Showing papers on "Graphite published in 1979"
TL;DR: A condensed monolayer of carbon on the surface of C-doped nickel single crystals has been observed at different bulk doping levels in the range of 10−1 to 1 at as discussed by the authors.
470 citations
TL;DR: In this article, the friction and wear behavior of composites (i.e., uniaxially oriented graphite fiber-epoxy, Kevlar and glass fiber-MoS2-polytetrafluoroethylene (PTFE) was investigated as a function of varying fiber orientations with respect to the sliding direction.
284 citations
260 citations
Patent•
02 Jan 1979TL;DR: A bipolar collector-separator for electrochemical cells consists of a molded aggregate of electroconductive graphite and a thermoplastic fluoropolymer combined in a weight ratio of 2.5:1 to 16:1 as discussed by the authors.
Abstract: A bipolar current collector-separator for electrochemical cells consists of a molded aggregate of electro-conductive graphite and a thermoplastic fluoropolymer combined in a weight ratio of 2.5:1 to 16:1. The bulk resistivity of such a molded bipolar current collector-separator is less than 4×10 -3 ohm inches (Ω in.). It has excellent corrosion resistance to a variety of feedstocks such as brine, aqueous HCl, etc. and to various electrolysis products such as caustic, chlorine, hydrogen, etc. In one alternative form the anodic side of a current collector-separator for a water electrolyzer is covered by a thin layer of a passivated metallic foil thus protecting the graphite current collector against attack by oxygen.
171 citations
TL;DR: Two commensurate crystalline phases for first stage C 6 Li in various temperature ranges by use of electron diffraction techniques are reported in this article, and the implication of these observations on the relations between the structure of a graphite intercalation compound and its parent materials is discussed.
132 citations
TL;DR: In this paper, the possible effects of substrate orientation on the occurrence and characteristics of the transition have been investigated on surfaces vicinal to (111) and on the (311) and (110) planes abrupt segregation of a graphitic monolayer was observed.
Abstract: A first order phase transition occurs at Ni (111) surfaces under conditions of controlled chemical potential. For a dilute Ni–C alloy of fixed bulk composition an abrupt change occurs (as temperature is lowered) in the surface carbon coverage from a very low coverage state to a two dimensional crystalline C overlayer. In the present work the possible effects of substrate orientation on the occurrence and characteristics of the transition have been investigated. On surfaces vicinal to (111) and on the (311) and (110) planes abrupt segregation of a graphitic monolayer was observed. The observed coverage–temperature relationship was similar to that for (111) with the monolayer formation occurring at a temperature between 10% and 12% higher than the equilibrium precipitation temperature. Surface reconstruction accompanies the monolayer condensation and precipitation processes. At dilute carbon coverages and high temperatures the vicinal planes have arrays of monoatomic height steps; upon monolayer formation rearrangement of the surface steps occurs to produce facets of (111) and (110) for surfaces along the [110] zone and of (111) and (311) for surfaces along the [011] zone. Qualitatively different behavior was observed with (100) and (210). Monolayer graphite condensation was also observed with both of the surfaces but the high temperature region was characterized by a gradually decreasing carbon coverage for which the Auger line shape was that of nickel carbide. Upon graphite precipitation at the solubility limit all surfaces become unstable with respect to formation of {111} facets.
125 citations
TL;DR: The natural frequencies and mode shapes of a number of Graphite/Epoxy and Graphite-Epoxy-Aluminum plates and shells were determined in this article, and the results were compared with those calculated by a finite element analysis.
Abstract: The natural frequencies and mode shapes of a number of Graphite/ Epoxy and Graphite/Epoxy-Aluminum plates and shells were experimen tally determined. The samples tested include 8 ply Graphite/Epoxy plates, cyclindrical shell sections, and Graphite/Epoxy-Aluminum hybrid plates of various laminates and aspect ratio. Fabrication and test procedures are described. Natural frequency and mode shape results are compared with those calculated by a finite element analysis. Agreement between calcu lated and observed mode shapes is excellent; while reasonable agreement is found for frequencies. Among the sources of this discrepancy in frequency results is the possibility of a difference between dynamic-flexural moduli and static in-plane moduli.
124 citations
TL;DR: In this paper, the electronic properties of mesophase pitch-based carbon fibers have been studied in relation to the fiber structure and processing conditions, and it was shown that resistivity, magnetoresistance, and electron spin resonance are a sensitive indicator of the degree of graphite order in the fibers.
121 citations
TL;DR: In this article, the authors describe liquid phase syntheses of stage 1 and stage 2 lithium-graphite intercalation compounds obtained by immersing large pieces of pyrolytic graphite in the appropriate liquid metal at 350°C for 8 h.
121 citations
TL;DR: In this paper, the stage dependence of the IR and Raman-active optic graphitic modes in a graphite acceptor intercalation compound was studied. But the spectral properties of the graphitic layers were not investigated.
112 citations
TL;DR: In this paper, the effects of elastic coherency strains in graphite intercalation compounds are investigated and the long-range interaction energies of two-dimensional islands of intercalant are calculated.
Abstract: We investigate the effects of elastic coherency strains in graphite intercalation compounds. The long-range interaction energies of two-dimensional islands of intercalant are calculated. Using the domain model of Daumas and H\'erold, we show that these strains drive a mixed-stage or randomly staged crystal to pure-stage ordering.
Patent•
10 Oct 1979
TL;DR: In this article, a power transmission-energy absorption device and carbon composite friction facing material for use therein having superior friction characteristics was presented. But the material is particularly suited for use with cooling mediums, such as oil, and performs in an outstanding manner in heavy load, high temperature, hostile environments.
Abstract: A power transmission-energy absorption device and carbon composite friction facing material for use therein having superior friction characteristics. Through appropriate selection of the starting carbon substrate material and through precise control over the amount and character of pyrolytic carbon, or graphite deposited interstitially of the substrate, the friction facing material can be optimized for a wide variety of applications. The material is particularly suited for use with cooling mediums, such as oil, and performs in an outstanding manner in heavy load, high temperature, hostile environments.
TL;DR: Detailed interference studies reveal that the use of the "gas stop" mode minimizes the influence of many ions that are frequently either introduced by the decomposition reagents or present in the sample itself.
TL;DR: In this paper, the authors investigated the ordering of nitrogen-molecule overlayers on graphite and found that the ordering transition occurs at 30 K in both the registered and dense-solid phases despite a 5% difference in the nearest-neighbor distance.
Abstract: Orientational ordering of nitrogen-molecule overlayers on graphite has been investigated by neutron diffraction. The ordering transition is found to occur at 30 K in both the registered and dense-solid phases despite a 5% difference in the nearest-neighbor distance.
TL;DR: Amorphous SixC1−x as discussed by the authors alloys are prepared by simultaneous reactive sputtering of silicon and graphite in a H2•Ar gas mixture, and hydrogen contents are measured for the entire range of x by electron spectroscopy for chemical analysis (ESCA), Rutherford•backscattering method, and thermal evolution of hydrogen.
Abstract: Amorphous SixC1−x : H alloys are prepared by simultaneous rf reactive sputtering of silicon and graphite in a H2‐Ar gas mixture. Silicon, carbon, and hydrogen contents are measured for the entire range of x by electron spectroscopy for chemical analysis (ESCA), Rutherford‐backscattering method, and thermal evolution of hydrogen. Evolution temperature dependence of the number of evolved hydrogen atoms is measured. The hydrogen‐evolution behavior and the optical gap are x dependent. These phenomena are discussed in the light of chemical‐bonding states.
TL;DR: In this article, the thermodynamics of graphite, carbide, and carbonate formation in the presence of a solar-composition gas is examined, including the feasibility of producing solid solutions of carbon and carbides in metallic iron-nickel alloy.
TL;DR: The phase diagram of absorbed films of molecules on (002) surfaces of graphite has been measured in the range of densities from submonolayer to 1.6 monolayer as mentioned in this paper.
Abstract: The phase diagram of absorbed films of ${\mathrm{O}}_{2}$ molecules on (002) surfaces of graphite has been measured in the range of densities from submonolayer to 1.6 monolayer. This system is particularly interesting because it orders magnetically below 11.9 K for dense monolayer and higher coverages. This magnetic order is observed both through the antiferromagnetic-superstructure-Bragg reflection as well as through the accompanying magnetostrictive distortion which is seen as a splitting of the nuclear Bragg scattering peak. In all, three distinct two-dimensionally ordered phases have been found, each being incommensurate with the graphite surface lattice. Both first-order and continuous transitions have been observed between these phases.
TL;DR: In this paper, the binding energies of selectively adsorbed states of two isotopes of helium on the basal plane of graphite were measured using atomic beam scattering and the results were used to determine semi-empirical potential parameters, and the ground state energies were compared with values derived from adsorption studies.
Patent•
24 Sep 1979TL;DR: In this paper, a vermicular expanded graphite composite material and an improved method for preparing such material by blending vermicula expanded graphites with a corrosion resistant resin dispersed in a carrier, vaporizing the carrier, and heating the composite material to sinter the resin.
Abstract: The present invention relates to a vermicular expanded graphite composite material and to an improved method for preparing such material by blending vermicular expanded graphite with a corrosion resistant resin dispersed in a carrier, vaporizing the carrier, and heating the composite material to sinter the resin. Compressed forms of the composite material are useful for protecting corrosion vulnerable substrates.
TL;DR: In this article, the Born-von Karman force constant model was used to calculate phonon dispersion relations of graphite, and eight force parameters were introduced to take anisotropic properties of graphites into account, and determined so as to fit available experimental data.
Abstract: Phonon dispersion relations of graphite are calculated by using the Born-von Karman force constant model. Eight force parameters are introduced to take anisotropic properties of graphite into account, and are determined so as to fit available experimental data including a new finding that A 2u out of plane mode occurs at 868 cm -1 .
01 Jan 1979
01 Mar 1979-Metallurgical and Materials Transactions B-process Metallurgy and Materials Processing Science
TL;DR: In this paper, the rate of reduction of stannic oxide (cassiterite) with carbonaceous materials was investigated in the temperature range 1073 to 1273 K, using thermogravimetic analysis.
Abstract: The rate of reduction of stannic oxide (cassiterite) with carbonaceous materials was investigated in the temperature range 1073 to 1273 K, using thermogravimetic analysis. The effects of the type, the particle size, and the relative amount of carbon were studied. The results indicate that cassiterite is reduced directly to Sn proceeding through the gaseous intermediates of CO and CO2. The overall rate of reduction is controlled by the oxidation of carbon by CO2 · An energy of activation of 220.9 kj/mole (52.8 kcal/mole) was calculated for the reduction of SnO2 with coconut charcoal within the temperature range 1073 to 1173 K and 323.8 kjJ.mole (77.4 kcalJ.mole) with graphite within the temperature range 1198 to 1273 K. A direct comparison was made between the rate of oxidation of coconut charcoal in CO2- CO mixtures and the rate of reduction of SnO2 with coconut charcoal, which are not in agreement. The reason for this disagreement was found to be the catalytic action of the tin formed during the reduction.
TL;DR: In this paper, the authors used autoradiographic analysis and gas chromatography to measure the solubility in silicate melts of CO-CO2 vapors in equilibrium with graphite at temperatures up to 1700 deg C and pressures to 30 kbar.
TL;DR: In this paper, the kinetics of the gasification of graphite by water vapor have been found to be strongly influenced by the presence of salts of the Group IIA alkaline earth metals.
TL;DR: In this article, an experimental investigation of the coating of graphite with TiB 2 by chemical vapor deposition using the H 2 reduction of BCl 3 and TiCl 4 at 925 °C and 1 atm.
Abstract: In this paper we describe an experimental investigation of the coating of graphite with TiB 2 by chemical vapor deposition using the H 2 reduction of BCl 3 and TiCl 4 at 925 °C and 1 atm. Reasonable matching of the thermal expansion of TiB 2 and graphite was necessary to eliminate cracking. A suitable graphite was POCO DFP-1. Adhesion was improved by using a slightly rough graphite surface. Heat treatment at 2000 °C and above resulted in a certain degree of diffusion. No melting or solid phases other than TiB 2 and graphite were detected up to 2400 °C. The coatings showed no failure when repeatedly submitted to an electron beam pulse of 2 kW cm −2 for 0.8 s.
TL;DR: In this article, it was shown that at low coverage of these metals on amorphous carbon, the spectra show that the valence d -bands have decreased widths and larger binding energies than the bulk metals.
TL;DR: In this article, the authors measured stresses in graphite/epoxy composites by diffracting X-rays from crystalline filler particles embedded in unidirectional laminates before curing.
Abstract: The purpose of this work was to measure stresses in graphite/epoxy composites by diffracting X-rays from crystalline filler particles embedded in unidirectional laminates before curing. Particles used were Ag, Nb and CdO, having sharp diffraction peaks at large diffraction angles, θ. The diffraction peaks shift linearly with applied stress in the fiber direction and have stress sensitivities of (2.6, 3.9 and 1.9) X 10-4 deg 2θ/MPa for Ag, Nb and CdO respectively. Elastic strains in filler particles measured by X-rays are proportional to the corresponding composite strains in agreement with the model of H. T. Hahn. Residual strains and stresses in filler particles were also obtained.
TL;DR: In this article, it was shown that carbon films can be interpreted as extremely fine-crystalline phases with coherently scattering regions of about 0.8 nm in diameter, and the intensity functions obtained by electron diffraction are not consistent with those of a known carbon phase.