Maryory Astrid Gómez

Some Properties of Natural Fibers (Sisal, Pineapple, and Banana) in Comparison to Man-Made Technical Fibers (Aramide, Glass, Carbon)

In this paper, we analyze the results of the delignification treatments performed on three natural fibers (sisal, pineapple, and banana) and of the thermal treatments at 400, 600, and 800°C on three industrial fibers (aramid, carbon, and glass). The fibers were analyzed by TGA, SEM, and EDS, as well as tested for tensile strength before and after the delignification and thermal treatments. Contact angle measurements were also carried out on the natural fibers. With the delignification treatments, the removal of Si, K, and Mg on pineapple and banana fibers was achieved. Thermal treatments lowered significantly the tensile strength of industrial fibers, while delignification treatments decreased slightly the mechanical resistance of natural fibers, except in the case of the pineapple fiber.

High Temperature Cracking Damage of Calcium Aluminate Cements

Different formulations of calcium aluminate cements (CAC) with 51 and 71 wt% Al2O3, have been exposed to high temperature oxidation environments. Cement paste samples of 0.25, 0.30, and 0.40 water to cement (W/C) ratios were fabricated in this research. Both the raw cement powders and their corresponding samples after hydration were characterized in their microstructure by scanning electron microscopy, X-ray diffraction, Fourier-transform infrared spectroscopy and x-ray fluorescence. Samples were exposed to 500, 800 and 1000 °C in a furnace open to air. Damage occurred while samples were in the furnaces. Damage was analyzed by digital image processing.

Effect of heat treatment on the tribological properties of Nickel-Boron electroless coating

Nickel-Boron autocatalytic coatings are widely used in several industries to improve mechanical properties of materials such as hardness and wear resistance. Tribological properties were evaluated in Ni-B autocatalytic coatings deposited on AISI/SAE 1018 carbon steel before and after a heat treatment at 450 °C for one hour. Tribological tests were carried out by dry sliding, using a load of 5 N and a sliding speed of 0.012 m/s, in a homemade ball-on-disk tribometer, which followed ASTM G99 standard. According to the tribological evaluation, the heat treatments applied to Ni-B coatings improved their tribological performance. This research corroborates that by applying an adequate heat treatment, hardness and wear resistance of Ni-B coatings can be improved significantly.

High Resolution Morphological Changes of Cu, Ni, Al, and Au Surfaces Due to Atmospheric Corrosion

As atmospheric corrosion of electrical contacts is a common cause of failure in electronics industry and at the same time miniaturization is a requirement in any modern electronic device, it is important to study the effects of corrosion in the surface morphology of metals widely used in that industry sector, such as gold, copper, nickel, and aluminium. Here, atomic force microscopy (AFM) has been used with that purpose, analysing flat surfaces of those metals both before and after exposure by several weeks to the effects of a contaminated atmosphere containing both NO2 and SO2 at constant temperature and humidity. Results indicate all metals suffered changes both in surface morphology and roughness. AFM phase mode images also indicated the occurrence of different species on the Ni and Cu surfaces after 11 weeks of exposure. Evidence of defects due to the corrosion attack was only observed for Ni.