Characterization of Joints Between Aluminum and Galvanized Steel Sheets

International audienceSound joints between an AA6016 aluminum sheet of 1.2-mm thickness and a low-carbon galvanized steel sheet of 0.77-mm thickness are obtained using the laser pseudo-brazing method. A zinc-based aluminum alloy is used as a filler wire with optimized process parameters for laser pseudo-brazing. Metallurgical investigation of the joint is carried out using a scanning electron microscope and energy-dispersive X-ray analysis. Joints produced using Al-Zn filler wire showed a moderate strength and quality with a layer containing principally Fe2Al5Zn (x) type intermetallics of similar to 10-mu m thickness. Failure in the heat-affected zone of aluminum is found to be dominative, while in some cases, fracture along the interface between the intermetallic layer and the steel sheet is observed

Inhibition of heat resistant molds: Aspergillus fumigatus and Paecilomyces variotii by some plant essential oils

In this study, the inhibitory properties of some essential oils including citrus (Citrus sinensis L. Osbeck), laurel (Latin's nob ills L.), myrtle (Myrtus communis L.), oregano (Origanum vulgare L.), and savory (Satureja thymbra L.) were investigated against the heat resistant molds Aspergillus fumigatus and Paecilomyces variotii isolated from margarine in a previous study in order to assess the potential for using these essential oils as a natural food preservative. In this study, the essential oils of the plants were obtained by steam distillation using Clevenger apparatus and were tested for antifungal activities at 0.25, 0.50, and 1.00% concentrations. Inhibitory effects of the essential oils on the growth of the fungi followed the sequence: oregano=citrus>savory>laurel>myrtle. P variotii was more resistant against the essential oils than A. fumigants

Interfacial Structure and Photocatalytic Activity of Magnetron Sputtered TiO2 on Conducting Metal Substrates

International audienceThe photocatalytic behavior of magnetron sputtered anatase TiO2 coatings on copper, nickel, and gold was investigated with the aim of understanding the effect of the metallic substrate and coating-substrate interface structure. Stoichiometry and nanoscale structure of the coating were investigated using X-ray diffraction, Raman spectroscopy, atomic force microscope, and scanning and transmission electron microscopy. Photocatalytic behavior of the coating was explored by using optical spectrophotometry and electrochemical methods via photovoltage, photocurrent, and scanning kelvin probe microscopy measurements. The nature of the metal substrate and coating-substrate interface had profound influence on the photocatalytic behavior. Less photon energy was required for TiO2 excitation on a nickel substrate, whereas TiO2 coating on copper showed a higher band gap attributed to quantum confinement. However, the TiO2 coating on gold exhibited behavior typical of facile transfer of electrons to and from the CB, therefore requiring only a small amount of photon energy to make the TiO2 coating conductive