Neutron reflectometry under high shear in narrow gap for tribology study

Area of Science:

• Tribology
• Materials Science
• Surface Chemistry

Background:

• Understanding lubricant additive behavior at interfaces is crucial for tribological applications.
• Evaluating interfacial structure under dynamic, high-shear conditions presents significant challenges.

Purpose of the Study:

• To establish an operando analysis method for evaluating interfacial structure of adsorbed lubricant additive layers under fluid-lubricated conditions.
• To investigate the structural changes of adsorbed additive layers under high shear rates.

Main Methods:

• Utilized a parallel-face narrow gap viscometer integrated with an energy-resolved neutron reflectometer.
• Operated the viscometer at high shear rates within a micrometer-order constant gap.
• Measured neutron reflectivity profiles under static and rotating (shear) conditions.

Main Results:

• Confirmed accurate neutron reflectivity measurements irrespective of surface rotation.
• Observed reduced thickness and density of polymethacrylate-based additive layers under shear compared to static conditions.
• Demonstrated the method's capability to analyze structural changes in adsorbed layers.

Conclusions:

• The developed operando method effectively analyzes interfacial structure changes in adsorbed lubricant additive layers under shear.
• The combination of neutron reflectometry and narrow gap viscometry offers a promising approach for future tribological studies.
• High shear conditions alter the structure of adsorbed polymethacrylate additive layers.