Degradation of carbon materials by intercalation

Degradation of carbon materials after various intercalation reactions was investigated by means of microscope observation of the products and a new aspect to characterize carbon materials was revealed. The degradation of cokes occurred due to the stress to the coke particles accompanied by enlargement of interlayer spacing between carbon layers with intercalation and it depended on the size of intercalates acid the stage number of the resultant compounds. For intercalation of alkali metals in ether solutions, the degradation of cokes occurred by the co-intercalation of ether molecules with alkali metal ions. Natural graphite and pyrolytic carbons, on the other hand, were not degraded because of their high degree of planar orientation of crystallites which could relax the stress because of their easy expansion perpendicular to the flake and plate surface. From the comparison between the present observations of degradation and the X-ray diffraction measurements of intercalation compounds, the resistance in the host carbon against the degradation by intercalation and the expansion force to enlarge interlayer spacing in the host by intercalation were closely related to each other, and this resistance was revealed as one of the important factors to govern intercalation. (C) 1999 Elsevier Science Ltd. All rights reserved.