This article deals with the microstructural strengthening mechanisms of aluminium by means of hard α-Al2O3 alumina fine particles. A broad of understanding views covering materials preparations, elaboration process, characterization techniques and associated microstructural characteristic parameters measurements is given.In order to investigate the microstructural characteristic parameters and the mechanical strengthening mechanisms of pure aluminium by hard fine particles, a set of Al-(α-Al2O3) alloys samples were made under vacuum by high fusion temperature melting, the high frequency (HF) process, and rapidly solidified under ambient temperature from a mixture of cold-compacted high-pure fine Al and α-Al2O3 powders. The as-solidified Al-(α-Al2O3) alloys were characterized by means of X-ray diffraction (XRD) analyses, optical microscopy observations and Vickers microhardness tests in both brut and heat-treated states. It was found that the as-solidified HF Al-(α-Al2O3) alloys with compositions below 4 wt.% (α-Al2 O3) are single-phase microstructures of the solid solution FCC Al phase and over two-phase microstructures of the solid solution FCC Al and the Rhombohedral α-Al2O3 phases. The optical micrographs reveal the presence of a grain size refinement in these alloys. Vickers microhardness of the as-solidified Al-(α-Al2O3) is increased by means of pure fine α-Al2O3 alumina particles. These combined effects of strengthening and grain size refinement observed in the as-solidified Al-(α-Al2O3) alloys are essentially due to a strengthening of Al by the α-Al2O3 alumina particles insertion in the (HF) melted and rapidly solidified alloys.
Persistent organic pollutants (POPs) have become a major global concern due to their large amount of utilization every year and their calcitrant nature. Due to their continuous utilization and calcitrant nature, it has led to several environmental hazards. The conventional approaches are expensive, less efficient, laborious, time-consuming, and expensive. Therefore, here in this review the authors suggest the shortcomings of conventional techniques by using nanoparticles and nanotechnology. Nanotechnology has shown immense potential for the remediation of such POPs within a short period of time with high efficiency. The present review highlights the use of nanoremediation technologies for the removal of POPs with a special focus on nanocatalysis, nanofiltration, and nanoadsorption processes. Nanoparticles such as clays, zinc oxide, iron oxide, aluminum oxide, and their composites have been used widely for the efficient remediation of POPs. Moreover, filtrations such as nanofiltration and ultrafiltration have also shown interest in the remediation of POPs from wastewater. From several pieces of literature, it has been found that nano-based techniques have shown complete removal of POPs from wastewater in comparison to conventional methods, but the cost is one of the major issues when it comes to nano- and ultrafiltration. Future research in nano-based techniques for POP remediation will solve the cost issue and will make it one of the most widely accepted and available techniques. Nano-based processes provide a sustainable solution to the problem of POPs.
The microstructure properties of rapidly solidified Al–0–40 wt% (α-Al2O3) alloys by high-frequency (HF) melting were investigated by means of x-ray diffraction measurements, optical observations and combined scanning electronic microscopy and energy-dispersive x-ray spectroscopy (SEM/EDX) analyses. Phase transformation was correlated by heat treatment with pure Al and solid α-Al2O3 alumina spectra. It was found that the microstructure is a solid solution of the Al phase with a notable solubility of α-Al2O3 in the Al matrix for lower contents. For 4wt.% of alumina compositions and above, it was a mixture of phases, Al solid solution and α-Al2O3, with a tendency to reach the α-Al2O3 alumina morphology. Other forms of alumina phases are observed in the heat-treated (HF) alloys.
Rapidly solidified Al-Zn alloys with Zn contents ranging up to 50 wt.% were made under vacuum, by high-frequency (HF) induction melting, from compacted mixture targets of Al and Zn of fine (99.99 % purity) elemental powders. The microstructural characteristics and strengthening mechanisms were investigated. The crystallographic microstructures were characterized by means of X-ray diffraction (XRD) analyses and optical microscopy observations as well as Vickers microhardness testing. Detailed overviews of alloying solubility of zinc in aluminium were given. Extensive solid solutions of CFC Al were found in the (HF) Al-Zn alloys, and a higher Vickers microhardnesses compared to that of pure (HF) aluminium.
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