Abstract The properties of aluminum alloys can be improved by the processing conditions that cause changes in the microstructure and by the addition of alloy elements. In order to understand the physical behavior and mechanical properties of aluminum alloys, it is important to be aware of some of the microstructural characteristics. Some of these characteristics are the morphology, alloy elements, volume and size, and second phase. In this study, we analyzed the effect of annealing on the mechanical and microstructural properties of the laminated AA 5182 aluminum alloy, when subjected to different annealing conditions. The alloy was heated to temperatures of 50º C, 100º C, 150º C, 200º C, 250º C and 300º C for 10 minutes and left to cool naturally. The evolution of the microstructure was characterized by optical and electronic microscopy with EDS, and, to obtain the mechanical properties, a tensile test was performed and the fractures were subsequently analyzed. The results showed that the heat treatment used reduced the amount of second phase particles and this influenced the mechanical properties.

Abstract Natural fibres have many advantages over synthetic ones, making them attractive for reinforcing polymer materials. This work evaluates the use of an Amazonian plant, namely Curauá (Ananas erectifolius), as a reinforcement phase of biocomposites fabricated by cold pressing. Curauá fibres have been shown to be a promising fibre for composite materials, especially due to their higher elastic modulus than other plant species. An L9 Taguchi design is used to investigate the effect of fibre fraction, NaOH concentration and immersion time on the tensile properties of biocomposites. Statistical models are able of predicting and revealing the optimal composition of the biocomposites. The tensile strength of Curauá biocomposites is significantly affected by the fibre fraction, followed by the factors of immersion time and NaOH concentration. High tensile strength is obtained by adding 25 wt.% of Curauá fibres treated under different conditions. There is an interaction between NaOH concentration and the immersion time; a higher concentration requires less time or vice versa to achieve ideal roughness, promoting strong fibre/matrix adhesion.

The present work aims at the preliminary evaluation of the Paspalun repens macrophyte dry biomass adsorbent material of zinc (Zn) and copper (Cu) metals from water. The diversity of Species is due to the extensive aquatic environment where it is inserted. The Paspalun repens species comes from the Buiuçu lake located in the region of Parintins-Amazonas- Brazil. The macrophyte was dried in a mill and then a digestion through biomass microwaves was done before and after its exposure to the solutions containing different concentrations of zinc and copper (1.00, 1.50, 2.00, 3.00 mg mL-1 of metals) for a period of 48 hours. As a source of the metals, zinc sulfate (ZnSO4 7H2O) for zinc, and copper sulfate (CuSO4 5H2O) for copper were used as the source. As a result, the efficiency of Paspalun repens was observed in the metals removal, the highest removal percentage, of 29.67 and 37.07% in the leaves, whereas in the root it was 25.25 and 32.84% (at the concentration 1.0 and 2.0 mg/mL consequently), was of zinc, therefore the dry biomass of this species can be considered as a low cost alternative material in the removal of these heavy metals, contributing to the improvement of water quality.