Amorphous carbon materials pyrolytic carbons

See amorphous carbon, carbon fibers, carbon material, glass-like carbon, graphitic carbon, non-graphitic carbon, pyrolytic carbon... 

Pyrolytic Carbon. Polished LTI carbon is composed of a crystalline graphitic-like microstructure, combined with amorphous material ( ). The polished samples have been shown to be oxidized with a C 0 ratio of about 10 1, containing three major types of carbon-oxygen functionalities quinone-like, ether-... 

Elemental carbon is usually handled in three forms graphite, diamond, and amorphous carbon. Graphite and amorphous carbon have been extensively used in electrochemistry because of their high electrical conductivity, chemical stability, versatility, and low cost. For electrochemical applications, such materials can be manufactured in bars, powders, and fibers or can even form conducting composites when appropriate binders are used. A number of carbon-based materials, such as pyrolytic carbon, carbon blacks, activated carbons, graphite fibers, whiskers, glassy carbon, etc., have been used in electrochemistry for decades (Yoshimura and Chang, 1998). 

The uniqueness and versatility of carbonaceous porous materials is demonstrated by Mukai et al. (2004) in their attempt to reduce the phenomenon of irreversibility of the LIB. As indicated above, irreversibility is associated with the formation of solid electrolyte films on surfaces of carbons by an irreversible reaction of lithium ions with the electrolytes. For the isotropic porous carbons (not amorphous carbons as quoted by Mukai et al., 2004), the electrolyte film is formed preferentially in the entrances to the porosity (mainly microporosity). Should it be possible to prevent this deposition, then the irreversible component of battery performance could be reduced. It is established that increasing the heat treatment of carbons (normally beyond about 800 °C) decreases the pore dimensions, but at the same time there is reduction in volume of porosity which is available for lithium entry. Quite separately, Suzuki et al. (2003) report on the impossibility of bringing about a meaningful reduction in the irreversible component, maintaining the reversible component, by changing the porosity of the material. That is, an improvement automatically creates a deterioration. The use of an approach of carbon vapor deposition (as for pyrolytic carbons) has been tried whereby carbon is deposited in the entrances to the microporosity. There is no overall change to carbon structure. This method was successful but applications on an industrial scale are expensive. 

The organic/inorganic transition occurs within both the second and third temperature domains [28] [47] with a fresh but minor weight loss and a density increase. The gaseous species which are formed are mainly CH4 and H2 from scission of the relatively weak SI-CH3 and Si-H lateral bonds in domain 2, and mainly H2 from scission of the stronger C-H bonds from the Si-CH2-SI backbone in domain 3. At the end of domain 2, i.e., at 800-900°C, the pyrolytic residue is an amorphous Si-C (or Si-C-0) material with a composition close to SiCi eHoe [6]. It is still hydrogenated and contains an excess of carbon with respect to the stoichiometric PSP having a C/Si at. = 1. It also displays numerous structural defects and its density (2.21 g/cm ) is still low. A tentative structural model has been proposed [6]. 

---