Scientific Papers in SCI

2014


Title: Influence of the acid–base properties over NiSn/MgO–Al2O3 catalysts in the hydrogen production from glycerol steam reforming
Author(s): Bobadilla, LF; Penkova, A; Romero-Sarria, F; Centeno, MA; Odriozola, JA
Source: International Journal of Hydrogen Energy, 39 (2014) 5704-5712

abstract | fulltext

In this work we have investigated the hydrogen production from glycerol steam reforming. The effect of the acid-base properties was evaluated using four catalysts based in an alloy Ni-Sn as active phase supported over (Upsilon)-Al2O3 with different content in MgO, varying between 0 and 30 wt.% The incorporation of MgO results in the formation of MgAl2O4 spinel, which modifies the acid-base properties of the catalyst. Addition of MgO favored the glycerol conversion into gas, and the catalyst loaded with 10 wt.% MgO exhibited better catalytic performance and higher stability. A blank test with quartz was performed indicating that pyrolysis of glycerol takes place in the quartz.

April, 2014 | DOI: 10.1016/j.ijhydene.2014.01.136

Title: Understanding the Role of the Cosolvent in the Zeolite Template Function of Imidazolium-Based Ionic Liquid
Author(s): Ayala, R; Ivanova, S; Blanes, JMM; Romero-Sarria, F; Odriozola, JA
Source: Journal of Physical Chemistry B, 118 (2014) 3650–3660

abstract | fulltext

In this work, a study for understanding the role played by [ClBmim], [BF4Bmim], [PF6Bmim], and [CH3SO3Bmim] ionic liquids (ILs) in the synthesis of zeolites is presented. The use of [ClBmim] and [CH3SO3Bmim] ILs, as reported earlier [ Chem. Eur. J. 2013, 19, 2122] led to the formation of MFI or BEA type zeolites. Contrary, [BF4Bmim] and [PF6Bmim] ILs did not succeed in organizing the Si–Al network into a zeolite structure. To try to explain these results, a series of quantum mechanical calculations considering monomers ([XBmim]) and dimers ([XBmim]2) by themselves and plus cosolvent (water or ethanol) were carried out, where X ≡ Cl–, BF4–, PF6–, or CH3SO3–. Our attention was focused on the similarities and differences among the two types of cosolvents and the relation between the structure and the multiple factors defining the interactions among the ILs and the cosolvent. Although a specific pattern based on local structures explaining the different behavior of these ILs as a zeolite structuring template was not found, the calculated interaction energies involving the Cl– and CH3SO3– anions were very close and larger than those for BF4– and PF6– species. These differences in energy can be used as an argument to describe their different behavior as structure directing agents. Moreover, the topology of the cosolvent is also an ingredient to take into account for a proper understanding of the results.

April, 2014 | DOI: 10.1021/jp410260g

Title: The Use of Fluorocarbons to Mitigate the Oxygen Dependence of Glucose Microbiosensors for Neuroscience Applications
Author(s): Martin, M; O'Neill, RD; Gonzalez-Mora, JL; Salazar, P
Source: Journal of The Electrochemical Society, 161 (2014) H689-H695

abstract | fulltext

First-generation amperometric glucose biosensors are the most commonly used method for glucose monitoring in neuroscience. Nevertheless, biosensors of this genre suffer from the so-called "oxygen deficit". This problem is particularly acute when the oxygen concentration is low, as is the case in brain extracellular fluid. In the present work we use different fluorocarbons, such as Nafion and H700, to mitigate the oxygen deficit. These fluorocarbon-derived materials display a remarkable solubility for oxygen, and are able to act as oxygen reservoirs supporting the enzymatic reaction. Different biosensor configurations are presented, evaluating their sensitivity, linear range and oxygen dependence. Optimized Nafion- and H700-modified biosensors displayed a remarkable oxygen tolerance, with K-M(O-2) values as low as 11 and 4 mu mol L-1, respectively, and an appropriate sensitivity for in-vivo applications. Finally, in-vivo data are reported in order to illustrate the application of such devices in neuroscience applications.

October, 2014 | DOI: 10.1149/2.1071410jes

Title: Enhanced general analytical equation for the kinetics of the thermal degradation of poly(lactic acid)/montmorillonite nanocomposites driven by random scission
Author(s): Carrasco, F; Perez-Maqueda, LA; Santana, OO; Maspoch, ML
Source: Polymer Degradation and Stability, 101 (2014) 52-59

abstract | fulltext

An enhanced general analytical equation has been developed in order to evaluate the kinetic parameters of the thermal degradation of nanocomposites, composed of poly(lactic acid) (PLA) and organo-modified montmorillonite (OMMT) nanoparticles. This improvement has consisted of replacing the n-order conversion function by a modified form of the Sestak–Berggren equation f(α) = c (1 − α)nαm that led to a better adjustment of experimental data and also adequately represented the conventional mechanisms for solid-state processes. The kinetic parameters so obtained have been compared to those determined by conventional differential and isoconversional methods. Given that the thermal degradation of PLA has been argued to be caused by random chain scission reactions of ester groups, the conversion function f(α) = L (L − 1)x(1 − x)L−1, corresponding to a random scission mechanism, has been tested. Once optimized the kinetic model, the thermal degradation kinetics of nanocomposites (0.5 and 2.5% of OMMT) was compared to that of the polymer matrix. Moreover, the thermal stability of nanocomposites was tested and compared to that of the polymer matrix.

March, 2014 | DOI: 10.1016/j.polymdegradstab.2014.01.014

Title: Improvement of the thermal stability of branched poly(lactic acid) obtained by reactive extrusion
Author(s): Carrasco, F; Cailloux, J; Sanchez-Jimenez, PE; Maspoch, ML
Source: Polymer Degradation and Stability, 104 (2014) 40-49

abstract | fulltext

One-step reactive extrusion-calendering process (REX-calendering) has been used in order to obtain sheets of 1 mm from poly(lactic acid) modified with a styrene-acrylic multifunctional oligomeric agent. In a preliminary internal mixer study, torque versus time has been monitored in order to ascertain chain extender ratios and reaction time. Once all the parameters were optimized, reactive extrusion experiments have been performed. An enhanced general analytical equation has been developed in order to evaluate the kinetic parameters of the thermal degradation of PLA sheets manufactured by reactive extrusion. This improvement has consisted of replacing the n-order conversion function by a modified form of the Sestak–Berggren equation f(α) = c (1 − α)nαm that led to a better adjustment of experimental data and also adequately represented the conventional mechanisms for solid-state processes. The kinetic parameters so obtained have been compared to those determined by conventional differential methods and n-order reaction kinetics. Given that the thermal degradation of PLA has been argued to be caused by random chain scission reactions of ester groups, the conversion function f(α) = 2 (α1/2 − α), corresponding to a random scission mechanism for L = 2 (as well as other functions for L values up to 8), has been tested. Once optimized the kinetic model, the thermal degradation kinetics of sheets obtained by REX-calendering process was compared to that of conventional sheets and polymer matrix.

June, 2014 | DOI: 10.1016/j.polymdegradstab.2014.03.026

Title: Structure determination and electronic structure of Cu3Au0.5N
Author(s): Soto, G; Ponce, I; Moreno, MG; Yubero, F; De la Cruz, W
Source: Journal of Alloys and Compounds, 594 (2014) 48-51

abstract | fulltext

This study investigated the formation of a Cu3Au-nitride alloy using both experimental and computational methods. The alloy was produced as thin film by sputtering a Cu3Au target in a nitrogen atmosphere. The films were characterized for structure and composition by spectroscopic and diffraction techniques. The structure was established by Rietveld and ab inito methods. The structure is cubic and of the Fm3m space group, with a composition close to Cu6AuN2. Relative to the Cu3N structure, the Cu atoms occupy the faces, Au the half corners, and N the centers. The compound is a narrow-gap semiconductor with a positive hall coefficient that could be used for infrared detection.

May, 2014 | DOI: 10.1016/j.jallcom.2014.01.113

Title: An investigation on the formation mechanism of nano ZrB2 powder by a magnesiothermic reaction
Author(s): Jalaly, M; Bafghi, MS; Tamizifar, M; Gotor, FJ
Source: Journal of Alloys and Compounds, 588 (2014) 36-41

abstract | fulltext

Nanocrystalline zirconium diboride (ZrB2) powder was produced by mechanochemistry from the magnesiothermic reduction in the Mg/ZrO2/B2O3 system. The use of high-energy milling conditions was essential to induce a mechanically induced self-sustaining reaction (MSR) and significantly reduce the milling time required for complete conversion. Under these conditions, it was found that the ignition time for ZrB2 formation was only about a few minutes. In this study, the mechanism for the formation of ZrB2 in this system was determined by studying the relevant sub-reactions, the effect of stoichiometry, and the thermal behavior of the system.

March, 2013 | DOI: 10.1016/j.jallcom.2013.11.050

Title: Spinodal decomposition and precipitation in Cu–Cr nanocomposite
Author(s): Sheibani, S; Heshmati-Manesh, S; Ataie, A; Caballero, A; Criado, JM
Source: Journal of Alloys and Compounds, 587 (2014) 670-676

abstract | fulltext

In this study, spinodal decomposition and precipitation mechanism of mechanically alloyed supersaturated Cu–3wt.%Cr and Cu–5wt.%Cr solid solutions was investigated under nonisothermal aging. Decomposition mechanism and kinetics were studied using differential scanning calorimetry (DSC) and X-ray diffraction (XRD) techniques. Also, the microstructure was characterized by transmission electron microscopy (TEM). Effect of Al2O3 reinforcement on the aging kinetics was also evaluated. It was found that Cu–3wt.%Cr and Cu–5wt.%Cr solid solutions undergo spinodal decomposition at initial stages of ageing. However, decomposition mechanism was changed to nucleation and growth by the aging progress. The aging kinetics for the Cu–Cr/Al2O3 composition appeared to be slightly faster than that for Cu–Cr, since the ageing activation energy is decreased in presence of Al2O3 nano-particles. This behavior is probably due to the higher dislocation density and other structural defects previously produced during ball milling. A detailed comparison of the DSC results with those obtained by TEM, showing good consistency, has been presented. The average size of Cr-rich precipitates was about 10 nm in the copper matrix.

February, 2014 | DOI: 10.1016/j.jallcom.2013.11.019

Title: The role of boron oxide and carbon amounts in the mechanosynthesis of ZrB2–SiC–ZrC nanocomposite via a self-sustaining reaction in the zircon/magnesium/boron oxide/graphite system
Author(s): Jalaly, M; Bafghi, MS; Tamizifar, M; Gotor, FJ
Source: Journal of Alloys and Compounds, 598 (2014) 113-119

abstract | fulltext

Herein, ZrSiO4/B2O3/Mg/C system was used to synthesize a ZrB2-based composite by means of a high energy ball milling process. A mechanically induced self-sustaining reaction was achieved in this system. A nanocomposite powder of ZrB2–SiC–ZrC was prepared with an ignition time of approximately 6 min of milling. The role of the stoichiometric amounts of B2O3 and carbon was investigated to clarify the governing mechanism for the formation of the product.

June, 2014 | DOI: 10.1016/j.jallcom.2014.02.033

Title: Effect of high SWNT content on the room temperature mechanical properties of fully dense 3YTZP/SWNT composites
Author(s): Poyato, R; Gallardo-Lopez, A; Gutierrez-Mora, F; Morales-Rodriguez, A; Munoz, A; Dominguez-Rodriguez, A
Source: Journal of the European Ceramic Society, 34 (2014) 1571-1579

abstract | fulltext

This paper is devoted to correlate the microstructure and room temperature mechanical properties of single-wall carbon nanotube (SWNT) reinforced 3 mol% yttria stabilized tetragonal zirconia with high SWNT content (2.5, 5 and 10 vol%). Fully dense composites were prepared by using a combination of aqueous colloidal powder processing and Spark Plasma Sintering. SWNTs were located at the ceramic grain boundaries and they were not damaged during the sintering process. The weak interfacial bonding between SWNTs and ceramic grains together with the detachment of SWNTs within thick bundles have been pointed out as responsible for the decrease of hardness and fracture toughness of the composites in comparison with the monolithic 3YTZP ceramic.

June, 2014 | DOI: 10.1016/j.jeurceramsoc.2013.12.024

Centro de Investigaciones Científicas Isla de la Cartuja. C/Américo Vespucio, 49 - 41092 Sevilla (España)
Tel.: [+34] 954489527 | Fax: [+34] 954460165 | buzon@icmse.csic.es