic testing technique was employed to determine the volume fraction of alumina particulate reinforcement in 6061 aluminum matrix composites. this study was performed on various composites with Al{sub 2}O{sub 3} nominal volume fractions of 10, 15, and 20%. For comparison, other techniques were employed as well, including the Archimedes method, metallographic image analysis, X-ray diffraction, and acid dissolution. Observations indicated that ultrasonic testing and acid dissolution methods are more reliable than the other techniques, while ultrasonic testing is faster than the acid dissolution method.

Fang, C.K.; Fang, R.L.; Weng, W.P.; Chuang, T.H.

1999-10-01

52

Strengthening Aluminum Alloys for High Temperature Applications Using Nanoparticles of Al203 and Al3-X Compounds (X= Ti, V, Zr)  

NASA Technical Reports Server (NTRS)

In this paper the effect of nanoparticles A12O3 and A13-X compounds (X= Ti, V, Zr) on the improvement of mechanical properties of aluminum alloys for elevated temperature applications is presented. These nanoparticles were selected based on their chemical stability and low diffusions rates in aluminum matrix at high temperatures. The strengthening mechanism for aluminum alloy is based on the mechanical blocking of dislocation movements by these nanoparticles. Samples were prepared from A12O3 nanoparticle preforms, which were produced using ceramic injection molding process and pressure infiltrated by molten aluminum. A12O3 nanoparticles can also be homogeneously mixed with aluminum powder and consolidated into samples through hot pressing and sintering. On the other hand, the Al3-X nanoparticles are produced as precipitates via in situ reactions with molten aluminum alloys using conventional casting techniques. The degree of alloy strengthening using nanoparticles will depend on the materials, particle size, shape, volume fraction, and mean inter-particle spacing.

Lee, Jonathan A.

2007-01-01

53

Aluminum-matrix electrotechnical composite alloys hardened by endogenous nano- and microphases  

NASA Astrophysics Data System (ADS)

A method is developed to manufacture aluminum-matrix composite alloys hardened by endogenous nano- and microphases. The formation of the structure and properties of the composite materials is studied. The experimental results demonstrate that the developed alloys are promising to produce electro-technical wire rods and other electrotechnical products.

Babkin, V. G.; Terent'ev, N. A.; Cherepanov, A. I.

2014-09-01

54

Interaction of an aluminum atom with a closed subshell metal atom: Spectroscopic analysis of AlZn  

E-print Network

Interaction of an aluminum atom with a closed subshell metal atom: Spectroscopic analysis of Al-block main group element, aluminum, and the 3d series of transi- tion metal atoms. Although the bonding in Al

Morse, Michael D.

55

Interfacial shear strength estimates of NiTi-Al matrix composites fabricated via ultrasonic additive manufacturing  

NASA Astrophysics Data System (ADS)

The purpose of this study is to understand and improve the interfacial shear strength of metal matrix composites fabricated via very high power (VHP) ultrasonic additive manufacturing (UAM). VHP-UAM NiTi-Al composites have shown a dramatic decrease in thermal expansion compared to Al, yet thermal blocking stresses developed during thermal cycling have been found to degrade and eventually cause interface failure. Consequently, to improve understanding of the interface and guide the development of stronger NiTi- Al composites, the interface strength was investigated through the use of single ber pullout tests. It was found that the matrix yielded prior to the interface breaking since adhered aluminum was consistently observed on all pullout samples. Additionally, measured pullout loads were utilized as an input to a nite element model for stress and shear lag analysis, which, in turn showed that the Al matrix experienced a peak shear stress near 230 MPa. This stress is above the Al matrix's ultimate shear strength of 150-200 MPa, thus this large stress corroborates with matrix failure observed during testing. The in uence of various ber surface treatments on bond mechanisms was also studied with scanning electron microscopy and energy dispersive X-ray spectroscopy.

Hehr, Adam; Pritchard, Joshua; Dapino, Marcelo J.

2014-03-01

56

Adiabatic shear failure of high reinforcement content aluminum matrix composites  

Microsoft Academic Search

Dynamic failure behaviors of high reinforcement content TiB2\\/Al composites were experimentally investigated using split Hopkinson pressure bar (SHPB). The TiB2\\/Al composites showed high flow stresses and good plastic deformation ability at high strain rates. Adiabatic temperature\\u000a rise decreased the flow stresses of TiB2\\/Al composites, which was verified by the prediction of JohnsonCook model. While the predictions by CowperSymonds model\\u000a exhibited

G. H. Wu; D. Z. Zhu; G. Q. Chen; L. T. Jiang; Q. Zhang

2008-01-01

57

Fabrication of carbon nanofiber-reinforced aluminum matrix composites assisted by aluminum coating formed on nanofiber surface by in situ chemical vapor deposition  

NASA Astrophysics Data System (ADS)

The van der Waals agglomeration of carbon nanofibers (CNFs) and the weight difference and poor wettability between CNFs and aluminum hinder the fabrication of dense CNF-reinforced aluminum matrix composites with superior properties. In this study, to improve this situation, CNFs were coated with aluminum by a simple and low-cost in situ chemical vapor deposition (in situ CVD). Iodine was used to accelerate the transport of aluminum atoms. The coating layer formed by the in situ CVD was characterized using scanning electron microscopy, transmission electron microscopy, x-ray diffraction, Fourier transform-infrared spectroscopy, and x-ray photoelectron spectroscopy. The results confirmed that the CNFs were successfully coated with aluminum. The composites were fabricated to investigate the effect of the aluminum coating formed on the CNFs. The dispersion of CNFs, density, Vickers micro-hardness and thermal conductivity of the composites fabricated by powder metallurgy were improved. Pressure-less infiltration experiments were conducted to fabricate composites by casting. The results demonstrated that the wettability and infiltration were dramatically improved by the aluminum coating layer on CNFs. The aluminum coating formed by the in situ CVD technique was proved to be effective for the fabrication of CNF-reinforced aluminum matrix composites.

Ogawa, Fumio; Masuda, Chitoshi

2015-01-01

58

In-situ deformation studies of an aluminum metal-matrix composite in a scanning electron microscope  

NASA Technical Reports Server (NTRS)

Tensile specimens made of a metal-matrix composite (cast and extruded aluminum alloy-based matrix reinforced with Al2O3 particulate) were tested in situ in a scanning electron microscope equipped with a deformation stage, to directly monitor the crack propagation phenomenon. The in situ SEM observations revealed the presence of microcracks both ahead of and near the crack-tip region. The microcracks were primarily associated with cracks in the alumina particles. The results suggest that a region of intense deformation exists ahead of the crack and corresponds to the region of microcracking. As the crack progresses, a region of plastically deformed material and associated microcracks remains in the wake of the crack.

Manoharan, M.; Lewandowski, J. J.

1989-01-01

59

Radiofluorination using aluminum-fluoride (Al18F)  

PubMed Central

Targeted agents are increasingly used for treating cancer and other diseases, but patients may need to be carefully selected to maximize the potential for therapeutic benefit. One way to select patients is to bind an imaging radionuclide to a targeting agent of interest, so that its uptake in specific sites of disease can be visualized by positron-emission tomography (PET) or single-photon emission computed tomography. 18F is the most commonly used radionuclide for PET imaging. Its half-life of approximately 2 h is suited for same-day imaging of many compounds that clear quickly from the body to allow visualization of uptake in the intended target. A significant impediment to its use, however, is the challenging coupling of 18F to a carbon atom of the targeting agent. Because fluorine binds to aluminum, we developed a procedure where the Al18F complex could be captured by a chelate, thereby greatly simplifying the way that imaging agents can be fluorinated for PET imaging. This article reviews our experience with this technology. PMID:23651690

2013-01-01

60

On the Understanding of Aluminum Grain Refinement by Al-Ti-B Type Master Alloys  

NASA Astrophysics Data System (ADS)

Al-Ti-B type master alloys have been widely used in the grain refinement of aluminum since 1940s. The introduction of Al3Ti and TiB2(AlB2) particles reduces the grain sizes down to about 200 micrometer level and makes aluminum alloys castable. However, the mechanism for the grain refinement is still not clear, though it is believed that TiB2 particles in the presence of Al3Ti nucleate ?-Al grains during solidification. This paper presents our finding on the formation of (Ti,Al)B2 solid solution, which leads to a proposed theory on grain refinement by Al-Ti-B type master alloys that upon addition into aluminum melt stable TiB2 particles react with aluminum slowly and release titanium into the melt. The titanium thus released in combination with titanium in the melt through dissolution of Al3Ti particles maintains a dynamic titanium-rich layer on the surface of (Ti,Al)B2. This layer offers a low crystal mismatch with ?-Al and promotes the nucleation of aluminum grains.

Wang, Xiaoming; Liu, Zhiwei; Dai, Wei; Han, Qingyou

2014-11-01

61

Characterization of centrifugal cast functionally graded aluminum-silicon carbide metal matrix composites  

Microsoft Academic Search

The present investigation is on characterization of functionally graded composites based on 356 cast and 2124 wrought aluminum alloys reinforced with SiC particles of 23?m average particle size processed by liquid metal stir casting followed by horizontal centrifugal casting. A maximum of 45 and 40% SiC particles are obtained at the outer periphery of the Al(356)-SiC and Al(2124)-SiC FGMMC casting

T. P. D. Rajan; R. M. Pillai; B. C. Pai

2010-01-01

62

Mechanical properties of aluminum matrix composites reinforced with sintered ferrous compacts  

Microsoft Academic Search

The current investigation involves fabrication and characterization of squeeze-cast aluminum metal matrix composites reinforced with sintered metal compacts. Four types of metallic powder compacts were used: plain carbon steel, 409 stainless steel, A6 tool steel, and a wear-resistant stainless steel. All the composites were cast under the same nominal conditions, but only the plain carbon steel-reinforced composites contained a significant

Richard P Baron; Coleman Jones; Frank E Wawner; John A Wert

1999-01-01

63

First principles predictions of intrinsic defects in aluminum arsenide, AlAs : numerical supplement.  

SciTech Connect

This Report presents numerical tables summarizing properties of intrinsic defects in aluminum arsenide, AlAs, as computed by density functional theory. This Report serves as a numerical supplement to the results published in: P.A. Schultz, 'First principles predictions of intrinsic defects in Aluminum Arsenide, AlAs', Materials Research Society Symposia Proceedings 1370 (2011; SAND2011-2436C), and intended for use as reference tables for a defect physics package in device models.

Schultz, Peter Andrew

2012-04-01

64

Patterned aluminum nanowires produced by electron beam at the surfaces of AlF3 single crystals  

E-print Network

Patterned aluminum nanowires produced by electron beam at the surfaces of AlF3 single crystals C is demonstrated for fabricating patterned aluminum nanowires in AlF3 substrate in a scanning electron microscope nanowires of different sizes. The aluminum nanowires may act as nano- interconnects for nanoelectronics

Wang, Zhong L.

65

On the electronic and structural properties of aluminum diboride Al 0.9B 2  

Microsoft Academic Search

Single crystals of aluminum diboride (space group P6\\/mmm, No. 191) a=3.0050(1), c=3.2537 (8) ; Z=1) were prepared by the aluminum flux method. Crystal structure refinement shows defects at the aluminum site and resulted in composition Al0.894(9)B2?Al0.9B2. The defect structure model is confirmed by the measured mass density ?exp=2.9(1)g\\/cm3 in comparison with a calculated value ?x=3.17g\\/cm3 for full occupancy of the

Ulrich Burkhardt; Vladimir Gurin; Frank Haarmann; Horst Borrmann; Walter Schnelle; Alexander Yaresko; Yuri Grin

2004-01-01

66

Recycling of aluminum and caustic soda solution from waste effluents generated during the cleaning of the extruder matrixes of the aluminum industry.  

PubMed

Anodising industries use a concentrated caustic soda solution to remove aluminum from extruder matrixes. This procedure produces very alkaline effluents containing high amounts of aluminum. The work reported here was focussed on recycling aluminum, as aluminum hydroxide, from these effluents and regenerating an alkaline sodium hydroxide solution. Briefly, the method comprises a dilution step (necessary for reducing the viscosity of the effluent and allowing the subsequent filtration) followed by a filtration to eliminate a substantial amount of the insoluble iron. Then, sulphuric acid was added to neutralize the waste solution down to pH 12 and induce aluminum precipitation. The purity of the aluminum salt was improved after washing the precipitate with deionised water. The characterization of the solid recovered, performed by thermogravimetric analysis, Fourier transform infrared spectroscopy and X-ray diffraction, indicated characteristics typical of bayerite. The proposal method allowed recovering 82% of the aluminum present in the wastewater with high purity (99.5%). Additionally, a sufficiently concentrated caustic soda solution was also recovered, which can be reused in the anodising industries. This procedure can be easily implemented and ensures economy by recycling reagents (concentrated caustic soda solution) and by recovering commercial by-products (aluminum hydroxide), while avoiding environmental pollution. PMID:21300435

Tansens, Pieter; Rodal, Alberto T; Machado, Carina M M; Soares, Helena M V M

2011-03-15

67

Friction Stir Welding of SiC/Aluminum Metal Matrix Composites  

NASA Technical Reports Server (NTRS)

Friction Stir Welding (FSW) is a new solid state process for joining metals by plasticizing and consolidating materials around the bond line using thermal energy producing from frictional forces. A feasibility study for FSW of Metal Matrix Composites (MMC) was investigated using aluminum 6092 alloy reinforced with 17% SiC particulates. FSW process consists of a special rotating pin tool that is positioned to plunge into the MMC surface at the bond line. As the tool rotates and move forward along the bond line, the material at the bond line is heated up and forced to flow around the rotating tip to consolidate on the tip's backside to form a solid state joint. FSW has the potential for producing sound welds with MMC because the processing temperature occurs well below the melting point of the metal matrix; thereby eliminating the reinforcement-to-matrix solidification defects, reducing the undesirable chemical reactions and porosity problems.

Lee, Jonathan A.

1999-01-01

68

Effect of aluminum concentration and boron dopant on environmental embrittlement in FeAl aluminides  

SciTech Connect

The room-temperature tensile properties of FeAl aluminides were determined as functions of aluminum concentration (35 to 43 at. % Al), test environment, and surface (oil) coating. The two lower aluminum alloys containing 35 and 36.5% Al are prone to severe environmental embrittlement, while the two higher aluminum alloys with 40 and 43% Al are much less sensitive to change in test environment and surface coating. The reason for the different behavior is that the grain boundaries are intrinsically weak in the higher aluminum alloys, and these weak boundaries dominate the low ductility and brittle fracture behavior of the 40 and 43% Al alloys. When boron is added to the 40% Al alloy as a grain-boundary strengthener, the environmental effect becomes prominent. In this case, the tensile ductility of the boron-doped alloy, just like that of the lower aluminum alloys, can be dramatically improved by control test environment (e.g. dry oxygen vs air). Strong segregation of boron to the grain boundaries, with a segregation factor of 43, was revealed by Auger analyses. 28 refs., 2 figs., 3 tabs.

Liu, C.T.; George, E.P.

1990-01-01

69

Aluminum surface-film growth in Al\\/FeO thermites during accelerated aging  

Microsoft Academic Search

The aluminum and iron oxide surfaces of Al\\/FeO thermite in powder and pressed pellet form were studied before and after accelerated aging at 180°C by x-ray photoelectron spectroscopy (XPS). The AlO surface film thicknesses on Al metal were deduced from the intensity ratio of Al KLL Auger signals induced by x-ray radiation on AlO and Al metal. Based on the

P. S. Wang; L. D. Haws

1982-01-01

70

ALUMINUM  

E-print Network

This fact sheet answers the most frequently asked health questions (FAQs) about aluminum. For more information, call the ATSDR Information Center at 1-800-232-4636. This fact sheet is one in a series of summaries about hazardous substances and their health effects. It is important you understand this information because this substance may harm you. The effects of exposure to any hazardous substance depend on the dose, the duration, how you are exposed, personal traits and habits, and whether other chemicals are present. HIGHLIGHTS: Everyone is exposed to low levels of aluminum from food, air, water, and soil. Exposure to high levels of aluminum may result in respiratory and neurological problems. Aluminum (in compounds combined with other elements) has been found in at least 596 of the 1,699 National Priority List (NPL) sites identified by the Environmental Protection Agency (EPA). What is aluminum? Aluminum is the most abundant metal in the earths crust. It is always found combined with other elements such as oxygen, silicon, and fluorine. Aluminum as the metal is obtained from

unknown authors

71

Development of an electronic device quality aluminum antimonide (AlSb) semiconductor for solar cell applications  

DOEpatents

Electronic device quality Aluminum Antimonide (AlSb)-based single crystals produced by controlled atmospheric annealing are utilized in various configurations for solar cell applications. Like that of a GaAs-based solar cell devices, the AlSb-based solar cell devices as disclosed herein provides direct conversion of solar energy to electrical power.

Sherohman, John W; Yee, Jick Hong; Combs, III, Arthur W

2014-11-11

72

Morphology Control for Al2O3 Inclusion Without Ca Treatment in High-Aluminum Steel  

NASA Astrophysics Data System (ADS)

Nozzle blockage is a major problem during continuous casting of Al-containing steel. Herein, we analyzed the thermodynamic equilibrium behavior between aluminum and oxygen in steel at 1873 K (1600 C) and demonstrated that, the dissolved [O] initially decreases with increasing the dissolved [Al] until approximately 0.1 wt pct [Al], and after that, the dissolved [O] increases with dissolved [Al]. Thus, for high-aluminum steel with 1.0 wt pct dissolved [Al], the precipitation of Al2O3 inclusion can be avoided during cooling from deoxidation temperature to the liquidus temperature, if the actual dissolved [O] can be kept from increasing when the dissolved [Al] further increases from 0.1 to 1.0 wt pct. Hence, a method of inclusion control for high-aluminum steel without traditional Ca treatment technology was proposed based on the thermodynamic analysis. Industrial tests confirmed that low-melting point Ca-aluminate inclusions were observed typically through a slag washing with SiO2-minimized high-basicity slag during tapping, accompanied by two-step Al-adding process for production of high-aluminum steel. Moreover, there was no nozzle clogging occurred for five heats of continuous casting.

He, Shengping; Chen, Gujun; Guo, Yintao; Shen, Boyi; Wang, Qian

2015-01-01

73

Laser cladding of quasicrystal forming AlCuFe on aluminum Krishanu Biswas a  

E-print Network

Laser cladding of quasicrystal forming Al­Cu­Fe on aluminum Krishanu Biswas a , Rolf Galun b-Zellerfeld, Germany Abstract Composite quasicrystalline coatings are developed by laser cladding of an elemental of the primary phase inside the clad layers during laser processing. The formation of Al13Fe4 with a ten

Srivastava, Kumar Vaibhav

74

High temperature dynamic modulus and damping of aluminum and titanium matrix composites  

NASA Technical Reports Server (NTRS)

Dynamic modulus and damping capacity property data were measured from 20 to over 500 C for unidirectional B/Al (1100), B/Al (6061), B/SiC/Al (6061), Al2O3/Al, SiC/Ti-6Al-4V, and SiC/Ti composites. The measurements were made under vacuum by the forced vibration of composite bars at free-free flexural resonance near 2000 Hz and at amplitudes below 0.000001. Whereas little variation was observed in the dynamic moduli of specimens with approximately the same fiber content (50 percent), the damping of B/Al composites was found at all temperatures to be significantly greater than the damping of the Al2O3/Al and SiC/Ti composites. For those few situations where slight deviations from theory were observed, the dynamic data were examined for information concerning microstructural changes induced by composite fabrication and thermal treatment. The 270 C damping peak observed in B/Al (6061) composites after heat treatment above 460 C appears to be the result of a change in the 6061 aluminum alloy microstructure induced by interaction with the boron fibers. The growth characteristics of the damping peak suggest its possible value for monitoring fiber strength degration caused by excess thermal treatment during B/Al (6061) fabrication and use.

Dicarlo, J. A.; Maisel, J. E.

1979-01-01

75

High temperature deformation of NiAl matrix composites  

SciTech Connect

The intermetallic compound, NiAl, has many attractive properties at a high temperature structural materials. However, its lack of creep resistance prevents practical applications. Adding ceramic reinforcements, such as TiB{sub 2} particles, Al{sub 2}O{sub 3} particles or whiskers can significantly improve the strength of binary NiAl at high temperatures. However, the increase in the yield stress of the discontinuous NiAl matrix composites as compared with monolithic NiAl is difficult to explain. The purposes of this research were to understand the deformation mechanisms which cause the increase in strength achieved by adding TiB{sub 2} particles, Al{sub 2}O{sub 3} particles or whiskers to NiAl, and to recognize the principles of the deformation process in NiAl matrix composites. In order to accomplish these objectives, mechanical properties and thermal activation parameters in NiAl matrix composites with different types, shapes and sizes of reinforcements have been systematically evaluated. Microstructures and dislocation structures in NiAl matrix composites have also been thoroughly characterized before and after deformation. It was found that the size of the reinforcement had a large influence on the microstructures of the composites, and the nominal activation energies for all the composites were the same and within the range of the activation energy of self-diffusion for pure NiAl. It was further concluded that the reinforcement addition only increased the non-thermally activated component of the yield stress.

Xu, K.; Arsenault, R.J. [Univ. of Maryland, College Park, MD (United States)] [Univ. of Maryland, College Park, MD (United States)

1999-08-10

76

Pressureless Reaction Sintering of AlON using Aluminum Orthophosphate as a Transient Liquid Phase  

SciTech Connect

Use of aluminum oxynitride (AlON) in transparent armor systems has been difficult due to the expense and limitations of the processing methods currently necessary to achieve transparency. Development of a pressureless processing method based on direct reaction sintering of alumina and aluminum nitride powders would reduce costs and provide a more flexible and practical manufacturing method. It may be possible to develop such a processing method using liquid phase sintering; as long as the liquid phase does not remain in the final sample. AlPO4 forms a liquid phase with Al2O3 and AlN at the temperatures required to sinter AlON, and slowly decomposes into P2O5 and alumina. Therefore, it was investigated as a possible transient liquid phase for reaction-sintered AlON. Small compacts of alumina and aluminum nitride with up to of 15wt% AlPO4 additive were pressed and sintered. It was found that AlPO4 formed the requisite transient liquid phase, and it was possible to adjust the process to produce AlON samples with good transmission and densities of 3.66-3.67 g/cc. XRD confirmed the samples formed were AlON, with no trace of any remaining phosphate phases or excess alumina or aluminum nitride. Based on the results, it was concluded that AlPO4 could be utilized as a transient liquid phase to improve the density and transmission of AlON produced by pressureless reaction sintering.

Michael Bakas; Henry Chu

2009-01-01

77

Fabrication and Characterization of Squeezed Cast Aluminum Matrix Composites Containing Boride Reinforcements  

NASA Astrophysics Data System (ADS)

Aluminum alloys containing 2 and 4 wt.% copper reinforced with aluminum dodecaborides were successfully fabricated by squeeze casting employing pressures up to 62 MPa. The distribution of reinforcements throughout the composites was quantified, whereas the effect of pressure on the composites density and hardness was determined. In addition, the reinforcement chemical stability was examined using high-temperature x-ray diffraction which permitted to confirm the formation of AlB2 phase a result of AlB12 decomposition. The pressure effect on the squeezed composites was investigated by optical microscopy, Vickers microhardness testing, superficial Rockwell hardness testing, and differential thermal analysis. At the highest applied pressures, the castings density increased when the shrinkage porosity was practically eliminated. The composite superficial hardness improved by increasing the applied squeeze. The indirect squeeze cast technique caused Al2Cu phase segregation to upper regions of the specimens, while conversely, the AlB12 reinforcements segregated preferentially at lower regions of the casting.

Olaya-Luengas, L.; Estremera-Prez, E.; Muoz, L.; Surez, O. M.

2010-12-01

78

Retention and release of tritium in aluminum clad, Al-Li alloys  

SciTech Connect

Tritium retention in and release from aluminum clad, aluminum-lithium alloys is modeled from experimental and operational data developed during the thirty plus years of tritium production at the Savannah River Site. The model assumes that tritium atoms, formed by the {sup 6}Li(n,{alpha}){sup 3}He reaction, are produced in solid solution in the Al-Li alloy. Because of the low solubility of hydrogen isotopes in aluminum alloys, the irradiated Al-Li rapidly becomes supersaturated in tritium. Newly produced tritium atoms are trapped by lithium atoms to form a lithium tritide. The effective tritium pressure required for trap or tritide stability is the equilibrium decomposition pressure of tritium over a lithium tritide-aluminum mixture. The temperature dependence of tritium release is determined by the permeability of the cladding to tritium and the local equilibrium at the trap sites. This model is used to calculate tritium release from aluminum clad, aluminum-lithium alloys. 9 refs., 3 figs.

Louthan, M.R. Jr.

1991-01-01

79

Retention and release of tritium in aluminum clad, Al-Li alloys  

SciTech Connect

Tritium retention in and release from aluminum clad, aluminum-lithium alloys is modeled from experimental and operational data developed during the thirty plus years of tritium production at the Savannah River Site. The model assumes that tritium atoms, formed by the {sup 6}Li(n,{alpha}){sup 3}He reaction, are produced in solid solution in the Al-Li alloy. Because of the low solubility of hydrogen isotopes in aluminum alloys, the irradiated Al-Li rapidly becomes supersaturated in tritium. Newly produced tritium atoms are trapped by lithium atoms to form a lithium tritide. The effective tritium pressure required for trap or tritide stability is the equilibrium decomposition pressure of tritium over a lithium tritide-aluminum mixture. The temperature dependence of tritium release is determined by the permeability of the cladding to tritium and the local equilibrium at the trap sites. This model is used to calculate tritium release from aluminum clad, aluminum-lithium alloys. 9 refs., 3 figs.

Louthan, M.R. Jr.

1991-12-31

80

Some studies into wire electro-discharge machining of alumina particulate-reinforced aluminum matrix composites  

Microsoft Academic Search

Non-traditional process like wire electro-discharge machining is found to show a promise for machining metal matrix composites.\\u000a However, the machining information for the difficult-to-machine particle-reinforced material is inadequate. This paper is\\u000a focused on experimental investigation to examine the effect of electrical as well as non-electrical machining parameters on\\u000a performance in wire electro-discharge machining of metal matrix composites (Al\\/Al2O3p). Taguchi orthogonal

Nilesh G. Patil; P. K. Brahmankar

2010-01-01

81

The melting behavior of lutetium aluminum perovskite LuAlO3  

E-print Network

DTA measurements with mixtures of aluminum oxide and lutetium oxide around the 1:1 perovskite composition were performed up to 1970 deg. C. A peak with onset 1901 deg. C was due to the melting of the eutectic Lu4Al2O9 (monoclinic phase) and LuAlO3 (perovskite). Neither peritectic melting of the perovskite nor its decomposition in the solid phase could be resolved experimentally. The maximum of the eutectic peak size near x=0.44, on the Lu-rich side of the perovskite, leads to the conclusion that LuAlO3 melts peritectically at ca. 1907 deg. C as proposed by Wu, Pelton, J. Alloys Compd. 179 (1992) 259. Under strongly reducing conditions (oxygen partial pressure <10^{-13} bar) aluminum(III) oxide can be reduced to suboxides or even Al metal. It is shown that under such conditions a new phase field with liquid Al can appear.

Klimm, Detlef

2009-01-01

82

In situ fabrication and properties of AlN dispersion strengthened 2024 aluminum alloy  

NASA Astrophysics Data System (ADS)

Nanoscaled aluminum nitride (AlN) dispersion strengthened 2024 aluminum alloy was fabricated using a novel approach in which Al-Mg-Cu compacts were partially nitrided in flowing nitrogen gas. The compacts were subsequently consolidated by sintering and hot extrusion. The microstructure and mechanical properties of the material were preliminarily investigated. Transmission electron microscopy and X-ray diffraction results revealed that AlN particles were generated by the nitridation of Al-Mg-Cu compacts. The material exhibited excellent mechanical properties after hot extrusion and heat treatment. The ultimate tensile and yield strengths of the extruded samples containing 8.92vol% AlN with the T6 heat treatment were 675 and 573 MPa, respectively.

Yang, Wei-wei; Guo, Zhi-meng; Guo, Lei-chen; Cao, Hui-qin; Luo, Ji; Ye, An-ping

2014-12-01

83

Identification of Aluminum Responsive Genes in Al-Tolerant Soybean Line PI 416937  

PubMed Central

Soybean is one of the most aluminum (Al) sensitive plants. The complex inheritance of Al tolerance trait has so far undermined breeding efforts to develop Al-tolerant soybeans. Discovering the genetic factors underlying the Al tolerance mechanisms would undoubtedly accelerate the pace of such endeavor. As a first step toward this goal, we analyzed the transcriptome profile in roots of Al-tolerant soybean line PI 416937 comparing Al-treated and untreated control plants using DNA microarrays. Many genes involved in transcription activation, stress response, cell metabolism and signaling were differentially expressed. Patterns of gene expression and mechanisms of Al toxicity and tolerance suggest that Cys2His2 and ADR6 transcription activators, cell wall modifying enzymes, and phytosulfokines growth factor play role in soybean Al tolerance. Our data provide insights into the molecular mechanisms of soybean Al tolerance and will have practical value in genetic improvement of Al tolerance trait. PMID:20953355

Duressa, Dechassa; Soliman, Khairy; Chen, Dongquan

2010-01-01

84

The influence of microstructure on the tensile behavior of an aluminum metal matrix composite  

NASA Technical Reports Server (NTRS)

The relationship between tensile properties and microstructure of a powder metallurgy aluminum alloy, 2009 was examined. The alloy was investigated both unreinforced and reinforced with 15 v/o SiC whiskers or 15 v/o SiC particulate to form a discontinuous metal matrix composite (MMC). The materials were investigated in the as-fabricated condition and in three different hot-rolled sheet thicknesses of 6.35, 3.18, and 1.8 mm. Image analysis was used to characterize the morphology of the reinforcements and their distributions within the matrix alloy. Fractographic examinations revealed that failure was associated with the presence of microstructural inhomogeneities which were related to both the matrix alloy and to the reinforcement. The results from these observations together with the matrix tensile data were used to predict the strengths and moduli of the MMC's using relatively simple models. The whisker MMC could be modeled as a short fiber composite and an attempt was made to model the particulate MMC as a dispersion/dislocation hardened alloy.

Birt, Michael J.; Johnson, W. Steven

1990-01-01

85

Atomic Layer Deposition of Aluminum Oxide Thin Film on BaMgAl10O17:Eu Phosphor  

Microsoft Academic Search

An investigation is reported by the coating of BaMgAl10O17:Eu phosphor by aluminum oxide using atomic layer deposition. Aluminum oxide films were prepared the chamber temperature of 350C using Al(CH3)3 and H2O as precursors and reactant gas, respectively. EDX and FTIR analysis showed the surface composition of coated phosphor was aluminum oxide. The photoluminescence intensity of coated phosphors showed 10.3?36% higher

Hyug Jong Kim; Min Wan Kim; Hyung su Kim; Hyu Suk Kim; Suk Hwan Kim; Sang Woo Lee; Byung Ho Choi; Bong Kyo Jeong; Hyuoung ho Lee

2006-01-01

86

Investigation of Thermo-Mechanical Fatigue Characteristics for Cast Aluminum (AL319-T7)  

NASA Astrophysics Data System (ADS)

In today's transient economy, the demand for new alternative technologies is increasing. Vehicle fuel economy has become the most important phrase in the automotive industry. The ability to achieve optimal fuel economy has many trade-offs. In terms of engine components, this trade-off comes in the form of component reliability. In the past, most engine components were constructed of cast iron. Currently many cast iron components have been replaced by aluminum components to reduce part weight. In parallel with the use of light weight components, higher thermal loadings have been applied to engine components due to the increasing use of fuel saving technologies. Current aluminum reliability concerns have led to a thermal mechanical fatigue (TMF) investigation of the aluminum casting alloy, AL319-T7. This thesis attempts to model TMF behaviour for an AL319-T7 cylinder head using a combined hardening material model, in which the effects of creep and oxidation have been neglected.

Miller, Luke W.

87

An experimental and analytical study of scuffing in aluminum based metal matrix composites  

Microsoft Academic Search

Scuffing is a surface damage phenomenon in tribology characterized by the formation of local welds between sliding surfaces. Many previous studies focused on scuffing of ferrous materials due to their extensive use in tribological systems. Information about scuffing behavior of Al metal matrix composites (MMC) is scarce, especially quantitative modeling of the effects of volume percentage, size as well as

Feng Bin

1998-01-01

88

Behavior of aluminum oxide, intermetallics and voids in CuAl wire bonds  

Microsoft Academic Search

Nanoscale interfacial evolution in CuAl wire bonds during isothermal annealing from 175C to 250C was investigated by high resolution transmission electron microscopy (HRTEM). The native aluminum oxide film (?5nm thick) of the Al pad migrates towards the Cu ball during annealing. The formation of intermetallic compounds (IMC) is controlled by Cu diffusion, where the kinetics obey a parabolic growth law

H. Xu; C. Liu; V. V. Silberschmidt; S. S. Pramana; T. J. White; Z. Chen; V. L. Acoff

2011-01-01

89

A Comparison Between ECAP and Conventional Extrusion for Consolidation of Aluminum Metal Matrix Composite  

NASA Astrophysics Data System (ADS)

In this study, two powder consolidation techniques, equal channel angular pressing (ECAP) and extrusion, were utilized to consolidate attritioned aluminum powder and Al-5 vol.% nano-Al2O3 composite powder. The effect of ECAP and extrusion on consolidation behavior of composite powder and mechanical properties of subsequent compacts are presented. It is found that three passes of ECAP in tube at 200 C is capable of consolidating the composite to 99.29% of its theoretical density whereas after hot extrusion of the composite the density reached to 98.5% of its theoretical density. Moreover, extrusion needs higher temperature and pressing load in comparison to the ECAP method. Hardness measurements show 1.7 and 1.2 times higher microhardness for the consolidated composite and pure aluminum after ECAP comparing with the extruded ones, respectively. Microstructural investigations and compression tests demonstrate stronger bonds between the particles after three passes of ECAP than the extrusion. Furthermore, the samples after three passes of ECAP show better wear resistance than the extruded ones.

Haghighi, R. Derakhshandeh; Jahromi, S. A. Jenabali; Moresedgh, A.; Khorshid, M. Tabandeh

2012-09-01

90

Electro-thermo-mechanical coupling analysis of deep drawing with resistance heating for aluminum matrix composites sheet  

NASA Astrophysics Data System (ADS)

Recently, electro-plastic forming to be a focus of attention in materials hot processing research area, because it is a sort of energy-saving, high efficient and green manufacturing technology. An electro-thermo-mechanical model can be adopted to carry out the sequence simulation of aluminum matrix composites sheet deep drawing via electro-thermal coupling and thermal-mechanical coupling method. The first step of process is resistance heating of sheet, then turn off the power, and the second step is deep drawing. Temperature distribution of SiCp/2024Al composite sheet by resistance heating and sheet deep drawing deformation were analyzed. During the simulation, effect of contact resistances, temperature coefficient of resistance for electrode material and SiCp/2024Al composite on temperature distribution were integrally considered. The simulation results demonstrate that Sicp/2024Al composite sheet can be rapidly heated to 400 in 30s using resistances heating and the sheet temperature can be controlled by adjusting the current density. Physical properties of the electrode materials can significantly affect the composite sheet temperature distribution. The temperature difference between the center and the side of the sheet is proportional to the thermal conductivity of the electrode, the principal cause of which is that the heat transfers from the sheet to the electrode. SiCp/2024Al thin-wall part can be intactly manufactured at strain rate of 0.08s-1 and the sheet thickness thinning rate is limited within 20%, which corresponds well to the experimental result.

Zhang, Kaifeng; Zhang, Tuoda; Wang, Bo

2013-05-01

91

Mechanical behavior of a continuous fiber reinforced aluminum matrix composite subjected to transverse and thermal loading  

NASA Technical Reports Server (NTRS)

The transverse properties of an aluminum alloy metal matrix composite reinforced by continuous alumina fibers were investigated. The composite is subjected to both mechanical and cyclic thermal loading. The results of an experimental program indicate that the shakedown concept of structural mechanics provides a means of describing the material behavior. When the loading conditions are within the shakedown region, the material finally responds in an elastic manner after initial plastic response, and for loading conditions outside the shakedown region, the material exhibits a rapid incremental plastic strain accumulation. The failure strain varies by an order of magnitude according to the operating conditions. Hence, for high mechanical and low thermal loading, the failure strains is small; for low mechanical and high thermal loading, the failure strain is large.

Jansson, S.; Leckie, F. A.

1991-01-01

92

Reinforcement/matrix interaction in SiC fiber-reinforced Ni3Al matrix composites  

SciTech Connect

The interfacial reaction characteristics of two different types of SiC fibers with Ni3Al (Ni-Al-Cr-Zr-B) matrix have been investigated. The microstructure and chemical compositions across the reaction zones have been analyzed quantitatively using microscopy and electron probe microanalysis. In both types of SiC/Ni3Al composites, it was found that Ni was the dominant diffusing species responsible for the overall reaction. The C-rich layer outside the SCS-6 fiber provided an incubation period, but could not stop the inward diffusion of Ni. It could, however, effectively stop the diffusion of Al, Zr, and Cr. No significant increase in reaction zone thickness after exposure at temperatures below 900/degree/C for up to 100 hours was observed. When the C-rich layer was depleted, a rapid increase in reaction zone thickness and the formation of multilayer reaction products occurred. In the case of Sigma/Ni3Al composite, extensive reaction between the fiber and the matrix occurred at all the temperatures studied. Diffusion barrier coating for both types of fibers is required to develop nickel aluminide matrix composites. 17 refs., 3 figs.

Yang, J.-M.; Kao, W.H.; Liu, C.T.

1988-01-01

93

49 CFR Appendix C to Part 180 - Eddy Current Examination With Visual Inspection for DOT 3AL Cylinders Manufactured of Aluminum...  

Code of Federal Regulations, 2014 CFR

...DOT 3AL Cylinders Manufactured of Aluminum Alloy 6351-T6 C Appendix C to Part 180...DOT 3AL Cylinders Manufactured of Aluminum Alloy 6351-T6 1. Examination Procedure...DOT-3AL cylinder manufactured of aluminum alloy 6351-T6 to be inspected must be...

2014-10-01

94

Manufacturing of Aluminum Matrix Composites Reinforced with Iron Oxide (Fe3O4) Nanoparticles: Microstructural and Mechanical Properties  

NASA Astrophysics Data System (ADS)

The purpose of this paper is to demonstrate the low-cost manufacturing of aluminum matrix composites reinforced with nano iron oxide as light and efficient materials for engineering applications. It is very desirable to use reinforced aluminum matrix composites in structural applications (automotive, aeronautical, etc.) because of their outstanding stiffness-to-weight and strength-to-weight ratios. In modern industry, it is increasingly important to develop new composites as alternative materials to fabricate multifunctional pieces. Detailed information is presented on the manufacturing process of this composite, and a preliminary study was performed on the cryogenic-cycling behavior to evaluate the interface between the matrix and the reinforcement. Microindentation tests were carried out to evaluate the micromechanical properties of these materials; a simple and practical finite element model is proposed to predict certain parameters related to the composition of the composite.

Bayraktar, Emin; Ayari, Fayza; Tan, Ming Jen; Tosun-Bayraktar, Ayse; Katundi, Dhurata

2014-04-01

95

Analysis of stress-strain, fracture and ductility behavior of aluminum matrix composites containing discontinuous silicon carbide reinforcement  

NASA Technical Reports Server (NTRS)

Mechanical properties and stress-strain behavior for several types of commercially fabricated aluminum matrix composites, containing up to 40 vol % discontinuous SiC whisker, nodule, or particulate reinforcement were evaluated. It was found that the elastic modulus of the composites was isotropic, to be independent of type of reinforcement, and to be controlled solely by the volume percentage of SiC reinforcement present. The yield/tensile strengths and ductility were controlled primarily by the matrix alloy and temper condition. Ductility decreased with increasing reinforcement content, however, the fracture strains observed were higher than those reported in the literature for this type of composite. This increase in fracture strain is attributed to cleaner matrix powder and increased mechanical working during fabrication. Conventional aluminum and titanium structural alloys were compared and have shown that the properties of these low cost, lightweight composites have good potential for application to aerospace structures.

Mcdanels, D. L.

1984-01-01

96

High-energy - high-rate power processing of aluminum-silicon carbide metal-matrix composites  

SciTech Connect

Discontinuous, silicon-carbide-reinforced, aluminum metal-matrix composite metals were made by consolidating powder constituents using a novel high-energy - high-rate process that employs a fast-rising high-current pulse. The powder mixtures were contained in an insulated die, under pressure, and were rapidly densified during the discharge from a homopolar generator, in a processing time of about one second. Several types of rapidly solidified Al-based powders, X7091, CW67, and 7064, were reinforced with different types and volume fractions of discontinuous SiC. The consolidate materials were evaluated using optical and analytical electron microscopy and Auger spectroscopy to determine the microstructure and to identify the phases evolved. Processing/structure/property interrelationships were established. Energy inputs of 400 kJ/kg to 2500 kJ/kg at applied pressures of 105 to 315 MPa resulted in consolidated forms, having a homogeneous distribution of the SiC particles within the composite. Densities of 95% to 99% of theoretical were obtained with local interparticle melting contributing to densification at the highest energy levels. A direct correlation exists between the density, hardness, and fracture tensile strength, and the specific input energy, indicating that metallurgical bonding and densification scaled with input energy.

Elkabir, G.

1987-01-01

97

Hydrolysis Studies and Quantitative Determination of Aluminum Ions Using [superscript 27]Al NMR: An Undergraduate Analytical Chemistry Experiment  

ERIC Educational Resources Information Center

This article describes a novel experiment focused on metal ion hydrolysis and the equilibria related to metal ions in aqueous systems. Using [superscript 27]Al NMR, the students become familiar with NMR spectroscopy as a quantitative analytical tool for the determination of aluminum by preparing a standard calibration curve using standard aluminum

Curtin, Maria A.; Ingalls, Laura R.; Campbell, Andrew; James-Pederson, Magdalena

2008-01-01

98

The electronic structure of ultrathin aluminum oxide film grown on FeAl,,110...: A photoemission spectroscopy  

E-print Network

The electronic structure of ultrathin aluminum oxide film grown on FeAl,,110...: A photoemission; published online 23 March 2007 The electronic structure of the ultrathin aluminum oxide grown on the Fe, the atomic and electronic properties of the oxide surface play an essential role to enhance or diminish

99

Composite propellant aluminum agglomeration reduction using tailored Al/PTFE particles  

NASA Astrophysics Data System (ADS)

Micron aluminum is widely used in propellants; however, performance could be significantly improved if ignition barriers could be disrupted and combustion tailored. In solid propellants for example, aluminum increases theoretical specific impulse performance, yet theoretical levels cannot be achieved largely because of two-phase flow losses. These losses could be reduced if particles quickly ignited, more gaseous products were produced, and if particle breakup occurred during combustion. To achieve altered aluminum ignition and particle combustion, this work explores the use of low level (10-30 wt.%) fluorocarbon (polytetrafluoroethylene (PTFE) or poly(carbon monofluoride) (PMF)) inclusion inside of aluminum via low or high energy mechanical activation. Aluminum/PTFE particles are found to be amenable to use in binder based energetics, having average particle sizes ranging from 15 to 78 ?m, ~2-7 m2/g, specific surface area, and combustion enthalpies as high as 20.2 kJ/g. Differential scanning calorimetry (DSC) experiments indicate high energy MA reduces both reaction and oxidation onset to ~440 C that is far below aluminum alone. Safety testing shows these particles have high electrostatic discharge (ESD) (89.9-108 mJ), impact (> 213 cm), and friction (> 360 N) ignition thresholds. The idea of further increasing reactivity and increasing particle combustion enthalpy is explored by reducing fluorocarbon inclusion content to 10 wt.% and through the use of the strained fluorocarbon PMF. Combustion enthalpy and average particle size range from 18.9 to 28.5 kJ/g and 23.0 to 67.5 ?m, respectively and depend on MA intensity, duration, and inclusion level. Specific surface areas are high (5.3 to 34.8 m2/g) and as such, Al/PMF particles are appropriate for energetic applications not requiring a curable liquid binder. Mechanical activation reduces oxidation onset (DSC) from 555 to 480 C (70/30 wt.%). Aluminum/PMF particles are sensitive to ESD (11.5-47.5 mJ) and some can be ignited via optical flash. Propellant aluminum agglomeration is assessed through replacement of reference aluminum powders (spherical, flake, or nanoscale) with Al/PTFE (90/10 or 70/30 wt.%) particles. The effects on burning rate, pressure dependence, and aluminum ignition, combustion, and agglomeration are quantified. Microscopic imaging shows tailored particles promptly ignite at the burning surface and appear to breakup into smaller particles. Replacement of spherical aluminum with Al/PTFE 70/30 wt.% also increases the pressure exponent from 0.36 to 0.58, which results in a 50% increase in propellant burning rate at 13.8 MPa. Combustion products were quench collected using a liquid-free technique at 2.1 and 6.9 MPa. Sizing of products indicates that composite particles result in nominally 25 ?m coarse products, which are smaller than the original, average particle size and are also 66% smaller in diameter (96% by volume) than the 76 ?m products collected from reference spherical aluminized propellant. Smaller diameter condensed phase products and more gaseous products will likely decrease two-phase flow loss and reduce slag accumulation in solid rocket motors.

Sippel, Travis R.

100

The aluminum electrode in AlCl3-alkali-halide melts  

NASA Technical Reports Server (NTRS)

Passivation phenomena were observed upon cathodic and anodic polarization of the Al electrode in AlCl3-KCl-NaCl melts between 100 and 160 C. They are caused by formation of a solid salt layer at the electrode surface resulting from concentration changes upon current flow. The anodic limiting currents increased with temperature and with decreasing AlCl3 content of the melt. Current voltage curves obtained on a rotating aluminum disk showed a linear relationship between the anodic limiting current and 1/sq root of 2 pi (rps). Upon cathodic polarization dentrite formation occurs at the Al electrode. The activation overvoltage in AlCl3-KCl-NaCl (57.5-12.5-20 mol%) was determined by galvanostatic current step methods. An apparent exchange current density of 270 mA/cm2 at 130 C and a double layer capacity of 40 plus or minus 10 microfarad/cm2 were measured.

Holleck, G. L.; Giner, J.

1972-01-01

101

Effective n-type doping strategy through codoping SiAlFN in aluminum nitride  

NASA Astrophysics Data System (ADS)

Using a first-principles pseudopotential method, we studied an effective n-type doping strategy through codoping SiAlXN (X = F, Cl, Br, and I) in aluminum nitride. Results revealed that the donor ionization energy of the SiAlXN complex is much lower than that of the corresponding isolated SiAl impurity. Theoretically obtained ?(+/0) ionization energies are all near the conduction band minimum (CBM), which is only 1.4 meV below the CBM of the SiAlFN pair. The low ?(+/0) ionization energy of the SiAlXN complex can be explained by the combined repulsion between the X element (X = F, Cl, Br, and I)- and Si donor-induced levels.

Wang, Zhiguo; Li, Jingbo; Qing Fu, Yong

2014-11-01

102

Preparation of plate-like nano ?-Al 2O 3 using nano-aluminum seeds by wet-chemical methods  

Microsoft Academic Search

Alumina particles with plate-like shape were prepared successfully by a wet chemical processes with nano-size aluminum additive. The seed-effect of nano-size aluminum and its effect on the final ?-Al2O3 particle size and shape were investigated. TEM, XRD, XPS, Zeta potential and DSC\\/TG were used to observe the microstructure of the ?-Al2O3 particle and analysis this wet chemical processes. It was

Hongxia Lu; Hongwei Sun; Aixia Mao; Huizhi Yang; Hailong Wang; Xing Hu

2005-01-01

103

Measurement of mercury in flue gas based on an aluminum matrix sorbent.  

PubMed

The measurement of total mercury in flue gas based on an economical aluminum matrix sorbent was developed in this paper. A sorbent trap consisted of three tubes was employed to capture Hg from flue gas. Hg trapped on sorbent was transferred into solution by acid leaching and then detected by CVAAS. Hg adsorbed on sorbent was recovered completely by leaching process. The 87.7% recovery of Hg in flue gas by tube 1 and tube 2 was obtained on the equipment of coal combustion and sampling in lab. In order to evaluate the ability to recover and accurately quantify Hg(0) on the sorbent media, the analytical bias test on tube 3 spiked with Hg(0) was also performed and got the average recovery of 97.1%. Mercury measurements based on this method were conducted for three coal-fired power plants in China. The mercury in coal is distributed into bottom ash, electrostatic precipitator (ESP) ash, wet flue gas desulfurization (WFGD) reactant, and flue gas, and the relative distribution varied depending on factors such as the coal type and the operation conditions of plants. The mercury mass balances of three plants were also calculated which were 91.6%, 77.1%, and 118%, respectively. The reliability of this method was verified by the Ontario Hydro (OH) method either in lab or in field. PMID:22235178

Wang, Juan; Xu, Wei; Wang, Xiaohao; Wang, Wenhua

2011-01-01

104

Analysis of stress-strain, fracture, and ductility behavior of aluminum matrix composites containing discontinuous silicon carbide reinforcement  

Microsoft Academic Search

Mechanical properties and stress-strain behavior were evaluated for several types of commercially fabricated aluminum matrix\\u000a composites, containing up to 40 vol pct discontinuous SiC whisker, nodule, or particulate reinforcement. The elastic modulus\\u000a of the composites was found to be isotropic to be independent of type of reinforcement, and to be controlled solely by the\\u000a volume percentage of SiC reinforcement present.

David L. McDanels

1985-01-01

105

High-energy - high-rate power processing of aluminum-silicon carbide metal-matrix composites  

Microsoft Academic Search

Discontinuous, silicon-carbide-reinforced, aluminum metal-matrix composite metals were made by consolidating powder constituents using a novel high-energy - high-rate process that employs a fast-rising high-current pulse. The powder mixtures were contained in an insulated die, under pressure, and were rapidly densified during the discharge from a homopolar generator, in a processing time of about one second. Several types of rapidly solidified

Elkabir

1987-01-01

106

Formation of nanocrystalline h-AlN during mechanochemical decomposition of melamine in the presence of metallic aluminum  

SciTech Connect

Decomposition of melamine was studied by solid state reaction of melamine and aluminum powders during high energy ball-milling. The milling procedure performed for both pure melamine and melamine/Al mixed powders as the starting materials for various times up to 48 h under ambient atmosphere. The products were characterized by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The results revealed that Al causes melamine deammoniation at the first stages of milling and further milling process leads to the s-triazine ring degradation while nano-crystallite hexagonal aluminum nitride (h-AlN) was the main solid product. Comparison to milling process, the possibility of the reaction of melamine with Al was also investigated by thermal treatment method using differential scanning calorimeter (DSC) and thermo gravimetric analyzer (TGA). Melamine decomposition occurred by thermal treatment in the range of 270-370 Degree-Sign C, but no reaction between melamine and aluminum was observed. - Graphical Abstract: Mechanochemical reaction of melamine with Al resulted in the formation of nanocrystalline AlN after 7 h milling time Highlights: Black-Right-Pointing-Pointer High energy ball milling of melamine and aluminum results decomposition of melamine with elimination of ammonia. Black-Right-Pointing-Pointer Nano-crystalline AlN was synthesized by the mechanochemical route. Black-Right-Pointing-Pointer Milling process has no conspicuous effect on pure melamine degradation. Black-Right-Pointing-Pointer No reaction takes place by heating melamine and aluminum powder mixture in argon.

Rounaghi, S.A., E-mail: s.a.rounaghi@gmail.com [Department of Materials Engineering, Ferdowsi University of Mashhad, P.O. Box No. 91775-1111, Mashhad (Iran, Islamic Republic of); Kiani Rashid, A.R. [Department of Materials Engineering, Ferdowsi University of Mashhad, P.O. Box No. 91775-1111, Mashhad (Iran, Islamic Republic of); Eshghi, H., E-mail: heshghi@ferdowsi.um.ac.ir [Department of Chemistry, Ferdowsi University of Mashhad, P.O. Box No. 91775-1436, Mashhad (Iran, Islamic Republic of); Vahdati Khaki, J. [Department of Materials Engineering, Ferdowsi University of Mashhad, P.O. Box No. 91775-1111, Mashhad (Iran, Islamic Republic of)

2012-06-15

107

Al-Si-Mn Alloy Coating on Aluminum Substrate Using Cold Metal Transfer (CMT) Welding Technique  

NASA Astrophysics Data System (ADS)

The cold metal transfer (CMT) process was explored as a weld overlay technique for synthesizing Al-Si-Mn alloy coating on a commercially pure Al plate. The effect of welding speed on the bead geometry, deposition rate, and the dilution were studied and the best parameter was used to synthesize the coatings. The CMT process can be used to produce thick coatings (>2.5 mm) without porosity and with low dilution levels. The Vickers hardness number of the Al substrate increased from 28 in the bulk to 57 in the coating. It is suggested that the CMT process can be an effective and energy-efficient technique for depositing thick coatings and is useful in weld repair of aluminum alloy components.

Rajeev, G. P.; Kamaraj, M.; Bakshi, S. R.

2014-06-01

108

Al4H7? is a resilient building block for aluminum hydrogen cluster materials  

PubMed Central

The formation and oxygen etching of AlnHm? clusters are characterized in a flow reactor experiment with first-principles theoretical investigations to demonstrate the exceptional stability of Al4H7?. The origin of the preponderance of Al4H7? in the mass spectra of hydrogenated aluminum anions and its resistance to O2 etching are discussed. Al4H7? is shown to have the ability to bond with ionic partners to form stable hydrides through addition of an alkali atom [XAl4H7 (X = Li-Cs)]. An intuitive model that can predict the existence of stable hydrogenated cluster species is proposed. The potential synthetic utility of the superatom assemblies built on these units is addressed. PMID:17823245

Roach, P. J.; Reber, A. C.; Woodward, W. H.; Khanna, S. N.; Castleman, A. W.

2007-01-01

109

Energy-Saving Melting and Revert Reduction Technology (E-SMARRT): Development of Elevated Temperature Aluminum Metal Matrix Composite (MMC) Alloy and Its Processing Technology  

SciTech Connect

The objective of this project was to provide a production capable cast aluminum metal matrix composite (MMC) alloy with an operating temperature capability of 250-300C. Important industrial sectors as well as the military now seek lightweight aluminum alloy castings that can operate in temperature ranges of 250-300C. Current needs in this temperature range are being satisfied by the use of titanium alloy castings. These have the desired strength properties but the end components are heavier and significantly more costly. Also, the energy requirements for production of titanium alloy castings are significantly higher than those required for production of aluminum alloys and aluminum alloy castings.

Weiss, David C. [Eck Industreis, Inc.] [Eck Industreis, Inc.; Gegal, Gerald A.

2014-04-15

110

Elementary surface chemistry during CuO/Al nanolaminate-thermite synthesis: copper and oxygen deposition on aluminum (111) surfaces.  

PubMed

The surface chemistry associated with the synthesis of energetic nanolaminates controls the formation of the critical interfacial layers that dominate the performances of nanothermites. For instance, the interaction of Al with CuO films or CuO with Al films needs to be understood to optimize Al/CuO nanolaminates. To that end, the chemical mechanisms occurring during early stages of molecular CuO adsorption onto crystalline Al(111) surfaces are investigated using density functional theory (DFT) calculations, leading to the systematic determination of their reaction enthalpies and associated activation energies. We show that CuO undergoes dissociative chemisorption on Al(111) surfaces, whereby the Cu and O atoms tend to separate from each other. Both Cu and O atoms form islands with different properties. Copper islanding fosters Cu insertion (via surface site exchange mechanism) into the subsurface, while oxygen islands remain stable at the surface. Above a critical local oxygen coverage, aluminum atoms are extracted from the Al surface, leading to oxygen-aluminum intermixing and the formation of aluminum oxide (?-alumina). For Cu and O co-deposition, copper promotes oxygen-aluminum interaction by oxygen segregation and separates the resulting oxide from the Al substrate by insertion into Al and stabilization below the oxide front, preventing full mixing of Al, Cu, and O species. PMID:25089744

Lanthony, Clo; Guiltat, Mathilde; Ducr, Jean Marie; Verdier, Agnes; Hmeryck, Anne; Djafari-Rouhani, Mehdi; Rossi, Carole; Chabal, Yves J; Estve, Alain

2014-09-10

111

Effect of aluminum treatment on proteomes of radicles of seeds derived from Al-treated tomato plants  

Technology Transfer Automated Retrieval System (TEKTRAN)

Aluminum (Al) toxicity is a major constraint to plant growth and crop yield in acid soils. Tomato cultivars are especially susceptible to excessive A1 3+ accumulated in the root zone. In this study, tomato plants were grown in a hydroponic culture system supplemented with 50 uM AlK(SO4)2. Seeds harv...

112

Ballistic Impact Testing of Aluminum 2024 and Titanium 6Al-4V for Material Model Development  

NASA Technical Reports Server (NTRS)

An experimental program is underway to develop a consistent set of material property and impact test data, and failure analysis, for a variety of materials that can be used to develop improved impact failure and deformation models. Unique features of this set of data are that all material property information and impact test results are obtained using identical materials, the test methods and procedures are extensively documented and all of the raw data is available. This report describes ballistic impact testing which has been conducted on aluminum (Al) 2024 and titanium (Ti) 6Al-4vanadium (V) sheet and plate samples of different thicknesses and with different types of projectiles, one a regular cylinder and one with a more complex geometry incorporating features representative of a jet engine fan blade.

Pereira, J. Michael; Revilock, Duane M.; Ruggeri, Charles R.; Emmerling, William C.; Altobelli, Donald J.

2012-01-01

113

Spray pyrolytic deposition of transparent aluminum oxide (Al 2O 3) films  

NASA Astrophysics Data System (ADS)

Optically transparent Al2O3 films has been synthesized, on quartz substrates at 500, 600 and 700 C, from 0.02 M aluminum acetyl acetonate (Al(acac)3) in ethanol, by using ultrasonic spray pyrolysis technique. The films synthesized at 500, 600 and 700 C are amorphous having average particle sizes 27 6, 18 3 and 14 3, respectively. The films are found to be 95% optically transparent in the visible region. The optical transparency of the films in the ultraviolet region is found to increase with increase in deposition temperature. The observed increase in optical band gap and decrease in refractive index is attributed to the decrease in particle size with increase in deposition temperature. The stoichiometry and chemical bonding of the amorphous film studied using XPS and FTIR spectroscopy revealed the presence chemisorbed oxygen.

Dhonge, Baban P.; Mathews, Tom; Sundari, S. Tripura; Thinaharan, C.; Kamruddin, M.; Dash, S.; Tyagi, A. K.

2011-11-01

114

Colloidal processing of silcon carbide whiskers/aluminum oxide ceramic matrix composites  

NASA Astrophysics Data System (ADS)

By manipulating the interparticle forces of ceramic colloidal systems, suspensions of different dispersing abilities were obtained. Changing the concentration of ionic species, pH, polyelectrolyte and the solution altered the net interparticle force. The zeta potentials of single component suspensions of varying concentration of ionic species, polyelectrolyte addition, pH and solution (electrolyte, ethanol, or a mixture of electrolyte and ethanol) were measured. The stability ratio, W, which measures the effectiveness of the potential barrier in preventing the particles from coagulation, and the interaction between the components were discussed. SiC whisker reinforced Al2O 3 suspensions were slip cast at different processing conditions (SiC whisker volume fraction, solids loading, ball milling, sintering aids, polyelectrolyte and pH). Green specimens were cold-isostatically pressed and pressureless sintered in a flowing nitrogen atmosphere. Homogeneous SiCw/Al2O3 green bodies with densities of 2.55 +/- 0.07 g/cm3 (~65% theoretical density) were obtained. Bulk densities of 3.80 +/- 0.06 g/cm3 (96% theoretical density), 3.79 +/- 0.06 g/cm3 (97% theoretical density), and 3.40 +/- 0.07 g/cm3 (89% theoretical density) were obtained at 1600C for composite samples containing 5, 10 and 20 vol% SiC whiskers, respectively. Bulk densities of the 10 vol% SiCw/Al2O3 composites were 3.79 +/- 0.06 g/cm3 at PH 11 and 3.66 +/- 0.07 g/cm3 at pH 4, respectively. pH 11 was determined to be the optimum processing pH for SiCw/Al2O3 composites with sintering aids (2 wt% Y2O3 and 0.5 wt% MgO) and 2.5 vol% polyelectrolyte (Ammonia salt of a polymeric carboxylic acid). The final microstructure revealed homogeneous and near fully densified composites. Compositions of the composites were characterized using Energy Dispersive X-ray Spectrum (EDX). The effect of the aspect ratio of SiC whisker, the Y2O 3 content and the choice of polyelectrolyte were examined. The whisker aspect ratio reduction had a more dramatic effect on achieving dense composites in 20 vol% SiC whisker when compared to 5 or 10 vol% SiC whisker composites. High densities with 10 vol% SiC whisker were attainable without aspect ratio reduction. Sintered densities increased with increasing Y2O 3 content. For 10 vol% SiCw/ Al2O3, the densities remained almost constant at Y2O3 additions greater than 0.5 wt% 2.5 vol% polyelectrolyte stabilized the suspension and resulted in high composite densities. However, further addition of polyelectrolyte, past the adsorption saturation limit, served to leave excess polyelectrolyte in suspension. This excess polyelectrolyte lowered the composite density due to depletion flocculation. Sintered densities of 10 vol% SiCw/Al 2O3 composites slip cast from a mixture of ethanol and water were only 2.92 +/- 0.08 g/cm3 (75% theoretical density). The fracture toughness of Al2O3 was remarkably improved with increasing whisker content. The fracture toughness of 20 vol% SiCw/Al2O3 composite was twice the fracture toughness of the unreinforced Al2O3 matrix.

Zhang, Mingli

115

Aluminum distribution in the boron framework of ?-AlB 12  

NASA Astrophysics Data System (ADS)

The crystal structure of ?-AlB 12 ( P2 12 12 1; a = 16.573(4), b = 17.510(3), c = 10.144(1)) was reinvestigated by single-crystal X-ray diffractometry and the nature of the metal distribution in the boron framework examined. Starting from the structure data published by Hughes et al. (Journal of the American Chemical Society 83, 2337 (1977)), 458 independent parameters, including the occupancies of 11 Al sites, were finally refined to a conventional R value of 2.9%. A total of 5282 observed unique reflections (Mo K? radiation; 2? < 64) were used. Although distributed in an apparently complicated manner, the aluminum atoms occur in the boron framework according to a simple rule as in the crystals of the ?-AlB 12 structure type. The numbers of the valence electrons of Al, allotted to the six boron subunits, B 12(i-iv), B 20-(C 2, C s), proportionately to the contact frequencies of Al with the units, are 2.2, 1.9, 2.2, 1.9, 5.3, and 5.2, respectively. The charge assignment is compatible with the ionic formula {20}/{3}Al+3 4B 12-2 2 B20-6, proposed from preliminary molecular orbital calculations. A negative charge balance among the six boron units at about 1:1:1:1:3:3 seems to be essential for making up the stable boron framework of ?-AlB 12.

Higashi, Iwami

1983-05-01

116

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

SciTech Connect

The microstructure and interface between metal matrix and ceramic reinforcement of a composite play an important role in improving its properties. In the present investigation, the interface and intermetallic compound present in the samples were characterized to understand structural stability at an elevated temperature. Aluminum based 2124 alloy with 10 wt.% silicon carbide (SiC) particle reinforced composite was prepared through vortex method and the solid ingot was deformed by hot rolling for better particle distribution. Heat treatment of the composite was carried out at 575 C with varying holding time from 1 to 48 h followed by water quenching. In this study, the microstructure and interface of the SiC particle reinforced Al based composites have been studied using optical microscopy, scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDS), electron probe micro-analyzer (EPMA) associated with wavelength dispersive spectroscopy (WDS) and transmission electron microscopy (TEM) to identify the precipitate and intermetallic phases that are formed during heat treatment. The SiC particles are uniformly distributed in the aluminum matrix. The microstructure analyses of AlSiC composite after heat treatment reveal that a wide range of dispersed phases are formed at grain boundary and surrounding the SiC particles. The energy dispersive X-ray spectroscopy and wavelength dispersive spectroscopy analyses confirm that finely dispersed phases are CuAl{sub 2} and CuMgAl{sub 2} intermetallic and large spherical phases are Fe{sub 2}SiAl{sub 8} or Al{sub 15}(Fe,Mn){sub 3}Si. It is also observed that a continuous layer enriched with Cu and Mg of thickness 5080 nm is formed at the interface in between Al and SiC particles. EDS analysis also confirms that Cu and Mg are segregated at the interface of the composite while no carbide is identified at the interface. - Highlights: The composite was successfully heat treated at 575C for 1-48 hrs. A layer of 50-75 nm is formed at interface after heat treatment. No Carbide formation and SiC dissolution is observed at this temperature. MgAl{sub 2}O{sub 4}, CuMgAl{sub 2} phases are segregated at interface of Al-SiC composite. Mg and Cu are also segregated at near to the grain boundary.

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

2013-11-15

117

Electrochemical behavior and localized corrosion associated with Al 7Cu 2Fe particles in aluminum alloy 7075-T651  

Microsoft Academic Search

Initiation of localized corrosion upon high strength aluminum alloys is often associated with cathodic intermetallic particles within the alloy. Electrochemical measurements and metallurgical characterization have been made to clarify and quantify the physical properties of Al7Cu2Fe particles in AA7075-T651. Prior studies regarding either the stereology or electrochemical properties of Al7Cu2Fe are scarce. Quantitative microscopy revealed a significant population of Al7Cu2Fe

N. Birbilis; M. K. Cavanaugh; R. G. Buchheit

2006-01-01

118

Aluminum particle surface studies in Al\\/CuO by electron spectroscopy for chemical analysis and Auger electron spectroscopy  

Microsoft Academic Search

Surface chemistry of Al\\/CuO thermite powders and pressed pellets undergoing accelerated aging was studied by x-ray photelectron spectroscopy (XPS) and Auger electron spectroscopy (AES). Al 1s, Cu 2P, Cu 2P, Cu L-M M , O 1S, Al K-L , L, C 1S, and Cu 3S signals were observed. The AlO film thicknesses on aluminum metal surfaces were deduced from

P. S. Wang; L. D. Haws; W. E. Moddeman; A. Rengan

1979-01-01

119

Aluminum bromide fused-salt battery. [Al\\/Al+ alkali halides\\/C, 50 to 250° operating temp  

Microsoft Academic Search

A battery which operates at lower temperatures (50 to 250°) than other molten salt batteries is described. It has an aluminum anode, a carbon cathode, and an electrolyte of aluminum and alkali metal halides. (RWR)

Buzzelli

1972-01-01

120

Reactivity of aluminum cluster anions with ammonia: Selective etching of Al{sub 11}{sup -} and Al{sub 12}{sup -}  

SciTech Connect

Reactivity of aluminum cluster anions toward ammonia was studied via mass spectrometry. Highly selective etching of Al{sub 11}{sup -} and Al{sub 12}{sup -} was observed at low concentrations of ammonia. However, at sufficiently high concentrations of ammonia, all other sizes of aluminum cluster anions, except for Al{sub 13}{sup -}, were also observed to deplete. The disappearance of Al{sub 11}{sup -} and Al{sub 12}{sup -} was accompanied by concurrent production of Al{sub 11}NH{sub 3}{sup -} and Al{sub 12}NH{sub 3}{sup -} species, respectively. Theoretical simulations of the photoelectron spectrum of Al{sub 11}NH{sub 3}{sup -} showed conclusively that its ammonia moiety is chemisorbed without dissociation, although in the case of Al{sub 12}NH{sub 3}{sup -}, dissociation of the ammonia moiety could not be excluded. Moreover, since differences in calculated Al{sub n}{sup -}+NH{sub 3} (n=9-12) reaction energies were not able to explain the observed selective etching of Al{sub 11}{sup -} and Al{sub 12}{sup -}, we concluded that thermodynamics plays only a minor role in determining the observed reactivity pattern, and that kinetics is the more influential factor. In particular, the conversion from the physisorbed Al{sub n}{sup -}(NH{sub 3}) to chemisorbed Al{sub n}NH{sub 3}{sup -} species is proposed as the likely rate-limiting step.

Grubisic, Andrej; Li Xiang; Gantefoer, Gerd; Bowen, Kit H. [Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218 (United States); Schnoeckel, Hansgeorg [Institut fuer Anorganische Chemie, Karlsruhe Universitaet, Karlsruhe 76128 (Germany); Tenorio, Francisco J. [Departamento de Ciencias Exactas y Tecnologia, Centro Universitario de Los Lagos, Universidad de Guadalajara, Jalisco 47460 (Mexico); Martinez, Ana [Departamento de Materia Condensada y Criogenia, Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico, Coyoacan 04510, Distrito Federal (Mexico)

2009-11-14

121

Fabrication of aluminum based nanomaterials  

NASA Astrophysics Data System (ADS)

Structural applications in transportation necessitate materials with high specific strength and stiffness. With its low density, aluminum (Al) is an interesting candidate, but further strengthening would be beneficial. In this work, the benefits and limitations of nanoreinforcements for aluminum strengthening has been assessed through the addition of carbon nanotube (CNTs) and nanometric alumina (n-Al2O3) to an aluminum matrix by powder metallurgy. It has been found that mechanical milling can homogeneously disperse n-Al2O3 in aluminum. Furthermore, mechanical milling offers the advantages of strengthening the aluminum powder through grain refinement, cold working, solid solution and precipitation. However, CNTs are damaged by mechanical milling, and their homogeneous dispersion cannot be achieved with a chemical dispersant. Nanocomposite consolidation has presented several challenges as hot pressing resulted in a lack of bonding, grain growth and the formation of Al4C3 from damaged CNTs. Cold spraying of Al2O3/Al has resulted in a porous coating with decreased hardness. The microhardness and compression properties of an Al2O 3/Al nanocomposite produced by mechanical milling followed by hot pressing were measured. Comparison with modeled values and literature results indicates that higher experimental yield strength obtained with the addition of n-Al 2O3 versus micron size Al2O3 is due to in-situ matrix strengthening. Modeling shows that CNTs offer high potential gains in stiffness due to their high aspect ratio and their high Young modulus. On the other hand, as yield gains associated with the addition of nanoreinforcement are mainly due to matrix strengthening, discontinuous nanocomposites do not benefit from the CNT's exceptional strength. In this case, n-Al 2O3 would be selected over CNTs as it is cheaper and more easily dispersed.

Poirier, Dominique

2009-11-01

122

Friction Stir Welding for Aluminum Metal Matrix Composites (MMC's) (Center Director's Discretionary Fund, Project No. 98-09)  

NASA Technical Reports Server (NTRS)

This technical memorandum describes an investigation of using friction stir welding (FSW) process for joining a variety of aluminum metal matrix composites (MMC's) reinforced with discontinuous silicon-carbide (SiC) particulate and functional gradient materials. Preliminary results show that FSW is feasible to weld aluminum MMC to MMC or to aluminum-lithium 2195 if the SiC reinforcement is <25 percent by volume fraction. However, a softening in the heat-affected zone was observed and is known to be one of the major limiting factors for joint strength. The pin tool's material is made from a low-cost steel tool H-13 material, and the pin tool's wear was excessive such that the pin tool length has to be manually adjusted for every 5 ft of weldment. Initially, boron-carbide coating was developed for pin tools, but it did not show a significant improvement in wear resistance. Basically, FSW is applicable mainly for butt joining of flat plates. Therefore, FSW of cylindrical articles such as a flange to a duct with practical diameters ranging from 2-5 in. must be fully demonstrated and compared with other proven MMC joining techniques for cylindrical articles.

Lee, J. A.; Carter, R. W.; Ding, J.

1999-01-01

123

Strengthening of NiAl matrix composites. Annual report, Oct 90-Sep 91  

SciTech Connect

Deformation of titanium boride/nickel aluminum composites at high temperatures exhibit low temperature deformation characteristics, and grain size refinement in these composites could account for the strengthening of the composites. Interfaces of TiB2-NiAl and alpha--aluminum oxides--NiAR in TiB2/NiAl composites have been investigated by analytical electron microscopy. Although no consistent crystallographic orientation relationships have been found between NiAl and TiB2 or Al2O3, semicoherent interfaces between alpha-Al2O3 and NiAl have been observed in areas where the low indexed crystallographic planes of alpha-Al2O3 aligned with that of NiAl. No semicoherent interfaces between NiAl and TiB2 have been observed. Silicon segregation was consistently detected by at the TiB2/NiAl interface region. Segregation has not been detected in the alpha-Al2O3-NiAl interface region. The segregation layer observed at the TiB2-NiAl interface is too thin to absorb any of the thermal residual stress.

Arsenault, R.J.

1991-10-01

124

ANALYSIS OF ANISOTROPY IN ELASTIC CONSTANTS OF SiCp/2124 Al METAL MATRIX COMPOSITES  

E-print Network

ANALYSIS OF ANISOTROPY IN ELASTIC CONSTANTS OF SiCp/2124 Al METAL MATRIX COMPOSITES H.K. Jung* , Y; Metal matrix composite; Elastic constants; Aspect ratio; Anisotropy 1. Introduction Metal matrix composites (MMCs) are becoming attractive materials for advanced aerospace structures because

Hong, Soon Hyung

125

Aluminum-Metal Reactive Composites  

Microsoft Academic Search

Three binary Al-based reactive composite powders are prepared by mechanical milling. The particles have an aluminum matrix and inclusions of Fe, Ni, or Zn comprising 10 at % of the bulk composition. For additives of Ni and Zn, only short milling times can be used to prepare composites; intermetallic phases form at longer milling. Short milling times yield relatively coarse

Yasmine Aly; Mirko Schoenitz; Edward L. Dreizin

2011-01-01

126

The use of polyimide-modified aluminum nitride fillers in AlN@PI/Epoxy composites with enhanced thermal conductivity for electronic encapsulation  

PubMed Central

Polymer modified fillers in composites has attracted the attention of numerous researchers. These fillers are composed of core-shell structures that exhibit enhanced physical and chemical properties that are associated with shell surface control and encapsulated core materials. In this study, we have described an apt method to prepare polyimide (PI)-modified aluminum nitride (AlN) fillers, AlN@PI. These fillers are used for electronic encapsulation in high performance polymer composites. Compared with that of untreated AlN composite, these AlN@PI/epoxy composites exhibit better thermal and dielectric properties. At 40?wt% of filler loading, the highest thermal conductivity of AlN@PI/epoxy composite reached 2.03?W/mK. In this way, the thermal conductivity is approximately enhanced by 10.6 times than that of the used epoxy matrix. The experimental results exhibiting the thermal conductivity of AlN@PI/epoxy composites were in good agreement with the values calculated from the parallel conduction model. This research work describes an effective pathway that modifies the surface of fillers with polymer coating. Furthermore, this novel technique improves the thermal and dielectric properties of fillers and these can be used extensively for electronic packaging applications. PMID:24759082

Zhou, Yongcun; Yao, Yagang; Chen, Chia-Yun; Moon, Kyoungsik; Wang, Hong; Wong, Ching-ping

2014-01-01

127

The use of polyimide-modified aluminum nitride fillers in AlN@PI/epoxy composites with enhanced thermal conductivity for electronic encapsulation.  

PubMed

Polymer modified fillers in composites has attracted the attention of numerous researchers. These fillers are composed of core-shell structures that exhibit enhanced physical and chemical properties that are associated with shell surface control and encapsulated core materials. In this study, we have described an apt method to prepare polyimide (PI)-modified aluminum nitride (AlN) fillers, AlN@PI. These fillers are used for electronic encapsulation in high performance polymer composites. Compared with that of untreated AlN composite, these AlN@PI/epoxy composites exhibit better thermal and dielectric properties. At 40?wt% of filler loading, the highest thermal conductivity of AlN@PI/epoxy composite reached 2.03?W/mK. In this way, the thermal conductivity is approximately enhanced by 10.6 times than that of the used epoxy matrix. The experimental results exhibiting the thermal conductivity of AlN@PI/epoxy composites were in good agreement with the values calculated from the parallel conduction model. This research work describes an effective pathway that modifies the surface of fillers with polymer coating. Furthermore, this novel technique improves the thermal and dielectric properties of fillers and these can be used extensively for electronic packaging applications. PMID:24759082

Zhou, Yongcun; Yao, Yagang; Chen, Chia-Yun; Moon, Kyoungsik; Wang, Hong; Wong, Ching-Ping

2014-01-01

128

[sup 31]P and [sup 27]Al NMR investigations of highly acidic, aqueous solutions containing aluminum and phosphorus  

Microsoft Academic Search

[sup 31]P and [sup 27]Al NMR spectroscopies have been used to characterize acidic, aqueous solutions of orthophosphoric acid, aluminum chloride, and tetramethylammonium (TMA) hydroxide. The final compositions of the solutions range from 0.1 to 1 mol % P, 0.0 to 20 mol % HCl, P\\/Al = 0.1 to 20, and P\\/(TMA)[sub 2]O = 2 to 20. Soluble aluminophosphate cations form

R. F. Mortlock; A. T. Bell; C. J. Radke

1993-01-01

129

Equilibrium and Kinetic Studies of Systems of Hydrogen Isotopes, Lithium Hydrides, Aluminum and LiAlO2  

SciTech Connect

This paper described measurements of (1) the distribution of tritium and helium throughout both phases of irradiated Li-Al alloy, (2) the migration rate of tritium during moderate heating, (3) equilibrium pressures as functions of temperature of H2, D2, or T2 in contact with lithium hydrides + aluminum, Li-Al alloy, or irradiated Li-Al alloy, (4) the equilibrium constant for the reaction as a function of temperature, and (5) extraction rates of tritium from irradiated LiAlO2 targets at elevated temperatures.

Owen, J.H.

2001-10-23

130

CO sub 2 induced inhibition of the localized corrosion of aluminum, Al-0. 5% Cu, and Al-2% Cu in dilute HF solution  

SciTech Connect

This study presents work on corrosion of aluminum, Al-.5% Cu, and Al-2% Cu. Electrochemical tests were performed in dilute HF solutions both with and without CO{sub 2} sparging. It is suggested that CO{sub 2} or its reaction products interact with the passive film so that exposure of Cu in the oxide-solution interface is minimized. CO{sub 2} is investigated as a corrosion inhibitor. 4 refs. (JDL)

Scully, J.R. (Virginia Univ., Charlottesville, VA (USA). Dept. of Materials Science); Peebles, D.E. (Sandia National Labs., Albuquerque, NM (USA))

1991-01-01

131

Spectrophotometric method free of matrix effects for the sensitive quantitation of aluminum  

Microsoft Academic Search

It is commonly thought that aluminum is a comparatively nontoxic element in its substances. Though it is ubiquitous, most of its naturally occurring compounds e.g. the silicates and oxides, are relatively inert, chemically as well as physically. However, water soluble compounds such as the chloride and nitrate have rat oral LDs0 values of 3.7 (STECHER 1960) and 4.3 g\\/kg (SMYTH

Shane S. Que Hee; James Boyle; Vincent N. Finelli

1979-01-01

132

THE PROTOTYPE ALUMINUM - CARBON SINGLE, DOUBLE, AND TRIPLE BONDS: Al - CH3, Al = CH2, AND Al. = CH  

SciTech Connect

Nonempirical quantum mechanical methods have been used to investigate the A{ell}CH{sub 3}, A{ell}CH{sub 2}, and A{ell}CH molecules, which may be considered to represent the simplest aluminum-carbon single, double, and triple bonds. Equilibrium geometries and vibrational frequencies were determined at the self-consistent-field level of theory using double zeta basis set: A{ell}(11s7p/6s4p), C(9s5p/4s2p), H(4s/2s). The {sup 1}A{sub 1} ground state of A{ell}CH{sub 3} has a reasonably conventional A{ell}-C single bond of length 2.013 {angstrom}, compared to 1.96 {angstrom} in the known molecule A{ell}(CH{sub 3}){sub 3}. The CH equilibrium distance is 1.093 {angstrom} and the A{ell}-C-H angle 111.9{sup o}. The structures of three electron states each of A{ell}CH{sub 2} and A{ell}CH were similarly predicted, The interesting result is that the ground state of A{ell}CH{sub 2} does not contain an A{ell}-C double bond, and the ground state of A{ell}CH is not characterized by an A{ell}{triple_bond}C bond. The multiply-bonded electronic states do exist but they lie 21 kcal (A{ell}CH{sub 2}) and 86 kcal (A{ell}CH) above the respective ground states. The dissociation energies of the three ground electronic states are predicted to be 68 kcal (A{ell}CH{sub 3}), 77 kcal (A{ell}CH{sub 2}), and 88 kcal (A{ell}CH), Vibrational frequencies are also predicted for the three molecules, and their electronic structures are discussed with reference to Mulliken populations and dipole moments.

Fox, Douglas J.; Ray, Douglas; Rubesin, Philip C.; Schaefer III, Henry F.

1980-06-01

133

Thermal diffusivity of Al-Mg based metallic matrix composite reinforced with Al2O3 ceramic particles  

NASA Astrophysics Data System (ADS)

Thermal diffusivities of Al-Mg based metallic matrix composite reinforced with ceramic particles of Al2O3 are reported in this article. The samples were produced by rheocasting and the studied operational condition in this case is the shear rate: 800, 1400 and 2000 rpm. Additionally, the AlMg base alloy was tested. Measurements of thermal diffusivity were performed at room temperature by using photoacoustic technique.

Cruz-Orea, A.; Morales, J. E.; Saavedra S, R.; Carrasco, C.

2010-03-01

134

Adhesion-enhanced thick copper film deposition on aluminum oxide by an Ion-beam-mixed Al seed layer  

NASA Astrophysics Data System (ADS)

We report a highly-adherent 30-m Cu conductive-path coating on an aluminum-oxide layer anodized on an aluminum-alloy substrate for a metal-printed circuit-board application. A 50-nm Al layer was first coated with an e-beam evaporative deposition method on the anodized oxide, followed by ion bombardment to mix the interfacial region. Subsequently, a Cu coating was deposited onto the mixed seed layer to the designed thickness. Adhesions of the interface were tested by using tape adhesion test, and pull-off tests and showed commercially acceptable adhesions for such thick coating layers. The ion beam mixing (IBM) plays the role of fastening the thin seed coating layer to the substrate and enhancing the adhesion of the Cu conductive path on the anodized aluminum surface.

Kim, Hyung-Jin; Park, Jae-Won

2012-07-01

135

The 1200 C cyclic oxidation behavior of two nickel-aluminum alloys (Ni3AL and NiAl) with additions of chromium, silicon, and titanium  

NASA Technical Reports Server (NTRS)

The alloys Ni3Al and NiAl with and without 1 and 3 atomic percent chromium, silicon, and titanium replacing the aluminum were cyclically oxidized at 1200 C for times to 200 hours, and the results were compared with those obtained with the alloy B-1900 subjected to the same oxidation process. The evaluation was based on metal recession, specific weight change, metallography, electron microprobe analysis, and X-ray diffraction. The oxidation resistance of Ni3Al was improved by Si, unaffected by Ti, and degraded by Cr. The oxidation resistance of NiAl was slightly improved by Ti, unaffected by Si, and degraded by Cr. The oxidation resistance of Ni3Al with 1 atomic percent Si was nearly equal to that of NiAl. Alloy B-1900 exhibited oxidation resistance comparable to that of Ni3Al + Cr compositions.

Lowell, C. E.; Santoro, G. J.

1972-01-01

136

Particles and Zinc on the Absorbed Impact Energy of Gravity Cast Aluminum Matrix Composites  

NASA Astrophysics Data System (ADS)

The effect of different amounts of boron, in the form of AlB2 particles, as well as zinc concentration in a gravity cast Al-B-Zn composite, was studied and related to the absorbed energy upon fracture during Charpy impact experiments. In addition, the authors correlated the composite Brinell hardness with the quantitative assessment of brittle and ductile fracture areas of the Charpy fractured specimens and found that increasing AlB2 particle concentration resulted in a reduction of absorbed impact energy. Although larger zinc levels produced somewhat similar results, the AlB2 effect was prevalent. The energy absorption upon impact reached a maximum when no particles were present; conversely, the lowest amount of absorbed energy corresponded to a composite with a composition of 15 wt.% Zn and 8% in volume of AlB2, i.e., the highest concentration of AlB2 and zinc studied. Raising the amount of AlB2 as well as zinc, as expected, resulted in higher Brinell hardness. A statistical analysis allowed studying of the particle size distribution, whereas values for crack tip opening displacement were subsequently calculated for the range of particle sizes found and the corresponding AlB2 particle volume percent. Higher porosity values were measured for larger AlB2 volume percent. Finally, analyses of fracture surfaces corroborated that brittle fracture was favored in composites with higher amounts of AlB2 and zinc.

Corchado, Marcos; Reyes, Fernando; Surez, Oscar Marcelo

2014-06-01

137

Microstructure and abrasive wear performance of chromium carbide reinforced Ni 3Al matrix composite coating  

Microsoft Academic Search

A NiAlCr3C2 welding wire was produced by metalpowdercore technique. When the welding wires were welded on the surface of carbon steel, under the effect of the physical heat of arc, Ni reacted with Al to form Ni3Al and carbide particles reinforced Ni3Al matrix composite was formed. Cr3C2 was decomposed during welding and dispersed Cr7C3 with stripe shape formed, which strengthened

Shangping Li; Di Feng; Heli Luo

2007-01-01

138

Effect of a solid solution on the steady-state creep behavior of an aluminum matrix composite  

SciTech Connect

The effect of an alloying element, 4 wt pct Mg, on the steady-state creep behavior of an Al-10 vol pct SiC{sub p} composite has been studied. The Al-4 wt pct Mg-10 vol pct SiC{sub p} composite has been tested under compression creep in the temperature range 573 to 673 K. The steady-state creep data of the composite show a transition in the creep behavior (regions 1 and 2) depending on the applied stress at 623 and 673 K. The low stress range data (region 1) exhibit a stress exponent of about 7 and an activation energy of 76.5 kJ mol{sup {minus}1}. These values conform to the dislocation-climb-controlled creep model with pipe diffusion as a rate-controlling mechanism. The intermediate stress range data (region 2) exhibit high and variable apparent stress exponents, 18 to 48, and activation energy, 266 kJ mol{sup {minus}1}, at a constant stress, {sigma} = 50 MPa, for creep of this composite. This behavior can be rationalized using a substructure-invariant model with a stress exponent of 8 and an activation energy close to the lattice self-diffusion of aluminum together with a threshold stress. The threshold stress and the creep strength of the Al-Mg-SiC{sub p} composite are compared with those of the Al-Mg-Al{sub 2}O{sub 3f} and 6061 Al-SiC{sub p,w} composites and discussed in terms of the load-transfer mechanism. Magnesium has been found to be very effective in improving the creep resistance of the Al-SiC{sub p} composite.

Pandey, A.B.; Mahajan, Y.R. [Defence Metallurgical Research Lab., Hyderabad (India); Mishra, R.S. [Univ. of California, Davis, CA (United States). Dept. of Chemical Engineering and Materials Science

1996-02-01

139

Impact Testing of Aluminum 2024 and Titanium 6Al-4V for Material Model Development  

NASA Technical Reports Server (NTRS)

One of the difficulties with developing and verifying accurate impact models is that parameters such as high strain rate material properties, failure modes, static properties, and impact test measurements are often obtained from a variety of different sources using different materials, with little control over consistency among the different sources. In addition there is often a lack of quantitative measurements in impact tests to which the models can be compared. To alleviate some of these problems, a project is underway to develop a consistent set of material property, impact test data and failure analysis for a variety of aircraft materials that can be used to develop improved impact failure and deformation models. This project is jointly funded by the NASA Glenn Research Center and the FAA William J. Hughes Technical Center. Unique features of this set of data are that all material property data and impact test data are obtained using identical material, the test methods and procedures are extensively documented and all of the raw data is available. Four parallel efforts are currently underway: Measurement of material deformation and failure response over a wide range of strain rates and temperatures and failure analysis of material property specimens and impact test articles conducted by The Ohio State University; development of improved numerical modeling techniques for deformation and failure conducted by The George Washington University; impact testing of flat panels and substructures conducted by NASA Glenn Research Center. This report describes impact testing which has been done on aluminum (Al) 2024 and titanium (Ti) 6Al-4vanadium (V) sheet and plate samples of different thicknesses and with different types of projectiles, one a regular cylinder and one with a more complex geometry incorporating features representative of a jet engine fan blade. Data from this testing will be used in validating material models developed under this program. The material tests and the material models developed in this program will be published in separate reports.

Pereira, J. Michael; Revilock, Duane M.; Lerch, Bradley A.; Ruggeri, Charles R.

2013-01-01

140

Synthesis of intermetallic NiAl by SHS reaction using coarse-grained nickel and ultrafine-grained aluminum produced by wire electrical explosion  

Microsoft Academic Search

Nickel aluminide NiAl was synthesized by using aluminum nanoparticles via the thermal explosion mode of the self-propagating high temperature synthesis (SHS). Differential scanning calorimetry (DSC) was used to investigate the reaction process and mechanism. It was found that the mode and mechanism of reaction strongly depended on the charateristics of aluminum nanoparticles that have small grain size, high surface areas,

Shushan Dong; Ping Hou; Haibin Yang; Guangtian Zou

2002-01-01

141

Fractionation of residual Al in natural water treatment from reservoir with poly-aluminum-silicate-chloride (PASiC): effect of OH/Al, Si/Al molar ratios and initial pH.  

PubMed

An aluminum fractionation study was conducted for a surface reservoir water treatment to understand the performance of poly-aluminum-silicate-chloride (PASiC) in terms of the residual Al fractions as a function of initial pH. The coagulation performance expressed as turbidity and organic matter removal was established as supporting data. Some extra data were evaluated in terms of the residual Al ratio of the composite PASiC coagulant. The main residual Al sources were the Al fractions derived from the use of PASiC. The turbidity and organic matter removal ability was optimal at initial pH 6.00-7.00, while the concentrations of various residual Al species and the residual Al ratio of PASiC were minimal at an initial pH range of 7.00-8.00. Under the conditions of OH/Al molar ratio = 2.00 and Si/Al molar ratio = 0.05, PASiC had superior coagulation performance and comparatively low residual Al concentrations. The Al fraction in the composite PASiC coagulant seldom remained under such conditions. Experimental data also indicated that the suspended (filterable) Al fraction was the dominant species, and organic-bound or organo-Al complex Al was considered to be the major species of dissolved Al in water treated by PASiC coagulation. Additionally, the dissolved inorganic monomeric Al species dominated the dissolved monomeric Al fraction. PMID:23534222

Yang, Zhonglian; Gao, Baoyu; Wang, Yan; Zhao, Yaqin; Yue, Qinyan

2012-01-01

142

Failure Modeling of Titanium-6Al-4V and 2024-T3 Aluminum with the Johnson-Cook Material Model  

SciTech Connect

A validated Johnson-Cook model could be employed to perform simulations that conform to FAA standards for evaluating aircraft and engine designs for airworthiness and containment considerations. A previous LLNL report [1] described the motivation for using the Johnson-Cook material model in simulations involving engine containment and the effect of uncontained engine debris on aircraft structures. In that report, experimental studies of the deformation and failure behavior of Ti-6Al-4V and 2024-T3 aluminum at high strain rates and large strains were conducted. The report also describes the generation of material constants for the Johnson-Cook strength model. This report describes the determination and validation of parameters for Ti-6Al-4V and 2024-T3 aluminum that can be used in the failure portion of the Johnson-Cook material.

Kay, G

2002-09-16

143

Optimal welding parameters for very high power ultrasonic additive manufacturing of smart structures with aluminum 6061 matrix  

NASA Astrophysics Data System (ADS)

Ultrasonic additive manufacturing (UAM) is a recent solid state manufacturing process that combines ad- ditive joining of thin metal tapes with subtractive milling operations to generate near net shape metallic parts. Due to the minimal heating during the process, UAM is a proven method of embedding Ni-Ti, Fe-Ga, and PVDF to create active metal matrix composites. Recently, advances in the UAM process utilizing 9 kW very high power (VHP) welding has improved bonding properties, enabling joining of high strength materials previously unweldable with 1 kW low power UAM. Consequently, a design of experiments study was conducted to optimize welding conditions for aluminum 6061 components. This understanding is critical in the design of UAM parts containing smart materials. Build parameters, including weld force, weld speed, amplitude, and temperature were varied based on a Taguchi experimental design matrix and tested for me- chanical strength. Optimal weld parameters were identi ed with statistical methods including a generalized linear model for analysis of variance (ANOVA), mean e ects plots, and interaction e ects plots.

Wolcott, Paul J.; Hehr, Adam; Dapino, Marcelo J.

2014-03-01

144

Damping mechanisms in alumina borate whisker-reinforced-aluminum matrix composites with or without SnO{sub 2} coatings  

SciTech Connect

SnO{sub 2} was successfully coated on the surface of alumina borate whiskers. The pure aluminum matrix composites reinforced with a SnO{sub 2}-coated alumina borate whisker were fabricated by squeeze casting. The effects of coating contents on the damping properties of the coated composites at various temperatures, frequencies, and strain amplitudes were examined. The microstructures of the coated composites were also investigated through transmission electron microscopy observations. These results indicate that the introduction of Sn at the interface between whisker and matrix in the coated composites during the squeeze casting process alters not only the interface structures but also the dislocation status of the matrices in the vicinity of the interface. The results of damping characterization indicate that the damping capacities of the coated composites strongly depend on the coating contents and strain amplitudes. A damping peak at low temperatures appeared not only in the coated composites but also in the noncoated one, which is related to dislocation motion and interfacial slip caused by Sn. A damping peak at high temperatures appeared only in the coated composites, and the damping mechanisms at high temperature change with the increase in strain amplitudes. Sn played an important role on the damping mechanisms of the coated composites all along.

Hu, J.; Wang, X. F.; Zheng, Z. Z. [School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China)

2010-01-15

145

Formation of metal matrix composite layer on aluminum alloy with TiC-Cu powder by laser surface alloying process  

Microsoft Academic Search

Thick hardened metal matrix composite (MMC) layer was formed to improve the wear resistance of a commercial AlMg alloy (A5083) plate by using laser surface alloying with Cu coated TiC powders in the size of between 20 and 40 ?m. A continuous wave CO2 laser beam (2100 W) was irradiated on the pre-placed TiC-Cu powder to melt them together with

S. Tomida; K. Nakata; S. Saji; T. Kubo

2001-01-01

146

Physical and Chemical Properties of Aluminum Oxide Film Deposited by AlCl3CO2-H2 System  

Microsoft Academic Search

The changes of structure and physico-chemical properties of aluminum oxide film with deposition and heat treatment temperatures have been investigated by infra-red spectroscopy, X-ray diffraction analysis, electron probe analysis, ellipsometry, microscopy and etch rate measurement. The films have been deposited on a heated silicon substrate in the temperature range of 4001000C by AlCl3-CO2-H2 system and heat-treated in H2, O2 and

Kiyoto Iida; Tohru Tsujide

1972-01-01

147

Al2O3 fiber strength degradation in metal and intermetallic matrix composites  

NASA Technical Reports Server (NTRS)

The mechanisms for fiber damage in single crystal Al2O3 fiber-reinforced composites were investigated. Both fiber fragmentation and fiber strength degradation were observed in composites with a variety of matrix compositions. Four mechanisms that may be contributing to the fiber strength loss have been proposed and include matrix reaction, reaction with binders, residual stress-induced damage, and pressure from hot pressing. The effect of matrix reaction was separated from the other three effects by sputter-coating the matrices on cleaned fibers and annealing with a temperature profile that simulates processing conditions. These experiments revealed that Y and Cr in FeCrAlY base alloys and Zr in NiAl alloys reacted with the fiber, and grooves and adherent particles were formed on the fiber surface which were responsible for the strength loss. The effects of the matrix reaction appeared to dominate over the other possible mechanisms, although evidence for reaction with binders was also found. Ridges on the fiber surface, which reflected the grain boundaries of the matrix, were also observed. In order for single-crystal Al2O3 to be used as a fiber in MMC's and IMC's, a matrix or protective coating which minimizes matrix reaction during processing will be necessary. Of the matrices investigated, the Thermo-span(sup TM) alloy was the least damaging to fiber properties.

Draper, S. L.; Locci, I. E.

1994-01-01

148

InGaN nanoinclusions in an AlGaN matrix  

SciTech Connect

GaN-based structures with InGaN quantum dots in the active region emitting in the near-ultraviolet region are studied. In this study, two types of structures, namely, with InGaN quantum dots in a GaN or AlGaN matrix, are compared. Photoluminescence spectra are obtained for both types of structures in a temperature range of 80-300 K and at various pumping densities, and electroluminescence spectra are obtained for light-emitting (LED) structures with various types of active region. It is shown that the structures with quantum dots in the AlGaN matrix are more stable thermally due to the larger localization energy compared with quantum dots in the GaN matrix. Due to this, the LED structures with quantum dots in an AlGaN matrix are more effective.

Sizov, V. S., E-mail: sizovviktor@mail.ru; Tsatsul'nikov, A. F.; Lundin, V. V. [Russian Academy of Sciences, Ioffe Physicotechnical Institute (Russian Federation)

2008-07-15

149

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

Microsoft Academic Search

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

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

2002-01-01

150

Modeling of Interaction Layer Growth Between U-Mo Particles and an Al Matrix  

SciTech Connect

Interaction layer growth between U-Mo alloy fuel particles and Al in a dispersion fuel is a concern due to the volume expansion and other unfavorable irradiation behavior of the interaction product. To reduce interaction layer (IL) growth, a small amount of Si is added to the Al. As a result, IL growth is affected by the Si content in the Al matrix. In order to predict IL growth during fabrication and irradiation, empirical models were developed. For IL growth prediction during fabrication and any follow-on heating process before irradiation, out-of-pile heating test data were used to develop kinetic correlations. Two out-of-pile correlations, one for the pure Al matrix and the other for the Al matrix with Si addition, respectively, were developed, which are Arrhenius equations that include temperature and time. For IL growth predictions during irradiation, the out-of-pile correlations were modified to include a fission-rate term to consider fission enhanced diffusion, and multiplication factors to incorporate the Si addition effect and the effect of the Mo content. The in-pile correlation is applicable for a pure Al matrix and an Al matrix with the Si content up to 8 wt%, for fuel temperatures up to 200 degrees C, and for Mo content in the range of 6 10wt%. In order to cover these ranges, in-pile data were included in modeling from various tests, such as the US RERTR-4, -5, -6, -7 and -9 tests and Koreas KOMO-4 test, that were designed to systematically examine the effects of the fission rate, temperature, Si content in Al matrix, and Mo content in U-Mo particles. A model converting the IL thickness to the IL volume fraction in the meat was also developed.

Yeon Soo Kim; G. L. Hofman; Ho Jin Ryu; Jong Man Park; A. B. Robinson; D. M. Wachs

2013-12-01

151

Continuous synthesis of high-surface-area aluminum hydroxide methoxide nano- and microparticles in supercritical methanol and their conversion into ?-Al 2O 3  

Microsoft Academic Search

High-surface-area aluminum hydroxide methoxide (CH4Al2O4) nano- and microparticles are synthesized continuously in supercritical methanol (scMeOH). The properties of the particle synthesized in scMeOH are compared with those synthesized in supercritical water (scH2O). The XRD analysis reveals that the particles synthesized in scMeOH retain aluminum hydroxide methoxide crystalline structure while the particles synthesized in supercritical water retain boehmite (AlOOH) crystalline structure.

Bambang Veriansyah; Ratna F. Susanti; Agung Nugroho; Byoung Koun Min; Jaehoon Kim

2011-01-01

152

Aluminum for nonlinear plasmonics: resonance-driven polarized luminescence of Al, Ag, and Au nanoantennas.  

PubMed

Resonant optical antennas are ideal for nanoscale nonlinear optical interactions due to their inherent strong local field enhancement. Indeed second- and third-order nonlinear response of gold nanoparticles has been reported. Here we compare the on- and off-resonance properties of aluminum, silver, and gold nanoantennas, by measuring two-photon photoluminescence. Remarkably, aluminum shows 2 orders of magnitude higher luminescence efficiency than silver or gold. Moreover, in striking contrast to gold, the aluminum emission largely preserves the linear incident polarization. Finally, we show the systematic resonance control of two-photon excitation and luminescence polarization by tuning the antenna width and length independently. Our findings point to aluminum as a promising metal for nonlinear plasmonics. PMID:21970569

Castro-Lopez, Marta; Brinks, Daan; Sapienza, Riccardo; van Hulst, Niek F

2011-11-01

153

Pretreatment effects on the morphology and properties of aluminum oxide thermally grown on NiCoCrAlY  

NASA Technical Reports Server (NTRS)

The effect of pretreatments on the morphology and properties of aluminum oxide thermally grown from NiCoCrAlY was investigated. The goal was to optimize process steps to produce a highly adherent, continuous, and insulating aluminum oxide. Two pretreatments were carried out, one in vacuum (about 0.0001 Torr) at 1350 K for 5 h, and the other consisting of deposition of a 1-micron thick Al2O3 film by activated reactive evaporation. Samples were subsequently oxidized thermally at 1000 C for 50 h at 0.5 Torr oxygen pressure. The two pretreatments were carried out on electron-beam evaporation NiCoCrAlY, about 120 microns thick, deposited on a superalloy turbine blade substrate. The results showed that the thermally grown oxide was significantly different in microstructure, surface topography and in its adherence to the NiCoCrAlY for the two pretreatments. Optimum results were obtained by combining the two pretreatments to produce an adherent, continuous, and insulating oxide film on the NiCoCrAlY-coated superalloy substrate.

Prakash, S.; Budhani, R.; Doerr, H. J.; Deshpandey, C. V.; Bunshah, R. F.

1985-01-01

154

Stress Corrosion Cracking in Al-Zn-Mg-Cu Aluminum Alloys in Saline Environments  

NASA Astrophysics Data System (ADS)

Stress corrosion cracking of Al-Zn-Mg-Cu (AA7xxx) aluminum alloys exposed to saline environments at temperatures ranging from 293 K to 353 K (20 C to 80 C) has been reviewed with particular attention to the influences of alloy composition and temper, and bulk and local environmental conditions. Stress corrosion crack (SCC) growth rates at room temperature for peak- and over-aged tempers in saline environments are minimized for Al-Zn-Mg-Cu alloys containing less than ~8 wt pct Zn when Zn/Mg ratios are ranging from 2 to 3, excess magnesium levels are less than 1 wt pct, and copper content is either less than ~0.2 wt pct or ranging from 1.3 to 2 wt pct. A minimum chloride ion concentration of ~0.01 M is required for crack growth rates to exceed those in distilled water, which insures that the local solution pH in crack-tip regions can be maintained at less than 4. Crack growth rates in saline solution without other additions gradually increase with bulk chloride ion concentrations up to around 0.6 M NaCl, whereas in solutions with sufficiently low dichromate (or chromate), inhibitor additions are insensitive to the bulk chloride concentration and are typically at least double those observed without the additions. DCB specimens, fatigue pre-cracked in air before immersion in a saline environment, show an initial period with no detectible crack growth, followed by crack growth at the distilled water rate, and then transition to a higher crack growth rate typical of region 2 crack growth in the saline environment. Time spent in each stage depends on the type of pre-crack ("pop-in" vs fatigue), applied stress intensity factor, alloy chemistry, bulk environment, and, if applied, the external polarization. Apparent activation energies ( E a) for SCC growth in Al-Zn-Mg-Cu alloys exposed to 0.6 M NaCl over the temperatures ranging from 293 K to 353 K (20 C to 80 C) for under-, peak-, and over-aged low-copper-containing alloys (<0.2 wt pct) are typically ranging from 80 to 85 kJ/mol, whereas for high-copper-containing alloys (>~0.8 wt pct), they are typically ranging from 20 to 40 kJ/mol for under- and peak-aged alloys, and based on limited data, around 85 kJ/mol for over-aged tempers. This means that crack propagation in saline environments is most likely to occur by a hydrogen-related process for low-copper-containing Al-Zn-Mg-Cu alloys in under-, peak- and over-aged tempers, and for high-copper alloys in under- and peak-aged tempers. For over-aged high-copper-containing alloys, cracking is most probably under anodic dissolution control. Future stress corrosion studies should focus on understanding the factors that control crack initiation, and insuring that the next generation of higher performance Al-Zn-Mg-Cu alloys has similar longer crack initiation times and crack propagation rates to those of the incumbent alloys in an over-aged condition where crack rates are less than 1 mm/month at a high stress intensity factor.

Holroyd, N. J. Henry; Scamans, G. M.

2013-03-01

155

Synthesis and processing of Al{sub 2}O{sub 3}/Al composites by in situ reaction of aluminum and mullite  

SciTech Connect

Al{sub 2}O{sub 3}/Al composites, were formed by reacting molten aluminum metal with dense mullite ceramic preforms. The composites produced by this reactive metal penetration process (RMP) have a two phase, interpenetrating microstructure in which both the ceramic and the metal are continuous in three dimensions. Scanning electron microscopy (SEM) micrographs of composites produced by RMP show a fine microstructure comprised of interlocked metal and ceramic phases, with a feature size of approximately 2 {mu}m. RMP is a relatively rapid process with metal penetration rates of nearly 5 mm/hour at 1100{degrees}C after a short incubation period. An activation energy of 92 kJ/mole was calculated from reaction rate data. Transmission electron microscopy (TEM) micrographs reveal that aluminum metal penetrates along the mullite grain boundaries before reaction with the mullite grains, indicating that diffusion along grain boundaries may be the rate limiting step for the reaction. Thermodynamic information, results of microstructure analyses, and kinetic data indicate that RMP proceeds in 4 stages: (1) Al melting and the formation of a thermodynamically stable metal/ceramic interface; (2) depletion of oxygen from the grain boundaries intersecting the ceramic/metal interface; (3) Al metal penetration into the ceramic preform along grain boundaries; and (4) Al reaction with and conversion of individual mullite grains.

Fahrenholtz, W.G. [Univ. of New Mexico, Albuquerque, NM (United States); Ewsuk, K.G.; Loehman, R.E. [Sandia National Labs., Albuquerque, NM (United States); Tomsia, A.P. [Pask Research and Engineering, Berkeley, CA (United States)

1995-02-01

156

Interaction of Al2O3-ZrO2 fibers with a Ti-Al matrix during pressure casting  

NASA Astrophysics Data System (ADS)

Electron and optical electron microscopy, together with energy dispersive X-ray (EDX) chemical microanalysis, were employed to examine the microstructure of a pressure-cast composite consisting of a Ti-48.4 at. pct Al-1 at. pct Mn matrix reinforced with DuPonts PRD-166 A12O3 fibers containing 20 wt pct partially stabilized ZrO2. The originally cylindrical fibers were found to have a scalloped surface, and a zone just below the surface was free of ZrO2. In addition, the fibers contained entrapped TiAl, and a small portion of the fiber periphery was covered by ZrO2 particles, which were free of the Y2O3 and HfO2 oxides present in the ZrO2 within the fibers. The matrix consisted of a mixture of TiAl and a lamellar structure of TiAl and Ti3Al and contained Zr not originally present in the matrix alloy. An analysis of the origin of this microstructure is presented.

Nourbakhsh, S.; Liang, F. L.; Margolin, H.

1990-01-01

157

The surface tension of molten aluminum and Al-Si-Mg alloy under vacuum and hydrogen atmospheres  

NASA Astrophysics Data System (ADS)

The surface tensions of pure molten aluminum, A356 alloy (Al-7 pct Si-0.3 pct Mg), and strontium-modified A356 alloy have been measured under vacuum and hydrogen atmospheres using the sessile drop technique. The values obtained for pure aluminum at 680 C and for A356 alloy and modified A356 alloy at 630 C are 1.007, 0.889, and 0.844 N/m, respectively, when measured under vacuum. The addition of hydrogen gas to the atmosphere of the liquid droplet has no significant effect on the surface tension of the unmodified A356 alloy, while it lowers the surface tension of the modified alloy to 0.801 N/m. This effect is possibly due to the formation of SrH2.

Anson, J. P.; Drew, R. A. L.; Gruzleski, J. E.

1999-12-01

158

Laser-induced spallation of aluminum and Al alloys at strain rates above 2106 s-1  

NASA Astrophysics Data System (ADS)

Material microstructure is a significant determinant of the tensile stress at which materials fail. Using a high-energy laser to drive shocks in thin slabs, we have explored the role material microstructure plays on the spall strength of high-purity and alloyed aluminum at strain rates of (2-7.5)106s-1. Slabs of pure recrystallized Al and recrystallized or cold worked Al +3wt% Mg were shock driven using the Z-Beamlet Laser at Sandia National Laboratories. Velocity interferometer measurements determined the spall strength of the materials, and postshot target analysis explored the microscopic fracture morphology. We observed the greatest spall strength for large-grained, recrystallized high-purity aluminum, with the dominant failure mode being ductile and transgranular. We observe for the first time at these strain rates fracture features for a fine-grained Al +3wt% Mg that were a combination of brittle intergranular and ductile transgranular fracture types. Postshot analysis of target cross sections and hydrocode simulations indicate that this mixed-mode failure results from spall dynamics occurring on spatial scales on the order of the grain size. Differences in spall strength between these Al samples were experimentally significant and correlate with the damage morphologies observed.

Dalton, D. A.; Brewer, J. L.; Bernstein, A. C.; Grigsby, W.; Milathianaki, D.; Jackson, E. D.; Adams, R. G.; Rambo, P.; Schwarz, J.; Edens, A.; Geissel, M.; Smith, I.; Taleff, E. M.; Ditmire, T.

2008-07-01

159

Electric discharge machining of Al10%SiC P as-cast metal matrix composites  

Microsoft Academic Search

The use of unconventional machining techniques in shaping aluminium metal matrix composites (Al-MMC) has generated considerable interest as the manufacturing of complicated die contours in these hard materials to a high degree of accuracy and surface finish is difficult. Electrical discharge machining (EDM) is an important process for machining difficult-to-machine materials like metal matrix composites. Among the many unconventional processing

P. Narender Singh; K. Raghukandan; M. Rathinasabapathi; B. C. Pai

2004-01-01

160

Micro Joining of Aluminum Graphite Composites  

E-print Network

techniques. Laser welding of Al-Gr composite showed that a power density above 30kW/mm2 gives a weld with microstructure defects. Also the laser beam melts the matrix and delaminates the graphite fibers. The molten aluminum reacts with graphite to form...

Velamati, Manasa

2012-07-16

161

Improvement of Mechanical Properties in the Functionally Graded Aluminum Matrix Nanocomposites Fabricated via a Novel Multistep Friction Stir Processing  

NASA Astrophysics Data System (ADS)

In the present study, the functionally graded bulk Al-SiC nanocomposites were successfully fabricated by applying a novel multistep friction stir processing. Microstructural observations by scanning electron microscope indicated a proper distribution of SiC nanoparticles in the Al 6061 matrix. Microhardness profiles descended to 50 from 160 Hv due to the formation of compositionally gradient of SiC nanoparticles along the thickness. The tensile behavior of graded samples revealed a simultaneous enhancement of ultimate tensile strength (44 pct), strain at maximum stress (244 pct), and work of fracture (492 pct) with respect to the homogeneous sample. Furthermore, the graded samples sustained up to 4 pct strain after initiation of primary cracking, while the catastrophic fracture occurred instantly after cracking in the homogenous sample. A dimple-like ductile fracture surface was observed for the graded layers in which an increase in the SiC particle content will result in smaller dimple size.

Salehi, Mojtaba; Farnoush, Hamidreza; Heydarian, Arash; Aghazadeh Mohandesi, Jamshid

2015-02-01

162

The Microstructure-Processing-Property Relationships in an Al Matrix Composite System Reinforced by Al-Cu-Fe Alloy Particles  

SciTech Connect

Metal matrix composites (MMC), especially Al matrix composites, received a lot of attention during many years of research because of their promise for the development of automotive and aerospace materials with improved properties and performance, such as lighter weight and better structural properties, improved thermal conductivity and wear resistance. In order to make the MMC materials more viable in various applications, current research efforts on the MMCs should continue to focus on two important aspects, including improving the properties of MMCs and finding more economical techniques to produce MMCs. Solid state vacuum sintering was studied in tap densified Al powder and in hot quasi-isostatically forged samples composed of commercial inert gas atomized or high purity Al powder, generated by a gas atomization reaction synthesis (GARS) technique. The GARS process results in spherical Al powder with a far thinner surface oxide. The overall results indicated the enhanced ability of GARS-processed Al and Al alloy powders for solid state sintering, which may lead to simplification of current Al powder consolidation processing methods. Elemental Al-based composites reinforced with spherical Al-Cu-Fe alloy powders were produced by quasi-isostatic forging and vacuum hot pressing (VHP) consolidation methods. Microstructures and tensile properties of AYAl-Cu-Fe composites were characterized. It was proved that spherical Al-Cu-Fe alloy powders can serve as an effective reinforcement particulate for elemental Al-based composites, because of their high hardness and a preferred type of matrix/reinforcement interfacial bonding, with reduced strain concentration around the particles. Ultimate tensile strength and yield strength of the composites were increased over the corresponding Al matrix values, far beyond typical observations. This remarkable strengthening was achieved without precipitation hardening and without severe strain hardening during consolidation because of the matrix choice (elemental Al) and the ''low shear'' consolidation methods utilized. This reinforcement effectiveness is further evidenced by elastic modulus measurements of the composites that are very close to the upper bound predictions of the rule of mixtures. The load partitioning measurements by neutron diffraction showed that composite samples made from GARS powders present significantly higher load transfer efficiency than the composites made from commercially atomized powders. Also, the composite samples made from GARS powders show a higher strengthening effect and ductility than the samples made from commercial purity powders. The higher load transfer efficiency and higher strength and ductility may result from an enhanced inter-particle bonding strength, promoted by the ''clean'' interfaces between particles. Further analysis of the load sharing measurements and the calculated values of the mismatch of coefficient of thermal expansion (CTE) and the geometrically necessary dislocation (GND) effects suggest that these strengthening mechanisms can be combined to predict accurately the strength of the composites.

Fei Tang

2004-12-19

163

Low coverage spontaneous etching and hyperthermal desorption of aluminum chlorides from Cl2 Al,,111...  

E-print Network

for integrated circuit processing of aluminum films. Because plasma etching environments are typically very,,111... Tyler J. Grassman, Gary C. Poon, and Andrew C. Kummel Department of Chemistry and Biochemistry many times in the last quarter century.1­13 Most of the work has focused on Cl2 plasma etching

Kummel, Andrew C.

164

Aluminum extraction from aluminum industrial wastes  

NASA Astrophysics Data System (ADS)

Aluminum dross tailings, an industrial waste from the Egyptian Aluminum Company (Egyptalum), was used to produce two types of alums: aluminum sulfate alum (Al2(SO4)312H2O) and ammonium aluminum alum {(NH4)2SO4AL2 (SO4)324H2O}. This was carried out in two processes. The first involves leaching the impurities using diluted H2SO4 with different solid/liquid ratios at different temperatures to dissolve the impurities present in the starting material in the form of aluminum sulfates. The second process is the extraction of aluminum (as aluminum sulfate) from the purified aluminum dross tailings thus produced. This was carried out in an autoclave. The effects of temperature, time of reaction, and acid concentration on pressure leaching and extraction processes were studied in order to specify the optimum conditions to be applied in the bench scale production as well as the kinetics of leaching process.

Amer, A. M.

2010-05-01

165

Tribological properties of Ti-aluminide reinforced Al-based in situ metal matrix composite  

Microsoft Academic Search

For structural application of moving components, the tribological properties (friction and wear) are considered to be one of the major factors controlling the performance. In recent years, lightweight metal matrix composites (MMC) have received wider attention for their technological application, such as automotive parts etc. This paper reports the tribological behavior of Al based composites reinforced with in situ TixAly

Debdas Roy; Bikramjit Basu; Amitava Basu Mallick

2005-01-01

166

Development of a job-exposure matrix for exposure to total and fine particulate matter in the aluminum industry  

PubMed Central

Increasing evidence indicates that exposure to particulate matter (PM) at environmental concentrations increases the risk of cardiovascular disease, particularly PM with an aerodynamic diameter of less than 2.5?m (PM2.5). Despite this, the health impacts of higher occupational exposures to PM2.5 have rarely been evaluated. In part, this research gap derives from the absence of information on PM2.5 exposures in the workplace. To address this gap, we have developed a job-exposure matrix (JEM) to estimate exposure to two size fractions of PM in the aluminum industry. Measurements of total PM (TPM) and PM2.5 were used to develop exposure metrics for an epidemiologic study. TPM exposures for distinct exposure groups (DEGs) in the JEM were calculated using 8,385 personal TPM samples collected at 11 facilities (1980-2011). For 8 of these facilities, simultaneous PM2.5 and TPM personal monitoring was conducted from 2010-2011 to determine the percent of TPM that is composed of PM2.5 (%PM2.5) in each DEG. The mean TPM from the JEM was then multiplied by %PM2.5 to calculate PM2.5 exposure concentrations in each DEG. Exposures in the smelters were substantially higher than in fabrication units; mean TPM concentrations in smelters and fabrication facilities were 3.86 mg/m3 and 0.76 mg/m3, and the corresponding mean PM2.5 concentrations were 2.03 mg/m3 and 0.40 mg/m3. Observed occupational exposures in this study generally exceeded environmental PM2.5 concentrations by an order of magnitude. PMID:24022670

Noth, Elizabeth M.; Dixon-Ernst, Christine; Liu, Sa; Cantley, Linda; Tessier-Sherman, Baylah; Eisen, Ellen A.; Cullen, Mark R.; Hammond, S. Katharine

2014-01-01

167

Aluminum monocarbonyl and aluminum isocarbonyl Steve S. Wesolowski,a)  

E-print Network

Aluminum monocarbonyl and aluminum isocarbonyl Steve S. Wesolowski,a) T. Daniel Crawford,b) Justin of the aluminum monocarbonyl species AlCO and AlOC have been performed to predict the geometries, fragmentation, Ogden, and Oswald6 first isolated aluminum dicarbonyls in solid krypton and identified the species

Crawford, T. Daniel

168

The influence of reinforcement homogeneity on the deformation and fracture of a discontinuously reinforced aluminum matrix composite  

NASA Astrophysics Data System (ADS)

Deformation processing (extrusion) has been used to homogenize reinforcement distribution in a discontinuously reinforced aluminum matrix composite (DRA 6092/SiC/25p). Reinforcement distribution after three conditions of varying extrusion reduction has been quantified using the homogenous length scale technique. Results indicate that deformation processing positively influences reinforcement homogeneity---increasing deformation asymptotically leads to an increasingly uniform reinforcement distribution. After heat treatment to peak age, the compressive flow behavior both along and transverse to the extrusion axis has been determined for each condition. Using chevron notch short rods, the fracture toughness behavior in several orientations has also been assessed. Variations in flow behavior with deformation processing are mainly rationalized in terms of matrix texture with the combined effect of particle alignment along the extrusion axis and reinforcement homogenization being relatively small. Regardless of orientation, toughness is shown to increase with reinforcement homogeneity; in a particular transverse orientation, chevron notch fracture toughness (KIv) demonstrates a nearly two-fold increase (10.8 MPa?m to 19.3 MPa?m) as a result of reinforcement cluster breakdown. Qualitative fractography indicates a generally ductile fracture process. Quantitative fractography indicates a strong positive relationship between fracture surface average roughness (RA---a measure of out-of-plane crack deflection) and toughness (KIv ), while a fractal technique used to characterize the fracture surface indicates a decrease in fractal dimension with increasing toughness. Using a simple model, the trend of increasing average roughness is interpreted as an increase in the fracture process length scale, while the decrease in fractal dimension is interpreted as a subtle decrease in the mean angle of crack deflection---a result expected with reinforcement homogenization. The increase in toughness is rationalized as a combined effect of decreasing crack deflection (leading to slower strain accumulation during crack blunting) in addition to a nominal improvement in plastic strain that can be supported by the interparticle ligament after reinforcement homogenization. Such a change in local ductility is qualitatively validated with SEM fractography.

Wilks, Garth Barrett

169

Microstructure of multilayer interface in an Al matrix composite reinforced by TiNi fiber.  

PubMed

A multilayer interface was formed in the Al matrix composite which was reinforced by 30% volume fraction of TiNi fiber. The composite was fabricated by pressure infiltration process and the interface between the TiNi fiber and Al matrix was investigated by transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS). When the TiNi fiber was pre-oxidized in the air at 773 K for 1 h, three layers have been found and characterized in the interface: TiNi-B2 layer near the TiNi fiber, Ti-Al compound layer with Ti and granular TiO2 near the Al matrix, and Ti-Ni compound layer between TiNi-B2 and Ti-Al compound layers. The effect of the multilayer interface on the mechanical properties of the composite was also discussed. The result showed that the uniaxial tensile strength of the composite at room temperature was 318 MPa, which was very close to the theoretical calculation value of 326 MPa. Moreover, the composite with good ductility exhibited a typical ductile-fracture pattern. PMID:24981215

Hu, Jie; Wu, Gaohui; Zhang, Qiang; Kang, Pengchao; Liu, Yan

2014-09-01

170

Dendrite-Free Aluminum Electrodeposition from AlCl3-1-Ethyl-3-Methyl-Imidazolium Chloride Ionic Liquid Electrolytes  

NASA Astrophysics Data System (ADS)

A novel, dendrite-free electrorefining of aluminum scrap alloys (A360) was investigated by using a low-temperature AlCl3-1-ethyl-3-methyl-imidazolium chloride (EMIC) ionic liquid electrolyte on copper/aluminum cathodes. The bulk electrodeposition of aluminum was carried out at a fixed voltage of 1.5 V, temperatures 323 K to 383 K (50 C to 110 C), stirring rate (0 to 120 rpm), concentration (molar ratio AlCl3:EMIC = 1.25 to 2.0), and electrode surface modification (modified/unmodified). The study investigated the effect of electrode surface modification, cathode materials, temperature, stirring rate, electrolyte concentration, and deposition time on the deposit morphology of aluminum, cathode current density, and their role in production of dendrite-free aluminum deposit, which is essential for decreasing the production cost. The deposits were characterized using scanning electron microscope (SEM), energy-dispersive spectroscopy (EDS), and X-ray diffraction (XRD). It was shown that electrode surface modification, cathode overpotential, and stirring rate play an important role in dendrite-free deposit. Modified electrodes and stirring (60 rpm) eliminate dendritic deposition by reducing cathode overpotential below critical overpotential ( ?_{{crt}} ? - 0.53V ) for dendrite formation. Pure aluminum (>99 pct) was deposited for all experiments with a current efficiency of 84 to 99 pct and energy consumption of 4.51 to 5.32 kWh/kg Al.

Pradhan, Debabrata; Reddy, Ramana G.

2012-06-01

171

Al:ZnO thin film: An efficient matrix for cholesterol detection  

NASA Astrophysics Data System (ADS)

Al doped ZnO thin film (Al:ZnO) has been realized as a potential matrix for the development of efficient cholesterol biosensor. The correlation between the structural and electrical properties of ZnO thin film with varying Al doping concentration (1% to 5%) and their cyclic voltammetric (CV) response has been studied. 2% Al doped ZnO films were found to give the best CV response and were further utilized for immobilization of cholesterol oxidase (ChOx) to detect cholesterol. Amperometric and photometric studies reveal that the prepared bioelectrode based on 2% Al doped ZnO matrix (ChOx/Al:ZnO/Pt/glass) is highly sensitive (sensitivity = 173 ?AmM-1 cm-2) to the detection of cholesterol in the wide range from 0.6-12.9 mM (25-500 mg/dl). A relatively low value of enzyme's kinetic parameter (Michaelis menten constant, 2.53 mM) indicates enhanced affinity of the immobilized ChOx toward cholesterol. The prepared bioelectrode is found to be exhibiting high shelf life (10 weeks) having negligible interference with the presence of other biomolecules in human serum indicating promising application of Al doped ZnO thin films for cholesterol biosensing.

Batra, Neha; Tomar, Monika; Gupta, Vinay

2012-12-01

172

The Role of Oriented Growth in P Texture Development in Al-Mn-Mg Aluminum Alloy  

NASA Astrophysics Data System (ADS)

The deformation and recrystallization textures in straight-rolled and cross-rolled AA 3105 aluminum alloy were investigated by x-ray diffraction to determine the role of oriented growth in the formation of the P recrystallization texture. A very strong P texture was developed in the straight-rolled sheet after recrystallization annealing. In contrast, the cross-rolled sheet did not develop the P texture on annealing even though the cross-rolling (i.e., rolling along the original transverse direction) texture contained more orientations close to the P orientation than the straight-rolling texture. The formation of the P texture in aluminum alloys requires the presence of the C component, since the P orientation has a 31.1<122> orientation relationship with respect to the C orientation. The recrystallization texture in the cross-rolled sheets was in excellent agreement with the oriented growth theory.

Ma, M.; Wang, W. X.; Zhang, J. X.; Liu, W. C.

2014-09-01

173

Evidence for oxygen bubbles in subsurface Al2O3 layers formed in aluminum by oxygen implantation  

NASA Astrophysics Data System (ADS)

In an earlier paper [R. G. Musket, D. W. Brown, and H. C. Hayden, Nucl. Instrum. Methods B 7/8, 31 (1985)] we showed that high-dose oxygen ion implantation into bulk aluminum results in the formation of subsurface layers of Al2O3. However, for oxygen doses exceeding that required for oxidation of all the locally available aluminum atoms, the implanted layer contained excess oxygen with the ratio O/Al reaching 3.2. At that time we proposed that excess oxygen was trapped physically at point defects and/or microviods (i.e., bubbles). We have now examined these implanted layers using cross-sectional transmission electron microscopy and cross-sectional scanning electron microscopy. Both of these techniques have provided clear evidence for the existence of 20-100 nm oxygen bubbles. Combining these results with those from Rutherford backscattering and conventional transmission electron microscopy has led to a more complete understanding of the formation process.

Musket, R. G.; Brown, D. W.; Pinizzotto, R. F.

1986-08-01

174

Evolution of the optical properties of DyNi5 - x Al x compounds in dependence of aluminum concentration  

NASA Astrophysics Data System (ADS)

The refractive ( n) and absorption ( k) indices of intermetallic DyNi5 - x Al x compounds ( x = 0, 0.5, 1, 1.5, 2) have been measured by ellipsometry at room temperature in the spectral range of 0.22-15 ?m. It is established that the replacement of nickel by aluminum atoms leads to significant changes in the dispersion relations of the optical conductivity ?( E) in the interband absorption range. With an increase in Al content, the spectrum ?( E) (containing three maxima for DyNi5) is gradually transformed into a single-peak structure. The results obtained are discussed on the basis of the data on the electronic spectrum of these compounds. Concentration dependences of the plasma and relaxation frequencies of conduction electrons are determined.

Knyazev, Yu. V.; Kuz'min, Yu. I.; Kuchin, A. G.

2009-06-01

175

Microstructure and Growth Process of Al2O3 Film on Pure Aluminum by Micro-Arc Oxidation  

NASA Astrophysics Data System (ADS)

Ceramic coatings were formed on a pure aluminum substrate in an aqueous solution of phosphate salt, using the pulsating micro-arc oxidation method. XRD indicated that the film composed of pure ?-Al2O3. SEM showed that the surface of the film was micro-porous with 1-5 ?m pores. EDS gave the element distributions of the cross-section. The result indicated that elements from the electrolyte like P could be incorporated into the film during MAO process. The microhardness test showed that the film had an average hardness of 654 HV0.025. The growth process of the Al2O3 ceramic-like film was discussed on the basis of the structure analysis.

Chen, Chuanzhong; Dong, Qing; Wang, Diangang; Ji, Qianmao

176

Correlation of mechanical and ultrasonic properties of Al-SIC metal-matrix composite  

NASA Astrophysics Data System (ADS)

Test specimens fabricated from a silicon-carbide (SiC) reinforced aluminum metal-matrix composite forging were examined ultrasonically and subjected to fracture testing. A-scans of ultrasonic back-scatter were recorded, and the velocities of longitudinal and shear waves and the mean density were measured from which elastic moduli were computed. Tensile and fracture toughness specimens were made, and respectively subjected to mechanical testing followed by careful metallographic and frac-tographic examinations. Correlation of mechanical test results, fractographic and metallographic evaluations, and observed ultrasonic back-scatter and reflection phenomena indicates that an inho-mogeneous distribution of SiC significantly degrades mechanical properties. Furthermore, nonuni-formity of SiC concentrations is shown to be detectable by ultrasonic examination. The ultrasonic method shows promise for differentiating between regions in a composite sample that has varying mechanical properties.

Mott, G.; Aw, P. K. Li

1988-09-01

177

Inter-wall bridging induced peeling of multi-walled carbon nanotubes during tensile failure in aluminum matrix composites.  

PubMed

In situ scanning electron microscopy (SEM) observation of a tensile test was performed to investigate the fracturing behavior of multi-walled carbon nanotubes (MWCNTs) in powder metallurgy Al matrix composites. A multiple peeling phenomenon during MWCNT fracturing was clearly observed. Its formation mechanism and resultant effect on the composite strength were examined. Through transition electron microscopy characterizations, it was observed that defective structures like inter-wall bridges cross-linked adjacent walls of MWCNTs. This structure was helpful to improve the inter-wall bonding conditions, leading to the effective load transfer between walls and resultant peeling behaviors of MWCNTs. These results might provide new understandings of the fracturing mechanisms of carbon nanotube reinforcements for designing high-performance nanocomposites. PMID:25437849

Chen, Biao; Li, Shufeng; Imai, Hisashi; Umeda, Junko; Takahashi, Makoto; Kondoh, Katsuyoshi

2015-02-01

178

RE(AuAl2)nAl2(AuxSi1-x)2: a new homologous series of quaternary intermetallics grown from aluminum flux.  

PubMed

The combination of early rare earth metals (La- to Gd and Yb), gold, and silicon in molten aluminum results in the formation of intermetallic compounds with four related structures, forming a new homologous series: RE[AuAl2]nAl2(AuxSi(1-x))2, with x approximately 0.5 for most of the compound and n = 0, 1, 2, and 3. Because of the highly reducing nature of the Al flux, rare earth oxides instead of metals can also be used in these reactions. These compounds grow as large plate-like crystals and have tetragonal structure types that can be viewed as intergrowths of the BaAl4 structure and antifluorite-type AuAl2 layers. REAuAl2Si materials form with the BaAl4 structure type in space group I4/mmm (cell parameters for the La analogue are a = 4.322(2) A, c = 10.750(4) A, and Z = 2). REAu2Al4Si forms in a new ordered superstructure of the KCu4S3 structure type, with space group P4/nmm and cell parameters of the La analogue of a = 6.0973(6) A, c = 8.206(1) A, and Z = 2. REAu3Al6Si forms in a new I4/mmm symmetry structure type with cell parameters of a = 4.2733(7) A, c = 22.582(5) A, and Z = 2 for RE = Eu. The end member of the series, REAu4Al8Si, forms in space group P4/mmm with cell parameters for the Yb analogue of a = 4.2294(4) A, c = 14.422(2) A, and Z = 1. New intergrowth structures containing two different kinds of AuAl2 layers were also observed. The magnetic behavior of all these compounds is derived from the RE ions. Comparison of the susceptibility data for the europium compounds indicates a switch from 3-D magnetic interactions to 2-D interactions as the size of the AuAl2 layer increases. The Yb ions in YbAu(2.91)Al(6)Si(1.09) and YbAu(3.86)Al(8)Si(1.14) are divalent at high temperatures. PMID:18198865

Latturner, Susan E; Kanatzidis, Mercouri G

2008-03-17

179

Effects of pH, surface finish and thermal treatment on the corrosion of AlFeNi aluminum alloy. Characterization of oxide layers  

NASA Astrophysics Data System (ADS)

The aluminum alloy AlFeNi used as fuel cladding for the Jules Horowitz Reactor (JHR) may undergo corrosion in the reactor environment. In order to qualify the corrosion behavior of the fuel elements of the JHR in accidental conditions, several specimens of AlFeNi have been corroded at 250 C for different durations (9-34 days) in distilled water at various pH (4.9, 5.2 and 5.6) chosen to simulate that currently considered for the JHR. On all specimens, the only crystalline corrosion product formed is boehmite (AlOOH). The corrosion film is composed of three oxide layers which show through thickness chemical composition variations. The iron-nickel precipitates pre-existing in the metal matrix are present in the inner and intermediate oxide layers though oxidized. For long corrosion times, some of the iron and nickel particles are released in the water and some precipitation is observed at the surface of the oxide layer. The effect of surface finish (as received or polished) and thermal treatment (annealed and not annealed) on the oxide growth rate has also been investigated. For durations over 25 days, pH = 5.6 appears to be more favorable than pH = 5.2 and 4.9 in terms of oxide thickness and weight gain limitation. This effect of pH is however reduced on unpolished specimens. The effect of surface finish on the corrosion behavior as measured by optical microscopy appears to be strong, especially for pH = 4.9 where polished samples exhibited an accelerated evolution of the oxide thickness and of the mass gain. This could be due to the combined effect of a strong acid solution (pH = 4.9) and of the local microstructural changes formed at the interface through polishing. The effect of thermal treatment on the behavior of unpolished AlFeNi specimens during corrosion tests in the conditions investigated was found to be small. In this study, microstructural and chemical analyses were performed on the corroded specimens in order to get a better understanding of the corrosion kinetics. The crystallographic nature of the boehmite layers investigated by X-ray diffraction is unaffected by the pH of the solution. Iron precipitates were identified on the oxide surface beyond 34 days of corrosion by Environmental Scanning Electron Microscope (ESEM). Finally, Electron Probe Micro-Analysis (EPMA) was used to determine the chemical composition of the metal matrix and of the different oxide layers and precipitates versus the pH of the solution.

Nabhan, D.; Kapusta, B.; Billaud, P.; Colas, K.; Hamon, D.; Dacheux, N.

2015-02-01

180

Study on bulk aluminum matrix nano-composite fabricated by ultrasonic dispersion of nano-sized SiC particles in molten aluminum alloy  

Microsoft Academic Search

Lightweight metal matrix nano-composites (MMNCs) (metal matrix with nano-sized ceramic particles) can be of significance for automobile, aerospace and numerous other applications. It would be advantageous to produce low-cost as-cast bulk lightweight components of MMNCs. However, it is extremely difficult to disperse nano-sized ceramic particles uniformly in molten metal. This paper presents a new method for an inexpensive fabrication of

Yong Yang; Jie Lan; Xiaochun Li

2004-01-01

181

A theoretical approach for the thermal expansion behavior of the particulate reinforced aluminum matrix composite Part I A thermal expansion model for composites with mono-dispersed spherical particles  

Microsoft Academic Search

Microstructural observation revealed that the increase in the volume fraction of SiC particles lowers the coefficient of thermal expansion (CTE) of the composite, and the CTE of the metal matrix composites is proportional to the size of the Si phase. To analyze the thermal expansion behavior of aluminum matrix composites, a new model for the CTE of the mono-dispersed binary

Chong-Sung Park; Myung-Ho Kim; Chongmu Lee

2001-01-01

182

Statistical analysis of process parameters in drilling of AL\\/SIC P metal matrix composite  

Microsoft Academic Search

This paper presents a statistical analysis of process parameters for surface roughness in drilling of Al\\/SiCp metal matrix\\u000a composite. The experimental studies were conducted under varying spindle speed, feed rate, drill type, point angle of drill,\\u000a and heat treatment. The settings of drilling parameters were determined by using Taguchi experimental design method. The level\\u000a of importance of the drilling parameters

Gl Tosun

2011-01-01

183

Microstructure characterization of Al matrix composite reinforced with Ti-6Al-4V meshes after compression by scanning electron microscope and transmission electron microscope.  

PubMed

Compressive properties of Al matrix composite reinforced with Ti-6Al-4V meshes (TC4(m)/5A06 Al composite) under the strain rates of 10(-3)S(-1) and 1S(-1) at different temperature were measured and microstructure of composites after compression was characterized by scanning electron microscope (SEM) and transmission electron microscope (TEM). Compressive strength decreased with the test temperature increased and the strain-rate sensitivity (R) of composite increased with the increasing temperature. SEM observations showed that grains of Al matrix were elongated severely along 45 direction (angle between axis direction and fracture surface) and TC4 fibres were sheared into several parts in composite compressed under the strain rate of 10(-3)S(-1) at 25C and 250C. Besides, amounts of cracks were produced at the interfacial layer between TC4 fibre and Al matrix and in (Fe, Mn)Al(6) phases. With the compressive temperature increasing to 400C, there was no damage at the interfacial layer between TC4 fibre and Al matrix and in (Fe, Mn)Al(6) phases, while equiaxed recrystal grains with sizes about 10 ?m at the original grain boundaries of Al matrix were observed. However, interface separation of TC4 fibres and Al matrix occurred in composite compressed under the strain rate of 1S(-1) at 250C and 400C. With the compressive temperature increasing from 25C to 100C under the strain rate of 10(-3) S(-1), TEM microstructure in Al matrix exhibited high density dislocations and slipping bands (25C), polygonized dislocations and dynamic recovery (100C), equiaxed recrystals with sizes below 500 ?m (250C) and growth of equiaxed recrystals (400C), respectively. PMID:21963048

Guo, Q; Sun, D L; Han, X L; Cheng, S R; Chen, G Q; Jiang, L T; Wu, G H

2012-02-01

184

Cryomilled Aluminum Stabilized by Diamondoid Nanoparticles  

NASA Astrophysics Data System (ADS)

Nanocrystalline aluminum powder with an average grain size of 22nm was prepared via cryomilling. Hot Isostatic Pressing was used to consolidate the powder followed by hot extrusion to homogenize the consolidated material. The high homologous temperature processes tend to increase the average grain diameter beyond the nanoscle classification, which is less than 100 nm. Diamantane was added during cryomilling to enhance the thermal stability in nanocrystalline aluminum. The thermal stability test data show that aluminum reinforced with 1 wt% diamantane exhibit two to three fold better thermal stability than non-reinforced aluminum when annealed at 773K (0.84 Tm) for ten hours. A similar trend is shown for the samples consolidated at 693K. This finding is explained through Burke's model for grain growth in materials containing secondary particles to inhibit grain boundary motion. The mechanical properties of cryomilled aluminum stabilized by 0.5 wt% and 1 wt% diamantane particles are compared with cryomilled commercial purity (CP) aluminum with no diamantane after high strain rate deformation (trap extrusion). The grain size of cryomilled CP aluminum is 0.6 to 1.2 times larger than the samples containing diamantane. In contrast to Hall-petch predictions, cryomilled aluminum with diamantane has relatively lower flow stress while demonstrating a 2.7-3.7 time higher ductility compared to cryomilled CP aluminum. Possible reasons for this behavior are suggested in mechnical property section. A combination of higher temperature and pressure resulted in formation of Aluminum tris (Al(C9H6NO)3) precipitates from diamantane in the cryomilled aluminum matrix. The precipitates were formed during trap extrusion process but only seen in samples containing 1 wt% diamantane and HIP'ed at 521C. Therefore, the HIP'ng temperature plays an important role in formation of these precipitates.

Maung, Khinlay

185

Design of high frequency piezoelectric resonators utilizing laterally propagating fast modes in thin aluminum nitride (AlN) films.  

PubMed

Highly c-oriented aluminum nitride (AlN) thin piezoelectric films have been grown by pulsed direct-current (DC) magnetron reactive sputter deposition. The films were deposited at room temperature and had a typical full width half maximum (FWHM) value of the (0 0 2) rocking curve of around 2 degrees. Resonant devices in thin film plates having surface acoustic wave (SAW) based designs were fabricated by means of low resolution photolithography. The devices were designed to operate with the fast Rayleigh and Lamb modes respectively. Both types of devices exhibited propagation velocities in excess of 10,000 m/s and sufficient electromechanical couplings. The device measurements illustrate the big potential of these modes for the development of low cost IC compatible electroacoustic devices in the lower GHz range. The basic properties of the modes studied are discussed in a comparative manner. Potential commercial applications are also outlined. PMID:17097706

Yantchev, V; Enlund, J; Biurstrm, J; Katardjiev, I

2006-12-01

186

Friction and wear studies of die cast aluminum alloy-aluminum oxide-reinforced composites  

Microsoft Academic Search

Purpose Metal matrix composites (MMCs) are engineered materials formed by the combination of metal matrix and reinforcement materials. They have a stiff and hard reinforcing phase in metallic matrix. The matrix includes metals such as aluminum, magnesium, copper and their alloys. The purpose of this paper is to describe the development of an aluminum alloy-aluminum oxide composite using a

M. Kathiresan; T. Sornakumar

2010-01-01

187

Analysis of electrochemical noise from metastable pitting in aluminum, aged Al-2%Cu, and AA 2024-T3  

SciTech Connect

The authors compare methods of analyzing electrochemical current (ECN) and potential (EPN) noise data associated with metastable pitting and the transition from metastable to stable pitting. Various analysis methods were applied to electrochemical noise data associated with metastable pit events on aluminum, aged Al-2%Cu, and AA 2024-T3 ST. Two experimental approaches were used. High-purity Al, roughly simulating copper-depleted grain boundary zones in aged Al-Cu alloys, was potentiostatically polarized so that current spikes associated with individual pitting events could be analyzed. Second, the coupling current between nominally identical galvanically coupled Al, aged Al-2%Cu, and AA 2024-T3 ST electrodes was recorded in conjunction with couple potential using a saturated calomel reference electrode. Pit stabilization occurred when individual pits exceeded a threshold of I{sub pit}/r{sub pit} > 10{sup {minus}2} A/cm at all times during pit growth as established from potentiostatic measurements. The magnitude of this ratio is linked directly to the concentration of the aggressive solution within pits. Two related statistical pit stabilization factors (I{sub rms}/r{sub pit total} from ECN data and the mean of (I{sub peak}-I{sub ox})/r{sub pit} values from each pit current spike) were obtained from galvanic ECN data containing a large number of pit current spikes. These parameters provided a better indication of the transition to stable pitting than the pitting index or noise resistance but also had shortcomings. Spectral analysis using current and potential spectral power density (SPD) data provided qualitative information on pit susceptibility. However, the transition to stable pitting could not be accurately defined because of a lack of information on pit sizes in spectral data.

Pride, S.T.; Scully, J.R.; Hudson, J.L. [Univ. of Virginia, Charlottesville, VA (United States)

1996-12-31

188

Development of Crystallographic Texture and Grain Refinement in the Aluminum Layer of CU-AL-CU Tri-Layer Composite Deformed by Equal Channel Angular Extrusion  

NASA Astrophysics Data System (ADS)

The present research is concerned with the aluminum layer of a loosely packed tri-layer copper-aluminum-copper composite deformed by ECAE process. Electron back scattered diffraction (EBSD), transmission electron microscope, and X-ray technique were employed to investigate the detailed changes occurring in the microtexture, microstructure (cell size and misorientation), and dislocation density evolution during consecutive passes of ECAE process performed on the composite based on route Bc. According to tensile test results, the yield stress of the aluminum layer was increased significantly after application of ECAE throughout the four repeated passes and then slightly decreased. An ultrafine grain size within the range of 500-600 nm was obtained in the Al layer by increasing the thickness of copper layers. It was observed that the reduction of grain size in the aluminum layer is nearly 57% more than that of an ECAE-ed single layer aluminum billet. Also, the grain refinement of the aluminum layer is accelerated throughout 8 passes. This observation was attributed to the higher rate of dislocation interaction, cell formation and texture development during the ECAE of the composite compared to those of the single billet.

Tolaminejad, B.; Taheri, A. Karimi; Shahmiri, M.; Arabi, H.

189

FORMING Al-Al2O3 NANOCOMPOSITE SURFACES USING FRICTION STIR PROCESSING  

SciTech Connect

This study presents a solid state surface engineering process to form a nanocomposite layer on aluminum surface. Friction stir processing (FSP) was used to stir and mix nano-sized Al2O3 particles into a commercially pure aluminum surface to form an Al-Al2O3 nanocomposite layer of up to several millimeters thick. Compared with a non-processed aluminum surface, a nanocomposite surface with 15 vol% nano-particles has demonstrated increased hardness (by 3X) and yield strength (by 10X), and reduced friction coefficient (by 55%) and wear rate (by 100X). Transmission electron microscopy (TEM) has revealed high matrix dislocation density in the nanocomposite surface that is believed to be largely responsible to such significant property improvements. Neutron diffraction measurements suggested tensile residual stress in the aluminum matrix. The stress was mainly induced by thermal-expansion-mismatch between aluminum and alumina.

Qu, Jun [ORNL; Xu, Hanbing [ORNL; Feng, Zhili [ORNL; An, Ke [ORNL; Battiste, Rick [ORNL; An, Linan [University of Central Florida; Heinrich, Helge [University of Central Florida

2009-01-01

190

Investigations on NiAl composites fabricated by matrix coated single crystalline Al 2 O 3 -fibers with and without hBN interlayer  

Microsoft Academic Search

The intermetallic compound NiAl has excellent potential for high temperature structural applications but suffers from low\\u000a temperature brittleness and insufficient high temperature strength. One way to remove these deficiencies is the reinforcement\\u000a by high strength ceramic fibers. Such intermetallic matrix composites can be conveniently fabricated by the hot pressing of\\u000a matrix coated fibers. Al2O3 single crystal fibers show excellent chemical

Weiping Hu; Hao Chen; Yunlong Zhong; Jia Song; Gnter Gottstein

2008-01-01

191

PII S0016-7037(98)00136-7 The kinetics of mixed Ni-Al hydroxide formation on clay and aluminum oxide minerals  

E-print Network

PII S0016-7037(98)00136-7 The kinetics of mixed Ni-Al hydroxide formation on clay and aluminum. LAMBLE,3 and DONALD L. SPARKS 1 1 Department of Plant and Soil Sciences, University of Delaware, Newark investigations were combined with X-ray Absorption Fine Structure (XAFS) measurements to determine Ni sorption

Sparks, Donald L.

192

A nanoporous AlN layer patterned by anodic aluminum oxide and its application as a buffer layer in a GaN-based light-emitting diode.  

PubMed

This work investigates a nanoporous aluminum nitride (AlN) layer prepared using an anodic aluminum oxide (AAO) process and its application as a buffer layer for a GaN-based light-emitting diode (LED) fabricated on sapphire substrate. Following this AAO process, the average pore spacing and pore diameter of the nanoporous AlN layer were in the ranges 180-200 nm and 100-150 nm, respectively. The light output power of the GaN-based LED with a nanoporous AlN layer was about 53% higher than that of a GaN-based LED without a nanoporous AlN layer at an injection current of 20 mA. At an injection current of 80 mA, the light output power was increased by about 34%. PMID:19417447

Chen, Lung-Chien; Wang, Chih-Kai; Huang, Jenn-Bin; Hong, Lu-Sheng

2009-02-25

193

Investigation of aluminum induced degradation in sputtered Al:ZnO for CIGS solar cells applications  

Microsoft Academic Search

The long term performance of Cu(In, Ga)Se2 (CIGS) solar cells were strongly affected by their ability in withstanding surrounding weather change, including temperature, humidity, and light, etc. In our experiment, we focused on the stability study of window layer materials of undoped ZnO (IZO) and Al:ZnO (AZO) using damp heat and dry heat treatment. We found that the Al dopant

Jie Pan; Lei Kerr; Xiaonan Li; Heather J. Gulley-Stahl; Andre J. Sommer

2009-01-01

194

Influence of the starting aluminum salt on the surface and acid properties of AlPO catalysts precipitated with ammonium hydroxide  

Microsoft Academic Search

In this paper, the influence of the starting aluminum salt (chloride, nitrate, or sulfate) and the pretreatment temperature (773-1273 K) on textural properties, crystal structure, and surface acidity of AlPO (Al\\/P = 1) catalysts was studied in order to learn how preparation conditions affect catalyst activity in organocationic reactions. The catalysts were characterized using nitrogen adsorption, X-ray diffraction, infrared spectroscopy,

J. M. Campelo; A. Garcia; D. Luna; J. M. Marinas

1988-01-01

195

Clarification of isomeric structures and the effect of intermolecular interactions in blue-emitting aluminum complex Alq3 using first-principles 27Al NMR calculations  

NASA Astrophysics Data System (ADS)

We have performed structure analysis of the blue-emitting aluminum complex Alq3 using 27Al NMR and gauge-including projector-augmented wave calculations. The results clearly show that 27Al NMR spectra are insensitive to intermolecular interactions, thus providing a means of carrying out precise intramolecular structure determination. The key determinant of the blue-shifted emission of Alq3 is the facial isomerization.

Suzuki, Furitsu; Nishiyama, Yusuke; Kaji, Hironori

2014-06-01

196

High-k Al2O3 gate dielectrics prepared by oxidation of aluminum film in nitric acid followed by high-temperature annealing  

Microsoft Academic Search

A simple, cost-effective, and room temperature process was proposed to prepare high-k gate dielectrics. An aluminum oxide (Al2O3) gate dielectric was prepared by oxidation of ultrathin Al film in nitric acid (HNO3) at room temperature then followed by high-temperature annealing in O2 or N2. The substrate injection current behavior and interface trap-induced capacitance were introduced to investigate the interfacial property

Chih-Sheng Kuo; Jui-Feng Hsu; Szu-Wei Huang; Lurng-Shehng Lee; Ming-Jinn Tsai; Jenn-Gwo Hwu

2004-01-01

197

Hardness and tensile strength of zircon particles and TiB 2 reinforced Al-A356.1 alloy matrix composites: comparative study  

NASA Astrophysics Data System (ADS)

Aluminum matrix composites are important engineering materials in automotive, aerospace, thermal, wear, and other applications because of excellent low weight, high specific strength, and better physical and mechanical properties compared to pure aluminum. In this paper, zircon and TiB II ceramic particles with different amounts were incorporated into Al-A356.1 alloy by stir-casting route. The ceramic particles size and adding temperature were 1 micron and 750C respectively. Microstructure of samples has been investigated by scanning electron microscopy (SEM); hence the dispersion of reinforcement was noted. Situation of compounds of composites was examined by XRD. Mechanical tests such as hardness measurement, tensile and physical (density) tests were used. Results showed that the mechanical properties and microstructure behavior of composites have improved compared to monolithic alloy. Microstructures of the composites in as-cast conditions show uniform distribution particles and reveal better bonding in the case of zircon reinforced composite compare to TiB II, but increasing the amount of reinforcement shows better conditions in the case of TiB II reinforced composite. It is observed that TiB II reinforced composites have a better wetting condition compare to zircon reinforced composites.

Shirvani Moghaddam, K.; Abdizadeh, H.; Baharvandi, H. R.; Ehsani, N.; Abdi, F.

2007-07-01

198

Density of Low-Temperature KF-AlF3 Aluminum Baths with Al2O3 and AlPO4 Additives  

NASA Astrophysics Data System (ADS)

The density of the KF-AlF3 melts of various KF and AlF3 ratio with Al2O3 and AlPO4 addition has been measured using the Archimedean method. On the basis of the obtained density data the molar volumes of the melts were calculated. These molar volumes decrease with concentration of Al2O3 or AlPO4. In the system containing AlPO4, the relation between cryolite ratios (CRs) vs slopes of molar volume trend lines was identified with excellent correlation factor of R 2 = 0.9844, while in the system containing Al2O3 a discontinuity at CR = 2.5 can be observed.

Vaskov, Zuzana; Kontrk, Martin; Mlynrikov, Jarmila; Bo?a, Miroslav

2015-02-01

199

Nonradiative recombination in GaN quantum dots formed in the AlN matrix  

SciTech Connect

The mechanisms of temperature quenching of steady-state photoluminescence are studied for structures with hexagonal GaN quantum dots embedded in the AlN matrix. The structures are grown by molecular beam epitaxy. The study is conducted for structures with differently sized quantum dots, for which the peak of the photoluminescence band is in the range from 2.5 to 4.0 eV. It is found that the activation energy of thermal quenching of photoluminescence varies from 27 to 110 meV, as the quantum-dot height is decreased from 5 to 2 nm. A model is suggested to interpret the results. According to the model, the photo-luminescence signal is quenched because of the transfer of charge carriers from energy levels in the quantum dots to defect levels in the matrix.

Aleksandrov, I. A., E-mail: Aleks.Ivan@gmail.com; Zhuravlev, K. S.; Mansurov, V. G. [Russian Academy of Sciences, Institute of Semiconductor Physics, Siberian Division (Russian Federation)

2009-06-15

200

Microstructural Development in Irradiated U-7Mo/6061 Al Alloy Matrix Dispersion Fuel  

SciTech Connect

A U-7Mo alloy/6061 Al alloy matrix dispersion fuel plate was irradiated in the Advanced Test Reactor and then destructively examined using optical metallography and scanning electron microscopy to characterize the developed microstructure. Results were compared to the microstructures of as-fabricated dispersion fuel to identify changes that occurred during irradiation. The interaction layers that formed on the surface of the fuel U-7Mo particles during fuel fabrication exhibited stable irradiation performance as a result of the ~0.88 wt% Si present in the fuel meat matrix. During irradiation, the interaction layers changed very little in thickness and composition. The overall irradiation performance of the fuel plate to moderate power and burnup was considered excellent.

Dennis D. Keiser, Jr.; Adam B. Robinson; Jan-Fong Jue; Pavel G. Medvedev; Daniel M. Wachs; M. Ross Finlay

2009-09-01

201

Plasticity-improved Zr-Cu-Al bulk metallic glass matrix composites containing martensite phase  

SciTech Connect

Zr{sub 48.5}Cu{sub 46.5}Al{sub 5} bulk metallic glass matrix composites with diameters of 3 and 4 mm were produced through water-cooled copper mold casting. Micrometer-sized bcc based B2 structured CuZr phase containing martensite plate, together with some densely distributed nanocrystalline Zr{sub 2}Cu and plate-like Cu{sub 10}Zr{sub 7} compound, was found embedded in a glassy matrix. The microstructure formation strongly depends on the composition and cooling rate. Room temperature compression tests reveal significant strain hardening and plastic strains of 7.7% and 6.4% before failure are obtained for the 3-mm- and 4-mm-diam samples, respectively. The formation of the martensite phase is proposed to contribute to the strain hardening and plastic deformation of the materials.

Sun, Y.F.; Wei, B.C.; Wang, Y.R.; Li, W.H.; Cheung, T.L.; Shek, C.H. [Research Center for Materials, Department of Materials Science and Engineering, Zhengzhou University, Zhengzhou 450002 (China); National Microgravity Lab, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100080 (China); Department of Physics and Materials Science, City University of Hong Kong, Hong Kong (China)

2005-08-01

202

Effect of alloying elements in the brazing sheet on the bonding strength between Al{sub 2}O{sub 3} and aluminum  

SciTech Connect

Ceramics have several outstanding mechanical properties especially at high temperatures, but a difficulty in machining has been hindering the cost-effective use. Hence, bonding between ceramics and metals has become an important technology. Among many bonding techniques such as brazing, diffusion bonding, frictional bonding and so forth, brazing is one of the most promising methods for practical applications. There are several bonding parameters such as temperature, time, pressure and atmosphere. In this work, Al{sub 2}O{sub 3}/aluminum bonding using an aluminum alloy as a filler sheet is dealt with, and the effects of some parameters on the bonding strength are mainly discussed.

Kobashi, M.; Ninomiya, T.; Kanetake, N.; Choh, T. [Nagoya Univ. (Japan)] [Nagoya Univ. (Japan)

1996-02-01

203

Quasicrystals in an aluminium alloy matrix and the transformation to ??AlMnSi via intermediate stages  

Microsoft Academic Search

During heat treatment of an industrially produced Al high-Mn alloy, small particles of the quasicrystalline icosahedral AlMnSi phase were precipitated, with a definite orientation relation to the Al matrix. Upon further annealing, the particles coarsen and transform, through intermediate stages into the cubic ?-AlMnSi phase. The intermediate stage is characterized by faults on {110}? planes, with fault vectors of type

V. Hansen; J. Gjnnes

1996-01-01

204

Prediction of Thermal Conductivity of Aluminum Nanocluster-Filled Mesoporous Silica (Al/MCM-41)  

NASA Astrophysics Data System (ADS)

MCM-41 consists of a hexagonal array of long, unconnected cylindrical pores with diameters that can be tailored within the range 1.6 nm to 10 nm. As a porous silica nanomaterial, MCM-41 is a promising porous substrate for mesoporous composites with extremely high or low thermal conductivity. In this article, the structural unit of MCM-41 was established first and an equilibrium molecular dynamics simulation was performed to determine the shell thermal conductivity of MCM-41. Then, based on one-dimensional (1D) heat transfer analysis, a mathematical expression for the effective thermal conductivity (ETC) of Al nanocluster-filled mesoporous MCM-41 (Al/MCM-41) was obtained. The effects of porosity and the filling ratio of nanoclusters in the mesochannels were further investigated. As the porosity is greater than 75 %, the ETC of only-air-filling mesoporous MCM-41 in all directions tends to approach the thermal conductivity of air. It seems that Al nanoclusters have negligible effects on the ETC of the composite, except that mesochannels are almost completely filled with Al nanowires.

Huang, Congliang; Feng, Yanhui; Zhang, Xinxin; Li, Jing; Cui, Liu; Wang, Ge; Yang, Mu

2013-12-01

205

Study on Mold Slag with High Al2O3 Content for High Aluminum Steel  

NASA Astrophysics Data System (ADS)

The slag-steel equilibrium reaction between the newly developed mold slag ND-MSL and 20Mn23AlV steel has been studied at high temperatures in the laboratory. The crystal morphology, microanalysis, and phase analysis of the original and final ND-MSL slags were studied by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD). Results show that, in the final ND-MSL slag, the constitution of SiO2 decreased by 0.7 wt pct and Al2O3 increased by 6.46 wt pct, while the melting temperature, viscosity, and crystallization rate increased by 62 K, 0.66 dPa s, and 15 pct, respectively. NaAlSi3O8 and CaAl2Si2O8 were found to be precipitated in the final ND-MSL slag. Both the original and final ND-MSL slags have a small amount of LiF crystal and good glass form. The ND-MSL slag has little change in the composition and properties compared with the two currently used mold slags.

Wang, Qiang; Sun, Min; Qiu, Shengtao; Tian, Zhiling; Zhu, Guoling; Wang, Longmei; Zhao, Pei

2014-04-01

206

In situ SEM thermal fatigue of Al/graphite metal matrix composites  

NASA Technical Reports Server (NTRS)

Several thermal fatigue-induced failure mechanisms are deduced for unidirectional graphite-reinforced 6061 Al-alloy MMCs subjected to in situ thermal cycling. These thermal cycling conditions are representative of MMC service cycles in aerospace environments, where thermal fatigue is primarily associated with changes in the stress states near the interfaces due to coefficient of thermal expansion mismatch between fiber and matrix. This in situ SEM thermal-cycling study clarified such factors affecting MMCs' thermal fatigue as local fiber content and distribution, void volume, fiber stiffness, thermal excursion magnitude, and number of thermal cycles. MMC microfailure modes in thermal fatigue have been deduced.

Zong, G. S.; Rabenberg, L.; Marcus, H. L.

1990-01-01

207

Synthesis and structural characterization of a new aluminum oxycarbonitride, Al{sub 5}(O, C, N){sub 4}  

SciTech Connect

A new aluminum oxycarbonitride, Al{sub 5}(O{sub x}C{sub y}N{sub 4-x-y}) (x{approx}1.4 and y{approx}2.1), has been synthesized and characterized by X-ray powder diffraction, transmission electron microscopy and electron energy loss spectroscopy (EELS). The title compound was found to be hexagonal with space group P6{sub 3}/mmc, Z=2, and unit-cell dimensions a=0.328455(6) nm, c=2.15998(3) nm and V=0.201805(6) nm{sup 3}. The atom ratios O:C:N were determined by EELS. The final structural model, which is isomorphous with that of (Al{sub 4.4}Si{sub 0.6})(O{sub 1.0}C{sub 3.0}), showed the positional disordering of one of the three types of Al sites. The maximum-entropy method-based pattern fitting (MPF) method was used to confirm the validity of the split-atom model, in which conventional structure bias caused by assuming intensity partitioning was minimized. The reliability indices calculated from the MPF were R{sub wp}=6.94% (S=1.22), R{sub p}=5.34%, R{sub B}=1.35% and R{sub F}=0.76%. The crystal was an inversion twin. Each twin-related individual was isostructural with Al{sub 5}C{sub 3}N (space group P6{sub 3}mc, Z=2). - Graphical abstract: A new oxycarbonitride discovered in the Al-O-C-N system, Al{sub 5}(O{sub 1.4}C{sub 2.1}N{sub 0.5}). The crystal is an inversion twin, and hence the structure is represented by a split-atom model. The three-dimensional electron density distributions are determined by the maximum-entropy methods-based pattern fitting, being consistent with the disordered structural model. Display Omitted

Inuzuka, Haruya; Kaga, Motoaki; Urushihara, Daisuke [Department of Environmental and Materials Engineering, Nagoya Institute of Technology, Nagoya 466-8555 (Japan); Nakano, Hiromi [Cooperative Research Facility Center, Toyohashi University of Technology, Toyohashi 441-8580 (Japan); Asaka, Toru [Department of Environmental and Materials Engineering, Nagoya Institute of Technology, Nagoya 466-8555 (Japan); Fukuda, Koichiro, E-mail: fukuda.koichiro@nitech.ac.j [Department of Environmental and Materials Engineering, Nagoya Institute of Technology, Nagoya 466-8555 (Japan)

2010-11-15

208

Magnetic properties of nickel nanoparticles embedded in amorphous Al2O3 matrix  

NASA Astrophysics Data System (ADS)

Multilayer thin films consisting of 10 bilayers of (Al2O3+Ni)/Al2O3 were deposited by magnetron sputtering onto Si(100) substrate. Nickel nanoparticles are formed inside amorphous alumina matrix by self-assembly growth process. It was determined by GISAXS measurements that nickel particles are spheroidal with diameter < 3 nm and that they form paracrystal-like body-centered tetragonal lattice. Magnetic properties of the prepared thin films were studied. Due to the nanometer size of nickel particles, their magnetic structure is single domain and they show superparamagnetic behaviour. Anisotropy of magnetic properties was observed when magnetic field is applied parallel or perpendicular to the thin film surface and it was attributed to dipole-dipole interactions between particles. This was confirmed using simulations of the M(H) curve of the 2D superlattice of the identical superparamagnetic particles, which was performed using Monte Carlo method and Metropolis algorithm.

Novosel, Nikolina; Reissner, Michael; Zadro, Kreo; Paji?, Damir; Jer?inovi?, Marko; Buljan, Maja; Radi?, Nikola

2014-12-01

209

Effects of Cu\\/Al intermetallic compound (IMC) on copper wire and aluminum pad bondability  

Microsoft Academic Search

Copper wire bonding is an alternative interconnection technology that serves as a viable, and cost saving alternative to gold wire bonding. Its excellent mechanical and electrical characteristics attract the high-speed, power management devices and fine-pitch applications. Copper wire bonding can be a potentially alternative interconnection technology along with flip chip interconnection. However, the growth of Cu\\/Al intermetallic compound (IMC) at

Hyoung-Joon Kim; Joo Yeon Lee; Kyung-Wook Paik; Kwang-Won Koh; J. Won; Sihyun Choe; Jin Lee; Jung-Tak Moon; Yong-Jin Park

2003-01-01

210

Temperature distribution study during the friction stir welding process of Al2024-T3 aluminum alloy  

NASA Astrophysics Data System (ADS)

Heat flux characteristics are critical to good quality welding obtained in the important engineering alloy Al2024-T3 by the friction stir welding (FSW) process. In the present study, thermocouples in three different configurations were affixed on the welding samples to measure the temperatures: in the first configuration, four thermocouples were placed at equivalent positions along one side of the welding direction; the second configuration involved two equivalent thermocouple locations on either side of the welding path; while the third configuration had all the thermocouples on one side of the layout but with unequal gaps from the welding line. A three-dimensional, non-linear ANSYS computational model, based on an approach applied to Al2024-T3 for the first time, was used to simulate the welding temperature profiles obtained experimentally. The experimental thermal profiles on the whole were found to be in agreement with those calculated by the ANSYS model. The broad agreement between the two kinds of profiles validates the basis for derivation of the simulation model and provides an approach for the FSW simulation in Al2024-T3 and is potentially more useful than models derived previously.

Yau, Y. H.; Hussain, A.; Lalwani, R. K.; Chan, H. K.; Hakimi, N.

2013-08-01

211

Wear mechanisms in hybrid composites of graphite-20 pct SiC in A356 aluminum alloy (Al-7 pct Si-0. 3 pct Mg)  

SciTech Connect

The wear behavior of A356 aluminum alloy (Al-7 pct Si-0.3 pct Mg) matrix composites reinforced with 20 vol pct SiC particles and 3 or 10 vol pct graphite was investigated. These hybrid composites represent the merging of two philosophies in tribological material design: soft-particle lubrication by graphite and hard-particle reinforcement by carbide particles. The wear tests were performed using a block-on-ring (SAE 52100 steel) wear machine under dry sliding conditions within a load range of 1 to 441 N. The microstructural and compositional changes that took place during wear were characterized using scanning electron microscopy (SEM), Auger electron spectroscopy (AES), energy-dispersive X-ray spectroscopy (EDXA), and X0ray diffractometry (XRD). The wear resistance of 3 pct graphite-20 pct SiC-A356 hybrid composite was comparable to 20 pct SiC-A356 without graphite at low and medium loads. At loads below 20 N, both hybrid and 20 pct SiC-A356 composites without graphite demonstrated wear rates up to 10 times lower than the unreinforced A356 alloy due to the load-carrying capacity of SiC particles. The wear resistance of 3 pct graphite 20 pct SiC-A356 was 1 to 2 times higher than 10 pct graphite-containing hybrid composites at high loads. However, graphite addition reduced the counterface wear. The unreinforced A356 and 20 pct SiC-A356 showed a transition from mild to severe wear at 95 N and 225 N, respectively. Hybrid composites with 3 pct and 10 pct graphite did not show such a transition over the entire load range, indicating that graphite improved the seizure resistance of the composites.

Ames, W.; Alpas, A.T. (Univ. of Windsor, Ontario (Canada). Dept. of Mechanical Engineering)

1995-01-01

212

Aluminum composite driveshafts  

SciTech Connect

This article examines the development and performance of a metal matrix composite lightweight driveshaft tube of 6061 aluminum alloy with an even dispersion of 20[percent] aluminum oxide particles. The topics of the article include evolution of the lightweight design, raw material production, tubing fabrication, driveshaft performance, and modulus testing.

Not Available

1994-02-01

213

Microstructure and mechanical properties of twin-wire arc sprayed Ni-Al composite coatings on 6061-T6 aluminum alloy sheet  

NASA Astrophysics Data System (ADS)

We have systematically studied the microstructure and mechanical properties of Ni-5wt%Al and Ni-20wt%Al composite coatings fabricated on 6061-T6 aluminum alloy sheet by twin-wire arc spraying under different experimental conditions. The abrasive wear behavior and interface diffusion behavior of the composite coatings were evaluated by dry/wet rubber wheel abrasive wear tests and heat treatment, respectively. Experimental results indicate that the composite coatings exhibit features of adhesive wear. Besides, the Vickers microhardness of NiAl and Ni3Al intermetallic compounds is relatively larger than that of the substrate, which is beneficial for enhancing the wear resistance. With the increase of annealing temperature and time, the interface diffusion area between the Ni-Al coating and the substrate gradually expands with the formation of NiAl3 and Ni2Al3 phases, and is controlled by diffusion of aluminum atoms. The grain growth exponent n of diffusion kinetics of the Ni-Al coating, calculated via a high-temperature diffusion model at 400, 480, and 550C, is between 0.28 and 0.38. This satisfies the cubic law, which is consistent with the general theoretical relationship of high-temperature diffusion.

Wang, Ji-xiao; Liu, Jing-shun; Zhang, Lun-yong; Sun, Jian-fei; Wang, Zhi-ping

2014-05-01

214

Aluminum reference electrode  

DOEpatents

A stable reference electrode is described for use in monitoring and controlling the process of electrolytic reduction of a metal. In the case of Hall cell reduction of aluminum, the reference electrode comprises a pool of molten aluminum and a solution of molten cryolite, Na[sub 3]AlF[sub 6], wherein the electrical connection to the molten aluminum does not contact the highly corrosive molten salt solution. This is accomplished by altering the density of either the aluminum (decreasing the density) or the electrolyte (increasing the density) so that the aluminum floats on top of the molten salt solution. 1 fig.

Sadoway, D.R.

1988-08-16

215

The effect of sulfate on aluminum concentrations in natural waters: some stability relations in the system Al2O3-SO3-H2O at 298 K  

USGS Publications Warehouse

While gibbsite and kaolinite solubilities usually regulate aluminum concentrations in natural waters, the presence of sulfate can dramatically alter these solubilities under acidic conditions, where other, less soluble minerals can control the aqueous geochemistry of aluminum. The likely candidates include alunogen, Al2(SO4)3 ?? 17H2O, alunite, KAl3(SO4)2(OH)6, jurbanite, Al(SO4)(OH) ?? 5H2O, and basaluminite, Al4(SO4)(OH)10 ?? 5H2O. An examination of literature values shows that the log Ksp = -85.4 for alunite and log Ksp = -117.7 for basaluminite. In this report the log Ksp = -7.0 is estimated for alunogen and log Ksp = -17.8 is estimated for jurbanite. The solubility and stability relations among these four minerals and gibbsite are plotted as a function of pH and sulfate activity at 298 K. Alunogen is stable only at pH values too low for any natural waters (<0) and probably only forms as efflorescences from capillary films. Jurbanite is stable from pH < 0 up to the range of 3-5 depending on sulfate activity. Alunite is stable at higher pH values than jurbanite, up to 4-7 depending on sulfate activity. Above these pH limits gibbsite is the most stable phase. Basaluminite, although kinetically favored to precipitate, is metastable for all values of pH and sulfate activity. These equilibrium calculations predict that both sulfate and aluminum can be immobilized in acid waters by the precipitation of aluminum hydroxysulfate minerals. Considerable evidence supports the conclusion that the formation of insoluble aluminum hydroxy-sulfate minerals may be the cause of sulfate retention in soils and sediments, as suggested by Adams and Rawajfih (1977), instead of adsorption. ?? 1982.

Nordstrom, D.K.

1982-01-01

216

RE2MAl6Si4 (RE = Gd, Tb, Dy; M = Au, Pt): layered quaternary intermetallics featuring CaAl2Si2-type and YNiAl4Ge2-type slabs grown from aluminum flux.  

PubMed

Six new intermetallic aluminum silicides--Gd(2)PtAl(6)Si(4), Gd(2)AuAl(6)Si(4), Tb(2)PtAl(6)Si(4), Tb(2)AuAl(6)Si(4), Dy(2)PtAl(6)Si(4), and Dy(2)AuAl(6)Si(4)--have been obtained from reactions carried out in aluminum flux. The structure of these compounds was determined by single-crystal X-ray diffraction. They form in space group Rthremacr;m with cell constants of a = 4.1623(3) A and c = 51.048(5) A for the Gd(2)PtAl(6)Si(4) compound. The crystal structure is comprised of hexagonal nets of rare earth atoms alternating with two kinds of layers that have been observed in other multinary aluminide intermetallic compounds (CaAl(2)Si(2) and YNiAl(4)Ge(2)). All six RE(2)MAl(6)Si(4) compounds show antiferromagnetic transitions at low temperatures (T(N) < 20 K); magnetization studies of the Dy compounds show metamagnetic behavior with reorientation of spins at 6000 G. Band structure calculations indicate that the AlSi puckered hexagonal sheets in this structure are electronically distinct from the other surrounding structural motifs. PMID:14632514

Latturner, Susan E; Bilc, Daniel; Mahanti, S D; Kanatzidis, Mercouri G

2003-12-01

217

Sporadic ALS has compartment-specific aberrant exon splicing and altered cellmatrix adhesion biology  

PubMed Central

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by progressive weakness from loss of motor neurons. The fundamental pathogenic mechanisms are unknown and recent evidence is implicating a significant role for abnormal exon splicing and RNA processing. Using new comprehensive genomic technologies, we studied exon splicing directly in 12 sporadic ALS and 10 control lumbar spinal cords acquired by a rapid autopsy system that processed nervous systems specifically for genomic studies. ALS patients had rostral onset and caudally advancing disease and abundant residual motor neurons in this region. We created two RNA pools, one from motor neurons collected by laser capture microdissection and one from the surrounding anterior horns. From each, we isolated RNA, amplified mRNA, profiled whole-genome exon splicing, and applied advanced bioinformatics. We employed rigorous quality control measures at all steps and validated findings by qPCR. In the motor neuron enriched mRNA pool, we found two distinct cohorts of mRNA signals, most of which were up-regulated: 148 differentially expressed genes (P ? 10?3) and 411 aberrantly spliced genes (P ? 10?5). The aberrantly spliced genes were highly enriched in cell adhesion (P ? 10?57), especially cellmatrix as opposed to cellcell adhesion. Most of the enriching genes encode transmembrane or secreted as opposed to nuclear or cytoplasmic proteins. The differentially expressed genes were not biologically enriched. In the anterior horn enriched mRNA pool, we could not clearly identify mRNA signals or biological enrichment. These findings, perturbed and up-regulated cellmatrix adhesion, suggest possible mechanisms for the contiguously progressive nature of motor neuron degeneration. Data deposition: GeneChip raw data (CEL-files) have been deposited for public access in the Gene Expression Omnibus (GEO), www.ncbi.nlm.nih.gov/geo, accession number GSE18920. PMID:19864493

Rabin, Stuart J.; Kim, Jae Mun Hugo; Baughn, Michael; Libby, Ryan T.; Kim, Young Joo; Fan, Yuxin; Libby, Randell T.; La Spada, Albert; Stone, Brad; Ravits, John

2010-01-01

218

Scanning Electron Microscopy Analysis of Fuel/Matrix Interaction Layers in Highly-Irradiated UMo Dispersion Fuel Plates with Al and AlSi Alloy Matrices  

SciTech Connect

In order to investigate how the microstructure of fuel/matrix-interaction (FMI) layers change during irradiation, different U7Mo dispersion fuel plates have been irradiated to high fission density and then characterized using scanning electron microscopy (SEM). Specifially, samples from irradiated U7Mo dispersion fuel elements with pure Al, Al2Si and AA4043 (~4.5 wt.%Si) matrices were SEM characterized using polished samples and samples that were prepared with a focused ion beam (FIB). Features not observable for the polished samples could be captured in SEM images taken of the FIB samples. For the Al matrix sample, a relatively large FMI layer develops, with enrichment of Xe at the FMI layer/Al matrix interface and evidence of debonding. Overall, a significant penetration of Si from the FMI layer into the U7Mo fuel was observed for samples with Si in the Al matrix, which resulted in a change of the size (larger) and shape (round) of the fission-gas bubbles. Additionally, solid-fission-product phases were observed to nucleate and grow within these bubbles. These changes in the localized regions of the microstructure of the U7Mo may contribute to changes observed in the macroscopic swelling of fuel plates with AlSi matrices.

Dennis D. Keiser, Jr.; Jan-Fong Jue; Brandon D. Miller; Jian Gan; Adam B. Robinson; Pavel Medvedev; James Madden; Dan Wachs; Mitch Meyer

2014-04-01

219

Experimental determination of the temperature range of AlO molecular emission in laser-induced aluminum plasma in air  

NASA Astrophysics Data System (ADS)

Measurements with laser-induced breakdown spectroscopy (LIBS) usually take place in the atmospheric air. For quantitative analysis of metallic elements, oxidation may represent an important issue which can significantly modify the stoichiometry of the plasma. Molecule formation in plasma should be therefore studied and taken into account in the LIBS practice. In this work, we experimentally investigated the temporal evolution and transformation of the plasma induced on an aluminum target by a nanosecond infrared (1064 nm) laser in the atmospheric air, in terms of its temperatures over a large interval of time from hundreds of nanoseconds to tens of microseconds. Such evolution was then correlated to the temporal evolution of the emission intensity from AlO molecules in the ablation plume. In particular, for a given ablation laser pulse energy, the appearance of the molecular emission while the plume cools down allows determining a minimal delay, ?min, which corresponds to a maximal value of the temperature, Tmax, below which the molecular emission begins to be clearly observed and to grow as a function of the delay. Such delay or such temperature indicates the longest delay or the lowest temperature for laser-induced plasma to be suitable for a correct analysis of metallic elements without significant influence of the alternation of the stoichiometry by oxidation. In our experiment, the values of ?min and Tmax have been determined for a range of ablation laser pulse energies from 5 mJ to 50 mJ. These values lie respectively in the range of 3 to 15 ?s for ?min, and 4500 K to 6600 K in terms of the molecule temperature for Tmax. Beyond the practical interest for LIBS, our results provide also insights to the kinetics of the AlO molecule formation in laser-induced plasma.

Bai, Xueshi; Motto-Ros, Vincent; Lei, Wenqi; Zheng, Lijuan; Yu, Jin

2014-09-01

220

Micro-strain Evolution and Toughening Mechanisms in a Trimodal Al-Based Metal Matrix Composite  

NASA Astrophysics Data System (ADS)

A trimodal metal matrix composite (MMC) based on AA (Al alloy) 5083 (Al-4.4Mg-0.7Mn-0.15Cr wt pct) was synthesized by cryomilling powders followed by compaction of blended powders and ceramic particles using two successive dual mode dynamic forgings. The microstructure consisted of 66.5 vol pct ultrafine grain (UFG) region, 30 vol pct coarse grain (CG) region and 3.5 vol pct reinforcing boron carbide particles. The microstructure imparted high-tensile yield strength (581 MPa) compared to a conventional AA 5083 (242 MPa) and enhanced ductility compared to 100 pct UFG Al MMC. The deformation behavior of the heterogeneous structure and the effects of CG regions on crack propagation were investigated using in situ scanning electron microscopy micro-tensile tests. The micro-strain evolution measured using digital image correlation showed early plastic strain localization in CG regions. Micro-voids due to the strain mismatch at CG/UFG interfaces were responsible for crack initiation. CG region toughening was realized by plasticity-induced crack closure and zone shielding of disconnected micro-cracks. However, these toughening mechanisms did not effectively suppress its brittle behavior. Further optimization of the CG distribution (spacing and morphology) is required to achieve toughness levels required for structural applications.

Zhang, Yuzheng; Topping, Troy D.; Yang, Hanry; Lavernia, Enrique J.; Schoenung, Julie M.; Nutt, Steven R.

2015-01-01

221

Comparison of the Booster Interface Temperature in Stainless Steel (SS) V-Channel Versus the Aluminum (Al) Y-Channel Primer Chamber Assemblies (PCAs). Volume 2; Appendices  

NASA Technical Reports Server (NTRS)

NASA's Technical Fellow for Propulsion, requested a technical assessment of the performance improvement achieved by the introduction of the stainless steel (SS) V-channel compared to the aluminum (Al) Y-channel Primer Chamber Assembly (PCA) design. The SS V-channel PCA was developed for NASA's Mars Science Laboratory (MSL) Project. The principle focus of the assessment was to measure the transient temperature at the booster interface with both designs. This document contains the Appendices to the Volume I main report.

Garcia, Roberto; Saulsberry, Regor L.

2011-01-01

222

Quaternary Germanides Formed in Molten Aluminum: Tb2NiAl4Ge2 and Ce2NiAl6-xGe4-y (x 0.24, y 1.34)  

E-print Network

Quaternary Germanides Formed in Molten Aluminum: Tb2NiAl4Ge2 and Ce2NiAl6-xGe4-y (x 0.24, y 1 Tb2NiAl4Ge2 and Ce2NiAl6-x- Ge4-y (x 0.24, y 1.34) were synthesized in molten Al at tem- peratures.1346(2) A° c 19.3437(7) A° for Tb2NiAl4Ge2 and a 4.1951(9) A° and c 26.524(7) A° for Ce2NiAl6-xGe4-y. The Tb

Trikalitis, Pantelis N.

223

High temperature stability, interface bonding, and mechanical behavior in (beta)-NiAl and Ni3Al matrix composites with reinforcements modified by ion beam enhanced deposition  

NASA Astrophysics Data System (ADS)

Diffusion-bonded NiAl-Al2O3 and Ni3Al-Al2O3 couples were thermally fatigued at 900 C for 1500 and 3500 cycles. The fiber-matrix interface weakened after 3500 cycles for the Saphikon fibers, while the Altex, PRD-166, and FP fibers showed little, if any, degradation. Diffusion bonding of fibers to Nb matrix is being studied. Coating the fibers slightly increases the tensile strength and has a rule-of-mixtures effect on elastic modulus. Push-out tests on Sumitomo and FP fibers in Ni aluminide matrices were repeated. Al2O3 was evaporated directly from pure oxide rod onto acoustically levitated Si carbide particles, using a down-firing, rod-fed electron beam hearth; superior coatings were subsequently produced using concurrent irradiation with 200-eV argon ion-assist beam. The assist beam produced adherent films with reduced tensile stresses. In diffusion bonding in B-doped Ni3Al matrices subjected to compressive bonding at 40 MPa at 1100 C for 1 hr, the diffusion barriers failed to prevent catastrophic particle-matrix reaction, probably because of inadequate film quality. AlN coatings are currently being experimented with, produced by both reactive evaporation and by N(+)-ion enhanced deposition. A 3-kW rod-fed electron-beam-heated evaporation source has been brought into operation.

Grummon, D. S.

1993-01-01

224

Atomic layer deposition of Al-doped ZnO films using ozone as the oxygen source: A comparison of two methods to deliver aluminum  

SciTech Connect

Aluminum-doped ZnO films were prepared by atomic layer deposition at 250 deg. C using diethylzinc (DEZ), trimethylaluminum (TMA), and ozone as the precursors. Two deposition methods were compared to assess their impact on the composition, structural, electrical, and optical properties as a function of Al concentration. The first method controlled the Al concentration by changing the relative number of Al to Zn deposition cycles; a process reported in the literature where water was used as the oxygen source. The second method involved coinjection of the DEZ and TMA during each cycle where the partial pressures of the precursors control the aluminum concentration. Depth profiles of the film composition using Auger electron spectroscopy confirmed a layered microstructure for the films prepared by the first method, whereas the second method led to a homogeneous distribution of the aluminum throughout the ZnO film. Beneath the surface layer the carbon concentrations for all of the films were below the detection limit. Comparison of their electrical and optical properties established that films deposited by coinjection of the precursors were superior.

Yuan Hai; Luo Bing; Yu Dan; Cheng, An-jen; Campbell, Stephen A.; Gladfelter, Wayne L. [Department of Electrical and Computer Engineering and Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455 and School of Materials Science and Engineering, Northwestern Polytechnical University, Xi'an, Shaan'xi 710025 (China); Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455 (United States); Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, Minnesota 55455 (United States); Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455 (United States)

2012-01-15

225

Liquid oxygen LOX compatibility evaluations of aluminum lithium (Al-Li) alloys: Investigation of the Alcoa 2090 and MMC weldalite 049 alloys  

NASA Technical Reports Server (NTRS)

The behavior of liquid oxygen (LOX) compatibility of aluminum lithium (Al-Li) alloys is investigated. Alloy systems of Alcoa 2090, vintages 1 to 3, and of Martin Marietta Corporation (MMC) Weldalite 049 were evaluated for their behavior related to the LOX compatibility employing liquid oxygen impact test conditions under ambient pressures and up to 1000 psi. The developments of these aluminum lithium alloys are of critical and significant interest because of their lower densities and higher specific strengths and improved mechanical properties at cryogenic temperatures. Of the different LOX impact tests carried out at the Marshall Space Flight Center (MSFC), it is seen that in certain test conditions at higher pressures, not all Al-Li alloys are LOX compatible. In case of any reactivity, it appears that lithium makes the material more sensitive at grain boundaries due to microstructural inhomogeneities and associated precipitate free zones (PFZ). The objectives were to identify and rationalize the microstructural mechanisms that could be relaxed to LOX compatibility behavior of the alloy system in consideration. The LOX compatibility behavior of Al-Li 2090 and Weldalite 049 is analyzed in detail using microstructural characterization techniques with light optical metallography, scanning electron microscopy (SEM), electron microprobe analysis, and surface studies using secondary ion mass spectrometry (SIMS), electron spectroscopy in chemical analysis (ESCA) and Auger electron spectroscopy (AES). Differences in the behavior of these aluminum lithium alloys are assessed and related to their chemistry, heat treatment conditions, and microstructural effects.

Diwan, Ravinder M.

1989-01-01

226

Reactions of liquid and solid aluminum clusters with N2: The role of structure and phase in Al114+, Al115+, and Al117+  

NASA Astrophysics Data System (ADS)

Kinetic energy thresholds have been measured for the chemisorption of N2 onto Al114+, Al115+, and Al117+ as a function of the cluster's initial temperature, from around 200 K up to around 900 K. For all three clusters there is a sharp drop in the kinetic energy threshold of 0.5-0.6 eV at around 450 K, that is correlated with the structural transition identified in heat capacity measurements. The decrease in the thresholds corresponds to an increase in the reaction rate constant, k(T) at 450 K, of around 106-fold. No significant change in the thresholds occurs when the clusters melt at around 600 K. This contrasts with behavior previously reported for smaller clusters where a substantial drop in the kinetic energy thresholds is correlated with the melting transition.

Cao, Baopeng; Starace, Anne K.; Judd, Oscar H.; Bhattacharyya, Indrani; Jarrold, Martin F.

2014-11-01

227

Role of Al2O3 intermediate layer for improving the quality of polycrystalline-silicon film in inverted aluminum-induced layer exchange  

NASA Astrophysics Data System (ADS)

A thin Al2O3 intermediate layer prepared by atomic layer deposition was introduced into inverted aluminum-induced layer exchange (inverted-ALILE) to form high-quality polycrystalline silicon (poly-Si) thin layer. It was demonstrated that the continuity and quality of poly-Si were obviously improved by the Al2O3 layer. The fraction of (1 0 0)-oriented crystals reached 93%, and the average grain size of 28 ?m with uniform surface morphology and low defect density were achieved at the optimal Al2O3 thickness of 4 nm. It was also found that an a-AlOx layer always existed at the poly-Si/Al interface after inverted-ALILE process, which is independent on the original surface states. The results suggested that the thin poly-Si layer would be a promising epitaxial template for Si based thin film solar cells.

Duan, Weiyuan; Meng, Fanying; Bian, Jiantao; Yu, Jian; Zhang, Liping; Liu, Zhengxin

2015-02-01

228

Influence of pH modifiers and HPMC viscosity grades on nicotine-magnesium aluminum silicate complex-loaded buccal matrix tablets.  

PubMed

Hydroxypropyl methylcellulose (HPMC) tablets containing nicotine-magnesium aluminum silicate (NCT-MAS) complex particles and pH modifiers, namely, sodium chloride, citric acid, and magnesium hydroxide, were prepared using the direct compression method. The effects of HPMC viscosity grades and pH modifiers on NCT release and permeation of the matrix tablets were examined. The results showed that the higher the viscosity grade of HPMC that was used in the tablets, the lower was the unidirectional NCT release rate found. The unidirectional NCT permeation was not affected by the viscosity grade of HPMC because the NCT diffusion through the mucosal membrane was the rate-limiting step of the permeation. Incorporation of magnesium hydroxide could retard NCT release, whereas the enhancement of unidirectional NCT release was found in the tablets containing citric acid. Citric acid could inhibit NCT permeation due to the formation of protonated NCT in the swollen tablets at an acidic pH. Conversely, the NCT permeation rate increased with the use of magnesium hydroxide as a result of the neutral NCT that formed at a basic microenvironmental pH. The swollen HPMC tablets, with or without pH modifiers, gave sufficient adhesion to the mucosal membrane. Furthermore, the addition of magnesium hydroxide to the matrix tablets was the major factor in controlling buccal delivery of NCT. This study suggests that the NCT-MAS complex-loaded HPMC tablets, which contained magnesium hydroxide, are potential buccal delivery systems of NCT. PMID:22552930

Pongjanyakul, Thaned; Kanjanabat, Sopaphan

2012-06-01

229

Characterization of tool wear and weld optimization in the friction-stir welding of cast aluminum 359+20% SiC metal-matrix composite  

Microsoft Academic Search

Tool wear for threaded steel pin tools declines with decreasing rotation speed and increasing traverse or weld speeds for the friction-stir welding (FSW) of Al 359+20% SiC metal-matrix composite (MMC). Less than 10% tool wear occurs when the threaded tool erodes to a self-optimized shape resembling a pseudo-hour glass at weld traverse distances in excess of 3 m. There is

G. J. Fernandez; L. E Murr

2004-01-01

230

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

SciTech Connect

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

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

2004-07-15

231

Effect of a solid solution on the steady-state creep behavior of an aluminum matrix composite  

Microsoft Academic Search

The effect of an alloying element, 4 wt pct Mg, on the steady-state creep behavior of an Al-10 vol pct SiCp composite has been studied. The Al-4 wt pct Mg-10 vol pct SiCp composite has been tested under compression creep in the temperature range 573 to 673 K. The steady-state creep data of the\\u000a composite show a transition in the

A. B. Pandey; R. S. Mishra; Y. R. Mahajan

1996-01-01

232

Effect of a solid solution on the steady-state creep behavior of an aluminum matrix composite  

Microsoft Academic Search

The effect of an alloying element, 4 wt pct Mg, on the steady-state creep behavior of an Al-10 vol pct SiCp composite has been studied. The Al-4 wt pct Mg-10 vol pct SiCp composite has been tested under compression creep in the temperature range 573 to 673 K. The steady-state creep data of the composite show a transition in the

A. B. Pandey; R. S. Mishra; Y. R. Mahajan

1996-01-01

233

STUDIES ON GROOVING OF DISPERSION STRENGTHENED METAL MATRIX COMPOSITES  

Microsoft Academic Search

Machinability studies of silicon carbide reinforced aluminum alloy (Al\\/SiC) composites have attracted widespread scientific and public attention. The metal matrix composites (MMCs) are difficult to machine, since the matrix and reinforcement possess widely different properties and the cutting tool alternately encounters matrix and reinforcement, demanding higher wear resistance coupled with fracture toughness, owing to the hard SiC reinforcement embedded in

B. Anand Ronald; L. Vijayaraghavan; R. Krishnamurthy

234

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

PubMed

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

Calta, Nicholas P; Kanatzidis, Mercouri G

2013-09-01

235

Study on the Mechanical Properties of Cast 6063 Al Alloy Using a Mixture of Aluminum Dross and Green Sand as Mold  

NASA Astrophysics Data System (ADS)

The mechanical characteristics of 6063 aluminum alloy cast in a mixture of aluminum dross and silica sand as mold have been examined. The amount of dross in the green silica sand was varied in the range of 0-80% with bentonite as binder. In all, 40 samples were cast, and 8 of these were left in the as-cast condition for control while 32 were first homogenized at 470C for 6 h and then rolled in a two-high mill at ambient temperature to 10% reduction in one pass. The rolled samples were solution heat treated at 515C for 8 h followed by normalizing, annealing, and quench tempering, respectively. The samples were then simulated and tensile behavior coupled with the evaluation of microhardness and microstructures developed. The results obtained demonstrate significant improvement in mechanical properties from 50% to 80% dross in the mold. Tensile strength increased to 177 MPa and 15% elongation compared with conventional 6063-T5 aluminum alloy with 145 MPa tensile strength and 8% elongation. The improvement in mechanical properties by the quench-tempered samples can be attributed to the inducement of fine and coherent Mg2Si crystals within the matrix. Furthermore, the overall analysis of the proportion of dross to the size of cast show that about 64% of dross generated can be utilized as mold material.

Adeosun, S. O.; Sekunowo, O. I.; Balogun, S. A.; Obembe, O. O.

2012-08-01

236

Microstructural Characterization of U-7Mo/Al-Si Alloy Matrix Dispersion Fuel Plates Fabricated at 500C  

SciTech Connect

The starting microstructure of a dispersion fuel plate will impact the overall performance of the plate during irradiation. To improve the understanding of the as-fabricated microstructures of UMo dispersion fuel plates, particularly the interaction layers that can form between the fuel particles and the matrix, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses have been performed on samples from depleted U7Mo (U7Mo) dispersion fuel plates with either Al2 wt.% Si(Al2Si) or AA4043 alloy matrix. It was observed that in the thick interaction layers, U(Al, Si)3 and U6Mo4Al43 were present, and in the thin interaction layers, (U, Mo) (Al, Si)3, U(Al, Si)4, U3Si3Al2, U3Si5, and possibly USi-type phases were observed. The U3Si3Al2 phase contained some Mo. Based on the results of this investigation, the time that a dispersion fuel plate is exposed to a relatively high temperature during fabrication will impact the nature of the interaction layers around the fuel particles. Uniformly thin, Si-rich layers will develop around the U7Mo particles for shorter exposure times, and thicker, Si-depleted layers will develop for the longer exposure times.

Dennis D. Keiser, Jr.; Jan-Fong Jue; Bo Yao; Emmanuel Perez; Yongho Sohn; Curtis R. Clark

2011-05-01

237

Microstructure and Grain Growth of the Matrix of SiCf/Ti-6Al-4V Composites Prepared by the Consolidation of Matrix-Coated Fibers in the ?+ ? Phase Field  

NASA Astrophysics Data System (ADS)

Both the microstructural characteristics and the grain growth of the matrix materials in the SiCf/Ti-6Al-4V composites were investigated by means of experimental tests coupled with theoretical assessment. A very fine matrix microstructure was obtained in the SiCf/Ti-6Al-4V composites that were prepared by the consolidation of matrix-coated fiber (MCF) in the ?+ ? phase field. During a fabrication process through the MCF method, the matrix microstructure after consolidation processing will evolve from the columnar crystals to a fully-lamellar microstructure. The experimental results especially the grain sizes of matrix microstructure were reasonably explained based on theoretical calculations.

Zhao, Guangming; Yang, Yanqing; Zhang, Wei; Luo, Xian; Huang, Bin; Chen, Yan

2015-02-01

238

The mechanical properties of a composite coating with a polymer matrix based on sodium carboxymethylcellulose and aluminum powder  

Microsoft Academic Search

The influence of the contents of sodium carboxymethylcellulose, glycerol, Al powder, and its particle size on the mechanical\\u000a strength and relative deformation of the composite coating (CC) made of these components is investigated at various temperatures.\\u000a The regression models describing the interrelation between the mechanical properties of the CC and its composition, which\\u000a allow one to predict the final characteristics

N. M. Antonova

2009-01-01

239

Comparison of post-detonation combustion in explosives incorporating aluminum nanoparticles: Influence of the passivation layer  

NASA Astrophysics Data System (ADS)

Aluminum nanoparticles and explosive formulations that incorporate them have been a subject of ongoing interest due to the potential of aluminum particles to dramatically increase energy content relative to conventional organic explosives. We have used time-resolved atomic and molecular emission spectroscopy to monitor the combustion of aluminum nanoparticles within the overall chemical dynamics of post-detonation fireballs. We have studied the energy release dynamics of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) charges incorporating three types of aluminum nanoparticles: commercial oxide-passivated nanoparticles, oleic acid-capped aluminum nanoparticles (AlOA), and nanoparticles in which the oxide shell of the particle has been functionalized with an acrylic monomer and copolymerized into a fluorinated acrylic matrix (AlFA). The results indicate that the commercial nanoparticles and the AlFA nanoparticles are oxidized at a similar rate, while the AlOA nanoparticles combust more quickly. This is most likely due to the fact that the commercial nano-Al and the AlFA particles are both oxide-passivated, while the AlOA particles are protected by an organic shell that is more easily compromised than an oxide layer. The peak fireball temperatures for RDX charges containing 20 wt. % of commercial nano-Al, AlFA, or AlOA were 3900 K, 3400 K, and 4500 K, respectively.

Lewis, W. K.; Rumchik, C. G.; Smith, M. J.; Fernando, K. A. S.; Crouse, C. A.; Spowart, J. E.; Guliants, E. A.; Bunker, C. E.

2013-01-01

240

ISSN 1537-744X; doi:10.1100/2011/756264 Measurement of Mercury in Flue Gas Based on an Aluminum Matrix Sorbent  

E-print Network

The measurement of total mercury in flue gas based on an economical aluminum matrix sorbent was developed in this paper. A sorbent trap consisted of three tubes was employed to capture Hg from flue gas. Hg trapped on sorbent was transferred into solution by acid leaching and then detected by CVAAS. Hg adsorbed on sorbent was recovered completely by leaching process. The 87.7 % recovery of Hg in flue gas by tube 1 and tube 2 was obtained on the equipment of coal combustion and sampling in lab. In order to evaluate the ability to recover and accurately quantify Hg 0 on the sorbent media, the analytical bias test on tube 3 spiked with Hg 0 was also performed and got the average recovery of 97.1%. Mercury measurements based on this method were conducted for three coal-fired power plants in China. The mercury in coal is distributed into bottom ash, electrostatic precipitator (ESP) ash, wet flue gas desulfurization (WFGD) reactant, and flue gas, and the relative distribution varied depending on factors such as the coal type and the operation conditions of plants. The mercury mass balances of three plants were also calculated which were 91.6%, 77.1%, and 118%, respectively. The reliability of this method was verified by the Ontario Hydro (OH) method either in lab or in field.

Juan Wang; Wei Xu; Xiaohao Wang; Wenhua Wang

2011-01-01

241

Thermodynamics of aqueous aluminum: standard partial molar heat capacities of Al/sup 3 +/ from 10 to 55/sup 0/C  

SciTech Connect

The thermodynamic properties of aqueous aluminum species are required over wide ranges of temperature in order to model mineral dissolution and transport in steam injection and combustion processes for the in situ recovery of bitumen. The same data are needed to model aqueous solutions associated with the formation of hydrothermal ore deposits, geothermal power generation, the marine chemistry of deep hydrothermal vents, hydrometallurgy, and the corrosion behavior of aluminum alloys. Apparent molar heat capacities and volumes of Al(NO/sub 3/)/sub 3/ and AlCl/sub 3/ have been measured at 25/sup 0/C in dilute aqueous acid solutions to suppress hydrolysis. Heat capacity results for AlCl/sub 3/ span the range 10-55/sup 0/C. The measurements yield standard partial molar heat capacities, anti C/sub p//sup 0/, and volumes, anti V/sup 0/, for the Al/sup 3 +/ (aq) ion: anti V/sub 298//sup 0/ (Al/sup 3 +/, aq) = -45.3 cm/sup 3/ mol/sup -1/, anti C/sub pT//sup 0/(Al/sup 3 +/, aq) = 566.2 - 1.452% - 27338/(T - 190), where T is the absolute temperature (K). Their result for anti V/sub 298//sup 0/ is consistent with published semi-empirical correlations. The result for anti C/sub p298//sup 0/ is more negative than that predicted from the entropy correspondence principle by 135 J K/sup -1/ mol/sup -1/ and casts doubt upon the correspondence method as a predictive tool. The heat capacities approach born behavior at elevated temperatures and appear to be consistent with the Helgeson-Kirkham-Flowers model for extrapolations to higher temperatures.

Hovey, J.K.; Tremaine, P.R.

1986-03-01

242

Composite propellant combustion with low aluminum agglomeration  

NASA Astrophysics Data System (ADS)

Aluminum behavior---accumulation, agglomeration and ignition---is studied in a unique, wide-distribution, ammonium perchlorate/hydroxyl-terminated polybutadiene (AP/HTPB) propellant formulation that results in low Al agglomeration, even at low pressures (1--30 atm). Variations in formulation---such as fine-AP/binder ratio, Al particle size, Al loading, coarse-AP size---are also examined. A fuel-rich, oxygenated binder matrix highly loaded with fine (2-mum) AP (FAP) at 75/25:FAP/binder (by mass) is found to have premixed flame conditions that produce minimal agglomeration (without ignition) of 15-mum Al. Coarse AP (CAP) is added to the system in the form of either particles (200 or 400 mum) or pressed-AP laminates (simulated CAP). In the 2-D laminate system the CAP/oxyfuel-matrix flame structure is seen to be similar to that previously described for non-aluminized laminates with split (diffusion) and merged (partially-premixed) flame regimes, depending on pressure and fuel-matrix thickness. Both laminate and particulate systems show that with CAP present, Al can agglomerate more extensively on CAP via lateral surface migration from fuel matrix to the CAP region. The particulate CAP system also shows that Al can accumulate/agglomerate via settling on CAP from above (in the direction of burning). Both systems, but more clearly the 2-D laminates, show that with CAP present, Al is ignited by the outer CAP/fuel-matrix canopy flames. Thus, a propellant formulation is proposed for reducing overall Al agglomeration through intrinsically reduced agglomeration in the fuel-matrix and a reduced number of CAP-particle agglomerates via higher FAP/CAP ratio.

Mullen, Jessica Christine

243

In-situ scanning electron microscope studies of crack growth in an aluminum metal-matrix composite  

NASA Technical Reports Server (NTRS)

Edge-notched specimens of a cast and extruded Al alloy-based, alumina particulate-reinforced composite in the annealed condition were tested in situ in a SEM apparatus equipped with a deformation stage permitting the direct observation of crack growth phenomena. Fracture in this composite is seen to proceed by initiation of microcracks ahead of the macrocrack; as deformation proceeds, the microcracks lengthen, and crack propagation occurs when the region of intense plastic straining becomes comparable to the macrocrack-microcrack distance. The sequence is then repeated.

Manoharan, M.; Lewandowski, J. J.

1990-01-01

244

Development of mathematical models of superplasticity properties as a function of parameters of aluminum alloys of Al-Mg-Si system  

NASA Astrophysics Data System (ADS)

The article discusses the superplasticity properties and structure parameters of cold-worked alloys of a quasi-binary section of the Al-Mg-Si system with a volume fraction of eutectic particles of 0.08-0.18. Mathematical models of yield stress and effective elongation as a function of the structure and engineering parameters have been developed for alloys of this system. An analysis of the developed models shows that, in the temperature range of 520-560C, superplastic deformation is controlled by the rate of diffusion of aluminum atoms in the grain bulk.

Churyumov, A. Yu.; Mikhailovskaya, A. V.; Kotov, A. D.; Bazlov, A. I.; Portnoi, V. K.

2013-03-01

245

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

Microsoft Academic Search

In this study, mechanically alloyed Al12Si\\/SiO2 composite powder was deposited onto an aluminum substrate by atmospheric plasma spraying. The composite coating consisting of in situ formed Al2O3 reinforced hypereutectic Al18Si matrix alloy was achieved. The produced coatings were extensively analyzed with respect to X-ray diffraction (XRD). The XRD patterns of the coatings include Al, Si and Al2O3 phase formation. Mechanical

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

2010-01-01

246

Effects of mercury on thermally sprayed aluminum coatings  

SciTech Connect

The quantification of liquid metal embrittling effects of mercury on thermally sprayed aluminum was investigated. The program consisted of heat treatments at 250 and 300 C of thermally sprayed (aluminum on lead) cylinders with mercury additions of 0.25, 0.50, 1.00, and 3.00 wt.%. The cylinders were then tested to determine the adhesion/cohesion strength of the thermally sprayed bond. The Pb/Al interfaces were evaluated using energy dispersive spectroscopy (EDS). The results of the testing indicate that there was no noticeable embrittling effects of the mercury, up to 3.0 wt.% Hg in the Pb matrix.

Czajkowski, C.J.; Usmani, S.; Greene, G.A.

1999-09-01

247

Theoretical study of aluminum arsenide clusters: equilibrium geometries and electronic structures of Al(n)As(n) (n=1-4).  

PubMed

The geometry, electronic configurations, harmonic vibrational frequencies and stability of the structural isomers of Al(n)As(n) clusters (n=1-4) have been investigated using density functional theory. For dimers and trimers, the lowest energy structures are planar cumulenic rings (IIs, VIs) with D(nh) symmetry. The caged structure with T(d) symmetry (IXs) lie lowest in energy among the tetramers. The AlAs bond dominates the structures for many isomers so that one preferred dissociation channel is loss of the AlAs monomer. The atomic charges, hybridization and chemical bonding in the different structures are also discussed. Comparisons with valence-isoelectronic Si(2n), Al(n)P(n) and Ga(n)As(n) clusters of same size, the properties of the aluminum arsenide clusters are analogous to those of their corresponding Al(n)P(n), Si(2n) counterparts. The results can explain the modification and refinement of Si phase in AlSi alloy in the molecular level. PMID:16169760

Qu, Yuhui; Ma, Wanyong; Bian, Xiufang; Tang, Hongwei; Tian, Weixing

2005-12-01

248

Electron Diffraction Evidence for the Ordering of Excess Nickel Atoms by Relation to Stoichiometry in Nickel-Rich Beta'-Nial Formation of a Nickel-Aluminum (Ni2al) Superlattices  

NASA Technical Reports Server (NTRS)

In electron diffraction patterns of nickel-rich beta-NiAl alloys, many anomalies are observed. One of these is the appearance of diffuse intensity maxima between the reflexions of the B2 structure. This is explained by the short-range ordering of the excess nickel atoms on the simple cubic sublattice occupied only by aluminum atoms in the stoichiometric, perfectly ordered NiAl alloy. After annealing Ni 37.5 atomic percent Al and Ni 37.75 atomic percent Al for 1 week at 300 and 400 C, the diffuse intensity maxima transformed into sharp superstructure reflexions. These reflexions are explained by the formation of the four possible variants of an ordered hexagonal superstructure corresponding to the Ni2Al composition. This structure is closely related to the Ni2Al3 structure (same space group) formed by the ordering of vacancies on the nickel sublattice in aluminum-rich beta-NiAl alloys.

Reynaud, F.

1988-01-01

249

Molecular aspects of aluminum toxicity  

Microsoft Academic Search

The focus in this review is directed to molecular aspects of aluminum toxicity in animal and plant cells. Unique thermodynamic features of Al(lII) ions impart biological specificity which may form the biochemical basis of aluminum interactions with cellular constituents. Current knowledge about aluminum?specific, molecular interactions is rather scanty. Al(III) ions may coordinate with nucleotides or complex to phospholipids resulting in

Alfred Haug; Charles E. Foy

1984-01-01

250

Visible photoluminescence in polycrystalline terbium doped aluminum nitride (Tb:AlN) ceramics with high thermal conductivity  

SciTech Connect

Thermal management continues to be one of the major challenges in the development of high powered light sources such as solid state lasers. In particular, the relatively low thermal conductivity of standard photoluminescent (PL) materials limits the overall power output and/or duty cycle. We present a method based on current activated pressure assisted densification for the fabrication of high thermal conductivity PL materials: rare earth doped polycrystalline bulk aluminum nitride. Specifically, the ceramics are translucent and are doped with Tb{sup 3+}, allowing for emission in the visible. Remarkably, the ceramics have a room temperature thermal conductivity of 94 W/(m K) which is almost seven times higher than that of the state of the art host material, Nd-doped yttrium aluminum garnet. These light emitting properties coupled with very high thermal conductivity should enable the development of a wide variety of more powerful light sources.

Wieg, A. T.; Kodera, Y.; Wang, Z.; Garay, J. E. [Department of Mechanical Engineering, Materials Science and Engineering Program, University of California, Riverside, California 92521 (United States); Imai, T. [Department of Materials Chemistry, Ryukoku University, Ohtsu (Japan); Dames, C. [Department of Mechanical Engineering, University of California, Berkeley, California 94720 (United States)

2012-09-10

251

Irradiation performance of U-Mo-Ti and U-Mo-Zr dispersion fuels in Al-Si matrixes  

NASA Astrophysics Data System (ADS)

Performance of U-7 wt.%Mo with 1 wt.%Ti, 1 wt.%Zr or 2 wt.%Zr, dispersed in an Al-5 wt.%Si alloy matrix, was investigated through irradiation tests in the ATR at INL and HANARO at KAERI. Post-irradiation metallographic features show that the addition of Ti or Zr suppresses interaction layer growth between the U-Mo and the Al-5 wt.%Si matrix. However, higher fission gas swelling was observed in the fuel with Zr addition, while no discernable effect was found in the fuel with Ti addition as compared to U-Mo without the addition. Known to have a destabilizing effect on the ?-phase U-Mo, Zr, either as alloy addition or fission product, is ascribed for the disadvantageous result. Considering its benign effect on fuel swelling, with slight disadvantage from neutron economy point of view, Ti may be a better choice for this purpose.

Kim, Yeon Soo; Hofman, G. L.; Robinson, A. B.; Wachs, D. M.; Ryu, H. J.; Park, J. M.; Yang, J. H.

2012-08-01

252

Review of stress-corrosion cracking in high-strength aluminum alloys. [Al alloys 7090, 7091, IN 9052 and Al-Li ingot metallurgy  

Microsoft Academic Search

Developments in understanding the mechanisms of stress-corrosion cracking (SCC) of high-strength aluminum alloys are highlighted from early dissolution models, to present hydrogen embrittlement dominated theories. Uncertainties in the present view of the SCC mechanism are identified. The means by which SCC susceptibility has been reduced in ingot metallurgy (I\\/M) alloys are described. The susceptibility of new powder metallurgy (P\\/M) alloys

J. R. Pickens; L. Christodoulou; T. J. Langan

2008-01-01

253

Experimentally measured thermal transport properties of aluminumpolytetrafluoroethylene nanocomposites with graphene and carbon nanotube additives  

Microsoft Academic Search

Reactive materials such as aluminum (Al) and polytetrafluoroethylene (Teflon) are used for energy generation applications and specifically in ordnance technologies. With the advent of nanotechnology various nano-scale additives have become incorporated into reactive material formulations with the hope of enhanced performance. An important component to the study of energy generation is an examination of energy transport through a reactant matrix.

Keerti Kappagantula; Michelle L. Pantoya

254

Formation of ordered films of axially bridged aluminum phthalocyanine [(tBu){sub 4}PcAl]{sub 2}O via magnetic field-induced reaction  

SciTech Connect

The ?-(oxo)bis[tetra-tert-butylphthalocyaninato] aluminum(III) [(tBu){sub 4}PcAl]{sub 2}O films with the crystallites oriented preferably in one direction were obtained via chemical transformation of tetra-tert-butylsubstituted chloroaluminum(III) phthalocyanine (tBu){sub 4}PcAlCl film upon its annealing in magnetic field. A comparative analysis of the influence of post-deposition annealing process without and under applied magnetic field of 1 T, on the orientation and morphology of (tBu){sub 4}PcAlCl and [(tBu){sub 4}PcAl]{sub 2}O films, has been carried out by the methods of UV-vis, Infrared and Raman spectroscopies, XRD as well as atomic force microscopy. The formation of [(tBu){sub 4}PcAl]{sub 2}O films with elongated crystallites having preferential orientation was observed upon heating of the films in magnetic field while annealing without magnetic field under the same conditions does not demonstrate any effect on the structure and morphology of these films. The reasons of the sensitivity of this reaction to the presence of such magnetic field is discussed and studied by electronic paramagnetic resonance spectroscopy.

Basova, Tamara, E-mail: basova@niic.nsc.ru; Berezin, Aleksei; Nadolinny, Vladimir [Nikolaev Institute of Inorganic Chemistry, Russian Academy of Sciences, Lavrentiev Pr., 3, 630090 Novosibirsk (Russian Federation)] [Nikolaev Institute of Inorganic Chemistry, Russian Academy of Sciences, Lavrentiev Pr., 3, 630090 Novosibirsk (Russian Federation); Peisert, Heiko; Chass, Thomas [Institute for Physical and Theoretical Chemistry, Auf der Morgenstelle 18, 72076 Tbingen (Germany)] [Institute for Physical and Theoretical Chemistry, Auf der Morgenstelle 18, 72076 Tbingen (Germany); Banimuslem, Hikmat; Hassan, Aseel [Materials and Engineering Research Institute, Sheffield Hallam University, Sheffield S1 1WB (United Kingdom)] [Materials and Engineering Research Institute, Sheffield Hallam University, Sheffield S1 1WB (United Kingdom)

2013-11-28

255

Reaction synthesis of Ni-Al based particle composite coatings  

SciTech Connect

Electrodeposited metal matrix/metal particle composite (EMMC) coatings were produced with a nickel matrix and aluminum particles. By optimizing the process parameters, coatings were deposited with 20 volume percent aluminum particles. Coating morphology and composition were characterized using light optical microscopy (LOM), scanning electron microscopy (SEM), and electron probe microanalysis (EPMA). Differential thermal analysis (DTA) was employed to study reactive phase formation. The effect of heat treatment on coating phase formation was studied in the temperature range 415 to 1,000 C. Long-time exposure at low temperature results in the formation of several intermetallic phases at the Ni matrix/Al particle interfaces and concentrically around the original Al particles. Upon heating to the 500--600 C range, the aluminum particles react with the nickel matrix to form NiAl islands within the Ni matrix. When exposed to higher temperatures (600--1,000 C), diffusional reaction between NiAl and nickel produces ({gamma})Ni{sub 3}Al. The final equilibrium microstructure consists of blocks of ({gamma}{prime})Ni{sub 3}Al in a {gamma}(Ni) solid solution matrix, with small pores also present. Pore formation is explained based on local density changes during intermetallic phase formation and microstructural development is discussed with reference to reaction synthesis of bulk nickel aluminides.

SUSAN,DONALD F.; MISIOLEK,WOICECK Z.; MARDER,ARNOLD R.

2000-02-11

256

Production and mechanical properties (strength, wear, and fracture toughness) of chilled aluminum-quartz castable particulate composite  

Microsoft Academic Search

Structural composite materials offer an excellent opportunity to produce components that achieve weight savings and improved\\u000a mechanical properties. This paper describes a chilled Al-quartz particulate composite that can be cast using metallic and\\u000a nonmetallic chill blocks, much like nonreinforced aluminum, using conventional aluminum casting equipments. Unlike other metal\\u000a matrix composites (MMCs), this material is produced economically by a simple ingot

J. Hemanth

2001-01-01

257

Effect of forging parameters on low cycle fatigue behaviour of Al/basalt short fiber metal matrix composites.  

PubMed

This paper deals with metal matrix composites (MMCs) of Al 7075 alloy containing different weight percentage (2.5, 5, 7.5, and 10) basalt short fiber reinforcement and unreinforced matrix alloy. The samples were produced by the permanent stir casting technique. The casting ingots were cut into blanks to be forged in single stage and double stage, using MN press and graphite-based lubricant. The microstructures and fatigue properties of the matrix alloy and MMC samples were investigated in the as cast state and in the single and double stage forging operations. The microstructure results showed that the forged sample had a uniform distribution of the basalt short fiber throughout the specimens. Evaluation of the fatigue properties showed that the forged samples had higher values than those of the as cast counterparts. After forging, the enhancement of the fatigue strength of the matrix alloy was so significant and high in the case of 2.5 and 5.0?wt. percentage basalt short fiber reinforced MMC, and there was no enhancement in 7.5 and 10?weight percentages short fiber reinforced MMCs. The fracture damage was mainly due to decohesion at the matrix-fiber interface. PMID:24298207

Karthigeyan, R; Ranganath, G

2013-01-01

258

Study on effects of powder and flake chemistry and morphology on the properties of Al-Cu-Mg-X-X-X powder metallurgy advanced aluminum alloys  

NASA Technical Reports Server (NTRS)

A study was conducted: (1) to develop rapid solidification processed (RSP) dispersoid-containing Al-3Cu-2Li-1Mg-0.2Zr alloys as substitutes for titanium alloys and commercial 2XXX aluminum alloys for service to at least 150 C; and (2) to develop RSP Al-4Li-Cu-Mg-Zr alloys as substitutes for high-strength commercial 7XXX alloys in ambient-temperature applications. RSP Al-3Cu-2Li-1Mg-0.2Zr alloys have density-normalized yield stresses at 150 C up to 52% larger than that of 2124-T851 and up to 30% larger than that of Ti-6Al-4V. Strength at 150 C in these alloys is provided by thermally stable delta' (Al3Li), T1 (Al2LiCu), and S' (Al2CuMg) precipitates. Density-normalized yield stresses of RSP Al-3Cu-2Li-1Mg-0.2Zr alloys are up to 100% larger than that of 2124-T851 and equivalent to that of Al-8Fe-4Ce at 260 C. Strength in the RSP alloys at 260 C is provided by incoherent dispersoids and subboundary constituent particles such as T1 and S. The RSP alloys are attractive substitutes in less than or = 100-h exposures for 2xxx and Al-4Fe-Ce alloys up to 260 C and for titanium alloys up to 150 C. RSP Al-4Li-Cu-Mg-Zr alloys have ambient-temperature yield and ultimate tensile stresses similar to that of 7050-T7651, and are 14% less dense. RSP Al-4Li-0.5Cu-1.5Mg-0.2Zr has a 20% higher specific yield stress, 40% higher specific elastic modulus, and superior corrosion resistance compared to the properties of 7050-T7651. Strength in the Al-4Li-Cu-Mg-Zr alloy class is primarily provided by the substructure and delta' precipitates and is independent of Cu:Mg ratio. Improvements in fracture toughness and transverse-orientation properties in both alloy classes depend on improved melt practices to eliminate oxide inclusions which are incorporated into the consolidated forms.

Meschter, P. J.; Lederich, R. J.; Oneal, J. E.

1986-01-01

259

A new phase in the system lithium-aluminum: Characterization of orthorhombic Li{sub 2}Al  

SciTech Connect

Investigation of the Li rich part of the binary Li-Al system revealed the existence of a new phase, orthorhombic Li{sub 2}Al, which is isostructural to Li{sub 2}Ga and Li{sub 2}In. The crystal structure was determined from single crystal X-ray diffraction data (Cmcm, a=4.658(2) A, b=9.767(4) A, c=4.490(2) A, Z=4). Refinement of atomic position site occupancies yielded a composition Li{sub 1.92}Al{sub 1.08} (64 at% Li) indicating a small homogeneity range, Li{sub 2-x}Al{sub 1+x}. Li{sub 2}Al is the peritectic decomposition product of the stoichiometric compound Li{sub 9}Al{sub 4}, which is stable below 270{+-}2 {sup o}C. Li{sub 2}Al itself decomposes peritectically to Li{sub 3}Al{sub 2} and Li rich melt at 335{+-}2 {sup o}C. The discovery of Li{sub 2}Al (Li{sub 2-x}Al{sub 1+x}) settles a long standing inconsistency in the Li-Al phase diagram which was based on the assumption that Li{sub 9}Al{sub 4} possesses a high temperature modification. - Graphical abstract: A new phase, Li{sub 2}Al, has been discovered in the binary Li-Al system. The structure of orthorhombic Li{sub 2}Al is closely related to that of the established monoclinic phase Li{sub 9}Al{sub 4}.

Puhakainen, Kati [Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287-1604 (United States); Bostroem, Magnus [Sandvik Materials Technology, S-881 81 Sandviken (Sweden); Groy, Thomas L. [Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287-1604 (United States); Haeussermann, Ulrich, E-mail: Ulrich.Haussermann@asu.ed [Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287-1604 (United States)

2010-11-15

260

Electronic and magnetic properties of manganese impurities in aluminum  

Microsoft Academic Search

We studied the electronic structure of manganese impurities in a fcc aluminum matrix by means of calculations for a free MnAl18 cluster. Our ab initio self-consistent computations employed the Rajagopal-Singhal-Kimball local-spin-density potential and a symmetrized Gaussian-orbital basis. The local and cluster magnetic moments are, respectively, 1.74muB and 1.0muB. Substantial screening of the Mn moment by opposite polarization of the surrounding

D. Bagayoko; N. Brener; D. Kanhere; J. Callaway

1987-01-01

261

Aluminum in Superconducting Magnets Robert J. Weggel  

E-print Network

Aluminum in Superconducting Magnets Robert J. Weggel Magnet Optimization Research Engineering is aluminum, either ultrapure, as quenchstabilization matrix metal, and/or alloyed and coldworked and heat for magnets in which the stresses and strains are modest. The strongest aluminum alloy commercially available

McDonald, Kirk

262

Aluminum for plasmonics.  

PubMed

Unlike silver and gold, aluminum has material properties that enable strong plasmon resonances spanning much of the visible region of the spectrum and into the ultraviolet. This extended response, combined with its natural abundance, low cost, and amenability to manufacturing processes, makes aluminum a highly promising material for commercial applications. Fabricating Al-based nanostructures whose optical properties correspond with theoretical predictions, however, can be a challenge. In this work, the Al plasmon resonance is observed to be remarkably sensitive to the presence of oxide within the metal. For Al nanodisks, we observe that the energy of the plasmon resonance is determined by, and serves as an optical reporter of, the percentage of oxide present within the Al. This understanding paves the way toward the use of aluminum as a low-cost plasmonic material with properties and potential applications similar to those of the coinage metals. PMID:24274662

Knight, Mark W; King, Nicholas S; Liu, Lifei; Everitt, Henry O; Nordlander, Peter; Halas, Naomi J

2014-01-28

263

Identification of interfacial parameters in a particle reinforced metal matrix composite Al606110%Al2O3  

E-print Network

­10%Al2O3 by hybrid method and genetic algorithm X.H. Lin, Y.L. Kang *, Q.H. Qin, D.H. Fu School genetic algorithm (GA). A non-continuum four-node interface element is adopted to simulate the interface the mechanical behavior and investigate the effects of interface properties on the composites, a novel hybrid

Qin, Qinghua

264

Physicotechnical properties of wurtzitic AlN-based ceramics and composites with ceramic matrix  

Microsoft Academic Search

Wurtzitic aluminum nitride-based ceramic materials having the following high characteristics: structural ceramics with a Vickers\\u000a hardness of HV = 16.8 GPa, fracture toughness K\\u000a Ic\\u000a = 4.7?4.9 MPam1\\/2, bending strength ? = 370430 MPa; functional ceramics for heatsinks with a thermal conductivity of 140 W\\/(mK) and for microwaves\\u000a absorption with dielectric constant ? = 23, dielectric loss tangent tan ?

I. P. Fesenko; T. B. Serbenyuk; V. I. Chasnyk; V. S. Bilovol; V. M. Kolodnitskyi; M. G. Loshak; A. A. Marchenko; Yu. M. Tuz; Yu. O. Strunina; S. V. Tkach; E. I. Fesenko; I. P. Shashurin

2010-01-01

265

Synthesis and Characterization of Novel Al-Matrix Composites Reinforced with Ti3SiC2 Particulates  

NASA Astrophysics Data System (ADS)

In this paper, we report for the first time, the synthesis and characterization of novel Ti3SiC2 reinforced Al-matrix composites. All the composites were cold pressed and sintered in the temperature range of 700-750 C for 5-30 min in an inert Ar atmosphere. Microstructure analysis by scanning electron microscopy and phase analysis by x-ray diffraction confirmed that there was minimal interfacial reaction between Ti3SiC2 particles and Al. The addition of Ti3SiC2 enhanced the mechanical performance of the composites. For example, the pure Al samples had a yield strength of 97 6 MPa, where as the volume fraction of Ti3SiC2 was increased to 5 and 10 vol.% in the composites, the yield strength increased significantly to 212 27 and 273 52 MPa, respectively. As the volume fraction of Ti3SiC2 was further increased to 20 and 35 vol.%, the yield strength mildly increased to 278 48 MPa, and then decreased to 134 20 MPa, respectively. The decrease in yield strength after 35 vol.% Ti3SiC2 addition in the Al matrix was attributed to the presence of higher amount of porosity in these samples. The addition of Ti3SiC2 particles also had a beneficial effect on the tribological performance of these composites against alumina substrates.

Gupta, S.; Hammann, T.; Johnson, R.; Riyad, M. F.

2014-12-01

266

Studies of waste-canister compatibility. [Waste forms: Al-Si and Pb-Sn matrix alloys, FUETAP, glass, Synroc D, and waste particles coated with carbon or carbon plus SiC  

SciTech Connect

Compatibility studies were conducted between 7 waste forms and 15 potential canister structural materials. The waste forms were Al-Si and Pb-Sn matrix alloys, FUETAP, glass, Synroc D, and waste particles coated with carbon or carbon plus silicon carbide. The canister materials included carbon steel (bare and with chromium or nickel coatings), copper, Monel, Cu-35% Ni, titanium (grades 2 and 12), several Inconels, aluminum alloy 5052, and two stainless steels. Tests of either 6888 or 8821 h were conducted at 100 and 300/sup 0/C, which bracket the low and high limits expected during storage. Glass and FUETAP evolved sulfur, which reacted preferentially with copper, nickel, and alloys of these metals. The Pb-Sn matrix alloy stuck to all samples and the carbon-coated particles to most samples at 300/sup 0/C, but the extent of chemical reaction was not determined. Testing for 0.5 h at 800/sup 0/C was included because it is representative of a transportation accident and is required of casks containing nuclear materials. During these tests (1) glass and FUETAP evolved sulfur, (2) FUETAP evolved large amounts of gas, (3) Synroc stuck to titanium alloys, (4) glass was molten, and (5) both matrix alloys were molten with considerable chemical interactions with many of the canister samples. If this test condition were imposed on waste canisters, it would be design limiting in many waste storage concepts.

McCoy, H.E.

1983-01-01

267

Influence of shear force on floc properties and residual aluminum in humic acid treatment by nano-Al??.  

PubMed

The impacts of various shear forces on floc sizes and structures in humic acid coagulations by polyaluminum chloride (PACl) and nano-Al13 were comparatively studied in this paper. The dynamic floc size was monitored by use of a laser diffraction particle sizing device. The floc structure was evaluated in terms of fractal dimension, analyzed by small-angle laser light scattering (SALLS). The effect of increased shear rate on residual Al of the coagulation effluents was then analyzed on the basis of different floc characteristics generated under various shear conditions. The results showed that floc size decreased with the increasing shear rate for both Al13 and PACl. Besides, floc strength and re-formation ability were also weakened by the enhanced shear force. Al13 resulted in small, strong and better recoverable flocs than PACl and moreover, in the shear range of 100-300 revolution per minute (rpm) (G=40.7-178.3s(-1)), the characteristics of HA-Al13 flocs displayed smaller scale changes than those of HA-PACl flocs. The results of residual Al measurements proved that with shear increased, the residual Al increased continuously but Al13 presented less sensitivity to the varying shear forces. PACl contributed higher residual Al than Al13 under the same shear condition. PMID:24583809

Xu, Weiying; Gao, Baoyu; Du, Bin; Xu, Zhenghe; Zhang, Yongfang; Wei, Dong

2014-04-30

268

Characterization of Hypereutectic Al20wt%Si\\/TiCp Metal Matrix Composite  

Microsoft Academic Search

Hypereutectic Al-Si alloys are one of the most interesting material for high strength structural components because they have low coefficient of thermal expansion (CTE) as well as high wear resistance and mechanical properties. However, Al-based alloys have lower hardness and wear resistance than ferrous alloys and these disadvantages restrict the use of al-based alloy. They could be overcome by making

Jinmyung Choi; Yongho Park; Yongjin Kim

2009-01-01

269

Photoemission study of tris(8-hydroxyquinoline) aluminum/aluminum oxide/tris(8-hydroxyquinoline) aluminum interface  

SciTech Connect

The evolution of the interface electronic structure of a sandwich structure involving aluminum oxide and tris(8-hydroxyquinoline) aluminum (Alq), i.e. (Alq/AlO{sub x}/Alq), has been investigated with photoemission spectroscopy. Strong chemical reactions have been observed due to aluminum deposition onto the Alq substrate. The subsequent oxygen exposure releases some of the Alq molecules from the interaction with aluminum. Finally, the deposition of the top Alq layer leads to an asymmetry in the electronic energy level alignment with respect to the AlO{sub x} interlayer.

Ding Huanjun; Zorba, Serkan; Gao Yongli; Ma Liping; Yang Yang [Department of Physics and Astronomy, University of Rochester, Rochester, New York 14627 (United States); Department of Materials Science and Engineering, University of California, Los Angeles, California 90095 (United States)

2006-12-01

270

Molecular cluster models of aluminum oxide and aluminum hydroxide surfaces  

Microsoft Academic Search

Ab initio, molecular orbital calculations for two different Hartree-Fock basis levels were performed on clusters in the system Al-O-H, and tested by comparing derived vibrational frequencies to the measured values for aluminum oxides and aluminum oxyhydroxide minerals. Models were chosen to reflect surface groups that may be present on aluminous minerals such as a-Al2O3 (corundum) and Al(OH)3 (gibbsite). Protonation and

J. D. KUBICKI; S. E. APITZ

1998-01-01

271

Aluminum Hydroxide  

MedlinePLUS

Aluminum hydroxide is used for the relief of heartburn, sour stomach, and peptic ulcer pain and to ... Aluminum hydroxide comes as a capsule, a tablet, and an oral liquid and suspension. The dose and ...

272

Effect of Long Aging on the Resistivity Properties of Aluminum Doped YBa2Cu3- y Al y O7- ? Single Crystals with a Given Twin Boundary Topology  

NASA Astrophysics Data System (ADS)

We investigate the conducting properties in the basal ab-plane before and after a long time exposure in air atmosphere of aluminum doped YBa2Cu3- y Al y O7- ? single crystals. Prolonged exposure leads to an increase of the effective scattering centers of the normal carriers. The excess conductivity in a wide temperature range has exponential temperature dependence and near the critical temperature ( T c ) can be adequately described within the Aslamazov-Larkin theoretical model. Nevertheless, the description of the excess conductivity through the relation , can be interpreted in terms of the mean-field theory, where T ? is the mean field temperature of the superconducting transition and the temperature dependence of the pseudo-gap is satisfactorily described by the BEC-BCS crossover theory. It is determined that the prolonged exposure increases significantly the temperature range of the implementation of the pseudogap state, thus narrowing the linear section of the resistivity dependence ? ab ( T).

Vovk, R. V.; Vovk, N. R.; Goulatis, I. L.; Chroneos, A.

2014-02-01

273

'Forbidden' reflections in resonant diffraction of synchrotron radiation in yttrium aluminum garnet Y{sub 3}Al{sub 5}O{sub 12}  

SciTech Connect

The purely resonant Bragg reflections (13, 13, 0) and (14, 0, 0) in yttrium aluminum garnet Y{sub 3}Al{sub 5}O{sub 12} at energies near the K absorption edge of yttrium have been studied experimentally and theoretically. The anisotropic tensor atomic factor of yttrium corresponding to dipole-dipole resonance transitions depends on three independent parameters changing with energy. The intensities of the reflections (14, 0, 0) and (13, 13, 0) are shown to depend on the parameter difference f{sub 1}(E) - f{sub 2}(E) and the parameter f{sub 3}(E), respectively, which are attributable to distortions of the wave functions of the excited atoms and change greatly with photon energy E. Studying various reflections has allowed one to determine the various components of the tensor atomic factor and to compare them with the results of numerical calculations.

Mukhamedzhanov, E. Kh.; Kovalchuk, M. V.; Borisov, M. M. ['Kurchatov Institute' Russian Research Center (Russian Federation); Ovchinnikova, E. N., E-mail: ovtchin@gmail.com; Oreshko, A. P. [Moscow State University (Russian Federation); Dmitrienko, V. E. [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation)

2011-01-15

274

Extracting aluminum from dross tailings  

NASA Astrophysics Data System (ADS)

Aluminum dross tailings, an industrial waste, from the Egyptian Aluminium Company (Egyptalum) was used to produce two types of alums: aluminum-sulfate alum [itAl2(SO4)3.12H2O] and ammonium-aluminum alum [ (NH 4)2SO4AL2(SO4)3.24H2O]. This was carried out in two processes. The first process is leaching the impurities using diluted H2SO4 with different solid/liquid ratios at different temperatures to dissolve the impurities present in the starting material in the form of solute sulfates. The second process is the extraction of aluminum (as aluminum sulfate) from the purifi ed aluminum dross tailings thus produced. The effects of temperature, time of reaction, and acid concentration on leaching and extraction processes were studied. The product alums were analyzed using x-ray diffraction and thermal analysis techniques.

Amer, A. M.

2002-11-01

275

Growth of aluminum-free porous oxide layers on titanium and its alloys Ti-6Al-4V and Ti-6Al-7Nb by micro-arc oxidation.  

PubMed

The growth of oxides on the surfaces of pure Ti and two of its ternary alloys, Ti-6Al-4V and Ti-6Al-7Nb, by micro-arc oxidation (MAO) in a pH 5 phosphate buffer was investigated. The primary aim was to form thick, porous, and aluminum-free oxide layers, because these characteristics favor bonding between bone and metal when the latter is implanted in the human body. On Ti, Ti-6Al-4 V, and Ti-6Al-7Nb, the oxides exhibited breakdown potentials of about 200 V, 130 V, and 140 V, respectively, indicating that the oxide formed on the pure metal is the most stable. The use of the MAO procedure led to the formation of highly porous oxides, with a uniform distribution of pores; the pores varied in size, depending on the anodizing applied voltage and time. Irrespective of the material being anodized, Raman analyses allowed us to determine that the oxide films consisted mainly of the anatase phase of TiO2, and XPS results indicated that this oxide is free of Al and any other alloying element. PMID:24907769

Duarte, Las T; Bolfarini, Claudemiro; Biaggio, Sonia R; Rocha-Filho, Romeu C; Nascente, Pedro A P

2014-08-01

276

Morphological effects in the chemical and photoluminescent behavior of aluminum tris(8-hydroxyquinoline) (AlQ{sub 3})  

SciTech Connect

Light emitting diodes (LEDs) based either on sublimable organics or polymeric materials have attracted considerable attention from both the scientific and technological fields. Aluminum tris(8-hydroxyquinoline) (Alq{sub 3}) is presently considered one of the most reliable electron transporting and emitting materials for molecular-based organic light emitting diodes (OLEDs). This paper discusses the effects of sample morphology on the hydrolysis and photoluminescence response of Alq{sub 3}. The evolution of 8-hydroxyquinoline (8-Hq), a volatile byproduct of the hydrolysis of Alq{sub 3}, was quantified using gas chromatography/mass spectroscopy (GC/MS) analysis on samples of different morphology. Annealed (more crystalline) samples exhibited greater chemical stability than freshly sublimed films, at the expense of photoluminescence efficiency. These phenomena are discussed with respect to possible failure mechanisms that Alq{sub 3}-based OLEDs might undergo during prolonged operation.

Higginson, K.A.; Zhang, X.M.; Papadimitrakopoulos, F.

1998-07-01

277

Ultrathin aluminum oxide films: Al-sublattice structure and the effect of substrate on ad-metal adhesion  

SciTech Connect

First principles density-functional slab calculations are used to study 5 {angstrom} (two O-layer) Al{sub 2}O{sub 3} films on Ru(0001) and Al(111). Using larger unit cells than in a recent study, it is found that the lowest energy stable film has an even mix of tetrahedral (t) and octahedral (o) site Al ions, and thus most closely resembles the {kappa}-phase of bulk alumina. Here, alternating zig-zag rows of t and o occur within the surface plane, resulting in a greater average lateral separation of the Al-ions than with pure t or o. A second structure with an even mix of t and o has also been found, consisting of alternating stripes. These patterns mix easily, can exist in three equivalent directions on basal substrates, and can also be displaced laterally, suggesting a mechanism for a loss of long-range order in the Al-sublattice. While the latter would cause the film to appear amorphous in diffraction experiments, local coordination and film density are little affected. On a film supported by rigid Ru(0001), overlayers of Cu, Pd, and Pt bind similarly as on bulk truncated {alpha}-Al{sub 2}O{sub 3}(0001). However, when the film is supported by soft Al(111), the adhesion of Cu, Pd, and Pt metal overlayers is significantly increased: Oxide-surface Al atoms rise so only they contact the overlayer, while substrate Al metal atoms migrate into the oxide film. Thus the binding energy of metal overlayers is strongly substrate dependent, and these numbers for the above Pd-overlayer systems bracket a recent experimentally derived value for a film on NiAl(110).

JENNISON,DWIGHT R.; BOGICEVIC,ALEXANDER

2000-03-06

278

Microstructure and wear properties of Al2O3-CeO2/Ni-base alloy composite coatings on aluminum alloys by plasma spray  

NASA Astrophysics Data System (ADS)

Al2O3 and CeO2 particles reinforced Ni-base alloy composite coatings were prepared on aluminum alloy 7005 by plasma spray. The microstructure, microhardness, fracture toughness, critical bonding force and the wear behavior and mechanisms of the composite coatings were investigated. It is found that CeO2 particles can refine crystal grains, reduce porosity and unmelted Al2O3 particles in the composite coatings. The microhardness, fracture toughness, critical bonding force and wear resistance of the composite coatings are enhanced due to synergistic strengthening effects of Al2O3 and CeO2 particles. The friction coefficients and wear losses increase as loads increase. At the loads of 3-6 N, the composite coatings experience local plastic deformation and micro-cutting wear. At the loads in the range of 9-12 N, the calculated maximum contact stress and maximum tensile stress on friction surfaces increase leading to plastic deformation induced working hardening. The wear mechanisms change into micro-brittle fracture wear and slight oxidative wear.

He, Long; Tan, Yefa; Wang, Xiaolong; Xu, Ting; Hong, Xiang

2014-09-01

279

Design and fabrication of a lightweight laser scanning mirror from metal-matrix composites  

Microsoft Academic Search

This paper discusses the design and fabrication of ultra lightweight laser scanning mirrors from two types of metal-matrix composites for the next generation Space Vision System (SVS). The materials selected for this study were SiC particulate reinforced aluminum composite and beryllium-aluminum (AlBeMet) composite. Three mirror designs were made and compared in terms of mass, rotating inertia and first mode natural

Xin-Xiang Jiang; Denis G. Laurin; Daniel Levesque; Darius Nikanpour

2001-01-01

280

Production of aluminum metal by electrolysis of aluminum sulfide  

DOEpatents

Production of metallic aluminum by the electrolysis of Al.sub.2 S.sub.3 at 700.degree.-800.degree. C. in a chloride melt composed of one or more alkali metal chlorides, and one or more alkaline earth metal chlorides and/or aluminum chloride to provide improved operating characteristics of the process.

Minh, Nguyen Q. (Woodridge, IL); Loutfy, Raouf O. (Tucson, AZ); Yao, Neng-Ping (Clarendon Hills, IL)

1984-01-01

281

Production of aluminum metal by electrolysis of aluminum sulfide  

DOEpatents

Metallic aluminum may be produced by the electrolysis of Al/sub 2/S/sub 3/ at 700 to 800/sup 0/C in a chloride melt composed of one or more alkali metal chlorides, and one or more alkaline earth metal chlorides and/or aluminum chloride to provide improved operating characteristics of the process.

Minh, N.Q.; Loutfy, R.O.; Yao, N.P.

1982-04-01

282

Tungsten wire/FeCrAlY matrix turbine blade fabrication study  

NASA Technical Reports Server (NTRS)

The objective was to establish a viable FRS monotape technology base to fabricate a complex, advanced turbine blade. All elements of monotape fabrication were addressed. A new process for incorporation of the matrix, including bi-alloy matrices, was developed. Bonding, cleaning, cutting, sizing, and forming parameters were established. These monotapes were then used to fabricate a 48 ply solid JT9D-7F 1st stage turbine blade. Core technology was then developed and first a 12 ply and then a 7 ply shell hollow airfoil was fabricated. As the fabrication technology advanced, additional airfoils incorporated further elements of sophistication, by introducing in sequence bonded root blocks, cross-plying, bi-metallic matrix, tip cap, trailing edge slots, and impingement inserts.

Melnyk, P.; Fleck, J. N.

1979-01-01

283

Development of Ta-matrix Nb3Al Strand and Cable for High-Field Accelerator Magnet  

SciTech Connect

Research and development of Nb{sub 3}Al strands and cables for a high field accelerator magnet is ongoing under the framework of the CERN-KEK collaboration. In this program, new Ta-matrix Nb{sub 3}Al strands were developed and their mechanical properties and superconducting properties were studied. The non-Cu J{sub c} values of these strands were 750 {approx} 800 A/mm{sup 2} at 15 T and 4.2 K. Using these strands, test fabrication of 27-strand Rutherford cable was carried out in collaboration with NIMS and Fermilab. The properties of the strands extracted from the cable were examined and it was found that there was no degradation of the superconducting properties of the strands. In this paper, we report the fabrication of the strands and the cable in brief and present some of the results obtained by studying their properties.

Tsuchiya, K.; Ghosh, A.; Kikuchi, A.; Takeuchi, T.; Banno, N.; Iijima, Y.; Nimori, S.; Takigawa, H.; Terashima, A.; Nakamoto, T.; Kuroda, Y.; Maruyama, M.; Takao, T.; Tanaka, K.; Nakagawa, K.; Barzi, E.; Yamada, R.; Zlobin, A.

2011-08-03

284

Effect of chromium and aluminum on the mechanical and oxidation properties of an iron-nickel-base superalloy. [Cr varied from 12-0 wt % and Al from 1. 5-6 wt %  

Microsoft Academic Search

The effects of Cr and Al on the mechanical and oxidation properties of a series of γ strengthened alloys based on CG27 were studied. The series was based on the reduction of Cr from 12 w\\/o to Ow\\/o. Aluminum was increased from 1.5w\\/oAl to 6w\\/o. Alloys were tested in tension at RT and 760C and stress rupture tested at 760C,

Schuon

2008-01-01

285

Effect of aluminum on mechanical solid-state alloying of iron with nitrogen in ball mill  

NASA Astrophysics Data System (ADS)

Mssbauer spectroscopy and X-ray diffraction analysis have been used to study mechanical solidstate alloying with nitrogen and chromium of iron and an Fe-3Al alloy in the process of the mechanical activation with chromium nitrides in a ball mill. It is shown that the deformation-induced dissolution of chromium nitrides in iron and Fe-3Al matrices results in the formation of substitutional chromium and interstitial nitrogen solid solutions. The alloying of iron with aluminum accelerates the process of the deformation-induced dissolution of chromium nitrides, but reduces the nitrogen content in the interstitial solid solution. Post-deformation annealing generally leads to the escape of aluminum from the matrix, the substitution of chromium for aluminum, and the formation of fine nitrides AlN.

Shabashov, V. A.; Kozlov, K. A.; Lyashkov, K. A.; Litvinov, A. V.; Dorofeev, G. A.; Titova, S. G.; Fedorenko, V. V.

2012-10-01

286

Influence of Cr and W alloying on the fiber-matrix interfacial shear strength in cast and directionally solidified sapphire NiAl composites  

SciTech Connect

Sapphire-reinforced NiAl matrix composites with chromium or tungsten as alloying additions were synthesized using casting and zone directional solidification (DS) techniques and characterized by a fiber pushout test as well as by microhardness measurements. The sapphire-NiAl(Cr) specimens exhibited an interlayer of Cr rich eutectic at the fiber-matrix interface and a higher interfacial shear strength compared to unalloyed sapphire-NiAl specimens processed under identical conditions. In contrast, the sapphire-NiAl(W) specimens did not show interfacial excess of tungsten rich phases, although the interfacial shear strength was high and comparable to that of sapphire-NiAl(Cr). The postdebond sliding stress was higher in sapphire-NiAl(Cr) than in sapphire-NiAl(W) due to interface enrichment with chromium particles. The matrix microhardness progressively decreased with increasing distance from the interface in both DS NiAl and NiAl(Cr) specimens. The study highlights the potential of casting and DS techniques to improve the toughness and strength of NiAl by designing dual-phase microstructures in NiAl alloys reinforced with sapphire fibers.

Asthana, R. [National Aeronautics and Space Administration, Cleveland, OH (United States). Lewis Research Center; Tiwari, R.; Tewari, S.N. [Cleveland State Univ., OH (United States). Dept. of Chemical Engineering

1995-08-01

287

Matrix effects in the energy dispersive X-ray analysis of CaO-Al(2)O(3)-MgO inclusions in steel.  

PubMed

Energy dispersive X-ray microanalysis of micron-sized inclusions in steel is of considerable industrial importance. Measured spectra and Monte Carlo simulations show a significant effect of the steel matrix on analysis of CaO-Al(2)O(3)-MgO inclusions: the steel matrix filters the softer (Al and Mg) characteristic X-rays, increasing the relative height of the Ca peak. Bulk matrix correction methods would not result in correct inclusion compositions, but operating at a lower acceleration voltage shifts the effect to smaller inclusion sizes. PMID:22051086

Pistorius, Petrus Christiaan; Verma, Neerav

2011-12-01

288

Aluminum toxicity and albumin.  

PubMed

During a study of priming solutions for extracorporeal membrane oxygenation (ECMO) in the intensive care nursery, it was discovered that those solutions using certain brands of 25% albumin contained aluminum levels within the toxic range. When the brand was changed to a brand known to have a lower aluminum (Al) content, a marked drop in priming solution Al levels was measured. The heat exchanger was examined as a possible source of soluble Al. No evidence of elevated Al levels was found in fluids perfusing this heat exchanger when compared with a stainless steel heat exchanger. The Al content of various blood products was evaluated along with various brands of 5% albumin and 25% albumin. PMID:2597561

Kelly, A T; Short, B L; Rains, T C; May, J C; Progar, J J

1989-01-01

289

Abrasive Wear Behavior of In Situ TiC Reinforced with Al-4.5%Cu Matrix  

NASA Astrophysics Data System (ADS)

The present work deals with the investigation on weight loss and coefficient of friction of TiC reinforced Al-4.5%Cu in situ metal matrix composites. Experiments were conducted using pin-on-disc apparatus against abrasive paper by varying the applied load, sliding distance, and weight percentage of TiC. The results indicated significant improvement in the mechanical properties and wear resistance of experimental composites as compared to the parent metal matrix. The percentage of porosity though increased with increasing TiC reinforcement. The variation of weight loss of composites increased linearly with increasing applied load and sliding distance, whereas decreased with increasing weight percentage of TiC reinforcement. The coefficient of friction decreased linearly with increasing applied load and TiC reinforcement. SEM micrographs of worn surfaces show a well compacted transfer layer of wear debris along with wear track over the sliding surface. Grooves, delamination, and crack propagation were also observed in all test samples. The effective depth of penetration and size of debris was seen to reduce with increasing wt.% of TiC reinforcement in metal matrix.

Kumar, Anand; Jha, P. K.; Mahapatra, M. M.

2014-03-01

290

Characterization of tool wear and weld optimization in the friction-stir welding of cast aluminum 359+20% SiC metal-matrix composite  

SciTech Connect

Tool wear for threaded steel pin tools declines with decreasing rotation speed and increasing traverse or weld speeds for the friction-stir welding (FSW) of Al 359+20% SiC metal-matrix composite (MMC). Less than 10% tool wear occurs when the threaded tool erodes to a self-optimized shape resembling a pseudo-hour glass at weld traverse distances in excess of 3 m. There is only a 7% reduction in the SiC mean particle size in the weld zone for self-optimized pin tools with no threads as compared with a 25% variation for threaded tools wearing significantly at the start of welding. The weld zone becomes more homogeneous for efficient welding with self-optimized tools, and there is a reduction in the weld zone grain size due to dynamic recrystallization, which facilitates the solid-state flow. Transmission electron microscopy shows little difference in the dislocation density from the base material to the weld zone, but there is a propensity of dislocation loops in the weld zone. The weld zone is observed to harden by as much as 30%, in contrast to the base material, as a consequence of the recrystallized grain size reduction and the SiC particles distributed therein.

Fernandez, G.J.; Murr, L.E

2004-03-15

291

Morphology and properties of a hybrid organic-inorganic system: Al nanoparticles embedded into CuPc thin film  

SciTech Connect

The evolution of the morphology and the electronic structure of the hybrid organic-inorganic system composed of aluminum nanoparticles (NPs) distributed in an organic semiconductor matrixcopper phthalocyanine (CuPc)as a function of nominal aluminum content was studied by transmission electron microscopy and by photoemission spectroscopy methods. The aluminum atoms deposited onto the CuPc surface diffuse into the organic matrix and self-assemble to NPs in a well-defined manner with a narrow diameter distribution, which depends on the amount of aluminum that is evaporated onto the CuPc film. We find clear evidence of a charge transfer from Al to CuPc and we have been able to determine the lattice sites where Al ions sit. The finally at high coverage about 64? the formation of metallic aluminum overlayer on CuPc thin film takes place.

Molodtsova, O. V.; Babenkov, S. V. [Deutsches Elektronen-Synchrotron DESY, Notkestrae 85, 22607 Hamburg (Germany); Aristova, I. M. [Institute of Solid State Physics of Russian Academy of Sciences, Chernogolovka 142432 (Russian Federation); Vilkov, O. V. [Helmholtz-Zentrum Berlin (HZB) fr Materialien und Energie, Albert-Einstein-Strae 15, 12489 Berlin (Germany); Aristov, V. Yu., E-mail: aristov@issp.ac.ru [Deutsches Elektronen-Synchrotron DESY, Notkestrae 85, 22607 Hamburg (Germany); Institute of Solid State Physics of Russian Academy of Sciences, Chernogolovka 142432 (Russian Federation); Institut fr Theoretische Physik, Universitt Hamburg, Jungiusstrae 9, D-20355 Hamburg (Germany)

2014-04-28

292

Durability of nickel-metal hydride (Ni-MH) battery cathode using nickel-aluminum layered double hydroxide/carbon (Ni-Al LDH/C) composite  

NASA Astrophysics Data System (ADS)

We report the durability of the optimized nickel-aluminum layered double hydroxide/carbon (Ni-Al LDH/C) composite prepared by liquid phase deposition (LPD) as cathode active materials in nickel metal hydride (Ni-MH) secondary battery. The positive electrode was used for charge-discharge measurements under two different current: 5mA for 300 cycles in half-cell conditions, and 5.8mA for 569 cycles in battery regime, respectively. The optimized Ni-Al LDH/C composite exhibits a good lifespan and stability with the capacity retention above 380mAhgcomp-1 over 869 cycles. Cyclic voltammetry shows that the ?-Ni(OH)2/?-NiOOH redox reaction is maintained even after 869 cycles, and the higher current regime is beneficial in terms of materials utilization. X-ray diffraction (XRD) patterns of the cathode after charge and discharge confirms that the ?-Ni(OH)2/?-NiOOH redox reaction occurs without any intermediate phase.

Blk, Alexis Bienvenu; Higuchi, Eiji; Inoue, Hiroshi; Mizuhata, Minoru

2014-02-01

293

Microstructure and high-temperature oxidation resistance of TiN/Ti3Al intermetallic matrix composite coatings on Ti6Al4V alloy surface by laser cladding  

NASA Astrophysics Data System (ADS)

A high-temperature oxidation resistant TiN embedded in Ti3Al intermetallic matrix composite coating was fabricated on titanium alloy Ti6Al4V surface by 6kW transverse-flow CO2 laser apparatus. The composition, morphology and microstructure of the laser clad TiN/Ti3Al intermetallic matrix composite coating were characterized by optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive spectrometer (EDS). In order to evaluate the high-temperature oxidation resistance of the composite coatings and the titanium alloy substrate, isothermal oxidation test was performed in a conventional high-temperature resistance furnace at 600C and 800C respectively. The result shows that the laser clad intermetallic composite coating has a rapidly solidified fine microstructure consisting of TiN primary phase (granular-like, flake-like, and dendrites), and uniformly distributed in the Ti3Al matrix. It indicates that a physical and chemical reaction between the Ti powder and AlN powder occurred completely under the laser irradiation. In addition, the microhardness of the TiN/Ti3Al intermetallic matrix composite coating is 844HV0.2, 3.4 times higher than that of the titanium alloy substrate. The high-temperature oxidation resistance test reveals that TiN/Ti3Al intermetallic matrix composite coating results in the better modification of high-temperature oxidation behavior than the titanium substrate. The excellent high-temperature oxidation resistance of the laser cladding layer is attributed to the formation of the reinforced phase TiN and Al2O3, TiO2 hybrid oxide. Therefore, the laser cladding TiN/Ti3Al intermetallic matrix composite coating is anticipated to be a promising oxidation resistance surface modification technique for Ti6Al4V alloy.

Zhang, Xiaowei; Liu, Hongxi; Wang, Chuanqi; Zeng, Weihua; Jiang, Yehua

2010-11-01

294

Aluminum-fly ash metal matrix composites for automotive parts. [Reports for October 1 to December 31, 1999, and January 1 - to March 31, 2000  

SciTech Connect

The highlights of this report are: (1) fly ash classified by less than 100 microns in size was mixed into a 300 lb melt of alloy 535 without the need of a magnesium additive; (2) a vibratory feeder fitted with a sieve was used as the means to minimize particle clustering while introducing fly ash into the aluminum alloy 535 melt; and (3) the industrial-size field test was successful in that sand mold castings and permanent mold castings of tensile bars, K mold bars, and ingots were made from aluminum alloy 535-fly ash mix. Use of aluminum alloy 535 containing 7% magnesium precluded the need to introduce additional magnesium into the melt. The third round of sand mold castings as well as permanent mold castings produced components and ingots of alloy 535 instead of alloy 356. The ingots will be remelted and cast into parts to assess the improvement of flyash distribution which occurs through reheating and the solidification wetting process. Microstructure analysis continues on sand and permanent mold castings to study particle distribution in the components. A prototype sand cast intake manifold casting was found to be pressure tight which is a major performance requirement for this part. Another heat of pressure die cast brackets of A380-classified fly ash will be made to examine their strength and fly ash distribution. Ingots of A356-fly ash have been made at Eck for remelting at Thompson Aluminum for squeeze casting into motor mounts.

Weiss, David; Purgert, Robert; Rhudy, Richard; Rohatgi, Pradeep

2000-04-21

295

Luminescent properties of trivalent praseodymium-doped lanthanum aluminum germanate LaAlGe2O7  

NASA Astrophysics Data System (ADS)

The luminescent characteristics of Pr3+-activated LaAlGe2O7 were investigated. In response to excitement using 448 nm blue light, the emission spectra involved most of the 3P0?3HJ transitions. The dominant emission came from the 3P0?3H4 transition at 487 nm. 1D2 fluorescence quenching was observed in highly doped samples and is related to the cross-relaxation processes among neighboring Pr3+ ions. In contrast with conventional Pr3+-activated phosphors, the extraordinary excitation spectra showed only intense f f transition of Pr3+ ions, while the 4f 5d transition was eliminated. This is ascribed to photoionization. By analyzing absorption and excitation spectra, it is recognized that no efficient energy transfer occurs between Pr3+ and the host lattice in LaAlGe2O7.

Li, Yu-Chun; Chang, Yen-Hwei; Lin, Yu-Feng; Chang, Yee-Shin; Lin, Yi-Jing

2007-10-01

296

Physical and Microstructure Properties of MgAl2C2 Matrix Composite Coating on Titanium  

NASA Astrophysics Data System (ADS)

This work is based on the dry sliding wear of the MgAl2C2-TiB2-FeSi composite coating deposited on a pure Ti using a laser cladding technique. Scanning electron microscope images indicate that the nanocrystals and amorphous phases are produced in such coating. X-ray diffraction result indicated that such coating mainly consists of MgAl2C2, Ti-B, Ti-Si, Fe-Al, Ti3SiC2, TiC and amorphous phases. The high resolution transmission electron microscope image indicated that the TiB nanorods were produced in the coating, which were surrounded by other fine precipitates, favoring the formation of a fine microstructure. With increase of the laser power from 0.85 kW to 1.00 kW, the micro-hardness decreased from 1350 1450 HV0.2 to 1200 1300 HV0.2. The wear volume loss of the laser clad coating was 1/7 of pure Ti.

Li, Peng

2014-12-01

297

Review Article Aluminum-Induced Entropy in Biological Systems  

E-print Network

Review Article Aluminum-Induced Entropy in Biological Systems: Implications for Neurological years, mining, smelting, and refining of aluminum (Al) in various forms have increasingly exposed living of the Al toxicants to which we are being exposed. 1. Introduction Aluminum (Al) is the most common metal

Seneff, Stephanie

298

Effect of processing cycles on aluminum/tungsten carbide composites prepared by continual annealing and press bonding process  

NASA Astrophysics Data System (ADS)

In the present work, a novel technique is introduced called CAPB (continual annealing and press bonding) for the manufacturing of a bulk aluminum matrix composite dispersed with 10 vol.% WC particles (Al/WCp). The microstructure of the fabricated composite after fourteen cycles of CAPB showed an excellent and homogenous distribution of the WC particles in the aluminum matrix and strong bonding between the various layers. The results indicated that the tensile strength of the composites increased with the number of CAPB cycles, and reached a maximum value of 140 MPa at the end of fourteenth cycle, which was 1.6 time higher than the obtained value for annealed aluminum (raw material, 88 MPa). Even though the elongation of the Al/WCp composite was reduced during the initial cycles of CAPB-ing, it increased significantly during the final cycles.

Amirkhanlou, Sajjad; Ketabchi, Mostafa; Parvin, Nader; Khorsand, Shohreh; Carreo, Fernando

2014-08-01

299

Pitting corrosion of aluminum  

Microsoft Academic Search

This review describes the experiments performed during the last few decades which enhance knowledge of the pitting of aluminum. Specifically, metastable and stable pits, pit chemistry and the effect of intermetallics on pitting are discussed. The properties of metastable alloys and inhibition of Al are also discussed.

Z Szklarska-Smialowska

1999-01-01

300

Mechanisms of aluminum tolerance  

Technology Transfer Automated Retrieval System (TEKTRAN)

Aluminum (Al) toxicity limits agricultural productivity over much of the worlds arable land by inhibiting root growth and development. Affected plants have difficulty in acquiring adequate water and nutrition from their soil environments and thus have stunted shoot development and diminished yield....

301

Preparation of aluminum(III) (bis(amido)pyridine)(thiolate) complexes: unexpected transmetalation mediated by LiAlH4  

PubMed Central

Treatment of an unsymmetrical bis(imino)pyridyl-thiolate zinc(II) complex [ZnII(LN3S)(OTf)] (1) with LiAlH4 results in the double reduction of the two imino groups in the ligand backbone, and at the same time causes a rare transmetalation reaction to occur. The products formed in this reaction are two novel aluminium(III) bis(amido)pyridyl-thiolate complexes [(R,S/S,R-[AlIII(LH2N3S)(THF)] (2a) and [(R,R/S,S-[AlIII(LH2N3S)(THF)] (2b), which are diastereomers of each other. These complexes have been characterized by single-crystal X-ray diffraction and 1H NMR spectroscopy. Single crystal X-ray structure analysis shows that the AlIII ion is bound in an almost idealized square pyramidal geometry in 2a, while being held in a more distorted square pyramidal geometry in 2b. The major difference between 2a and 2b arises in the orientation of the terminal methyl groups of the ligand backbone in relation to the AlIIIN3S plane. These two complexes are crystallized at different temperatures (room temperature vs ?35 C), allowing for their separate isolation. Structural analysis shows that these complexes are reduced by the formal addition of one hydride ion to each imino group, resulting in a deprotonated bis(amido)pyridyl-thiolate ligand. A detailed analysis of metrical parameters rules out the possibility of pure one- or two-electron reduction of the ?-conjugated bis(imino)pyridine framework. 1H NMR spectra reveal a rich pattern in solution indicating that the solution state structures for 2a and 2b match those observed in the solid-state crystal structures, and reveal that both complexes are severely conformationally restricted. Direct organic synthetic methods failed to produce the reduced bis(amino)pyridyl-thiol ligand in pure form, but during the course of these efforts an unusual unsymmetrical aminopyridyl ketone, 1-(6-(1-(2,6-diisopropylphenylamino)ethyl)pyridin-2-yl)ethanone was synthesized in good yield and can be used as a possible precursor for further ligand development. PMID:22345823

Badiei, Yosra M.; Jiang, Yunbo; Widger, Leland R.; Siegler, Maxime A.

2011-01-01

302

Effect of alternative aging process on the fracture and interfacial properties of particulate Al2O3-reinforced Al (6061) metal matrix composite  

NASA Astrophysics Data System (ADS)

The effects of different aging processes on ductility, fracture, and interfacial properties in particulate Al2O3-reinforced Al (6061) metal-matrix composite (MMCs) were studied. Tensile tests based on relevant ASTM standards were performed to investigate the mechanical responses of specimens under different heat-treatment conditions. Scanning electron microscopy (SEM), field-emission SEM (FESEM), and transmission electron microscopy (TEM) studies were carried out to correlate fracture mechanism(s) with microstructural features. Based on the experimental results, the overall effect of heat treatment on tensile properties is similar to that in the monolithic alloy, however, the rate of recovery in fracture-related properties, such as elongation to fracture, is lower in the overaged condition for the MMC samples. To explain this low recovery behavior of overaged MMCs, the following observations have been taken into account: (1) a shift of the materials behavior from particle fracture to interface (or near-interface) debonding fracture, when moving from the underaged to overaged regime, and (2) more frequent observations of interfacial reaction products (spinel) on the fracture surface of overaged specimens. The presence/formation of spinel phase at the interface was recognized as the main cause of this behavior. Although spinel products mainly form during material processing, they may continue to form in the solid state as well. As a result, the surface morphology of the spinel phase in the underaged specimens is different from that in the overaged specimens.

Shakeri, H. R.; Wang, Zhirui

2002-06-01

303

Li.sub.2 O-Al.sub.2 O.sub.3 -SiO.sub.2 glass ceramic-aluminum containing austenitic stainless steel composite body and a method of producing the same  

DOEpatents

The present invention relates to a hermetically sealed Li.sub.2 O-Al.sub.2 O.sub.3 -SiO.sub.2 glass ceramic-aluminum containing stainless steel composite body and a method of producing the body. The composite body includes an oxide interfacial region between the glass ceramic and metal, wherein the interfacial region consists essentially of an Al.sub.2 O.sub.3 layer. The interfacial Al.sub.2 O.sub.3 region includes constituents of both the metal and glass ceramic.

Cassidy, Roger T. (Monroe, OH)

1990-05-01

304

Stress Corrosion Cracking of Al-Mg and Mg-Al Alloys  

SciTech Connect

Aluminum and magnesium based alloys are being used for reducing the weight of automobiles. For structural applications they must have adequate stress corrosion resistance and yet, under some circumstances, stress corrosion cracking can occur in both alloy systems. Precipitation of the Mg rich Beta-phase (Al3Mg2) at grain boundaries of Al-Mg alloys and the Beta-phase (Mg17Al12) at grain boundaries of the Mg-Al alloys are critical factors in their stress corrosion performance. In Mg-Al, the Beta-phase is cathodic to the matrix while in the Al-Mg case, the Beta-phase is anodic to the matrix. These phases produce localized galvanic induced-corrosion that leads to intergranular stress corrosion cracking and cracking growth rates of 5 and 103 times faster than the solution treated condition, for Al-Mg and Mg-Al, respectively.

Jones, Russell H.; Vetrano, John S.; Windisch, Charles F.

2004-12-01

305

Influence of Lubricants on Wear and Self-Lubricating Mechanisms of Ni3Al Matrix Self-Lubricating Composites  

NASA Astrophysics Data System (ADS)

A research is conducted on the possible beneficial synergistic effects of multiple additives in self-lubricating composites for use in high temperature friction and wear-related mechanical assemblies. Dry sliding tribological tests of Ni3Al matrix self-lubricating composites (NMSCs) on a HT-1000 ball-on-disk high-temperature tribometer are undertaken against Si3N4 at 25-800 C. The results show that the subsurface microstructures beneath wear scar of NMSCs change with addition of different lubricants, which have great effects on tribological mechanisms and tribological performances. NMSC with addition of MoS2 and Ti3SiC2 exhibits distinct subsurface microstructure beneath wear scar and excellent tribological performance among all samples.

Yao, Jie; Shi, Xiaoliang; Zhai, Wenzheng; Xu, Zengshi; Ibrahim, Ahmed Mohamed Mahmoud; Zhu, Qingshuai; Xiao, Yecheng; Chen, Long; Zhang, Qiaoxin

2015-01-01

306

Tribological Properties of Al-SiC Metal Matrix Composites: A Comparison Between Sand Cast and Squeeze Cast Techniques  

NASA Astrophysics Data System (ADS)

Tribological behaviour of Al-SiC metal matrix composites prepared using two different fabrication techniques, viz. sand cast and squeeze cast techniques are studied in a multi- tribotester (TR-25, DUCOM, India) under dry sliding conditions and ambient atmosphere for varying volume fraction of reinforcement, applied load and sliding speed. Friction increases with increase in applied load and sliding speed and volume fraction of reinforcement. Wear test results show increased wear rates at higher load and speed, while increase in SiC volume fraction yields decrease in wear rate. Corrosion study conducted in 3.5 % NaCl solution shows that squeeze cast composites have better corrosion resistance than sand cast composites. Vickers's microhardness test shows improved hardness properties for squeeze cast composites compared to sand cast ones. The microstructure study of wear tracks reveals domination of abrasive wear with minor traces of adhesive wear.

Ghosh, S.; Sahoo, P.; Sutradhar, G.

2014-10-01

307

Electron Microscopy Characterization of an As-Fabricated Research Reactor Fuel Plate Comprised of U-7Mo Particles Dispersed in an Al-2Si Alloy Matrix  

SciTech Connect

To understand the microstructural development of nuclear fuel plates during irradiation, it is imperative to know the microstructure of a fuel plate after all the fabrication steps have been completed and before it is inserted into the reactor. To this end, a U7 wt.% Mo alloy research reactor dispersion fuel plate with Al2 wt.% Si matrix was destructively examined using scanning and transmission electron microscopy to characterize the developed microstructure after fabrication. Of particular interest for this study was how the Si that was added to the fuel matrix partitioned between the various fuel plate phases during fabrication. Si was added to the matrix so that the microstructure that developed during fuel fabrication would exhibit good irradiation behavior. SEM analysis was used to identify the representative microstructure, the compositions of the various phases, and the partitioning behavior of the fuel and matrix constituents. TEM analysis was employed to definitively identify the phases in the U7Mo alloy and the phases that formed due to diffusional interactions between the fuel particles and matrix during fuel plate fabrication. The TEM results are the first reported for an as-fabricated U7 wt.% Mo dispersion fuel plate with an Al alloy matrix. SEM results showed that a significant portion of the original ?-(UMo) fuel particles had transformed to a lamellar microstructure, comprised of a-U and either ? or ?' phases, and the fuel/matrix interaction layers were enriched in Si. TEM analysis identified an ordered fcc (UMo)(AlSi)3 type of phase, which formed at the decomposed U7Mo/matrix interface and extended into the lamellar microstructure. Some regions of the U7Mo particles retained the single-phase ?-(UMo). Small precipitate phases were observed in the fuel meat matrix that contained Fe, Al, and Si. The Si that is added to the matrix of a UMo dispersion fuel plate to improve irradiation performance appears to result in the creation of a Si-rich (UMo)(AlSi)3 type of fuel/matrix interaction layer during fabrication that appears to exhibit favorable behavior during irradiation compared to the behavior of the layers that form in UMo dispersion fuel plates without Si in the matrix.

Dennis D. Keiser, Jr.; J. Gan; J. F. Jue; B. D. Miller

2010-11-01

308

Aluminum Boats  

NSDL National Science Digital Library

Test the buoyancy of an aluminum foil boat and an aluminum foil ball. Why does the same material in different shapes sink or float? This activity explores the fact that the amount of water pushed aside by an object equals the force of water pushing upward on the object.

Center, Reuben H.

1999-01-01

309

The adhesion strength of the composition coating with a polymer matrix based on sodium carboxymethylcellulose with a metallic filler made from aluminum powder  

Microsoft Academic Search

In order to interpret the adhesion regularities, a way to make coagulants from fine fractions of aluminum powder on the microroughness\\u000a of steel surface, providing the adhesion strength of coating due to the van der Waals interaction forces, is suggested. The\\u000a role of the plasticizer as a factor increasing the adhesion strength of coatings via decreasing the internal stresses in

N. M. Antonova; V. I. Kulinich; V. Yu. Dorofeev

2008-01-01

310

In Situ Observation of Solidification Conditions in Pulsed Laser Welding of AL6082 Aluminum Alloys to Evaluate Their Impact on Hot Cracking Susceptibility  

NASA Astrophysics Data System (ADS)

The influence of laser pulse parameters on solidification conditions and hot crack formation in pulsed laser welding of Al6082 aluminum alloys was studied with the aid of high-speed cameras capturing visible and infrared radiation. Hot cracking was evaluated with respect to strain rate, strain, and metallurgical outcome. The strain rate was approximated by the product of interface velocity and temperature gradient at the interface. The temperature gradient decreases during the course of solidification and followed a specific course. The interface velocity was therefore used as an indicator for the strain rate, which increased in a logarithmic manner with respect to the slope of the laser pulse's cooling time. The accumulated strain was calculated by measuring the spot weld deformation during solidification. Within the heat-conduction welding regime, hot cracking can be reduced by lowering the interface velocity leading to a reduced strain rate and enhanced permeability of the dendritic microstructure. An over-proportional increase of the accumulated strain was observed for keyhole welding, which led to a high susceptibility to hot cracking regardless of the interface velocity. At low interface velocities, hot cracking was induced by extensive hydrogen diffusion at the solid-liquid interface, which promotes crack initiation.

von Witzendorff, Philipp; Kaierle, Stefan; Suttmann, Oliver; Overmeyer, Ludger

2015-01-01

311

Regeneration of aluminum hydride  

DOEpatents

The present invention provides methods and materials for the formation of hydrogen storage alanes, AlH.sub.x, where x is greater than 0 and less than or equal to 6 at reduced H.sub.2 pressures and temperatures. The methods rely upon reduction of the change in free energy of the reaction between aluminum and molecular H.sub.2. The change in free energy is reduced by lowering the entropy change during the reaction by providing aluminum in a state of high entropy, and by increasing the magnitude of the change in enthalpy of the reaction or combinations thereof.

Graetz, Jason Allan; Reilly, James J; Wegrzyn, James E

2012-09-18

312

Regeneration of aluminum hydride  

DOEpatents

The present invention provides methods and materials for the formation of hydrogen storage alanes, AlH.sub.x, where x is greater than 0 and less than or equal to 6 at reduced H.sub.2 pressures and temperatures. The methods rely upon reduction of the change in free energy of the reaction between aluminum and molecular H.sub.2. The change in free energy is reduced by lowering the entropy change during the reaction by providing aluminum in a state of high entropy, by increasing the magnitude of the change in enthalpy of the reaction or combinations thereof.

Graetz, Jason Allan (Mastic, NY); Reilly, James J. (Bellport, NY)

2009-04-21

313

Corrosion of Magnesium-Aluminum Alloys with Al-11Si/SiC Thermal Spray Composite Coatings in Chloride Solution  

NASA Astrophysics Data System (ADS)

Depositions of Al-11Si coatings reinforced with 5, 15, and 30 vol.% SiC particles (SiCp) were performed onto AZ31, AZ80, and AZ91D magnesium alloys. The influence of substrate composition and SiCp proportion on the anti-corrosion properties of composite coatings was evaluated using DC and AC electrochemical measurements in 3.5 wt.% NaCl solution at 22 C. The as-sprayed coatings were permeable to the saline solution, and galvanic corrosion occurred at the substrate/coating interface after immersion in the saline solution for a few hours. The addition of SiCp yielded coatings with higher porosity and less effectiveness against corrosion. The application of a cold-pressing post-treatment produced denser coatings with reduced surface roughness, improved hardness, and superior corrosion resistance. However, galvanic corrosion was observed after several days of immersion because of penetration of the 3.5 wt.% NaCl solution through the remaining pores in the coatings.

Arrabal, R.; Pardo, A.; Merino, M. C.; Mohedano, M.; Casajs, P.; Matykina, E.

2011-03-01

314

Comparison of the Booster Interface Temperature in Stainless Steel (SS) V-Channel versus the Aluminum (Al) Y-Channel Primer Chamber Assemblies (PCAs). Volume 1; Technical Assessment Report  

NASA Technical Reports Server (NTRS)

NASA's Technical Fellow for Propulsion, requested a technical assessment of the performance improvement achieved by the introduction of the stainless steel (SS) V-channel compared to the aluminum (Al) Y-channel Primer Chamber Assembly (PCA) design. The SS V-channel PCA was developed for NASA's Mars Science Laboratory (MSL) Project. The principle focus of the assessment was to measure the transient temperature at the booster interface with both designs. This document contains the findings of the assessment.

Garcia, Roberto; Saulsberry, Regor L.

2011-01-01

315

Aluminum induced proteome changes in tomato cotyledons  

Technology Transfer Automated Retrieval System (TEKTRAN)

Cotyledons of tomato seedlings that germinated in a 20 M AlK(SO4)2 solution remained chlorotic while those germinated in an aluminum free medium were normal (green) in color. Previously, we have reported the effect of aluminum toxicity on root proteome in tomato seedlings (Zhou et al. J Exp Bot, 20...

316

Application of noncontacting electromagnetic acoustic transducers (EMATS) for the characterization of the temperature dependent elastic properties in Gr/Al metal matrix composites  

NASA Astrophysics Data System (ADS)

Changes in the ultrasonic wave velocity along the direction of the reinforcing fibers in a graphite/aluminum composite sample were measured as a function of temperature. Plates of 6061 aluminum containing 35 percent continuous graphite fibers were subjected to repeated cooling-heating-cooling cycles, using a pair of electromagnetic acoustic transducers to measure temperature-dependent symmetric Lamb wave velocity. Compared with the temperature dependence of the Lamb wave in a homogeneous aluminum alloy plate and with usual dependence of wave propagation perpendicular to the fibers in reinforced metal composites, the temperature dependence for wave propagation along the direction of fibers in the Al/graphite plates was unusual in that the velocity increased with increasing temperature and with the development of hysteresis loops. This unusual behavior of the symmetric Lamb wave appeared to be closely related to the generation and relaxation of thermally induced stresses in the composite. The phenomenon appears to be dominated by the stress-dependent elastic properties of the fibers.

Liu, J. M.

317

High temperature stability, interface bonding, and mechanical behavior in {beta}-NiAl and Ni{sub 3}Al matrix composites with reinforcements modified by ion beam enhanced deposition. Progress summary report, June 1, 1993--May 31, 1994  

SciTech Connect

Diffusion-bonded NiAl-Al{sub 2}O{sub 3} and Ni{sub 3}Al-Al{sub 2}O{sub 3} couples were thermally fatigued at 900 C for 1500 and 3500 cycles. The fiber-matrix interface weakened after 3500 cycles for the Saphikon fibers, while the Altex, PRD-166, and FP fibers showed little, if any, degradation. Diffusion bonding of fibers to Nb matrix is being studied. Coating the fibers slightly increases the tensile strength and has a rule-of-mixtures effect on elastic modulus. Push-out tests on Sumitomo and FP fibers in Ni aluminide matrices were repeated. Al{sub 2}O{sub 3} was evaporated directly from pure oxide rod onto acoustically levitated Si carbide particles, using a down-firing, rod-fed electron beam hearth; superior coatings were subsequently produced using concurrent irradiation with 200-eV argon ion-assist beam. The assist beam produced adherent films with reduced tensile stresses. In diffusion bonding in B-doped Ni{sub 3}Al matrices subjected to compressive bonding at 40 MPa at 1100 C for 1 hr, the diffusion barriers failed to prevent catastrophic particle- matrix reaction, probably because of inadequate film quality. AlN coatings are currently being experimented with, produced by both reactive evaporation and by N{sup +}-ion enhanced deposition. A 3-kW rod-fed electron-beam-heated evaporation source has been brought into operation.

Grummon, D.S.

1993-01-21

318

High temperature stability, interface bonding, and mechanical behavior in [beta]-NiAl and Ni[sub 3]Al matrix composites with reinforcements modified by ion beam enhanced deposition  

SciTech Connect

Diffusion-bonded NiAl-Al[sub 2]O[sub 3] and Ni[sub 3]Al-Al[sub 2]O[sub 3] couples were thermally fatigued at 900 C for 1500 and 3500 cycles. The fiber-matrix interface weakened after 3500 cycles for the Saphikon fibers, while the Altex, PRD-166, and FP fibers showed little, if any, degradation. Diffusion bonding of fibers to Nb matrix is being studied. Coating the fibers slightly increases the tensile strength and has a rule-of-mixtures effect on elastic modulus. Push-out tests on Sumitomo and FP fibers in Ni aluminide matrices were repeated. Al[sub 2]O[sub 3] was evaporated directly from pure oxide rod onto acoustically levitated Si carbide particles, using a down-firing, rod-fed electron beam hearth; superior coatings were subsequently produced using concurrent irradiation with 200-eV argon ion-assist beam. The assist beam produced adherent films with reduced tensile stresses. In diffusion bonding in B-doped Ni[sub 3]Al matrices subjected to compressive bonding at 40 MPa at 1100 C for 1 hr, the diffusion barriers failed to prevent catastrophic particle- matrix reaction, probably because of inadequate film quality. AlN coatings are currently being experimented with, produced by both reactive evaporation and by N[sup +]-ion enhanced deposition. A 3-kW rod-fed electron-beam-heated evaporation source has been brought into operation.

Grummon, D.S.

1993-01-21

319

Suppression of activation energy and superconductivity by the addition of Al2O3 nanoparticles in CuTl-1223 matrix  

NASA Astrophysics Data System (ADS)

Low anisotropic (Cu0.5Tl0.5)Ba2Ca2Cu3O10-? (CuTl-1223) high Tc superconducting matrix was synthesized by solid-state reaction and Al2O3 nanoparticles were prepared separately by co-precipitation method. Al2O3 nanoparticles were added with different concentrations during the final sintering cycle of CuTl-1223 superconducting matrix to get the required (Al2O3)y/CuTl-1223, y = 0.0, 0.5, 0.7, 1.0, and 1.5 wt. %, composites. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy, energy dispersive X-ray, and dc-resistivity (?) measurements. The activation energy and superconductivity were suppressed with increasing concentration of Al2O3 nanoparticles in (CuTl-1223) matrix. The XRD analysis showed that the addition of Al2O3 nanoparticles did not affect the crystal structure of the parent CuTl-1223 superconducting phase. The suppression of activation energy and superconducting properties is most probably due to weak flux pinning in the samples. The possible reason of weak flux pinning is reduction of weak links and enhanced inter-grain coupling due to the presence of Al2O3 nanoparticles at the grain boundaries. The presence of Al2O3 nanoparticles at the grain boundaries possibly reduced the number of flux pinning centers, which were present in the form of weak links in the pure CuTl-1223 superconducting matrix. The increase in the values of inter-grain coupling (?) deduced from the fluctuation induced conductivity analysis with the increased concentration of Al2O3 nanoparticles is a theoretical evidence of improved inter-grain coupling.

Jabbar, Abdul; Qasim, Irfan; Mumtaz, M.; Zubair, M.; Nadeem, K.; Khurram, A. A.

2014-05-01

320

Aluminum Analysis.  

ERIC Educational Resources Information Center

Presents three problems based on the price of aluminum designed to encourage students to be cooperative and to use an investigative approach to learning. Students collect and synthesize information, analyze results, and draw conclusions. (AIM)

Sumrall, William J.

1998-01-01

321

High-field transport properties of aluminum-embedded aluminum oxide films  

Microsoft Academic Search

Current-voltage characteristics of aluminum-embedded aluminum oxide thin films with Al or Au electrodes, between 1501000 in thickness, prepared by thermic evaporation of pure aluminum in partial air pressure are studied. I-V characteristics of these films showed metallic conductivity, switching, and memory effects different than those observed in amorphous materials, and metal-oxide-metal diode characteristics as the amount of metallic aluminum

1973-01-01

322

Preparation of micro/nano-structure superhydrophobic film on aluminum plates using galvanic corrosion method.  

PubMed

A simple and novel approach has been developed to obtain a microporous film with compound nanoparticles on the surface of aluminum alloy substrate using the galvanic corrosion method. The wettability of the surface changes from hydrophilicity to superhydrophobicity after chemical modification with stearic acid (SA). The water contact angle (WCA) and sliding angle (WSA) of superhydrophobic aluminum alloy surface (SAAS) are 154 degrees and 9 degrees, respectively. The roughness of the aluminum substrate increases after the oxidation reaction. The porous aluminum matrix surface is covered with irregularly shaped holes with a mean radius of about 15 microm, similar to the surface papillae of natural Lotus leaf, with villus-like nanoparticles array on pore surfaces. The superhydrophobic property is attributed to this special surface morphology and low surface energy SA. X-ray powder diffraction (XRD) pattern and Energy Dispersive X-Ray Spectroscopy (EDS) spectrum indicate that Al2O3, Al(OH)3 and AIO(OH) has been formed on the surface of aluminum substrate after the oxidation reaction. The Raman spectra indicate that C-H bond from SA and the Al-O are formed on the SAAS. The as-formed SAAS has good stability. PMID:24245140

Wu, Ruomei; Chao, Guang Hua; Jiang, Haiyun; Pan, Anqiang; Chen, Hong; Yuan, Zhiqing; Liu, Qilong

2013-10-01

323

Combustion synthesis of TiB2-Al2O3-Al composite materials  

NASA Technical Reports Server (NTRS)

The oxide-aluminum exothermic reduction reaction is presently used in the combustion-synthesis of ceramic/metal composites. An excess of Al is used in the reacting materials, which rapidly generate enough heat to exceed Al's melting point. The molten Al thus evolved is allowed to infiltrate the porous ceramic matrix as the exothermic reaction proceeds; this feature of the process turns the disadvantage of high porosity levels in combustion-synthesized materials into an advantage. Attention is given to the system obtained with 3TiO2 + 3B2O3 + (10-x)Al starting materials.

Feng, H. J.; Moore, J. J.; Wirth, D. G.

1991-01-01

324

Aluminum Zintl anion moieties within sodium aluminum clusters  

SciTech Connect

Through a synergetic combination of anion photoelectron spectroscopy and density functional theory based calculations, we have established that aluminum moieties within selected sodium-aluminum clusters are Zintl anions. Sodiumaluminum cluster anions, Na{sub m}Al{sub n}{sup ?}, were generated in a pulsed arc discharge source. After mass selection, their photoelectron spectra were measured by a magnetic bottle, electron energy analyzer. Calculations on a select sub-set of stoichiometries provided geometric structures and full charge analyses for both cluster anions and their neutral cluster counterparts, as well as photodetachment transition energies (stick spectra), and fragment molecular orbital based correlation diagrams.

Wang, Haopeng; Zhang, Xinxing; Ko, Yeon Jae; Grubisic, Andrej; Li, Xiang; Gantefr, Gerd; Bowen, Kit H., E-mail: AKandalam@wcupa.edu, E-mail: kiran@mcneese.edu, E-mail: kbowen@jhu.edu [Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218 (United States); Schnckel, Hansgeorg [Institute of Inorganic Chemistry, Karlsruhe Institute of Technology, 76128 Karlsruhe (Germany)] [Institute of Inorganic Chemistry, Karlsruhe Institute of Technology, 76128 Karlsruhe (Germany); Eichhorn, Bryan W. [Department of Chemistry, University of Maryland at College Park, College Park, Maryland 20742 (United States)] [Department of Chemistry, University of Maryland at College Park, College Park, Maryland 20742 (United States); Lee, Mal-Soon; Jena, P. [Department of Physics, Virginia Commonwealth University, Richmond, Virginia 23284 (United States)] [Department of Physics, Virginia Commonwealth University, Richmond, Virginia 23284 (United States); Kandalam, Anil K., E-mail: AKandalam@wcupa.edu, E-mail: kiran@mcneese.edu, E-mail: kbowen@jhu.edu [Department of Physics, West Chester University of Pennsylvania, West Chester, Pennsylvania 19383 (United States); Kiran, Boggavarapu, E-mail: AKandalam@wcupa.edu, E-mail: kiran@mcneese.edu, E-mail: kbowen@jhu.edu [Department of Chemistry, McNeese State University, Lake Charles, Louisiana 70609 (United States)] [Department of Chemistry, McNeese State University, Lake Charles, Louisiana 70609 (United States)

2014-02-07

325

Reinforcement architectures and thermal fatigue in diamond particle-reinforced aluminum  

Microsoft Academic Search

Aluminum reinforced by 60vol.% diamond particles has been investigated as a potential heat sink material for high power electronics. Diamond (CD) is used as reinforcement contributing its high thermal conductivity (TC?1000WmK?1) and low coefficient thermal expansion (CTE?1ppmK?1). An Al matrix enables shaping and joining of the composite components. Interface bonding is improved by limited carbide formation induced by heat treatment

M. Schbel; H. P. Degischer; S. Vaucher; M. Hofmann; P. Cloetens

2010-01-01

326

Nucleation Catalysis in Aluminum Alloy A356 Using Nanoscale Inoculants  

NASA Astrophysics Data System (ADS)

Different types of nanoparticles in aluminum (Al) alloy A356 nanocomposites were shown to catalyze nucleation of the primary Al phase. Nanoparticles of SiC ?, TiC, Al2O3 ?, and Al2O3 ? were added to and dispersed in the A356 matrix as nucleation catalysts using an ultrasonic mixing technique. Using the droplet emulsion technique (DET), undercoolings in the nanocomposites were shown to be significantly reduced compared to the reference A356. None of the nanocomposites had a population of highly undercooled droplets that were observed in the reference samples. Also, with the exception of the A356/Al2O3 ? nanocomposite, all nanocomposites showed a reduction in undercooling necessary for the onset of primary Al nucleation. The observed nanocomposite undercoolings generally agreed with the undercooling necessary for free growth. The atomic structure of the particles showed an influence on nucleation potency as A356/Al2O3 ? nanocomposites had smaller undercoolings than A356/Al2O3 ? nanocomposites. The nucleation catalysis illustrates the feasibility of, and basis for, grain refinement in metal matrix nanocomposites (MMNCs).

de Cicco, Michael P.; Turng, Lih-Sheng; Li, Xiaochun; Perepezko, John H.

2011-08-01

327

Laser Welding of Aluminum and Aluminum Alloys  

E-print Network

.. ) Laser Welding of Aluminum and Aluminum Alloys Welds made with sharp bevel-groove weld aluminum and by aluminum alloy 5456 have been studied. The results indicate that initial absorption varies of the most dramatic illustrations of the differences in beam characteristics occurs when welding aluminum

Eagar, Thomas W.

328

Investigation on mechanical properties of AlZrCr- A12O3 nanocomposites fabricated by stir casting  

NASA Astrophysics Data System (ADS)

Aluminum alloy composite with nano Al2O3 reinforcement will be designed to have good mechanical properties that correspond to its application. The addition of nano Al2O3 in aluminum is to increase strength and stiffness. In this study aluminum matrix made as a master alloy with the addition of zirconium (Zr) and cerium (Ce) to form Al-Zr-Ce alloys which was reinforced with nanoscale alumina particles known as nano aluminum composite which has high strength and stiffness. Master alloy Al-Zr-Ce used as a matrix content of 0.12 wt% Zr and 0.13 wt% Ce, while Al2O3 nano particles (<100nm) used as reinforcement was various in the range of 0-3 Vf%. Aluminum composite was produced by stirring of molten metal with a rotational speed of 500 rpm at a temperature of 750C in an inert argon gas environment then characterized both mechanical properties and microstructure analysis. The tensile strength increased with increasing Al2O3 nano particles up to 1 Vf%. Mechanical properties of composites were slightly increased and there was no significant change in elongation and hardness, perhaps due to the non-uniformity distribution or clustering formation of particles in the matrix.

M, Kirman; Zulfia, Anne; Sutopo; Suharno, Bambang

2014-06-01

329

Fabrication and Characterization of Aluminum-Carbon Nanotube Powder and Polycarbonate\\/Aluminum-Carbon Nanotube Composites  

Microsoft Academic Search

Carbon nanotube reinforced aluminum powders (Al-CNT) were fabricated by ball milling. The morphology observed by a scanning electron microscope showed impregnation of CNTs on the surface of aluminum flakes (Al-flakes). Polycarbonate (PC)\\/Al-CNT nanocomposites were prepared by a twin-screw extruder. The electrical resistivity of PC\\/Al-flake composites did not change with Al-flake content, while that of PC\\/CNT nanocomposites decreased with increasing CNT

San Ha Hwang; Dae-Suk Bang; Kwan Han Yoon; Young-Bin Park; Dae-Yeol Lee; Sung-Sil Jeong

2010-01-01

330

Micromechanical analysis of filamentary metal matrix composites under longitudinal loading  

Microsoft Academic Search

A two-material composite cylinder model (CCM) was considered for the study of the mechanical behavior at different temperatures of a fiber-reinforced silicon carbide\\/aluminum (SiC\\/Al) composite. An elastoplastic analysis of the model was performed in which the fiber was assumed to be linear elastic and the matrix elastoplastic with work-hardening. The analysis was based on the deformation theory of plasticity in

E. E. Gdoutos; D. Karalekas; I. M. Daniel

1991-01-01

331

Properties of sulfur sorbents containing dispersed nickel in an Al{sub 2}O{sub 3} matrix  

SciTech Connect

For advanced coal gasification systems, regenerable sorbents are being developed to remove sulfur (S) from the hot product gas prior to its use in gas turbines and high-temperature fuel cells. Whereas zinc (Zn) base sorbents are attractive for these applications, they have limitations in high-temperature capability and in durability. Materials containing dispersed nickel (Ni) in an Al{sub 2}O{sub 3} matrix have the potential to be better in both respects. Their main limitation is that they do not reduce H{sub 2}S concentrations to the low parts per million (ppm) level. Results are reported here on the second phase of a program on dispersed Ni sorbents. Included are the results of crush strength, thermogravimetric analysis, and fixed-bed reactor experiments. An important conclusion drawn from the results is that chemisorption of H{sub 2}S plays a major role in reducing its concentration in gas exiting the bed below the levels expected from the Ni-Ni sulfide equilibrium.

Swisher, J.H.; Jhunjhunwala, M. [Southern Illinois Univ., Carbondale, IL (United States); Gasper-Galvin, L.D.; Gardner, T.H. [Dept. of Energy, Morgantown, WV (United States). Morgantown Energy Technology Center; Hammerbeck, K. [Oak Ridge Associated Universities, TN (United States)

1996-04-01

332

Charge storage behavior of nanostructures based on SiGe nanocrystals embedded in Al2O3 matrix  

NASA Astrophysics Data System (ADS)

The charge storage behavior of nanostructures based on Si1- x Ge x (0 ? x ? 1) nanocrystals (NCs) in an Al2O3 matrix was investigated. The structures have been grown by RF magnetron sputtering and subsequently annealed at temperatures ranging from 700 C to 1000 C for 30 min in nitrogen ambient. The stoichiometry of the SiGe NCs and the alumina crystalline structure were found to be significantly dependent on the RF power and the annealing temperature. The sizes of the SiGe NCs and their distribution were investigated by grazing incidence small angle X-ray scattering (GISAXS). The capacitance-voltage ( C- V) and conductance-voltage ( G- V) measurements were performed to investigate the charge trapping characteristics of the memory structures. The C- V hysteresis width depends on variations in the crystalline structure resulting from different annealing temperatures. It is also shown that charge injection is governed by the Fowler-Nordheim tunnel mechanism for higher electric fields.

Vieira, Eliana M. F.; Levichev, Sergey; Dias, Carlos J.; Igreja, Rui; Buljan, Maja; Bernstorff, Sigrid; Conde, Olinda; Chahboun, Adil; Rolo, Anabela G.; Gomes, Maria J. M.

2013-07-01

333

Synthesis of high-surface-area ?-Al2O3 from aluminum scrap and its use for the adsorption of metals: Pb(II), Cd(II) and Zn(II)  

NASA Astrophysics Data System (ADS)

Several types of alumina were synthesized from sodium aluminate (NaAlO2) by precipitation with sulfuric acid (H2SO4) and subsequently calcination at 500 C to obtain ?-Al2O3. The precursor aluminate was derived from aluminum scrap. The various ?-Al2O3 synthesized were characterized by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), adsorption-desorption of N2 (SBET) and scanning electron microscopy (SEM). XRD revealed that distinct phases of Al2O3 were formed during thermal treatment. Moreover, it was observed that conditions of synthesis (pH, aging time and temperature) strongly affect the physicochemical properties of the alumina. A high-surface-area alumina (371 m2 g-1) was synthesized under mild conditions, from inexpensive raw materials. These aluminas were tested for the adsorption of Cd(II), Zn(II) and Pb(II) from aqueous solution at toxic metal concentrations, and isotherms were determined.

Asencios, Yvan J. O.; Sun-Kou, Mara R.

2012-10-01

334

NASA-UVa light aerospace alloy and structures technology program supplement: Aluminum-based materials for high speed aircraft  

NASA Technical Reports Server (NTRS)

This report on the NASA-UVa light aerospace alloy and structure technology program supplement: Aluminum-Based Materials for High Speed Aircraft covers the period from July 1, 1992. The objective of the research is to develop aluminum alloys and aluminum matrix composites for the airframe which can efficiently perform in the HSCT environment for periods as long as 60,000 hours (certification for 120,000 hours) and, at the same time, meet the cost and weight requirements for an economically viable aircraft. Current industry baselines focus on flight at Mach 2.4. The research covers four major materials systems: (1) Ingot metallurgy 2XXX, 6XXX, and 8XXX alloys, (2) Powder metallurgy 2XXX alloys, (3) Rapidly solidified, dispersion strengthened Al-Fe-X alloys, and (4) Discontinuously reinforced metal matrix composites. There are ten major tasks in the program which also include evaluation and trade-off studies by Boeing and Douglas aircraft companies.

Starke, E. A., Jr. (editor)

1995-01-01

335

21 CFR 73.1010 - Alumina (dried aluminum hydroxide).  

Code of Federal Regulations, 2010 CFR

...hydroxide). (a) Identity. (1) The color additive alumina (dried aluminum hydroxide) is a white, odorless, tasteless, amorphous powder consisting essentially of aluminum hydroxide (Al2 O3 XH2 O). (2) Color...

2010-04-01

336

Light-weight, high-performance metal matrix composites  

NASA Technical Reports Server (NTRS)

Recent years have seen the development of a wide range of light-weight, high-performance aluminum powder metallurgy composites that combine both standard (6061 and 2124) and specialty matrix compositions (Al-Mg-Cu-Li and Al-Fe-Ce) with a wide variety of discontinuous reinforcements (Al2O3, B4C, and SiC). This paper reviews the fabrication and damage tolerance performance of these light-weight, high-performance composites. Particular attention is given to developing a general framework for understanding the interrelationship existing between microstructure, thermomechanical processing and ductility/fracture toughness behavior in these composite systems.

Rack, H. J.

1988-01-01

337

Crystallographic study of grain refinement in aluminum alloys using the edge-to-edge matching model  

SciTech Connect

The edge-to-edge matching model for describing the interfacial crystallographic characteristics between two phases that are related by reproducible orientation relationships has been applied to the typical grain refiners in aluminum alloys. Excellent atomic matching between Al{sub 3}Ti nucleating substrates, known to be effective nucleation sites for primary Al, and the Al matrix in both close packed directions and close packed planes containing these directions have been identified. The crystallographic features of the grain refiner and the Al matrix are very consistent with the edge-to-edge matching model. For three other typical grain refiners for Al alloys, TiC (when a = 0.4328 nm), TiB{sub 2} and AlB{sub 2}, the matching only occurs between the close packed directions in both phases and between the second close packed plane of the Al matrix and the second close packed plane of the refiners. According to the model, it is predicted that Al{sub 3}Ti is a more powerful nucleating substrate for Al alloy than TiC, TiB{sub 2} and AlB{sub 2}. This agrees with the previous experimental results. The present work shows that the edge-to-edge matching model has the potential to be a powerful tool in discovering new and more powerful grain refiners for Al alloys.

Zhang, M.-X. [Division of Materials, School of Engineering, University of Queensland, St. Lucia, QLD 4072 (Australia)]. E-mail: m.zhang@minmet.uq.edu.au; Kelly, P.M. [Division of Materials, School of Engineering, University of Queensland, St. Lucia, QLD 4072 (Australia); Easton, M.A. [School of Physics and Materials Engineering, Monash University, Clayton, VIC 3800 (Australia); Taylor, J.A. [Division of Materials, School of Engineering, University of Queensland, St. Lucia, QLD 4072 (Australia)

2005-03-01

338

Ultrasonic-assisted synthesis of surface-clean TiB2 nanoparticles and their improved dispersion and capture in Al-matrix nanocomposites.  

PubMed

Metal-matrix nanocomposites (MMNCs) have great potential for a wide range of applications. To provide high performance, effective nanoparticle (NP) dispersion in the liquid and NP capture within the metal grains during solidification is essential. In this work, we present the novel synthesis and structural characterization of surface-clean titanium diboride (TiB2) NPs with an average particle size of 20 nm, by ultrasonic-assisted reduction of fluorotitanate and fluoroboride salts in molten aluminum. The high-intensity ultrasonic field restricts NP growth. Using a master nanocomposite approach, the as-prepared TiB2 NPs are effectively incorporated into A206 alloys during solidification processing because of their clean surface, showing partial capture and significant grain refinement. PMID:23957877

Estruga, Marc; Chen, Lianyi; Choi, Hongseok; Li, Xiaochun; Jin, Song

2013-09-11

339

Electrochemical study of Aluminum-Fly Ash composites obtained by powder metallurgy  

SciTech Connect

In this paper, two different ASTM C 618 Class C fly ashes (FA) were used for the production of aluminum metal matrix composites (MMCs) using powder metallurgy (PM) technology. Calcareous FAs were sampled from the electrostatic precipitators of two different lignite-fired power stations: from Megalopolis, Southern Greece (MFA) and from Kardia, Northen Greece (KFA), under maximum electricity load. FAs were milled in order to reduce the mean particle diameter and Aluminum-FA composites containing 10% and 20% of FA were then prepared and compacted. The green products were sintered for 2 h at 600 Degree-Sign C. Sintered Al-FA MMCs showed increased hardness and wear resistance suggesting their possible use in industrial applications for example in covers, casings, brake rotors or engine blocks. As most possible industrial applications of MMCs not only require wear resistance, but also corrosion resistance in different mild aggressive medias, this paper aims to study the electrochemical behavior of FA MMCs in order to evaluate their corrosion resistance. The morphology and chemical composition of the phases in the Aluminum-FA composite samples were investigated using Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDXS). Moreover, topographic and Volta potential maps were acquired by Scanning Kelvin Probe Force Microscopy (SKP-FM). Volta potential maps provide information about the electrochemical behavior of the different phases in absence of electrolyte. The electrochemical behavior was investigated by Open Circuit Potential measurements and potentiodynamic polarization, while the corrosion mechanisms were studied by SEM observations after different times of immersion in a mild corrosive medium. In all cases it could be stated that the addition of the FA particles into the Al matrix might cause an increase of the hardness and mechanical properties of the pure aluminum but deteriorates the corrosion resistance. The degradation phenomena occurring on the FA containing samples might be related to the following mechanisms: 1) Partial detachment or dissolution of the FA soluble phases, in particular based on Si, Fe and Ca; 2) dissolution of the Al matrix surrounding the FA particles due to crevice corrosion; 3) Al localized dissolution due to galvanic coupling between the Fe-rich intermetallics and the matrix. - Highlights: Black-Right-Pointing-Pointer Aluminum metal matrix composites containing two types of fly ashes have been characterized. Black-Right-Pointing-Pointer The microstructure and the electrochemical behavior have been studied using different techniques. Black-Right-Pointing-Pointer The addition of FA deteriorates the corrosion resistance of the aluminum. Black-Right-Pointing-Pointer Degradation mechanisms: galvanic coupling, crevice corrosion, detachment of FA particles.

Marin, E. [Department of Chemistry, Physics and Environment, University of Udine, Via Cotonificio 108, 33100, Udine (Italy); Lekka, M., E-mail: maria.lekka@uniud.it [Department of Chemistry, Physics and Environment, University of Udine, Via Cotonificio 108, 33100, Udine (Italy); Andreatta, F.; Fedrizzi, L. [Department of Chemistry, Physics and Environment, University of Udine, Via Cotonificio 108, 33100, Udine (Italy); Itskos, G. [School of Chemical Engineering, National Technical University of Athens, Iroon Polytechneiou 9, Zografou 15780, Athens (Greece); Centre for Research and Technology Hellas/Institute for Solid Fuels Technology and Applications, Mesogeion Avenue 357-359, Halandri 15231, Athens (Greece); Moutsatsou, A. [School of Chemical Engineering, National Technical University of Athens, Iroon Polytechneiou 9, Zografou 15780, Athens (Greece); Koukouzas, N. [Centre for Research and Technology Hellas/Institute for Solid Fuels Technology and Applications, Mesogeion Avenue 357-359, Halandri 15231, Athens (Greece); Kouloumbi, N. [School of Chemical Engineering, National Technical University of Athens, Iroon Polytechneiou 9, Zografou 15780, Athens (Greece)

2012-07-15

340

and Carbon Fiber Reinforced 2024 Aluminum Alloy Composites  

NASA Astrophysics Data System (ADS)

The microstructure and mechanical properties of 2024 aluminum alloy composite materials strengthened with Al2O3 Saffil fibers or together with addition of carbon fibers were investigated. The fibers were stabilized in the preform with silica binder strengthened by further heat treatment. The preforms with 80-90% porosity were infiltrated by direct squeeze casting method. The microstructure of the as-cast specimens consisted mainly of ?-dendrites with intermetallic compounds precipitated at their boundaries. The homogenization treatment of the composite materials substituted silica binder with a mixture of the ? phase and silicon precipitates distributed in the remnants of SiO2 amorphous phase. Outside of this area at the binder/matrix interface, fine MgO precipitates were also present. At surface of C fibers, a small amount of fine Al3C4 carbides were formed. During pressure infiltration of preforms containing carbon fibers under oxygen carrying atmosphere, C fibers can burn releasing gasses and causing cracks initiated by thermal stress. The examination of tensile and bending strength showed that reinforcing of aluminum matrix with 10-20% fibers improved investigated properties in the entire temperature range. The largest increase in relation to unreinforced alloy was observed for composite materials examined at the temperature of 300 C. Substituting Al2O3 Saffil fibers with carbon fibers leads to better wear resistance at dry condition with no relevant effect on strength properties.

Kaczmar, Jacek W.; Naplocha, Krzysztof; Morgiel, Jerzy

2014-08-01

341

Structure of Framework Aluminum Lewis Sites and Perturbed Aluminum Atoms in Zeolites as Determined by (27) Al{(1) H} REDOR (3Q) MAS NMR Spectroscopy and DFT/Molecular Mechanics.  

PubMed

Zeolites are highly important heterogeneous catalysts. Besides Brnsted SiOHAl acid sites, also framework AlFR Lewis acid sites are often found in their H-forms. The formation of AlFR Lewis sites in zeolites is a key issue regarding their selectivity in acid-catalyzed reactions. The local structures of AlFR Lewis sites in dehydrated zeolites and their precursors-"perturbed" AlFR atoms in hydrated zeolites-were studied by high-resolution MAS NMR and FTIR spectroscopy and DFT/MM calculations. Perturbed framework Al atoms correspond to (SiO)3 AlOH groups and are characterized by a broad (27) Al NMR resonance (?i =59-62 ppm, CQ =5 MHz, and ?=0.3-0.4) with a shoulder at 40 ppm in the (27) Al MAS NMR spectrum. Dehydroxylation of (SiO)3 AlOH occurs at mild temperatures and leads to the formation of AlFR Lewis sites tricoordinated to the zeolite framework. Al atoms of these (SiO)3 Al Lewis sites exhibit an extremely broad (27) Al NMR resonance (?i ?67 ppm, CQ ?20 MHz, and ??0.1). PMID:25393612

Brus, Ji?; Kobera, Libor; Schoefberger, Wolfgang; Urbanov, Martina; Klein, Petr; Sazama, Petr; Tabor, Edyta; Sklenak, Stepan; Fishchuk, Anna V; D?de?ek, Ji?

2014-11-13

342

Mesoporous aluminum phosphite  

NASA Astrophysics Data System (ADS)

High surface area pure mesoporous aluminum-phosphorus oxide-based derivatives have been synthesized through an S +I - surfactant-assisted cooperative mechanism by means of a one-pot preparative procedure from aqueous solution and starting from aluminum atrane complexes and phosphoric and/or phosphorous acids. A soft chemical extraction procedure allows opening the pore system of the parent as-prepared materials by exchanging the surfactant without mesostructure collapse. The nature of the pore wall can be modulated from mesoporous aluminum phosphate (ALPO) up to total incorporation of phosphite entities (mesoporous aluminum phosphite), which results in a gradual evolution of the acidic properties of the final materials. While phosphate groups in ALPO act as network building blocks (bridging Al atoms), the phosphite entities become basically attached to the pore surface, what gives practically empty channels. The mesoporous nature of the final materials is confirmed by X-ray diffraction (XRD), transmission electron microscopy (TEM) and N 2 adsorption-desorption isotherms. The materials present regular unimodal pore systems whose order decreases as the phosphite content increases. NMR spectroscopic results confirm the incorporation of oxo-phosphorus entities to the framework of these materials and also provide us useful information concerning the mechanism through which they are formed.

El Haskouri, Jamal; Prez-Cabero, Mnica; Guillem, Carmen; Latorre, Julio; Beltrn, Aurelio; Beltrn, Daniel; Amors, Pedro

2009-08-01

343

Microstructural Evolution and Mechanical Properties of Nanointermetallic Phase Dispersed Al65Cu20Ti15 Amorphous Matrix Composite Synthesized by Mechanical Alloying and Hot Isostatic Pressing  

NASA Astrophysics Data System (ADS)

The structure and mechanical properties of nanocrystalline intermetallic phase dispersed amorphous matrix composite prepared by hot isostatic pressing (HIP) of mechanically alloyed Al65Cu20Ti15 amorphous powder in the temperature range 573 K to 873 K (300 C to 600 C) with 1.2 GPa pressure were studied. Phase identification by X-ray diffraction (XRD) and microstructural investigation by transmission electron microscopy confirmed that sintering in this temperature range led to partial crystallization of the amorphous powder. The microstructures of the consolidated composites were found to have nanocrystalline intermetallic precipitates of Al5CuTi2, Al3Ti, AlCu, Al2Cu, and Al4Cu9 dispersed in amorphous matrix. An optimum combination of density (3.73 Mg/m3), hardness (8.96 GPa), compressive strength (1650 MPa), shear strength (850 MPa), and Young's modulus (182 GPa) were obtained in the composite hot isostatically pressed ("hipped") at 773 K (500 C). Furthermore, these results were compared with those from earlier studies based on conventional sintering (CCS), high pressure sintering (HPS), and pulse plasma sintering (PPS). HIP appears to be the most preferred process for achieving an optimum combination of density and mechanical properties in amorphous-nanocrystalline intermetallic composites at temperatures ?773 K (500 C), while HPS is most suited for bulk amorphous alloys. Both density and volume fraction of intermetallic dispersoids were found to influence the mechanical properties of the composites.

Roy, D.; Mitra, R.; Ojo, O. A.; Lojkowski, W.; Manna, I.

2011-08-01

344

Aluminum Cans  

NSDL National Science Digital Library

In this data analysis activity students investigate data in connection with recyclable materials and develop plans to help the environment. Students collect data about aluminum can usage and graph that data in a line plot. The lesson includes student worksheet and extension suggestions.

2008-01-01

345

Aluminum Pannier  

USGS Multimedia Gallery

This aluminum pannier was made for the storage of meat, vegetables and other food products. The pannier could be buried in the ground or placed in water in order to keep the contents cool. It was designed by Dr. J. D. Love and made for him in 1945. For transportation, this pannier, along with two re...

2009-07-22

346

The formation and structure of the oxide and hydroxide chemisorbed phases at the aluminum surface, and relevance to hydrogen embrittlement  

NASA Astrophysics Data System (ADS)

Aluminum alloys used in aerospace structures are susceptible to environmentally assisted cracking (EAC) induced by hydrogen embrittlement (HE) (Gangloff and Ives 1990). Crack growth experiments have demonstrated a linear relation between the relative humidity of the environment and crack growth rates, indicating the importance of water (Speidel and Hyatt 1972). While the presence of water has been demonstrated to be necessary for EAC of aluminum, crack growth rates have been linked to the diffusivity of hydrogen in aluminum (Gangloff 2003) and hydrogen densities at the crack tip as high as Al2H have been observed (Young and Scully 1998). While the mechanism by which hydrogen embrittles aluminum is yet not well understood, without the entry of hydrogen into the aluminum matrix, embrittlement would not occur. While at the crack tip high hydrogen concentrations exist, the solubility of hydrogen in aluminum is normal near 1 ppm (Wolverton 2004). In this work combined first principles and kinetic Monte Carlo methods will be used to examine the oxide and hydroxide structure resulting from exposure of aluminum to H2O or O2 and relevance to hydrogen entry as well as EAC is discussed.

Francis, Michael; Kelly, Robert; Neurock, Matthew

2010-03-01

347

Evaluation of aluminum tolerance in grapevine rootstocks  

Technology Transfer Automated Retrieval System (TEKTRAN)

Aluminum (Al) toxicity is a major worldwide agricultural problem. At low pH, Al speciates into the soluble and phyto-toxic form Al3+, causing inhibition of root growth and affecting plant development. In Brazil, agriculture in acidic soils regions with elevated concentration of Al has significantly ...

348

Comparison in the Oxidation and Corrosion Behavior of Aluminum and Alumina-Reinforced Ni/Ni-Co Alloy Coatings  

NASA Astrophysics Data System (ADS)

In this study, a comparison in the oxidation and corrosion behavior of Ni/Ni-Co aluminum and alumina-reinforced electrodeposited composites has been made. The developed coatings were characterized for the morphology, structure, microhardness, oxidation, and corrosion resistance. It was found that the incorporation of Al particles in NiCo matrix is higher (9 wt pct) compared to Ni matrix (1 wt pct). In the case of aluminum oxide particles, about 5 and 7 wt pct had been obtained in Ni and NiCo matrices respectively. The difference in the surface morphology was observed with respect to metallic (Al) and inert ceramic (Al2O3) particle incorporation. X-ray diffraction studies showed the presence of predominant Ni (200) reflection in the coatings. Also, peaks corresponding to Al and Al2O3 particles were present. The Ni/NiCo-Al coatings exhibited higher microhardness values at 1273 K (1000 C) compared to alumina-reinforced coatings, indicating better thermal stability of the former coatings. The NiAl coating showed one and two orders of magnitude improved oxidation resistance compared to NiCoAl and Ni/NiCo-Al2O3 coatings, respectively. It was observed that the Ni-Al composite coating exhibited poor corrosion resistance in 3.5 pct NaCl solution compared to the other coatings studied.

Srivastava, Meenu; Balaraju, J. N.; Ravisankar, B.; Grips, V. K. William

2013-02-01

349

An Investigation on the Interface in a NiTi Short-Fiber-Reinforced 6061 Aluminum Composite by Transmission Electron Microscope  

NASA Astrophysics Data System (ADS)

It has already been demonstrated that NiTi shape-memory alloy fiber-reinforced composites show enhanced mechanical properties by adding a compressive stress to the matrix when the shape-memory effect is activated. The bonding quality between NiTi fiber and the matrix directly affects the stress transfer across the interface, through which the novel functionality of the smart composite is achieved. In the present study, the interface in a NiTi short-fiber-reinforced 6061 aluminum matrix has been investigated by transmission electron microscopy and energy dispersive spectroscopy. Three layers at the interface between NiTi fiber and 6061 aluminum alloy matrix have been found and characterized, i.e., Al3Ti with DO22 ordered structure near the NiTi fiber, Al9FeNi with Al9Co2 (or Al9Fe2) type ordered structure near the Al alloy matrix, and Mg-O layer with 20 nm in thickness between Al3Ti and Al9FeNi layers. The potential effects of these layers on the mechanical properties of the composite are discussed. Evidence indicates that extensive diffusion from both NiTi fiber and Al alloy matrix occurred during the fabrication of the composite at 570 C to 580 C within 20 to 30 minutes. The minor elements in the matrix could be the major elements at the interface. By selecting the chemical composition of the Al alloy matrix, it is possible to control the chemical composition at the interface and further control the mechanical properties of the composites.

Liu, Yi; Al-Matar, Basem; Newaz, Golam

2008-11-01

350

Thermodynamic Modeling of Aqueous Aluminum Chemistry and Solid-Liquid Equilibria to High Solution Concentration and Temperature. I. The Acidic H-Al-Na-K-Cl-H 2 O System from 0 to 100?C  

Microsoft Academic Search

In this paper, we describe the development of a thermodynamic model that calculates solute\\/solvent activities and solid-liquid\\u000a equilibria in the acidic aluminum system, H-Al3+-Na-K-Cl-H2O, to high molality from 0? to ?100?C. The model incorporates the concentration-dependent, specific interaction equations\\u000a for aqueous solutions of Pitzer (Activity Coefficients in Electrolyte Solutions, 2nd edn., pp.75153, CRC Press, Boca Raton,1991). Parameterization of this model

Christomir Christov; Andrew G. Dickson; Nancy Moller

2007-01-01

351

Defect assisted thermal synthesis of crystalline aluminum borate nanowires I. Gonzalez-Martinez, A. Bachmatiuk, S. Gorantla, J. Kunstmann, V. Bezugly et al.  

E-print Network

over a more traditional material, SiC, in that it does not readily oxidize at high temperature and can be produced at lower cost. In this study, we demonstarte a facile route to grow single crystal aluminum borate expansion.1­5 Moreover, alumi- num borate has advantages over a more traditional material, SiC,6­8 in which

Cuniberti, Gianaurelio

352

Mesoporous aluminum phosphite  

SciTech Connect

High surface area pure mesoporous aluminum-phosphorus oxide-based derivatives have been synthesized through an S{sup +}I{sup -} surfactant-assisted cooperative mechanism by means of a one-pot preparative procedure from aqueous solution and starting from aluminum atrane complexes and phosphoric and/or phosphorous acids. A soft chemical extraction procedure allows opening the pore system of the parent as-prepared materials by exchanging the surfactant without mesostructure collapse. The nature of the pore wall can be modulated from mesoporous aluminum phosphate (ALPO) up to total incorporation of phosphite entities (mesoporous aluminum phosphite), which results in a gradual evolution of the acidic properties of the final materials. While phosphate groups in ALPO act as network building blocks (bridging Al atoms), the phosphite entities become basically attached to the pore surface, what gives practically empty channels. The mesoporous nature of the final materials is confirmed by X-ray diffraction (XRD), transmission electron microscopy (TEM) and N{sub 2} adsorption-desorption isotherms. The materials present regular unimodal pore systems whose order decreases as the phosphite content increases. NMR spectroscopic results confirm the incorporation of oxo-phosphorus entities to the framework of these materials and also provide us useful information concerning the mechanism through which they are formed. - Abstract: TEM image of the mesoporous aluminum phosphite showing the hexagonal disordered pore array that is generated by using surfactant micelles as template. Also a scheme emphasizing the presence of an alumina-rich core and an ALPO-like pore surface is presented.

El Haskouri, Jamal, E-mail: haskouri@uv.e [Institut de Ciencia dels Materials de la Universitat de Valencia (ICMUV), P. O. Box 22085, 46071 Valencia (Spain); Perez-Cabero, Monica; Guillem, Carmen; Latorre, Julio; Beltran, Aurelio; Beltran, Daniel [Institut de Ciencia dels Materials de la Universitat de Valencia (ICMUV), P. O. Box 22085, 46071 Valencia (Spain); Amoros, Pedro, E-mail: pedro.amoros@uv.e [Institut de Ciencia dels Materials de la Universitat de Valencia (ICMUV), P. O. Box 22085, 46071 Valencia (Spain)

2009-08-15

353

TEM investigations of the fibre\\/matrix interface in SCS6 SiC\\/Ti25Al10Nb3V1Mo composites  

Microsoft Academic Search

Interfacial reactions in SCS-6 SiC\\/Ti25Al10Nb3V1Mo composites processed by fibre coating with matrix material, hot isostatic pressing and thermal treating for simulation of service conditions were studied by analytical transmission electron microscopy. In the as-processed specimen three reaction layers were observed. Adjacent to C coating of the SCS-6 fibre no mixture of TiC and Ti5Si3 was found reported in literature [Rhodes,

Y. Q. Yang; H. J. Dudek; J. Kumpfert

1998-01-01

354

The influence of interfacial characteristics between SiC p and Mg\\/Al metal matrix on wear, coefficient of friction and microhardness  

Microsoft Academic Search

The aim of the present investigation is to characterize the interface between the SiCp as the reinforcement and Al and Mg metals of the metal matrix composites (MMCs) prepared through vacuum infiltration technique. The weight loss as an index of abrasive wear using pin-on-disc apparatus, the coefficient of friction, the microhardness value and the interparticle distance were determined under dry

Sanjay Kumar Thakur; Brij Kumar Dhindaw

2001-01-01

355

The effect of Al 2O 3, TiN and Ti (C,N) based CVD coatings on tool wear in machining metal matrix composites  

Microsoft Academic Search

The effect of Al2O3, TiN and Ti (C,N) based CVD coatings on tool wear in machining metal matrix composites containing 10 wt.% SiC particles produced by liquid metallurgy was investigated at different cutting conditions. In turning tests, various cutting speeds and two cutting tools having different chip breaker geometry were used at a constant feed rate and depth of cut.

Y. Sahin; G. Sur

2004-01-01

356

Detoxification of endotoxin by aluminum hydroxide adjuvant.  

PubMed

Langmuir adsorption isotherms of endotoxin and aluminum-containing adjuvants at pH 7.4 and 25 degrees C revealed that aluminum hydroxide adjuvant has a greater adsorption capacity (283 microg/mg Al) and adsorption coefficient (1.3x10(4) ml/miccrog) than aluminum phosphate adjuvant (3.0 microg/mg Al, 0.20 ml/microg). The difference in endotoxin adsorption was related to two adsorption mechanisms: electrostatic attraction and covalent bonding. The isoelectric point (iep) of endotoxin is approximately 2. An electrostatic attractive force will be present with aluminum hydroxide adjuvant (iep=11.4), and an electrostatic repulsive force will operate with aluminum phosphate adjuvant (iep=4.6). Endotoxin contains two phosphate groups in the lipid A portion. Covalent bonding occurs with surface aluminum in aluminum hydroxide adjuvant but is inhibited by surface phosphate in aluminum phosphate adjuvant. In-vitro desorption experiments using components of interstitial fluid showed that endotoxin adsorbed by aluminum hydroxide adjuvant was not desorbed by interstitial anions (5 mM phosphate or 2.7 mM citrate) or interstitial proteins (25 mg albumin/ml). The effect of aluminum-containing adjuvants on the systemic response of Sprague-Dawley rats to a 15 microg/kg subcutaneous dose of endotoxin was determined by measuring the serum concentration of tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6). TNF-alpha and IL-6 were observed in the group which received an endotoxin solution or endotoxin and aluminum phosphate adjuvant. No TNF-alpha or IL-6 was detected in the group that received endotoxin and aluminum hydroxide adjuvant. Aluminum hydroxide adjuvant detoxifies endotoxin by adsorbing it in the vaccine and then not releasing it in interstitial fluid upon administration. PMID:11166900

Shi, Y; HogenEsch, H; Regnier, F E; Hem, S L

2001-02-01

357

Liquid-phase impact diffusion welding of SiC p\\/6061Al and its mechanism  

Microsoft Academic Search

Liquid-phase impact diffusion welding (LPIDW) technique was used to join the aluminum matrix composite SiCp\\/6061Al. The composite joints welded successfully, gave tensile strength up to 260MPa and radial deformation below 3%. Analysis of the microstructure and tensile strength of the welded joints showed: (i) the achievement of prominent joint interface between SiC particles and the matrix; (ii) the change of

Wei Guo; Meng Hua; Hang Wai Law; John Kin Lim Ho

2008-01-01

358

Influence of nanoparticles and nanofibers of aluminum oxide on the properties of epoxy composites  

Microsoft Academic Search

The strength properties of epoxy composites filled with aluminum oxide nanoparticles and reinforced by aluminum oxide nanofibers\\u000a are compared. It is demonstrated that these fillers have a specific effect on the properties of the epoxy matrix.

B. N. Dudkin; G. G. Zainullin; P. V. Krivoshapkin; E. F. Krivoshapkina; M. A. Ryazanov

2008-01-01

359

Aluminum Carbothermic Technology  

SciTech Connect

This report documents the non-proprietary research and development conducted on the Aluminum Carbothermic Technology (ACT) project from contract inception on July 01, 2000 to termination on December 31, 2004. The objectives of the program were to demonstrate the technical and economic feasibility of a new carbothermic process for producing commercial grade aluminum, designated as the ''Advanced Reactor Process'' (ARP). The scope of the program ranged from fundamental research through small scale laboratory experiments (65 kW power input) to larger scale test modules at up to 1600 kW power input. The tasks included work on four components of the process, Stages 1 and 2 of the reactor, vapor recovery and metal alloy decarbonization; development of computer models; and economic analyses of capital and operating costs. Justification for developing a new, carbothermic route to aluminum production is defined by the potential benefits in reduced energy, lower costs and more favorable environmental characteristics than the conventional Hall-Heroult process presently used by the industry. The estimated metrics for these advantages include energy rates at approximately 10 kWh/kg Al (versus over 13 kWh/kg Al for Hall-Heroult), capital costs as low as $1250 per MTY (versus 4,000 per MTY for Hall-Heroult), operating cost reductions of over 10%, and up to 37% reduction in CO2 emissions for fossil-fuel power plants. Realization of these benefits would be critical to sustaining the US aluminum industries position as a global leader in primary aluminum production. One very attractive incentive for ARP is its perceived ability to cost effectively produce metal over a range of smelter sizes, not feasible for Hall-Heroult plants which must be large, 240,000 TPY or more, to be economical. Lower capacity stand alone carbothermic smelters could be utilized to supply molten metal at fabrication facilities similar to the mini-mill concept employed by the steel industry. Major accomplishments for the program include definition of the system thermo-chemistry, demonstration of reactor stage 1, development of reactor stage 2 critical components in a 500 kW module, experimental determination of the vapor recovery reactor fundamentals, detailed design and installation of an advanced stage 1/vapor recovery reactor, feasibility of efficient separation of Al-C metal alloy product, updated capital and operating cost estimates, and development of computer models for all steps of the Advanced Reactor Process.

Bruno, Marshall J.

2005-03-31

360

Phase formation due to high dose aluminum implantation into silicon carbide  

NASA Astrophysics Data System (ADS)

High doses of 350 keV aluminum (Al) ions were implanted into hexagonal silicon carbide (6H-SiC) single crystals at 500 C. Phase formation was studied by transmission electron microscopy, secondary-ion mass spectrometry, and Auger electron spectrometry. A critical Al concentration of about 10 at. % was found below which the 6H-SiC structure remains stable. The Al atoms occupy preferentially silicon (Si) sites in the SiC lattice. The replaced Si atoms seem to be mobile under the implantation conditions and diffuse out. At higher Al concentrations the SiC matrix is decomposed and precipitates of Si and aluminum carbide (Al4C3) are formed. The Al4C3 precipitates have a perfect epitaxial orientation to the SiC matrix. The phase transformation is accompanied by atomic redistribution and strong volume swelling. The resulting changes in the atomic depth profiles can be accounted for by a simple chemical reaction model.

Heera, V.; Reuther, H.; Stoemenos, J.; Pcz, B.

2000-01-01

361

Mobilizing aluminum in crustal and mantle fluids Craig E. Manning  

E-print Network

Mobilizing aluminum in crustal and mantle fluids Craig E. Manning Department of Earth and Space December 2005 Available online 9 March 2006 Abstract Aluminum is a major rock-forming element, but its low by formation of polynuclear Na­Al­Si­O clusters and/or polymers. Aluminum should not be assumed to be immobile

Manning, Craig

362

Oxidation kinetics of aluminum diboride  

NASA Astrophysics Data System (ADS)

The oxidation characteristics of aluminum diboride (AlB2) and a physical mixture of its constituent elements (Al+2B) were studied in dry air and pure oxygen using thermal gravimetric analysis to obtain non-mechanistic kinetic parameters. Heating in air at a constant linear heating rate of 10 C/min showed a marked difference between Al+2B and AlB2 in the onset of oxidation and final conversion fraction, with AlB2 beginning to oxidize at higher temperatures but reaching nearly complete conversion by 1500 C. Kinetic parameters were obtained in both air and oxygen using a model-free isothermal method at temperatures between 500 and 1000 C. Activation energies were found to decrease, in general, with increasing conversion for AlB2 and Al+2B in both air and oxygen. AlB2 exhibited O2-pressure-independent oxidation behavior at low conversions, while the activation energies of Al+2B were higher in O2 than in air. Differences in the composition and morphology between oxidized Al+2B and AlB2 suggested that Al2O3-B2O3 interactions slowed Al+2B oxidation by converting Al2O3 on aluminum particles into a Al4B2O9 shell, while the same Al4B2O9 developed a needle-like morphology in AlB2 that reduced oxygen diffusion distances and increased conversion. The model-free kinetic analysis was critical for interpreting the complex, multistep oxidation behavior for which a single mechanism could not be assigned. At low temperatures, moisture increased the oxidation rate of Al+2B and AlB2, but both appear to be resistant to oxidation in cool, dry environments.

Whittaker, Michael L.; Sohn, H. Y.; Cutler, Raymond A.

2013-11-01

363

Polarization properties of real aluminum mirrors; I. Influence of the aluminum oxide layer  

E-print Network

In polarimetry it is important to characterize the polarization properties of the instrument itself to disentangle real astrophysical signals from instrumental effects. This article deals with the accurate measurement and modeling of the polarization properties of real aluminum mirrors, as used in astronomical telescopes. Main goals are the characterization of the aluminum oxide layer thickness at different times after evaporation and its influence on the polarization properties of the mirror. The full polarization properties of an aluminum mirror are measured with Mueller matrix ellipsometry at different incidence angles and wavelengths. The best fit of theoretical Mueller matrices to all measurements simultaneously is obtained by taking into account a model of bulk aluminum with a thin aluminum oxide film on top of it. Full Mueller matrix measurements of a mirror are obtained with an absolute accuracy of ~1% after calibration. The determined layer thicknesses indicate logarithmic growth in the first few hou...

van Harten, G; Keller, C U

2009-01-01

364

Deposition of duplex Al 2O 3\\/TiN coatings on aluminum alloys for tribological applications using a combined microplasma oxidation (MPO) and arc ion plating (AIP)  

Microsoft Academic Search

Microplasma oxidation (MPO) has recently been studied as a cost-effective plasma electrolytic process to provide thick and hard ceramic coatings with excellent surface load-bearing capacity on aluminum alloys. However, for sliding wear applications, such ceramic coatings often exhibit relatively high friction coefficients against many counterface materials. Although coatings deposited by physical vapour deposition (PVD) techniques such as TiN coatings are

Samir H. Awad; H. C. Qian

2006-01-01

365

ALUMINUM 245 8. REGULATIONS AND ADVISORIES  

E-print Network

The international and national regulations and guidelines regarding aluminum and aluminum compounds in air, water, and other media are summarized in Table 8-1. ATSDR has derived an intermediate-duration oral minimal risk level (MRL) of 1 mg Al/kg/day for aluminum. This MRL is based on a NOAEL of 26 mg Al/kg/day and a LOAEL of 130 mg Al/kg/day for neurodevelopmental effects in the offspring of mice exposed to aluminum lactate in the diet on gestation day 1 through lactation day 21 followed by pup exposure until postnatal day 35 (Golub and Germann 2001). The MRL was derived by dividing the NOAEL by an uncertainty factor of 100 (10 for animal to human extrapolation and 10 for human variability) and a modifying factor of 0.3 to account for the higher bioavailability of the aluminum lactate used in the principal study, as compared to the bioavailability of aluminum in the human diet and drinking water. ATSDR has derived a chronic-duration oral MRL of 1 mg Al/kg/day for aluminum. This MRL is based on a LOAEL of 100 mg Al/kg/day for neurological effects in mice exposed to aluminum lactate in the diet during gestation, lactation, and postnatally until 2 years of age (Golub et al. 2000). The MRL was derived by dividing the LOAEL by an uncertainty factor of 300 (3 for the use of a minimal LOAEL, 10 for animal to human extrapolation, and 10 for human variability) and a modifying factor of 0.3 to account for the higher bioavailability of the aluminum lactate used in the principal study, as compared to the bioavailability of aluminum in the human diet and drinking water. EPA has not derived a reference dose (RfD) or reference concentration (RfC) for aluminum, but has derived an RfD for aluminum phosphide of 4x10-4 mg/kg/day based on a NOAEL of 0.51 mg/kg of food or 0.025 mg/kg/day (phosphine) converted to 0.043 mg/kg/day of aluminum phosphide for body weight and clinical parameters observed in a rats during a chronic oral study (IRIS 2008).ALUMINUM 246

unknown authors

366

Method of winning aluminum metal from aluminous ore  

DOEpatents

Aluminous ore such as bauxite containing alumina is blended with coke or other suitable form of carbon and reacted with sulfur gas at an elevated temperature. For handling, the ore and coke can be extruded into conveniently sized pellets. The reaction with sulfur gas produces molten aluminum sulfide which is separated from residual solid reactants and impurities. The aluminum sulfide is further increased in temperature to cause its decomposition or sublimation, yielding aluminum subsulfide liquid (AlS) and sulfur gas that is recycled. The aluminum monosulfide is then cooled to below its disproportionation temperature to again form molten aluminum sulfide and aluminum metal. A liquid-liquid or liquid-solid separation, depending on the separation temperature, provides product aluminum and aluminum sulfide for recycle to the disproportionation step.

Loutfy, Raouf O. (Naperville, IL); Keller, Rudolf (Naperville, IL); Yao, Neng-Ping (Clarendon Hills, IL)

1981-01-01

367

Low-aluminum content iron-aluminum alloys  

SciTech Connect

The low-aluminum-content iron-aluminum program deals with the development of a Fe-Al alloy with aluminum content such as a produce the minimum environmental effect at room temperature. The FAPY is an Fe-16 at. % Al-based alloy developed at the Oak Ridge National Laboratory as the highest aluminum-containing alloy with essentially no environmental effect. The chemical composition for FAPY in weight percent is: aluminum = 8.46, chromium = 5.50, zirconium = 0.20, carbon = 0.03, molybdenum = 2.00, yttrium = 0.10 and iron = 83.71. The ignots of the alloy can be hot worked by extrusion, forging, and rolling processes. The hot-worked cast structure can be cold worked with intermediate anneals at 800{degrees}C. Typical room-temperature ductility of the fine-grained wrought structure is 20 to 25% for this alloy. In contrast to the wrought structure, the cast ductility at room temperature is approximately 1% with a transition temperature of approximately 100 to 150{degrees}C, above which ductility values exceed 20%. The alloy has been melted and processed into bar, sheet, and foil. The alloy has also been cast into slabs, step-blocks of varying thicknesses, and shapes. The purpose of this section is to describe the welding response of cast slabs of three different thicknesses of FAPY alloy. Tensile, creep, and Charpy-impact data of the welded plates are also presented.

Sikka, V.K.; Goodwin, G.M.; Alexander, D.J. [and others

1995-06-01

368

Composite propellant combustion with low aluminum agglomeration.  

E-print Network

??Aluminum behavior???accumulation, agglomeration and ignition???is studied in a unique, wide-distribution, ammonium perchlorate/hydroxyl-terminated polybutadiene (AP/HTPB) propellant formulation that results in low Al agglomeration, even at low (more)

Mullen, Jessica C.

2010-01-01

369

Molecular Structure of Aluminum bromide  

NSDL National Science Digital Library

Aluminum bromide is hygroscopic and appears as white to yellow-red lumps. It is corrosive and causes severe burns. It should be stored in a cool, dry and well ventilated place. AlBr3 reacts violently with water and evolves HBr, and also reacts quickly with alcohols and acids.

2002-10-09

370

Synthesis of bifunctional catalysts Al-SBA-15-NH2 with high aluminum content and the catalytic application for different one-pot reactions  

NASA Astrophysics Data System (ADS)

Acid-base bifunctional mesoporous catalysts Al-SBA-15-NH2 containing high content of Al and organic amine functional groups have been synthesized through the "pH-adjusting" method. The materials were characterized by X-ray diffraction (XRD), scanning electron micrographs (SEM), transmission electron micrographs (TEM), Fourier-transform infrared spectroscopy (FTIR), IR spectra of pyridine adsorption, NH3-TPD and elemental analysis. Catalytic results showed that 6-Al-SBA-15-NH2 (Si/Al = 6 mol%) was more active than 10-Al-SBA-15-NH2 (Si/Al = 10 mol%) in one-pot deacetalization-Knoevenagel and deacetalization-nitroaldol (Henry) reactions.

Wang, Chunhua; Shang, Fanpeng; Yu, Xiaofang; Guan, Jingqi; Kan, Qiubin

2012-07-01

371

Mercury-free dissolution of aluminum fuels in nitric acid  

Microsoft Academic Search

Since the 1950s, most chemical flow sheets for the dissolution of aluminum-clad nuclear fuels have utilized mercury-catalyzed nitric acid dissolvent to dissolve aluminum. Apparently the mercury, as dissolved mercuric nitrate, reacts with the aluminum oxide surface layers on the aluminum alloy to form a Hg-Al amalgam that dissolves readily in nitric acid. The reaction is rapid, efficient, and highly exothermic.

P. A. Anderson; J. D. Christian

1993-01-01

372

Microstructural effects on the formation and degradation of zinc phosphate coatings on 2024-Al alloy  

NASA Astrophysics Data System (ADS)

The formation of zinc phosphate (ZPO) coatings on 2024-T3 aluminum alloy was studied using scanning electron microscopy (SEM), scanning Auger microscopy (SAM) and X-ray photoelectron spectroscopy (XPS), with an emphasis on microstructural effects involving second-phase particles and the alloy matrix. Surface polishing results in an Al-Cu-Mg particle surface that contains metallic Cu as well as an overlayer of aluminum and magnesium oxide, while larger amounts of aluminum oxide are present on the Al-Cu-Fe-Mn particle and matrix. When dipped in an acidic ZPO coating solution, the oxide covering the Al-Cu-Mg particle is etched most easily, and metallic Cu near the surface makes that region most cathodic, allowing more coating deposition compared with the other regions. The oxides on the Al-Cu-Fe-Mn and matrix regions are similar, thereby confirming that the observed differences in ZPO coating characteristics at these two regions arise from their underlying electrochemical characteristics. Immersion of a coated 2024-Al sample in corrosive NaCl solution for extended periods indicates that the ZPO provides better protection to the second-phase particles than to the matrix.

Akhtar, A. S.; Wong, P. C.; Wong, K. C.; Mitchell, K. A. R.

2008-05-01

373

Mechanism of reaction in NaAlCl4 molten salt batteries with nickel felt cathodes and aluminum anodes. 1: Modeling of the battery properties of thermodynamic equilibrium  

Microsoft Academic Search

A theoretical description of the thermodynamic properties of the battery systems: Al\\/NaCl-AlCl3 -Al2X3\\/Ni-felt (X = S, Se, Te) and the corresponding system without chalcogen has been provided for cells with basic to slightly acidic NaCl-AlCl3 melts containing small amounts of chalcogen. The model developed describes the equilibrium concentrations of constituent species in the electrolyte and equilibrium potentials of the electrodes

B. C. Knutz; H. A. Hjuler; R. W. Berg; N. J. Bjerrum

1993-01-01

374

High conductivity, low cost aluminum composite for thermal management  

SciTech Connect

In order to produce an inexpensive packaging material that exhibits high thermal conductivity and low CTE, Technical Research Associates, Inc. (TRA) has shown in Phase I the feasibility of incorporating natural flake graphite in an aluminum matrix. TRA has developed a proprietary coating technique where graphite flakes have been coated with a thin layer of molybdenum/molybdenum carbide (approximately 0.2 microns). This barrier coating can protect the graphite flake from chemical reaction and high temperature degradation in molten aluminum silicon alloys. Methods to successfully vacuum infiltrate coated flake with molten aluminum alloys were developed. The resulted metal matrix composites exhibited lower CTE than aluminum metal. The CTE of the composites were significantly lower than aluminum and its alloys. The CTE can potentially be tailored for specific applications. The in plane thermal conductivity was higher than the aluminum matrix alloy. The thermal conductivity and CTE of the composite may be significantly improved by improving the bond strength of the molybdenum coating on the graphite flake. The flake can potentially be incorporated in the molten aluminum and pressure die cast to align the flakes within the aluminum matrix. By preferentially aligning high conductivity graphite flakes within a plane or direction, the thermal conductivity of the resulting composite will be above pure aluminum in the alignment direction.

Sommer, J.L.

1997-04-01

375

Development of Cf\\/Al lens barrel for space infrared telescope  

Microsoft Academic Search

The superior mechanical and thermal properties of continuous graphite fiber reinforced aluminum matrix composite (Cf\\/Al) make it attractive from a design standpoint for space-based system for which the lightweight, high stiffness structure is one of the key technologies. This paper describes the development process of a Cf\\/Al lens barrel used in space infrared optical system including fabrication technology, structure design

Shao-wen Guo; Guang-yu Zhang; Wu-yi Wang; Xue-zeng Zhao

2007-01-01

376

Observation of the temperature dependence of the dynamics of photoexcited states in pristine tris(8-hydroxyquinoline) aluminum (AlQ{sub 3})  

SciTech Connect

The authors have investigated the temperature dependence of the dynamics of radiative excited states in pristine thin films of tris(8-hydroxyquinoline) aluminum (Alq{sub 3}). By measuring the transient photoluminescence (PL) response with subnanosecond resolution, their results revealed an increase in the radiative excited state lifetime and fluorescence quantum yield with decreasing temperature from 300K to 77K. At low temperature the authors observed a decrease in the bimolecular recombination rate constant, singlet exciton diffusion coefficient and diffusion length. A singlet exciton trapping model is used to explain these results.

Priestley, R.; Walser, A.D.; Dorsinville, R.

1998-07-01

377

Ignition of Aluminum Particles and Clouds  

SciTech Connect

Here we review experimental data and models of the ignition of aluminum (Al) particles and clouds in explosion fields. The review considers: (i) ignition temperatures measured for single Al particles in torch experiments; (ii) thermal explosion models of the ignition of single Al particles; and (iii) the unsteady ignition Al particles clouds in reflected shock environments. These are used to develop an empirical ignition model appropriate for numerical simulations of Al particle combustion in shock dispersed fuel explosions.

Kuhl, A L; Boiko, V M

2010-04-07

378

Preparation Al2O3/ZrO2 composite coating in an alkaline phosphate electrolyte containing K2ZrF6 on aluminum alloy by microarc oxidation  

NASA Astrophysics Data System (ADS)

Al2O3/ZrO2 composite coating was prepared on 2A70 aluminum alloy by microarc oxidation (MAO) in a phosphate electrolyte containing K2ZrF6. The effects of K2ZrF6 in the electrolyte on the coating thickness, surface morphology, elemental composition and abrasive resistance were investigated. The results indicated that the MAO coating thickness increase due to the addition of K2ZrF6 in the electrolyte. In the electrolyte containing 6.0 g/L K2ZrF6, the coating was the most uniform and compact. The MAO coating formed in the electrolyte without K2ZrF6 was mainly composed of ?-Al2O3 and a little ?-Al2O3. Zirconium in the form of t-ZrO2 was detected in the MAO coatings formed in the electrolyte containing K2ZrF6, and the Zr content increases with increasing concentration of K2ZrF6. A ?-Al2O3 and t-ZrO2 nanocomposite coating was formed in the electrolyte containing 6.0 g/L K2ZrF6, and which exhibited the highest abrasive resistance.

Tang, Mingqi; Li, Weiping; Liu, Huicong; Zhu, Liqun

2012-05-01

379

Physiological and molecular characterization of aluminum resistance in Medicago truncatula  

Microsoft Academic Search

BACKGROUND: Aluminum (Al) toxicity is an important factor limiting crop production on acid soils. However, little is known about the mechanisms by which legumes respond to and resist Al stress. To explore the mechanisms of Al toxicity and resistance in legumes, we compared the impact of Al stress in Al-resistant and Al-sensitive lines of the model legume, Medicago truncatula Gaertn.

Divya Chandran; Natasha Sharopova; Kathryn A VandenBosch; David F Garvin; Deborah A Samac

2008-01-01

380

Coordination between Apoplastic and Symplastic Detoxification Confers Plant Aluminum Resistance1[C][W][OPEN  

PubMed Central

Whether aluminum toxicity is an apoplastic or symplastic phenomenon is still a matter of debate. Here, we found that three auxin overproducing mutants, yucca, the recessive mutant superroot2, and superroot1 had increased aluminum sensitivity, while a transfer DNA insertion mutant, xyloglucan endotransglucosylase/hydrolases15 (xth15), showed enhanced aluminum resistance, accompanied by low endogenous indole-3-acetic acid levels, implying that auxin may be involved in plant responses to aluminum stress. We used yucca and xth15 mutants for further study. The two mutants accumulated similar total aluminum in roots and had significantly reduced cell wall aluminum and increased symplastic aluminum content relative to the wild-type ecotype Columbia, indicating that altered aluminum levels in the symplast or cell wall cannot fully explain the differential aluminum resistance of these two mutants. The expression of Al sensitive1 (ALS1), a gene that functions in aluminum redistribution between the cytoplasm and vacuole and contributes to symplastic aluminum detoxification, was less abundant in yucca and more abundant in xth15 than the wild type, consistent with possible ALS1 function conferring altered aluminum sensitivity in the two mutants. Consistent with the idea that xth15 can tolerate more symplastic aluminum because of possible ALS1 targeting to the vacuole, morin staining of yucca root tip sections showed more aluminum accumulation in the cytosol than in the wild type, and xth15 showed reduced morin staining of cytosolic aluminum, even though yucca and xth15 had similar overall symplastic aluminum content. Exogenous application of an active auxin analog, naphthylacetic acid, to the wild type mimicked the aluminum sensitivity and distribution phenotypes of yucca, verifying that auxin may regulate aluminum distribution in cells. Together, these data demonstrate that auxin negatively regulates aluminum tolerance through altering ALS1 expression and aluminum distribution within plant cells, and plants must coordinate exclusion and internal detoxification to reduce aluminum toxicity effectively. PMID:23776189

Zhu, Xiao Fang; Lei, Gui Jie; Wang, Zhi Wei; Shi, Yuan Zhi; Braam, Janet; Li, Gui Xin; Zheng, Shao Jian

2013-01-01

381

The effect of aluminum doping on crystallinity, non-lattice oxygen, and resistance switching of Al-doped HfO2 films deposited by reactive sputtering  

NASA Astrophysics Data System (ADS)

In this work, the resistance switching characteristics of Al-doped HfO2 thin films were investigated with by systematically varying the Al concentration and analyzing of the microstructure and the chemical bonding states. TiN/Al-doped HfO2/Pt metal-insulator-metal stacks were fabricated with various Al concentrations of up to 16.8% by using reactive DC magnetron co-sputtering. X-ray diffraction and transmission electron microscopy measurement showed that HfO2 doped with more than 10.4% Al had an amorphous structure, while HfO2 doped with Al of less than 5.6% had a crystalline structure. X-ray photoelectron spectroscopy (XPS) showed that the concentration of non-lattice oxygen in Aldoped HfO2 films increased with increasing Al up to 5.6% and was saturated for Al concentrations above 5.6%. TiN/Al-doped HfO2/Pt stacks showed typical bipolar resistance switching characteristics. HfO2 doped with Al = 5.6% showed the smallest grains and the smallest uniformity in the forming electric field and the SET/RESET resistance distribution. We conclude that the grain boundaries play a more important role than point defects such as non-lattice oxygen in the resistance switching.

Lee, Kyumin; Na, Heedo; Sohn, Hyunchul; Kim, Jonggi

2014-09-01

382

Alloying of aluminum-beryllium alloys  

NASA Astrophysics Data System (ADS)

The existing phase diagrams of Al-Be- X alloys, where X is an alloying element, are analyzed. Element X is noted to poorly dissolve in both aluminum and beryllium. It is shown that the absence of intermetallic compounds in the Al-Be system affects the phase equilibria in an Al-Be- X system. Possible phase equilibria involving phases based on aluminum, beryllium, and intermetallic compounds are proposed, and the types of strengthening of Al-Be alloys by an addition of a third element are classified.

Molchanova, L. V.; Ilyushin, V. N.

2013-01-01

383

/Al-Si Composites Fabricated by Reaction Hot Pressing  

NASA Astrophysics Data System (ADS)

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

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

2014-12-01

384

Nanoclusters of MoO3-x embedded in an Al2O3 matrix engineered for customizable mesoscale resistivity and high dielectric strength  

NASA Astrophysics Data System (ADS)

We have synthesized a material consisting of conducting metal oxide (MoO3-x) nanoclusters embedded in a high-dielectric-strength insulator (Al2O3) matrix. The resistivity of this material can be customized by varying the concentration of the MoO3-x nanoclusters. The Al2O3 protects the MoO3-x from stoichiometry change, thus conserving the number of carriers and maintaining a high dielectric strength. This composite material is grown by atomic layer deposition, a thin film deposition technique suitable for coating 3D structures. We applied these atomic layer deposition composite films to our 3D electron-optical micro electrical mechanical systems devices and greatly improved their performance.

Tong, William M.; Brodie, Alan D.; Mane, Anil U.; Sun, Fuge; Kidwingira, Franoise; McCord, Mark A.; Bevis, Christopher F.; Elam, Jeffrey W.

2013-06-01

385

In Situ Synthesis, Microstructure, and Properties of TiC and (Ti,W)C-Reinforced Fe-Mn-Al Austenitic Steel Matrix Composites  

NASA Astrophysics Data System (ADS)

In situ synthesis, microstructures, and properties of 10 vol.% TiC and (Ti,W)C-reinforced Fe-Mn-Al austenitic steel matrix composites have been reported in this paper. The microstructure of the prepared samples has been characterized by using scanning electron microscopy and X-ray diffraction technique. The abrasion wear resistance and mechanical properties such as hardness and impact energy of both the composites as well as the unreinforced Fe-Mn-Al austenitic steel have been evaluated. The (Ti,W)C-reinforced composite has higher impact energy and slightly lower hardness values compared to that of TiC-reinforced composite. The TiC-reinforced composite exhibits the best abrasive wear resistance of all the materials tested.

Srivastava, Ashok Kumar; Das, Karabi

2012-11-01

386

Effects of Irradiation on the Microstructure of U-7Mo Dispersion Fuel with Al-2Si Matrix  

SciTech Connect

The Reduced Enrichment for Research and Test Reactor program is developing low-enriched uranium U-Mo dispersion fuels for application in research and test reactors around the world. As part of this development, fuel plates have been irradiated in the Advanced Test Reactor and then characterized using optical metallography (OM) and scanning electron microscopy (SEM) to determine the as-irradiated microstructure. To demonstrate the irradiation performance of U-7Mo dispersion fuel plates with 2 wt% Si added to the matrix, fuel plates were tested to medium burnups at intermediate fission rates as part of the RERTR-6 experiment. Further testing was performed to higher fission rates as part of the RERTR-7A experiment, and very aggressive testing (high temperature, high fission density, high fission rate) was performed in the RERTR-9A, RERTR-9B and AFIP-1 experiments. As-irradiated microstructures were compared to those observed after fabrication to determine the effects of irradiation on the microstructure. Based on comparison of the microstructural characterization results for each irradiated sample, some general conclusions can be drawn about how the microstructure evolves during irradiation: there is growth of the fuel/matrix interaction layer (FMI), which was present in the samples to some degree after fabrication, during irradiation; Si diffuses from the FMI layer to deeper depths in the U-7Mo particles as the irradiation conditions are made more aggressive; lowering of the Si content in the FMI layer results in an increase in the size of the fission gas bubbles; as the FMI layer grows during irradiation more Si diffuses from the matrix to the FMI layer/matrix interface, and interlinking of fission gas bubbles in the fuel plate microstructure that may indicate breakaway swelling is not observed.

Dennis D. Keiser, Jr.; Jan-Fong Jue; Adam B. Robinson; Pavel Medvedev; Jian Gan; Brandon D. Miller; Daniel M. Wachs; Glenn A. Moore; Curtis R. Clark; Mitchell K. Meyer; M. Ross Finlay

2012-06-01

387

Evaluation of tool wear when machining SiC p-reinforced Al2014 alloy matrix composites  

Microsoft Academic Search

SiCp-reinforced metal matrix composites (MMCs) containing two levels of SiC particles (8 and 16 wt%) of different mean particle sizes 30, 45 and 110 ?m were prepared using a melt stirringsqueeze casting route. Machining tests were carried out on the composites using uncoated and triple-layer coated carbide cutting tools at various cutting speeds under a constant feed rate and depth

Ibrahim Ciftci; Mehmet Turker; Ulvi Seker

2004-01-01

388

Mechanism of reaction in NaAlCl4 molten salt batteries with nickel felt cathodes and aluminum anodes. 2: Experimental results and comparison with model calculations  

Microsoft Academic Search

The battery systems: Al\\/NaCl-AlCl3-Al2 X3\\/Ni-felt (X = S, Se, Te) and the corresponding system without chalcogen have been studied experimentally at 175 C. Charge\\/discharge experiments, performed on cells with NaCl saturated melts, show that advantages with regard to rate capability and cyclability can be obtained with systems containing dissolved chalcogen compared with the chalcogen-free system. Exchange of chalcogen between cathode

B. C. Knutz; R. W. Berg; H. A. Hjuler; N. J. Bjerrum

1993-01-01

389

Characterization of Metal Matrix Composites  

NASA Technical Reports Server (NTRS)

Experimental methods were developed, adapted, and applied to the characterization of a metal matrix composite system, namely, silicon carbide/aluminim (SCS-2/6061 Al), and its constituents. The silicon carbide fiber was characterized by determining its modulus, strength, and coefficient of thermal expansion. The aluminum matrix was characterized thermomechanically up to 399 C (750 F) at two strain rates. The unidirectional SiC/Al composite was characterized mechanically under longitudinal, transverse, and in-plane shear loading up to 399 C (750 F). Isothermal and non-isothermal creep behavior was also measured. The applicability of a proposed set of multifactor thermoviscoplastic nonlinear constitutive relations and a computer code was investigated. Agreement between predictions and experimental results was shown in a few cases. The elastoplastic thermomechanical behavior of the composite was also described by a number of new analytical models developed or adapted for the material system studied. These models include the rule of mixtures, composite cylinder model with various thermoelastoplastic analyses and a model based on average field theory. In most cases satisfactory agreement was demonstrated between analytical predictions and experimental results for the cases of stress-strain behavior and thermal deformation behavior at different temperatures. In addition, some models yielded detailed three-dimensional stress distributions in the constituents within the composite.

Daniel, I. M.; Chun, H. J.; Karalekas, D.

1994-01-01

390

New methods for corrosion testing of aluminum alloys  

Microsoft Academic Search

This symposium presents papers on a modification of the EXCO test method for exfoliation corrosion susceptibility in 7XXX, 2XXX, and aluminum-lithium alloys; materials evaluation using wet-dry mixed salt-spray tests; a comparison of potentiodynamic polarization tests with wet-dry mixed salt-spray testing of Al-Mg-Si alloy; an accelerated test for determining microbiological-influenced corrosion resistance of aluminum alloys; and corrosion of aluminum in Al

V. S. Agarwala; G. M. Ugiansky

1992-01-01

391

Effect of cutting fluid on the machinability of metal matrix composites  

Microsoft Academic Search

This paper utilizes models for cumulative tool wear to study the effect of cutting fluid on the machinability of aluminum-based matrix composites reinforced with SiC or Al2O3 particles. Pressurized cutting fluid neither improves nor worsens the tool life because of either effective flushing of the chips or lack of a lubricating film. The surface finish and the cutting forces are

N. P. Hung; S. H. Yeo; B. E. Oon

1997-01-01

392

Matrix effects in ion-induced emission as observed in Ne collisions with Cu-Mg and Cu-Al alloys  

NASA Technical Reports Server (NTRS)

Ion induced Auger electron emission is used to study the surfaces of Al, Mg, Cu - 10 at. % Al, Cu - 19.6 at. % Al, and Cu - 7.4 at. % Mg. A neon (Ne) ion beam whose energy is varied from 0.5 to 3 keV is directed at the surface. Excitation of the lighter Ne occurs by the promotion mechanism of Barat and Lichten in asymmetric collisions with Al or Mg atoms. Two principal Auger peaks are observed in the Ne spectrum: one at 22 eV and one at 25 eV. Strong matrix effects are observed in the alloys as a function of energy in which the population of the second peak is greatly enhanced relative to the first over the pure materials. For the pure material over this energy range this ratio is 1.0. For the alloys it can rise to the electronic structure of alloys and to other surface tools such as secondary ion mass spectroscopy.

Ferrante, J.; Pepper, S. V.

1983-01-01

393

Effects of Effective Dendrite Size on Tensile Deformation Behavior in Ti-Based Dendrite-Containing Amorphous Matrix Composites Modified from Ti-6Al-4V Alloy  

NASA Astrophysics Data System (ADS)

Five composite sheets having different thicknesses were fabricated by varying cooling rates after a vacuum arc melting of a Ti-based amorphous matrix composite fabricated by adding alloying elements of Ti, Zr, V, Ni, Al, and Be into a Ti-6Al-4V alloy. These composite sheets contained 72 to 75 vol. pct of dendrites sized by 9 to 27 ?m, and showed excellent tensile properties of yield strength of 1.3 GPa and elongation up to 6.5 pct. According to the observation of tensile deformation behavior of the 3-mm-thick composite sheet, many deformation bands were formed inside dendrites in several directions, and deformation bands met crossly each other to form widely deformed areas. Since the wide and homogeneous deformation in this sheet beneficially worked for the tensile strength and elongation simultaneously, the optimum effective dendrite size (12.1 ?m) and sheet thickness (3 mm) were determined for the Ti-based amorphous matrix composite. The finite element method (FEM) analysis based on real microstructures was also conducted to theoretically explain the enhanced elongation in terms of effective dendrite size. The shape and location of deformation bands estimated from the FEM simulations were well matched with the experimental observations.

Jeon, Changwoo; Lee, Hyungsoo; Kim, Choongnyun Paul; Joo, Soo-Hyun; Kim, Hyoung Seop; Lee, Sunghak

2015-01-01

394

Effects of the composition on the properties of nickel-aluminum layered double hydroxide/carbon (Ni-Al LDH/C) composite fabricated by liquid phase deposition (LPD)  

NASA Astrophysics Data System (ADS)

We report the optimized preparation by liquid phase deposition (LPD) of nickel-aluminum layered double hydroxide/carbon (Ni-Al LDH/C) composites as nickel-based cathode materials. We investigate the influence of the LDH content on the properties of the composites prepared with various total volumes of the reaction solution while the solution composition and the amount of carbon are maintained constant. Diffraction patterns show that the crystallinity of the composite increases with increasing the LDH content. Gravimetric studies indicate that there is no correlation between the amount of the deposit and the total volume of the reaction solution. Inductively coupled plasma-atomic emission spectroscopy (ICP-AES) reveals that the optimal Al3+/(Al3+ + Ni2+) is obtained for the sample with the highest LDH content. The optimized composition results in high performance cathode materials; a high discharge capacity (>390 mAh gcomp-1) at the 1.0 C-rate, a good cycle life at 2.0 C-rate over 300 cycles and excellent electrochemical stability.

Blk, Alexis Bienvenu; Higuchi, Eiji; Inoue, Hiroshi; Mizuhata, Minoru

2013-03-01

395

Active metal-matrix composites with embedded smart materials by ultrasonic additive manufacturing  

NASA Astrophysics Data System (ADS)

This paper presents the development of active aluminum-matrix composites manufactured by Ultrasonic Additive Manufacturing (UAM), an emerging rapid prototyping process based on ultrasonic metal welding. Composites created through this process experience temperatures as low as 25 C during fabrication, in contrast to current metal-matrix fabrication processes which require temperatures of 500 C and above. UAM thus provides unprecedented opportunities to develop adaptive structures with seamlessly embedded smart materials and electronic components without degrading the properties that make these materials and components attractive. This research focuses on developing UAM composites with aluminum matrices and embedded shape memory NiTi, magnetostrictive Galfenol, and electroactive PVDF phases. The research on these composites will focus on: (i) electrical insulation between NiTi and Al phases for strain sensors, investigation and modeling of NiTi-Al composites as tunable stiffness materials and thermally invariant structures based on the shape memory effect; (ii) process development and composite testing for Galfenol-Al composites; and (iii) development of PVDF-Al composites for embedded sensing applications. We demonstrate a method to electrically insulate embedded materials from the UAM matrix, the ability create composites containing up to 22.3% NiTi, and their resulting dimensional stability and thermal actuation characteristics. Also demonstrated is Galfenol-Al composite magnetic actuation of up to 54 ?(see manuscript), and creation of a PVDF-Al composite sensor.

Hahnlen, Ryan; Dapino, Marcelo J.

2010-04-01

396

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

SciTech Connect

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

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

2013-12-16

397

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

398

The viability of aluminum Zintl anion moieties within magnesium-aluminum clusters  

SciTech Connect

Through a synergetic combination of anion photoelectron spectroscopy and density functional theory based calculations, we have investigated the extent to which the aluminum moieties within selected magnesium-aluminum clusters are Zintl anions. Magnesium-aluminum cluster anions were generated in a pulsed arc discharge source. After mass selection, photoelectron spectra of Mg{sub m}Al{sub n}{sup ?} (m, n = 1,6; 2,5; 2,12; and 3,11) were measured by a magnetic bottle, electron energy analyzer. Calculations on these four stoichiometries provided geometric structures and full charge analyses for the cluster anions and their neutral cluster counterparts, as well as photodetachment transition energies (stick spectra). Calculations revealed that, unlike the cases of recently reported sodium-aluminum clusters, the formation of aluminum Zintl anion moieties within magnesium-aluminum clusters was limited in most cases by weak charge transfer between the magnesium atoms and their aluminum cluster moieties. Only in cases of high magnesium content, e.g., in Mg{sub 3}Al{sub 11} and Mg{sub 2}Al{sub 12}{sup ?}, did the aluminum moieties exhibit Zintl anion-like characteristics.

Wang, Haopeng; Jae Ko, Yeon; Zhang, Xinxing; Gantefoer, Gerd; Bowen, Kit H., E-mail: kiran@mcneese.edu, E-mail: akandalam@wcupa.edu, E-mail: kbowen@jhu.edu [Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218 (United States); Schnoeckel, Hansgeorg [Institute of Inorganic Chemistry, Karlsruhe Institute of Technology, 76128 Karlsruhe (Germany)] [Institute of Inorganic Chemistry, Karlsruhe Institute of Technology, 76128 Karlsruhe (Germany); Eichhorn, Bryan W. [Department of Chemistry, University of Maryland, College Park, Maryland 20742 (United States)] [Department of Chemistry, University of Maryland, College Park, Maryland 20742 (United States); Jena, Puru [Department of Physics, Virginia Commonwealth University, Richmond, Virginia 23284 (United States)] [Department of Physics, Virginia Commonwealth University, Richmond, Virginia 23284 (United States); Kiran, Boggavarapu, E-mail: kiran@mcneese.edu, E-mail: akandalam@wcupa.edu, E-mail: kbowen@jhu.edu [Department of Chemistry, McNeese State University, Lake Charles, Louisiana 70609 (United States)] [Department of Chemistry, McNeese State University, Lake Charles, Louisiana 70609 (United States); Kandalam, Anil K., E-mail: kiran@mcneese.edu, E-mail: akandalam@wcupa.edu, E-mail: kbowen@jhu.edu [Department of Physics, West Chester University, West Chester, Pennsylvania 19383 (United States)

2014-03-28

399

Residual microstructure and damage geometry associated with high speed impact crater in Al{sub 2}O{sub 3} and TiB{sub 2} particles reinforced 2024 Al composite  

SciTech Connect

The resistance of Al{sub 2}O{sub 3} + TiB{sub 2}/2024Al composite to hypervelocity impact was tested by a two-stage light gas gun. The impact damage behaviors of the Al{sub 2}O{sub 3} + TiB{sub 2}/2024Al composite by different-sized Al projectiles with a velocity of 2.49 km/s and the residual microstructures associated with the crater impacted by a 1.2 mm aluminum projectile were investigated by transmission electron microscopy and high-resolution transmission electron microscopy. Both the diameters of craters at front face and spalling areas at back face increased with the aluminum projectile diameter. The diameter of perforation on the 2 mm thick Al{sub 2}O{sub 3} + TiB{sub 2}/Al composite target was zero when impacted by 1.2 mm aluminum projectile and it increased to 2.4 mm when the projectile diameter was 1.5 mm, indicating that the critical perforation diameter of the aluminum projectile was between 1.2 mm and 1.5 mm when the 2 mm thick Al{sub 2}O{sub 3} + TiB{sub 2}/Al composite target was impacted by 2.49 km/s aluminum projectiles. The diameter of perforation increases with the diameter of Al projectile. In addition, under each impact condition, the diameters of craters at front face were smaller than that of spalling areas at back face. Microstructure observations by transmission electron microscopy demonstrated four characteristics: stacking faults around TiB{sub 2} particle and dislocations within the TiB{sub 2} particle; twins in the Al{sub 2}O{sub 3} particle; recrystal grains in 2024 Al matrix; and mixture of amorphous microstructure and nanograins in the matrix. - Highlights: Black-Right-Pointing-Pointer Stacking faults were produced around the edge of TiB{sub 2} particle after impact. Black-Right-Pointing-Pointer Twins with the twin plane of (2{sup Macron }112) were observed in Al{sub 2}O{sub 3} particle after impact. Black-Right-Pointing-Pointer Recrystal grains with size of 100 nm were formed in aluminum matrix after impact. Black-Right-Pointing-Pointer Mixture of amorphous microstructure and nanograins was also found in matrix.

Guo, Q.; Sun, D.L., E-mail: sdl602@hit.edu.cn; Jiang, L.T.; Wu, G.H.; Chen, G.Q.

2012-04-15

400

ALUMINUM AIR BRAZING FOR JOINING CERAMICS  

SciTech Connect

Aluminum foils were used to braze ceramic plates directly in air. Since aluminum forms an inert oxide layer, aluminum air brazing can provide significant benefits in ceramic joining such as chemical tolerance in dual atmospheres. In using aluminum to air braze, the key factor is optimizing the brazing conditions in order to obtain good interface between braze and substrates by controling the kinetics of melting and oxidation of aluminum and sintering of oxide scale. In this study, joint strength was found to be largely dependent on brazing conditions such as temperature and hold time. Effects of these conditions on the mechanical properties and the microstructure of the Al-brazed ceramic joints will be discussed in this paper.

Kim, Jin Yong Y.; Hardy, John S.; Weil, K. Scott

2008-01-01

401

Effect of magnesium on the aging behavior of Al-Zn-Mg-Cu/Al{sub 2}O{sub 3} metal matrix composites  

SciTech Connect

The effect of magnesium content on the aging behavior of Al-Zn-Mg-Cu alloy reinforced with alumina (Al{sub 2}O{sub 3}) was studied by using the differential scanning calorimetry (DSC) technique and hardness measurement. The magnesium contents were studied in the range from 1.23 to 2.97 wt pct. The addition of magnesium was found to increase the coherent Guinier-Preston (GP) zones in composites. The apparent formation enthalpy of GP zones of composites (0.1 V{sub f}) was 0.932 cal/g for 1.23 wt pct magnesium content and 1.375 cal/g for 2.97 wt pct magnesium content. The precipitation time to achieve the maximum hardness in the composites depends on the magnesium content. The time changed from 12 to 48 hours as the magnesium content increased from 1.23 to 2.97 wt pct. Both Vickers microhardness and Rockwell hardness increased with increasing magnesium content. The maximum hardness occurred in the composites that contained maximum amounts of GP zones and {eta}{prime} precipitates. However, the microhardness of the composites was always lower than that of monolithic alloys due to the alumina fibers which caused the suppression of GP zones and {eta}{prime} formation in the composites.

Chou, M.C.; Chao, C.G. [National Chiao Tung Univ., Hsinchu (Taiwan, Province of China). Inst. of Materials Science and Engineering

1996-07-01

402

Mechanical properties and dual atmosphere tolerance of Ag-Al based braze  

SciTech Connect

Reactive air brazing (RAB) based on the silver-copper oxide system was recently developed for use in sealing high-temperature electrochemical devices such as solid oxide fuel cells. One of the concerns regarding the viability of this joining technique is the long-term stability of silver-based alloys under a high-temperature, dual oxidizing/reducing gas environment. One possible solution to improve the dual atmosphere tolerance of the silver-based system is the addition of elements which can preferentially react with oxygen over hydrogen and minimize the pore formation caused by the reaction of oxygen with hydrogen in the silver matrix. In this paper, the effects of aluminum addition into silver-based air braze filler materials on microstructure, mechanical properties, and high temperature dual atmosphere tolerance were investigated using foils and pastes of aluminum-added braze filler materials. Joints brazed with binary Ag-Al braze foils containing more than 2 at% of Al retained a metallic form of aluminum in the metallic braze filler matrix after brazing at 1000?C in air. The flexural strength of joints prepared with binary Ag-Al braze foils decreased with increase in Al content due to the formation of interfacial aluminum oxide. The existence of metallic aluminum in the braze filler matrix, however, enhanced the high temperature dual atmosphere tolerance of the silver-based braze filler, showing smaller size of porosity after dual reducing/oxidizing atmosphere tests at 800?C for 1000 hrs. The Binary and ternary braze pastes based on the Ag-Al(-Cu) system were also tried as a sealant. Alumina joints brazed with these pastes showed increase in flexural strength with Cu content. However, a braze filler containing 5 at% Al and 8 at% Cu possessed nearly no metallic aluminum in the braze filler matrix after brazing, while the as-brazed sample prepared using a binary braze filler with 5 at% Al kept some metallic Al in the braze matrix. Thus, the addition of copper did not give a positive influence on the dual atmosphere tolerance of the silber-based braze filler materials as indicated by large pores caused by dual atmosphere embrittlement.

Kim, Jin Yong; Choi, Jung-Pyung; Weil, K. Scott

2008-12-01

403

Studies of aluminum in rat brain  

SciTech Connect

The effects of high aluminum concentrations in rat brains were studied using /sup 14/C autoradiography to measure the uptake of /sup 14/C 2-deoxy-D-glucose (/sup 14/C-2DG) and microbeam proton-induced x-ray emission (microPIXE) with a 20-..mu..m resolution to measure concentrations of magnesium, aluminum, potassium, and calcium. The aluminum was introduced intracisternally in the form of aluminum tartrate (Al-T) while control animals were given sodium tartrate (Na-T). The /sup 14/C was administered intravenously. The animals receiving Al-T developed seizure disorders and had pathological changes that included cerebral cortical atrophy. The results showed that there was a decreased uptake of /sup 14/C-2DG in cortical regions in which increased aluminum levels were measured, i.e., there is a correlation between the aluminum in the rat brain and decreased brain glucose metabolism. A minimum detection limit of about 16 ppM (mass fraction) or 3 x 10/sup 9/ Al atoms was obtained for Al under the conditions employed. 14 refs., 4 figs., 1 tab.

Lipman, J.J.; Brill, A.B.; Som, P.; Jones, K.W.; Colowick, S.; Cholewa, M.

1985-01-01

404

High-velocity-oxidation performance of metal-chromium-aluminum (MCrAl), cermet, and modified aluminide coatings on IN-100 and type VIA alloys at 1093 C  

NASA Technical Reports Server (NTRS)

Cermet, MCrAl, and modified aluminide types of coatings applied to IN-100 and NASA-TRW-VIA alloy specimens were cyclically oxidation tested in a high velocity (Mach 1) gas flame at 1093 C. Several coating compositions of each type were evaluated for oxidation resistance. The modified aluminide coating, Pt-Al, applied to alloy 6A proved to be the best, providing oxidation protection to approximately 750 hours based on weight change measurements. The second best, a CoCrAlY coating applied to 6A, provided protection to 450 hours. The third best was a cermet + aluminide coating on 6A with a protection time to 385 hours.

Deadmore, D. L.

1974-01-01

405

Evaluation of Precipitation Hardening Characteristics of Rheology-Forged Al 7075 Aluminum Alloy Using Nano- or Microindentation and Atomic Force Microscopy  

NASA Astrophysics Data System (ADS)

The mechanical and tribological properties of rheo-formed Al 7075 wrought alloys are investigated using nano- or microindentation and nanoscratch techniques, incorporating optical microscopy and atomic force microscopy (AFM). The results are compared to results from a Vickers hardness test. The peak hardness and surface roughness of specimens aged for 24 hours are obtained for Al 7075 alloy. The tribological characteristics of rheologically formed materials are investigated using the constant load scratch (CLS) method. Using this technique, the heat treatment condition for rheologically formed wrought Al 7075 alloys is optimized.

Kim, H. H.; Kang, C. G.

2010-03-01

406

Microstructure and wear properties of aluminum\\/aluminumsilicon composite coatings prepared by cold spraying  

Microsoft Academic Search

Composite coatings containing aluminum and aluminum11.6wt.% silicon eutectic alloy phases of varying compositions were fabricated using cold spraying. Coating contained a uniform distribution of the two phases. The hardness of the coatings increased as the volume fraction of AlSi in the coating increased. The length to width ratio of the splats was found to be larger for Al particles compared

Srinivasa R. Bakshi; Di Wang; Timothy Price; Deen Zhang; Anup K. Keshri; Yao Chen; D. Graham McCartney; Philip H. Shipway; Arvind Agarwal

2009-01-01

407

Formation of aluminum oxide films from aluminum hexafluoroacetylacetonate at 350450 c  

Microsoft Academic Search

A study of the thermally activated decomposition of Al(hfa)3 (aluminum hexafluoroacetylacetonate) from the gas phase to form Al2O3 on silicon substrates is reported. The decomposition process was carried out in an open tube atmospheric pressure reactor\\u000a in either argon or oxygen\\/argon mixtures in the temperature range, 350450 C. The chemical vapor deposition process resulted\\u000a in the formation of aluminum oxide

D. Temple; A. Reisman

1990-01-01

408

Accumulation and localization of extensin protein in apoplast of pea root nodule under aluminum stress.  

PubMed

Cell wall components such as hydroxyproline-rich glycoproteins (HRGPs, extensins) have been proposed to be involved in aluminum (Al) resistance mechanisms in plants. We have characterized the distribution of extensin in pea (Pisum sativum L.) root nodules apoplast under short (for 2 and 24h) Al stress. Monoclonal antibodie LM1 have been used to locate extensin protein epitope by immunofluorescence and immunogold labeling. The nodules were shown to respond to Al stress by thickening of plant and infection thread (IT) walls and disturbances in threads growth and bacteria endocytosis. Immunoblot results indicated the presence of a 17-kDa band specific for LM1. Irrespective of the time of Al stress, extensin content increased in root nodules. Further observation utilizing fluorescence and transmission electron microscope showed that LM1 epitope was localized in walls and intercellular spaces of nodule cortex tissues and in the infection threads matrix. Al stress in nodules appears to be associated with higher extensin accumulation in matrix of enlarged thick-walled ITs. In addition to ITs, thickened walls and intercellular spaces of nodule cortex were also associated with intense extensin accumulation. These data suggest that Al-induced extensin accumulation in plant cell walls and ITs matrix may have influence on the process of IT growth and tissue and cell colonization by Rhizobium bacteria. PMID:25004847

Sujkowska-Rybkowska, Marzena; Borucki, Wojciech

2014-12-01

409

Effect of bi-layer ratio in ZnO/Al2O3 multilayers on microstructure and functional properties of ZnO nanocrystals embedded in Al2O3 matrix  

NASA Astrophysics Data System (ADS)

Zinc oxide (ZnO) nanocrystals (NCs) embedded in alumina (Al2O3) matrix were produced via rapid thermal annealing (RTA) of pulsed laser deposited ZnO/Al2O3 multilayered nanostructures. The effect of the thickness ratio ( R) between Al2O3 and ZnO in one bi-layer on the microstructure and functional properties of NCs has been investigated. Grazing incidence small angle X-ray scattering confirmed the formation of nanocrystals after RTA. Grazing incidence wide angle X-ray scattering studies revealed that ZnO NCs have a high crystalline quality with (100) as preferred orientation. Tensile strain of NCs decreases with increasing R and is correlated to the distribution of NCs. From Raman analysis, it is noticed that the phonon frequency of the E2 mode, related to the ZnO wurtzite phase, in NCs is shifted towards that of bulk ZnO with increasing R. Photoluminescence studies revealed that the near edge peak position shifts from 382 nm to 371 nm as the ratio R changes from 1.5 to 4 and is attributed to the strain effect. The intensity of emission in the yellow-green region due to defects decreases significantly with increasing R. Current-voltage ( I- V) characteristics of Al/ZnO NCs embedded in Al2O3/n-Si (100)/Al have shown a hysteresis behavior. The increasing width of the hysteresis with increasing R revealed that the origin of the hysteresis might be due to the existence of polar surface charges on well-separated NCs. The high-resistance and low-resistance states in I- V hysteresis curves seem to be governed by Fowler-Nordheim tunneling and Schottky emission mechanisms, respectively.

Sekhar, K. C.; Levichev, S.; Buljan, M.; Bernstorff, S.; Kamakshi, Koppole; Chahboun, A.; Almeida, A.; Agostinho Moreira, J.; Pereira, M.; Gomes, M. J. M.

2014-04-01

410

A New Method for Preparation of Metal Matrix Nanocomposites  

NASA Astrophysics Data System (ADS)

Particulate metal matrix composites (MMCs) can involve ceramic particulates ranging in size from few nanometers to 500 ?m. Particulates are added to the metal matrix for strengthening. In particular, addition of nanoparticles, even in quantities as small as 2 weight percent can enhance the hardness or yield strength by a factor as high as 2. There are several methods for the production of metal matrix nanocomposites including mechanical alloying , vertex process and spray deposition. However, the above processes are expensive. Solidification processing is a relatively cheaper route. However, during solidification processing nanoparticulates tend to agglomerate as a result of van der Waals forces and thus proper dispersion of the nano-particulate in metal matrix is a challenge. Yang et al dispersed nanoparticles in metal matrix by ultrasonic casting. However their technique has several drawbacks such as the oscillating probe, which is in direct contact with liquid metal, may dissolve in the liquid metal and contaminate it. Moreover, the extent of dispersion is not uniform. It is maximum near the probe and gradually decreases as one move away from the probe. Lastly in the method developed by Yang et al, the oscillating probe is removed from the liquid metal before cooling and solidification begin. This may lead to partial reagglomeration of nanoparticles. To overcome these difficulties a non-contact method, where the ultrasonic probe is not in direct contact with the liquid metal, was attempted to disperse nano-sized Al2O3 particulates in aluminum matrix. In this method the mold was subjected to ultrasonic vibration. Hardness measurements and microstructural studies using HRTEM were carried out on samples taken from different locations of the nanocomposite ingot cast by the non-contact method. Commercially pure liquid aluminum was used as matrix of the composite. The Al2O3 nano-powder was prepared by ball milling for 22 hr. The nanopowders were characterized using High Resolution Transmission Electron Microscope. The crystallite size of Al2O3 was mostly below 10 nm. Nanocomposite having 3 wt% of Al2O3 was cast. The total weight of the ingot was 205 gm. From HRTEM studies it is seen that the Al2O3 particles are distributed uniformly. Both hardness and micro hardness were measured at different locations. It was found that the variations in hardness from location to location are not so significant. In micro scale the hardness is uniform throughout the sample.

Padhi, Payodhar; Panigrahi, S. C.; Ghosh, Sudipto

2008-10-01

411

Cryogenic properties of aluminum alloys and composites  

SciTech Connect

Several aluminum-based materials have been evaluated for possible application at cryogenic temperatures. These included the Al-Li alloy 2090, a high purity mechanically alloyed Al, SiC whisker reinforced Al 2124, and SiC particulate reinforced Al 6061. Mechanical properties, thermal properties and electrical properties were measured for these materials. Their performance in a radio frequency cavity was also determined. 4 refs., 6 figs.

Hill, M.A.; Rollett, A.D.; Jacobson, L.A.; Borch, N.R.; Gibbs, W.S.; Patterson, R.A.; Carter, D.H.

1989-01-01

412

Aluminum exclusion and aluminum tolerance in woody plants  

PubMed Central

The aluminum (Al) cation Al3+ is highly rhizotoxic and is a major stress factor to plants on acid soils, which cover large areas of tropical and boreal regions. Many woody plant species are native to acid soils and are well adapted to high Al3+ conditions. In tropical regions, both woody Al accumulator and non-Al accumulator plants occur, whereas in boreal regions woody plants are non-Al accumulators. The mechanisms of these adaptations can be divided into those that facilitate the exclusion of Al3+ from root cells (exclusion mechanisms) and those that enable plants to tolerate Al3+ once it has entered the root and shoot symplast (internal tolerance mechanisms). The biochemical and molecular basis of these mechanisms have been intensively studied in several crop plants and the model plant Arabidopsis. In this review, we examine the current understanding of Al3+ exclusion and tolerance mechanisms from woody plants. In addition, we discuss the ecology of woody non-Al accumulator and Al accumulator plants, and present examples of Al3+ adaptations in woody plant populations. This paper complements previous reviews focusing on crop plants and provides insights into evolutionary processes operating in plant communities that are widespread on acid soils. PMID:23781222

Brunner, Ivano; Sperisen, Christoph

2013-01-01

413

Thixoforming A356 Aluminum Bipolar Plates at High Solid Fractions  

NASA Astrophysics Data System (ADS)

Thixoforming investigations have been developed primarily for the manufacturing of bulk components, and the current knowledge is very limited with respect to the fabrication of thin cross sections of alloys. We studied the effectiveness of thixoforming process for the fabrication of A356 aluminum alloy bipolar plates with microchannels on both sides. Feedstock semisolid slurries, with different solid contents of ~55, 50, and 45 pct, were prepared at 858 K, 863 K, and 868 K (585 C, 590 C, and 595 C), respectively, and were used to thixoform 1.20-mm-thick bipolar thin plates. The microstructures of the thixoformed thin plates consisted of (i) large primary ?-Al globular grains, (ii) a quenched liquid phase, and (iii) fine secondary ?-Al particles. The fraction and size of the primary ?-Al globular grains decreased, and the primary ?-Al globular grains became more spherical with the increasing thixoforming temperature. It seemed that these changes in the microstructural features led to the reduction in the agglomeration and interaction among the primary ?-Al globular grains surrounded by the liquid matrix during thixoforming. This enabled the semisolid slurry to effectively flow and fill in the sharp corners (such as the microchannels) of the die cavity at higher thixoforming temperatures. The thin plates thixoformed at 868 K (595 C), consequently, exhibited the highest dimensional stability and the fewest internal defects. The liquid matrix surrounding the primary ?-Al grains solidified inside the die cavity after thixoforming. Either the liquid phase was instantly quenched or fine secondary ?-Al particles were formed inside the die cavity. The fraction and size of the latter increased with increasing thixoforming temperature. The surface hardness of the thixoformed plates was measured, and the hardness values were correlated with the microstructural features of the thixoformed plates.

Bolouri, Amir; Jang, Chang Hyun; Kang, Chung Gil

2014-04-01

414

Electrical and thermal conductivity of discontinuously reinforced aluminum composites at sub-ambient temperatures  

SciTech Connect

The electrical and thermal conductivities of two SiC particle-reinforced aluminum-matrix composites were measured over the temperature range of 80--300 K. Because of the relatively low value of electrical conductivity of the SiC, the composite conductivity data agreed closely with those of the matrix with spherical pores, as predicted by the theory of Maxwell. The experimental data for the thermal conductivity of the composite exceeded the values predicted for the matrix phase with spherical holes, indicative of a contribution by the silicon carbide reinforcement. This contribution was significant at the higher temperatures but approached zero at the lowest temperature levels. Data analysis suggested that this effect could be attributed to a decrease in the thermal conductance at the Al-SiC interface with decreasing temperature, due to a corresponding increase in phonon scattering or other mechanisms.

Geiger, A.L. [Advanced Composite Materials Corp., Greer, SC (United States)] [Advanced Composite Materials Corp., Greer, SC (United States); Hasselman, D.P.H. [Virginia Polytechnic Inst. and State Univ., Blacksburg, VA (United States). Dept. of Materials Science and Engineering] [Virginia Polytechnic Inst. and State Univ., Blacksburg, VA (United States). Dept. of Materials Science and Engineering; Welch, P. [Gencorp Aerojet, Azusa, CA (United States). Electronic Systems Div.] [Gencorp Aerojet, Azusa, CA (United States). Electronic Systems Div.

1997-09-01

415

Ultrafine-grained Aluminm and Boron Carbide Metal Matrix Composites  

NASA Astrophysics Data System (ADS)

Cryomilling is a processing technique used to generate homogenously distributed boron carbide (B4C) particulate reinforcement within an ultrafine-grained aluminum matrix. The motivation behind characterizing a composite consisting of cryomilled aluminum B4C metal matrix composite is to design and develop a high-strength, lightweight aluminum composite for structural and high strain rate applications. Cryomilled Al 5083 and B4C powders were synthesized into bulk composite by various thermomechanical processing methods to form plate and extruded geometries. The effects of processing method on microstructure and mechanical behavior for the final consolidated composite were investigated. Cryomilling for extended periods of time in liquid nitrogen has shown to increase strength and thermal stability. The effects associated with cryomilling with stearic acid additions (as a process-control agent) on the degassing behavior of Al powders is investigated and results show that the liberation of compounds associated with stearic acid were suppressed in cryomilled Al powders. The effect of thermal expansion mismatch strain on strengthening due to geometrically necessary dislocations resulting from quenching is investigated and found not to occur in bulk cryomilled Al 5083 and B 4C composites. Previous cryomilled Al 5083 and B4C composites have exhibited ultrahigh strength associated with considerable strain-to-failure (>14 pct.) at high strain rates (>103/s) during mechanical testing, but only limited strain-to-failure (0.75 pct.) at quasi-static strain rates (10-3/s). The increased strain to failure at high strain rates is attributed to micro-flaw developments, including kinking, extensive axial splitting, and grain growth were observed after high strain rate deformation, and the significance of these mechanisms is considered.

Vogt, Rustin

416

Effect of milling time and CNT concentration on hardness of CNT/Al{sub 2024} composites produced by mechanical alloying  

SciTech Connect

Carbon nanotube/2024 aluminum alloy (CNT/Al{sub 2024}) composites were fabricated with a combination of mechanical alloying (MA) and powder metallurgy routes. Composites were microstructurally and mechanically evaluated at sintering condition. A homogeneous dispersion of CNTs in the Al matrix was observed by a field emission scanning electron microscopy. High-resolution transmission electron microscopy confirmed not only the presence of well dispersed CNTs but also needle-like shape aluminum carbide (Al{sub 4}C{sub 3}) crystals in the Al matrix. The formation of Al{sub 4}C{sub 3} was suggested as the interaction between the outer shells of CNTs and the Al matrix during MA process in which crystallization took place after the sintering process. The mechanical behavior of composites was evaluated by Vickers microhardness measurements indicating a significant improvement in hardness as function of the CNT content. This improvement was associated to a homogeneous dispersion of CNTs and the presence of Al{sub 4}C{sub 3} in the aluminum alloy matrix. - Highlights: Black-Right-Pointing-Pointer The 2024 aluminum alloy was reinforced by CNTs by mechanical alloying process. Black-Right-Pointing-Pointer Composites were microstructural and mechanically evaluated after sintering condition. Black-Right-Pointing-Pointer The greater the CNT concentration, the greater the hardness of the composites. Black-Right-Pointing-Pointer Higher hardness in composites is achieved at 20 h of milling. Black-Right-Pointing-Pointer The formation of Al{sub 4}C{sub 3} does not present a direct relationship with the milling time.

Perez-Bustamante, R. [Centro de Investigacion en Materiales Avanzados (CIMAV), Laboratorio Nacional de Nanotecnologia, Miguel de Cervantes No.120, C.P. 31109, Chihuahua, Chih. (Mexico)] [Centro de Investigacion en Materiales Avanzados (CIMAV), Laboratorio Nacional de Nanotecnologia, Miguel de Cervantes No.120, C.P. 31109, Chihuahua, Chih. (Mexico); Perez-Bustamante, F. [Universidad Autonoma de Chihuahua (UACH), Facultad de Ingenieria, Circuito No. 1 Nuevo Campus Universitario, C.P. 31125, Chihuahua, Chih. (Mexico)] [Universidad Autonoma de Chihuahua (UACH), Facultad de Ingenieria, Circuito No. 1 Nuevo Campus Universitario, C.P. 31125, Chihuahua, Chih. (Mexico); Estrada-Guel, I. [Centro de Investigacion en Materiales Avanzados (CIMAV), Laboratorio Nacional de Nanotecnologia, Miguel de Cervantes No.120, C.P. 31109, Chihuahua, Chih. (Mexico)] [Centro de Investigacion en Materiales Avanzados (CIMAV), Laboratorio Nacional de Nanotecnologia, Miguel de Cervantes No.120, C.P. 31109, Chihuahua, Chih. (Mexico); Licea-Jimenez, L. [Centro de Investigacion en Materiales Avanzados S.C. (CIMAV), Unidad Mty, Autopista Monterrey-Aeropuerto Km 10, A. P. 43, C.P. 66600, Apodaca, N.L. (Mexico)] [Centro de Investigacion en Materiales Avanzados S.C. (CIMAV), Unidad Mty, Autopista Monterrey-Aeropuerto Km 10, A. P. 43, C.P. 66600, Apodaca, N.L. (Mexico); Miki-Yoshida, M. [Centro de Investigacion en Materiales Avanzados (CIMAV), Laboratorio Nacional de Nanotecnologia, Miguel de Cervantes No.120, C.P. 31109, Chihuahua, Chih. (Mexico)] [Centro de Investigacion en Materiales Avanzados (CIMAV), Laboratorio Nacional de Nanotecnologia, Miguel de Cervantes No.120, C.P. 31109, Chihuahua, Chih. (Mexico); Martinez-Sanchez, R., E-mail: roberto.martiez@cimav.edu.mx [Centro de Investigacion en Materiales Avanzados (CIMAV), Laboratorio Nacional de Nanotecnologia, Miguel de Cervantes No.120, C.P. 31109, Chihuahua, Chih. (Mexico)

2013-01-15

417

Dynamic deformation behavior of a high reinforcement content TiB 2\\/Al composite at high strain rates  

Microsoft Academic Search

Dynamic compressive properties of a 60vol.% TiB2\\/Al composite fabricated by squeeze casting method were measured using split Hopkinson pressure bar. The 60vol.% TiB2\\/Al composite showed significant strain-rate sensitivity compared with the rate insensitive aluminum alloy matrix. The flow stress and the strain-rate sensitivity both showed rise\\/fall tendency at high strain rates. Moreover, a large plastic strain as 7.8% was obtained

Dezhi Zhu; Gaohui Wu; Guoqin Chen; Qiang Zhang

2008-01-01

418

Metabolism and possible health effects of aluminum  

Microsoft Academic Search

An extensive literature review with over 950 references examines the biochemistry of aluminum and eight similar ions. A hypothetical model is presented for the metabolism, based on documented direct observations of Al\\/sup 3 +\\/ and analogies from other ions. Main characteristics are low intestinal absorption, rapid urinary excretion, and slow tissue uptake, mostly in skeleton and reticuloendothelial cells. Intracellular Al\\/sup

P. Ganrot

1986-01-01

419

Aluminum Toxicity and Tolerance in Plants  

Microsoft Academic Search

Aluminum (Al) is the most abundant metal in the earths crust, comprising about 7% of its mass. Since many plant species are sensitive to micromolar concentrations of Al, the potential for soils to be A1 toxic is considerable. Fortu- nately, most of the A1 is bound by ligands or occurs in other nonphytotoxic forms such as aluminosilicates and precip- itates.

Emmanuel Delhaize; Peter R. Ryan

420

July/August 20056 Casting aluminum  

E-print Network

includes `continuous' casting of Al, whereby the solid is formed in the water- cooled casterJuly/August 20056 Bob Rapp Casting aluminum Lay people unfamiliar with metallurgical processing to cast Al commercially. Perhaps I can interest the reader with a summary of this important process. I

Colton, Jonathan S.

421

Electron stimulated desorption of the metallic substrate at monolayer coverage: Sensitive detection via 193 nm laser photoionization of neutral aluminum desorbed from CH3O/Al(111)  

NASA Astrophysics Data System (ADS)

A fortuitous overlap between the gain profile of the 193 nm ArF excimer laser and the Al autoionizing transition (sup 2)S(sub 1/2) (512753/cm) yields to the left (sup 2)P(sup 0)J has been exploited in the direct observation of substrate metal atoms in an electron simulated desorption (ESD) process from the monolayer adsorbate system CH3O/Al(111). The identity of the mass 27 photoion was established as Al(+) by (1) isotopic substitution of C-13 in the methanol employed for methoxy formation, and (2) tunable laser scans utilizing the DJ-2 (J = 3/2, 5/2) intermediate levels at approximately 32436/cm and a 248 nm ionization step. An ESD yield of approximately x 10(exp -6) Al atoms/(electron at 1 keV) was established by comparison with a sputtering experiment in the same apparatus. Velocity distributions measured for the desorbed Al species showed some differences in comparison with methoxy velocity data: a slightly lower peak velocity and a significantly less prominent high-velocity component.

Young, C. E.; Whitten, J. E.; Pellin, M. J.; Gruen, D. M.; Jones, P. L.

422

Mechanism of reaction in NaAlCl4 molten salt batteries with nickel felt cathodes and aluminum anodes. 2: Experimental results and comparison with model calculations  

NASA Astrophysics Data System (ADS)

The battery systems: Al/NaCl-AlCl3-Al2 X3/Ni-felt (X = S, Se, Te) and the corresponding system without chalcogen have been studied experimentally at 175 C. Charge/discharge experiments, performed on cells with NaCl saturated melts, show that advantages with regard to rate capability and cyclability can be obtained with systems containing dissolved chalcogen compared with the chalcogen-free system. Exchange of chalcogen between cathode and electrolyte during cycling was confirmed by performing gravimetric analysis and Raman spectroscopy of the electrolytes. Cathode reactions were studied by coulometric titrations (performed on cells with slightly acidic NaCl-AlCl3 melts and small amounts of chalcogen) and compared with model calculations. Cells containing chalcogen revealed at least three voltage plateaus during cycling. The lowest plateau is associated with formation/decomposition of essentially Ni(y)S(z) an d Ni(y)Se(z) in the sulfide and selenide system, respectively. Cells containing selenide revealed extra capacity below the Ni(y) Se(z)-plateau, most probably associated with a Al(v)Ni(y)Se(z) compound. On the second plateau of sulfide systems NiCl2 or a Ni(y)S(z) Cl(2y - 2z) compound with y greater than (4.4 +/- 0.2), z is formed during charging. Reduction of the formed compound to Ni takes place via consumption of sodium chloride.

Knutz, B. C.; Berg, R. W.; Hjuler, H. A.; Bjerrum, N. J.

1993-12-01

423

Aluminum bioavailability from tea infusion  

PubMed Central

The objective was to estimate oral Al bioavailability from tea infusion in the rat, using the tracer 26Al. 26Al citrate was injected into tea leaves. An infusion was prepared from the dried leaves and given intra-gastrically to rats which received concurrent intravenous 27Al infusion. Oral Al bioavailability (F) was calculated from the area under the 26Al, compared to 27Al, serum concentration time curves. Bioavailability from tea averaged 0.37%; not significantly different from water (F = 0.3%), or basic sodium aluminum phosphate (SALP) in cheese (F = 0.1 to 0.3%), but greater than acidic SALP in a biscuit (F = 0.1%). Time to maximum serum 26Al concentration was 1.25, 1.5, 8 and 4.8 h, respectively. These results of oral Al bioavailability daily consumption by the human suggest tea can provide a significant amount of the Al that reaches systemic circulation. This can allow distribution to its target organs of toxicity, the central nervous, skeletal and hematopoietic systems. Further testing of the hypothesis that Al contributes to Alzheimer's disease may be more warranted with studies focusing on total average daily food intake, including tea and other foods containing appreciable Al, than drinking water. PMID:18848597

Yokel, Robert A.; Florence, Rebecca L.

2008-01-01

424

Aluminum geochemistry in peatland waters  

Microsoft Academic Search

The chemical speciation of aluminum was examined in surface water samples from Sphagnum peatlands in north-central Minnesota, from peatlands along the Canadian east coast, and from bogs in the Pennine Mountain area of England. In highly organic ([DOC] 50 mg L-1 ), low pH waters, 8090% of total dissolved Al was complexed with organic matter (OM), while in waters with

E. H. Helmer; N. R. Urban; S. J. Eisenreich

1990-01-01

425

Crystal structure, characterization and thermoelectric properties of the type-I clathrate Ba{sub 8-y}Sr{sub y}Al{sub 14}Si{sub 32} (0.6{<=}y{<=}1.3) prepared by aluminum flux  

SciTech Connect

The title compound was prepared as single crystals using an aluminum flux technique. Single crystal and powder X-ray diffraction indicate that this composition crystallizes in the clathrate type-I structure, space group Pm3-bar n. Electron microprobe characterization indicates the composition to be Ba{sub 8-y}Sr{sub y}Al{sub 14.2(2)}Si{sub 31.8(2)} (0.77Al content fixed at the microprobe value (12 K data: R{sub 1}=0.0233, wR{sub 2}=0.0441) on a crystal of compositions Ba. The Sr atom preferentially occupies the 2a position; mixed Al/Si occupancy was found on all framework sites. These refinements are consistent with a fully occupied framework and nearly fully occupied cation guest sites as found by microprobe analysis. Temperature dependent electrical resistivity and thermal conductivity have been measured from room temperature to 1200 K on a hot-pressed pellet. Electrical resistivity reveals metallic behavior. The negative Seebeck coefficient indicates transport processes dominated by electrons as carriers. Thermal conductivity is between 22 and 25 mW/cm K. The sample shows n-type conductivity with a maximum figu