Industrial Carbon and Graphite Materials. Группа авторов. Читать онлайн. Newlib. NEWLIB.NET

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      The term ARTIFICIAL GRAPHITE is often used as a synonym for SYNTHETIC GRAPHITE. The term SYNTHETIC GRAPHITE is preferred, however, since graphite crystals can be considered to consist of carbon macromolecules.

      Although the term SYNTHETIC GRAPHITE also covers the CVD product PYROLYTIC GRAPHITE as well as the residues of carbide decomposition, it is predominantly used for GRAPHITIZED CARBON. Such common use is in line with the above definition. Synonyms for this most important type of SYNTHETIC GRAPHITE are ACHESON GRAPHITE and ELECTROGRAPHITE.

      See: ACHESON GRAPHITE, ARTIFICIAL GRAPHITE, ELECTROGRAPHITE, GRAPHITIZED CARBON, PYROLYTIC GRAPHITE.

      Thermal Black

      Description

      THERMAL BLACK is a special type of CARBON BLACK produced by pyrolysis of gaseous hydrocarbons in a preheated chamber in the absence of air. THERMAL BLACK consists of relatively large individual spheres (100–500 nm diameter) and aggregates of a small number of pseudospherical particles. The preferred alignment of the layer planes is parallel to the surface of the spheres.

      See: CARBON BLACK.

      1 1 Recommended terminology for the description of carbon as a solid (IUPAC recommendations 1995) (1995). Pure Appl. Chem. 67 (3): 473–506.

      2 2 Fitzer, E., Köchling, K.‐H., Boehm, H.P., and Marsh, H. (1998). Terminology for the description of Carbon as a Solid. Köln: Deutsche Keramische Gesellschaft e.V. (DKG). ISBN: 3‐925543‐15‐5.

      3 3 These recommendations, “Nomenclature for the C60‐Ih and C70‐D5h(6) Fullerenes” (IUPAC recommendations 2002) (2002). Pure Appl. Chem. 74 (4): 629–695.

      4 4 Anderson, P.W. (1958). Phys. Rev. 109: 1492.

      5 5 Baker, R.T.K. and Harris, P.S. (1978). Chemistry and Physics of Carbon, vol. 14 (eds. P.L. Walker Jr. and P.A. Thrower), 83–165. New York, NY: Marcel Dekker.

      6 6 IUPAC Manual of Symbols and Terminology, Appendix 2, Pt. 1, Colloid and Surface Chemistry (1972). Pure Appl. Chem. 31: 518.

      Note

      1 † Deceased.

       Otto Vohler1,†, Ferdinand von Sturm1, Erhard Wege1,†, and Wilhelm Frohs2

       1 Sigri GmbH, Werner‐von‐Siemens Straße 18, 86405 Meitingen, Germany

       2 SGL Carbon GmbH, Werner‐von‐Siemensstr. 18, 86405 Meitingen, Germany

      The bonding angle between the carbon atoms is 120°. The overlapping p‐orbitals perpendicular to the C atom planes are filled with delocalized electrons forming the weak π‐bonds with a distance of 0.354 nm between the planes. The bonding energy between the basal planes (graphene layers) is in the range of van der Waals forces only.

      Remarkable is the negative coefficient of thermal expansion (CTE) within the plane. Thus, below 670 K graphite contracts in a direction whereas it expands in c‐direction. Parallel to the basic planes graphite is a metallic conductor, whose electrical resistivity increases with temperature. Perpendicular to the planes graphite behaves like a semiconductor. The thermal conductivity decreases with temperature. At room temperature the in‐plane thermal conductivity is higher than that of copper perpendicular to the planes since graphite is a thermal insulator. The high Young’s modulus of 1060 GPa within the plane should allow a theoretical strength of 100 000 MPa. This unique potential in mechanical properties is partially exploited in carbon fibers, which are used to reinforce different matrices (See Carbon Fibers Chapter 11).

Schematic illustration of the (a) Lattice of the cubic diamond and the hexagonal graphite crystal. (b) sp3 hybridization in the diamond lattice. (c) sp2 hybridization in the graphite lattice.

      Due to the weak forces between the planes, these can easily be shifted against each other. This gives graphite its lubrication properties that are widely used in industrial and private applications (locks). Two modifications of graphite are known. The energetically preferred stacking sequence is ABAB… (hexagonal modification). Formation of the rhombohedral modification ABCABC… can be achieved to a certain degree by strong mechanical impact and shearing during milling. In some cases natural graphite can contain 30% of the rhombohedral modification. The rhombohedral modification can be re‐transferred into the hexagonal modification by annealing. This change in modification has not yet found any industrial application.


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