Effect of DC current polarization on the electrochemical behaviour of La2NiO4+δ and La3Ni2O7+δ-based systems

The electrode performance of La₂NiO₄ and La₃Ni₂O₇ as cathode materials for solid oxide fuel cells (SOFC) was analyzed. The study was focused on the electrode polarization resistance of the interfaces formed by the cathodes with Ce_0.8Sm_0.2O_2−δ + 2%Co electrolyte. The study was extended to cathodes based on La₂NiO₄-Ce_0.8Sm_0.2O_2−δ composite and Pt to analyze the effect of changing the electronic and/or ionic transport properties on the electrode interface resistance. The electrode performance was studied in open circuit conditions and with DC current polarization. Important differences in the performance of the pure cathode materials were obtained as function of DC current flux. However, in La₂NiO₄-Ce_0.8Sm_0.2O_2−δ composite the DC current flux produces minor changes in the electrode polarization resistance. The aging process also affects the OCV electrode performance of cathodes based on Pt and pure ceramics, whereas the effect is practically invaluable in La₂NiO₄-Ce_0.8Sm_0.2O_2−δ composite. The electrode performance is higher for the composite cathode compared to pure ceramic electrodes for OCV or for low values of DC polarization. However, the important decrease in the interface resistance obtained for high values of DC current flux for La₂NiO₄ and La₃Ni₂O₇ cathodes increases their electrode performances to values close to those obtained in La₂NiO₄-Ce_0.8Sm_0.2O_2−δ composite. This retains the cathode overpotential with values as low as 140 mV at 750 °C for values of current load of 530 mA cm⁻² for both pure and composite La₂NiO₄-based cathodes. The low cathode overpotential allows to estimate values of power density between 300 and 350 mW cm⁻² at 750 °C for La₂NiO₄, La₃Ni₂O₇ and La₂NiO₄-Ce_0.8Sm_0.2O_2−δ composite, operating with Ce_0.8Sm_0.2O_2−δ + 2%Co electrolyte, with 300 μm in thickness, and a Ni-Ce_0.8Sm_0.2O_2−δ cermet anode with H₂ as fuel.     

Structure, thermal stability and electrical properties of Ca(V0.5Mo0.5)O3 as solid oxide fuel cell anode

The Ca(V_0.5Mo_0.5)O₃ perovskite has been prepared in order to study its potential use as anode in SOFC. The crystal structure has been refined, by neutron powder diffraction, in the orthorhombic Pbnm space group (no. 62). The electrical conductivity values were over 525 S cm⁻¹ in the studied temperature range (25-800 °C). The sample is stable under reducing working conditions (H₂/N₂ 10:90, 25-900 °C). This orthorhombic phase transforms at 500 °C in air to the tetragonal I4₁/a scheelite phase. This transition is reversible and, due to the fact that the thermal expansion coefficients of both, the reduced and oxidized phases, are very similar and match well with those of the other cell components ((10-13) × 10⁻⁶ K⁻¹) this materials are presented as excellent candidates as anodes in SOFCs.     

Prediction of body composition of Iberian pigs by means bioelectrical impedance

Twelve barrow Iberian pigs with an average weight at slaughter of 109.2kg were used to evaluate bioelectrical impedance procedures to predict the body composition of live pigs. Twelve hours before slaughter pigs were weighed, and a four-terminal body composition analyser (Model BIA-101, RJL Systems, Detroit, MI) was utilized to determine resistance (R(s) in Ω) and reactance (X(c) in Ω). The length values (L in cm) were measured between detector electrodes with a flexible steel tape. Twenty four hours after slaughter the left side of each carcass was separated using a scalpel into fat, lean, bone and skin. Multiple regression equations for estimating lean, fat, bone and skin amounts and lean, fat, bone and skin proportions with respect to slaughter weight were calculated. The live weight (LW) and L independent variables predicted 85.3% and 64.3% of the variability of the lean amount and lean proportion, respectively. The LW, X(c) and L variables accounted for 96% and 91.6% of the variation in fat quantity and fat proportion, respectively. The LW and R(s) accounted for 58.9% of the variation in bone amount, and the same variables predict 79.1% of the variability of bone percentage. The R(s) and L variables explained 68% of the variability of skin quantity and LW, R(s) and X(c) predicted 83.1% of the variation of skin proportion. Results from this experiment indicate that bioelectrical impedance may be of interest for body composition prediction of live Iberian pigs.     

On Dynamic Distribution of Private Keys over MANETs

Identity-Based cryptography has been proposed in mobile ad-hoc networks (MANETs) to provide security. However, the figure of the Private Key Generator (PKG) is not adequate in the MANET setting, since it may not be reachable by all nodes, can fail during the life-time of the protocol or can even be attacked, compromising the whole system. Previous works distribute the task of the PKG among a set of nodes by means of a secret sharing scheme.In this paper we propose an efficient solution to emulate in a dynamic and distributed way the role of the PKG in so that even new nodes joining the network are able to issue shares of the master key of an Identity-Based scheme. In this way, the distributed PKG spreads dynamically among the nodes as the network increases. Furthermore, the techniques we propose may be suitable for other protocols over MANETs.     

Porous nickel MCFC cathode coated by potentiostatically deposited cobalt oxide: II. Structural and morphological behavior in molten carbonate

Cobalt oxide was deposited on porous nickel by an electrodeposition technique as precursor of a novel MCFC cathode. The behavior of this cathode in molten (Li_0.52Na_0.48)₂CO₃ eutectics at 650 °C under an atmosphere of CO₂:air (30:70) was studied before and after 50 h of exposure by different techniques. Before the exposure, the deposit of cobalt corresponded to a Co₃O₄ thin layer of. This crystalline structure was identified by XRD and Raman spectroscopy. After its exposure in the eutectic melt a loss of cobalt was observed by XRD, Raman spectroscopy, XPS, EDS and ICP-AES. The change in the Co₃O₄ structure into lithium–cobalt–nickel oxide (LiCo_1−yNi_yO₂) was observed by Raman spectroscopy. The SEM micrographs for Co₃O₄-coated porous nickel showed different angular shapes with respect to porous Ni. The nickel solubility for the coated porous nickel, measured by ICP-AES, decreased with respect to uncoated nickel. The Co₃O₄-coated porous nickel cathode showed, after its immersion in the molten carbonate melt, a similar porosity but a higher pore size. LiCo_1−yNi_yO₂-coated NiO offers interesting features which combine the properties of nickel, lithium and cobalt in molten carbonate. This could be a promising novel MCFC cathode material.     

Lignin‐polyethylene glycol matrices and ethylcellulose to encapsulate highly soluble herbicides

The blending of lignin with polyethylene glycol (PEG) allowed us to obtain formulations with controlled release properties in which metribuzin have been successfully trapped with encapsulation efficiency higher than 85%. Moreover, the modification of the lignin's viscoelastic properties by the addition of PEG led to obtain herbicide formulations with active ingredient contents lower than 15%, suitable for its application in soil. Fourier transformed infrared spectroscopy and differential scanning calorimetry studies indicated the compatibility between polymers and metribuzin in lignin‐based controlled release formulations (CRFs). Lignin‐based formulations were coated in a Wurster‐type fluidized‐bed equipment using ethylcellulose and dibutylsebacate. Scanning electron microscope pictures showed a homogeneous film in ethylcellulose‐coated CRFs. The kinetic release studies showed that the release rate of metribuzin was mainly controlled either by selecting the granule size of controlled release lignin‐PEG matrixes, or by changing the thickness of coating film for ethylcellulose coated CRFs. These results could help to increase the efficiency of delivery of the highly soluble herbicide metribuzin and prevent the environmental pollution derived from its use. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41422.     

Minimal water activity for growth of Listeria monocytogenes as affected by solute and temperature.

Two strains of Listeria monocytogenes, Scott A (serotype 4b) and Brie 1 (serotype 1b) were characterized in terms of minimum aw requirements for growth at 4 and 30 degrees C, using NaCl, glycerol and sucrose as test solutes. Both strains grew well at 30 degrees C in glycerol-supplemented tryptic soy broth (TSB), but not in NaCl- and sucrose-supplemented TSB at aw 0.90. Sucrose was more inhibitory than NaCl and glycerol. The Brie 1 strain was less tolerant to sucrose compared to the strain Scott A at both 4 and 30 degrees C. The effects of all three solutes were magnified at 4 degrees C, where tolerance to low aw was markedly less than at 30 degrees C. Results confirm that the type of solute as well as the osmotic conditions created by the solute affects the ability of Listeria monocytogenes to grow at 4 and 30 degrees C.     

Porous nickel MCFC cathode coated by potentiostatically deposited cobalt oxide: III. Electrochemical behaviour in molten carbonate

A cobalt oxide coating was deposited on porous nickel by a potentiostatic electrochemical technique and studied in molten (Li_0.52Na_0.48)₂CO₃ eutectics at 650 °C under an atmosphere of CO₂:Air (30:70). The structural and morphological characteristics of this coating before and after immersion in the molten electrolyte were described in a previous paper, showing that the initial Co₃O₄ layer is rapidly transformed into LiCoO₂ and afterwards probably into LiCo_1−yNi_yO₂. In the present part, the electrical and electrochemical behaviour of this promising novel MCFC cathode material was thoroughly analysed during 50 h by impedance spectroscopy. A porous nickel cathode was tested in the same conditions and taken as a reference. The oxidation and lithiation reactions are accelerated by the presence of cobalt. The charge transfer resistance is higher with the coated cathode but the diffusion resistance through this new material is lower in comparison with the state-of-the-art cathode.     

Solid-state reactivity of iron molybdate artificially contaminated by antimony ions and its relation with catalytic activity in the selective oxidation of isobutene to methacrolein

Catalysts were prepared by impregnation of Fe₂(MoO₄)₃ with different quantities of antimony butoxide. BET surface area measurement, XRD, Mössbauer spectroscopy, CTEM-AEM, XPS and ISS were used to characterize phase and surface architectures and their changes after calcination and catalytic reaction. Before calcination, antimony was present as pure oxide or hydroxide, partly as particles and partly as an incomplete monolayer on the surface of Fe₂(MoO₄)₃. After calcination at 400°C, antimony got detached from the Fe₂(MoO₄)₃ surface and aggregated very intensively, partly as Sb₂O₄ and partly, through reaction with the iron molybdate, as a mixture of distorted FeSbO₄ and MoO₃. After reaction or calcination at 500°C, more distorted FeSbO₄ and MoO₃ are formed, separated from Fe₂(MoO₄)₃. Selective oxidation of isobutene to methacrolein was carried out on the calcined material. Impregnated catalysts show considerably improved catalytic performances compared to the pure Fe₂(MoO₄)₃ phase or mechanical mixtures of it with α-Sb₂O₄. The catalytic performances are explained by several catalytic cooperations via spillover oxygen. These cooperative effects involve all the oxide phases present in the material having worked as catalyst: Fe₂(MoO₄)₃ (pure or possibly contaminated by small amounts of antimony oxide), FeSbO₄, MoO₃ and Sb_yO_x.

     

Dynamic simulation and experimental evaluation of EPDM synthesis with ET(IND)2ZRCL2/MAO catalyst system

A mathematical model for the homogeneous terpolymerization of ethylene–propylene–diene (EPDM) in a semibatch reactor using Et(Ind)₂ZrCl₂/MAO as a catalyst system was developed and reported herein. In this study, we developed a kinetic model in order to explain the catalyst and EPDM properties such as catalyst activity, weight‐average molecular weight, and terpolymer composition, which were experimentally and theoretically obtained. For this system, a lower E/P feed ratio leads to a lower molecular weight and a broader initial molecular weight distribution, while the increase in diene concentration leads to a decrease in the catalyst activity without broadening the MWD of the resulting polymers. The proposed model accounts for these experimental trends and for some data in the literature.