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Frictional forces between cohesive powder particles studied by AFM.
Robert Jones1, Hubert M Pollock, Derek Geldart
1Department of Physics, University of Lancaster, Lancaster LA1 4YB, UK. robert.jones@lancaster.ac.uk
Ultramicroscopy
|June 29, 2004
Summary
This study used atomic force microscopy to measure friction forces between various powders and glass beads. Particle-particle friction was load-dependent, while particle-wall friction was less dependent and more adhesive.
Area of Science:
- Materials Science
- Surface Science
- Tribology
Background:
- Understanding inter-particle friction is crucial for powder handling and processing.
- Atomic Force Microscopy (AFM) offers high-resolution insights into micro-scale contact mechanics.
Purpose of the Study:
- To investigate inter-particle and particle-wall friction forces using AFM.
- To correlate single-particle friction behavior with bulk material properties.
Main Methods:
- Attachment of various powders (alumina, limestone, titania, zeolite) and glass ballotini to AFM cantilevers.
- Lateral Force Microscopy (LFM) for in situ friction force measurement in air.
- Analysis of friction dependence on load (0-25 nN) for particle-particle and particle-wall (steel) contacts.
Main Results:
- Particle-particle contacts exhibited load-dependent friction, with linear (multi-asperity) and non-linear (single-asperity) behaviors.
- Particle-wall contacts showed minimal load dependence and increased adhesion.
- Friction results were compared with bulk shear stress-normal stress data (yield loci).
Conclusions:
- AFM provides valuable data on single-particle friction mechanisms.
- Friction behavior varies significantly between particle-particle and particle-wall interactions.
- The study links micro-scale tribological measurements to macro-scale material properties.