Abstract
Nanometer-sized materials are solids which may be considered as a dense ensemble of atomic clusters with a diameter of a few nanometers. Depending on whether the individual clusters have a crystalline or a glassy structure, nanocrystalline materials or nanometer-sized glasses are formed.
Nanocrystalline materials (NCM) are single or multiphase ploy-crystals, the crystal size of which is in the order of a few (typically 1 to 10) nanometers. These materials are of interest for the following three reasons:
i. | NCM seem to exhibit an atomic structure which differs from the crystalline state (with long range order) and the glassy state (with short range order). NCM seem to represent a new type of solid state structure. | ||||
ii. | The properties of NCM differ (in some cases by several orders of magnitude) from the properties of glasses and/or crystals with the same chemical composition. | ||||
iii. | NCM seem to permit the alloying of conventionally immiscible components such as metals and ceramics. The resulting alloys have been observed to exhibit new properties. |
If small (1 to 10 nm diameter) glass particles are consolidated, a new type of glasses, called nanometer-sized glasses, are obtained. These nanometer-sized glasses differ structurally from conventional glasses. Their short range order comprises nearest or next nearest neighbours only. The atomic arrangement beyond nearest neighbours seems random.