NIST Digital Archives
Not a member yet
149436 research outputs found
Sort by
Properties of nanostructured hydroxyapatite prepared by a spray drying technique
No full textIn previous studies nano sized hydroxyapatite (HA) particles were prepared by sol-gel or precipitation methods, in which the products were washed by aqueous or nonaqueous liquids to remove impurities or undesired components. The washing is know to modify the surfaces of the cystalline particles. This study evaluated properties of nano HA materials prepared by a spray drying method in which the HA product was not exposed to any liquid after its formation. The spray drying apparatus consisted of a nozzle that sprayed an acidic calcium phosphate solution in the form of a fine mist into a stream of filtered air flowing through a heated glass column. The water and volatile acid were evaporated by the time the mist reached the end of the column, and the fine particles were collected by an electrostatic precipitator. Powder x ray diffraction patterns suggested the material was amorphous, exhibiting a single broad peak at 30.5degrees2theta.. However, high resolution transmission electron microscopic analysis showed that the particles, some of which were 5 nm in size, exhibited well ordered HA lattice fringes. Small area diffraction patterns were indicative of HA. Fourier transfer infrared spectroscopy showed patterns of typical of HA with small amounts of HPO42-. The thermodynamic solubility product of the nano HA was 3.3 x 10(-94) compared to 1 x 10(-117) for macro scale crystalline HA. These results showed that a spray drying technique can be used to prepare nanometer sized crystalline HA that have significantly different physicochemical properties than those of its bulk-scale counterpart
Diffraction line broadening analysis if broadening is caused by both dislocations and limited crystallite size
No full textThe determination of dislocation distribution parameters is discussed for specimens where both strain broadening caused by dislocations and size broadening occur. If the strain broadening is well described by a model due to Wilkens, several methods are possible for the analysis of the broadening of diffraction lines. In sputter deposited nickel layers, three different methods for diffraction line broadening analysis yield identical results. The recrystallization of the nickel layers was investigated by annealing the layers at various temperatures in the range 300 K to 500 K. With increasing annealing temperature, the microstructure of the layers changed from a microstructure with small grains and high dislocation density, via a microstructure that is a mixture of small grains with high dislocation density and large grains with low dislocation density, to a microstructure with large grains and low dislocation density
Characterization of combinatorial polymer blend composition gradients by FTIR microspectroscopy
No full textA new FTIR technique was developed for characterizing thin polymer films used in combinatorial materials science. Fourier transform infrared microspectroscopy mapping technique was used to determine the composition of polymer blend gradients. Composition gradients were made from poly(L-lactic acid) (PLLA) and poly(D, L-lactic acid) (PDLLA) in the form of thin films (6 cm x 2 cm) deposited on IR reflective substrates. Three composition gradient films were prepared and characterized. The results demonstrate the reproducibility and feasibility of a new, high-throughput approach for preparing and characterizing polymer composition gradients. The combination of composition gradient film technology and automated nondestructive FTIR microspectroscopy makes it possible to rapidly and quantitatively characterize polymer composition gradients for use in combinatorial materials science
Polycapillary optics for materials science studies: Instrumental effects and their correction
No full textThe instrumental effects related to the use of a polycapillary x-ray lens as primary beam collimator are here studied and the features observed in the measurements modelled via Monte-Carlo ray-tracing. Comparison with existing procedures is presented and experimental evidence of the accuracy improvements due to the use of a correction algorithm is shown
Standard reference materials (SRMs) for the calibration and validation of analytical methods for PCBs (as Aroclor mixtures)
No full textSix Standard Reference Materials (SRMs(R)) have been prepared by the National Institute of Standards and Technology (NIST) for the determination of PCBs as different Aroclor mixtures in methanol. Six additional SRMs of the same Aroclors in transformer oil have also been prepared. Specifically, solutions of Aroclors 1016, 1232, 1242, 1254, and 1260 have been gravimetrically prepared ( individually) in methanol and transformer oil, mixed, and transferred to amber glass ampoules in approximately 1.2 mL aliquots. Gas chromatography with electron capture detection (GC-ECD) has been used to verify the gravimetric data for each solution and transformer oil SRM. Liquid chromatography was used for the isolation of the Aroclors from the transformer oil SRMs prior to GC-ECD analysis. Separate calibration solutions and oils were prepared with Aroclor levels similar to those in each methanol solution and transformer oil SRM and were processed alongside the samples. The GC-ECD response of each Aroclor was monitored relative to internal standards that were added to the complex mixtures for quantification. The gravimetric concentrations of Aroclors 1242 and 1254 in methanol were also examined by the same method of analysis (GC-ECD) using several different sources of Aroclors and two different capillary GC columns: a 5% phenyl methylpolysiloxane phase and a relatively non-polar phase. The preparation of the materials, the gas chromatographic results, and the certified concentration values for each Aroclor SRM are described in this paper
High-resolution observations of the infrared spectrum of neutral neon
No full textWe have observed the spectrum of neutral neon (Ne 1) emitted by a microwave-excited electrodeless discharge lamp with the National Institute of Standards and Technology 2 m Fourier transform spectrometer. The spectra cover the regions 6929 Angstrom to 11000 Angstrom with a resolution of 0.01 cm(-1) and 11000 Angstrom to 47 589 Angstrom with a resolution of 0.007 cm(-1). We present a line list that includes more than 650 classified lines and provides an accurate and comprehensive description of the infrared spectrum. The response of the Fourier transform spectrometer was determined by using a radiometrically calibrated tungsten strip lamp, providing relative intensities that for moderate to strong lines are accurate to approximately 10% over the entire range of the observations. The identities of many lines that were previously multiply classified are unambiguously resolved
Development of a high throughput method incorporating traditional analytical devices
No full textA high-throughput (high throughput is the ability to process large numbers of samples) and companion informatics system has been developed and implemented. High throughput is defined as the ability to autonomously evaluate large numbers of samples, while an informatics system provides the software control of the physical devices, in addition to the organization and storage of the generated electronic data. This high throughput system includes both an ultra-violet and visible light spectrometer (UV-Vis) and a Fourier transform infrared spectrometer (FTIR) integrated with a multi sample positioning table. This method is designed to quantify changes in polymeric materials occurring from controlled temperature, humidity and high flux UV exposures. The integration of the software control of these analytical instruments within a single computer system is presented. Challenges in enhancing the system to include additional analytical devices are discussed
Uncertainty and traceability for the CEESI Iowa natural gas facility
No full textThis paper analyzes the uncertainty of a secondary flow measurement facility that calibrates a significant fraction of United States and foreign flow meters used for custody transfer of natural gas. The facility, owned by the Colorado Experimental Engineering Station Incorporated (CEESI), is located in Iowa. This facility measures flow with nine turbine meter standards, each of which is traceable to the NIST primary flow standard. The flow capacity, of this facility ranges from 0.7 actual m(3)/s to 10.7 actual m(3)/s at nominal pressures of 7174 kPa and at ambient temperatures. Over this flow range the relative expanded flow uncertainty varies from 0.28% to 0.30% (depending on flow)
Donald B. Sullivan
No full textDONALD B. SULLIVAN
NBS/NIST: 1967 - 2003
B: June 13, 1939, Phoenix, Arizona
EDUCATION:
University of Texas at El Paso, BS (Physics), 1961
Vanderbilt University, MA (Physics), 1963
Vanderbilt University, PhD (Physics), 1965
PRINCIPAL FIELDS:
Superconductivity, Josephson effect, and electron tunneling; precision measurements; atomic clocks and atomic timekeeping; dissemination of time and frequency signals.
POSITIONS HELD AT NBS/NIST:
Chief, Time and Frequency Division
Acting Deputy Director, Center for Electronics and Electrical Engineering
Program Analyst, Program Office
Chief, Cryoelectronics Section
Scientist, Cryoelectronics Section
HONORS:
National Research Council Postdoctoral Fellow, 1967-1969
Samuel Wesley Stratton Award, NIST, 1985
Presidential Rank Award: Meritorious Government Executive, 1990
Department of Commerce Gold Medal, 1995
C.B. Sawyer Memorial Award, IEEE, 1998
MEMBERSHIPS:
American Physical Society
Institute of Electrical and Electronics Engineers
PUBLICATIONS:
Over 70 publications including:
D.B. Sullivan, “Time and frequency measurement at NIST: the first 100 years”, Proceedings of the IEEE International Frequency Control Symposium, IEEE Cat. No. 01CH37218, pp. 4-17 (2001).
D.B. Sullivan and J. Levine, “Time and Frequency Measurement”, American Association of Physics Teachers: College Park, MD, 140 pps. (1996).
D.B. Sullivan and J. Levine, “Time generation and distribution”, Proceedings of the IEEE, 79, pp. 906-914 (1991).
D.B. Sullivan and J.E. Zimmerman, “Mechanical analogs of time dependent Josephson phenomena”, American Journal of Physics 39, pp. 1505-1517 (1971)
Morris Krauss
No full textMORRIS KRAUSS
NBS/NIST: 1955 - 2004
Birth: April 9, 1932, New Haven Connecticut
Education:
City College, BS (Chemistry), 1952
University of Utah, PhD (Chemistry), 1955
Principal fields:
Mass spectrometry, computational chemistry with applications to atmospheric chemistry, laser and photochemistry, enzyme mechanisms and electronic structure of biomolecules.
Positions held at NBS /NIST:
Research Chemist
Quantum Chemistry Group Leader, CSTL (1984-1993)
CARB/NIST Fellow (1983-2004)
NIST Scientist Emeritus
Honors:
U.S. Department of Commerce Silver (1965) and Gold Medal (1983)
NBS Stratton Award (1984)
Memberships:
American Physical Society (Fellow)
American Chemical Society
Biophysical Society
Publications:
198 publications including:
M. Krauss, Electronic Structure of Some Diatomic Hydrides, J. Chem. Phys. 28, 1021, 1957
W.J. Stevens, H. Basch, M. Krauss, Compact Effective Potentials and Efficient Shared Exponent Basis Sets for the First- and Second-Row Atoms, J. Chem. Phys. 81, 6026, 1984
Y.S. Lee and M. Krauss, Structure and Reaction in the Active Site of Mammalian Adenylyl Cyclase, J. Phys. Chem. B108, 4508, 2004
Y.S. Lee and M. Krauss, Dynamics of Proton Transfer in Bacteriorhodopsin, J. Am. Chem. Soc.126, 2225, 200