High-Temperature Surface Oxide Growth Kinetics of Al–Si–Zr Bulk Alloys and Ribbons

A typical modification technique of the functional properties of Al–Si based alloys is the addition of some third element in trace level. In the present work, ternary Al–Si–Zr bulk and ribbon alloys have been prepared. The kinetics of high-temperature surface oxidation has been studied by thermogravimetric method. It was found that at the start of the experiment the chemical reaction velocity is rate-controlling while for longer times the (oxygen) diffusion is the rate-controlling process. Activation energy of the two stages of oxidation has been obtained. Additional studies such as thermochemical analysis, optical and electron microscopy, and microhardness tests have been done.

Crystal Growth of Cubic and Hexagonal GaN Bulk Alloys and Their Thermal-Vacuum-Evaporated Nano-Thin Films

In this study, we investigate a novel simple methodology to synthesize gallium nitride nanoparticles (GaN) that could be used as an active layer in light-emitting diode (LED) devices by combining the crystal growth technique with thermal vacuum evaporation. The characterizations of structural and optical properties are carried out with different techniques to investigate the main featured properties of GaN bulk alloys and their thin films. Field emission scanning electron microscopy (FESEM) delivered images in bulk structures that show micro rods with an average diameter of 0.98 µm, while their thin films show regular microspheres with diameter ranging from 0.13 µm to 0.22 µm. X-ray diffraction (XRD) of the bulk crystals reveals a combination of 20% hexagonal and 80% cubic structure, and in thin films, it shows the orientation of the hexagonal phase. For HRTEM, these microspheres are composed of nanoparticles of GaN with diameter of 8–10 nm. For the optical behavior, a band gap of about from 2.33 to 3.1 eV is observed in both cases as alloy and thin film, respectively. This article highlights the fabrication of the major cubic structure of GaN bulk alloy with its thin films of high electron lifetime.

Grain Size and Phase Transformation Behavior of TiNi Shape-Memory-Alloy Thin Film under Different Deposition Conditions

TiNi shape-memory-alloy thin films can be used as small high-speed actuators or sensors because they exhibit a rapid response rate. In recent years, the transformation temperature of these films, manufactured via a magnetron sputtering method, was found to be lower than that of the bulk alloys owing to the small size of the grain. In this study, deposition conditions (growth rate, film thickness, and substrate temperature) affecting the grain size of thin films were investigated. The grain size of the thin film alloys was found to be most responsive to the substrate temperature.