William Aperador

A Practical Application of X-Ray Spectroscopy in Ti-Al-N and Cr-Al-N Thin Films

Binary and ternary transition metal nitrides coatings have been used in numerous applications to increase the hardness and improve the wear and corrosion resistance of structural materials, as well as in various high-tech areas, where their functional rather than tribological and mechanical properties are of prime importance (Munz, 1986; Chen & Duh, 1991; PalDey & Deevi, 2003; Ipaz et al., 2010). Up to now, Ti-Al-N and Cr-Al-N films have been synthesized by a variety of deposition techniques including cathodic arc evaporation (Cheng et al., 2001), ion plating (Setsuhara et al., 1997), chemical vapor deposition (CVD) or plasma-enhanced CVD (Shieh & Hon, 2001) and d.c. / r.f. reactive magnetron sputtering (Musil & Hruby, 2000; Sanchez et al., 2010). Performance of these coatings is equally dependent on their chemical composition and long-range crystalline structure, as well as on the nature and amount of impurities and intergranular interactions. Significant improvement in the mechanical properties has recently been achieved with multicomponent superlattice, multilayers and nanocomposite nitride coatings. In the case of such multilayers systems, not only is close control of the elemental composition (stoichiometry) and modulation period necessary to optimize the properties of the coatings, but the influence of chemical bond formation between the components is also of prime importance. Therefore, it is necessary to take special care when the conditions of preparation are nonequilibrium, activation of CVD and PVD by plasmas or energetic particle beams are applied, occasionally leading to unpredicted deviations, both in composition and structure. As is highlighted in this study, nitride coatings or nitrided surfaces based in Chromium and Aluminium materials can be analyzed in detail by X-ray photoelectron spectroscopy (XPS) due to its excellent element selectivity, quantitative character and high surface sensitivity. More importantly, XPS reflects the atomic scale chemical interactions, i.e. the bonds between neighboring atoms Cr-N, Al-N, Ti-N, Ti-Al-N and thus it also provides reliable structural characteristics for amorphous or nano-crystalline coatings of complex composition, for which application of diffraction techniques is not straightforward.

ESTUDIO DE LA SINERGIA CORROSIÓN-EROSIÓN DE RECUBRIMIENTOS DUROS DE TiN Y CrN OBTENIDOS SOBRE ACERO AISI 1045

Resumen es: En este trabajo se presentan los resultados del estudio de los efectos sinergeticos de la corrosion-erosion en recubrimientos duros de TiN y CrN obtenido...

Tribo-electrochemical characterization of hafnium multilayer systems deposited on nitride/vanadium nitride AISI 4140 steel

In this work is presented the synergistic behaviour among corrosion/wear (tribocorrosion) of the multilayer coatings hafnium nitride/vanadium nitride [HfN/VN]n. The multilayers were deposited on AISI 4140 steel using the technique of physical vapor deposition PVD magnetron sputtering, the tests were performed using a pin-on-disk tribometer, which has an adapted potentiostat galvanostat with three-electrode electrochemical cell. Tribocorrosive parameters such as: Friction coefficient between the coating and the counter body (100 Cr6 steel ball); Polarization resistance by means of electrochemical impedance spectroscopy technique and corrosion rate by polarization curves were determined. It was observed an increase in the polarization resistance, a decrease in the corrosion rate and a low coefficient of friction in comparison with the substrate, due to an increase on the number of bilayers.

Estudio Comparativo del Poder Lubricante y Estabilidad Oxidativa entre el Aceite de Ajonjolí y Aceite Mineral 360

A comparative study of the lubricant properties and oxidative stability of sesame oil and a mineral oil, without additives is presented. The superior power of vegetable oil lubricant compared to that of mineral oil was verified by preventive wear tests and extreme pressure in a four-ball tribometer. According to atomic absorption test, there are traces of metals in the areas that are in contact with the sesame oil during the development of the preventative wear test. These particles catalyze the oxidation of the oil during the differential scanning calorimetry test, decreasing the oxidation starting temperature. The preventive wear test partially degraded the sesame oil and increased the peroxide value. This change in the oil was not possible to find by Fourier transform with infrared spectroscopy and acidity. The stability of the mineral oil is superior to that of the vegetable oil.

Propiedades mecánicas del concreto para viviendas de bajo costo

La resistencia a cortante de muros de concreto y los nuevos materiales y tecnicas de construccion han posicionado a la vivienda industrializada de concreto como una opcion eficiente para proporcionar seguridad ante eventos sismicos, para incentivar la conservacion del medio ambiente y para promover la reduccion de los costos de construccion, operacion y mantenimiento. Con el proposito de desarrollar ayudas de diseno que promuevan la utilizacion de diferentes tipos de concreto, se llevo a cabo un estudio experimental para caracterizar las propiedades mecanicas de los concretos de peso normal, peso ligero y autocompactable. El programa experimental incluyo el ensayo de 603 especimenes en forma de cilindros y vigas. En el estudio se determinaron las propiedades mecanicas de los tres tipos de concreto sometidos a esfuerzos de compresion, tension y flexion. A partir de las tendencias de los resultados experimentales, se proponen correlaciones numericas para estimar las propiedades mecanicas basicas de los concretos, tales como modulo de elasticidad, resistencia a tension indirecta y resistencia a flexion. Adicionalmente, en el estudio se proponen recomendaciones respecto a la resistencia minima a compresion del concreto para vivienda y a la edad de descimbrado de los muros. Las recomendaciones de este estudio se podrian implantar facilmente en un reglamento para construccion de vivienda de baja altura y de bajo costo.

Evaluation of erosion-corrosion resistance in Fe-Mn-Al austenitic steels

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.

Efecto del modo de obtención de la sílice amorfa a partir de la cascarilla de arroz en las propiedades de durabilidad del concreto armado

In this article the effect of rice husk ash on mechanics and durability properties of concrete was investigated. At 28 age curing, compressive strength of concrete, rapid chloride ion penetration, electrochemical impedance spectroscopy and polarization resistance were made with the aim of understand such effect. The results show the locally available rice husk ash grows the compressive strength and the permeability by aggressive agents is minimized just if the RHA is added in finely grounded particles.

OBTENCIÓN DE ELECTRORECUBRIMIENTOS DE COBRE - NÍQUEL DEPOSITADOS SOBRE SUBSTRATOS DE ZAMAK POR MEDIO DE LA TÉCNICA DE CORRIENTE PULSANTE INVERSA

This work shows the implementation of the of the technologies of current pulsant inverse, pulse direct current and direct current for electrodeposition thin films Cu-Ni in double-layer shape on Zamak substrate. The morphologic analysis was realized using microscopy of atomic force (AFM) allowing to identify that the films obtained with inverse current pulsant are denser and of better grain that those of other two technologies. To evaluate the protective power anticorrosive of the thin films there was in use the technique EIS and TAFEL. Here I observe in the same way as the deposition using the inverse current pulsant technique generates deposits of minor porosity and increases the resistance to the corrosion of the obtained films

Electrochemical characterization of the steel wire used as reinforcement in the conductors transmission networks electricity nitride by ion implantation

The power company feature infrastructure, which are generally shaped so the transmission and distribution lines, here is why it is necessary to characterize the process of electrochemical corrosion of these components. In this case the steel wire coated with zinc or aluminium, as it is undergoes the rigor of corrosive environments. Given the geographical diversity and different climatic environments, atmospheric corrosion carried affecting service life of structures. For example in very humid environments such as coasts and high altitudes, wetting time (TOW), parameter that meets the conditions of temperature and relative humidity, it affects large proportion, accelerating the corrosion of ferrous materials. Given the importance of establishing mechanisms that lessen the impact on degradation in transmission and distribution lines of both the reliability and the availability of the same. This paper presents the implementation in nitride steels as an alternative or complement to zinc coating.

Estudio del Poder Lubricante del Aceite de Ajonjolí con Adición de Nanopartículas de Cobre

espanolEl poder lubricante del aceite de ajonjoli extra virgen con aditivos de nanoparticulas de cobre fue evaluado mediante ensayos de desgaste preventivo y presion extrema. El desempeno como lubricante del aceite vegetal fue comparado con el de un lubricante hidraulico comercial. La lubricidad de los aceites fue evaluada a traves de la medicion del diametro promedio de la huella de desgaste, la carga anterior al desgaste visible y el punto de soldadura. Los resultados experimentales indican que las nanoparticulas de cobre en dispersion actuan como aditivos antidesgaste y como aditivos de extrema presion. Se encontro que una concentracion de 1% de nanoparticulas de cobre en dispersion en el aceite base, puede superar el desempeno como lubricante de un aceite hidraulico comercial. EnglishThe lubricant power of extra virgin sesame oil with the addition of copper nanoparticles was evaluated by tests of preventive wear and extreme pressure. The performance of the vegetable oil as a lubricant was compared with a commercial hydraulic oil. The lubricity of the oils was evaluated by measuring wear scare diameter, last nonseizure load and the weld point. Experimental results indicate that the copper nanoparticles in dispersion act as both anti-wear and extreme pressure additives. It was found that a concentration of 1% copper nanoparticles dispersed in the base oil has better lubricant performance than commercial hydraulic oil.