Hypoeutectic Al-Ni alloys are characterised by the formation of as-cast structures composed by a dendritic aluminium-rich matrix surrounded by a eutectic mixture ( þ ), where is the Al-rich phase and is the Al 3 Ni intermetallics. The morphology, size and distribution of the intermetallic particles decisively affect the mechanical properties of these alloys. This study aims to determine experimental laws relating the primary dendritic arm spacing ( 1 ) and Vickers microhardness (HV) of hypoeutectic Al-Ni alloys. Upward unidirectional solidification experiments were performed in order to obtain castings with significant differences in the scale of microstructural parameters along the casting length. It was found that the microhardness values were directly influenced by both the amount of solute and 1 and Hall-Petch-type equations relating the microindentation and 1 are proposed.
Ni metal particles, with sizes ranging from 70 to 110 nm, dispersed in activated carbon produced from the babassu coconut endocarp (BAC) were successfully synthesized and evaluated by scanning electron microscopy, dispersive energy X-ray spectroscopy, flame atomic absorption spectroscopy and powder X-ray diffraction. These hybrid BACNi-X materials (where X is the Ni / BAC ratio, equal to 10, 20 or 30) exhibit crystalline Ni particles with suitable magnetic properties, shown by increased saturation magnetization and a gradual reduction in coercive fields (varying 80 to 150 Oe) as the Ni content increases. Relatively large values of pore volume (in the range of 0.28-0.37 cm3/g), specific surface area (560-740 m2/g) are achieved, favoring their applications for magnetic remediation of mimetic contaminated effluents. All hybrid samples were tested positively for the adsorption of methylene blue in contaminated synthetic effluents and the greatest removal was achieved by the hybrid sample BACNi-10, which has the largest specific area and reasonable magnetic properties that allowed the manipulation of the sample by an external field.
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