Estudio del mecanismo de eliminación demagnesio de aleaciones Al-Si en estado líquido mediante inyección de minerales base sílice

RESUMEN Se empleó el método de inyección sumergida de polvos por medio de un gas de arrastre inerte (Ar) con el fin de eliminar el magnesio de la aleación Al-Si A380 a 750 °C. Los polvos inyectados al baño de metal fundido fueron zeolita mineral, arena sílice y mezclas de ambas. Las variables de respuesta medidas fueron el contenido de magnesio en el baño metálico respecto al tiempo de inyección y las mermas de metal al final de cada experimento. En el análisis de resultados, la mezcla sílice:zeolita 66:34 % e.p. obtuvo la mayor eficiencia, lográndose una disminución en el contenido de magnesio en el baño metálico de 1 a 0.0066 % e.p. Los productos de reacción se analizaron por difracción de rayos-X, microscopía electrónica de barrido y de transmisión. Los resultados de estos análisis y el empleo del paquete termodinámico FactSage, versión 6, permitieron justificar el mecanismo de reacción entre los minerales y el aluminio líquido. ABSTRAC In order to eliminate magnesium from an A 380 Al-Si alloy at 750°C, the submerged powder injection method, using an inert carrier gas (Ar), was applied. The injected powders in the liquid aluminum bath were zeolite, silica and mixtures of zeolite-silica minerals. For each experiment the response variables were: eliminated magnesium versus injection time and quantity of drosses produced. Chemical analysis by atomic absorption spectrometry showed that mixtures of silica-zeolite 66:34 wt% have the best results with regarding to the removal magnesium from 1 to 0.0066 wt%. During the elimination of magnesium complex stoichiometry compounds were formed due to the reactions among zeolite, water steam and liquid aluminum. These compounds were analyzed by XRD, SEM and TEM. The results obtained, along with using the FactSage 6 thermodynamic software, allowed to elucidate the reaction mechanism between the minerals used and liquid aluminum

Electrochemical formation of novel nanowires and their dynamic effects

Novel and uniform β-Sn nanowires surrounded by graphitic material (fully filled tubes; 40–50% of the overall material, length ≤2 μm; ≤100 nm o.d.) are produced by passage of a current between graphite rods immersed in molten mixtures of LiCl and SnCl2 under argon at 600°C. Prolonged electron beam irradiation (under HRTEM) of the nanowires leads to axial growth, re-orientations and allied dynamic transformations. The technique may be applied to other soft metals in order to generate filled nanotubes

An alternative route to molybdenum disulfide nanotubes

Molybdenum disulfide ((MoS2)n) nanotubes are generated when polycrystalline MoS2 powder, covered by Mo foil, is heated to ca. 1300 °C in the presence of H2S. Electron diffraction reveals the presence of zigzag arrangements within the tube walls