L. Sziráki | Eötvös Loránd University Budapest (original) (raw)
Papers by L. Sziráki
Materials
Sn-Fe-Ni-Co quaternary alloys, in the composition range of 37–44 at% Sn, 35–39 at% Fe, 6–8 at% Ni... more Sn-Fe-Ni-Co quaternary alloys, in the composition range of 37–44 at% Sn, 35–39 at% Fe, 6–8 at% Ni and 13–17 at% Co, were prepared by direct current (DC) and pulse plating (PP) electrodeposition. The alloy deposits were characterized by XRD, 57Fe and 119Sn conversion electron Mössbauer spectroscopy, SEM-EDX and magnetization measurements. XRD revealed the amorphous character of the quaternary alloy deposits. The dominant ferromagnetic character of the deposits was shown by magnetization and Mössbauer spectroscopy measurements. Room temperature Mössbauer spectra showed minor paramagnetic phases, where their occurrences (~3–20%) are correlated to the electrodeposition parameters (Jdep from −16 to −23 mA/cm2 for DC, Jpulse from −40 to −75 mA/cm2 for PP), the composition and the saturation magnetization (~52–73 emu/g). A considerable difference was found in the magnetization curves applying parallel or perpendicular orientation of the applied fields, indicating magnetic anisotropy both i...
Hyperfine Interactions, 2017
A constant current technique electrochemical deposition was used to obtain quaternary alloys of S... more A constant current technique electrochemical deposition was used to obtain quaternary alloys of Sn-Fe-Co-Ni, which to date have not been reported in the literature, from a gluconate electrolyte. For the characterization of electroplated alloys 57 Fe and 119 Sn conversion electron Mössbauer spectroscopy (CEMS) and XRD were used. XRD revealed the amorphous character of the novel Sn-Fe-Co-Ni electrodeposited alloys. 57 Fe Mössbauer spectrum of quaternary deposit displayed a magnetically split sextet with broad lines typical of iron bearing ferromagnetic amorphous alloys. Magnetically split 119 Sn spectra reflecting a transferred hyperfine field were also observed. New quaternary Sn-Fe-Co-Ni alloys were successfully prepared.
Hyperfine Interactions, 2016
Mössbauer spectroscopy has been used to investigate the nature of the Zinc-Iron alloys present wi... more Mössbauer spectroscopy has been used to investigate the nature of the Zinc-Iron alloys present within the Hot Dip Galvanized (HDG) layers of steel with a silicon content of 0.35%. The investigation also studied the impact of the powder coating pretreatment on the nature of the alloy layers. The acid etching process within the pretreatment process in particular would be expected to have a significant impact on the HDG layer. This study utilized 57 Fe Mössbauer spectroscopy to examine identically processed samples prior to and post pre treatment. XRD and 57 Fe CEMS measurements were performed on hot galvanized S355J2+N samples, forming sandwiched structure. Both XRD and CEMS reveal the presence of dominant steel phase in accordance with its estimated occurrence on the surface of the sandwiched samples. Minor -Fe3Zn10, -FeZn15 and solid solution Fe-Zn as well as minor Fe-Si phases could also be identified.
Hyperfine Interactions, 2016
Aluminium alloy free CS1 type steel (0.06 wt% C, 0.45 wt% Mn) and samples of cold roll bonded ste... more Aluminium alloy free CS1 type steel (0.06 wt% C, 0.45 wt% Mn) and samples of cold roll bonded steel bimetal alloys (MAS15 and MAS16) were fabricated and investigated by Xray diffraction (XRD), 57 Fe conversion electron Mössbauer spectroscopy (CEMS) at room temperature. XRD has revealed only the existence of the alpha iron solid solution (steel) phase in the steel only sample, while identified steel and metallic Al and Sn constituent phases in the bimetallic alloys. 57 Fe Mössbauer spectroscopy revealed the presence of 4% secondary iron-bearing phase attributed mainly to iron oxide/ oxyhydroxides (ferrihydrite) besides the steel matrix on the surface of the steel sample. A significant difference between the occurrences of the secondary phase of differently prepared bimetal alloys found in their 57 Fe CEM spectra allowed to identify the main phase of debris as different iron oxide/ oxyhydroxides.
Hyperfine Interactions, 2016
Sn-Fe thin films were electrodeposited by constant current deposition on copper substrates using ... more Sn-Fe thin films were electrodeposited by constant current deposition on copper substrates using an aqueous gluconate based electrolyte with varying concentrations of the organic additive peptone. Good quality metallic deposits were obtained with surface morphologies which varied with the concentration of peptone present in the electrolyte. The effect of peptone concentration on the deposition process was studied using electrochemical polarization curves and EDX analysis. The effect of peptone concentration on deposit structure and surface morphology was investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and 57 Fe and 119 Sn conversion electron Mössbauer spectroscopy (CEMS). It was concluded that the addition of small amounts of peptone to the electrolyte slightly increased the bath stability and led to changes in the alloy composition of the electrodeposits. It was found that increases in the peptone content increased the amount of the crystalline structure in the deposits with corresponding reductions in the amounts of amorphous structure present in the deposits. Keywords Amorphous alloys • Sn-Fe binary alloys • Electroplating • Electrochemical properties • Mössbauer spectroscopy • X-ray diffraction • Scanning electron microscopy (SEM) • Energy dispersive microanalysis of X-ray (EDX) This article is part of the Topical Collection on
AIP Conference Proceedings, 2012
ABSTRACT New Sn-Fe binary, Sn-Co-Fe, and Sn-Ni-Fe ternary alloys were successfully deposited from... more ABSTRACT New Sn-Fe binary, Sn-Co-Fe, and Sn-Ni-Fe ternary alloys were successfully deposited from an electrolyte based on sodium gluconate. X-ray diffraction and 57Fe and 119Sn Mössbauer results confirmed the existence of new metastable amorphous ferromagnetic and paramagnetic alloy phases within these deposits. It was possible to find deposition conditions at which the amorphous alloy phase was found to be a dominant phase for all the electrodeposits investigated. A nearly random distribution of alloying elements may be considered as a model of short-range order in the amorphous phases.
Fogorvosi szemle, 1993
The studies were focused on the corrosion stability of dental alloys (containing NiCr and stainle... more The studies were focused on the corrosion stability of dental alloys (containing NiCr and stainless steel), for a possible release of Nickel (Ni). The investigations were carried out in artificial saliva at 37 degrees C. The potential range, where Ni dissolution may occur, was determined by transient measurements. It has been established, that: 1. Under in vivo conditions the probability of the pitting corrosion is very low. 2. The Ni release takes place on the temporarily damaged, locally activated parts of the surfaces.
Fogorvosi szemle, 1993
The studies were focused on the corrosion stability of dental alloys (containing NiCr and stainle... more The studies were focused on the corrosion stability of dental alloys (containing NiCr and stainless steel), for a possible release of Nickel (Ni). The investigations were carried out in artificial saliva at 37 degrees C. The potential range, where Ni dissolution may occur, was determined by transient measurements. It has been established, that: 1. Under in vivo conditions the probability of the pitting corrosion is very low. 2. The Ni release takes place on the temporarily damaged, locally activated parts of the surfaces.
Radiation Physics and Chemistry, 2013
We give information on the effect of swift heavy ion irradiation in novel electrodeposited ternar... more We give information on the effect of swift heavy ion irradiation in novel electrodeposited ternary amorphous alloys. We observed changes in the short range order of Sn-Co-Fe irradiated with 246 MeV energy Kr ions. We observed changes in the short range order of Sn-Ni-Fe irradiated with 600 MeV energy Xe ions. Mössbauer spectroscopy measurements supplied important information about the changes in the short range order of ternary alloys due to swift heavy ion irradiation.
Materials Chemistry and Physics, 2012
ABSTRACT Results obtained by studying the electrochemical characterisation of the passive dissolu... more ABSTRACT Results obtained by studying the electrochemical characterisation of the passive dissolution and corrosion behaviour of amorphous chromium coatings are reported and discussed. An electrolyte based on trivalent chromium, complexed with glycine, was used in conjunction with a high speed flow electrodeposition cell. The structure, morphology and elemental analysis of chromium coatings deposited on copper substrates using various bath variables (bath temperatures of 30 and 60 °C; current densities of 0.3–1.8 A cm−2; and flow rates of 0.2, 0.3 and 1.4 m s−1) were investigated by XRD and SEM/EDS. As a network of micro-cracks was found on all the amorphous chromium deposits running from the deposit surface to the copper substrate, mild electrochemical passivation conditions were applied to avoid the copper substrate being subjected to corrosive attack.Potentiodynamic and potential step chronoamperometric curves were recorded after vigorous cathodic activation in de-aerated sulphuric acid solution. The corrosion potentials of the Cr coatings, after a 2 h immersion time were established to be around −0.3 V vs. SCE. The evaluations of the impedance spectra measured at the quasi-stationary corrosion potential, Ecorr were based on complex nonlinear least-squares (CNLS) fit to an equivalent circuit model of the corrosion kinetics in passive state.The polarisation resistance Rp of the overall corrosion process showed differences in the function of the deposition parameters, as the surface morphology and irregularities changed. The Rp values of amorphous chromium (a-Cr) deposits in passive state compared to the self-passivated crystalline chromium (c-Cr), revealed that the bright a-Cr coatings deposited at 60 °C using a medium flow rate and a high current outperform the corrosion protection ability of the c-Cr.
Abstract. 57Fe and 119Sn CEMS, XRD and electrochemical measurements were used to investigate the ... more Abstract. 57Fe and 119Sn CEMS, XRD and electrochemical measurements were used to investigate the effect of the preparation parameters and the components on the structure and phase composition of electrodeposited FeNiCr alloys in connection with their corrosion behavior. XRD of ...
Surface and Coatings Technology, 2007
Amorphous NiP layers with 8-10 wt.% phosphorus were deposited by sodium hypophosphite onto AlMg2 ... more Amorphous NiP layers with 8-10 wt.% phosphorus were deposited by sodium hypophosphite onto AlMg2 type aluminium alloy substrates after different pre-treatments. Prior to the electroless nickel-phosphorus (ENP) deposition in an acetate and lactic acid based nickel bath, the widely applied Zn (zincate) or Ni displacement (Ni strike) pre-treatments for aluminium substrates as well as a non-conventional surface conditioning one (soaking in a warm solution containing only hypophosphite and lactic acid) were all tested and their effects evaluated on the corrosion and other properties of the NiP layers developed right afterwards. The surface morphology and structure of the ENP layers were characterized by scanning electron microscopy and X-ray diffraction analysis. Polarization resistances were measured in 0.5 mol dm − 3 Na 2 SO 4 solution at pH 3. Compared to the direct electroless plating on the bare aluminium alloy AlMg2, it was found, that the hypophosphite adlayer (hypophosphite immersion pre-treatment) have also increased the corrosion resistance as the displacement pre-coatings, but without decreasing the deposition rate unlike conventional displacement methods. In the studied ENP deposition systems the decrease of corrosion rate could mainly be attributed to the lower microporosity and smoother morphology of the nickel-phosphorus coatings.
Electrochemistry Communications, 2008
Impedance analysis of electrochemically prepared WO 3 films has been carried out in order to inve... more Impedance analysis of electrochemically prepared WO 3 films has been carried out in order to investigate the applicability of the diffusion-trapping model to the analysis of impedance spectra related to electrochemical hydrogen insertion. The impedance spectra measured under different conditions have been analyzed by using CNLS fitting. It has been shown, that the expressions derived for the diffusion-trapping model adequately describe the impedance response of the system. Despite of the great number of adjustable parameters many of them could be determined with a good statistics, and reasonable estimated mean values have been obtained for the others. The reliability of the estimated parameters was checked by comparing the results with existing experimental data.
Central European Journal of Chemistry
The corrosion properties of the passive layers formed on iron-nickel-chromium electrodeposits of ... more The corrosion properties of the passive layers formed on iron-nickel-chromium electrodeposits of Fe29Ni51Cr20 were investigated in 0.3 M borate solution at a‘ pH of 8.4. On the basis of measurements by cyclic voltammetry, chronopotentiometry and electrochemical impedance spectroscopy, a low passive dissolution/corrosion rate was identified for the electrodeposited Fe-Ni-Cr alloys due to the nature of the established corrosion layer. The stability of this passive layer was further enhanced after corrosion under oxidizing conditions. Mössbauer spectroscopic measurements confirmed the existence of a thin passive layer on the amorphous electrodeposits.
Electrochimica Acta, 2002
The aim of this work is to analyse voltammetric and impedance behavior of the hydrated Ir oxide f... more The aim of this work is to analyse voltammetric and impedance behavior of the hydrated Ir oxide film grown on Ir by 10 Hz potential pulsing in 0.5 mol dm (3 H 2 SO 4 (AIROF). The solid-solution type Ir('/III)/Ir('/IV) redox reaction has been manifested in two-peak cyclic voltammograms both in 0.5 mol dm (3 H 2 SO 4 and 1 mol dm (3 NaOH solutions, but with different reversibility. In order to elucidate the high charge storage capability of the oxidized Ir oxide film and to separate of the bulk and interfacial processes a structural analysis of electrochemical impedance diagrams was carried out in terms of bulk proton hopping coupled to electron transfer and electrolytic migration-diffusion and different acidic dissociation of the redox couple. #
Surface and Coatings Technology, 2012
ABSTRACT Novel Sn–Ni–Fe ternary phases, which never occur in the metallurgical alloys, were succe... more ABSTRACT Novel Sn–Ni–Fe ternary phases, which never occur in the metallurgical alloys, were successfully prepared by deposition from an electrolyte based on sodium gluconate, using DC electrodeposition conditions. 57Fe and 119Sn conversion electron Mössbauer spectroscopy and PXRD investigations of these alloys showed that they are amorphous and dominantly ferromagnetic. The occurrence of amorphous Sn–Fe–Ni ternary alloy phase in deposits was found to increase with the current density applied during the deposition. The co-deposition kinetics is mainly governed by the electrodeposition behavior of the tin–gluconate complex that forms in the electrolyte. The high cathodic polarization due to the tin–gluconate discharge causes an apparent mass transfer coupled co-deposition of iron. The nickel deposition rate is independent of the potential and of the partial current of the co-depositing species.
Hyperfine Interactions, 2013
Hyperfine Interactions, 2013
ABSTRACT Effect of pulse plating on novel electrodeposited binary and ternary amorphous alloys wa... more ABSTRACT Effect of pulse plating on novel electrodeposited binary and ternary amorphous alloys was studied by 57Fe and 119Sn conversion electron Mössbauer spectroscopy and X-ray diffraction. Our results show that by adjusting the parameters of pulse plating a fine tuning of the composition and current efficiency can be achieved within these systems. On the contrary to direct current deposition, where the crystalline FeSn2 phase dominates, pulse plating technique produces amorphous Sn-Fe alloy phases, of which the ferromagnetic phase is the dominant one. Both, direct current and pulse plated Sn-Ni deposits consist of paramagnetic alloy phases and minor amounts of β-Sn, the occurrence of which correlates with the tin content of the samples. Pulse plated Sn-Ni-Fe coatings are amorphous and in a dominantly ferromagnetic state, however at long on- and off-pulse times and high peak current density the paramagnetic state dominates and β-Sn segregation also occurs.
Hyperfine Interactions, 2009
Abstract This study involved the use of a flow circulation cell, using varying circula-tion rates... more Abstract This study involved the use of a flow circulation cell, using varying circula-tion rates as a room temperature process (20 ◦ C). Mössbauer and XRD analysis were conducted to ascertain whether amorphous or microcrystalline structures could be obtained at 20 ◦ C using a ...
Electrochimica Acta, 2001
The kinetic consequences of morphological changes due to the zinc exchange process have been rela... more The kinetic consequences of morphological changes due to the zinc exchange process have been related to the corrosion performance and a further understanding of the initial stage of the white rust formation occurring preferentially in a thin layer of moisture in the absence of oxygen. Electrochemical impedance diagrams for a uniformly covered Zn corrosion product layer can be interpreted by a one-step dissolution mechanism, while on a non-uniform, partially active surface a consecutive dissolution occurs via adsorbed Zn(I) and Zn(II) species. The in situ EC-STM and EC-AFM observations revealed oriented Zn dissolution, deposition along the atomic steps and oriented oxide formation on the redeposited crystal planes in the early stages of each process.
Materials
Sn-Fe-Ni-Co quaternary alloys, in the composition range of 37–44 at% Sn, 35–39 at% Fe, 6–8 at% Ni... more Sn-Fe-Ni-Co quaternary alloys, in the composition range of 37–44 at% Sn, 35–39 at% Fe, 6–8 at% Ni and 13–17 at% Co, were prepared by direct current (DC) and pulse plating (PP) electrodeposition. The alloy deposits were characterized by XRD, 57Fe and 119Sn conversion electron Mössbauer spectroscopy, SEM-EDX and magnetization measurements. XRD revealed the amorphous character of the quaternary alloy deposits. The dominant ferromagnetic character of the deposits was shown by magnetization and Mössbauer spectroscopy measurements. Room temperature Mössbauer spectra showed minor paramagnetic phases, where their occurrences (~3–20%) are correlated to the electrodeposition parameters (Jdep from −16 to −23 mA/cm2 for DC, Jpulse from −40 to −75 mA/cm2 for PP), the composition and the saturation magnetization (~52–73 emu/g). A considerable difference was found in the magnetization curves applying parallel or perpendicular orientation of the applied fields, indicating magnetic anisotropy both i...
Hyperfine Interactions, 2017
A constant current technique electrochemical deposition was used to obtain quaternary alloys of S... more A constant current technique electrochemical deposition was used to obtain quaternary alloys of Sn-Fe-Co-Ni, which to date have not been reported in the literature, from a gluconate electrolyte. For the characterization of electroplated alloys 57 Fe and 119 Sn conversion electron Mössbauer spectroscopy (CEMS) and XRD were used. XRD revealed the amorphous character of the novel Sn-Fe-Co-Ni electrodeposited alloys. 57 Fe Mössbauer spectrum of quaternary deposit displayed a magnetically split sextet with broad lines typical of iron bearing ferromagnetic amorphous alloys. Magnetically split 119 Sn spectra reflecting a transferred hyperfine field were also observed. New quaternary Sn-Fe-Co-Ni alloys were successfully prepared.
Hyperfine Interactions, 2016
Mössbauer spectroscopy has been used to investigate the nature of the Zinc-Iron alloys present wi... more Mössbauer spectroscopy has been used to investigate the nature of the Zinc-Iron alloys present within the Hot Dip Galvanized (HDG) layers of steel with a silicon content of 0.35%. The investigation also studied the impact of the powder coating pretreatment on the nature of the alloy layers. The acid etching process within the pretreatment process in particular would be expected to have a significant impact on the HDG layer. This study utilized 57 Fe Mössbauer spectroscopy to examine identically processed samples prior to and post pre treatment. XRD and 57 Fe CEMS measurements were performed on hot galvanized S355J2+N samples, forming sandwiched structure. Both XRD and CEMS reveal the presence of dominant steel phase in accordance with its estimated occurrence on the surface of the sandwiched samples. Minor -Fe3Zn10, -FeZn15 and solid solution Fe-Zn as well as minor Fe-Si phases could also be identified.
Hyperfine Interactions, 2016
Aluminium alloy free CS1 type steel (0.06 wt% C, 0.45 wt% Mn) and samples of cold roll bonded ste... more Aluminium alloy free CS1 type steel (0.06 wt% C, 0.45 wt% Mn) and samples of cold roll bonded steel bimetal alloys (MAS15 and MAS16) were fabricated and investigated by Xray diffraction (XRD), 57 Fe conversion electron Mössbauer spectroscopy (CEMS) at room temperature. XRD has revealed only the existence of the alpha iron solid solution (steel) phase in the steel only sample, while identified steel and metallic Al and Sn constituent phases in the bimetallic alloys. 57 Fe Mössbauer spectroscopy revealed the presence of 4% secondary iron-bearing phase attributed mainly to iron oxide/ oxyhydroxides (ferrihydrite) besides the steel matrix on the surface of the steel sample. A significant difference between the occurrences of the secondary phase of differently prepared bimetal alloys found in their 57 Fe CEM spectra allowed to identify the main phase of debris as different iron oxide/ oxyhydroxides.
Hyperfine Interactions, 2016
Sn-Fe thin films were electrodeposited by constant current deposition on copper substrates using ... more Sn-Fe thin films were electrodeposited by constant current deposition on copper substrates using an aqueous gluconate based electrolyte with varying concentrations of the organic additive peptone. Good quality metallic deposits were obtained with surface morphologies which varied with the concentration of peptone present in the electrolyte. The effect of peptone concentration on the deposition process was studied using electrochemical polarization curves and EDX analysis. The effect of peptone concentration on deposit structure and surface morphology was investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and 57 Fe and 119 Sn conversion electron Mössbauer spectroscopy (CEMS). It was concluded that the addition of small amounts of peptone to the electrolyte slightly increased the bath stability and led to changes in the alloy composition of the electrodeposits. It was found that increases in the peptone content increased the amount of the crystalline structure in the deposits with corresponding reductions in the amounts of amorphous structure present in the deposits. Keywords Amorphous alloys • Sn-Fe binary alloys • Electroplating • Electrochemical properties • Mössbauer spectroscopy • X-ray diffraction • Scanning electron microscopy (SEM) • Energy dispersive microanalysis of X-ray (EDX) This article is part of the Topical Collection on
AIP Conference Proceedings, 2012
ABSTRACT New Sn-Fe binary, Sn-Co-Fe, and Sn-Ni-Fe ternary alloys were successfully deposited from... more ABSTRACT New Sn-Fe binary, Sn-Co-Fe, and Sn-Ni-Fe ternary alloys were successfully deposited from an electrolyte based on sodium gluconate. X-ray diffraction and 57Fe and 119Sn Mössbauer results confirmed the existence of new metastable amorphous ferromagnetic and paramagnetic alloy phases within these deposits. It was possible to find deposition conditions at which the amorphous alloy phase was found to be a dominant phase for all the electrodeposits investigated. A nearly random distribution of alloying elements may be considered as a model of short-range order in the amorphous phases.
Fogorvosi szemle, 1993
The studies were focused on the corrosion stability of dental alloys (containing NiCr and stainle... more The studies were focused on the corrosion stability of dental alloys (containing NiCr and stainless steel), for a possible release of Nickel (Ni). The investigations were carried out in artificial saliva at 37 degrees C. The potential range, where Ni dissolution may occur, was determined by transient measurements. It has been established, that: 1. Under in vivo conditions the probability of the pitting corrosion is very low. 2. The Ni release takes place on the temporarily damaged, locally activated parts of the surfaces.
Fogorvosi szemle, 1993
The studies were focused on the corrosion stability of dental alloys (containing NiCr and stainle... more The studies were focused on the corrosion stability of dental alloys (containing NiCr and stainless steel), for a possible release of Nickel (Ni). The investigations were carried out in artificial saliva at 37 degrees C. The potential range, where Ni dissolution may occur, was determined by transient measurements. It has been established, that: 1. Under in vivo conditions the probability of the pitting corrosion is very low. 2. The Ni release takes place on the temporarily damaged, locally activated parts of the surfaces.
Radiation Physics and Chemistry, 2013
We give information on the effect of swift heavy ion irradiation in novel electrodeposited ternar... more We give information on the effect of swift heavy ion irradiation in novel electrodeposited ternary amorphous alloys. We observed changes in the short range order of Sn-Co-Fe irradiated with 246 MeV energy Kr ions. We observed changes in the short range order of Sn-Ni-Fe irradiated with 600 MeV energy Xe ions. Mössbauer spectroscopy measurements supplied important information about the changes in the short range order of ternary alloys due to swift heavy ion irradiation.
Materials Chemistry and Physics, 2012
ABSTRACT Results obtained by studying the electrochemical characterisation of the passive dissolu... more ABSTRACT Results obtained by studying the electrochemical characterisation of the passive dissolution and corrosion behaviour of amorphous chromium coatings are reported and discussed. An electrolyte based on trivalent chromium, complexed with glycine, was used in conjunction with a high speed flow electrodeposition cell. The structure, morphology and elemental analysis of chromium coatings deposited on copper substrates using various bath variables (bath temperatures of 30 and 60 °C; current densities of 0.3–1.8 A cm−2; and flow rates of 0.2, 0.3 and 1.4 m s−1) were investigated by XRD and SEM/EDS. As a network of micro-cracks was found on all the amorphous chromium deposits running from the deposit surface to the copper substrate, mild electrochemical passivation conditions were applied to avoid the copper substrate being subjected to corrosive attack.Potentiodynamic and potential step chronoamperometric curves were recorded after vigorous cathodic activation in de-aerated sulphuric acid solution. The corrosion potentials of the Cr coatings, after a 2 h immersion time were established to be around −0.3 V vs. SCE. The evaluations of the impedance spectra measured at the quasi-stationary corrosion potential, Ecorr were based on complex nonlinear least-squares (CNLS) fit to an equivalent circuit model of the corrosion kinetics in passive state.The polarisation resistance Rp of the overall corrosion process showed differences in the function of the deposition parameters, as the surface morphology and irregularities changed. The Rp values of amorphous chromium (a-Cr) deposits in passive state compared to the self-passivated crystalline chromium (c-Cr), revealed that the bright a-Cr coatings deposited at 60 °C using a medium flow rate and a high current outperform the corrosion protection ability of the c-Cr.
Abstract. 57Fe and 119Sn CEMS, XRD and electrochemical measurements were used to investigate the ... more Abstract. 57Fe and 119Sn CEMS, XRD and electrochemical measurements were used to investigate the effect of the preparation parameters and the components on the structure and phase composition of electrodeposited FeNiCr alloys in connection with their corrosion behavior. XRD of ...
Surface and Coatings Technology, 2007
Amorphous NiP layers with 8-10 wt.% phosphorus were deposited by sodium hypophosphite onto AlMg2 ... more Amorphous NiP layers with 8-10 wt.% phosphorus were deposited by sodium hypophosphite onto AlMg2 type aluminium alloy substrates after different pre-treatments. Prior to the electroless nickel-phosphorus (ENP) deposition in an acetate and lactic acid based nickel bath, the widely applied Zn (zincate) or Ni displacement (Ni strike) pre-treatments for aluminium substrates as well as a non-conventional surface conditioning one (soaking in a warm solution containing only hypophosphite and lactic acid) were all tested and their effects evaluated on the corrosion and other properties of the NiP layers developed right afterwards. The surface morphology and structure of the ENP layers were characterized by scanning electron microscopy and X-ray diffraction analysis. Polarization resistances were measured in 0.5 mol dm − 3 Na 2 SO 4 solution at pH 3. Compared to the direct electroless plating on the bare aluminium alloy AlMg2, it was found, that the hypophosphite adlayer (hypophosphite immersion pre-treatment) have also increased the corrosion resistance as the displacement pre-coatings, but without decreasing the deposition rate unlike conventional displacement methods. In the studied ENP deposition systems the decrease of corrosion rate could mainly be attributed to the lower microporosity and smoother morphology of the nickel-phosphorus coatings.
Electrochemistry Communications, 2008
Impedance analysis of electrochemically prepared WO 3 films has been carried out in order to inve... more Impedance analysis of electrochemically prepared WO 3 films has been carried out in order to investigate the applicability of the diffusion-trapping model to the analysis of impedance spectra related to electrochemical hydrogen insertion. The impedance spectra measured under different conditions have been analyzed by using CNLS fitting. It has been shown, that the expressions derived for the diffusion-trapping model adequately describe the impedance response of the system. Despite of the great number of adjustable parameters many of them could be determined with a good statistics, and reasonable estimated mean values have been obtained for the others. The reliability of the estimated parameters was checked by comparing the results with existing experimental data.
Central European Journal of Chemistry
The corrosion properties of the passive layers formed on iron-nickel-chromium electrodeposits of ... more The corrosion properties of the passive layers formed on iron-nickel-chromium electrodeposits of Fe29Ni51Cr20 were investigated in 0.3 M borate solution at a‘ pH of 8.4. On the basis of measurements by cyclic voltammetry, chronopotentiometry and electrochemical impedance spectroscopy, a low passive dissolution/corrosion rate was identified for the electrodeposited Fe-Ni-Cr alloys due to the nature of the established corrosion layer. The stability of this passive layer was further enhanced after corrosion under oxidizing conditions. Mössbauer spectroscopic measurements confirmed the existence of a thin passive layer on the amorphous electrodeposits.
Electrochimica Acta, 2002
The aim of this work is to analyse voltammetric and impedance behavior of the hydrated Ir oxide f... more The aim of this work is to analyse voltammetric and impedance behavior of the hydrated Ir oxide film grown on Ir by 10 Hz potential pulsing in 0.5 mol dm (3 H 2 SO 4 (AIROF). The solid-solution type Ir('/III)/Ir('/IV) redox reaction has been manifested in two-peak cyclic voltammograms both in 0.5 mol dm (3 H 2 SO 4 and 1 mol dm (3 NaOH solutions, but with different reversibility. In order to elucidate the high charge storage capability of the oxidized Ir oxide film and to separate of the bulk and interfacial processes a structural analysis of electrochemical impedance diagrams was carried out in terms of bulk proton hopping coupled to electron transfer and electrolytic migration-diffusion and different acidic dissociation of the redox couple. #
Surface and Coatings Technology, 2012
ABSTRACT Novel Sn–Ni–Fe ternary phases, which never occur in the metallurgical alloys, were succe... more ABSTRACT Novel Sn–Ni–Fe ternary phases, which never occur in the metallurgical alloys, were successfully prepared by deposition from an electrolyte based on sodium gluconate, using DC electrodeposition conditions. 57Fe and 119Sn conversion electron Mössbauer spectroscopy and PXRD investigations of these alloys showed that they are amorphous and dominantly ferromagnetic. The occurrence of amorphous Sn–Fe–Ni ternary alloy phase in deposits was found to increase with the current density applied during the deposition. The co-deposition kinetics is mainly governed by the electrodeposition behavior of the tin–gluconate complex that forms in the electrolyte. The high cathodic polarization due to the tin–gluconate discharge causes an apparent mass transfer coupled co-deposition of iron. The nickel deposition rate is independent of the potential and of the partial current of the co-depositing species.
Hyperfine Interactions, 2013
Hyperfine Interactions, 2013
ABSTRACT Effect of pulse plating on novel electrodeposited binary and ternary amorphous alloys wa... more ABSTRACT Effect of pulse plating on novel electrodeposited binary and ternary amorphous alloys was studied by 57Fe and 119Sn conversion electron Mössbauer spectroscopy and X-ray diffraction. Our results show that by adjusting the parameters of pulse plating a fine tuning of the composition and current efficiency can be achieved within these systems. On the contrary to direct current deposition, where the crystalline FeSn2 phase dominates, pulse plating technique produces amorphous Sn-Fe alloy phases, of which the ferromagnetic phase is the dominant one. Both, direct current and pulse plated Sn-Ni deposits consist of paramagnetic alloy phases and minor amounts of β-Sn, the occurrence of which correlates with the tin content of the samples. Pulse plated Sn-Ni-Fe coatings are amorphous and in a dominantly ferromagnetic state, however at long on- and off-pulse times and high peak current density the paramagnetic state dominates and β-Sn segregation also occurs.
Hyperfine Interactions, 2009
Abstract This study involved the use of a flow circulation cell, using varying circula-tion rates... more Abstract This study involved the use of a flow circulation cell, using varying circula-tion rates as a room temperature process (20 ◦ C). Mössbauer and XRD analysis were conducted to ascertain whether amorphous or microcrystalline structures could be obtained at 20 ◦ C using a ...
Electrochimica Acta, 2001
The kinetic consequences of morphological changes due to the zinc exchange process have been rela... more The kinetic consequences of morphological changes due to the zinc exchange process have been related to the corrosion performance and a further understanding of the initial stage of the white rust formation occurring preferentially in a thin layer of moisture in the absence of oxygen. Electrochemical impedance diagrams for a uniformly covered Zn corrosion product layer can be interpreted by a one-step dissolution mechanism, while on a non-uniform, partially active surface a consecutive dissolution occurs via adsorbed Zn(I) and Zn(II) species. The in situ EC-STM and EC-AFM observations revealed oriented Zn dissolution, deposition along the atomic steps and oriented oxide formation on the redeposited crystal planes in the early stages of each process.