A custom designed nanocomposite was characterized in terms of particle dispersion and mechanical properties. The nanocomposite consisted of a custom particle, formed by bonding of graphene oxide (GO) with nanodiamond (ND) particles, infused into a polystyrene film. Results from this nanocomposite are compared to neat polystyrene films and to GO-only nanocomposites. Three main testing techniques were implemented to determine the characteristics of the custom nanocomposite – dynamic light scattering to measure particle dispersion, Vicker’s hardness testing to measure microscale mechanical properties, and atomic force microscopy to measure nanoscale mechanical properties.Dynamic light scattering was used to determine the particle dispersion ability of the GO and GO-ND particles. Using this technique, it was found that particle size ranged from 700 to 1200 nm for GO, while the GO-ND displayed a statistically significant reduction in particle size of 100 to 1000 nm. When the nanodiamonds are bonded to the graphene oxide, a unique morphology is formed, which, due to the shape, reduces particle affinity and, thereby, reduces agglomeration.&nbsp; As such, this unique particle addresses one of the primary difficulties of nanocomposite formation – the efficient dispersion of the particles.After dynamic light scattering testing, the two particle types – the GO particle and the custom GO-ND particles – were separately infused into a polystyrene / tetrahydrofuran (THF) solution at 0.1 weight percent. These solutions were then drop cast onto smooth metal plates. Separate samples of neat polystyrene were also drop cast as a control group. The solvent was then fully evaporated, resulting in solid films.These nanocomposites, along with the neat polymer control sample, were then tested for Vicker’s hardness to examine the microscale properties. Each of the three sample types – neat polymer, GO infused nanocomposite, and GO-ND infused nanocomposite – displayed similar hardness results. This indicates that, at the microscale examined using this hardness technique, the polymer matrix dominates the mechanical behavior and the nanoparticles have a negligible effect. It could be hypothesized that a micoscale effect may emerge at different weight percentage levels of nanoparticle infusion. &nbsp;&nbsp;&nbsp;Despite the similarity of properties seen on the microscale, differences did emerge when samples were tested on the nanoscale using atomic force microscopy. Resulting data suggested that the neat polystyrene had, on average, the highest mechanical stiffness, followed by the GO infused nanocomposite, and the GO-ND infused nanocomposite.&nbsp; This indicates that, while nanocomposite films can display increases in strength and hardness at the macroscale, the particles may be forming local, defects detectable when examined on the nanoscale. These defects may have effects, not only on the nanoscale, but also on the macroscale via crack initiation sites, and reductions in strength.&nbsp; In fact, these defects may explain the negligible effect of nanoparticle infusion on the microscale Vicker’s properties.&nbsp; While the nanoparticles provide some enhancement of strength, hardness, and stiffness, this effect is counteracted and masked by the introduction of local, nanoscale defects. &nbsp;

Graphene Oxide / Nanodiamond Nanocomposites Characterized via Particle Dispersion and Micro- and Nanoscale Mechanical Properties

Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2021/volume/85543

ASME 2021 International Mechanical Engineering Congress and Exposition (IMECE2021)

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