Facile synthesis of lipophilic alkylated boron nitride nanosheets as lubricating oil additive to greatly enhance the friction and heat-conducting properties

Boron nitride (BN) is considered as a promising additive in lubricating oil due to its high friction performance and thermal conductivity, but its poor lipophilicity greatly limits its application. Herein, a facile and economic alkylamine-assisted ball milling method has been proposed to produce alkylated BN nanosheets (BNNS). Three different types of alkylamine including the octadecylamine, tetradecylamine, and trioctylamine, are developed as modifiers to probe into the structural effect on friction performance. It reveals that the trioctylamine functionalized BNNS (BNNS-TOA) deliver the best dispersion stability in mineral base oil due to their large steric hindrance. As a result, the mineral base oil with using BNNS-TOA as additive yields a lower friction coefficient (0.152) and smaller wear scar width (4 µm). Moreover, the thermal conductivity for the BNNS-TOA/mineral base oil is 8.83 times higher than that of pure mineral base oil, which effectively promotes the dissipation of friction heat and prolongs the service life of machines. This work opens a new route for the preparation of lipophilic BNNS toward lubrication and friction applications. Lipophilic boron nitride nanosheets are synthesized through a facile and economical alkylamine-assisted ball milling strategy and have greatly improved the friction and thermal conductivity properties of mineral base oils. • A facile ball milling method is proposed toproduce the lipophilic BNNS. • Trioctylamine (TOA)-functionalized BNNS presents the best lipophilicity. • The BNNS-TOA/mineral oil hasgreatly improved the friction performance. • The BNNS-TOA/mineral oil delivers an excellent thermal conductivity.