Browsing by Author "Rosenkranz, A."

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    Effect of surface etching and electrodeposition of copper on nitinol
    (2017) Ramos-Moore, E.; Rosenkranz, A.; Matamala, L.F.; Videla Leiva, Alvaro Rodrigo; Durán, A.; Ramos-Grez, J.
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    Influence of crystallographic texture on friction in a-Al2O3/Ti(C,N) ceramic tool coatings
    (2022) Ramos-Moore, E.; Rosenkranz, A.; Diaz-Droguett, D. E.; Espinoza, C.; El Azahri, I.; Muecklich, F.
    This work explores the influence of the crystallographic texture on the resulting frictional response in two ceramic coatings systems containing top alpha-Al2O3 layer with no and fiber texture. The microstructure was analyzed by electron backscatter diffraction, the surface roughness was characterized by white light interferometry, and the micro hardness was measured by standard Vickers testing. The coefficient of friction (COF) was measured using ball-on-disk tribometry under linear reciprocating sliding motion. Our results verified a strong correlation between the crystallographic texture of the top alpha-Al2O3 layer and the resulting COF. This effect can be mainly attributed to the lowest critical shear stress within the basal dislocation slip {0001} < 11-20 >, which facilitates the generation of plastic deformation at the top surface layer. This work highlights the understanding of the complex correlations between microstructure and tribological performance of ceramic coatings.
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    Mechanical and microstructural properties of broadband anti-reflective TiO2/SiO2 coatings for photovoltaic applications fabricated by magnetron sputtering
    (2021) Zambrano, D. F.; Villarroel, R.; Espinoza-Gonzalez, R.; Carvajal, N.; Rosenkranz, A.; Montano-Figueroa, A. G.; Arellano-Jimenez, M. J.; Quevedo-Lopez, M.; Valenzuela, P.; Gacitua, W.
    Anti-reflective coatings are used in photovoltaic systems to minimize reflectance thus optimizing efficiency. Besides excellent optical properties, these coatings need to provide good mechanical properties due to hostile environmental conditions. Therefore, this study aims at designing anti-reflective coatings based upon multi layers of TiO2 and SiO2 by magnetron sputtering on glass and silicon substrates at room temperature. Afterwards, these coatings were thermally annealed at 400, 500 and 600 degrees C to study the influence of such treatment on their optical and mechanical properties. Samples prepared at room temperature and annealed at 400 degrees C showed an optimized reflectance of about 2%. Advanced materials characterization techniques were used to elucidate the microstructural evolution of the multi-layers. The multi-layers annealed at 400 degrees C demonstrated a dense and smoothly packed microstructure with homogenous grains (50 nm in size), with a phase transformation from amorphous to anatase. In addition, exposure and damage of the glass substrate were detected for elevated temperatures (500 and 600 degrees C), thus increasing the reflectance. Nanoindentation revealed an improved hardness, elasticity, and resistance against plastic deformation for the sample annealed at 400 degrees C. Consequently, anti reflective coatings with post-annealing treatment at 400 degrees C, unify two complementary aspects such as improved mechanical properties (extended durability) and enhanced collection abilities over a broader wavelength range (increased efficiency).