489 Matching Results

Search Results

Advanced search parameters have been applied.

Working with the superabrasives industry to optimize tooling for grinding brittle materials

Description: The optics manufacturing industry is undertaking a significant modernization, as computer-numeric-controlled (CNC) equipment is joining or replacing open-loop equipment and hand lapping/polishing on the shop floor. Several prototype CNC lens grinding platforms employing ring tools are undergoing development and demonstration at the Center for Optics Manufacturing in Rochester, NY, and several machine tool companies have CNC product lines aimed at the optics industry. Benefits to using CNC ring tool grinding equipment include: essentially unlimited flexibility in selecting radii of curvature without special radiused tooling, the potential for CIM linkages to CAD workstations, and the cultural shift from craftsmen with undocumented procedures to CNC machine operators employing computerized routines for process control. In recent years, these developments, have inspired a number of US optics companies to invest in CNC equipment and participate in process development activities involving bound diamond tooling. This modernization process,extends beyond large optics companies that have historically embraced advanced equipment, to also include smaller optical shops where a shift to CNC equipment requires a significant company commitment. This paper addresses our efforts to optimize fine grinding wheels to support the new generation of CNC equipment. We begin with a discussion of how fine grinding fits into the optical production process, and then describe an initiative for improving the linkage between optics industry and the grinding wheel industry. For the purposes of this paper, we define fine wheels to have diamond sizes below 20 micrometers, which includes wheels used for what is sometimes called medium grinding (e.g. 10-20 micrometers diamond) and for fine grinding (e.g. 2-4 micrometers diamond).
Date: May 1, 1996
Creator: Taylor, J.S.; Piscotty, M.A.; Blaedel, K.L. & Gray, F.A.
Partner: UNT Libraries Government Documents Department

Cutting fluid study for single crystal silicon

Description: An empirical study was conducted to evaluate cutting fluids for Single Point Diamond Turning (SPDT) of single crystal silicon. The pH of distilled waster was adjusted with various additives the examine the effect of pH on cutting operations. Fluids which seemed to promote ductile cutting appeared to increase tool wear as well, an undesirable tradeoff. High Ph sodium hydroxide solutions showed promise for further research, as they yielded the best combination of reduced tool wear and good surface finish in the ductile regime. Negative rake tools were verified to improve the surface finish, but the negative rake tools used in the experiments also showed much higher wear than conventional 0{degree} rake tools. Effects of crystallographic orientation on SPDT, such as star patterns of fracture damage forming near the center of the samples, were observed to decrease with lower feedrates. Silicon chips were observed and photographed, indicative of a ductile materials removal process.
Date: May 5, 1998
Creator: Chargin, D.
Partner: UNT Libraries Government Documents Department

Fundamental studies of the chemical vapor deposition of diamond. Final technical report, April 1, 1988--December 31, 1994

Description: We submit here a final technical report for the research program entitled: Fundamental Studies of the Chemical Vapor Deposition of Diamond, DOE Grant No. DE-FG05-88ER45345-M006. This research program was initiated in 1988 under the direction of the late Professor David A. Stevenson and was renewed in 1992. Unfortunately, at the end of 1992, just as the last phase of this work was getting underway, Professor Stevenson learned that he had developed mesothelioma, a form of cancer based on asbestos. Professor Stevenson died from that disease in February of 1994. Professor William D. Nix, the Chairman of the Materials Science department at Stanford was named the Principal Investigator. Professor Nix has assembled this final technical report. Much of the work of this grant was conducted by Mr. Paul Dennig, a graduate student who will receive his Ph.D. degree from Stanford in a few months. His research findings are described in the chapters of this report and in the papers published over the past few years. The main discovery of this work was that surface topology plays a crucial role in the nucleation of diamond on silicon. Dennig and his collaborators demonstrated this by showing that diamond nucleates preferentially at the tips of asperities on a silicon surface rather than in the re-entrant comers at the base of such asperities. Some of the possible reasons for this effect are described in this report. The published papers listed on the next page of this report also describe this research. Interested persons can obtain copies of these papers from Professor Nix at Stanford. A full account of all of the research results obtained in this work is given in the regular chapters that follow this brief introduction. In addition, interested readers will want to consult Mr. Dennig`s Ph.D. dissertation when it is made available ...
Date: May 1, 1995
Creator: Nix, W.D.
Partner: UNT Libraries Government Documents Department

Diamond radiation detectors II. CVD diamond development for radiation detectors

Description: Interest in radiation detectors has supplied some of the impetus for improving the electronic properties of CVD diamond. In the present discussion, we will restrict our attention to polycrystalhne CVD material. We will focus on the evolution of these materials over the past decade and the correlation of detector performance with other properties of the material.
Date: May 16, 1997
Creator: Kania, D.R.
Partner: UNT Libraries Government Documents Department

Diamond Measuring Machine

Description: The fundamental goal of this project was to develop additional capabilities to the diamond measuring prototype, work out technical difficulties associated with the original device, and perform automated measurements which are accurate and repeatable. For this project, FM and T was responsible for the overall system design, edge extraction, and defect extraction and identification. AccuGem provided a lab and computer equipment in Lawrence, 3D modeling, industry expertise, and sets of diamonds for testing. The system executive software which controls stone positioning, lighting, focusing, report generation, and data acquisition was written in Microsoft Visual Basic 6, while data analysis and modeling were compiled in C/C++ DLLs. All scanning parameters and extracted data are stored in a central database and available for automated analysis and reporting. The Phase 1 study showed that data can be extracted and measured from diamond scans, but most of the information had to be manually extracted. In this Phase 2 project, all data required for geometric modeling and defect identification were automatically extracted and passed to a 3D modeling module for analysis. Algorithms were developed which automatically adjusted both light levels and stone focus positioning for each diamond-under-test. After a diamond is analyzed and measurements are completed, a report is printed for the customer which shows carat weight, summarizes stone geometry information, lists defects and their size, displays a picture of the diamond, and shows a plot of defects on a top view drawing of the stone. Initial emphasis of defect extraction was on identification of feathers, pinpoints, and crystals. Defects were plotted color-coded by industry standards for inclusions (red), blemishes (green), and unknown defects (blue). Diamonds with a wide variety of cut quality, size, and number of defects were tested in the machine. Edge extraction, defect extraction, and modeling code were tested for multiple runs of ...
Date: January 27, 2000
Creator: Krstulic, J.F.
Partner: UNT Libraries Government Documents Department

Low temperature growth of ultrananocrystalline diamond on glass substrates for field emission applications.

Description: Recent studies of field emission from diamond have focused on the feasibility of growing diamond films on glass substrates, which are the preferred choice for cost-effective, large area flat panel displays. However, diamond growth on glass requires temperatures {le} 500 C, which is much lower than the temperature needed for growing conventional microwave plasma chemical vapor deposition (CVD) diamond films. In addition, it is desirable to minimize the deposition time for cost-effective processing. The authors have grown ultrananocrystalline diamond (UNCD) films using a unique microwave plasma technique that involves CH{sub 4}-Ar gas mixtures, as opposed to the conventional CH{sub 4}-H{sub 2} plasma CVD method. The growth species in the CH{sub 4}-Ar CVD method are C{sub 2} dimers, resulting in lower activation energies and consequently the ability to grow diamond at lower temperatures than conventional CVD diamond processes. For the work discussed here, the UNCD films were grown with plasma-enhanced chemical vapor deposition (PECVD) at low temperatures on glass substrates coated with Ti thin films. The turn-on field was as low as 3 V/{mu}m for a film grown at 500 C with a gas chemistry of 1%CH{sub 4}/99%/Ar at 100 Torr, and 7 V/{mu}m for a film grown at 350 C. UV Raman spectroscopy revealed the presence of high quality diamond in the films.
Date: January 17, 2000
Creator: Corrigan, T. D.; Krauss, A. R.; Gruen, D. M.; Auciello, O. & Chang, R. P. H.
Partner: UNT Libraries Government Documents Department

In situ surface roughness measurement during PECVD diamond film growth

Description: To investigate the development of surface morphology and bulk optical attenuation in diamond films, we have followed diamond film growth on silicon by in-situ laser reflection interferometry in a microwave plasma chemical vapor deposition system. A model for the interpretation of the reflectivity data in terms of film thickness, rms surface roughness and bulk losses due to scattering and absorption is presented. Results are compared with ex situ measurements of these quantities and found to be in good agreement.
Date: June 1, 1995
Creator: Zuiker, C.D.; Gruen, D.M. & Krauss, A.R.
Partner: UNT Libraries Government Documents Department

Molecular dynamics simulation of impurities in nanocrystalline diamond grain boundaries

Description: Nanocrystalline diamond films grown on Si substrates at 800 C from hydrogen-poor plasmas have a number of highly desirable mechanical and electronic properties. Impurities were found by SIMS measurements to be uniformly distributed throughout the thickness of the films at a level of 10{sup 17}--10{sup 18} cm{sup {minus}3}. It is likely that the impurities are located at the grain boundaries, which play a crucial role in controlling important characteristics of the films, such as electrical conductivity and electron emission. Density-functional based tight-binding (DFTB) molecular dynamics simulations were performed for diamond light-energy high-angle (100) twist grain boundaries with impurities such as N, Si and H.
Date: January 12, 2000
Creator: Sternberg, M.; Zapol, P.; Frauenheim, T.; Gruen, D. M. & Curtiss, L. A.
Partner: UNT Libraries Government Documents Department

LIFE TIME OF CARBON STRIPPING FOILS FOR THE SPALLATION NEUTRON SOURCE.

Description: SNS requires thick carbon stripping foils (200 to 400 {micro}g/cm{sup 2} thick) to minimize the injection loss due to H{sup 0} emerging from the foil and the circulating beam loss due to Coulomb and nuclear scattering on the foil. Lifetimes of different types thick carbon foils had been measured in BNL Linac, using a 750 keV 6.7 Hz H{sup {minus}} beam. Beam current ({approximately}2 mA over a beam pulse) was selected such that the energy deposition on the foil would be equivalent to that by the SNS injected beam, which will be a 1 GeV 60 Hz H{sup {minus}} beam with a maximum average beam current of 2 mA (or 32 mA over a beam pulse). The tested foils included commercial carbon foils (made by Arizona Carbon Foil Co.), LANL carbon foils (by the mCADAD method), and diamond films prepared from a silicon wafer with a diamond film coating (made by Goodfellow Corp.). Foils were either single-layered or double-layered and were either with or without carbon fiber supports. The results showed that the diamond film had the longest lifetime. The relationship between the foil lifetime and the expected maximum temperature on the foil is also presented in the paper, using the 200{micro}g/cm{sup 2} thick Arizona carbon foils, which are supported by 5 {micro}m diameter carbon wires.
Date: June 18, 2001
Creator: LIAW,C.J.; LEE,Y.Y. & TUOZZOLO,J.
Partner: UNT Libraries Government Documents Department

Superhard nanophase cutter materials for rock drilling applications

Description: The Low Pressure-High Temperature (LPHT) System has been developed for sintering of nanophase cutter and anvil materials. Microstructured and nanostructured cutters were sintered and studied for rock drilling applications. The WC/Co anvils were sintered and used for development of High Pressure-High Temperature (HPHT) Systems. Binderless diamond and superhard nanophase cutter materials were manufactured with help of HPHT Systems. The diamond materials were studied for rock machining and drilling applications. Binderless Polycrystalline Diamonds (BPCD) have high thermal stability and can be used in geothermal drilling of hard rock formations. Nanophase Polycrystalline Diamonds (NPCD) are under study in precision machining of optical lenses. Triphasic Diamond/Carbide/Metal Composites (TDCC) will be commercialized in drilling and machining applications.
Date: June 23, 2000
Creator: Voronov, O.; Tompa, G.; Sadangi, R.; Kear, B.; Wilson, C. & Yan, P.
Partner: UNT Libraries Government Documents Department

Method of Dehalogenation using Diamonds

Description: A method for preparing olefins and halogenated olefins is provided comprising contacting halogenated compounds with diamonds for a sufficient time and at a sufficient temperature to convert the halogenated compounds to olefins and halogenated olefins via elimination reactions.
Date: February 26, 1999
Creator: Farcasiu, Malvina; Kaufman, Phillip B.; Ladner, Edward P. & Anderson, Richard R.
Partner: UNT Libraries Government Documents Department

Final Report: Very Low Friction Small Radius Dome Cutters for Percussion Bits - Phase II Development Efforts, April 1, 1997 - September 1, 1999

Description: Phase II efforts to develop very low friction (polished) small radius cutters for drill bits are discussed. Key developments under this contract include: (1) improvements to robustness of polycrystalline diamond coatings enabling their use on sharper cutter shapes; (2) polishable coating materials which exhibit improved polish retention; and (3) a means of polishing a non-planar polycrystalline diamond surface economically. Field tests have shown acceptability of new small radius cutters, but have yet to show benefits of polishing. Further field tests are planned.
Date: July 15, 1999
Creator: Pixton, David S.
Partner: UNT Libraries Government Documents Department

Science and technology of ultrananocrystalline diamond (UNCD) thin films for multifunctional devices

Description: MEMS devices are currently fabricated primarily in silicon because of the available surface machining technology. However, Si has poor mechanical and tribological properties, and practical MEMS devices are currently limited primarily to applications involving only bending and flexural motion, such as cantilever accelerometers and vibration sensors. However, because of the poor flexural strength and fracture toughness of Si, and the tendency of Si to adhere to hydrophyllic surfaces, even these simple devices have limited dynamic range. Future MEMS applications that involve significant rolling or sliding contact will require the use of new materials with significantly improved mechanical and tribological properties, and the ability to perform well in harsh environments. Diamond is a superhard material of high mechanical strength, exceptional chemical inertness, and outstanding thermal stability. The brittle fracture strength is 23 times that of Si, and the projected wear life of diamond MEMS moving mechanical assemblies (MEMS-MMAs) is 10,000 times greater than that of Si MMAs. However, as the hardest known material, diamond is notoriously difficult to fabricate. Conventional CVD thin film deposition methods offer an approach to the fabrication of ultra-small diamond structures, but the films have large grain size, high internal stress, poor intergranular adhesion, and very rough surfaces, and are consequently ill-suited for MEMS-MMA applications. A thin film deposition process has been developed that produces phase-pure nanocrystalline diamond with morphological and mechanical properties that are ideally suited for MEMS applications in general, and MMA use in particular. The authors have developed lithographic techniques for the fabrication of diamond microstructure including cantilevers and multi-level devices, acting as precursors to micro-bearings and gears, making nanocrystalline diamond a promising material for the development of high performance MEMS devices.
Date: August 24, 2000
Creator: Auciello, O.; Krauss, A. R.; Gruen, D. M.; Jayatissa, A.; Sumant, A.; Tucek, J. et al.
Partner: UNT Libraries Government Documents Department

Pressure dependence of Raman modes in the chalcopyrite quaternary alloy AgxCu1-xGaS2

Description: Raman scattering in the chalcopyrite quaternary alloy Ag{sub x}Cu{sub 1-x}GaS{sub 2} has been studied under high pressure (up to 7 GPa) and at low temperature (50 K) using a diamond anvil high pressure cell for alloy concentrations x=1, 0.75, 0.5, 0.25 and 0. This has allowed us to determine the dependence of their zone-center phonon modes on both pressure and alloy concentration. The resultant phonon pressure coefficients are helpful in understanding the nature of the phonon modes in these chalcopyrites.
Date: December 31, 2000
Creator: Choi, In-Hwan & Yu, Peter Y.
Partner: UNT Libraries Government Documents Department

Substrate heating measurements in pulsed ion beam film deposition

Description: Diamond-like Carbon (DLC) films have been deposited at Los Alamos National Laboratory by pulsed ion beam ablation of graphite targets. The targets were illuminated by an intense beam of hydrogen, carbon, and oxygen ions at a fluence of 15-45 J/cm{sup 2}. Ion energies were on the order of 350 keV, with beam current rising to 35 kA over a 400 ns ion current pulse. Raman spectra of the deposited films indicate an increasing ratio of sp{sup 3} to sp{sup 2} bonding as the substrate is moved further away from the target and further off the target normal. Using a thin film platinum resistor at varying positions, we have measured the heating of the substrate surface due to the kinetic energy and heat of condensation of the ablated material. This information is used to determine if substrate heating is responsible for the lack of DLC in positions close to the target and near the target normal. Latest data and analysis will be presented.
Date: May 1, 1995
Creator: Olson, J.C.; Davis, H.A.; Rej, D.J.; Waganaar, W.J.; Tallant, D.R. & Thompson, M.O.
Partner: UNT Libraries Government Documents Department

Development and Testing of a Jet Assisted Polycrystalline Diamond Drilling Bit. Phase II Development Efforts

Description: Phase II efforts to develop a jet-assisted rotary-percussion drill bit are discussed. Key developments under this contract include: (1) a design for a more robust polycrystalline diamond drag cutter; (2) a new drilling mechanism which improves penetration and life of cutters; and (3) a means of creating a high-pressure mud jet inside of a percussion drill bit. Field tests of the new drill bit and the new robust cutter are forthcoming.
Date: September 20, 1999
Creator: Pixton, David S.
Partner: UNT Libraries Government Documents Department

Electronic structure studies of nanocrystalline diamond grain boundaries

Description: Diamond growth from hydrogen-poor plasmas results in diamond structures that are profoundly different from conventionally CVD-grown diamond. High concentration of carbon dimers in the microwave plasma results in a high rate of heterogeneous renucleation leading to formation of nanocrystalline diamond with a typical grain size of 3--10 nm. Therefore, up to 10% of carbon atoms are located in the grain boundaries. In this paper the authors report on density-functional based tight-binding molecular dynamics calculations of the structure of a {Sigma}13 twist (100) grain boundary in diamond. Beginning with a coincidence site lattice model, simulated annealing of the initial structure was performed at 1,500 K followed by relaxation toward lower temperatures. About one-half of the carbons in the grain boundary are found to be three-coordinated. Coordination numbers, bond length and bond angle distributions are analyzed and compared to those obtained in previous studies.
Date: November 29, 1999
Creator: Zapol, P.; Sternberg, M.; Frauenheim, T.; Gruen, D. M. & Curtiss, L. A.
Partner: UNT Libraries Government Documents Department

Pollution Prevention Through Recycling at the SNL/NM Classified Waste Landfill Project

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, they 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: GALLOWAY,ROBERT B.; SLAVIN,PAULA JANE; METHVIN,RHONDA KAY & FRITTS,JOSEPH EDGAR
Partner: UNT Libraries Government Documents Department

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