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Details of Grant 

EPSRC Reference: EP/M003027/1
Title: Control of Crystal Nucleation on Surfaces
Principal Investigator: Christenson, Professor H
Other Investigators:
Meldrum, Professor F Burnell, Dr G Murray, Professor BJ
Researcher Co-Investigators:
Project Partners:
Asymptote Ltd
Department: Physics and Astronomy
Organisation: University of Leeds
Scheme: Standard Research
Starts: 10 November 2014 Ends: 07 January 2018 Value (£): 818,115
EPSRC Research Topic Classifications:
Materials Characterisation Materials Synthesis & Growth
EPSRC Industrial Sector Classifications:
No relevance to Underpinning Sectors
Related Grants:
Panel History:
Panel DatePanel NameOutcome
23 Jul 2014 EPSRC Physical Sciences Materials - July 2014 Announced
Summary on Grant Application Form
Crystallisation is a widespread phenomenon in nature and technology. Indeed, snowflakes, gemstones, table salt, boiler scale, metals and many advanced materials used for example in nanotechnology or advanced batteries are all crystalline. The ability to control when, where and how crystals form is therefore essential to areas as diverse as climate modelling, pharmaceutical formulation, the semiconductor industry and the design of dental and medical prostheses. At present, our ability to direct and control crystallisation is often very poor, so any improvement would be of far-reaching significance.

The majority of strategies used to control crystallization from solution relies on the use of soluble additives or on changing the reaction conditions. Here, we propose to develop a different and potentially quite general technique. Rather than varying the solution chemistry - which is specific to each different crystal - we will use the topography of the surfaces on which crystals grow to control their formation.

The formation of crystals requires that a substantial energy barrier be surmounted and is hence usually a rare event - liquids such as water may undergo sizeable supercooling before they freeze. The energy barrier is reduced, and crystallization rendered easier if it occurs on a surface rather than in bulk - during a frosty night ice crystals form on surfaces but not in the air away from any objects. Theoretical considerations show that crystallization will become even more favourable if there are pits or grooves in a surface, and there are many observations that attest to the validity of these ideas. There have, however, been very few systematic studies of the effect of topography on crystallization. Consequently, we have almost no understanding of the type of defects that best favour crystallisation, and to what extent they may depend on the nature of the surface and the nature of the crystallising substance. Part of the problem is that the surface defects which are likely to have a large effect are small - of the order of 5 nanometres or less, which is the typical size of a crystal nucleus. Clearly, features on such a length scale cannot be reproducibly created by methods such as scratching or abrading a surface.

Thanks to recent advances in surface engineering techniques we are now in a position to design and manufacture surfaces that contain defects with well-defined geometries and also with dimensions small enough to enable a detailed assessment of their effect on crystallisation. Indeed, our proposal is supported by preliminary data showing that this strategy works! We have succeeded in showing that surfaces in which nanoscale grooves have been deliberately cut nucleate crystals almost exclusively in the grooves, with negligible growth on the flat areas in between.

We now propose to study nucleation of crystals from vapour and from solution using surfaces with a range of different nanoscale surface features such as pits, grooves and trenches with undercuts. We will relate the density and rate of crystallisation of different substances to the type of feature and try to use these findings to establish criteria for the design of good nucleants, or crystallisation promoters. The breadth of the experiments will allow us to establish the extent to which optimisation of nucleation by surface features differs between vapour, liquid and solution and the differences between systems of simple organic molecules, water, and inorganic salts (electrolytes).

This project will therefore ultimately provide us with a novel and potentially quite general approach to control crystallization in a huge number of applications, ranging from the engineering of thin films for solar cell devices to the promotion of natural bone growth on implant surfaces, or to the prevention of crystallization in kettles, oil wells or in building materials (prevention of weathering).

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