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In the present work, Plasma Electrolytic Oxidation (PEO) coatings were produced on zinc-aluminized carbon steels (Galvalume commercial treatment). In addition, copper particles of various sizes were introduced into the coating in order to produce samples with antifouling properties. The particles were successfully embedded into the coating. A higher number of embedded particles was observed when these are in sub-micrometric size and obtained in pulsed current. The presence of particles produces significant antifouling properties on the sample’s surfaces during the first 20 days of immersion. The presence of the particles reduces the corrosion resistance in comparison to the samples PEO coated without the particles; however, the corrosion resistance remain higher than the one of the untreated sample.

Stress corrosion cracking (SCC) of laser powder bed fusion-fabricated 316L was studied under the variation in energy input density to emulate the existence of distinctive types of defects. Various electrochemical polarization measurements were performed in as-received polished and ground states, to elucidate the effect of defect type on corrosion and SCC behaviour in marine solution. The results revealed severe localized corrosion attack and SCC initiation for specimens with a lack of fusion pores (LOF). Moreover, the morphology of SCC was different, highlighting a more dominant effect of selective dissolution of the subgrain matrix for gas porosities and a more pronounced effect of brittle fracture at laser track boundaries for the specimens with LOF pores.

The use of grain refiners, such as iridium, in 18 kt gold alloys is a common practice in jewelry industrial applications. The use of these elements leads, however, to an increase in the costs of raw materials and greater attention during the solidification phases and during the refining and recycling of alloys is required. This work aims to demonstrate that through the optimization of thermo-mechanical processes, it is possible to obtain a result comparable to that obtained with refiner in terms of workability, mechanical and aesthetic properties and corrosion behavior. The study focused on evaluating the grain growth in annealing processes after plastic deformation, also examining the casting phase and the effect of the different cooling rates. The samples, after the different thermo-mechanical treatments, were characterized in terms of microstructure, grain size and micro-hardness comparing the results with the ones of an iridium-containing alloy. The results showed that with proper optimization of annealing time is possible to obtain, without grain refiners, gold alloys with properties similar to ones obtained with Iridium as a grain refiner.

Circular economy is considered a new chance to build a more sustainable world from both the social and the economic point of view. In this Essay, the possible contribution of inorganic chemistry towards a smooth transition to circularity in inorganic materials design and production is discussed by adopting an interdisciplinary approach.

Cu-Ti alloys are one of the main candidates to act as a substitute for Cu-Be alloys due to their more environmentally friendly nature. Cu-Ti alloys are age hardenable alloys, and their treatments can modify their microstructure, causing the formation of various Cu-Ti intermetallic that can strongly influence both the mechanical and corrosion properties. In this work, the effect of homogenization heat treatment at 1173 K followed by aging at 723 K for different times (0–24 h) on the microstructure, corrosion and mechanical properties of Cu-4.5 wt.%Ti alloy was investigated. Moreover, the corrosion mechanism based on the different kinetics for the formation of the protective oxide layer was studied. The microstructure and phase analyses were analyzed with SEM and XRD. The mechanical properties were investigated by microhardness test, whereas the corrosion properties were studied by potentiodynamic anodic polarization and potentiostatic tests in artificial sweat. The results showed that the cast sample had the highest corrosion resistance, and the mechanical properties decrease with the homogenization treatment and increase after the combination of homogenization and aging. A corrosion mechanism correlated to the amount and type of intermetallic material was proposed.

Experimental investigation on the relation of grinding induced surface residual stresses (RS) with stress corrosion cracking (SCC) susceptibility and electrochemical behaviour was conducted on 316L...

Stress corrosion cracking (SCC) behaviour of L-PBF processed alloy 718 in chloride-containing solution was revealed, utilizing the microcapillary method under constant tensile loading. Results were compared with conventionally produced counterparts. Passive layer resistance was compared quantitatively by implementing electrochemical polarization experiments, in as-received and under tensile loading states. Superior corrosion and SCC resistance of L-PBF specimens under tensile loading were identified. Submicron cracks were initiated adjacent to the subgrain boundaries and the underlying mechanisms were elucidated as the synergistic effect of various microstructural factors.

In the electrodeposition-anneal processes, the as-deposited film presents a deficiency of S which makes sulfurization inevitable. In this paper, an electrolyte was used for elaborating Cu2ZnSnS4 thin films with free annealing sulfurization onto indium-doped tin oxide-coated glass substrates for solar cell applications. For a one-step elaboration of CZTS thin films, a potentiostatic process has been adopted, and the deposition potential effect has been studied. The prepared samples were treated by annealing at different temperatures and subsequently were considered for structural and morphological properties with the aim to comprehend the growth behavior and to promote the film characteristics. X-ray diffraction (XRD) patterns showed the characteristic peaks at (112), (200) and (224) planes, which correlate with a Kesterite thin film structure and another phase impurity. The uniform area of the film and the grain size transformation of the particles relative to annealing temperature was investigated using scanning electron microscopy and the XRD analysis. From the optical study, the gap energy Eg was enlarged with changed annealing temperature in the range of 1.7–1.48 eV.

This paper concentrates on the electrodeposition of CZTS kesterite thin films on ITO coated glass. The main objective of the article is to compare the electrodeposition from an ionic liquid electrolyte, which is choline–urea, and from an aqueous electrolyte, that is the citrate buffer solution. The electrochemical behaviour of the citrate buffer shown a remarkable evolution of the hydrogen, which was less in the choline chloride–urea electrolyte. The XRD pattern of the films provided from the two electrolytes confirms the presence of the kesterite form of Cu2ZnSnS4. The surface morphology of the samples was examined using scanning electron microscopy and showed that electrodeposition from the citrate buffer electrolyte leads to have CZTS thin films with less porous morphology.

Aluminum alloys are one of the main materials employed in aerospace and automotive applications. One of the problems that affect these alloys in certain application is the poor corrosion resistance that can, however, be enhanced with proper surface treatments, such as anodizing. Among these treatments, Plasma Electrolytic Oxidation (PEO) is one of the most promising and the production of PEO coatings on traditional aluminum alloy was extensively studied in literature. Recently, the production of a lot of components is going into the direction of using innovative manufacturing systems and customized components, with improved mechanical and physical properties, can be manufactured by additive manufacturing (AM) techniques. Among the AM methods, laser-based AM has an immense potential for producing fully dense metallic structures, using a variety of available metal powders and has attracted more and more attention. The resulting AM samples are characterized by different microstructures in comparison with the conventionally manufactured ones and this can cause differences also in the production of PEO coatings and other surface treatments. Objective of the present work is to produce PEO coatings on AM samples in order to increase the corrosion and wear performances of the samples. PEO coating were produced on the samples testing different parameters and the coatings were characterized, in terms of microstructure and composition, with SEM analysis. The corrosion resistance of the samples was also evaluated with electrochemical tests. The results were compared with the ones obtained on traditionally manufactured samples. PEO coatings were successfully produced on AM samples obtaining samples with good coatings thickness and improved corrosion performances compared to the untreated ones.

Austenitic stainless steels are currently used for the manufacture of reusable medical instruments, thanks to their combination of elevated strength, corrosion resistance, biocompatibility and low cost. However, during their service life, they are subjected to repeated sterilization cycles, which lead to the loosening of the surface oxide stability and, thus, decrease their durability. In the present study, the influence of different machining cooling conditions on the in-service corrosion behaviour of the AISI 316L stainless steel is investigated with the aim of increasing its resistance to the sterilization cycles. In particular, the effects of low-temperature coolants, namely Liquid Nitrogen (LN2) and gaseous Nitrogen (N2) cooled by LN2 to -100 °C, were investigated and compared to those of dry and wet cutting. The machined surface integrity was characterized in terms of microstructure, hardness, residual stresses and surface roughness. Electrochemical studies, making use of potentiodynamic and cyclic polarization tests, were carried out to evaluate the corrosion resistance of the machined surfaces. It was found that the AISI 316L microstructure near the machined surface was significantly affected by the machining cooling strategies The effectiveness of using low-temperature coolants in machining of stainless steels for the manufacture of reusable medical devices was therefore demonstrated.

Non-thermal plasma technology is increasingly being applied in the plant biology field. Despite the variety of beneficial effects of plasma-activated water (PAW) on plants, information about the mechanisms of PAW sensing by plants is still limited. In this study, in order to link PAW perception to the positive downstream responses of plants, transgenic Arabidopsis thaliana seedlings expressing the Ca2+-sensitive photoprotein aequorin in the cytosol were challenged with water activated by low-power non-thermal plasma generated by a dielectric barrier discharge (DBD) source. PAW sensing by plants resulted in the occurrence of cytosolic Ca2+ signals, whose kinetic parameters were found to strictly depend on the operational conditions of the plasma device and thus on the corresponding mixture of chemical species contained in the PAW. In particular, we highlighted the effect on the intracellular Ca2+ signals of low doses of DBD-PAW chemicals and also presented the effects of consecutive plant treatments. The results were discussed in terms of the possibility of using PAW-triggered Ca2+ signatures as benchmarks to accurately modulate the chemical composition of PAW in order to induce environmental stress resilience in plants, thus paving the way for further applications in agriculture.

In this work, the composition of an electrolyte was selected and optimized to induce the formation of hydroxyapatite during Plasma electrolytic oxidation (PEO) treatment on an AZ31 alloy for application in bioabsorbable implants. In detail, the PEO process, called PEO-BIO (Plasma Electrolytic Oxidation-Biocompatible), was performed using a silicate-phosphate-based electrolyte with the addition of calcium oxide in direct-current mode using high current densities and short treatment times. For comparison, a known PEO process for producing anticorrosive coatings, called standard, was applied on the same alloy. The coatings were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and XPS analyses. The corrosion performance was evaluated in simulated body fluid (SBF) at 37 °C. The coating produced on the PEO-BIO sample was porous and thicker than the standard PEO one, with zones enriched in Ca and P. The XRD analysis showed the formation of hydroxyapatite and calcium oxides in addition to magnesium-silicon oxide and magnesium oxide in the PEO-BIO sample. The corrosion resistance of PEO-BIO sample was comparable with that of a traditional PEO treated sample, and higher than that of the untreated alloy.

In this work, Plasma Electrolytic Oxidation (PEO) coatings were produced on AZ91D Mg alloy, using as electrolyte an aqueous solution containing both silicates and phosphates. SiC particles, or borosilicate glass particles or a combination of them (SiC + borosilicate glass) were suspended into the electrolyte. The PEO-treated samples were characterized through Scanning Electron Microscope (SEM) (both on the surface and in cross section), X-Ray Diffraction (XRD) and X-Ray Photoelectron Spectroscopy (XPS) in order to study the morphology, thickness, adhesion, structure and composition of the coating as well as particle distribution. The corrosion behavior was analyzed by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The wear resistance was evaluated by dry sliding tests vs. AISI 52100 bearing steel (block-on-ring contact geometry). The results showed that both SiC and borosilicate glass particles were incorporated into the PEO layers. Glass particles contributed to enhance corrosion resistance, whereas SiC particles decreased it. On the other hand, SiC particles improved the wear resistance (due to enhanced load support), leading to an increase of the friction coefficient (due to an increase of the abrasive component of friction). The best combination of properties was obtained with the addition of glass particles for 3 min treatment time. In this way, both the corrosion and wear resistance were increased, minimizing the detrimental effects of SiC particles on the corrosion properties and the friction coefficient.

In Europe, an increasing amount of End of Life (EoL) photovoltaic silicon (PV) panels is expected to be collected in the next 20 years. The silicon PV modules represent a new type of electronic waste that shows challenges and opportunities. ReSiELP was a European project that aimed at recovery of valuable materials (aluminum, glass, copper, silicon, and silver) from EoL silicon PV modules. During the project a pilot plant, constituted by a furnace, a gas abatement system, an apparatus for the mechanical separation and a hydrometallurgical plant was designed and built. The pilot plan was realized to upscale recycling technology to TRL 7, with a 1500 panels/year capacity. The feasibility of industrial-scale recovery and the reintegration of all recovered materials in their appropriate value chain was investigated. The results obtained showed that 2N purity silicon and 2N purity silver can be recovered with high efficiency. In order to realize a zero-waste plant, a hydrometallurgical process was developed for the wastewater treatment. Moreover, the use of recovered glass for building materials was investigated and the obtained performance seemed comparable with commercial products.

During the production of forged metal components, the sequence of heat treatments that are carried out, as well as hot working, remarkably influences mechanical properties of the product, in particular impact toughness. It is possible to tailor impact toughness by varying tempering temperature and soaking time after hardening treatment, widening the application range of structural steels. In this work, we consider the effects of a second tempering treatment on the microstructural properties and impact toughness of a structural steel EN 10025-6 S690 (DIN StE690, W. n: 1.8931). The steel was first forged and quenched in water after austenitization at 890 &deg, C for 4 h. After quenching different tempering treatments were performed, at 590 &deg, C in single or multiple steps. The effect of these treatments was evaluated both in microstructural terms, by means of optical microscopy, scanning and transmission electron microscopy and X-ray diffraction, and in terms of impact toughness. The mechanical behavior was correlated with the microstructure and a remarkable increase in impact toughness was found after the second tempering treatment due to carbide shape change.

Cu2ZnSnS4 (CZTS) absorber layer for the photovoltaic application was successfully deposited on different substrates, indium tin oxide (ITO), fluorine-doped tin oxide (FTO) and molybdenum (Mo) using a single step electrodeposition process. The structural, morphological and optical properties of the CZTS films were analyzed by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), and photoluminescence (PL). The present study was designed to determine the effect of the substrate on the kesterite thin film properties grown by electrodeposition. The results confirm that the CZTS properties depend on the substrate nature. Furthermore, the CZTS films deposited on Mo substrate was found more appropriate for CZTS based solar cells due to their crystallinity and good morphology as well as their suitable energy bandgap around 1.6 eV.

Recently, magnesium alloys are attracting more and more attention as degradable materials for manufacturing temporary biomedical devices, although their rapid degradation in physiological environment limits their clinical applications to a great extent. Different Severe Plastic Deformation (SPD) processes have been recently applied to magnesium alloys in order to improve the surface integrity, which is directly correlated to their corrosion resistance. The current study investigates the possibility of exploiting Large Strain Extrusion Machining (LSEM) as a processing route to increase corrosion resistance of magnesium alloys for biomedical applications. Different cooling conditions and cutting speeds were adopted during LSEM and their effects on the surface integrity and corrosion resistance on both the machined workpiece and obtained chips were studied. For the first time, liquid nitrogen was used as cooling medium in LSEM and its effect was properly investigated. Results showed that LSEM, regardless of the adopted cutting parameters, is an effective method to obtain a workpiece with improved functional performances. Similar results pertain to the chips, but a careful choice of process parameters is even more mandatory than in the case of the workpiece.

Blackening process of steel is widely used in many industrial applications to create a protective layer against corrosion, environmental attack and to improve the aesthetic features. This study is focused on obtaining a black coating on a low carbon steel surface employing three different solution. In particular, two solution based on sodium nitrate and sodium hydroxide were used at boiling point, while the third based on selenous acid at ambient temperature. The samples were immersed for 5, 15 and 30 min in the boiling solutions, while for cold solution it was chosen 1 min of immersion time. The morphology of the protective layer were studied with stereo-microscope in order to evaluate the color, and Scanning Electron Microscope (SEM) to identify any defects in the surface, X-ray diffraction (XRD) was used to evaluate the composition of the protective layer. The corrosion resistance was measured performing potentiodynamic polarization tests and electrochemical impedance spectroscopy tests. The layer obtained with 15 min immersion time for the two boiling solutions is dense and adherent as shown by SEM analysis. For the other immersion times the layer was not uniform with porosities. Cold solution lead to a not homogenous layer reducing corrosion resistance.

In this work, SnO2 and Ag nanoparticles were produced with a raw material nitric acid solution, which came from the leaching of printed circuit boards. First, a precursor of tin oxide was precipitated from the nitric acid solution by three different techniques: (I) conventional heating, (II) microwave irradiation, and (III) ultrasound treatment. Second, this precursor was transformed into tin oxide nanoparticles by heat treatment in a furnace. Third, hydrochloric acid was added to the nitric acid solution to induce the precipitation of silver chloride. Fourth, silver chloride was reduced to metallic silver nanoparticles in an ammonia solution using glucose syrup as both the reducing agent and the capping agent. The reduction reaction was carried out through (I) conventional heating, (II) microwave irradiation, and (III) ultrasound treatment. The nanoparticles were characterized by scanning electron microscope (SEM), x-ray diffractometer (XRD), infrared (IR)-spectroscopy, transmission electron microscope (TEM), ultraviolet (UV)-spectroscopy, and laser diffraction particle size analyzer.

In this work, nanoparticles of ZnO and zero-valent Fe were sonochemically synthesised using a solution produced from electric arc furnace dust leaching as raw material. The leaching was previously carried out using ultrasound with various concentrations of sulphuric acid. The resulting solutions contained, in addition to varying amounts of Zn and Fe, elements such as Cr, Mn, Mg, Ca, and Si. Two methods were developed, one for Fe and one for ZnO, to obtain the nanoparticles and to avoid the precipitation of the additional elements during the nanoparticle production. The synthesis of ZnO nanoparticles was performed through the formation of a precursor by sonochemical reaction with NaOH, and the thermal decomposition of this precursor by heating in furnace. The production of Fe nanoparticles involved the precipitation of FeOOH, the dissolution of FeOOH in HCl solution, and the ultrasound-assisted reduction of the iron ions with NaBH4. The nanoparticles were characterised by scanning and transmission electron microscopy, X-ray diffraction, X-ray fluorescence, and UV spectroscopy. The nanoparticles of Fe had a particle size of 6 nm and resulted in zero-valent Fe, whereas the ZnO nanoparticles were between 30 and 50 nm.

In this work, PEO coatings were produced on AZ91 magnesium alloy, and a sealing treatment was successively performed with solutions containing Nd sulfate salt, recovered by magnets scraps, to produce a Nd-based conversion coating on the surface. For PEO process was employed a basic solution containing both silicates and phosphates as electrolyte, and high current densities (0.5 A/cm2) and short treatment times (2 min) were used. Different parameters were tested for sealing treatment. In detail, the concentration of the salt (6 or 12 g/l of NaNd(SO4)2) and the effect of H2O2 as accelerant were investigated. The conversion coating was produced by simple immersion in the Nd sulfate salt solution, maintained at 50 °C for 30 min. The thickness, composition and morphology of the obtained coatings were analyzed with SEM-EDS, XRD and XPS, whereas the corrosion performances were evaluated with potentiodynamic polarization, EIS and OCV decay tests. An oxide ceramic coating of about 20 μm thick resulted and all the samples treated with sealing process showed an increase in the corrosion resistance depending on the salt concentration. Moreover, the addition of hydrogen peroxide, which acts as accelerant in the formation of the protective layer, allowed to obtain the best results, decreasing the corrosion current density of the sealed samples of two orders of magnitude, in comparison with the untreated ones and producing a sealing layer on the surface more uniform and adherent to the substrate. The increased corrosion performances of the sealed samples can be due to the sealing of the pores that characterized PEO coatings and to the presence in the external layer of protective compounds such as Nd2O3, as evidenced by XRD and XPS.

Metal products in seawater have to face two important phenomena: corrosion and fouling. Corrosion represents a serious issue that can eventually compromise the integrity of the product. Biofouling, defined as the colonization by organisms (bacteria, algae, plants, and animals) on wetted surfaces, is problematic because it increases weight and consequently fuel consumption in boats. Moreover, the two phenomena are mutually sharpening. PEO is a quite new surface treatment, which increases corrosion and wear resistance of light alloys much more than traditional anodizing, and allows the introduction of particles into the coating. In this work, the corrosion and antifouling properties in seawater of copper containing PEO coating, produced on AA 7075, were studied. PEO coatings were produced working at high current densities and in short treatment times, and the particles were incorporated into the coatings by simple addition to the electrolyte. PEO coatings were also used as possible substrate for commercial painting and untreated samples were tested as comparison. The obtained coatings were characterized by SEM-EDS, XRD, and potentiodynamic tests. Corrosion and antifouling properties were evaluated in situ through immersion of several samples in seawater for 4 weeks, intermediate collections and analyses each week with stereomicroscope and SEM observations. The results showed that the PEO coated samples containing copper powder exhibited antifouling effect. The use of PEO coating as substrate for painting can improve performance both against corrosion and fouling, in presence of defects or damages in the paint.

Additive manufacturing involves a layer-by-layer build-up of mechanical parts and it is a manufacturing technology that can be adopted with different engineering metal materials like steels, aluminium and titanium alloys. Aim of the present investigation is to analyse the influence of the build orientation on static and axial fatigue properties of maraging steel specimens manufactured by Direct Metal Laser Sintering (DMLS) of EOS metal powders. After manufacturing, some of the specimens were subjected to age hardening heat treatment (490 °C for 6 hours, followed by air cooling). Both heat treated and as-manufactured specimens have been built at 0° as well as at 90° orientation with respect to the specimen’s axis. Analyses of the crack initiation point are performed in order to investigate the fatigue failure mechanisms. Finally, the fatigue strength of the additively manufactured specimens was compared with that exhibited by vacuum melted specimens of the same steel reported in literature.

A novel high silicon austempered (AHS) steel has been studied in this work. The effect of different austenitizing temperatures, in full austenitic and biphasic regime, on the final microstructure was investigated. Specimens were austenitized at 780 &deg, C, 830 &deg, C, 850 &deg, C and 900 &deg, C for 30 min and held isothermally at 350 &deg, C for 30 min. A second heat treatment route was performed which consisted of austenitizing at 900 &deg, C for 30 min and austempering at 300 &deg, C, 350 &deg, C and 400 &deg, C for 30 min. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) have been used to evaluate the microstructural evolution. These techniques revealed that the microstructures were composed of carbide-free bainite, ferrite, martensite and retained austenite (RA) in different volume fractions (V&gamma, ). An aqueous borate buffer solution with 0.3 M H3BO3 and 0.075 M Na2B4O7&part, 10H2O (pH = 8.4) was used for corrosion tests in order to evaluate the influence of the different volume fractions of retained austenite on the corrosion properties of the specimens. The results showed that when increasing the austenitization temperatures, the volume fractions of retained austenite reached a maximum value at 850 &deg, C, and decrease at higher temperatures. The corrosion properties were investigated after 30 min and 24 h immersion by means of potentiodynamic polarization (after 30 min) and electrochemical impedance spectroscopy (after both 30 min and 24 h) tests. The corrosion resistance of the samples increased with increases in the volume fraction of retained austenite due to lower amounts of residual stresses.

Plasma Electrolytic Oxidation (PEO) is a quite new process which allows the formation of porous ceramic oxide layer on metallic substrates. In this work, hybrid organic-inorganic sol-gel hydrophobic coatings, called M7T3, were deposited on PEO layers, produced on 7020 aluminum alloy and AZ80 magnesium alloy with silicates and phosphates solutions. The hydrophobic coating was a silica film functionalized with methyl groups and it was obtained by dip coating. In detail, was studied the effect of PEO layers on the surface characteristics of the top sol-gel coatings and, consequently, on the corrosion resistance of the two alloys. The samples were characterized in terms of microstructure, morphological features, composition and corrosion properties. The top sol-gel layer resulted uniform on the various samples thank to the presence of the PEO coating. The different substrate (7020AA or AZ80) influenced the morphology of the PEO layer and, consequently, the deposition of the Sol-Gel layer. Moreover, also the durability of the sol-gel resulted increased with the possibility to use samples with the combination of PEO and sol-gel in more severe conditions than the samples with only the sol-gel layer.

This work involves the synthesis and the characterization of CZTS layers. The films were prepared on ITO/glass substrate by one step electrodeposition technic without using the sulfurization step and compared with CZTS films prepared by sulfurization of electrodeposited Cu-Sn-Zn precursors. By adding Thiourea as a sulfur source and KSCN as a complexing agent, the electrodeposition process can give better results. Therefore, the effect of the sulfur source is investigated. The characterization of the absorber films was done by Cyclic Voltammetry (CV), ICP compositional analysis method, X-Ray Diffraction (XRD) and Scanning Electron Microscopy. The single step electrodeposition process is suggested to be better than the sulfurization and post-annealing treatment method.

Plasma electrolytic oxidation (PEO) process is a recently developed electrochemical method used to produce on the surface of various metals oxide ceramic coatings that improve corrosion and wear properties of the substrate. In this work, PEO process was applied on AZ91 magnesium alloy using low current densities (0.05 A/cm2) and an alkaline solution of silicates with different concentrations of sodium molybdate (0.3–3 g/l). The effect of the low current densities of process and of molybdate salts on the corrosion resistance of the coatings was studied with potentiodynamic polarization tests and electrochemical impedance spectroscopy (EIS) in chloride and sulfate environment. The morphology, the phases and the chemical composition of the coatings were examined using a scanning electron microscope equipped with EDS, X-ray diffraction, secondary ion mass spectrometry and X-ray photoelectron spectroscopy. The corrosion properties of the PEO coated samples were remarkably improved if compared with the uncoated samples. The addition of sodium molybdate, in determinate conditions, had a positive effect on the characteristics of the coatings in terms of corrosion resistance.

Electric arc furnace (EAF) slag is a by-product of steel production in electric arc furnaces. Several studies have tried to demonstrate its suitability in civil engineering application, such as in bituminous mixtures and cement-based materials, due to its good physical, chemical and mineralogical properties. Particularly the re-use as coarse aggregate for concrete production has been shown to be a promising valorisation, when physical and chemical stability is guaranteed. Additionally, EAF slag's high mechanical strength makes it suitable for high-performance concrete production. In this work three EAF concretes, with various cement content and also with silica fume addition, were compared with a reference concrete, to identify a convenient mix design to reach a concrete strength class between C50/60 and C60/75. Mechanical strength was evaluated analysing compressive and tensile strength, and elastic modulus. A complementary microstructural analysis was performed after the failure of the specimens, with the aim of analysing the morphology of the interfacial transition zone. Results indicate that the use of EAF slag in concrete allows reaching higher compressive strength than with coarse natural aggregates. EAF slag application in structural concrete promotes also the reduction of cement content in the mix to reach the same strength class.

Plasma electrolytic oxidation (PEO) is a relatively new surface treatment that permits to increase the corrosion and wear resistance of metals. One of the peculiarities of the process is the possib...

Platinum is one of the most precious metals in the world: 15 times rarer than gold and it is widely used in jewellery for its characteristic of unicity, incorruptibility, and colour neutrality. The standard grade in the jewellery industry is Platinum 950‰. In fact, pure platinum jewels are easily scratched, due to the poor hardness linked with the high purity. Among all the commercial alloys available, the Pt-Ru system is the one characterized by the highest mechanical properties. Aim of this work is to find an ideal softening heat treatment, in term of operating time and temperature. The heat treatment must be able to satisfy two main needs: it must permit to complete recrystallization of the work piece, preparing the material for further severe deformation by restoring high ductility and an equiaxed grain distribution; and at the same time, the final average grain size must be fine, in order to avoid counter side aesthetic effects that occur when grain size go over the micrometric scale. Due to its rarity, in literature there are few information about the alloy under discussion. To find the optimal parameters, several samples had been heat treated at different times and temperatures. Then they had been analysed by optical microscopy and with micro hardness tests, providing microstructure images and hardness data. By using a combination of three different temperatures and three different times, significant differences were found between the various samples both in terms of mechanical properties and of grain size. The comparison of the collected data permit to better understand the behaviour of the alloy under recrystallization conditions. In the end, it was observed that the dynamics of recrystallization changes significantly with relative small changes of temperature and was found that the optimal treatment to obtain a fine recrystallized microstructure with the desired mechanical properties is at 1000°C for 15 minutes.