ABSTRACT
Nanostructured materials, particularly those derived from nanoparticles, have evolved as a separate class of materials over the past decade. The most remarkable feature has been the way in which completely disparate disciplines have come together with nanomaterials as the theme. The breadth of the field is enormous, ranging from the use of nanoparticles of zinc oxide in hygiene products, such as diapers [1], to altering the characteristics of solid rocket propellants by the addition of nanoparticle fillers [2]. The enthusiasm is justified for the most part, as the fundamental materials’ properties appear to be different at the nanoscale. For example, according to Qi and Wang [3], when the ratio of the size of the atom to that of the particle becomes less than 0.01 to 0.1, the cohesive energy begins to decrease, which in turn reduces the melting point. In a related report, Nanda and co-workers [4] have shown that the surface energy of free nanoparticles is higher than that of
embedded nanoparticles, and is substantially higher compared to that of the bulk. There is also ample evidence that nanoparticles display characteristics that are distinctly different from their microcrystalline counterparts. For example, Reddy and co-workers [5] have shown that nanoparticles of anatase TiO2, synthesized by a precipitation technique, show direct bandgap semiconductor behavior, whereas microcrystalline TiO2 is an indirect bandgap material.
