Identification of rare earth minerals associated to K-feldspar: Capacsaya project in Peru

A recently discovered the rare-earth-rich site in Capacsaya, located at 123 km northwest of Cusco, at the south of Peru, contains signifcant quantities of light and heavy rare-earth elements such as neodymium, lanthanum, cerium, europium, and yttrium. This work reports the identifcation of rare-earth elements and their associated minerals using scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray difraction analyses. Five (5) samples extracted from diferent locations at the Capacsaya site were characterized and identifed K-feldspar as the mineral associated with the rare-earth elements in a representative sample with a high concentration of lanthanum and cerium. The results showed rare-earth elements contained within the mineral phase monazite, being cerium the dominant element in the phase (La, Ce, Nd)PO4. Finally, through the electrostatic separation process we demonstrate that it was possible to achieve an efcient separation of the K-feldspar phase in the particle size range 75–150 μm

Assessment of cellulose nanofibers from bolaina blanca wood obtained at three shaft heights

This study evaluated cellulose nanofibers from bolaina blanca wood (Guazuma crinita) obtained at different heights of the longitudinal axis of the shaft of trees from a three-and-a-half-year-old plantation. The wood was subjected to pulping, bleaching and subsequent mechanical milling using a Changsha Samy XYQM-2L planetary ball mill to obtain cellulose nanofibers. The product was characterised using analytical techniques: scanning electron microscopy, X-ray diffraction, thermogravimetric analysis, Fourier transform infrared spectroscopy, ultraviolet–visible spectroscopy. Additionally, the degree of polymerisation was determined. The effect of longitudinal position on cellulose nanofibers characteristics was evaluated by comparing means using ANOVA and Kruskal–Wallis statistical tests. The yield of cellulose nanofibers production from the high, middle and basal sections was 32,1 %, 33,6 % and 31 %, respectively. The obtained cellulose nanofibers exhibited a significantly larger diameter for the high zone (84 nm) compared with the middle (75 nm) and basal (69 nm) zones; the length remained above the micrometre range. With respect to degree of polymerisation, a decrease was evidenced with respect to the increase in shaft height; the basal zone exhibited a degree of polymerisation of 300, a significantly higher value than the middle and high zones, which exhibited degree of polymerisation of 249 and 211, respectively. The product showed typical cellulose type I polymorphism and crystallinity indexes of 76 %, 93 % and 96 % for the high, middle and basal sections, respectively. Regarding the thermostability of cellulose nanofibers, the maximum degradation rate of cellulose nanofibers occurred between 335 °C and 341 °C, with cellulose nanofibers from the basal area being the most stable. The adsorption of the methylene blue dye on cellulose nanofibers was evaluated; an efficiency > 60 % was found

Estudio de influencia del Freon (CF4) en el electrocromismo de películas delgadas de Dióxido de Titanio (Tio2)

Se han fabricado películas delgadas de TiO2 por la técnica “DC Reactive Magnetron Sputtering” para aplicaciones eletrocromicas. Depositadas a temperatura ambiente, las películas de TiO2 obtenidas presentan estructura amorfa o microcristalina que probablemente corresponde a la fase anatasa. El efecto electrocromico en estas películas es notable pero excesivamente lento para las aplicaciones. Se comporta como un material electrocromico catódico que deviene absorbente con la inserción de cationes de litio. La banda de absorción se produce en la zona visible y esta centrada en 0.69 um. Se ha encontrado que la edición de gas Freon (CF4) a la mezcla Ar+O2 usado en la fabricación de TiO2, durante el sputtering, mejora notablemente la rapidez del proceso de inserción iónica y por lo tanto de la modulación óptica. Con esta modificación en el proceso de fabricaciones, obtenemos películas de TiO2 : F que denominamos “fluoradas” y que alcanzan cambios de transmitancia de hasta 50% en pocos segundos. Con el propósito de evaluar las potenciales aplicaciones de este material, fue sometido a pruebas de durabilidad. Según los resultados las películas fluoradas de TiO2 pueden ser cicladas mas de 10^4 veces sin mostrar deterioro. El análisis de las ventajas notables encontradas en las películas fluoradas respecto a las de TiO2 (obtenidas sin la introducción CF4) es la principal contribución de este trabajo al estudio de los materiales electrocromico. Este efecto, a nuestro entender, no ha sido reportado anteriormente en la literatura.Tesi