The Dynamics of Nanolubricants within a Tribological Contact

Lead Research Organisation: Imperial College London
Department Name: Dept of Mechanical Engineering

Abstract

This proposal concerns research into the functioning mechanisms and effectiveness of nanoadditives (NAs) in lubricated contacts. This particular application is chosen here because NAs, such as molybdenum disulphide, fullerenes and dispersed PTFE (Teflon), are being increasingly considered for use in formulation of advanced lubricants. Lubricant nanoadditives (NAs) are broadly defined as nanoparticles (NPs) that are deliberately added to a lubricant to obtain desired properties. Greener, more efficient lubricants can only be developed through thorough molecular understanding on lubricating mechanisms under realistic working conditions. Currently, mechanisms of how NP interacts with lubricant contacts are not known. Previous research either infers behaviour from indirect methods, or only correlates macroscopic responses, such as friction & wear, to macroscopic control variables such as load, speed, etc. The proposed work is aimed at radically change the research landscape by introducing methods to directly observe NPs' behaviour, in the nano-scale, in and around the lubricated contact.

The proposed work will focus on the dynamics and behaviour of NPs around and within tribological contacts, and their effectiveness as NAs. The overall aim of the proposed research is to understand the interactions between NPs, base oil and the rubbing surfaces and how these influence NPs' lubricating properties and the rheology of a formulated lubricant. The effect of substrate properties and NP surface properties, NPs' size and the relative velocity of the two rubbing surfaces will also be explored. The proposed research constitutes a vital step towards exploring and understanding the lubricating mechanism of NPs. Various researchers have hypothesised different lubricating mechanisms when NPs is added in lubricant and the proposed work provide results that could be used to directly verify simulation works. The findings will contribute to improved understanding of the fundamental mechanisms of lubrication and the role of NPs in forming boundary films. The research will also contribute to improved strategies for wear and friction reduction both in lubricant formulations and engineering components design.

The study will develop advanced in-contact analytical techniques to allow in situ observation of the dynamics of NPs under confined conditions. A test apparatus for this purpose will be constructed, and advanced, single particle/molecule level fluorescence techniques will be applied to track NPs in-situ in very thin film lubricated contacts under engineering conditions. This will allow correlation of macroscopic observables, such as frictional force and wear damage, to nanoscopic/molecule level behaviour, such as self-assembly and adsorption-desorption kinetics of nanoadditives. It should be noted that the experimental approaches that will be devised during the research programme are generic and will have applications to several other engineering fields such as multiphase flow and microfluidics.

Planned Impact

The proposed work is aimed at introducing fluorescence imaging techniques, as a means to directly observe nanoparticle (NP) behaviour, at the nanoscale, in and around lubricated contacts. This capability augments traditional tribological research methods, which mostly depend on observations of macroscopic properties, and indirect deduction of the underlying mechanisms. Direct observation of NPs will provide definitive information about the mechanisms of how nano-additives (NAs) interact with lubricants. For example, in a proposed experiment, this method is going to be used to measure the motion of NPs and correlate this with the flow properties of specific lubricants.

1. Academic Impact

There are two areas of potential impact. First is methodological. Both tribologists and researchers in other areas will benefit because the fluorescence technique is general, and can be used to study NPs beyond just lubricant systems. The specific experimental platform and associated software methods being developed are versatile and should be applicable to areas such as, and not limited to, fluid flow, nanofluidics, adsorption-desorption kinetics, and molecular self-assembly. In fact, they should be useful to any research where nanometer scale phenomena are of interest, and where surface interactions dominate.

Secondly, the proposed studies will provide detailed information on the behaviour of NPs and other additives in lubricants. This can be used to understand the microscopic mechanisms that cause the macroscopic phenomena of friction and wear. Thus researchers in tribology, especially those interested in elastohydrodynamic lubrication, boundary lubrication, and additive interactions, will find such knowledge useful. The experimental quantities measured in the proposed experiments, for example, diffusion coefficients of NPs, will provide direct inputs to theoretical models and simulations of NAs and boundary lubrication.

2. Economic and societal impacts

The lubricant and additive industries invest a great deal of money and effort into additive and lubricant research and development. They should directly benefit from this research, as should lubricant users such as the automobile and machine component industries.

The proposed work will provide scientific information, as well as a new method to study the fundamental lubrication mechanisms by which nanoadditives act. This information will help develop more efficient lubricants, both in terms of lower friction and also reduced component wear. It is especially important at present to reduce friction and save energy so as to limit consumption of fossil fuels and thus CO2 emissions.

At the same time, the personal care industry should also benefit from the proposed work. Many personal care products, such as hand creams, lipsticks and toothpastes contain particles that can be tracked and observed directly by fluorescence techniques. The success of these products will partly depend on how these particles interact with human skin/teeth. Better understanding of relevant NPs can lead to better product designs.

Heat transfer is a major issue in enabling smaller and more powerful processors in the semi-conductor industry. Nano-fluid, a fluid that contains special nanoparticles, has been shown to have high potential in facilitating heat-transfer. The properties of nano-fluids that allow efficient heat transfer can be studied with the experimental platform developed.

Finally, the tribology group at Imperial College London is already collaborating with leaders in a wide range of industries including SKF, Infineum, Ford, Tata Motors and Unilever. These existing relationships will allow any scientific and methodological results from this proposal to disseminate to industry and create meaningful impact in an efficient manner.

Publications

10 25 50
 
Description Nanolubricants consists of nanoadditives (NAs), additives that are particles < 1 micron, dispersed in a base oil. This project concerns the use of NAs in a tribological contact, where the two rubbing surfaces are separated by a layer of lubricant film (full film lubrication). For these additives to work, they need to get into the rubbing contact. The project shows that dispersion of NAs in oil is challenging. It shows that the flow field at the inlet governs the entrance of NA to the contact. This may explain why NAs seem more effective in boundary lubrication regime (where there is minimal lubricant between rubbing surfaces).

We have found that in the full-film lubrication condition, where the two rubbing surfaces are completely separated, NA is likely to be entrained into the contact as clusters. Since the NAs used in this project are fluorescent, they are used as sensors for tracking the flow of lubricants in the contact in situ. We have shown that at low concentration, NA does not affect lubricant flow. Tracking these NAs shows that the flow of lubricant changes with pressure and confirmed results from the literature. Our work supports that these fluorescence NAs can be very powerful sensor for determining fluid flow, which is crucial to durability of machines.

Fluorinated base oils are used in applications where low vapour pressure and contamination are concerns. They are however very hard to additised, hence it is challenging to improve their tribological performance. We have incorporated various carbon based and PTFE based nanoadditives into fluorinated base oils. The focus is on mixed lubrication regime where there is insufficient lubricant to separate the two rubbing surfaces completely and some contact between the two surfaces are unavoidable. Additives are needed to reduce friction, and hopefully also to protect the surface. In an engineering conditions where the lubricants are constantly stirred, suspensions are formed. Our results show that the effectiveness of the NAs would depend on the degree of aggregation of the NAs and its ability to form protective film on surfaces. They also suggests that the geometry of the additives may be important.
Exploitation Route The project has highlighted technical difficulties that one needs to overcome into to obtain better understanding of nanoparticle dynamics in oil at high flow speed. The lubricant flow tracking method developed can be applied to other lubricants. The results can also be used to guide design of nanoadditives in the mixed lubrication condition.
Sectors Aerospace, Defence and Marine,Chemicals,Manufacturing, including Industrial Biotechology,Transport,Other

 
Description The work has attracted a lot of attention and has increased the industry awareness of the possibility of using nanoadditives in improving the performance of lubricant that may be hard to additised. Lots of discussion with the industry, specially lubricants, additives, and energy sectors, has been resulted. This concept has been taken up by a machine company which they intend to develop a lubricant that better fulfill their needs.
First Year Of Impact 2019
Sector Manufacturing, including Industrial Biotechology
Impact Types Economic

 
Description Afton 7-2013 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact A talk and a lab tour have been given and both have sparked questions and discussion afterwards.

We were asked to provide more information on our research activities and possible collaboration mechanisms
Year(s) Of Engagement Activity 2013
 
Description BASF 2-2013 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact A talk and a lab tour have been given and both have sparked questions and discussion afterwards.

We were asked to provide more information on our research activities and possible collaboration mechanisms.
Year(s) Of Engagement Activity 2013
 
Description BP 11-2012 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Professional Practitioners
Results and Impact A talk and a lab tour have been given and both have sparked questions and discussion afterwards.

We were asked to provide more information on our research activities and possible collaboration mechanisms
Year(s) Of Engagement Activity 2012
 
Description Baker Hughes 9-2013 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact A talk and a lab tour have been given and both have sparked questions and discussion afterwards.

We were asked to provide more information on our research activities and possible collaboration mechanisms
Year(s) Of Engagement Activity 2013
 
Description Company visit_EV_20190626 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Professional Practitioners
Results and Impact A presentation and discussion session that showcase our research on nanoadditives and lubricant flow to engineer from all parts of the company. It sparked a very lively discussion and follow up discussions were discussed.
Year(s) Of Engagement Activity 2019
 
Description Discussion with CRRC_20190329 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Industry/Business
Results and Impact Presentation and discussion of the group activities which are relevant to future transportation needs. Lots of questions were entertained.
Year(s) Of Engagement Activity 2019
 
Description Discussion with Edwards Vacuum (09/05/2016) 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Industry/Business
Results and Impact A discussion held to share our research findings and explore common research interest, An understanding was established and the participants requested more info.
Year(s) Of Engagement Activity 2016
 
Description Discussion with Lubrizol_20190317 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Industry/Business
Results and Impact A presentation, discussion and lab tour to highlight the research activity in the group. And NDA was signed as a result to facilitate further discussion.
Year(s) Of Engagement Activity 2019
 
Description EM 9-2012 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact A talk and a lab tour have been given and both have sparked questions and discussion afterwards.

We were asked to provide more information on our research activities and possible collaboration mechanisms
Year(s) Of Engagement Activity 2012
 
Description Evonik - 3 March 2016 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Industry/Business
Results and Impact I held discussion with the technical manager from Evonik about potential collaborations. I showed him my research through a short presentation and we held discussed on how I can apply my research knowhow into questions that Evonik interested in. We are identified areas of common interest. He will passed on the information he has received and we shall hold further discussions in the near future.
Year(s) Of Engagement Activity 2016
 
Description Evonik 11-2013 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Professional Practitioners
Results and Impact A talk and a lab tour have been given and both have sparked questions and discussion afterwards.

We were asked to provide more information on our research activities and possible collaboration mechanisms
Year(s) Of Engagement Activity 2013
 
Description Exxon Mobil discussion - 9th Aug 2015 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Industry/Business
Results and Impact A presentation was provided on our research and a discussion was held on how we can help the company with their area of interest
Year(s) Of Engagement Activity 2015
 
Description Gordon conference (27-30/06/2016) 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Schools
Results and Impact A presentation of research findings to researchers in tribology, which sparked questions and discussion afterwards.
Year(s) Of Engagement Activity 2016
 
Description Hoerbiger - 1st April 2015 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Industry/Business
Results and Impact Presentation on our research work was given. Discussion on potential collaboration was held.
Year(s) Of Engagement Activity 2015
 
Description IMechE Event - 50th Anniversary of Jost Report 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact The event was for celebration of 50th anniversary of Jost Report. We held a stand to showcase our research with posters, powerpoint slide shows and also held general discussion with participants. We have made contacts with potential sponsors.
Year(s) Of Engagement Activity 2016
 
Description Olen - 2nd Oct 2015 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Industry/Business
Results and Impact A presentation on our research work was given. We discussed on potential collaborations
Year(s) Of Engagement Activity 2015
 
Description Oleon - 19th March 2015 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Industry/Business
Results and Impact Presentation was provided on our research work and discussion was held about potential collaborations
Year(s) Of Engagement Activity 2015
 
Description Presentation and discussion with company (EV)_20190205 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Industry/Business
Results and Impact A 3 hour presentation and discussion that gave an overview on our latest results on nanoadditives and how that can be applied in relatively inert lubricant. The company showed strong interest in the findings.
Year(s) Of Engagement Activity 2019
 
Description Presentation and discussion with company on high speed bearing_20190828 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Industry/Business
Results and Impact A presentation and a lively discussion on our research in nanoadditives and how this can be applied to high speed bearing.
Year(s) Of Engagement Activity 2019
 
Description SKF lab visit - 9th June 2015 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Industry/Business
Results and Impact A presentation of our research and also a lab visit were provided. SKF showed interest in our work and request more information.
Year(s) Of Engagement Activity 2015
 
Description STLE conference_Nashville_20190520 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Industry/Business
Results and Impact Multiple presentations were done in STLE meeting (one of the largest professional lubrication engineering conference). They are have attracted large crowds and smaller groups discussion were held on various topics of our research.
Year(s) Of Engagement Activity 2019
 
Description Shell - 18th Nov 2015 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach Local
Primary Audience Industry/Business
Results and Impact A meeting was held between Shell representatives and us to discuss progress on Shell's projects and EPSRC projects which Shell are interested in.
Year(s) Of Engagement Activity 2015
 
Description Shell - Lab visit _ 25th Feb 2016 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Industry/Business
Results and Impact The new VP and also a technical manager from Shell visited our research facilities. Both showed strong interests in our work.
Year(s) Of Engagement Activity 2016
 
Description Shell - lab visit - 10th Feb 2015 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Industry/Business
Results and Impact A lab visit to showcase our research capability was provided. They showed interested in our work.
Year(s) Of Engagement Activity 2015
 
Description Shell 10-2013 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? No
Geographic Reach National
Primary Audience Professional Practitioners
Results and Impact A talk and a lab tour have been given and both have sparked questions and discussion afterwards.

We were asked to provide more information on our research activities and possible collaboration mechanisms.
Year(s) Of Engagement Activity 2013
 
Description Shell 4-2013 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact A talk and a lab tour have been given and both have sparked questions and discussion afterwards.

We were asked to provide more information on our research activities and possible collaboration mechanisms
Year(s) Of Engagement Activity 2013
 
Description Tribology showcase_20190708 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Participation in an event that showcase the research in the group both present and future. A laboratory demonstration followed. A lively discussion were conducted after.
Year(s) Of Engagement Activity 2019
 
Description Understanding the behaviour of lubricants with fluorescence imaging and spectroscopies 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Policymakers/politicians
Results and Impact The presentations showcases how the methodology developed in this project can be used to investigate both surface active molecules and nanoadditives in a tribology contact.

After the talk, company representatives have contacted me to arrange for lab visit to discuss potential collaborations.
Year(s) Of Engagement Activity 2011
 
Description Using Fluorescence Spectroscopy and Imaging in Tribology 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact The presentation highlights reveals opportunities the novel methodology developed from this project can provide to industrial audiences.

After the talk, lab tours for company representative were arrange to explore collaboration opportunities.
Year(s) Of Engagement Activity 2011
 
Description Visit Shell (Houston, 17/11/2016) 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Professional Practitioners
Results and Impact Presented our research and held panel discussions on how we can help the company.
Year(s) Of Engagement Activity 2016
 
Description World Tribology Congress Beijing (18/09/2017) 
Form Of Engagement Activity A talk or presentation
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Postgraduate students
Results and Impact Presentation of Current research work and discussion with potential sponsors.
Year(s) Of Engagement Activity 2017