Projects

• Supervisor - David Faux
• Type - Experimental

Techniques used

The atomistic simulations will be performed using DLPOLY, a software package created at Daresbury Laboratory. We have about 15 years experience using DLPOLY. The code can be run on the local super-computer. Local expertise exists through a PDRA and PGR students.

Raman measurements will be performed using to local Raman facility housed in the Physics Department. Dr Alan Dalton is an expert in this area.

Objectives

1. To undertake equilibrium atomistic simulations of graphene sheets using molecular dynamics to develop an improved understanding of its properties
2. To investigate the mechanical properties of graphene, particularly its Raman spectra (determined from its vibrational properties)
3. To undertake some Raman spectroscopy experiments on graphene sheets
4. Undertake simulations of graphene in different environments (stressed, aqueous).

Project description

Recently, there has been significant interest at the fundamental level in the behaviour of carbon nanoparticles (such as carbon nanotubes and graphene). Graphene (a single layer of graphite with a hexagonal sp2 hybridised structure)is the strongest material known to man (and currently the most expensive!). The mechanical properties of graphene is not well established and its Raman characteristics, for example, have only recently been established experimentally. This is therefore an opportunity to make an impact in a young field.

This project involves developing a fundamental understanding of the mechanical properties of graphene jointly with Dr Alan Dalton. The computational component involves molecular dynamics simulation using DLPOLY software on the local supercomputing cluster. The identification of appropriate interatomic potentials will be key. The interpretation of data and production of simulated Raman spectra has not been attempted before for graphene but the technique has been implemented successfully in other systems and, provisionally, for carbon nanotubes. The results will have implications for the interpretation of spectra from carbon nanotubes too.

• Supervisor - Richard Sear
• Type - Computational/theoretical

Project description

The cells our bodies are made of are driven out of equilibrium by the energy-consuming process of life, and this creates gradients in the concentrations of the molecules inside them. For example, ATP the molecule many protein nanomachines burn as fuel will be higher concentrations near where they are made, at a protein machine called ATP synthase, then far away from these sources. Concentration gradients also occur in may other contexts, for example in drying paint coatings, where the moving water/air surface pushes molecules before it, creating gradients. It has been known for many years that a gradient in the concentration of one molecule or ion, can drive motion of a different molecule or ion, a process called diffusiophoresis. But recent advances have led to a renewed interest in diffusiophoresis.

In particular Joe Keddie and I, working with two postdocs, found that diffusiophoresis could lead to coatings that spontaneously formed layers during drying. This was published in Physical Review Letters in 2016. I am continuing to work on this in collaboration with Joe, and I also working on applying our increasing knowledge of diffusiophoresis to the complex dynamics inside our cells, to better understand how proteins move around inside our cells.

• Supervisor - David Faux
• Type – EngD project (4 years) in experiment and modelling

Techniques used

The experimental (NMR) work will be undertaken at the Schlumberger Research facilities in Cambridge, UK. The random-walk modelling will require a bespoke code which the student will develop. It will be run using Surrey’s supercomputing facilities.

Objectives

1. To determine the microscopic length scales that control the macroscopic rheology using novel magnetic resonance imaging and optical light scattering techniques in combination with conventional tools
2. To validate the measured length scales and macroscopic properties against existing models for non-Newtonian fluids
3. To develop an improved understanding of the hierarchy of relevant structural lengths from the nanoscale to the macroscale to enable the design of improved complex fluid formulations with predictable rheological properties.

Project description

Complex fluids containing suspensions of colloidal particles are critical to a wide variety of industrial processes. Such complex fluids are used extensively in the petroleum industry, for well construction (drilling fluids, cements) and oil recovery (aqueous polymer and surfactant solutions). Prediction and control of the non-Newtonian rheological properties of these fluids, such as gel strength and ability to suspend non-colloid particles, is essential for successful operations. These macroscopic rheological properties are governed by the nanoscale interactions between the colloidal particles that result in phenomena such as shear banding and viscoelasticity. These properties are challenging to measure in conventional rheometers and there is considerable industrial and academic interest in developing new characterisation methods.

Schlumberger is an oilfield services company with a global footprint. Activities at the Cambridge centre focus on the development of new science and technology for well construction, with an emphasis on drilling and automation. The facilities available for this proposed project include a suite of low field magnetic resonance instruments, microscopy (optical and X-ray) platforms, conventional rheometers, and hydrodynamic flow experiments. A unique low field magnetic resonance rheometer will be a core technology, enabling the spatial variation of shear stress and non-colloidal particle migration to be visualised within complex fluids.

The project will be supervised by Dr Jonathan Mitchell (magnetic resonance) and Dr Andrew Clarke (nanoscience). Support for aspects of the project related to conventional rheology, fluid chemistry, and modelling/simulation will be provided by other scientists and engineers at Schlumberger Cambridge.