Showing papers on "Diamond published in 1985"

Calculation of bulk moduli of diamond and zinc-blende solids.

Abstract: Theoretical arguments on the role of covalency in determining the bulk moduli of diamond and zinc-blende semiconductors and insulators are shown to yield a surprisingly simple and accurate expression for determining the bulk moduli B of these materials. One resulting formula for compounds in the center of the Periodic Table depends only on the nearest-neighbor separation d. It has the form B=1761${d}^{\mathrm{\ensuremath{-}}3.5}$ for B in GPa and d in A\r{}.

Multi-component cutting element using triangular, rectangular and higher order polyhedral-shaped polycrystalline diamond disks

Abstract: A diamond cutter for use in a drill bit having a geometric size and shape normally characterized by unleached diamond product, such as STRATAPAX diamond cutters, can be fabricated by assembling a plurality of prefabricated leached polycrystalline diamond (PCD) elements in an array in a cutting slug. A cutting slug is formed of matrix material which in one embodiment is impregnated with diamond grit. The cutting face of the cutting slug is characterized by exposing at least one surface of each of the PCD elements disposed therein. The diamonds may be set within the cutting slug either in a compact touching array or in a spaced-apart relationship. More than one type of array may also be employed within a single cutting slug. The PCD elements can assume a variety of polyhedral shapes such as triangular prismatic elements, rectangular elements, hexagonal elements and the like. The plurality of diamond elements and the cutting slug are fabricated using hot pressing or infiltration techniques.

Cutting element having composite formed of cemented carbide substrate and diamond layer and method of making same

Abstract: A cutting element comprises a stud and a composite bonded thereto. The composite comprises a substrate formed of cemented carbide, and a diamond layer bonded to the substrate. The interface between the diamond layer and substrate is defined by alternating ridges of diamond and cemented carbide which are mutually interlocked.

Observation of a C-1s core exciton in diamond.

Abstract: A well-resolved core exciton at the bulk diamond C-$1s$ absorption edge has been observed using high-resolution partial-yield spectroscopy with synchrotron radiation. The obtained excitonic binding energy, 0.19\ifmmode\pm\else\textpm\fi{}0.015 eV, agrees well with a first-principles effective-mass approximation (EMA). This is in sharp contrast to other semiconductors (Si, Ge, and GaAs) where reported excitonic shifts far exceed EMA estimates. In light of these results, one must question whether previous measurements overestimate the core-hole interaction or if they indicate a breakdown of the EMA for core excitons.

Raman spectra of diamond at high pressures.

Abstract: The first-order Raman spectrum of diamond has been measured in a diamond-anvil cell up to 27 GPa. The fundamental phonon line varies linearly in pressure with a shift of 2.87 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$/GPa. This line appears to be an excellent pressure-calibration standard as an alternate to the ruby pressure scale.

Diamond sintered body for tools and method of manufacturing the same

Abstract: A diamond sintered body for tools contains a diamond content in excess of 93 percent and not more than 99 percent by volume and a residue including at least one of a metal or a carbide selected from groups IVa, Va and VIa of the periodic table and an iron group metal of 0.1 to 3 percent by volume in total and pores at least 0.5 percent and not more than 7 percent by volume.

Body with superhard coating

Abstract: The present invention relates to a compound body consisting of a substrate with a surface coating of one or more dense, finegrained diamond layers, where the diamond grains are directly bonded to each other. Extreme hardness makes the compound body suitable for wear parts- and tools applications. Very good heat conductivity and an extremely high electrical isolation resistance makes the compound body extremely useful to lead away heat in electronic components.

Laser sputtering: Part I. On the existence of rapid laser sputtering at 193 nm

Abstract: Irradiation, i.e.bombardment, with 193 nm laser pulses having an energy fluence of 2.5 J cm 2 and a duration of ~12 ns leads to rapid sputtering with Au, Al2O3, MgO, MgO. Al2O3, SiO2, glass and LaB6, relatively slow sputtering with MgF2 and diamond, and mainly thermal-stress cracking with W. Scanning electron microscopy (SEM) suggests that the mechanism for the sputtering of Au in either vacuum or air is one based on the hydrodynamics of molten Au, while an SEM-derived surface temperature estimate confirms that thermal sputtering (which might have been expected) is not possible. SEM with W shows that the near total lack of material removal is due to the thermal-stress cracking not leading to completed exfoliation, together with the surface temperature being too low for either hydrodynamical or thermal processes. Corresponding SEM with Al2O3 shows, in the case of specimens bombarded in vacuum, topography of such a type that all mechanisms except electronic ones can be ruled out. The topography of Al2O3 or other oxides bombarded in air through a mask is somewhat different, showing craters as for vacuum bombardments but ones which have a cone-like pattern on the bottom.

Multi-component cutting element using polycrystalline diamond disks

Abstract: A diamond cutting table having the geometric characteristics of larger unleached diamond compact products and yet characterized by the physical properties of smaller leached diamond products is fabricated by forming a diamond cutter incorporating a plurality of polycrystalline diamond (PCD) leached disks. The PCD leached disks are disposed in array in a cutting slug formed of matrix material. The matrix material is disposed between and around the plurality of diamond disks and in one embodiment incorporates a volume distribution of diamond grit. The cutting slug is hot pressed or infiltrated to form an integral mass or table. The diamond table is then bonded to a cutter or directly molded into an integral tooth within a matrix body bit.

Measurement of stress in diamond anvils with micro-Raman spectroscopy

Abstract: Micro-Raman spectroscopy has been used to measure first-order Raman spectra from selected volumes in diamonds under pressure in a high-pressure diamond-anvil cell in both the 180° and 135° scattering geometries. The high-frequency component of the diamond line at the diamond-sample interface is found to shift linearly with pressure and exhibits a pressure coefficient of 0.237 cm−1 kbar−1. This shift of the diamond line could be used for pressure determination. The Raman spectra from selected volumes of the diamond anvil at various depths provide useful information about stress distribution in the anvil.

Ion‐beam‐assisted etching of diamond

Abstract: The high thermal conductivity, low rf loss, and inertness of diamond make it useful in traveling wave tubes operating in excess of 500 GHz. Such use requires the controlled etching of type IIA diamond to produce grating like structures tens of micrometers deep. Previous work on reactive ion etching with O2 gave etching rates on the order of 20 nm/min and poor etch selectivity between the masking material (Ni or Cr) and the diamond. We report on an alternative approach which uses a Xe+ beam and a reactive gas flux of NO2 in an ion‐beam‐assisted etching system. An etching rate of 200 nm/min was obtained with an etching rate ratio of 20 between the diamond and an aluminum mask.

Pressure dependence of the first-order Raman mode in diamond

Abstract: The effect of isotropic pressure on the frequency of the fundamental Raman mode of diamond has been measured up to 40 GPa The mode frequency increases linearly with the change in wavelength of the ${R}_{1}$ luminescence of ruby, which is used for pressure measurement The mode frequency has been calculated theoretically for pressures up to 600 GPa and is found to vary sublinearly with pressure The possibility of using the Raman mode as a pressure gauge is discussed

Multi-component cutting element using consolidated rod-like polycrystalline diamond

Abstract: An enlarged diamond table for use as a cutter (10) in rotating drill bits is provided by disposing a plurality of thermally stable or leached polycrystalline diamond (PCD) rod- like elements (12) within a matrix body (16). In one embodiment the matrix body (16) is impregnated with diamond grit and completely fills the interstitial spaces between the plurality of diamond elements (12). Generally, the diamond elements (12) have their longitudinal axes arranged in a mutually parallel configuration. The bundle of rod-like diamond elements (12) are in one embodiment in a compact touching array and in another embodiment in a spaced-apart array. In the illustrated embodiment, a bundle of rod-like diamond elements are disposed so that their end surfaces are exposed on the cutting face (14) of the cutting slug (10). The slug (10) is then in turn mounted on a stud or directly infiltrated into a matrix body bit (Figure 1).

Visible color-center laser in diamond.

Abstract: Laser action at 530 nm using H3 centers in diamond was observed with an efficiency of 13.5% at room temperature. Optical double-resonance experiments on N3 centers provided direct evidence for a 2A metastable level. Its presence results in rapid decay of the excited 2E state and low quantum efficiency as well as significant excited-state absorption in the N3 luminescence region.

Growth of diamond at room temperature by an ion‐beam sputter deposition under hydrogen‐ion bombardment

Abstract: The structure and crystal phase of carbon films prepared by an ion‐beam sputter deposition were studied. The properties of the deposited carbon films were influenced by a hydrogen‐ion bombardment during the film growth. It is noted that the hydrogen‐ion bombardment activates the growth of diamond in the deposited carbon film. Diamond particles of 0.1∼1 μm in diameter, which showed well‐defined morphology of diamond, were successfully grown at room temperature on nondiamond substrates.

A Raman study of diamond anvils under stress

Abstract: First‐order Raman spectra from selected volume elements of diamonds used as anvils in a gasketed high‐pressure cell have been measured under applied load. The observed Raman profiles are interpreted on the basis of known isotropic and uniaxial stress effects in diamond‐type materials. It is demonstrated that Raman spectroscopy provides in situ experimental information on the stress distribution within the anvils. Up to at least 300 kbar, the prominent high‐frequency edge of the Raman profile measured at the center of the diamond tip face exhibits a linear dependence on pressure within the sample volume. The application of diamond anvil Raman scattering for pressure determination is discussed.

Genesis of diamond; a mantle saga

Abstract: A model for the genesis of natural diamond is presented based on the physical, chemical and mineralogical properties and features of diamond. Optical studies suggest that individual diamonds have had complex growth histories in which growth and dissolution may have occurred. Growth was not always continuous nor did diamonds grow in necessarily similar chemical environments. Evidence for this is provided by variation in the nitrogen and trace element contents in diamonds as well as information from studies of the minerals included in diamond. Isotopic data suggest that diamonds formed from carbon whose sources varied isotopically. The possibility exists that some diamonds may be products of recycled subducted carbon, whereas others have formed from primordial material either through magmatic or metasomatic processes. It is also likely that most diamonds formed in the Archaean or Proterozoic. The cognate host rocks for diamond in the mantle were several but can be broadly grouped into eclogitic and ultramafic (peridotitic); however, in mineralogic and chemical detail these rocks are quite diverse. Although diamond is commonly found in kimberlite and in lamproite at the earth's surface, these two rocks are not genetically related to diamond formation. Instead they are the transporting vehicles in which diamond ascended rapidly from mantle depths to the crust.

Wear resistant diamond cladding

Abstract: An erosion resistant article is formed by cladding a substrate with tiles having a surface layer of polycrystalline material such as diamond or cubic boron nitride. The tiles may be entirely polycrystalline diamond or may have a backing of cemented tungsten carbide. Such an article can be trim for a high pressure valve wherein a sleeve is partly lined with polycrystalline diamond tiles and a plug is clad with polycrystalline diamond tiles.

A composite bolometer as a charged-particle spectrometer

Abstract: The measurement of radioactivity by direct conversion of nuclear radiation into a temperature rise of a calorimeter is as old as nuclear physics itself. As part of a general programme aiming at a determination of the mass of the electron neutrino, we have designed an improved version of a He-cooled composite diamond bolometer with a monolithic germanium thermistor, developed at the Laboratoire de Physique Stellaire et Planetaire (LPSP)1. Our approach, based on an idea by De Rujula2, is to study the shape, near the upper end-point of the internal bremsstrahlung spectrum in electron-capture β decay. The best nucleus for a precise measurement seems to be 163Ho, for which we have determined3 the Q EC value to be 2.83±0.05 keV. A particularly interesting possibility is to use total absorption spectrometry4 (calorimetry), in which the radioactive holmium forms part of the sensitive volume of the detector. With 5–6-MeV α particles impinging on the diamond wafer of the bolometer, a full-width-at-half-maximum (FWHM) of 36 keV was obtained at a temperature of 1.3 K. The theoretical resolution at 100 mK is a few electron-volts, so this new detection technique should give greatly enhanced energy resolution compared with present solid-state conductors based on charge carrier collection.

Thermally stable diamond compacts

Abstract: A thermally stable diamond compact which has an alloy of liquidus above 700 DEG C bonded to a surface thereof. The alloy contains at least 40 percent by weight of silver or gold or a combination thereof and 1 to 10 percent by weight of an active metal selected from the group of tungsten, titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium and molybdenum and having a liquidus temperature above 700 DEG C.

Carbonado: Diamond aggregates from early impacts of crystal rocks?

Abstract: Carbonados are irregular polycrystalline aggregates of diamond that occur in placers and low-grade metamorphic rocks. They are characterized by fine grain size, light carbon isotope ratio, a wide variety of inclusions of crustal materials (silicates, phosphates, and oxides), and an absence of minerals characteristically associated with diamonds from the upper mantle. We propose that all these properties, and also the presence of lonsdaleite in one carbonado, can be explained by impact metamorphism of crustal rocks containing organic carbon or a graphitic derivative, including those of the Archean and Proterozoic eras.

AES and LEED study of the zinc blende SiC(100) surface

Abstract: Auger and LEED measurements have been carried out on the (100) surface of zinc blende SiC. Two different phases of the clean surface, in addition to two kinds of oxygen covered surfaces, have been obtained, identified, and discussed. In the oxygen covered surface, the oxygen is bonded to the Si. The carbon rich phase is reconstructed (2×1), similar to the (100) clean surfaces of Si, Ge, and diamond. The Si topped surface is reconstructed (×) R45°. A model of alternating Si dimers is suggested for this surface.

Diamond compacts and process for making same.

Abstract: A process for producing a diamond compact having a compressive strength of at least 10 kbars, the process being performed in the graphite stability field at a maximum pressure of 40 kbars at a temperature of between 1100oC and 1600oC for a time which permits plastic deformation of the diamond crystals giving face-to-face contacts therebetween and a substantial or complete degree of chemical equilibration between the bonding agent and the diamond crystals. Bonding agents are selected from elements and alloys which produce a bond with diamond having a melting point above 1600oC and which inhibit the formation of free graphite in the compact.