Graphitizing carbons, mechanisms

Graphite has an electron conductivity of about 200 to 700 d cm is relatively cheap, and forms gaseous anodic reaction products. The material is, however, mechanically weak and can only be loaded by low current densities for economical material consumption. Material consumption for graphite anodes initially decreases with increased loading [4, 5] and in soil amounts to about 1 to 1.5 kg A a at current densities of 20 A m (see Fig. 7-1). The consumption of graphite is less in seawater than in fresh water or brackish water because in this case the graphite carbon does not react with oxygen as in Eq. (7-1),... 

Chemical erosion can be suppressed by doping with substitutional elements such as boron. This is demonstrated in Fig. 14 [47] which shows data for undoped pyrolitic graphite and several grades of boron doped graphite. The mechanism responsible for this suppression may include the reduced chemical activity of the boronized material, as demonstrated by the increased oxidation resistance of B doped carbons [48] or the suppressed diffusion caused by the interstitial trapping at boron sites. 

Great promise exists in the use of graphitic carbons in the electrochemical synthesis of hydrogen peroxide [reaction (15.21)] and in the electrochemical reduction of carbon dioxide to various organic products. Considering the diversity in structures and surface forms of carbonaceous materials, it is difficult to formulate generalizations as to the influence of their chemical and electron structure on the kinetics and mechanism of electrochemical reactions occurring at carbon electrodes. 

H. Imamura, S. Tabata, N. Shigetomi, Y. Takesue, Y. Sakata, Composites for hydrogen storage by mechanical grinding of graphite carbon and magnesium, J. Alloys Compd. 330-332 (2002) 579-583. 

Fig. 7. Growth mechanism of graphitic carbon nanofibers. The illustration highlights the observation of spontaneous nickel step edge formation at the carbon-nickel interface. The observations in Reference (52) are consistent with a growth mechanism involving surface transport of carbon and nickel atoms along the graphene-nickel interface.

Graphitized carbon blacks, thus undoubtly display reinforcing abilities which become obvious when considering the tensile strength of the unfilled vulcanizate. It follows that the formation of a filler-elastomer chemical bond is not a requirement for reinforcement to occur. It strongly participates, however, in its effectiveness, and determines the good mechanical properties connected with rubber reinforce-... 

Carbon added to iron may exist in the iron in the combined form (i.e., Fe3C) or as elemental graphitic or flake carbon. Combined carbon increases hardness and mechanical strength in cast iron and steel graphitic carbon decreases both strength and hardness. 

Sn as well as Si was widely studied as an anodic material alternative to carbon for Li-ion batteries due to its much higher theoretical capacity of 991 mAh/g [167] than that of graphitic carbons. However, a pure Sn electrode suffers from poor cycle ability due to mechanical fatigue caused by volume change during Li insertion/deinsertion [168], Similar to the case of Si-based anode... 

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