Synergistic Effects of Nanoparticle Geometric Shape and Post Curing on Nanodiamond-Reinforced Epoxy Nanocomposites: Characterization, Microstructure and Mechanical Properties

Nanodiamond, a significant member of carbon-based nanoparticles, is characterized by a spherical geometric shape and typically classified as a 0-D material due to the extremely small diameter of individual nanoparticles. The unique characteristics of nanodiamonds distinguish them from other carbon-based nanoparticles and have gained considerable interest in the fields of medicine, electronics, sensors, and particularly as nanofillers in polymeric nanocomposites. One of the primary challenges associated with nanoparticle-reinforced nanocomposites is achieving a homogeneous and consistent dispersion of the nanoparticles within the polymer matrix. Compared to other commonly used carbon-based nanoparticles such as cylindrical carbon nanotubes and planar graphene, the enormous differences in shape and dimension may inevitably lead to notable variations in dispersion, which further greatly influences the overall properties of reinforced nanocomposites. This study explores the dispersion characteristics of nanodiamond in epoxy nanocomposites and examines the resulting effects on viscosity, microstructure, and mechanical properties of the epoxy nanocomposites. Systematic comparisons are made between nanodiamond along with carbon nanotube and graphene, while also considering the synergistic effects with post curing of epoxy. Experimental results indicate that the nanodiamond-reinforced epoxy nanocomposite exhibit a more homogenous nanoparticle dispersion, lower viscosity, reduced porosity, and stronger pull-off adhesion, while the graphene-reinforced epoxy nanocomposites achieve a higher lap shear strength. Although post curing is effective in reducing porosity and improving adhesion properties of the nanocomposites, its impact became less pronounced with the addition of nanoparticles.