9. A calculation of the lattice distortion produced by a vacancy in graphite

Preparation and Analyses of Chemically Sorptive Yarns from Rayon and Acrylic Precursors

“…3 The role of flame retardants is the same in fire prevention and carbLn fiber production: to catalyze the char-forming reactions (path a) at the expense of the depolymerization/tarring reactions (path b). The flame retardants promote the dehydration of the cellulose at low temperatures 4 (150o-200°C) and stabilize the molecule. Carbonization promotion is also effected through increased reaction rates, reaction spread over a wider temperature range, and improved carbonization yield.…”

“…Structurally, graphite fibers from rayon exhibit graphite c axes preferentially confined to the plane tranverse to the fiber axis, resulting in anisotropic mechanical properties. 4 The patent literature is extensive in production methods for producing [5][6][7][8][9][10][11] high performance graphite fibers (HPGF) from rayon. However, little information has been published on production of carbon fibers that possess high sorptivity characteristics.…”

“…The initial patent detailed various nitrogeneous salts, which, when utilized with boric acid, acted as carbonization promoters to yield flexible, strong carbon fibers. 4 A later patent, however, revealed more efficient results with four monobasic salts and boric acid, and in particular monosodium phosphate/boric acid combinations. 13 Sorptive yarn was produced continuously utilizing the following chemical impregnation bath: Several key factors were apparent from the Peters patents:…”

“…2.0%). The conclusion drawn was that some type of additional activation was necessary in order to attain the project objectives of 80% sorption by weight of CCI 4 . Carbon dioxide was selected as the activation agent with the highest probability of success.…”

“…1 gpd in Georgia Tech tests(Table 2), which was only 62% of the measured strength of the Enka Supreme Cordenka precursor yarn. The resulting yarn strengths of the carbonized Avtex material Were low, corresponding to the rule that a 60% drop in strength on carbonization of rayon at a maximum temperature of 1000 0 C is normal 4. Higher pyrolysis temperatures would result in regaining a portion of the tenacity by increasing the carbon crystallinity; such an increase in crystallinity, however, would result in a lower density of voids (less available surface area) due to the tighter packing, and would thus be detrimental to high sorptivity.…”