ionic liquid lubricants; design chemistry for engineering applications

Ionic liquids (ILs) have been achieving a rapid growth of interest in the last decade. It challenges conventional descriptions of fluids in a variety of ways. Unique properties of these new materials have influenced their potential and current applications.

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1. INTRODUCTION1.1 What is an Ionic Liquid (IL)1.2 Properties of Ionic Liquids

2. INTRODUCTION TO TRIBOLOGY2.1 What is Lubrication2.2 What is a Lubricant2.3 Types of Lubricants2.4 Lubrication Regimes2.5 What are Additives?

3. TRIBOLOGICAL APPLICATIONS OF IONIC LIQUIDS

3.1 Why can Ionic Liquids be Lubricants?3.2 What are the Applications of ILs in Tribology?

3.2.1 As Lubrication Oils3.3.2 As Additives3.3.3 As Thin Films

4. PROBLEMS OF IL LUBRICANTS AND SOLUTIONS4.1 Tribo-corrosion4.2 Oxidation

5. CONCLUSION

1. INTRODUCTION• Ionic liquids challenge conventional descriptions of fluids in a variety of ways.• In the past, it has been common to oversimplify their behavior and to ignore the complexity that was possible, given the burgeoning range of ionic liquids available

1.1 What is an Ionic Liquid• Ionic Liquid is an ionic compound which is liquid below 100 °C• Composed of ion pairs containing bulky, asymmetric cations and anions

• Thermal stability • low vapor pressure

• Electric conductivity • Better solvent properties

• High heat capacity • Non flammability

• Liquid crystalline structures • Biphasic systems possible

Eg:

1-ethyl-3-methylimidazolium ethylsulfate

N+

N

S

O

O

O O-

1.2 Properties of Ionic Liquids

1-ethyl-3-methylimidazolium tetrafluoroborate

N+

N

B-

F

F

F

F

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• Due to the remarkable properties of ionic liquids, they have wide range of applications

IONIC LQUIDS

• Ionic liquids have tribological properties and can be used as lubricants, additives or thin films

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Lubrication is; – the technique or process – reduce wear of one or both surfaces in close proximity, and moving relative to each other

2.1 What is Lubrication

2.2 What is a Lubricant

Lubricant is;– a interposing substance between the surfaces – to carry or to help carry the load (pressure generated) between the opposing surfaces

2. INTRODUCTION TO TRIBOLOGY

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2.3 Types of Lubricants

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Boundary Lubrication Mixed Lubrication Hydrodynamic Lubrication

FF F

Stribeck Curve

2.4 Lubrication Regimes

Beraring ParameterηV/F

η = ViscosityV = SpeedF = Load

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2.5 What are Additives?

• Additives are substances applied to lubrication oils to achieve a comprehensive performance that include;

- enhancement of anti-wear and frication reduction- prevention of oil degradation corrosion - contain N, P, S

Eg:

ZnS S

PP

SS

OCH3

OC2H5

H3CO

C2H5O

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3. TRIBOLOGICAL APPLICATIONS OF IONIC LIQUIDS

3.1 Why can Ionic Liquids be Lubricants?

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3.2 What are the Applications of ILs in Tribology?

Notation of Imidazolium based ILs [CmCnim]X

• Cm and Cn = n-alkyl chains• im = imadazolium• X = counteranion

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3.2.1 As Lubrication Oils

Ball-on-disc test for Steel-Steel at 1000C

[C2C6im]BF4

X-1P PEPF

Max Load 600N 300N 300N

Friction coefficient at -30, 100 and 2000C for Aluminum-Steel contacts

[C1C6im]BF4

[C1C8im]BF4

PGDOMineral Oil<

‘PGDO: Propylene Glycol Diolate’

Load/N

Friction Coefficient

[C2C6im]BF4

X-1P PFPE

200 0.060 0.070 0.120

300 0.055 0.065 0.110

400 0.050 - 0.105

500 0.045 - -

600 0.045 - -

Disc-on-disc test for Steel-Steel at 1000C

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[C2C6im]BF4

PFPE

Friction Coefficient

0.07 0.14

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FAP- Tf2N-

P

R1

R1

R1

R4

BF4

[(R1)3R2P]BF4

R1= n-C4H9

R2=CnH2n-1

n=6,8,10,12

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Metal Surface

Anion

Cation

Lubrication Mechanism

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3.3.2 As Additives

• Due to good tribological properties and strong boundary film formation capability, ILs can be used as additives in common lubrication oils

- Have better performance than normal additives- Have lower cost

• Lubrication and anti-wear properties were all better than for neat ILs when sliding velocities were relatively large• Molecular design of novel ILs should be considered to improve miscibility with conventional oils

3.3.3 As Thin Films

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4. PROBLEMS OF IL LUBRICANTS AND SOLUTIONS

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5. CONCLUSION

• Even without any additives, ILs have shown remarkably better lubrication and anti-wear properties than normally used synthetic oils

• Corrosion and thermo-oxidation are two problems to be solved

• In terms of additives, miscibility with conventional oils should be increased

• Molecular design can improve the miscibility as well as some functions such as anti-oxidation, anti-corrosion of ionic liquids

• Action mechanism needed to be revealed more closely at both molecular level and macroscopic level

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References

1. Zhou, F.; Liang, Y.; Liu, W. Chem. Soc. Rev. 2009, 38, 2590–25992. Ludema, K. C. Friction, wear lubrication: a textbook in tribology.

CRC Press, Inc. 1996, chapter 73. Bermúdez, M. D.; Jiménez, A. E.; Sanes, J.; Carrión, F. J.

Molecules. 2009, 14, 2888-29084. Neale, M. J. The Tribology Handbook. Eastbourne: Antony Rowe

Ltd. 1999, p E.7.15. Kondo, H. Tribology Letters. 2008, 31, 211-218

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THE END

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THANK YOU

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F

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bis(trifluoromethylsulfonyl)imide

tris(pentafluoroethyl)trifluorophosphate

Tf2N- FAP-

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