Iranian Journal of Materials Science and Engineering

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In this study different volume fractions of SiC particles of various sizes were introduced into the semisolid A356 aluminum alloy by a mechanical stirrer. Then the slurry was poured into a permanent die of certain dimensions either when the metal alloy was partially solid (semisolid-semisolid or SS route) or after reheating to above the liquidus temperature of the alloy (semisolid-liquid or SL route). Both the SS and SL composite samples were solution-treated at 520°C for 8 hours followed by quenching in water at room temperature. Microstructural characterization studies have been conducted on both the SL and SS samples to quantify the effects of the size andcontent of the SiC particles as well as the solutionizing treatment on the morphology and size ofthe eutectic silicon particles and the matrix grain (globule) size. The results were rationalized in terms of the different nucleation, fragmentation, spherodization and coarsening events, which had taken place during the processing of these composites. Finally the impact of these microstructural features in improving the wear properties of the composites has been discussed.

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Li₇La₃Zr₂O₁₂ (LLZO) garnets are one of the promising materials as electrolytes for solid-state batteries. In this study, Li_7-3xAl_xLa₃Zr₂O₁₂ (x= 0.22, 0.25, and 0.28) garnet is synthesized using the combustion sol-gel method to stabilize the cubic phase for higher ionic conductivity. The X-ray diffraction (XRD) results of as-synthesized powders reveal that by addition of 0.22 and 0.25 mole Al, the tetragonal phase still co-exist, whereas 0.28 mole Al addition resulted in a single cubic phase. Afterward, the as-synthesized powders are pressed and sintered at 1180°C for 10h. The hardness evaluation revealed that Al addition increases the hardness that shows better resistance against Li dendrite formation. Besides, the secondary electron microscopy results demonstrate that the dopant has not a huge impact on particle size and grain growth whereas the porosity content has been changed. Finally, the investigation of samples' electrochemical behavior reveals that the addition of Al increases the ionic conductivity of samples by increasing the density and stability of the cubic phase as well. The results declare that the 0.25 Al sample has the highest ionic conductivity. This behavior is thought to be due to the promotion of sintering and increment of bulk ionic conductivity by doping Al.

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The sensitivity of lead dioxide coating properties to the deposition conditions and electrolyte composition has allowed the preparation of coatings with different properties for different applications. In this study, the effects of electrolyte additives on the electrodeposition process were investigated using electrochemical measurements such as cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy. The results showed that the presence of fluoride ions significantly reduce the possibility of TiO₂ formation. The addition of copper ions not only prevents lead loss at the cathode, but also leads to the formation of copper oxide on the surface at initial stages, which hinders nucleation of PbO₂. The presence of sodium dodecyl sulfate (SDS) also interferes with the nucleation process as it occupies active nucleation sites. The α-PbO₂ interlayer prevents copper oxidation and solves the problem of lead dioxide nucleation. Finally, it was found that the simultaneous use of all additives together with the α-PbO₂ interlayer has a positive effect on the coating process.