State Key Laboratory of Tribology
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Confinement-induced nano-sandwich of liquid crystal in Thin Film
Lubrication
Ming Gao, Liran Ma, Jianbin LuoState Key Laboratory of Tribology,
Tsinghua University, Beijing 100084, China
State Key Laboratory of Tribology
Outline
Background
Experiments
Results and Discussion
Future research
2
State Key Laboratory of Tribology
Background3
Friction F
Surface 1
Surface 2Lubricant
Load N
Tribology is the science and engineering of interacting surfaces in relative motion. It includes the study
and application of the principles of friction, lubrication and wear.
Macroscopic tribology: Friction coefficient, Wear Rate, Lubrication.
Macroscopic
Nascimento F C, Foerster C E, Silva S L R, et al. A comparative study of mechanical and tribological properties of AISI-304 and AISI-316 submitted to glow discharge nitriding[J]. Materials Research, 2009, 12(2): 173-180.
Hwang S Y, Lee N R, Kim N. Experiment and Numerical Study of Wear in Cross Roller Thrust Bearings[J]. Lubricants, 2015, 3(2): 447-458.
http://www.jamet.com/lubrication.html
State Key Laboratory of Tribology
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Thin Film Lubrication (TFL) Physical Model
Luo J. On Experimental Technique and Characteristic of Thin Film Lubrication [D]. Doctoral dissertation, Tsinghua University, 1994.
Li J, Zhang C, Luo J. Superlubricity behavior with phosphoric acid–water network induced by rubbing[J]. Langmuir, 2011, 27(15): 9413-9417.
Li J, Zhang C, Sun L, et al. Tribochemistry and superlubricity induced by hydrogen ions[J]. Langmuir, 2012, 28(45): 15816-15823.
Nanotribology: Lubrication Mechanism at Nanoscale
Molecular structure in the lubrication film
Background
004.0
Friction c
oeffic
ient
Time (s)
Superlubricity Behavior with Phosphoric Acid
surface
fluidic layer
transition
layer
absorbed
layer
Time/s
Film
th
ickn
ess/n
m
Static state
n-decane
n-decane+ hexadecanoic acid
TFL state
State Key Laboratory of Tribology
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Notes:Raman Intensity is too weak;
Information of absorbed molecules on surfaces??
BackgroundIn-situ Testing Platform equipped with Raman Spectroscopy
Load:160g
Speed:31.4 mm/s
The alignment of 5CB at different stage
Lubricant: 5CB
Objective: The relationship between friction coefficient and molecular ordering
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Background
Thickness of TFL:n*10~m*100nm
Raman Spectra
Surface Enhanced Raman Spectra
Enhanced Signal
Low IntensityMolecular structure
Electromagnetic Enhancement
Chemical Enhancement
Nano Particles
Au, Ag, Cu
Li, Al, Pt
Nano structures
Au, Ag, Cu
Others
graphene
Quantum dots
Au
Ag
Suitable Substrate
SERS
substrate
State Key Laboratory of Tribology
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Experiments
50Xobjective
PC
P
Laser
Half-wave-plate Mirror
Analyzer
Video
Spectrometer
Apparatus
Raman Spectroscopy
Silica plate
Rotating
Lubricant
Steer ball
Load applied
Ball-on-disk
Silica plate
Rotating
LubricantConvex lens
covered
with Ag film Load applied
Fric
tion
Pla
tform
SERS
Effect
State Key Laboratory of Tribology
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Experiments-Fabrication of SERS substrate
Ag nanorod
Evaporation Flow
K9 lens
Electron Beam Evaporation
——oblique angle deposition (OAD) technique
Evaporation Flow
α
50nm Ti Film 500nm Ag Nanorods film
1mm 500nm
State Key Laboratory of Tribology
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Results and DiscussionSERS Effect Detection Lubricant: 6CB (p-n-hexyl-p’-cyanobiphenyl, C6H13(C6H6)2CN)
On K9 Lens
2230cm-1C-N bond
Silver surface
6CB
Ag Nanorod
SERS Effect:3~5nm near Surface
Absorption
SERS Spectra came from
molecules absorbed on
the surface
State Key Laboratory of Tribology
10Results and Discussion
Measurement Method:Orientation of 6CB molecules
0°
Orientation of 6CB could be obtained by calculating
the polarization anisotropy of the C-C aromatic
vibration mode of 6CB at 1606 cm-1.
State Key Laboratory of Tribology
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Results and DiscussionOrientation of absorbed 6CB molecules during shearing
Ag nanorods
Shearing
Static State 30s after shearing 400s after shearing
Point 1 Point 1
Point 2
Point 1
Point 1 Point 1 Point 1
Po
int 2
State Key Laboratory of Tribology
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Results and DiscussionMorphology of Ag nanorods during shearing
Static State 30s after shearing 400s after shearing
Structure of silver film is related to the orientation molecules in measured 6CB nano film.
State Key Laboratory of Tribology
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Results and DiscussionOrientation of absorbed 6CB molecules on Ag nanorods
State Key Laboratory of Tribology
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Results and DiscussionOrientation of absorbed 6CB molecules on different substrates
Orientation of 6CB
in the whole
lubrication film
Orientation of 6CB
in the absorbed
film
State Key Laboratory of Tribology
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Results and Discussion
Thin Film Lubrication (TFL) Molecular pattern
Shearing
Tilted Ag nanorods
Fluidic Layer:
Absorbed Layer: 3nm(Measured by Relative Light
Intensity Principle)
X
YZ
Shearing
Surface Absorption
Shearing Force
Transition Layer
TFL Model
State Key Laboratory of Tribology
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