Large-scale deformation of a single-phase TiAl alloy at elevated temperatures

Polystyrene foams have become more and more important owing to their lightweight potential and their insulation properties. Progress in this field is expected to be realized by foams featuring a microcellular morphology. However, large-scale processing of low-density foams with a closed-cell structure and volume expansion ratio of larger than 10, exhibiting a homogenous morphology with a mean cell size of approximately 10 µm, remains challenging. Here, we report on a series of 4,4′-diphenylmethane substituted bisamides, which we refer to as kinked bisamides, acting as efficient supramolecular foam cell nucleating agents for polystyrene. Self-assembly experiments from solution showed that these bisamides form supramolecular fibrillary or ribbon-like nanoobjects. These kinked bisamides can be dissolved at elevated temperatures in a large concentration range, forming dispersed nano-objects upon cooling. Batch foaming experiments using 1.0 wt.% of a selected kinked bisamide revealed that the mean cell size can be as low as 3.5 µm. To demonstrate the applicability of kinked bisamides in a high-throughput continuous foam process, we performed foam extrusion. Using 0.5 wt.% of a kinked bisamide yielded polymer foams with a foam density of 71 kg/m3 and a homogeneous microcellular morphology with cell sizes of ≈10 µm, which is two orders of magnitude lower compared to the neat polystyrene reference foam with a comparable foam density.

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Large scale magnetic anomalies over western Canada and the Arctic: a discussion

Canadian Journal of Earth Sciences ◽

10.1139/e76-082 ◽

1976 ◽

Vol 13 (6) ◽

pp. 790-802 ◽

Cited By ~ 37

Author(s):

R. L. Coles ◽

G. V. Haines ◽

W. Hannaford

Keyword(s):

Magnetic Field ◽

Large Scale ◽

Elevated Temperatures ◽

Magnetic Anomalies ◽

The Arctic ◽

Evolutionary Development ◽

Magnetic Feature ◽

Western Canada ◽

Arctic Regions ◽

The Magnetic Field

A contoured map of vertical magnetic field residuals (relative to the IGRF) over western Canada and adjacent Arctic regions has been produced by amalgamating new data with those from previous surveys. The measurements were made at altitudes between 3.5 and 5.5 km above sea level. The map shows the form of the magnetic field within the waveband 30 to 5000 km. A magnetic feature of several thousand kilometres wavelength dominates the map, and is probably due in major part to sources in the earth's core. Superimposed on this are several groups of anomalies which contain wavelengths of the order of a thousand kilometres. The patterns of the short wavelength anomalies provide a broad view of major structures and indicate several regimes of distinctive evolutionary development. Enhancement of viscous magnetization at elevated temperatures may account for the concentration of intense anomalies observed near the western edge of the craton.

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Oxidation behavior of a single phase γ-TiAl alloy in low-pressure oxygen and hydrogen

Acta Materialia ◽

10.1016/j.actamat.2004.10.013 ◽

2005 ◽

Vol 53 (3) ◽

pp. 601-608 ◽

Cited By ~ 21

Author(s):

D. Legzdina ◽

I.M. Robertson ◽

H.K. Birnbaum

Keyword(s):

Oxidation Behavior ◽

Single Phase ◽

Tial Alloy ◽

Low Pressure ◽

Pressure Oxygen

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Synthesis and Luminescence Properties of Chalcopyrite-Type CuAlS2

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.301.177 ◽

2006 ◽

Vol 301 ◽

pp. 177-180 ◽

Cited By ~ 3

Author(s):

Yuichiro Kuroki ◽

Tomoichiro Okamoto ◽

Masasuke Takata

Keyword(s):

Diffraction Analysis ◽

Room Temperature ◽

Single Phase ◽

Elevated Temperatures ◽

Emission Peak ◽

Maximum Intensity ◽

X Ray Diffraction ◽

Ultraviolet Emission ◽

X Ray ◽

Copper Aluminum

Copper aluminum disulfide (CuAlS2) powders were synthesized in an evacuated ampoule at elevated temperatures. X-ray diffraction analysis revealed that the powders heated at temperatures higher than 800oC were single-phase CuAlS2. In the cathodoluminescence (CL) spectra measured at room temperature, the powders heated at temperatures higher than 600oC exhibited a visible emission peak at approximately 1.8 eV and a distinct ultraviolet emission peak at 3.45 eV. The powder heated at 700oC showed the maximum intensity of ultraviolet emission which is considered to be associated with excitons.

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Friction and wear of diamond and diamond-like carbon films

Proceedings of the Institution of Mechanical Engineers Part J Journal of Engineering Tribology ◽

10.1243/135065002762355316 ◽

2002 ◽

Vol 216 (6) ◽

pp. 387-400 ◽

Cited By ~ 41

Author(s):

A Erdemir

Keyword(s):

Wear Mechanisms ◽

Friction And Wear ◽

Large Scale ◽

Microelectromechanical Systems ◽

Elevated Temperatures ◽

Diamond Like Carbon ◽

Mechanical Seals ◽

Wear Properties ◽

Specific Test ◽

Wide Range

Detailed tribological studies on diamond and diamond-like carbon (DLC) films have confirmed that these films are inherently self-lubricating and resistant to abrasive, adhesive and corrosive wear. Because of their high chemical inertness, they are also resistant to corrosion and oxidation (even at elevated temperatures). The combination of such exceptional qualities in these films makes them ideal for a wide range of demanding tribological applications (such as microelectromechanical systems, cutting tools, mechanical seals, magnetic hard disks, etc.). These films, available for more than three decades, have been used extensively for tooling and magnetic hard disk applications. Their potential in other application areas is currently being explored around the world. With the development of new and more robust deposition methods in recent years, it is envisioned that the production of high quality diamond and DLC films will become very cost effective and highly reliable for large-scale applications in the transportation and manufacturing sectors. In this paper, sliding wear mechanisms of diamond and DLC films will be presented. Specifically, it will be shown that, in general, the wear of these films is extremely low (mainly because of their exceptional hardness and low friction characteristics). Specific test conditions established during each sliding test, however, may dramatically affect the wear performance of certain diamond and DLC films. One of the dominant wear mechanisms relates to a phase transformation that is primarily the result of very high mechanical and thermal loadings of sliding contact interfaces. The transformation products (such as disordered graphite) trapped at the sliding interface may transfer to the mating surface and significantly affect friction and wear. This paper describes, in terms of structural and fundamental tribological knowledge, the ideal film microstructures and chemistry, as well as operational conditions under which diamond and DLC films perform the best and provide superlow friction and wear properties in sliding tribological applications.

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Mechanical behavior and related microstructural aspects of a nano-lamellar TiAl alloy at elevated temperatures

Acta Materialia ◽

10.1016/j.actamat.2017.02.050 ◽

2017 ◽

Vol 128 ◽

pp. 440-450 ◽

Cited By ~ 36

Author(s):

T. Klein ◽

L. Usategui ◽

B. Rashkova ◽

M.L. Nó ◽

J. San Juan ◽

...

Keyword(s):

Mechanical Behavior ◽

Tial Alloy ◽

Elevated Temperatures

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High-Temperature Mechanical Behavior of B2 Type IrAl Doped With Ni

MRS Proceedings ◽

10.1557/proc-460-707 ◽

1996 ◽

Vol 460 ◽

Author(s):

A. Chiba ◽

T. Ono ◽

X. G. Li ◽

S. Takahashi

Keyword(s):

Steady State ◽

Mechanical Behavior ◽

Constant Velocity ◽

Single Phase ◽

Elevated Temperatures ◽

Constant Load ◽

Secondary Creep ◽

Compression Tests ◽

Order Of Magnitude ◽

Multi Phase

ABSTRACTConstant-velocity and constant-load compression tests have been conducted to examine the mechanical behavior of polycrystalline IrAl and Ir1-xNixAl at ambient and elevated temperatures. Although IrAl exhibits brittle fracture before or immediately after yielding below 1073K, steady-state deformation takes place at temperatures higher than 1273K. Ductility of Ir1-xNixAl is improved with increasing x. On the contrary, strength decreases with increasing x. IrAl exhibits the 0.2% flow stress of 1200MPa at 1073K and 350MPa at 1473K, about an order of magnitude higher than NiAl. Secondary creep of IrAl and Ir0.2Ni0.8Al(i.e., modified NiAl) exhibits class II and class I behavior respectively. Creep strength of binary IrAl and modified NiAl with Ir is about a magnitude of 4 higher than that of single-phase and multi-phase NiAl at a given applied stress.

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Influence of Mechanical Surface Treatments on the Fatigue Performance of the Gamma TiAl Alloy Ti-45Al-9Nb-0.2C

Materials Science Forum ◽

10.4028/www.scientific.net/msf.539-543.1553 ◽

2007 ◽

Vol 539-543 ◽

pp. 1553-1558 ◽

Cited By ~ 1

Author(s):

Janny Lindemann ◽

Anja Kutzsche ◽

Michael Oehring ◽

Fritz Appel

Keyword(s):

Surface Roughness ◽

Shot Peening ◽

Tial Alloy ◽

Elevated Temperatures ◽

Lower Surface ◽

Fatigue Performance ◽

Ambient Temperatures ◽

Roller Burnishing ◽

Compressive Stresses ◽

Wide Range

The effect of shot peening and roller burnishing on the fatigue performance of the γ(TiAl) alloy Ti-45Al-9Nb-0.2C was investigated over a wide range of processing intensities. At optimized conditions shot peening and roller burnishing can markedly improve the fatigue strength at ambient temperatures. For temperatures above 650 °C, the residual compressive stresses induced by shot peening and roller burnishing quickly relax. This indicates that, at elevated temperatures, surface roughness and dislocation strengthening become more important for the fatigue performance of mechanically surface-treated components. Roller burnishing leads to much lower surface roughness than shot peening, resulting in more effective improvement of high temperature fatigue performance. However, surface strengthening by shot peening can also be beneficial for the fatigue performance at elevated temperatures, when the surface roughness is reduced by subsequent polishing.

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LDV and PIV Velocity Results in a Thermosiphon

Volume 2: Symposia, Parts A, B, and C ◽

10.1115/fedsm2003-45601 ◽

2003 ◽

Author(s):

J. Kulman ◽

D. Gray ◽

S. Sivanagere ◽

S. Guffey

Keyword(s):

Large Scale ◽

Single Phase ◽

Flow Characteristics ◽

Reynolds Numbers ◽

Flow Patterns ◽

Laser Doppler Velocimeter ◽

Mean Velocity ◽

Developed Turbulence ◽

The Mean ◽

Good Agreement

Heat transfer and flow characteristics have been determined for a single-phase rectangular loop thermosiphon. The plane of the loop was vertical, and tests were performed with in-plane tilt angles ranging from 3.6° CW to 4.2° CCW. Velocity profiles were measured in one vertical leg of the loop using both a single-component Laser Doppler Velocimeter (LDV), and a commercial Particle Image Velocimeter (PIV) system. The LDV data and PIV data were found to be in good agreement. The measured average velocities were approximately 2–2.5 cm/s at an average heating rate of 70 W, and were independent of tilt angle. Significant RMS fluctuations of 10–20% of the mean velocity were observed in the test section, in spite of the laminar or transitional Reynolds numbers (order of 700, based on the hydraulic diameter). These fluctuations have been attributed to vortex shedding from the upstream temperature probes and mitre bends, rather than to fully developed turbulence. Animations of the PIV data clearly show these large scale unsteady flow patterns. Multiple steady state flow patterns were not observed.

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Numerical Model of a Single Phase, Regenerative Fuel Cell

2nd International Conference on Fuel Cell Science, Engineering and Technology ◽

10.1115/fuelcell2004-2455 ◽

2004 ◽

Cited By ~ 1

Author(s):

A. Garrard ◽

S. Beck ◽

P. Styring

Keyword(s):

Fuel Cell ◽

Large Scale ◽

Single Phase ◽

Reaction System ◽

Reduction Reaction ◽

Dynamic Calculation ◽

Species Concentration ◽

Physical Interactions ◽

Regenerative Fuel Cell ◽

Future Work

A code for numerical simulating the fluid flow and electrochemistry of a single phase regenerative fuel cell is presented. Due to the potentially tiny geometries and complex multi-physical interactions, modeling presents a chance to obtain detailed quantitative data and much needed understanding about physics within the reactor. The Regenesys XL200 fuel cell has the industrial application of large scale energy storage and is the focus of this work. A two dimensional, binary reduction reaction system has been created to represent the XL200 and test the code. Commercially available CFD software Fluent was used to calculate the flow field and subroutines were used to create the dynamic calculation of electrochemistry at the reaction surface. The effect of changing the total applied potential across the domain on the potential and species concentration distribution within the domain was investigated. Results show that the code is producing qualitatively feasible results that represent the tight multi-physical coupling. The code is currently not validated against physical experimental results and this will be the focus of future work.

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