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Tribology and coatings

Description: The future use of fuel-efficient, low-emission, advanced transportation systems (for example, those using low-heat-rejection diesel engines or advanced gas turbines) presents new challenges to tribologists and materials scientists. High service temperatures, corrosive environments, and extreme contact pressures are among the concerns that make necessary new tribological designs, novel materials, and effective lubrication concepts. Argonne is working on methods to reduce friction, wear and corrosion, such as soft metal coatings on ceramics, layered compounds, diamond coatings, and hard surfaces.
Date: June 1995
Partner: UNT Libraries Government Documents Department

Performance Study of Scepter<sup>TM</sup> Metal Bond Diamond Grinding Wheel

Description: Advanced ceramics are attractive for many applications in the transportation, energy, military, and industrial markets because they possess properties of high-temperature durability, corrosion resistance, strength, hardness, stiffness, and wear resistance. Unfortunately, these same properties make advanced ceramics more difficult to machine than traditional materials. The reliability and manufacturing costs of advanced ceramic components are significant concerns that must be overcome. Nevertheless, the use of advanced ceramic materials is expected to increase dramatically in new transportation systems in response to more stringent energy conservation and pollution reduction requirements. This study discusses the goals, commercialization plans, phased development, scale-up, testing, and external verification of performance of the innovative grinding wheel that evolved from the project.
Date: June 17, 1999
Creator: Denison, S.K.; Licht, R.W.; McSpadden, S.B., Jr.; Parten, R.J.; Picone, J.W. & Shelton, J.E.
Partner: UNT Libraries Government Documents Department

Point Defect Incorporation During Diamond Chemical Vapor Deposition

Description: The incorporation of vacancies, H atoms, and sp{sup 2} bond defects into single-crystal homoepitaxial (100)(2x1)- and(111)-oriented CVD diamond was simulated by atomic-scale kinetic Monte Carlo. Simulations were performed for substrate temperatures from 600 C to 1200 C with 0.4% CH{sub 4} in the feed gas, and for 0.4% to 7% CH{sub 4} feeds with a substrate temperature of 800 C. The concentrations of incorporated H atoms increase with increasing substrate temperature and feed gas composition, and sp{sup 2} bond trapping increases with increasing feed gas composition. Vacancy concentrations are low under all conditions. The ratio of growth rate to H atom concentration is highest around 800-900 C, and the growth rate to sp{sup 2} ratio is maximum around 1% CH{sub 4}, suggesting that these conditions are ideal for economical diamond growth under the simulated conditions.
Date: August 2, 1999
Creator: Battaile, C.C.; Srolovitz, D.J. & Butler, J.E.
Partner: UNT Libraries Government Documents Department

Etching Effects During the Chemical Vapor Deposition of (100) Diamond

Description: Current theories of CVD growth on (100) diamond are unable to account for the numerous experimental observations of slow-growing, locally smooth (100)(2x1) films. In this paper they use quantum mechanical calculations of diamond surface thermochemistry and atomic-scale kinetic Monte Carlo simulations of deposition to investigate the efficacy of preferential etching as a mechanism that can help to reconcile this discrepancy. This etching mechanism allows for the removal of undercoordinated carbon atoms from the diamond surface. In the absence of etching, simulated growth on the (100)(2x1) surface is faster than growth on the (110) and (111) surfaces, and the (100) surface is atomically rough. When etching is included in the simulations, the (100) growth rates decrease to values near those observed experimentally, while the rates of growth on the other surfaces remain largely unaffected and similar to those observed experimentally. In addition, the etching mechanism promotes the growth of smooth (100) surface regions in agreement with numerous scanning probe studies.
Date: August 2, 1999
Creator: Battaile, C.C.; Srolovitz, D.J.; Oleinik, I.I.; Pettifor, D.G.; Sutton, A.P.; Harris, S.J. et al.
Partner: UNT Libraries Government Documents Department

High-heat-load studies of silicon and diamond monochromators using the APS/CHESS prototype undulator

Description: The results of the latest high-heat-load studies made on the APS/CHESS prototype undulator are summarized. Four different crystals were tested: two slotted, symmetrically cut silicon crystals and a core-drilled, asymmetrically cut silicon crystal and a diamond crystal that was jet cooled using water. The purpose of the silicon crystal tests was to reevaluate the surface power loading at which appreciable degradation of the diffraction efficiency was observed. The diamond tests, allotted only a brief period of time during the testing period, were our first attempt at using diamonds for high-heat-flux x-ray monochromators and were performed primarily to gain first-hand experience with diamond monochromators. Measurements with the silicon crystal at 5 keV reconfirmed our previous measurements of performance degradation at around 4-6 watts/mm{sup 2} using liquid gallium with slotted coolant channels. A value of only 2 watts/mm{sup 2} was observed to cause a degradation of the diffraction performance at 15 keV with the same crystals due to the increased sensitivity to strain because of the reduced Darwin widths. The performance of the asymmetric crystal, with its core-drilled coolant channels, was not found to be as good as that of the slotted crystals. This was probably due to poorer heat transfer properties of the core-drilled geometry in combination with the narrowing of the rocking curves because of the asymmetric cut. Fabrication issues for construction of the gallium-cooled crystals is also discussed. Although the diamonds were only successfully tested at low total power the results were very encouraging and motivated us to accelerate our program on the use of diamonds for high-heat-load monochromators.
Date: September 16, 1994
Creator: Mills, D.M.; Lee, W.K.; Smither, R.K. & Fernandez, P.B.
Partner: UNT Libraries Government Documents Department

Ultrashort-pulse lasers machining

Description: A new type of material processing is enabled with ultrashort (t &lt; 10 psec) laser pulses. Cutting, drilling, sculpting of all materials (biologic materials, ceramics, sapphire, silicon carbide, diamond, metals) occurs by new mechanisms which eliminate thermal shock or collateral damage. High precision machining to submicron tolerances is enabled resulting in high surface quality and negligible heat affected zone.
Date: January 22, 1999
Creator: Banks, P S; Feit, M D; Nguyen, H T & Perry, M D, Stuart, B C
Partner: UNT Libraries Government Documents Department

Shock Response of Diamond Crystals

Description: Sandia is investigating the shock response of single-crystal diamond up to several Mbar pressure in a collaborative effort with the Institute for Shock Physics (ISP) at Washington State University (WSU). This is project intended to determine (i) the usefulness of diamond as a window material for high pressure velocity interferometry measurements, (ii) the maximum stress level at which diamond remains transparent in the visible region, (iii) if a two-wave structure can be detected and analyzed, and if so, (iv) the Hugoniot elastic limit (HEL) for the [110] orientation of diamond. To this end experiments have been designed and performed, scoping the shock response in diamond in the 2-3 Mbar pressure range using conventional velocity interferometry techniques (conventional VISAR diagnostic). In order to perform more detailed and highly resolved measurements, an improved line-imaging VISAR has been developed and experiments using this technique have been designed. Prior to performing these more detailed experiments, additional scoping experiments are being performed using conventional techniques at WSU to refine the experimental design.
Date: December 1, 2001
Creator: KNUDSON, MARCUS D.; ASAY, JAMES R.; JONES, SCOTT C. & GUPTA, Y.M.
Partner: UNT Libraries Government Documents Department

Cylindrical Wire Electrical Discharge Machining of Metal Bond Diamond Wheels- Part II: Wheel Wear Mechanism

Description: The use of stereo scanning Electron Microscopy (SEM) to investigate the wear mechanism of the wire EDM true metal bond diamond wheel for ceramic grinding is presented. On the grinding wheel, a wedge-shape removal part was machined to enable the examination and measurement of the worn wheel surfaces using the stereo SEM. The stereo SEM was calibrated by comparing results of depth profile of a wear groove with the profilometer measurements. On the surface of the grinding wheel after wire EDM truing and before grinding, the diamond protruding heights were measured in the level of 35 {micro}m, comparing to the 54 {micro}m average size of the diamond in the grinding wheel. The gap between the EDM wire and rotating grinding wheel is estimated to be about 35 to 40 {micro}m. This observation indicates that, during the wire EDM, electrical sparks occur between the metal bond and EDM wire, which leaves the diamond protruding in the gap between the wire and wheel. The protruding diamond is immediately fractured at the start of the grinding process, even under a light grinding condition. After heavy grinding, the grinding wheel surface and the diamond protrusion heights are also investigated using the stereo SEM. The height of diamond protrusion was estimated in the 5 to 15 {micro}m range. This study has demonstrated the use of stereo SEM as a metrology tool to study the grinding wheel surface.
Date: January 22, 2002
Creator: McSpadden, SB
Partner: UNT Libraries Government Documents Department

Experimental Time Resolved Electron Beam Temperature Measurements Using Bremsstrahlung Diagnostics

Description: Electron beam temperature, {beta}{perpendicular} (= v{perpendicular}/v), is important to control for the development of high dose flash radiographic bremsstrahlung sources. At high voltage (&gt; 5 MV) increasing electron beam temperature has a serious deleterious effect on dose production. The average and time resolved behavior of beam temperature was measured during radiographic experiments on the HERMES III accelerator (10 MV, 50 kA, 70 ns). A linear array of thermoluminescent dosimeters (TLDs) were used to estimate the time integrated average of beam temperature. On and off-axis photoconducting diamond (PCD) detectors were used to measure the time resolved bremsstrahlung dose rate, which is dependent on beam energy and temperature. The beam temperature can be determined by correlating PCD response with accelerator voltage and current and also by analyzing the ratio of PCD amplitudes on and off axis. This ratio is insensitive to voltage and current and thus, is more reliable than utilizing absolute dose rate. The data is unfolded using comparisons with Monte Carlo simulations to obtain absolute beam temperatures. The data taken on HERMES III show abrupt increases in {beta}{perpendicular} midway through the pulse indicating rapid onset of beam instability.
Date: June 25, 1999
Creator: Menge, P.R.; Maenchen, J.E.; Mazarakis, M.G. & Rosenthal, S.E.
Partner: UNT Libraries Government Documents Department

Corrosive Resistant Diamond Coatings for the Acid Based Thermo-Chemical Hydrogen Cycles

Description: This project was designed to test diamond, diamond-like and related materials in environments that are expected in thermochemical cycles. Our goals were to build a High Temperature Corrosion Resistance (HTCR) test stand and begin testing the corrosive properties of barious materials in a high temperature acidic environment in the first year. Overall, we planned to test 54 samples each of diamond and diamond-like films (of 1 cm x 1 cm area). In addition we use a corrosion acceleration method by treating the samples at a temperature much larger than the expected operating temperature. Half of the samples will be treated with boron using the FEDOA process.
Date: June 25, 2009
Creator: Prelas, Mark A.
Partner: UNT Libraries Government Documents Department

Protected Polycrystalline Diamond Compact Bits For Hard Rock Drilling

Description: Two bits were designed. One bit was fabricated and tested at Terra-Tek's Drilling Research Laboratory. Fabrication of the second bit was not completed due to complications in fabrication and meeting scheduled test dates at the test facility. A conical bit was tested in a Carthage Marble (compressive strength 14,500 psi) and Sierra White Granite (compressive strength 28,200 psi). During the testing, Hydraulic Horsepower, Bit Weight, Rotation Rate, were varied for the Conical Bit, a Varel Tricone Bit and Varel PDC bit. The Conical Bi did cut rock at a reasonable rate in both rocks. Beneficial effects from the near and through cutter water nozzles were not evident in the marble due to test conditions and were not conclusive in the granite due to test conditions. At atmospheric drilling, the Conical Bit's penetration rate was as good as the standard PDC bit and better than the Tricone Bit. Torque requirements for the Conical Bit were higher than that required for the Standard Bits. Spudding the conical bit into the rock required some care to avoid overloading the nose cutters. The nose design should be evaluated to improve the bit's spudding characteristics.
Date: October 31, 2000
Creator: Cardenas, Robert Lee
Partner: UNT Libraries Government Documents Department

Plasma, photon, and beam synthesis of diamond films and multilayered structures. Progress report, July 1, 1990--September 1992

Description: In the area of nucleation, it was discovered that C{sub 70} thin films are perfect substitutes for diamond seeds in the growth of diamond films. This research, along with a careful study of diamond growth on carbon ion implanted single crystal copper, have clearly demonstrated that structured carbon is the best precursor for nucleation and growth of diamond films on non-diamond surfaces. In addition, by using fluorine chemistry during diamond growth, it has been shown that diamond films can grow on carbide substrates without the pretreatment of diamond seeding. The growth rates are higher and the film adhesion is much improved.
Date: September 1, 1992
Creator: Chang, R. P. H.
Partner: UNT Libraries Government Documents Department

Liquid jet impingement cooling with diamond substrates for extremely high heat flux applications

Description: The combination of impinging jets and diamond substrates may provide an effective solution to a class of extremely high heat flux problems in which very localized heat loads must be removed. Some potential applications include the cooling of high-heat-load components in synchrotron x-ray, fusion, and semiconductor laser systems. Impinging liquid jets are a very effective vehicle for removing high heat fluxes. The liquid supply arrangement is relatively simple, and low thermal resistances can be routinely achieved. A jet`s cooling ability is a strong function of the size of the cooled area relative to the jet diameter. For relatively large area targets, the critical heat fluxes can approach 20 W/mm{sup 2}. In this situation, burnout usually originates at the outer edge of the cooled region as increasing heat flux inhibits the liquid supply. Limitations from liquid supply are minimized when heating is restricted to the jet stagnation zone. The high stagnation pressure and high velocity gradients appear to suppress critical flux phenomena, and fluxes of up to 400 W/mm{sup 2} have been reached without evidence of burnout. Instead, the restrictions on heat flux are closely related to properties of the cooled target. Target properties become an issue owing to the large temperatures and large temperature gradients that accompany heat fluxes over 100 W/mm{sup 2}. These conditions necessitate a target with both high thermal conductivity to prevent excessive temperatures and good mechanical properties to prevent mechanical failures. Recent developments in synthetic diamond technology present a possible solution to some of the solid-side constraints on heat flux. Polycrystalline diamond foils can now be produced by chemical vapor deposition in reasonable quantity and at reasonable cost. Synthetic single crystal diamonds as large as 1 cm{sup 2} are also available.
Date: September 1, 1993
Creator: Lienhard, J. H. V & Khounsary, A. M.
Partner: UNT Libraries Government Documents Department

DIAMOND AMPLIFIER FOR PHOTOCATHODES.

Description: We report a new approach to the generation of high-current, high-brightness electron beams. Primary electrons are produced by a photocathode (or other means) and are accelerated to a few thousand electron-volts, then strike a specially prepared diamond window. The large Secondary Electron Yield (SEY) provides a multiplication of the number of electrons by about two orders of magnitude. The secondary electrons drift through the diamond under an electric field and emerge into the accelerating proper of the ''gun'' through a Negative Electron Affinity surface of the diamond. The advantages of the new approach include the following: (1) Reduction of the number of primary electrons by the large SEY, i.e. a very low laser power in a photocathode producing the primaries. (2) Low thermal emittance due to the NEA surface and the rapid thermalization of the electrons. (3) Protection of the cathode from possible contamination from the gun, allowing the use of large quantum efficiency but sensitive cathodes. (4) Protection of the gun from possible contamination by the cathode, allowing the use of superconducting gun cavities. (5) Production of high average currents, up to ampere class. (6) Encapsulated design, making the ''load-lock'' systems unnecessary. This paper presents the criteria that need to be taken into account in designing the amplifier.
Date: June 21, 2004
Creator: RAO,T.; BEN-ZVI,I.; BURRILL,A.; CHANG,X.; HULBERT,S.; JOHNSON,P. D. et al.
Partner: UNT Libraries Government Documents Department

MEASUREMENT OF THE SECONDARY EMISSION YIELD OF A THIN DIAMOND WINDOW IN TRANSMISSION MODE.

Description: The secondary emission enhanced photoinjector (SEEP) is a promising new approach to the generation of high-current, high-brightness electron beams. A low current primary electron beam with energy of a few thousand electron-volts strikes a specially prepared diamond window which emits secondary electrons with a current two orders of magnitude higher. The secondary electrons are created at the back side of the diamond and drift through the window under the influence of a strong electrical field. A hydrogen termination at the exit surface of the window creates a negative electron affinity (NEA) which allows the electrons to leave the diamond. An experiment was performed to measure the secondary electron yield and other properties. The results are discussed in this paper.
Date: May 16, 2005
Creator: CHANG, X.; RAO, T.; SMEDLEY, J. & AL., ET
Partner: UNT Libraries Government Documents Department

Molecular beam mass spectrometry studies of the chemical vapor deposition of diamond

Description: We have developed a novel molecular beam mass spectrometry technique that can quantitatively analyze the gas-phase composition in a CVD reactor. The technique simultaneously monitors a wide variety of radical and stable species, and their concentrations can be determined with sensitivities approaching 1 ppM. Measurements performed in a diamond deposition system have given us keen insights into the important phenomena that affect the growth environment. This paper first discusses the primary gas sampling design issues. In the second part, the details of the experimental results and their implications will be described.
Date: December 1, 1993
Creator: Hsu, Wen L.; McMaster, M. C.; Coltrin, M. E. & Dandy, D. S.
Partner: UNT Libraries Government Documents Department

A photoemission study of the diamond and the single crystal C{sub 60}

Description: This report studied the elctronic structure of diamond (100) and diamond/metal interface and C{sub 60}, using angle-resolved and core level photoemission. The C(100)-(2X1) surface electronic structure was studied using both core level and angle resolved valence band photoemission spectroscopy. The surface component of the C 1s core level spectrum agrees with theoretical existence of only symmetrical dimers. In the case of metal/diamond interfaces, core level and valence photoelectron spectroscopy and LEED studies WERE MADE OF B and Sb on diamond (100) and (111) surfaces. In the case of single-crystal C{sub 60}, photoemission spectra show sharp molecular features, indicating that the molecular orbitals are relatively undisturbed in solid C{sub 60}.
Date: March 1, 1994
Creator: Wu, Jin
Partner: UNT Libraries Government Documents Department

Atomic structure modifications of diamond-like nanocomposite films: Observation by Raman spectroscopy, FTIR and STM

Description: Raman spectroscopy, FTIR and scanning tunneling microscopy (STM) were used to study diamond-like nanocomposite (DLN) and metal containing DLN (Me-DLN) films. The FTIR spectra showed no appreciable absorption from the C-H stretch vibration band in DLN when 1 kV rf bias voltage was applied. Thermal annealing (450{degrees}C for 2 hrs) of (a) DLN and Cr-DLN films caused no change in the Raman spectra while (b) for Pt-DLN films there was a blue shift of both the crystalline (G) and microcrystalline (D) graphite-like features, an increase in the I{sub D}/I{sub G} intensity ratio and a decrease in the linewidths. The changes observed were more pronounced in the film with the highest Pt concentration. The STM image of this Pt-DLN film revealed a structure of aromatic graphite rings.
Date: June 1, 1994
Creator: Dorfman, B.; Abraizov, M.; Pollak, F. H.; Yan, D.; Strongin, M.; Yang, X. Q. et al.
Partner: UNT Libraries Government Documents Department

Turning soot into diamonds with microwaves

Description: Growth of diamond films using fullerene precursors in an argon microwave plasma without the addition of hydrogen or oxygen has recently been accomplished. Microwave discharges (2.45 GHz) were generated in C{sub 60}-containing Ar. The gas mixtures were produced by flowing Ar over fullerene-containing soot at a variety of temperatures. Optical spectroscopy shows that the spectrum is dominated by the d{sup 3}{Pi}{minus}a{sup 3}{Pi}{sub u}. Swan bands of C{sub 2} and particularly the {Delta}{nu} = {minus}2, {minus}1.0, +1, and +2 sequences, that C{sub 2} is one of the products of C{sub 60} fragmentation brought about, at least in part, by collisionally-induced dissociation. The nanocrystalline films were characterized with scanning and high-resolution transmission electron microscopy, x-ray diffraction, and Raman spectroscopy. Assuming a linear dependence on carbon concentration, a growth rate at least six times higher than commonly observed using methane as a precursor would be predicted at a carbon content of 1% based on C{sub 60}. Energetic and mechanistic arguments are advanced to rationalize this result based on C{sub 2} as the growth species.
Date: June 1, 1994
Creator: Gruen, D. M.; Krauss, A. R.; Luo, J.; Pan, X. & Liu, S.
Partner: UNT Libraries Government Documents Department

Barrier Foil Heating Simulations Using LASNEX

Description: It is necessary to place a barrier foil in front of the X-ray converter target to prevent the backstreaming ions. This research note presents the simulations of foil heating using the latest EOS tables. LASNEX simulations are carried out using both DARHT-II and ETA-II beam parameters. Results for all the foils studied here, using the DARHT-II beam parameters, show that the integrated line density along the axis at the end of the 4th pulse remains essentially unchanged even if the foils are heated by beams with relatively small beam spot sizes. The temperature can reach up to 3000 C on graphite foil but can only reach several hundred degree Celsius on Mylar foil. Simulations also show that ETA-II beam can create a ''burn-through'' hole on all the foils except graphite and diamond foils, which may require pre-heat. The threshold beam spot size required for hole formation will be compared with LASNEX simulation for the purpose of code verification.
Date: March 12, 2002
Creator: Ho, D. D.-M.
Partner: UNT Libraries Government Documents Department