To study the structure and dynamics of functional materials
Historical & General Perspectives
Our interests in industrial materials dates back to the times of the late J. D. Bernal who encouraged the use of crystallography for solving problems relevant to the needs of the times, particularly during the war years when for example the properties of sand beaches were a matter of strategic importance. Bernal's vision also was to create an environment where expertise in diverse areas, such as molecular biology, industrial materials and liquid/disordered systems, could mix together to promote new scientific thinking. In the late seventies, the arrival of Prof. T. L. Blundell coincided with a noticable climatic change in Universities: that of increased auditing and performance data which made it necessary to present a clearer profile of the Crystallography Department's various research directions; thus the name "Industrial Materials Group" was devised to represent the interests of our group which was already gaining some reputation for problem-solving in materials and industrial science. The group might have grown somewhat slowly when compared to the explosion in molecular biology, yet today it represents some 15-25% of the Department's overall activities.
Our mission statement requires some explanation. The underlying assumption is that in most materials science problems there is a link between "structure", "property" and "function" which needs to be unravelled and exploited. The term "structure" primarily refers to atomic structure, as befits a department of crystallography, though higher levels of structural organisation, such as micro-crystallites, defects, hetereogeneous phase existence, all come within our working definition of "structure". Neither is the term interpreted just in the static sense that marks so many investigations in crystallography, and so "dynamics" has been added to emphasise that variations of structure with time, both minor variations and more major chemical/physical transformations, are very much included. In fact the study of rapidly changing structures, using fast detectors and intense neutron/synchrotron radiation sources, has now become one of the main specialities of the group. Although X-ray/neutron diffraction remains the cornerstone technique of the group, the use of subsidiary techniques such as electron microscopy and computer-modelling are also required in this "all level" approach. Also the materials studied are not restricted to those of immediate industrial interest: any material which can be justifiably called a "functional" material is fair game. This mission has brought about consistent calls from industry to help solve their problems in materials synthesis and in-service performance, and therefore many of the materials inevitably turn out to be micro-crystalline and/or hetereogeneous. One consequence is that powder diffraction, in both static and dynamic modes, has become one of the speciality techniques of the group. Liquid/amorphous materials are also implicated in many of these problems and therefore skills in assessing and modelling non-crystalline structure are also required. This brings us back to Bernal who played such a valuable role in finding ways to describe the dynamic and structural nature of liquids and glasses.
Techniques: Tools of the Trade
As already mentioned, one of the main techniques of a Crystallography department has to be diffraction, and with industrial materials this usually has to be applied in the on}powder diffraction mode. The Industrial Materials Group has built up a state of the art powder diffraction facility which allows powder diffraction patterns to be collected with maximum monochromatisation and resolution, as required for the solution and refinement of atomic structures (the so-called "Rietveld" method), and with rapid speed by using position sensitive detectors to follow in real time any changes in atomic structure and phase transformations. These changes and transformations often result from imposing special temperature/pressure/chemical containment conditions upon the sample in order to mimic the conditions of some particular industrial or preparation process. So special specimen stages have been designed which permit temperatures of between 8 K and 1,500°C and allow the circulation of chosen gases above or through the sample.
However the ultimate in diffraction is not to be found in the home laboratory but at the very new intense radiation sources provided by Government and International centralised sites. So while our group members use extensive in-house diffraction facilities, they also travel to use synchrotron X-rays (at the Daresbury Synchrotron Radiation Source (SRS), UK and the European Synchrotron Radiation Facility (ESRF), Grenoble, France) and neutron sources (at the Rutherford Appleton Laboratory (RAL) ISIS facility, UK and the Institut Laue Langevin (ILL), Grenoble,). These produce the highest resolution powder diffraction patterns to date, and permit a phenomenal speed of data collection down to the second time scale. Many examples, "world firsts", of their use are to be found in the PhD projects listed and in the selected publications.