Browsing by Author "Calvo-Barrio, L."
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Item Zirconia coating of carbon nanotubes by a hydrothermal method(2008-11) Garmendia, N.; Bilbao, L.; Muñoz, R.; Imbuluzqueta, G.; García, A.; Bustero, I.; Calvo-Barrio, L.; Arbiol, J.; Obieta, I.; PRINTEX; SISTEMAS FOTOVOLTAICOS; Tecnalia Research & InnovationCarbon nanotubes have unique mechanical properties that open attractive possibilities in many fields, such as the biomedical one. Currently, zirconia ceramics are widely used as femoral heads, but case studies show that delayed failure can occur in vivo due to crack propagation. Nanotubes could avoid the slow crack propagation and enhance the toughness of the ceramic material used for prostheses fabrication. In this work, single-wall carbon nanotubes and multi-wall carbon nanotubes have been partially coated with nanozirconia via hydrothermal synthesis and characterized by several techniques: X-ray diffraction, infrared spectroscopy, scanning electron microscope, transmission electron microscope, electron energy loss spectra, X-ray photoelectronic spectroscopy and atomic force microscopy. By means of these techniques, the existence of bonds between zirconium and the carbon nanotube has been proved. The as covered nanotubes should offer a better wettability in the ceramic matrix and improve the dispersion of the carbon nanotubes, to obtain the desired new ceramic biomaterial with a longer lifetime and better reliability.Item Zr-metal adhesion on graphenic nanostructures(2008) Sanchez-Paisal, Y.; Sanchez-Portal, D.; Garmendia, N.; Muoz, R.; Obieta, I.; Arbiol, J.; Calvo-Barrio, L.; Ayuela, A.; Tecnalia Research & InnovationOur high resolution transmission electronic microscopy studies of multiwall carbon nanotubes show, after the growth of zirconia nanoparticles by a hydrothermal route, the presence of surface Zr, forming an atomically thin layer. Using first-principles calculations we investigate the nature of the Zr-C interaction, which is neither ionic nor covalent, and the optimal coverage for the Zr metal in a graphene flake. This preferred coverage is in agreement with that deduced from electron energy loss spectra experiments. We show also that the amount of charge transferred to the C layer saturates as the Zr coverage increases and the Zr-C bond becomes weaker.