Joint workshop on Frontier in Tribology between … workshop on “Frontier in Tribology” between ... Solid Lubrication and Imperial College London Program 22 ... Handbook of Space

Joint workshop on “Frontier in Tribology” between

Lanzhou Institute of Chemical Physics, State Key Lab of

Solid Lubrication and Imperial College London

Program

22 September, 2014

8:30-8:40 Welcome speech by Weimin Liu and Hugh Spikes

Chair: Feng Zhou

8:40-9:30 Hugh Spikes The Tribology Group, Imperial College p1

9:30-10:20 Weimin Liu The State Key Lab of Solid Lubrication p3

10:20-10:40 Coffee break

Chair: Daniele Dini

10:40-11:20 Janet Wong Probing lubricant rheology with fluorescence imaging

p5

11:20-11:50 Feng Guo Interferometry measurement of lubricating film under metal-ceramic contact

p7

11:50-12:10 Zhuhui Qiao/ Jun Yang

High Temperature Self-lubricating Materials

p9

12:10-14:30 Lunch

Chair: Philippa Can

14:30-14:50 Junhong Jia Tribological Behaviors of Self-lubricating Composites with Continues Lubricating Property in Wide Temperature Ranges

p11

14:50-15:30 Thom Reddyhoff Triboemission Imaging p13

15:30-15:50 Liping Wang Carbon-based coatings for potential space application: challenge and possibility

p15

15:50-16:10 Junyan Zhang The governing of fullerene like structure on the super low friction of carbon films

p17


Chair: Junyan Zhang

16:30-16:50 Fengyuan Yan The Sliding Tribocorrosion Phenomena of Some Ceramics and Metals in Seawater

p19

16:50-17:30 Amir Kadiric Initiation and Propagation of Rolling Contact Fatigue Cracks

p21

17:30-17:50 Ga Zhang

Formation mechanism and functionality of nanostructured tribofilms of polymer composites

p23

18:30- Welcome Dinner

23 September, 2014

Chair: Hugh Spikes

8:30-9:20 Daniele Dini A Multi-Physics Platform for Tribological Modelling

p25

9:20-9:40 Jinqing Wang Graphene Based Lubricant Materials: Preparation and Application

p27

9:40-10:00 Zhiguang Guo Biomimetic super-lyophobic and super-lyophilic materials applied for oil/water separation: A new strategy beyond nature

p29


Chair: Weimin Liu

10:20-11:00 Philippa Can Synovial Fluid Lubrication of Artificial Joints

p31

11:00-11:20 Xiaolong Wang 3D Lubricating materials p33

11:20-11:40 Feng Zhou Interfacial Friction Control p35

11:40-11:50 Closing remarks by Prof Weimin Liu, and Hugh Spikes

12:00 Lunch

14:30 Lab and local visit

25 September, 2014 Farewell

Joint workshop on “Frontier in Tribology” between LICP and Imperial College London Lanzhou, 22-23 Sep 2014

The Tribology Group, Imperial College

Hugh Spikes

E-mail: [email protected]

Abstract

In 1946 Professor Cameron established a Lubrication Section in the Mechanical Engineering Department at Imperial College London. Professor Cameron was a chemist by background and an engineer by temperament so the Section’s research has always, and continues to be, multidisciplinary in approach. Professor Cameron retired in 1982 but the Section continued to prosper, carrying out important work in the 1980s and 1990s in areas including fuel lubricity, EHD film thickness, boundary lubrication and rolling contact fatigue.

In 2005, the Section was renamed the Tribology Group and it received the Rector’s Research Excellence Award in 2008, confirming it as a leading research group in Imperial College. In 2010 the SKF University Technology Centre in Tribology was established within the Tribology Group and in 2013 a similar Shell University Technology Centre in Fuels and Lubricants was founded.

The Tribology Group currently has six academic staff, Professor Hugh Spikes who is head of the Group, Dr Daneile Dini, Dr Amir Kadiric, Dr Marc Masen, Dr Janet Wong and Dr Tom Reddyhoff, as well as a senior research fellow, Dr Philippa Cann and a junior research fellow, Dr Connor Myant. There are twelve postdoctoral staff and 32 PhD students as well as several academic visitors and three visiting professors. The Group is based in the Applied Mechanics Division of the Department of Mechanical Engineering, Imperial College but has close links with many other Departments within the College and at other academic institutions. Key research areas include machine component tribology, lubricants and lubricant additives, mechanisms of failure and damage, nanotribology and biotribology.

Three members of the Tribology Group have been awarded Tribology Trust Gold Medals. The Group has also received more than 20 annual best papers awards from the journals of the IMechE, ASME and STLE in recognition of the quality of its research.

Figure 1: The Tribology Group

1


Biography

Hugh Spikes graduated in Natural Sciences from the University of Cambridge in 1968 and obtained his PhD for research in Tribology from Imperial College in 1972. He retired from teaching in 2012 and is currently employed as a Senior Research Investigator and Emeritus Professor in the Tribology Group, Mechanical Engineering Department, Imperial College London.

Professor Spikes is a Fellow of the Institution of Mechanical Engineers (IMechE) the Society of Tribologists and Lubrication Engineers (STLE) and the Royal Academy of Engineering (RAE). He has been involved in research in tribology for over forty years and has received a number of recognitions for his research achievements including the ASME Mayo D Hersey Award and the STLE International Award. In 2004 he was awarded the Tribology Trust Tribology Gold Medal, the highest international honour in Tribology. Ten of his research publications have received best paper awards, from STLE, IMechE and ASME.

Professor Spikes’ research interests span a wide range of liquid lubrication research, including hydrodynamic, elastohydrodynamic and boundary lubrication. A particular interest has been thin film lubrication and the influence of lubricant composition on the film-forming properties of lubricants and thus on friction and wear performance.

Notes

2


An introduction to SK-LSL and ionic liquid lubricants

Weimin Liu

State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics,


Abstract

In Oct. 1999, the State Key Laboratory of Solid Lubrication (SK-LSL) was named with the approval of

the Ministry of Science and Technology of China, which was then officially established in April 2001.

Before that, it was Laboratory of Solid Lubrication in Lanzhou Institute of Chemical Physics, Chinese

Academy of Sciences (CAS). In responding to the call of the “Knowledge Innovation Program” of

CAS, the SK-LSL has being assigned to be a major research center in tribomaterial and solid lubrication,

a base for international academic exchange and for the training of scientific and technical personnel in

tribology.

The SK-LSL has 93 staffs including 2 academicians, 15 full professors, and 18 associate professors. The

laboratory enrolls 110 doctoral and master degree candidates in physical chemistry, tribology and

materials science. It also accepts post-doctoral fellows and visiting scholars. Key research areas involve

fundamental and applied research in tribology and high-tech fields, including novel lubricating and

protecting materials, solid lubricating materials such as polymer-, carbon- and ceramic-based film &

coating, lubricating oil/grease, ionic liquid, biomimetic lubrication, and tribochemical mechanism, etc.

Prof. Weimin Liu, the director of SK-LSL, is going to talk about lubrication by liquids, which is widely used in guarantee of smooth operation of compartments in relative motion, in reducing emission and improving energy efficiencies. It has the advantages of low frictional coefficient, long service life, etc. New lubricants are required to work under more harsh environment (better resistance to oxidation, high temperature stability etc), better lubricity and less oil replacement cycles. The presentation will summarize the research progress of synthetic lubricating oils including ionic liquids lubricants in my group and some criteria in molecular design are discussed. Ionic liquids have excellent lubricity and antiwear properties and are promising candidates for additive-free lubricants. Meanwhile, they offer a great pool of design flexibility for specific functions and for integration of different functionalities. By introducing sterically hindered phenol and benzotriazole or both into imidazolium salt, the antioxidation and anticorrosion properties are separately or simultaneously improved. Recently a novel way for application of ionic liquids has been developed by forming ionic liquids in-situ. The synthesis-free ionic liquids are very promising for future applications.

Figure 1. Functional ionic liquids

Reference

[1] Mingjin Fan, Zenghong Song, Yongmin Liang, Feng Zhou and Weimin Liu, In Situ Formed Ionic Liquids in Synthetic Esters for Significantly Improved Lubrication, ACS Appl. Mater. Interfaces, 2012, 4, 6683.

[2] Meirong Cai, Yongmin Liang, Feng Zhou, Weimin Liu，A novel imidazolium salt with antioxidation and

anticorrosion dual functionalities as the additive in poly(ethylene glycol) for steel/steel contacts, Wear, 2013, 306, 197. [3] Meirong Cai, Yongmin Liang, Feng Zhou, Weimin Liu, Anticorrosion Imidazolium Ionic Liquids as the Additive in Poly(ethylene glycol) for Steel/ Cu–Sn alloy Contacts, Faraday Discussions, 2012, 156, 147. [4] Zenghong Song, Mingjin Fan, Yongmin Liang, Feng Zhou, Weimin Liu, Lithium-Based Ionic Liquids: In Situ-Formed Lubricant Additive Only by Blending, Tribology Letters, 2013, 49, 127.

3


Biography

Weimin Liu received his Ph.D. degree in lubricating materials and tribology from the Lanzhou Institute of Chemical Physics (LICP) of the Chinese Academy of Sciences (CAS) in 1990. Then he joined the Laboratory of Solid Lubrication (LSL) of the LICP. From June 1993 to June 1994, he worked as a Visiting Scholar at Pennsylvania State University, USA. He has been the head of the State Key Laboratory of Solid Lubrication since 2000. He served as a vice director of the LICP from 2002 to 2005 and director of the LICP from 2005 to 2012. In 2013, he was elected the member of the CAS.

Professor Liu is the President of the Chinese Tribology Institute of the Chinese Mechanical Engineering Society, Member of the Editorial Board of Journal of Engineering Tribology and other academic journals. He also serves as the Chief Scientist for the “Fundamental Research on Lubricating and Antiwear Materials under Extreme Operating Conditions” project and “Research on High Performance Synthetic Lubricating Materials” project (projects funded by Chinese Ministry of Science and Technology), and the Chief Scientist for “The Program of Space Tribology of Materials at SZ-7 Spacecraft of China” project in 2008. He received 1 item National 2nd Class Invention Award of China, 1 item National 2nd Class Natural Science Award of China, and 8 items of 1st Class Science and Technology Award of Gansu Province, China.

Professor Liu’s research areas include space, aviation lubrication and high performance lubricating materials. His group and he have contributed greatly to the successful application of new solid lubricating films, synthetic lubricants and self-lubricating materials for China’s high-tech industries, with more than 400 papers, 50 Chinese Patents and 1 US Patent, and two books of “Lubricating Materials for Gears” and “Handbook of Space Lubricating Materials and Technology”.

Notes

4


Probing lubricant rheology with fluorescence imaging

Aleks Ponjavic, and Janet Wong*

Affiliations: Department of Mechanical Engineering, Imperial College London, UK SW7 2AZ


Abstract

The presentation gives an overview of the application of fluorescence-based imaging to the study of

some commonly observed tribological phenomena and their nanoscopic or molecular origin.

It then focuses on how the challenge of in-situ rheological measurement within an elastohydrodynamic

(EHD) contact is tackled by the newly developed photobleached fluorescence imaging velocimetry. The

newly developed method allows unprecedented access to local flow information through the

examination of through-thickness velocity profile in a circular point contact. Information on the local

rheology of lubricant in an EHD contact is necessary for friction prediction. The pressure and shear

experienced by the EHD lubricant mean that rheological models and flow curves are required to

predict lubricant rheology in the contact. It is unclear these commonly used models describe EHD

lubricants appropriately. Experiments show that anomalous flow can be observed under certain

conditions. It is suggested that a pressure-induced glass transition may cause such observations. This is

supported by an analytical solution highlighting the importance of how a pressure-sensitive viscosity

governs polymer rheology. As a result, the heterogeneous flow of the lubricant in the contact is

observed due to local pressure variation.

Key words: elastohydrodynamic lubrication, boundary conditions, rheology

Reference

[1] A. Ponjavic and J. S. S. Wong*, ‘The effect on Interfacial Slip on the Rheology of EHD lubricants,’ RSC

Advances, 4(40) 20821 (2014).

[2] A. Ponjavic. L. di Mare, and J. S. S. Wong, ‘Flow Behaviour of Polybutene in High Stress Conditions,’ Journal

of polymer science. Part B, Polymer physics, 52, 708 (2014).

5


Biography

Dr. Janet Wong received her Ph.D. from the University of Illinois at Urbana-Champaign in 2008 with a dissertation on the physics of confined polymers. She then joined the Tribology group, Mechanical Engineering Department, Imperial College London as Lecturer. Dr Wong is a specialist in interface phenomena, polymer dynamics and nano-tribology and has pioneered the application of fluorescence spectroscopy and imaging to in-situ measurements of velocity profiles, surface

reaction rates, additive interactions and phase stabilities of fluids at tribological contacts and under extreme conditions. The Wong research group focuses on establishing relationships among (1) properties of lubricants in bulk, and at the contact; (2) contact conditions, and (3) the resultant mechanical response, i.e. friction and wear

of the lubricated system. Her group works closely with numerical analysts towards fundamental

understanding and the development of effective tribological strategies. Her work is funded by governmental agencies and industry from Europe, Asia and the US.

Notes

6


Interferometry measurement of a lubricated

fixed-incline slider-on-disc contact

Feng Guo1, Patrick Pat Lam Wong2

Affiliations: 1School of Mechanical Engineering, Qingdao Technological University，

11 Fushun Road, Qingdao 266033, CHINA

2Department of Mechanical and Biomedical Engineering, City University of Hong Kong

Tat Chee Avenue, Kowloon, Hong Kong,China

Abstract

The fixed-incline slider bearing is one basic model in lubrication theory and large amounts of

theoretical work has been presented with it. Unfortunately there are very few reports on the lubricating

film measurement of this fixed-incline slider bearing and some theoretical postulations cannot be

validated. Interferometry has been successfully used to measure film thickness in a non-conformal

ball-on-disc contact (elastohydrodynamic lubrication or EHL). However, things are different for a

conformal flat-on-flat contact due to the difficulties in the alignment of the contact surfaces, in

particular, when very tiny fixed inclination is needed.

This presentation delivers some recent work by the authors on the development of an optical slider

bearing tester. In the tester, a lubricated conformal contact is built between a stationary slider and a

rotating transparent disc. A compliant parallel mechanism is adopted in the slider holder, enabling

accurate setting of slider inclination at a resolution better than 10-4 radian. When the disc rotates and

the slider is loaded, lubricating films are generated. Generally, the film thickness h0 at the exit is at

submicro/micro-scale depending on the working parameters and interferometry is used to get the film

thickness. Two interference methods are included in the tester. One is based on dichromatic

interference intensity modulation (DIIM), which can achieve a wide measurement range with no

wavelength ambiguities, in particular, under non-steady conditions. The other is the monochromatic

interferometry, and intensity variation is used to infer the film thickness. To measure slider inclination, a

Fourier transform based algorithm was devised to count fringes and particularly necessary for large

inclination angles. The credibility of the tester is demonstrated by the film thickness measurement

under different inclinations, loads, velocities, lubricants and slider materials.

With this optical slider bearing tester some fundamental problems of lubrication could perhaps be

explored in a different way. This is demonstrated by some application examples, including measurement

of load carrying capacity curve (6W vs. K), assessment of interface wettability and local hydrodynamic

effects of engineering surfaces.

Keywords: slider bearing; hydrodynamic lubrication; optical interferometry

7


Biography

Feng GUO(郭峰) got his Ph.D. from the City University of Hong Kong, and he is

now employed as a full-time professor in Qingdao Technological University. He has published more than 50 English papers in peer-reviewed international journals. His current research interests include numerical and experimental study of liquid film lubrication and optical interferometry for measuring thin lubricating films.

Notes

8


High Temperature Self-lubricating Materials

Shengyu Zhu, Zhuhui Qiao, Jun Yang*, Weimin Liu

Affiliations: State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics,

18 Middle Tianshui Road, 730000


Abstract

High temperature tribological materials have continued to play important roles in many engineering areas, such as power generation, aerospace, petrochemical, metal working etal, mainly because mechanical systems rely on them for high reliability, durability, and efficiency. In particular, the development of advanced tribological materials with low friction and high wear resistance over a wide range of temperatures (low temperatures to above 800 °C) has become a leading research activity in tribology.

However, achieving and maintaining low friction and wear at high temperatures have been very difficult in the past and still are the toughest problems encountered in the field of tribology. In this talk, we will show few kinds of high temperature self-lubricating materials developed by our group recently. (1) A high-temperature self-lubricating nickel-alloy-based composite, produced using the hot press technique, exhibited simultaneously superior lubricating properties, average friction coefficient below

0.25 from ‒60 oC to 800 oC, and high strength, 470 MPa of tensile strength and 1500 MPa of compressive strength. (2) To achieve the integration of structure and lubricating function in material, we have successfully developed Ni3Al intermetallics matrix self-lubricating composites, which possess favorable mechanical strength (compressive strength > 40 MPa at 1000 oC) and excellent tribological performance (friction coefficient < 0.35) at a broad temperature range from room temperature to 1000 oC. Moreover, we clarify the effects of the synergistic action of solid lubrications, reinforcement and microstructures on mechanical and tribological properties of the composites. (3) To meet the lubricating requirements above 1000 °C, we further developed ceramic matrix high temperature self-lubricating composites. ZrO2 matrix composites with addition of molybdenum disulfide and fluorides as lubricants exhibit low friction coefficient of 0.27 and high wear resistance of 1.54×10-5 mm3/Nm at 1000 oC. These works provide an inspiring clue for the design of high temperature self-lubricating materials, the establishment of high temperature tribological theory, and the potential applications.

Key words: high-temperature tribology, self-lubricating materials

0 200 400 600 8000.0

0.1

0.2

0.3

0.4

0.5

0.6

Fri

ctio

n c

oef

fici

ent

Temperature (C)

LICP-Nickel-Alloy-Based Composite

NASA-PS304 (NASA/TM-2009-215678)

Fig 1 The comparison of the friction coefficient of the produced high-temperature self-lubricating nickel-alloy-based composite with the notable NASA PS304 reported at different temperatures.

9

mailto:[email protected]


References

[1] Jinming Zhen, Fei Li, Shengyu Zhu, Jiqiang Ma, Zhuhui Qiao, Weimin Liu, Jun Yang*, Friction and Wear Behavior of Nickel-Alloy-Based High Temperature Self-Lubricating Composites Against Si3N4 and Inconel 718,

Tribology International, 2014, 75: 1-9.

[2] Fei Li, Jun Cheng, Zhuhui Qiao, Jiqiang Ma, Shengyu Zhu, Licai Fu, Jun Yang*, Weimin Liu*, A Nickel-Alloy-Based High-Temperature Self-Lubricating Composite with Simultaneously Superior Lubricity and

High Strength, Tribology Letters, 2013, 49: 573-577.

[3] Lingqian Kong, Qinling Bi*, Muyan Niu, Shengyu Zhu, Jun Yang, Weimin Liu, High-Temperature

Tribological Behavior of ZrO2–MoS2–CaF2 Self-Lubricating Composites, Journal of the European Ceramic

Society, 2013, 33: 51-59.

[4] Shengyu Zhu, Qinling Bi*, Jun Yang, Weimin Liu*, Qunji Xue, Ni3Al Matrix High Temperature

Self-Lubricating Composites, Tribology International, 2011, 44: 445-453.

Biography

Dr. Jun Yang is a full Professor in Lanzhou Institute of Chemical Physics. He gained PhD degree in Material Science and Engineering in 2005. He has published more than 100 journal papers that received more than 400 citations. His major research interests are in high-temperature tribology, tribology of nanomaterials, combustion synthesis of nanostructured materials, and powder metallurgical materials. He has published more than 100 journal papers in Adv Mater, Acta Mater, Scripta Mater, Intermetallics and Wear etal journals, also declared 26 China invention patents and 8 in which is authorized. He received an honor on Technology Invention Awards of Gansu Province (Class I) in 2009.

Notes

10


Tribological Behaviors of Self-lubricating Composites with Continues Lubricating Property in Wide

Temperature Ranges

Junhong Jia*


Chinese Academy of Sciences, Lanzhou 730000, China


Abstract

Lubrication and wear at high temperature is one of the key technical problems of advanced engine, aerospace crafts, nuclear technology, etc, as the high temperature lubricating materials directly affects the reliability and stability of high-tech. equipments. With the fast development of the of advanced engines, there emerges a urgent demand of self-lubricating composites with continues

lubricating properties in wide temperature range (RT~1000℃), which require the tribo-materials with

a stable lubricating performance adapt to different temperature changes. In present talk, I will discuss the selection of the matrix and lubricants for the high temperature lubricating and anti-wear materials as well as propose the material formulation with excellent mechanical and tribological properties at high temperature. Thereinto, understanding the mechanism responsible for the materials with continues lubricating properties and clarify the synergistic effect of multi-lubricants phases and tribochemical interaction. We show that with the change of temperature, the different compositions of friction layer and the transfer film are obtained, in order to maintain lubrication performance under different temperatures. The research results provide encouraging prospects for high temperature lubricating materials in aerospace field to solve the continuous lubricating problem in wide temperature range.

Key words: Self-lubricating composite, Continues lubricating property, Wide temperature range

Fig1. a- Comparison of the friction coefficients of the Licp-composites with that of NASA PM212 from RT to 1000 0C. b- Raman spectra of the worn surface of composites at different temperatures. c- XPS spectra of the worn surface of composites at different temperatures

Reference

[1] E. Liu, Y. Gao, W. Wang, X. Zhang, X. Wang, G. Yi, J. Jia, Effect of the synergetic action on tribological characteristics of Ni-Based composites containing multiple-lubricants. Tribology Letters., 2012, 47: 399-408

[2] E. Liu, W. Wang, Y. Gao, J. Jia, Tribological properties of Ni-based self-lubricating composites with addition of silver and molybdenum disulfide. Tribology International., 2013, 57: 235-241

[3]E. Liu, J. Jia, W. Wang, Y. Gao, Y Bai, Study on preparation and mechanical property of nanostructured NiAl intermetallic, Materials & Design, 53((2014) 596-601

0 200 400 600 800 1000 12000.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

Friction

coeffic

ien

t

Temperature (℃)

LICP-Ni3Al composites

NASA-PM212

0 200 400 600 800 1000 1200 1400

300℃

Ag2MoO

4

Raman shift(cm-1)

RT

500℃

700℃

0

5000

10000

15000

20000

25000

30000

35000

Inte

nsi

ty(a

rb u

nit

s)

Ag2MoO

4

Ag2MoO

4

Fe2O

3

NiO

Fe3O

4

360 362 364 366 368 370 372 374 376700

800

900

1000

1100

1200

Binding Energy(eV)

Inte

nsi

ty(a

rb u

nits

)

500C

300C

700C

Metallic Ag

Ag2MoO

4

20C

11


Biography

Dr. Junhong Jia is a full Professor in Lanzhou Institute of Chemical Physics, CAS, Group leader of Tribology on Metal-based lubrication materials. He received his B.Sc degree in 1996 in Applied Chemistry at Sichuan University in China and Ph.D. in physical chemistry in 2004 at Lanzhou institute of Chemical Physics, CAS. Subsequently, he moved to University of Wisconsin-Milwaukee and University of South Carolina as a postdoctoral researcher in tribology. He was awarded the “Hundred Talents Program” professor of Chinese Academy of Sciences in 2008. He has published more than 70 papers in international

journals such as Nano Letters，Carbon，Composites Science and Technology，Tribology Letters. He undertaken and completed more than 10 research projects including National Natural Science Foundation of China, Project from DOD and industry-business cooperation. The main research interests are focused on the novel self-adaptive high-temperature lubricating materials, functional nano-structured coatings, tribology of textured surfaces and their applications in engine and space technology.

Notes

12


Triboemission Imaging

Alessandra Ciniero, Julian Le Rouzic, Tom Reddyhoff*

Affiliations: Tribology Group, Imperial College London,

Exhibition Road, SW7 3AZ


Abstract

Triboemission is the term used to describe the emission of photons, electrons and other charged particles that occurs in sliding contacts. It has been suggested that this phenomena may play a crucial role in the formation of certain boundary lubricating films and in the degradation of lubricants of computer hard drives. Despite pioneering research, most notably by Nakayama and co-workers (e.g. [1]), there is still considerable uncertainty regarding the mechanisms that lead to triboemission. One of the main theories used to explain triboemission concerns the flow of electrons across the electric field generated between walls of cracks that are formed when certain surfaces become worn. However, little evidence has so far been provided to support this, largely because triboemission measurements are typically ensemble averages for the whole contact and contain no spatial information.

This presentation will outline a new imaging method to probe the origins of triboemission. The method involves performing scratch tests, under high vacuum conditions, while using a microchannel plate, coupled to a phosphor screen, to map the emission of electrons as the specimens become worn [2]. The spatial distributions of electrons obtained in this way suggest that emission occurs in discrete bursts caused by damage at specific locations on the specimen surface. This is confirmed when emission results are correlated with SEM images of the wear track to show that surface cracks are present at the locations of greatest emission. This provides evidence to support the theory that charge separation due to surface cracks is indeed a mechanism that can lead to triboemission of electrons. Furthermore it shows that this experimental technique can be used to monitor wear and the formation of surface defects in real time.

Key words: triboemission, electrons, wear

Fig 1 (left) Schematic diagram of experimental setup; (middle) SEM image of defect on specimen wear track; (left).Averaged map of friction stimulated electron emission obtained using microchannel plate equipment (acquired at same location on specimen as SEM image) .

References

[1] K. Nakayama, Triboemission of charged particles and resistivity of solids Tribology Letters, 1999.

[2] J. Le Rouzic, and T. Reddyhoff*. Spatially Resolved Triboemisison Measurements, Tribology Letters, 2014.

Video camera

e-

crack

e-

e-

High vacuum

Atmosphere

MCP

Phosphor screen

Video camera

1cm

13


Biography

Dr Tom Reddyhoff is a lecturer in the Department of Mechanical Engineering at Imperial Collage and a member of the Tribology Group. He also holds a five year Career Acceleration Fellowship from the UK Research Council. Before joining Imperial College, he completed a PhD in tribology at the University of Sheffield. Dr Reddyhoff ’s background is as a mechanical engineer, though the scope of his research has broadened to include the chemistry and physics of surfaces. He has specialised in developing a range of experimental methods, which he uses in combination with numerical modelling to analyse sliding interfaces. In addition to the work described in the abstract, Dr Reddyhoff ’s research addresses micro-electro-mechanical systems (MEMS) lubrication and elastohydrodynamic lubrication challenges. For his research, he has received the Tribology Trust Bronze Medal, a Tiaho Young Tribologist Award and two best paper awards.

Notes

14


Carbon-based coatings for potential space application:

challenge and possibility

Liping Wang*


Lanzhou 730000, China


Abstract

Solid lubricant coatings for space environment are widely used when conventional liquid lubrication is prohibited, either when the operating conditions become too severe (extreme temperatures, ultrahigh vacuum) or when a clean environment is required. While the well-known MoS2

lamellar solid lubricant is the most extensively used material today, carbon-based coatings are studied as potential candidates for a wear resistant material due to the outstanding tribology performance. However, the application of carbon-based coatings as solid lubricant in a vacuum or space environment presents significant challenges to the researchers. I will discuss the challenges and possibilities for space application of carbon-based coatings in present talk. Thereinto, understanding the mechanism responsible for their essential origins of low friction and prolonging the lifetime of carbon-based coatings in vacuum are two common bottleneck problems. We clarify the primary low-friction mechanism of carbon-based coatings, by investigating the effects of sliding velocity and vacuum pressure on the friction behavior of carbon-based coatings. By avoiding formation of carbonaceous transfer layers on the counterfaces, we show that the vacuum friction coeffcients can be lowered below 0.1 for a low hydrogenated carbon-based coating. Furthermore, we report the first demonstration of amorphous carbon film as a lubricant layer containing fluorine, silicon and hydrogen (a-C:H:F:Si)that exhibits low friction (~ 0.1), ultra-low wear rate (9.0 × 10-13 mm3 N-1 mm-1) and ultra-long lifetime (> 2 × 106 cycles) in high vacuum. The study results provide encouraging prospects in terms of space applications for carbon-based coatings.

Key words: Carbon-based coatings, space application, interface

Fig1. Interface structure of (a) SiC(001)/diamond(111), (b)Si3N4(001)/diamond(111), (c) Al2O3(001)/diamond(111), and (d) ZrO2(001)/diamond(001). Distributions of electron density of optimized (a) SiC(001)/diamond(111) and Al2O3(001)/diamond(111) are shown in upper right of the figure. The Wsep values in J/m2 are shown in the lower right of the figure.

Reference

[1] Longchen Cui, Zhibin Lu*, Liping Wang ,Toward low friction in high vacuum for hydrogenated diamond like

carbon by tailoring sliding interface, ACS Applied Materials & Interfaces, 5, 5589, 2013. [2] Longchen Cui, Zhibin Lu, Liping Wang *, Probing the low-friction mechanism of diamond-like carbon by

varying of sliding velocity and vacuum pressure, Carbon, 66.259, 2014

15


Biography

Dr. Liping Wang is a full Professor in Lanzhou Institute of Chemical Physics, CAS, Group leader of Tribology on Low-dimensional Materials, Deputy director of State Key Laboratory of Solid Lubrication. He spent few years (2008-2009) in Southampton University of UK, (2012) in Uppsala University in Sweden as a visiting professor. He has published more than 100 papers in international journals such as Carbon, APL, JMC, Acta Materialia, Tribology Letters, etc. that received more than 1000 citations. He undertaken and completed more than 15 research projects including National Natural Science Foundation of China, 863 projects and industry-business cooperation. The main research interests are focused on the micro/nano-structured functional films, novel solid lubrication coatings and their applications in engine, M/NEMS and space technology.

Notes

16


The governing of fullerene like structure on

the super low friction of carbon films

Junyan Zhang*



E-mail:[email protected]

Abstract

The hardness of carbon-based films is usually linked to the presence of sp3 C–C bonds and these films are called diamond-like carbon. However, the fullerene-like nanostructure hydrogenated carbon films exhibited high hardness and ultra high elasticity though having high sp2 hybrid carbon bonds, which implies that the hardness of carbon films is not only related to the content of sp3 hybrid carbon bonds, but also contributed by the microstructure. The reason may be due to the curvature structure of fullerene like structure, which extends the strength of graphite plane hexagon into three dimension space network, in turn, increasing the hardness and elasticity of carbon films. More importantly, the films demonstrated super low friction in air, meaning low friction solid lubricant with practical application value. With five- and seven-member ring as the representative of fullerene like structure, the fullerene like structure of the carbon films could be adjusted via the hydrogen content in the deposition gas sources. It was found that there is direct relationship between the fullerene like structure and the friction coefficient, the more fullerene like structure in the carbon film, the lower friction coefficient of the carbon film, indicating that the fullerene like structure could govern the friction behavior of the carbon film. Some applications of the fullerene like structure carbon films with super low friction are carried out to engine parts such as high pressure common rail fuel system to save energy and reduce emission. The results will expand and ensure the application of carbon films to most frictional parts of engine, and thus to save fuel and reduce emission much more.

Key words: Fullerene structure, super low friction, carbon film, solid lubrication

Fig1. The relationship between fullerene like structure and friction coefficient of the carbon films

Reference

[1] Qi Wang, Chengbing Wang, Zhou Wang, Junyan Zhang*, Deyan He, Fullerene nanostructure-induced

excellent mechanical properties in hydrogenated amorphous carbon，Applied Physics Letters, 91(14)141902,

2007

[2] Yongfu Wang, Junmeng Guo, Kaixiong Gao, Bin Zhang, Aimin Liang, Junyan Zhang*, Understanding the ultra-low friction behavior of hydrogenated fullerene-like carbon films grown with different flow rates of

hydrogen gas, Carbon, 77, 518–524, 2014

17


Biography

Dr. Junyan Zhang is Professor in Lanzhou Institute of Chemical Physics, CAS, Deputy director of R&D Center of Lubricating and Protecting Materials. He received bachelor degree in chemistry from Lanzhou University, China, in 1990, and MS and PhD from Lanzhou Institute of Chemical Physics in 1997 and 1999, respectively. He did postdoctoral research in University of California, Berkeley, University of Alabama, Rice University (2000-2005). He was a guest scientist at Argonne National Laboratory (2007). He now serves as editorial board member of Tribology Letters, Friction, Journal of Bio-&Tribo- Corrosion, Journal of Chemical Engineering and Materials, Journal of Tribology (in Chinese). He is now a member of International Energy Agency-Advanced Materials for Transportation Executive Committee. He has published more than 200 peer reviewed journal papers. The main research interests are focused on solid lubrication, graphene films as solid lubricant, the nanostructure carbon films with super low friction and the application in engine, solid-liquid synergy lubrication.

Notes

18


The Sliding Tribocorrosion Phenomena of Some

Ceramics and Metals in Seawater

Fengyuan Yan*, Yue Zhang and Ning Liu


Chinese Academy of Sciences, Gansu Province, Lanzhou 730000, P.R. China

*Corresponding email: [email protected]

Abstract

The ocean exploitation requires specialized equipments in which the friction component is one of the

key aspects. Friction and wear is the major cause leading to damage and failure of mechanical

equipment, while seawater corrosiveness adds to the complexity of damage of mechanical equipment

under sea environment. In seawater, the special medium in nature, frictional pairs will experience

abnormal accelerated damage. Tribocorrosion can be considered as a degradation process resulting

from the simultaneous action of mechanical wear and corrosion. As the most important tribomaterials,

ceramics and metals have been widely used in ocean equipments, such as bearings, valves, mooring

chains, etc. Up to now, due to limited facilities and methodology, it is infeasible to rationally explain the

abnormal damage of ceramic or metal frictional pairs under seawater. This significantly affects the

selection and design of materials suitable for frictional pairs working under seawater and retards the

study and development of relevant protective technology. In this work, the tribological behaviors of

several representative ceramics and 304 stainless steel with excellent corrosion resistance in seawater

were investigated. Some abnormal phenomena, interaction between wear and corrosion, and

mechanisms of damage in seawater for those materials are briefly reported.

The artificial seawater used in this study was prepared according to ASTM D 1141-98. The sliding

friction and wear behaviors of ceramics were evaluated using a ball-on-block reciprocating tribometer.

Sliding tests combined with in situ electrochemical measurements were performed with the

pin-on-block rotating tribometer for metallic specimens.

Fig.1 Friction curves of Al2O3/Al2O3 under dry friction and various aqueous conditions

Fig.2 SEM image of the tribochemical product on the worn surface of SiC in seawater

Fig.3 X-ray diffraction patterns of 304SS before and after tribocorrosion tests

As a summary of this work, some major results are obtained:

1. Normally, comparing with dry friction and pure water lubricating condition, seawater possesses

19


certain lubricity for ceramic/metal pairs and ceramic self-mated pairs (fig.1), but the anti-wear

properties of different pairs are very different. The wear behavior of Al2O3 self-mated pairs is

deteriorated in seawater, while the wear rates of Si-contained ceramics significantly improved.

2. Tribochemical products after friction tests with seawater lubricating are also found in this work. For

Al2O3 self-mated pairs, the tribochemical product on worn surface is estimated to be Al(OH)3. For

both Si-contained ceramics, Si3N4 and SiC, the silica gel formed on the worn surface is also

determined (fig.2). The experimental results also indicate that the formation of silica gel contributes

both the antifriction and antiwear performance for Si-contained tribopairs when sliding in seawater.

3. According to the suggestion of ASTM G119-2009, it is found, though the 304SS is a typical passive

metal, when sliding with Al2O3 pin under seawater lubricating condition, the considerable dynamic

corrosion of 304SS is much higher than its static corrosion. Among the total mass loss in seawater, the

ingredient due to the interaction between wear and corrosion takes a huge proportion. It means, not

only the friction can accelerate the corrosion but also the corrosion inversely accelerates the wear. The

synergistic effect between corrosion and wear is the most important reason of the accelerated damage

of tribopairs in seawater.

4. The surface hardening phenomenon of worn 304SS by friction in seawater is also found in this study.

The reason is mainly due to the phase transformation of Austenite to Martensite (fig.3) and the

formation of deformation twinning on the worn surface of 304SS. Because of the existence of

Martensite, the dynamic anticorrosive capacity of 304SS in seawater will be weakened. The damage

mechanism of 304SS during friction in seawater can be described by theory of deformation and

microscopic galvanic corrosion. In this work, the influences of speed, load, potential and chlorinity of

seawater on the proportion of Martensite formed by friction are also reported.

Biography

Fengyuan Yan is the professor and deputy director of State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences. He is also the group leader of Functional Materials Research in State Key Laboratory. His research interests are mainly on the study of Polymer Tribology, Development of Functional Materials and Tribological Testing Technique. He began his Ocean Tribology Research from 2007.

Notes

20


Initiation and Propagation of Rolling Contact Fatigue

Cracks

Amir Kadiric, Pawel Rycerz

Affiliations: Tribology Group, Department of Mechanical Engineering, Imperial College London

London SW7 2AZ, United Kingdom


Abstract

Rolling contact fatigue is a major failure mechanism in many tribological components including bearings

and gears. This talk first discusses the current understanding of rolling contact fatigue damage and the

mechanisms responsible for its onset and progression. Some typical examples observed in machine elements

are presented. The talk then builds on this by presenting recent research in the field designed to address some

of the gaps in the current understanding. This includes experimental work into initiation and propagation of

rolling contact fatigue cracks in bearing steels that uses a triple contact rig and a new sensor for crack

detection and monitoring. Parallels are made between the crack behaviour under rolling contact fatigue

conditions in hard steels and that observed in classical fatigue.

Key words: Rolling Contact Fatigue, Crack Propagation, Damage Accumulation

Figure 1: A typical example of a rolling contact fatigue crack generated in the present study

21


Biography

Dr Amir Kadiric is a Senior Lecturer in the Department of Mechanical Engineering and a member of Tribology Group. He is also Associate Director of the SKF University Technology Centre for Tribology at Imperial College.

He obtained his MEng degree in Mechanical Engineering followed by a PhD in Tribology from Imperial College in 2005. He subsequently took a post at SKF’s Engineering and Research Centre in the Netherlands where he worked on rolling bearing research, before returning to Imperial.

Dr Kadiric’s research focuses on efficiency and reliability of mechanical systems including: damage accumulation in rolling/sliding contacts through mechanisms of rolling contact fatigue, micro-pitting and scuffing; use of condition monitoring for contact damage prediction; frictional losses and efficiency in transmission systems; contact mechanics and surface coatings.

Notes

22


Formation mechanism and functionality of

nanostructured tribofilms of polymer composites

Ga Zhang*

State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics,



Abstract

Although many publications have shown the importance of tribofilms of polymer

nanocomposites, only quite few results provide information about their structure. On the other hand, the variety of film structures and functionalities is very large and many open questions still have to be solved. In the present work, the tribological properties of several formulated nanocomposites were investigated under dry and boundary lubrication conditions. It was identified that the incorporation of nanoparticles into conventional composites leads to striking effects on tribological properties. Our work has evidenced that thin tribofilms must play a key role in respect to tribological functionality of such systems. Surprisingly, the applied nanofillers are not known as typical solid lubricants, and therefore it is of fundamental interest to understand how the friction reduction works.

The thin and nano-structured tribofilms were characterized by analytical transmission electron microscopy. The method of target preparation with a DualBeam instrument (combination of focused ion beam (FIB) milling and imaging with a high resolution scanning electron microscope (SEM)) has been employed. The tribofilm compositions leading to desired tribological properties were determined. Moreover, an attempt was made to disclose the formation mechanism of the nanostructured surface films. Characterization of mechanical profiles of the tribofilm is of help towards a better understanding on the performance of the tribofilms. We did not only show the complicated nanostructure of the tribofilms, but also provided an explanation of their lubrication functionality by investigating their miro/nano-mechanical properties.

Keywords: Tribofilm; Polymer; Nanocomposite

23


Biography

Prof. Ga Zhang’s research interests are in the fields of polymer tribology and polymer composites. He obtained his PhD degree in 2005 from the Technical University of Belfort-Montbeliard in France. From 2007 to 2014 he worked at the Institute for Composite Materials (IVW) in Germany. Prof. Zhang performs research and development along the whole value chain of polymer composites, starting from polymer formulations, compounding and thorough characterizations. He acquired and guided various research projects, e.g. fundamental projects financed by German Research Foundation and industrial projects in direct bilateral cooperation with international companies. At the beginning of 2014 he was selected for the “Recruitment Program of Global Experts” and afterwards he joined the Lanzhou Institute of Chemical Physics. Currently Prof. Zhang is serving on the editorial boards of two international journals, i.e. Industrial Lubrication and Tribology, and Journal of Tribology Research.

Notes

24


A Multi-Physics Platform for Tribological Modelling

Daniele Dini*

Affiliations: Tribology Group, Department of Mechanical Engineering, Imperial College London,

South Kensington Campus, Exhibition Road, London SW7 2AZ, UK


Abstract

Macro-scale tribological phenomena are governed by events and mechanisms which find their roots at the smaller scales, even more so in environments where mechanical and chemical effects are intimately coupled. For example, nano-scale thermal and particle emission events control the formation of antiwear additive films and oxidation; surface damage, such us crack initiation results from the accumulation of strain at dislocations level; corrosion events are triggered and controlled by molecular interactions. The key challenge addressed in this talk is the need for the development of robust methodologies for the integration of the skills and modelling techniques developed by the applicant at different scales (see e.g. [1-5]) to capture physical, chemical and mechanical processes and interactions across the scales via a multi-physics modeling strategy (see Fig. 1).

Keywords: multi-physics, modelling, coupling

Figure 1. Tribology Modelling Roadmap showing the need for models at different scales, the requirement to pass information across the scales, and the importance of a multi-disciplinary approach – the key mechanisms can only be captured linking techniques, theories and analysis tools from Physics, Chemistry, Material Science and Biology, with advanced modelling and simulation techniques which make use of state-of-the-art Computing.

References

[1] Bodnarchuk, M.S., Heyes, D.M., Dini, D., Chahine, S., Edwards, S., “The role of deprotonation free-energies in pKa prediction and molecule ranking”, J. Chem. Theory Comput. (2014), 10(6), pp 2537–2545.

[2] Medina, S., Dini, D., “A numerical model for the deterministic analysis of adhesive rough contacts down to the nano-scale”, Int. J. Solids Struct. (2014), 51(14), pp. 2620–2632.

[3] Gattinoni, C., Heyes, D.M., Lorenz, C., Dini, D., “Traction and non-equilibrium phase behaviour of confined sheared liquids at high pressure”, Phys. Rev. E, 88, (2013), 052406.

[4] Bertocchi, L., Dini, D., Giacopini, M., Fowell, M.T., Baldini, A., “Fluid film lubrication in the presence of cavitation: a mass-conserving two-dimensional formulation for compressible, piezoviscous and non-newtonian fluids”, Tribol. Int., 67, (2013), pp. 61–71.

[5] Scaraggi, M., Carbone, G., Persson, B.N.J., Dini, D., “Mixed lubrication in soft contacts: A novel homogenized approach. Parts I and II”, Soft Matter, 7, (2011), 10395.

25



Biography

Dr. Daniele Dini is a Reader in Tribology and Deputy Head of the Tribology Group at Imperial College. His main research interests are in the application of advanced modelling strategies to tribology and structural integrity with a focus on (i) research on fundamental and theoretical aspects of molecular dynamics, fluid and solid mechanics, and biomechanics, (ii) development of numerical tools and software for the solution of advanced tribological, biomechanical and structural problems, and (iii) development of multi-physics solvers and multi-scale coupling strategies. He is the Assistant Editor of the International Journal of Solids and Structures and sits on a number of national (UK Tribology, IMechE, IET) and international advisory and editorial boards (Tribology International, Fracture and Structural Integrity). Dr. Dini has published over 120 papers in international journals and presented a number of invited talks and contributions at conferences in the areas of tribology, chemical physics, soft matter physics, fatigue and fracture, fundamentals of solid mechanics, and biomechanics. He is the recipient of four best paper awards and many other personal awards.

Notes

26


Graphene Based Lubricant Materials: Preparation and

Application

Jinqing Wang*

State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy

of Sciences, Lanzhou 730000, People’s Republic of China

[email protected]

Abstract

Graphene, a two-dimensional atomic thin layer of carbon nanostructure, has emerged as an ideal candidate for the basic building block of future micro- /nano-electromechanical systems (MEMs/NEMS) and other fields. Aside from its well-known merits, such as outstanding thermal conductivity, electronic properties, and mechanical behaviors, graphene is also expected to have good tribological performance for its derivation from self-lubricating graphite. However, up to now, no systematic works were referred to. In our group, graphene and graphene-based materials were prepared and their tribological behaviors were investigated in details. (1) MEMs/NEMS are generally made of different materials with complex shapes and solution deposition is more suitable for the preparation of graphene related films thereon. Therefore, a series of graphene based films have been prepared on different substrates and the tribological tests demonstrated that some films exhibited excellent friction reduction and wear resistance behaviors. (2) Fluorinated graphene (FG) is a novel fluorocarbon compound and derivative of graphene. It inherits the properties of both graphene and fluorographite (FGi), possessing high Young’s modulus, chemical inertness, temperature resistance and other related novel characteristics. Yet there is no easily applied method for larger-scale preparation of isolated FG nanosheets mostly due to the intrinsic technological difficulties or undesirable reagents used in the experiment, and this hinders its further applications. In our recent research, some routes have been explored to synthesize FG through simple exfoliation processes or hydrothermal fluorination. Then, its tribological performance as an additive in polyalphaolefin oil was explored. As a result, the effects of load and frequency on the tribological properties of FG-based oil suggested that the FG additives could enhance the bearing capacity of base oil, and deeper work is in progress.

Reference

[1] Y. J. Mi, J. Q. Wang, Z. G. Yang, et al., RSC Advances, 2014, 4 (75), 39743-39750.

[2] J. F. Ou, J. Q. Wang, S. Liu, et al., Langmuir, 2010, 26(20): 15830-15836.

[23 J. F. Ou, Y. Wang, J. Q. Wang, et al., J. Phys. Chem. C, 2011, 115(20): 10080-10086.

[4] P. W. Gong, Z. F. Wang, Z. J. Fan, et al., Carbon, 2014, 72, 176-184.

[5] Z. F. Wang, J. Q. Wang, Z. P. Li, P. W. Gong, et al., Carbon., 2012, 50, 5403-5410.

27



Biography

Dr. Jinqing Wang is a Professor in State Key Lab of Solid Lubrication, Lanzhou Institute of Chemical Physics under the name of ‘‘Top Hundred Talents’’ Program of Chinese Academy of Sciences. He got his PhD in 2004 in Lanzhou Institute of Chemical Physics. He spent two years (2005–2007) in the Department of Applied Science for Electronics and Materials, Kyushu University, Japan as a postdoctoral research associate supported by Japan Society for the Promotion of Science (JSPS) Postdoctoral Fellowship. He has published more than 100 journal papers. His research interest mainly focuses on the micro/nanostructured functional materials (ultrathin lubricating films, graphene, fluorographene, mesoporous bioactive glasses, etc.) for applications in lubrication, supercapacitors, and biomedical fields.

Notes

28


Biomimetic super-lyophobic and super-lyophilic

materials applied for oil/water separation: A new

strategy beyond nature

Zhiguang Guo*




Abstract

Oil spills and industrial organic pollutants have induced severe water pollutions and threatened every species in ecological system. To deal with the oily water, special wettability stimulated materials have been developed in the past decade to separate the oil-and-water mixtures. Basically, synergies between the surface chemical composition and surface topography are commonly known as the key factors to realize the opposite wettability to oils and water and dominate the selective wetting or absorbing of oils/water. Herein, I will mainly focus on the developments of materials with special wettability in oil/water separation applications where they can be classified into four kinds as follow: superhydrophobic and superoleophilic materials, superhydrophilic and under water superoelophobic materials, superhydrophilic and superoleophobic materials, smart oil/water separation materials with switchable wettability. These materials were already successfully applied into the separation of oil-and-water mixture: from simple oil/water layered mixture to oil/water emulsions (including oil-in-water emulsions and water-in-oil emulsions), and from non-intelligent materials to intelligent materials. Meanwhile, they also exhibited high absorption capacity or separation efficiency and selectivity, simple and fast separation/absorption ability, excellent recyclability, economical efficiency and can outstanding tolerance of harsh conditions. Then, theoretical considerations are proposed to understand the physical mechanisms of oil/water separation process. Finally, some challenges and promising breakthroughs in this field are also discussed. It is expected that special wettability stimulated oil/water separation materials can achieve industrial-scale production and be put into use for oil spill and industrial oily water treatment in the near future.

Key words: Biomimetic; Wettability; Oil-water separation

Fig. 1 (a) Optical images of superhydrophobic fabric/sponge from the in situ growth of Group VIII and IB

29


metal/metal oxide nanoparticles.The inset images in the upperright-hand corner of each panel are images of the static water droplets (5 μL) (b) Relationship between the proportion of weight increase ((mAg − m0)/m0) and the Ag+ concentration. The images of CAmodified with both n-octadecylthiol (upper left) and perfluorodecanethiol (lower right) at different concentrations are presented near the curve. (c) Photographs of the fabric-based oil/water separation process of water and chloroform. The water was dyed with Methylene Blue for clear observation.

Reference

[1] B. Wang, J. Li, G. Y. Wang, W. X. Liang, Y. B. Zhang, L. Shi, Z. G. Guo*, W. M. Liu. Methodology for robust superhydrophobic fabrics and sponges from in situ growth of transition metal/metal oxide nanocrystals with thiol modification and their applications in oil/water separation. ACS Appl. Mater. Interfaces. 2013, 5, 1827. [2] B. Wang, Z. G. Guo*. pH-responsive bidirectional oil-water separation material. Chem. Commun. 2013, 49, 9416. [3] H. Zhu, Z. G. Guo*, W. M. Liu. Adhesions of Superhydrophobic Surfaces. Chem. Commun. 2014, 50, 3900-3913. [4] B. Wang, Z. G. Guo*, W. M. Liu. pH-responsive smart fabrics with controllable wettability in different surroundings. RSC Adv 2014, 4, 14684-14690. [5] B. Wang, Y. B. Zhang, W. X. Liang, G. Y. Wang, Z. G. Guo*, W. M. Liu. A simple route to transform normal hydrophilic cloth into a superhydrophobic-superhydrophilic hybrid surface. J. Mater. Chem. A 2014, 2, 7845. [6] J. W. Zeng, Z. G. Guo*. Superhydrophilic and underwater superoleophobic MFI zeolite-coated film for oil/water separation. Colloids and Surfaces A: Physicochemical and Engineering Aspects 2014, 444, 283-288.

Biography

Dr Zhiguang GUO, received his PhD from Lanzhou Institute of Chemical Physics (LICP), Chinese Academy of Sciences (CAS) in 2007. After that, he joined Hubei University. From Oct 2007 to Aug 2008, he worked in University of Namur (FUNDP), Belgium, as a post-doctor. From Sep 2008 to Mar 2011, he worked in Funds of National Research Science (FNRS), Belgium, as a “Charge de Researcher”. During Feb 2009 to Feb 2010, he worked in Department of Physics, University of Oxford, UK, as a visiting scholar. Now he is a full professor in LICP financed by “Top Hundred Talents” program of CAS. Till now, he has published more than 80 papers about the interfaces of Materials and incited more than 1500 times.

Notes

30


Synovial Fluid Lubrication of Artificial Joints

Philippa Cann* and Connor Myant

Affiliation: Tribology Group, Department of Mechanical Engineering

Imperial College London


Abstract

Artificial implants offer an engineering solution to the loss of joint function due to trauma or disease. The number of procedures has rapidly increased over the last 50 years; for example there are over 90,000 total hip replacements yearly in the UK alone. However there are significant clinical concerns over the use of 2nd generation Metal-on-Metal (MoM) hip joints as these have been associated with the development of periprosthetic tissue lesions. The UK National Joint Register reports higher than expected revision rates for LHMoM joints (>5%) compared to 2% for conventional MoM hips. Implant failure is often linked to high levels of metal ions in the blood and severe implant wear often due to edge loading. The reasons for increased wear and failure are complex and include design, metallurgy, implantation (particularly cup position) and patient factors. The patient factors include gait, lifestyle and synovial fluid (SF) composition. Most studies of hip joint tribology have focussed on material and design aspects usually tested under optimised gait conditions, whilst research into fundamental mechanisms of synovial fluid lubrication and the effect of patient SF composition on implant wear has been ignored. Artificial hips are lubricated by periprosthetic SF which reforms in the synovial cavity after the operation. Healthy and periprosthetic SF contains a complex mixture of large and surface active molecules including proteins, phospholids and hyaluronan. The lubrication behaviour of SF is therefore complex and not described by simple fluid models and this has significant implications for the development of suitable screening methods and predictive models for implant lubrication. The talk will present some of the background to the MoM problem and recent research into the mechanisms of SF lubricant film formation and the implications of these findings for our understanding of implant tribology.

Key words: artifical hip joints, synovial fluid, lubrication

References

1. Myant, C.W., Cann, P. The effect of transient conditions on synovial fluid protein aggregation lubrication (2014) Journal of the Mechanical Behavior of Biomedical Materials, 34, pp. 349-357

2. Myant, C., Cann, P. On the matter of synovial fluid lubrication: Implications for Metal-on-Metal hip tribology (2014) Journal of the Mechanical Behavior of Biomedical Materials, 34, pp. 338-348

3. Myant, C., Cann, P. In contact observation of model synovial fluid lubricating mechanisms (2013) Tribology International, 63, pp. 97-104.

4. Fan, J., Myant, C., Underwood, R., Cann, P. Synovial fluid lubrication of artificial joints: Protein film formation and composition (2012) Faraday Discussions, 156, pp. 69-85.

5. Myant, C., Underwood, R., Fan, J., Cann, P.M. Lubrication of metal-on-metal hip joints: The effect of protein content and load on film formation and wear (2012) Journal of the Mechanical Behavior of Biomedical Materials, 6, pp. 30-40.

31


Biography

Dr Philippa Cann is a Principal Research Fellow in the Tribology Group; her main research interests are in experimental studies of the lubrication mechanisms of complex fluids and the application of advanced experimental methods to the study of bio-lubrication. Dr Cann’s first degree was in Chemistry and her PhD was in Tribology. Dr Cann has published over 130 journal papers in the field. In 2007 Dr Cann established the Biotribology Group with a focus on implant tribology, articular cartilage damage mechanisms and soft contact lubrication and in September 2011 organised the 1st

International Conference on Biotribology (ICoBT) which was held at Imperial College. The Conference brought together over 200 delegates from a wide cross-section of Biotribology research. A 2nd ICoBT meeting was held in Toronto in 2014 with a 3rd planned for 2016 at Imperial College.. In 2013 Dr Cann was joint winner of the SAGE Best Paper Prize in 2012 for a paper published in Journal of Engineering in Medicine and was awarded the Tribology Trust Silver Medal in 2004. Dr Cann is the Editor-in-Chief of Tribology International and Co-Editor of Biotribology launched in August 2014

Notes

32


3D printing biomimetic lubricating interface

Xiaolong Wang*




Abstract

Three-dimensional (3D) printing has emerged as a powerful additive manufacturing technology for creating sophisticated, bespoke and low-cost materials/devices that, if not impossible to construct, were traditionally made using complicated procedures and facilities. Despite the capability of completely changing the way that materials are turned into devices, which in my opinion is the most important reason that it is attracting more and more attentions from both scientific and engineering fields, there are still challenges for its practical applications in lots of fields except prototyping because of the limitations of printable materials. We addressed the challenge by integrating initiator into 3D printing materials to enable genetic post-printing surface-initiated modification to make functional structural materials[1-3]. Taking advantage of 3D printing and surface-initiated ATRP (Fig. 1), the feasible initiator-integrated 3D printing (i3DP) makes 3D printed complex architectures possible for nearly any desired surface modification for various applications, for examples from superhydrophilic to superhydrophobic, from biocompatible to antibacterial, and even metallic. These results provide encouraging prospects in terms of biomimetic lubrication for i3DP, where both complex 3D gradient architecture and surface chemical composition are crucial. Taking shark skin and articular cartilage as examples, I will discuss the challenges and possibilities for creating biomimetic lubricating interfaces using 3D printing in the presentation.

Key words: 3D printing, biomimetic lubricating interface, surface modification

Fig1. Schematic illustration of i3DP for functional structural materials.

Reference

[1] Xiaolong Wang, Xiaobing Cai, Qiuquan Guo, Tengyuan Zhang, Brad Kobe, Jun Yang*, i3DP, a robust 3D

printing approach enabling genetic post-printing surface modification, Chem. Commun., 49, 10064, 2013. [2] Xiaolong Wang, Qiuquan Guo, Xiaobing Cai, Shaolin Zhou, Brad Kobe, Jun Yang*, Initiator-integrated 3D

printing enables the formation of complex metallic architechtures, ACS Appl. Mater. Interfaces, 6.2583, 2014. [3] Qiuquan Guo, Xiaobing Cai, Xiaolong Wang*, Jun Yang*, “Paintable” 3D printed structures via a post-ATRP

process with antimicrobial function for biomedical applications, J. Mater. Chem. B, 1, 6644, 2013.

33


Biography

Dr. Xiaolong Wang is a full Professor in Lanzhou Institute of Chemical Physics (LICP), CAS. He joined the LICP at 2007 when he got his PhD in the major of polymer chemistry and physics at Lanzhou University. During his stay in LICP, he spent a year (2010-2011) in Hong Kong Polytechnic University as a Research Associate and two years (2011-2013) in University of Western Ontario (Canada) as a visiting professor. His research interests are biomimetic lubrication, 3D printing, functional soft materials, and printing electronics. He has published more than 50 papers in peer-reviewed international journals including Adv. Mater., Angew. Chem. Int. Ed., Chem. Commun., and J. Mater. Chem., etc., which have already got more than 1000 citations.

Notes

34


Interfacial Friction Control

Yang Wu, Qiangbing Wei, Guoqiang Liu, Feng Zhou*


18 Middle Tianshui Road, 730000


Abstract

Tissues, organs and cartilage etc are constituent of soft matters that usually provide extremely low friction. For example, the vitreous body of eyes, the organs of human body and synovial joints, such as hip, knee and finger joints. Also these organs excrete hydrophilic biopolymers with ultralow „coefficients of friction‟ onto their interface to improve their mobility in water environment. Their natural counterparts — hydrophilic biopolymers — are usually unable to react to external stimuli and therefore unable to alter their friction. Artificial hydrogels, which trap copious quantities of water molecules inside three-dimensional polymer networks also have low frictional coefficients and have been targeted for use as biomimetic artificial low friction materials. Most interestingly, the hydration state of an artificial hydrogel can be adjusted if the hydrogel was made of responsive polymer and so its frictional behavior can be tuned on demand. In this talk, I will show few examples of control over interfacial friction by changing a single external stimulus and further stepwise switching from ultralow to high friction states by changing multiple stimuli. This talk will also outlines the state-of-the-art research on the controllable interfacial friction on both solid/solid surfaces and solid/liquid surfaces regulated by external stimuli, which include solvent, electrolyte, pH, thermal, light, electric potential, magnetic, etc. By applying external stimuli, those sensitive materials react and render the changes in surface chemistry, interfacial charge, and/or topography, and then induce the changes of friction coefficient. In the similar way, controllable fluid-solid friction, i.e. boundary slippage vs non-slippage can also be achieved by reversibly generating gas lubricating film at the interface or changing the fluid-solid adhesion with physicochemical methods.

Key words: soft matter, lubrication, friction control

Fig 1 (left)Tuning friction coefficient with conformational change of surface grafted polymer brushes triggered by ionic pairing interaction; (right) COF can be reversibly switched in three steps by the sequential regulation of pH and testing temperature.

Reference

[1] Yang Wu, Xiaowei Pei, Xiaolong Wang,* Yongmin Liang, Weimin Liu, and Feng Zhou*. Biomimicking yet

beyond Fish Skin: Multiply Regulating Friction with Responsive Hydrogels, NPG Asia Materials, 2014

35


Biography

Dr. Feng Zhou is a full Professor in Lanzhou Institute of Chemical Physics, CAS and Deputy director of State Key Laboratory of Solid Lubrication. He gained PhD in 2004 and spent three years (2005-2008) in the Department of Chemistry, University of Cambridge as a research associate. He has published more than 200 journal papers that received more than 5800 citations and has the H-index 44. His research interests include the surfaces/interfaces of soft matters, drag-reduction and antibiofouling, and biolubrication. He has gained a number of awards including “Young Scholar Award in Tribology”, Chinese Engineering Institute, 2009; “National Young Excellence” Award from National Science Foundation of China, 2011; “Young Scholar Award of Chemistry”, Chinese Chemical Society, 2011 and “Outstanding Youth Award” of International Society of Bionic Engineering, 2013.

Notes

36

Documents

Joint workshop on Frontier in Tribology between … workshop on “Frontier in Tribology” between ... Solid Lubrication and Imperial College London Program 22 ... Handbook of Space