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Absorptance Measurements of Optical Coatings - A Round Robin (open access)

Absorptance Measurements of Optical Coatings - A Round Robin

An international round robin study was conducted on the absorption measurement of laser-quality coatings. Sets of optically coated samples were made by a ''reactive DC magnetron'' sputtering and an ion beam sputtering deposition process. The sample set included a high reflector at 514 nm and a high reflector for the near infrared (1030 to 1318 nm), single layers of silicon dioxide, tantalum pentoxide, and hafnium dioxide. For calibration purposes, a sample metalized with hafnium and an uncoated, superpolished fused silica substrate were also included. The set was sent to laboratory groups for absorptance measurement of these coatings. Whenever possible, each group was to measure a common, central area and another area specifically assigned to the respective group. Specific test protocols were also suggested in regards to the laser exposure time, power density, and surface preparation.
Date: October 26, 2000
Creator: Chow, R; Taylor, J R; Wu, Z L; Boccara, C A; Broulik, U; Commandre, M et al.
System: The UNT Digital Library
Commercial cokes and graphites as anode materials for lithium - ion cells (open access)

Commercial cokes and graphites as anode materials for lithium - ion cells

Several types of carbonaceous materials from Superior Graphite Co. were investigated for lithium ion intercalation. These commercially available cokes, graphitized cokes and graphites have a wide range of physical and chemical properties. The coke materials were investigated in propylene carbonate based electrolytes and the graphitic materials were studied in ethylene carbonate/dimethyl solutions to prevent exfoliation. The reversible capacities of disordered cokes are below 230 mAh/g and those for many highly ordered synthetic (artificial) and natural graphites approached 372 mAh/g (LiC{sub 6}). The irreversible capacity losses vary between 15 to as much as 200% of reversible capacities for various types of carbon. Heat treated cokes with the average particle size of 10 microns showed marked improvements in reversible capacity for lithium intercalation. The electrochemical characteristics are correlated with data obtained from scanning electron microscopy (SEM), high resolution transmission electron microscopy (TEM), X-ray diffraction (XRD) and BET surface area analysis. The electrochemical performance, availability, cost and manufacturability of these commercial carbons will be discussed.
Date: October 26, 2000
Creator: Derwin, D J; Kinoshita, K; Tran, T D & Zaleski, P
System: The UNT Digital Library
Development of semiconductor detectors for fast neutron radiography. (open access)

Development of semiconductor detectors for fast neutron radiography.

None
Date: October 26, 2000
Creator: Klann, R. T.; Fink, C. L.; McGregor, D. S. & Gersch, H. K.
System: The UNT Digital Library
The Direction Cosine Method of Scatterer Location Extended to Spotlight-Mode IFSAR (open access)

The Direction Cosine Method of Scatterer Location Extended to Spotlight-Mode IFSAR

In this paper we have shown how the direction cosine method of stripmap-mode IFSAR maybe modified for use in the spotlight-mode case. Spotlight-mode IFSAR geometry dictates a common aperture phase center, velocity vector, and baseline vector for every pixel in an image. Angle with respect to the velocity vector is the same for every pixel in a given column and can be computed from the column index, the Doppler of the motion compensation point and the Doppler column sample spacing used in image formation. With these modifications, the direction cosines and length of the line of sight vector to every scatterer in the scene may be computed directly from the raw radar measurements of range, Doppler, and interferometric phase.
Date: October 26, 2000
Creator: EICHEL,PAUL H.
System: The UNT Digital Library
Effects of processing conditions on the physical and electrochemical properties of carbon aerogel composites (open access)

Effects of processing conditions on the physical and electrochemical properties of carbon aerogel composites

The carbon aerogel/carbon paper composites have physical properties similar to those of monolithic carbon aerogels but do not require supercritical extraction during fabrication. The resorcinol-formaldehyde based carbon aerogel phase is intertwined between the fibers of a commercial carbon paper. The resulting composites have variable densities (0.4-0.6 g/cc), high surface areas (300-600 m{sup 2}/g), and controllable pore sizes and pore distribution. The effects of the resorcinol-formaldehyde concentrations (50-70% w/v) and the pyrolysis temperature (600-1050 C) were studied in an attempt to tailor the aerogel microstructure and properties. The composite physical properties and structure were analyzed by transmission electron microscopy and multipoint-BET analyses and related to electrochemical capacitive data in 5M KOH. These thin carbon aerogel/carbon paper composite electrodes are used in experiments with electrochemical double-layer capacitors and capacitive deionization.
Date: October 26, 2000
Creator: Tran, T D; Lenz, D; Kinoshita, K & Droege, M
System: The UNT Digital Library
Intrinsic Inhomogeneity and the Origin of the Pseudogap (open access)

Intrinsic Inhomogeneity and the Origin of the Pseudogap

Phenomenon of the pseudogap is caused by an intrinsic inhomogeneity and the dependence Tc(r).
Date: October 26, 2000
Creator: Kresin, V.; Ovchinnikov, Yu. & S., Wolf
System: The UNT Digital Library
Investigation of lithiated carbons by transmission electron microscopy and x-ray diffraction analysis (open access)

Investigation of lithiated carbons by transmission electron microscopy and x-ray diffraction analysis

The microstructures of lithiated synthetic graphite and carbon black were studied by high-resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD) analysis. Information about the crystal structure of carbon containing various Li compositions can provide useful insights to our understanding of the Li storage mechanism in carbonaceous materials. Samples with compositions of Li{sub 0.93}C{sub 6} or Li{sub 0.45}C{sub 6} were found to contain both stage-one and stage-two compounds. These observations are consistent with XRD data. The changes in sample microstructure as the results of lithiation and exposure to electron irradiation were observed by TEM and recorded over several minutes in the microscope environment. Selected area electron diffraction patterns indicated that the lithiated samples quickly changed composition to LiC{sub 24}, which appeared to dominate during the brief analysis period. The layer planes in the lattice image of a disordered carbon black after Li insertion are poorly defined, and changes in the microstructure of these lithiated carbons was not readily apparent. Observations on these lithium intercalation compounds as well as the limitation of the experimental procedure will be presented.
Date: October 26, 2000
Creator: Tran, T D; Song, X Y & Kinoshita, K
System: The UNT Digital Library
Lessons Learned and Present Day Challenges of Addressing 20th Century Radiation Legacies of Russia and the United States (open access)

Lessons Learned and Present Day Challenges of Addressing 20th Century Radiation Legacies of Russia and the United States

The decommissioning of nuclear submarines, disposal of highly-enriched uranium and weapons-grade plutonium, and processing of high-level radioactive wastes represent the most challenging issues facing the cleanup of 20th century radiation legacy wastes and facilities. The US and Russia are the two primary countries dealing with these challenges, because most of the world's fissile inventory is being processed and stored at multiple industrial sites and nuclear weapons production facilities in these countries.
Date: October 26, 2000
Creator: KRISTOFZSKI, J.G.
System: The UNT Digital Library
Modeling Igneous Disruption in Yucca Mountain Total System Performance Assessment (open access)

Modeling Igneous Disruption in Yucca Mountain Total System Performance Assessment

None
Date: October 26, 2000
Creator: SWIFT,PETER N.; SAUER,MICHAEL L.; GAITHER,KATHERINE N. & BARR,GEORGE E.
System: The UNT Digital Library
Radionuclide Transport Simulation Using Particle Tracking with Rock Matrix Diffusion (open access)

Radionuclide Transport Simulation Using Particle Tracking with Rock Matrix Diffusion

None
Date: October 26, 2000
Creator: Arnold, Bill W.; Zhang, Hubao & Robinson, Bruce A.
System: The UNT Digital Library