Showing papers on "Graphite published in 1974"
TL;DR: In this article, the authors observed the first equilibrium surface phase transition for carbon-doped nickel single crystals, which they attributed to the stronger binding of carbon to this monolayer phase than to bulk graphite.
472 citations
TL;DR: In this article, the authors studied carbonaceous coal, black slate, graphite schist, and mica schist in regionally metamorphosed coal, showing continuous changes with increasing metamorphic grade: increase in particle size; loss of hydrogen, nitrogen, and oxygen ; increase in the carbon content; a decrease in the peak width of the (002) reflection; and a shift of the reflection to a higher position.
Abstract: Carbonaceous material in regionally metamorphosed coal, black slate, graphite schist, and mica schist shows the following continuous changes with increasing metamorphic grade: increase in particle size; loss of hydrogen, nitrogen, and oxygen ; increase in the carbon content; a decrease in the peak width of the (002) reflection; and a shift of the (002) reflection to a higher $$2\theta$$ position. These changes are greatest in the chlorite zone, where distinct (111) lines replace an unmodulated (111) band. In this study, only carbonaceous material from the staurolite and sillimanite zones is pure carbon. A large extent of layer ordering is acquired in the chlorite and biotite zones, but well-ordered graphite, comparable with Ceylon graphite, is limited to the sillimanite zone. There is little growth in the carbonaceous particles until the staurolite zone; in lower-grade zones, they rarely exceed 0.02 mm. The temperature at which layer ordering first appears in regionally metamorphosed rock is roughly 300°-...
177 citations
Patent•
22 Jul 1974
TL;DR: In this paper, a fiber reinforced composite product is produced in accordance with a process in which yieldable, high strength carbon or graphite fibrous materials are formed into a substrate that has been optimized for final product application through the accurate control of its shape, cross-sectional configuration, density, fiber volume and internal fiber orientation.
Abstract: A fiber reinforced composite product produced in accordance with a process in which yieldable, high strength carbon or graphite fibrous materials are formed into a substrate that has been optimized for final product application through the accurate control of its shape, cross-sectional configuration, density, fiber volume and internal fiber orientation. While constrained to the desired configuration, the optimized substrate is infiltrated with a pyrolytic material in a manner as to structurally bond together the fibrous materials which make up the substrate. The article thus formed is then densified in a controlled manner by further infiltration with pyrolytic material to the degree necessary to achieve the desired final product density.
120 citations
TL;DR: A kinetic approach has been made to the atomisation process in nonflame atomic-absorption spectrometry as discussed by the authors, where time-absorbance profiles for the determination of copper, using a graphite furnace, have been investigated in the temperature range 1720 to 2220 K and a rate equation derived that describes the variation of the amount of copper atoms in the furnace with time.
Abstract: A kinetic approach has been made to the atomisation process in nonflame atomic-absorption spectrometry. Time-absorbance profiles for the determination of copper, using a graphite furnace, have been investigated in the temperature range 1720 to 2220 K and a rate equation derived that describes the variation of the amount of copper atoms in the furnace with time. It has been shown that a slow first-order reaction involving reduction of copper oxide by carbon followed by the rapid vaporisation of the copper formed is the most probable reaction mechanism. The greater sensitivity achieved in the determination of copper using a tantalum-lined graphite furnace has been attributed in part to the greater rate of reduction of copper oxide by tantalum.
114 citations
TL;DR: The role of graphite and metal oxides in non-flame atomizers has been examined in this paper, and it has been concluded that graphite probably acts as a reducing agent in the atomization of cobalt, iron, nickel, and tin.
104 citations
102 citations
95 citations
TL;DR: In this paper, the memory and threshold switching processes of polymethylmethacrylate, polystyrene, polyethylmethacetyl-poly(polybutylmethACrylate) and polybutyl poly(polymethylmethylamine) glass are described.
Abstract: Memory and threshold switching processes are described, as observed in systems consisting of thin (∼0.5 μ) polymer films (polymethylmethacrylate, polystyrene, polyethylmethacrylate, polybutylmethacrylate) between inert electrodes (graphite, molybdenum, NESA glass). The memory off‐state is highly linear, in contrast to the corresponding characteristics of multicomponent chalcogenide glasses. Switching speeds are probably similar or, at any rate, ≪10−7 sec.
95 citations
TL;DR: In this paper, wear rates of cast graphitic aluminium-silicon-nickel alloys were lower than those of pure Al, Al-Si and AlSi-Ni alloys especially above pressures of 0.02 kg/mm2.
94 citations
TL;DR: In this article, it was concluded that the sublimation temperature of graphite at one atmosphere pressure lies between 3895 and 4020 K, and that little further experimental work needs to be done to define it more precisely, and to establish a new high temperature standard.
77 citations
TL;DR: In this article, new methods for synthesizing poly(carbon monofluoride)(CFx)n and tetracarbon monoffluoride C4F are reported.
Abstract: New methods for synthesising poly(carbon monofluoride)(CFx)n and tetracarbon monofluoride C4F are reported. Pyrolytic graphite has been fluorinated and a new compound, graphite oxyfluoride, has been prepared. Poly(carbon monofluoride) has been prepared in a flow reactor, in a fluidized-bed reactor, and in a high-pressure bomb reactor and tetracarbon monofluoride has been prepared by a high-pressure bomb technique. Some new structural data are presented for poly(carbon monofluoride). Recently, poly(carbon monofluoride) has been found to have a high potential as a solid lubricant and as a cathode material in high-energy batteries.
TL;DR: In this paper, the integral heat of adsorption at the two-dimensional phase change (5.5 ± 0.1 kcal mole−1) was derived from the binding energy of an individual atom of xenon on the (0001) face of graphite.
TL;DR: In this paper, a phenolic resin filled with iron and graphite was investigated for its frictional properties sliding against gray cast iron, and the frictional force was found to be a power function of the normal load (P) and the sliding speed (V) at a fixed temperature.
TL;DR: From adsorption isotherms of krypton on graphite measured between 79.24 and 88.46 K in the monolayer domain, a two-dimensional triple point of 84.8 ± 0.5 K is determined for this system as discussed by the authors.
Abstract: From adsorption isotherms of krypton on graphite measured between 79.24 and 88.46 K in the monolayer domain a two-dimensional triple point of 84.8 ± 0.5 K is determined for this system. Thermodynamic analysis of these isotherms and of the isotherms of xenon on graphite measured by Thomy and Duval suggests that the surface structure plays a prominent role in the formation of dense monolayers on the (0001) face of graphite. To explain the striking difference of behaviour of the two rare gases, two factors have to be taken into account; the height of potential barriers to translation and dimensional incompatibility between the lattices of the bulk adsorbates and of the (0001) face of graphite, the first “solid” layer appearing being in registry with the substrate. A single isotherm of argon on graphite measured at 68.78 K suggests that a more exhaustive study of the Ar + graphite system could be useful in establishing the relative importance of both factors.
01 Jan 1974-Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science
TL;DR: In this paper, the rate of carbon deposition from purified carbon monoxide was directly proportional to the amount of porous iron catalyst present in the system, but this simple relation did not hold for H2-CO mixtures, as the porous iron granules disintegrated and were dispersed evenly in the carbon deposit.
Abstract: Hematite ore reduced with hydrogen was used as a catalyst in the present investigation of the rate of decomposition of carbon monoxide in H2-CO mixtures. It was found that the amount of carbon deposited from purified carbon monoxide was directly proportional to the amount of porous iron catalyst present in the system. However, this simple relation did not hold for H2-CO mixtures. During carbon deposition the porous iron granules dis-integrated and were dispersed evenly in the carbon deposit. The deposit consisted of graphite, cementite and iron, with cementite/iron ratio increasing as more soot accumulated. When most of the iron was converted to cementite, carbon deposition ceased. A small amount of hydrogen enhanced markedly the rate of decomposition of carbon monoxide. Indications are that hydrogen adsorbed on iron catalyzes the decomposition of carbon monoxide, 2CO → C + CO2, in addition to the occurrence of the second reaction H2 + CO → C + H2O.
TL;DR: A survey of graphite inclusion compounds is given in Table 1 as mentioned in this paper, where the authors define the concentration stage as the ratio of the number of carbon layers to that of reactant layers, and show that a compound of Stage 1 is always the most concentrated in a range of intercalation compounds of the same reactant.
Abstract: Graphite reacts with a large number of substances to give lamellar compounds in which the reactant is present in the form of monolayers separated by one or more carbon layers. The compositions of some of the compounds can differ in the repeat frequency of the reactant layer, and occasionally also in the arrangement of atoms within the reactant layer. The “concentration stage” of a compound is defined as the ratio of the number of carbon layers to that of reactant layers. Thus a compound of Stage 1 is always the most concentrated one in a range of intercalation compounds of the same reactant. A survey of some graphite inclusion compounds is given in Table 1.
TL;DR: In this paper, it was shown that chromium trioxide and graphite do not react directly to form an analogous intercalation product, yielding instead a mixture of lower oxides of chromium and unreacted graphite.
TL;DR: The effect of temperature and nitrogen partial pressure on the character of the deposited material was studied in more detail in this article, where felt-like fibers, whiskers, and thin plates of silicon nitride were also produced.
TL;DR: The role played by the additives to the melt, both in terms of their abilities to increase the density of nodules in castings and the more fundamental question of how they influence the mechanism of graphite nucleation was explored in this paper.
Abstract: This paper describes the results of an extensive microstructural study designed to explore the basic processes controlling the nucleation of graphite nodules in chill cast iron. The experimental melts were nodularized with magnesium ferrosilicon and then inoculated, either with foundry grade ferrosilicon or Superseed (a ferrosilicon which contains a small quantity of strontium). The work elucidates the role played by the additives to the melt, both in terms of their abilities to increase the density of nodules in castings and the more fundamental question of how they influence the mechanism of graphite nucleation. In addition, the phenomenon of inoculant fade is investigated and an explanation is presented for this behaviour. The results clearly demonstrate that graphite nodules are nucleated heterogeneously on particles formed in the melt from elements introduced via the additives, together with trace elements present in the molten iron. Electron microscopy and X-ray microanalysis techniques wer...
TL;DR: Graphite fibers with a high degree of crystallinity have been prepared by heat treatment of carbon fibers at temperatures above 2800°C as mentioned in this paper, and they have lengths ranging up to 25 cm, and diameters from 10 to several hundred microns.
Abstract: Graphite fibers with a high degree of crystallinity have been prepared by heat treatment of carbon fibers at temperatures above 2800°C. The original carbon fibers were produced through a deposition technique by cracking vaporized benzene in carrier gas of hydrogen at about 1100°C. They have lengths ranging up to 25 cm, and diameters from 10 to several hundred microns. The graphite fibers consist of concentric tubes of graphite layers having a three-dimensional crystallinity, and the c-axes of the crystallite are nearly perpendiclar to the fiber axis. The electrical resistivity is 60–100 µΩcm along the fiber axis at room temperature, the temperature dependence being similar to that of the graphite whiskers in the range from room temperature down to liquid helium temperature. They also show a high degree of strength and flexibility. A fiber with a diameter of about 10 µm exhibits tensile strength of 50 t/cm2 and Young's modulus of 2000–3000 t/cm2.
TL;DR: In this paper, the Bohr-Sommerfeld quantization condition is applied to calculate the Landau levels in graphite in the presence of trigonal warping, which results in unequally spaced leg and central electron and hole levels which can be supported between two cut-off energies.
Abstract: The Bohr-Sommerfeld quantization condition is applied to calculate the Landau levels in graphite in the presence of trigonal warping. The off-axis extrema arising from the trigonal warping result in unequally spaced leg and central electron and hole Landau levels which can be supported between two cut-off energies. Application to the de Haas-van Alphen effect and to interband Landau level transitions is discussed.
TL;DR: In this article, a continuous liquid metal infiltration process has been developed for making aluminum-graphite composite wire from commercially available multifiber graphite yarns, and composite specimens have been successfully fabricated by hot pressing the composite wire.
Abstract: A continuous liquid metal infiltration process has recently been developed for making aluminum-graphite composite wire from commercially available multifiber graphite yarns. Composite specimens have been successfully fabricated by hot pressing the composite wire. The longitudinal properties of both the composite wire and hot pressed specimens approximated rule of mixtures behavior, but the transverse tensile and compressive strengths of the specimens were lower than expected. Examination of the microstructure indicates that better transverse and compressive strengths may be achieved through refinement of the matrix grain size, elimination of continuous networks of intermetallic compounds in the matrix, and homogenization of the matrix alloy constituents.
TL;DR: In this paper, small (18-32 atoms) periodic clusters of two-dimensional hexagonal graphite and boron nitride are shown to represent high-symmetry points in the Brillouin zone of the infinite crystal.
Abstract: Small (18-32 atoms) periodic clusters of two-dimensional hexagonal graphite and boron nitride are shown to represent some high-symmetry points in the Brillouin zone of the infinite crystal Semi-empirical all-valence electron calculations are performed on these clusters and the binding energy, work function, bandwidth, band-to-band transition energy, band gap, charges and equilibrium distances are computed and compared with values obtained by tight binding and truncated crystal calculations Favourable agreement with experimental data is obtained with selfconsistent calculations on these clusters
Patent•
19 Jun 1974
TL;DR: An elongated continuous porous sheet of fibrous carbon, such as paper of matted graphite fibers, woven graphite cloth or carbonized filter paper is longitudinally traversed through a reduced pressure heating zone (5 mm. of Hg) in which hydrocarbon gas is perpendicularly directed at relatively high velocities through restricted flow passages at the sheet, which is heated to a temperature of about 2200°C as discussed by the authors.
Abstract: An elongated continuous porous sheet of fibrous carbon, such as paper of matted graphite fibers, woven graphite cloth or carbonized filter paper is longitudinally traversed through a reduced pressure heating zone (5 mm. of Hg.) in which hydrocarbon gas is perpendicularly directed at relatively high velocities through restricted flow passages at the sheet, which is heated to a temperature of about 2200°C. The sheets are traversed at a speed of about 60 to 3600 feet per hour at a temperature of about 2000° to 2400°C at a pressure of from about 4 to 20 mm. Hg. A hydrocarbon gas, at a flow rate of from about 5 to 20 c.f.m. effectively infiltrates the carbon sheet material and increases the sheet density by at least 20 grams per square meter. The velocity of the carbon depositing flow stream is maintained at from about 20 to 200 ft. per minute (STP).
TL;DR: In this article, atomic absorption spectrometric methods are described for the determination of cadmium, lead, silver, thallium and zinc in some international and other silicate rocks.
TL;DR: Aluminum trichloride can be intercalated in the lattice of graphite as mentioned in this paper, which is a milder catalyst than AlCl3 for the alkylation reactions and gives less polysubstituted reaction products.
Abstract: Aluminum trichloride can be intercalated in the lattice of graphite. This intercalate is a milder catalyst than AlCl3 for the alkylation reactions and gives less polysubstituted reaction products.
Patent•
16 Apr 1974TL;DR: In this paper, a graphite fiber reinforced metal matrix composite is presented, which consists of small additions of a metal selected from the group consisting of titanium, chromium, nickel, zirconium, hafnium and silicon in order to promote wetting and bonding between graphite fibers and the matrix metal.
Abstract: A graphite fiber reinforced metal matrix composite prepared by hot-pressing, comprising layers of a matrix metal selected from the group consisting of magnesium and magnesium based alloys; in combination with alternate layers of a graphite fiber. The improvement consists of small additions of a metal selected from the group consisting of titanium, chromium, nickel, zirconium, hafnium and silicon in order to promote wetting and bonding between the graphite fibers and the matrix metal.
TL;DR: In this paper, the nitrogen 1 s binding energy of nitric oxide adsorbed on nickel oxide, cobalt oxide and graphite was measured at several temperatures by X-ray photoelectron spectroscopy.