Alumnos Aceptados en el Ciclo 2012 - 1

Listado de Artículos Publicados en 2011

1. Infinite penetration of a projectile into a granular medium
   F. Pacheco-Vázquez. G. A. Caballero-Robledo, J. M. Solano-Altamirano, E. Altshuler, A. J. Batista-Leyva, and J. C. Ruiz-Suárez.
   Phys Rev Lett . F. I. 106. 218001- 218004, 2011. (2011)
   An object falling in a fluid reaches a terminal velocity when the drag force and its weight are balanced. Contrastingly, an object impacting into a granular medium rapidly dissipates all its energy and comes to rest always at a shallow depth. Here we study, experimentally and theoretically, the penetration dynamics of a projectile in a very long silo filled with expanded polystyrene particles. We discovered that, above a critical mass, the projectile reaches a terminal velocity and, therefore, an endless penetration
   Abstract
2. Multicommutation flow techniques in the hydride generation-atomic fluorescence determination of arsenic
   Leal, LO; Ferrer, L; Forteza, R; Cerda, V.
   Trac-Trend Anal Chem. F. I. 30. 761-770, 2011. (2011)
   This review outlines automated methodologies developed for measuring arsenic in environmental samples. We report the state of the art of the most significant methods exploiting multicommutation flow techniques coupled to hydride generation-atomic fluorescence determination. We review analytical methods used and present a comparative evaluation of them. We also discuss the on-line pre-concentration procedure as being of particular interest in the development of fully automated methods.
   Abstract
3. Synthesis, Structural Characterization, and Electrical Properties of (Sr(0.5)Ca(0.5))(Ca(0.5)Sb(0.5))O(3-delta) Double Perovskites
   Moreno, B; Urones-Garrote, E; Chinarro, E; Fuentes, L; Moran, E.
   Chem Mater. F. I. 23. 1779-1784, 2011. (2011)
   Double perovskites which exhibit 1:2 B-site ordering are under focus because of their interesting structure property relationships and high chemical versatility. Perovskites with a big cation, such as Sr(2+) or Ca(2+), occupying the octahedral B site are very scarce because the calculated Goldschmidt tolerance factor becomes quite small as these types of cations usually occupy the A-site. This work describes the synthesis and structural and microstructural characterization of a new calcium and strontium antimoniate which shows face-centered cubic symmetry and a rock-salt ordered distribution of Sb(s+) and Sr(2+). The ordered-cation distribution occurs due to the differences in both the ionic sizes and the bonding character of the two B-site cations. As a consequence of the cation stoichiometry of the title phase and assuming a pentavalent state for Sb, a large concentration of oxygen vacancies are created (y similar to 0.25). Diffraction studies reveal that these vacancies tend to arrange in a short-ordered way and are related to oxygen ionic conductivity (10(-3) S/cm at 700 degrees C) which makes these materials potential candidates to be used as electrolytes in solid oxide fuel cells (SOFC).
   Abstract
4. A comparison of the effects of multi-wall and single-wall carbon nanotube additions on the properties of zirconia toughened alumina composites
   Bocanegra-Bernal, MH; Echeberria, J Ollo; García-Reyes; Domínguez-Ríos, ; Reyes-Rojas, A ; Aguilar-Elguezabal, A.
   Carbon. F. I. 49. 1599-1607, 2011. (2011)
   The use of multi-wall carbon nanotubes (MWCNTs) or single-wall carbon nanotubes (SWCNTs) as filler in ceramic matrices could create composites with exceptional mechanical properties. We have prepared dense monolithic alumina (Al(2)O(3)) and zirconia-toughened alumina (ZTA) composites with additions of 0.01 wt% of MWCNTs or 0.01 wt% of SWCNTs by conventional sintering and have demonstrated that the mechanical properties depend on (a) the distribution of CNTs in the matrix and (b) the interaction between the ceramic phases and CNTs. The fracture toughness of Al(2)O(3) ceramics reinforced with SWCNTs was significantly better than those reinforced with MWCNTs. However, fracture toughness in MWCNT-reinforced ZTA increased 41% over ZTA free of the toughening agent and 44% over ZTA reinforced with SWCNTs. A well dispersed and small amount of MWCNTs was enough to produce an increase of fracture toughness in ZTA composites.
   Abstract
5. Nanostructured polyethylene glycol-titanium oxide composites as solvent-free viscous electrolytes for electrochromic devices
   Mendoza, N; Paraguay-Delgado, F; Hechavarria, L ; Nicho, ME; Hu, HL.
   Sol Energ Mat Sol C. F. I. 95. 2478-2484, 2011. (2011)
   Composites of polyethylene glycol (PEG) and titanium oxide compounds have been prepared by sol-gel method using different molar ratio between PEG and titanium isopropoxide. Transmission electron microscope (TEM) images and UV-vis absorption spectra of these composites indicate that titanium oxide particles or clusters were formed inside the composite materials and their maximum sizes were between 1.8 and 7 nm for PEG:Ti molar ratio changing from 24:1 to 4:1. Fourier Transform Infrared spectroscopy analysis of the same PEG-Ti composites suggests the presence of tetragonal titanium oxide compounds and its association with ether oxygen atoms of PEG molecules. As lithium iodide salt was added into PEG-Ti composites, iodide ions were oxidized into iodine and tri-iodides and, at the same time, titanium oxide compounds should be reduced. Color change speeds of tungsten oxide thin films were significantly improved when PEG-Ti-Lil composites were used as electrolytes compared to salt-in-polymer one (PEG-Lil); the bleaching time of tungsten oxide was reduced from 22 to 2.5 s under +1.0 V polarization, and the coloring time under -1.5 V lowered from 16 to 2.2 s. The transfer of negative charges from smaller iodide ions onto longer or crosslinked PEG-Ti macromolecules could be the origin of faster lithium ion transport/insertion speeds in PEG-Ti composite electrolyte based electrochromic devices.
   Abstract