Electrical conductivity through carbon

Controlling the electrical conductivity through carbon black localization in thermoplastic blends. (Drawn using data from F. Gubbels, E. Vanlathem, R. Jerome, R. Deltour, Ph. Teyssie. 2 International Conference on Carbon Black, Mulhouse, France, Sept. 27-30,1993,397.)... 

Carbon materials provide electrical conduction through the pi bonding system that exists between adjacent carbon atoms in the graphite structure [182]. Electrical properties of nanocomposites based on conducting nanofillers such as EG [183-187], CNTs [188-190], and CNFs [191], dispersed in insulating polymer matrix have found widespread applications in industrial sectors. 

Further improvements in anode performance have been achieved through the inclusion of certain metal salts in the electrolyte, and more recently by dkect incorporation into the anode (92,96,97). Good anode performance has been shown to depend on the formation of carbon—fluorine intercalation compounds at the electrode surface (98). These intercalation compounds resist further oxidation by fluorine to form (CF ), have good electrical conductivity, and are wet by the electrolyte. The presence of certain metals enhance the formation of the intercalation compounds. Lithium, aluminum, or nickel fluoride appear to be the best salts for this purpose (92,98). 

Electrical Uses. Dry cells (see Batteries, primary cells) use graphite to render the nonconductive pyrolusite (Mn02) conductive through intimate admixture. The degree of graphitization is a factor in that graphites with the same carbon content and from the same locaUty give different results. 

The specific electrical conductivity of dry coals is very low, specific resistance 10 ° - ohm-cm, although it increases with rank. Coal has semiconducting properties. The conductivity tends to increase exponentially with increasing temperatures (4,6). As coals are heated to above ca 600°C the conductivity rises especially rapidly owing to rearrangements in the carbon stmcture, although thermal decomposition contributes somewhat below this temperature. Moisture increases conductivity of coal samples through the water film. 

NOTE Pure condensate, for all practical purposes, does not conduct electricity (very pure condensate has an electrical conductivity of perhaps 0.1 to 0.05 pS/cm), and any impurities in the steam are reflected in an increase in conductivity. For the highest precision conductivity measurement testing, any volatile materials present such as ammonia (NH3) and carbon dioxide (C02) must be removed. Equipment such as a Larson-Lane Analyzer (which condenses the steam and passes it through an acid-regenerated cation resin) is employed to remove NHy while C02 is removed by reboiling. 

We can understand the differences in properties between the carbon allotropes by comparing their structures. Graphite consists of planar sheets of sp2 hybridized carbon atoms in a hexagonal network (Fig. 14.29). Electrons are free to move from one carbon atom to another through a delocalized Tr-network formed by the overlap of unhybridized p-orbitals on each carbon atom. This network spreads across the entire plane. Because of the electron delocalization, graphite is a black, lustrous, electrically conducting solid indeed, graphite is used as an electrical conductor in industry and as electrodes in electrochemical cells and batteries. Its... 

The reddish metal was already known in prehistoric times. It occasionally occurs as a native metal, but mostly in conspicuous green ores, from which it is extracted relatively easily. It is convenient to work, but not very hard. Not very optimal as a tool ("Otzi the Iceman" had a copper axe with him). Only through the addition of tin is the more useful bronze obtained. Its zinc alloy is the versatile and widely used brass. Copper is one of the coinage metals. Water pipes are commonly made of copper. Its very good thermal and electrical conductivity is commonly exploited (cable ), as well as its durability (roofs, gutters), as the verdigris (basic copper carbonate) protects the metal. Cu phthalocyanines are the most beautiful blue pigments. Seems to be essential to all life as a trace element. In some molluscs, Cu replaces Fe in the heme complex. A 70-kg human contains 72 mg. 

The air gas-diffusion electrode developed in this laboratory [5] is a double-layer tablet (thickness ca.1.5 mm), which separates the electrolyte in the cell from the surrounding air. The electrode comprises two layers a porous, from highly hydrophobic, electrically conductive gas layer (from the side of the air) and a catalytic layer (from the side of the electrolyte). The gas layer consists of a carbon-based hydrophobic material produced from acetylene black and PTFE by a special technology [6], The high porosity of the gas layer ensures effective oxygen supply into the reaction zone of the electrode simultaneously the leakage of the electrolyte through the electrode... 

Most suitable for electrically conducting materials such as carbon fibers, the electrochemical processes involve deposition of polymer coatings on the fiber surface through electrodeposition or electropolymerization techniques. The major advantage of these processes is that a uniform layer of controlled thickness and variable polymer structure and properties can be obtained by controlling the current and the solution concentration. 

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