Arriving at ultralow wear using cellulose/two-material composites

Area of Science:

• Materials Science
• Tribology
• Green Chemistry

Background:

• Conventional lubricants face environmental concerns and performance limitations in demanding applications.
• Development of eco-friendly solid lubricants with superior wear resistance is crucial.
• Hydroxypropyl methylcellulose (HPMC) offers potential as a biodegradable lubricant base.

Purpose of the Study:

• To investigate the wear resistance of HPMC/tungsten disulfide (WS2)/graphene composites.
• To evaluate the effect of varying WS2/graphene content on tribological performance.
• To understand the mechanisms behind the ultra-low wear rates achieved.

Main Methods:

• Systematic tribological testing under normal loads (2 and 4 N).
• Preparation and characterization of HPMC/WS2/graphene composites (CWG-0.2 and CWG-10).
• Surface analysis using X-ray photoelectron spectroscopy (XPS) and high-resolution transmission electron microscopy (HRTEM).

Main Results:

• HPMC composites achieved ultra-low wear rates (<10^-10 mm^3), a ~95% reduction compared to pristine HPMC.
• Wear rate showed distinct load dependence at fixed lubricant concentrations.
• Formation of a 10-50 nm transfer film (WS2 nanoflakes and C-O-W-S phase) confirmed after prolonged sliding.
• Localized carbon phase clusters and interconnected carbon skeleton chains were identified as key to ultra-low wear.

Conclusions:

• HPMC/WS2/graphene composites exhibit exceptional wear resistance and potential for superlubricity.
• These sustainable materials are suitable for precision machinery, aerospace bearings, and biodegradable micro-electromechanical systems.
• The study highlights a promising direction for developing next-generation eco-friendly solid lubricants.