Tribo-Chemical Reactions in DLC-Zirconia Sliding under Ethanol Gas Environment

Area of Science:

• Materials Science
• Tribology
• Computational Chemistry

Background:

• Ultralow friction, or friction fade-out, is a critical phenomenon in tribology.
• Understanding the chemical mechanisms underlying friction reduction is essential for advanced material applications.

Purpose of the Study:

• To investigate the molecular mechanisms of ethanol dissociation on diamond-like carbon (DLC) and yttria-stabilized zirconia (YSZ) surfaces during sliding.
• To elucidate the role of surface interactions and sliding conditions in the tribochemical reactions of ethanol.

Main Methods:

• Reactive force field (ReaxFF) molecular dynamics simulations were employed.
• Steered molecular dynamics (MD) and Jarzynski equality were used to calculate potentials of mean force and activation energies.

Main Results:

• Ethanol dissociates into ethoxy and hydrogen on YSZ, and into ethyl and hydroxy on DLC.
• Sliding enhances ethanol dissociation on YSZ, while high load pressure is required for dissociation on DLC.
• Both YSZ and DLC surfaces significantly reduce the activation energies for ethanol dissociation compared to vacuum.

Conclusions:

• The study provides a detailed molecular-level understanding of ethanol tribochemistry on DLC and YSZ surfaces.
• Surface-mediated chemical reactions are key to achieving ultralow friction in this system.
• The findings offer insights into designing advanced lubricants and coatings for extreme friction reduction.