Investigation into the precursor states for the graphitization of pyrene

Abstract

Pyrolysis of pyrene has been carried out to examine whether it is possible to produce condensed planar sheets of aromatic rings toform graphite and also to investigate whether the degree of graphitization relatively increases compared with other lower aromatic ring compounds or not. In the initial stages of nucleation and growth, a liquid-state mesophase of optical anisotropy appears as spherules in the sample. As carbonization progresses, the growing mesophase spherules change in shape in forming relatively complex bulk mesophase and mosaic texture. Reflected polarized-light micrography using cross polarizers with a gypsum plate at 45° with one of the polars [Sensitive Tint Technique] has been employed to investigate the microstructure of carbonaceous mesophase displaying maltese cross patterns and nodes as well as mosaic texture. Differential thermal analysis has been employed to locate the temperature region of mesophase formation. Thermogravimetric analysis has been used to see the quantitative analysis of the sample and to calculate the dynamic weight loss of the sample during carbonization. Interlayer spacing calculated from the X-ray diffractograms of the carbonized samples is found to decrease with heat-treatment temperature and duration. A comparative study has been carried out with the interlayer spacings of some lower aromatic compounds under. similar condition. IR spectra have been used to substantiate the above results about the structural modifications of the carbonized samples. The broadening of the peak area of the aromatic band by IR study reveals about the order of the degree of graphitization.