In this paper, the effects of Mn and Al against corrosion/errosion resistance of three samples of the Fe-Mn-Al austenitic alloys are evaluated. The samples have composition Fe-(4,9 ~ 11,0 wt. (%)) Al-(17,49 ~ 34,3 wt. (%)) Mn-(0,43 ~ 1,25 wt. (%))C, those were prepared in an induction furnace from high purity materials. The alloys were evaluated in a composed solution of NaCl 0,5 M and Silica in a special chamber and AISI 316 stainless steel as reference material. The electrochemical characterization was performed by Tafel curve polarizations technique. This microstructural characterization was by Scanning Electron Microscopy (SEM). It was observed the significant decrease in the corrosion rate for steels Fermanal with a lower percentage of aluminum and manganese under conditions of dynamic corrosion and erosion-corrosion. SEM allows assessment of the dominant damage mechanisms and corroborated the results obtained by electrochemical measurements.

Steel bar embedded in an alkali-activated slag (AAS) concrete was tested under complete immersion, in 3.5% NaCl solution by weight of the slag. Ordinary Portland cement (OPC) was also tested for comparative purposes and exposed to the same solution. Monitoring of open-circuit potential, polarization resistance measurement and electrochemical impedance spectroscopy (EIS) were used to evaluate the corrosion behavior of steel bar. The corrosion resistances of AAS and OPC concretes were performed at 0, 3, 6, 9 and 12 months. Electrochemical measurements shows that AAS concrete presents passive corrosion behavior the first 3 months, after this period of time, it presents corrosion resistance decreased due to the chlorides presence at the steel/AAS interface. For 0 months immersion (28 days of curing) the AAS and OPC concretes presented a 10% of corrosion probability. After 3 months of immersion the tested AAS and OPC concretes showed similar behavior, the active potentials in the range from "0.2 to "0.6 V vs. Cu/CuSO4, indicate a 90% probability of corrosion.

Se conformaron películas cerámicas del sistema SiO2-TiO2 sintetizadas por el método de los precursores poliméricos a partir del Tetraethylorthosilicate (TEOS), y Titaniumtetrabutoxide (TBT), un ácido hidroxicarboxílico (ácido cítrico) y alcohol polihidroxílico (etilenglicol). Las películas fueron depositadas, en monocapa, sobre sustratos de ace ro AISI 304 mediante la técnica de inmersión (dipcoating). Se utilizaron como concentraciones de los precursores Si (silicio) 10% Ti (titanio) 90%, Si 30% Ti 70% y Si 50% Ti 50% que conforman el sistema. Se estudió la influencia de los recubrimientos sobre el comportamiento anticorrosivo del sustrato en una solución de ácido clorhídrico (HCI), mediante la técnica de Espectroscopia de Impedancia Electroquímica (EIS). Adicionalmente, se evaluó la topografía por Microscopía Electrónica de Barrido (SEM) y de adhesión de los recubrimientos al sustrato. Se encontró que los valores de los parámetros estudiados cambian sustancialmente en función de las concentraciones de los precursores empleados en la síntesis.

Ceramic films were formed SiO2TiO2 system synthesized by the polymeric precursor method from tetraethyl orthosilicate (TEOS) and Titanium tetrabutoxide (TBT), a hydroxycarboxylic acid (citric acid) and polyhydric alcohol (ethylene glycol). The films were deposited monolayer on substrates of AISI 304 steel using the immersion technique (dipcoating). eoncentrations were used as precursors Si (silicon) 10% Ti (Titanium) 90%, Si 30% Ti 70% and Si 50% Ti 50% in the system. The influence of coatings on corrosion behavior of the substrate in a solution of hydrochloric acid (Hel), using the technique of Electrochemical Impedance Spectroscopy (EIS). Additionally, the topography was evaluated by scanning electron microscopy (SEM) and adhesion of coatings to the substrate. It was found that the values of these parameters change substantially depending on the concentrations of the precursors used in synthesis.

Se reporta la conductividad térmica (k) a temperatura ambiente de polvos de carbón térmico, en función del tipo y concentración del aglutinante (agua, alcohol, ACPM), los cuales variaron de porcentaje en peso (%wt), entre 5% y 40%. Las muestras fueron obtenidas de la mina Cerro Tasajero ubicada en el área metropolitana de San José de Cúcuta, Colombia, las cuales se pulverizaron manualmente, utilizando molino de rodillos y se tamizaron en malla pasante número 100 (150 urn), k se determinó, usando el principio físico de flujo lineal transitorio de calor, mediante el sistema KD2® Thermal Properties Analyzer (Decagon Devices, Inc). El porcentaje de ceniza presente en la muestra, se determinó según la norma ASTM D3174, y se encontró un valor de 1,75%; para hallar la concentración de azufre, se utilizó la norma ASTM D3177, y reportó un valor de 0,45%, mientras que el porcentaje de materia volátil presente en la muestra fue de 34,17%, que se halló, aplicando la norma ASTM D3175. El análisis de k en función del tipo y concentración del aglutinante, se realizó, usando el ajuste a los datos experimentales mediante la función logística <img src="img/revistas/cein/v21n1/v21n1a02ecu1.jpg">donde A2corresponde a los valores de la propiedad térmica (y) para la concentración inicial de aglutinante (x); A1 representa dicho valor para cuando la concentración de aglutinante (x) sea muy grande; x o corresponde al punto donde sucede el cambio de curvatura y n la razón de crecimiento o decrecimiento. Los resultados encontrados en este trabajo, podrán ser utilizados en el desarrollo de estudios que permitan la fabricación de cilindros de polvos de carbón prensados a altas presiones, los cuales se usarán en los procesos de combustión en hornos industriales que se utilizan en la sinterización de productos cerámicos como teja, bloque y baldosa.

This paper reports a thermal conductivity (k) given an environment temperature of thermal coal powder as a function of agglutinant concentration and type -i.e. water, alcohol, diesel- which changed their weight percentage (%wt) between 5-and-40 percent. Samples were obtained from Cerro Tasajero, a mine located at San Jose de Cucuta metropolitan area, which were pulverized manually using roller mill and sifted by a mesh No. 100 (150um). The /rvalue was determined using the physical principle of temporary linear heat flow by system KD2® Thermal Properties Analyzer (Decagon Devices, Inc.) The ash percentage in the sample was given by norm ASTM D 3174, providing a value of 1.75 percent. The sulfur concentration was obtained using norm ASTM 3177, reporting a value of 0.45 percent, while the percentage of matter volatile in the sample was 34.17 percent by applying norm ASTM 3175. The analysis of k as a function of agglutinant type and concentration was carried out adjusting the experimental data based on the logistical function <img src="img/revistas/cein/v21n1/v21n1a02ecu1.jpg">where A2 corresponds to values of the thermal property (y) for an initial concentration of agglutinant (x). Ai represents such a value as agglutinant (x) concentration may be very big; x0 reveals the point where bend is changing and n the reason of growth or falling. The results in this experience could be used to develop other studies in order to produce high-pressed coal powder cylinders, which will be used in industrial burning processes by sintering ceramic goods, such as roof tile, block and wall tile.