Powders Nb 2 O 5 were prepared by two different synthesis method, Sol-Gel and polymeric precursors (Pechini). In the Pechini method before adding the citric acid in the process, four different solutions were used to get the samples. For Sol-gel method, two different processes were also used in obtaining powders. The precursor was completely solubilized in ethanol and then hydrolyzed with ammonia and water. The calcination of the samples was between 500 and 750°C. The resulting powders were characterized by Scanning Electron Microscopy (SEM), Brunauer, Emmett and Teller (BET) surface area measurements, UV-visible and Raman spectroscopy. The formation of T−Nb 2 O 5 orthorhombic took place upon calcination at 7500C. Crystallite sizes were determined using the Scherrer method which resulted in an uniformed size of about 25 − 65nm. Ultraviolet-Visible diffuse reflectance spectroscopy indicated a variation in the optical band gap values (3.32-3.40 eV) in crystal growth process. The Raman vibrational modes indicate the presence of the orthorhombic phase of the material.

Maintaining a constant voltage the growth of titanium oxide (T iO 2 ) with a tubular geometry was studied. Therefore, the optimal parameters for the growth of TiO 2 were established using an organic electrolytic solution with a total volume of 150ml, composed of water/hydrofluoric acid/ammonium fluoride/ethylene glycol. The anodization conditions were varied, such as: time (60 -215 min), electric potential (5 -20 V), water content (0.0 -2.0 ml), and pH (4.8 -5.1). In this procedure, the conformation of long, open nanotubes with smooth walls was achieved, obtaining a maximum length of 1.90 µm for the nanotubes. However, in some samples before and after annealing a remnant layer can be seen that extends over some regions of the surface of the nanotubes. By means of the current density curves-time (J vs.t), we were able to specify the distinct growth zones of the nanotubes. The samples also were studied structurally by means of X-ray with thermal treatment (ambient−450 0 C). In addition, it was determined, via ultraviolet-visible (UV-Vis) spectroscopy, that the band gap energy varies (3.45 eV−3.03eV).

In this investigation, the compound Bi24Si40O2 was synthesized via sol-gel and applied on substrates of 316L stainless steel by spin coating varying speed. In the coatings obtained, the corrosion response in simulated physiological solution was evaluated by electrochemical impedance spectroscopy and polarization potentiodynamic curves. The morphology and surface topography was studied, also, were determined the microstructure, thickness values and roughness of the coatings. The results of this study allow establishing a high degree of anticorrosive effectiveness offered by the coatings as a function of the number of layers applied to the substrate and their possible application in the biomedical industry.

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ResumenSe evaluó la corrosión del acero estructural ASTM A 706 embebido en concretos obtenidos de subproductos industriales como escorias siderúrgicas y cenizas volantes activadas alcalinamente. En el estudio se emplearon técnicas de caracterización como potencial de circuito abierto, resistencia a la polarización lineal y espectroscopía de impedancia electroquímica en una disolución de cloruro de sodio al 3,5%. La interface acero-concreto fue caracterizada por espectroscopía Mössbauer de transmisión a temperatura ambiente y difracción de rayos X. Los resultados obtenidos por las diferentes técnicas de caracterización se compararon con valores obtenidos para concretos de cemento Portland. Los productos de corrosión identificados corresponden a magnetita (Fe 3 O 4 ), wuestita (FeO) y goethita (α-FeOOH). Palabras clave:cenizas volantes, escoria siderúrgica, espectroscopía de impedancia electroquímica, difracción de rayos X, espectroscopía Mössbauer Monitoring Corrosion of Concrete Embedded Steel obtained from Industrial Product Wastes AbstractCorrosion of ASTM A 706 structural steel embedded in concrete obtained from by-products as steel slag and fly ash alkali activated was evaluated. Characterization techniques such as open circuit potential, linear polarization resistance and electrochemical impedance spectroscopy in a solution of sodium chloride 3.5% were employed. The steel-concrete interface was characterized by transmission Mössbauer spectroscopy at room temperature and X-ray diffraction. The results obtained by the different characterization techniques were compared with values obtained for Portland cement concrete. The corrosion products identified are magnetite (Fe 3 O 4 ), wuestite (FeO) and goethite (α-FeOOH).