Materials science and materials engineering involves the investigation of structure property relationships and the use of these findings to produce materials with predetermined properties. Studies of this type play a major role at the ESRF and span a wide range of applications from chemical bonding, electronic applications, and novel synthesis to studies of grain growth, dynamic evolution of materials properties and design and understanding of catalytic processes. All aspects of materials science studies cannot be covered by this brief showcase. The trend in materials science research at the ESRF is that microfocussing; time-resolved studies in situ and the application of combinations of techniques are on the rise. In order to illustrate these trends we have chosen a few examples in the categories: extreme conditions, stress and strain studies and some general applications of X-ray diffraction to problems in materials science.

Enormous advantages in examining materials under non-ambient conditions such as high pressure or high temperature have been made due to developments in diamond-anvil cells, large-volume presses and laser heating in combination with the third-generation X-ray source at the ESRF.

The physical properties of materials can be dramatically changed under non-ambient conditions. In two studies of sulfur it is shown that non-incommensurate structures can exist at high pressures and that sulfur behaves like its group VI neighbours. It is also shown that molecular S6 is only formed under high pressure at high temperatures. These findings can explain the change in properties such as resistivity. In a study of neodymium/calcium manganites it was found that shear strain is of importance for the structure/property relationship in colossal magneto resistance. In a series of studies of actinides under high pressure it was found that a new structure of curium (Cm-III) is stabilised by magnetic interactions. An experimentally challenging study of hydrogen at high pressures reveals the structure of the high pressure phase II of D2 showing that a combination of neutron and X-ray diffraction can now determine complicated structures even at high pressures in diamond anvil cells.

X-ray diffraction and tomography are non-destructive methods providing data on bulk materials. A combination of these methods has revealed that void growth kinetics in bulk samples of CuZn40Pb2 brass can be studied and that void size and shape evolution can be followed during creep.

Control of relaxation processes and nucleation are important for the tailoring of materials to the desired properties. X-ray diffraction in situ is rapidly developing into an essential tool in this process. Bulk metallic glass, for instance, is an interesting new class of construction material and the control of the ductility in the nanocomposites are essential for the usefulness of these materials. In a temperature dependent diffraction study of Pd based metallic glasses the important relaxation processes of the excess free volume have been studied.

The crystallisation processes during solidification has been studied in a time-resolved diffraction of Al with solute Ti and TiB2 particles and the first in situ information on growth kinetics and nucleation of individual grains during solidification has been obtained. These processes govern the basic properties such as ductility and hardness. During deformation of metals and alloys dislocations are introduced and during subsequent annealing the stored energy is released. The 3D X-ray microscopy technique at ID11 was used to study the in situ recovery of cold rolled Al during annealing on a sub grain level.

High-resolution powder diffraction has proven to be a very useful tool in many materials science applications. A study of a C60 based polymer (Li4C60) revealed a new mixed bonding scheme for fullerides showing both [2+2] cycloadditions and single C-C bridging motifs indicating routes to the synthesis of new polymers with interesting properties. A combined X-ray diffraction/mass spectrometry study of anaerobic methane CH4 combustion explains the catalytic steps when CH4 under high temperature, using CeO2/Fe2O3 solid catalysts, is transformed to H2. Information of this type is of importance for the development of new, clean routes to the use of hydrogen as fuel.

A high resolution study of ferromagnetic La1-xCaxMnO3 manganite has provided information on the poorly understood ferromagnetic insulating state suggesting that a specific orbital ordering takes place.

X-ray diffraction at synchrotron facilities gives the possibility of obtaining information on the site occupancy by chemically different cations in powder. Examples of the determination of the cation distribution in bicationic zeolites illustrates the power of the resonant contrast diffraction.

A. Kvick