O-to-N Atom Substitution in h-BN Impedes its Interlayer Slip in Humid Environments

Area of Science:

• Materials Science
• Tribology
• Surface Chemistry

Background:

• Hexagonal boron nitride (h-BN) exhibits excellent solid lubrication properties, especially in humid and high-temperature environments.
• Understanding the factors influencing friction in h-BN, such as phase transitions, defects, and doping, is crucial for optimizing its performance.
• The complex interplay of these factors during macroscale friction presents a significant challenge in identifying dominant friction-reducing mechanisms.

Purpose of the Study:

• To explore the intrinsically low-friction characteristics of h-BN in humid environments.
• To investigate the effect of plasma pretreatment on the surface atomic conformation of h-BN.
• To elucidate the dominant interfacial interactions between water molecules and h-BN that lead to low friction and wear.

Main Methods:

• Altering the initial surface atomic conformation of h-BN through plasma pretreatment.
• Utilizing Argon/Oxygen plasma for direct oxygen atom introduction.
• Employing Hydrogen plasma for nitrogen atom locking and Nitrogen plasma for supplying additional nitrogen atoms.

Main Results:

• Plasma pretreatment efficiently modulated the surface of h-BN, impacting its interaction with water molecules.
• Effective adsorption of water molecules to form a nanostructured water layer on h-BN surfaces was identified as the dominant factor for low friction and wear.
• Oxygen doping, nitrogen locking, and nitrogen supply reduced water molecule aggregation, leading to increased friction forces.

Conclusions:

• The ability of h-BN to adsorb water molecules and form a nanostructured water layer promotes interlayer slip, crucial for low friction in humid environments.
• Targeted modulation of h-BN surfaces provides a theoretical basis for understanding its low-friction behavior.
• This study offers comprehensive guidance for designing advanced antifriction materials for humid conditions.