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Recent developments have seen breakthroughs in zero-, one-, two-, and three-dimensional AlN micro- and nanostructures, such as nanoparticles, nanowires, nanotubes, thin films and 3D multifold symmetry crystals. The attractive electrical, optical, and thermal properties of AlN make these materials irreplaceable for microelectrochemical systems (MEMS), surface acoustic waves (SAWs) and light emitting diodes (LED). The significant interest in the field of AlN nanostructure synthesis and application encouraged us to summarise the reported data to better understand the physical and chemical aspects of AlN crystal growth processes. Four main topics are covered in this review article: (1) the morphological diversity of AlN nano- and microstructures; (2) formation mechanisms and growth dynamics; (3) theoretical simulation of growth processes based on density functional theory (DFT) and phase field (PF) modelling approaches; (4) application and devices. This article also provides a perspective on future research relevant to AlN micro- and nanostructures. [ABSTRACT FROM AUTHOR]

The fabrication of high-quality metallic powders has been attracted considerable attention in terms of producing advanced materials through additive manufacturing (AM) technology. The efficiency of AM products mainly dependent on the initial powder, therefore, characterisation of pre-alloyed powders become important. In this study, we explored the fabrication of Al0.5CoCrFeMnNi high-entropy alloy (HEA) powders by gas atomisation process and investigated their powder characteristics according to particle size distribution. X-ray diffraction results revealed the formation of major face-centred cubic and minor body-centred cubic phase by the addition of Al content. The detailed characterisations such as scanning electron microscopy, Auger electron spectroscopy and XPS analysis was carried out to examine the chemical composition of HEA powders. The relationship between secondary dendrite arm spacing and cooling rate was evaluated. The results demonstrated that produced alloy powders are spherical in shape with smooth surfaces, compositional homogeneity, indicating the gas-atomised powders are widely acceptable for additive manufacturing applications. [ABSTRACT FROM AUTHOR]