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Ethylene glycol-based solutions containing metal precursor chloride salts were investigated for the electrodeposition of cobalt thin films and nanowires. The electrochemical behavior of 0.5 M Co(II) chloride solution at 70 °C was studied by means of cyclic voltammetry (CV) on a Pt substrate. The reduction process was shown to be irreversible, with high faradaic efficiencies (85–90 %). A diffusion coefficient (D0) of 2.29 × 10−6 cm2 s−1 for the Co species was estimated from the electrochemical behavior at different scan rates (from 25 to 125 mV s−1). The electrodeposition process was also studied on a copper substrate at different cathodic potentials (from −0.75 V vs Pt to −0.95 V vs Pt). Field-emission scanning electron microscopy (FE-SEM) and electron dispersive spectroscopy (EDS) revealed high-purity, compact films. Template-assisted electrodeposition resulted in ~16–18 μm long cobalt nanowires with an aspect ratio L/D > 100. X-ray diffraction (XRD) analysis of Co thin films showed a preferential orientation along the HCP [100] direction, which was even more marked for the nanowires. Vibrating sample magnetometry (VSM) highlighted that the fact that Co thin films were magnetized in-plane, while in nanowires a competition between shape and magnetocrystalline anisotropy led to similar magnetic behavior for the in-plane and out-of-plane directions. Keywords: Organic solvent, Magnetization, Non-aqueous, Electroplating, Alumina template

Abstract Earth-abundant and non-toxic Kesterite-based Cu2ZnSnS4 (CZTS) thin film solar cells are successfully fabricated on flexible Molybdenum (Mo) foil substrates by an electrodeposition-annealing route. A well-adherent, densely packed, homogeneous, compact, and mirror-like CZT precursor is initially produced through electrodeposition by using a rotating working electrode. Subsequently, the co-electrodeposited CuZnSn (CZT) precursor is sulfurized in quartz tube furnace at 550 °C for 2 h in N2 atmosphere with the presence of elemental sulfur in order to form CZTS. Different characterization techniques like XRD, SEM, HR-TEM, Raman, and Photoluminescence demonstrate that almost phase-pure CZTS formed after sulfurization. A flexible Al/Al-ZnO/i-ZnO/CdS/CZTS/Mo foil solar cell is produced, where CdS is deposited by chemical bath deposition and transparent conducting oxide (TCO) is deposited by DC sputtering. The CZTS solar device shows a 0.55% power conversion efficiency on flexible Mo foil substrate and it constitutes the first prototype of this kind of solar cell produced by electrodeposition-annealing route without any surface modification of the Mo substrate. Graphic abstract

The present work follows the trend to develop non-aqueous electrolytes for the deposition of corrosion resistant ZnNi alloys. It investigates the use of the choline chloride/ethylene glycol (1:2 molar ratio) eutectic mixture and of pure ethylene glycol as solvents for ZnNi electroplating. The electrochemical behavior of Zn and Ni is investigated via cyclic voltammetry, and potentiostatic ZnNi deposition is performed. Ni content is found to be precisely tunable in the 10-20% wt range, which presents the highest industrial interest for corrosion protection. ZnNi coatings obtained are characterized from the morphological and phase composition point of view. Evidence of the formation of a metastable γ ZnNi phase is observed for both choline chloride/ethylene glycol and pure ethylene glycol. Finally, potentiodynamic corrosion tests are performed to assess their corrosion properties.

In the 2D material framework, molybdenum disulfide (MoS2) was originally studied as an archetypical transition metal dichalcogenide (TMD) material. The controlled synthesis of large-area and high-crystalline MoS2 remains a challenge for distinct practical applications from electronics to electrocatalysis. Among the proposed methods, chemical vapor deposition (CVD) is a promising way for synthesizing high-quality MoS2 from isolated domains to a continuous film because of its high flexibility. Herein, we report on a systematic study of the effects of growth pressure, temperature, time, and vertical height between the molybdenum trioxide (MoO3) source and the substrate during the CVD process that influence the morphology, domain size, and uniformity of thickness with controlled parameters over a large scale. The substrate was pretreated with perylene-3,4,9,10-tetracarboxylic acid tetrapotassium salt (PTAS) seed molecule that promoted the layer growth of MoS2. Further, we characterized the as-grown MoS2 morphologies, layer quality, and physical properties by employing scanning electron microscopy (SEM), Raman spectroscopy, and photoluminescence (PL). Our experimental findings demonstrate the effectiveness and versatility of the CVD approach to synthesize MoS2 for various target applications.

Water splitting will be one of the most strategic techniques in the upcoming hydrogen-based economy. In this context, the development of efficient and low-cost Pt-free electrocatalysts is crucial t...

Large area molybdenum disulfide (MoS2) monolayers are typically obtained by using perylene-3,4,9,10-tetracarboxylic acid tetrapotassium salt (PTAS) as organic seeding promoter in chemical vapor deposition (CVD). However, the influence of the seeding promoter and the involvement of the functional groups attached to the seed molecules on the physical properties of the MoS(2)monolayer are rarely taken into account. Here, it is shown that MoS(2)monolayers exhibit remarkable differences in terms of the electronic polarizability by using two representative cases of seeding promoter, namely, the commercial PTAS and a home-made perylene-based molecule,N,N-bis-(5-guanidil-1-pentanoic acid)-perylene-3,4,9,10-tetracarboxylic acid diimide (PTARG). By thermogravimetric analysis, it is verified that the thermal degradation of the promoters occurs differently at the CVD working condition: with a single detachment of the functional groups for PTAS and with multiple thermal events for PTARG. As a consequence, the promoter-dependent electronic polarizability, derived by free charges trapped in the monolayer, impacts on the photoluminescence emission, as well as on the electrical performances of the monolayer channel in back-gated field-effect transistors. These findings suggest that the modification of the electronic polarizability, by varying the molecular promoter in a pre-growth stage, is a path to engineer the MoS(2)opto-electronic properties.

Ethylene glycol was studied as solvent for the electrodeposition of iron from both bivalent and trivalent iron chloride solutions. Using cyclic voltammetry (CV) on Pt electrodes, the impossibility to directly reduce Fe(III) ions to metallic state Fe(0) was evidenced with the formation of Fe(II) species as intermediate step for iron plating. Linear sweep voltammetries (LSVs) were carried out on copper substrate confirming the results previously obtained on platinum. Potentiostatic depositions were performed from both Fe(II) and Fe(III) solutions in a broad potential interval (from −1.5 to −2.3 V vs Pt) to define the threshold value for iron reduction and film formation: the best results were obtained at −1.7 V vs Pt for Fe(II) solution and at −2.3 V vs Pt for Fe(III) one. Deposits were characterized with field emission scanning electron microscope (FE-SEM) showing a nanostructured morphology with no traces of oxygen in the deposits, resulting in a pure metallic plated iron: films showed a corrosion potential (Ecorr = −0.54 V vs Ag/AgCl ) in 3.5 wt% NaCl aqueous solution similar to high purity metallurgical iron sheet (Ecorr = −0.4 V vs Ag/AgCl ). X-Ray diffraction patterns showed a preferential orientation of the nanocrystalline deposit along the BCC [110] direction. Vibrating sample magnetometer (VSM) analysis showed a good saturation magnetization (1500 ± 100 kA/m) and low coercivity (∼20 Oe) indicative of a high purity iron film.

Sb2Te3 exhibits several technologically relevant properties, such as high thermoelectric efficiency, topological insulator character, and phase change memory behavior. Improved performances are observed and novel effects are predicted for this and other chalcogenide alloys when synthetized in the form of high-aspect-ratio nanostructures. The ability to grow chalcogenide nanowires and nanopillars (NPs) with high crystal quality in a controlled fashion, in terms of their size and position, can boost the realization of novel thermoelectric, spintronic, and memory devices. Here, it is shown that highly dense arrays of ultrascaled Sb2Te3 NPs can be grown by metal organic chemical vapor deposition (MOCVD) on patterned substrates. In particular, crystalline Sb2Te3 NPs with a diameter of 20 nm and a height of 200 nm are obtained in Au-functionalized, anodized aluminum oxide (AAO) templates with a pore density of ?5 ? 1010 cm-2. Also, MOCVD growth of Sb2Te3 can be followed either by mechanical polishing and chemical etching to produce Sb2Te3 NPs arrays with planar surfaces or by chemical dissolution of the AAO templates to obtain freestanding Sb2Te3 NPs forests. The illustrated growth method can be further scaled to smaller pore sizes and employed for other MOCVD-grown chalcogenide alloys and patterned substrates.

Zn rich ZnNi alloys electrodeposition have recently attracted the attention of researchers due to their interesting corrosion properties [1]. In particular, alloys containing Ni in the 15 - 25 % range find application in a number of industrial fields, like automotive and constructions. ZnNi is normally electrodeposited from aqueous solutions, in which plating takes place following a typical anomalous mechanism [2]. In the last few years, however, new deposition approaches have been attempted to improve ZnNi plating performances. Specifically, III generation deep eutectic solvents comprising choline chloride have been tested [3]. The present work investigates the use of non-aqueous ethylene glycol based electrolytes for the deposition of Zn rich ZnNi alloys. The use of ethylene glycol as solvent introduces many advantages with respect to aqueous solutions: low oxygen contamination, high deposits purity and no pH dependance [4]. ZnNi codeposition was studied employing cyclic voltammetry and layers were deposited under potentiostatic control. Deposition potential was varied and its influence on final composition and morphology was determined. Addition of an additive (NH4Cl) to enhance surface morphology was attempted as well [3]. Phase composition was investigated using XRD to determine the possible presence of a metastable γ-ZnNi phase, which has already been observed in the case of ZnNi plated from alkaline aqueous solution [5]. Finally, corrosion behavior of layers obtained from ethylene glycol was assessed and compared with equivalent coatings deposited from commercial aqueous solutions. [1] M. Gavrila et al.; Surface and Coatings Technology, 123 (2-3), 164-172 (2000) [2] G. Roventi et al.; Journal of Applied Electrochemistry 30 (2), 173–179 (2000) [3] S Fashu et al.; Transactions of Nonferrous Metals Society of China 25 (6), 2054-2064 (2015) [4] G. Panzeri et al.; Electrochimica Acta 271 (1), 576-581 (2018) [5] S. Ieffa et al.; Transactions of the IMF 94, 321-324 (2014)

In an attempt to mitigate the effects of climate changes, modern societies are facing a revolution in energy supply. Future economy will be increasingly dominated by carbon-free and renewable energy sources. In this context, hydrogen will play a fundamental role in the energy transition from fossil to green sources. It offers the possibility to smooth the intermittency typical of many renewable energy sources and it constitutes an ideal complement for batteries in the transport sector. Hydrogen can be easily produced employing water electrolysis, stored in large amounts and subsequently re-electrified in fuel cells. Efficient water electrolysis, however, makes use of noble metal electrocatalysts to lower the overpotential required for the Hydrogen Evolution Reaction (HER) to take place. Due to the limited availability and consequent high cost of noble metals, research is currently focusing on the development of low-cost alternative catalytic materials. One of the most studied electrocatalytic compounds are transition metal phosphides [1]. These materials present remarkable advantages over commonly used Pt based catalysts: comparable performances, lower cost, high abundancy and ease of manufacturing. In the present work, transition metal phosphides were fabricated through a simple and costless codeposition-annealing process. Amorphous Ni-P and Co-P alloys were codeposited with red phosphorus particles and subsequently annealed [2]. The annealing step was applied to promote the formation of intermetallics through interdiffusion between pure phosphorus particles and the metallic matrix. As a result, different phase pure metal phosphides were obtained. The most important advantage of this methodology is the possibility to overcome the compositional limit typical of electrodeposited phosphorus-based alloys. Elemental phosphorus codeposition allows to reach P concentrations higher than 50 % at., whereas simple Ni-P solid solution electrodeposition is compositionally limited to 25 % at. Enhancing P content is fundamental to obtain phosphorus rich compounds like Ni2P and Co2P, which are characterized by high catalytic activities for HER [3]. Furthermore, the technique allows to confine elemental P inside the coating during the annealing step. This peculiarity strongly optimizes material usage and it limits the presence of gaseous phosphorus, which is typical of many phosphorization processes used in literature to obtain metal phosphides [4] and it can result into the formation of the unstable white P allotrope. Obtained nickel and cobalt phosphides were characterized with different techniques (SEM, XRD, EDS) to assess their morphology, phase structure and chemical composition. A special emphasis was placed on XPS characterization. Thanks to its ability to analyze the first superficial layers of the coatings, XPS was employed to determine the chemical state of the elements present on the surface of the electrocatalysts. Being electrocatalysis an interfacial phenomenon, this allowed to link material surface properties with observed electrocatalytic performances. The electrocatalytic HER activity and stability of the different transition metal phosphides were tested in 0.5 M H2SO4. In all cases, remarkable results were obtained, with the lowest overpotential obtained in the case of Co-P/P codeposition and subsequent annealing at 290 °C: 62 mV vs. RHE at a current density of 10 mA/cm2 in 0.5 M H2SO4 solution. This result is in line with the literature available on cobalt phosphides as electrocatalysts [5]. [1] P. Xiao et al., Adv. Energy Mater. 5, 1500985 (2015) [2] R. Bernasconi et al., ACS Appl. Energy Mater. 3(7), 6525–6535 (2020) [3] A. R. J. Kucernak et al., J. Mater. Chem. A 2, 17435 (2014) [4] X. Wang et al., Angew. Chem. 54(28), 8188 (2015) [5] Saadi et al., J. Phys. Chem. C 118(50), 29294–29300 (2014)

Protective coatings able to provide improved tribological behavior and corrosion resistance are demanded in many industrial applications. Although hard chrome is a very effective solution and is widely used, environmental issues related to hexavalent chromium push to develop alternative treatments. Within the framework of the HardAlt European Project, electrodeposited composite coatings have been developed and main results of this investigation are reported in this work. Boron carbide micro-particles were dispersed in a Ni-P matrix under different operating conditions, in order to produce coatings with different composition and particle content. Structural and morphological characterization was performed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Mechanical properties were evaluated by micro-indentation and the tribological performance was assessed by block-on-ring tests. Electrochemical experiments were carried out to examine the corrosion behavior of the composite coatings. Interesting results were obtained for composite coatings as regards hardness values, tribological behavior and corrosion resistance, even though some improvements can be realized. However, the results presented in this work show that composite coatings may represent a promising alternative to hard chrome for selected applications and also suggestions for further investigation are gained.

Nowadays, many different methods are used to produce graphene. Electrochemical techniques represent a low-cost and versatile route to deposit metals, although the characterization of graphene grown on electrochemically deposited polycrystalline metals is still in its infancy. In this work, several metal substrates were prepared by electrochemical processes and then covered with graphene layers grown by CVD. Free-standing foils of Cu and Ni-Cu alloy (20 wt.% of Cu) were prepared by electroforming, while a pure Ni film was obtained by galvanic displacement on a Si wafer. The thickness of Ni film on Si wafer was about 0.7 µm, whereas the Ni-Cu foils were much thicker (12 µm). The characterization of the graphene films was performed by using Raman spectroscopy, XPS and AES. Copyright © 2016 John Wiley & Sons, Ltd.

In the perspective of sustainable development, future economy will be increasingly dominated by carbon-free and renewable energy sources. In this context, hydrogen will play a fundamental role in the energy transition from fossil to green sources. Hydrogen can be easily produced employing water electrolysis, stored in large amounts and subsequently re-electrified in fuel cells. It offers the possibility to smooth the intermittency typical of many renewable energy sources and it constitutes an ideal complement for batteries in the transport sector. Efficient water electrolysis, however, makes use of noble metal electrocatalysts to lower the overpotential required for the Hydrogen Evolution Reaction (HER) to take place. Due to the limited availability and consequent high cost of noble metals, research is currently focusing on the development of low-cost alternative catalytic materials. One of the most studied electrocatalytic compounds are transition metal phosphides [1]. These materials present remarkable advantages over commonly used Pt based catalysts: lower cost, high abundancy and ease of manufacturing. In many cases, phosphides offer performances comparable to the noble metal electrocatalysts. In the present work, transition metal phosphides were fabricated through a simple and costless codeposition-annealing process. Amorphous Ni-P and Co-P alloys were codeposited with red phosphorus particles and subsequently annealed. The annealing step was applied to promote the formation of intermetallics and the interdiffusion between pure phosphorus particles and the metallic matrix. As a result, different phase pure metal phosphides were obtained. The most important advantage of this methodology is the possibility to overcome the compositional limit typical of electrodeposited phosphorus-based alloys [2]. Elemental phosphorus codeposition allows to reach P concentrations higher than 50 % at., whereas simple Ni-P solid solution electrodeposition is compositionally limited to 25 % at. Enhancing P content is fundamental to obtain phosphorus rich compounds like Ni2P and Co2P, which are characterized by high catalytic activities for HER [3]. Another interesting benefit of the technique presented is the confinement of elemental P inside the coating during the annealing step. This peculiarity strongly optimizes material usage and it limits the presence of gaseous phosphorus, which is typical of many phosphorization processes used in literature to obtain metal phosphides [4] and it can result into the formation of the unstable white P allotrope. Specifically, Ni-P and Co-P were codeposited with red P particles and process conditions were optimized to maximize elemental P particles concentration. Annealing temperature and duration were varied to investigate their influence on final electrocatalytic perfrormances. Characterization techniques like XRD, SEM, EDS, cross-sectional analysis and XPS were used to determine phase composition of the materials obtained and to characterize their morphology. The electrocatalytic HER activity and stability of the different transition metal phosphides were tested in 0.5 M H2SO4. In all the cases, remarkable results were obtained, which matched up well with present existing literature where similar electrocatalysts have been fabricated through different methods [5]. The lowest overpotential was obtained in the case of Co-P/P codeposition and subsequent annealing at 290 °C: 62 mV vs. RHE at a current density of 10 mA/cm2 in 0.5 M H2SO4 solution. [1] P. Xiao et al., Adv. Energy Mater. 5, 1500985 (2015) [2] R. L. Zeller and U. Landau, J. Electrochem. Soc. 139(12), 3464 (1992) [3] A. R. J. Kucernak et al., J. Mater. Chem. A 2, 17435 (2014) [4] X. Wang et al., Angew. Chem. 54(28), 8188 (2015) [5] Z. Pu et al., Chem.Mater. 26(15), 4326 (2014)

Ultrathin carbon films were grown on different types of metallic substrates. Free-standing foils of Cu and Ni were prepared by electroforming, and a pure Ni film was obtained by galvanic displacement on a Si wafer. Commercial foil of Ni 99.95% was used as a reference substrate. Carbon films were grown on these substrates by chemical vapour deposition in a CH4-H2 atmosphere. Obtained films were characterized by Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy, and ultraviolet photoemission spectroscopy. The XPS at grazing collection angle was used to determine the thickness of carbon films. Depending on the deposition parameters, the films of graphene or graphite were obtained on the different substrates. The uniformity of graphene and its distribution over the sample area were investigated from Raman data, optical images, and XPS chemical maps. The presence of graphene or graphite in the films was determined from the Raman spectra and Auger peak of C KVV. For this purpose, the D parameter, which is a fingerprint of carbon allotropes, was determined from C KVV spectra acquired by using X-rays and electron beam. A formation of an intermediate layer of metal hydroxide was revealed in the samples with graphene overlayer.

Cu-Ag alloys are promising materials for electrical interconnections due to their combination of high conductivity and superior mechanical strength. In the present work, Cu-Ag alloys were electrodeposited from a cyanide-free electrolytic bath and different Ag percentages, ranging from 3 to 15 at.%, were obtained by controlling the deposition conditions. Electrochemical processes occurring during Cu-Ag deposition were investigated by means of cyclic voltammetry. Structural properties were examined by TEM and XRD and hardness was assessed by microindentation. TEM observations revealed the presence of nano-sized Ag precipitates at low Ag content, and the composition of the Cu-rich and Ag-rich phases in high-Ag alloys was deduced from XRD measurements. As-deposited alloys exhibited high hardness values and the contribution of solid-solution hardening was highlighted.

Zinc alloy offers superior sacrificial protection to steel as the alloy dissolves more slowly than pure zinc. The degree of protection and the rate of dissolution depend on the alloying metal and its composition. In this work, the physico-chemical characterization of zinc–nickel electrodeposits obtained from an alkaline bath is carried out and a description of the structural and thermodynamic properties of these alloys is proposed. Contrary to the common acceptance, XRD spectra and DSC thermal analysis show that the electrodeposited γ alloy has to be regarded as a metastable phase, whose atomic arrangement is different from that of the equilibrium γ intermetallic compound. A model for atomic distribution in the electrodeposited alloy is proposed. The Gibbs free-energy function for the electrodeposited phase has been evaluated and the metastable boundaries of the single-phase and two-phase fields have been calculated. Reasonable agreement is found with experimental values reported in the literature for Zn–Ni coatings with different composition.

A widely used method to protect steel surfaces from corrosion is the application of a sacrificial layer of a less noble metal, which undergoes preferential corrosion due to galvanic coupling. The most used material is zinc, a metal readily available and easy to apply on components presenting large areas. However, zinc is far more reactive than iron, and the thickness of material needed to effectively prevent corrosion represents an issue for some applications, such as coatings for the automotive sector or the aerospace field. A possible solution can be the alloying of zinc with a metal of the iron group, thus increasing the nobility of the layer. By doing this the corrosion potential is shifted to values closer to iron, inducing a slower consumption of the sacrificial layer. Nickel, having a suitable equilibrium potential, is the most used metal, providing an excellent corrosion protection with respect to pure zinc. The coatings obtained are times more resistant to corrosion than pure zinc and are currently studied as alternatives to cadmium. Zn–Ni alloys are reasonably easy to electrodeposit, and the plating of corrosion efficient coatings was performed in the past from acidic and alkaline electrolytes. It is well-known that the best protective properties are achieved when the alloy presents a single γ phase, a condition that can be attained by controlling properly the plating parameters and electrolyte formulation. It is interesting to point out that the plated γ phase can be a metastable structure, as the Zn–Ni phase diagram predicts lattice distributions of the Ni atoms in contrast with the experimental results. The reasons for the observed metastability and the thermodynamic properties of Zn–Ni have been elucidated previously starting from the analysis of the equilibrium conditions of the different phases. It was demonstrated that Zn–Ni electroplated alloys from an alkaline bath follow the theoretical simulations, thus validating the interpretation provided. Zn–Ni can be plated also by means of pulsed electrodeposition, a method suitable to achieve more refined microstructures and compact layers. This change in microstructure also improves the corrosion behavior and the distribution of the residual stresses. Zn–Ni alloys having compositions in the range 14–18 wt-% are electrodeposited using direct current DC and pulse current PC in a cyanide-free alkaline electrolyte. Homogeneous and compact layers, suitable for corrosion protection, are obtained. Contrary to the common acceptance, X-ray diffraction spectra and differential scanning calorimetry thermal analysis show that the electrodeposited γ alloy by DC plating in electrolytes with complexant-additive agents has to be regarded as a metastable phase, whose atomic arrangement is different from that of the equilibrium γ intermetallic compound. A model for atomic distribution and the Gibbs free-energy function for the DC electrodeposited phase are discussed. It is found that PC deposited alloys from additive-free electrolytes present the same metastable behavior attributed to the DC plated homologues in electrolytes with complexant-additive agents. The corrosion behavior is found to be dependent on the duty cycle applied during PC deposition, as evidence of the different microstructures obtained in varying the parameters.

Graphene grown by CVD on Cu foils has generated interest due to low cost and the prospect of large-area monolayer coverage. The initial nucleation and growth dynamics of graphene play a critical role in determining the final film quality. In this work, we investigate the effects of the electrochemical synthesis onto graphene quality, showing the influence of the Cu-Ru interdiffusion. The growth of good quality graphene layers is also discussed in terms of the role played by grain boundaries and diffusion at the grain boundaries. This comparison shows that the graphene having the best quality is produced using a ruthenium sandwich covering a copper core. This setting avoids contaminations from evaporation and recondensation of copper during thermal cycling due to the CVD process.

Zinc alloys containing transition metals (Ni, Co and Fe) have attracted the attention because of their high corrosion resistance [1,2]; particularly high is the interest of ZnNi system for practical application. In addition, electrodeposition of ZnNi alloys is generally described as anomalous codeposition (Brenner [3]). In this work ZnNi electrodeposition from ionic liquid system is studied; particular attention is paid to the formation Zn rich alloys (15-25 % Ni). The plating bath consists of 1 choline chloride: 2 ethylene glycol containing metal salts in different concentration. All the electrodepositions have been carried out at constant temperature T=70°C on steel. Codeposition of ZnNi is studied by means of potentiostatic electrodeposition. Compositional and morphological analysis are performed to evaluate the effect of the plating conditions and bath formulation. Electrochemical characterization of the solution is performed for those baths compositions allowing the formation of 𝛾-phase ZnNi. Metastable 𝛾-ZnNi with short-range order has been observed with XRD analysis; thermal treatment are carried out to evaluate phase reorganization. [1] R Fratesi, G Roventi. Corrosion resistance of Zn-Ni alloy coatings in industrial production, Surface and Coatings Technology. 82 (1996) 158. [2] R Ramanauskas, P Quintana, L Maldonado, R Pomés, MA Pech-Canul. Corrosion resistance and microstructure of electrodeposited Zn and Zn alloy coatings, Surface and Coatings Technology. 92 (1997) 16. [3] A Brenner. A. Electrodeposition of Alloys. Vol. 1, General Survey, Principals, and Alloys of Copper and of Silver, (1963).

A rational understanding of what occurs during electrocrystallization, defined at a nanolevel, is developed to control electrodeposition processes. The electrokinetic behavior of the elements in solutions and the electrodeposits structure resulting from the electron exchange reaction at the cathodic surface are taken into consideration and compared. Transient electrokinetic parameters are measured with the secondary current pulse (SCP) technique, where a square galvanostatic pulse of a few ms duration is superimposed on the cathode while electrodeposition is running. Two parameters are obtained, the transient Tafel slope and the adsorption pseudo-capacitance; whilst a third parameter, the diffusive time constant, must be introduced if the overvoltage does not arrive to a steady state during the short pulse period. These parameters are related to the growth of different structures and permit a good control of the process. Control of the growth with nanodefinition is key to the development of innovative processes to keep pace with more and more demanding applications and environmental challenges. Examples are given to stress the relevance of the theoretical framework and to show possible implications for electrodeposition technology and its applications.

Gas-carburizing kinetics of a low-alloy steel (Pyrowear 53) was investigated by thermogravimetric experiments. Kinetic curves were modeled by adapting the approximate integral method, and the diffusion coefficient of carbon as well as the rate constant of the surface reaction were estimated. These parameters were evaluated after several carburizing procedures, which differ from each other in the surface treatments performed before the carburizing step. It is known that the carbon enrichment is low when this steel is carburized without any pretreatment, and this behavior was found to be related to a low value of carbon diffusivity. The interaction between the selective oxidation of alloying elements by the carburizing atmosphere and carbon diffusion is discussed. The pretreatment procedures investigated in this work consist of different combinations of oxidation, reduction, and grit-blasting processes. The most effective procedures involve oxidation in dry air or oxidation in wet air followed by grit blasting.

Replacement of lubricating oils with water or low-viscosity fluids is highly desirable in many industrial fields, on account of the environmental and economical advantages. Low lubricity of water might be insufficient for proper operation of hydraulic components, and diamond-like carbon(DLC) coatings are very attractive as solid lubricant films. A remote-plasma PACVD process was utilized to deposit hydrogenated DLC coatings (a-C:H) on different substrates. Microindentation measurements show that the coating hardness is around 35 GPa. Tribological behavior was evaluated by block-on-ring tests performed in water and water with alumina. The wear rate was calculated after measuring the wear volume by a laser profilemeter. Morphological and compositional analysis of the wear tracks reveal that coating failure may occur by abrasive wear or delamination, depending on the substrate properties. Hard and smooth substrates give the best results and dispersed alumina particles increase the wear rate.

By electrodeposition it is possible to obtain alloy phases of metastable structure; these phases may be different from those reported for metallurgical equilibrium conditions or may have different compositions for the solubility limits, in some cases with very important enlargement. Typical cases are examined, discussing published results and presenting new findings. To understand the general behaviour, free energy versus composition g/x diagrams were calculated and are presented for the alloys examined in equilibrium conditions and after modification to obtain composition limits for the electrodeposited phases in stable and metastable state. The first reported case is Ni–Sn alloy, where the well known metastable phase NiSn is obtained. The second case is the electrodeposition of IB–Sn alloys from non-cyanide electrolytes. Phase structure of Zn-rich electrodeposited Zn–Ni alloys is also discussed as representative of grain size effect on phase stability. From the different cases examined, the occurrence of electrodeposited intermediate phases can be interpreted according to a local thermodynamic equilibrium, whilst long range order is difficult to observe in as-deposited layers. These phases depend on bath composition and operation conditions (temperature, stirring, direct or pulse current density) giving phases of different grain size which in turn can influence their stability.

Fluorinated amorphous carbon films were deposited by plasma assisted chemical vapour deposition from C 2 H 2 and CF 4 gases. Gas mixture and bias voltage were changed. We analysed film structure by Raman and infrared spectroscopies and film hardness by micro-indentation. Raman spectra show a transition from diamond-like carbon films to polymer-like films as the CF 4 content in the plasma increases. The presence of a strong fluorescence background in the spectra of fluorine rich films indicates a polymer-like structure. Infrared spectra confirm the presence of CF x , F 2 CCF 2 and F 2 CC(HF) groups in the films. Hardness values are correlated with the trends of the D to G peak intensity ratio, I D / I G . Mechanisms involved in film growth and formation are discussed especially regarding fluorine substitution for hydrogen.

Graphene has become a promising material for many different applications, such as nanoelectronic devices, physical, chemical and biochemical sensors, transparent conductive films, clean energy scavenging and storage devices, and nanocomposite formulation. Recently, gas sensing, as a critical application in intelligent systems, is receiving increasing attention in both industry and academia. Sensing applications using graphene sheets as transducers have experienced a surge of activities in recent years, especially for gas sensing platforms and electrochemical sensing, because of the high electrical conductivity and high surface area of graphene. Despite the significant amount of work on graphene electronic devices such as the field effect transistor, its use in sensors, actuators or micro and nano-electromechanical systems (MEMS/NEMS) in general, is relatively less explored. By combining graphene's electronic and mechanical properties, monolithic sensors can be developed with superior sensitivity. Furthermore, proper functionalization of graphene enables enhanced selectivity. In this work, we investigate the synthesis of graphene by methane decomposition at 1000 °C onto free standing electrodeposited substrates, studying the effects of the electrochemical synthesis onto graphene quality. The growth of good quality graphene layers is also discussed in terms of the role played by grain boundaries and diffusion at the grain boundaries. Results on graphene properties when grown on ruthenium, copper and Ni-Cu alloys are reported, together with the possibility to grow 3D graphene layers on porous substrates, obtained by selective electrochemical de-alloying in the Ni-Cu system. Our results demonstrate the synthesis of graphene on Cu with presence of the D-peak and with the 2D-peak not higher than the G-peak (shifting of the 2D-peak) and on Ru with a high D-peak but with the 2D-peak still higher than the G-peak. The growth of graphene on NiCu is affected by the amount of copper in the alloy: a transition from graphitic to graphenic layers is observed with increasing copper content. Transfer procedures in order to integrate thus-produced graphene layers into MEMS device are presented, including the electrochemical approaches to decorate the graphene sheets with catalytic nanoparticles. The possibility of using this simple approach to develop new transducing materials for sensing applications integrated with a silicon microdevices is demonstrated.

Galvanic displacement from fluoride containing solution is a well established technique for the deposition of metals on semiconductor substrates, with a very broad plethora of applications in the electronic, photovoltaic and MEMS industries, due to the film conformal nature and process high selectivity towards silicon surfaces. Immersion plating is able to produce very homogeneous thickness metal seeds. Particularly, Copper and Nickel were the chosen species for silicon plating due to their wide application range and variety of different exploitable properties, also in thin films engineering. Copper has a very good electrical conductivity and charge mobility, while Nickel has good electron transport properties too as well as magnetic features that are exploited in several micro- and nano-devices. Very good results have already been achieved in the past years for Copper and Nickel systems in terms of metal film homogeneity and aspect ratio. In order to have a complete substrates characterization, newly adapted plating baths were used for p-doped Silicon wafers metallization just after a suitable surface cleaning step was performed. The resulting metallic layers showed high homogeneity and high reflectivity, achieving mirror-like appearances as well as very low mean surface roughness. SEM characterization was also used to appreciate the metal layer thickness control achieved by the proposed processes, as well as gathering information about the different metals growth rate. Subsequently, X-rays photoelectrons spectroscopy has been employed to understand the surface state of Silicon, Nickel and Copper in the plated substrate; furthermore X-rays diffraction analysis was used to characterize the crystalline structure of the metallic thin films on top of the semiconductor. The collected data have been employed as input for Density Functional Theory calculations on the Nickel-Silicon and Copper-Silicon interfaces, aiming at the description of the interactions at the interfaces from an atomistic point of view.

In the present work, a chemical treatment with perfluorinated peroxides is proposed to obtain protective layers covalently linked to a diamond-like carbon (DLC) surface. The lubricant properties of perfluorinated compounds and the stability of the chemical modification of DLC surface simultaneously cooperate in this technical approach. Each fluorinated layer is deposed on an bare DLC surface by a dip coating application technique and the covalent linkage of the fluorinated layers is obtained by the thermal decomposition of the peroxidic moieties of the perfluorinated peroxides. Reactive perfluorinated radicals are generated close to the sp2 sites of the DLC surface, allowing the formation of covalent bonds. The fluorinated peroxides used in this work belong to the class of the PFPE peroxides and to the class of the perfluorodiacyl (PFDA) peroxides. The effect of the fluorinated coatings on the DLC surface is studied using X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), with contact angle (CA) measurements and, in particular, the friction forces are evaluated by means of lateral force microscopy (LFM).

Le depot chimique en milieu aqueux de films de Ni-P et de Co-P a ete controle par une technique de pulsation de courant secondaire, donnant des informations sur le processus de depot. Les resultats ont ete correles avec l'analyse de la structure des depots.

A statistical thermodynamic approximation for cooperative phenomena in magnetic materials is proposed, improving constant coupling approximation by introduction of a second pairs quasichemical reaction after averaging atomic groups. With suitable temperature functions related to fluctuations, analytical expressions for free energies of Ising and Heisenberg systems are obtained and applied.

A novel electrolyte based on CuSO4 complexed by K4P2O7 and AgNO3 complexed by KI is studied for the deposition of CuAg alloys having a range of Ag compositions between 3 %at. and 16 %at. The deposition occurred in non stirred conditions at 50°C. A characterization of the coatings is presented with a focus on the properties of the supersaturated alloy and the demonstration of its metastable behavior. The electrochemical characterization of the solution is also reported.

Alloy thin films of interest for possible electronic applications were obtained by electrodeposition: NiFe for magnetic heads, Co alloys for magnetic recording and CuSb as a possible underlayer for electric contacts. Permalloy ECD NiFe films were deposited from acid baths on Si wafers, patterned by photolithography; CoPt and CoPd films from baths of similar composition, obtaining hard CoPt and soft CoPd layers; CuSb as oversaturated solid solutions or as multilayers depending on the deposition conditions. Electrokinetic behaviour and related structures are interpreted by means of the normality-inertia parameter P ni .

Physical adsorption occurs at low pressure on most active sites of heterogeneous powders, describing their reactivity and dispersibility. A method to obtain the adsorption energy distribution function of surface sites (w) is presented, based on the determination of the parameters of a suitable physisorption isotherm. Two parameters of the isotherm equation, TF and X, determine the surface energy distribution function and are physically interpreted: TF as the formation temperature, i.e. the temperature of surface equilibrium; X as an energy parameter, decreasing when the relative importance of the side interaction energy between adsorbate molecules increases with respect to the adsorbate-adsorbate interaction energy. Many types of magnetic particles have been examined by this method and the results compared with those of other investigation methods. The influence of milling type and time on the surface properties of Ba and Sr ferrite powders for permanent magnets is presented, determining the conditions to obtain optimum magnetic properties after sintering. Iron oxide powders, both as such and after surface modification with cobalt, for magnetic recording tapes and digital floppy disks have been examined by several techniques: physisorption, mercury porosimetry and electron microscopy. Surface properties, in particular acicularity and heterogeneity, have been related to the powder rheological behaviour and their magnetic characteristics. The relation has been extended to the performance of drawdown coatings and of experimental floppy disks. Particles showing high and uniform dispersibility had a narrow particle size distribution and a relatively large number of high energy sites.

A statistical thermodynamic approximation -for cooperative phenomena in model systems is presented, to improve the quasichemical constant coupling approximation by introduc in a second pairs quasichemical reaction after averaging atomic groups. By means o-P two suitable temperature -functions related to -Fluctuations, an analytical expression of the free energy function is obtained. The first parameter takes into account the change of the order parameter after averaging and the decreasing importance of the second reaction at increasing temperatures. The second one is a correction of the system temperature as a consequence of fluctuations’ influence on the mean thermodynamic behaviour. Relations to obtain the right critical exponents and well approximaterfthermodynamic critical quantities for ordering systems are given. The approximation is applied to real systems, such as beta brass, taking into account next nearest neighbour interaction.

Carbide coatings deposited by PVD techniques can provide different properties according to their structural and compositional features. In particular, MC/a-C(:H) composite coatings (where M is a carbide-forming element) receive increasing attention as wear resistant films with low coefficient of friction. In this work, Ti-C:H coatings were prepared by reactive magnetron sputtering and their atomic ratio Ti/C was varied between 0.14 and 5.3. Maximum hardness values were achieved for Ti/C ratios corresponding to the carbide formation. Nanocomposite coatings with hydrocarbon matrix were deposited after growing a functionally graded interlayer and their tribological properties were investigated both in air and in water.

SUMMARYCold sealing of anodized aluminium with solutions containing nickel fluorides is A process in increasing industrial use. Experiments suggest the combined action of Ni2+ and promotes the hydration of Al oxides, which continues after immersion. The anodic oxide composition and structure was compaired with hot water sealed layers by EDAX and by X-ray diffraction. Ni and F decrease together from the surface towards the inner oxide layer. A compact surface layer is obtained, which is resistant to alkalies. Weathering affects the oxide. Chlorine is observed in weathered oxide layers, if hot sealed; cold sealed layers are less prone to chloride attack. Immersion in warm baths with Ni acetate and other salts seals the oxide layer at low cost, reduced treatment time, diminished time for drying, less staining, and limited need for waste water treatment. Crazing problems are reduced.

Hydrogenated carbon films and hydrogenated carbon films containing nitrogen have been synthesized by direct ion beam deposition (IBD) using cyclohexane and methane as precursors and by plasma-assisted chemical vapour deposition (PACVD) using cyclohexane and acetylene as precursors. The elemental composition has been assessed by gas chromatography. The films' structure has been analysed by FTIR, Raman, NEXAFS spectroscopy and X-ray reflectivity. The hardness has been determined by nanoindentation and microhardness measurements, and the stress by optical profilometry. FTIR measurements reveal an increasing nitrile and amine group absorption with a corresponding decrease of C–H stretching modes as the nitrogen concentration in the film increases. The nitrogen-containing functional groups are proposed to be at peripheral positions of graphitic domains. The corresponding reduction of the domain size is detected in the Raman data, and the increase of delocalized bonding in a-CH(:N) films with respect to a-CH films is confirmed by the NEXAFS results. In the carbon K-edge spectra, the intensity of the π* CC resonance at ≃285.3 eV has been found to increase as a function of N content. This indicates principally an increment of the sp2 hybridization. Such a structural change leads to a decrease in the hardness and the internal compressive stress with respect to a-CH films. In a film containing 15 at% N, the hardness is reduced to 44% and the stress to 36% of that for a-CH.

Hydrogenated amorphous carbon films (a-C:H) and hydrogenated carbon films containing as much as 15 at.% nitrogen (a-CN x :H) were synthesised by a plasma-assisted chemical vapour deposition (PACVD) apparatus. By changing the gaseous precursor (CH 4 , C 6 H 12 , C 6 H 6 , C 2 H 2 ) the hydrogen content of the films can be varied between 26 and 58 at.%; serious adhesion problems were found when the hydrogen percentage attains the highest value. Hydrogen-free layers were deposited by magnetron sputtering in Ar (a-C) and N 2 (a-CN x ): nitrogen fractions range from 8 to 28 at.% and increase when the substrate is closer to the graphite target during deposition. Film hardness was evaluated by nanoindentation in order to avoid inflation of the assessed value consequent to the elastic recovery, which results to be quite large in the examined layers. The hardness measurements show values up to ∼30 GPa and point out that both nitrogenation of a-C:H films and deposition by magnetron of hydrogen-free a-C layers lead to softer materials (∼18 GPa). Main features of Raman spectra are broad `G' and `D' peaks, characteristic of DLC layers: correlation between parameters of these peaks is discussed.