Ugo Bardi | Università degli Studi di Firenze (University of Florence) (original) (raw)

Papers by Ugo Bardi

This paper describes a simulation of the dynamic process of resource depletion in the form of an ... more This paper describes a simulation of the dynamic process of resource depletion in the form of an operational game. It is designed as a simple boardgame, conceived in order to provide students with a hands-on experience that may help them to understand the basic features of the dynamic approach to depletion. The game requires no computers and no special equipment. It can be played by up to four teams for a game time of one-two hours.

Energy Sources, Part B: Economics, Planning, and Policy, 2007

Abstract The Hubbert model assumes that the worldwide production of crude oil will follow a bell-... more Abstract The Hubbert model assumes that the worldwide production of crude oil will follow a bell-shaped curve. Oil prices are expected to increase, or even to spike up, at or after the production peak. However, the Hubbert model provides no description of price trends. We ...

Langmuir, 1996

... Claudio Sangregorio, Monica Galeotti, Ugo Bardi, and Piero Baglioni*. Department of Chemistry... more ... Claudio Sangregorio, Monica Galeotti, Ugo Bardi, and Piero Baglioni*. Department of Chemistry ... 12 Capping Agents. Mandeep Singh Bakshi, Fred Possmayer, and Nils O. Petersen. Chemistry of Materials 2007 19 (6), 1257-1266. ...

Journal of Physical Chemistry B, 2002

In this report we describe a new method to obtain nanostructured coatings or powders based on the... more In this report we describe a new method to obtain nanostructured coatings or powders based on the flame decomposition of microcompartmentalized solutions. Metal nanoclusters of well-defined size are obtained by reduction of a metal salt inside the water compartment of water in oil (w/o) microemulsions, formed by water in hexane and stabilized by an appropriate surfactant. Metal nanoclusters can be separated from the mother solution by spraying the microemulsion solution into an air/acetylene flame. In this way, nanostructured coating or powder, almost preserving the original structure of the nanoparticles synthesized in the microemulsion system, can be obtained in quantities sufficient for industrial applications. As an example we report the flame spraying of gold microemulsions to produce gold coating onto silicon wafers. To the best of our knowledge, this study reports a new method allowing the use of a microemulsion synthetic pathway for the production of consistent amount of nanoparticles. This method could be of great utility in many applications involving nanoparticles in the fields of physics, chemistry, biotechnology, and biology.

Surface & Coatings Technology, 2007

The influence of temperature on the kinetics and the morphology of silver deposits obtained from ... more The influence of temperature on the kinetics and the morphology of silver deposits obtained from an air and water-stable ionic liquid (the 1butyl-3-methyl imidazolium tetrafluoroborate) was studied by means of cyclic voltammetry and chronoamperometry. The nucleation and growth mechanisms have been investigated and the effect of temperature evaluated up to 200°C. Dense, pure and very thin (about 0.3 μm) silver coatings, with decorative properties, have been obtained on commercial copper electrodes at different temperatures. The characterization of the deposits morphology has been performed by visual investigation and SEM microscopy. Data about thickness were acquired by Calotest® measurements. The deposits result constituted by pure silver as determined by combination of EDX microanalysis and Auger Electron Spectroscopy (AES). The deposition method promises to be a new, environmentally friendly, method for silver electrodeposition which is the reason for the absence of cyanide and volatile toxic solvents in the electroplating bath.

Applied Surface Science, 2006

Ion-induced secondary electron emission determined via sample current measurements (SCM) was empl... more Ion-induced secondary electron emission determined via sample current measurements (SCM) was employed as a useful adjunct to conventional secondary ion mass spectrometry (SIMS). This paper reports on the results of 3-6 keV O 2 + SIMS-SCM sputter depth profiling through CrN/AlN multilayer coatings on nickel alloy, titanium dioxide films deposited on stainless steel, and corrosion layers formed onto surface of magnesium alloy after long-term interaction with an ionic liquid. For Au/AlNO/Ta films on silicon, in addition to SIMS-SCM profiles, the signal of mass-energy separated backscattered Ne + ions was monitored as a function of the depth sputtered as well. The results presented here indicate that secondary electron yields are less affected by ''matrix effect'' than secondary ion yields, and at the same time, more sensitive to work function variations and surface charging effects. SCM depth profiling, with suppression of ''the crater effect'' by electronic gating of the registration system is capable of monitoring interfaces in the multilayer structure, particularly, metal-dielectric boundaries. In contrast to SIMS, SCM data are not influenced by the angle and energy windows of an analyser. However, the sample current measurements provide lower dynamic range of the signal registration than SIMS, and SCM is applicable only to the structures with different secondary electron emission properties and/or different conductivity of the layers. To increase the efficiency, SCM should be accompanied by SIMS measurements or predetermined by proper calibration using other elemental-sensitive techniques. #

Solar Energy Materials and Solar Cells, 2008

The AISI 304 and AISI 1018 steels (frequently used in solar collectors' plants) in contact with f... more The AISI 304 and AISI 1018 steels (frequently used in solar collectors' plants) in contact with four different ionic liquids (ILs) suitable as diathermic fluids, were studied. Immersion tests were performed at 220 1C (the working temperature in such plants) for 10 days. The corrosion morphologies of the steels were investigated by scanning electron microscopy coupled with energy dispersive X-ray (EDX) microanalysis and the content of metals in the solution were detected via ICP-OES. The tests showed that the most performing IL is the ethyl-dimethyl-propyl-ammonium-bis(trifluoromethylsulphonyl)imide. The corrosion properties of the two alloys in contact with such IL were investigated by means of Tafel plots and resistance polarization at room temperature in open-to-air vessels. r

Corrosion Science, 2006

The corrosion behaviour of several metals and metal alloys (copper, nickel, AISI 1018 steel, bras... more The corrosion behaviour of several metals and metal alloys (copper, nickel, AISI 1018 steel, brass, Inconel 600) exposed to a typical ionic liquid, the 1-butyl-3-methyl-imidazolium bis-(trifluoromethanesulfonyl) imide, ([C 4 mim][Tf 2 N]), has been investigated by electrochemical and weight-loss methods. Corrosion current densities have been determined by extrapolation from Tafel plots and by polarization resistance measurements and 48 h immersion tests were performed at 150, 250, 275 and 325°C. Room temperature results show low corrosion current densities (0.1-1.2 lA/ cm 2 ) for all the metals and alloys investigated. At 70°C, the corrosion current for copper dramatically increases showing a strongly dependence on temperature. At 150°C copper shows significant weight-loss while nickel, AISI 1018, brass and Inconel do not. At higher temperatures (P275°C), the copper sample crumbles and localized corrosion occurs for the other metals and alloys.

Electrochemistry Communications, 2004

... We wish to thank the Italian–French University for providing a PhD Grant to Andrea Balducci a... more ... We wish to thank the Italian–French University for providing a PhD Grant to Andrea Balducci as part of the Vinci Project 2003, involving Paul Sabatier University of Toulouse (France) and Bologna University (Italy), and INSTM for Dr. Francesca Soavi's post-doctoral research ...

Surface & Coatings Technology, 2007

TiO 2 thin coatings were prepared, on various substrates, through evaporation of metallic titaniu... more TiO 2 thin coatings were prepared, on various substrates, through evaporation of metallic titanium in an oxidizing atmosphere by modified electric arc-physical vapor deposition (EA-PVD). The coatings were characterized chemically (by means of XPS and SIMS) and from the structural point of view (by means of XRD and Raman spectroscopy), in order to understand the factors which lead to homogeneous coatings with high anatase content. The type of substrate is the main parameter that influences the crystal structure of the coatings: when stainless steel is used as substrate the coatings consist essentially of rutile, while on glass substrates coatings containing mainly anatase are obtained. The photocatalytic activity of the samples upon UVA irradiation was tested by using phenol as the target molecule. Phenol in the solution can be photocatalytically and rapidly degraded through the EA-PVD anatase TiO 2 coatings.

Journal of Fuel Cell Science and Technology, 2008

The development of high-performing planar solid oxide fuel cell (SOFC) stacks operating at interm... more The development of high-performing planar solid oxide fuel cell (SOFC) stacks operating at intermediate temperature (700-850°C) is based on thin-electrolyte anode supported cells (ASCs) and interconnects made by ferritic stainless steels. These metallic materials match very well the thermal expansion behavior of the ASCs and can be manufactured and formed using cheaper and easier processes than ceramics or chromium alloys. Nevertheless, some problems remain to be solved with these components as the performance degradation due to the oxide scale growth at the cathodic contact surface and the evaporation of volatile Cr-containing species, which poisons the cathodic materials. Both effects strongly limit the stack performance compared to single cells and increase the degradation rate with time. Providing the steel composition is carefully controlled, the above problems can be limited and some special ferritic stainless steels have been developed in the past years for SOFC application. Unfortunately, no commercial alloy is still able to satisfy the limit in degradation rate required for stationary applications (SECA target is Ͻ0.25% upon 1000 h on a minimum service life of 40,000 h). To achieve these goals a further improvement of composition should be required but this cannot be easily obtained in a cost-effective large-scale metallurgical production. An alternative and probably simpler way is to coat the surface of the steel with a protective layer with the twofold aim to limit Cr evaporation and to develop a conductive scale. In the present work, the effect of different oxide coatings on the chromium evaporation rate and on the contact resistance of ferritic stainless steel has been investigated. To obtain a conductive layer, spinel compositions containing Co, Mn, and Cu have been considered. Steels surfaces have been spray-coated using alcoholic suspensions, and the microstructural evolution of the interface between the metallic substrate and oxide layers has been investigated by scanning electron microscopy and energy dispersive X-ray spectroscopy linescan analysis for exposure at high temperature. The variation with time of the areaspecific resistance at 800°C has been recorded up to 1000 h. The evaporation rate of Cr-containing species has been also evaluated by a qualitative method.

Surface & Coatings Technology, 2009

In this paper we report on the electrodeposition of thin aluminium layers on P90 lithiumaluminium... more In this paper we report on the electrodeposition of thin aluminium layers on P90 lithiumaluminium alloy at room temperature from a chloroaluminate ionic liquid (1-butyl-3-methyl imidazolium heptachloroaluminate [BMIm]Al 2 Cl 7 ). We found that the treatment of the P90 sample's surface is a key point to obtain good quality coatings. On freshly mechanically polished surfaces, thin (about 24µm), homogeneous and dense aluminium layers were obtained at 10µm.h -1 deposition rate. Finally, the corrosion resistance of the uncoated and Alcoated samples was investigated by means of electrochemical techniques such as electrochemical open-circuit potential, impedance spectroscopy and potentiodynamic polarization in 3.5 wt% NaCl aqueous solution.

Sensors and Actuators B-chemical, 2000

The aim of this study is to obtain data useful to elucidate the sensing mechanism of solid state ... more The aim of this study is to obtain data useful to elucidate the sensing mechanism of solid state microsensors for hydrocarbon detection based on mixed vanadium/tin oxides. The sensors studied here were prepared by deposition of an active layer of Sn and V oxides on preoxidized porous silicon. The surface composition of these sensors was studied by a combination of low energy ion scattering (LEIS) and Xray photoelectron spectroscopy (XPS). Parallel studies were performed on a`model' system prepared by depositing a thin ®lm of vanadium on a single crystal SnO 2 (1 1 0) surface and by successive thermal treatment. The results obtained show that vanadium is detectable by LEIS in the topmost atomic layer of both the polycrystalline and the s.c. sample in similar amounts. On the model system, the results of X-ray photoelectron diffraction (XPD) measurements show the formation of epitaxial VO 2 . The main conclusions of the present study are that in these sensors vanadium and tin oxide form separate phases and that vanadium species are present in the outermost surface. Both phases may take an active part in the mechanism of hydrocarbon detection in these sensors. #

Surface and Interface Analysis, 2006

The surface modification of Inconel 600, Naval Brass and AISI 1018 carbon steel after immersion i... more The surface modification of Inconel 600, Naval Brass and AISI 1018 carbon steel after immersion into the [C4mim][Tf2N] ionic liquid (IL) at 225 °C for 20 days has been studied using SIMS, XPS and by surface topography measurements. The trace concentration of alloys' components in the IL solution after the immersion test was measured by inductively coupled plasma-optical emission spectroscopy (ICP-OES). Appreciable amounts of carbon, nitrogen, oxygen, sulphur and fluorine were detected on the surface of the alloys after the immersion test because of thermal decomposition of the IL. The corrosion layer formed onto the surface of Inconel was found to be rather thick (ca 400–500 nm) and rough (Ra∝ 100–200 nm) due to the dominant adsorption of the IL decomposition products. At the same time, Inconel exhibited minor weight loss (2.5 × 10−5 g × cm−2) after the immersion test. On the contrary, for Brass, the thickness (70–100 nm) and roughness (Ra∝ 80–100 nm) of the corrosion layer were the smallest among the alloys studied, and the weight loss was the greatest (1.3 × 10−2 g × cm−2). It is assumed that IL decomposition might be catalysed by some metallic atoms, for instance Ni, that, in turn, could slow down the surface corrosion and migration of metal atoms into the ionic liquid. Copyright © 2006 John Wiley & Sons, Ltd.

Corrosion Science, 2008

The protective action of thin layers of aluminium electroplated on a carbon steel (UNI Fe360B) ha... more The protective action of thin layers of aluminium electroplated on a carbon steel (UNI Fe360B) has been studied. The coatings were obtained via electroreduction, at room temperature, from an ionic liquid constituted by 1-butyl-3-methyl-imidazolium heptachloroaluminate. Coatings of different thickness, ranging from 10 to 40 lm, were obtained. Their morphology and chemical composition were investigated using SEM microscopy coupled with EDX microanalysis and X-ray diffraction. Electrochemical tests (potentiodynamic polarization curves, open-circuit potential and electrochemical impedance spectroscopy) were performed in order to characterise the corrosion resistance of the coating in 3.5% NaCl aqueous solution. Visual investigation of the samples during long term of exposition to neutral salt spray gave an evaluation of their free corrosion properties. It was found that the aluminium layers deposited from ionic liquids significantly protect the substrate from the general corrosion and this action increases with the coating thickness.

Energies, 2009

The well known "Hubbert curve" assumes that the production curve of a crude oil in a free market ... more The well known "Hubbert curve" assumes that the production curve of a crude oil in a free market economy is "bell shaped" and symmetric. The model was first applied in the 1950s as a way of forecasting the production of crude oil in the US lower 48 states. Today, variants of the model are often used for describing the worldwide production of crude oil, which is supposed to reach a global production peak ("peak oil") and to decline afterwards. The model has also been shown to be generally valid for mineral resources other than crude oil and also for slowly renewable biological resources such as whales. Despite its widespread use, Hubbert's modelis sometimes criticized for being arbitrary and its underlying assumptions are rarely examined. In the present work, we use a simple model to generate the bell shaped curve curve using the smallest possible number of assumptions, taking also into account the "Energy Return to Energy Invested" (EROI or EROEI) parameter. We show that this model can reproduce several historical cases, even for resources other than crude oil, and provide a useful tool for understanding the general mechanisms of resource exploitation and the future of energy production in the world's economy.

Thin Solid Films, 2001

Reactive plasma spraying of titanium in a nitrogen-containing plasma gas allows the formation of ... more Reactive plasma spraying of titanium in a nitrogen-containing plasma gas allows the formation of hard titanium composite Ž . coatings reinforced by in situ formed titanium nitrides TiN and Ti N . In the present study, the formation of titanium nitrides 2 Ž . during the reactive spraying of titanium was studied by means of two different analysis techniques: X-ray diffraction XRD and Ž . X-ray photoelectron spectroscopy XPS . The diffusion and solidification sequence predicted by the Ti-N phase diagram was consistent with the experimental results. The nitrogen retained in the coating was found mainly as titanium nitrides and not as interstitial nitrogen in the titanium lattice. It is hypothesised that the formation and direct solidification of TiN occurs during the flight of the sprayed particles. The presence of solid TiN constrains the thermal contraction of titanium splats upon solidification. The observed cell distortion of the residual ␣-Ti is thus attributed to tensile stresses arising from the solidification process. ᮊ

Journal of Thermal Spray Technology, 2007

High-temperature thermal fatigue causes the failure of thermal barrier coating (TBC) systems. Thi... more High-temperature thermal fatigue causes the failure of thermal barrier coating (TBC) systems. This paper addresses the development of thick TBCs, focusing on the microstructure and the porosity of the yttria partially stabilized zirconia (YPSZ) coating, regarding its resistance to thermal fatigue. Thick TBCs, with different porosity levels, were produced by means of a CoNiCrAlY bond coat and YPSZ top coat, both had been sprayed by air plasma spray. The thermal fatigue resistance of new TBC systems and the evolution of the coatings before and after thermal cycling was then evaluated. The limit of thermal fatigue resistance increases depending on the amount of porosity in the top coat. Raman analysis shows that the compressive in-plane stress increases in the TBC systems after thermal cycling, nevertheless the increasing rate has a trend which is contrary to the porosity level of top coat.

Journal of Cleaner Production, 2009

The RAMseS project, under the European Commission's 6th Framework Program, is dedicated to the co... more The RAMseS project, under the European Commission's 6th Framework Program, is dedicated to the construction and test of low-power operations based on photovoltaic power and a multipurpose electric vehicle. In the present study, the life-cycle costs and economical indices for the vehicle during its life span were assessed, compared to those of a standard internal combustion engine vehicle (ICEV). The results indicated that the life-cycle costs for the RAMseS vehicle and the ICEV are the same for a fuel unit price of 1.8 V/L. Also, the levelized cost of energy (LCE) for the RAMseS vehicle, was found to be 2.13 V/ kWh, while RAMseS LCE, without EV taken into account, was shown to be 0.62 V/kWh. The RAMseS payback period (PBP) without EV taken into account was calculated to be 9 years if the value of the produced energy becomes at least 0.35 V/kWh. Vehicles that use PV systems as their power source, such as RAMseS, will be economically effective for fuel costs higher than 1.8 V/L, but considering the environmental benefits that are provided in terms of external costs, they can be considered profitable even at lower fuel costs.

Journal of Thermal Spray Technology, 2003

In the aerospace field as well as in the stationary gas turbine field, thermally sprayed coatings... more In the aerospace field as well as in the stationary gas turbine field, thermally sprayed coatings are used to improve the surface properties of nickel-super-alloys materials. Coatings are commonly used as bond coat and antioxidation materials (mainly MCrAlY alloys) and as thermal barrier coatings (mainly yttria partially stabilized zirconia). The purpose of the current study was to assess the properties of thermally sprayed bond coat CoNiCrAlY alloys comparing the performance of three different techniques: vacuum plasma spray (VPS), high velocity oxygen fuel (HVOF), and axial plasma spray (AxPS). The quality of the deposited films has been assessed and compared from the point of view of microstructural (porosity, oxide concentration, unmelted particles presence) and mechanical (hardness) characteristics. The surface composition and morphology of the coatings were also determined. Specific efficiency tests were performed for the three examined technologies. The highest quality coatings are obtained by VPS, but also high velocity oxygen fuel and AxPS sprayed films have interesting properties, which can make their use interesting for some applications.

This paper describes a simulation of the dynamic process of resource depletion in the form of an ... more This paper describes a simulation of the dynamic process of resource depletion in the form of an operational game. It is designed as a simple boardgame, conceived in order to provide students with a hands-on experience that may help them to understand the basic features of the dynamic approach to depletion. The game requires no computers and no special equipment. It can be played by up to four teams for a game time of one-two hours.

Energy Sources, Part B: Economics, Planning, and Policy, 2007

Abstract The Hubbert model assumes that the worldwide production of crude oil will follow a bell-... more Abstract The Hubbert model assumes that the worldwide production of crude oil will follow a bell-shaped curve. Oil prices are expected to increase, or even to spike up, at or after the production peak. However, the Hubbert model provides no description of price trends. We ...

Langmuir, 1996

... Claudio Sangregorio, Monica Galeotti, Ugo Bardi, and Piero Baglioni*. Department of Chemistry... more ... Claudio Sangregorio, Monica Galeotti, Ugo Bardi, and Piero Baglioni*. Department of Chemistry ... 12 Capping Agents. Mandeep Singh Bakshi, Fred Possmayer, and Nils O. Petersen. Chemistry of Materials 2007 19 (6), 1257-1266. ...

Journal of Physical Chemistry B, 2002

In this report we describe a new method to obtain nanostructured coatings or powders based on the... more In this report we describe a new method to obtain nanostructured coatings or powders based on the flame decomposition of microcompartmentalized solutions. Metal nanoclusters of well-defined size are obtained by reduction of a metal salt inside the water compartment of water in oil (w/o) microemulsions, formed by water in hexane and stabilized by an appropriate surfactant. Metal nanoclusters can be separated from the mother solution by spraying the microemulsion solution into an air/acetylene flame. In this way, nanostructured coating or powder, almost preserving the original structure of the nanoparticles synthesized in the microemulsion system, can be obtained in quantities sufficient for industrial applications. As an example we report the flame spraying of gold microemulsions to produce gold coating onto silicon wafers. To the best of our knowledge, this study reports a new method allowing the use of a microemulsion synthetic pathway for the production of consistent amount of nanoparticles. This method could be of great utility in many applications involving nanoparticles in the fields of physics, chemistry, biotechnology, and biology.

Surface & Coatings Technology, 2007

The influence of temperature on the kinetics and the morphology of silver deposits obtained from ... more The influence of temperature on the kinetics and the morphology of silver deposits obtained from an air and water-stable ionic liquid (the 1butyl-3-methyl imidazolium tetrafluoroborate) was studied by means of cyclic voltammetry and chronoamperometry. The nucleation and growth mechanisms have been investigated and the effect of temperature evaluated up to 200°C. Dense, pure and very thin (about 0.3 μm) silver coatings, with decorative properties, have been obtained on commercial copper electrodes at different temperatures. The characterization of the deposits morphology has been performed by visual investigation and SEM microscopy. Data about thickness were acquired by Calotest® measurements. The deposits result constituted by pure silver as determined by combination of EDX microanalysis and Auger Electron Spectroscopy (AES). The deposition method promises to be a new, environmentally friendly, method for silver electrodeposition which is the reason for the absence of cyanide and volatile toxic solvents in the electroplating bath.

Applied Surface Science, 2006

Ion-induced secondary electron emission determined via sample current measurements (SCM) was empl... more Ion-induced secondary electron emission determined via sample current measurements (SCM) was employed as a useful adjunct to conventional secondary ion mass spectrometry (SIMS). This paper reports on the results of 3-6 keV O 2 + SIMS-SCM sputter depth profiling through CrN/AlN multilayer coatings on nickel alloy, titanium dioxide films deposited on stainless steel, and corrosion layers formed onto surface of magnesium alloy after long-term interaction with an ionic liquid. For Au/AlNO/Ta films on silicon, in addition to SIMS-SCM profiles, the signal of mass-energy separated backscattered Ne + ions was monitored as a function of the depth sputtered as well. The results presented here indicate that secondary electron yields are less affected by ''matrix effect'' than secondary ion yields, and at the same time, more sensitive to work function variations and surface charging effects. SCM depth profiling, with suppression of ''the crater effect'' by electronic gating of the registration system is capable of monitoring interfaces in the multilayer structure, particularly, metal-dielectric boundaries. In contrast to SIMS, SCM data are not influenced by the angle and energy windows of an analyser. However, the sample current measurements provide lower dynamic range of the signal registration than SIMS, and SCM is applicable only to the structures with different secondary electron emission properties and/or different conductivity of the layers. To increase the efficiency, SCM should be accompanied by SIMS measurements or predetermined by proper calibration using other elemental-sensitive techniques. #

Solar Energy Materials and Solar Cells, 2008

The AISI 304 and AISI 1018 steels (frequently used in solar collectors' plants) in contact with f... more The AISI 304 and AISI 1018 steels (frequently used in solar collectors' plants) in contact with four different ionic liquids (ILs) suitable as diathermic fluids, were studied. Immersion tests were performed at 220 1C (the working temperature in such plants) for 10 days. The corrosion morphologies of the steels were investigated by scanning electron microscopy coupled with energy dispersive X-ray (EDX) microanalysis and the content of metals in the solution were detected via ICP-OES. The tests showed that the most performing IL is the ethyl-dimethyl-propyl-ammonium-bis(trifluoromethylsulphonyl)imide. The corrosion properties of the two alloys in contact with such IL were investigated by means of Tafel plots and resistance polarization at room temperature in open-to-air vessels. r

Corrosion Science, 2006

The corrosion behaviour of several metals and metal alloys (copper, nickel, AISI 1018 steel, bras... more The corrosion behaviour of several metals and metal alloys (copper, nickel, AISI 1018 steel, brass, Inconel 600) exposed to a typical ionic liquid, the 1-butyl-3-methyl-imidazolium bis-(trifluoromethanesulfonyl) imide, ([C 4 mim][Tf 2 N]), has been investigated by electrochemical and weight-loss methods. Corrosion current densities have been determined by extrapolation from Tafel plots and by polarization resistance measurements and 48 h immersion tests were performed at 150, 250, 275 and 325°C. Room temperature results show low corrosion current densities (0.1-1.2 lA/ cm 2 ) for all the metals and alloys investigated. At 70°C, the corrosion current for copper dramatically increases showing a strongly dependence on temperature. At 150°C copper shows significant weight-loss while nickel, AISI 1018, brass and Inconel do not. At higher temperatures (P275°C), the copper sample crumbles and localized corrosion occurs for the other metals and alloys.

Electrochemistry Communications, 2004

... We wish to thank the Italian–French University for providing a PhD Grant to Andrea Balducci a... more ... We wish to thank the Italian–French University for providing a PhD Grant to Andrea Balducci as part of the Vinci Project 2003, involving Paul Sabatier University of Toulouse (France) and Bologna University (Italy), and INSTM for Dr. Francesca Soavi's post-doctoral research ...

Surface & Coatings Technology, 2007

TiO 2 thin coatings were prepared, on various substrates, through evaporation of metallic titaniu... more TiO 2 thin coatings were prepared, on various substrates, through evaporation of metallic titanium in an oxidizing atmosphere by modified electric arc-physical vapor deposition (EA-PVD). The coatings were characterized chemically (by means of XPS and SIMS) and from the structural point of view (by means of XRD and Raman spectroscopy), in order to understand the factors which lead to homogeneous coatings with high anatase content. The type of substrate is the main parameter that influences the crystal structure of the coatings: when stainless steel is used as substrate the coatings consist essentially of rutile, while on glass substrates coatings containing mainly anatase are obtained. The photocatalytic activity of the samples upon UVA irradiation was tested by using phenol as the target molecule. Phenol in the solution can be photocatalytically and rapidly degraded through the EA-PVD anatase TiO 2 coatings.

Journal of Fuel Cell Science and Technology, 2008

The development of high-performing planar solid oxide fuel cell (SOFC) stacks operating at interm... more The development of high-performing planar solid oxide fuel cell (SOFC) stacks operating at intermediate temperature (700-850°C) is based on thin-electrolyte anode supported cells (ASCs) and interconnects made by ferritic stainless steels. These metallic materials match very well the thermal expansion behavior of the ASCs and can be manufactured and formed using cheaper and easier processes than ceramics or chromium alloys. Nevertheless, some problems remain to be solved with these components as the performance degradation due to the oxide scale growth at the cathodic contact surface and the evaporation of volatile Cr-containing species, which poisons the cathodic materials. Both effects strongly limit the stack performance compared to single cells and increase the degradation rate with time. Providing the steel composition is carefully controlled, the above problems can be limited and some special ferritic stainless steels have been developed in the past years for SOFC application. Unfortunately, no commercial alloy is still able to satisfy the limit in degradation rate required for stationary applications (SECA target is Ͻ0.25% upon 1000 h on a minimum service life of 40,000 h). To achieve these goals a further improvement of composition should be required but this cannot be easily obtained in a cost-effective large-scale metallurgical production. An alternative and probably simpler way is to coat the surface of the steel with a protective layer with the twofold aim to limit Cr evaporation and to develop a conductive scale. In the present work, the effect of different oxide coatings on the chromium evaporation rate and on the contact resistance of ferritic stainless steel has been investigated. To obtain a conductive layer, spinel compositions containing Co, Mn, and Cu have been considered. Steels surfaces have been spray-coated using alcoholic suspensions, and the microstructural evolution of the interface between the metallic substrate and oxide layers has been investigated by scanning electron microscopy and energy dispersive X-ray spectroscopy linescan analysis for exposure at high temperature. The variation with time of the areaspecific resistance at 800°C has been recorded up to 1000 h. The evaporation rate of Cr-containing species has been also evaluated by a qualitative method.

Surface & Coatings Technology, 2009

In this paper we report on the electrodeposition of thin aluminium layers on P90 lithiumaluminium... more In this paper we report on the electrodeposition of thin aluminium layers on P90 lithiumaluminium alloy at room temperature from a chloroaluminate ionic liquid (1-butyl-3-methyl imidazolium heptachloroaluminate [BMIm]Al 2 Cl 7 ). We found that the treatment of the P90 sample's surface is a key point to obtain good quality coatings. On freshly mechanically polished surfaces, thin (about 24µm), homogeneous and dense aluminium layers were obtained at 10µm.h -1 deposition rate. Finally, the corrosion resistance of the uncoated and Alcoated samples was investigated by means of electrochemical techniques such as electrochemical open-circuit potential, impedance spectroscopy and potentiodynamic polarization in 3.5 wt% NaCl aqueous solution.

Sensors and Actuators B-chemical, 2000

The aim of this study is to obtain data useful to elucidate the sensing mechanism of solid state ... more The aim of this study is to obtain data useful to elucidate the sensing mechanism of solid state microsensors for hydrocarbon detection based on mixed vanadium/tin oxides. The sensors studied here were prepared by deposition of an active layer of Sn and V oxides on preoxidized porous silicon. The surface composition of these sensors was studied by a combination of low energy ion scattering (LEIS) and Xray photoelectron spectroscopy (XPS). Parallel studies were performed on a`model' system prepared by depositing a thin ®lm of vanadium on a single crystal SnO 2 (1 1 0) surface and by successive thermal treatment. The results obtained show that vanadium is detectable by LEIS in the topmost atomic layer of both the polycrystalline and the s.c. sample in similar amounts. On the model system, the results of X-ray photoelectron diffraction (XPD) measurements show the formation of epitaxial VO 2 . The main conclusions of the present study are that in these sensors vanadium and tin oxide form separate phases and that vanadium species are present in the outermost surface. Both phases may take an active part in the mechanism of hydrocarbon detection in these sensors. #

Surface and Interface Analysis, 2006

The surface modification of Inconel 600, Naval Brass and AISI 1018 carbon steel after immersion i... more The surface modification of Inconel 600, Naval Brass and AISI 1018 carbon steel after immersion into the [C4mim][Tf2N] ionic liquid (IL) at 225 °C for 20 days has been studied using SIMS, XPS and by surface topography measurements. The trace concentration of alloys' components in the IL solution after the immersion test was measured by inductively coupled plasma-optical emission spectroscopy (ICP-OES). Appreciable amounts of carbon, nitrogen, oxygen, sulphur and fluorine were detected on the surface of the alloys after the immersion test because of thermal decomposition of the IL. The corrosion layer formed onto the surface of Inconel was found to be rather thick (ca 400–500 nm) and rough (Ra∝ 100–200 nm) due to the dominant adsorption of the IL decomposition products. At the same time, Inconel exhibited minor weight loss (2.5 × 10−5 g × cm−2) after the immersion test. On the contrary, for Brass, the thickness (70–100 nm) and roughness (Ra∝ 80–100 nm) of the corrosion layer were the smallest among the alloys studied, and the weight loss was the greatest (1.3 × 10−2 g × cm−2). It is assumed that IL decomposition might be catalysed by some metallic atoms, for instance Ni, that, in turn, could slow down the surface corrosion and migration of metal atoms into the ionic liquid. Copyright © 2006 John Wiley & Sons, Ltd.

Corrosion Science, 2008

The protective action of thin layers of aluminium electroplated on a carbon steel (UNI Fe360B) ha... more The protective action of thin layers of aluminium electroplated on a carbon steel (UNI Fe360B) has been studied. The coatings were obtained via electroreduction, at room temperature, from an ionic liquid constituted by 1-butyl-3-methyl-imidazolium heptachloroaluminate. Coatings of different thickness, ranging from 10 to 40 lm, were obtained. Their morphology and chemical composition were investigated using SEM microscopy coupled with EDX microanalysis and X-ray diffraction. Electrochemical tests (potentiodynamic polarization curves, open-circuit potential and electrochemical impedance spectroscopy) were performed in order to characterise the corrosion resistance of the coating in 3.5% NaCl aqueous solution. Visual investigation of the samples during long term of exposition to neutral salt spray gave an evaluation of their free corrosion properties. It was found that the aluminium layers deposited from ionic liquids significantly protect the substrate from the general corrosion and this action increases with the coating thickness.

Energies, 2009

The well known "Hubbert curve" assumes that the production curve of a crude oil in a free market ... more The well known "Hubbert curve" assumes that the production curve of a crude oil in a free market economy is "bell shaped" and symmetric. The model was first applied in the 1950s as a way of forecasting the production of crude oil in the US lower 48 states. Today, variants of the model are often used for describing the worldwide production of crude oil, which is supposed to reach a global production peak ("peak oil") and to decline afterwards. The model has also been shown to be generally valid for mineral resources other than crude oil and also for slowly renewable biological resources such as whales. Despite its widespread use, Hubbert's modelis sometimes criticized for being arbitrary and its underlying assumptions are rarely examined. In the present work, we use a simple model to generate the bell shaped curve curve using the smallest possible number of assumptions, taking also into account the "Energy Return to Energy Invested" (EROI or EROEI) parameter. We show that this model can reproduce several historical cases, even for resources other than crude oil, and provide a useful tool for understanding the general mechanisms of resource exploitation and the future of energy production in the world's economy.

Thin Solid Films, 2001

Reactive plasma spraying of titanium in a nitrogen-containing plasma gas allows the formation of ... more Reactive plasma spraying of titanium in a nitrogen-containing plasma gas allows the formation of hard titanium composite Ž . coatings reinforced by in situ formed titanium nitrides TiN and Ti N . In the present study, the formation of titanium nitrides 2 Ž . during the reactive spraying of titanium was studied by means of two different analysis techniques: X-ray diffraction XRD and Ž . X-ray photoelectron spectroscopy XPS . The diffusion and solidification sequence predicted by the Ti-N phase diagram was consistent with the experimental results. The nitrogen retained in the coating was found mainly as titanium nitrides and not as interstitial nitrogen in the titanium lattice. It is hypothesised that the formation and direct solidification of TiN occurs during the flight of the sprayed particles. The presence of solid TiN constrains the thermal contraction of titanium splats upon solidification. The observed cell distortion of the residual ␣-Ti is thus attributed to tensile stresses arising from the solidification process. ᮊ

Journal of Thermal Spray Technology, 2007

High-temperature thermal fatigue causes the failure of thermal barrier coating (TBC) systems. Thi... more High-temperature thermal fatigue causes the failure of thermal barrier coating (TBC) systems. This paper addresses the development of thick TBCs, focusing on the microstructure and the porosity of the yttria partially stabilized zirconia (YPSZ) coating, regarding its resistance to thermal fatigue. Thick TBCs, with different porosity levels, were produced by means of a CoNiCrAlY bond coat and YPSZ top coat, both had been sprayed by air plasma spray. The thermal fatigue resistance of new TBC systems and the evolution of the coatings before and after thermal cycling was then evaluated. The limit of thermal fatigue resistance increases depending on the amount of porosity in the top coat. Raman analysis shows that the compressive in-plane stress increases in the TBC systems after thermal cycling, nevertheless the increasing rate has a trend which is contrary to the porosity level of top coat.

Journal of Cleaner Production, 2009

The RAMseS project, under the European Commission's 6th Framework Program, is dedicated to the co... more The RAMseS project, under the European Commission's 6th Framework Program, is dedicated to the construction and test of low-power operations based on photovoltaic power and a multipurpose electric vehicle. In the present study, the life-cycle costs and economical indices for the vehicle during its life span were assessed, compared to those of a standard internal combustion engine vehicle (ICEV). The results indicated that the life-cycle costs for the RAMseS vehicle and the ICEV are the same for a fuel unit price of 1.8 V/L. Also, the levelized cost of energy (LCE) for the RAMseS vehicle, was found to be 2.13 V/ kWh, while RAMseS LCE, without EV taken into account, was shown to be 0.62 V/kWh. The RAMseS payback period (PBP) without EV taken into account was calculated to be 9 years if the value of the produced energy becomes at least 0.35 V/kWh. Vehicles that use PV systems as their power source, such as RAMseS, will be economically effective for fuel costs higher than 1.8 V/L, but considering the environmental benefits that are provided in terms of external costs, they can be considered profitable even at lower fuel costs.

Journal of Thermal Spray Technology, 2003

In the aerospace field as well as in the stationary gas turbine field, thermally sprayed coatings... more In the aerospace field as well as in the stationary gas turbine field, thermally sprayed coatings are used to improve the surface properties of nickel-super-alloys materials. Coatings are commonly used as bond coat and antioxidation materials (mainly MCrAlY alloys) and as thermal barrier coatings (mainly yttria partially stabilized zirconia). The purpose of the current study was to assess the properties of thermally sprayed bond coat CoNiCrAlY alloys comparing the performance of three different techniques: vacuum plasma spray (VPS), high velocity oxygen fuel (HVOF), and axial plasma spray (AxPS). The quality of the deposited films has been assessed and compared from the point of view of microstructural (porosity, oxide concentration, unmelted particles presence) and mechanical (hardness) characteristics. The surface composition and morphology of the coatings were also determined. Specific efficiency tests were performed for the three examined technologies. The highest quality coatings are obtained by VPS, but also high velocity oxygen fuel and AxPS sprayed films have interesting properties, which can make their use interesting for some applications.