Zr-metal adhesion on graphenic nanostructures

3 pages, 3 figures.-- PACS nrs.: 68.35.Np, 61.46.Fg, 61.46.Df.Our 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.We want to acknowledge the support by the ETORTEK (NANOMAT) program of the Basque government, the Intramural Special Project (Reference No. 2006601242), the Spanish Ministerio de Ciencia y Tecnología (MCyT) of Spain (Grant No. Fis 2007-66711-C02-C01), and the European Network of Excellence NANOQUANTA (NM4-CT-2004-500198). Y.S.P. gratefully acknowledges his DIPC grant.Peer reviewe

Biomedical applications of ceramic nanocomposites

Bioceramics and bioceramic composites have been widely used for biomedical applications for the last 50 years. This chapter discusses the advantages of using ceramic nanocomposites. The application of both inert and bioactive ceramics for orthopaedic and dental implants, as well as in the novel field of tissue engineering, is discussed and future trends are presented.Peer reviewe

Zirconia-MWCNT nanocomposites for biomedical applications obtained by colloidal processing

Zirconia ceramics are widely used as femoral heads, but case studies show that delayed failure can occur in vivo due to crack propagation. The addition of carbon nanotubes (CNT) is aimed to avoid the slow crack propagation and to enhance the toughness of the ceramic material used for prostheses. However, to really enhance the mechanical properties of the material it is necessary to achieve a uniform distribution of the CNT in the zirconia matrix. Colloidal processing has demonstrated to be suitable for obtaining ceramic-based composites with homogeneous distribution of the phases and high green density. This work compares the colloidal behavior of the as-received multi wall carbon nanotubes (ar-MWCNT) and the partially coated MWCNT (pc-MWCNT) when immersed in a nanozirconia matrix. With pc-MWCNT an improvement in the dispersion is proved. Moreover, the sintered samples that contain pc-MWCNT show higher density, lower grain size, improved toughness and enhanced hardness under the same sintering cycle when compared to the samples with ar-MWCNT.Acknowledgments Supported by Spanish Ministry of Science and Innovation (project CIT-420000-2008-7 and Ramón y Cajal fellowship, RYC-2008-03523), Basque Government (PI-2004-2, BF105.R2.555 and Etortek: Nanomaterials).Peer reviewe

Surface energy and frictional / adhesive properties of polymeric resist films

The effect of plasma treatment on surface properties of resist films devoted for nanoimprint lithography (NIL) was studied. The Atomic Force Microscope was used to identify surface topography, pull-off force and lateral (friction ) force of the resist film before and after plasma treatment with the presence of nitrogen and hydrogen gases. The wettability was studied to estimate surface energy of the films both with polar and dispersion components. The AFM-based microtribometer enabled to study the frictional behavior of the resist films. The results of these extended studies have shown that the used plasma functionalization is effective to modify dramatically the surface properties of the resist films.Peer reviewe

XRD study of the effect of the processing variables on the synthesis of nanozirconia in the presence of MWCNT

Several challenges must be solved to obtain an effective introduction of carbon nanotubes in a ceramic matrix. Dispersion, good load transfer, and wettability are the major issues to be overcome to obtain good final properties of a zirconia nanocomposite. We have developed a process to coat multi-wall carbon nanotubes with nanozirconia to deal with these challenges. The process is based on the hydrothermal synthesis of tetragonal zirconia nanoparticles in the presence of multi-wall carbon nanotubes (MWCNT). In this work, X-ray diffraction has been used to study the influence of the processing variables in order to optimize this process. The theoretical mathematical models that relate the percentage of tetragonal zirconia and their crystallinity in relation to the processing variables have been extracted.Peer reviewe

Compact LED based nanoimprinter for UV-NIL

UV-based nanoimprint lithography (UV-NIL) is a cheap and fast way to imprint patterns ranging from nanometres to micrometres. However, commonly used equipment can be expensive and require a clean room infrastructure. Here we present the design and testing of a simple UV-NIL system based on a light emitting diode. The current design permits imprints of 10 × 10 mm 2 in size using a 25 × 25 mm2 master. This printer can be used in a semi-clean environment such as a laminar flow bench. The imprinter was used to imprint photoresists as well as UV sensitised hydrogels. The best results were obtained using SU-8 photoresist with features down to 50 nm in size, only limited by the imprint master. Patterns in SU-8 resist were also transferred into silicon substrates by reactive ion etching demonstrating its full potential as a lithographic tool.The authors acknowledge technical assistance in the James Watt Nanofabrication Centre at Glasgow and the mechanical work shop in the School of Engineering. The work has been supported by the EC funded project NaPANIL (Contract No. FP7-CP-IP 214249-2).Peer reviewe

Carbon nanotubes for biological devices

The unique properties of carbon nanotubes open attractive possibilities in many applications areas, for instance as biological devices. Multi Wall Carbon Nanotubes (MWNT) have been synthesized by Chemical Vapour Deposition (CVD) and the influence of certain process variables in the final product yield have been studied. In addition, purification treatment applied at synthesized carbon nanotubes, has been developed. Biocompatibility tests have demonstrated that purified carbon nanotubes are non-cytotoxic. Finally, a functionalization process is developed to help in carbon nanotubes-biomolecule interaction.Peer reviewe

The effect of the addition of carbon nanotubes in the hydrothermal synthesis and in the thermal phase stability of nanozirconia

The yttria partially stabilized zirconia is a very attractive material for orthopaedic applications. It exhibits excellent biocompatibility, high fracture toughness, high strength and low wear rates. But case studies show that delayed failure can occur in vivo due to crack propagation. Carbon nanotubes could avoid the slow crack propagation and enhance the toughness of the ceramic material used for prostheses fabrication. In this work, X-ray diffraction has been used to study the influence of the addition of MWCNT on the hydrothermal synthesis of tetragonal zirconia nanoparticles and on the phase stability of the CNT-nanozirconia nanocomposite with the temperature. First, the influence of the processing variables on the hydrothermal synthesis has been studied. The theoretical mathematical models that relate the percentage of tetragonal zirconia nanocrystals and the relative crystallinity with the processing variables in the range of analyzed values have been obtained. The values that give the maximum percentage and crystallinity of tetragonal phase in the studied range have been established. No significant differences were observed in the crystalline phases obtained when adding MWCNT during the synthesis. Nanozirconia partially coated MWCNT synthesized under the optimized parameters were added to commercially available nanozirconia particles and their influence in the phase stability of the zirconia with the temperature was studied by XRD. It was concluded that the addition of the carbon nanotubes delays both the monoclinic phase decomposition and the grain growth.Peer reviewe

New sensitive layers for surface acoustic wave gas sensors based on polymer and carbon nanotube composites

Surface acoustic wave (SAW) gas sensors based on carbon nanotube polymer composites as sensitive layers were investigated for the detection of low concentrations of volatile organic compounds as octane and toluene. Several nanocomposites based on polyepichlorohydrin (PECH) and polyetherurethane (PEUT) with different percentage of multiwalled carbon nanotubes (MWCNT) were tested to study the effect of MWCNTs in the response of sensors.This work has been supported by Spanish MEC project (NAN2004-09380-C04-02). The authors wish to thank Dr. C. Cané and Dr. I. Gràcia from the Centro Nacional de Microelectrónica IMB-CSIC for supplying the micro-machined SAW substrates.Peer reviewe