This brief article describes the content of the December 2003 issue of MRS Bulletin on New Frontiers in the Application of Neutron Scattering to Materials Science. New techniques, new instrumentation, and new sources are providing exciting opportunities for the use of neutron scattering in materials research at a time when the pace of research and development is accelerating while the complexity of the issues governing materials use is increasing. At a time such as this, it is critical to use the best tool for the job, and neutron scattering is evolving into a tool that can be used with many others, rather than a technique only for the specialist. It is also providing unprecedented resolution in energy to allow the study of the slow dynamics characteristic of many problems in soft matter and to probe surfaces and interfaces in a unique way. In this issue, we have chosen three areas to emphasize these trends: neutron reflectivity as a probe of surfaces and interfaces, the use of neutrons to study complex fluids, and high-resolution neutron scattering studies of dynamics. We also give a view of the future of neutron sources, with an article outlining the opportunities to be provided by sources proposed or under construction in Europe, Japan, and the United States. It is our hope that this sampling of new opportunities in neutron scattering will encourage wider use of these techniques to help solve the challenging materials research problems of today and tomorrow.

Among the experimental techniques used to characterize complex fluids, neutron scattering has played a unique and successful role, primarily for two reasons: (1) neutrons access the proper length and time scales, especially small-angle neutron scattering and reflectometry for structural and kinetic studies and neutron spin echo for dynamic investigations; and (2) for hydrogen-containing substances, the exchange of hydrogen by deuterium facilitates labeling on a molecular scale, an extremely important method for deciphering complex structures in multicomponent materials. In this short review, we give a number of examples for successful neutron studies of dense particle suspensions, including aggregation phenomena, in situ kinetic studies on shape transformations, shear-induced surfactant self-assembly phenomena near surfaces, and dynamics of complex fluids. Finally, we give an outlook on future developments.

Knowledge of the dynamic dimension of materials is an extremely important ingredient for understanding their properties. Neutron scattering is uniquely capable of revealing aspects of the atomic and molecular geometry of motions over a wide range of time scales. To illustrate this fact, we give a number of examples from different areas of materials science. We discuss the diffusion of hydrogen in protonic conductors; the hydration of portland cement; and aspects of the molecular rheology of polymers, emphasizing in particular the effect of branching. All of these experiments have added important basic information to the understanding of the respective systems. With the advent of the new megawatt neutron spallation sources, the role of neutron scattering in revealing the dynamical properties of materials is expected to increase substantially.

Neutron reflectivity has matured in recent years from an exotic method used only by a few experts to an essential tool for the investigation of thin films and interfaces on the nanoscale. In contrast to x-ray reflectivity, which provides electron density profiles, neutron reflectivity reveals the nuclear density profile. This is an essential difference when exploring hydrogenous materials such as polymers, Langmuir–Blodgett films, and membranes. Furthermore, neutrons carry a magnetic moment that interacts with the magnetic induction of the film, revealing, in addition to the nuclear density profile, the magnetic density profile in layers and superlattices. Recent developments in the analysis of off-specular neutron reflectivity data enable the characterization of chemical and magnetic correlations within the film plane on nanometer to micron length scales. A new generation of pulsed neutron sources, featuring flux enhancements of factors of 10–100 over existing sources, will make these types of measurements even more exciting, while kinetic studies, pump-probe, and small-sample experiments will become feasible, opening new windows onto nanoscale materials science.

This article gives an overview of current neutron-scattering facilities and illustrates the capabilities of third-generation sources that are now under development. The new science that is driving this development has been illustrated in the articles in this issue of MRS Bulletin and in a previous issue published in 1999 [MRS Bull.24 (12) (1999) p. 14]. The scale of these facilities is such that only three of them are envisaged worldwide, in the Asia Pacific region, Europe, and America. Two construction projects, the spallation neutron sources in the United States (SNS) and in Japan (J-PARC), are now well under way, while the European proposal for a spallation source (ESS) is still awaiting a decision to start construction.