Graphite electrical resistivity

Typical thermal conductivity values (all in W/mK) are 0.2 to 0.3 for pol5Tners, 1 to 2 for carbon black, 10 to 20 for polyacrylonitrile (PAN) based carbon fiber, 100 to 800 (depends on the heat treatment temperature) for petrolaim pitch-based carbon fiber, 400 for copper, and 600 for graphite. Electrical resistivity (1/electrical conductivity) values (all in ohm-cm) for various materials are lO to 10 for polymers, 10" for electrically conductive carbon black, 10 for PAN-based carbon fiber, 10" for pitch based carbon fiber, 10 for graphite, and lO" for metals such as aluminum and copper. One proach to inqjroving the conductivity of a polymer is through the addition of conductive filler, such as carbon and metal [1, 2]. Typically for a bipolar plate, the desired thermal and electricM conductivity are 20 W/mK and 50 S/cm (0.02 ohm-cm). 

Heating and Cooling. Heat must be appHed to form the molten zones, and this heat much be removed from the adjacent sohd material (4,70). In principle, any heat source can be used, including direct flames. However, the most common method is to place electrical resistance heaters around the container. In air, nichrome wine is useflil to ca 1000°C, Kanthal to ca 1300°C, and platinum-rhodium alloys to ca 1700°C. In an inert atmosphere or vacuum, molybdenum, tungsten, and graphite can be used to well over 2000°C. 

Test Method for Electrical Resistivity of Manufactured Carbon and Graphite Articles at Room Temperature Test Method for Compressive Strength of Carbon and Graphite... 

Fig. 5. Electrical resistance as a function of the temperature at the indicated magnetic fields for a single microbundle of carbon nanotubes. The solid line is a fit using the two-band model for graphite (see inset) with an overlap A = 3.7 meV and a Fermi level right in the middle of the overlap (after Langer et at. l9 ).

Graphite anodes when used in soils are invariably placed in a carbonaceous backfill. This helps to compensate for the lower electrical resistivity of graphite when compared with silicon iron. In such an environment, no build-up of a film of high resistance between the anode and backfill occurs, unlike silicon-iron anodes where the resistance can increase with... 

Changes in electrical resistivity (V3) and mechanical properties (V3, V4) of graphite fibers upon nitration have been studied. Increases in elastic modulus, and decreases in tensile strengths, have been related to removal of boundary dislocations by the intercalation process proposed elsewhere iN4). 

The optical gap of a-C H films was found to continuously decrease with increasing self-bias [42]. The gap shrinking was found to be strongly correlated to the variation of Raman spectra that is related to the increase of the graphitic clusters present in the a-C H films. Accordingly, the electrical resistivity of C H films was found to strongly decrease with substrate bias [43]. 

The idea of electronic conductivity in the crystals of this cluster is stimulated by the metallic reflectance of the crystals. A potential conductivity is expected to be anisotropic because of the anisotropic order of the clusters inside the crystal. As a consequence, the electric resistance is expected to be smaller in the direction of the tubes than in the vertical direction where there is no graphite-like bridging between the clusters. 

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