Physico-chemical characterization of passive films on 316L stainless steel grown in high temperature water

Electrochemical synthesis and physico-chemical characterization of CdSe nanotubes

Synergistic Use of Electrochemical Impedance Spectroscopy and Photoelectrochemical Measurements for Studying Solid State Properties of Anodic HfO2

Within the past years, intense research has been carried out on HfO2 as high k material, promising candidate to replace SiO2 as gate dielectric in CMOS based devices (1), and as metal oxide for resistive random access memory (ReRAM) (2). For both technological applications compact, uniform and flat oxides are necessary, and a detailed understanding of their physical properties as a function of the fabrication conditions is strongly. Hafnia performance can be significantly influenced by carrier trapping taking place at pre-existing precursors states (induced by oxygen vacancies, interstitial ions, impurities acting as dopants), or by self-trapping in a perfect lattice, where the potential we…

Photocurrent Spectroscopy in Corrosion and Passivity Studies. A Critical Assessment

Photocurrent Spectroscopy (PCS) is currently employed for the characterization of solid-state properties of semiconducting and insulating materials, since the knowledge of their band gap is a prerequisite to any possible application in different fields such as: solar energy conversion (photoelectrochemical and photovoltaic solar cells, photocatalysis) and microelectronics (high-k, high band-gap materials) (1-2). In the last 20-30 years an increasing number of scientists working in the area of corrosion has been attracted by this technique owing to its versatility and ability to scrutinize in situ corrosion layers and passive films having semiconducting or insulating behaviour. In previous w…

In situ stress, strain and dielectric measurements to understand electrostriction in anodic oxides

Fuel Cell Performances of Bio-Membranes Made of Chitosan-Polyelectrolyte Thin Films and Nanowires into Anodic Alumina Membranes

Chitosan (CS) / Phosphotungstic acid (PTA) polyelectrolytes in the shape of thin films and nanowires supported by Anodic Alumina Membranes (AAM) have been fabricated through solution cast and filtration techniques, respectively. Their ability to function in a H2/O2 fuel cell under mild conditions (room temperature, low humidity and low Pt loading) is proved for the first time. The fabricated membrane electrode assemblies produce power peaks of ~20 mW cm-2 for both films and nanowires. The CS/PTA films (20-40 μm thick) are able to produce a quite constant power density of ~10 mW cm-2 recorded for at least 7 h. The gradual decrease of the power output with time observed for CS/PTA nanowires i…

Photoelectrochemical Characterization of Oxide Layers on 316L Stainless Steel Grown in High temperature Water

Physico-Chemical Characterization of Polypyrrole Film Grown in Aqueous and Non Aqueous Solution on Different Substrates

Kinetic of growth and physico-chemical characterization of anodic films on magnesium

Photoelectrochemical evidence of Nitrogen Incorporation during Anodizing of valve metals alloys

Amorphous and/or nanocrystalline oxide films can be easily prepared electrochemically by anodizing. The anodizing allows to grow oxides with structural and compositional features easily and strictly controlled by the process parameters.

The Influence of Surface Treatment on the Kinetic of Growth of Anodic Films on Magnesium in Alkaline Solution

Structural and Photoelectrochemical Characterization of Porous Anodic Films on Iron

Use of Mott-Schottky Plots to Characterise the Amorphous Passive Film/Electrolyte Junction

Poster: Polar Dielectrics, Optics, and Ionics

The Effect of Nb Incorporation on the Electronic Properties of Anodic HfO2

Hafnium oxide and Nb doped HfO2 were grown by anodizing sputtering-deposited Hf and Hf-4at.%Nb. Photoelectrochemical characterization was carried out in order to estimate solid state properties such as band gap, flat band potential and electrons internal photoemission threshold energy as a function of thickness and composition of anodic oxides. Optical transitions at energy lower than the band gap value of the investigated anodic films were evidenced, and they are attributed to optical transitions involving localized states inside the band gap. Such states were located at 3.6 eV and 3.9 eV below the conduction band edge for the Nb free and Nb containing hafnium oxide, respectively. Impedanc…

Redshift of absorption threshold of TiO2 Nanotubes due to Cu2O electrodeposition

Physico-chemical characterization of anodic films on sputter-deposited Al-Nb alloys.

The influence of surface treatment on the anodizing of Magnesium in Alkaline Solution

Electrochemical cell for the preparation of large area Anodic Alumina Membranes

Monitoring of Rouging and De-Rouging of Stainless Steel for Chemical Reactors by Photoelectrochemical and Impedance Measurements

The food and fine-chemical industry has for a long time been troubled by red brown to dark violet deposits in distillation columns, storage vessels and distribution systems for purified water and clean steam. Owing to the visual appearance of those deposits, the phenomena was referred as rouge. Although formation of rouge, i.e. rouging, is a commonly known phenomenon in stainless steel systems, the basic mechanism is still not fully understood. The phenomenon causes precipitation of iron as fine red-brown ferric oxide or hydroxide particles. Moreover adherent discoloration of the stainless steel surface is often observed in conjunction with the loosely adhered rouge particles. The affected …

Influences of structure and composition on the photoelectrochemical behaviour of anodic films on Ti-Zr alloys

Electrodeposition and physico-chemical characterisation of Fe, Ti and mixed Fe/Ti oxides nanotubes

Composite Anodic Alumina /CsHSO4 Membranes for Intermediate Temperature Fuel Cell

Heteropolyacids - Chitosan Membranes for H2/O2 Low Temperature Fuel Cells

Proton exchange membrane fuel cells (PEMFCs) have received much attention in recent years because of their high power density, efficiency and zero-environmental pollution. As one of the key components in fuel cells, the proton exchange membrane is expected to have high proton conductivity and good electrochemical stability. In the attempt to promote PEMCFs commercialization, high cost of fuel cell systems and short lifecycle are the two main issues that need to be addressed, thus large research effort has been devoted in developing new polymer electrolytes that can replace the usually employed proton conductors, e.g. Nafion®, with other membranes of comparable performances but lower cost.A…

Photoelectrochemical monitoring of rouging and de-rouging process on AISI 316L for chemical reactors

The food and fine-chemical industry has for a long time been troubled by red brown to dark violet deposits in distillation columns, storage vessels and distribution systems for purified water and clean steam. Owing to the visual appearance of those deposits, the phenomena was referred as rouge. Although formation of rouge, i.e. rouging, is a commonly known phenomenon in stainless steel systems, the basic mechanism is still not fully understood. The phenomenon causes precipitation of iron as fine red-brown ferric oxide or hydroxide particles. Moreover adherent discoloration of the stainless steel surface is often observed in conjunction with the loosely adhered rouge particles. The affected …

The Influence of Thermal Treatment on the Electronic Properties of a-Nb2O5

The effect of thermal treatments for 1h at 250{degree sign}C in air or under vacuum on the electronic structure of thick amorphous anodic niobia was characterized by electrochemical impedance, differential admittance (DA) and photocurrent spectroscopy (PCS). The analysis of anodized niobia has revealed that it behaves as a pure dielectric. The thermal treatment in air increases the value of the differential capacitance of the niobia sample. The effect is stronger when the thermal treatment is carried out in vacuum and can be cancelled out by reanodizing the oxide to the initial formation potential. In the case of thermally vacuum-treated sample, a behavior typical of semiconducting amorphou…

The influence of composition on band gap and dielectric constant of anodic Al-Ta mixed oxides

Al-Ta mixed oxides were grown by anodizing sputter-deposited Al-Ta alloys of different composition. Photocurrent spectra revealed a band gap, Eg, slightly independent on Ta content and very close to that of anodic Ta2O5 (∼4.3 eV) with the exception of the anodic film on Al-10at% Ta, which resulted to be not photoactive under strong anodic polarization. The photoelectrochemical characterization allowed to estimate also the oxides flat band potential and to get the necessary information to sketch the energetic of the metal/oxide/electrolyte interfaces. Impedance measurements allowed to confirm the formation of insulating material and to estimate the dielectric constant of the oxides, which re…

Photocurrent Spectroscopy Applied to the Characterization of Compositionally and Structurally Graded Materials: from Thin Films to Nanostructures

Tensiostatic studies on formation and breakdown of anodic oxide films on tungsten in acidic chloride solutions

Abstract The anodic behaviour of tungsten in HCl and HCl + KCl solutions has been extensively studied. For each solution, the applied voltage was increased from 1 V up to the breakdown voltage. Values of the current and open circuit voltage decays were recorded. The HCl concentration was varied from 0.05 M to 12 M while appropriate addition to KCl was made to reach assigned molarities of the Cl − ion. The results are discussed and qualitatively interpreted in terms of the different influence of the H + and Cl − ions.

The effect of Annealing Conditions on the Impedance and on the Photoelectrochemical behavior of TiO2 Nanotubes

Titanium oxide nanotubes (NTs) have attracted much attention during last decade due to their special characteristics such as one-dimensional highly ordered geometry with large surface area and good chemical and optical stability.

Photoelectrochemical Characterization of Porous Anodic Films on Iron Grown in Fluoride-containing Ethylebe Glycol Electrolyte

Structural and compositional analysis of anodic films on Al-Nb sputter-deposited alloys

The photoelectrochemical behavior of anodic films on Al alloys, containing titanium, tantalum, and tungsten (valve metals), has been studied as a function of alloy composition and anodizing conditions. Photocurrent spectroscopy has been used to get information on bandgap and the flatband potential values of different mixed oxides. Both insulator-like and semiconducting behavior has been observed for anodic oxides grown on Al-W and Al-Ti alloys dependent on alloy initial composition. Optical bandgap values, Eg,opt, of different oxides are in accordance with predictions based on the correlation between Eg,opt and the difference of electronegativities of the oxide constituents, indicating pote…

Photoelectrochemical Characterization of Ta/Ta2O5/Polypyrrole Heterojunctions

A photodeposition of polypyrrole on anodic tantalum oxide thin films was performed in both organic and aqueous media. Pyrrole was photo-oxidised on insulating tantalum oxide by irradiating the electrode with light of suitable energy. Tantalum/ tantalum oxide/ polypyrrole heterojunctions were then characterized by means of photocurrent spectroscopy. The comparison between the photoelectrochemical response of the heterojunctions fabricated in organic and aqueous media, shows that the solvent used for the photodeposition of polypyrrole influences the location of the inversion potential. This result can be attributed to the different structure of polypyrrole films, which strongly depends on the…

1D cerium oxy-hydroxide nanostructures deposition via electrogeneration of base into anodic alumina membrane

Electrochemical fabrication of high k Al-Ta mixed oxides

Influence of heteropolyacid in enhancing proton conductivity of chitosan membranes for H2/O2 Fuel Cells

To promote Proton Exchange Membrane Fuel Cells (PEMFCs) commercialization, large research effort has been devoted in developing new polymer electrolytes that can replace the usually employed proton conductors, e.g. Nafion®, with other membranes of comparable performances but lower cost. Chitosan (CS)-based membrane electrolyte is currently studied as alternative candidate for PEMFC application. Several works have shown that Heteropolyacids (HPAs) can be used to prepare Chitosan polyelectrolytes (PECs) to be employed as proton exchange membrane in low temperature fuel cell. In previous works [1-3] we have shown that CS/PTA membranes, prepared using alumina porous medium for the slow release …

Fabbricazione per via elettrochimica e caratterizzazione di membrane nanoporose di allumina

Photoelectrochemical behaviour of passive layers on Co in alkaline solutions

Photoelectrochemical Techniques in Corrosion Studies

Growth and Characterization of Anodic Films on Magnesium in Alkaline Solution

Physico-Chemical Characterization of Anodic Oxides on Hf as a Function of the Anodizing Conditions

Anodic films were grown to 5 V (Ag/AgCl) on mechanically polished Hf in 0.1 M ammonium biborate and 0.1 M NaOH. Independent of the anodizing conditions, the photoelectrochemical characterization allowed the observation of optical transitions at 3.25 eV, i.e. at photon energy lower than the bandgap of HfO2. They are attributed to localized states inside the gap of the oxide induced by the presence of oxygen vacancies. From the cathodic photocurrent spectra, it was possible to estimate an energy threshold of ∼2.15 eV for internal electron photoemission phenomena. The impedance measurements proved the formation of insulating oxides with ϵ =19. The anodizing occurs under a high field regime wit…

Electrochemical Fabrication of Inorganic/Organic Field Effect Transistor

After discovery of conducting polymers and the possibility to modify their electrical properties (from insulating to metallic-like behaviour) by doping and a careful choice of the processing conditions, a large amount of research effort has been devoted to the theoretical understanding of their solid state properties as well as to exploit the possible application of conducting polymers in many technological fields including: large area organic electronics, polymer photovoltaic cell and sensors (1-2). Organic thin-film transistors appears very promising for the development of low cost, flexible and disposable plastic electronics. In order to reduce the operating voltage it has been suggested…

A Critical Assessment of Mott-Schottky Analysis for the Characterisation of Passive Film-Electrolyte Junctions

Critical Review—Photocurrent Spectroscopy in Corrosion and Passivity Studies: A Critical Assessment of the Use of Band Gap Value to Estimate the Oxide Film Composition

A critical assessment of the Photocurrent Spectroscopy (PCS) Technique for the semi-quantitative characterization of passive film and corrosion layers composition is carried out. We take into account more than three decades of PCS usage as "in-situ" analytical technique and related results as well as the criticism of the underlying semi-empirical correlation relating the measured optical bandgap (Eg) to the passive film composition. The discrepancies between the experimental data, gathered by PCS measurements, and Egestimates originating from recently developed Density Functional Theory based modeling of solid state properties are stressed with particular emphasis on the case of anodic pass…

Structural and compositional analysis of anodic films on Al-Nb sputter-deposited alloys

Porous Anodic Alumina as template for the cathodic electrodeposition of oxide and hydroxide nanostructures

Physico-chemical characterization and corrosion properties of friction stir welded Al2024-T4 alloys

Oxide and Hydroxide nanostructures embedded into Anodic alumina membranes prepared by means of electrogeneration of base

Preparation and characterization of novel proton conducting membranes for thin film fuel cell

Chitosan (CS) / Phosphotungstic acid (PTA) polyelectrolytes in the shape of thin films and nanowires supported by Anodic Alumina Membranes (AAM) have been fabricated through solution cast and filtration techniques, respectively. Their ability to function in a H2/O2 fuel cell under mild conditions (room temperature, low humidity and low Pt loading) is proved for the first time. The fabricated membrane electrode assemblies produce power peaks of ∼20 mW cm-2 for both films and nanowires. The CS/PTA films (20-40 μm thick) are able to produce a quite constant power density of ∼10 mW cm-2 recorded for at least 7 h. The gradual decrease of the power output with time observed for CS/PTA nanowires i…

Solid State Properties of Anodic Hf-Nb Mixed Oxides

In last decades, HfO2 and Nb2O5 have been extensively studied due to their many potential applications, from corrosion protection to CMOS (as high-k gate dielectrics) [1-2] and ReRAM technologies [3-4]. For these technological applications compact, uniform and flat oxides are necessary, and a detailed understanding of their physical properties as a function of the fabrication conditions is needful. Scientific community gradually shifted its interest from pure metal oxides to mixed metal oxides trying to exploit the advantages of pure oxides and to suppress their disadvantages. Mixed oxides can be grown on valve metals alloys by anodizing, a simple and low cost electrochemical process for pr…

Fabrication and characterization of micrometer-scale ZnO memristors

Memristors are an interesting class of resistive random access memory (RRAM) based on the electrical switching of metal oxide film resistivity . They are characterized for exhibiting resistive switching between a high-resistance state (HRS) and a low-resistance state (LRS) and have been recently considered as one of the most promising candidates for next-generation nonvolatile memory devices because of their low power consumption, fast switching operation, nondestructive readout, and remarkable scalability. The device structure is simply an oxide layer sandwiched between two metal electrodes. The switching behaviour is dependent both on the oxide material and the choice of metal electrodes.…

Cs0.86(NH41.14SO4Te(OH)6 in porous anodic alumina for micro fuel cell applications.

Abstract Cs0.86(NH4)1.14SO4Te(OH)6 supported by anodic alumina membranes (AAMs) has been characterized for the first time in H2/O2 fuel cell. The fabricated membrane electrode assemblies are able to produce peak power densities in the range 15–30 mW cm−2 under mild conditions (room temperature, low humidity and low Pt loading) and show an increased durability with cycling with respect to previous results obtained with AAM-based fuel cell. The physico-chemical characterization of the electrolytes has been carried out through X-ray diffractometry, scanning electron microscopy and micro-raman analysis. An estimation of the composite membranes conductance under fuel cell operation has been carr…

Phosphomolybdic Acid and Mixed Phosphotungstic/Phosphomolybdic Acid Chitosan Membranes for H2/O2 Fuel Cells

Proton exchange membrane fuel cells (PEMFCs) have received much attention in recent years because of their high power density, efficiency and zero-environmental pollution. As one of the key components in fuel cells, the proton exchange membrane is expected to have high proton conductivity and good electrochemical stability. In the attempt to promote PEMCFs commercialization, high cost of fuel cell systems and short lifecycle are the two main issues that need to be addressed, thus large research effort has been devoted in developing new polymer electrolytes that can replace the usually employed proton conductors, e.g. Nafion®, with other membranes of comparable performances but lower cost. A…

Tuning of the optical and dielectric properties of anodic film on sputtered deposited Ta-Nb alloys

Photocurrent Spectroscopy in Corrosion and Passivity Studies. A Critical Assessment

Photocurrent Spectroscopy (PCS) is currently employed for the characterization of solid-state properties of semiconducting and insulating materials, since the knowledge of their band gap is a prerequisite to any possible application in different fields such as: solar energy conversion (photoelectrochemical and photovoltaic solar cells, photocatalysis) and microelectronics (high-k, high band-gap materials) (1-2). In the last 20-30 years an increasing number of scientists working in the area of corrosion has been attracted by this technique owing to its versatility and ability to scrutinize in situ corrosion layers and passive films having semiconducting or insulating behaviour. In previous w…

Anodic TiO2 in ReRAM: Influence of Si-doping on the Resistive Switching Properties of Titanium Oxide

TiO2 has attracted much attention due to its potential widespread applications, including capacitors, photocatalysis, solar energy conversion and, more recently, redox-based random access memories (ReRAM). For micro and nano-electronics applications, TiO2 is usually grown through Chemical and Physical Vapour Deposition techniques, such as Atomic Layer Deposition (ALD), Pulsed Laser Deposition (PLD), Sputtering and so on. In ReRAM field, the control of oxide structure (crystallinity, defects concentration etc.) and the choice of electrodes are crucial to have resistive switching phenomena inside the oxide. Thus, anodizing can be proposed as a simple and low cost way to grow TiO2 and to tune …

Photoelectrochemical characterization of conversion coatings and passive films formed on mg in different electrolytes

Performance evaluation Anodic Alumina Membranes-based fuel cell: CsH2PO4 pore-filler as proton conductor operating at room temperature

Effect of ammonium hydroxide addition in the anodizing electrolyte on the electronic properties of anodic oxides on Niobium

Electrochemical methods for carrier type identification of ZnO films grown by pulsed laser deposition on InP.

Process for manufacturing a porous body

Preparation and characterization of Porous Anodic Alumina Membranes as templates for the growth of metals and semiconductors nanostructures

Behaviour of Nb2O5/PPy contacts: From Schottky barriers to p-n junctions

In this work, a study of the photoelectrochemical responses of Nb O /PPy contacts fabricated in both organic 2 5 and aqueous solutions is performed. From the comparison between the experimental data of PPy photodeposited on Nb O in organic and in aqueous solutions, it is evident that the medium used for the photodeposition 2 5 influences the absorption coefficient, the band gap and flat band potential values.

The influence of composition on the solid state properties of anodic films on Al-Ta alloys

Microelectronics is very important for almost all kinds of technology evolutions in the past four decades. In this area, the dielectrics science occupies a prominent place in providing the dominant technology in integrated capacitors or gate insulators.

The Influence of Composition in Determining the Solid State Properties of Al Mixed Oxides

Electrochemical Oxidation of Hf-Nb Alloys as a Valuable Route to Prepare Mixed Oxides of Tailored Dielectric Properties

Metal oxides with high dielectric constant are extensively studied in the frame of substituting SiO2 as gate dielectric in nanoelectronic devices. Here, high-k mixed HfO2/Nb2O5 oxides are prepared by a facile electrochemical route starting from sputtering-deposited Hf–Nb alloys with several compositions. Transmission electron microscopy, grazing incidence X-ray diffraction, and glow discharge optical emission spectroscopy are employed to study the oxide structures, disclosing a crystalline–amorphous transition of the electrochemically prepared oxides by increasing the Nb content. Photo-electrochemical measurements allow the observation of optical transitions ascribed to localized states ins…

A Chemical Approach to the Modelling of Band Gap of Passive Films for Corrosion Studies

Photocurrent Spectroscopy (PCS) has gained a large consideration in the last decades as in situ technique for the characterization of semiconductors and photoconducting passive film/electrolyte junctions being able to provide information on the location of characteristic energy levels like: flat band potential (Ufb), internal photoemission threshold (Eth) and band gap value (Eg)

Composite Porous Alumina/CsH2PO4 membranes for H2/O2 room temperature fuel cell

Mott-Schottky analysis of differential capacitance data of passive-film electrolyte junctions. Is it really providing correct physical insights on the electronic properties of passive films and corrosion layers?

Photoelectrochemical evidence of inhomogeneous composition at nm length scale of anodic films on valve metals alloys

Abstract Anodic films of different thickness (∼30 nm and 70 nm) were grown by anodizing sputtering-deposited Ta-19at% Al to different formation voltages. N incorporation into the anodic films was inducing by performing the anodizing process in ammonium containing solutions. Layered anodic films were prepared by a double formation procedure with a first anodizing step in ammonium biborate solution and second anodizing step in borate buffer solution, or vice versa. Glow Discharge Optical Emission Spectroscopy was employed to show the distribution of N across the oxide. Photoelectrochemical measurements evidenced a red shift of the light absorption threshold due to N incorporation. A model was…

Amorphous to Crystalline Transition in Anodic Oxide on Ti and Ti-Si alloys: A Photoelectrochemical Study.

Electrochemical fabrication of amorphous TiO2/Poly-3,4 Ethylenedioxythiophene (PEDOT) hybrid structures for electronic devices.

Influence of post formation proceses on electrochemical and photoelectrochemical behaviour of TiO2 nanotubes

Template-assisted electrodeposition of cerium oxy-hydroxide nanostructures in aqueous and organic electrolytes

Photoelectrochemical Characterization of Polypyrrole Electrodeposited in Aqueous and Non-Aqueous Solutions

Growth and Characterization of Anodic Films on Al-Nb Alloys

Physico -chemical Characterization of Conversion Layers on Magnesium

Electrochemical fabrication of Cu2O/TiO2 nanotubes junctions with visible light photoactivity

Electrochemical Materials Science: Challenges and Opportunities

Flamed pyrolysis titanium oxide as functional coating for Al substrate

A Chemical Approach to the Estimate of the Optical Band Gap and Bowing Parameter in Mixed d,d-Metal Oxides

Photoelectrochemical Polymerization of 3-4 Ethylene dioxythiophene on Anodic Niobium- Tantalum Mixed Oxides.

Characterization of the Solid State Properties of Anodic Oxides Grown on Sputter-deposited Al-Nb Alloys.

Semiempirical correlation between the optical band gap of oxides and hydroxides and the electronegativity of their constituents

AbstractOn the basis of new experimental results a previous proposed correlation between the optical band gap of oxides and the difference of electronegativity of their constituents is extended to mixed crystalline and amorphous TiO2-Fe2O3 (d,d-metal oxides) as well as to amorphous passive films grown on Al-Ta, Al-Ti, Al-Nb and Al-W alloys (sp,d-metal oxides). Moreover in analogy with previous results on anhydrous oxides, a correlation is proposed between the optical band gap of hydroxides and the electronegativities of their constituents after substituting the electronegativity of hydroxilic group to that of the oxygen. Like in the case of anhydrous oxides, two different interpolation line…

Dynamic response of thin-film semiconductors to AC voltage perturbations

A theoretical treatment of a Schottky barrier dynamic response is developed on the basis of a general model of a semiconductor with thickness comparable in length to the space charge region width. It is shown that, when the space charge region approaches the metal/semiconductor interface, the electric field at this interface, induced by the charge accumulated on the metal, becomes significant with respect to the electric field induced by the charge accumulated on the semiconductor. Under this condition, the total capacitance of the Schottky barrier becomes independent of the polarization potential and tends to the value ε/L, like in a pure dielectric insulator. The term thin film is intende…

Physico-chemical Characterisation of Polypyrrole Film Grown in Aqueous and Non-aqueous Solution on Different Substrates

Porous Anodic Alumina proton conductors composites for H2/O2 thin film fuel cell

Electrodeposition of supported gadolinium-doped ceria solid solution nanowires

Gadolinium-ceria solid solution nanowires with tunable composition have been prepared through template cathodic electrodeposition from solutions containing Ce 3+Gd 3+ in a variable ratio. The employed template is Porous Anodic Alumina because it can function as thermal resistant separator supporting the nanowires if used as ionic conductor in Solid Oxide Fuel Cell (SOFC). Scanning Electron Microscopy of the deposited nanostructures revealed that the use of ethanol as solvent and metal chloride as electrolyte allowed to prepare continuous, compact and well defined nanowires with morphological features stable even after thermal treatment. EDX compositional analysis confirms the presence of bo…

Characterization of Anodic Oxides on Magnetron Sputtered Ta-Nb Alloys by Photocurrent Spectroscopy and Differential Admittance Measurements

Photoelectrochemical and XPS Characterization of Passive films Grown on 316L Stainless Steel in High Temperature Water

One of the major materials challenge for continued safe, reliable and cost-effective utilization of watercooled nuclear reactors for electricity production is development of improved understanding of the synergistic fundamental mechanisms responsible for corrosion and stress corrosion cracking degradation of austenitic steels and nickel base alloys

A Generalized Semiempirical Approach to the Modeling of the Optical Band Gap of Ternary Al-(Ga, Nb, Ta, W) Oxides Containing Different Alumina Polymorphs

A generalization of the modeling equation of optical band gap values for ternary oxides, as a function of cationic ratio composition, is carried out based on the semiempirical correlation between the differences in the electronegativity of oxygen and the average cationic electronegativity proposed some years ago. In this work, a novel approach is suggested to account for the differences in the band gap values of the different polymorphs of binary oxides as well as for ternary oxides existing in different crystalline structures. A preliminary test on the validity of the proposed modeling equations has been carried out by using the numerous experimental data pertaining to alumina and gallia p…

Chitosan-heteropolyacid complex as high performance membranes for low temperature H2-O2 fuel cell

Electrodeposition and characterization of 1-D cerium based nanostructures

A semiempirical approach to the estimate of optical band gap in group-III nitrides alloys

Tuning of Solid-sate Properties of Al Mixed Oxides Grown on Sputter-deposited Al Alloys.

AMORPHOUS SEMICONDUCTOR-ELECTROLYTE JUNCTION. A NEW INTERPRETATION OF THE IMPEDANCE DATA OF AMORPHOUS SEMICONDUCTING FILMS ON METALS.

On the basis of the theory of amorphous semiconductor Schottky barrier an equivalent electrical circuit of the amorphous oxide film/electrolyte interface is proposed.—The analytical expressions for the equivalent conductance and capacitance of the barrier are reported in the hypothesis of a constant density of states within the mobility gap.—According to this model, the semiconducting properties and the impedance behaviour at different frequencies of anodic oxide films on Niobium are interpreted by taking into account the amorphous nature of the films.—An explanation for the anomalous behaviour of the Mott-Schottky plots usually observed with amorphous anodic oxide films is presented.—The p…

A critical analysis of the theory of amorphous semiconductor Schottky barrier for oxides

Advances in Anodic Alumina Membranes-based fuel cell: CsH2PO4 pore-filler as proton conductor at room temperature

Abstract Anodic alumina membranes (AAM) filled with cesium hydrogen phosphate proton conductor have been tested as inorganic composite electrolyte for hydrogen–oxygen thin film (≤50 μm) fuel cell (TFFC) working at low temperatures (25 °C), low humidity ( T gas  = 25 °C) and low Pt loading (1 mg cm −2 ). Single module TFFC delivering a peak power of around 15–27 mW cm −2 , with open circuit voltage (OCV) of about 0.9 V and short circuit current density in the range 80–160 mA cm −2 have been fabricated. At variance with pure solid acid electrolytes showing reproducibility problems due to the scarce mechanical resistance, the presence of porous alumina support allowed to replicate similar fuel…

Recent advance in Anodic Alumina Membranes-based fuel cell: CsH2PO4 pore-filler as proton conductor operating at room temperature

Heteropolyacids - Chitosan Membranes for H2/O2 Low Temperature Fuel Cells

Proton exchange membrane fuel cells (PEMFCs) have received much attention in recent years because of their high power density, efficiency and zero-environmental pollution. As one of the key components in fuel cells, the proton exchange membrane is expected to have high proton conductivity and good electrochemical stability. In the attempt to promote PEMCFs commercialization, high cost of fuel cell systems and short lifecycle are the two main issues that need to be addressed, thus large research effort has been devoted in developing new polymer electrolytes that can replace the usually employed proton conductors, e.g. Nafion®, with other membranes of comparable performances but lower cost. A…

A Critical Analysis on the Use of Mott-Schottky Plots to Characterise the Passive Film/Electrolyte Junction

Spettroscopia di fotocorrente e ammettenza differenziale per lo studio delle proprietà elettroniche e di stato solido di film passivi e ossidi anodici di interesse tecnologico.

Electrochemical Fabrication of High K Niobium-Tantalum Mixed Oxides/Poly 3-4 Ethylene Dioxythiophene Junctions.

Anodizing Science and Technology: achievements and perspectives. A personal view

Characterization of Initial Films and Passivating Layers Grown on Magnesium Metal in Alkaline Solution

Electrosynthesis of Ce–Co Mixed Oxide Nanotubes with High Aspect Ratio and Tunable Composition

Cerium oxide and cobalt oxides have attracted the interest of several researchers due to their potential application in several technological fields electrochromism, lithium batteries, catalysis, etc.. Ceria has been used as a promoter in the so-called “three-way catalyst” for the control of toxic emission from automobile exhaust. The promotion consists of the enhancement of the noble metal dispersion, as well as stabilization of the supporting medium toward thermal sintering. 1,2 A direct catalytic effect of CeO2 in chemical processes such as water–gas shift reaction or NOx decomposition has been also evidenced. 3,4

Multiscale Approach in Studying the Influence of Annealing Conditions on Conductivity of TiO2 Nanotubes

Titanium oxide nanotubes (NTs) have attracted much attention during last decade due to their special characteristics such as one-dimensional highly ordered geometry with large surface area and good chemical and optical stability.

Modeling of differential admittance behaviour of thin amorphous semiconducting film

The understanding of the electronic properties of thin oxide film is an important step toward the understanding of the mechanisms of film dissolution and breakdown as well as for their application in the field of electrolytic capacitors and solar energy conversion. From this point of view the correct location of the characteristic energy levels (flat band potential, Ufb, and conduction (valence) band edge EC (EV)), of a passive film/electrolyte junction is the preliminary task for a deeper understanding of the mechanism of charge transfer at oxide/electrolyte interface. At this aim the most frequently employed method to locate such characteristic energy levels of semiconductor oxide/electro…

Characterization of Thin Passive Film-Electrolyte Junctions.The Amorphous Semiconductor (a-SC) Schottky Barrier Approach

The knowledge of the solid-state properties of passive film is a preliminary task for a full understanding of the electron and ion transfer processes at the metal/oxide and oxide/electrolyte interface. Both processes are of paramount importance in determining the mechanism of film growth and dissolution as well as in determining the nature of the breakdown during the growth of anodic oxide films or the onset of generalized or localized corrosion process (1-2). With very few exceptions, it is a common belief, that most of anodic oxide films, grown on metals and alloys in aqueous solutions, display a semiconducting or insulating behaviour. It is also very well known that in many cases the ini…

Effect of Composition on the Photoelectrochemical Behaviour of Anodic Oxides grown on Aluminium Alloys

Photoelectrochemical evidence of inhomogeneous composition at nm length scale of anodic films on valve metals alloys

Anodic films of different thickness (∼30 nm and 70 nm) were grown by anodizing sputtering-deposited Ta-19at% Al to different formation voltages. N incorporation into the anodic films was inducing by performing the anodizing process in ammonium containing solutions. Layered anodic films were prepared by a double formation procedure with a first anodizing step in ammonium biborate solution and second anodizing step in borate buffer solution, or vice versa. Glow Discharge Optical Emission Spectroscopy was employed to show the distribution of N across the oxide. Photoelectrochemical measurements evidenced a red shift of the light absorption threshold due to N incorporation. A model was proposed…

Cerium oxyhydroxide nanowire growth via electrogeneration of base in nonaqueous electrolytes

The preparation of compact cerium oxyhydroxide nanowires into anodic alumina membranes from cerium chloride in ethanol solution via electrogeneration of base is reported. Scanning electron microscopy analyses indicate that dense, well-aligned, and highly ordered nanowires can be formed in a wide range of applied potentials and current densities in alcoholic solution. The employment of water brings to a hybrid nanotube/nanowire structure, suggesting a key role of the electrolyte nature in determining the morphology of the deposit. Electrochemical findings and X-ray diffraction analysis have shown that nanowires are constituted by a Ce(III)/Ce(IV) oxyhydroxide that can be completely oxidized …

Microporous alumina membranes electrochemically grown

Abstract The electrochemical fabrication of alumina membranes by anodizing of aluminium in phosphoric acid and oxalic acid solutions, in the temperature interval from −1 to 16 °C, was investigated in order to study the influence of different parameters (initial treatment of aluminium surface, nature and composition of electrolyte, temperature) on the final characteristics of the membranes. Porous layers were grown using a linear potential scan at 0.2 V s −1 up to 160 V in H 3 PO 4 solution and 70 V in oxalic acid solution. The efficiency of porous layer formation was calculated by using Faraday's law and weight measurements. Pore size distribution and porosity of membranes prepared in 0.4 M…

Tuning of solid state properties of Al-Ta mixed oxides

Amorphous semiconductor-electrolyte junctions. Photoelectrochemical behaviour of thin Nb2O5anodic films

An approach to the study of the photocharacteristics of amorphous semiconductor/electrolyte junctions is proposed which takes into account the main differences in the electronic structure and the transport properties of the amorphous semiconductors (a-SC) with respect to the crystalline counterparts. The influence of the wavelength of the incident light on the photocurrent vs electrode potential curves is explained on the basis of the geminate recombination theory in a-SC. The implications of the model are shortly discussed.

Tailoring of the solid state properties of Al-Nb mixed oxides: A photoelectrochemical study

Al-Nb containing mixed oxides were grown by anodizing sputter-deposited Al-Nb alloys of different compositions. A photoelectrochemical investigation was carried out in order to estimate the band gap, flat band potential, and conductivity type of these oxides as a function of their composition. The dependence of the band gap on the composition of mixed sp-d metal oxides has been rationalized by using a semiempirical correlation between the difference of electronegativity and band gap of oxides proposed in the literature some years ago and recently tested for regular d-d metal mixed oxides. The band gap increase observed as a function of Al content into the oxides seems mainly depending on th…

Photoelectrochemical Polymerization of 3-4 Ethylenedioxythiophene on High k Niobium-Tantalum Mixed Oxides.

Physico-chemical Properties of Anodic Oxide Films: from Passivity to Electronics

Anodized Ti-Si Alloy as Gate Oxide of Electrochemically-Fabricated Organic Field-Effect Transistors

Organic field-effect transistors were fabricated using an electrochemical route. The dielectric oxide was grown by anodization of a Ti:Si alloy, while 3,4-polyethylenedioxythiophene has been employed as a semiconducting polymer. OutputI-Vcharacteristics showed a transistor effect dependent on dielectric thickness. Fitting between I-V measurements and theoretical simulations in the triode region confirmed the presence of a conduction path through the polymer which degrades the electrical characteristics of the devices.

Physicochemical Characterization of anodic film on Titanium prepared by Pedeferri’s Treatment.

One-step electrochemical synthesis and physico-chemical characterization of CdSe nanotubes

Abstract Stoichiometric CdSe nanotubes (NTs) with a length of ∼700 nm have been successfully grown by one-step electrochemical technique into anodic alumina membranes. Cyclovoltammetric method has been performed using porous anodic alumina as template electrode and an electrochemical bath containing Cd 2+ ions and SeO 2 . The as-prepared NTs have been identified as face-centred-cubic CdSe by XRD, while micro-Raman analysis reveals the typical peaks of nanostructured CdSe. The stoichiometric deposition of CdSe NTs formation is suggested by EDX analysis, with an average atomic percentage of Cd:Se of ∼0.93. Photoelectrochemical measurements reveal that CdSe NTs are photoactive materials with d…

Electrochemical Tantalum Oxide for Resistive Switching Memories

Redox-based resistive switching memories (ReRAMs) are strongest candidates for the next-generation nonvolatile memories fulfilling the criteria for fast, energy efficient, and scalable green IT. These types of devices can also be used for selector elements, alternative logic circuits and computing, and memristive and neuromorphic operations. ReRAMs are composed of metal/solid electrolyte/metal junctions in which the solid electrolyte is typically a metal oxide or multilayer oxides structures. Here, this study offers an effective and cheap electrochemical approach to fabricate Ta/Ta2O5-based devices by anodizing. This method allows to grow high-quality and dense oxide thin films onto a metal…

Formation and photo-electrochemical characterization of anodic films on different valve-metal alloys

Hybrid organic-inorganic membranes for low temperature H2-O2 fuel cell

The influence of electrolyte composition on the solid state properties of anodic films on Ta-Nb alloys

Effect of Incorporation of Foreign Species on the Solid State Properties of Anodic Films on Ti

Photoelectrochemical Synthesis of Conducting Polymers on Large Band Gap Nb2O5 and Ta2O5 Anodic Oxide Films

Physico-chemical Characterization of Aluminium Oxide Films Grown on Etched Foils for Electrolytic Capacitors

A phenomenological approach to the mechanical breakdown of anodic oxide films on zirconium

Abstract A phenomenological theory of the mechanical breakdown of films growing on valve metals during galvanostatic oxidation is presented and discussed in detail for ZrO2 anodic films. It is shown that the mechanical breakdown voltage, Vmb, can be linearly related to the logarithm of the anodizing current density both in the case of constant and variable critical thickness, Lc, at which the breakdown occurs. It is also shown that the Amb and Bmb parameters of the relationship: Vmb = Amb + Bmb log i are strictly related to the kinetic parameters of growth of the films in the different solutions. The expressions of Amb and Bmb parameters are derived for films grown in the presence as well a…

Photoelectrochemical Synthesis of Conducting Polymers Layers on Large Band Gap Nb2O5 and Ta2O5 Anodic Oxides Films

Photoelectrochemical evidence of Nitrogen Incorporation during Anodizing of Sputtering-Deposited Al-Ta alloys

Anodic films were grown to 20 V on sputtering-deposited Al–Ta alloys in ammonium biborate and borate buffer solutions. According to glow discharge optical emission spectroscopy, anodizing in ammonium containing solution leads to the formation of N containing anodic layers. Impedance measurements did not evidence significant differences between the dielectric properties of the anodic films as a function of the anodizing electrolyte. Photoelectrochemical investigation allowed evidencing that N incorporation induces a red-shift in the light absorption threshold of the films due to the formation of allowed localized states inside their mobility gap. The estimated Fowler threshold for the intern…

An Electrochemical Investigation on the Adhesion of As-Formed Anodic TiO2 Nanotubes Grown in Organic Solvents

A photoelectrochemical characterization of passive films on stainless steels

Abstract Passive films on stainless steels for sea water service have been studied by means of photocurrent measurements. Four experimental ELI (Extra Low Interstitital) ferritic stainless steels (types 25Cr-4Ni-4Mo) and a commercial superaustenitic stainless steel (type 20Cr-18Ni-6Mo-N) have been investigated. Differences in the photoelectrochemical behaviour have been attributed to the different nature of the passive films grown on ferritic or superaustenitic stainless steels. An interpretation is provided to explain the complex dependence of the photocurrent transients on the applied potential. Manuscript received 27 February 1986; in amended form 19 June 1986.

Synthesis and characterization of zinc hydroxystannate films

Growth and field crystallization of anodic films on Ta–Nb alloys

The growth behavior of amorphous anodic films on Ta–Nb solid solution alloys has been investigated over a wide composition range at a constant current density of 50 Am−2 in 0.1 mol dm−3 ammonium pentaborate electrolyte. The anodic films consist of two layers, comprising a thin outer Nb2O5 layer and an inner layer consisting of units of Ta2O5 and Nb2O5. The outer Nb2O5 layer is formed as a consequence of the faster outward migration of Nb5+ ions, compared with Ta5+ ions, during film growth under the high electric field. Their relative migration rates are independent of the alloy composition. The formation ratio, density, and capacitance of the films show a linear relation to the alloy compos…

Physicochemical Characterization of Passive Films and Corrosion Layers by Differential Admittance and Photocurrent Spectroscopy

Two different electrochemical techniques, differential admittance and photocurrent spectroscopy, for the characterization of electronic and solid state properties of passive films and corrosion layers are described and critically evaluated. In order to get information on the electronic properties of passive film and corrosion layers as well as the necessary information to locate the characteristic energy levels of the passive film/electrolyte junction like: flat band potential (Ufb), conduction band edge (EC) or valence band edge (EV), a wide use of Mott-Schottky plots is usually reported in corrosion science and passivity studies. It has been shown, in several papers, that the use of simpl…

Characterization of Anodic Oxides on Titanium by Photocurrent and Differential Admittance Techniques

Photo-Electrochemical deposition of Poly-3,4 Ethylenedioxythiophene on Anodic Films on Ti-Si Alloys.

Pulsed laser deposition of ZnO and VO2 films for memristor fabrication

Memristors are resistive switching memory devices which have attracted much attention over the last years for high-density memory applications because of their simple structure, small cell size, high speed, low power consumption, potential for 3-D stacking and excellent compatibility with the complementary metal-oxide-semiconductor (CMOS) technology [1]. Beside nonvolatile memory applications, memristors have been also proposed for other different applications including biosensors [2] and neuromorphic [3] circuits. The device structure is simply an oxide material sandwiched between two metal electrodes. The switching behavior is not only dependent on the oxide material but also on the choic…

Anodic Alumina Membranes for Fuel Cell Technology and Nanostructure Template-assisted Deposition

Anodic alumina membranes (AAMs) with ordered porous structure have been investigated as possible ionic conducting membranes for thin film (= 50μm) fuel cells (TFFC) and as templates for the production of a variety of nanostructure arrays. The aims of this work are to present some of our recent results pertaining to the functionalisation of AAM with proton conductors for the production of membranes to be used in hydrogen/oxygen TFFC, at low or intermediate temperature (25°C ≦ T ≦ 250°C), and to the fabrication by template technique of nanowires/nanotubes arrays of oxide and hydroxides for possible future technological application.

Verfahren zur Herstellung einer porosen Membran aus Aluminiumoxide fur Brennstoffzellen

From CeO2 Nanotubes to Nanowires through Electrogeneration of Base

Abstract not Available.

Growth and characterization of anodic films on Sc in aqueous solutions

Size-confinement of CsH2PO4 in anodic alumina membranes for thin film electrolyte solid acid fuel cell

Structural and Photocurrent Characterization of Anodic Oxides on Titanium

Room temperature electrodeposition of photoactive Cd(OH)2 nanowires

Improvements in H2/O2 thin film fuel cell working with Porous Anodic Alumina-supported electrolytes

Characterization of the Solid State Properties of Anodic Oxides on Ta-Nb Alloys as a Function of the Anodizing Conditions

Tantalum oxide, niobium oxide and Ta-Nb containing mixed oxides were grown by anodizing sputter-deposited TaxNb(1-x) alloys with 0 ≤ x ≤ 1. A photoelectrochemical investigation was performed in order to estimate the band gap values of the oxides as a function of their composition as well as to estimate their flat band potential. Differential capacitance curves were recorded for all the investigated oxides in a wide range of electrode potential and for several frequencies of the alternative signal. The dependence of C on the applied potential and a.c. frequency was interpreted on the basis of amorphous semiconductor Schottky barrier, and allowed to estimate the dielectric constant of the inv…

Anodic Alumina Membranes for Fuel Cell Technology and Nanostructure Template -assisted Deposition

Characterization of Thin Passive Film-Electrolyte Junctions. The Amorphous Semiconductor (a-SC) Schottky Barrier Approach.

A detailed study of the electronic properties of thin (< 20 nm) anodic TiO2 potentiostatically grown on titanium in two different solutions is presented. The results show that the nature of the anodizing solution affects the electronic properties of the anodic film and in particular the density of electronic state (DOS) distribution. Different DOS were derived from the experimental data analyzed according to the theory of amorphous semiconductor (a-SC) Schottky barrier. It is shown that the usual non-linear and frequency dependent Mott-Schottky plots are in agreement with expected theoretical behaviour of a-SC Schottky barrier. It is shown the importance of the DOS distribution in determini…

Optimization of anodizing process of tantalum for Ta2O5-based capacitors

Anodic oxides were grown to 50 V on Ta in several organic ions containing anodizing baths. Their properties were compared with anodic Ta oxide film grown to the same formation voltage in 0.1 M NaOH. Anodizing process carried out in sodium citrate led to the growth of the anodic oxide with the best blocking properties whilst, when Ta is anodized in sodium adipate, a significant part of the circulated charge is wasted in side reactions, such as oxygen evolution. Photoelectrochemical measurements showed the presence of optical transitions at energy lower than the band gap for the anodic films grown in citrate and tartrate electrolytes, attributed to localized electronic states located close to…

Influence of film thickness and amorphous nature on the differential capacitance measurements of a-Nb2O5/electrolyte junction