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Displaying 2051 - 2075 of 2347

Modelling of Thermodynamics and Diffusion in Multicomponent Systems

April 1, 2009
Author(s)
Ursula R. Kattner, Carelyn E. Campbell
The availability of reliable materials data is key to the successful design of materials and manufacturing processes. Commercial alloys rarely consist of only two or three elements, but rather may contain a large number of elements for which the needed

Hydrogen-Steel Compatibility Research at NIST-Boulder

March 30, 2009
Author(s)
Thomas A. Siewert
The NIST Materials Reliability Division is outfitting a high pressure (100 MPa) hydrogen testing facility to collect mechanical and thermodynamic property data on various candidate structural materials, and is developing data on nondestructive sensors that

Dielectric Spectroscopy Investigation of Relaxation in C60-Polyisoprene Nanocomposites

March 23, 2009
Author(s)
Yifu Ding, Sebastian Pawlus, Alexei Sokolov, Jack F. Douglas, Alamgir Karim, Christopher Soles
We investigate the influence of adding C60 nanoparticles on the dielectric relaxation spectra of both unentangled and entangled polyisoprene (PIP). Relaxation modes corresponding to both segmental and chain relaxation were analyzed over a broad temperature

Examination of thin film modulus for a series of poly(alkyl methacrylates)

March 22, 2009
Author(s)
Jessica M. Torres, Christopher Stafford, Bryan D. Vogt
In this work, the modulus of polymer thin films for a homologous series of poly(n-alkyl methacrylate)s will be discussed. In particular, the impact of the degree of undercooling from bulk Tg on the deviations will be explored as Tg is significantly

Quantifying Residual Stress in Nanoscale Thin Polymer Films via Surface Wrinkling

March 19, 2009
Author(s)
Jun Y. Chung, Thomas Q. Chastek, Michael J. Fasolka, Hyun W. Ro, Christopher Stafford
Residual stress, a pervasive consequence of solid materials processing, is stress that remains in a material after external forces have been removed. In polymeric materials, residual stress results from processes, such as film formation, that force and

Polymerization Stress Development in Dental Composites: Effect of Cavity Design Factor

March 13, 2009
Author(s)
Joseph M. Antonucci, Anthony A. Giuseppetti, Justin N. O'Donnell, Gary E. Schumacher, Drago Skrtic
Objective: To assess the effect of the cavity design factor (C-factor) on polymerization stress development (PSD) in resin composites. Methods: An experimental resin (BT resin) was prepared, which contained 2,2-bis[p-(2 hydroxy-3 -methacryloxypropoxy

Structural Changes behind the Diffuse Dielectric Response in AgNbO3

March 13, 2009
Author(s)
Igor Levin, Victor L. Krayzman, Joseph C. Woicik, J. Karapetrova, T. Proffen, M. G. Tucker, I. M. Reaney
Structural changes among the so-called M-polymorphs of AgNbO3 were analyzed using combined high-resolution X-ray diffraction, neutron total scattering, electron diffraction, and X-ray absorption fine structure measurements. These polymorphs crystallize

Adhesion Research at the National Institute of Standard and Technology (NIST)

March 11, 2009
Author(s)
Donald L. Hunston, Christopher M. Stafford
Over the years, NIST has been very active in adhesion research. Although there has never been an organizational group or large-scale program that focused specifically on this topic, a wide variety of projects have had adhesion, or related properties, as a

Summary of Charpy Impact Verificaiton Data: 1994-1996

March 2, 2009
Author(s)
Christopher N. McCowan, C M. Wang, D P. Vigliotti
We present a summary of Charpy impact verification test data that were evaluated by the National Institute of Standards and Tecnology (NIST) from January 1994 to December 1996. The Charpy impact machines that met the verification rule that limits the range

The molecular basis of mesophase ordering in a thiophene-based copolymer

February 18, 2009
Author(s)
Dean M. DeLongchamp, Regis J. Kline, Youngsuk Jung, Eric K. Lin, Daniel A. Fischer, David J. Gundlach, Andrew Moad, Lee J. Richter, Michael F. Toney, Martin Heeney, Iain McCulloch
The carrier mobility of poly(2,5-bis(3-alkylthiophen-2-yl) thieno[3,2-b]thiophene) semiconductors can be substantially enhanced after heating through a thermotropic mesophase transition, which causes a significant improvement in thin film structural order

Adhesion at layer-by-layer surfaces in aqueous environments

February 15, 2009
Author(s)
Adam J. Nolte, Jun Y. Chung, Marlon L. Walker, Christopher M. Stafford
Adhesion between materials is often governed by the ambient environment, which can mediate or change the types of molecular interactions present at an interface. Biological interactions, for example, can be mediated by factors such as temperature, ionic

Ultrathin Adhesives: Confinement Effect on Modulus

February 15, 2009
Author(s)
Jessica M. Torres, Christopher Stafford, Bryan D. Vogt
In this work, we will employ this wrinkling metrology to extract the modulus of polymer thin films for a homologous series of poly(n-alkyl methacrylate)s. In particular, we take advantage of the decrease in Tg as the alkyl chain length increases for these

Adhesive bonding to dentin improved by polymerizable cyclodextrin derivatives

January 5, 2009
Author(s)
Rafael L. Bowen, Gary E. Schumacher, Anthony A. Giuseppetti, Kathleen M. Flynn, Charles M. Guttman, Clifton M. Carey
Objectives. Determine bonding characteristics of a hydrophilic monomer formulation containing PCDs (Polymerizable Cyclodextrin Derivatives). The hypothesis was that a formulation containing hydrophilic cross-linking diluent comonomers and PCD molecules

ADVANCED NON-DESTRUCTIVE HYDROGEN SENSORS TO PREVENT MATERIAL DEGRADATION FROM HYDROGEN DAMAGE

January 5, 2009
Author(s)
Angelique N. Lasseigne, Kamalu Koenig, David Olson, Brajendra Mishra, Joshua Jackson, Thomas A. Siewert, Joseph D. McColskey
New higher strength pipeline steels (X100 and X120) exhibit lower tolerance for hydrogen (diffusible and formed hydrides) before significant degradation or failure occurs. It is essential to have advanced sensors to monitor the hydrogen content and

MATRIX RELAXATION AFTER FRACTURE IN A TOUGHENED EPOXY

December 10, 2008
Author(s)
Aaron M. Forster, Cyril Clerici, Donald L. Hunston
An efficient method to increase the Mode I fracture energy of a polymer adhesive is to incorporate a rubbery phase within the glassy matrix. In general, the failure surface of a toughened polymer is characterized by cavitated rubber particles and plastic
Displaying 2051 - 2075 of 2347
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