Nanostructured materials

Interest in the physics of condensed matter at size scales larger than that of atoms and smaller than that of bulk solids has grown rapidly over the past two decades owing to the increasing realization that the properties of these mesoscopic atomic ensembles are different than those of conventional solids. As a consequence, interest in artificially assembling materials from nanometer sized building blocks, whether layers or clusters of atoms, arose from discoveries that by controlling the sizes in the range of 1-100 nm and the assembly of such costituents one could begin to alter and prescribe the properties of the assembled nanostructures. Nature had already learned the value of nanostructuring, since many examples of naturally formed nanostructures can be found in biological systems from sea shells to the human body. Nanostructured materials are modulated over nanometer length scales in from zero to three dimensions. They can be assembled with modulation dimensionalities of zero (atom clusters or filaments), one (multilayers), two (ultrafine-grained overlayers or coatings or buried layers), and three (nanophase materials), or also with intermediate dimensionalities. Thus, nanocomposite materials containing multiple phases can range from the most conventional case in which a nanoscale phase is embedded in a phase of conventional sizes to the case in which all the constituent phases are of nanoscale dimensions. All nanostructured materials share three features: atomic domains (grains, layers or phases) spatially confined to less than 100 nm in at least one dimension, significant atom fractions associated with interfacial environments, and interactions between their constituent domains