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NIST Authors in Bold

Displaying 1826 - 1850 of 2146

Determination of the Electron Escape Depth for NEXAFS Spectroscopy

June 2, 2009
Author(s)
Daniel A. Fischer, K E. Sohn, M D. Dimitriou, Jan Genzer, C Hawker, E. J. Kramer
Depth profiling using near-edge X-ray absorption fine structure (NEXAFS) spectroscopy was used to determine the carbon atom density as a function of depth by analyzing the post-edge signal in NEXAFS spectra. We show that the common assumption in the

High Strain Rate Tissue Simulant Measurements Using digital Image Correlation

June 1, 2009
Author(s)
Steven P. Mates, Richard L. Rhorer, Richard Everett, Kirth Simmonds, Amit Bagchi
Measuring the response of soft materials to high strain rate deformation is extremely challenging because of the difficulty of achieving dynamic equilibrium during high strain rate mechanical testing such as Kolsky bar testing. Digital image correlation

Carbon Nanomaterials Standards Efforts at NIST

May 24, 2009
Author(s)
Jeffrey A. Fagan
Development of carbon nano-materials for applications has been hindered to date by a lack of standard protocols, i.e. documentary standards, and physical standards such as reference materials, which enable the common inter-comparison between laboratories

Capillary Instability in Nanoimprinted Polymer Films

May 21, 2009
Author(s)
Kyle J. Alvine, Yifu Ding, Hyun Wook Ro, Brian C. Okerberg, Alamgir Karim, Christopher L. Soles, Jack F. Douglas
Capillary forces play an active role in defining the equilibrium structure of nanoscale structures. This effect can be especially pronounced in soft materials such as polymers near or above their glass transition temperatures where material flow is

The Origin of Critical Relative Humidity in Adhesion

May 11, 2009
Author(s)
Christopher C. White, Kar T. Tan, Bryan D. Vogt, Donald L. Hunston
Water is ubiquitous in the atmosphere. Unfortunately, adhesive bonding is susceptible to the environmental attack of water leading to significant depreciation in joint strength and subsequently to premature failures [1-6]. This susceptibility of bonding to

Demonstration of Impedance Matching Using a mu-Negative (MNG) Metamaterial

April 14, 2009
Author(s)
Christopher L. Holloway, R. B. Greegor, C. G. Parazzoli, J. A. Nielsen, M. H. Tanielian, D Vier, S Schultz, Richard Ziolkowski
A mu-negative (MNG) metamaterial hemisphere was used to demonstrate impedance matching for a magnetic loop. The metamaterial was comprised of copper spirals deposited on an alumina substrate. The spirals, hemisphere, and magnetic loop were designed to

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
Displaying 1826 - 1850 of 2146