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Scientific Papers in SCI



2021


Nanotecnología en Superficies y Plasma

Mechanically Switchable Wetting Petal Effect in Self-Patterned Nanocolumnar Films on Poly(dimethylsiloxane)

Parra-Barranco, J; Lopez-Santos, C; Sanchez-Valencia, JR; Borras, A; Gonzalez-Elipe, AR; Barranco, A
Nanomaterials, 11 (2021) 2566

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Switchable mechanically induced changes in the wetting behavior of surfaces are of paramount importance for advanced microfluidic, self-cleaning and biomedical applications. In this work we show that the well-known polydimethylsiloxane (PDMS) elastomer develops self-patterning when it is coated with nanostructured TiO2 films prepared by physical vapor deposition at glancing angles and subsequently subjected to a mechanical deformation. Thus, unlike the disordered wrinkled surfaces typically created by deformation of the bare elastomer, well-ordered and aligned micro-scaled grooves form on TiO2/PDMS after the first post-deposition bending or stretching event. These regularly patterned surfaces can be reversibly modified by mechanical deformation, thereby inducing a switchable and reversible wetting petal effect and the sliding of liquid droplets. When performed in a dynamic way, this mechanical actuation produces a unique capacity of liquid droplets (water and diiodomethane) transport and tweezing, this latter through their selective capture and release depending on their volume and chemical characteristics. Scanning electron and atomic force microscopy studies of the strained samples showed that a dual-scale roughness, a parallel alignment of patterned grooves and their reversible widening upon deformation, are critical factors controlling this singular sliding behavior and the possibility to tailor their response by the appropriate manufacturing of surface structures.


October, 2021 | DOI: 10.3390/nano11102566

Materiales Coloidales

Si sputtering yield amplification: a study of the collisions cascade and species in the sputtering plasma

Cruz, J; Sangines, S; Soto-Valle; Muhl; Sierra, I; De Lucio-Morales, O; Mitrani, A; Calderon-Olvera, RM; Mendoza-Perez, R; Machorro-Mejia, R
Journal of Physics D-Applied Physics, 54 (2021) 375201

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The sputtering yield amplification (SYA) is a phenomenon based on doping a sputtering target with atoms of higher atomic mass. This doping changes the depth and the direction of the collision cascade in the target surface promoting a higher ejection of target atoms. In this work, we present a new way of generating the SYA phenomenon without the need of expensive and complex deposition systems. This was accomplished by increasing the working pressure and adding small pieces of W, as dopant element, on the racetrack of a Si target. The physical phenomena necessary to promote the SYA, for our experimental parameters, were analysed in two different deposition chambers and two sizes of sputtering targets. Based on the collisions in the gas phase, a calculation on the number of W atoms returning to the racetrack area was made, considering the number of atoms deposited on the thin films, to determine their effect on the cascade of collisions. In addition, calculations with the simulation of metal transport code were developed to determine the location on the racetrack zone the returning atoms were redeposited. By using reference samples placed on the racetrack of the Si target, we found that the percentage of SYA depends on the number of dopant atoms redeposited as well as the depth distribution these atoms had in the racetrack surface.


September, 2021 | DOI: 10.1088/1361-6463/ac0c4e

Materiales Nanoestructurados y Microestructura

Pd-C Catalytic Thin Films Prepared by Magnetron Sputtering for the Decomposition of Formic Acid

Arzac, GM; Fernandez, A; Godinho, V; Hufschmidt, D; de Haro, MCJ; Medran, B; Montes, O
Nanomaterials, 11 (2021) 2326

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Formic acid is an advantageous liquid organic hydrogen carrier. It is relatively nontoxic and can be synthesized by the reaction of CO2 with sustainable hydrogen or by biomass decomposition. As an alternative to more widely studied powdery catalysts, supported Pd-C catalytic thin films with controlled nanostructure and compositions were newly prepared in this work by magnetron sputtering on structured supports and tested for the formic acid decomposition reaction. A two-magnetron configuration (carbon and tailored Pd-C targets) was used to achieve a reduction in Pd consumption and high catalyst surface roughness and dispersion by increasing the carbon content. Activity and durability tests were carried out for the gas phase formic acid decomposition reaction on SiC foam monoliths coated with the Pd-C films and the effects of column width, surface roughness and thermal pre-reduction time were investigated. Activity of 5.04 mol(H2)center dot g(Pd)(-1)center dot h(-1) and 92% selectivity to the dehydrogenation reaction were achieved at 300 degrees C for the catalyst with a lower column width and higher carbon content and surface roughness. It was also found that deactivation occurs when Pd is sintered due to the elimination of carbon and/or the segregation and agglomeration of Pd upon cycling. Magnetron sputtering deposition appears as a promising and scalable route for the one-step preparation of Pd-C catalytic films by overcoming the different deposition characteristics of Pd and C with an appropriate experimental design.


September, 2021 | DOI: 10.3390/nano11092326

Materiales y Procesos Catalíticos de Interés Ambiental y Energético

Examination of the Deactivation Cycle of NiAl- and NiMgAl-Hydrotalcite Derived Catalysts in the Dry Reforming of Methane

Abdelsadek, Z.; Holgado, J.P.; Halliche, D.; Caballero, A.; Cherifi, O.; Gonzalez-Cortes, S.; Masset, P.J.
Catalysis Letters, 151 (2021) 2696-2715

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The importance of the dry reforming of methane (DRM) lies in its capability to upgrade two greenhouse gases (CH4 and CO2) into synthesis gas (CO and H-2), which is one of the main building block for synthesizing hydrocarbons. However, the Ni-based catalysts for DRM reaction usually have a major catalytic stability drawback. This works aims to assess the catalytic activity and stability of two Ni-based catalysts obtained from hydrotalcite (HT) precursors (i.e., NiAl-HT and NiMgAl-HT). The precursors, calcined (-c), reduced (-R) and spent samples were characterized by a series of techniques to gain insight into the influence of MgO over Ni-based catalyst in the drying reforming of methane. An in-situ ageing cycle process to speed up the deactivation of hydrotalcite-derived catalysts showed that the NiMgAl-HTc-R catalyst displayed a higher activity and resistance to coke formation (stability) than NiAl-HTc-R because of the introduction of Mg into hydrotalcite structure in the catalyst precursor. The presence of this element enhances several factors involved in the stability of Ni-based catalysts for the DRM process such as the reducibility and textural features of the catalysts, size and dispersion of Ni-0 nanoparticles and also maintains a good compromise between the acid and base properties of the solid catalysts.


September, 2021 | DOI: 10.1007/s10562-020-03513-4

Química de Superficies y Catálisis

Structure-sensitivity of formic acid dehydrogenation reaction over additive-free Pd NPs supported on activated carbon

Santos, J.L.; Megías-Sayago, C.; Ivanova, S.; Centeno, M.A.; Odriozola, J.A.
Chemical Engineering Journal, 420 (2021) 127641

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In this study the size-activity dependence of palladium based catalysts in formic acid dehydrogenation reaction was investigated and evaluated. A wide range of particle sizes was considered and the catalyst series were prepared upon variation of some synthetic parameters, precursor and solvent nature in particular. Synthesis method variations affect significantly Pd particle size and results in diverse activity toward hydrogen production. An optimal size was observed and explained by the diverse proportion of low and high coordinated Pd states available for different samples within the series. The evaluation of particles much bigger than 6 nm changes importantly the fraction of high and low coordination atoms and allows the clear confirmation of the importance of the presence of low coordination atoms on the surface of catalyst.


September, 2021 | DOI: 10.1016/j.cej.2020.127641

 

 

 

 

 

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