Electrical resistivity of carbon

Koyama T, Endo M. Electrical resistivity of carbon fiber prepared from benzene. Jpn J Appl Phys 1974 13 1175-1176. 

The electrical resistance of a packed bed of carbon particles is a function of the contact resistance between the particles (major fraction) and the intraparticle resistance. A reasonable compari.son of the electrical resistivities of carbon powders measured by different investigators is often difficult because the resistivity varies with the pressure that is applied to compact the powder particles. The pressure increase leads to a resistivity decrease as a result of the lower contact resistance between carbon particles [139]. 

Kavan, L. Dousek, F.P. Micka, K. Time-dependent electrical resistivity of carbon. J. Phys. Chem. 1990, 94, 5127-5134. 

Hydrogen influences the carbon properties for example, the electrical resistance of carbon black is related to its hydrogen content [112]. Moreover, the presence of hydrogen at the edge sites on carbon blacks inhibits graphitization... 

Ding, T. Wang, L. Wang, P., Changes in Electrical Resistance of Carbon-Black-Filled Silicone Rubber Composite During Compressions. J. Polym. Sci., Part B Polym. Phys. 2007,45,2700-2706. 

Chemisorption of oxygen increases the electrical resistance of carbons. When a thoroughly outgassed powdered carbon was oxidized to about 4% oxygen content on treatment with oxygen in the 500 to 700°C temperature range, the electrical resistance inaeased almost by a hundredfold. ... 

Krause B, Potschke P and Haubler L (2009) Influence on small scale melt mixing conditions on electrical resistivity of carbon nanotube-polyamide composites. Compos Sci Technol 69 1505-1515. 

Electrical Resistivity. Like the thermal properties, the electrical resistivity of carbon fibers, measured along the axis, is similar to that of pyrolytic graphite in the ab direction and approximately an order of magnitude higher than metal conductors such as aluminum or copper, as shown in Table 8.11. 

Table 8.11. Electrical Resistivity of Carbon Fibers and Selected Metals...

Figure 9.7. Room-temperature thermal conductivity and electrical resistivity of carbon fibers and selected metals.l ...

Fischbach and Komaki, "Electrical Resistance of Carbon Fibers", Biannual Conference on Carbon, 1979. 

Electrically calcined anthracite is considered to be a more advanced raw material for semigraphitic blocks compared with gas-calcined anthracite, because it gives a lower electrical resistivity of carbon cathode blocks and a very small (but detected)... 

Table 2.6 The change in electrical resistivity of carbon cathode blocks with time (lab tests during electrolysis) [17, 18])...

IR detection by bolometers and microbolometers depends on the change in electrical resistance of a material as the temperature of the material changes. The electrical resistance of carbon increases exponentially with l/T as its temperature is reduced below 5 K. This allows it to be used as an inexpensive cryogenic thermometer, and any material that can make a thermometer is a candidate for use as a thermal detector. The behavior of carbon resistors at low temperatures and their use as thermometers and bolometers are described by Clement and Quinell (1952), Boyle and Rogers (1959), and Shephard (1964). 

A minimum of 10 to 35 parts carbon black to 100 parts of mbber is required to obtain a resistivity in the order of 10 Q-cm. At that loading the carbon black particles, which have an average radius of 10 nm, form grapelike aggregates that provide continuous paths for the electrical current. Special purpose mbbers containing even more carbon black have resistances as low as 1 Q-cm (129). The electrical resistivity of mbber with carbon black is sensitive to strain history, probably because of temporary dismptions of the continuity of the carbon black aggregates. 

The principles pertaining to carbon blast furnace hearths apply as well to submerged-arc furnace hearths. In some processes, such as in d-c arc furnaces, the electrical conductance of carbon is a most important factor. The long life of carbon linings in these appHcations is attributable to carbon s exceptional resistance to corrosive slags and metals at very high temperatures. 

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

An improved approach from the point of view of thermal efficiency is the electrothermal process in which the mixture of zinc oxide and carbon, in the form of briquettes, are heated in a vertical shaft furnace using the electrical resistance of the briquettes to allow for internal electrical heating. The zinc vapour and CO(g) which are evolved are passed tluough a separate condenser, the carbon monoxide being subsequently oxidized in air. 

Langer et al. [10] measured also electrical resistance of individual MWCNTs at very low temperatures and in the presence of a transverse magnetic field. As for the case of the microbundle, the CNTs were synthesised using the standard carbon arc-discharge technique. Electrical gold contacts have been attached to the CNTs via local electron beam lithography with an STM. The measured individual MWCNT had a diameter of about 20 nm and a total length of the order of 1 im. 

In conclusion, wc have shown the interesting information which one can get from electrical resistivity measurements on SWCNT and MWCNT and the exciting applications which can be derived. MWCNTs behave as an ultimate carbon fibre revealing specific 2D quantum transport features at low temperatures weak localisation and universal conductance fluctuations. SWCNTs behave as pure quantum wires which, if limited in length, reduce to quantum dots. Thus, each type of CNT has its own features which are strongly dependent on the dimensionality of the electronic gas. We have also briefly discussed the very recent experimental results obtained on the thermopower of SWCNT bundles and the effect of intercalation on the electrical resistivity of these systems. 

We did not feel any of these methods would work reliably on a commercial scale at current densities in the range of 300 mA cm"2 or for commercial periods (at least 4000 hr). Rudge s work9,10 with porous carbon anodes was a very elegant solution to the problem (and formed the basis for the Phillips Electrochemical Fluorination process), but the high electrical resistance of the porous carbon limited it to small anodes at high current densities or lower current densities on large anodes. 

As discussed in Chapter 10, a wide variety of additives is used in the polymer industry. Stabilizers, waxes, and processing aids reduce degradation of the polymer during processing and use. Dyes and pigments provide the many hues that we observe in synthetic fabrics and molded articles, such as household containers and toys. Functional additives, such as glass fibers, carbon black, and metakaolins can improve dimensional stability, modulus, conductivity, or electrical resistivity of the polymer. Fillers can reduce the cost of the final part by replacing expensive resins with inexpensive materials such as wood flour and calcium carbonate. The additives chosen will depend on the properties desired. 

Now an equivalent circuit, which takes into account both the ion transport along the TC and the charge transfer through the carbon electrode material to the current collector, may be represented as in Fig. 2, wherein N = a(c)/4r, Cm and Rm are the total NP capacitance and resistance in a unit electrode volume (defined here as a product of a unit electrode area and the tier thickness), Re is the electrical resistance of an electrode in the same unit... 

In carbon monoxide the bond between the atoms depends, as in the N2O molecule, on an asymmetrical electron shift, electrons of the 0 atom moving toward the C atom, and the CO molecule having a dipole character. In this case, too, metal electrons are displaced toward the adsorbed molecule and taken from the electron gas, as shown by the change of the electrical resistance of thin nickel films on carbon monoxide adsorption (18). 

Electrical Conductivity. The electrical conductivity of carbon blacks is inferior to that of graphite, and is dependent on the type of production process, as well as on the specific surface area and structure. Since the limiting factor in electrical conductivity is generally the transition resistance between neighboring particles, compression or concentration of pure or dispersed carbon black, respectively, plays an important role. Special grades of carbon black are used to donate to polymers antistatic or electrically conductive properties. Carbon blacks with a high conductivity and high adsorption capacity for electrolyte solutions are used in dry-cell batteries. 

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