Abstract
The novel spiral alumina nanowires are produced via the annealing of HEAs and it is found that Cr is automatically incorporated into the alumina during the nanowire growth. Nanowires exhibit a blue-green light, together with a small emission at 662nm. Nanowires show a well-defined field emission profile and lower threshold field. CASTEP calculations show that single substitution occurs at different O sites will not influence the physical properties, whereas Two-substitution of O site, different Al-substitution by Si and interstitial, will influence physical properties of alumina cell. The Al and O atoms on surface of nanostructure will create many sub-bands between upper valance and conduction band, and peaks are shifted to lower energy in loss function profiles. Equimolar mixture of fine Al and Si powder annealed generates four kinds of nanostructures especially of aluminum nanowires, which are characterized accordingly. This thesis consists of four parts, (1) synthesis of alumina nanowires using HEA system; (2) CASTEP calculation of alumina related nanostructres, (3) synthesis of alumina nanostructures in an Al-Si system; (4) synthesis aluminum nanowires in an Al-Si system