The structure and physical properties of novel nanocarbon hybrids of single-walled carbon nanotubes and ultra-dispersed diamonds forming a tetragonal-trigonal nanocomposite ensemble, with and without gamma irradiation, were reported. They were subjected to 50, 100 and 103kGy doses and were characterized using analytical tools including electron microscopy, X-ray diffraction, resonance Raman spectroscopy and electrical measurements. Experiments showed that irradiation generated microscopic defects (probably vacancies) in a hierarchical manner much below the amorphization threshold (103kGy) and that nanocomposites tended to be radiation-resilient, elucidated through the intensity, band-width and position variation in prominent Raman spectroscopy signatures. In interpreting the results, it was noted that a defect-mediated double-resonance mechanism might not explain the intensity variation, that there was a softening or violation of the q = 0 selection rule, that differences in electronegativity of sp2 C (single-walled carbon nanotubes) and sp3 C (ultra-dispersed diamond) could result in charge transfer and bond misalignment at the interface and that the nanotubes were stabilized by nanodiamond particles. An attempt was made to identify the nature of the defects (charged versus residual) via the in-plane correlation length or sp2 C cluster size. A decreasing trend in the latter for both single-walled carbon nanotubes and nanocomposites, with gamma irradiation, implied charging defects: described in terms of dangling bonds in contrast to passivating residual or neutral defects. The electrical properties were relatively more labile to irradiation than were structural and vibrational properties.

Novel Nanocarbon Hybrids of Single-Walled Carbon Nanotubes and Dispersed Nanodiamond: Structure and Hierarchical Defects Evolution Irradiated with Gamma Rays. S.Gupta, A.M.Scuttler, J.Farmer: Journal of Applied Physics, 2010, 107[10], 104308