Effect of 2D Boron Nitride Nanoplate Additive on Tribological Properties of Natural Oils

Abstract

Green tribology is a novel area of engineering that focuses on reducing friction, wear and the release of toxins to the environment caused by synthetic lubricants. The present study investigates the possibilities of utilizing natural, biodegradable olive and almond oils as a lubricant in place of synthetic oils. Boron nitride nanoplatelets (BNNP) are used as an additive (with concentrations of 0.1, 0.25 and 0.5 vol%) to olive and almond oils to enhance their tribological performance. BNNP have been selected as an additive because it is composed of a two-dimensional (2D) layered structure with weak van der Waals bonds between layers. Weak interlayer forces in BNNP enable easy shearing along the basal plane to promote lubrication. Wear experiments were also conducted using synthetic motor oil as a lubricant for a comparison with natural oils. As BNNP were added to olive and almond oil, the coefficient of friction (COF) decreased up to 84 %. The synthetic motor lubricant shows higher COF (0.189) in comparison with almond oil with BNNP (COF = 0.100) and olive oil with BNNP (COF = 0.028) at 20 N loads. Furthermore, coefficient of wear (k) of natural oils decreased up to 25 % on adding BNNP. The addition of BNNP resulted in a tribofilm formation, thereby enhancing the lubrication behavior of natural oils. However, a discontinuous layer of polymerized mixture of BNNP in almond oil was observed and this resulted in increased COF compared to olive oil with BNNP.