Showing papers on "Diamond published in 1977"

Transformation of the state of nitrogen in diamond

Abstract: High temperature–high pressure annealing experiments on diamond transform type IB dispersed nitrogen into type IA aggregate nitrogen. The activation energy for the transformation is approximately 60 kcal mol−l (2.6 eV). An estimate is given for the diffusivity of nitrogen in diamond for this transformation

Electrical, structural and optical properties of amorphous carbon

Abstract: The planar and transverse electrical resistivity of amorphous carbon (a-C) films getter-sputtered at low temperature (77–95 K) is well-fitted by the expression ϱ = ϱ 0 exp (T 0 /T) 1 4 The exponent T0 being approximately the same in both cases (≈ 7 × 107 K) suggests that the amorphous films are isotropic. Films thinner than 600 A display a two-dimensional hopping conductivity from which one deduces a density of states N(EF) at the Fermi level of 1018 eV−1 cm−3 and a radius of the localized wave functions (a) of 12 A. Tunneling experiments and optical absorption measurements are consistent with a pseudogap of approximately 0.8 eV. Electron diffraction experiments indicate that a-C films consist of a mixture of diamond and graphite bonds; this fact taken in the light of the other experiments would suggest that the graphite bonds act as the localized conduction states.

Pressure distribution in the diamond anvil press and the shear strenght of fayalite

Abstract: High‐pressure cells, using opposed diamond anvils, have become an increasingly sophisticated tool for high‐pressure research as the high‐pressure environment within th cell becomes more quantitatively established. We have used the ruby fluorescence technique for measuring pressure to obtain the radial distribution of pressure between the diamond anvils for samples of fayalite (Fe2SiO4). Precompacted specimens appeared to be in a conditon of extrusion, limited by the plastic strength of the fayalite aggregate formed. Specimens which were not precompacted were too thin to show this condition.

Charge states of the vacancy in diamond

Abstract: KNOWLEDGE of radiation damage processes in diamond has increased substantially in the past few years. I present here a concise summary of these data, and suggest that the 25,410 cm−1 (ND1) absorption band occurs at a negatively charged vacancy. It will be shown that with this interpretation, the optical effects of radiation damage fall into a self-consistent pattern.

Rock bit with diamond reamer to maintain gage

Abstract: A rock drill bit comprises a bit body and at least one rolling cone cutter mounted on the bit body, the rolling cone cutter comprising a plurality of tungsten carbide inserts including a plurality of gage inserts for drilling adjacent the peripheral wall of the hole being drilled. At least one diamond cutter protrudes from the bit body to provide a cutting edge substantially on the gage diameter of the rock bit so that such a diamond insert can engage the peripheral wall of the hole being drilled, thereby maintaining the hole gage. Each diamond cutter comprises a carbide slug inserted in the bit body and a diamond plate bonded to the slug. Such diamond cutters are on a peripheral portion of the bit body above the cutter cones.

Hard conducting implanted diamond layers

Abstract: Hard conducting diamond layers were produced by carbon implantation. Above a threshold implantation dose (≃3×1016/cm2), these layers possess the high conductivity of graphite (≃10−2 Ω−1 cm−1) and a hardness intermediate between that of silicon and diamond.

Zirconium layer for bonding diamond compact to cemented carbide backing

Abstract: An abrasive body comprising a diamond compact bonded to a cemented carbide backing by means of a continuous zirconium layer, the thickness of which is less than 0.5 mm, the diamond compact being substantially free of graphite and having a bonding matrix selected from a metal of Group VIII of the Periodic Table or an alloy containing one or more such metals and at least 70 percent by volume of diamond particles, and the cemented carbide backing being selected from cemented tantalum carbide, cemented tungsten carbide and cemented titanium carbide and mixtures thereof.

Polycrystalline diamond emitter

Abstract: Ultrasharp diamond edges and points which are usable as high intensity point sources for the emission of electrons, ions, X-rays, coherent and incoherent light and high frequency electromagnetic radiation are produced by preparing and classifying ultrafine diamond powder having a particle size of 10 to 100 angstroms, placing the powder in a diamond mold defining the ultrasharp edge or point to be produced and applying a pressure of the order of 80 to 90 kb while heating the powder to a temperature of the order of 2440° K. in an ultrahigh vacuum or inert atmosphere after degasing to avoid oxidation of the diamond powder.

Diamond dosimeter for x-ray and δ-radiation

Abstract: Some characteristics of diamond detectors have been investigated with a view to finding out the possibilities of their application for X-ray and δ-radiation dosimetry in medical radiology. The results of this investigation are described. The design of a tissue-equivalent diamond dosimeter is shown. It possesses a uniform energy dependence and threshold sensitivity of lμR/s to the dose rate.

High pressures on small areas.

Abstract: Small diamond indentors with spherical tips were pressed against a polished diamond flat. Pressures were calculated from Hertz contact theory. Very high pressures were achieved on small areas.

The Chemical Nature of Ion-Bombarded Carbon: A Photoelectron Spectroscopic Study of "Cleaned" Surfaces of Diamond and Graphite

Abstract: The effects of ion-bombardment on single-crystal carbon surfaces have been studied by X-ray photoelectron spectroscopy (X.p.s.) partly to establish whether, as previously suggested, the bombardment of diamond leads to surface graphitization. Changes in the x.p.s. of graphite were monitored as a function of exposure to both Ar and $^{57}$Fe ions; and the chemical natures of ion-bombarded diamond and graphite were examined in comparative electron spectroscopic studies of their uptakes of various oxygen species. X.p.s. revealed significant differences between Ar-ion bombarded diamond and graphite both in their C 1s spectra (which also differed significantly from that of cleaved graphite) and in the 2p binding energy of the embedded argon. The C 1s spectra of the $^{57}$Fe implanted graphite specimens (10$^{15}$- 10$^{16}$ cm$^{-2}$, 12.5-85 kV) were identical with those of Ar-ion bombarded graphite, although the Fe was buried beneath the X.p.s. sampling depth. These results show that ion bombardment produces partially disordered but nevertheless structurally distinct surface phases on graphite and diamond crystals. The bombarded surfaces were rather unreactive to O$_{2}$ taking up only a small fraction of a monolayer, although exposure to oxygen (or, more effectively, nitric oxide) excited by a microwave discharge resulted in the uptake of several monolayer equivalents of oxygen. Embedded Ar was only very slowly lost during oxidation, confirming the expected low erosion rate under the conditions used. The O 1s X.p.s. from the two substrates showed significant differences although the rates of uptake of oxygen were closely similar. The O 1s peaks were broad, indicating the presence of a minimum of two major oxygen species. Our results, taken in conjunction with others, suggest that [Note: Diagram omitted. See the image of page 103 for this diagram.] surface groups were probably present in roughly equal concentrations on the oxygenated carbon surfaces. He I and He II spectra of Ar-ion bombarded diamond obtained before and after oxidation are also intelligible on this basis.

50‐kilobar gasketed diamond anvil cell for single‐crystal x‐ray diffractometer use with the crystal structure of Sb up to 26 kilobars as a test problem

Abstract: A single‐crystal gasketed diamond anvil cell of a new design for use on a diffractometer is described. It has achieved hydrostatic pressures of 50 kilobars as determined from the ruby fluorescence shift. The design combines several advantages. Nearly half the area of the Ewald sphere is available without having to remount the crystal. For reflecting planes nearly parallel to the diamond anvil faces, all reflections in the angular range ∼4°⩽ϑ⩽85° can be observed. Alignment of the diamonds, as well as loading and alignment of the sample crystals, is very simple and quick. The diffractometer geometry allows accurate measurements of weak reflections as well as accurate determinations of the x‐ray absorption corrections for the cell. The materials of construction are nontoxic except for one diamond mount, a small beryllium cylinder situated so that it is never touched, scraped, or rubbed. As a test problem, the z parameter of antimony has been found to increase linearly from z=0.23357 at 1 bar to z =0.2380±0.0...

Phonon transmission from incoherent radiators into quartz, sapphire, diamond, silicon and germanium within anisotropic continuum acoustics

Abstract: The phonon excitation in monocrystals by phonon transmission from an adjacent incoherent phonon radiator is treated within continuum acoustics for several crystal cuts of sapphire, quartz, diamond, silicon and germanium. Whereas the theoretical treatment is made as general as possible, in numerical computation the radiator material is assumed to be mechanical isotropic, the monocrystal however anisotropic. For a diffuse phonon field with equilibrium distribution between the different polarizations in the radiator, the $$\vec q$$ -space phonon intensity in the crystal substrate is calculated and presented graphically for the most important cases. Numerical values of halfspace emissivities as well as of the differential emissivities normal to the crystal faces are given for a large variety of material combinations.

An optical study of the TR12 and 3H defects in irradiated diamond

Abstract: The defects are observed in the optical spectrum of irradiated diamond. TR12 has many very sharp phonon replicas in absorption, but fewer in photoluminescence. During electron irradiation at room temperature the defect is produced initially as the cube of the dose. It can be induced only in type II diamonds, and is probably an interstitial complex. The photoluminescence spectrum of 3H has been recorded for the first time. The defect is quite distinct from the H3 and S1 centres, in spite of the similarity in energy of their zero phonon lines.

Momentum densities and Compton profiles of diamond, silicon and silicon carbide

Abstract: Momentum densities and Compton profiles were calculated for the tetrahedral semiconductors diamond, silicon carbide and silicon, making use of approximate Hartree-Fock-Slater crystal wavefunctions. Reasonable agreement is found with available experimental data and also with the calculations of Wepfer, et al. (1974) on diamond. Anisotropies of momentum densities and Compton profiles are analysed by means of spherical harmonic expansions. Although the spherical components are remarkably similar when scaled according to lattice momentum 2 pi /a, the anisotropic components of the three crystals show distinctive features.

Spectroscopic Mode Gruneisen Parameters for Diamond

Abstract: Room temperature measurements are reported of the first and second order Raman spectra of diamond in the hydrostatic pressure range 0-2.4 GPa. Values calculated from the data for the optic mode Gruneisen parameters have been fitted in terms of a simple lattice dynamical model for diamond involving volume dependent interatomic forces. The interpolated set of mode Gruneisen parameters are shown to be in substantial agreement with thermodynamic data. The simple model for the anharmonicity of the interatomic forces in the diamond group materials is shown to provide a qualitative explanation for the contrasting low temperature behaviour of the thermal expansion exhibited by these materials.

On the formation of the diamond grain configuration during high temperature creep and fatigue

Abstract: A study has been made of the influence of test variables on the formation of the diamond grain configuration during high temperature creep and fatigue deformation of a wide variety of metals. The proposed mechanisms for the formation of this interesting grain morphology are reviewed. It is concluded that the diamond grain configuration arises from a balance between grain-boundary sliding, grain-boundary mobility, intragranular deformation and defect imbalance across the grain boundaries and that it tends to be stabilized by intergranular cavitation. While the phenomenon occurs during high temperature fatigue in a variety of metals irrespective of their crystal structure, during creep it has been observed only in to h c p metals. It is surmised that the occurrence of the diamond array of grain boundaries during creep deformation in h c p metals is aided by the limited number of slip systems which leads to high defect imbalances in adjacent grains and consequently high driving forces for grain-boundary migration. On the basis of quantitative metallography involving measurements of the number of edges per grain section, the number of grains meeting at vertices, angular distribution histograms and grain-boundary lengths in different angular orientations with respect to the stress axis in "annealed" and "diamond" microstructures, it is concluded that the shape of the "diamond" grain is essentially the same as that of the "annealed" grain but in a distorted form.

Compact-grained diamond material

Abstract: The proposed compact-grained diamond material consisting of powdered diamond particles is characterized in that the diamond particles therein are coated with a titanium carbide or zirconium carbide film, which film forms a cellular structure over the entire body of the material, and are bound with copper-titanium intermetallides filling the spacing between said diamond particles.

Annealing type Ib or mixed type Ib-Ia natural diamond crystal

Abstract: Type Ib or mixed type Ib-Ia natural diamond crystal is annealed at an annealing temperature ranging from about 1500° C to about 2200° C under a pressure which prevents significant graphitization of the diamond during the annealing to convert at least 20% of the total amount of type Ib nitrogen present in the crystal to type Ia nitrogen.

Theory of two-phonon Raman spectrum of diamond

Abstract: The Raman spectrum of diamond in the high-frequency part of the two-phonon region is investigated. An interpretation of the sharp line at the two-phonon cutoff as a simple overtone is supported in terms of a harmonic model for the potential and a bond polarizability approximation for the scattering Hamiltonian. Polarization features as well as the anomalous position and width of the peak are discussed and interpreted, giving general agreement between theory and experiment. A comparison is made with the Raman spectrum of silicon, and differences in the spectra are accounted for by a different behavior of the dispersion relation along $\ensuremath{\Delta}$ for the two lattices, which has its origin in the greater angle-stiffness forces in diamond, ultimately due to greater covalency in diamond. A new set of critical points for the LO branch of diamond is also proposed.