Scientific Papers in SCI
2010
2010
Fotocatálisis Heterogénea: Aplicaciones
Photocatalytic degradation of phenolic compounds with new TiO2 catalysts
Araña, J; Dona-Rodriguez, JM; Portillo-Carrizo, D; Fernandez-Rodriguez, C; Perez-Pena, J; Diaz, OG; Navio, JA; Macias, MApplied Catalysis B-Environmental, 100 (2010) 346-354 DOI: 10.1016/j.apcatb.2010.08.011

Abstract
New TiO2 catalysts have been synthesised by means of a sol-gel method in which aggregates have been selected before thermal treatment. Sieving and calcination temperature have been proved to be key factors in obtaining catalysts with greater photoactivity than that of Degussa P-25. These new catalysts have been characterized by means of transmission electron microscopy (TEM), BET surface area, diffuse reflectance spectroscopy (DRS). UV-vis spectroscopy, Fourier transformed infrared (FTIR) and X-ray diffraction (XRD). The different parameters studied were compared to those obtained from two commercial catalysts (Degussa P-25 and Hombikat-UV100). The photocatalytic efficiency of the new catalysts was evaluated by the degradation of various phenolic compounds using UV light (maximum around 365 nm, 9 mW). The catalyst sieved and calcinated at 1023 K, ECT-1023t, showed phenol degradation rates 2.7 times higher than those of Degussa P-25. Also in the degradation of different phenolic compounds, this catalyst showed a higher activity than that of the commercial one. The high photoactivity of this new catalyst has been attributed to the different distribution of surface defects (determined from FTIR studies) and its increased capacity to yield H2O2.
October, 2010 · DOI: 10.1016/j.apcatb.2010.08.011
Nanotecnología en Superficies y Plasma
A transparent TMPyP/TiO2 composite thin film as an HCl sensitive optochemical gas sensor
Cano, M; Castillero, P; Roales, J; Pedrosa, JM; Brittle, S; Richardson, T; Gonzalez-Elipe, AR; Barranco, ASensors and Actuators B-Chemical, 150 (2010) 764-769 DOI: 10.1016/j.snb.2010.07.059

Abstract
Tetracationic porphyrin (TMPyP) molecules were incorporated Into an optically transparent TiO2 thin film prepared by Glancing Angle Physical Vapour Deposition (GAPVD) by simple infiltration (at pH 6 4) The preparation of optically transparent TMPyP/TiO2 composite thin films provides a method for the integration of the porphyrin molecules Into photonic devices for direct monitoring of gases Previously UV-visible and fluorescence spectral techniques have been used to study the reversible protonation of TMPyP in aqueous solution The optical spectrum of TMPyP shows an intense Soret band at 423 nm with a 22 nm red shift upon protonation by HCl The experimental conditions for monitoring the concentration of HCl gas by absorption spectroscopy have been optimized The maximum absorbance change was observed at the Sorer band wavelength A selected temperature of 80 C and a 300 s recovery period were found to be the optimum operating parameters (response time t(50) = 16 8 7 s) The composite with smaller surface concentration of TMPyP (Gamma = 03 x 10(-9) mol cm(-2)) presented the best detection limit (0 1 ppm) The response of the composite sensor was highly stable for several months.
October, 2010 · DOI: 10.1016/j.snb.2010.07.059
Fotocatálisis Heterogénea: Aplicaciones
Characterisation and photocatalytic properties of titania-silica mixed oxides doped with Ag and Pt
Llano, B; Restrepo, G; Marin, JM; Navio, JA; Hidalgo, MCApplied Catalysis A-General, 387 (2010) 135-140 DOI: 10.1016/j.apcata.2010.08.021

Abstract
TiO2-SiO2 mixed oxides have been synthesised and modified by Ag and Pt deposition. Due to the effect of the silica on the mixed oxide, the prepared materials presented high surface areas and stabilised anatase as the only crystalline phase after calcination at 700 degrees C. Even using the same photodeposition experimental conditions, the yield for metal deposition depended highly on the metal considered, being much lower for Ag deposition. XPS studies permitted to estimate metal dispersion and oxidation state of the different samples, being both factors of high importance regarding photocatalytic improvement by metal deposition.
October, 2010 · DOI: 10.1016/j.apcata.2010.08.021
Hydraulic structures of the Roman Mithraeum house in Augusta emerita, Spain
Robador, MD; Perez-Rodriguez, JL; Duran, AJournal of Archaeological Science, 37 (2010) 2426-2432 DOI: 10.1016/j.jas.2010.05.003

Abstract
This paper deals with some of the hydraulic structures of Augusta Emerita (Merida, Spain), specifically those found in the Mithraeum House. In particular, we describe and characterise the hydraulic mortars and coatings of the viridarium water channel. The recipient of the channel was covered with two hydraulic mortars and a finishing coating. Hydrated lime was used as binder. Calcite grains with different morphology have been observed in the mortars studied. The siliceous aggregate was composed of quartz, mica and feldspars. Ceramic fragments, which were added to the mortar to improve its hydraulic properties, were composed of quartz, mica, iron oxides, anorthite and an amorphous phase; aluminium-iron silicates were used as raw materials for their manufacture. We discuss the interactions between the hydrated lime and the surface of the ceramics in the mortars.
October, 2010 · DOI: 10.1016/j.jas.2010.05.003
Nanotecnología en Superficies y Plasma - Materiales y Procesos Catalíticos de Interés Ambiental y Energético
Structure and microstructure of EB-PVD yttria thin films grown on Si (111) substrate
Hartmanova, M; Jergel, M; Holgado, JP; Espinos, JPVacuum, 85 (2010) 535-540 DOI: 10.1016/j.vacuum.2010.09.003

Abstract
Structure and microstructure of yttria thin films grown by electron beam physical vapour deposition on a stationary Si (111) substrate at room temperature (RT), 500 degrees and 700 degrees C, were investigated by the grazing-incidence X-ray diffraction and scanning electron microscopy, respectively. X-ray photoelectron spectroscopy provided information on the surface contamination from the atmosphere and the oxidation state. A strong effect of the deposition temperature and the vapour flux incidence angle was found. The film deposited at RT is polycrystalline with very fine grains of the body-centered cubic (bcc) crystallographic symmetry. An increase of deposition temperature results in a rapid growth of bcc grains with an improved crystalline structure. Moreover, the based-centered monoclinic phase appears for the deposition temperature of 700 degrees C. Preferred grain orientation (texture) with two main components, (400) and (622), was observed in the films deposited at 500 degrees C whereas no texture was found for 700 degrees C. The microstructure exhibits the columnar feather-like structure of different degrees of perfection which can be explained by the shadowing effects caused by an oblique vapour flux incidence angle. Surface morphology of the films is governed by a combination of the triangular and four-sided (square) columns. All films were found to be dense with a little porosity between the columns.
October, 2010 · DOI: 10.1016/j.vacuum.2010.09.003
Nanotecnología en Superficies y Plasma
Wetting Properties of Polycrystalline TiO2 Surfaces: A Scaling Approach to the Roughness Factors
Borras, A; Gonzalez-Elipe, ARLangmuir, 26 (2010) 15875-15882 DOI: 10.1021/la101975e

Abstract
This work presents a thorough study on the wettability of polycrystalline anatase TiO2 thin films prepared at 250 degrees C in a microwave plasma enhanced chemical vapor deposition (MW-PECVD) reactor with Ar/O-2 plasmas. Anatase polycrystalline thin films with different microstructures, textures, and surface roughness were obtained as a function of their thickness. The water contact angle of the samples was analyzed within the assumptions of the Wenzel, Cassie, and Miwa models to ascertain the effect of roughness and other surface heterogeneities on their characteristic parameters. The roughness factors defined in the different models were calculated from the atomic force microscopy (AFM) images of the films for two different observation scales within the premises of the dynamic scaling theories. The obtained results indicate that the wetting angle of an equivalent flat anatase surface with a value of 82 degrees can only be properly estimated for observation scales of 5 x 5 mu m(2) and using the Miwa model. The analysis of the UV induced hydrophilization of the surface state of the anatase films and the posterior recovery of the partially hydrophobic character of these surfaces in the absence of UV photons suggest a clear dependence of the light induced wettability on their texture and size of crystalline domains.
October, 2010 · DOI: 10.1021/la101975e
Materiales Nanoestructurados y Microestructura
Microstructural study of the LiBH4-MgH2 reactive hydride composite with and without Ti-isopropoxide additive
Deprez, E; Justo, A; Rojas, TC; Lopez-Cartes, C; Minella, CB; Bosenberg, U; Dornheim, M; Borrnann, R; Fernandez, AActa Materialia, 58 (2010) 5683-5694 DOI: 10.1016/j.actamat.2010.06.043

Abstract
An exhaustive microstructural characterization is reported for the LiBH4-MgH2 reactive hydride composite (RHC) system with and without titanium isopropoxide additive. X-ray diffraction with Rietveld analysis, transmission electron microscopy coupled to energy dispersive X-ray analysis, selected-area electron diffraction and electron energy loss spectroscopy are presented in this paper for the first time for this system for all sorption steps. New data are reported regarding average crystallite and grain size, microstrain, phase formation and morphology; these results contribute to the understanding of the reaction mechanism and the influence of the additives on the kinetics. Microstructural effects, related to the high dispersion of titanium-based additives, result in a distinct grain refinement of MgB2 and an increase in the number of reaction sites, causing acceleration of desorption and absorption reactions. Considerations on the stability of phases under electron beam irradiation have also been reported.
October, 2010 · DOI: 10.1016/j.actamat.2010.06.043
Nanotecnología en Superficies y Plasma
Tilt angle control of nanocolumns grown by glancing angle sputtering at variable argon pressures
Garcia-Martin, JM; Alvarez, R; Romero-Gomez, P; Cebollada, A; Palmero, AApplied Physics Letters, 97 (2010) - 173103 DOI: 10.1063/1.3506502

Abstract
We show that the tilt angle of nanostructures obtained by glancing angle sputtering is finely tuned by selecting the adequate argon pressure. At low pressures, a ballistic deposition regime dominates, yielding high directional atoms that form tilted nanocolumns. High pressures lead to a diffusive regime which gives rise to vertical columnar growth. Monte Carlo simulations reproduce the experimental results indicating that the loss of directionality of the sputtered particles in the gas phase, together with the self-shadowing mechanism at the surface, are the main processes responsible for the development of the columns.
October, 2010 · DOI: 10.1063/1.3506502
Química de Superficies y Catálisis
Synthesis of biodiesel from the methanolysis of sunflower oil using PURAL (R) Mg-Al hydrotalcites as catalyst precursors
Navajas, A; Campo, I; Arzamendi, G; Hernandez, WY; Bobadilla, LF; Centeno, MA; Odriozola, JA; Gandia, LMApplied Catalysis B-Environmental, 100 (2010) 299-309 DOI: 10.1016/j.apcatb.2010.08.006

Abstract
A series of commercial Mg-Al hydrotalcites have been used as catalyst precursors for the methanolysis of sunflower oil.The solids were characterized by low Mg/Al molar ratios in the 0.5-2.3 range. Additionally, a solid consisting mainly of Mg(OH)(2) but containing some Al (4.2 wt.%) was also employed. The as-received materials were inactive for biodiesel synthesis so calcination and rehydration in boiling water were considered as activation treatments. Among the calcined solids, only the material consisting of MgO was significantly active, achieving about 50% oil conversion after 24h at 60 degrees C, methanol/oil molar ratio of 12 and 2 wt.% of catalyst. The effects of the calcination temperature in the 350-700 degrees C range have been investigated; calcination at 500 degrees C led to the best catalytic performance. In the case of the rehydrated materials, only the solids with the highest Mg/Al molar ratios recovered a well-ordered layered double hydroxide structure. These samples showed an improved catalytic activity compared with their calcined counterparts. A good correlation between catalytic activity and the basic properties determined using Hammett indicators and benzoic acid titration has been found. Rehydrated hydrotalcites were slightly more selective to biodiesel (75%) at intermediate levels of oil conversion than the calcined counterparts (66%). It has been verified that no Mg or Al leaching in the reaction mixture took place; however, the rehydrated samples deactivated significantly. In the case of MgO, after washing and calcination. the recycled catalyst gave 68% of the original oil conversion.
October, 2010 · DOI: 10.1016/j.apcatb.2010.08.006
Materiales Coloidales
Citrate mediated synthesis of uniform monazite LnPO(4) (Ln = La, Ce) and Ln:LaPO4 (Ln = Eu, Ce, Ce plus Tb) spheres and their photoluminescence
Nuñez, NO; Liviano, SR; Ocaña, MJournal of Colloid and Interface Science, 349 (2010) 484-491 DOI: 10.1016/j.jcis.2010.05.079

Abstract
A simple method for the synthesis of spherical LaPO4 (monazite) particles with narrow size distribution and tailored size in the 150-500 nm range is reported. The procedure is based on a homogeneous precipitation process at low temperature (120 degrees C) from solutions containing La3+, citrate and phosphate ions under a very restrictive set of experimental conditions, which involves the use of La nitrate, citric acid and phosphoric acid as precursors and ethylene glycol as solvent. The growth mechanism of the spheres was investigated aiming at explaining the differences in particle size and shape observed when varying the experimental conditions. The applicability of this method for the synthesis of spherical particles of other lanthanide (Ce, Tb, Eu) phosphates is also analyzed. Finally, it is shown that the developed procedure can be used to dope the lanthanum phosphate particles with lanthanide cations, which resulted in spherical phosphors as illustrated for the Eu-doped, Ce-doped and Ce, Tb codoped systems, whose luminescent properties are also evaluated.
September, 2010 · DOI: 10.1016/j.jcis.2010.05.079
Nanotecnología en Superficies y Plasma
Surface nanostructuring of TiO2 thin films by high energy ion irradiation
Romero-Gomez, P; Palmero, A; Ben, T; Lozano, JG; Molina, SI; Gonzalez-Elipe, ARPhysical Review B, 82 (2010) - 115420 (8 pages) DOI: 10.1103/PhysRevB.82.115420
Abstract
The effects of a high ion dose irradiation on TiO2 thin films under different conditions of temperature and ion nature are discussed. We have shown that anatase TiO2 thin films irradiated with N+ ions at room temperature develop a typical microstructure with mounds and voids open to the surface whereas irradiations at 700 K generate a surface pattern of well-ordered nanorods aligned with the ion beam. The formation of these patterns is caused by the simultaneous effect of ion irradiation near the film surface and a film temperature favoring the structural mobilization of the defective network of the material. To explain these phenomena, a qualitative model has been proposed and further tested by irradiating the TiO2 thin films with F+ and S+ ions under different conditions. The obtained results demonstrate that ion irradiation techniques enable the formation of tilted nanorod surface patterns with lengths of about 100 nm on anatase TiO2 thin films.
September, 2010 · DOI: 10.1103/PhysRevB.82.115420
Materiales Coloidales
Uniform YF3:Yb,Er up-conversion nanophosphors of various morphologies synthesized in polyol media through an ionic liquid
Nuñez, NO; Quintanilla, M; Cantelar, E; Cusso, F; Ocaña, MJournal of Nanoparticle Research, 12 (2010) 2553-2565 DOI: 10.1007/s11051-009-9824-6

Abstract
We describe a facile procedure for the synthesis at low temperature (120 A degrees C) of water-dispersible uniform YF3:Yb,Er up-conversion nanophosphors of various morphologies (rhombic and spheroidal) by homogeneous precipitation in polyol solutions containing different lanthanide salts and an ionic liquid (1-butyl, 2-methylimidazolium tetrafluoroborate) as fluoride source. It is shown that the shape of the obtained nanoparticles is mainly determined by the nature of both, the polyol and the lanthanide precursors, which also affects to their colloidal stability in water suspensions. These morphological differences are explained on the basis of a different mechanism of particle formation. The efficiency of the up-conversion processes in the synthesized rhombic and spheroidal nanoparticles is also comparatively analyzed and the observed differences are justified on the basis of the different impurities incorporated to the nanophosphors during their synthesis process.
September, 2010 · DOI: 10.1007/s11051-009-9824-6
Materiales de Diseño para la Energía y Medioambiente
Aleuritic (9,10,16-trihydroxypalmitic) acid self-assembly on mica
Heredia-Guerrero, JA; San-Miguel, MA; Sansom, MSP; Heredia, A; Benitez, JJPhysical Chemistry Chemical Physics, 12 (2010) 10423-10428 DOI: 10.1039/c0cp00163e

Abstract
Aleuritic (9,10,16-trihydroxypalmitic) acid self-assembly on mica from solution has been studied using AFM, ATR-FTIR and MD simulations. The goal of this study is to define the role of hydroxyl groups in the interaction between molecules as reference data to understand the mechanism of formation of synthetic and natural biopolyesters from polyhydroxylated long chain carboxylic acids. In a confined structure, such as the one imposed by a vertically self-assembled layer on mica, aleuritic acid has a tendency to adopt a monolayer configuration ruled by the lateral interactions between molecules via the two secondary hydroxyl groups. This (2D) growth competes with the multilayer formation (3D), which is conditioned by the terminal primary hydroxyl group. As the self-assembly spatial constraint is relaxed, MD has shown that the structure tends to become an amorphous and crosslinked phase that can be characterized by topographic and friction force AFM data.
September, 2010 · DOI: 10.1039/c0cp00163e
Reactividad de Sólidos
Sintering by SPS of ultrafine TiCxN1-x powders obtained using mechanically induced self sustaining reaction
Borrell, A; Fernandez, A; Torrecillas, R; Cordoba, JM; Aviles, MA; Gotor, FJBoletin de la Sociedad Española de Cerámica y Vidrio, 49 (2010) 357-360 DOI: 10.3989/cyv.2010.v49.i5
Abstract
In this work high purity and nanometer character titanium carbonitride TiCxN1-x powders were obtained by mechanically induced self sustaining reaction (MSR) in a high-energy planetary ball mill, from a mixture of titanium with graphite or carbon nanofiber (CNFs) in a nitrogen atmosphere. A promising method for developing these materials is the coupling of the MSR with SPS sintering technique. The product is sintered at 1400 degrees C and 1700 degrees C, obtaining a completely dense monolithic ceramic (>99% t.d). In this work, the influence of SI'S treatment and carbon precursor on material microstructures was studied and the main mechanical properties of the end material were evaluated.
September, 2010 · DOI: 10.3989/cyv.2010.v49.i5
Nanotecnología en Superficies y Plasma
Tunable In-Plane Optical Anisotropy of Ag Nanoparticles Deposited by DC Sputtering onto SiO2 Nanocolumnar Films
Sanchez-Valencia, JR; Toudert, J; Borras, A; Lopez-Santos, C; Barranco, A; Feliu, IO; Gonzalez-Elipe, ARPlasmonics, 5 (2010) 241-250 DOI: 10.1007/s11468-010-9139-6
Abstract
This work reports an easy-to-handle method for growing two-dimensional assemblies of Ag nanostructures presenting a tunable in-plane optical anisotropy. Ag is deposited by DC sputtering in an Ar plasma at room temperature onto bundled nanocolumnar SiO2 thin films grown by glancing angle physical vapor deposition. In contrast with previously reported processes involving the grazing angle deposition of the metal, DC sputtering is performed at normal incidence. By varying the deposition angle of SiO2 and the Ar pressure, it was possible to tune the deposited amount of Ag and thus the topology of the Ag deposit from isolated spherical Ag nanoparticles with isotropic optical properties to strongly dichroic Ag nanostripes oriented along the bundling direction of the SiO2 nanocolumns. Based on simple calculations taking into account the shadowing effects during metal deposition, it is proposed that the width and shape of the tip of the bundled SiO2 nanocolumns influence significantly the metal local atom flux arriving to them and thus the final structure of the deposit.
September, 2010 · DOI: 10.1007/s11468-010-9139-6
Nanotecnología en Superficies y Plasma
On the microstructure of thin films grown by an isotropically directed deposition flux
Alvarez, R; Romero-Gomez, P; Gil-Rostra, J; Cotrino, J; Yubero, F; Palmero, A; Gonzalez-Elipe, ARJournal of Applied Physics, 108 (2010) 64316 DOI: 10.1063/1.3483242

Abstract
The influence of isotropically directed deposition flux on the formation of the thin film microstructure at low temperatures is studied. For this purpose we have deposited TiO2 thin films by two different deposition techniques: reactive magnetron sputtering, in two different experimental configurations, and plasma enhanced chemical vapor deposition. The obtained results indicate that films grown under conditions where deposition particles do not possess a clear directionality, and in the absence of a relevant plasma/film interaction, present similar refractive indices no matter the deposition technique employed. The film morphology is also similar and consists of a granular surface topography and a columnarlike structure in the bulk whose diameter increases almost linearly with the film thickness. The deposition has been simulated by means of a Monte Carlo model, taking into account the main processes during growth. The agreement between simulations and experimental results indicates that the obtained microstructures are a consequence of the incorporation of low-energy, isotropically directed, deposition particles.
September, 2010 · DOI: 10.1063/1.3483242
Química de Superficies y Catálisis
AISI 304 austenitic stainless steel monoliths: Modification of the oxidation layer and catalytic coatings after deposition and its catalytic implications
Martinez, LMT; Sanz, O; Centeno, MA; Odriozola, JAChemical Engineering Journal, 162 (2010) 1082-1090 DOI: 10.1016/j.cej.2010.07.005

Abstract
Monolithic CeO2 and Au/CeO2 catalysts were prepared using austenitic stainless steel (AISI 304) as metallic substrate. Both monolithic and powdered catalysts were characterized before and after CO oxidation reaction by N-2 adsorption desorption, XRD, SEM, TEM and GD-OES. Catalyst deposition on the stainless steel surface results in modifications of the catalyst, the oxide scale and the oxide scale/alloy interface through the interaction between the coating and the steel oxidation layer. Besides this, oxidation of the alloy is also detected. The extension and nature of these modifications depends on the catalyst nature, and on the reaction conditions. As a result of these modifications CO oxidation on Au/CeO2 catalysts is enhanced and gold surface dynamics is modified.
September, 2010 · DOI: 10.1016/j.cej.2010.07.005
Materiales Ópticos Multifuncionales - Nanotecnología en Superficies y Plasma
TiO2-SiO2 one-dimensional photonic crystals of controlled porosity by glancing angle physical vapour deposition
Gonzalez-Garcia, L; Lozano, G; Barranco, A; Miguez, H; Gonzalez-Elipe, ARJournal of Materials Chemistry, 20 (2010) 6408-6412 DOI: 10.1039/C0JM00680G

Abstract
Herein we present a synthetic route to attain porous one-dimensional photonic crystals of high optical quality. The method employed, based on the alternate deposition of TiO2 and SiO2 porous layers by glancing angle physical vapour deposition, yields a highly accessible interconnected pore network throughout the entire multilayer structure. Furthermore, it allows a strict control over the average size and density of the interstitial sites, which results in the precise tuning of the refractive index of the individual layers and thus of the optical response of the ensemble. The controlled environmental response of the multilayer is confirmed by the optical monitoring of the infiltration of liquids of different refractive index.
August, 2010 · DOI: 10.1039/C0JM00680G
Fotocatálisis Heterogénea: Aplicaciones
Determination of the local structure of a highly dispersed Pd-Nanosystem located on a titanium dioxide carrier
Kriventsov, VV; Novgorodov, BN; Yakimchuk, EP; Kochubey, DI; Zyuzin, DA; Simakova, IL; Chistyakov, AV; Zhmakin, VV; Bukhtenko, OV; Tsodikov, MV; Kozitsyna, NY; Vargaftik, MN; Moiseev, II; Maksimovskii, EA; Nechepurenko, SF; Navio, JA; Nikitenko, SGJournal of Surface Investigation-X-Ray Synchrotron and Neutron Techniques, 4 (2010) 636-639 DOI: 10.1134/S1027451010040166
Abstract
This work is devoted to a structural study of a highly dispersed Pd nanosystem, which is stabilized in the TiO2 matrix, by XAFS spectroscopy. Nanocomposite was prepared from bimetallic PdCo(mu-OOCMe)(4)(NCMe) precursor followed by processing in several ways: calcination in air and in argon and microwave irradiation. The local structure of Pd catalysts formed by different methods was studied. Possible structural models were considered in detail.
August, 2010 · DOI: 10.1134/S1027451010040166
Reactividad de Sólidos
Mechanochemical synthesis of vanadium nitride
Roldan, MA; Lopez-Flores, V; Alcala, MD; Ortega, A; Real, CJournal of the European Ceramic Society, 30 (2010) 2099-2107 DOI: 10.1016/j.jeurceramsoc.2010.04.008

Abstract
Vanadium nitride (VN) has been prepared by mechanosynthesis from vanadium metal under a pressurized nitrogen atmosphere in a short milling time. The characterization of the final product by X-ray diffraction, scanning electron microscopy, electron energy loss (EELS), and X-ray absorption spectroscopy (XAS) is presented. The final product, VN with 96% of purity, is obtained at room temperature with nanometric particle size and a very high microhardness after sintering. A relationship between microstructure and microhardness as well as a comparison between the VN obtained mechanical and thermal method is also presented.
August, 2010 · DOI: 10.1016/j.jeurceramsoc.2010.04.008
Materiales Nanoestructurados y Microestructura
Tailored synthesis of nanostructured WC/a-C coatings by dual magnetron sputtering
Abad, MD; Munoz-Marquez, MA; El Mrabet, S; Justo, A; Sanchez-Lopez, JCSurface and Coatings Technology, 204 (2010) 3490-3500 DOI: 10.1016/j.surfcoat.2010.04.019

Abstract
Nanostructured coatings with variable contents of tungsten carbide (WC) and amorphous carbon (a-C) are prepared by controlling the sputtering power ratio using WC and graphite targets. XRD and TEM/ED analysis shows that increasing the C incorporation. the WC nanocrystalline phases evolve from gamma-W2C to beta-WC1-x. Further C enrichment leads to a nanocomposite structure of small WC1-x crystals dispersed in a-C matrix. The a-C at.% is estimated by XPS analysis and correlated with the observed tribo-mechanical properties. The hardness and friction properties vary from hard/high friction (36-40 GPa; mu=0.6-0.8) to moderate-hard/low friction (16-20 GPa; mu similar to 0.2) coatings depending on the film composition. The transition point is found for a-C content of 10 at.%. This correlates with a change from nanocrystalline WC to nanocomposite WC1-x/a-C coatings. The overall study will help to understand the previous literature data and will serve as guide for a tailored synthesis of these WC/a-C nanocomposites.
August, 2010 · DOI: 10.1016/j.surfcoat.2010.04.019
Study of the Dehydroxylation-Rehydroxylation of Pyrophyllite
Perez-Rodriguez, JL; Duran, A; Sanchez-Jimenez, PE; Franquelo, ML; Perejon, A; Pascual-Cosp, J; Perez-Maqueda, LAJournal of the American Ceramic Society, 93 (2010) 2392-2398 DOI: 10.1111/j.1551-2916.2010.03750.x

Abstract
Pyrophyllite is a raw material of significant interest due to its large number of applications. Most of these applications require a thermal transformation of pyrophyllite; this thermal transformation implies the release of structural OH groups and the formation of new phases. In this paper, we report on the dehydroxylation of pyrophyllite and the reversibility of the process. A value of 224 +/- 16 kJ/mol for the dehydroxylation of pyrophyllite was obtained. In addition, it was observed that the partially or totally dehydroxylated pyrophyllite suffered a partial reversible rehydroxylation when cooled to room temperature. This rehydroxylation was substantiated by thermogravimetric measurements, while infrared spectroscopic studies showed that, during the rehydroxylation, the intensity of the OH band at 3675 cm-1 increased as two new bands at 3690 and 3702 cm-1 appeared. This rehydroxylation process was heavily influenced by the particle size of the pyrophyllite. Thus, smaller particles (< 1 mu m) showed a larger rehydroxylation percentage (about 12%), while the larger ones (20-40 mu m) showed a smaller percentage (about 1.6%). The extent of rehydroxylation also depended on the dehydroxylation temperature and reached a maximum value at 750 degrees C.
August, 2010 · DOI: 10.1111/j.1551-2916.2010.03750.x
Materiales y Procesos Catalíticos de Interés Ambiental y Energético
Study of nanostructured Ni/CeO2 catalysts prepared by combustion synthesis in dry reforming of methane
Gonzalez-Delacruz, VM; Ternero, F; Pereniguez, R; Caballero, A; Holgado, JPApplied Catalysis A-General, 384 (2010) 1-9 DOI: 10.1016/j.apcata.2010.05.027

Abstract
This work reports the study of several catalysts of Ni-CeO2 active for dry methane reforming process (CH4 + CO2 -> 2CO + 2H(2)). The use of Ni as active phase is highly preferred, due to its availability, high activity and low cost, although its main lack is the coke formation on the surface of Ni metal particles, resulting in a severe deactivation. Here we report a new synthesis method that allows a simple, effective and fast way to prepare Ni-CeO2 catalysts, in a wide range of metallic loadings, resulting in all the cases in well-formed NiO crystallites with sizes in the range of 12-18 nm. The use of CeO2 as a support has been based on its massive use in TWC catalysts formulations, where it is recognized to activate CH4 and lower hydrocarbon dissociation. Moreover, CeO2 has been reported to have an intrinsic activity in the CH4 reforming reaction. Besides the metallic loading, several factors that control the preparation method of the catalyst have been varied, in order to optimize their performance. Most of the catalysts prepared show activity and selectivity values close to thermodynamic ones, maintaining a good stability on long periods of time and severe conditions. Nevertheless, formation of some carbon nano-fibers has been observed, which could result in a drawback for their application at large scale.
August, 2010 · DOI: 10.1016/j.apcata.2010.05.027
Reactividad de Sólidos
Generalized Kinetic Master Plots for the Thermal Degradation of Polymers Following a Random Scission Mechanism
Sanchez-Jimenez, PE; Perez-Maqueda, LA; Perejon, A; Criado, JMJournal of Physical Chemistry A, 114 (2010) 7868-7876 DOI: 10.1021/jp103171h

Abstract
In this paper, the f(alpha) conversion functions for random scission mechanisms have been proposed to allow for the construction of generalized master plots suitable for these kinds of mechanisms. The master plots have been validated by their application to simulated data and to the thermal degradation of poly(butylene terephthalate), polyethylene, and poly(tetrafluoroethylene).
August, 2010 · DOI: 10.1021/jp103171h
Reactividad de Sólidos
Mechanochemical preparation of BaTiO3-Ni nanocomposites with high dielectric constant
Sanchez-Jimenez, PE; Perez-Maqueda, LA; Dianez, MJ; Perejon, A; Criado, JMComposite Structures, 92 (2010) 2236-2240 DOI: 10.1016/j.compstruct.2009.08.011

Abstract
A mechanochemical procedure is proposed for an easy preparation of a BaTiO3-Ni composite in a single step. BaTiO3 and Ni powders available in the market are mixed by dry ball milling producing a decrease of particle size and an evenly distribution of both phases. In the sintered pellets the nickel particles are homogeneously distributed into the BaTiO3 matrix and isolated from others Ni particles. The dielectric constant of the composite is considerably higher than that of the barium titanate. Moreover, the temperature of the ferroelectric <-> paraelectric transition of the BaTiO3-Ni composite here prepared is much lower than the one of the pure BaTiO3 single phase.
August, 2010 · DOI: 10.1016/j.compstruct.2009.08.011
Nanotecnología en Superficies y Plasma - Materiales Nanoestructurados y Microestructura - Tribología y Protección de Superficies
Characterization of Ti1-xAlxN coatings with selective IR reflectivity
Godinho, V; Philippon, D; Rojas, TC; Novikova, NN; Yakovlev, VA; Vinogradov, EA; Fernandez, ASolar Energy, 84 (2010) 1397-1401 DOI: 10.1016/j.solener.2010.04.021

Abstract
Ti1-xAlxN thin films were deposited by reactive magnetron sputtering. The obtained different stoichiometries give rise to different optical properties as the films change from metallic to dielectric. In this work the IR reflectivity of these coatings is investigated taking into account different application fields for IR selective Ti1-xAlxN thin films. Low Al content coatings present high reflectivity, high absorptance and low thermal emittance. High Al compositions give raise to coatings with high absorptance and high thermal emittance. The composition of the coatings was evaluated combining electron energy loss spectroscopy (EELS) and energy dispersive spectroscopy. Scanning electron microscopy (SEM) revealed a columnar structure. Reflectance spectra for the visible and infrared spectral ranges were used to obtain the solar absorptance and thermal emittance values, used to calculate the equilibrium temperature of the coatings. The thermal stability in air from 300 to 600 degrees C was also evaluated.
August, 2010 · DOI: 10.1016/j.solener.2010.04.021
Reactividad de Sólidos
Kinetic model for thermal dehydrochlorination of poly(vinyl chloride)
Sanchez-Jimenez, PE; Perejon, A; Criado, JM; Dianez, MJ; Perez-Maqueda, LAPolymer, 51 (2010) 3998-4007 DOI: 10.1016/j.polymer.2010.06.020

Abstract
In this paper, a novel method for calculating degradation kinetics is presented. The method has been applied to the thermal dehydrochlorination of two different samples of PVC. It has been observed that this dehydrochlorination is complex and involves two different processes. A model that accounts for the entire dehydrochlorination is proposed. This model involves nucleation and growth and diffusion controlled mechanisms. The kinetic parameters are obtained from linear heating rate, isothermal and sample controlled thermal analysis experiments. Kinetic results obtained from the macroscopic thermal analysis measurements demonstrate the correlation between the kinetics of the thermal dehydrochlorination of PVC and the structure of this macromolecule.
August, 2010 · DOI: 10.1016/j.polymer.2010.06.020
Materiales Ópticos Multifuncionales
Anomalous group velocity at the high energy range of a 3D photonic nanostructure
Botey, M; Martorell, J; Dorado, LA; Depine, RA; Lozano, G; Miguez, HOptics Express, 18 (2010) 15682-15690 DOI: 10.1364/OE.18.015682

Abstract
We report on a study of electromagnetic waves propagation in thin periodically ordered photonic nanostructures in the spectral range where the light wavelength is on the order of the lattice parameter. The vector KKR method we use allows us to determine the group index from finite photonic structures including extinction providing confirmation of recently emerged results. We show that for certain frequencies the group velocity of opal slabs can either be superluminal or approach zero depending on the crystal thickness and the unavoidable presence of losses. In some cases, group velocity can be negative. Such behavior can be clearly attributed to the finite character of the three-dimensional structure and reproduces previously reported experimental observations. Calculations show that contrary to the predictions of extraordinary group velocity reductions for infinite periodic structures, the group velocity of real opals may exhibit strong fluctuations at the high energy range. Hence, a direct identification between the calculated anomalous group velocities, for an actual opal film, and the predicted propagating low dispersion modes for an ideal infinite ordered structure seems difficult to establish.
July, 2010 · DOI: 10.1364/OE.18.015682
Fotocatálisis Heterogénea: Aplicaciones
Sunlight highly photoactive Bi2WO6-TiO2 heterostructures for rhodamine B degradation
Colon, G; Lopez, SM; Hidalgo, MC; Navio, JAChemical Communications, 46 (2010) 4809-4811 DOI: 10.1039/c0cc00058b

Abstract
Highly efficient Bi2WO6-TiO2 heterostructures are synthesized by means of a hydrothermal method; they have high photoactivity for the degradation of rhodamine B under sunlike irradiation. An interesting synergetic effect between TiO2 and Bi2WO6 leads to an improved charge carrier separation mechanism, causing the excellent photocatalytic performance.
July, 2010 · DOI: 10.1039/c0cc00058b
Materiales Ópticos Multifuncionales
Porous One-Dimensional Photonic Crystal Coatings for Gas Detection
Hidalgo, N; Calvo, ME; Colodrero, S; Miguez, HIEEE Sensors Journal, 10 (2010) 1206-1212 DOI: 10.1109/JSEN.2010.2043525
Abstract
Herein, we present an overview of recent progress on the development of different types of porous 1-D photonic crystal coatings which are optically responsive to gas pressure changes in the environment. Modification of the surrounding vapor pressure gives rise to adsorption and condensation phenomena within the porous networks of the photonic crystal building blocks, varying their refractive index and hence their optical features. This effect can be put into practice to precisely detect and monitor changes in the ambient through the spectral shift of either the photonic bandgap of the structure or of some other optical features. Our results demonstrate the potential of these optical coatings as new materials for gas sensing devices.
July, 2010 · DOI: 10.1109/JSEN.2010.2043525
Materiales Nanoestructurados y Microestructura
Influence of carbon chemical bonding on the tribological behavior of sputtered nanocomposite TiBC/a-C coatings
Abad, MD; Sanchez-Lopez, JC; Brizuela, M; Garcia-Luis, A; Shtansky, DVThin Solid Films, 518 (2010) 5546-5552 DOI: 10.1016/j.tsf.2010.04.038

Abstract
The tribological performance of nanocomposite coatings containing Ti-B-C phases and amorphous carbon (a-C) are studied. The coatings are deposited by a sputtering process from a sintered TiB2:TiC target and graphite, using pulsed direct current and radio frequency sources. By varying the sputtering power ratio, the amorphous carbon content of the coatings can be tuned, as observed by X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy. The crystalline component consists of very disordered crystals with a mixture of TiB2/TiC or TiBxCy phases. A slight increase in crystalline order is detected with the incorporation of carbon in the coatings that is attributed to the formation of a ternary TiBxCy phase. An estimation of the carbon present in the form of carbide (TiBxCy or TiC) and amorphous (a-C) is performed using fitting analysis of the C 1s XPS peak. The film hardness (22 to 31 GPa) correlates with the fraction of the TiBxCy phase that exists in the coatings. The tribological properties were measured by a pin-on-disk tribometer in ambient conditions, using 6 mm tungsten carbide balls at 1 N. The friction coefficients and the wear rates show similar behavior, exhibiting an optimum when the fraction of C atoms in the amorphous phase is near 50%. This composition enables significant improvement of the friction coefficients and wear rates (mu similar to 0.1; k < 1 x 10(-6) mm(3)/Nm), while maintaining a good value of hardness (24.6 GPa). Establishing the correlation between the lubricant properties and the fraction of a-C is very useful for purposes of tailoring the protective character of these nanocomposite coatings to engineering applications.
July, 2010 · DOI: 10.1016/j.tsf.2010.04.038
Materiales de Diseño para la Energía y Medioambiente
Steering the Self-Assembly of Octadecylamine Monolayers on Mica by Controlled Mechanical Energy Transfer from the AFM Tip
Benitez, JJ; Heredia-Guerrero, JA; Salmeron, MJournal of Physical Chemistry C, 114 (2010) 12630-12634 DOI: 10.1021/jp102813s

Abstract
We have studied the effect of mechanical energy transfer from the tip of an atomic force microscope on the dynamics of self-assembly of monolayer films of octadecylamine on mica. The formation of the self-assembled film proceeds in two successive stages, the first being a fast adsorption from solution that follows a Langmuir isotherm. The second is a slower process of island growth by aggregation of the molecules dispersed on the surface. We found that the dynamics of aggregation can be altered substantially by the addition of mechanical energy into the system through controlled tip surface interactions. This leads to both the creation of pinholes in existing islands as a consequence of vacancy concentration and to the assembly of residual molecules into more compact islands.
July, 2010 · DOI: 10.1021/jp102813s
Nanotecnología en Superficies y Plasma
Preparation and structural properties of YBCO films grown on GaN/c-sapphire hexagonal substrate
Chromik, S; Gierlowski, P; Spankova, M; Dobrocka, E; Vavra, I; Strbik, V; Lalinsky, T; Sojkova, M; Liday, J; Vogrincic, P; Espinos, JPApplied Surface Science, 256 (2010) 5618-5622 DOI: 10.1016/j.apsusc.2010.03.035

Abstract
Epitaxial YBCO thin films have been grown on hexagonal GaN/c-sapphire substrates using DC magnetron sputtering and pulsed laser deposition. An MgO buffer layer has been inserted between the substrate and the YBCO film as a diffusion barrier. X-ray diffraction analysis indicates a c-axis oriented growth of the YBCO films. Φ-scan shows surprisingly twelve maxima. Transmission electron microscopy analyses confirm an epitaxial growth of the YBCO blocks with a superposition of three a–b YBCO planes rotated by 120° to each other. Auger electron spectroscopy and X-ray photoelectron spectroscopy reveal no surface contamination with Ga even if a maximum substrate temperature of 700 °C is applied.
July, 2010 · DOI: 10.1016/j.apsusc.2010.03.035
Nanotecnología en Superficies y Plasma
Effect of surface roughness and sterilization on bacterial adherence to ultra-high molecular weight polyethylene
Kinnari, TJ; Esteban, J; Zamora, N; Fernandez, R; Lopez-Santos, C; Yubero, F; Mariscal, D; Puertolas, JA; Gomez-Barrena, EClinical Microbiology and Infection, 16 (2010) 1036-1041 DOI: 10.1111/j.1469-0691.2009.02995.x/full

Abstract
Sterilization with ethylene oxide (EO) and gas plasma (GP) are well-known methods applied to ultra-high molecular weight polyethylene (UHMWPE) surfaces in the belief that they prevent major material changes caused by gamma irradiation. However, the influence of these surface sterilization methods on bacterial adherence to UHMWPE is unknown. UHMWPE samples with various degrees of roughness (0.3, 0.8 and 2.0 mu m) were sterilized with either GP or EO. The variations in hydrophobicity, surface free energy and surface functional groups were investigated before and after sterilization. Sterilized samples were incubated with either Staphylococcus aureus or Staphylococcus epidermidis in order to study bacterial adherence to these materials. Fewer bacteria adhered to UHMWPE after sterilization with EO than after sterilization with GP, especially to the smoothest surfaces. No changes in chemical composition of the UHMWPE surface due to sterilization were observed using X-ray photoemission spectroscopy analysis. The decreased bacterial adherence to UHMWPE found at the smoothest surfaces after sterilization with EO was not directly related to changes in chemical composition. Increased bacterial adherence to rougher surfaces was associated with increased polar surface energy of EO-sterilized surfaces.
July, 2010 · DOI: 10.1111/j.1469-0691.2009.02995.x/full
Nanotecnología en Superficies y Plasma
Structure of Glancing Incidence Deposited TiO2 Thin Films as Revealed by Grazing Incidence Small-Angle X-ray Scattering
Gonzalez-Garcia, L; Barranco, A; Paez, AM; Gonzalez-Elipe, AR; Garcia-Gutierrez, MC; Hernandez, JJ; Rueda, DR; Ezquerra, TA; Babonneaum, DChemphyschem, 11 (2010) 2205-2208 DOI: 10.1002/cphc.201000136

Abstract
For the first time, grazing incidence small-angle X-ray scattering (GISAXS) analysis is used to characterize the Morphology of TiO2 thin films grown by glancing angle physical vapor deposition (GLAD). According to cross-section scanning electron microscopy (SEM) images, the films consist of near isotilted TiO2 columns of different length and width depending on film thickness. The obtained GISAXS patterns show a characteristic asymmetry with respect to the incidence plane, which is associated with the titled of the TiO2 columns. The patterns also show the existence of two populations of columns in these GLAD TiO2 films. The population of the thinnest columns appears related to the first grown layer and is common for all the films investigated, while the second population of columns grows with the thickness of the films and has been related to wider columns formed by shadowing at the expense of the initially formed columns.
July, 2010 · DOI: 10.1002/cphc.201000136
Materiales de Diseño para la Energía y Medioambiente
Sc-45 Spectroscopy of Solids: Interpretation of Quadrupole Interaction Parameters and Chemical Shifts
Alba, MD; Chain, P; Florian, P; Massiot, DJournal of Physical Chemistry C, 114 (2010) 12125-12132 DOI: 10.1021/jp1036525

Abstract
The aims of the present study is to describe for the first time the Sc-45 MAS NMR spectra of X-2-Sc2SiO5 and C-Sc2Si2O7, to combine the spectroscopic information with the structures published from diffraction data, and to propose a rational interpretation of the chemical shifts and quadrupolar parameters. For that purposed, we have correlated the experimental quadrupole coupling parameters of Sc-45 determined for a number of scandium compounds to those found by a simple electrostatic calculation and we have found that the isotropic chemical shift of the Sc-45 is linearly correlated to the shift parameter, calculated by bond-valence theory. We also show that a simple point charge calculation can approximate the electric field gradient to a sufficiently good approximation that it provides a valuable mean to assign the NMR spectra.
July, 2010 · DOI: 10.1021/jp1036525
Materiales Ópticos Multifuncionales
Flexible, Adhesive, and Biocompatible Bragg Mirrors Based on Polydimethylsiloxane Infiltrated Nanoparticle Multilayers
Calvo, ME, Miguez, HChemistry of Materials, 22 (2010) 3909-3915 DOI: 10.1021/cm1001016

Abstract
Herein we present a series of self-standing, flexible, and biocompatible optical interference filters obtained through infiltration and polymerization of an elastomer (polydimethylsiloxane) in a porous Bragg mirror prepared by alternating deposition of layers of TiO2 and SiO2 nanoparticles. The method proposed yields the uniform filling of the nanopores of the multilayer by the polymer, which allows lifting off the hybrid structure as long as the ensemble is cooled to temperatures below the glass transition of the polymer. This multifunctional material combines the optical properties of the periodic nanoporous multilayer and the structural and physicochemical characteristics of polydimethylsiloxane. Experimental demonstrations of their potential use as flexible and adhesive UV-protecting filters, as well as of light, highly-efficient conformal back reflectors to enhance the efficiency of photovoltaic devices are provided.
July, 2010 · DOI: 10.1021/cm1001016
Nanotecnología en Superficies y Plasma
Improved wear performance of ultra high molecular weight polyethylene coated with hydrogenated diamond like carbon
Puertolas, JA; Martinez-Nogues, V; Martinez-Morlanes, MJ; Mariscal, MD; Medel, FJ; Lopez-Santos, C; Yubero, FWEAR, 269 (2010) 458-465 DOI: 10.1016/j.wear.2010.04.033

Abstract
Hydrogenated diamond like carbon (DLCH) thin films were deposited on medical grade ultra high molecular weight polyethylene (UHMWPE) by radio frequency plasma enhanced chemical vapor deposition. The DLCH coating thicknesses ranged from 250 to 700 nm The substrates were disks made of UHMWPEs typically used for soft components in artificial Joints, namely virgin GUR 1050 and highly crosslinked (gamma irradiated in air to 100 kGy) UHMWPEs Mechanical and tribological properties under bovine serum lubrication at body temperature were assessed on coated and uncoated polyethylenes by means of nano-hardness and ball-on-disk tests, respectively Morphological features of the worn surfaces were obtained by confocal microscopy and scanning electron microscopy This study confirms an increase in surface hardness and good wear resistance for coated materials after 24 h of sliding test compared to uncoated polyethylene. These results point out that to coat UHMWPE with DLCH films could be a potential method to reduce backside wear in total hip and knee arthroplasties.
July, 2010 · DOI: 10.1016/j.wear.2010.04.033
Reactividad de Sólidos - Propiedades mecánicas, modelización y caracterización de cerámicos avanzados
Microstructural Effects on the Creep Deformation of Alumina/Single-Wall Carbon Nanotubes Composites
Gomez-Garcia, D; Poyato, R; Lee, Z; Castillo-Rodriguez, M; Dominguez-Rodriguez, A; Radmilovic, V; Padture, NPJournal of the American Ceramic Society, 93 (2010) 2042-2047 DOI: 10.1111/j.1551-2916.2010.03681.x

Abstract
The enhanced high-temperature creep resistance in alumina/single-wall carbon nanotubes (SWNTs) composites has been attributed to the unprecedented grain-boundary structure of these composites, where the SWNTs bundles segregated at the alumina grain boundaries partially impede grain-boundary sliding. In this study, the effect of SWNTs distributions at alumina grain boundaries on the creep behavior of alumina/SWNTs composites has been investigated. Microstructures of two different alumina/10 vol% SWNTs composites, one with heterogeneous and the other with homogenous distributions of SWNTs at grain boundaries, have been characterized quantitatively. The steady-state creep rate (uniaxial compression) in the heterogeneous composite has been found to be over three times higher than that in the homogeneous composite at 1300° and 1350°C (argon atmosphere). It is argued that the less uniform distribution of SWNTs at the alumina grain boundaries in the heterogeneous composite results in less effective obstruction of grain-boundary sliding, and attendant higher creep rate. This also results in more efficient recovery in that composite.
July, 2010 · DOI: 10.1111/j.1551-2916.2010.03681.x
Materiales Ópticos Multifuncionales
Gallium Arsenide Infiltration of Nanoporous Multi layers: A Route to High-Dielectric-Contrast One-Dimensional Photonic Crystals
Sanchez-Sobrado, O; Thomas, K; Povey, I; Pemble, ME; Miguez, HSmall, 6 (2010) 1283-1287 DOI: 10.1002/smll.200902190

Abstract
Periodic multilayers of wide photonic bandgap and high reflectance in the visible and near infrared regions are fabricated. Optical properties show that reflectance intensities close to 90% are reached for stacks of only six layers, as well as gap-to-midgap ratios of 50%. The optical response of the hybrid ensemble can be accurately tuned through the number of infiltration cycles performed.
June, 2010 · DOI: 10.1002/smll.200902190
Nanotecnología en Superficies y Plasma
Study of the morphology of NiO nanostructures grown on highly ordered pyrolytic graphite, by the Tougaard method and atomic force microscopy: a comparative study
Preda, I; Soriano, L; Alvarez, L; Mendez, J; Yubero, F; Gutierrez, A; Sanz, JMSurface and Interface Analysis, 42 (2010) 869-873 DOI: 10.1002/sia.3222
Abstract
We studied the morphology of the deposits of NiO grown on highly ordered pyrolytic graphite (HOPG), by means of inelastic peak shape analysis and atomic force microscopy. The results obtained by both techniques show an excellent agreement. The results indicate that NiO grows on HOPG by following the Stransky-Krastanov type of growth.
June, 2010 · DOI: 10.1002/sia.3222
Murillo's paintings revealed by spectroscopic techniques and dedicated laboratory-made micro X-ray diffraction
Duran, A; Siguenza, MB; Franquelo, ML; de Haro, MCJ; Justo, A; Perez-Rodriguez, JLAnalytica Chimica Acta, 671 (2010) 1-8 DOI: 10.1016/j.aca.2010.05.004

Abstract
This paper describes one of the first case studies using micro-diffraction laboratory-made systems to analyse painting cross-sections. Pigments, such as lead white, vermilion, red ochre, red lac, lapis lazuli, smalt, lead tin yellow type I, massicot, ivory black, lamp black and malachite, were detected in cross-sections prepared from six Bartolome Esteban Murillo paintings by micro-Raman and micro-XRD combined with complementary techniques (optical microscopy, SEM-EDS, and FT-IR). The use of micro-XRD was necessary due to the poor results obtained with conventional XRD. In some cases, pigment identification was only possible by combining results from the different analytical techniques utilised in this study.
June, 2010 · DOI: 10.1016/j.aca.2010.05.004
Materiales Coloidales - Materiales Ópticos Multifuncionales
Environmentally responsive nanoparticle-based luminescent optical resonators
Sanchez-Sobrado, O; Calvo, ME; Nunez, N; Ocana, M; Lozano, G; Miguez, HNanoscale, 2 (2010) 936-941 DOI: 10.1039/b9nr00338j

Abstract
In this work, we demonstrate that optical resonators built using all-nanoparticle-based porous building blocks provide a responsive multifunctional matrix, totally different emission spectra being attained from the same embedded luminescent nanophosphors under varying environmental conditions. We show a clear correlation between modifications in the ambient surroundings, the induced changes of the resonant modes, and the resulting variations in the emission response. The method is versatile and allows nanophosphors of arbitrary shape to be integrated in the cavity. By precise control of the spectral features of the optical resonances, luminescence is strongly modulated in selected and tuneable wavelength ranges. Applications in the fields of sensing and detection are foreseen for these materials.
June, 2010 · DOI: 10.1039/b9nr00338j
Reactividad de Sólidos
Nonisothermal calorimetric study of the precipitation processes in a Cu-1Co-0.5Ti alloy
Donoso, E; Zuniga, A; Dianez, MJ; Criado, JMJournal of Thermal Analysis and Calorimetry, 100 (2010) 975-980 DOI: 10.1007/s10973-009-0642-y

Abstract
The precipitation processes in a Cu-1.0 at.%Co-0.5 at.%Ti (Cu-1.5 at.%Co2Ti) alloy were studied using differential scanning calorimetry (DSC), transmission electron microscopy (TEM), and microhardeness measurements. The analysis of the calorimetric curves from room temperature to 900 K shows the presence of two exothermic reactions attributed to the formation of CoTi and Co2Ti particles in the copper matrix. On the basis of enthalpy calculations, it was found that the decomposition begins with the precipitation of CoTi, followed by the formation of Co2Ti particles. The activation energies calculated using the modified Kissinger method were lower than the ones corresponding to diffusion of cobalt and titanium in copper. Kinetic parameters were obtained by a convolution method based on the Johnson-Mehl-Avrami (JMA) formalism. The values obtained for the parameter n were indicative of a particle nucleation process from preexistent nuclei. Microhardness measurements and TEM micrographs confirmed the formation of the mentioned phases.
June, 2010 · DOI: 10.1007/s10973-009-0642-y
Química de Superficies y Catálisis
In Situ Characterization of the Dynamic Gold-Support Interaction over Ceria Modified Eu3+. Influence of the Oxygen Vacancies on the CO Oxidation Reaction
Hernandez, WY; Romero-Sarria, F; Centeno, MA; Odriozola, JAJournal of Physical Chemistry C, 114 (2010) 10857-10865 DOI: 10.1021/jp1013225

Abstract
Gold-supported ceria and europium-doped ceria catalysts were prepared by the deposition-precipitation method. The influence of the pretreatment atmosphere and temperature on the concentration of oxygen vacancies and gold dispersion on the Au/CeEti(10) catalyst under actual reaction conditions was investigated by "in situ" X-ray diffraction and Raman analysis. By Raman spectroscopy, a preferential interaction of the gold with the support across the oxygen vacancies was established and correlated with the gold dispersion. The increase in the concentration of oxygen vacancies in the presence of hydrogen induces changes in the gold crystallite size by breaking-off and migration of gold nanoparticles toward the oxygen vacancies on the CeEu(10) support. The activity of the Au/CeEu(10) solid in the CO oxidation reaction was significantly improved when the catalyst was preactivated in a reducing atmosphere. This trend could be associated with the redispersion of gold together with the increase in the concentration of oxygen vacancies in the support.
June, 2010 · DOI: 10.1021/jp1013225
Materiales Ópticos Multifuncionales
Angular dependence of the intensity of light beams diffracted by colloidal crystals
Lozano, G; Mazzaferri, JE; Dorado, LA; Ledesma, S; Depine, RA; Miguez, HJournal of the Optical Society of America B-Optical Physics, 27 (2010) 1394-1399 DOI: 10.1364/JOSAB.27.001394
Abstract
An experimental and theoretical analysis of the angular dependence of the diffracted light beams emerging from three-dimensional colloidal photonic crystals is herein presented. Diffracted beams are identified according to their associated reciprocal-lattice vectors, and their intensities are obtained as a function of the zenithal and azimuthal incidence angles. Significant changes in the beam intensities are observed for large zenithal incidence angles as the azimuthal angle is varied. This phenomenon is related to the excitation of new resonant modes inside the photonic crystal which cannot be observed under normal incidence conditions.
June, 2010 · DOI: 10.1364/JOSAB.27.001394
Química de Superficies y Catálisis
Computational fluid dynamics study of heat transfer in a microchannel reactor for low-temperature Fischer-Tropsch synthesis
Arzamendi, G; Dieguez, PM; Montes, M; Odriozola, JA; Sousa-Aguiar, EF; Gandia, LMChemical Engineering Journal, 160 (2010) 915-922 DOI: 10.1016/j.cej.2009.12.028

Abstract
A three-dimensional computational fluid dynamics (CFD) study of heat transfer in a microchannel reactor for the low-temperature Fischer-Tropsch synthesis (FTS) is presented. The microreactor studied is a steel block with 80 square microchannels of 1 mm of side arranged in cross-flow configuration for the transport of syngas and cooling water. Syngas space velocities in the 5000-30,000 h(-1) (SIP) range have been considered. The microreactor exhibited good isothermicity under most simulated conditions. The FTS can be conducted with very low-temperature change between 483 and 523 K within a wide range of CO conversions using boiling water as coolant. To this end the pressure has to be set at the appropriate value between about Sand 35 atm. The pressure would have to be reduced as the CO conversion increases which might have a negative effect on the FTS selectivity to middle distillates. However, adjusting the cooling water flow rate in the range 0.25-250 g min(-1) allows maintaining the FTS temperature at suitable values while avoiding the use of low pressures. Relatively high values of the overall heat transfer coefficient in the 20-320 W m(-2) K-1 range have been obtained. A significant effect of the buoyancy forces on the thermal performance of the microreactor has been found.
June, 2010 · DOI: 10.1016/j.cej.2009.12.028
Materiales de Diseño para la Energía y Medioambiente
Self-assembly of supramolecular lipid nanoparticles in the formation of plant biopolyester cutin
Dominguez, E; Heredia-Guerrero, JA; Benitez, JJ; Heredia, AMolecular Biosystems, 6 (2010) 948-950 DOI: 10.1039/b927186d

Abstract
The implication of a self-assembly process in the early stages of cutin biosynthesis has been shown by means of antibodies raised against polyhydroxy fatty acid nanoparticles (cutinsomes).
June, 2010 · DOI: 10.1039/b927186d
Reactividad de Sólidos
Microstructural characterization of ceramic-intermetallic composites using TEM related techniques
Sayagues, MJ; Aviles, MA; Cordoba, JM; Alcala, MD; Gotor, FJJournal of the European Ceramic Society, 30 (2010) 1765-1774 DOI: 10.1016/j.jeurceramsoc.2010.01.039

Abstract
TiCxVy/Ni and TiCxNy/Ti-Co composites formed by ceramic and intermetallic binder phases were produced by pressureless sintering at 1400 degrees C from powders synthesized by a mechanically induced self-sustaining reaction (MSR) process. Four different composites were characterized using high-resolution electron microscopic techniques, in both scanning (SEM, HRSEM) and transmission (TEM, HRTEM, ED, EDS and EELS) modes and using an energy filtered technique (EFTEM) associated with electron energy loss spectroscopy (EELS). The microcharacterization showed that the ceramic phase with an fcc-cubic structure displayed a short-range order in many crystals detected by diffuse scattering in the ED patterns. This was possibly due to a sequence of C, N, and vacancies of both atoms along certain directions in the structure. On the other hand, even though the binder phase was introduced as metal in the reaction process, it was formed by Ni-Ti or Co-Ti known intermetallic compounds (NiTi2, Ni3Ti, and Co3Ti). An unknown Ni-Ti intermetallic structure with a Ni:Ti ratio close to 2:1 was only found in one of the synthesized composites and displayed a cubic structure with a lattice parameter, a, of about 8.7 angstrom.
June, 2010 · DOI: 10.1016/j.jeurceramsoc.2010.01.039
Química de Superficies y Catálisis
The Effect of Water on Particle Size, Porosity and the Rate of Drug Release From Implanted Titania Reservoirs
Lopez, T; Ortiz, E; Alexander-Katz, R; Odriozola, JA; Quintana, P; Gonzalez, RD; Lottici, PP; Marino, LGJournal of Biomedical Materials Research Part-B Applied Biomaterials, 93B (2010) 401-406 DOI: 10.1002/jbm.b.31595

Abstract
The implantation of controlled drug release devices represents a new strategy in the treatment of neurodegenerative disorders Sol-gel titania implants filled with valproic acid, have been used for this purpose to treat induced epilepsy in rats The kinetics of the drug release depend on. (a) porosity, (b) chemical interactions between valproic acid and surface hydroxyl groups of titania, (c) particle size, and (d) particle size agglomerates The concentration of water used in the hydrolysis reaction is an important variable in the degree of porosity, hydroxylation, and structural defects of the nanostructured titanium oxide reservoir The titanium n-butoxide/water ratio was systematically varied during the sol-gel synthesis, while maintaining the amount of valproic acid constant. Characterization studies were performed using DTA-TGA, FTIR, Raman, TEM, SEM, BET, and in vitro release kinetic measurements The particle agglomerate size and porosity were found to depend on the amount of water used in the sol-gel reactio.
May, 2010 · DOI: 10.1002/jbm.b.31595
Identification of cellulose fibres belonging to Spanish cultural heritage using synchrotron high resolution X-ray diffraction
Herrera, LK; Justo, A; Duran, A; de Haro, MCJ; Franquelo, M; Rodriguez, JLPApplied Physics A-Materials Science & Processing, 99 (2010) 391-398 DOI: 10.1007/s00339-010-5626-z
Abstract
A complete characterisation of fibres used in Spanish artwork is necessary to provide a complete knowledge of these natural fibres and their stage of degradation. Textile samples employed as painting supports on canvas and one sample of unprocessed plant material were chosen for this study. All the samples were investigated by synchrotron radiation X-ray diffraction (SR-XRD). Flax and cotton have the Cellulose I structure. The values of the crystalline index (CI) were calculated for both types of fibres. The structure of Cellulose IV was associated with the unprocessed plant material. The information obtained by SR-XRD was confirmed by laboratory techniques including scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR).
May, 2010 · DOI: 10.1007/s00339-010-5626-z
Materiales Nanoestructurados y Microestructura
Permanent magnetism in phosphine- and chlorine-capped gold: from clusters to nanoparticles
Munoz-Marquez, MA; Guerrero, E; Fernandez, A; Crespo, P; Hernando, A; Lucena, R; Conesa, JCJournal of Nanoparticle Research, 12 (2010) 1307-1318 DOI: 10.1007/s11051-010-9862-0

Abstract
Magnetometry results have shown that gold NPs (similar to 2 nm in size) protected with phosphine and chlorine ligands exhibit permanent magnetism. When the NPs size decreases down to the subnanometric size range, e.g. undecagold atom clusters, the permanent magnetism disappears. The near edge structure of the X-ray absorption spectroscopy data points out that charge transfer between gold and the capping system occurs in both cases. These results strongly suggest that nearly metallic Au bonds are also required for the induction of a magnetic response. Electron paramagnetic resonance observations indicate that the contribution to magnetism from eventual iron impurities can be disregarded.
May, 2010 · DOI: 10.1007/s11051-010-9862-0
Propiedades mecánicas, modelización y caracterización de cerámicos avanzados
On the microstructure of single wall carbon nanotubes reinforced ceramic matrix composites
Zapata-Solvas, E; Gomez-Garcia, D; Dominguez-Rodriguez, AJournal of Materials Science, 45 (2010) 2258-2263 DOI: 10.1007/s10853-009-4126-z
Abstract
A microstructural modelling of the microstructure in single wall carbon nanotubes reinforced alumina ceramics has been developed. The model accounts for the main microstructural features, being quite useful to describe the carbon nanotube distribution along the ceramic matrix. The microstructural analysis derived from this model is found to give a deeper insight into the high-temperature creep of these composites.
May, 2010 · DOI: 10.1007/s10853-009-4126-z
Nanotecnología en Superficies y Plasma - Materiales Nanoestructurados y Microestructura
SiOxNy thin films with variable refraction index: Microstructural, chemical and mechanical properties
Godinho, V; de Haro, MCJ; Garcia-Lopez, J; Goossens, V; Terryn, H; Delplancke-Ogletree, MP; Fernandez, AApplied Surface Science, 256 (2010) 4548-4553 DOI: 10.1016/j.apsusc.2010.02.045

Abstract
In this work amorphous silicon oxynitride films with similar composition (ca. Si0.40N0.45O0.10) were deposited by reactive magnetron sputtering from a pure Si target under different N-2-Ar mixtures. Rutherford backscattering (RBS) studies revealed that the coatings presented similar composition but different density. The mechanical properties evaluated by nanoindentation show also a dependence on the deposition conditions that does not correlate with a change in composition. An increase in nitrogen content in the gas phase results in a decrease of hardness and Young's modulus. The microstructural study by high resolution scanning electron microscopy (SEM-FEG) on non-metalized samples allowed the detection of a close porosity in the form of nano-voids (3-15 nm in size), particularly in the coatings prepared under pure N-2 gas. It has been shown how the presence of the close porosity allows tuning the refraction index of the films in a wide range of values without modifying significantly the chemical, thermal and mechanical stability of the film.
May, 2010 · DOI: 10.1016/j.apsusc.2010.02.045
Reactividad de Sólidos
A new model for the kinetic analysis of thermal degradation of polymers driven by random scission
Sanchez-Jimenez, PE; Perez-Maqueda, LA; Perejon, A; Criado, JMPolymer Degradation and Stability, 95 (2010) 733-739 DOI: 10.1016/j.polymdegradstab.2010.02.017

Abstract
In this paper, a series of f(alpha) kinetic equations able to describe the random scission degradation of polymers is formulated in such a way that the reaction rate of the thermal degradation of polymers that go through a random scission mechanism can be directly related to the reacted fraction. The proposed equations are validated by a study of the thermal degradation of poly(butylene terephthalate) (PBT). The combined kinetic analysis of thermal degradation curves of this polymer obtained under different thermal pathways have shown that the proposed equation fits all these curves while other conventional models used in literature do not.
May, 2010 · DOI: 10.1016/j.polymdegradstab.2010.02.017
Nanotecnología en Superficies y Plasma
Excitation transfer mechanism along the visible to the Near-IR in rhodamine J-heteroaggregates
Sanchez-Valencia, JR; Toudert, J; Gonzalez-Garcia, L; Gonzalez-Elipe, AR; Barranco, AChemical Communications, 46 (2010) 4372-4374 DOI: 10.1039/c0cc00087f

Abstract
An enhanced fluorescent emission of the dye Rhodamine 800 in the Near-IR is observed in the presence of other xanthene dye molecules (RhX) when they are hosted in different matrices due to the formation of a new type of fluorescent J-heteroaggregates.
This enhanced emission of the acceptor occurs despite the low spectral overlapping and the low quantum yield of Rh800.
May, 2010 · DOI: 10.1039/c0cc00087f
Determination of pigments and binders in Pompeian wall paintings using synchrotron radiation - High-resolution X-ray powder diffraction and conventional spectroscopy-chromatography
Duran, A; De Haro, MCJ; Perez-Rodriguez, JL; Franquelo, ML; Herrera, LK; Justo, AArchaeometry, 52 (2010) 286-307 DOI: 10.1111/j.1475-4754.2009.00478.x

Abstract
The employment of synchrotron techniques complemented by conventional laboratory systems has allowed us to deepen and improve our knowledge of Roman wall painting procedures. The palette identified in wall paintings from Pompeii and Herculaneum from the second century bc includes goethite, hematite, cinnabar, glauconite, Egyptian blue, and other components such as calcite and aragonite. Proof of the use of organic binders is provided by FTIR and PY-GC/MS. Therefore, the possibility of the use of 'a secco' techniques cannot be ruled out. Pigments in wall paintings are usually found in small percentages and conventional X-ray diffractometers do not detect them. Synchrotron radiation - high-resolution X-ray powder diffraction has allowed identification with only a few micrograms of sample.
April, 2010 · DOI: 10.1111/j.1475-4754.2009.00478.x
Fotocatálisis Heterogénea: Aplicaciones
N- and/or W-(co)doped TiO2-anatase catalysts: Effect of the calcination treatment on photoactivity
Kubacka, A; Colon, G; Fernandez-Garcia, MApplied Catalysis B-Environmental, 95 (2010) 238-244 DOI: 10.1016/j.apcatb.2009.12.028

Abstract
A series of nanosized W,N-codoped and single-doped N- and W-anatase-TiO2 catalysts have been prepared by a microemulsion method and calcined at different temperatures. The activity in the sunlight selective photo-oxidation of toluene and styrene has been correlated with structural, electronic, and surface examinations of the catalysts done with the help of XRD-Rietveld, N-2 physisorption, X-ray photoelectron, infrared, electron paramagnetic resonance (EPR) and UV-vis spectroscopies. Irrespective of the reaction, W,N-codoped nanocatalysts showed an enhanced photoactivity with respect to bare anatase and single-doped N-TiO2 and W-TiO2 materials. A strong W-N synergistic interaction appears to play a decisive role in driving the excellent photoactivity performance of W,N-codoped materials by affecting (i) electronic properties, particularly maximizing the anatase band gap decrease and enhancing the subsequent visible light photon absorption, and (ii) surface properties, in turn related to the formation of OH radicals upon light excitation. The maximum photoactivity is reached by calcination at 450 degrees C and is concomitantly observed with a near complete selectivity to partial oxidation products. Higher calcination temperatures yielded solids with significantly inferior photocatalytic performance. The properties of the W-N interaction are discussed as a function of the calcination temperature.
April, 2010 · DOI: 10.1016/j.apcatb.2009.12.028
Nanotecnología en Superficies y Plasma
One-Step Dry Method for the Synthesis of Supported Single-Crystalline Organic Nanowires Formed by pi-Conjugated Molecules
Borras, A; Groning, O; Aguirre, M; Gramm, F; Groning, PLangmuir, 26 (2010) 5763-5771 DOI: 10.1021/la1003758

Abstract
We present for the first time a general vacuum process for the growth of supported organic nanowires formed by pi-conjugated molecules, including metalloporphyrins, metallophthalocyanines, and perylenes. This methodology consists on a one-step physical vapor deposition of the pi-conjugated molecules. The synthesis is carried out at controlled temperature on substrates with tailor morphology which allows the growth or organic nanowires in the form of squared nanofibers and nanobelts. The study of the nanowires by electron diffraction and HRTEM combining with the results of a theoretical analysis of the possible arrangement of the pi-conjugated molecules along the nanowires reveals that the nanowires show a columnar structure along the fiber axis consisting of pi-stacked molecules having a herringbone-like arrangement. The formation of these nanowires on different substrates demonstrates that the growth mechanism is independent of the substrate chemical composition. An in-depth phenomenological study of the Formation of the nanowires drives us to propose a growth mechanism based on a crystallization process. Furthermore, the growth method allows the fabrication of two particular ID heterostructures: binary and open core@shell organic nanofibers.
April, 2010 · DOI: 10.1021/la1003758
Nanotecnología en Superficies y Plasma
Non-destructive depth compositional profiles by XPS peak-shape analysis
Lopez-Santos, MC; Yubero, F; Espinos, JP; Gonzalez-Elipe, ARAnalytical and Bioanalytical Chemistry, 396 (2010) 2757-2768 DOI: 10.1007/s00216-009-3312-9

Abstract
The measured peak shape and intensity of the photoemitted signal in X-ray photoelectron spectroscopy (XPS) experiments (elastic and inelastic parts included) are strongly correlated, through electron-transport theory, with the depth distribution of photoelectron emitters within the analyzed surface. This is the basis of so-called XPS peak-shape analysis (also known as the Tougaard method) for non-destructive determination of compositional in-depth (up to 6-8 nm) profiles. This review describes the theoretical basis and reliability of this procedure for quantifying amounts and distributions of material within a surface. The possibilities of this kind of analysis are illustrated with several case examples related to the study of the initial steps of thin-film growth and the modifications induced in polymer surfaces after plasma treatments.
April, 2010 · DOI: 10.1007/s00216-009-3312-9
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