Formation of Molybdenum Blue Nanoparticles in the Organic Reducing Area

Molybdenum blue dispersions were synthesized by reducing an acidic molybdate solution with glucose, hydroquinone and ascorbic acid. The influence of the H/Mo molar ratio on the rate of formation of molybdenum particles was established. For each reducing agent, were determined the rate constant and the order of the particle formation and were established the conditions for the formation of aggregative stable dispersion with the maximum concentration of particles. The dispersed phase is represented by toroidal molybdenum oxide nanoclusters, which was confirmed by the results of UV/Vis, FTIR, XPS spectroscopy and DLS.

Dispersion Stability And Tribological Properties of Covalently Modified Graphene As A Lubricating Oil Additive

Graphene has excellent mechanical properties with a low coefficient of friction and wear resistance and has a wide range of tribological applications. However, the stable dispersion of graphene in lubricating media is challenging. In this study, graphene is processed via covalent modification. A mild oxidation method selectively grafts carboxyl groups on the edge of the graphene sheet, before connecting tertiary alkyl primary amines through amide bonds. The alkyl chain allows graphene to be stably dispersed in hydrocarbon solvents.. FT-IR, XPS, Raman, XRD, SEM, etc. are used to characterize the covalently modified graphene (MG). Dispersion stability experiments showed that MG exhibited stable dispersion in 500N base oil and 15w-40 commercial lubricants, with stability for over 2 months. Tribological test results show that MG in 500N and 15w-40 significantly reduces the friction and wear of steel-steel friction pairs. The stable dispersion of MG in lubricating oil enables the formation of a stable chemical reaction film and graphene physical deposition film during the friction, protects the worn surface, and reduces direct contact, thereby significantly reducing friction and wear.

Green Preparation of Aqueous Graphene Dispersion and Study on Its Dispersion Stability

The large-scale preparation of stable graphene aqueous dispersion has been a challenge in the theoretical research and industrial applications of graphene. This study determined the suitable exfoliation agent for overcoming the van der Waals force between the layers of expanded graphite sheets using the liquid-phase exfoliation method on the basis of surface energy theory to prepare a single layer of graphene. To evenly and stably disperse graphene in pure water, the dispersants were selected based on Hansen solubility parameters, namely, hydrophilicity, heterocyclic structure and easy combinative features. The graphene exfoliation grade and the dispersion stability, number of layers and defect density in the dispersion were analysed under Tyndall phenomenon using volume sedimentation method, zeta potential analysis, scanning electron microscopy, Raman spectroscopy and atomic force microscopy characterization. Subsequently, the long-chain quaternary ammonium salt cationic surfactant octadecyltrimethylammonium chloride (0.3 wt.%) was electrolyzed in pure water to form ammonium ions, which promoted hydrogen bonding in the remaining oxygen-containing groups on the surface of the stripped graphene. Forming the electrostatic steric hindrance effect to achieve the stable dispersion of graphene in water can exfoliate a minimum of eight layers of graphene nanosheets; the average number of layers was less than 14. The 0.1 wt.% (sodium dodecylbenzene sulfonate: melamine = 1:1) mixed system forms π–π interaction and hydrogen bonding with graphene in pure water, which allow the stable dispersion of graphene for 22 days without sedimentation. The findings can be beneficial for the large-scale preparation of waterborne graphene in industrial applications.