Water-induced entropy reduction and its impact on friction and hardness of alumina borate solid lubricant

SY Kim and NJ Wilson and MR Pederson and E Kim, COMPUTATIONAL MATERIALS SCIENCE, 251, 113779 (2025).

DOI: 10.1016/j.commatsci.2025.113779

This study investigates the intricate interplay of chemical reactions, mechanical dynamics, and material properties in friction simulations, focusing on Alumina borate as a solid lubricant. Contrary to conventional expectations, our findings reveal that specific combinations of temperature and velocity lead to unexpected increases in the coefficient of friction (COF), influenced by the elemental distribution in the lubricant's surface layer. While Alumina borate generally maintains its structure across various conditions, certain thermal and mechanical environments cause deviations that negatively affect COF and hardness. Notably, the introduction of water molecules to the lubricant surface improves both COF and hardness, a result linked to the reduction of system entropy through water-lubricant interactions. This mechanism, which counters the typical trade-off between friction and hardness, introduces two saturation points where optimal performance for each property is observed. Our finding of this entropy-reducing interaction suggests the potential for other substances to outperform water in lubrication, providing a new direction for future research in material science and tribology.

Return to Publications page