Showing papers on "Diamond published in 1980"
TL;DR: In this article, a model based solely on a threefold coordinated random network structure was presented to explain the diamond-like physical properties of a-C films and their changes with annealing.
Abstract: Evaporated and sputtered a-C films deposited at L.N. temperature were prepared and studied as a function of annealing using Raman, electron energy loss, and ESR techniques. The reduced Raman spectra of virgin films reflect the one phonon density of states of graphite. Moreover, no evidence for diamond bonding is found from the electron energy loss experiment. Upon annealing, graphitic structural correlations develop within bounded islands of carbon atoms. This picture is consistent with ESR measurements which yield 3 × 1019 spins/cm3 independent of annealing but a resonnance line (g = 2.002 ± .0005) that narrows with annealing. A model based solely on a three-fold coordinated random network structure will be presented to explain the “diamond-like” physical properties of a-C films and their changes with annealing.
345 citations
TL;DR: The sintered masses are produced on a commercial scale and are increasingly used as cutting tools on hard or abrasive materials, as wire-drawing dies, in rock drills, and in special high-pressure apparatus.
Abstract: Diamond or cubic boron nitride particles can be sintered into strong masses at high temperatures and very high pressures at which these crystalline forms are stable. Most of the desirable physical properties of the sintered masses, such as hardness and thermal conductivity, approach those of large single crystals; their resistance to wear and catastrophic splitting is superior. The sintered masses are produced on a commercial scale and are increasingly used as cutting tools on hard or abrasive materials, as wire-drawing dies, in rock drills, and in special high-pressure apparatus.
320 citations
TL;DR: A brief history of the many investigations of the pressure/temperature phase diagrams of elemental carbon is given in this article, where the strengths and weaknesses of various proposed diagrams are discussed, and the areas where additional or better experimental data are needed are pointed out.
Abstract: A brief history of the many investigations of the pressure/temperature phase diagrams of elemental carbon is given. The strengths and weaknesses of the various proposed diagrams are discussed, and the areas where additional or better experimental data are needed are pointed out. Many questions still remain about linear solid carbons; about the low-pressure/high-temperature solid/liquid/vapor triple point; about the melting line of diamond; about the existence of a high-pressure metallic phase; and about the existence of two liquid phases, one insulator and the other metallic.
299 citations
TL;DR: In this paper, three hundred and thirty new 13C analyses of diamonds are presented, indicating, in conjunction with earlier published work, a range of about 30% in the carbon isotopic composition of diamonds.
272 citations
TL;DR: In this paper, the authors investigated the accuracy of the self-consistent LMTO-ASA method with interstitial spheres for open structure materials by studying the electronic structure of Si, Ge and diamond.
169 citations
Patent•
22 Dec 1980
TL;DR: In this article, an improved process for preparing a composite compact consisting of a mass of abrasive crystals, metal carbide, and a bonding medium is presented. And the resulting improved composite compact also is disclosed.
Abstract: Disclosed is an improved process for preparing a composite compact wherein a mass of abrasive crystals, a mass of metal carbide, and a bonding medium are subjected to a high-temperature/high pressure process for providing a composite compact. The sintered carbide mass supports the mass of abrasive crystals and bonding or catalyst metal, and the abrasive crystal grains are directly bonded to adjacent crystal grains in the mass thereof. Such improved process comprises disposing the mass of abrasive crystals in layers wherein the coarsest layer is closest to the carbide mass and is composed of crystals having a largest dimension of between about 75 and 500 microns and the finest layer is disposed farthest away in the carbide mass and is composed of crystals having a largest dimension of less than 10 microns. The abrasive crystals are selected from the group consisting of diamond and cubic boron nitride and preferably are diamond; the metal carbide preferably is tungsten carbide; and the bonding metal preferably is cobalt. The resulting improved composite compact also is disclosed.
167 citations
TL;DR: A Monte Carlo analysis of electron drift velocity data enables for the first time the electron effective masses to be determined in natural diamond as discussed by the authors, where the Si-like conduction band of natural diamond is identified.
156 citations
TL;DR: In this article, the aggregation of nitrogen in type Ib diamond, at 1500 degrees C in vacuo, has been investigated for natural and synthetic samples containing around 50 ppm and 500 ppm isolated substitutional nitrogen respectively.
Abstract: The aggregation of nitrogen in type Ib diamond, at 1500 degrees C in vacuo, has been investigated for natural and synthetic samples containing around 50 ppm and 500 ppm isolated substitutional nitrogen respectively. The rate constant for the aggregation process in untreated diamonds is very much less than that reported previously for samples subjected to a hydrostatic pressure of approximately 6 GPa, but may be increased by a factor of at least 50 if the diamonds are irradiated with approximately 1022 2 MeV electrons/m2. The vacancy concentration produced by such an irradiation is only approximately 5 ppm and is proposed that at high nitrogen concentrations the aggregation process involves the multiple release and retrapping of vacancies. Analysis of infrared absorption spectra before and after aggregation of the nitrogen suggests that the conversion factor normally used to calculate substitutional nitrogen concentrations from the strength of the 1130 cm-1 absorption band is too low by a factor of almost two.
137 citations
TL;DR: It is concluded that natural diamond can be used for the manufacture of reliable, small and near soft-tissue-equivalent dosemeters but that until the crystal selection and final product testing have been adequately standardised, the user needs to select the reliable dosemeter from a batch.
Abstract: The effect of beam energy, dose rate and temperature on seven commercial diamond electrical conductivity detectors was studied. The diamond dimensions were approximately 1 mm X 1 mm X 3 mm. Clinical photon nd electron beams were used for irradiation. The photon energy response normalised to 60Co was observed to have a maximum of 1.37 +/- 0.06 at 122 keV and the dose rate response was slightly non-linear, in agreement with the theory for insulators. Temperature effects were small and different for each detector. Two of the seven detectors gave repeatable results (+/- 5%) over five years, two others were much less satisfactory and three were rejected after preliminary tests. It is concluded that natural diamond can be used for the manufacture of reliable, small and near soft-tissue-equivalent dosemeters but that until the crystal selection and final product testing have been adequately standardised, the user needs to select the reliable dosemeters from a batch.
128 citations
TL;DR: In this article, an apparatus and technique for loading diamond anvil cells with gases at high pressure was devised. But this was done at room temperature with helium and hydrogen isotopes to initial densities exceeding those of the normal liquids.
Abstract: We devised an apparatus and technique for loading diamond‐anvil cells with gases at high pressure. Cells were filled quickly and conveniently at room temperature with helium and hydrogen isotopes to initial densities exceeding those of the normal liquids. We report preliminary values of 4He and D2 melting points based on the ruby pressure scale and compare them with extrapolations from our earlier melting curves measured to 20 kbar in a piston‐cylinder device. Our filling procedure now makes it possible to use 4He as a pressure medium in diamond cells. The technique is also useful for loading cells with gaseous mixtures.
127 citations
TL;DR: In this paper, a graphite-to-diamond phase transition with high pressure was described. Butts et al. showed that the phase transition from diamond to a metallic state at very high pressure is not instantaneous.
Abstract: Shock-induced graphite-to-diamond phase transition pressures and Hugoniot parameters to 120 GPa are presented for pyrolytic, Ceylon natural, and synthetic graphites. The response of amorphous carbon to shock loading, including a shock-induced phase transition, is reported. Interpretations of discontinuities found in the shock-velocity versus particle-velocity plots are discussed in terms of the carbon phase diagram. Evidence of a solid-to-solid phase transition from diamond to a metallic state at very high pressure is described.
TL;DR: The physical fact that diamond is electrically insulating while amorphous carbon and graphite are conducting is used in the present work to study the local damage that each implanted ion creates around its track and to conclude about the processes through which implanted diamond turns amomorphous as mentioned in this paper.
Abstract: The physical fact that diamond is electrically insulating while amorphous carbon and graphite are conducting is used in the present work to study the local damage that each implanted ion creates around its track and to conclude about the processes through which implanted diamond turns amorphous. Experimental data for the conductivity of Sb implanted diamond for various gometries, energies and doses are analyzed by the use of percolation theory. It seems that the amorphization of implanted diamond proceeds gradually with no well defined amorphous regions formed around the ion track. Amorphization in implanted diamond seems to occur in a way different than is believed to be the case for implanted silicon, where some direct amorphization around an ion track is suggested. This major difference can be attributed to the abnormally large change in densities between diamond and amorphous carbon or graphite which suppresses the growth of local amorphous regions in diamond.
TL;DR: In this article, the role of nitrogen in diamond characterisation has been quantified using ion beam analysis and it has been shown that hydrogen, nitrogen and oxygen are all major impurities in diamond.
TL;DR: In this article, a revised model of assisted diffusion in a highly defective lattice is proposed to explain the observations of graphite-to-diamond transformation by impact-produced shock waves.
Abstract: The transformation of graphite to diamond by impact‐produced shock waves has been examined using a gas gun to launch projectiles onto graphite and a graphite‐metal mixture. Analysis of the mechanism of transformation is complicated by the post shock graphitization of most of the diamond produced. It is argued that the previously proposed models of shock‐wave transformation are incomplete and a revised model of assisted diffusion in a highly defective lattice is proposed to explain the observations.
Patent•
31 Jul 1980
TL;DR: In this paper, a method of producing diamond and diamond-like modifications of boron nitride from a material to be transformed, such material being carbon and/or Boron Nitride, with the use of explosive power, was described.
Abstract: A method of producing diamond and/or diamond-like modifications of boron nitride from a material to be transformed, such material being carbon and/or boron nitride, with the use of explosive power, said explosive power being used by way of performing detonation of a charge comprising an explosive and a material to be transformed.
TL;DR: In this paper, an investigation was conducted to examine the adhesion and friction of single-crystal diamond in contact with various transition metals and the nature of metal transfer to diamond.
IBM1
TL;DR: In this article, the Schottky barrier heights for Al on (p-type) diamond(1 1 1)−(1 × 1) were measured using photoelectron spectroscopy with synchroton radiation.
TL;DR: In this article, photo-emission, LEED, and AES measurements were made on the mechanically polished (111) surface of a type IIa diamond and no emission from filled states in the fundamental gap was found over the photon energy range 13.3 eV?h/ω?200 eV. This result, coupled with the sharp 1×1 LEED patterns which were obtained and the relative cleanliness of elements which can be detected by AES, suggests hydrogen termination of the lattice.
Abstract: Photoemission, LEED, and AES measurements were made on the mechanically polished (111) surface of a type IIa diamond. No emission from filled states in the fundamental gap was found over the photon energy range 13.3 eV?h/ω?200 eV. This result, coupled with the sharp 1×1 LEED patterns which were obtained and the relative cleanliness (of elements which can be detected by AES) of the diamond (≲1 at.% oxygen, <0.5 at.% Si) suggests hydrogen termination of the lattice. Photoelectric yield measurements demonstrate the photoelectric threshold to be at band gap energy radiation. Investigation of the photoemission electron distribution curves (EDC’s) shows that, while the electron affinity at the surface is always positive, band bending is sufficient to result in an effective negative electron affinity under certain conditions. A variable surface dipole on the atomic scale, possibly due to the adsorption–desorption of a background gas, is reported. A study of the relative cross section of the upper (p‐like) versus...
TL;DR: In this article, the g-values of the GR1-GR8 levels are obtained from axial Zeeman and magnetic circular dichroism (MCD) measurements using a diamond sample which has minimal strain.
Abstract: The g-values of the GR1-GR8 levels are obtained from axial Zeeman and magnetic circular dichroism (MCD) measurements using a diamond sample which has minimal strain The presence of large Zeeman interactions and the occurrence of doublets which are mixed by the magnetic field are not understood
TL;DR: In this paper, radiation damage and annealing in Sb implanted diamond is discussed. But the authors focus on the Sb implant and do not discuss the effect of the implant on the implant itself.
Abstract: (1980). Radiation damage and annealing in Sb implanted diamond. Radiation Effects: Vol. 48, No. 1-4, pp. 139-143.
TL;DR: The linear combination of atomic-orbitals self-consistent field ab initio Hartree-Fock method was applied to diamond as mentioned in this paper, where a minimal basis set, total, binding, and correlation energy, equilibrium lattice constant, bulk modulus, band structure, population analysis, x-ray factors, and directional Compton profiles were calculated.
Abstract: The linear-combination-of-atomic-orbitals self-consistent field ab initio Hartree-Fock method previously presented [Int. J. Quantum Chem. 17, 501 (1980)] is here applied to diamond. Using a minimal basis set, total, binding, and correlation energy, equilibrium lattice constant, bulk modulus, band structure, population analysis, x-ray factors, and directional Compton profiles have been calculated. The results are compared with those previously obtained with Hartree-Fock and local-exchange Hamiltonians. A comparison is made for some properties with results for graphite obtained using the same approximation.
TL;DR: In this article, the authors considered the E to E electric-dipole transition at trigonal centers in cubic crystals and showed that the ground E state interacting under stress with a non-degenerate state approximately 100 cm-1 above it.
Abstract: E to E electric-dipole transitions at trigonal centres in cubic crystals are considered. Expressions for the intensities and energies of the stress-split components of the transition are tabulated for (001), (111) and (110) stress axes. As an example, uniaxial stress data for the 594 nm line in a diamond are reported. They are shown to be consistent with an E to E (trigonal) transition, the ground E state interacting under stress with a non-degenerate state approximately 100 cm-1 above it.
TL;DR: In this paper, the wear of diamond tools turning mild steel has been investigated and it was shown that the very high rates of wear arise from the degeneration of the diamond to graphite, the details of the wear mechanisms depending on the cutting conditions.
01 Jan 1980
TL;DR: In this paper, the group of non-metal crystals comprises a vast variety of materials with extremely different properties, ranging from the high hardness of diamond or corundum to the wax-like softness of organic compounds.
Abstract: The group of non-metal crystals comprises a vast variety of materials with extremely different properties. Their mechanical strength ranges from the high hardness of diamond or corundum to the wax-like softness of organic compounds. They are grown by diverse methods from the melt, from the vapour phase and from solution. The growth temperatures vary from values above 2000° C (e.g. for high-melting oxides) to values close to or even below room temperature for melts of organic compounds and solutions in aqueous or organic solvents. In hydrothermal growth (quartz, zinc oxide) pressures of several kbars are applied.
TL;DR: In this article, a study of the friction in air of a spherically tipped diamond stylus over the 100 face of a flat diamond surface was carried out and the results showed that the friction is greater when sliding occurs along the K100> direction than along the kt110> direction.
Abstract: This paper describes a study of the friction, in air, of a spherically tipped diamond stylus over the {100} face of a flat diamond surface. The results show that in general the friction is greater when sliding occurs along the K100> direction than along the Kt110> direction. This cannot be explained in terms of a Coulomb frictional mechanism where the friction is attributed to the climbing of one surface over the asperities on the other, for in that case the coefficient of friction is determined solely by the surface topography and is independent of load. By contrast, the experiments described in this paper show that below a critical load Wc the frictional anisotropy virtually disappears. This critical load is proportional to R2, where R is the radius of curvature of the stylus, implying, for Hertzian deformation, a critical contact pressure. For both type I and type II diamonds this critical pressure has a value of the order of 20 GN rn-2. At these and larger contact pressures cathodoluminescent studies of the flat diamond surfaces indicate that the frictional anisotropy is largely due to surface and sub-surface damage produced in preferred crystallographic directions by the sliding process itself. The results are discussed in terms of crack formation and plastic deformation. However, the results do not, as yet, provide an unequivocal account of the mechanism of energy dissipation.
TL;DR: In this article, a diamond octahedron was etched at temperatures of 800 to 1400° C and at pressures of 15 and 40 kbar under controlled oxygen partial pressure in the range 10−17 to 104 atm by use of oxygen buffers.
Abstract: Etching of a natural diamond octahedron was carried out at temperatures of 800 to 1400° C and at pressures of 15 and 40 kbar under controlled oxygen partial pressure in the range 10−17 to 104 atm by use of oxygen buffers. Well-defined etch pits of equiangular triangule outline were formed. When the results were plotted based on log PO2 versus 1/T, reversal of the pit orientation clearly occurred on a boundary curve expressed by an equation, log PO2=−9.0×104/T+63, where PO2 (atm) and T (K) are oxygen partial pressure and temperature, respectively. Etch pits with the same orientation as an octahedral face were produced in a low temperature and high PO2 region, and those with the opposite orientation, i.e. the same as for natural “trigon”, were produced in the other region.
TL;DR: In this article, the authors used a temperature gradient method to grow diamond crystals using Ni, Ni-Fe alloy and Fe as solvent metals, and the results showed that the surface patterns became finer with the increase of the content of Fe in Ni alloy.
Abstract: Diamond crystals of about 2 mm in size were grown by the temperature gradient method using Ni, Ni-Fe alloy and Fe as solvent metals. Several characteristic patterns were seen on the surfaces of the grown diamonds and were found to correspond to the texture of the quenched solvent metals. A vague vein-like pattern appeared when Ni was used. The surface patterns became finer with the increase of the content of Fe in Ni-Fe alloy, and when 70 wt% Fe-30 wt% Ni alloy was used, very fine dendritic patterns were seen on all of the faces of diamond in accordance with the symmetries of the lattice. The patterns are formed by the precipitation of carbon atoms in the space of the dendrites of the solvent metals during the quenching process. Lamellar patterns and etch pits were seen when Fe was used. The patterns are formed when Fe dissolves the diamond surfaces to produce Fe3C during the quenching process.
TL;DR: In this article, an improved semi-empirical self-consistent scheme is described for calculating the band structures of three-dimensional solids, based on CNDO theory, and tested on the standard systems; polyethylene, graphite, diamond, and hexagonal and cubic boron nitride.
Abstract: An improved semi-empirical self-consistent scheme is described for calculating the band structures of three-dimensional solids. The basic level is that of CNDO theory. The non-orthogonality of the Bloch functions is recognised and allowance is made for all degrees of involvement of the overlap matrix. The calculation of the electron-repulsion integrals is formulated in a way suitable for solid-state problems. The method is tested on the standard systems; polyethylene, graphite, diamond, and hexagonal and cubic boron nitride. It is found that the valence band properties are satisfactorily reproduced. For optical spectra a configurational interaction scheme is required.