1

Nanomaterials in TribologyA Tutorial

Hong Liang (hliang@tamu.edu)Mechanical EngineeringTexas A&M University

Presented at the Nanotribology Tutorial/Panel SessionSTLE/ASME International Joint Tribology Conference

October 20-22, 2008, Miami, Florida, USA

2

Acknowledgements

Dr. Subrata Kundu, TAMU

3

Outline

• Brief Introduction to Nanomaterials

• Nanomaterials in tribology• as friction modifier• for anti-wear

• Future trend

4ICD

Nanomaterials are made into various forms

5Top-down vs. bottom-up method

High surface to volume ratio

Methods of synthesis

Physical Process

Chemical Process

Force

Bulk Metal

Metal Particles

Physical Process

Chemical Process

Mn+ Reduction

M(n-1)+

Mo

+

Nanoparticles formation by physical and chemical processes

6

M. Faraday (1857) Ist prepared colloidal gold using phosphorous in CS2 and the pink color solution is still stable and kept in RSC, UK

Synthesis methods

Vapor transportWet chemical methodPhotoactivation (UV-light)γ-Radiolysis techniqueLaser pulse techniqueSonochemical method

Gustav Mie

1857

RSC, London

1908

Michael Faraday Gustav Mie

1857

RSC, London

1908

Michael Faraday

Kundu et al., New J Chem. 2003, 27, 656. & J. Phys. Chem. B. 2005, 109, 13166.M. Faraday, Philos. Trans. 1857, 147, 145.G. Frens, Nature 1973, 241, 20.West et al., PNAS., 2003, 100, 13549.

7

Step-1Nucleation

M etal Ion M etal (0)Reduction

Mn+ + ne = M0

Step-2Growth

metal

Mn+Mn+

Mn+

Mn+

Reduction

8

Step-3

Stabilization

WithoutStabilizer

W i t hS t a b i l i z e r

Agglomeration Stabilization

Micelle

Reverse Micelle Polymers

Thiol : Brust et al., Chem. Comm., 1994, 801.Dendrimer : Esumi et al., Langmuir, 2000, 16, 2604.Surfactants: Kundu et al., J. Am. Chem. Soc., 2005, 127, 17600.

PSS =PAH =

Stabilizer:

Surfactants

9El-Sayed (GT), Murphy (USC), Mirkin (NWU), Yang (UCB), Kundu & Liang (TAMU)

Gold nanorods

10

Tribomaterials

Friction reduction

Anti-wear

Lubricant additives

NanoparticulatesThin films/layersNanocomposites

11

Single Layer GrapheneSymmetric Double Layer Graphene

Asymmetric Double Layer Graphene

graphite diamond

Crystal structures of materials

Buckyball

OhtaOhta and and BostwickBostwick et al., Science, (2006)et al., Science, (2006)

12TiS2

MoS2

Layered structures for lubrication

WS2

13

Comparison of Mechanical Properties[26][27][28][29][30][31][32]

~2~3.5~0.15Kevlar

15-50~0.65-1~0.2Stainless Steel

12

150

170

0.8-0.9

1.2

0.25-0.5

0.15

MWNT

BN

GaN

WS2

1613-531 to 5SWNT

Elongation at Break (%)

Tensile Strength (GPa)

E (TPa)

Materials

14

(a) Without film; (b) with NPs.

A Si3N4 ball against Al2O3 flat.

Rapoport, Nanosci. & Nanotech., 2004.

As a solid lubricant for self-lubricating

15

As a thinfilm

Cardinal & Liang et al., submitted.

16

Fullerene C60; Hydroxylated Fullerene C60 (OH) 24, Crown Ether

As additives to base fluids

17

As additives to base fluids

0

0.2

0.4

0.6

0.8

0 0.2 0.4 0.6 0.8 1 1.2

Fric

tion

Coe

ffici

ent

Speed*Viscosity/Load

Crown Ether

Water

Fullerene

Pendleton and Liang et al., in review.

18

Fullerene

Tribo-reactions in NPsBefore test After test

Crown Ether

Pendleton and Liang et al., JNR, (2009).

19

Wea

r de

pth

(μm

)

Water Water+CE Water+FU

Wea

r de

pth

(μm

)

Water Water+CE Water+FU

Ra

(μm

)

Water Water+CE Water+FU

Wear mechanisms due to nanofluid

Water+CE Water+FU

Wear track Uniform grooves

Original Ti Surface

RandomScratches

Thick layer detached with scatter debris

Wear debris

16μm 16μm 16μm

20

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0 0.002 0.004 0.006 0.008 0.01 0.012 0.014 0.016 0.018Sommerfield number

coef

feci

ent o

f fric

tion

1N-0%C

1N-25%C

1N-50%C

1N-75%C

3N-0%C

3N-25%C

3N-50%C

3N-75%C

5N-0%C

5N-25%C

5N-50%C

5N-75%C

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0 0.002 0.004 0.006 0.008 0.01 0.012 0.014 0.016Sommerfield number

Coe

ffec

ient

of f

rictio

n

1N-0%C

1N-25%C

1N-50%C

1N-75%C

3N-0%C

3N-25%C

3N-50%C

3N-75%C

5N-0%C

5N-25%C

5N-50%C

5N-75%C

ROD-SHAPED

NANOPARTICLES

SPHERICAL

NANOPARTICLES

Shape effects on friction

21

Effects of concentration on friction

22

Electrostatic attraction

Positively charged particle

+ negative regions of protein

CORONA

Repulsive force

Positively charged particle

+ positive regions of protein

J. Klein, Proc. Natl Acad Sci USA 104 (2007) 2029-2030,

NP – fluid interaction

23

In CMPInterfacial forces in wafer-particle-pad

interfaces

Ff1.4R

Fdrag

Fvdw Fel +F H - bond

ParticleU

+F

Polishing pad

Fapplied

wafer

Ff1.4R

Fdrag

Fvdw Fel +F H - bond

ParticleU

+F

Polishing pad

Fapplied

wafer

• van der Waals • Electrostatic• H-bond• Fluid drag• Friction

24

Interfacial forces as a function of particle radius

-4

-2

0

2

4

6

8

0 0.05 0.1 0.15 0.2 0.25

Particle diameter (μm)

log-

Forc

e (n

N)

vdw electrostatic H-bond drag force v=0.1m/s drag force v=0.4m/s

Ng & Liang, ASME J. Tribology (2007)

25

Modified Stribeck curve for CMP:

Without modification Modified Stribeck curve for rotational Polyurethane pad

0.0000

0.5000

1.0000

1.5000

0 5E-07 0.000001 1.5E-06 0.000002 2.5E-06 0.000003 3.5E-06 0.000004 4.5E-06 0.000005

Sommerfeld

Fric

tion

coef

ficie

nt

Polyurethane-rotating motion

0.0

0.2

0.4

0.6

0.8

1.0

1.2

1.4

0.E+00 2.E-08 4.E-08 6.E-08 8.E-08 1.E-07 1.E-07

Modified Sommerfeld Number

Fric

tion

Coe

ffici

ent

26

0

0.05

0.1

0.15

0.2

0.25

0.3

0 2 4 6 8 10 12 14 16 18 20

Load ( N)

Mod

ulus

( G

Pa)

Change in composite modulus for the polyurethane pad

)1(' 2α−= − bulkLN EkEComposite modulus:

27

Summary

0

0.2

0.4

0.6

0.8

0 0.2 0.4 0.6 0.8 1 1.2

Fri

cti

on

Co

eff

icie

nt

Speed*Viscosity/Load

Crown Ether

Water

Fullerene

28

Outlook

• Novel nanomaterials emerge in near future

• New understanding is needed in nanomaterials-properties-tribologicalperformance

• Unconventional applications