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Micromilling of Metal Alloys with Focused Ion Beam-Fabricated Tools

Description: This work combines focused ion beam sputtering and ultra-precision machining as a first step in fabricating microstructure in metals and alloys. Specifically, {approx}25{micro}m diameter micro-end mills are made from cobalt M42 high-speed steel and C2 micrograin tungsten carbide tool blanks by ion beam sputtering. A 20 keV focused gallium beam defines tool cutting edges having radii of curvature < 0.1{micro}m. Micro-end mills having 2, 4 and 5 cutting edges successfully machine small trenche… more
Date: November 5, 1999
Creator: ADAMS,DAVID P.; VASILE,M.J.; BENAVIDES,GILBERT L. & CAMPBELL,ANN N.
Item Type: Refine your search to only Article
open access

Observations of Non-Close-Packed Arrangements in Multilayers of Passivated Gold Clusters

Description: The stacking of second and third layers of supercrystals of self-assembled passivated gold nanoparticles has been investigated using transmission electron microscopy. We report for the first time nanoparticles occupying the twofold saddle site in the third layer.
Date: October 5, 1999
Creator: AINDOW, M.; Brown, P.; Kiely, C. J.; Wellner, A. & Wilcoxon, Jess P.
Item Type: Refine your search to only Article
open access

Behavior of W and WSi(x) Contact Metallization on n- and p- Type GaN

Description: Sputter-deposited W-based contacts on p-GaN (N{sub A} {approximately} 10{sup 18} cm{sup {minus}3}) display non-ohmic behavior independent of annealing temperature when measured at 25 C. The transition to ohmic behavior occurs above {approximately} 250 C as more of the acceptors become ionized. The optimum annealing temperature is {approximately} 700 C under these conditions. These contacts are much more thermally stable than the conventional Ni/Au metallization, which shows a severely degraded … more
Date: January 5, 1999
Creator: Abernathy, C. R.; Cao, X. A.; Cole, M. W.; Eizenberg, M.; Lothian, J. R.; Pearton, S. J. et al.
Item Type: Refine your search to only Article
open access

Inductively Coupled Plasma Etching of III-Nitrides in Cl(2)/Xe,Cl(2)/Ar and Cl(2)/He

Description: The role of additive noble gases He, Ar and Xe to C&based Inductively Coupled Plasmas for etching of GaN, AIN and InN were examined. The etch rates were a strong function of chlorine concentration, rf chuck power and ICP source power. The highest etch rates for InN were obtained with C12/Xe, while the highest rates for AIN and GaN were obtained with C12/He. Efficient breaking of the 111-nitrogen bond is crucial for attaining high etch rates. The InN etching was dominated by physical sputtering,… more
Date: January 5, 1999
Creator: Abernathy, C.R.; Cho, H.; Donovan, S.M.; Hahn, Y.B.; Hays, D.C.; Jung, K.B. et al.
Item Type: Refine your search to only Article
open access

Biological Conversion of Synthesis Gas

Description: Syngas is known to contain approximately 1 percent H[sub 2]S, along with CO[sub 2], C0[sub 2], H[sub 2] and CH[sub 4]. Similarly, the syngas may become contaminated with oxygen, particularly during reactor start-up and during maintenance. Previous studies with the water-gas shift bacterium Rhodospirillum rubrum have shown that the bacterium is tolerant of small quantities of oxygen, but the effects of oxygen on CO-consumption are unknown. Similarly, R. rubrum is known to be tolerant of H[sub 2]… more
Date: January 5, 1993
Creator: Ackerson, M. D.; Clausen, E. C. & Gaddy, J. L.
Item Type: Refine your search to only Report
open access

Biological Conversion of Synthesis Gas. Project Status Report, October 1, 1992--December 31, 1992

Description: Syngas is known to contain approximately 1 percent H{sub 2}S, along with CO{sub 2}, C0{sub 2}, H{sub 2} and CH{sub 4}. Similarly, the syngas may become contaminated with oxygen, particularly during reactor start-up and during maintenance. Previous studies with the water-gas shift bacterium Rhodospirillum rubrum have shown that the bacterium is tolerant of small quantities of oxygen, but the effects of oxygen on CO-consumption are unknown. Similarly, R. rubrum is known to be tolerant of H{sub 2}… more
Date: January 5, 1993
Creator: Ackerson, M. D.; Clausen, E. C. & Gaddy, J. L.
Item Type: Refine your search to only Report
open access

Microstructural dependence of cavitation damage in polycrystalline materials. Final report, 1 November 1992--31 October 1994

Description: Microstructure of a sample of Inconel X-750 damaged by ISCC (intergranular stress corrosion cracking) was examined after fatigue precracking in a high-temperature environment of deaerated water. Orientation imaging microscopy was used to reveal the microstructure adjacent to the crack path. General high-angle boundaries were found to be most susceptible to cracking. An ordering of the susceptibilities to ISCC damage was proposed; all boundaries have been classified into one of 12 categories. A … more
Date: February 5, 1996
Creator: Adams, B.L.
Item Type: Refine your search to only Report
open access

Ion Beam Sputter Fabrication of Micro-Grooving and Micro-Threading Tools

Description: This paper presents techniques for fabricating microscopic, nonplanar features in a variety of materials. Micro-grooving and micro-threading tools having cutting dimensions of 10-30{micro}m are made by focused ion beam sputtering and used in ultra-precision machining. Tool fabrication involves directing a 20 keV gallium beam at polished cylindrical punches made of cobalt M42 high-speed steel or C2 tungsten carbide. This creates cutting edges having radii of curvature less than 0.4 {micro}m, and… more
Date: November 5, 1999
Creator: Adams,David P.; Vasile,M. J. & Krishnan,A. S. M.
Item Type: Refine your search to only Article
open access

Carbon transport in the bottom boundary layer. Final report

Description: This report summarizes the activities and findings from a field experiment devised to estimate the rates and mechanisms of transport of carbon across the continental shelves. The specific site chosen for the experiment was the mid-Atlantic Bight, a region off the North Carolina coast. The experiment involved a large contingent of scientists from many institutions. The specific component of the program was the transport of carbon in the bottom boundary layer. The postulate mechanisms of transpor… more
Date: October 5, 1998
Creator: Agrawal, Yogesh C.
Item Type: Refine your search to only Report
open access

Determining thermal diffusivity and defect attributes in ceramic matrix composites by infrared imaging.

Description: Ceramic matrix composites are being developed for numerous high temperature applications, including rotors and combustors for advanced turbine engines, heat exchanger and hot-gas filters for coal gasification plants. Among the materials of interest are silicon-carbide-fiber-reinforced-silicon-carbide (SiC{sub (f)}/SiC), silicon-carbide-fiber-reinforced-silicon-nitride (SiC{sub (f)}/Si{sub 3}N{sub 4}), aluminum-oxide-reinforced-alumina (Al{sub 2}O{sub 3(f)}/Al{sub 2}O{sub 3}), etc. In the manufa… more
Date: December 5, 1997
Creator: Ahuja, S.; Ellingson, W. A.; Koehl, E. R. & Stuckey, J.
Item Type: Refine your search to only Article
open access

Empirical Calculations of {sup 29}Si NMR Chemical Shielding Tensors: A Partial Charge Model Investigation of Hydrolysis in Organically Modified Alkoxy Silanes

Description: Organically modified alkoxy silanes play an important role in tailoring different properties of silica produced by the sol-gel method. Changes in the size and functionality of the organic group allows control of both physical and chemical properties of the resulting gel, with the kinetics of the polymerization process playing an important role in the design of new siloxane materials. High resolution {sup 29}Si NMR has proven to be valuable tool for monitoring the polymerization reaction, and ha… more
Date: August 5, 1999
Creator: Alam, Todd M. & Henry, Marc
Item Type: Refine your search to only Article
open access

Survey of high voltage electron microscopy worldwide in 1998.

Description: High voltage TEMs were introduced commercially thirty years ago, with the installations of 500 kV Hitachi instruments at the Universities of Nagoya and Tokyo. Since that time 53 commercial instruments, having maximum accelerating potentials of 0.5-3.5 MV, will have been delivered by the end of 1998. Table 1 summarizes the sites and some information regarding those HVEMS which are available in 1998. This corrects, updates and expands an earlier report of this sort [2]. There have been three comm… more
Date: March 5, 1998
Creator: Allen, C. W.
Item Type: Refine your search to only Article
open access

Radiation damage of a glass-bonded zeolite waste form using ion irradiation.

Description: Glass-bonded zeolite is being considered as a candidate ceramic waste form for storing radioactive isotopes separated from spent nuclear fuel in the electrorefining process. To determine the stability of glass-bonded zeolite under irradiation, transmission electron microscope samples were irradiated using high energy helium, lead, and krypton. The major crystalline phase of the waste form, which retains alkaline and alkaline earth fission products, loses its long range order under both helium a… more
Date: December 5, 1997
Creator: Allen, T. R. & Storey, B. G.
Item Type: Refine your search to only Article
open access

The correlation between swelling and radiation-induced segregation in iron-chromium-nickel alloys.

Description: The magnitudes of both void swelling and radiation-induced segregation (RIS) in iron-chromium-nickel alloys are dependent on bulk alloy composition. Because the diffusivity of nickel via the vacancy flux is slow relative to chromium, nickel enriches and chromium depletes at void surfaces during irradiation. This local composition change reduces the subsequent vacancy flux to the void, thereby reducing void swelling. In this work, the resistance to swelling from major element segregation is esti… more
Date: March 5, 1998
Creator: Allen, T. R.; Busby, J. T.; Kenik, E. A. & Was, G. S.
Item Type: Refine your search to only Article
open access

Modeling the effect of irradiation and post-irradiation annealing on grain boundary composition in austenitic Fe-Cr-Ni alloys.

Description: Many irradiation effects in Fe-Cr-Ni alloys such as radiation-induced segregation, radiation-enhanced diffusion, and void swelling are known to vary with bulk alloy composition. The development of microstructural and microchemical changes during irradiation and during post-irradiation annealing is determined by the rate of diffusion of point defects and alloying elements. To accurately predict the changes in grain boundary chemistry due to radiation-induced segregation and post-irradiation anne… more
Date: March 5, 1998
Creator: Allen, T.; Busby, J. T.; Kenik, E. A. & Was, G. S.
Item Type: Refine your search to only Article
open access

An Anticipatory Model of Cavitation

Description: The Anticipatory System (AS) formalism developed by Robert Rosen provides some insight into the problem of embedding intelligent behavior in machines. AS emulates the anticipatory behavior of biological systems. AS bases its behavior on its expectations about the near future and those expectations are modified as the system gains experience. The expectation is based on an internal model that is drawn from an appeal to physical reality. To be adaptive, the model must be able to update itself. To… more
Date: April 5, 1999
Creator: Allgood, G. O.; Dress Jr., W. B.; Hylton, J. O. & Kercel, S. W.
Item Type: Refine your search to only Article
open access

Analysis of Enriched Uranium and Weapons Plutonium Reloads for PWRs Using BRACC

Description: Comparisons of the multicycle results demonstrate that the correlation coefficients based on the CASMO3 data were implemented correctly and that the Linear Reactivity Model is acceptably accurate for missed reloads containing both uranium and weapons plutonium fuel. The expanded set of correlation coefficients make BRACC a useful tool for performing multi-cycle in-core fuel management studies of PWR cores containing weapons plutonium.
Date: June 5, 1997
Creator: Alonso, G. & Parish, T. A.
Item Type: Refine your search to only Article
open access

High Efficiency Release Targets for Use at ISOL Facilities: Computational Design

Description: This report describes efforts made at the oak Rklge NatiOnrd Laboratory to design high- efficiency-release targets that simultaneously incorporate the short diffusion lengths, high permeabilities, controllable temperatures, and heat-removal properties required for the generation of useful radioactive ion beam (RIB) intensities for nuclear physics and astrophysics research using the isotope separation on-line (ISOL) technique. Short diffusion lengths are achieved either by using thin fibrous tar… more
Date: October 5, 1999
Creator: Alton, G. D. & Liu, Y.
Item Type: Refine your search to only Article
open access

A Multi-Sample Cs-Sputter Negative Ion Source

Description: A multi-sample Cs sputter negative-ion source, equipped with a conical-geometry, W-surface-ionizer has been designed and fabricated that permits sample changes without disruption of on-line accelerator operation. Sample changing is effected by actuating an electro-pneumatic control system located at ground potential that drives an air-motor-driven sample-indexing-system mounted at high voltage; this arrangement avoids complications associated with indexing mechanisms that rely on electronic pow… more
Date: October 5, 1998
Creator: Alton, G. D.; Ball, J. A.; Bao, Y.; Cui, B.; Reed, C. A. & Williams, C.
Item Type: Refine your search to only Article
open access

ECR Ion Source Developments at the Oak Ridge National Laboratory

Description: New techniques for enhancing the performances of electron cyclotron resonance (ECR) ion sources are being investigated at the Oak Ridge National Laboratory. We have utilized the multiple discrete frequency technique to improve the charge state distributions extracted from conventional magnetic field geometry ECR source by injecting three frequencies into the source. A new flat central magnetic field concept, has been incorporated in the designs of a compact all-permanent-magnet source for high … more
Date: October 5, 1998
Creator: Alton, G. D.; Liu, Y. & Meyer, F. W.
Item Type: Refine your search to only Article
open access

A High Efficiency, Kinetic-Ejection Negative Ion Source for RIB Generation

Description: Chemically active radioactive species, diffused from RIB target materials, often arrive at the ionization chamber of the source in a variety of molecular forms. Because of the low probability for simultaneously dissociating and efficiently ionizing the individual atomic constituents of molecules with conventional hot-cathode electron-impact ion sources, the species of interest are often distributed in several mass channels in the form of molecular side-band beams and consequently, their intensi… more
Date: October 5, 1998
Creator: Alton, G. D.; Liu, Y.; Murray, S. N. & Williams, C.
Item Type: Refine your search to only Article
open access

Investigation of moisture-induced embrittlement of iron aluminides. Final report

Description: Iron-aluminum alloys with 28 at.% Al and 5 at.% Cr were shown to be susceptible to hydrogen embrittlement by exposure to both gaseous hydrogen and water vapor. This study examined the effect of the addition of zirconium and carbon on the moisture-induced hydrogen embrittlement of an Fe{sub 3}Al,Cr alloy through the evaluation of tensile properties and fatigue crack growth resistance in hydrogen gas and moisture-bearing air. Susceptibility to embrittlement was found to vary with the zirconium co… more
Date: June 5, 1997
Creator: Alven, D. A. & Stoloff, N.S .
Item Type: Refine your search to only Report
open access

Material characterization of the clay bonded silicon carbide candle filters and ash formations in the W-APF system after 500 hours of hot gas filtration at AEP. Appendix to Advanced Particle Filter: Technical progress report No. 11, January--March 1993

Description: (1) After 500 hours of operation in the pressurized fluidized-bed combustion gas environment, the fibrous outer membrane along the clay bonded silicon carbide Schumacher Dia Schumalith candles remained intact. The fibrous outer membrane did not permit penetration of fines through the filter wall. (2) An approximate 10-15% loss of material strength occurred within the intact candle clay bonded silicon carbide matrix after 500 hours of exposure to the PFBC gas environment. A relatively uniform st… more
Date: April 5, 1993
Creator: Alvin, M. A.
Item Type: Refine your search to only Report
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