Crystallisation in the Real World: Delivering Control through Theory and Experiment

Crystallisation is a fascinating process. From common observations such as the formation of ice on a window or scale in a kettle, crystallisation is important to virtually every area of science, and lies at the heart of processes as varied as the production of ceramics, pharmaceuticals, fine chemicals, nanomaterials and biominerals. Equally important is the prevention of unwanted crystallisation in the form of weathering, scale or kidney stones.

Understanding crystallisation

Only by understanding how materials crystallise can we hope to control these processes. Despite the importance of crystallisation, we still have a poor understanding of many of the mechanisms that underlie this fundamental phenomenon. This is due to the fact that crystallisation is governed by molecular scale processes that are very difficult to study experimentally. For example, while experiments can identify reaction conditions that generate specific crystal polymorphs, they cannot alone explain why this occurred.

This Programme Grant will couple experiment and theory to address this challenge. Our experimental programme brings to the fore such frontier analytical techniques as liquid-phase TEM and functional scanning probe microscopies that will allow us to study the changes in solid and solution during crystallisation as never before. With recent advances in modelling we shall be able to perform simulations of nucleation and growth processes on comparable time- and length-scales, providing a unique opportunity to fully understand crystal nucleation and growth at the nanoscale.

Industry applications

These studies will be linked to simpler bulk experiments to provide a holistic view of crystallisation in the real world. We will use this approach to address six major challenges in the crystallisation of inorganic compounds. Each challenge, as well as being of fundamental importance, is ultimately significant to industry and has practical applications as varied as scale prevention in dishwashers, dental remineralisation and tailoring particle shape for paper coatings.

Research objectives

Investigations of homogeneous crystallisation in bulk solution will lay the foundation for our nucleation studies, revealing how we can direct nucleation pathways by varying solution and environmental conditions. We will then build on this work to explore the fascinating question of polymorphism, giving us predictive understanding of conditions which deliver specific crystal polymorphs. Turning then to the ubiquitous phenomenon of surface-directed crystallisation, both theory and cutting-edge analytical methods will bring new understanding of how surfaces - and the changes they cause in the adjacent solution - govern crystallisation.

This naturally leads us to a search for effective nucleating agents, which, despite the promises of classical nucleation theory, are known for only a small number of systems. Control of crystal growth to generate particles with defined shapes and sizes is another topic of great industrial importance, and soluble additives are widely used to achieve this goal. By understanding crystal/ additive interactions we aim to pre-select additives to grow crystals with target properties, or to inhibit unwanted crystallisation.

Finally, we will study crystallisation within confined volumes; this will ultimately enable us to use confinement to control crystallisation. These ambitious objectives can only be met within the framework of a Programme Grant, which provides the flexibility and long-term funding to bring together the very different disciplines of theory and experiment. While each of the individual tasks focuses on a distinct problem in crystallisation, they are intimately linked over the entire project by common methods and understanding, and developments in one task will drive advances in others.

Project website

https://realworldcrystals.leeds.ac.uk/