The contact angle of nanofluids as thermophysical property.

Droplet volume and temperature affect contact angle significantly. Phase change heat transfer processes of nanofluids - suspensions containing nanometre-sized particles - can only be modelled properly by understanding these effects. The approach proposed here considers the limiting contact angle of a droplet asymptotically approaching zero-volume as a thermophysical property to characterise nanofluids positioned on a certain substrate under a certain atmosphere. Graphene oxide, alumina, and gold nanoparticles are suspended in deionised water. Within the framework of a round robin test carried out by nine independent European institutes the contact angle of these suspensions on a stainless steel solid substrate is measured with high accuracy. No dependence of nanofluids contact angle of sessile droplets on the measurement device is found. However, the measurements reveal clear differences of the contact angle of nanofluids compared to the pure base fluid. Physically founded correlations of the contact angle in dependency of droplet temperature and volume are obtained from the data. Extrapolating these functions to zero droplet volume delivers the searched limiting contact angle depending only on the temperature. It is for the first time, that this specific parameter, is understood as a characteristic material property of nanofluid droplets placed on a certain substrate under a certain atmosphere. Together with the surface tension it provides the foundation of proper modelling phase change heat transfer processes of nanofluids.

Note: development of ESS Bilbao's proton ion source: Ion Source Hydrogen positive.

The Ion Source Hydrogen positive is a 2.7 GHz off-resonance microwave discharge ion source. It uses four coils to generate an axial magnetic field in the plasma chamber around 0.1 T that exceeds the ECR resonance field. A new magnetic system was designed as a combination of the four coils and soft iron in order to increase the reliability of the source. The description of the simulations of the magnetic field and the comparison with the magnetic measurements are presented. Moreover, results of the initial commissioning of the source for extraction voltage until 50 kV will be reported.

Multifunctional bioactive glass scaffolds coated with layers of poly(D,L-lactide-co-glycolide) and poly(n-isopropylacrylamide-co-acrylic acid) microgels loaded with vancomycin.

A new family of multifunctional scaffolds, incorporating selected biopolymer coatings on basic Bioglass® derived foams has been developed. The polymer coatings were investigated as carrier of vancomycin which is a suitable drug to impart antibiotic function to the scaffolds. It has been proved that coating with PLGA (poly(lactic-co-glycolic acid)) with dispersed vancomycin-loaded microgels provides a rapid delivery of drug to give antibacterial effects at the wound site and a further sustained release to aid mid to long-term healing. Furthermore, the microgels also improved the bioactivity of the scaffolds by acting as nucleation sites for the formation of HA crystals in simulated body fluid.

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.

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.

Zirconia coating of carbon nanotubes by a hydrothermal method.

Carbon 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.