Alkali-Assisted Hydrothermal Exfoliation and Surfactant-Driven Functionalization of <i>h</i>-BN Nanosheets for Lubrication Enhancement
Sangita Kumari, Ajay Chouhan, Om P. Sharma, Sherif Abdulkader Tawfik, Michelle J. S. Spencer, Suresh K. Bhargava, Sumeet Walia, Anjan Ray, Om P. Khatri
Abstract
Intrinsic low shear strength, excellent mechanical properties, and high thermal conductivity of two-dimensional h-BN nanomaterials make them promising alternatives to conventional metal-/phosphorus-/sulfur-based additives for the development of eco-friendly lubricant formulation. However, the poor dispersibility of h-BN nanomaterials in lubricating oils is a major challenge. Herein, a facile approach of strong alkali-assisted hydrothermal exfoliation and defect-sensitive etching of h-BN powder is demonstrated. The cetyltrimethylammonium bromide (CTAB) is grafted on the active and polar sites of h-BN nanosheets (h-BNNSs). DFT calculations, along with FTIR and XPS results, confirmed the synthesis of h-BNNS-CTAB, which showed good dispersibility in SN-150 mineral lube base oil. The uninterrupted supply of highly dispersible minute dose of h-BNNS-CTAB (0.003 wt %) to tribo interfaces of steel balls improved the lubrication properties of lube oil by decreasing friction (34%) and wear volume (75%). The enhanced tribo-performance is attributed to low shear strength arising from weakly stacked atomic lamellae in h-BNNS-CTAB and the tribo-induced deposition of h-BN lamellae on the contact interfaces of steel balls. The present work proposes a novel strategy for developing h-BNNS-based high-performance lubricant formulation, which can effectively minimize frictional energy and material losses.