title: Engineered silica nanoparticles as additives in lubricant oils.
abstract: Silica nanoparticles (SiO2NPs) synthesized by the sol-gel approach were engineered for size and surface properties by grafting hydrophobic chains to prevent their aggregation and facilitate their contact with the phase boundary, thus improving their dispersibility in lubricant base oils. The surface modification was performed by covalent binding of long chain alkyl functionalities using lauric acid and decanoyl chloride to the SiO2NP surface. The hybrid SiO2NPs were characterized by scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, simultaneous differential thermal analysis, nuclear magnetic resonance and dynamic light scattering, while their dispersion in two base oils was studied by static multiple light scattering at low (0.01% w/v) and high (0.50%w/v) concentrations. The nature of the functional layer and the functionalization degree seemed to be directly involved in the stability of the suspensions. The potential use of the functional SiO2NPs as lubricant additives in base oils, specially designed for being used in hydraulic circuits, has been outlined by analyzing the tribological properties of the dispersions. The dendritic structure of the external layer played a key role in the tribological characteristics of the material by reducing the friction coefficient and wear. These nanoparticles reduce drastically the waste of energy in friction processes and are more environmentally friendly than other additives.
authors.affiliation: Department of Physical and Analytical Chemistry, Faculty of Chemistry, University of Oviedo, Av. Julián Clavería, 8, 33006-Oviedo, Spain.
authors.forename: Teresa Díaz-Faes
authors.initials: TD
authors.lastname: López
authors.affiliation: Department of Physical and Analytical Chemistry, Faculty of Chemistry, University of Oviedo, Av. Julián Clavería, 8, 33006-Oviedo, Spain.
authors.forename: Alfonso Fernández
authors.initials: AF
authors.lastname: González
authors.affiliation: Department of Construction and Manufacturing Engineering, University of Oviedo, Gijón, Spain.
authors.forename: Ángel
authors.initials: Á
authors.lastname: Del Reguero
authors.affiliation: Department of Chemical and Environmental Engineering, Faculty of Chemistry, University of Oviedo, Av. Julián Clavería, 8, 33006-Oviedo, Spain.
authors.forename: María
authors.initials: M
authors.lastname: Matos
authors.affiliation: Department of Physical and Analytical Chemistry, Faculty of Chemistry, University of Oviedo, Av. Julián Clavería, 8, 33006-Oviedo, Spain.
authors.forename: Marta E
authors.initials: ME
authors.lastname: Díaz-García
authors.affiliation: Department of Physical and Analytical Chemistry, Faculty of Chemistry, University of Oviedo, Av. Julián Clavería, 8, 33006-Oviedo, Spain.
authors.forename: Rosana
authors.initials: R
authors.lastname: Badía-Laíño
keywords: base oil; dispersion stability; engineered hybrid SiO2 nanoparticles; surface functionalization; tribological properties