In this work results regarding microstructural characterization of a melt-spun intermetallic compound Fe40Al5Cr (% at.) produced by rapid solidification employing the melt spinning technique at three different tangential wheel speeds (12, 16 and 20 ms-1) are presented. Melt spun ribbons were characterized by optical and scanning electron microscopy (SEM) in order to observe morphology, grain size, ribbon thickness and also fracture surfaces after tensile tests. EDS coupled to SEM was employed to perform punctual and scan line chemical analyses on samples, x-ray diffraction (XRD) was utilized to identify crystal structure and phases. Transmission electron microscopy (TEM) was employed to confirm crystal structure and also to characterize nanopores formed in the specimens by vacancy clustering. With regard to mechanical properties, micro hardness Vickers measurements as well as tensile tests at room temperature were applied to the rapidly solidified ribbons. The grain size of rapidly solidified Fe40Al5Cr ribbons suffered a drastic reduction as compared with alloys of the same composition produced by conventional melting and casting methods, and in melt-spun ribbons it decreases as the wheel speed increases. Punctual and line-scanning chemical analyses revealed that Cr enters in solid solution in FeAl matrix. Hardness measurements revealed a softening in rapidly solidified FeAlCr ribbons as compared with FeAl alloys and tensile test exhibited a (transgranular + intergranular) mode of fracture, reaching up to 3 % of elongation in FeAlCr alloys. The presence of porous (meso and nano) were also characterized.

En este trabajo se presentan resultados concernientes a la caracterización microestructural de cintas de aleación Fe40Al5Cr que fueron producidas mediante solidificación rápida empleando la técnica de melt-spinning (rueda girante), a tres diferentes velocidades tangenciales de rueda (12, 16 y 20 ms-1). Las cintas solidificadas rápidamente fueron caracterizadas mediante microscopía óptica y electrónica, con el propósito de observar morfología, tamaño de los granos y espesor de las cintas y también observar las superficies de fractura despues de los ensayos de tensión en las cintas metálicas. Asimismo, se realizaron análisis químicos puntuales mediante EDS y de barrido en línea, también se realizaron análisis de rayos X (DRX) con el objeto de determinar la estructura cristalina, constantes de red y fases. De la misma manera, los especímenes se observaron mediante microscopía electrónica de transmisión (MET) con la finalidad de confirmar la estructura cristalina y caracterizar nanoporos formados en los especímenes originados por la aglomeración de vacancias. Respecto a las propiedades mecánicas, las cintas fueron sometidas a ensayos de dureza y tensión a temperatura ambiente en aire. Se observó que el tamaño de grano de las cintas solidificadas rápidamente sufrió un considerable decremento en comparación con aleaciones de la misma composición producida por métodos convencionales de producción, además, tanto el espesor de las cintas como el tamaño de grano se redujeron con el incremento de velocidad de rueda o rapidez de enfriamiento. Los análisis químicos puntuales y de barrido en línea revelaron que el cromo entra en solución sólida en la matriz FeAl. Los mesoporos superficiales, así como también los nanoporos observados en el interior de las cintas fueron caracterizados mediante microscopía electrónica. Los ensayos de dureza revelaron un ablandamiento del material en las cintas de aleación ternaria FeAlCr en comparación con cintas de aleación binaria FeAl producidas por solidificación rápida. Los ensayos de tensión revelaron un modo de fractura mixto (intergranular + transgranular) con un 3 % de elongación total.

Using the reactive magnetron rf co-sputtering technique and a Ti target partially covered with a small Al plate, TiAlN coatings were made on c-Si in a reactive atmosphere of nitrogen and argon. Coatings were deposited on substrates at 22°C and at 150°C. The substrate temperature notably affected the thickness, crystalline grain size, and hardness of the coatings. We analyzed the dependence of both structure and crystalline grain sizes on substrate temperature and the chemical composition of the coatings. The structural properties and the chemical composition were obtained by means of XRD and EDS techniques. High aluminum content was found in the coatings for the samples grown at the lower substrate temperature when samples were measured by electron dispersive spectroscopy technique. Atomic force microscopy measurements showed a surface morphology dependent on the nitrogen content. Scanning electron microscopy measurements showed a clear pyramidal microstructure of TiAlN coatings grown at 22°C, while the microstructure of those grown at a substrate temperature of 150°C were not well defined.

In this work, a new process to obtain palladium powders from their salts by using a cementation process (in aqueous solution) through an iron electrode and a catalyst agent was studied. The process gives results that in practice can also be applied to obtain bulk metal from secondary sources. Nano and micrometric particles could be obtained from this new process. The physicochemical and morphological characteristics of these powders are heavily dependent on the method used for their production. For the Palladium test and PdCl2 solution 0.093 M, a minimum quantity of catalyst agent was added to accelerate the reaction. In the palladium powders only small round particles were obtained, which can be easily suspended in solution. For the reaction, there is no considerable temperature dependence. Thus, the process can be carried out at room temperature resulting in considerable energy saving.