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CSIC Staff Scientist Departamento
de Ingeniería de Materiales Centro Nacional de
Investigaciones Metalúrgicas, CENIM Consejo Superior de
Investigaciones Científicas, CSIC Av.
Gregorio del Amo 8, 28040 MADRID
(SPAIN) Phone: +34-915538900 (extension
340) Fax: +34-915347425 e-mail: jcgalvan@cenim.csic.es |
ABSTRACTS
OF SOME PAPERS:
1. ELECTROCHEMISTRY
OF MATERIALS
1.
ELECTROCHEMISTRY OF MATERIALS
Casal B, Ruiz-Hitzky E, Crespin M, Tinet D, Galvan JC
Mechanism of intercalation of nitrogenated bases into V2O5
xerogel
JOURNAL CHEMICAL SOCIETY, FARADAY TRANS. I, 85,
pp 4167- 4177 (1989)
It
has been shown by i.r. and XPS techniques that protonation of nitrogenated
bases (ammonia, pyridine and pyrazine) is the major process that occurs on
adsorption of these compounds in the intracrystalline environment of V2O5·1.5H2O
xerogel. At room temperature the intercalation process takes place mainly by a
proton-transfer reaction involving protons inherent to the solid and interlayer
water molecules. Thermal treatments of the intercalated compounds gives rise to
coordination of guest species to vanadium ions included in the host lattice,
and VV / VIV transformations are found to different
extents depending on the nature of the intercalated molecules. The protons of
the solid and the interlayer water appear to be the origin of the prrotonic
conductivity on the V2O5·1.5H2O xerogel, as
shown by the impedance spectra. The VV / VIV couples
formed in the intercalation process produce the electronic conductivity
detected when the bases are intercalated in the layer solid.
Aranda P, Galvan JC, Casal B, Ruiz-Hitzky E
Charactirazation of clay-polyoxyethilene based membranes using ac
impedance spectroscopy
KEY ENGINEERING MATERIALS, 61-62, pp
469-472 (1991)
Preliminary
results showing the utility of the impedance spectroscopy technique to
characterize composite membranes based in montmorillonite-polyoxyethylene
intercalation compounds are presented. The ionic resistance of these membranes
as a function of the contact time with different saline solutions are studied.
Amarilla JM, Casal B,
Galvan JC, Ruiz-Hitzky E
Lithium
MVO5 (M=Nb,Ta) Bronzes
CHEMISTRY OF MATERIALS, 4, pp 62-67 (1992)
Mixed
oxides NbVO5 and TaVO5 have been synthesized by a sol-gel
procedure. Both compounds are isostructural with the so-called ''monophosphate
tungsten bronzes'' (MPTB, (PO2)4(WO3)2m,
with m=2). In such structures single MO4 tetrahedra (M= P,V), share
corners with M'O6 octahedral (M' = W, Ta, Nb) building pentagonal tunnels
along the [010] direction. In this work, we have studied lithium insertion
redox reactions carried out by treatments with LiI in acetonitrile in MVO5 (M =
Nb, Ta) hosts. Lithium insertion appears as a topotactic and reversible
process. The intercalated compounds constitute a new family of Li bronzes
showing LixMVO5 compositions with 0 < x < 0.3, which have been
characterized by X-ray diffraction, conventional chemical analysis, and X-ray
photoelectron spectroscopy. Complex impedance spectroscopy reveals the ionic
character of the electrical conductivity in LixMVO5. Typical values of the specific conductivity are in the 10-6-10-8
W-1cm-1
range at 573 K, with activation energies on the order of 0.5 eV.
Aranda P, Galvan
JC, Casal B, Ruiz-Hitzky E
Ionic-Conductivity
in Layer Silicates Controlled by Intercalation of Macrocyclic and Polymeric
Oxyethylene Compounds
ELECTROCHIMICA ACTA, 37, pp
1573-1577 (1992)
This
contribution concerns intercalation materials based on the formation of
intracrystalline polymer-salt complexes obtained by insertion of poly(ethylene
oxide) (PEO) and crown-ether compounds in a layer silicate (montmorillonite),
containing Na+ exchangeable cations in their interlayer space. Polyoxyethylene
compounds (crown ethers and PEO) are able to associate interlayer cations
modifying dramatically the ionic conductivity of the natural silicate. The new
organo-inorganic materials exhibit a two-dimensional structure able to induce
an anisotropic character in their electrical properties.
Aranda P Casal B
Galvan JC Ruiz-Hitzky E
Title: Electrical-Properties of Oxyethylene
Intercalated Compounds
CHEMICAL PHYSICS OF INTERCALATION II, 305, pp 397-400 (1993)
Bernier,
P, Ed.
Intercalation
materials of high stability have been obtained by insertation of oxyethylene
compounds (crown-ethers and poly(ethylene oxide), into layered solids as
phyllosilicates and vanadium oxide xerogels. Cationic or protonic conductivity,
both in the layer silicate and in vanadium oxide xerogel intercalated
materials, respectively, varies as a function of the nature of the guest oxyethylene
compound.
Galvan JC, Aranda P,
Amarilla JM, Casal B, Ruiz-Hitzky E
Organosilicic
Membranes Doped with Crown-Ethers
JOURNAL OF MATERIALS CHEMISTRY, 3, pp 687-688 (1993)
Composite
membranes have been prepared via the sol-gel process by controlled hydrolysis
of ethyltriethoxysilane incorporating in the sol phase a selected crown-ether.
The membranes are supported on borosilicate porous discs forming a continuous network as shown by scanning
electron microscopy. The crown-ether (12-crown-4, 15-crown-5, 18-crown-6)
remains homogeneously distributed in the organosilicic matrix as evidenced by
IR and C-13 NMR spectroscopies. A C. impedance plots vary with the nature of
the doped crown-ether as well as with the electrolyte used (alkali-metal
chloride aqueous solutions).
Aranda P, Galvan JC,
Casal B, Ruiz-Hitzky E
Electrochemical
Characterization of Composite Membranes Based on Crown-Ethers Intercalated into
Montmorillonite
COLLOID AND POLYMER SCIENCE, 272, pp 712-720 (1994)
Oxyethylene
macrocyclic compounds (crown-ethers) act as ligands of intracrystalline cations
of certain layered silicates as montmorillonites. Stable intercalation
materials are formed which are used to
prepare organic-inorganic membranes by encapsulating these intercalation compounds
with a polybutadiene thin coating. Electrochemical Impedance Spectroscopy (EIS)
is used to study the resulting
composite membranes in contact with aqueous electrolytes. From the impedance
plots, the ionic resistance of the membranes is obtained. The thickness of the
polybutadiene coating is an important factor determining the ability of ions to
pass across the membrane. Marked differences in the ionic resistance are
observed as a function of the nature of the interlayer macrocyclic compound.
For non-intercalated montmorillonite membranes, the ionic resistance is
strongly reduced, whereas for some crown-ether intercalated materials such as
18- crown-6 and dibenzo 24-crown-8, iono-selective membranes are obtained.
Concerning the nature of the electrolyte, cations exhibiting greater hydration
energies show higher difficulties to pass through the membrane and,
consequently, the ionic resistance increases.
Ruiz-Hitzky E, Aranda P,
Casal B, Galvan JC
Nanocomposite
Materials with Controlled Ion Mobility
ADVANCED MATERIALS, 7, pp 180-184 (1995)
The
intercalation or entrapment of oxyethylene compounds, crown ethers, and
poly(ethylene oxide) into inorganic hosts provides the opportunity to design
and prepare nanocomposite materials useful for membrane and solid electrolyte
applications. Crown ethers incorporated into the membranes produced by
intercalation can act as ion-selective sensors. The field is reviewed and
several recently developed applications described.
Aranda P,
Jimenez-Morales A, Galvan JC, Casal B,
Ruiz-Hitzky E
Composite
Membranes Based on Macrocycle/Polysiloxanes Preparation, Characterization and
Electrochemical Behavior
JOURNAL OF MATERIALS CHEMISTRY, 5, pp 817-825 (1995)
Composite
membranes based on complexing macrocyclic compounds (crown ethers and
cryptands) have been studied. These compounds were included into a
polyorganosiloxanic matrix in an attempt to obtain new ion-selective materials.
This macrocycle/polyorganosiloxane constitutes
the active phase of the membrane which
was prepared via the sol-gel method and then used to fill a fibrous support of
borosilicate. Characterization, by chemical and thermal analysis, FTIR and NMR spectroscopies and scanning electron
microscopy (SEM), reveals a homogeneous distribution of the entrapped
macrocycles in the polyorganosiloxane network. Electrochemical impedance
spectroscopy studies of the composite membranes have been carried out in order
to evaluate their ionic transport properties when they are in contact with
aqueous salt solutions. From the impedance spectra, the ionic resistance values
of the membranes are obtained which vary according to the nature and concentration of the involved macrocyclic
compound. The presence of these macrocycles produces a significant decrease in
the ionic resistance compared with membranes without macrocyclic compounds. The
ionic resistance of these systems is also strongly related to the nature of the
electrolyte and to its concentration. Thus, cations exhibiting greater
hydration energies show a higher ionic resistance. As an example, for a
membrane doped with 12C4 crown-ether the Ri values are 213,
128, 109 and 99 kW
when the electrolyte consists of 10-2 mol·l-1 solutions
of LiCl, NaCl, KCl and CsCl, respectively. The selectivity of the membranes
towards different ions, as well as the reversibility of the electrochemical
response when the nature and concentration of the ions is changed, highlights
the potential of these materials for sensor applications.
Ruiz-Hitzky E, Galvan
JC, Merino J, Casal B, Aranda P, Jimenez-Morales A
Proton
Conductivity in Al-Montmorillonite Pillared Clays
SOLID STATE IONICS, 85, Iss 1-4, pp 313-317 (1996)
Pillared
clays (PILCs) are materials derived from smectite clay minerals (2:1
phyllosilicates) in which an interlayer formation of metal oxides, acting as
pillars, produces a permanent
separation between the silicate layers. It is assumed that protons are
generated during the thermal treatment necessary for the pillar oxide
formation, as it is the case for Al-montmorillonite PILCs. We have applied the
electrochemical impedance technique
with the aim of studying the proton conductivity of these pillared materials.
Enhancement of electrical conductivity has been observed upon adsorption
of oxyethylene compounds (crown-ethers
and PEO) into the PILC galleries.
Galvan JC, Jimenez-Morales A, Jimenez R, Merino J, Villanueva A, Crespin M, Aranda P,
Ruiz-Hitzky E
Application
of the Electrochemical Impedance Technique
to Study of Pillared Clays
CHEMISTRY OF MATERIALS, 10, pp 3379-3385 (1998)
The
electrochemical impedance technique combined with other conventional
characterization techniques (XRD, NMR, TG, DSC, CRTA, specific surface area and
porosity determinations, etc.) has been applied to study the in situ formation
of alumina pillared smectite clay
materials (Al-PILCs). The main objective of this work is to clarify the
mechanism of pillar formation and, simultaneously, to explore the usefulness of
the electrochemical impedance
technique to correlate experimental conditions (e.g. temperature range) for H+
generation with the electrical
conductivity of the system. It is shown that the changes in the conductivity could be associated with the mobility
and/or concentration of the protons formed during the thermal decomposition of
the interlayered polyoxyhydroxy cations to the pillar oxide. This study has
also been extended to other PILCs prepared either with different clays (e.g.
montmorillonite, saponite) or by incorporating oxide pillars of different
nature (e.g. alumina, zirconia).
Jimenez-Morales
A, Galvan JC, Aranda P, Ruiz-Hitzky E
Hybrid
Organic-Inorganic Electrode-Membranes Based on Organo-Polysiloxane/Macrocycle
Systems
ORGANIC/INORGANIC HYBRID MATERIALS, 519, pp 211-216 (1998)
Laine,
RM, Ed. Warrendale: Materials Research
Society (Series: Materials Research Society Symposium Proceedings)
Specific
complexing agents for alkaline ions such as some crown-ethers of different
intramolecular cavity size (12-crown-4, 15-crown-5 and 18-crown-6) are
incorporated into a organo-polyorganosiloxane network generated via the sol-gel
process. The resulting xerogels embody macrocycle compounds with different
ion-selectivity. These xerogels are deposited onto porous supports
(borosilicate, polyacrylonitrile,...) to obtain new composite electrode-membranes. The electrochemical
characterization of the membranes and the electrode-membranes by
electrochemical impedance spectroscopy (EIS) shows information about the reversible
behavior and the ion resistance of the
membranes, which are a function of both, nature and content of the
entrapped macrocycle as well as the salt solution concentration. The
electrochemical response of these systems acting as electrode-membranes shows
their sensitivity towards different metal ions at variable concentrations.
Aranda P, Galvan JC,
Ruiz-Hitzky E
Microwave-Assisted
Blending-Intercalation of Ion-Conductor Polymers into Layered Silicates
ORGANIC/INORGANIC HYBRID MATERIALS, 519, pp 375-380 (1998)
Laine,
RM, Ed. Warrendale: Materials Research
Society (Series: Materials Research Society Symposium Proceedings)
Organo-inorganic
hybrid nancomposites derived from poly(ethylene oxide) and montmorillonite
silicate are prepared by an alternative procedure to classical polymer
intercalation either from solutions or by polymer melt-intercalation. XRD,
FTIR, DSC, elemental microanalysis and SEM techniques are applied for
structural characterization of the resulting
materials. The electrical properties of these nanocomposites are studied
by means of the electrical impedance spectroscopy (EIS) showing enhanced ionic
conductivity compared to similar samples prepared by intercalation from
solution.
Wang JF, Merino J,
Aranda P, Galvan JC, Ruiz-Hitzky E
Reactive
Nanocomposites Based on Pillared Clays
JOURNAL OF MATERIALS CHEMISTRY, 9, pp 161-168 (1999)
This
work concerns the preparation of novel nanocomposite materials deriving from
pillared clays, which have been functionalised by treatment with either
vanadium pentoxide or p-toluenesulfonic acid, with the aim to obtain porous
materials with oxidant or strong acid character, respectively. The synthesis
involves the use of montmorillonites and saponites, as starting 2:1 charged
phyllosilicates to give the alumina pillared clays employed as host matrices
for reagent inclusion. Characterisation
of the resulting materials was provided by chemical and thermal analyses, XRD,
SEM-EDX, FTIR and XPS spectroscopies, specific surface area and porosity
measurements, and electrochemical impedance technique. The reactivities of the
nanocomposite materials have been tested with positive results in the oxidation
of alcohols to carbonyl compounds, in particular in the oxidation of benzyl
alcohol to benzaldehyde, and also in the syntheses of methyl tert-butyl ether
(MTBE) and bisphenol A. Good
correlation between the proton conductivity obtained from electrochemical
impedance and the acid catalytic activity of nanocomposites containing
p-toluenesulfonic acid has been found.
Manriquez V, Galdamez A,
Villanueva A, Aranda P, Galvan JC,
Ruiz-Hitzky E
Insertion
of In(III) and Ga(III) into MPS3 (M = Mn, Cd)
MATERIALS RESEARCH BULLETIN, 34, pp 673-683 (1999)
In0.20
Mn0.70 PS3, Ga0.28Cd0.58PS3
and In0.33Cd0.50PS3 compounds were synthesized
by insertion of trivalent cations (In3+ and Ga3+) into
MPS3 (M = Mn, Cd). The insertion process requires the previous
intercalation of K+ ions into these matrices, giving rise to new materials
belonging to the MPS3 family. Such compounds were characterized by
X-ray diffraction (XRD). Fourier transform infrared (FTIR) spectroscopy,
scanning electron microscopy (SEM),
transmission electron microscopy (TEM), energy-dispersive X-ray (EDX)
microprobe, differential thermal and thermogravimetric analyses (DTA/TGA),
magnetic susceptibility measurements, and electrochemical impedance
spectroscopy. It is inferred that the trivalent cations were incorporated,
rather than intercalated, into the intralamellar region, i.e., the cations were
located in the interlamellar space, following the typical topotactic
ion-exchange processes of the monovalent cations. Clement and Michowicz
reported a similar case for Ni2+ insertion into MnPS3 in 1984.
De Andres AM, Merino J,
Galvan JC, Ruiz-Hitzky E
Synthesis
of Pillared Clays Assisted by Microwaves
MATERIALS RESEARCH BULLETIN, 34, pp 641-651 (1999)
Microwave
(MW) irradiation was used to synthesize aluminum- pillared clays (MW-Al-PILCs)
by replacing the conventional calcination of Al-PILCs pre cursors
(pre-Al-PILCs). X-ray diffraction (XRD) patterns acid nitrogen
adsorption/desorption isotherms showed
that the MW-irradiated pre-Al-PILCs gave a series of MW-Al-PILC materials
exhibiting some characteristics comparable to Al-PILCs obtained by conventional
heating. However, differential thermal analysis (DTA), thermogravimetric analysis (TGA), impedance spectroscopy,
Al-27 MAS NMRI and intercalative adsorption of methylene blue (MB), indicated
that the MW-Al-PILC samples were intermediate between Al-pre-PILCs and
conventional Al-PILCs, The Al-27 MAS NMR spectra showed that in MW-Al-PILCs obtained after 18 min of MW
irradiation, the Al- IV/Al-VI ratio was
1/9, which is comparable to that in Al-pre-PILCs (8% Al-IV; 92% Al-VI) and significantly
different from the typical values of conventional Al-PILCs (23% Al-IV; 77%
Al-VI). It is assumed that the MW-induced calcination gives PILCs containing a fraction of residual,
hydroxylated Al-polycations. The good thermal stability of the MW-Al-PILCs
supports their possible use as acid catalysts.
E. E.
Ruiz-Hitzky, P. Aranda, B. Casal, J.C. Galván
Inorganic-organic
nanocomposite materials based on macrocyclic compounds
REVIEWS IN INORGANIC
CHEMISTRY, 21, 125-159 (2001)
The
synthesis, structural characterisation, properties and applications of
inorganic-organic hybrid materials (nanocomposites) containing macrocycles are
reviewed. Three different ways to prepare such materials are discussed: i)
intercalation in layered host solids, ii) entrapping into inorganic matrices
generated by sol-gel, and iii) grafting of macrocycles on inorganic surfaces.
Macrocyclic compounds as crown ethers and cryptands, were the guest organic
species used in intercalation processes. The host inorganic solids were layered
silicates, vanadium pentoxide xerogel, transition-metal dichalcogenides and
phosphorus trichalcogenides. The resulting nanocomposites present synergic
host-guest properties useful for applications as solid electrolytes, ion-selective
membranes and electrochemical sensors. Alternatively, nanocomposites based on
macrocycles can be obtained by entrapping of such compounds into inorganic
matrices generated by sol-gel, using different organosilanes as precursors
(TMOS, TEOS, ETEOS, MAPTMS, etc ). Electrodes
based on such systems are sensitive to alkaline cations, lead, silver and
ammonium ions giving linear potentiometric responses in a wide concentration
range. Finally, the grafting of macrocycles on inorganic surfaces is also
discussed. Silica can be functionalised by anchorage of macrocycles able to
confer specific properties and reactivity to the inorganic substrate. The main
applications of this last class of nanocomposites have been found for
chromatography purposes, including separation of cations, anions and
non-electrolytic organic compounds.
M.L. Rojas, B. Casal, P. Aranda, M. Savirón,
J.C. Galván, E. Ruiz-Hitzy
Hybrid
materials based on vanadium pentoxide intercalation complexes
COLLOID AND POLYMER
SCIENCE, 279, 990-1004 (2001)
Neutral macrocyclic compounds (crown
ethers and cryptands) and charged molecular species (alkylammonium iodides)
have been intercalated into vanadium oxide xerogel (V2O5·nH2O)
to study their influence in the electrical behaviour of this inorganic 2D host
lattice. Treatment with alkyl- or aryl-ammonium iodide solutions produces the
intercalation of organic cations accompanied by the reduction of a fraction of
V(V) to V(IV). Characterisation by different techniques allows to postulate the
interlayer disposition of the guest species. The study of electrical behaviour
at different temperatures indicates that the properties of the nanocomposites
can be mainly related with: i) the
nature of guest species, ii) the host lattice reduction degree, iii) the interlayer
water content and, iv) the presence of metal ions deliberately introduced in
the system.
A.
Jiménez-Morales,
J.C. Galván, P. Aranda
A new
silver-ion selective sensor based on a polythiacrown-ether entrapped by sol-gel
ELECTROCHIMICA ACTA, Vol 47, Iss 13-14, 2281-2287 (2002)
We
report a new electrode based on a selective complexing agent for Ag+ ions, the
6-oxa-3,9-dithiabicicle[9.3.1]pentadeca-1(15),11,13-triene (MAO), incorporate
into an organopolysiloxane matrix prepared via sol-gel from a mixture of g-methacryloxypropyltrimetoxysilane (MAPTMS) and
tetramethoxysilane (TMOS). The modified electrode is prepared by coating the
surface of graphite electrodes with a thin film of the nanocomposite material.
SEM and EDX were used to determine the continuous coverage and composition of
the films constituting the active phase of the electrodes. The application of
electrochemical impedance spectroscopy (EIS) and potentiometric techniques,
allows establishing the selective response of the electrode towards the Ag+
ions. The selectivity over other cations as Cd2+, Pb2+, NH4+, Na+, etc., is
explained by the molecular recognition character of the electrode introduced by
the presence of the MAO ionophere into the xerogel film. These new hybrid
organic-inorganic systems constitute an alternative to classical PVC-matrices
for preparation ion-selective electrodes showing also additional advantages
such as higher reproducibility, lifetime, detection limits and adhesion with
the electrode,.
A. Jiménez-Morales, P. Aranda, J.C. Galván
Nanocomposite
materials based on organopolysiloxane/macrocycle systems for
electrochemical sensors
JOURNAL OF MATERIALS
PROCESSING TECHNOLOGY, Vol. 143-144, pp5-10 (2003)
Hybrid inorganic–organic nanocomposite
materials are prepared via sol–gel from metacryloxypropyltrimetoxysilane (MAPTMS) and
tetramethoxysilane (TMOS) precursors of a organopolysiloxane matrix in which
ionophore ligands (crown-ethers: 12-crown-4, 15-crown-5 and 18-crown-6) are
incorporated under controlled experimental conditions. Chemical analysis, FTIR
and solid-state NMR (13C and 29Si) spectroscopies, TG and DTA thermal analyses
and specific surface area determinations indicate that the ionophore remains
homogeneously distributed in the organopolysiloxane network. Ion-selective
electrodes are prepared by coating metal substrates with gels to form
homogeneous and continuous thin xerogel films. Impedance and potentiometric
techniques are applied for electrochemical characterisation of the sensors. The
resulting electrodes are very sensitive towards alkaline metal ions giving
linear potentiometric responses with near-Nernstian slopes in wide cation
concentration ranges. Additional advantages of this new type of sensors are
better adhesion, sensibility, reproducibility, and detection limit compared to
"conventional" (i.e., with internal solutions or PVC) electrodes.
2. ELECTROCHEMICAL CORROSION
Morcillo M, Feliu S, Galvan JC, Bastidas JM
The effect of water-soluble contaminants at steel/paint interface on
durability of the paint coating
JOCCA (JOURNAL OF THE OIL AND COLOUR CHEMISTS' ASSOCIATION), 71, pp 11-18 (1988)
Painting on steel, which has been corroded in polluted atmosphere, can
noticeably shorten the planned life of the paint system.
Feliu S, Galvan JC, Morcillo M
Limitations and possibilities of the typical electrochemical impedance
measurements for studying anti-corrosive paint
coatings
KEY ENGINEERING MATERIALS, 20-28, No.2,
pp 1235-1242 (1988)
10th International
Corrosion Congress (International Corrosion Council)
An attempt is made to
analyse the behaviour of paint coatings on galvanized steel by way of the
values of the parameters of the equivalent circuit. The possibility of
determining from the impedance diagrams the ionic resistance of paint coatings,
the charge transfer resistance and the capacitance of the double layer at the
base of the pores exists only during advanced stage of deterioration of the
coating, when the values of these parameter reflect the dominant influence of
macroscopic failures, and the reproducibility of these measurements is affected
by the poor reproducibility of the failure incubation period. On the other
hand, good reproducibility is obtained for the value of the capacitance of the
paint coating, since it depends almost exclusively on the deterioration on a
microscopic level. This parameter gives indirect information regarding the
stability of the coating.
Feliu S, Galvan JC,
Morcillo M
An interpretation of electrical impedance diagrams of painted
galvanized steel.
PROGRESS IN ORGANIC COATINGS, 17,
pp 143-153 (1989)
The physical meaning of
various arcs, which appear on impedance diagrams for painted galvanized steel exposed
to an aggressive medium, is discussed. These diagrams undergo various changes
during exposure, i.e. when the paint coating is still intact the response is
almost purely capacitive, but as the coating degrades the impedance value
decreases and the plots exhibits two arcs. Measurements with detached films
confirm the relationship between the single arc appearing in the impedance
diagrams during early stages of paint degradation and the intrinsic paint
prperties. However, it is more difficult to find an interpretation for the
two-arcs diagrams. The hypothesis that the low-frequency arc arises from
effects associated with the double-layer capacitance and charge-transfer
control at the pore base leads to unacceptable conclusions. Various arguments
seem to support the view that the low-frequency arc is determined by a
finitediffusion impedance.
Galvan JC, Feliu S, Morcillo M
Reproducibility of electrical impedance data in the metal/paint system
PROGRESS IN ORGANIC COATINGS, 17,
135-142 (1989)
The corrosion protection
characteristics of a paint/metal combination have been investigated via
measurements of the electrical impedance, and specifically via an
interpretation of the electrical parameters comprising the system’s equivalent
circuit. Unfortunately, the reproducibility of the ionic resistance of the
coating and the charge transfer resistance of the metal was affected by the
uncertain character macroscopic failures. In contrast, good reproducibility was
obtained for the coating capacitance values which depend almost exclusively
upon changes occurring at the microscopic level.
Feliu S, Morcillo M,
Galvan JC
Some questions regarding the evaluation of the anticorrosive behaviour
of paint coatings by impedance measurements; in "Advances in corrosion
protection by organic coatings". Ed. D. Scantlebury & M. Kending.
PROCEEDINGS OF THE ELECTROCHEMICAL SOCIETY, PV-13, pp 280-291 (1989)
An effort is made to relate
the shape and the characteristic parameters of the impedance diagrams (Nyquist
plots) with the behaviour of the metal-coating-electrolyte system. The
following points are examined in the paper: (i) significance of the arc obtained at the higher frequencies,
(ii) significance of the arc obtained at the lower frequencies, (iii) absence of
the arc relative to the charge transfer reaction, (iv) lack of sensitivity of
the diagrams with regard to some failures of the metal-paint system and (v)
lack of reproducibility of the diagrams.
Feliu S, Galvan JC, Morcillo M
The
charge transfer reaction in Nyquist diagrams of painted steel
CORROSION SCIENCE, 30, pp 989-998 (1990)
When
applying the AC impedance technique to metal-paint systems, it is of interest
to identify the corrosion reaction of the metallic substrate in the arcs
appearing on the complex plane of the Nyquist diagrams. This article shows how
difficult it sometimes is to obtain direct information on this reaction on the
basis of the diagrams obtained. The use of peelable films has been demonstrated
to be very useful for this research. With these films it is possible to
separate the effect of the metallic substrate from that of the film in the
impedance diagrams, first measuring with the film adhered to the metallic
surface and then with the same film detached from the substrate.
Morcillo M, Feliu S, Galvan JC, Bastidas JM, Simancas J,
Feliu Jr. S, Almeida E
Some observations on tannic acid as a rust converter
CORROSION'91, the NACE Annual Conference
(National Association of Corrosion Engineers), Cincinnati, Ohio (USA), Paper
562,12 pgs (1991)
The potential of tannic
acid as a protective agent against steel corrosion was studied. Research was
carried out on steel sheets rusted in an unpolluted inland atmosphere.
Different experimental techniques such as x-ray, photoelectron spectroscopy,
others involving climatic chamber tests and various electrochemical variants
(polarization curves, zero-resistance ammeter measurements and electrochemical
impedance spectroscopy) were applied. Treatment of rust with tannic acid
seemingly brought about no significant improvement in the protective features
of corrosion products formed outdoors.
Morcillo M Feliu S
Simancas J Bastidas JM Galvan JC
Feliu S Almeida EM
Corrosion
of Rusted Steel in Aqueous-Solutions of Tannic-Acid
CORROSION, 48,
pp 1032-1039 (1992)
The
use of tannic acid to inhibit metal corrosion has been a controversial issue,
particularly in relation to its application to rusted steel prior to painting.
In this work, the protective efficiency of aqueous solutions of tannic acid
applied on uncontaminated rusted steel is studied investigating the changes
undergone by the rust layer, the solubility of the tannate films formed, and
the resulting inhibition efficiency does this. This required the use of a
variety of experimental techniques including climatic chamber tests,
electrochemical measurements, and x-ray photoelectron spectroscopy. The high
solubility of the films and the low anti-corrosion efficiency of the treatment
question the suitability of tannic acid solutions for protection of rusted
steel prior to painting
Galvan JC, Feliu S,
Simancas J, Morcillo M, Bastidas JM, Almeida E, Feliu S
Effect
of Treatment with Tannic, Gallic and Phosphoric-Acids on the
Electrochemical-Behavior of Rusted Steel
ELECTROCHIMICA ACTA, 37, pp
1983-1985 (1992)
The
present paper studies the effect of different treatments with tannic, gallic
and phosphoric acids, which are applied on a rusted steel surface for
stabilizing the rust layer before a paint coating is applied. Impedance,
polarization resistance and chemical analysis data suggest that none of
the applied treatments effectively
block the activity in the rusted steel surface.
Feliu S, Bastidas JM, Galvan JC, Feliu S, Simancas J,
Morcillo M, Almeida E
Electrochemical
Determination of Rusted Steel Surface Stability
JOURNAL OF APPLIED ELECTROCHEMISTRY, 23, pp 157-161 (1993)
The stability of a rusted steel
surface exposed to a 0.1 M sodium sulphate solution has been studied. Electrochemical
impedance spectroscopy, polarization resistance and atomic absorption analysis
techniques were used in conjunction with mild steel specimens rusted in a rural
atmosphere and treated with different concentrations of phosphoric acid. Since most
of the impedance diagrams obtained differ from the typical semicircle, it is
not clear how to obtain kinetic information on the corrosion process. The
polarization resistance technique gives more useful data.
Morcillo M, Simancas
J, Fierro JLG, Feliu S, Galvan JC
Accelerated
Degradation of a Chlorinated Rubber Paint System Applied over Rusted Steel
PROGRESS IN ORGANIC COATINGS, 21, pp 315-325 (1993)
Chlorinated
rubber coatings have proved to be effective anticorrosion materials for steel
structures. However, their formulation and manufacture must be undertaken with
extreme care - particularly as regards the chlorination process and the
stabilizers and plasticizers added - in order to avoid early failures. This
paper reports on the premature failure of a chlorinated rubber system that was
applied directly over uncontaminated rusted steel. The accelerated formation of
rust at the steel/paint interface rapidly resulted in complete degradation of
the organic coating. Interfacial rust appears to catalyze the cleavage of
the C-Cl covalent bonds in the polymer,
which gives rise to the formation of chloride ions. These in turn have a
dramatic accelerating effect on the corrosion of the base steel, thereby
deteriorating the paint system.
Feliu S, Galvan JC, Feliu S, Bastidas JM, Simancas J, Morcillo
M, Almeida EM
An
Electrochemical Impedance Study of the Behavior of Some Pretreatments Applied
to Rusted Steel Surfaces
CORROSION SCIENCE, 35, pp 1351-1358 (1993)
The
electrochemical impedance technique was applied to study the corrosive and
electrochemical activity at the metal/rust interface in connection with the
application of protective treatments to rusted steel. The pretreatments assayed
were tannic or gallic acid solutions of different concentrations. The impedance
diagrams of the treated samples with these solutions were only slightly
modified with reference to those obtained with untreated rusted steel. The
shape of the low-frequency arcs or
tails in the Nyquist diagrams seems to be markedly influenced by diffusion
processes in the rust layer and/or by the porous nature of the rusted steel
electrode.
Escudero ML, Lopez V, Jiménez-Morales A, Vida E, Galvan
JC
Laser melting of plasma sprayed alumina coatings
CORROSION CONTROL FOR LOW-COST RELIABILITY, Volume 1 (coatings), pp 241-250. (1993)
NACE International,
The effect of laser melting of a plasma-deposited
pure alumina coating (g-alumina) on a microalloyed steel was analyzed. The thickness of the
alumina coatings was 100, 200 and 380 µm, respectively. These coatings were
subjected to a multimode laser beam with an elliptical cross-section, with 4
and 6 mm axes and output power of 5, 2.5 and 1.5 kW. The scanning rate was
varied between 4.5 and 172 m/min in order to achieve different surface states. The main aim of
this study is to change the alumina coating characteristics obtained by plasma
projection. Although this coating is a good thermal barrier and resistant to
wear, it is permeable and hence an unsuitable protection barrier against
corrosion. We therefore attempted to achieve a coating melt to seal coating
porosity and use it as a corrosion barrier. Optical microscopy and scanning
electron microscopy (SEM) were used to analyze how the melting process affected
the alumina layer, the thickness which had melted, possible defects in the
coating and transformations in the alumina. Corrosion behaviour was evaluated
by the polarization resistance method and anodic polarization curves. Complete
melting of the coating leads to the formation of nonporous alumina layers which
exhibit macroscopic cracks and a loss of adherence to the base material.
Partial melting of the coating leads to a reduction of the porosity in the
alumina layer, although microscopic cracks appear in a grid formation over the
melted material. The melting of the alumina layer results in a transformation
into a-alumina.
Corrosion tests show that the laser-melted coating is less permeable than the
plasma-deposited coating. In both cases, however, the corrosion behaviour of
the metallic material covered by alumina is always controlled by that of the
base material.
Rodriguez FJ, Galvan JC, Morcillo M
Effect of some variables on underfilm corrosion induced by
water-soluble sulphates at the metal-paint interface
PROGRESS IN THE UNDERSTANDING AND PREVENTION OF CORROSION, pp 210-214, 1993. Ed. J.M. Costa and A.D. Mercer. The
The effects of
some variables on underfilm corrosion of painted steel are studied.
Garcia MC, V. Lopez V, Escudero ML, Galvan JC, Pierna AR
The effect of rapid quenching by laser processing on the microstructure
of Ni-P alloys
PROGRESS IN THE UNDERSTANDING AND PREVENTION OF CORROSION, pp 1136-1140, 1993. Ed. J.M. Costa and A.D. Mercer. The
The effect of surface
laser treatment of Ni-P electrolytic coatings obtained on microalloyed steel is
analized. The coating thickness varied from 45 to 180 mm. The power
of the elliptical multimode beam was 3kW and sweep speeds ranged from 1180 to
5952 mm/min. Operating conditions for the laser treatment highlight the fact
that different microstructures are obtained on the coating during the specimen
cooling process. For constant beam powers, at low speeds there is generally a
loss of coating amorphousness, which shows precipitations in diverse forms and
the presence of dendrites. At high sweeps speeds, there is no penetration and
dendrites only appear with the base material and in zones that are isolated
from coating, which appears to remain amorphous.
Escudero ML, Pierna AR,
Galvan JC, Fernandez F
Pitting Corrosion Susceptibility of Oxide Layers in the Amorphous Alloy
(FexNi1-x)0.8(X,Y)0.2
MODIFICATIONS OF PASSIVE FILMS, pp.
322-325, 1994. The Institute of Materials (Book Number 577, 1994),. Eds. P.
Marcus, B. Baroux, M. Keddam. Published by the Institute of Materials (London)
for the European Federation of Corrosion (EFC Publications, Number 12)
(ISBN 0-901716-52-9)
(FexNi1-x)0.8(Si,B)0.2
metallic glasses were obtained by a rapid solidification technique. Reversible
oxide layers of variable thickness were generated in an alkaline medium on the
surface of these metallic glasses, using an electrochemical technique of
potential triangular sweeps. The composition of the metallic matrix as well as
the oxide layer electrochemically generated have been studied both by X-ray
photoelectron spectroscopy and specular reflactance spectroscopy. Pitting
corrosion susceptibility tests were realised in NaCl solutions 0.05 M, pH 6.8±0.1 at room temperature on the basis of a study of anodic polarization
curves. The generated layers are not only stable in the medium in which they
were generated, but also in other corrosive media with different pH, such as a
NaCl neutral solution. The glass with a generation of layers of maximum thickness
substantially improve pitting resistance in comparison to control specimens in
reception state. The best behaviour corrosion was found in the Fe38.5Ni38.5Mo2Si13B8
glass, with a typical curve for material in a passive state. Finally, the
different peaks observed in the SRS spectra of this last glass insinuate the
existence of different chemical species and/or different state oxidation of the
elements of these layers when they were generated after 200 or 400 potential
cycles.
Feliu S, Galvan JC,
Feliu S, Simancas J, Bastidas JM, Morcillo M, Almeida E
Differences
Between Apparent Polarization Resistance Values Obtained in the Time and
Frequency Domains
JOURNAL OF ELECTROANALYTICAL CHEMISTRY,
381, Iss 1-2, pp 1-4 (1995)
Anomalously
large differences between values of the polarization resistance Rp measured
in the time and frequency domains pose a serious problem in determination of
the corrosion rate from the Stern-Geary equation. A theoretical model is used
to derive expressions for a quantitative interpretation of the effect of a
number of parameters on the apparent Rp values obtained by de and ac
measurements. Problems associated with the determination of the true Rp
value are discussed, and some relevant questions concerning the minimum
frequency needed for impedance measurements are identified.
Galvan JC, Bastidas JM, Feliu S
A
Study of the Corrosive Effect of Soldering Fluxes on Printed-Circuit Boards
WELDING JOURNAL, 75, Iss 11, pp S366-S371 (1996)
The corrosiveness
of six commercial rosins used by the electronics industry was studied. The
copper sheet test, drop test and copper electrodeposition test were used. The
chloride content, pH and conductivity of the aqueous rosin extracts were determined. Finally, the electrochemical
impedance spectroscopy (EIS) method was used. All six tests allowed rosin
corrosiveness to be studied. The EIS method allowed the corrosion rate to be
quantified.
Jimenez-Morales A,
Galvan JC, Rodriguez R, de Damborenea
JJ
Electrochemical
Study of the Corrosion Behavior of Copper Surfaces Modified by Nitrogen
Ion-Implantation
JOURNAL OF APPLIED ELECTROCHEMISTRY, 27, pp 550-557 (1997)
Electrochemical
impedance spectroscopy (EIS) and d.c polarization resistance measurements (R-p)
were used to study the corrosion resistance of surface layers produced by
nitrogen ion implantation into copper
substrates. Ion implantation was
carried out using a Wickham ion beam generator, applying an acceleration
voltage of 100 keV, a mean current of 0.40 mA and a nitrogen dosage of 4 x 1017
ions·cm-2. Surface analyses were made by Auger electron spectroscopy
(AES). Electrochemical measurements (EIS and Rp) performed in a 0.6M
sodium chloride solution show nitrogen-implanted specimens have greater a.c.
and d.c. apparent polarization resistance than nonimplanted specimens. The
results obtained with electrochemical measurements indicate that nitrogen ion
implantation in copper forms a protective surface layer which improves the
corrosion resistance of the pristine
material, a feature of great interest for the design of new contact materials
for the electricity and electronic
industries.
Jiménez-Morales A, Simancas J, García J A, Galván JC
Nanocomposite
materials with controlled ion-mobility for the development of anticorrosive
coatings
Proceedings of the15th International Corrosion
Congress. Frontiers in Corrosion Science and
Technology,
New
protective coatings based on tailor-made hybrid organic/inorganic nanocomposite
materials with predetermined properties (high resistance to corrosion/or and
cathodic delamination) have been prepared. It is known that the
rate-controlling step of the corrosion and cathodic delamination processes of
the metal/paint systems in most circumstances is the rate of charge transport
through the coating. Taking in account this hypothesis we have designed new
nanocomposites based in the dispersion of different additives (crown-ethers
and/or powdered vermiculite) in polymer matrices of vinyl-polybutadiene (VPB).
The additives were selected on the assumption that they are able to interact
with sodium ions in the nanoscopic confinements of the host matrix to control
thus the ion mobility of the resulting coatings. Several batches of vermiculite
powders were previously treated with methylvinyldichlorosilane, g-methacryloxypropyltrimetoxysilane
and/or crown-ethers to give them hydrophobic properties and improve in this way
the corrosion resistance of the resulting coatings. In parallel studies, the
metallic surfaces were pretreated before the painting operation by applying a
sol-gel film generated from a mixture of two organopolysiloxane precursors (g-methacryloxypropyltrimetoxysilane
and tetrametoxysilane). It would expect that the crown-ethers, as complexing
agents of the alkaline cations, could to be an impediment to the Na+
motion through the coating provoking in this way a decreasing of the disbonding
rate. Nevertheless, the first results obtained in this work are indicating that
these macrocyclic compounds act as charge carriers which facilitating the
arrival of the Na+ cations to the site of
García-Heras M., González-Mena
E. , Galvan J.C., Villegas M.A.
Superficial modification of
aluminium-base alloys (anodising and non-anodising) by silica coatings
REV. METAL. (MADRID), Vol. 40 (2) pp 127-131 (2004)
Transparent and
colourless silica coatings were deposited on anodising and non-anodising substrates
of aluminium-base alloys (series 6063). Coatings were prepared by sol-gel
(dipping method) from a silica alkoxide and a mixture of both silica alkoxide
and silica alkylalkoxide. Preparations were optimised from viscosity, density,
surface tension, and contact angle measurements. Densification was carried out
at 60 and 120°C. Reflectance attenuation of coated samples was analysed by
UV-VIS-NIR spectroscopy. The results indicated that ~10 % of attenuation is
reached. Durability and resistance against degradation tests of the
metal/coating system were undertaken by immersion into aqueous solutions.
Electrochemical impedance measurements and potential corrosion of the metallic
substrate for variable times were performed.
Garcia-Heras M,
Jiménez-Morales A, Casal B, Galván JC, Radzki S, Villegas MA
Preparation and electrochemical study of Cerium-silica sol-gel thin
films
JOURNAL OF
ALLOYS AND COMPOUNDS, Vol. 380, Iss 1-2, pp219-224 (2004)
Design
and development of suitable multilayered systems for delaying corrosion advance
in metals requires that both the alteration mechanisms of the metal and the
behaviour and properties of the protective coatings be known. Coatings prepared
by the sol–gel method provide a good approach as protective layers on metallic
surfaces. This kind of coatings can be prepared from pure chemical reagents at
room temperature and atmospheric pressure, with compositions in a very wide
range of environmentally non-aggressive precursors. Sol–gel coatings based on
siloxane bonded units were prepared starting from an organic–inorganic hybrid
system. The precursors were -methacryloxypropyltrimethoxysilane
(MAP) and tetramethoxysilane (TMOS). Cerium nitrate hexahydrate in three
different concentrations was added. Cerium salts may perform a similar
protective effect to that carried out by the well-known lead oxides and
chromium salts, even though in this case a negative environmental impact is not
expected. Application of coatings upon pure zinc substrates and common glass
slides were performed by spinning. Coated samples were heat treated at
40 °C for 6 days. Optical measurements (UV-Vis absorption and diffuse
reflectance spectroscopies) pointed out that the coatings were colourless and
transparent, reducing the diffuse reflectance of the metallic surface up to
~60%. Optical and scanning electron microscopies (SEM) allowed observation of
the texture and microstructure of the coated samples, both before and after the
corrosion tests were carried out. Likewise, the remaining sols were kept to
gelify at 60 °C for 4 days and then powdered to obtain suitable samples
for analysing them by other characterisation techniques (Fourier transformed
infrared, FTIR and differential thermal analysis, DTA). Electrochemical
measurements were performed by impedance spectroscopy. This technique was used
to clarify the anticorrosive protection role of cerium ions incorporated into
the hybrid sol–gel network. The effect of cerium concentration on the impedance
spectra was analysed, as well as the system behaviour against the corrosive
medium (0.6 M NaCl aqueous solutions), as a function of exposure time.
From the electrochemical point of view, the sol–gel films behave as a
conversion coating on the metallic surface.
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