Towards a neutron and X-ray reflectometry environment for the study of solid-liquid interfaces under shear

Area of Science:

• Surface science
• Tribology
• Materials science

Background:

• Understanding interfacial behavior of surface-active molecules is crucial for lubrication and material performance.
• Studying interfaces under dynamic conditions, such as shear, presents significant experimental challenges.

Purpose of the Study:

• To present a novel sample environment for neutron and X-ray reflectometry.
• To investigate the behavior of surface-active molecules at solid-liquid interfaces under shear.
• To characterize the structure of glycerol monooleate (GMO) at the iron oxide-dodecane interface under shear.

Main Methods:

• Development and application of a novel neutron and X-ray reflectometry sample environment.
• Utilizing neutron reflectometry to analyze the iron oxide-dodecane interface.
• Employing conventional reflectometry theory and intensity summation for thicker film analysis.
• Developing a model for X-ray reflectometry data analysis under shear.

Main Results:

• Successful characterization of the iron oxide-dodecane interface under shear using neutron reflectometry.
• Demonstration that glycerol monooleate (GMO) forms a stable surface layer at the iron oxide-dodecane interface, unaffected by shear.
• Quantification of GMO layer thickness under shear ([Formula: see text] Å) and without shear ([Formula: see text] Å).
• Application of a new model to analyze X-ray reflectometry data collected with the sample environment.

Conclusions:

• The novel sample environment is effective for studying interfacial phenomena under shear.
• GMO acts as a robust organic friction modifier, maintaining its structural integrity under shear.
• The findings provide insights into the mechanisms of friction reduction at solid-liquid interfaces.