| A series of partially graphitized Precambrian geological carbon samples was studied with transmission electron microscopy. These samples have been graphitized at low temperatures (less than 350;The interlayer spacing between graphite-like layers was visible in TEM images of all samples. The degree of order, with respect to the number and spacing of parallel layers, was determined using autocorrelation functions from small (17 x 17 A) regions of the digitized images. The effects of focus, particle orientation, contrast and sharpness of the digitized images were studied. The degree of order for each sample is not perfectly correlated either to age or maximum processing temperature. The contributions to the width of the d;The imaged grains were also examined with electron energy-loss (EELS) and energy-dispersive X-ray (EDS) spectroscopy. EELS detection limits for impurities in carbon matrices were found to be very close to theoretical values for a carbon matrix.;The structure-dependent electron-energy-loss signal was also studied. Thickness- and resolution-dependent parameters in the low-loss region and the carbon K-region were analyzed for all kerogens and for partially graphitized acenapthalene samples. The near-edge features are seen to be dependent on order within the layer planes. In contrast to the pattern of graphitization that has been accepted for laboratory graphitization, it is observed (from EELS) that a significant degree of order within the plane is attained in some samples that have very few parallel planes (TEM observation).;The intensities of the Raman disorder peaks are large. For one kerogen that has reasonably well-developed order according to the TEM images, but has a lower degree of order within the plane, the width of the Raman disorder peak is the narrowest that has been recorded for any carbon sample. This contradicts the conventional theory that the width of the peak is dependent on disorder within the plane. |
