The compositional and microstructural transformations induced by heavy ions (GeV/amu Fe and Si ions) on nanocomposite carbon (n-C) films were investigated by Raman Spectroscopy (RS), Atomic Force Microscopy (AFM), and X-ray Photoelectron Spectrscopy (XPS). Two identical sets of n-C films were prepared in a sulfur-assisted hot filament chemical vapor deposition (HFCVD) system using methane, hydrogen and hydrogen sulfide. Films with various sp3 C and sp2 C bonding distributions were present within each set, which were obtained by varying the substrate temperature (400-600 °C). One set of films was submitted to a 20 krad dose of energetic Si and Fe ions at the NASA space radiation simulation facility hosted in Brookhaven National Laboratory's Alternating Gradient Synchrotron (AGS). All the films showed the characteristic diamond (tetragonal sp3 C) band at around 1332 cm-1 and the graphitic (trigonal sp2 C) D and G bands at around 1350 and 1590 cm-1, respectively, evidencing their composite nature. The results indicate that sp2 C ←sp3 C interconversions take place in the nanocomposite carbon material during heavy ion irradiation. A mechanism is proposed to explain this behavior. The overall results imply that there could be a range of sp3/sp2 C ratios for which carbon bonding interconversion takes place under ion radiation without significant changes to the average composition of the material. Nanocomposite carbon materials with this characteristic would be radiation insensitive. A technique could be developed based on this carbon bonding interconversion property by using focused energetic beams onto carbon films to produce a robust information storage technology that would survive catastrophic events.