COMPARATIVE NMR STUDY OF NEW CARBON FORMS

摘要

A comparative C-13-NMR study of several new phases of pressure/temperature-treated C-60, a bundle of carbon nanotubes, graphite and diamond was carried out in the 4-300 K temperature range. It was found that face-centered cubic and rhombohedral high-pressure phases of C-60 reveal very unusual NMR lines at 110 and 70 ppm, respectively, shifted from that of pristine C-60 (143 ppm). These lines disappear in a hard carbon phase prepared by compression of C-60 at more severe conditions. Comparison with NMR spectra of pristine C-60, diamond and graphite showed that the fullerenes acquire some partial sp(3) character when they are pressure-treated at 3-4.6 GPa and various temperatures (720 degrees C). However they are apparently not transformed into four-fold-coordinated diamond-like carbon clusters. NMR spectra of carbon nanotubes exhibited an anomalous shift which may be attributed to their cylindrical geometry. Copyright (C) 1996 Elsevier Science Ltd [References: 21]