Showing papers on "Graphite published in 1970"
TL;DR: Raman spectra are reported from single crystals of graphite and other graphite materials as mentioned in this paper, and the Raman intensity of this band is inversely proportional to the crystallite size and is caused by a breakdown of the k-selection rule.
Abstract: Raman spectra are reported from single crystals of graphite and other graphite materials. Single crystals of graphite show one single line at 1575 cm−1. For the other materials like stress‐annealed pyrolitic graphite, commercial graphites, activated charcoal, lampblack, and vitreous carbon another line is detected at 1355 cm−1. The Raman intensity of this band is inversely proportional to the crystallite size and is caused by a breakdown of the k‐selection rule. The intensity of this band allows an estimate of the crystallite size in the surface layer of any carbon sample. Two in‐plane force constants are calculated from the frequencies.
9,373 citations
TL;DR: The elastic constants of pyrolytic graphite which has been highly ordered by annealing under compressive stress have been determined by ultrasonic, sonic resonance, and static test methods.
Abstract: The elastic constants of pyrolytic graphite which has been highly ordered by annealing under compressive stress have been determined by ultrasonic, sonic resonance, and static test methods. Ultrasonic tests yielded the elastic constants c11, c12, c33, c44 = 1/s44, and the stress derivative of c33. The moduli 1/s11 and c44 were determined from the free flexural resonant vibrations of bars, and the shear modulus c44 also was determined from the fundamental torsional resonance of the bars and from the resonance of compound torsion oscillators composed of thin graphite disks with steel end pieces. Static tension, compression, and torsion tests on the pyrolytic graphite yielded a complete set of compliances (s11, s12, s13, s33, and s44). The following self‐consistent set of elastic constants (cij in units of 1011 dyn/cm2; sij in 10−11 cm2/dyn) has been deduced from the results: c11 = 106±2, c12 = 18±2, c33 = 3.65±0.10, c13 = 1.5±0.5, c44 = 0.018 to 0.035, 1/s11 = 102±3, 1/s33 = 3.65±0.10, s12 = −0.0016±0.0006,...
819 citations
TL;DR: In this paper, a correlation exists between the Raman spectrum of the fiber surface and the shear strength of the graphite and carbon fibers, which is used for fiber characterization.
Abstract: Raman spectroscopy is used to characterize the fiber surface of graphite and carbon fibers. A correlation exists between the Raman spectrum of the fiber surface and the shear strength of the com po...
433 citations
418 citations
BP1
TL;DR: In this paper, a study was made of adsorption of n -dotriacontane and n -butanol dissolved in n-heptane onto graphitized carbon black and various ground graphites having surface areas ranging from 5 to 700 m 2 g -1.
Abstract: A study was made of adsorption of n -dotriacontane and n -butanol dissolved in n -heptane onto graphitized carbon black and various ground graphites having surface areas ranging from 5 to 700 m 2 g -1 . It was established that the adsorption of n -dotriacontane by the graphites is confined entirely to the basal planes of graphite crystals. This is attributed to a remarkable fit between the hydrogen atoms attached to one side of the zig-zag carbon chain in the normal paraffins and the centres of hexagons formed by the carbon atoms in the basal planes of the substrate. The longer the chain the more contacts it can form with the graphite surface and the more strongly it is adsorbed. More detailed studies of the adsorption of n -paraffins on ground graphites have shown that they form close-packed monolayers of horizontally disposed molecules on the basal planes. There is little further adsorption after the monolayers are complete. The heat of adsorption per molecule increases uniformly with the chain length reaching very high values for the normal paraffins having more than 30 carbon atoms. The formation of the close-packed layers has been used for the measurement of the proportion of basal plane surface in different types of graphites. n -Butyl alcohol also forms closely packed monolayers, but on the polar sites of graphites, which can be used for the estimation of their area. The basal plane and polar sites act independently in adsorption and their relative proportions characterize the adsorptive properties of graphites. Examination of graphite ground in n -heptane, which consists of plates of average area of several square micrometres and average thickness of 5 nm, shows that its surface consists predominantly of basal planes having a high adsorptive capacity for n -paraffins.
269 citations
TL;DR: In this paper, the capacity of electrodes prepared from high pressure stress-annealed pyrolytic graphite has been examined in aqueous solutions using an a.c. impedance bridge.
Abstract: : The non-faradaic capacity of electrodes prepared from high pressure stress-annealed pyrolytic graphite has been examined in aqueous solutions using an a.c. impedance bridge. SUCH MATERIALS HAVE A ROCKING ANGLE (x-ray diffraction) as small as 0.4 degrees and the properties of surfaces oriented parallel to the basal plane approach rather closely those of single crystal graphite. The differential capacity measured on this surface has a near parabolic dependence on electrode potential with no evidence of a hump and a minimum of about 3 microfarads/sq. cm in 0.9 M NaF. This low value is explained on the basis that a substantial fraction of the potential change between the electrode bulk and the solution bulk occurs across a space charge layer within the graphite.
227 citations
TL;DR: In this paper, the oxides of a number of transition metals have been studied as catalysts for the oxidation of graphite by dry oxygen, and the localized action of the catalyst particles gave rise to catalytic channeling and/or the promotion of etch pit formation on the graphite basal plane.
223 citations
TL;DR: The cathodic and anodic properties of the oxygen-peroxide couple have been studied on ordinary pyrolytic graphite, high-pressure annealed graphite and single crystal graphite in alkaline solutions using the rotating disk technique as mentioned in this paper.
205 citations
TL;DR: In this article, the core lines and valence bands of LiF, BeO, BN and graphite have been studied by the ESCA technique and the energy differences between inner levels and the valence band are compared with X-ray transition energies.
Abstract: The core lines and valence bands of LiF, BeO, BN and graphite have been studied by the ESCA technique. The energy differences between inner levels and valence bands are compared with X-ray transition energies. The changes in binding energy for the Bels level when going from metal to oxide and fluoride are compared with X-ray spectroscopic data and with a study of the disintegration constant in electron capture of 7Be in the same compounds.
169 citations
TL;DR: In this paper, the effects of alloying additions on the wetting of two types of carbon, HX30 graphite and vitreous carbon, have been investigated, with a view to developing a system for metal impregnation of carbon fibre assemblies.
Abstract: The effects of alloying additions on the wetting of two types of carbon, HX30 graphite and vitreous carbon, have been investigated, with a view to developing a system for metal impregnation of carbon fibre assemblies. Pure copper is inert and non-wetting but two additions caused the copper to wet: Cr on both substrates and V on the vitreous carbon only. Many of the additions formed a carbide reaction layer at the interface, and in the two wetting systems this was a thin, continuous, coherent layer. The data have been analysed in terms of the chemical and physical properties of the system and it was found that the wetting behaviour of copper alloys on HX30 graphite and vitreous carbon could be explained in terms of the behaviour of the reaction product carbides of the alloying addition when these existed.
TL;DR: In this article, compression-annealed pyrolytic graphite and single-crystal graphite specimens were irradiated with neutrons for total exposures of 3 to 71×1017 neutrons/cm2 (nvt) at 50°C, 3 to 8×1019 nvt at 650°C and 1.2×1020nvt at 1000°C.
Abstract: Compression‐annealed pyrolytic graphite and single‐crystal graphite specimens were irradiated with neutrons for total exposures of 3 to 71×1017 neutrons/cm2 (nvt) at 50°C, 3 to 8×1019 nvt at 650°C and 1.2×1020 nvt at 1000°C. The elastic constants of the materials were determined before and after irradiation by ultrasonic‐, sonic‐resonance‐, and static‐test methods. The only elastic constant that changed significantly with irradiation was the shear modulus c44 although a small change was also seen in c33. The natural crystals after irradiation had shear moduli in the range of 0.16–0.46×1011 dyn/cm2, the modulus after irradiation showing no correlation with irradiation temperature, exposure, or modulus before irradiation. The average values of the shear modulus of the pyrolytic graphite were 0.22−0.40×1011 dyn/cm2 after irradiation at 50°C, 0.030−0.033×1011 dyn/cm2 after irradiation at 650°C, and 0.042×1011 dyn/cm2 after irradiation at 1000°C; the shear modulus c44 of graphite when all dislocations are pinn...
TL;DR: In this article, the rate of oxidation of coconut charcoal, electrode graphite and metallurgical coke granules in CO 2-CO and CO2-CO-He gas mixtures at various pressures was measured within the range of 700°-1400°C.
TL;DR: The role of copper as a catalyst in the oxidation of graphite has been studied by optical microscopy and thermogravimetric analysis as mentioned in this paper, which suggests that the catalytic effect involves the localized reduction of cupric oxide by graphite and subsequent reoxidation of the resulting metal.
TL;DR: In this paper, the structure of carbon deposited on metal substrates has been studied by thermally decomposing methane over iron, cobalt and nickel surfaces, and electron and X-ray diffraction properties of the former afforded evidence for its perfectly crystalline graphite nature.
TL;DR: In this article, the reversible segregation of carbon to the (100) surface of nickel has been observed at temperature through measurements of work function changes and observations of LEED patterns and Auger spectra.
Abstract: The reversible segregation of carbon to the (100) surface of nickel has been observed. The surface was studied at temperature through measurements of work function changes and observations of LEED patterns and Auger spectra. The work function increases with temperature by about 0.63 eV in the temperature range 500°–800°K. This difference is close to that obtained from reported values of the work function for Ni (100) and for carbon. Below about 650°K the diffraction pattern contains rings characteristic of a graphite layer with its basal plane parallel to the substrate. In contrast with previous LEED observations of graphite precipitation at single‐crystal surfaces, the segregation described here is reversible under temperature cycling.
TL;DR: In this paper, the effect of substitution with boron at six concentrations between 6 × 10−6 and 10−2 B C atom ratios has been studied as a function of temperature (550 −650°C), carbon burn-off, O2 pressure and pre-treatment in water at 625°C.
Book•
01 Jan 1970
TL;DR: Reading is a hobby to open the knowledge windows and concomitant with the technology development, many companies serve the e-book or book in soft file.
Abstract: Reading is a hobby to open the knowledge windows. Besides, it can provide the inspiration and spirit to face this life. By this way, concomitant with the technology development, many companies serve the e-book or book in soft file. The system of this book of course will be much easier. No worry to forget bringing the modern aspects of graphite technology book. You can open the device and get the book by on-line.
Patent•
30 Oct 1970TL;DR: In this paper, a covering for a structural component subjected to complicated and nonhomogeneous loads in which high stiffness and light weight are necessary is provided, which is prepared from a graphite fiber composite in which the strength characteristics of the graphite fibre are efficiently utilized through multi-directional orientation of graphite fibers in the inplane shear plies of the covering.
Abstract: A covering for a structural component subjected to complicated and non-homogeneous loads in which high stiffness and light weight are necessary is provided. The covering is prepared from a graphite fiber composite in which the strength characteristics of the graphite fiber are efficiently utilized through multi-directional orientation of graphite fibers in the in-plane shear plies of the covering. The fibers in the inplane shear plies are oriented in at least two angles from a reference axis through the in-plane shear ply, whereby the number of fibers in this ply loaded lenghwise of the filaments is maximized.
TL;DR: In this paper, a number of low-angle parameters have been evaluated for a high-modulus carbon fibre, the most useful is considered to be lp, Porod's ''distance of heterogeneity''.
Abstract: A number of low-angle parameters have been evaluated for a high-modulus carbon fibre, the most useful is considered to be lp, Porod's `distance of heterogeneity'. When I−½ is linearly related to θ2, lp=2a, where a is the correlation length obtained from the (I−½, θ2) plot. The parameter lp and the internal surface area have been evaluated for carbon fibres heat treated in the range 1000-2800°c. There is good correlation between the low-angle parameters and strength, but a marked discontinuity at about 1900°c. This discontinuity is related to a change from highly cross-linked graphite with many small pores and small crystallite size, to graphite with little crosslinking, a lower internal surface, but larger individual pores and crystallites where crystallite perfection is an important factor. High strength in stress-graphitized carbon fibres would appear to be a result of strain-induced crystallization with the removal of lattice defects.
TL;DR: In this paper, the performance of singly bent graphite monochromators of radius of curvature R = 79 cm has been studied and a maximum reflectivity of 0.74 was measured.
TL;DR: The heat capacity of Glassy carbon was measured by adiabatic calorimetry from 5 to 350 K and has no transitions or thermal anomalies as mentioned in this paper, and the measured heat capacity at constant pressure (Cp), the entropy (So − S0o), and the enthalpy function }(Ho − H0o)T{ are 2.055, 1.406, and 0.857 cal K−1 mol−1.
TL;DR: In this article, the authors measured the capillary rise of water on partially immersed graphite plates and calculated the contact angle for cleavage graphite/water system, which was found to be 110.6 dynes/cm.
TL;DR: In this laboratory high performance, highly oriented continuous graphite fibres have been produced from a number of readily available and inexpensive pitch precursors.
Abstract: FIBRE composite technology has advanced rapidly in recent years with the development of several types of strong, stiff fibres, for example, S-glass, boron and graphite. The superior structural efficiency of graphite fibres is due to a combination of high strength and modulus and low specific gravity. The high modulus, and to some extent the high strength, is thought to be a consequence of the high degree of orientation and the small size of the graphite crystallites1,2. To date such graphite fibres have only been obtained from synthetic, oriented, polymeric precursor fibres, of which the two main examples are rayon and polyacrylonitrile (PAN). In this laboratory high performance, highly oriented continuous graphite fibres have been produced from a number of readily available and inexpensive pitch precursors.
TL;DR: In this paper, the construction and operation of a shielded hollow-cathode tube for emission spectrometric trace element analysis of solution is described, and the demountable tube design also permits the tube to be used as a versatile line source in atomic absorption spectrometry.
TL;DR: In this paper, a new theory of the principal thermal expansion coefficients of a graphite crystal was derived using the lattice dynamics obtained by Komatsu, and the theory was compared with new data on the low temperature thermal expansion coefficient of very highly oriented pyrolytic graphite and high temperature X-ray data.
TL;DR: Carbon fibres of Young modulus 410 GN m -2 (60 x 10 6 lbf in -2 ) consist of graphite crystal-lites with their basal planes having a preferred orientation of within 10° to the fibre axis.
Abstract: Carbon fibres of Young modulus 410 GN m -2 (60 x 10 6 lbf in -2 ) consist of graphite crystallites ( L a about 9 nm) with their basal planes having a preferred orientation of within 10° to the fibre axis. They are made by the pyrolysis of polyacrylonitrile textile fibres. Inter-molecular reactions occur between the polymer chains and, by maintaining the chains parallel to the fibre axis by tension in the early stages of pyrolysis, a primitive oriented structure arises which becomes an oriented graphite structure at higher temperatures. Stereochemical factors are important and since the textile fibre contains fibrils of about 15 nm width, with distinct boundaries, the pyrolysis reactions are confined within the fibrils so that the carbon fibre also has a fibrillar structure with the oriented graphite crystallites contained within the fibrils. The mean strength of the carbon fibres 2.0 GN m -2 (300 x 10 3 lbf in -2 ) is limited by defects; e. g. the mean strength increases as the gauge length decreases. Some of these defects are due to inclusions or voids in the parent fibre. By stretching the carbon fibres at 2700°C, crystallite orientation is increased and the Young modulus rises to about 689 GN m -2 (100 x 10 6 lbf in -2 ).
Patent•
19 Jan 1970
TL;DR: A packing material comprising graphite strands of fibrous material, and interstices there between, being thoroughly impregnated with impregnating material comprising a fluorocarbon resin and a solid lubricant, such as graphite as discussed by the authors.
Abstract: A packing material comprising graphite strands of fibrous material, said strands and interstices therebetween, being thoroughly impregnated with impregnating material comprising a fluorocarbon resin and a solid lubricant, such as graphite.
TL;DR: Carbon fibres have been prepared by the controlled thermal decomposition of fibres of vinylidene chloride/vinyl chloride copolymer (Saran), and changes in structure and morphology occurring during carbon formation and subsequent heat treatment to about 2500°C have been followed by X-ray diffraction, and by optical and electron microscopy, and have been related to the chemistry of decomposition as discussed by the authors.