171 Matching Results

Search Results

Advanced search parameters have been applied.

in subjects: "Optical Microscopy"

open access

Surface properties of photo-oxidized bituminous coals; Technical progress report, September--November 1993

Five of the eight coals to be studied in this project have been selected on the basis of economic importance as well as geologic and chemical histories. Plans have been initiated to collect the first sample, a Pittsburgh seam coal from southwestern Pennsylvania. However, we have as yet not received permission from the mine to collect our working face sample. In addition, preliminary work was completed on development and testing of a procedure to photo-oxidize vitrinite containing coal blocks us… more

Date: December 1, 1993

Creator: Mitchell, G. & Davis, A.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Diamond-like atomic-scale composite films: Surface properties and stability studied by STM and AFM

Amorphous ``diamond-like/quartz-like`` composites a-(C:H/Si:O) and metal containing a-(C:H/Si:O/Me) constitute a novel class of diamond-related materials with a number of unique bulk and surface properties. In order to gain a more fundamental understanding of the surface properties and stability of these solids we have performed a scanning tunneling and atomic force microscopy investigation of both a-(C:H/Si:O) and a-(C:H/Si:O/Me) films, including the effects of ion bombardment and annealing.

Date: October 1, 1995

Creator: Dorfman, B.; Abraizov, M.; Pollak, F.H.; Eby, R.; Rong, Z.Y.; Strongin, M. et al.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Mechanical properties and microstructural characteristics of laser and electron-beam welds in V-4Cr-4Ti.

Mechanical properties and microstructural characteristics of laser and electron-beam welds of a 500-kg heat of V4Cr4Ti were investigated in as-welded condition and after postwelding heat treatment by impact testing, microhardness measurement, optical microscopy, X-ray diffraction, and transmission electron microscopy (TEM). Ductile-brittle transition temperatures of the laser and electron-beam welds were significantly higher than that of the base metal. However, excellent impact properties coul… more

Date: May 18, 1998

Creator: Chung, H. M.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Catastrophic failure of contaminated fused silica optics at 355 nm

For years, contamination has been known to degrade the performance of optics and to sometimes initiate laser-induced damage to initiate. This study has W to quantify these effects for fused silica windows used at 355 mm Contamination particles (Al, Cu, TiO{sub 2} and ZrO{sub 2}) were artificially deposited onto the surface and damage tests were conducted with a 3 ns NdYAG laser. The damage morphology was characterized by Nomarski optical microscopy. The results showed that the damage morphology… more

Date: December 3, 1996

Creator: Genin, F. Y., LLNL

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Research on hydrogen effects on phase distribution ahead of propagating cracks in stainless steel. Final report

This research was performed in support of computations to determine the distribution of hydrogen at a crack tip in an unstable stainless steel. It involved metallographic observations of the distribution of martensite at a stressed crack tip. It is concluded that the martensite phase distribution is much too fine to model realistically by the finite element method when far-field stress effects must be included. The mesh size would have to be less than 50 micrometers in order to include the effe… more

Date: December 31, 1993

Creator: Altstetter, C.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Near-Field Spectroscopy of Selectively Oxidized Vertical Cavity Surface Emitting Lasers

Selectively oxidized vertical cavity surface emitting lasers (VCSELS) have been studied by spectrally resolved near field scanning optical microscopy (NSOM). We have obtained spatially and spectrally resolved images of both subthreshold emission and lasing emission from a selectively oxidized VCSEL operating at a wavelength of 850 nm. Below threshold, highly local high gain regions, emitting local intensity maxima within the active area, were observed; these were found to serve as lasing center… more

Date: December 9, 1999

Creator: Kim, J.; Boyd, J. T.; Jackson, Howard E. & Choquette, Kent D.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Mechanistic interpretation of glass reaction: Input to kinetic model development

Actinide-doped SRL 165 type glass was reacted in J-13 groundwater at 90{degree}C for times up to 278 days. The reaction was characterized by both solution and solid analyses. The glass was seen to react nonstoichiometrically with preferred leaching of alkali metals and boron. High resolution electron microscopy revealed the formation of a complex layer structure which became separated from the underlying glass as the reaction progressed. The formation of the layer and its effect on continued gl… more

Date: May 1, 1991

Creator: Bates, J. K.; Ebert, W. L.; Bradley, J. P. & Bourcier, W. L.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Mechanical properties and failure mechanisms of carbon fiber reinforced epoxy laminated composites

The mechanical behavior of quasi-isotropic and unidirectional epoxy-matrix carbon-fiber laminated composites subjected compressive loading at strain rates of 10{sup {minus}3} and 2000 s{sup {minus}1} are described. Failure in the studied composites was dominated by delamination which proceeded by brittle fracture of the epoxy-matrix. The matrix-fiber bonding in these composites is very strong and prevented the occurrence of significant fiber-pullout. The mode I delamination strain energy releas… more

Date: September 1, 1995

Creator: Thissell, W.R.; Zurek, A.K. & Addessio, F.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Shock compression of quartz and aluminum powder mixtures

The authors report about the shock-compression response of highly porous (55% and 65% dense) mixtures of 4Al + 3SiO{sub 2} powders having shock-induced phase transitions and chemical reactions. Shock recovery experiments were performed using the CETR/Sawaoka plate-impact system (P = 40 to 100 GPa) and the Sandia Momma Bear A Comp B fixture (P = 22 to 45 GPa). The recovered compacts contained the high pressure stishovite phase, products of chemical reaction, as well as unreacted constituents. Th… more

Date: November 1, 1995

Creator: Joshi, V. S.; Thadhani, N. N.; Graham, R. A. & Holman, G. T., Jr.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Effects of radiation exposure on glass alteration in a steam environment

Several Savannah River Plant (SRL) glass compositions were reacted in steam at temperatures of 150 to 200{degrees}C. Half of the tests utilized actinide-doped monoliths and were exposed to an external ionizing gamma source, while the remainder were doped only with U and reacted without gamma exposure. All glass samples readily reacted to form secondary mineral phases within the first week of testing. An in situ layer of smectite initially developed on nonirradiated SRL 202 glass test samples. A… more

Date: December 31, 1992

Creator: Wronkiewicz, D. J.; Bates, J. K.; Tani, B. S. & Wang, L. M.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Solidification behavior during directed light fabrication

Directed light fabrication (DLF) is a process that fuses gas delivered metal powders within a focal zone of a laser beam to produce fully dense, 3-dimensional metal components. A variety of materials have been processed with DLF, ranging from steels to tungsten, and including intermetallics such as NiAl and MoSi{sub 2}. To evaluate the processing parameters and resulting microstructures, solidification studies have been performed on defined alloy systems. For example, solidification cooling rat… more

Date: October 1, 1995

Creator: Thoma, D.J.; Lewis, G.K. & Nemec, R.B.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Room temperature observation of quantum jumps of single molecule into dark states

Fluctuations in the room temperature emission rate from single dye molecules which are excited with the near field scanning optical microscope reveal long (seconds) and short ({approximately} milliseconds) lived dark states.

Date: November 1, 1995

Creator: Ha, T.; Enderle, T.; Ogletree, D. F.; Selvin, P. R.; Weiss, S. & Chemla, D. S.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Nonlinear optical microscopy for imaging thin films and surfaces

We have used the inherent surface sensitivity of second harmonic generation to develop an instrument for nonlinear optical microscopy of surfaces and interfaces. We have demonstrated the use of several nonlinear optical responses for imaging thin films. The second harmonic response of a thin film of C{sub 60} has been used to image patterned films. Two photon absorption light induced fluorescence has been used to image patterned thin films of Rhodamine 6G. Applications of nonlinear optical micr… more

Date: March 1, 1995

Creator: Smilowitz, L. B.; McBranch, D. W. & Robinson, J. M.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Development program for magnetically assisted chemical separation: Evaluation of cesium removal from Hanford tank supernatant

Magnetic particles (MAG*SEP{sup SM}) coated with various absorbents were evaluated for the separation and recovery of low concentrations of cesium from nuclear waste solutions. The MAG*SEP{sup SM} particles were coated with (1) clinoptilolite, (2) transylvanian volcanic tuff, (3) resorcinol formaldehyde, and (4) crystalline silico-titanate, and then were contacted with a Hanford supernatant simulant. Particles coated with the crystalline silico-titanate were identified by Bradtec as having the … more

Date: December 1, 1994

Creator: Nunez, L.; Buchholz, B. A.; Ziemer, M.; Dyrkacz, G.; Kaminski, M.; Vandegrift, G. F. et al.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Infrared transient-liquid-phase joining of SCS-6/{beta}21S titanium matrix composite

Fiber-reinforced titanium matrix composites (TMCs) are among the advanced materials being considered for use in the aerospace industry due to their light weight, high strength, and high modulus. A rapid infrared joining process has been developed for the joining of composites and advanced materials. Rapid infrared joining has been shown not to have many of the problems associated with conventional joining methods. Two models were utilized to predict the joint evolution and fiber reaction zone g… more

Date: February 1, 1996

Creator: Blue, Craig A.; Sikka, Vinod K.; Blue, Randall A. & Lin, Ray Y.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Metal oxide coatings for piezoelectric exhaust gas sensors

We have deposited ZrO{sub 2}, TiO{sub 2}, and SnO{sub 2} films on ST-cut quartz surface acoustic wave (SAW) devices via sol-gel techniques. The films range from 100 to 300 nm thick and have porosities after calcination at 300{degrees}C that range from 82-88 % for ZrO{sub 2}, 77-81% for TiO{sub 2}, and 57-66% for SnO{sub 2}. In all cases, we have varied the synthesis and processing parameters over a wide range to optimize film properties: metal ion concentration (0.05-1.0 M), the H{sub 2}O:metal… more

Date: June 1, 1996

Creator: Anderson, M.T. & Cernosek, R.W.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Polishing procedure and surface characterization lead tungstate crystal scintillator Road No. 723 and No. 754

Step by step procedures are given for polishing the scintillator rods. A Strasbaugh spindle polishing machine was used along with visual inspection and hand polishing. Extensive data is given on pre-polish surface characterization, profilometry, microphotography, and interferometry.

Date: May 1, 1996

Creator: Kellam, M

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

EUVL reticle factory model and reticle cost analysis

The key issues in reticle manufacturing are cost and delivery time, both of which are dependent upon the yield of the process line. To estimate the cost and delivery time for EUVL reticles in commercial manufacturing, we have developed the first model for an EUV reticle factory which includes all the tools required for a presumed EUVL reticle fabrication process. This model includes the building, support tools and sufficient ``in-line`` process tools for the manufacture of (more than) 2500 reti… more

Date: May 22, 1996

Creator: Hawryluk, A.M.; Shelden, G. & Troccolo, P.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Nonlinear optical studies of surfaces

The possibly of using nonlinear optical processes for surface studies has attracted increasing attention in recent years. Optical second harmonic generation (SHG) and sum frequency generation (SFG), in particular, have been well accepted as viable surface probes. They have many advantages over the conventional techniques. By nature, they are highly surface-specific and has a submonolayer sensitivity. As coherent optical processes, they are capable of in-situ probing of surfaces in hostile envir… more

Date: July 1, 1994

Creator: Shen, Y.R.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

The oxidation behavior of iron aluminides at 1300{degrees}C

The oxidation behavior of iron-aluminum alloys, in air and oxygen, at 1300{degrees}C has been studied with particular emphasis on the time to loss of protectiveness with onset of breakaway attack. The role of alloy aluminum content between 8.4 and 15.8 w/o and of the addition of a reactive element, zirconium, up to 0.2 w/o, were examined. The periods over which the oxide scales remained protective were quantitatively correlated with aluminum depletion in the alloy substrate. Times to the onset … more

Date: November 1, 1996

Creator: Bennett, M. J.; DeVan, J. H. & Tortorelli, P. F.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

An image cancellation approach to depth-from-focus

Depth calculation of an object allows computer reconstruction of the surface of the object in three dimensions. Such information provides human operators 3D measurements for visualization, diagnostic and manipulation. It can also provide the necessary coordinates for semi or fully automated operations. This paper describes a microscopic imaging system with computer vision algorithms that can obtain the depth information by making use of the shallow depth of field of microscopic lenses.

Date: March 1, 1995

Creator: Lu, Shin-yee & Graser, M.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Testing of optical components to assure performance in a high acerage power environment

Evaluation and testing of the optical components used in the Atomic Vapor Laser Isotope Separation (AVLIS) plant is critical for qualification of suppliers, development of new optical multilayer designs and monufacturing processes, and assurance of performance in the production cycle. The range of specifications requires development of specialized test equipment and methods which are not routine or readily available in industry. Specifications are given on material characteristics such as index… more

Date: June 24, 1997

Creator: Chow, R.; Taylor, J. R.; Eickelberg, W. K. & Primdahl, K. A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Defect study in fused silica using near field scanning optical microscopy

Surface defects in fused silica have been characterized using Near Field Scanning Optical Microscopy (NSOM). Using total internal reflection of a p- or s- polarized laser beam, optical scattering from defects located on the surface itself as well as in the subsurface layer of polished fused silica has been measured by NSOM. The local scattering intensity has been compared with simultaneously measured surface topography. In addition, surface defects intentionally created on a fused silica surfac… more

Date: January 21, 1998

Creator: Yan, M.; Wang, L.; Siekhaus, W.; Kozlowski, M.; Yang, J. & Mohideen, U.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Application of total internal reflection microscopy for laser damage studies on fused silica

Damage studies show that the majority of damage on ultraviolet grade fused silica initiates at the front or rear surface. The grinding and polishing processes used to produce the optical surfaces of transparent optics play a key role in the development of defects which can ultimately initiate damage. These defects can be on or breaking through the surface or can be sub-surface damage. Total Internal Reflection Microscopy has been documented as a tool for revealing both sub-surface and surface d… more

Date: December 1997

Creator: Sheehan, L. M.

Item Type: Article

Partner: UNT Libraries Government Documents Department