This article presents the implementation and the evaluation of the blended learning program Training of Lifelong Learning Adult Trainers, which was organized by the Center of Training and Lifelong Learning of the Aristotle University of Thessaloniki in Greece, during the last two years (2016-2017). The aim of the training program was to give the opportunity to adult trainers to certify their educational competence and update their knowledge in the field of adult education, enhancing their employability. After the completion of the program, the trainees assessed the implementation methodology, the educational content, the microteachings, the quality, and the organization of the program. The results of the evaluation showed that the program was of a high level, flawlessly organized, and with excellent educational material, while the blended learning model worked effectively, receiving positive reviews by the participants. It was concluded that blended learning is indeed adequate in adult educational programs increasing the participation and facilitating adult trainees to better integrate their learning experiences.
A simple and versatile chemical solution deposition process is reported to manipulate the wettability properties of copper sheets. The whole process has the advantage of being time-saving low cost and environment-friendly. An adherent silver coating was achieved under optimal conditions. Scanning electron microscopy and X-ray diffraction were used to examine the silver film structure. A confocal microscope was used to record the 3D topography and assess the film roughness of the surface. A dual morphology was revealed, consisting of broad regions with feather-like structured morphologies and some areas with spherical morphologies. Such silver-coated copper samples exhibited a sufficiently stable coating with superhydrophobicity, having a maximum water contact angle of 152°, along with an oleophilic nature. The corrosion behavior of the produced hydrophobic copper under optimal conditions was evaluated by means of potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) using a 3.5% NaCl solution. The corrosion protection mechanism was elucidated by the proposed equivalent circuits, indicating that the superhydrophobic silver coating acted as an effective barrier, separating the Cu substrate from the corrosive solution. The superhydrophobic coating demonstrated enhanced anti-corrosion properties against NaCl aqueous solution in relation to the copper substrate as indicated from both EIS and potentiodynamic polarization experiments.
Boronizing of steel is a widely used method for superficial protection and strengthening of various components. Although it is an effective solution for most applications, it can be improved by adding metallic elements to enrich the coating with mixed borides that have exceptional properties. In the present study, we investigated the actual upgrade of a boronized AISI 4140 steel after an additional chromizing process in terms of corrosion resistance. Samples of boronized and borochromized steel were immersed in 10% vol. HCl or H2SO4 solutions for 0.5-4 h and assessed with Electrochemical Impedance Spectroscopy. It is shown by the results that the borochromized specimens started with higher impedance values than the boronized ones, but they gradually degraded by immersion time and tended to approach the values of the boronized specimens, a fact attributed to the weakening of the resistance of the coating due to the corrosion. On the contrary, the boronized samples showed lower but stable values of impedance. The porosity of the boronized specimens did not contribute to their total impedance, as deduced by equivalent electrical circuit analysis. The impedance of the bulk region of both coatings did not decrease significantly during the corrosion. XRD and SEM/EDS measurements supported our findings.
In many applications, even high-performance alloys have to be covered with protective coatings, providing higher corrosion and oxidation resistance, as compared to the alloy itself. This study investigates the feasibility to apply boron coatings on P91 steel by pack cementation process, to increase the steel durability in oxidative and corrosive environments, as well as its mechanical strength. Micro-indentation and the coating impact test were used to characterize the hardness and fatigue properties of the film respectively. The coating corrosion resistance versus the one of the uncoated P91 steel was tested in a salt spray chamber. The coating performance was characterized by optical and scanning electron microscopy to check the consistency of the coated and uncoated surfaces and the oxidation extend. The results show an increased film strength, good fatigue performance and adequate corrosion resistance.
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