Mariapia Pedeferri - Academia.edu (original) (raw)

Papers by Mariapia Pedeferri

Research paper thumbnail of Mechanistic insights into photogenerated electrons store-and-discharge in hydrogenated glucose template synthesized Pt: TiO2/WO3 photocatalyst for the round-the-clock decomposition of methanol

Materials Research Bulletin

Research paper thumbnail of Immobilized Nano-TiO2 Photocatalysts for the Degradation of Three Organic Dyes in Single and Multi-Dye Solutions

Coatings

Heterogeneous photocatalysis with titanium dioxide (TiO2) is considered one of the most promising... more Heterogeneous photocatalysis with titanium dioxide (TiO2) is considered one of the most promising Advanced Oxidation Processes (AOPs). In order to solve issues related to catalyst recovery and possible agglomeration, which are typical of catalysts in nanoparticle form, self-organized nanotubular TiO2 films directly immobilized on a metal substrate can be produced through anodization. In this study, a nanotubular anodic oxide was tested in the degradation of three organic dyes, namely Direct Red 80, Methylene Blue, and Rhodamine B, in single, binary, and ternary mixtures, to simulate industrial effluents with the co-presence of multiple dyes. To better understand the dyes’ behavior and possible interaction effects, spectrophotometry was used to analyze the degradation of each dye in the mixture. The zero-crossing first-order derivative approach and double divisor ratio spectra derivative method were used for the analysis of binary and ternary mixtures, respectively, to overcome quant...

Research paper thumbnail of Towards a better preservation of current and future outdoor architectural heritage; maximum suppression of discolouration in anodized and non-anodized titanium sheets

Environmental Technology Reviews

Research paper thumbnail of Effect of environmental conditions on the durability of polycarbonate for the protection of cultural heritage sites

Journal of Applied Biomaterials & Functional Materials

Polycarbonate is a good material for covering and protecting cultural heritage sites because of i... more Polycarbonate is a good material for covering and protecting cultural heritage sites because of its durability, mechanical properties, and transparency. However, polycarbonate degrades under environmental weathering with a significant decrease of physical and mechanical properties and loss of transparency. In this work, the contemporary presence of ultraviolet irradiation and different temperature and moisture conditions have been taken into account to study the environmental degradation of this polymer with regard to its mechanical and optical properties. The photo-oxidation reactions cause a decrease in the molecular weight and the formation of many oxygenated species. The hydrolytic scission, instead, gives rise to a remarkable reduction in the molecular weight. These two different degradation mechanisms do not seem interconnected because at the lowest degradation temperature and high humidity levels, the reduction of the molecular weight is more pronounced than that observed at ...

Research paper thumbnail of Effect of polymer modified cementitious coatings on chloride‐induced corrosion of steel in concrete

Research paper thumbnail of Memristive electronic synapses made by anodic oxidation

Research paper thumbnail of Experimental design to study the influence of temperature, pH, and chloride concentration on the pitting and crevice corrosion of UNS S30403 stainless steel

Corrosion Science

Localized corrosion of stainless steel, namely pitting and crevice, affects seriously the perform... more Localized corrosion of stainless steel, namely pitting and crevice, affects seriously the performance of these materials in service. In this paper, the design of experiment (DOE) is used to study the influence of temperature, pH and chloride concentration on the pitting and crevice corrosion of AISI 304L (UNS S30403) stainless steel. DOE approach enables to reduce the number of tests (anodic potentiodynamic polarization) necessary to study the effect of several parameters on the passivity breakdown potential. The use of DOE provided a regression equation that was analyzed by comparison with laboratory and literature results. Among all these parameters, the temperature has the most significant effect on pitting corrosion resistance.

Research paper thumbnail of Self-cleaning building materials: The multifaceted effects of titanium dioxide

Construction and Building Materials

The physical integrity and photocatalytic performance of titanium dioxide (TiO2) deteriorate with... more The physical integrity and photocatalytic performance of titanium dioxide (TiO2) deteriorate with aging. Here we propose a pre-treatment with nitric or sulfuric acid of commercial TiO2 nanopowders used in coating, mortars, or paints. The diffuse reflectance is increased between 1500 and 2500 nm by 0.04 and 0.06, respectively, with nitric and sulfuric acid (unaffected by neutralization). Nitric acid causes a decrease in crystallinity and photocatalytic activity, which drops by almost 20%; this drawback is prevented by post-treatment neutralization, which allows to recover initial photocatalytic efficiency and even increase it. Treatment with sulfuric acid shows no significant effect on photoactivity, instead.

Research paper thumbnail of Chemical oxidation as repairing technique to restore corrosion resistance on damaged anodized titanium

Surface and Coatings Technology

Research paper thumbnail of Pitting corrosion on anodized titanium: Effect of halides

Materials and Corrosion

Titanium corrosion resistance is high in the majority of environments. However, titanium is susce... more Titanium corrosion resistance is high in the majority of environments. However, titanium is susceptible to different forms of corrosion, if exposed to high concentrated halides containing solutions. To face this corrosion problem, expensive titanium alloys are used. An alternative method, consisting of electrochemical anodizing treatment, which promote the formation of a compact titanium oxide on the surface, could be applied to increase titanium corrosion resistance. In this work, titanium samples anodized at 20 V in H 2 SO 4 0.5 M have been tested in sodium fluorides, chlorides, bromides and iodides at 0.5 M and 2.0 M in order to define halides aggressiveness.

Research paper thumbnail of Enhancement of pure titanium localized corrosion resistance by anodic oxidation

Materials and Corrosion

The corrosion behavior of commercially pure titanium (UNS R50400) was investigated in presence of... more The corrosion behavior of commercially pure titanium (UNS R50400) was investigated in presence of aggressive, bromides containing, species; reported to cause severer localized corrosion compared to chlorides. To enhance localized corrosion resistance of the metal, several surface treatments were performed. Samples anodized at potentials between 10 V and 200 V were characterized in term of oxide thickness and morphology and tested with potentiodynamic analyses in NH 4 Br. This treatment was found to greatly enhance corrosion resistance of titanium but it suffers localized removal of the oxide due to wrong handling of the part before their installation. For this reason, another treatment, suitable for in-situ surface recovering was developed through chemical oxidation in NaOH 10 M.

Research paper thumbnail of Corrosion resistance enhancement of chemically oxidized titanium through NaOH and H2 O2 exposure

Materials and Corrosion

Titanium owes its astounding corrosion resistance to a thin, compact oxide layer that is formed s... more Titanium owes its astounding corrosion resistance to a thin, compact oxide layer that is formed spontaneously when the metal is exposed to the environment. However, even titanium can be subject to corrosion in very aggressive environments. To enhance its corrosion resistance, it is possible to exploit the same mechanism that leads to the formation of the protective oxide layer and force its growth with an external contribution. Oxidation can be easily stimulated with the use of an electrochemical cell.

Research paper thumbnail of Electrochemical anodizing treatment to enhance localized corrosion resistance of pure titanium

Journal of applied biomaterials & functional materials, Jan 26, 2017

Titanium has outstanding corrosion resistance due to the thin protective oxide layer that is form... more Titanium has outstanding corrosion resistance due to the thin protective oxide layer that is formed on its surface. Nevertheless, in harsh and severe environments, pure titanium may suffer localized corrosion. In those conditions, costly titanium alloys containing palladium, nickel and molybdenum are used. This purpose investigated how it is possible to control corrosion, at lower cost, by electrochemical surface treatment on pure titanium, increasing the thickness of the natural oxide layer. Anodic oxidation was performed on titanium by immersion in H2SO4 solution and applying voltages ranging from 10 to 80 V. Different anodic current densities were considered. Potentiodynamic tests in chloride- and fluoride-containing solutions were carried out on anodized titanium to determine the pitting potential. All tested anodizing treatments increased corrosion resistance of pure titanium, but never reached the performance of titanium alloys. The best corrosion behavior was obtained on tita...

Research paper thumbnail of Corrosion of titanium: Part 1: aggressive environments and main forms of degradation

Journal of applied biomaterials & functional materials, Jan 11, 2017

Titanium has outstanding corrosion resistance due to the external natural oxide protective layer ... more Titanium has outstanding corrosion resistance due to the external natural oxide protective layer formed when it is exposed to an aerated environment. Despite this, titanium may suffer different forms of corrosion in severe environments: uniform corrosion, pitting and crevice corrosion, hydrogen embrittlement, stress-corrosion cracking, fretting corrosion and erosion. In this first review, forms of corrosion affecting titanium are analyzed based on a wide literature review. For each form of corrosion, the mechanism and most severe environment are reported according to the current understanding.In the second part, this review will address the possible surface treatments that can increase corrosion resistance on commercially pure titanium: Electrochemical anodizing, thermal oxidation, chemical oxidation and bulk treatments such as alloying will be considered, highlighting the advantages of each technique.

Research paper thumbnail of Corrosion of titanium: Part 2: Effects of surface treatments

Journal of applied biomaterials & functional materials, 2018

Titanium is well known as one of the most corrosion-resistant metals. However, it can suffer corr... more Titanium is well known as one of the most corrosion-resistant metals. However, it can suffer corrosion attacks in some specific aggressive conditions. To further increase its corrosion resistance, it is possible either to modify its surface, tuning either thickness, composition, morphology or structure of the oxide that spontaneously forms on the metal, or to modify its bulk composition. Part 2 of this review is dedicated to the corrosion of titanium and focuses on possible titanium treatments that can increase corrosion resistance. Both surface treatments, such as anodization or thermal or chemical oxidation, and bulk treatments, such as alloying, are considered, highlighting the advantages of each technique.

Research paper thumbnail of Photocatalytic Activity of Nanotubular TiO₂ Films Obtained by Anodic Oxidation: A Comparison in Gas and Liquid Phase

Materials (Basel, Switzerland), Jan 24, 2018

The availability of immobilized nanostructured photocatalysts is of great importance in the purif... more The availability of immobilized nanostructured photocatalysts is of great importance in the purification of both polluted air and liquids (e.g., industrial wastewaters). Metal-supported titanium dioxide films with nanotubular morphology and good photocatalytic efficiency in both environments can be produced by anodic oxidation, which avoids release of nanoscale materials in the environment. Here we evaluate the effect of different anodizing procedures on the photocatalytic activity of TiO₂ nanostructures in gas and liquid phases, in order to identify the most efficient and robust technique for the production of TiO₂ layers with different morphologies and high photocatalytic activity in both phases. Rhodamine B and toluene were used as model pollutants in the two media, respectively. It was found that the role of the anodizing electrolyte is particularly crucial, as it provides substantial differences in the oxide specific surface area: nanotubular structures show remarkably differen...

Research paper thumbnail of Cathodic protection monitoring of buried carbon steel pipeline: measurement and interpretation of instant-off potential

Corrosion Engineering, Science and Technology, 2017

Research paper thumbnail of Effects of AC-interference on chloride-induced corrosion of reinforced concrete

Construction and Building Materials, 2017

Research paper thumbnail of Monitoring cathodic protection of buried pipeline by means of a potential probe with an embedded zinc reference electrode

Research paper thumbnail of TiO2 alterations with natural aging: Unveiling the role of nitric acid on NIR reflectance

Solar Energy Materials and Solar Cells, 2016

The development of photoactive materials with self-cleaning and depolluting qualities is a hot to... more The development of photoactive materials with self-cleaning and depolluting qualities is a hot topic in materials science, given their impact on several technologies, in a wide range of contexts of applications. Anatase phase titanium dioxide (TiO2) is the largest used photocatalyst, with increasing applications ranging from air quality control to renewable energies, to green building materials for zero energy communities. Yet, it is partially transmissive in the near infrared (NIR), which negatively affects the solar reflectance of TiO2 containing materials. In this contribution we describe an unexpected increase in anatase near infrared (NIR) reflectance observed during environmental exposure. We unveil its complex mechanisms, based on the contact with nitric acid generated by NOx photocatalytic degradation, which causes partial reduction and decrease in crystallinity to TiO2. This may open the way for introducing multiple environmentally beneficial effects on TiO2 pollutants degradation, self-cleaning, and energy performance.

Research paper thumbnail of Mechanistic insights into photogenerated electrons store-and-discharge in hydrogenated glucose template synthesized Pt: TiO2/WO3 photocatalyst for the round-the-clock decomposition of methanol

Materials Research Bulletin

Research paper thumbnail of Immobilized Nano-TiO2 Photocatalysts for the Degradation of Three Organic Dyes in Single and Multi-Dye Solutions

Coatings

Heterogeneous photocatalysis with titanium dioxide (TiO2) is considered one of the most promising... more Heterogeneous photocatalysis with titanium dioxide (TiO2) is considered one of the most promising Advanced Oxidation Processes (AOPs). In order to solve issues related to catalyst recovery and possible agglomeration, which are typical of catalysts in nanoparticle form, self-organized nanotubular TiO2 films directly immobilized on a metal substrate can be produced through anodization. In this study, a nanotubular anodic oxide was tested in the degradation of three organic dyes, namely Direct Red 80, Methylene Blue, and Rhodamine B, in single, binary, and ternary mixtures, to simulate industrial effluents with the co-presence of multiple dyes. To better understand the dyes’ behavior and possible interaction effects, spectrophotometry was used to analyze the degradation of each dye in the mixture. The zero-crossing first-order derivative approach and double divisor ratio spectra derivative method were used for the analysis of binary and ternary mixtures, respectively, to overcome quant...

Research paper thumbnail of Towards a better preservation of current and future outdoor architectural heritage; maximum suppression of discolouration in anodized and non-anodized titanium sheets

Environmental Technology Reviews

Research paper thumbnail of Effect of environmental conditions on the durability of polycarbonate for the protection of cultural heritage sites

Journal of Applied Biomaterials & Functional Materials

Polycarbonate is a good material for covering and protecting cultural heritage sites because of i... more Polycarbonate is a good material for covering and protecting cultural heritage sites because of its durability, mechanical properties, and transparency. However, polycarbonate degrades under environmental weathering with a significant decrease of physical and mechanical properties and loss of transparency. In this work, the contemporary presence of ultraviolet irradiation and different temperature and moisture conditions have been taken into account to study the environmental degradation of this polymer with regard to its mechanical and optical properties. The photo-oxidation reactions cause a decrease in the molecular weight and the formation of many oxygenated species. The hydrolytic scission, instead, gives rise to a remarkable reduction in the molecular weight. These two different degradation mechanisms do not seem interconnected because at the lowest degradation temperature and high humidity levels, the reduction of the molecular weight is more pronounced than that observed at ...

Research paper thumbnail of Effect of polymer modified cementitious coatings on chloride‐induced corrosion of steel in concrete

Research paper thumbnail of Memristive electronic synapses made by anodic oxidation

Research paper thumbnail of Experimental design to study the influence of temperature, pH, and chloride concentration on the pitting and crevice corrosion of UNS S30403 stainless steel

Corrosion Science

Localized corrosion of stainless steel, namely pitting and crevice, affects seriously the perform... more Localized corrosion of stainless steel, namely pitting and crevice, affects seriously the performance of these materials in service. In this paper, the design of experiment (DOE) is used to study the influence of temperature, pH and chloride concentration on the pitting and crevice corrosion of AISI 304L (UNS S30403) stainless steel. DOE approach enables to reduce the number of tests (anodic potentiodynamic polarization) necessary to study the effect of several parameters on the passivity breakdown potential. The use of DOE provided a regression equation that was analyzed by comparison with laboratory and literature results. Among all these parameters, the temperature has the most significant effect on pitting corrosion resistance.

Research paper thumbnail of Self-cleaning building materials: The multifaceted effects of titanium dioxide

Construction and Building Materials

The physical integrity and photocatalytic performance of titanium dioxide (TiO2) deteriorate with... more The physical integrity and photocatalytic performance of titanium dioxide (TiO2) deteriorate with aging. Here we propose a pre-treatment with nitric or sulfuric acid of commercial TiO2 nanopowders used in coating, mortars, or paints. The diffuse reflectance is increased between 1500 and 2500 nm by 0.04 and 0.06, respectively, with nitric and sulfuric acid (unaffected by neutralization). Nitric acid causes a decrease in crystallinity and photocatalytic activity, which drops by almost 20%; this drawback is prevented by post-treatment neutralization, which allows to recover initial photocatalytic efficiency and even increase it. Treatment with sulfuric acid shows no significant effect on photoactivity, instead.

Research paper thumbnail of Chemical oxidation as repairing technique to restore corrosion resistance on damaged anodized titanium

Surface and Coatings Technology

Research paper thumbnail of Pitting corrosion on anodized titanium: Effect of halides

Materials and Corrosion

Titanium corrosion resistance is high in the majority of environments. However, titanium is susce... more Titanium corrosion resistance is high in the majority of environments. However, titanium is susceptible to different forms of corrosion, if exposed to high concentrated halides containing solutions. To face this corrosion problem, expensive titanium alloys are used. An alternative method, consisting of electrochemical anodizing treatment, which promote the formation of a compact titanium oxide on the surface, could be applied to increase titanium corrosion resistance. In this work, titanium samples anodized at 20 V in H 2 SO 4 0.5 M have been tested in sodium fluorides, chlorides, bromides and iodides at 0.5 M and 2.0 M in order to define halides aggressiveness.

Research paper thumbnail of Enhancement of pure titanium localized corrosion resistance by anodic oxidation

Materials and Corrosion

The corrosion behavior of commercially pure titanium (UNS R50400) was investigated in presence of... more The corrosion behavior of commercially pure titanium (UNS R50400) was investigated in presence of aggressive, bromides containing, species; reported to cause severer localized corrosion compared to chlorides. To enhance localized corrosion resistance of the metal, several surface treatments were performed. Samples anodized at potentials between 10 V and 200 V were characterized in term of oxide thickness and morphology and tested with potentiodynamic analyses in NH 4 Br. This treatment was found to greatly enhance corrosion resistance of titanium but it suffers localized removal of the oxide due to wrong handling of the part before their installation. For this reason, another treatment, suitable for in-situ surface recovering was developed through chemical oxidation in NaOH 10 M.

Research paper thumbnail of Corrosion resistance enhancement of chemically oxidized titanium through NaOH and H2 O2 exposure

Materials and Corrosion

Titanium owes its astounding corrosion resistance to a thin, compact oxide layer that is formed s... more Titanium owes its astounding corrosion resistance to a thin, compact oxide layer that is formed spontaneously when the metal is exposed to the environment. However, even titanium can be subject to corrosion in very aggressive environments. To enhance its corrosion resistance, it is possible to exploit the same mechanism that leads to the formation of the protective oxide layer and force its growth with an external contribution. Oxidation can be easily stimulated with the use of an electrochemical cell.

Research paper thumbnail of Electrochemical anodizing treatment to enhance localized corrosion resistance of pure titanium

Journal of applied biomaterials & functional materials, Jan 26, 2017

Titanium has outstanding corrosion resistance due to the thin protective oxide layer that is form... more Titanium has outstanding corrosion resistance due to the thin protective oxide layer that is formed on its surface. Nevertheless, in harsh and severe environments, pure titanium may suffer localized corrosion. In those conditions, costly titanium alloys containing palladium, nickel and molybdenum are used. This purpose investigated how it is possible to control corrosion, at lower cost, by electrochemical surface treatment on pure titanium, increasing the thickness of the natural oxide layer. Anodic oxidation was performed on titanium by immersion in H2SO4 solution and applying voltages ranging from 10 to 80 V. Different anodic current densities were considered. Potentiodynamic tests in chloride- and fluoride-containing solutions were carried out on anodized titanium to determine the pitting potential. All tested anodizing treatments increased corrosion resistance of pure titanium, but never reached the performance of titanium alloys. The best corrosion behavior was obtained on tita...

Research paper thumbnail of Corrosion of titanium: Part 1: aggressive environments and main forms of degradation

Journal of applied biomaterials & functional materials, Jan 11, 2017

Titanium has outstanding corrosion resistance due to the external natural oxide protective layer ... more Titanium has outstanding corrosion resistance due to the external natural oxide protective layer formed when it is exposed to an aerated environment. Despite this, titanium may suffer different forms of corrosion in severe environments: uniform corrosion, pitting and crevice corrosion, hydrogen embrittlement, stress-corrosion cracking, fretting corrosion and erosion. In this first review, forms of corrosion affecting titanium are analyzed based on a wide literature review. For each form of corrosion, the mechanism and most severe environment are reported according to the current understanding.In the second part, this review will address the possible surface treatments that can increase corrosion resistance on commercially pure titanium: Electrochemical anodizing, thermal oxidation, chemical oxidation and bulk treatments such as alloying will be considered, highlighting the advantages of each technique.

Research paper thumbnail of Corrosion of titanium: Part 2: Effects of surface treatments

Journal of applied biomaterials & functional materials, 2018

Titanium is well known as one of the most corrosion-resistant metals. However, it can suffer corr... more Titanium is well known as one of the most corrosion-resistant metals. However, it can suffer corrosion attacks in some specific aggressive conditions. To further increase its corrosion resistance, it is possible either to modify its surface, tuning either thickness, composition, morphology or structure of the oxide that spontaneously forms on the metal, or to modify its bulk composition. Part 2 of this review is dedicated to the corrosion of titanium and focuses on possible titanium treatments that can increase corrosion resistance. Both surface treatments, such as anodization or thermal or chemical oxidation, and bulk treatments, such as alloying, are considered, highlighting the advantages of each technique.

Research paper thumbnail of Photocatalytic Activity of Nanotubular TiO₂ Films Obtained by Anodic Oxidation: A Comparison in Gas and Liquid Phase

Materials (Basel, Switzerland), Jan 24, 2018

The availability of immobilized nanostructured photocatalysts is of great importance in the purif... more The availability of immobilized nanostructured photocatalysts is of great importance in the purification of both polluted air and liquids (e.g., industrial wastewaters). Metal-supported titanium dioxide films with nanotubular morphology and good photocatalytic efficiency in both environments can be produced by anodic oxidation, which avoids release of nanoscale materials in the environment. Here we evaluate the effect of different anodizing procedures on the photocatalytic activity of TiO₂ nanostructures in gas and liquid phases, in order to identify the most efficient and robust technique for the production of TiO₂ layers with different morphologies and high photocatalytic activity in both phases. Rhodamine B and toluene were used as model pollutants in the two media, respectively. It was found that the role of the anodizing electrolyte is particularly crucial, as it provides substantial differences in the oxide specific surface area: nanotubular structures show remarkably differen...

Research paper thumbnail of Cathodic protection monitoring of buried carbon steel pipeline: measurement and interpretation of instant-off potential

Corrosion Engineering, Science and Technology, 2017

Research paper thumbnail of Effects of AC-interference on chloride-induced corrosion of reinforced concrete

Construction and Building Materials, 2017

Research paper thumbnail of Monitoring cathodic protection of buried pipeline by means of a potential probe with an embedded zinc reference electrode

Research paper thumbnail of TiO2 alterations with natural aging: Unveiling the role of nitric acid on NIR reflectance

Solar Energy Materials and Solar Cells, 2016

The development of photoactive materials with self-cleaning and depolluting qualities is a hot to... more The development of photoactive materials with self-cleaning and depolluting qualities is a hot topic in materials science, given their impact on several technologies, in a wide range of contexts of applications. Anatase phase titanium dioxide (TiO2) is the largest used photocatalyst, with increasing applications ranging from air quality control to renewable energies, to green building materials for zero energy communities. Yet, it is partially transmissive in the near infrared (NIR), which negatively affects the solar reflectance of TiO2 containing materials. In this contribution we describe an unexpected increase in anatase near infrared (NIR) reflectance observed during environmental exposure. We unveil its complex mechanisms, based on the contact with nitric acid generated by NOx photocatalytic degradation, which causes partial reduction and decrease in crystallinity to TiO2. This may open the way for introducing multiple environmentally beneficial effects on TiO2 pollutants degradation, self-cleaning, and energy performance.