Synthesis and characterization of biocompatible stimuli-responsive hydrogels

Nanostructures of Lanthanide Oxy/Hydroxides Obtained by Metal Displacement Deposition

PVA-based acidic hydrogel electrolyte

Study of a Novel Electrochemical Method for Copper Recovery from Waste Printed Circuit Boards

This study was carried out to recover copper from printed circuit boards of waste computers through an electrochemical process. To simplify the overall recovery process, large pieces of printed circuit boards were used instead of pulverized samples. In particular, these large pieces were directly used as an anode for copper electrorefining. For this purpose, electronic components and solder mask were initially removed from the boards. The electronic components can be treated separately to recover precious metals using various methods. The removal of solder mask was necessary to expose copper layers to the electrolytic solution and it was removed by a chemical treatment with sodium hydroxide…

Fabrication of Nanostructured Ni and Ni-Pd electrodes for wateralkaline electrolyzer

In the last years many attention has been dedicated to the increase of performance of Nichel based electrodes to use in water-alkaline electrolyzes. In our preliminary work we have shown that alkaline electrolyzer made with Ni nanowires covered with IrO2 (side oxygen evolution) nanoparticles and a Ni sheet (side hydrogen evolution) have very good and stable performance also at room temperature [1]. In this work, to obtain a complete nanostructured electrolyzer, the attention was focused on the fabrication of electrodes for hydrogen evolution. In particular, by metal displacement deposition we have grown on Ni nanowires electrodes, nanoparticles of Pd with the aim to enhance the electrocatal…

ELECTROCHEMICAL PREPARATION OF CERIUM OXIDE NANOSTRUCTURES

Growth and photoelectrochemical behavior of electrodeposited ZnO thin films for solar cells

Electrodeposition and Photo-electrochemical behaviour of CIGS Thin Films and Nanowires arrays for Solar Cell

Nanostructures Fabrication by Template Deposition in Anodic Alumina Membranes

Photoelectrochemistry in corrosion studies: achievements and perspectives

Elettrodeposizione di leghe nanostrutturate a base di stagno

Naporous alumina membranes grown electrochemically: fabrication and modification by metal deposition

Co-Deposition and Characterization of Hydroxyapatite-Chitosan and Hydroxyapatite-Polyvinylacetate Coatings on 304 SS for Biomedical Devices

During the last decades, biomaterials have been deeply studied to perform and improve coatings for biomedical devices. Metallic materials, especially in the orthopedic field, represent the most common material used for different type of devices thanks to their good mechanical properties. Nevertheless, low/medium resistance to corrosion and low osteointegration ability characterizes these materials. To overcome these problems, the use of biocoatings on metals substrate is largely diffused. In fact, biocoatings have a key role to confer biocompatibility properties, to inhibit corrosion and thus improve the lifetime of implanted devices. In this work, the attention was focused on Hydroxyapatit…

Electrically conductive polyaniline-hydrogel composites, produced via “in situ” dispersion polymerization

Calcium phosphate/polyvinyl acetate coatings on SS304 via galvanic co-deposition for orthopedic implant applications

Abstract In this work, the galvanic deposition method is used to deposit coatings of brushite/hydroxyapatite/polyvinyl acetate on 304 stainless steel. Coatings are obtained at different temperatures and with different sacrificial anodes, consisting of a mixture of brushite and hydroxyapatite. Samples are aged in a simulated body fluid (SBF), where a complete conversion of brushite into hydroxyapatite with a simultaneous change in morphology and wettability occurred. The corrosion tests show that, compared with bare 304, the coating shifts Ecorr to anodic values and reduces icorr Ecorr, and icorr has different values at different aging times due to chemical interactions at the solid/liquid i…

Preparation of Pd coated anodic alumina membranes for gas separation media

Different procedures of Pd electroless deposition onto anodic alumina membranes were investigated to form a dense metal layer covering pores. The main difficulty was related to the amorphous nature of anodic alumina membranes, determining low chemical stability in solutions at pH > 9, where Pd plating works more efficiently. As a consequence, it was necessary to find the operative conditions allowing Pd deposition without damaging the membrane: to reduce alumina dissolution, the plating bath was buffered at pH 8.5 by addition of either NaHCO 3 or Na 2 B 4 O 7 ·H 2 O. Acceptable conversion of Pd was found after a deposition time of 3 min. Single and multiple deposition steps (each lasting 3 …

Electrodeposition and Caracterization of Nanostructured Ni and Ni-IrO2

Characterization of Sn-Co nanowires grown into alumina template

Nanowires of Sn-Co alloys were grown inside the channels of anodic alumina membrane by potentiostatic deposition. The scanning electron microscope images showed the formation of cylindrical nanowires whose height was increasing with deposition time. The X-ray patterns did not show significant diffraction peaks, suggesting the formation of amorphous phases. The higher content of Co in the nanowires, in comparison to the initial composition of the electrolytic bath, was attributed to a higher rate of Co electrodeposition. These nanowires seem to possess specific features suitable for innovative application in the field of Li-ion batteries due to their dimensional stability and high specific s…

ELECTROCHEMICAL H2O2 SENSORS BASED ON Pd and Cu NANOSTRUCUTERS

In the last decades, with the fast improvement of electronics, the field of sensors is highly expanding. The basic idea of sensors is to detect something and then trigger a corresponding action. This simple, but very important, concept can be used in different fields: from chemical industries to farms, from the environmental monitoring [1] to a point of care analysis [2]. Currently, talking about sensing of chemical species, different techniques are used, such as Atomic Absorption Spectroscopy (AAS), Graphite Furnace Atomic Absorption Spectroscopy (GFAAS), Inductively Coupled Plasma Mass Spectroscopy (ICP-MS), IR spectroscopy, redox titration and so on. Despite they are highly efficient in …

Electrodeposition and ILGAR process to obtain Ni-In2S3 core-shell nanowires

NANOSTRUCTURED ANODE MATERIAL FOR Li-ION BATTERY OBTAINED BY GALVANIC PROCESS

The accumulation of energy by batteries plays a fundamental role for the production of electrical energy and for its efficient management. Between different storage systems the lithium-ion battery are considered very interesting. Although they are now a well-established commercial reality, they are still subject of vigorous research efforts, in order to make improvements primarily in terms of costs, safety and energy density. The latter is in fact still low compared to that of fossil fuels, if you think to the automotive field. In particular efforts are focused towards the identification of valid alternatives to the electrode materials so as to overcome the limitations and extend the use of…

Template electrosynthesis of aligned Cu2O nanowires Part I. Fabrication and characterization

Large arrays of aligned copper oxide nanowires were produced by electrodeposition, using anodic alumina membranes as template. We have studied the effect of two fundamental parameters involved in fabrication process: potential perturbation and bath composition. Performing electrodeposition from a copper acetate/sodium acetate bath (pH 6.5), we found that chemical composition of nanowires varied in dependence on the shape of the applied potential perturbation: pure copper oxide nanowires were produced by pulsed potential, whilst continuous electrodeposition resulted in a co-deposition of Cu and Cu2O. In a copper lactate bath, buffered at pH 10, the shape of perturbation did not influence the…

Photocurrent spectroscopy of thin passive films

Publisher Summary This chapter reviews theoretical background on the photoelectrochemistry of metal and semiconductor electrodes on which photocurrent spectroscopy (PCS) relies, by focusing particularly on new features that are typical of the photoelectrochemical behavior of thin passive films and usually absent in the behavior of bulk crystalline semiconductors. The chapter also highlights the advantages of PCS in getting in situ information on the structure of the metal-passive-film-electrolyte systems and shows a more recent quantitative use of this technique in characterizing the composition of passive films. The formation of a protective film on a metallic surface is a key step in esta…

Investigation of electrodeposited ZnO thin films as transparent conducting oxide for application in CIGS-based solar cells

Synthesis and characterization of nanostructured materials applied to energy devices

Amorphous semiconductor—electrolyte junction. Energetics at the a-WO3—electrolyte junction

In order to elucidate the influence of thickness and amorphous structure on the kinetics of electron exchange with redox couples in solution, a critical re-examination of the energetics at the amorphous anodic WO3 films (a-WO3)—electrolyte junction has been performed, based on a recent theory of amorphous semiconductor (a-SC) Schottky barrier. The admittance study of the barrier performed in a large interval of electrode potential at changing frequency and film thickness allowed the determination of the energy levels as well as the distribution of localized electronic states within the mobility gap of the films. The new energetic picture derived is able to explain some features of the kinet…

Influence of the crystallization process on the photoelectrochemical behaviour of anodic TiO2 films

On the basis of kinetic and photoelectrochemical studies we show that the formation of amorphous or strongly disordered TiO2 films on electropolished titanium rods can occur upon anodization in 0.5 M H2SO4 solution in a range of thickness which depends on the anodization rate. This finding is confirmed both by the changes in the shape of the photocurrent vs. potential curves with the energy of the incident photons, and by the impedance behaviour of the junction. Our data indicate that TiO2 films having different degree of disorder are formed depending on the anodization rate and oxide thickness. Crystalline films are formed at very low growth rates since very low thicknesses. Amorphous or s…

Deposition of very thin uniform indium sulfide layers over metallic nano-rods by the Spray-Ion Layer Gas Reaction method

Abstract Very thin and uniform layers of indium sulfide were deposited on nickel nano-rods using the sequential and cyclical Spray-ILGAR® (Ion Layer Gas Reaction) technique. Substrates were fabricated by electrodeposition of Ni within the pores of polycarbonate membranes and subsequent chemical dissolution of the template. With respect to the depositions on flat substrates, experimental conditions were modified and optimized for the present geometry. Our results show that nano-rods up to a length of 10 μm were covered uniformly along their full length and with an almost constant film growth rate, thus allowing a good control of the coating thickness; the effect of the deposition temperature…

Synthesis and Characterization of Nanostructured Electrodes for Innovative Lead Acid Batteries

In vitro corrosion and biocompatibility of brushite/hydroxyapatite coatings obtained by galvanic deposition on 316LSS

Corrosion behavior and cytotoxicity was reported for mixed brushite (BS)/hydroxyapatite (HA) coatings deposited on 316LSS substrate through a displacement reaction. Corrosion tests, carried out in a simulated body fluid, showed that in comparison with bare 316L, coating shifts Ecorrto anodic values and reduces icorreven if oscillations were observed, which were explained in terms of the chemical interactions at the solid/liquid interface. Cell biocompatibility of the coating was investigated through osteoblastic cell line MC3T3-E1, evidencing the absence of any cytotoxicity Taken together, the results show that galvanic deposition is a simple and cost-effective method for producing bioactiv…

Electrochemical Fabrication of Sn-Co Nanowires in Anodic Alumina Templates

Electrochemical deposition of CZTS thin films on flexible substrate

Solar cells based on semiconductor thin films are emerging as alternative to silicon;however,the materials giving the highest efficiency,CdTe and CuInGaSe,contain toxic (Cd) and rare (In) elements.In this field,the challenge is to substitute In and Cd with abundant and non-toxic elements without lowering the high efficiency achieved with these technologies.Compounds based on copper,zinc,tin and sulfur (CZTS) are potentially promising materials,because they present all the above listed features.Among the different methods to obtain CZTS,the electrochemical route appears of great interest because easy to conduct.Up to date,the literature shows that non-uniformity in composition and/or the pre…

ChemInform Abstract: Photoelectrochemical Study of Electrochemically Formed Semiconducting Yttrium Hydride (YH3-x).

Abstract The first photoelectrochemical study of semiconducting YH 3− x films formed by etching bulk Y metal in 0.5 M H 2 SO 4 solution is reported. The formation of semiconducting hydride having an indirect optical band gap, E g opt , of about 2.35 eV is confirmed by in situ photocurrent spectroscopy. The photoelectrochemical behaviour of such a phase was investigated both in alkaline and in acidic solutions. The flat band potential was estimated to be U fb =−1.25 V/NHE, independent of pH.

Controlled solution-based fabrication of perovskite thin films directly on conductive substrate

Abstract Organometallic perovskites are one of the most investigated materials for high-efficiency thin-film devices to convert solar energy and supply energy. In particular, methylammonium lead iodide has been used to realize thin-film perovskite solar cells, achieving an efficiency higher than 20%. Different fabrication procedures based on the spin-coating technique have been proposed, which do not ensure homogenous morphologies. In this work, we present a scalable process to fabricate methylammonium lead iodide thin films directly on conductive substrates, consisting of electrodeposition and two subsequent chemical conversions. A thorough investigation of the morphological, structural an…

NANOWIRES AND THIN FILMS OF CIS/CIGS OBTAINED BY ELECTRODEPOSITION AS ABSORBER FOR SOLAR CELLS

Impedance spectroscopy characterization of functionalized alumina membranes

Abstract Anodic alumina membranes have been impregnated with a protonic conductor either by immersion or by vacuum permeation of a saturated aqueous solution of CsHSO4 for different times. Synthetized salt, obtained through the reaction of cesium carbonate with sulphuric acid (in excess), contained a small quantity of Cs2SO4. Unmodified membranes consist of amorphous Al2O3 with a regular distribution of pores (average diameter: 200 nm) and are stable up to 850 °C. Long impregnation times caused partial dissolution of alumina, with formation of Al(HSO4)3 on the front surfaces as well as into pore walls. From the frequency dispersion of the impedance, the “macroscopic conductivity” of membran…

Processo di produzione di filamenti nanometrici in lega amorfa Sn-Co

The photoelectrochemistry of thin passive layers. Investigation of anodic oxide films on titanium metal

Abstract A photoelectrochemical investigation has been performed on thin TiO2 films grown anodically in 0.5 M H2SO4 solution at high growth rates. The shape of the photocurrent vs. potential curves under monochromatic irradiation (photocharacteristics) depends on the photon energy of the incident light at energies above the optical band gap of the films (3.25 ± 0.05 eV). This finding has been explained by considering the presence of geminate recombination of the photogenerated electron-hole pairs. In order to fit the experimental photocharacteristics, an expression for the photocurrent is proposed which takes into account the low drift range of photocarriers and possible recombination in th…

Porosity of anodic alumina membranes from electrochemical measurements

A procedure based on the high-field mechanism of the growth of anodic oxides was developed in order to evaluate the morphological features of porous layers. Since the thickness of the barrier film, separating the porous layer from the metal, does not change during the steady-state growth of an anodic porous layer, the rate of displacement of the metal-oxide interface to the metal direction must be equal to the rate of displacement of the pore base to the oxide direction. As a consequence, porosity can be expressed in terms of the ratio i diss/i ion, where i diss is the dissolution current density at the pore base, and i ion is the ionic current density at the metal-oxide interface. Pore dia…

Photo-electrochemical investigation of anodic oxide films on cast Ti–Mo alloys. I. Anodic behaviour and effect of alloy composition

Abstract The anodic behaviour of cast Ti–Mo alloys, having different Mo contents (6–20 wt.%), was investigated in acidic and neutral aerated aqueous solutions. All sample showed a valve-metal behaviour, owing to formation and thickening of barrier-type anodic oxides displaying interference colours. Growth kinetics of passive films is influenced by both anodizing electrolyte and composition of the starting alloy. This last parameter was found to change also the solid-state properties of the films, explored by photoelectrochemical and impedance spectroscopy experiments. Thicker films ( U f  = 8 V/MSE) grown on alloys richer in Mo showed more resistive character and a photocurrent sign inversi…

Nanostructures of different oxides/hydroxides grown in nanoporous templates by electrochemical methods.

ChemInform Abstract: A Photocurrent Spectroscopic Study of the Initial Stages of Anodic Oxide Film Formation on Niobium.

Abstract An extensive electrochemical and photoelectrochemical investigation has been carried out with very thin anodic oxide layers grown on niobium metal in sulphuric acid solutions. From the experiments the presence of an initial suboxide layer on the metal surface was inferred. Upon anodic polarization a strongly non-stoichiometric pentoxide film is formed, which is subsequently oxidized to the normal amorphous pentoxide phase (a-Nb 2 O 5 ). The use of photocurrent spectroscopy (PCS) allowed this oxidation process to be followed at various potentials and polarization times. Moreover, from the experimental results we obtain information both on the composition and the solid-state structur…

Compositi elettroattivi costituiti da nanoparticelle di polianilina disperse in polivinilpirrolidone

An electrochemical route towards the fabrication of nanostructured semiconductor solar cells

This work presents our preliminary results regarding an electrochemical process which allows the growth of nanostructured materials by means of nanopore templates. Also we analyze possible applications of this process to fabricate nanostructured semiconductors, such as CIGS, suitable for photovoltaic devices, and we consider the implications from the perspective of characterization techniques and device modelling when using such a technology.

SnCo nanowire array as negative electrode for lithium-ion batteries

Abstract Amorphous SnCo alloy nanowires (NWs) grown inside the channels of polycarbonate membranes by potentiostatic codeposition of the two metals (SnCo- PM ) were tested vs. Li by repeated galvanostatic cycles in ethylene carbonate-dimethylcarbonate – LiPF 6 for use as negative electrode in lithium ion batteries. These SnCo electrodes delivered an almost constant capacity value, near to the theoretical for an atomic ratio Li/Sn of 4.4 over more than 35 lithiation–delithiation cycles at 1 C. SEM images of fresh and cycled electrodes showed that nanowires remain partially intact after repeated lithiation–delithiation cycles; indeed, several wires expanded and became porous. Results of amorp…

Elettrodo al piombo, metodo per la sua realizzazione ed accumulatore comprendente l’elettrodo

High Efficiency Electrodes Based on Nanostructured Materials for Energy Devices

Nanostructured materials for solar cells: electrochemical fabrication and characterization

Photoelectrochemical study of electrochemically formed semiconducting yttrium hydride (YH3−x)

Abstract The first photoelectrochemical study of semiconducting YH 3− x films formed by etching bulk Y metal in 0.5 M H 2 SO 4 solution is reported. The formation of semiconducting hydride having an indirect optical band gap, E g opt , of about 2.35 eV is confirmed by in situ photocurrent spectroscopy. The photoelectrochemical behaviour of such a phase was investigated both in alkaline and in acidic solutions. The flat band potential was estimated to be U fb =−1.25 V/NHE, independent of pH.

Self-ordering of porous alumina by aluminium anodising

Template electrosynthesis of nanostructures for water electrolysis

Chitosan-Coating Deposition via Galvanic Coupling

A galvanic method to deposit chitosan coatings on stainless steel substrate is reported. Deposition of suitable coatings is desired to improve biocompatibility and corrosion resistance of metallic medical devices to be implanted in human body. In the present work, a thin hydrogel layer of chitosan was deposited on 304SS by a galvanic displacement reaction, which is advantageous first as it does not require external power supply. 304SS was immersed into an aqueous solution of chitosan/lactic acid and electrochemically coupled with magnesium acting as a sacrificial anode. SEM images showed the formation of a uniform layer of chitosan with a thickness controlled by deposition time. Corrosion t…

Metodi elettrochimici per la preparazione di nanostrutture in membrane di allumina anodica

ChemInform Abstract: Electrical Breakdown and Pitting in Anodic Films on Tungsten in Halogen Ion-Containing Solutions.

Abstract The systematic investigation of the anodic behaviour of W in halogen ion-containing solutions reveals noticeable differences in the presence of different anions. Strong generalized dissolution is observed in fluoride solutions, the oxide growth being hindered at low anodizing current densities. Sparking phenomena occur in the presence of Br− and I− anions as in nitrate and sulphate solutions. Only in Cl− containing solutions is the growth of the anodic films limited by the occurrence of pitting phenomena at a critical thickness of the oxide. The laws of dependence of the phenomenon on the experimental parameters and the influence of ferrous ions on the voltage at which pitting occu…

Toward Tin-Based High-Capacity Anode for Lithium-Ion Battery

Electrochemical deposition of SnCo alloys inside the nanometric pores of commercial membranes is described. Composition, morphology and crystallographic structure of the synthesized nanostructured alloys are reported as well as the results of electrochemical tests carried out both in half-cell and in full battery configuration to investigate the performance of these SnCo alloys as anodes for lithium-ion batteries. Optimized depositions yielded nanostructured alloys that performed 200 deep galvanostatic cycles at C/2 and 30 °C with 80 % capacity retention and coulombic efficiency higher than 97 % after 40 cycles Moreover, charge-discharge rate capability tests showed the high performance of …

CulnSe2/Zn(S,O,OH) junction on Mo foil by electrochemical and chemical route for photovoltaic applications

Electrodeposition is a convenient technique for the development of low cost materials for photovoltaic (PV) device processing. Using a single step electrodeposition route, several groups have fabricated CIS (CuInSe) and CIGS (CuInGaSe) films [1]. One of the most important requirements for successful application of one-step electrodeposition film formation, is the ability to control composition of the deposited films and to develop polycrystalline microstructures with a low surface roughness and high sintered density. In this preliminary work, CIS films were produced by single bath electrodeposition finding the optimal conditions in order to achieve a dense film with high crystallinity and u…

Amorphous semiconductor—electrolyte junction. Impedance study on the a-Nb2 O5—electrolyte junction

Abstract A systematic study of the impedance behaviour of the anodic niobium oxide film/aqueous electrolyte interface was carried out using the lock-in technique at different signal frequencies. The dependence of both components of the impedance on the electrode potential and on frequency is analysed by taking into account the amorphous nature of the films. The lack of long-range order in these oxide layers modifies the physical picture in respect to the case of single crystal semiconductors. A new equivalent circuit has been assumed, based on recent theory of an amorphous semiconductor Schottky barrier. Such a new approach allows the characterization of the interface and the determination …

Template electrosyntesis of CeO2 nanotubes

Nanotube arrays of CeO2 were produced in a single step by potentiostatic electrochemical deposition from a non-aqueous electrolyte, using anodic alumina membrane templates. The CeO2 nanotubes showed a polycrystalline structure, and they were assembled in the membrane nanochannels. The nanotubes had somewhat uniform diameters, with an average external value of about 210 nm, and a maximum length of about 60 µm; the latter parameter was controlled by the electrodeposition time. Each single nanotube was found to consist of crystalline grains having a size of about 3 nm. Raman analysis shows that these CeO2 nanotubes are suitable for catalytic applications.

Fabbricazione per via elettrochimica e caratterizzazione di membrane nanoporose di allumina

Radiation processing: an alternative and environmentally friendly way to produce advanced Materials. Synthesis of PANI/hydrogels composites

Nanostructured Material Fabrication for Energy Conversion

Performance of Nanostructured Electrode in Lead Acid Battery

Lead acid batteries have a large number of potential advantages, but the high weight of lead limits their use in new technologies, like hybrid or electrical cars, which require light batteries with high specific energy. We tried to overtake this limit with nanostructured electrodes of PbO2 and Pb, obtained by electrodeposition in polycarbonate template. In the case of lead, to obtain electrodes with very good mechanical stability, a systematic investigation of electrodeposition process was needed to overcome the formation of dendrites that is the principal limitation of electrochemical production of metal lead. Nanostructured electrodes were tested in a zero gap configuration, using commerc…

Metal displacement deposition: a new route for template fabrication of metal and metal oxide nanostructures

Amorphous semiconductor-electrolyte junction

Abstract The photoelectrochemical behaviour of amorphous anodic films on niobium (a-Nb 2 O 5 ) grown in a wide range of thicknesses (20 ⩽ d ox ⩽ 25 nm) is presented. The influence of the wavelength, light intensity and film thickness on the photocharacteristics of the a-Nb 2 O 5 /electrolyte junction is investigated. Expressions for the photocurrent curves under steady-state conditions are derived by assuming a variable efficiency of photocarrier generation and different distributions of the electrical potential inside the amorphous films. The influence of the light intensity on the photocharacteristics and the existence of a sub-band-gap photoresponse are explained by assuming a finite den…

Electrochemical synthesis and characterization of self-standing metal oxide nanostructures

Template Electrochemical Growth and Properties of Mo Oxide Nanostructures

This work is aimed at studying the growing process of nanostructures electrodeposited from molybdate aqueous solutions at different pH values into pores of polycarbonate membrane templates. The challenging issue was the opportunity to investigate a rather complex deposition process in a confined ambient, where electrochemical conditions are quite different from those usually established for deposition on a flat substrate. Nanostructures were grown from a bath containing Mo7O246– (NH4)6Mo7O24·4H2O) at different concentrations (50–100 g/L), at a constant cathodic current density of 2 mA/cm2 (electrodeposition area ∼8 cm2). Nanostructured deposit was characterized by XRD, EDS, Raman, XPS, and …

Nanostructured Material Fabrication for Energy Conversion

The electrochemical deposition is a suitable via to fabricate nanostructured materials for energy conversion, and for other purposes. This paper deals with the electrochemical synthesis of nanostructured alloys and ruthenium oxide, which can be used in Li-ion batteries and polymer electrolyte membrane electrolyzers.

Electric properties of gamma-crosslinked hydrogels incorporating organic conducting polymers

Electrically conductive hydrogel composites made of polyaniline nanoparticles and poly(N-vinyl-2 pyrrolidone)

Investigation of amorphous oxide film-electrolyte junctions by AC techniques

Current AC (alternating current) techniques are used often to characterize the energetics at a semiconducting solid phase/electrolyte interface. For thin layers having a strongly disordered or amorphous structure (such as oxide-passive layers anodically grown on valve metals), interpretative models currently used for crystalline semiconductors may produce misleading data. A new interpretation of the admittance data, based on recent models for amorphous semiconductors (a-Sc) Schottky barriers, is presented for passive films of Nb, W and Ti. The physical bases of the model are presented as well as its advantages and disadvantages. The new theory views the solid/electrolyte interface more sati…

Nanostructured anode material for Li-ion batteries

The present paper focuses on a nanostructured SnCo alloy electrochemically prepared by template method in view of its use as anode material alternative to graphite in lithium-ion batteries. The fabrication of SnCo nanowire arrays was carried out by potentiostatic co-deposition of the two metals by using nanostructured anodic alumina membranes as template. Electrochemical tests on lithiation-delithiation of these SnCo electrodes in conventional organic electrolyte (EC:DMC LiPF6) at 30°C showed that their specific capacity was stable for about the first 12 cycles at a value near to the theoretical one for Li22Sn5 and, hence, progressively decayed.

Electrodeposition of lead dioxide nanowires with a high aspect ratio

Semiempirical Correlation between Optical Band Gap Values of Oxides and the Difference of Electronegativity of the Elements. Its Importance for a Quantitative Use of Photocurrent Spectroscopy in Corrosion Studies

A semiempirical correlation between the optical band gap of binary oxides and the difference of electronegativity between the oxygen and metallic elements (Pauling's extraionic energy) is proposed. In the frame of the proposed correlation an estimate of the repulsive term in the total lattice energy of ionic oxides is obtained in very good agreement with the existing data. An extension of the correlation to the ternary oxides and hydroxides is proposed by using the concept of average cationic or anionic group electronegativity. The usefulness of the proposed correlation for the in situ characterization of passive films on metals and alloys by photocurrent spectroscopy is illustrated by repo…

Novel acidic hydrogel electrolytes based on PVA and PVA blends

Optimized bath for electroless deposition of palladium on amorphous alumina membranes

A new bath for the electroless deposition of palladium on anodic alumina (AA) membranes is proposed. It was found that the optimal conditions for the uniform deposition of palladium, with minimal damage to the AA membranes, were under conditions of pH 8.4 and plating times shorter than 30 min. The deposited Pd layer was detected by X-ray diffraction (XRD) and energy dispersive X-ray (EDX) analysis. The morphology of the AA membrane before and after plating was examined by scanning electron microscopy (SEM). EDX analysis revealed that palladium was deposited only on the surfaces of the membrane and Sn ions, coming from the sensitizing bath, were incorporated into the palladium layer. EDTA in…

Fabrication of Metal Oxide Nano-structured electrodes by Template Electrosynthesis

Metodo di realizzazione di un elettrodo ad elevata densità energetica ed elettrodo ottenibile con tale metodo

Nanostructured Electrochemical Devices for Sensing, Energy Conversion and Storage

Nanomaterials are very promising to enhance device performances for sensing, sustainable energy production, and energy conversion and storage, as extensively reported in the literature [1-3]. In this field, one of the most severe challenge is to find suitable methods for fabricating nanomaterials. Over the years, numerous preparation methods were proposed in the literature, but not all of them are easily scalable and economically advantageous for industrial application. In this context, electrochemical deposition in template is a facile method for fabricating either two- or one-dimensional nanostructured materials because it allows to easily adjust the fundamental parameters controlling the…

Photo-Electrochemical Investigation of Anodic Oxide Films on cast Ti-Mo Alloys

Electrochemical and chemical synthesis of CIS/Zn(S,O,OH) for thin film solar cells

In this work, we are reporting results on the electrodeposition of the CuInSe2 thin films on molybdenum thin foil substrates. We have used an aqueous non-buffered electrolyte and a careful choice of deposition parameters to ensure a good quality and composition of the deposited films. In addition, CdS was replaced in the buffer layer with a wider bandgap Zn(S,O,OH) film obtained by chemical bath deposition. The deposited films were annealed in inert atmosphere at different temperatures. The influence of annealing temperature on the properties of the films is briefly discussed. Films were also characterized by photoelectrochemical and I-V measurements. Structural characterization was carried…

A new route to grow oxide nanostructures based on metal displacement deposition. Lanthanides oxy/hydroxides growth

Abstract A metal displacement reaction has been used in order to cause precipitation of oxide nanostructures within pores of anodic alumina membrane (AAM) templates. Here, we focus on the displacement deposition of LnO/OH (Ln = La, Ce, Sm, Er) nanostructures using Zn as sacrificial anode, employing a specific cell arrangement where a galvanic couple was formed between zinc anode and the Au thin layer covering template pore bottom. Progress of displacement deposition reaction into template channels was monitored measuring the open circuit potential as well as pH changes of the electrolyte. A progressive de-activation of the anode surface was observed for long deposition times, caused by depo…

The effect of thickness on the composition of passive films on a Ti–50Zr at% alloy

Abstract Anodic films were grown potentiodynamically in different electrolytes (pH = 1–14) on a Ti–50Zr at% cast alloy, obtained by fusion in a voltaic arc under argon atmosphere. The thickness of the films was varied by changing formation potential from the open circuit potential up to about 9 V; growth was followed by 30 min stabilization at the forming potential. Films having different thicknesses were characterized by photocurrent spectroscopy (PCS) and electrochemical impedance spectroscopy (EIS). Moreover, film composition was analyzed by X-ray photoelectron spectroscopy (XPS). Regardless of the anodizing conditions, passive films on the Ti–50Zr at% alloy consist of a single layer mix…

Preparation and characterization of anodic alumina membranes modified by electroless deposition of Pd

Fabbricazione e caratterizzazione di elettrodi di PbO2 nanostrutturati

Nanostructured lead acid battery for electric vehicles applications

This paper presents an innovative lead acid battery, based on nanostructured active materials. Both charging time and specific energy are greatly enhanced in comparison with commercial lead acid battery. Starting from the extremely valuable performances of the nanostructured battery, also a circuital model, for application in electric vehicle traction, has been specifically developed. The circuital model has demonstrated that an enhanced nanostructured battery allows an increase of traveled distance by electric vehicles.

Developing a procedure to optimize electroless deposition of thin palladium layer on anodic alumina membranes

In recent years, the increased demand for hydrogen in many industrial applications, like petrochemical and semiconductor processing, and sustainable energy (fuel cells) has led to a renewed interest in methods for separation and purification of hydrogen from gas mixtures. In particular, palladium-based membranes have been the subject of many studies, due to their potential use as hydrogen-selective membranes for gas separation or purification [1,2]. Owing to the high cost of palladium and in order to increase the flow rate of hydrogen, composite membranes, formed by a thin layer of palladium deposited on a porous support, are largely preferred to thick self-standing metal membranes. Differe…

A viable path toward a high energy density anode for lithium-ion batteries

Nickel-Indium Sulphide Core-Shell Nonostructures Obtained by Spray-ILGAR Deposition

Ni nanowires (NWs) of different lengths were fabricated by pulsed potentiostatic deposition within pores of polycarbonate membranes. After template dissolution, substrates underwent sequential Spray-ILGAR® depositions of thin indium sulphide films. The effect of deposition temperature was also investigated. For low number of deposition cycles, results showed complete and uniform covering of metal over the entire length of NWs, with formation of Ni - In2S3 core-shell structures. However, with increasing number of deposition cycles films became uneven and crusty, especially at higher temperatures, owing to the simultaneous formation of nickel sulfide. This drawback was almost eliminated doubl…

Influence of initial treatments of aluminium on the morphological features of electrochemically formed alumina membranes

Abstract The fabrication of alumina membranes by electrochemical oxidation of annealed aluminium was investigated. Porous layers were grown in 0.4 M H3PO4 at −1 and 5 °C at different anodising times. The morphology of the outer surface was found to be dependent on temperature and charge density, with both determining the extent of chemical dissolution of the anodic oxide. The inner-surface morphology was found to depend on the applied voltage only. The chemical dissolution rate of anodic oxide grown on annealed aluminium was found to be lower than that formed on unannealed aluminium under otherwise identical conditions. Such a difference in behaviour is explained in terms of a higher finish…

ChemInform Abstract: Electrical and Mechanical Breakdown of Anodic Films on Tungsten in Aqueous Electrolytes.

Abstract Different types of breakdown are reported to occur during the galvanostatic growth of WO3 films in different aqueous electrolytes. Stresses inside the growing film cause the occurrence of cracks at a critical thickness which varies with the anodizing solution. The electrical breakdown is caused by avalanche ionization of the electronic current inside the film. The influence of the different experimental parameters on both the mechanical and the electrical breakdown voltages is discussed. For the electrical breakdown a model is proposed which explains the dependence of the sparking voltage on the electrolyte resistivity by assuming a double layer effect on the oxygen evolution react…

Photoelectrochemical characterization of Cu2O-nanowire arrays electrodeposited into anodic alumina membranes

Perfectly aligned nanowire arrays of polycrystalline Cu2O were grown by template-pulsed electrodeposition from a cupric acetate-sodium acetate bath into anodic alumina membranes (AAM). The photoelectrochemical behavior of arrays with different nanowire lengths (0.5 mu m and 2 mu m) was investigated in neutral solution, and the results compared to those pertaining to Cu2O films grown with the same procedure. Although all samples displayed the same indirect bandgap (similar to 1.9 eV), differences were observed both in photocurrent intensity and sign. The latter changed with potential and wavelength in different ways for nanowires and films, revealing a different defect concentration in the t…

Template Electrosynthesis of SnCo Nanowire Arrays for Lithium-ion Batteries

Synthesis and characterization of biocompatible responsive hydrogels

Pb-PbOHCl Composite Nanowires Synthesized by Galvanic Deposition in Template

In this paper, we report a detailed study on the synthesis of composite nanowires of Pb-PbOHCl via galvanic deposition into the pores of a membrane acting as a template. PbOHCl deposition quantitatively occurs as the solution pH exceeds the value of about 4.12. Simultaneously, owing to the galvanic coupling, electro-deposition of lead occurs, so composite nanowires were formed. The role of different parameters controlling the kinetic evolution of the process, such as oxygen bubbling, solution pH, surface area and type of sacrificial anode were investigated one at a time. The results suggest that every modification accelerating the alkalization of the solution inside the template pores favor…

A semiempirical correlation between the optical band gap of hydroxides and the electronegativity of their constituents

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. Based on the experimental results on passive hydrated layers on metals obtained in our laboratory and the literature data, it is found that the hydroxide band gap varies with the square of the difference between the electronegativities of the metallic cation and the hydroxyl group. Like in the case of anhydrous oxides, two different interpolation lines have been found forsp-metal andd-metal hydroxides, respectively. The proposed correlations predict semiconducting or insulating behavior even for the most electronegative…

GROWTH AND PHOTOELECTROCHEMICAL BEHAVIOUR OF ELECTRODEPOSITED ZnO THIN FILMS FOR SOLAR CELLS

Thin zinc oxide films were deposited potentiostatically from zinc nitrate aqueous solutions on ITO substrates. The influence of experimental parameters (temperature, electrolyte concentration, deposition potential) on structure and morphology of films was investigated. Deposited films were generally polycrystalline in structure, even if growth according to preferential planes occurs in certain conditions. The effect of thermal treatments in air at 150 and 350 °C was also studied. In some cases, Cl species were incorporated into deposit by adding zinc chloride to the electrolyte. A photoelectrochemical investigation, performed in neutral solution before and after thermal treatment, gives mor…

Nano-structured soft composites: materials for an interactive interface between human and the environment

Metodo Per l’Accrescimento di Nanostrutture in Silicio E Dispositivo Elettrico Comprendente Tali Nanostrutture

Anodic alumina membranes modified by electroless deposition of Pd and Ni

Monodimensional Amorphous SnCo Arrays As High Performing Anodes for Lithium Ion Batteries

Nanostructured Pd-AAM composite membranes

Nanostructured anode and cathode materials for Li-ion batteries

Fabrication of CIS and CIGS nanowires for application in micro-photovoltaic device

Ni/NiO thin film Sensors for Mercury ions detection by Square wave anodic stripping voltammetry

Square wave anodic stripping voltammetry (SWASV) is considered a very interesting electrochemical method for heavy metals detection in comparison to conventional techniques [1]. The main features of this technique are the high sensitivity and reproducibility (standard deviation lower than 5%), besides, the limit of detection is in the ppb level so is comparable with standard techniques such as AAS or ICP, the instrumentation is very inexpensive and easy to use and the detection time is very low. Among heavy metals, mercury is one of the most toxic for both environment and humans. In fact, it may cause serious health problems to brain, kidney and DNA. The concentration limit imposed by US En…

THIN ZNS FILMS OBTAINED BY ELECTRODEPOSITION AS BUFFER FOR SOLAR CELLS

In situ characterization of passive films on al-ti alloy by photocurrent and impedance spectroscopy

Abstract The anodic behaviour of an Al-Ti alloy (Ti-48Al-1V, atomic %) was investigated in different aqueous electrolytes. In all cases the alloy was passive owing to the growth of a barrier-like oxide film according to the high field mechanism. The study of the growth curves suggests partial dissolution of the film during the formation process in acidic solution. The kinetic parameters for film formation have been estimated in neutral solutions and the dielectric constant of the passive layer was roughly estimated. The in-situ characterization of the passive film revealed a n-type behaviour only for very low thicknesses, whilst thicker films showed insulator-like characteristics. The analy…

ChemInform Abstract: Photoelectrochemical Characterization of Thin Anodic Oxide Films on Zirconium Metal.

Abstract The effect of metal surface preparation on the properties of thin oxide films grown on zirconium in different electrolytes was investigated by photocurrent spectroscopy. Both passive layers grown by free corrosion of the samples in a solution and thin oxides grown anodically at a constant rate were investigated. The photoelectrochemical results give a complex picture of the interface, being influenced by the metal surface preparation, the solution pH and the electrode potential. A duplex structure of the films has been suggested on the basis of the photocurrent spectra, with an external hydrous layer (amorphous or strongly defective) having an optical gap ( E g 2 ~ 3 eV) lower resp…

Template Fabrication of Nano-Structures using Anodic Alumina Membranes

The influence of experimental parameters on the morphology of the porous structure and on the formation kinetics has been investigated for anodic alumina membranes (AAM) grown in aqueous H3PO4 at 160 V. It was found that pore aspect ratio and membrane porosity on the solution-side surface are influenced by tensiostatic charge, bath temperature and the presence of Al3+ ions in solution. Morphological and kinetic data, recorded in different conditions, give useful information on the growth mechanism of pore channels in phosphoric acid solution. Nickel nano-structures have been fabricated using AAM as ternplate.

Sintesi per via elettrochimica di nanowires di leghe Co-Sn

Nanostructured soft composites for an interactive interface between Human and the environment

Metal Displacement Deposition: a facile via to grow metal and metal oxide nanostructures

Nanostructured materials have received increasing attention because of their high chemical reactivity that allows an extensive use in many fields, like catalysis, electrosynthesis, sensors, and so on [1]. Taking into account that size plays a fundamental role for the properties of nanostructures, it is of relevant importance for their applications to develop a facile method of synthesis. In our previous works, we have described a template synthesis of metal nanowires through a simple novel route [2-4]. In particular, using a combination of template deposition and metal displacement reaction, we have fabricated pure metal nanowires with a well-defined morphology. This type of template synthe…

Fabrication and characterization of nanostructured Ni–IrO2 electrodes for water electrolysis

Abstract Nanostructured Ni–IrO2 electrodes were fabricated by electrodeposition in a two-step procedure: first arrays of nickel nanowires (NWs) were electrodeposited within pores of polycarbonate (PC) membranes, then iridium oxide nanoparticles were deposited on the Ni metal after membrane dissolution, for improving the catalytic activity. The aim was to compare performance of these electrodes with traditional ones consisting of Ni film. Different methods of deposition of the IrO2 electrocatalyst were investigated and the effect on electrodes stability and activity is discussed. Despite a low coverage of Ni NWs by the electrocatalyst, results indicate a faster kinetics of O2 evolution in 1 …

Photoelectrochemical investigation of passive layers formed on Fe in different electrolytic solutions

Abstract The passive films formed on Fe in different electrolytic solutions, spanning almost the overall pH range, and with different growth procedures were investigated systematically by photocurrent spectroscopy. The potentiodynamic growth curves are compared both in aerated and de-aerated electrolytes and a potentiostatic growth procedure is also employed. For high positive formation potentials, similar anodic spectra are recorded in all solutions giving an optical gap very close to that expected for crystalline Fe2O3. The origin of photocurrent spikes is also investigated and the effect of the formation potential upon the measured absorption threshold is discussed taking into account th…

Nanostructured PbO2 electrode for lead-acd batery

One-dimensional nanostructures of lead and lead dioxide for application in lead-acid batteries

Fabrication of Pb and PbO2 nanostructures was undertaken with the aim of building low cost lead acid micro-batteries with high performance. Despite environmental problems and the relatively low specific energy in comparison with other galvanic generators, lead acid batteries are still extensively used in the field of energy accumulation, owing to a well known and reliable technology. Thus, it is of high technological interest to develop procedures for fabricating these devices at a micrometer scale or less. PbO2 nanowires were grown in different electrochemical deposition conditions leading to pure -PbO2, pure -PbO2 and  mixture [1-2]. Several parameters, like temperature, electrolyte…

Electrosynthesis of Sn-Co nanowires in alumina membranes

A fabrication process of amorphous nanowires of Sn-Co alloys, based on electrodeposition into anodic alumina membranes, is described. It is shown that nanowires of tin-cobalt alloys with different compositions can be produced by varying electrodeposition time and concentration ratio of salts dissolved into the electrolytic bath. Importance of the chelating agent to produce amorphous Sn-Co alloys has also been addressed. Electrodepositions were carried out potentiostatically at -1 V versus Saturated Calomel Electrode and 60 degrees C for times ranging from 10 to 90 minutes; the atomic fraction of Co2+ in the aqueous electrolyte (Co2+/(Co2+ + Sn2+)) was varied from 0.33 to 0.67. Nanowires asp…

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…

Photoelectrochemical and Impedance Studies of Passive Films on different Ti-Mo Alloys

A Photoelectrochemical Study of Passivating Layers on Nickel

Formation of lead by reduction of electrodeposited PbO2: comparison between bulk films and nanowires fabrication

Metallic lead was deposited, both in form of bulk films and nanowire array within pores of anodic alumina membranes, following a new two-step procedure, consisting in anodic electrodeposition of α-PbO2, followed by its reduction to metallic lead. This method allows to overcome drawbacks of the “direct” electrodeposition of lead from aqueous solution, consisting, essentially, in the formation of dendritic deposits. Here, we report the comparison between results obtained in the two cases and discuss the kinetic of oxide reduction both for films and nanowires. Deposit morphology and structure are also discussed. We have found that reduction of α-PbO2 films proceeds always at high speed and uni…

Effect of temperature on the growth of alfa-PbO2 nanostructures

Abstract Ordered arrays of α-PbO 2 nanostructures were grown by galvanostatic anodic deposition into the channels of alumina templates. Electrodepositions were performed in an aqueous solution containing lead acetate and sodium acetate at pH 5.4. Bath temperature and electrodeposition time were varied to check their effect on the growth of nanostructures. It has been found that filling of alumina pores is independent of the time and electrodeposition temperature, whilst height and growth kinetics of nanostructures vary with both parameters. Temperature greatly influences morphology: wires grown at room temperature consisted of clusters of particles, leading to poorly compact structures, whi…

Growth and Electrochemical Performance of Lead and Lead Oxide Nanowire Arrays as Electrodes for Lead-Acid Batteries

n this work, we present the growth and electrochemical performance of nanostructured lead and lead oxide electrodes for lead-acid batteries. The electrodes were obtained by template electrodeposition in polycarbonate membranes, acting as template. Electrochemical tests were conducted at constant current in 5M aqueous solution of sulphuric acid, after assembling nanostructured lead and lead oxide electrodes in a zero-gap configuration using a commercially available separator. The main advantages of these electrodes are the high specific energy and power density, and the wide surface area, about 70 times higher than the geometrical one. These features allowed high discharge rates, up to 20C. …

Nanowire fabrication by metal dislacement deposition into anodic alumina membranes templates

EFFECT OF ANNEALING PROCESS ON CIGS FILMS PREPARED BY ONE-STEP ELECTRODEPOSITION

Ruthenium Oxide Nanotubes Via Template Electrosynthesis

Ruthenium oxide nanotubes were fabricated by a single-step galvanostatic deposition using porous anodic alumina membrane as template. For the electrodeposition process, we used a electrochemical cell specifically designed in order to employ only 0.5 ml of 0.02 M RuCl3•xH2O solution. The deposition from a very small volume was specifically addressed owing to the high cost of ruthenium compounds, which could be of some relevance from an applicative point of view. Several techniques were used to characterize the samples prior to and after thermal treatment, which was carried out at different temperatures in order to study the crystallization process of the deposit. Raman spectroscopy of as-dep…

CuZnSnSe NANOTUBES AND NANOWIRES BY TEMPLATE ELECTROSYNTHESIS

In this work we present some results of an extensive investigation aimed to find suitable conditions to grow CuZnSnSe (CZTSe) nanostructures through single-step electrodeposition into the channels of polycarbonate membranes. After the optimization of several electrodeposition parameters, we have found that pulsed current deposition, between 0 and -1 mA cm-2, is the best way to obtain CZTSe nanostructures mechanically attached to the support. An interesting result concerns the effect of supporting electrolyte in the deposition bath. In fact, changing its concentration it is possible to vary morphology of nanostructures from nanotubes to nanowires. In both case uniform arrays of ordered nanos…

Growth and photo-electrochemical behaviour of Cu2O nanowires

Investigation of the kinetics of growth of anodic oxide films on niobium by galvanostatic and tensiodynamic experiments

Abstract The kinetics of growth of anodic oxide films on niobium has been investigated by interferometric methods. Tensiodynamic experiments allow the growth of the films at constant rate. Photoeffects during the growth of the films under absorbed light give additional information on the growth process.

Electrodeposition and Photoelectrochemical Behaviour of CIGS Thin Films and Nanowire Arrays for Solar Cells

One-dimensional nanostructures as electrode materials for water electrolysis

Galvanic deposition and characterization of brushite/hydroxyapatite coatings on 316L stainless steel

In this work, brushite and brushite/hydroxyapatite (BS, CaHPO4·H2O; HA, Ca10(PO4)6(OH)2) coatings were deposited on 316L stainless steel (316LSS) from a solution containing Ca(NO3)2·4H2O and NH4H2PO4 by a displacement reaction based on a galvanic contact, where zinc acts as sacrificial anode. Driving force for the cementation reaction arises from the difference in the electrochemical standard potentials of two different metallic materials (316LSS and Zn) immersed in an electrolyte, so forming a galvanic contact leading to the deposition of BS/HA on nobler metal. We found that temperature and deposition time affect coating features (morphology, structure, and composition). Deposits were char…

Growth and Characterization of Ordered PbO[sub 2] Nanowire Arrays

Large arrays of PbO 2 nanowires having high aspect ratios (length-to-width ratio) were grown by potentiostatic electrodeposition into anodic alumina templates under anodic polarization. Different electrolytic solutions were used in order to obtain nanowires of pure α-PbO 2 , pure β-PbO 2 , and a a + β mixture, We have found that, in a lead nitrate bath, a crystallographic structure of nanowires depends on pH; this latter was varied adding diluted nitric acid to the electrolyte. Nanowires of pure β-PbO 2 were obtained at pH 0.6, while mixed α-PbO 2 + β-PbΟ 2 nanowires were grown at pH 2. Pure α-phase was obtained in a bath containing lead acetate at pH 6.6. In all deposition conditions, nano…

A Route to Grow Oxide Nanostructures Based on Metal Displacement Deposition: Lanthanides Oxy/Hydroxides Characterization

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…

Valve-metal behavior of cast Ti-Mo alloys

Electrically conductive hydrogel composites made of polyaniline nanoparticles and poly(N-vinyl-2-pyrrolidone)

Abstract A novel electrically conductive composite material, consisting of polyaniline (PANI) nanoparticles dispersed in a polyvinyl pyrrolidone (PVP) hydrogel, was prepared ‘in situ’ by water dispersion polymerisation (DP) of aniline using PVP as steric stabiliser, followed by γ-irradiation induced crosslinking of the PVP component. Conversion yield of aniline into PANI particles was determined via HPLC and gas chromatography, while structural confirmation of the synthesised polymer was sought by FTIR. Morphology and dimensions of PANI particles into the coloured, optically transparent hydrogel was determined by electronic microscopy; moreover, swelling behaviour of composite hydrogels in …

Ultrafast cycling of lead-acid battery with nanostructured Pb and PbO2 electrodes

EIS characterization of functionalized alumina membranes

Una Via Elettrochimica per la Fabbricazione di Celle Solari a Semiconduttori Nanostrutturati

Nella memoria si presentano i risultati preliminari su un processo di crescita elettrochimica di materiali nanostrutturati mediante l’impiego di stampi nanoporosi. Vengono quindi analizzate le possibili applicazioni del processo alla fabbricazione di semiconduttori nanostrutturati di interesse nel settore fotovoltaico, quali il CIGS, e le implicazioni dal punto di vista delle tecniche di caratterizzazione e di modellazione per dispositivi basati su tale tecnologia.

Recent improvements in PbO2 nanowire electrodes for lead-acid battery

Abstract Lead oxide nanowires are an attractive alternative to conventional pasted electrodes, owing to their high surface area leading to high specific energy batteries. Here, we report the performance of template electrodeposited PbO 2 nanowires used as positive electrodes. Nanostructured electrodes were tested at constant charge/discharge rate from 2 C to 10 C, with a cut-off potential of 1.2 V and discharge depth up to 90% of the gravimetric charge. These new type of electrodes are able to work at very high C-rate without fading, reaching an efficiency of about 90% with a very good cycling stability. In particular, after an initial stabilization, a specific capacity of about 200 mAh g −…

INFLUENCE OF THE ANODIZATION CONDITIONS ON THE ELECTRONIC PROPERTIES AND CRYSTALLOGRAPHIC STRUCTURES OF THE CORROSION LAYERS ON TUNGSTEN. A PHOTOELECTROCHEMICAL APPROACH.

ABSTRACT The influence of morphology, composition and crystallographic structure on the photoelectrochemical behaviour of anodic oxide films on tungsten obtained in various conditions of anodization has been investigated. Different photocurrent spectra and absorption edges were obtained for each type of film. Optical band gaps ranging between 2.55 eV and 3.15 eV were determined for crystalline and amorphous WO 3 films grown in different conditions. The low quantum efficiency of the anodic films must be attributed to the presence of an amorphous (a-W0 3 ) film which controls the transport of the injected photocarriers.

Amorphous Silicon Nanotubes via Galvanic Displacement Deposition

Amorphous silicon nanotubes were grown in a single step into a polycarbonate membrane by a galvanic displacement reaction conducted in aqueous solution. In order to optimize the process, a specifically designed galvanic cell was used. SEM images, after polycarbonate dissolution, showed interconnected nanotube bundles with an average length of 18 μm and wall thickness of 38 nm.The deposited silicon was revealed by EDS analysis, whilst X-ray diffraction and Raman spectroscopy showed that nanotubes have an amorphous structure. Silicon nanotubes were also characterized by photo-electrochemical measurements that showed n-type conductivity and optical gap of ~1.6 eV. Keywords: Silicon nanotubes, …

Metallic lead recovery from lead-acid battery paste by urea acetate dissolution and cementation on iron

Abstract A suitable hydrometallurgical and environmentally friendly process was studied to replace the currently used practices for recycling lead-acid batteries via smelting. Metallic lead was recovered by cementation from industrial lead sludge solutions of urea acetate (200 to 500 g/L) using different types of metallic iron substrates (nails, shaving or powder) as reducing agents. Under specific operating conditions, up to 99.7% of lead acid battery paste, mainly composed of PbSO4, PbO2 and PbO·PbSO4 species, was converted to metallic lead.. The conversion of the metallic lead and rate of the cementation reaction were strictly dependent on the type of iron substrate used as the reductant…

Copper and Palladium NWs for Hydrogen Peroxide detection

H2O2 is a wide used chemical in different field, like in paper and textile industries and pharmaceutical applications. Furthermore, H2O2 concentration in human body is related to glucose concentration because the reaction between glucose and glucosidase produce hydrogen peroxide [1] . Moreover, is used as a biomarker of oxidative stress, being an oxidative specie [2] . For all these reasons, researcher all over the world are working to develop new and novel strategies for in situ, non-invasive and fast detection of this chemical. One of these fields concern the electrochemical sensors, that are sensors with an electrical (current, potential, impedance) output. The surface area the electrode…

A photocurrent spectroscopic investigation of passive films on chromium

Abstract Photoelectrochemical experiments have been carried out in order to identify the passive layers grown on chromium metal in different conditions. Changes in the values of the band gap of the films have been related to changes of composition, due to the different water content of the films.

Electrochemical deposition of CZTS thin films on flexible substrate

Abstract In this work, we report some preliminary results concerning the fabrication of quaternary semiconductor Cu2ZnSnS4 (CZTS) thin films on a flexible substrate through the simultaneous electrodeposition of elements having different standard electrochemical potentials. CZTS thin films were obtained by potentiostatic deposition from aqueous baths at room temperature and under N2 atmosphere, varying bath composition. Chemical composition and structure of the electrodeposited films were evaluated by EDS, SEM, RAMAN and XRD. Preliminary results on the photoelectrochemical behaviour of the films will be also presented.

Nanostructured alloys for energy devices

Enhanced Recovery after Implementation of Surgery Protocol in Living Kidney Donors: The ISMETT Experience

Abstract Introduction Laparoscopic living donor nephrectomy (LLDN) has become the standard procedure for living kidney transplantation. Enhanced recovery after surgery (ERAS) is a multimodal perioperative management aimed at facilitating rapid patient recovery after major surgery by modifying the response to stress induced by exposure to surgery. This association can further reduce hospital stay, surgical stress, and perioperative morbidity of living kidney donors. Material and methods In this retrospective analysis conducted at our institute, we compared the first 21 patients who underwent LLDN enrolled with the ERAS protocol with 55 patients who underwent LLDN with the fast-track protocol…

Electrochemical deposition of Ag2Se nanostructures

Abstract AgSe based nanostructures (nanowires or nanotubes) were obtained by electrodeposition. A systematic investigation was carried out, varying concentration of the precursors, pH of the electrolytic solution, ligands, and deposition mode, to study the effect of all these parameters on the growth of nanostructures. Nanostructure morphology depends also on the type of metal that was used as support, due to the secondary reaction of hydrogen evolution. On Ni support, the H2 evolution reaction led to formation of only nanotubes, while on copper substrate also nanowires were obtained. Composition of nanostructures depends strongly on solution pH. X-ray diffraction and Raman spectroscopy sho…

High-performance of PbO2 nanowire electrodes for lead-acid battery

Abstract PbO2 nanowires were obtained by template electrodeposition in polycarbonate membranes and tested as positive electrode for lead-acid battery. Nanowires were grown on the same material acting as current collector that was electrodeposited too. The nanostructured electrodes were assembled in a zero-gap configuration using commercial negative plate and separator. Cell performance was tested by galvanostatic charge/discharge cycles in a 5 M H2SO4 aqueous electrolyte. PbO2 nanostructured electrodes were able to deliver at 1C rate an almost constant capacity of about 190 mAh g−1 (85% of active material utilization), close to the theoretical value (224 mAh g−1). The nanowire array provide…

A photoelectrochemical study on anodic tantalum oxide films

Both anodic and cathodic photocurrents have been detected on tantalum oxide films depending on polarization. The optical band gap, E g opt , has been derived for anodic films grown in different conditions as well as for native oxides. Cathodic photocurrents at hv<E g opt have been attributed to electron injection at the metal/oxide interface. A change in the sign of the photocurrent with the wavelength of the incident light has been observed near to the flat band potential. The latter has been estimated from the fitting of the photocurrent vs potential curves

Utilization of impedance spectroscopy to investigate the self-assembly behavior of amphiphiles soluble in supercritical carbon dioxide: Preliminary results

Abstract A mixture of CO 2 , water, methyl orange (MO) and Dynol 604 surfactant was analyzed at 309 K and 20 MPa simultaneously by impedance and UV–vis spectroscopy. A plot of the static dielectric constant as a function of the surfactant concentration was obtained using a suitable equivalent circuit to elaborate impedance data. Experimental points can be fitted by two different straight lines whose intersection occurs at about 0.13% (w/w) concentration of Dynol. When the surfactant concentration crossed the aforementioned value, a peak was detectable in the UV–vis spectrum at a wavelength range corresponding to the absorption of MO; absorbance of the peak increased with the surfactant conc…

Amorphous silicon nanotubes

In the following, the attention will be focused on the silicon nanotube (SiNTs) that is a highly desired form of silicon for its fundamental role in the miniaturization trend of the electronic devices. After a description of the properties and applications of SiNTs and their fabrication methods, the attention will be focused on chemical vapour deposition (CVD) template synthesis that is the most usual synthetic method for this material. Then, galvanic template synthesis will be described as a general method for the fabrication of different metals and oxides nanostructures, therefore the use of this technique for synthesizing SiNTs will be detailed. Characterization methods will be also desc…

Metodo ed apparato per la produzione di nanowires metallici, nonché nanowires ottenibili mediante tale metodo

CIGS THIN FILM BY ONE-STEP ELECTRODEPOSITION FOR SOLAR CELLS

In this work, we present a cost-effective technique to produce CIGS thin films for solar cells by means of a single-step electrodeposition. In fact, electrodeposition is known as an easy technique for building low cost materials for photovoltaic device processing. Morphological, structural and optical characterization of these films has been performed.

Photoelectrochemical study on anodic aluminum oxide films. Internal photoemission processes at the metal-oxide interface

A photoelectrochemical investigation has been carried out on aluminum oxide films grown anodically at constant rate up to different thicknesses. Depending on the potential both anodic and cathodic photocurrents were observed at photon energies well below the optical bandgap expected for these layers. This finding is explained with the presence of internal photoinjection processes both for electrons and holes from the base metal into the oxide film. The analysis of the photocurrent spectra has given the threshold energies for both processes. The effect of the image force at the metal/oxide interface has been taken into account in order to derive the mobility gap of the films and the energeti…

Raman spectroscopy of lead dioxide nanowires

Pd-NWs ordered arrays for electrochemical sensing of H2O2

In this work, we present the performance of nanostructured array of Pd (Pd-NWs) for electrochemical sensors of hydrogen peroxide. Hydrogen peroxide is widely used in several fields, because to its oxidizing and reducing properties, like for treatment of waste water, paper and contaminated soils, as reagent in many chemical industries or like rocket propellant [1]. Furthermore, its presence or absence may be connected with many neurological deseases or/and with cancer [2].Today the most used methods for detection of that chemical are IR spectroscopy, spectrophotometry, fluorimetry, chemioluminescence and redox titration. However these methods are often uneconomical, have very high detection …

Electrical properties of γ-crosslinked hydrogels incorporating organic conducting polymers

Abstract Hydrogel composites containing nanoparticles of the protonated emeraldine form of polyaniline (PANI-PE) have been synthesised by γ-irradiation, using either polyvinyl pyrrolidone (PVP) or polyvinyl alcohol (PVA) as steric stabilisers. Swelling behaviour of both hydrogels is reported, together with an electrical characterisation of composites, before and after gel network formation, performed by cyclic voltammetry and impedance spectroscopy. Similarities and differences between the two composite systems are discussed.

Sintesi e caratterizzazione di idrogeli biocompatibili stimolo-sensibili

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.

Fabrication of Nanostructured Ni and Ni-IrO2 electrodes for wateralkaline electrolyzer

In the field of water-alkaline electrolyzer, the develop of nanoporous nickel electrodes with low cost and high electrocatalysis efficiency is one of the potential approaches to increase their performance [1]. To obtain nanostructured electrodes, a facile approach is that of template electrosynthesis. With this method we have obtained electrodes made of nanowires of Ni that have a very high surface area. These electrode were obtained by a two-step procedure allowing to obtain an ordered array of Ni nanowires that completely covering the surface of current collector made of the same material. Besides, by amperostatic deposition we have covered these electrode with nanoparticles of IrO2 elect…

Fabbricazione elettrochimica e caratterizzazione di materiali nanostrutturati

High-performing Sn-Co nanowire electrodes as anodes for lithium-ion batteries

Abstract The preparation of Sn 2 Co 3 nanowire arrays (NWs) electrogrown inside the channels of polycarbonate membranes and their characterization as anodes for Li-ion batteries both in half-cell vs. Li and in battery configuration are reported. The Sn 2 Co 3 NW electrodes tested by deep galvanostatic charge/discharge cycles in ethylene carbonate-dimethylcarbonate (1:1) – LiPF 6 1 M displayed 80% capacity retention after 200 cycles at C/2 and 30 °C, and a high charge and discharge rate capability at C-rate from C/3 (0.33 A/g) to 10C (10 A/g) at 30° and 10 °C. Electrodes with the highest alloy loading delivered up to 0.6 mAh cm −2 at C/2. The performance of these electrodes in battery config…

Template electrosynthesis of aligned Cu2O nanowires

Abstract Large arrays of aligned copper oxide nanowires were produced by electrodeposition, using anodic alumina membranes as template. We have studied the effect of two fundamental parameters involved in fabrication process: potential perturbation and bath composition. Performing electrodeposition from a copper acetate/sodium acetate bath (pH 6.5), we found that chemical composition of nanowires varied in dependence on the shape of the applied potential perturbation: pure copper oxide nanowires were produced by pulsed potential, whilst continuous electrodeposition resulted in a co-deposition of Cu and Cu 2 O. In a copper lactate bath, buffered at pH 10, the shape of perturbation did not in…

Fabrication of metal nano-structures using anodic alumina membranes grown in phosphoric acid solution: Tailoring template morphology

Abstract The influence of experimental parameters on the morphology of the porous structure and on the formation kinetics has been investigated for anodic alumina membranes (AAM) grown in aqueous H 3 PO 4 at 160 V. It was found that pore aspect ratio and membrane porosity on the solution-side surface are influenced by tensiostatic charge, bath temperature and the presence of Al 3+ ions in solution. Morphological and kinetic data, recorded in different conditions, give useful information on the growth mechanism of pore channels in phosphoric acid solution. Nickel nano-structures have been fabricated using AAM as template. Electroless deposition, performed by adding the reducing agent to a su…

Novel procedure for the template synthesis of metal nanostructures

In this work we describe a novel method for the fabrication of a regular and uniform array of Cu nanowires into anodic alumina membranes. It is based on galvanic contact between the metal sputtered film covering the bottom of template and a less noble metal. The growth rate was estimated as function of the immersion time. Nanowires with aspect ratio from 12 to 286 were obtained by adjusting the deposition time. Copper nanowires were found to be polycrystalline with an average crystalline size of about 40 nm. This procedure can be applied for the preparation of a wide range of metallic nanostructures and it can be easily scaled up for industrial processing. Keywords: Displacement deposition,…

Lead Electrode, Method for its Manufacturing and Accumulator Comprising the Electrode

Electrodeposition from molybdate aqueous solutions: a preliminary study

The electrochemistry of molybdenum (Mo) and its oxides is very important for several applications in electrocatalysis,batteries,sensors and in particular for CIGS-based solar cells,where metal Mo is used as back contact.Properties and the fabrication method of Mo films are of fundamental importance,because they could induce significant changes in solar cell performances.The most important issues in the electrochemical behaviour of Mo are the nature and stability of its surface oxides,which are strongly dependent on deposition bath pH.Ivanova et al. (2006) reported that it is possible to accomplish the cathodic reduction of molybdate ions to metallic Mo from electrolytes containing HF.The ad…

Sn-Co nanowire-based anodes for lithium-ion batteries

The demand of improvement in lithium-ion battery technology in terms of specific capacity and safety has stimulated the search for anode materials alternative to graphite. Among them, tin-based materials have been widely studied because tin can intercalate lithium up to atomic ratio Li/Sn of 4.4 to deliver a impressive specific capacity of 993 mAhg−1 (while graphite gives 372 mAhg−1). Unfortunately the high volume change of about 300%, which is related to the insertion/removal of lithium, causes the alloy pulverization and loss of electric contact that causes a poor cycle life. The synthesis of nanometric materials, intermetallic compounds and carbon composites are strategies that have been…

CIGS Thin Film by One-Step Electrodeposition Deposition for Solar Cells

Electrochemical deposition of CIGS on electropolished Mo

Method for Producing an Electrode with Nanometric Structure and Electrode with Nanometric Stucture

Recent advances in photocurrent spectroscopy of passive films

Abstract The quantitative application of photocurrent spectroscopy (PCS) for the in-situ determination of the composition of passive films and corrosion layers is reviewed in the light of recent theoretical advances, that have allowed to relate the measured optical gaps to the Pauling electronegativities of the film components. The correlations derived are tested versus recent experimental results regarding mixed oxides, anhydrous passive films on metallic alloys and hydroxide layers. The effect of the eventual long-range disorder into the passive film on the optical band gap values is also discussed. New experimental evidence reported for mixed d,d-metal oxides and passive films on sp,d-me…

Performance analysis of nanostructured PbO2 electrodes in lead-acid batteries

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…

Investigation of Annealing Conditions on Electrochemically Deposited CZTS Film on Flexible Molybdenum Foil

In thiswork, the electrodeposition of Cu2ZnSnS4 thin films on molybdenum thin foilwas reported. In order to guarantee co-deposition of elements with different standard electrochemical potential, an aqueous electrolyte added with ligand agents was used. I addition, deposition parameters were carefully chosen, in order to ensure good quality and suitable composition of the films. The deposited films were sulfurized in controlled atmosphere at 580?C, scrutinizing the influence of the annealing conditions on the features of the films. Structure, morphology and composition were investigated by XRD SEM, EDS and Raman spectroscopy. Results reveal the growth of good quality films, with a uniform mo…

NANOWIRE FABRICATION BY METAL DISPLACEMENT DEPOSITION INTO ANODIC ALUMINA MEMBRANES TEMPLATES

Thin Films of Semiconductors for Flexible Solar Cells: Electrochemical Deposition and Characterization

A nanostructured sensor of hydrogen peroxide

Abstract A nanostructured electrochemical sensor of hydrogen peroxide was fabricated growing self-standing Pd nanowires (Pd NWs) into polycarbonate (PC) membranes through a simple metal galvanic deposition. Conditions of deposition were adjusted in order to attain 2–5 μm long Pd wires. Characterization of Pd-NWs was performed by scanning electrode microscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction. Properties of the nanostructured sensor were studied by cyclic voltammetry and chronoamperometry in phosphate buffer—ethanol solution. Addition of pure ethanol to the test solution was essential in order to increase wettability of the nanostructures. Sensing features were comp…

In-situ polymerization of polyaniline in radiation functionalized polypropylene films

Abstract In-situ generation of a nanodispersed conductive polymer within a polypropylene matrix has been pursued in order to obtain flexible, conductive films. Radiation grafting of acrylic acid to polypropylene (PP) has been applied to insert carboxyl functionalities on PP. The radiation-grafted films have been further derivatized with a variety of diamines and used as substrates for in-situ chemical oxidative polymerization of polyaniline (PANI). PANI grows as a thin skin from the surface of the film as well as an interpenetrated network in its interiors. Evidence of chemical attachment of PANI to PP has been sought by performing FTIR and XPS analyses after extraction of the unbound polym…

One-Step Electrodeposition of CZTS for Solar Cell Absorber Layer

CZTS thin films were obtained by one-step electrochemical deposition from aqueoussolution at room temperature. Films were deposited on two different substrates, ITOon PET, and electropolished Mo. Differently from previous studies focusing exclu‐sively on the formation of kesterite (Cu4ZnSnS4), here, the synthesis of a phase withthis exact composition was not considered as the unique objective. Really, startingfrom different baths, amorphous semiconducting layers containing copper–zinc–tin–sulphur with atomic fraction Cu0.592Zn0.124Sn0.063S0.221 and Cu0.415Zn0.061Sn0.349S0.175, werepotentiostatically deposited. Due to the amorphous nature, it was not possible to de‐tect if one or more phases…

Crucial Role of Extended Criteria Donors in Deceased Donor Single Kidney Transplantation to Face Chronic Shortage in the Heart of the Mediterranean Basin: A Single-Center Experience.

Background: The gap between organ availability and patients on the waiting list for deceased donor kidney transplants has resulted in the wide use of extended criteria donors (ECDs).We aimed to compare the surgical outcomes of single kidney transplantation (KT) performed at our institute with standard criteria donor (SCD) or ECD grafts, according to the Organ Procurement and Transplantation Network definition. Patients and methods. Our retrospective analysis studied 115 adult recipients of KT from January 2016 to July 2018, with kidney grafts procured from adult donors after brain or circulatory death, performed at our institute. Among the 2 recipients’ groups, we compared the incidence of …

Anodic Alumina Membranes: From Electrochemical Growth to Use as Template for Fabrication of Nanostructured Electrodes

The great success of anodic alumina membranes is due to their morphological features coupled to both thermal and chemical stability. The electrochemical fabrication allows accurate control of the porous structure: in fact, the membrane morphological characteristics (pore length, pore diameter and cell density) can be controlled by adjusting the anodizing parameters (bath, temperature, voltage and time). This article deals with both the fabrication and use of anodic alumina membranes. In particular, we will show the specific role of the addition of aluminum ions to phosphoric acid-based anodizing solution in modifying the morphology of anodic alumina membranes. Anodic alumina membranes were …

CuInSe2/Zn(S,O,OH) junction by electrochemical and chemical route for photovoltaic applications (GE 2014)

Electrodeposition is a convenient technique for the development of low cost materials for photovoltaic (PV) device processing. Using a single step electrodeposition route, several groups have fabricated CIS (CuInSe) and CIGS (CuInGaSe) films. One of the most important requirements for successful application of one-step electrodeposition film formation is the ability to control composition of the deposited films and to develop polycrystalline microstructures with a low surface roughness and high sintered density.

Brushite/Hydroxyapatite Coatings obtained by galvanic deposition on 316L Stainless Steel

Hydroxyapatite (HA, Ca10(PO4)6(OH)2) is a basic calcium phosphate mineral with chemical composition similar to that of bones and teeth. Owing to this peculiarity HA is a biocompatible material of high medical interest. Unfortunately, it possesses poor mechanical properties, because is brittle, has a low fracture resistance and a poor wear resistance. For these reasons, in the last years the research was been focused on the use of HA as a coating of another biomaterial that acts as support. The best choice is that to use a substrate that must be bionert and mechanically stable, such as 316L stainless steel (316LSS). This is useful for biomedical implants, because of its excellent biocompatib…

Fabrication and characterization of nanostructured materials

Ti-Mo cast alloys for biomedical applications. Anodic behavior and passive film properties

Influence Of The Electrical Parameters On The Fabrication Of Copper Nanowires Into Anodic Alumina Templates

Abstract Metallic copper nanowires have been grown into the pores of alumina membranes by electrodeposition from an aqueous solution containing CuSO 4 . and H 3 BO 3 at pH 3. In order to study the influence of the electrical parameters on growth and structure of nanowires, different deposition potentials (both in the region where hydrogen evolution reaction is allowed or not) and voltage perturbation modes (constant potential or unipolar pulsed depositions) were applied. In all cases, pure polycrystalline Cu nanowires were fabricated into template pores, having lengths increasing with the total deposition time. These nanowires were self-standing, because they retain their vertical orientati…

SPEEDAM 2010 Poster REC0616: An electrochemical route towards the fabrication of nanostructured semiconductor solar cells

Fabrication and Characterization of Different Nanostructures

Photo-electrochemical and impedance investigation of passive layers grown anodically on titanium alloys

Abstract The anodic behaviour of two titanium cast alloys, obtained by fusion in a voltaic arc under argon atmosphere, was analyzed in aerated aqueous solutions having different pH values. In all solutions the alloys, having nominal compositions Ti–50Zr at.% and Ti–13Zr–13Nb wt.%, displayed a valve-metal behaviour, owing to the formation of barrier-type oxide films. Passive films, grown potentiodynamically up to about 9 V, were investigated by photocurrent spectroscopy (PCS) and electrochemical impedance spectroscopy (EIS). These passive layers show photoactivity under anodic polarizations, with optical gaps close to 3.55 and 3.25 eV for the binary and the ternary alloy, respectively, indep…

Template Electrodeposition of CIS and CIGS Nanowires for Application in Solar Cells

Fabrication and Photoelectrochemical Behavior of Ordered CIGS Nanowire Arrays for Application in Solar Cells

In this work, we report some preliminary results concerning the fabrication of quaternary copper, indium, gallium, and selenium CIGS nanowires that were grown inside the channels of an anodic alumina membrane by one-step potentiostatic deposition at different applied potentials and room temperature. A tunable nanowire composition was achieved through a manipulation of the applied potential and electrolyte composition. X-ray diffraction analysis showed that nanowires, whose chemical composition was determined by energy-dispersive spectroscopy analysis, were amorphous. A composition of Cu0.203In0.153Ga0.131Se0.513, very close to the stoichiometric value, was obtained. These nanostructures wer…

The Stochastic Intelligence. A Technical Model from Ancient Greece to Robotics

What do we mean when we talk about the “intelligence” of robots? In what sense does a robot “reason” and “take decisions”? Answering these questions can give food for thought towards understanding whether there is either something so specific in human beings that cannot be reproduced in robots, or—as an alternative—the way to improve robots in emulating human behavior. In the following pages I will try to give my contribution by shedding light on some characteristics concerning human reasoning and rationality, mainly referring to the ancient Greek philosophical tradition.

Nanostructured binary tin alloy fabrication

Nanostructured Electrochemical Devices for Sensing, Energy Conversion and Storage

Nanostructured materials are attracting growing interest for improving performance of devices and systems of large technological interest. In this work, the principal results about the use of nanostructured materials in the field of electrochemical energy storage, electrochemical water splitting, and electrochemical sensing are presented. Nanostructures were fabricated with two different techniques. One of these was the electrodeposition of the desired material inside the channels of a porous support acting as template. The other one was based on displacement reaction induced by galvanic contact between metals with different electrochemical nobility. In the present work, a commercial polyca…

Synthesis of self-standing Pd nanowires via galvanic displacement deposition

This work shows that it is possible to obtain self-standing Pd nanowires into anodic alumina membranes by a simple metal displacement deposition. By using a proper arrangement, specifically designed in order to optimize the process, polycrystalline Pd nanowires were deposited from a solution containing Pd(NH3)4(NO3)2 as precursor. Morphological analysis showed the formation of perfectly aligned nanowires with a uniform diameter throughout the entire length. This last parameter was controlled by both the deposition time and the ratio between the anodic area (active metal) and the cathodic area (pore bottom). Keywords: Displacement deposition, Template synthesis, Palladium nanowires, Alumina …

Nanowire Ordered Arrays for Electrochemical Sensing of H2O2

Today, electrochemical sensors are considered very interesting in comparison to conventional techniques because they are very adaptable, cheap, have very low limit of detection and low detection time. The most used electrochemical technique is the amperometry . In amperometric sensors, a fixed potential is applied to the electrochemical cell, and a corresponding current, due to a reduction or oxidation reaction, is then obtained. This current it can be correlated with the bulk concentration of the detecting species (the solute) such as H2O2. Hydrogen peroxide is an essential mediator in food, pharmaceutical, clinical, industrial, and environmental analyses therefore, it is of great importan…

A Simple Model for the Photoelectrochemical Behavior of Corrosion Layers with Variable Hydration Degree

Abstract With the goal of quantitatively applying photocurrent spectroscopy to corrosion studies, the photoelectrochemical behavior of layered passive films having a decreasing hydration/hydroxylation degree, from the solution interface toward the metal interface, has been modeled. The model makes use of the correlations between optical gap and electronegativity of the constituents previously proposed for surface oxides and hydroxides. In this paper, the model was tested successfully against the experimental data pertaining to three high band gap insulating oxide-forming metals, like Zr, Al, and Y. In the first case, the fitting of the experimental spectra was compatible with the occurrence…

ULTRAFAST LEAD ACID BATTERIES USING NANOSTRUCTURED ELECTRODES

Studio del processo di recupero di membrane di policarbonato

Electrochemical deposition of different semiconductors for application in solar cells

Influence of electrodeposition techniques on Ni nanostructures

Abstract Different Ni nanostructure arrays were fabricated by pulsed electrodeposition from a Watts bath inside the pores of anodic alumina membrane (AAM) templates. Under a trapezoidal waveform of potential, consisting of fast linear sweeps between 0 and −3 V (SCE) interleaved by delay times at 0 (10 s) and −3 V (0.1 s), Ni nanowires were grown. The rate of nanowires growth was constant up to 60 min of deposition. For longer times, the growth of nanowires was not uniform, and after about 180 min some nanowires reached the template surface exposed to the electrolyte. Under square potential pulses between the same potentials (pulse length 1 s), nanotubes of Ni are obtained. Morphological ana…

Electrodeposition and characterization of CZTS for solar cells

Fabrications of Nanostructures And Nano-Structured Devices Using Electrochemical Methods

Electrochemical deposition of CIGS on electropolished Mo

Lead Nanowires for Microaccumulators Obtained Through Indirect Electrochemical Template Deposition

Metallic lead nanowires were deposited within pores of commercial anodic alumina membranes having an average pore diameter of 210 nm. "Direct" electrodeposition was attempted from 0.1 M Pb(NO 3 ) 2 aqueous solution with a variable concentration of H 3 BO 3 as a chelating agent, but it gave unsatisfactory results. An "indirect" two-step deposition procedure was then adopted, consisting of the anodic electrodeposition of α-PbO 2 nanowires, followed by their in situ reduction to metallic lead. Both these processes occurred at a high rate so that the indirect method led to a complete template pore filling with pure polycrystalline Pb in short times and with a high current efficiency.

Sn-Co Nanowires: High-Performing Electrodes as Anodes for Lithium-ion Batteries

Metal displacement deposition: a new method to grow amorphous silicon nanotubes

Deposition and characterization of Hydroxyapatite-Chitosan coatings on 304 SS for biomedical devices

During the last years biomaterials have been largely investigated in order to perform and improve biomedical devices. As regards orthopedic field, the most common equipment used (such as implants, bone grafts or screws) are constituted by metallic materials (steel and titanium alloys), characterized by low/medium resistance to corrosion and low osteointegration ability. Furthermore, these factors could produce local inflammations of the tissues surrounding the implants, increasing kinetics of corrosion phenomena. Scientific community has focused the attention on biocoatings interposed between metal and aggressive environment in order to inhibit corrosion. Furthermore, these coatings are abl…