Resource Type

13 Matching Results

Results open in a new window/tab.

Synthesis, properties and applications of pure and covalently doped DLC films prepared by energetic condensation (open access)

Synthesis, properties and applications of pure and covalently doped DLC films prepared by energetic condensation

Hyper-thermal species have been used to produce carbon-based films with mechanical and tribological properties that have greatly expanded the applications of amorphous carbon coatings. Tetragonally bonded amorphous carbon films have properties that approach that of diamond in several ways. The major drawback, namely intrinsic stresses, preventing the production of thick ta-C films has been overcome by heat treating these films, and presently several micrometer-thick films of ta-C are regularly produced. Yet another area where superhard coatings are of great interest is for wear applications at elevated temperatures, namely around 500 degrees C and above. Such temperatures may be environment temperatures, or localized (flash) temperatures resulting for instance from wear. For this applications, doping the ta-C with elements that are covalently bonded to C (such as Si and B) offers a promising alternative. In this article, I will discuss some treatments that have allowed expanding the applications of pure ta-C, and the incorporation of Si and B on ta-C films. Film properties are presented and discussed.
Date: December 4, 2001
Creator: Monteiro, Othon R.
System: The UNT Digital Library
Status and Future Directions of the ENERGY STAR Program (open access)

Status and Future Directions of the ENERGY STAR Program

In 1992 the U.S. Environmental Protection Agency (EPA) introduced ENERGY STAR (registered trademark) a voluntary labeling program designed to identify and promote energy-efficient products, in order to reduce carbon dioxide emissions. Since then, the EPA, now in partnership with the U.S. Department of Energy (DOE), has expanded the program to cover nearly the entire buildings sector, spanning new homes, commercial buildings, residential heating and cooling equipment, major appliances, office equipment, commercial and residential lighting, and home electronics. This paper is based on our experience since 1993 in providing technical support to the ENERGY STAR program. We provide a snapshot of the ENERGY STAR program in the year 2000, including a general overview of the program, its accomplishments, and the possibilities for future development.
Date: December 4, 2001
Creator: Brown, Richard; Webber, Carrie & Koomey, Jonathan
System: The UNT Digital Library
Exploring new physics through contact interactions in lepton pair production at a linear collider (open access)

Exploring new physics through contact interactions in lepton pair production at a linear collider

If a contact interaction type correction to a Standard Model process is observed, studying its detailed properties can provide information on the fundamental physics responsible for it. Assuming that such a correction has been observed in lepton pair production at a 500 GeV-1 TeV linear collider, we consider a few possible models that could explain it, such as theories with large and TeV-scale extra dimensions and models with lepton compositeness. We show that using the measured cross-sections and angular distributions, these models can be distinguished with a high degree of confidence.
Date: December 4, 2001
Creator: Perelstein, Maxim & Pasztor, Gabriella
System: The UNT Digital Library
Integrated fuel processor development. (open access)

Integrated fuel processor development.

The Department of Energy's Office of Advanced Automotive Technologies has been supporting the development of fuel-flexible fuel processors at Argonne National Laboratory. These fuel processors will enable fuel cell vehicles to operate on fuels available through the existing infrastructure. The constraints of on-board space and weight require that these fuel processors be designed to be compact and lightweight, while meeting the performance targets for efficiency and gas quality needed for the fuel cell. This paper discusses the performance of a prototype fuel processor that has been designed and fabricated to operate with liquid fuels, such as gasoline, ethanol, methanol, etc. Rated for a capacity of 10 kWe (one-fifth of that needed for a car), the prototype fuel processor integrates the unit operations (vaporization, heat exchange, etc.) and processes (reforming, water-gas shift, preferential oxidation reactions, etc.) necessary to produce the hydrogen-rich gas (reformate) that will fuel the polymer electrolyte fuel cell stacks. The fuel processor work is being complemented by analytical and fundamental research. With the ultimate objective of meeting on-board fuel processor goals, these studies include: modeling fuel cell systems to identify design and operating features; evaluating alternative fuel processing options; and developing appropriate catalysts and materials. Issues and outstanding …
Date: December 4, 2001
Creator: Ahmed, S.; Pereira, C.; Lee, S. H. D. & Krumpelt, M.
System: The UNT Digital Library
Highly Efficient Tabletop Optical Parametric Chirped Pulse Amplifier at 1 (micron)m (open access)

Highly Efficient Tabletop Optical Parametric Chirped Pulse Amplifier at 1 (micron)m

Optical parametric chirped pulse amplification (OPCPA) is a scalable technology, for ultrashort pulse amplification. Its major advantages include design simplicity, broad bandwidth, tunability, low B-integral, high contrast, and high beam quality. OPCPA is suitable both for scaling to high peak power as well as high average power. We describe the amplification of stretched 100 fs oscillator pulses in a three-stage OPCPA system pumped by a commercial, single-longitudinal-mode, Q-switched Nd:YAG laser. The stretched pulses were centered around 1054 nm with a FWHM bandwidth of 16.5 nm and had an energy of 0.5 nJ. Using our OPCPA system, we obtained an amplified pulse energy of up to 31 mJ at a 10 Hz repetition rate. The overall conversion efficiency from pump to signal is 6%, which is the highest efficiency obtained With a commercial tabletop pump laser to date. The overall conversion efficiency is limited due to the finite temporal overlap of the seed (3 ns) with respect to the duration of the pump (8.5 ns). Within the temporal window of the seed pulse the pump to signal conversion efficiency exceeds 20%. Recompression of the amplified signal was demonstrated to 310 fs, limited by the aberrations initially present in the low energy …
Date: December 4, 2001
Creator: Jovanovic, I.; Ebbers, C. A.; Comaskey, B. J.; Bonner, R. A. & Morse, E. C.
System: The UNT Digital Library
Electrical Properties of Sand-Clay Mixtures Containing Trichloroethylene and Ethanol (open access)

Electrical Properties of Sand-Clay Mixtures Containing Trichloroethylene and Ethanol

A series of laboratory experiments, including the measurement of electrical properties and permeability, were performed on carefully characterized sand-clay mixtures. Different mixtures and configurations of quartz sand and 0 to 10% Na-montmorillonite clay were investigated using solutions of NaCl, CaCl{sub 2}, and deionized water. Samples containing 10% distributed clay were also studied using fluids containing 20 and 500 ppm trichloroethylene (TCE). Electrical properties were measured at frequencies between 10{sup 6} and 10{sup -2} Hz using the four-electrode method and Ag-AgCl inner electrodes on saturated samples at room temperature and 412 kPa confining pressure, corresponding to a soil depth of 15 to 20 m. Our results show that the addition of TCE has a small effect on electrical resistivity, with resistivity increasing with the addition of TCE. The influence of TCE on the electrical properties was most prominent in plots of loss tangent as a function of frequency. A loss tangent peak occurred at {approx}200 Hz. The height of the peak and the peak frequency both decrease with the addition of TCE. Further experiments were performed on samples containing a distinct clay layer parallel to current flow. Electrical properties were measured on water saturated samples and as a mixture of ethanol …
Date: December 4, 2001
Creator: Roberts, J. J. & Wildenschild, D.
System: The UNT Digital Library
Mapping Phase Transformations in the Heat-Affected-Zone of Carbon Manganese Steel Welds using Spatially Resolved X-Ray Diffraction (open access)

Mapping Phase Transformations in the Heat-Affected-Zone of Carbon Manganese Steel Welds using Spatially Resolved X-Ray Diffraction

Spatially Resolved X-Ray Diffraction (SRXRD) was used to investigate phase transformations that occur in the heat affected zone (HAZ) of gas tungsten arc (GTA) welds in AISI 1005 carbon-manganese steel. In situ SRXRD experiments performed at the Stanford Synchrotron Radiation Laboratory (SSRL) probed the phases present in the HAZ during welding, and these real-time observations of the HAZ phases were used to construct a map of the phase transformations occurring in the HAZ. This map identified 5 principal phase regions between the liquid weld pool and the unaffected base metal for the carbon-manganese steel studied in this investigation. Regions of annealing, recrystallization, partial transformation and complete transformation to {alpha}-Fe, {gamma}-Fe, and {delta}-Fe phases were identified using SRXRD, and the experimental results were combined with a heat flow model of the weld to investigate transformation kinetics under both positive and negative temperature gradients in the HAZ. From the resulting phase transformation map, the kinetics of phase transformations that occur under the highly non-isothermal heating and cooling cycles produced during welding of steels can now be better understood and modeled.
Date: December 4, 2001
Creator: Elmer, J W; Wong, J; Ressler, T & Palmer, T A
System: The UNT Digital Library
Fabrication by inclined-substrate deposition of biaxially textured buffer layer for coated conductors. (open access)

Fabrication by inclined-substrate deposition of biaxially textured buffer layer for coated conductors.

None
Date: December 4, 2001
Creator: Balachandran, U.; Ma, B.; Li, M.; Koritala, R. E.; Fisher, B. L.; Erck, R. A. et al.
System: The UNT Digital Library
Corrosion of glass-bonded sodalite and its components as a function of pH and temperature. (open access)

Corrosion of glass-bonded sodalite and its components as a function of pH and temperature.

None
Date: December 4, 2001
Creator: Jeong, S.-Y.; Morss, L. R. & Ebert, W. L.
System: The UNT Digital Library
Optical Spectroscopy of the Structural Phase Transition of VO{sub 2} Nanocrystals in Optical Fibers and Thin Films (open access)

Optical Spectroscopy of the Structural Phase Transition of VO{sub 2} Nanocrystals in Optical Fibers and Thin Films

The optical spectroscopy of VO{sub 2} nanocrystals in planar and fiber-waveguide geometries shows a size- and doping-dependent structural semiconductor-to-metal phase transition and a shape-dependent surface plasmon resonance, with unusual linear and nonlinear applications possibilities.
Date: December 4, 2001
Creator: Lopez, R.
System: The UNT Digital Library
ESR transmission experiments on {beta}'-(ET){sub 2}SF{sub 5}CF{sub 2}SO{sub 3} and (ET){sub 2}SF{sub 5}NNO{sub 2} investigations of spin-peierls systems. (open access)

ESR transmission experiments on {beta}'-(ET){sub 2}SF{sub 5}CF{sub 2}SO{sub 3} and (ET){sub 2}SF{sub 5}NNO{sub 2} investigations of spin-peierls systems.

None
Date: December 4, 2001
Creator: Rutel, B.; Brooks, J.; Ward, B. H.; VanDerveer, D.; Sitzmann, M. E.; Schlueter, J. et al.
System: The UNT Digital Library
What Xe nanocrystals in Al can teach us in materials science. (open access)

What Xe nanocrystals in Al can teach us in materials science.

None
Date: December 4, 2001
Creator: Allen, C. W.; Birtcher, R. C.; Dahmen, U.; Furuya, K.; Song, M. & Donnelly, S. E.
System: The UNT Digital Library
Reforming petroleum-based fuels for fuel cell vehicles : composition-performance relationships. (open access)

Reforming petroleum-based fuels for fuel cell vehicles : composition-performance relationships.

Onboard reforming of petroleum-based fuels, such as gasoline, may help ease the introduction of fuel cell vehicles to the marketplace. Although gasoline can be reformed, it is optimized to meet the demands of ICEs. This optimization includes blending to increase the octane number and addition of oxygenates and detergents to control emissions. The requirements for a fuel for onboard reforming to hydrogen are quite different than those for combustion. Factors such as octane number and flame speed are not important; however, factors such as hydrogen density, catalyst-fuel interactions, and possible catalyst poisoning become paramount. In order to identify what factors are important in a hydrocarbon fuel for reforming to hydrogen and what factors are detrimental, we have begun a program to test various components of gasoline and blends of components under autothermal reforming conditions. The results indicate that fuel composition can have a large effect on reforming behavior. Components which may be beneficial for ICEs for their octane enhancing value were detrimental to reforming. Fuels with high aromatic and naphthenic content were more difficult to reform. Aromatics were also found to have an impact on the kinetics for reforming of paraffins. The effects of sulfur impurities were dependent on the …
Date: December 4, 2001
Creator: Kopasz, J. P.; Miller, L. E.; Ahmed, S.; Devlin, P. R. & Pacheco, M.
System: The UNT Digital Library