U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Search Publications

NIST Authors in Bold

Displaying 1551 - 1575 of 1721

Determination of the Molecular Mass Distribution of Narrow Polydispersity Polystyrene by MALDI-TOF-MS: Interlaboratory Comparison

March 1, 2000
Author(s)
Kathleen M. Flynn, S Wetzel, William E. Wallace, William R. Blair, R J. Goldschmidt, David L. VanderHart, B M. Fanconi
NIST has sponsored a matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) interlaboratory comparison using a well-characterized polystyrene to determine the reproducibility in determining the molecular mass

Hydrogels Formed by Endlinking PEG to Dendrimer Crosslink Agents

March 1, 2000
Author(s)
B D. Viers, Barry J. Bauer, Y A. Akpalu, F Groehn, Da-Wei Liu, G Kim
Hydrogels were formed by endlinking telechelic vinyl sulfone end-functionalized poly(ethylene glycol) with the terminal amines on dendrimers of different generation. These structures are unique in that the dendrimer crosslink sites were very large, and

MALDI-TOF Mass Spectrometry of Polymeric Silsesquioxanes

March 1, 2000
Author(s)
William E. Wallace, Charles M. Guttman, Joseph M. Antonucci
Matrix-assisted laser desorption ionization time-of-flight mass spectrometry has been shown to be an effective method to determine the degree-of-intramolecular-condensation of polymeric silsesquioxanes. The nature of the organic R' leaving group was found

Preparation and Characterization of Polymer/Dendrimer Blends: Final Report, March 2000

March 1, 2000
Author(s)
Eric J. Amis, Barry J. Bauer, A Topp, F Groehn, T J. Prosa, B D. Viers, Da-Wei Liu, K A. Barnes, C L. Jackson, G Nisato, Alamgir Karim, Jack F. Douglas
This report is a summary of the results of measurement and characterization on dendritically branched polymers that was done under Army Research Office Grant contract 35109-CH. This summary encompasses 3 previous NISTIR's for consecutive 12 month periods

The Orientation of Semifluorinated Alkanes Attached to Polymers at the Surface of Polymer Films

March 1, 2000
Author(s)
Jan Genzer, E Sivaniah, E K. Kramer, J G. Wang, H Kerner, M Xiang, K Char, Christopher K. Ober, B M. DeKoven, Robert A. Bubeck, M K. Chaudhury, S Sambasivan, Daniel A. Fischer
The surface molecular orientation of a liquid crystalline (LC) layer made up a semi-fluorinated (SF) single side-groups [-CO-(CH 2) x-1-(CF 2) yF] (single SF groups) attached to polyisoprene homopolymer or the isoprene block of a styrene-isoprene diblock

Neutron Irradiation to Increase the C-Axis Compressive Strength of Sapphire at Elevated Temperature

February 29, 2000
Author(s)
T M. Regan, D C. Harris, D W. Blodgett, K C. Baldwin, J A. Miragliotta, M E. Thomas, M J. Linevsky, J W. Giles, R M. Stroud, T A. Kennedy, M Fatemi, David R. Black
Neutron irradiation of sapphire with 1 x 10 18 neutrons (≥ 1 MeV)/cm 2 increases the c-axis compressive strength by a factor of 3 at 600 C. The mechanism of strength enhancement is the retardation of r-plane twin propagation by radiation-induced defects

Subcritical Crack Growth: Mechanisms

February 28, 2000
Author(s)
Brian R. Lawn
A brief survey is given of mechanisms of subcritical crack growth in ceramics, for a solicited article in Encyclopedia of Materials: Science and Technology.

Ceramic Coatings Metrology Workshop Report

February 1, 2000
Author(s)
S J. Dapkunas
The Ceramic Coatings Metrology Workshop was held at NIST to identify the measurement needs of the various industries that manufacture and use ceramic coatings. The industrial perspectives were complemented by reviews of the scientific issues that require

Effect of Ag on the Primary Phase Field of High T c (Bi,Pb)-2223 Superconductor

February 1, 2000
Author(s)
Winnie K. Wong-Ng, Lawrence P. Cook, W Greenwood, Anthony J. Kearsley
The subsolidus equilibria and the primary phase field (crystallization field) of the 110K high T c (Bi,Pb)-2223 ([Bi,Pb]:Sr:Ca:Cu) superconductor in the presence of Ag have been determined under 7.5 volume % O 2 (92.5 % Ar). A total of 29 six-phase volumes

Hole State Density of La 1-x Sr x CoO^d3-D} (0less then or equal to}xless then or equal to}0.5) Across the Insulator/Metal Phase Boundary

February 1, 2000
Author(s)
A R. Moodenbaugh, B Nielson, S Sambasivan, Daniel A. Fischer, T Friessnegg, S Aggarwal, R Ramesh, B Pfeffer
The oxygen K near edge x-ray absorption fine structure (NEXAFS) of polycrystalline and film La1-xSrxCoO3-d at room temperature was studied using fluorescence yield techniques. The bulk sensitive nature of fluorescence yield (relative to electron yield)

Lifetime-Limiting Strength Degradation From Contact Fatigue in Dental Ceramics

February 1, 2000
Author(s)
Yeon-Gil G. Jung, I M. Peterson, D H. Kim, Brian R. Lawn
Indentation damage and associated strength degradation from multi-cycle contacts with spherical indenters in water are evaluated in four dental ceramics, to examine the hypothesis that the lifetimes of dental restorations are limited by the accumulation of

Measuring Bimodal Crystallographic Texture in Ferroelectric PZT Thin Films

February 1, 2000
Author(s)
Mark D. Vaudin, G R. Fox
A powder x-ray diffraction method has been developed to measure the volume fraction of (111), (100), and randomly oriented PZT in 200 nm thick films used for FRAM applications. The integrated and peak intensities of 100, 110, 200 and 222 Bragg peaks from

New Calcium Tantalate Polytypes in the System Ca 2 Ta 2 O 7 - Sm 2 Ti 2 O 7

February 1, 2000
Author(s)
I E. Grey, Robert S. Roth
New calcium tantalate polytypes, with weberite related structures have been prepared by doping Ca 2Ta 2O 7 with Sm 2Ti 2O 7. Trigonal 6-layer (6T) and monoclinic 5-layer (5M) polytypes containing approximately equal to} 6 mol % and 10 mol % respectively of

Phase Relations of the SrO-Ho 2 O 3 -CuO x System

February 1, 2000
Author(s)
Winnie K. Wong-Ng, J Dillingham, Lawrence P. Cook
The phase diagram of the SrO-R 2O 3-CuOx system, where R=Ho, was investigated in air. The tie-line relationships of this system were determined. Two ternary phases were found, namely, the green phase SrHo 2CuO 5 and the A14-24 solid solution (Sr 14-xHo x

Subsolidus Phase Relations and Dielectric Properties in the SrO-Al 2 O 3 -Nb 2 O 5 System

February 1, 2000
Author(s)
Julia Y. Chan, Igor Levin, Terrell A. Vanderah, Richard G. Geyer, Robert S. Roth
Subsolidus phase equilibria in the SrO-Al 2O 3-Nb 2O 5 system were determined by synthesis of 75 compositions in air in the temperaturerange 1200-1600 C. Phase assemblages were determined by X-ray powder diffraction at room temperature. Two new ternary

Temperature Dependence of Molecular Orientation on the Surfaces of Semi-Fluorinated Polymer Thin Films

February 1, 2000
Author(s)
Jan Genzer, E Sivaniah, E K. Kramer, J G. Wang, H Koerner, K Char, Christopher K. Ober, B M. DeKoven, Robert A. Bubeck, Daniel A. Fischer, S Sambasivan
Near-edge X-ray absorption fine structure is used to investigate the temperature dependence of molecular orientation of semi-fluorinated liquid crystalline (SF-LC) mesogens, which are attached to the modified isoprene backbone of i) a polyisoprene

The Elastic Constants of Single Crystal Beta-Si 3 N 4

February 1, 2000
Author(s)
R Vogelgesang, M Grimsditch, Jay S. Wallace
Using Brillouin scattering, we have determined the five independent elastic constants of Β-Si 3N 4 single crystals. They are (in units of GPa) c 11 = 433(3), C 33=574(3), c 13 = 127(5), c 44 = 108(2), C 66 =119(4), and C 12 = C 11-2c 66 = 195(8), giving a
Displaying 1551 - 1575 of 1721