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CuO structures were synthesized by microwave hydrothermal treatment using two different mineralizing agents (NaOH and NH 4 OH) and were evaluated as photocatalysts. The materials were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and Brunauer-Emmett-Teller (BET) surface area analysis. The XRD patterns indicated the formation of the monoclinic phase in both samples with 13.78 and 14.23 nm crystallite size. SEM analysis showed different agglomerates morphologies based on the mineralization agent employed. The CuO nanostructure synthesized with NH 4 OH presented agglomerated like-plates which results in a spherical shape, whereas the material synthesized with NaOH presented an agglomerate of larger plates. Both samples showed photocatalytic activity against RNL azo dye. The quasi-spherical shape CuO material reached 93 % of the discoloration.

The purpose of this work was to produce submicrometric hydroxyapatite (HA) and beta-tricalcium phosphate (β-TCP) biphasic fibers by means of solution blow spinning (SBS). This method was chosen due to its lower cost and higher production rate than those of electrospinning, which is normally employed in ceramic fiber production. The fibers thus obtained were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). The in vitro bioactivity and cytotoxicity of the fibers were also investigated. The XRD patterns indicated the formation of biphasic HA/βTCP fibers. SEM analysis revealed an interconnected cylindrical morphology with the presence of beads. Fiber diameters in the submicrometric range varied from 374 to 451 nm. TGA results indicated that organic losses occurred solely below 600ºC. All the fibers were non-cytotoxic, presenting an inhibitory concentration (IC) of > IC50. All the samples successfully formed acicular apatite layers when immersed in SBF, indicating a high potential for in vivo bone bioactivity.

ResumoLigas com memória de forma (LMF) de NiTi são materiais inteligentes que possibilitam o desenvolvimento de diversas aplicações de engenharia devido suas propriedades funcionais chamadas de efeito de memória de forma e superelasticidade. No entanto, fabricar componentes com geometria complexa a partir destes materiais é um desafio tecnológico que poderá ser superado com o desenvolvimento de técnicas efetivas de união destas ligas por soldagem. Objetivou-se neste trabalho avaliar os efeitos dos diferentes parâmetros de soldagem nas propriedades mecânicas de juntas soldadas obtidas de chapas finas de uma LMF de NiTi austenítica. As soldagens foram realizadas pelo processo de soldagem à laser (LBW -Laser Beam Welding) variando a potência e velocidade de soldagem e a realização ou não do tratamento térmico pós-soldagem (TTPS). Como ferramenta de otimização foi utilizado um planejamento experimental 2 3 e a metodologia da superfície de resposta. Foi observado que o TTPS promoveu a estabilização de um estado misto de fases na chapa de NiTi, entre a fase R e a austenita à temperatura ambiente e que após a soldagem foi possível observar uma redução dos valores aferidos de dureza no metal de solda (MS). Além disso, as juntas soldadas com velocidade de soldagem de 900 mm/min e que foram submetidas ao TTPS apresentaram resistência mecânica à tração satisfatória independentemente da potência empregada. Palavras-chave:Ligas com memória de forma, Ligas de NiTi, Processo de soldagem a laser. AbstRActNiTi shape memory alloys (SMA) are smart materials that enable the development of various engineering applications due to their functional properties called shape memory effect and superelasticity. However, to manufacture components with complex geometry from these materials is a technological challenge that can be overcome with the development of effective joint techniques of these alloys by welding. The objective of this work was to evaluate the effects of the different welding parameters on the mechanical properties of welded joints of thin sheets of austenitic NiTi SMA. The joints were performed by the laser welding process varying the power and speed of welding and the influence of post-weld heat treatment (PWHT) was verified. As an optimization and evaluation tool, a design of experiments and the response surface methodology were respectively used. It was observed that the PWHT promoted the stabilization of a phase mixed state in the thin sheet, between the R phase and the austenite at room temperature and that after welding it was possible to observe a reduction of the average values of hardness in the weld metal (WM). Furthermore, welded joints with welding speed of 900 mm/min and were submitted to PWHT showed satisfactory tensile mechanical strength independent of the welding power used.

The objective of the present work was to evaluate welding of thin sheets (thickness < 1 mm) of similar and dissimilar NiTi alloys with AISI 304 stainless steel using the Gas Tungsten Arc Welding (GTAW) process and to study the mechanical and metallurgical properties of the joints with and without post-welding heat treatment (PWHT). The GTAW process was chosen because it is more economical than the usual welding processes for NiTi alloys, such as the Laser Beam Welding (LBW). The welded joints were characterized by the techniques of SEM, OM, electrical resistance in temperature (ERT), tensile test and Vickers microhardness. It was observed that the dissimilar joints presented a brittle behavior due to the formation of brittle elements along the weld metal by the excessive increase of the hardness in this region with peaks of hardness higher than 900HV. Similar joints presented superior mechanical behavior, with extensive plastic deformation before rupture and fracture surface with ductile appearance. The PWHT in the similar joints promoted a decrease in the rigidity of the material by minimizing the thermal stresses from the welding process, the PWHT did not influence the dissimilar joints mechanical behavior.