Papers by Luis Fernández-Mérida
Activity coefficients for aqueous potassium succinate solutions (K2Succ) have been determined at ... more Activity coefficients for aqueous potassium succinate solutions (K2Succ) have been determined at 25 °C from the e.m.f. measurements of cells: ISE-K | K2Succ (m)| Hg2 Succ|Hg. The results obtained were analysed by using various theoretical equations (extended Debye–Huckel, Pitzer etc.) and compared with those reported in a previous paper for the sodium salt.
Activity coefficient values for NaCl in ethanol-water mixtures containing 20, 40, 60, YO, 80 and ... more Activity coefficient values for NaCl in ethanol-water mixtures containing 20, 40, 60, YO, 80 and 90 weight % ethanol are calculated from the emf for the galvanic cell Na-glass I NaCI (m), I120 (IO0-Y), EtOIl (I1), AgCI I Ag in which the weight % of the corresponding solvent is indicated in parentheses. The results obtained are analyzed by using different theoretical models. Chemical models which take into account the presence of ion pairs in solutions of high ethanol content are also used. There is good agreement between the results obtained from all the models.
Materials Chemistry and Physics
Abstract Over the last decade, new titanium alloys are developed in different areas of implantolo... more Abstract Over the last decade, new titanium alloys are developed in different areas of implantology. The aim of this study was to characterize a new Ti-Al-Nb-Ta-Mo based alloy, with high potential for being used as a biomedical implant. The evaluation of Ti-6Al-2Nb-2Ta-1Mo was performed both in vitro (by monitoring its corrosion resistance in Hank's Balanced Salt Solution, HBSS) and in vivo (by evaluating the osseointegration following rabbit tibia implantation), by comparison with titanium and Ti-6Al-7Nb alloy. Electrochemical impedance spectroscopy (EIS) data showed high impedance values for all titanium samples after 1 week immersion times in HBSS at 37 °C. According to EIS analysis, the corrosion resistance of the Ti-6Al-2Nb-2Ta-1Mo alloy immersed in HBSS was higher compared to the standard cp-Ti or with the Ti-6Al-7Nb alloy. In addition, a higher degree of osseointegration was achieved by the Ti-6Al-2Nb-2Ta-1Mo alloy, thus probing that a higher resistance to electrochemical corrosion provided enhanced protection to the implant surface against biodegradation, thus positively affecting the qualitative and quantitative evolution of bone tissue repair.
Portugaliae Electrochimica Acta
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Portugaliae Electrochimica Acta
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Journal of the Chemical Society Faraday Transactions
Portugaliae Electrochimica Acta
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Portugaliae Electrochimica Acta
The Pitzer thermodn. formalism for electrolyte-monoelectrolyte mixts. is examd. Anal. of publishe... more The Pitzer thermodn. formalism for electrolyte-monoelectrolyte mixts. is examd. Anal. of published exptl. data for systems contg. zwitterions (NaCl-amino acid) indicates a linear variation of interaction coeffs. as amino acid concn. varies. Equations are derived to fit the variation of amino acid activity coeffs. in mixed electrolytes. [on SciFinder(R)]
ABSTRACT Passive film breakdown and pit nucleation on 304 and 316 stainless steels in chloride-co... more ABSTRACT Passive film breakdown and pit nucleation on 304 and 316 stainless steels in chloride-containing media were investigated using scanning microelectrochemical microscopy (SECM) and the scanning vibrating electrode technique (SVET). Experiments were performed for the alloys either at their corresponding open circuit potential, or under applied polarization, as to image domains of similar topography but different resistance against breakdown of the passive layers formed on these steels. Identification of the iron released species was accomplished, showing that pitting occurs with the formation of iron (II) species only. Detection of iron (III) species occurred when the steel sample was polarized at high positive overpotentials because it served as the reaction site to oxidize the iron (II) ions released from a propagating pit. The obtained results have revealed some difference of the reactivity of both specimens. Moreover the effect of the galvanic coupling has been investigated.
The Journal of Chemical Thermodynamics, 1994
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Journal of Solution Chemistry, 1992
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Journal of Solution Chemistry, 1996
... F. Hermindez-Luis, 1'* M. Barrera, 1 HR Galleguillos, z L. Fermlndez-M6rida, ~ and M. P6... more ... F. Hermindez-Luis, 1'* M. Barrera, 1 HR Galleguillos, z L. Fermlndez-M6rida, ~ and M. P6rez 1 ... Table IV collects the values of the characteristic mixing parameters resulting from each of these methods, the standard deviations cr(mV), max-imun deviation, Amax, the number of ...
Electrochimica Acta, 2010
Herein, the redox competition mode of scanning electrochemical microscopy (RC-SECM) has been appl... more Herein, the redox competition mode of scanning electrochemical microscopy (RC-SECM) has been applied to in situ monitor the local reactivity arising from a circular holiday operated in a painted metal. The metal-coating system consisted of a carbon steel substrate coated with an epoxy-polyamine polymeric film containing glass flakes as pigment. The present work demonstrates the possibility to use RC-SECM for investigation of the corrosion reactions occurring when protective coatings are applied on a metal surface without the addition of a redox mediator to the experimental system. Oxygen reduction was employed to monitor the reactive metal-polymer system, though the onset of a redox competition for this redox species between the SECM tip and the bare metal inside the holiday could be found in certain conditions. Whether attack predominated inside the holiday or the system became non-reactive depended on the composition of the test electrolyte, with borate ions acting as corrosion inhibitor.
Journal of …, 1998
To prove the applicability of the Pitzer equations, modified by us after taking into account the ... more To prove the applicability of the Pitzer equations, modified by us after taking into account the dependence of the solution concentration on the mixing parameters related with the binary solute-solute interactions, we are presenting the analysis of accurate experimental activity coefficient values here determined for the mixed system NaCl + i-alanine +H 2 O up to medium concentrations of both NaCl and the aminoacid. These activity coefficient values were obtained from the emfs of the galvanic cell: Na-glass i-Alanine (m A), NaCl (m B =I), AgCl Ag. The fitting was done by considering only the binary interaction mixing parameters, i.e. by neglecting the ternary ones (ion-zwitterion-zwitterion and ion-ion-zwitterion). The standard deviation thus found for the fitting (90.16 mV, i.e. 90.003 in ln k 9) was of the same order as the accepted experimental uncertainty. Activity coefficients for i-alanine in these aqueous solutions, calculated from the use of these modified Pitzer equations, are also presented.
Berichte der …, 1997
Mean activity coefficients of NaCl in NaCl+ MgCl 2+ H 2 O mixed system were determined from the e... more Mean activity coefficients of NaCl in NaCl+ MgCl 2+ H 2 O mixed system were determined from the emf measurements of galvanic cells without transport and at 15, 25, 35 and 45 C. The measurements were carried out at total ionic strengths of 0.1, 0.3, 0.5, 1, 2, ...
Chemistry - A European Journal, 2002
Spectroelectrochemical studies on the reactivity of butanol isomers on Pt electrodes in perchlori... more Spectroelectrochemical studies on the reactivity of butanol isomers on Pt electrodes in perchloric acid medium led to the observation of structural effects that result from the different arrangements of atoms in the organic molecules. The use of differential electrochemical mass spectrometry (DEMS) to detect volatile products showed that all four isomers react on the electrode, though different product yields were observed for each compound. In spite of the differences in the electrochemical behaviour of the butanol isomers, a series of general processes accounts for the results obtained. The formation of strongly adsorbed residues by a dehydration process leading to the formation of a C=C bond was proposed for all isomers. Electroreduction of the adsorbates produces C(4) and C(3) alkanes, and the latter reveal the existence of a fragmentation process. The C(4) hydrocarbons can be formed by hydrogenation of these residues and by hydrogenolysis of alcohol molecules in the bulk solution which react at the electrode with adsorbed hydrogen. On the other hand, CO(2) is formed during electrooxidation of the adsorbed species. Partial-oxidation products containing a carbonyl group were detected from 0.2 M solutions of 1-butanol, isobutyl alcohol and sec-butyl alcohol. The tertiary alcohol tert-butyl alcohol only reacts in its adsorbed state.
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Papers by Luis Fernández-Mérida