Showing papers by "Anabela G. Rolo published in 2016"

The effect of ionic Co presence on the structural, optical and photocatalytic properties of modified cobalt-titanate nanotubes.

Abstract: With the aim of producing materials with enhanced optical and photocatalytic properties, titanate nanotubes (TNTs) modified by cobalt doping (Co-TNT) and by Na+ → Co ion-exchange (TNT/Co) were successfully prepared by a hydrothermal method. The influence of the doping level and of the cobalt position in the TNT crystalline structure was studied. Although no perceptible influence of the cobalt ion position on the morphology of the prepared titanate nanotubes was observed, the optical behaviour of the cobalt modified samples is clearly dependent on the cobalt ions either substituting the Ti4+ ions in the TiO6 octahedra building blocks of the TNT structure (doped samples) or replacing the Na+ ions between the TiO6 interlayers (ion-exchange samples). The catalytic ability of these materials on pollutant photodegradation was investigated. First, the evaluation of hydroxyl radical formation using the terephthalic acid as a probe was performed. Afterwards, phenol, naphthol yellow S and brilliant green were used as model pollutants. Anticipating real world situations, photocatalytic experiments were performed using solutions combining these pollutants. The results show that the Co modified TNT materials (Co-TNT and TNT/Co) are good catalysts, the photocatalytic performance being dependent on the Co/Ti ratio and on the structural metal location. The Co(1%)-TNT doped sample was the best photocatalyst for all the degradation processes studied.

Lithium cobalt oxide crystallization on flexible polyimide substrate

Abstract: This work reports the fabrication and charac- terization of lithium cobalt oxide films (LiCoO2) on flexi- ble Kapton substrate. LiCoO2 is commonly used as cathode of lithium microbatteries but needs an annealing of 700 C, which is not compatible with most flexible sub- strates. LiCoO2 films were deposited by reactive RF sput- tering followed by an annealing process at 400 C for 1 h in vacuum and air atmospheres both in silicon and Kapton substrates. Raman spectroscopy, X-ray diffraction patterns and scanning electron microscopy images were used to evaluate samples crystallinity and morphology. Films fabricated in Kapton and silicon substrates were compared.

Ordered La0.7Sr0.3MnO3 nanohole arrays fabricated on a nanoporous alumina template by pulsed laser ablation

Abstract: Highly ordered nanohole arrays of [Formula: see text] manganite have been synthesized using pulsed laser deposition on nanoporous alumina template. Their structure and phase formation were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), energy dispersive x-ray spectroscopy (EDX) and x-ray diffraction (XRD). The magnetic measurements were performed with respect to temperature and field and exhibit a ferromagnetic to paramagnetic transition at 284 K. In addition, the temperature dependence of electrical resistance was measured at different magnetic fields and an insulating phase throughout all the temperatures was observed. The low temperature ferromagnetic insulating state is discussed by the presence of a canted ferromagnetic state induced by the nanoholes. The present work shows the feasibility of combining both the nanoporous alumina template and pulsed laser ablation for the fabrication of perovskite manganite nanohole arrays which can also be extended to fabricate other multicomponent oxide nanohole materials.