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Group Members: Kaustav Guha

Photo of Kaustav Guha

kaustav.guha@durham.ac.uk

Bain Group History

Ph.D. Student, Durham University, 2006–present

Project Title

Molecular Tribology

Research- Outline

Tribology is the study of sliding and wear. My interest is in the molecular basis of lubrication, to find out exactly what happens when one solid surface slides across another. The art of lubrication has been practiced for thousands of years from the early days of our human civilization. The development, however, has been mostly empirical in nature, where the detailed mechanisms of the chemistry and why they worked were not understood. Rapid advancements in analytical instrumentations and techniques in the last several decades offer an unprecedented opportunity to analyze the complex chemistry and probe the surfaces for chemical evidence. We have derived knowledge about the molecular vibrations and conformations of organic lubricants at the interface between two solids from total internal reflection (TIR) RAMAN SPECTROSCOPY and SUM-FREQUENCY SPECTROSCOPY, and we are undertaking the development of an in-situ infrared spectroscopy of thin lubricant films. We are using Langmuir-Blodgett monolayers of surfactants as model boundary lubricants.

Research- A Closer Look

Our group has been involved in studying thin liquid films of hexadecane, octamethyltetrasiloxane (OMCTS), 1-undecanol and Langmuir-Blodgett (LB) monolayers consisting of zinc stearate, zinc arachidate and zinc behenate, using Raman scattering, all at the solid-solid interface. The LB monolayers were also investigated with sum-frequency spectroscopy in order that comparisons could be made between results from the two techniques. Thin films were confined between an optical prism and an optical lens at pressures ranging from 30 MPa to 200 MPa.

We observed that the deposited LB monolayers are conformationally ordered and that this high degree of order is retained at applied pressures of up to 200 MPa, which, however, causes the hydrocarbon chains to tilt away from the surface normal. The sensitivity of this technique is sufficiently increased by use of total internal reflection (TIR) excitation geometry in the Raman experiments for spectra to be obtained from sub-monolayer amounts of material that is collected in small surface defects, with acquisition times of minutes.

The figure below shows the layout of the TIR Raman optical bench.

Photo of TIR Raman optical bench

We are presently improving the experimental geometry, replacing triangular prisms with hemispherical optics in order to reduce astigmatism and simplify alignment. We are also interested in looking at the changes in molecular conformation and orientation at the solid-solid interface when one surface is in motion while pressing against the other, which will enable us to understand how the process of lubrication works at the molecular level.

Project Funding

BP- EPSRC Dorothy Hodgkin Postgraduate Award (DHPA) 2006

Interests

I am interested in games and sports, having played a lot of table tennis and cricket since my school days. I also enjoy watching football, although far from playing it.