Carbon nanotubes (CNTs) were dispersed by mechanical milling into a 2024 aluminum alloy (Al 2024 ) in order to produce composites and study the influence of CNTs content over the mechanical and microstructural behavior of them. The time of milling was set to 5 h [1] and the addition of CNTs was of 0.0 to 5.0 wt. %. Powders obtained from milling process were cold compacted and then sintered under argon atmosphere by 2h with 5ºC/min for heating and cooling rates. The microstructural analysis was carried out by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD). In the other hand, their mechanical performance was evaluated by microhardness Vickers. Microhardness values from several aluminum commercial alloys reported in literature were compared with these experimental results.CNTs used as material reinforced are shown in Figs. 1(a,b). Diameters of ~80 nm and lengths of ~0.8 mm were observed. Fig. 1c displays the microstructure after sintering process. It can be observed a well dispersion Al 2 Cu phase produced by low cooling rate in sintering treatment. Figs. 1 (d,e) present bright field TEM micrographs from the composites with 1.0 and 5.0 wt.%, respectively. CNTs are observed in Fig. 1f from the composite with 1.0 wt.% of nanotubes. A second phase characterized as Al 4 C 3 is shown in Fig. 1g. Fig. 2a shows the results from XRD of the Al 2024 -CNTs composites as a function of the CNTs content. An increase in the peaks intensity attained to the aluminum carbides (Fig. 1e, marked with circles, and 1g) is observed as function of the CNTs content. However no variation was observed for the Al 2 Cu intensity peaks. The presence of CNTs after milling process and sintering heat treatment was verified by TEM as is shown in Fig. 1g.The mechanical characterization of the composites indicates that a rapid increament in mechanical properties is observed as a function of the addition of the CNTs (Fig. 2b). The maximum Vickers hardness value (219.74 VHN) observed in this work was reached by the sample with 5.0 wt.% of CNTs, this value represents ~346% (170.56 hardness units) over the pure Al hardness value. The composite with 3

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In this work, the assessment of Azadirachta indica, Tagetes erecta, Chrysanthemum morifolium, and Lentinula edodes extracts as catalysts for the green synthesis of zinc oxide nanoparticles (ZnO NPs) was performed. The photocatalytic properties of ZnO NPs were investigated by the photodegradation of methylene blue (MB) dye under sunlight irradiation. UV-visible (UV-Vis) spectroscopy, Fourier Transform Infrared (FTIR) spectroscopy, Transmission Electron Microscopy (TEM), X-ray Diffraction (XRD), Thermogravimetric (TGA), and Brunauer-Emmett-Teller analysis (BET) were used for the characterization of samples. The XRD results indicate that all synthesized nanoparticles have a hexagonal wurtzite crystalline structure, which was confirmed by TEM. Further, TEM analysis proved the formation of spherical and hemispherical nanoparticles of ZnO with a size in the range of 14–32 nm, which were found in aggregate shape; such a size was well below the size of the particles synthesized with no extract (~43 nm). ZnO NPs produced with Tagetes erecta and Lentinula edodes showed the best photocatalytic activity, matching with the maximum adsorbed MB molecules (45.41 and 58.73%, respectively). MB was completely degraded in 45 min using Tagetes erecta and 120 min using Lentinula edodes when subjected to solar irradiation.

The control of a homogeneous distribution of the reinforcing phase in aluminum matrix composites is the main issue during the synthesis of this kind of material. In this work, 2024 aluminum matrix composites reinforced with boron carbide were produced by mechanical milling, using 1 and 2 h of milling. After milling, powdered samples were cold consolidated, sintered and T6 heat treated. The morphology and microstructure of Al2024/B4C composites were investigated by scanning electron microscopy; analysis of X-ray diffraction peaks were used for the calculation of the crystallite size and microstrains by the Williamson–Hall method. The mechanical properties were evaluated by compression and hardness tests. B4C particles were found to be well dispersed into the aluminum matrix as a result of the high-energy milling process. The crystallite size of composites milled for 2 h was lower than those milled for 1 h. The hardness, yield strength and maximum strength were significantly improved in the composites processed for 2 h, in comparison to those processed for 1 h and the monolithic 2024 alloy.

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