Transcript RESEARCH PROPOSAL STUDY OF LAYERED MoS2, WITH …

RESEARCH PROPOSAL
STUDY OF LAYERED MoS2, WITH
MoTe2, AND MoSe2
Warren Courtney
University of Waterloo
March 29, 2006
Background
 Numerous studies have looked at the tribology of
multi-layered dry lubricants, for myriad reasons (ref
1, 2, 3, 8)
 Studies have also been done on the orientation of
molecules in the lubricating layers to determine the
effects. Dramatic increase in friction can occur when
molecules align (ref 9)
 This study proposes looking at a nano-structured
material composed of layers of MoS2, MoTe2, and
MoSe2 in which the material are deemed to have
similar properties but different crystal structures
which should reduce friction by not allowing coincidence structure.
Nanoscale friction
 Graph of atomic
force microscopy
probe moving
across a smooth
surface of NaCl
(monet.unibas.ch/gue/uhvafm/tribo.html)
 Proposed
mechanism based
on Tomlinson’s
model of atomic
friction
(www.nanoscience.de/group_r/theory/)
the sample surface
Phononic friction

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As surfaces pass over one another the theory of friction indicates that
attachments are made and broken between materials resulting in the
production of phonons
It should be more difficult for multilayer materials to pass over one another
since there are more ways for the atoms to move and interact and create
heat and phonons
Such "phononic" friction is particularly great when the surface atoms are
equally spaced, and when they are aligned with the counter face atoms
upon which they are sliding.
physics
web.org/articles/world/18/2/9
Structure of MoS2
 Structure of MoS2
 Strong bonds within
layers and very weak
bonds between layers
 Similar structures are
proposed for MoSe2
and MoTe2
 However the
structure are altered
due the size
differences in the
dichalcogenes
ref4 Lince, R. L. and Frantz, P.P.
Crystal Structures Analogous to Molybdenum
Disulphide
 Prototypical structure:

www.webelements.com
Multilayer graphite structure
Friction is reduced each time a new layer starts to move
relative to the others
Geike, T. Popov, v. L. ref 1
Nano-tractor to measure very low frictional forces
This image obtained using a scanning electron microscope shows a "nanotractor" that can measure ultra low frictional forces as it creeps along a surface.
In the centre of the device is a tangential-force actuation plate, flanked by two
electrostatic "clamps" that respond to an applied voltage.
Sandia National Laboratories
Preparation of Nanolayered
Molybendum Dichalcogenides
 High purity films can be created by laser ablation
using an excimer laser UV radiation at 248 nm
wavelength, 20 ns duration 50 Hz.
 Characteristics and composition of the layers will be
determined with x-ray photoelectric spectroscopy
 Samples for testing will consist of layers of MoS2
with MoSe2; MoS2 with MoTe2; MoSe2 with MoTe2;
and MoS2 alone as a standard for comparison
Hu, J. J., Bultman, J. E., Zabinski,
J. S. ref 7
Testing of Multilayer Molybdenum
Dichalcogenides
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Initial testing will be performed at the nanoscale using the
nanotractor shown previously
Should result show promise a further set of testing will be
conduced in a nitrogen purged pin on disc tribometer
CSM Instruments SA
Environmental Testing
 Further test comparisons will be
made after 200 hours conditioning in
environments containing air at
relative humidity of 15%, 25%, 50%,
and 75% relative humidity in air at
35o C; testing will be performed in
the conditioning environment
References
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
Geike, T., Popov, V. L. Tribology International 39 (2006) pp 437-443, Multi-layer models of friction
between solids
Lince, J. R. Tribology Letters, Vol 17, No. 3, October 2004, Tribology of co-saputtered nanocomposite
Au/MoS2 solid lubricant films over a wide contact stress range.
Popov, V. L., Psakhie, S. G., Tribology International 39 (2006) pp 426-430, Physical nature and
properties of dynamic surface layers in friction
Lince, J. R., Frantz, P. P., Tribology Letters, Vol 9, No. 3-4, 2000, Anistropic oxidation of MoS2
crystallites studied by angle- resolved X-ray photoelectron spectroscopy
Hu, J. J., Zabinski, J. S., Tribology Letters, Vol. 18, No. 2, February 2005, Nanotribology and
lubrication mechanisms of inorganic fullerene-like MoS2 nanoparticles investigated using lateral force
microscopy (LFM)
Tagawa, M. Muromoto, M., et al Tribology Letters, Vol. 18, No. 4, April 2005, Hyperthermal atomic
oxygen interaction with MoS2 lubricants and relevance to space environmental effects in low earth
orbit – effects on friction coefficient and wear life
Hu. J. J., Bultman, J. E., Zabinski, J. S., Tribology Letters, Vol. 18, No. 1 January, 2006,
Microstructure and lubrication mechanism of multilayered MoS2/Sb2O3 thin films
Editorial Popov V. L. Tribology International 39, (2006), pp 369, Development of surface topography
in friction processes
www. nanoscience.de/group_r/theory/
physicsweb.org/articles/world/18/2/9
Monet.unibas.ch/gue/uhvafm/tribo.html