BUSCADOR RECOLECTA

a-C:Ag coatings (1.2–23.4 at.% of Ag) were deposited using magnetron sputtering. Ag nanoparticles appear embedded in the carbon matrix or segregated to the column boundaries or surface. The silver doping has not promoted significant changes of the sp2/sp3 ratio although a decrease of the hardness is observed (from 17 to 7 GPa). The tribological behavior did not show a clear dependence on the silver concentration in unlubricated or lubricated conditions (fetal bovinum serum) against alumina or UHMWPE balls. Ag nanoparticle dispersion enhanced the bactericide behavior as determined by the released Ag+ ion in the fluid media. There is no clear effect of friction rubbing on the released silver indicating that diffusion and top segregation are prevalent mechanisms for its dissolution., European Regional Development Funds program (EU-FEDER), Leverhulme International Network Grant (CARBTRIB), Spanish Ministry of Economy, Industry and Competitiveness (projects n° MAT2015-65539-P and MAT2015-69035-REDC), Junta de Andalucía (project P10-TEP 06782) and CSIC (201560E013) are acknowledged for financial support., Peer reviewed

High power impulse magnetron sputtering (HiPIMS) technology has been employed to prepare TiC/a-C:H nanocomposite coatings from a titanium target in acetylene (C2H2) reactive atmospheres. Gas fluxes were varied from 1.3 to 4.4 sccm to obtain C/Ti ratios from 2 to 15 as measured by electron probe microanalysis (EPMA). X-ray diffraction and transmission electron microscopy demonstrate the presence of TiC nanocrystals embedded in an amorphous carbon-based matrix. The hardness properties decrease from 17 to 10 GPa as the carbon content increases. The tribological properties were measured using a pin-on-disk tribometer in ambient air (RH= 30-40%) at 10 cm/s with 5 N of applied load against 6-mm 100Cr6 balls. The friction coefficient and the film wear rates are gradually improved from 0.3 and 7×10-6 mm3/Nm to 0.15 and 2×10-7 mm3/Nm, respectively, by increasing the C2H2 flux. To understand the tribological processes appearing at the interface and to elucidate the wear mechanism, microstructural and chemical investigations of the coatings were performed before and after the friction test. EPMA, X-ray photoelectron and electron energy-loss spectroscopies were employed to obtain an estimation of the fraction of the a-C:H phase, which can be correlated with the tribological behavior. Examination of the friction counterfaces (ball and track) by Raman microanalysis reveals an increased ordering of the amorphous carbon phase concomitant with friction reduction. The tribological results were compared with similar TiC/a-C(H) composites prepared by the conventional direct current process., The authors are grateful to the Spanish Ministry of Economy, Industry and Competitiveness (Projects Nos. MAT2015-65539-P and MAT2015-69035-REDC) and Leverhulme International Network Grant (CARBTRIB) for financial support.

Two multilayer solar selective absorber coatings [Al/CrN0.95/Cr0.96Al0.04N1.08/Cr0.53Al0.47N1.12/Al2O3
(stack #1) and Cr0.96Al0.04N0.89/Cr0.62Al0.38N1.00/Cr0.53Al0.47N1.12/Al2O3 (stack #2)] were deposited on
316L steel by combining direct current (DC) and high power impulse magnetron sputtering
(HiPIMS) technologies with the aim of increasing the working limit temperature. The
composition and thickness of the constituent layers were optimized using CODE software to
achieve a high solar absorptance (α) and low values of thermal emittance (ɛ) in the infrared
region. The deposited multilayered stacks were heated during 2 hours in air at 600, 700 and 800
ºC to study their thermal stability and optical performance. Compositional, structural and optical
characterization of the stacks (as-prepared and after thermal treatment) was performed. Both
stacks presented a good solar selectivity with  > 95% and 25 ºC < 15%, were stable up to 600 ºC
and fulfilled the performance criterion PC < 5% after 600 and 700 ºC treatments. Despite the
stacks suffered chemical transformations above 600 ºC, partial oxidation (stack #1) and Cr2N
formation (stack #1 and #2), the optical properties were optimum up to 700 ºC for stack #1 (α =
94%, ε(25 ºC) =12%) and 600 ºC for stack #2 (α = 93%, ε25 ºC =13%).The solar-to-mechanical energy
conversion efficiencies () of the as-deposited and annealed (600 and 700 ºC) samples were up
to 20 percentage points higher than the absorber paint commercially used (Pyromark). At 800
ºC, they underwent a further structural transformation, provoked by the oxidation of the inner
layers, and they consequently lost their solar selectivity., Peer reviewed

This study reports the synthesis and characterization of ternary Cr-Al-O and quaternary Cr-Al-O-N coatings deposited by cathodic arc physical vapour deposition, for various nitrogen and oxygen mass flow ratios during the growth process. The composition, microstructure, indentation hardness and modulus of the films have been characterized by scanning electron microscopy, electron probe micro-analysis, X-ray diffraction, and nanoindentation techniques. The evolution of the microstructure and mechanical properties of the coatings after ambient air annealing from 800 °C up to 1100 °C have been investigated. As the oxygen to nitrogen mass flow increases, the as-deposited coatings exhibit lower hardness, higher roughness, lower crystallinity and a more marked columnar structure. At oxygen to nitrogen mass flow ratios bigger than 10/90, the coatings exhibit a stoichiometry of the type (CrAl)2+εO3−ε. Only the coatings with an oxygen to nitrogen mass flow ratio smaller than 10/90 retained nitrogen in their compositions. In all cases, the coatings developed a cubic fcc lattice structure. After annealing at 1100 °C the resulting microstructure showed a clear dependency upon the initial composition of the films. The evolution of the microstructure during the high temperature tests, as well as the analysis of the nanoindentation hardness, composition and thickness also provided valuable information about the combined effects of the thermal stability and the oxidation of the deposited coatings., This work has been funded by the Spanish Ministry of Economy and Competitiveness through the project PROTEOX MAT2013-45391-P. The European Commission is also acknowledged through the FP7-FOFNMP project MICROFAST under contract Nr 608720. The Research Group of Surface Engineering and Nanostructured Materials in the Universidad Complutense de Madrid also acknowledges financial support of the Spanish MINECO (project MAT2015-65539-P).