Novel nanocarbon hybrids of single-walled carbon nanotubes and dispersed nanodiamond: Structure and hierarchical defects evolution irradiated with gamma rays

Abstract

We report the structure and physical properties of novel nanocarbon hybrids of single-walled carbon nanotubes (SWCNT) and ultradispersed diamond (UDD) forming truly tetragonal-trigonal nanocomposite ensemble with and without gamma irradiation. They were subjected to 50, 100, and 103 kGy doses and were characterized using analytical tools including electron microscopy, x-ray diffraction, resonance Raman spectroscopy (RS), and electrical measurements. Experiments showed that irradiation generates microscopic defects (the most likely vacancies) in a hierarchical manner much below amorphization threshold (≥103 kGy) and that nanocomposites tend to be radiation resilient, elucidated through the intensity, bandwidth, and position variation in prominent RS signatures. In the interpretation of findings the possibilities for these complex system are: (1) defect-mediated double-resonance mechanism may not explain intensity variation; (2) softening or violation of the q=0 selection rule; (3) difference in electronegativity of sp2 C (SWCNT) and sp3 C (UDD) can result in charge transfer and bond misalignment at the interface; and (4) the nanotubes are stabilized by nanodiamond particles. Furthermore, an attempt was made to identify the nature of defects (charged versus residual) through in-plane correlation length or sp2 C cluster size (La). The decreasing trend of La for both SWCNT and nanocompo sites with gamma irradiation implies charging defects described in terms of dangling bonds in contrast to passivating residual or neutral defects. Moreover, the electrical properties were relatively more labile to irradiation than structural and vibrational properties.