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Opposed Jet mixers contact two opposed high-speed streams in a semi-confined mixing chamber. The turbulent energy for mixing is injected from the smaller scales of the inlet streams width and grows into larger vortices extending to the chamber width. The energy distribution associated to the flow scales mainly concentrates in the inertial sub-range, ranging from the injectors width to the mixing chamber width. This energy cascade and respective wavelengths are controlled by the geometry of the mixer. This paper introduces the control of 2D turbulent energy spectrum from an external stimulus, the modulation of the jets flow rate, which induces several dynamic behaviors. A new flow regime is induced from active mixing, where a state of resonance with a single flow frequency throughout the CIJs is associated to the formation of large vortices occupying the entire width of the mixing chamber. This work addresses a novel implementation of CIJs with modulation of inlet flow rate for process intensification of mixing sensitive operations.

The oblique angle deposition (OAD) is a versatile and easily controllable method appropriate for the production of nanoporous structures with pores in nanometric range and high surface area. In this study, aluminum thin films were deposited by sputtering on both commercial and homemade porous aluminum oxide substrates, tilted 85° and 89°. The morphology of substrates and the shadowing effect created by the OAD led to the deposition of densely packed columnar Al thin films with surface pores which sizes range between 19 and 75 nm depending on the substrate, tilt angle, time of deposition and power density. Focused ion beam (FIB) nanotomography allowed the 3D reconstruction of the whole nanoporous structures, in which the substrate, the thin film and the interface could be easily observed. Moreover, these results showed the hourglass-like shape of pores in the Al thin films, as well as the pores interconnectivity and the existence of open porosity that ensures the passage of the gas/liquid flow through the nanoporous structure. This study provides further insights into the production patterns of nanoporous structures by OAD, with a potential application in nanofiltration systems able to filter nanoparticles, which are often found in industrial environments and can represent a risk for human health and environment.

Conventional industrial processes are emission sources of unintended nanoparticles which are potentially harmful for the environment and human health. The aim of this study is to assess airborne nanoparticle release from aluminum surface treatment processes in various workplaces. Two direct reading instruments, a scanning mobility particle sizer to measure size distribution and a nanoparticle surface area monitoring to measure the surface area of particles deposited in the human lung, were employed to perform area monitoring.The lacquering paint was the process which released the highest concentration of particles from 10–487 nm (7.06 × 106 particles/cm3). The lacquering baths process emitted particles of the largest average size (76.9 nm) and the largest surface area deposited in the human lung (167.4 µm2/cm3). Conversely, the anodizing bath process generated particles of the smallest average size (44.3 nm) and the lowest human lung-deposited surface area (1.2 µm2/cm3). The total number of partic...

Nickel and titanium alternated nanolayers were deposited from Ti and Ni targets. The multilayer thin films were designed in order to have equiatomic overall chemical composition with a period from 5 to 70 nm. The chemical composition, morphology, structure and phase transformation behaviour were studied. The surface and cross-section morphology of the as-deposited thin films was analysed by atomic force microscopy (AFM) and scanning electron microscopy (SEM). The Ni/Ti thin films present in their surface nanograins and for higher periods in cross section it was possible to distinguish the alternated layers and measure their thickness. The structural evolution with temperature was analysed by in-situ hot stage X-ray diffraction (XRD). The as-deposited multilayer thin films exhibit a tendency to a transitory disorder as the period decreases. For the smaller periods a disordered phase forms during the deposition process, while in Ni/Ti multilayers with higher periods this phase is only observed during annealing. By increasing the temperature an exothermic reaction occurs with the formation of the B2-NiTi austenitic phase. In spite of moderate enthalpy of mixing, the multilayers with intermediate modulation period of Ni/Ti films show potential to be used for joining purposes.

Liquid Dynamic Compaction (LDC) is a two-stage powder metallurgy process comprising inert gas atomization followed by deposition of the variously sized droplets produced on a suitable substrate surface. The paper describes the effects of process parameters, mainly gas pressure, on the microstructure of a spray-deposited Zn-4Al-1Cu alloy using optical microscopy and scanning electron microscopy. This alloy exhibited very interesting and unpublished variations in its microstructure, which had well defined equiaxed grains of primary zinc-rich phase (η) embedded in a fine eutectoid phase a + η, resulted from the eutectic decomposition β + η, at 275 °C. The results showed that the microstructures of the deposits are quite different from those presented in the droplets. To estimate the solidification rates of the alloy obtained in this work, it was cast in a wedge-shaped cast-iron chill mold. This technique allows important predictions to be made without having to perform gas atomization-deposition.

An a-C:H thin film deposited by plasma immersion ion implantation and deposition on alloy steel (16MnCr5) was analyzed using a self-consistent ion beam analysis technique. In the self-consistent analysis, the results of each individual technique are combined in a unique model, increasing confidence and reducing simulation errors. Self-consistent analysis, then, is able to improve the regular ion beam analysis since several analyses commonly used to process ion beam data still rely on handling each spectrum independently. The sample was analyzed by particle-induced x-ray emission (for trace elements), elastic backscattering spectrometry (for carbon), forward recoil spectrometry (for hydrogen) and Rutherford backscattering spectrometry (for film morphology). The self-consistent analysis provided reliable chemical information about the film, despite its “heavy” substrate. As a result, we could determine precisely the H/C ratio, contaminant concentration and some morphological characteristics of the film, such as roughness and discontinuities.

In the present study, small-sized porous scaffolds were obtained from the freeze-drying of sodium hyaluronate/chitosan polyelectrolyte complexes. The obtained materials were characterized by a set of techniques including attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, swelling determination and weight loss studies. The morphology of the scaffolds was observed using scanning electron microscopy. Thermal characterization of the scaffolds was also performed by dynamic mechanical thermal analysis and thermogravimetric analysis. Finally, the cytotoxic profile of the prepared scaffolds was evaluated in vitro, using mesenchymal stem cells. The results obtained showed that cells adhered to scaffolds and proliferated. This study also confirmed that the degradation by-products of sodium hyaluronate/chitosan scaffold are noncytotoxic, which is fundamental for its application in the biomedical field.