562 Matching Results

Search Results

Advanced search parameters have been applied.

Progress toward a performance based specification for diamond grinding wheels

Description: This work sought to improve the communication between users and makers of fine diamond grinding wheels. A promising avenue for this is to formulate a voluntary product standard that comprises performance indicators that bridge the gap between specific user requirements and the details of wheel formulations. We propose a set of performance specifiers of figures-of-merit, that might be assessed by straightforward and traceable testing methods, but do not compromise proprietary information of the wheel user of wheel maker. One such performance indicator might be wheel hardness. In addition we consider technologies that might be required to realize the benefits of optimized grinding wheels. A non-contact wheel-to- workpiece proximity sensor may provide a means of monitoring wheel wear and thus wheel position, for wheels that exhibit high wear rates in exchange for improved surface finish.
Date: November 12, 1996
Creator: Taylor, J.S.; Piscotty, M.S. & Blaedel, K.L.
Partner: UNT Libraries Government Documents Department

Tensile properties of amorphous diamond films

Description: The strength and modulus of amorphous diamond, a new material for surface micromachined MEMS and sensors, was tested in uniaxial tension by pulling laterally with a flat tipped diamond in a nanoindenter. Several sample designs were attempted. Of those, only the single layer specimen with a 1 by 2 {micro}m gage cross section and a fixed end rigidly attached to the substrate was successful. Tensile load was calculated by resolving the measured lateral and normal forces into the applied tensile force and frictional losses. Displacement was corrected for machine compliance using the differential stiffness method. Post-mortem examination of the samples was performed to document the failure mode. The load-displacement data from those samples that failed in the gage section was converted to stress-strain curves using carefully measured gage cross section dimensions. Mean fracture strength was found to be 8.5 {+-} 1.4 GPa and the modulus was 831 {+-} 94 GPa. Tensile results are compared to hardness and modulus measurements made using a nanoindenter.
Date: December 2, 1999
Creator: Lavan, D.A.; Hohlfelder, R.J.; Sullivan, J.P.; Friedmann, T.A.; Mitchell, M.A. & Ashby, C.I.
Partner: UNT Libraries Government Documents Department

Measurement and analysis of chatter in a compliant model of a drillstring equipped with a PDC bit

Description: Typical laboratory testing of Polycrystalline Diamond Compact (PDC) bits is performed on relatively rigid setups. Even in hard rock, PDC bits exhibit reasonable life using such testing schemes. Unfortunately, field experience indicates otherwise. In this paper, the authors show that introducing compliance in testing setups provides better simulation of actual field conditions. Using such a scheme, they show that chatter can be severe even in softer rock, such as sandstone, and very destructive to the cutters in hard rock, such as sierra white granite.
Date: November 9, 1999
Creator: Elsayed, M.A. & Raymond, D.W.
Partner: UNT Libraries Government Documents Department

Friction and wear performance of diamondlike carbon films grown in various source gas plasmas

Description: In this study, the authors investigated the effects of various source gases (methane, ethane, ethylene, and acetylene) on the friction and wear performance of diamondlike carbon (DLC) films prepared in a plasma enhanced chemical vapor deposition (PECVD) system. Films were deposited on AISI H13 steel substrates and tested in a pin-on-disk machine against DLC-coated M50 balls in dry nitrogen. They found a close correlation between friction coefficient and source gas composition. Specifically, films grown in source gases with higher hydrogen-to-carbon ratios exhibited lower friction coefficients and higher wear resistance than films grown in source gases with lower hydrogen-to-carbon (H/C) ratios. The lowest friction coefficient (0.014) was achieved with a film derived from methane with an WC ratio of 4, whereas the coefficient of films derived from acetylene (H/C = 1) was of 0.15. Similar correlations were observed for wear rates. Specifically, films derived from gases with lower H/C values were worn out and the substrate material was exposed, whereas films from methane and ethane remained intact and wore at rates that were nearly two orders of magnitude lower than films obtained from acetylene.
Date: January 18, 2000
Creator: Erdemir, A.; Nilufer, I. B.; Eryilmaz, O. L.; Beschliesser, M. & Fenske, G. R.
Partner: UNT Libraries Government Documents Department

Species-resolved imaging and gated photon counting spectroscopy of laser ablation plume dynamics during KrF- and ArF-laser PLD of amorphous diamond films

Description: Gated photon counting spectroscopy and species-resolved ICCD photography were used to study the weak plasma luminescence following the propagation of the initial ablation plume in vacuum and during the rebound of the plume with a substrate during pulsed laser deposition of amorphous diamond. These methods techniques were required in order to investigate notable differences between amorphous diamond-like carbon films formed by pulsed laser deposition from ArF (193 nm) and KrF (248 nm) irradiation of pyrolytic graphite in vacuum. Three principal regions of plume emission were found: (1) a bright luminescent ball (v {approximately}3--5 cm/{mu}s) displaying nearly entirely C{sup +} emission which appears to result from laser interaction with the initial ejecta, (2) a spherical ball of emission (v {approximately} 1 cm/{mu}s) displaying neutral carbon atomic emission lines and, at early times, jets of excited C{sub 2}, and (3) a well-defined region of broadband emission (v {approximately} 0.3 cm/{mu}s) near the target surface first containing emission bands from C{sub 2}, then weak, continuum emission thought to result from C{sub 3} and higher clusters and/or blackbody emission from hot clusters or nanoparticles.
Date: December 1, 1995
Creator: Geohegan, D.B. & Puretzky, A.A.
Partner: UNT Libraries Government Documents Department

High rate PLD of diamond-like-carbon utilizing high repetition rate visible lasers

Description: Pulsed Laser Deposition (PLD) has been shown to be an effective method for producing a wide variety of thin films of high-value-added materials. The high average powers and high pulse repetition frequencies of lasers under development at LLNL make it possible to scale-up PLD processes that have been demonstrated in small systems in a number of university, government, and private laboratories to industrially meaningful, economically feasible technologies. A copper vapor laser system at LLNL has been utilized to demonstrate high rate PLD of high quality diamond-like-carbon (DLC) from graphite targets. The deposition rates for PLD obtained with a 100 W laser were {approx} 2000 {mu}m{center_dot}cm{sup 2}/h, or roughly 100 times larger than those reported by chemical vapor deposition (CVD) or physical vapor deposition (PVD) methods. Good adhesion of thin (up to 2 pm) films has been achieved on a small number of substrates that include SiO{sub 2} and single crystal Si. Present results indicate that the best quality DLC films can be produced at optimum rates at power levels and wavelengths compatible with fiber optic delivery systems. If this is also true of other desirable coating systems, this PLD technology could become an extremely attractive industrial tool for high value added coatings.
Date: September 15, 1994
Creator: McLean, W. II; Fehring, E.J.; Dragon, E.P. & Warner, B.E.
Partner: UNT Libraries Government Documents Department

Friction and wear properties of smooth diamond films grown in fullerene-argon plasmas

Description: In this study, we describe the growth mechanism and the ultralow friction and wear properties of smooth (20-50 nm rms) diamond films grown in a microwave plasma consisting of Ar and fullerene (the carbon source). The sliding friction coefficients of these films against Si{sub 3}N{sub 4} balls are 0.04 and 0.1 in dry N{sub 2} and air, which are comparable to that of natural diamond sliding against the same pin material, but is lower by factors of 5 to 10 than that afforded by rough diamond films grown in conventional H{sub 2}-CH{sub 4} plasmas. Furthermore, the smooth diamond films produced in this work afforded wear rates to Si{sub 3}N{sub 4} balls that were two to three orders of magnitude lower than those of H{sub 2}-CH{sub 4} grown films. Mechanistically, the ultralow friction and wear properties of the fullerene-derived diamond films correlate well with their initially smooth surface finish and their ability to polish even further during sliding. The wear tracks reach an ultrasmooth (3-6 nm rms) surface finish that results in very little abrasion and ploughing. The nanocrystalline microstructure and exceptionally pure sp{sup 3} bonding in these smooth diamond films were verified by numerous surface and structure analytical methods, including x-ray diffraction, high-resolution AF-S, EELS, NEXAFS, SEM, and TEM. An AFM instrument was used to characterize the topography of the films and rubbing surfaces.
Date: August 1, 1995
Creator: Erdemir, A.; Fenske, G.R.; Bindal, C.; Zuiker, C.; Krauss, A.R. & Gruen, D.M.
Partner: UNT Libraries Government Documents Department

Dymalloy: A composite substrate for high power density electronic components

Description: High power density electronic components such as fast microprocessors and power semiconductors must operate below the maximum rated device junction temperature to ensure reliability. function temperatures are determined by the amount of heat generated and the thermal resistance from junction to the ambient thermal environment. Two of the Largest contributions to this thermal resistance are the die attach interface and the package base. A decrease in these resistances can allow increased component packing density in MCMs, reduction of heat sink volume in tightly packed systems, enable the use of higher performance circuit components, and improve reliability. The substrate for high power density devices is the primary thermal link between the junctions and the heat sink. Present high power multichip modules and single chip packages use substrate materials such as silicon nitride or copper tungsten that have thermal conductivity in the range of 200 W/mK. We have developed Dymalloy, a copper-diamond composite, that has a thermal conductivity of 420 W/mK and an adjustable coefficient of thermal expansion, nominally 5.5 ppm/C at 25 C, compatible with silicon and gallium arsenide. Because of the matched coefficient of thermal expansion it is possible to use low thermal resistance hard die attach methods. Dymalloy is a composite material made using micron size Type I diamond powder that has a published thermal conductivity of 600 to 1000 W/mK in a metal matrix that has a thermal conductivity of 350 W/mK. The region of chemical bonding between the matrix material and diamond is limited to approximately 1000 A to maintain a high effective thermal conductivity for the composite. The material may be fabricated in near net shapes. Besides having exceptional thermal properties, the mechanical properties of this material also make it an attractive candidate as an electronic component substrate material.
Date: June 29, 1995
Creator: Kerns, J.A.; Colella, N.J.; Makowiecki, D. & Davidson, H.L.
Partner: UNT Libraries Government Documents Department

Diamond switches for high temperature electronics

Description: Diamond switches are well suited for use in high temperature electronics. Laboratory feasibility of diamond switching at 1 kV and 18 A was demonstrated. DC blocking voltages up to 1 kV were demonstrated. A 50 {Omega} load line was switched using a diamond switch, with switch on-state resistivity {approx}7 {Omega}-cm. An electron beam, {approx}150 keV energy, {approx}2 {mu}s full width at half maximum was used to control the 5 mm x 5 mm x 100 {mu}m thick diamond switch. The conduction current temporal history mimics that of the electron beam. These data were taken at room temperature.
Date: April 25, 1996
Creator: Prasad, R.R.; Rondeau, G. & Qi, Niansheng
Partner: UNT Libraries Government Documents Department

Diamond and diamond-like carbon films for advanced electronic applications

Description: Aim of this laboratory-directed research and development (LDRD) project was to develop diamond and/or diamond-like carbon (DLC) films for electronic applications. Quality of diamond and DLC films grown by chemical vapor deposition (CVD) is not adequate for electronic applications. Nucleation of diamond grains during growth typically results in coarse films that must be very thick in order to be physically continuous. DLC films grown by CVD are heavily hydrogenated and are stable to temperatures {le} 400{degrees}C. However, diamond and DLC`s exceptional electronic properties make them candidates for integration into a variety of microelectronic structures. This work studied new techniques for the growth of both materials. Template layers have been developed for the growth of CVD diamond films resulting in a significantly higher nucleation density on unscratched or unprepared Si surfaces. Hydrogen-free DLC with temperature stability {le} 800{degrees}C has been developed using energetic growth methods such as high-energy pulsed-laser deposition. Applications with the largest system impact include electron-emitting materials for flat-panel displays, dielectrics for interconnects, diffusion barriers, encapsulants, and nonvolatile memories, and tribological coatings that reduce wear and friction in integrated micro-electro-mechanical devices.
Date: March 1, 1996
Creator: Siegal, M.P.; Friedmann, T.A. & Sullivan, J.P.
Partner: UNT Libraries Government Documents Department

Dynamics of laser ablation for thin film growth by pulsed laser deposition

Description: Fundamental gas dynamic and laser-material interactions during pulsed laser deposition are explored through sensitive imaging and plasma spectroscopic diagnostics. Two recent phenomena, plume-splitting in background gases and the unusual dynamics of graphite ablation for amorphous diamond film growth, are presented.
Date: February 1, 1996
Creator: Geohegan, D.B. & Puretzky, A.A.
Partner: UNT Libraries Government Documents Department

First-principles study of {pi}-bonded (100) planar defects in diamond.

Description: A periodic density functional study of the high-energy {pi}-bonded (100) stacking fault in diamond that can serve as a prototype of a twist grain boundary has been carried out. Information on formation energies, geometries and the electronic structure has been obtained. A single point electronic structure calculation of a {Sigma}5 twist grain boundary based on the geometry taken from a molecular dynamics simulation has also been performed.
Date: December 16, 1998
Creator: Zapol, P.
Partner: UNT Libraries Government Documents Department

Grain boundaries and grain size distributions in nanocrystalline diamond films derived from fullerene precursors

Description: Film growth from C{sub 60}/Ar mixtures results in very pure diamond. Diamond films grown using C{sub 60} as a carbon source have been shown to be nanocrystalline with average grain sizes of 15 nm and standard deviations of 13 nm. The measured grain size distribution for two separate films, each based on measurements of over 400 grains, were found to be very similar and well approximated by a gamma distribution. Unlike typical CVD grown diamond films, these nanocrystalline films do not exhibit columnar growth. From the measured grain size distributions, it is estimated that 2% of the carbon atoms are located in the grain boundaries. The structure of the carbon in the grain boundaries is not known, but the films survive extended wear tests and hold together when the substrate is removed, indicating that the grains are strongly bound. The grain boundary carbon may give rise to additional features in the Raman spectrum and result in absorption and scattering of light in the films. We also expect that the grain boundary carbon may affect film properties, such as electrical and thermal conductivity.
Date: December 31, 1995
Creator: Csencsits, R.; Zuiker, C.D.; Gruen, D.M. & Krauss, A.R.
Partner: UNT Libraries Government Documents Department

Dynamical studies of periodic and disordered systems

Description: The time evolution of two classes of systems is studied with real time molecular dynamics simulations. The first consists of a coupled electron-lattice system. For a periodic system, we present results for the time evolution of a one-dimensional system consisting of an electron, described by a tight-binding Hamiltonian, and a harmonic lattice, coupled by a deformation-type potential. We solve numerically the nonlinear system of equations of motion for this model in order to study the effects of varying the electronic effective mass for several initial conditions and coupling strengths. A large effective mass favors localized polaron formation for initially localized electrons. For initially extended electronic states, increasing the effective mass of an electron initially close to the bottom of the band makes localization more difficult, while for an initially highly excited electronlocalized polaron formation is possible only when the electronic effective mass and the atomic masses of the lattice become of the same order.
Date: November 1, 1995
Creator: Kopidakis, G.
Partner: UNT Libraries Government Documents Department

Copper-diamond composite substrates for electronic components

Description: High-power density electronic components such as fast microprocessors and power semiconductors are often limited by inability to keep the device junctions below their max rated operating temperature. Present high power multichip module and single chip package designs use substrate materials such as Si nitride or copper tungsten with thermal conductivity in the range of 200 W/m{center_dot}K. We have developed a copper-diamond composite (Dymalloy) with a thermal conductivity of 420 W/m{center_dot}K, better than Cu, and an adjustable thermal expansion coefficient (TCE=5.5 ppM/C at 25 C), compatible with Si and GaAs. Because of the matched TCE, it is possible to use low thermal resistance hard die attach methods. The mechanical properties of the composite also make it attractive as an electronic component substrate material.
Date: January 25, 1995
Creator: Davidson, H.L.; Colella, N.J.; Kerns, J.A. & Makowiecki, D.
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


Description: The industry cost shared program aims to benchmark drilling rates of penetration in selected simulated deep formations and to significantly improve ROP through a team development of aggressive diamond product drill bit--fluid system technologies. Overall the objectives are as follows: Phase 1--Benchmark ''best in class'' diamond and other product drilling bits and fluids and develop concepts for a next level of deep drilling performance; Phase 2--Develop advanced smart bit-fluid prototypes and test at large scale; and Phase 3--Field trial smart bit-fluid concepts, modify as necessary and commercialize products. As of report date, TerraTek has concluded all major preparations for the high pressure drilling campaign. Baker Hughes encountered difficulties in providing additional pumping capacity before TerraTek's scheduled relocation to another facility, thus the program was delayed further to accommodate the full testing program.
Date: October 1, 2004
Creator: Black, Alan & Judzis, Arnis
Partner: UNT Libraries Government Documents Department

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