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Corrosion 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 (Fe3O4), wuestite (FeO) and goethite (α-FeOOH). [ABSTRACT FROM AUTHOR]

This work characterizes the materials of the polichromed stone sculpture "The Virgin of Snows", which was exposed to the elements from principles of the XX century and up to the 2004, in the town of Luyanó, City of Havana and is nowaday exposed in the room museum of the University School of San Geronimo of Havana located in the Historical Center of Havana. The study was carried out with reason of the restoration of the piece. The vestiges of pigments were characterized by Portable X-ray Fluorescence and microchemical test, the stratigraphic analysis by Optic Microscopy, the mineral of the original rock by X-ray Diffraction and Atomic Absorption Spectrometry. The porosity and the stability of the mineral were determined by Small Angles X-ray Scattering Dispersion (SAXS) and Potentiometry, respectively. Pigments were identified: blue-green pigment based on copper and blue pigment based on silicates; the white pigments: zinc white and lithopone; the golden colour in pupurin, the silver colour based on aluminium paint and the use of earth pigments in the colors: black, pink and clear (soft) ochre. The rock was identified as calcite. The transformation of the particles toward a laminate transitive form and the increase of big pores in the exfoliation of the sculpture, corresponds with a highly degraded mineral. [ABSTRACT FROM AUTHOR]

Coatings of TiN and TiSiN were prepared by reactive direct current magnetron co-sputtering on steel and on silicon substrates, using a Ti target and a small Si plate in a reactive atmosphere of nitrogen, oxygen and argon. Using the Warren-Averbach method the structural changes were analyzed in function of the variation of the nitrogen flow. Stoichiometry calculations obtained by X-ray Energy Dispersive Spectroscopy and corroborated by Glow Discharge Spectroscopy, show that the TiSiNO coatings contain two solid solutions of TiSixN(Oy) and SiNxOy and have a strong domain on titanium oxynitrure phase. The sample made on steel and silicon wafers substrates with nitrogen flow of 3 sscm, presented the highest hardness and the lowest resistivity values, respectively, due to its preferential crystalline orientation, structure and crystalline phases present. [ABSTRACT FROM AUTHOR]

In this work we report experimental studied by X-ray difraction and Mössbauer espectroscopy at room temperature for (Fe70Al30)100-xNix alloys. The alloys with x=10 and 20 were prepared by mechanical alloying using milling times of 12, 24 and 48 hours. We observed of the X-ray diffraction spectral fits an unique BCC phase for all alloys group. Addicionally, we founded that the lattice parameter is decrease while Ni and milling time increases. All alloys are ferromagnetics and they were fit with a field distribution. The hyperfine field shows a tendency to increase while the milling time increase. For 20 at. % Ni, we found an additional paramagnetic singlet to the field distribution. It is produced from a paramagnetic phase FCC, this phase did not detected by DRX. The mean hyperfine field is lower for this alloys. [ABSTRACT FROM AUTHOR]