Materials have been invented by mankind in the course of prehistory and history and have evolved during this long period of time to fit the parallel changes in technological epistemes. Materials, therefore, have been a cumulative technological commodity, because of the continuity that this mechanism of change has ensured Structural materials, of which all anthropogenic artefacts are made and with which they are made (machines, process tools, etc.), have been more especially enduring and have carved themselves specific roles in our world that survive across major paradigm shifts and Kondratief cycles. Materials are analyzed here in terms of their physico-chemical nature (or physio-chemical in the case of natural, renewable materials) and of their footprints on energy consumption and greenhouse gas emissions, two of the major lenses through which the sustainability of our economic world is presently observed. The picture that comes out of this examination is that of complementarity and cooperation between materials, with competition acting as a sting to avoid a slack in technology but no pushing any of them out of their market, at least globally. This cohabitation, akin to a natural selection mechanism in a global ecosystem, may be the real driver of dematerialization, a trend which population growth and urbanization forces on mankind.

This introductory article provides the background for the September 2003 issue of MRS Bulletin on Ultrahigh-Temperature Materials for Jet Engines. It covers the need for these materials, the history of their development, and current challenges driving continued research and development. The individual articles that follow review achievements in four different material classes (three in situ composites—based on molybdenum silicide, niobium silicide, and silicon carbide, respectively—and high-melting-point platinum-group-metal alloys), as well as advances in coating systems developed both for oxidation protection and as thermal barriers. The articles serve as a benchmark to illustrate the progress made to date and the challenges ahead for ultrahigh-temperature jet-engine materials.

This article discusses three main points. First, ultrahigh-temperature materials offer a large return to the propulsion community and to the economy, but replacing Ni-based alloys is a very difficult problem for both technical and financial reasons. Second, the oxidation resistance of selected Mo-Si-B alloys and the prospects for combining this with useful structural properties are remarkable, given the nature of conventional Mo alloys; however, there are nagging issues associated with their low-temperature (∼700°C) behavior. Third, further advances in the processing of such materials, together with assessments of their affordability and reliability, are vital for achieving a successful engineering technology.

Metallic foams have become an attractive research field both from a scientific viewpoint and the prospect of industrial applications. Various methods for making such foams are available. Some techniques start from specially prepared molten metals with adjusted viscosities. Such melts can be foamed by injecting gases or by adding gas-releasing blowing agents that decompose in situ, causing the formation of bubbles. Another method is to prepare supersaturated metal–gas systems under high pressure and initiate bubble formation by pressure and temperature control. Yet a further class of techniques begins with solid precursors containing a blowing agent. These can be prepared by mixing metal powders with a blowing agent, compacting the mix, and then foaming the compacted mix by melting. Alternatively, casting routes can be used to make such precursors. The unique properties of foams offer promise in a variety of applications ranging from lightweight construction and impact-energy absorption to various types of acoustic damping and thermal insulation.

Packaging of solid-state power electronics is a highly interdisciplinary process requiring knowledge of electronics, heat transfer, mechanics, and materials science. Consequently, there are numerous opportunities for innovations at the interfaces of these complementary fields. This article offers a perspective of the current state of the art and identifies six specific areas for materials-based research in power electronics packaging. The emphasis is on identifying the underlying physical relationships that link the performance of the power electronics system to the microstructure and architectural arrangement of the constituents.

Combinatorial methods are high-efficiency methods to create large composition “libraries” of materials, for example, continuous composition variations, and test those compositions systematically in parallel for specific properties of interest, in contrast to the time-consuming one-composition-at-a-time approach. These methods have captured the attention of the materials industry with the promise of providing new discoveries “faster, better, and cheaper.” However, in the academic community, combinatorial methods often meet with less enthusiasm, perhaps due to the perception of combinatorial methodology as an Edisonian approach to science. The facts are quite to the contrary. In addition to impressive successes arising from the application of combinatorial methods to materials discovery, results coming out of systematic high-throughput investigations of complex materials phenomena (which would be too time-consuming or expensive to undertake) provide data leading to improvement in theories and models of materials chemistry and physics. Indeed, combinatorial methods provide a new paradigm for advancing a central scientific goal—the fundamental understanding of structure–property relationships of materials behavior.