Ph D Thesis: Nanoparticle assisted tribofilm formation and material transfer studied with SEM and TEM
Friday 24 April 2015
to 12:00 at
István Zoltán Jenei (Stockholm University, Department of Physics)
The discovery and subsequent synthesis of metal containing fullerenes- IFS (Inorganic Fullerene-like Structures) by R.
Tenne et al. has generated considerable scientific interest with great potential impact in many industrial application areas
such as lubrication. The lubrication mechanism (tribofilm formation) via exfoliation and deposition of the atomic layers
from this cage-like IF-particles was revealed and demonstrated first by this research group. The incorporation of the
nanoparticles into lubricants (oils, greases) is however not straightforward.
When two surfaces are sliding against each other and a lubricant is used, a thin layer (tribofilm) is formed on the contact
area. The friction reducing effects of the nanoparticles can be altered or hindered by certain additives that are used in
lubricative oils. The effects of such additives on the tribological behavior of the nanoparticles are investigated by analyzing
the tribofilms formed on the worn surfaces using energy-dispersive X-ray spectroscopy in a scanning electron microscope.
Another challenge of nanoparticles in lubricants is the penetration of the nanoparticles into the contact zone. A possible
solution of this problem is briefly discussed.
A modified burnishing technique can be used to coat sliding metallic surfaces with a friction reducing tribofilm. The
morphology and composition of these tribofilms was investigated with analytical electron microscopy techniques.
In the second part of the thesis electron microscopy was used to investigate the material transfer. Titanium is an elements
with high adhesive ability to the counter surface, it displays poor tribological properties in sliding metallic contacts. This
can lead to material transfer and consequently severe surface damage. The cold formation and machining of titanium, thus
can lead rapid tool wear and poor surface finish. Electron microscopy techniques were used to study the mechanism of
titanium transfer to different counter surfaces.