An investigation was carried out on oxidation behaviour of Kevlar- and Kynol-based carbon fibres in a carbon dioxide atmosphere.A relationship was established between the void structure and either the precursor or the conditions of oxidation.Significant oxidation took place from 650°C for Kevlar and from 750°C for Kynol.The oxidation mechanism differed depending on the precursor and, in the case of Kevlar, on the oxidation conditions. Void structure, as characterized by a purpose-made procedure based on x-ray small angle scattering, also differed accordingly.Kynol-based products contained one type of voids i.e. small voids.Kevlar-based products contained other types of voids i.e.larger or longer voids, in addition to the same type of voids as found in the Kynol-based products.When Kevlar was brought to a lower oxidizing temperature, e.g.700°C, through a slower heating rate, e.g.0.5°C/min, the preferential type of voids to develop was oblong voids extending along the fibre axis.In other cases, it was the type of void commonly seen in Kynol-and Kevlarbased products.Depending on the degree of the oxidation, variation was observed in void size distribution within each type of the voids.

View full abstract

Conditions for obtaining the stage 1 Sr-GIC from natural graphite flake, Grafoil andartificial graphite (petroleum coke HTT 2600°C) by a convenient two-bulb technique weredetermined.The stage 1 Sr-GIC was isolated for natural graphite flake and the identityperiod and chemical composition were determined to be 4.95 Å and SrC₆, respectively inaccordance with those reported by Guerard et al.
Temperature favorable to obtain the stage 1 Sr-GIC was found to be in the region between 460°C and 490°C, although reaction period also should be controlled because the stage 1 Sr-GIC was not the final product but an intermediate one toward the carbide.
Grafoil and artificial graphite also gave the stage 1 Sr-GIC, but the isolation was not performed.
The stage 1 Sr-GIC was found to be very stable in the air.Even after 6 days of exposure to the air at 120°C, it was not fully decomposed but a large part remained in the residue.

View full abstract