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Thin film lubrication and mixed lubrication in nano scale
LUO Jianbin
State Key Laboratory of Tribology Tsinghua University, Beijing, China
Contents
1. Introduction 2. Testing technology 3. Properties of thin film lubrication (TFL) 4. Failure of fluid films 5. Lubrication model & map 6. Contact ratio in nano-mixed lubrication 7. Conclusion
Film thickness in contact region a-b-c-d
3. TFL properties
3.1 Film thickness v.s. influencing factors 3.2 Film thickness v.s. solid surface energy 3.3 Effect of running time on TFL 3.4 Effect of external electric field on TFL 3.5 Effect of nano-particles on TFL 3.6 TFL viscosity
Resolution of film thickness v.s. optical interference intensity
膜厚 nm
-40-30-20-10 Y
0 10 μm
20
30
40
0
20 40
60 80 100
120 140 160 180 200 -30-20-入10口x 0—μ1—0m>20出3口0
1. Introduction (1)
1.1 What’s Thin film lubrication (TFL)?
HDL(1886)
EHL(1950s) ？ Boundary
Lurication(1921)
Dry slide (Coulomb,1785)
1.2 My questions: What’s the state of the region？ What’s its lubrication mechanism?
Optical intensity
1.0
0.8
n=1.5
n=1.47
n=1.4
0.6
0.4
பைடு நூலகம்0.2
0.0
20
40
60
80
100 120 140 160 180
Optical intensity
(a) Different wavelengths
(b) Different refractive indexes
2. Testing technology (2)
Resolution of film thoickness /nm Resolution of film thoickness /nm
1.0
=700 nm
0.8
=600 nm
=450 nm
0.6
0.4
0.2
0.0
20
40
60
80
100 120 140 160 180
Main Qualifications:
Measure range: 0 ~ 500 nm Vertical resolution: 0.5 nm Horizontal resolution: 1 m Velocity: 0.2~1900 mm/s Friction force resolution: 0.1 mN Temperature range: ~ 120°C
1. Introduction (3)
Experiment on Thin film lubrication (TFL) – Spikes’s group (UK) – Wen and Luo’s group (SKLT, TU, China) – Hartal’s group (Czechoslovakia)
What’s the relationship between such regime and EHL or Boundary lubrication?
1. Introduction (2)
1.3 Jost’s questions (Tribology 2000): ➢ What’s the definition of boundary lubrication?
3.1 Film thickness v.s. parameters
1000
Film thickness (nm)
100
10 1
Polyplycol oil 1, 47 mm2/s Polyplycol oil 2, 145 mm2/s Polyplycol oil 3, 329 mm2/s Polyplycol oil 4, 674 mm2/s Polyplycol oil 5, 1530 mm2/s
1.4 Granick’s questions (Science, 1991) ➢What determines the effective viscosity of such ultrathin film? ➢What makes the film change into solid state from liquid when it is enough thin? ➢Why dose the solid film can endue a continuous sliding？
– Israelachvili’s group (USA) – Granick’s group (USA)
Calculation in TFL – Tichy, Thompson, Robbins, Hu, Popov, et al.
2. Testing technology (1)
Schematic of NGY-2
10
100
1000
Speed (mm/s)
Film thickness v.s. viscosity and speed
Film thickness curve
LUO Jianbin
State Key Laboratory of Tribology Tsinghua University, Beijing, China
Contents
1. Introduction 2. Testing technology 3. Properties of thin film lubrication (TFL) 4. Failure of fluid films 5. Lubrication model & map 6. Contact ratio in nano-mixed lubrication 7. Conclusion
Film thickness in contact region a-b-c-d
3. TFL properties
3.1 Film thickness v.s. influencing factors 3.2 Film thickness v.s. solid surface energy 3.3 Effect of running time on TFL 3.4 Effect of external electric field on TFL 3.5 Effect of nano-particles on TFL 3.6 TFL viscosity
Resolution of film thickness v.s. optical interference intensity
膜厚 nm
-40-30-20-10 Y
0 10 μm
20
30
40
0
20 40
60 80 100
120 140 160 180 200 -30-20-入10口x 0—μ1—0m>20出3口0
1. Introduction (1)
1.1 What’s Thin film lubrication (TFL)?
HDL(1886)
EHL(1950s) ？ Boundary
Lurication(1921)
Dry slide (Coulomb,1785)
1.2 My questions: What’s the state of the region？ What’s its lubrication mechanism?
Optical intensity
1.0
0.8
n=1.5
n=1.47
n=1.4
0.6
0.4
பைடு நூலகம்0.2
0.0
20
40
60
80
100 120 140 160 180
Optical intensity
(a) Different wavelengths
(b) Different refractive indexes
2. Testing technology (2)
Resolution of film thoickness /nm Resolution of film thoickness /nm
1.0
=700 nm
0.8
=600 nm
=450 nm
0.6
0.4
0.2
0.0
20
40
60
80
100 120 140 160 180
Main Qualifications:
Measure range: 0 ~ 500 nm Vertical resolution: 0.5 nm Horizontal resolution: 1 m Velocity: 0.2~1900 mm/s Friction force resolution: 0.1 mN Temperature range: ~ 120°C
1. Introduction (3)
Experiment on Thin film lubrication (TFL) – Spikes’s group (UK) – Wen and Luo’s group (SKLT, TU, China) – Hartal’s group (Czechoslovakia)
What’s the relationship between such regime and EHL or Boundary lubrication?
1. Introduction (2)
1.3 Jost’s questions (Tribology 2000): ➢ What’s the definition of boundary lubrication?
3.1 Film thickness v.s. parameters
1000
Film thickness (nm)
100
10 1
Polyplycol oil 1, 47 mm2/s Polyplycol oil 2, 145 mm2/s Polyplycol oil 3, 329 mm2/s Polyplycol oil 4, 674 mm2/s Polyplycol oil 5, 1530 mm2/s
1.4 Granick’s questions (Science, 1991) ➢What determines the effective viscosity of such ultrathin film? ➢What makes the film change into solid state from liquid when it is enough thin? ➢Why dose the solid film can endue a continuous sliding？
– Israelachvili’s group (USA) – Granick’s group (USA)
Calculation in TFL – Tichy, Thompson, Robbins, Hu, Popov, et al.
2. Testing technology (1)
Schematic of NGY-2
10
100
1000
Speed (mm/s)
Film thickness v.s. viscosity and speed
Film thickness curve