Comparison between thermophysical and tribological properties of two engine lubricant additives: electrochemically exfoliated graphene and molybdenum disulfide nanoplatelets

Surface Modification of Transition Metal Dichalcogenide Nanosheets for Intrinsically Self-Healing Hydrogels with Enhanced Mechanical Properties

Nanocomposites with enhanced mechanical properties and efficient self-healing characteristics can change how the artificially engineered materials' life cycle is perceived. Improved adhesion of nanomaterials with the host matrix can drastically improve the structural properties and confer the material with repeatable bonding/debonding capabilities. In this work, exfoliated 2H-WS₂ nanosheets are modified using an organic thiol to impart hydrogen bonding sites on the otherwise inert nanosheets by surface functionalization. These modified nanosheets are incorporated within the PVA hydrogel matrix and analyzed for their contribution to the composite's intrinsic self-healing and mechanical strength. The resulting hydrogel forms a highly flexible macrostructure with an impressive enhancement in mechanical properties and a very high autonomous healing efficiency of 89.92%. Interesting changes in the surface properties after functionalization show that such modification is highly suitable for water-based polymeric systems. Probing into the healing mechanism using advanced spectroscopic techniques reveals the formation of a stable cyclic structure on the surface of nanosheets, mainly responsible for the improved healing response. This work opens an avenue toward the development of self-healing nanocomposites where chemically inert nanoparticles participate in the healing network rather than just mechanically reinforcing the matrix by slender adhesion.

Carbon Nanoparticles of Varying Shapes as Additives in Mineral Oil Assessment of Comparative Performance Potential

In this work, carbonaceous nanoparticles (NPs) of varying morphology, viz., multilayer graphene (lamellar, thickness ∼ 3-7 nm), graphite (spherical ∼70 nm), and multi-walled carbon nanotubes (tubular), were selected to explore their tribo-potential in oil under identical operating conditions. A series of nano-oils were prepared using API group III mineral base oil with a dispersant (1%) and selected NPs in incremental concentration (0.5-4%). The tribo-performance of oils was evaluated on a four-ball tester and SRV-IV for extreme-pressure, antiwear (AW), and antifriction performance. Formulations were characterized for density, viscosity, and viscosity index. The stability of oils was monitored through visual observation weekly. Results revealed that the graphene particles showed excellent wear-preventive ability as an AW additive with (41-50) % increase followed by nanographite. Worn surfaces were studied to understand the plausible wear mechanism using a different spectroscopic technique. Tribo-behavior performance was supported with lateral force microscopy on the surfaces of tribo-films.