A nanostructure is a structure of intermediate size between microscopic and molecular structures. Nanostructural detail is microstructure at nanoscale. In describing nanostructures it is necessary to differentiate between the number of dimensions on the nanoscale. Nanotextured surfaces have one dimension on the nanoscale, i.e., only the thickness of the surface of an object is between 0.1 and 100 nm. Nanotubes have two dimensions on the nanoscale, i.e., the diameter of the tube is between 0.1 and 100 nm; its length could be much greater. Finally, spherical nanoparticles have three dimensions on the nanoscale, i.e., the particle is between 0.1 and 100 nm in each spatial dimension. The terms nanoparticles and ultrafine particles (UFP) often are used synonymously although UFP can reach into the micrometre range. The term 'nanostructure' is often used when referring to magnetic technology.

 

W–AlO nanostructured composite has been produced by mechanical milling of ammonium paratungstate (APT) and Al powder mixture at room temperature. The milled products have been characterized by X-ray diffraction (XRD), and scanning electron microscopy (SEM) equipped with energy dispersive spectrometry (EDS). The XRD and EDS results confirmed that direct reduction of APT to α-W took place after 25 min milling. It was observed that α → β phase transition took place after 24 h mechanical milling. SEM micrographs showed that alumina matrix composite reinforced with W could be obtained by one step MSR (mechanically induced self-propagation reaction) process. X-ray diffraction peak broadening equation confirmed that the mean grain size of these particles was in nanometer range which gradually decreased with increasing the milling time.