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Materials

Ceramics

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Displaying 551 - 575 of 1323

Phase Relations in the Ba-Y-Cu-O Films on SrTiO3 for the -Ex Situ BaF2- Process

March 5, 2007
Author(s)
Winnie K. Wong-Ng, Makoto Otani, Lawrence P. Cook, Mark D. Vaudin, James P. Cline, Ron Feenstra, T G. Holesinger
In situ x-ray diffraction was used to establish the phase relations in high-Tc superconductor Ba–Y– Cu–O films grown on SrTiO3 through the ex situ BaF2 process. These relations differ from bulk equilibrium phase assemblages in the BaO–Y2O3–CuOx system. In

Enhancement of Engine Oil Wear and Friction Control Performance Through Titanium Additive Chemistry

February 27, 2007
Author(s)
J M. Guevremont, G H. Guinther, D Szemenyei, Mark Devlin, T-C Jao, Cherno Jaye, Joseph Woicik, Daniel A. Fischer
Traditionally, wear protection and friction modification by engine oil are provided by zinc dithiophosphate (ZDDP) or other phosphorus compounds. These additives provide effective wear protection and friction control on engine parts through formation of a

Interrogation of 'Surface', 'Skin' and 'Core' Orientation in Thermotropic Liquid-Crystalline Copolyester Moldings by Near-Edge X-Ray Absorption Fine Structure and Wide-Angle X-Ray Scattering

February 26, 2007
Author(s)
S Rendon, Robert A. Bubeck, L S. Thomas, W R. Burghardt, A Hexemer, Daniel A. Fischer
Injection molding of thermotropic liquid-crystalline polymers (TLCPs) can result in molded articles the exhibit complex orientation states that vary considerably as a function of depth in the part. Skin-core morphologies are often observed in TLCP moldings

Chemical Twinning of the Pyrochlore Structure in the System Bi 2 O 3-Nb 2O 5

January 28, 2007
Author(s)
Ian E. Grey, W G. Mumme, Terrell A. Vanderah, Robert S. Roth, C Bougerol-Chaillout
New ternary bismuth iron niobates having structures based on chemical twinning of pyrochlore are described. Bi5.67Nb10FeO35 has hexagonal symmetry, P63/mmc, a = 7.432(1) , c = 31.881(2) , Z = 2 and Bi9.3Nb16.9Fe1.1O57.8 has rhombohedral symmetry, R-3m, a =

Contact Mechanics of Layered Elastic Materials: Experiment and Theory

January 26, 2007
Author(s)
P M. McGuiggan, Jay S. Wallace, Douglas T. Smith, I Sridhar, Z Zheng, K L. Johnson
This paper reports an experimental and theoretical investigation of the indentation of a layered elastic solid, with special reference to the surface force apparatus (SFA). The contacting surfaces of the SFA comprise a 3-layer material: a thin mica surface

A High-Throughput Thermoelectric Power-Factor Screening Tool for Rapid Construction of Thermoelectric Property Diagrams

January 23, 2007
Author(s)
Makoto Otani, Nathan Lowhorn, Peter K. Schenck, Winnie K. Wong-Ng, Martin L. Green, K Itaka, H Koinuma
We have developed a high throughput screening tool that maps out thermoelectric power factors of combinatorial composition-spread film libraries. The screening tool allows us to measure the electrical conductivity and Seebeck coefficient of over 1000

Influence of Oxygen Vacancies on the Dielectric Properties of Hafnia

January 22, 2007
Author(s)
Eric J. Cockayne
First-principles calculations were used to study the effects of neutral and 2+ charged oxygen vacancies on the dielectric properties of crystalline HfO2. In agreement with previous results, the neutral vacancy is more stable on the 4-fold coordinated site

Analysis of C-S-H Gel and Cement Paste by Small-Angle Neutron Scattering

January 16, 2007
Author(s)
Andrew J. Allen, J Thomas
The role of small-angle x-ray and neutron scattering (SAXS and SANS) in the characterization of cement is briefly reviewed. The unique information obtainable from SANS analysis of C-S-H gel in hydrating cement is compared with that obtainable by other

Composition and Density of Amorphous Calcium-Silicate-Hydrate in Cement

January 16, 2007
Author(s)
Andrew J. Allen, J Thomas, Hamlin M. Jennings
Despite intensive research for over a century, the main binding reaction product of cement hydration, calcium-silicate-hydrate (C-S-H) gel, is not fully understood. By combining absolute-calibrated small-angle and ultrasmall-angle neutron and x-ray

Biaxial Stress Dependence of AlxGa 1-x As Photoluminescence

January 13, 2007
Author(s)
Grady S. White, Albert J. Paul, Kristine A. Bertness, Lawrence H. Robins
A study was conducted of the room temperature photoluminescence behavior of AlxGa1-xAs as a function of tensile, equi-biaxial stress for x = 0, 0.198, 0.36, 0.498, and 0.809. The composition range included both the direct and the indirect band gap regions

On the Vickers Indentation Fracture Toughness Test

January 4, 2007
Author(s)
George D. Quinn, Richard Bradt
The Vickers indentation fracture toughness test or VIF is addressed by considering its origins and the numerous equations that have been applied along with the technique to estimate the fracture resistance, or the KIc of ceramics. Initiation and
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