Papers by Aitor Larrañaga
Ceramics International, Jun 1, 2018
A family of cuspidine-type rare-earth aluminates with the general formula Ln 4 Al 2 O 9 (Ln= Y, S... more A family of cuspidine-type rare-earth aluminates with the general formula Ln 4 Al 2 O 9 (Ln= Y, Sm, Eu, Gd, Tb) has been prepared as a strategy to improve the thermal barrier coating (TBC) fulfilment. Varying trivalent lanthanides is applied to tailor the properties of oxides as ceramic top coats, for high temperature applications. After different heat treatments, X-ray diffraction (XRD) results concluded that Eu 4 Al 2 O 9 has the highest structural stability at 1200 and 1300 ºC. Moreover, the Y 4 Al 2 O 9 has a long lifetime at 1000 ºC and is stable at 1100 ºC. Sm 4 Al 2 O 9 and Gd 4 Al 2 O 9 showed higher stability at 1200 ºC than that of Tb 4 Al 2 O 9. However, terbium aluminate exhibited at 300-1000 ºC the highest thermal expansion coefficient. For five compositions thermal diffusivity measurements indicated favourable values at 600 ºC, which are lower than that of YSZ.
Nucleation and Atmospheric Aerosols, 2020
Solid State Ionics, 2015
The perovskite LaNi 0.6 Fe 0.4 O 3 has been prepared by the glycine-nitrate route using different... more The perovskite LaNi 0.6 Fe 0.4 O 3 has been prepared by the glycine-nitrate route using different amounts of glycine/ fuel ratio (G/N = 0.5, 1.0 and 1.5), in order to study the sample preparation influence on the properties in the context of their application as a cathode contact material for solid oxide fuel cells (SOFCs). The obtained materials have been characterized by X-ray diffraction, scanning electron microscopy, dilatometry and electrical conductivity measurements. All the compounds have rhombohedral symmetry and a porous microstructure with fine grain sizes. The sample obtained at the G/N of 1.0 has more suitable conductivity values for application as SOFC contact material.
Micromachines, Jul 23, 2022
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Boletin De La Sociedad Espanola De Ceramica Y Vidrio, Jul 1, 2022
Abstract In this article, it is intended to evaluate the performances of previously synthesized d... more Abstract In this article, it is intended to evaluate the performances of previously synthesized different nanometric compounds as SOFC components under real conditions. For this purpose, anodic supports SOFCs have been manufactured in different configurations. The compounds NiO-(Y2O3)0.08(ZrO2)0.92 (NiO–YSZ), (Y2O3)0.08(ZrO2)0.92 (YSZ), Sm0.2Ce0.8O1.9 (SDC), La0.6Sr0.4FeO3 (LSF) and LaNi0.6Fe0.4O3 (LNF) were used as anode support, electrolyte, barrier, cathode and contact layer, respectively. To obtain the cells, the anode supports were produced by uniaxial pressing and the remaining layers were added using the airbrush technique, assembling them by different sintering processes. The cells developed have been electrochemically tested in a temperature range between 750 and 865 °C. Additionally, degradation tests have been carried out under constant current. Moreover, to characterize the microstructure of the cells, a scanning electron microscope (SEM) equipped with an energy dispersive X-ray spectroscopy (EDX) analyzer has been used. The results obtained show that the incorporation of cathode and contact layers increases the power densities and decreases the total resistances of the cells with respect to the cell without cathode, especially with the addition of the LNF contact layer. Despite the improvement obtained, more tests have to be carried out in order to optimize the performance of SOFC devices in degradation tests.
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, Mar 1, 2008
Mn(SeO(3)).2H(2)O (1) and Fe(2)(SeO(3))(3).3H(2)O (2) have been synthesized by slow evaporation f... more Mn(SeO(3)).2H(2)O (1) and Fe(2)(SeO(3))(3).3H(2)O (2) have been synthesized by slow evaporation from an aqueous solution in the case of (1) and using mild hydrothermal conditions for (2). The crystal structures of both phases have been refined by the Rietveld method. The compounds crystallize in different spatial groups, the P2(1)/n monoclinic one with parameters a=6.649(1)A, b=6.542(1)A, c=10.890(1)A and beta=103.85(1) degrees being Z=4 for (1) and the R3c trigonal space group with parameters a=9.361(1)A, c=20.276(1)A and Z=6 for (2). The crystal structure of compound (1) consists of a three-dimensional framework formed by MnO(6) octahedra and (SeO(3))(2-) oxoanions with trigonal pyramidal geometry, which gives rise to Mn(2)O(10) dimers of edge-sharing octahedra. The crystal structure of phase (2) can be described as a three-dimensional framework formed by MnO(6) octahedra and (SeO(3))(2-) oxoanions with trigonal pyramidal geometry. In this phase the octahedral entities are linked along the three crystallographic axes through the selenite anions. Diffuse reflectance spectrum and luminescent measurements for (1) indicate the existence of Mn(2+) cations in a slightly distorted octahedral environment. Diffuse reflectance spectrum and Mössbauer spectroscopy, in the paramagnetic region, for (2) show the existence of Fe(3+) cations in slightly distorted octahedral symmetry. ESR spectra of both compounds are isotropic with a g-value of 1.99(1) and 2.00(1), respectively. Magnetic measurements of both phases indicate an antiferromagnetic behavior. For phase (2), both, the ESR and magnetic measurements suggest a spin change from Fe(3+) (S=5/2) to Fe(2+) (S=2) at low temperatures.
Journal of Magnetism and Magnetic Materials, Aug 1, 2018
Abstract Gd-Co/Ti multilayers were prepared by magnetron sputtering deposition onto glass substra... more Abstract Gd-Co/Ti multilayers were prepared by magnetron sputtering deposition onto glass substrates. The temperature dependence of magnetization of the multilayered structures depends on the Gd-Co layer thickness. It was shown that the obtained experimental results can be satisfactorily described in the framework of the joint application of models of the “size factor” and the “molecular field”. In addition, the possible effect of the electronic structure of titanium on the average magnetic moment of Co atoms, the efficiency of which depends on the thickness of the magnetic layers was also taken into account.
Materials Science And Engineering: B, Oct 1, 2014
ABSTRACT The microstructure and magnetic properties of sputtered permalloy films and FeNi-based m... more ABSTRACT The microstructure and magnetic properties of sputtered permalloy films and FeNi-based multilayers prepared by magnetron sputtering have been studied. X-ray diffraction measurements indicate that Ti/FeNi films exhibit good (1 1 1) texture and crystallinity. Ti/FeNi bilayers with high crystallographic quality have relatively low resistivity. The Ti seed layer does not influence the magnetic properties of FeNi film in Ti/FeNi bilayers, but the thick Cu seed layer leads to an increase of the coercive force of the magnetic layer. For the FeNi films deposited on thick Cu seed layer, the (0 1 0) and (0 0 2) diffraction peaks of hcp nickel were clearly observed. The thin Ti spacer between Cu and FeNi layers prevents the formation of the nickel phase and restores the magnetic softness of the FeNi layer in the Cu/Ti/FeNi sample. Obtained results can be important for the development of multilayer sensitive elements for giant magnetoimpedance or magnetoresistance detectors.
Boletín de la Sociedad Española de Mineralogía, 2001
Boletín de la Sociedad Española de Mineralogía, 2002
Structural chemistry & crystallography communication, Jun 13, 2018
Macla: revista de la Sociedad Española de Mineralogía, 2006
2 ºC/min 2 ºC/min 1400 ºC (5h) 2 ºC/min 2 ºC/min 1100-1400 ºC (5h) P Pr ro oc ce es sa ad do o Se... more 2 ºC/min 2 ºC/min 1400 ºC (5h) 2 ºC/min 2 ºC/min 1100-1400 ºC (5h) P Pr ro oc ce es sa ad do o Se han prensado los materiales de YSZ aplicando 7 Tn en un molde de 31 mm de diámetro.
El análisis de DRX en muestra policristalina indica una única fase pura que cristaliza en sistema... more El análisis de DRX en muestra policristalina indica una única fase pura que cristaliza en sistema cúbico. Para la optimización de la síntesis de Sm 0.2 Ce 0.8 O 1.9 (SDC) [4], se ha reducido la relación de G/N debido a las pérdidas de material ocasionadas en la combustión, consecuencia del menor tamaño de partícula como se puede apreciar en las micrografías de MEB. En la figura se observan partículas nanométricas de tamaño homogéneo distribuidas en aglomerados. Electrolito(YSZ) DRX MEB Se han obtenido lotes de 10gr de compuesto por cada síntesis de Zr 0.8 Y 0.2 O 1.9 (YSZ). La difracción de rayos X muestra un sistema cúbico con ausencia de impurezas. Para obtener una mayor densidad del compuesto, se ha elevado la temperatura de sinterización a 1400°C, obteniéndose, tal y como muestran las micrografías, unas partículas sinterizadas en tamaños micrométricos heterogéneos. DRX MEB La difracción de rayos X en muestra policristalina [2] indica un sistema cúbico y una única fase pura para el compuesto MnCo 1.9 Fe 0.1 O 4 (MCF10) tras efectuar un sinterizado a 950°C durante 8 horas. Las micrografías MEB de la superficie de las muestras en polvo, muestran partículas poco aglomeradas de unos tamaños nanométricos heterogéneos.
Ultramarine blue are a family of mineral pigments that are commonly dispersed in construction mat... more Ultramarine blue are a family of mineral pigments that are commonly dispersed in construction materials (concrete, paints, and polymers) to obtain colored materials. Two different methods for encapsulating phase change materials (PCM) in pigments have been studied to obtain PCM/pigment composites with thermal storage capacity: capillary and vacuum impregnation methods. The aim is to obtain a pigment providing thermal storage capacity to construction materials (apart from color) by an easily scalable process. The optimized vacuum impregnation process provides an hexadecane/pigment composite having a latent heat of fusion of 44 J/g (around a 20%wt. hexadecane adsorbed in the pigment) while the optimized capillary impregnation process allows the fabrication of a pigment with a latent heat of fusion of 41 J/g (around a 18%wt. hexadecane). Durability of both materials has been tested by the rmodiffrac to metric measurements indicating in both cases, slow reductions of the area intensity of the XRD signals (up to 10% and 15% after 100 cycles). The long term degradation behavior at room temperature was tested by DSC showing a reduction of a 3% of the thermal storage capability after 1000h.Considering the degradation and scalability issues, capillary impregnation seems to be the most suitable process for the mass production of pigments having high thermal storage capacity.
Journal of Magnetism and Magnetic Materials, Nov 1, 2018
The influence of the nanoscale thicknesses of the ferrimagnetic Tb-Co layers on the structure and... more The influence of the nanoscale thicknesses of the ferrimagnetic Tb-Co layers on the structure and magnetic properties of magnetron sputtered Tb-Co/Ti and Tb-Co/Al 2 O 3 magnetic multilayers were comparatively studied. Low angle X-ray diffraction patterns testified to the existence of a well defined layered structure in all the cases under consideration. For all samples, the magnetization was positioned in the plane of the films in the entire investigated temperature interval from 5 to 350 K. The temperature dependence of magnetization of the multilayered structures is the function of the Tb-Co layer thickness. The material of the spacers was shown to significantly influence the magnetic properties of the multilayers.
ECS transactions, Jun 2, 2015
A Fe-22Cr mesh/LaNi0.6Fe0.4O3-δ (LNF) composite, obtained via dip coating technique, was machined... more A Fe-22Cr mesh/LaNi0.6Fe0.4O3-δ (LNF) composite, obtained via dip coating technique, was machined using a femtosecond laser as a possible gas permeable contact layer for solid oxide fuel cells (SOFCs). Both electrical performance and processing reproducibility of {Crofer22APU channeled interconnect-ablated composite contact material-La0.6Sr0.4FeO3 (LSF) cathode} structure were studied through electrochemical measurements on four replicas. For comparison, the obtained area specific resistance (ASR) data, under similar measurement conditions, for {flat Crofer22APU/LNF contact perovskite/LSF} and {channeled Crofer22APU/contact composite} setups are also presented. The results support the reproducibility for the measured ablated final systems, obtaining average ASR value of 0.06(1) Ω cm2 at 800 ºC, in air.
Powder Technology, Dec 1, 2017
Effect of the synthesis conditions on the properties of La0.15Sm0.35Sr0.08Ba0.42FeO3- cathode ma... more Effect of the synthesis conditions on the properties of La0.15Sm0.35Sr0.08Ba0.42FeO3- cathode material for SOFCs
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Papers by Aitor Larrañaga