Ungraphitized carbon

The best value for the effective molecular cross-sectional area, o(Kr), of krypton in the BET monolayer at 77 K has been under discussion for many years. In their original work on krypton adsorption, Beebe et al. (1945) recommended the value 0.195 nm2 for o(Kr) and this empirical value is still used by many investigators. For the adsorption of krypton on graphitized carbon, Ismail (1990, 1992) gives preference to the value molecular area calculated from the liquid density and determined by X-ray scattering. This, of course, implies that Kr and N2 molecules undergo localized adsorption on the same sites. For ungraphitized carbons, Ismail (1992) recommends cr(Kr) = 0.214 nm2. 

An early detailed work in hot phosphoric acid is that of Kinoshita and Bett49,50 who reported corrosion rates for four different carbons in phosphoric acid at temperatures up to 160 °C. All of the carbons tested showed similar behavior as a function of time. At constant potential the corrosion currents were relatively large but declined rapidly with time. These authors concluded that the rate of oxidation was dependent on the surface micro-structure for each specific carbon sample. Graphitized carbons showed lower specific oxidation rates than ungraphitized carbons. 

Steel or copper cathodes with ungraphitized carbon anodes are used. Although fluorine is often handled in metal apparatus, it can be handled in the laboratory in glass apparatus provided traces of HF, which attack glass rapidly, are removed by passing the gas through sodium or potassium fluoride with which HF forms the bifluorides MHF2. 

Turning now to nitrogen adsorption at 77 K, we find that ungraphitized carbons, oxides and other nonporous adsorbents all give typical Type II isotherms 11... 

Graphite, although it may be pure, can have poorly defined physical properties due to a close association with other forms of carbon, such as char, lampblack and soot. Perfectly crystalline graphite has a brilliant silvery surface and planar morphology but it is dark grey in the polycrystalline form. An ungraphitized carbon does not mark paper, whereas graphite will. 

Manocha [26,27] reported that graphitized fiber produced a better densified carbon-carbon than ungraphitized carbon fibers. This was attributed to the weaker bond in the HM fibers shrinking away to give voids, that could subsequently be filled with resin, whereas... 

Recent information can be found in an article by Ismail [165], who has reviewed the use of the BET equation to obtain the cross-sectional area of Ar, Kr, N2, and O2 on graphitized carbons, ungraphitized carbons, activated graphitized carbons, and silicas. For Ar on nonporous graphite, the value 0.138 nm /atom is proposed, being 0.157 nm /atom for adsorption on ungraphitized... 

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