To Turnbull's study of the kinetic problem of nucleation and growth of crystals, we add the further enquiry into what lies behind the slow nucleation kinetics of glass-formers. Our answer to this question leads to the proposal of conditions in which a pure liquid metal, monatomic and elemental, can be vitrified. Using the case of high-pressure liquid germanium, we give electron microscope evidence for the validity of our thinking.

On the question of how liquids behave when crystals do not form, Turnbull pioneered the study of glass transitions in metallic alloys, measuring the heat capacity change at the glass transition Tg for the first time, and developing with Cohen the free volume model for the temperature dependence of liquid transport properties approaching Tg. We extend the phenomenological picture to include networks where free volume does not play a role and reveal a pattern of behavior that provides for a classification of glass-formers (from “strong” to “fragile”). Where Turnbull studied supercooled liquid metals and P4 to the homogeneous nucleation limit using small droplets, we studied supercooled water in capillaries and emulsions to the homogeneous nucleation limit near −40°C. We discuss the puzzling divergences observed that are now seen as part of a cooperative transition that leads to very untypical glass-transition behavior at lower temperatures (when crystallization is bypassed by hyperquenching). Finally, we show how our interpretation of water behavior can be seen as a bridge between the behavior of the “strong” (network) liquids of classical glass science (e.g., SiO2) and the “fragile” behavior of typical molecular glass-formers. The link is made using a “Gaussian excitations” model by Matyushov and the author in which the spike in heat capacity for water is pushed by cooperativity (disorder stabilization of excitations) into a first-order transition to the ground state, at a temperature typically below Tg. In exceptional cases like triphenyl phosphite, this liquid-to-glass first-order transition lies above Tg and can be studied in detail.

This article discusses the importance of the choice of synthetic methodology in the purity, and therefore performance, of both small-molecule and polymeric organic semiconductors. We discuss common methodologies used in the preparation of organic semiconductors, paying particular attention to the impurities and by-products that can arise during these synthetic approaches and how they can have an impact on semiconductor performance.

There has been considerable recent interest in natural bone as a material, due in part to its interesting combination of mechanical properties: bone is stiff and tough but lightweight. This unusual combination of properties results from a nanocomposite structure of approximately equal volumes of mineral and hydrated organic matter. Much recent effort has been focused on the structure, properties, and performance at different length scales relative to the hierarchical organization of bone. Historically, such bone research has emphasized clinical and medical aspects, including engineering materials for bone augmentation or replacement, bone–biomaterial interactions and interfaces, and more recently, scaffolds for bone tissue engineering. However, within the fast-growing biomimetics field, the bone extracellular matrix is taken as a model for materials development. Efforts have been made both to mimic the bony material itself as well as to mimic the process by which bone forms.

The discovery that gas hydrates (also called clathrate hydrates) can crystallize (Figure 1) as a solid by the combination of water and several types of gases exposed to low temperatures and elevated pressure goes back to the 1800s. French researchers were the frst to report the formation of methane, ethane, and propane hydrates.1 Results of these studies remained as scientifc novelties until the mid-1930s, when it was discovered in Germany that gas hydrates forming as solids above 0°C in gas pipelines blocked the fow of natural gas.2 This observation initiated a furry of activities both in Europe and in the United States to fnd various inhibitors to prevent hydrate formation in gas transmission lines. During the mid-1960s, it was recognized that nature, over millions of years, has deposited vast amounts of methane hydrates along most of the continental margins in the ocean sediments, as well as along the permafrost regions in Alaska, Canada, and Russia.3 Figure 2 shows the presence of methane hydrate deposits in the ocean sediments and in the permafrost regions of the world. These deposits are byproducts of microbial decomposition of organic matter or of Earth's geothermal heating distributed worldwide where temperature and pressure are suitable for hydrate formation. The distribution of organic carbon in Earth's crust as methane

Global energy demand is expected to increase steeply, creating an urgent need to evolve a judicious global energy policy, exploiting the potential of all available energy resources, including nuclear energy. With increasing awareness of environmental issues, nuclear energy is expected to play an important role on the energy scenario in the coming decades. The immediate thrust in the science and technology of nuclear materials is to realize a robust reactor technology with associated fuel cycle and ensure the cost competitiveness of nuclear power and to extend the service life of reactors to 100 years. Accordingly, the present-generation materials need to be modified to meet the demands of prolonged exposure to irradiation and extended service life for the reactor. Emerging nuclear systems incorporate features to ensure environmental friendliness, effective waste management, enhanced safety, and proliferation resistance and require development of high-temperature materials and the associated technologies. Fusion, on a longer horizon of about fve decades, also requires the development of a new spectrum of materials. The development of next-generation materials technology is expected to occur in short times and is likely to be further accelerated by strong international collaborations.