Francesco Di Quarto | Università degli Studi di Palermo (original) (raw)
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Papers by Francesco Di Quarto
UPB Scientific Bulletin, Series B: Chemistry and Materials Science
Corros Sci, 1980
Scanning electron microscopy was used to investigate the morphology of anodic oxide films on tung... more Scanning electron microscopy was used to investigate the morphology of anodic oxide films on tungsten, obtained in various conditions of anodization. Studies were made of the growth of porous films, whose thickness increases with time and depends upon the current density. Temperature and electrolyte composition influence the film morphology. Gravimetric measurements of film dissolution at 70°C show that after a transient time, the rate of metal dissolution and that of film formation coincide. The porous films thicken because tungsten dissolves as we22+ and precipitates as WO3.H20.
Corros Eng Sci Technol, 2004
A critical appraisal of the use of the theory of semiconductors in characterising passive lms on ... more A critical appraisal of the use of the theory of semiconductors in characterising passive lms on metals and alloys is provided, with special emphasis on the use of Mott -Schottky theory for the location of characteristic energy levels of the passive lm -electrolyte junction. Some inconsistencies between theory and experimental results in the case of thin passive lms are discussed together with possible alternative ways for overcoming such problems. The role of semiconducting properties in determining the pitting behaviour of passive lms on W in solutions containing halide is presented and discussed. The validity of a recently proposed correlation between the solid state properties of passive lms and the pitting potential is critically reviewed.
Electrochim Acta, 1981
ABSTRACT
Journal of the Electrochemical Society, 2013
CeO 2 and Co containing CeO 2 thin films were deposited on indium tin oxide and stainless steel b... more CeO 2 and Co containing CeO 2 thin films were deposited on indium tin oxide and stainless steel by anodic electrodeposition. Scanning electron microscopy showed that the films are flat and show globular morphology and cracks resulting from volume shrinking. According to XRD and Raman Spectroscopy pure ceria layers are crystalline, while the presence of Co induces the formation of amorphous films. The good adhesion and the compactness allowed the photoelectrochemical characterization of the films. A band gap value of 2.9 eV was estimated for CeO 2 , while slightly higher values (∼3.0 eV) were estimated for Co containing films. A mechanism for ceria anodic electrodeposition is proposed and discussed.
Journal of Applied Electrochemistry, Aug 31, 2002
Alumina membranes were fabricated by anodizing aluminium metal in 0.15 M oxalic acid. The growth ... more Alumina membranes were fabricated by anodizing aluminium metal in 0.15 M oxalic acid. The growth kinetics of the porous layer were investigated in the temperature range À1 to 16°C using linear potential scans up to 70 V. The faradaic efficiencies of metal oxidation and of porous layer formation, determined by applying Faraday's law, were found to be independent of both temperature and electrical charge. SEM analysis of the metal-side and solution-side surfaces revealed different morphologies. After dissolution of the barrier layer in phosphoric acid, the metal-side surface showed circular pores whose size of about 90 nm was found to be uniform and independent of temperature. The pore population was also practically independent of temperature and a value of about 4 · 10 13 pores m À2 was determined. On the solution-side surface the presence of a deposit partially occluding the mouths of pores was observed. This coating could be removed by chemical etching in NaOH or thermal treatment at 870°C, where decomposition of oxalate occurs. This supports the hypothesis that the deposit consists of an aluminium salt containing oxalate anions precipitated from the solution. The results show that it is possible to control the morphological characteristics of the anodic alumina membranes by careful choice of experimental conditions.
Electrochimica Acta, 2008
A photoelectrochemical investigation on anodic films of different thickness grown on sputter-depo... more A photoelectrochemical investigation on anodic films of different thickness grown on sputter-deposited Zr and Zr20 at.%Ti was carried out. The estimated optical band gap and flat band potential of thick (U F ≥ 50 V) anodic films were related to their crystalline structure and compared ...
Electrochimica Acta, 1978
instability of anodically formed TiO, films which gives rise to a peculiar electrical behaviour w... more instability of anodically formed TiO, films which gives rise to a peculiar electrical behaviour was studied with electrochemical, optical, and electron microscopy techniques. It was found that the films formed in corroding (phosphoric acid) and not corroding (borax) solutions had weak spots which permitted the solution to penetrate the film. The Pilling-Bedworth ratio of 1.95 for the formation of Anatase from the Titanium metal together with poor adherence of the oxide film are proposed to be the source of the film instability.
Nanotechnol, 2010
New experimental evidence concerning the formation of La(OH)3 nanowires on anodic alumina membran... more New experimental evidence concerning the formation of La(OH)3 nanowires on anodic alumina membranes by cathodic polarization in 0.05 M lanthanum nitrate solution is provided to further support the conclusions previously reached in our work (Bocchetta et al 2007 Electrochem. Commun. 9 683-8) and recently criticized by González-Rovira et al (Nanotechnology 2008 19 495305). Some unconvincing aspects of the paper of González-Rovira et al, according to which the same electrochemical process should lead to the formation of hydroxycarbonate nanotubes, are also discussed.
J Appl Electrochem, 1982
The electrochemical oxidation of maleic acid on tungsten anodes has been investigated. Glyoxal an... more The electrochemical oxidation of maleic acid on tungsten anodes has been investigated. Glyoxal and carbon dioxide were the main products together with tartaric acid and acetaldehyde. Glyoxal is also obtained as the main product from the oxidation ofd-tartaric acid. Under the same conditions succinic acid is completely oxidized to carbon dioxide and water. The anodic dissolution of tungsten and the
Electrochimica Acta, Sep 30, 2003
The electrochemical fabrication of alumina membranes by anodizing of aluminium in phosphoric acid... more The electrochemical fabrication of alumina membranes by anodizing of aluminium in phosphoric acid and oxalic acid solutions, in the temperature interval from (/1 to 16 8C, was investigated in order to study the influence of different parameters (initial treatment of aluminium surface, nature and composition of electrolyte, temperature) on the final characteristics of the membranes. Porous layers were grown using a linear potential scan at 0.2 V s (1 up to 160 V in H 3 PO 4 solution and 70 V in oxalic acid solution. The efficiency of porous layer formation was calculated by using Faraday's law and weight measurements. Pore size distribution and porosity of membranes prepared in 0.4 M H 3 PO 4 were found to be dependent on temperature, while in 0.04 M smaller pore size and lower porosity were obtained, independent of temperature. Highly ordered structures were formed by aluminium anodizing in 0.15 M oxalic acid solution at 70 V. A uniform pore diameter of about 90 nm was found, independent of temperature. A porosity value of about 26% was achieved and it was found to be independent of temperature for membranes prepared in oxalic acid. Porous layers grown either in H 3 PO 4 or oxalic acid solution crystallized at temperatures around 870 Á/890 8C. For membranes formed in oxalic acid the pyrolysis of oxalate anions also occurs. #
Electrochim Acta, 1993
ABSTRACT
UPB Scientific Bulletin, Series B: Chemistry and Materials Science
Corros Sci, 1980
Scanning electron microscopy was used to investigate the morphology of anodic oxide films on tung... more Scanning electron microscopy was used to investigate the morphology of anodic oxide films on tungsten, obtained in various conditions of anodization. Studies were made of the growth of porous films, whose thickness increases with time and depends upon the current density. Temperature and electrolyte composition influence the film morphology. Gravimetric measurements of film dissolution at 70°C show that after a transient time, the rate of metal dissolution and that of film formation coincide. The porous films thicken because tungsten dissolves as we22+ and precipitates as WO3.H20.
Corros Eng Sci Technol, 2004
A critical appraisal of the use of the theory of semiconductors in characterising passive lms on ... more A critical appraisal of the use of the theory of semiconductors in characterising passive lms on metals and alloys is provided, with special emphasis on the use of Mott -Schottky theory for the location of characteristic energy levels of the passive lm -electrolyte junction. Some inconsistencies between theory and experimental results in the case of thin passive lms are discussed together with possible alternative ways for overcoming such problems. The role of semiconducting properties in determining the pitting behaviour of passive lms on W in solutions containing halide is presented and discussed. The validity of a recently proposed correlation between the solid state properties of passive lms and the pitting potential is critically reviewed.
Electrochim Acta, 1981
ABSTRACT
Journal of the Electrochemical Society, 2013
CeO 2 and Co containing CeO 2 thin films were deposited on indium tin oxide and stainless steel b... more CeO 2 and Co containing CeO 2 thin films were deposited on indium tin oxide and stainless steel by anodic electrodeposition. Scanning electron microscopy showed that the films are flat and show globular morphology and cracks resulting from volume shrinking. According to XRD and Raman Spectroscopy pure ceria layers are crystalline, while the presence of Co induces the formation of amorphous films. The good adhesion and the compactness allowed the photoelectrochemical characterization of the films. A band gap value of 2.9 eV was estimated for CeO 2 , while slightly higher values (∼3.0 eV) were estimated for Co containing films. A mechanism for ceria anodic electrodeposition is proposed and discussed.
Journal of Applied Electrochemistry, Aug 31, 2002
Alumina membranes were fabricated by anodizing aluminium metal in 0.15 M oxalic acid. The growth ... more Alumina membranes were fabricated by anodizing aluminium metal in 0.15 M oxalic acid. The growth kinetics of the porous layer were investigated in the temperature range À1 to 16°C using linear potential scans up to 70 V. The faradaic efficiencies of metal oxidation and of porous layer formation, determined by applying Faraday's law, were found to be independent of both temperature and electrical charge. SEM analysis of the metal-side and solution-side surfaces revealed different morphologies. After dissolution of the barrier layer in phosphoric acid, the metal-side surface showed circular pores whose size of about 90 nm was found to be uniform and independent of temperature. The pore population was also practically independent of temperature and a value of about 4 · 10 13 pores m À2 was determined. On the solution-side surface the presence of a deposit partially occluding the mouths of pores was observed. This coating could be removed by chemical etching in NaOH or thermal treatment at 870°C, where decomposition of oxalate occurs. This supports the hypothesis that the deposit consists of an aluminium salt containing oxalate anions precipitated from the solution. The results show that it is possible to control the morphological characteristics of the anodic alumina membranes by careful choice of experimental conditions.
Electrochimica Acta, 2008
A photoelectrochemical investigation on anodic films of different thickness grown on sputter-depo... more A photoelectrochemical investigation on anodic films of different thickness grown on sputter-deposited Zr and Zr20 at.%Ti was carried out. The estimated optical band gap and flat band potential of thick (U F ≥ 50 V) anodic films were related to their crystalline structure and compared ...
Electrochimica Acta, 1978
instability of anodically formed TiO, films which gives rise to a peculiar electrical behaviour w... more instability of anodically formed TiO, films which gives rise to a peculiar electrical behaviour was studied with electrochemical, optical, and electron microscopy techniques. It was found that the films formed in corroding (phosphoric acid) and not corroding (borax) solutions had weak spots which permitted the solution to penetrate the film. The Pilling-Bedworth ratio of 1.95 for the formation of Anatase from the Titanium metal together with poor adherence of the oxide film are proposed to be the source of the film instability.
Nanotechnol, 2010
New experimental evidence concerning the formation of La(OH)3 nanowires on anodic alumina membran... more New experimental evidence concerning the formation of La(OH)3 nanowires on anodic alumina membranes by cathodic polarization in 0.05 M lanthanum nitrate solution is provided to further support the conclusions previously reached in our work (Bocchetta et al 2007 Electrochem. Commun. 9 683-8) and recently criticized by González-Rovira et al (Nanotechnology 2008 19 495305). Some unconvincing aspects of the paper of González-Rovira et al, according to which the same electrochemical process should lead to the formation of hydroxycarbonate nanotubes, are also discussed.
J Appl Electrochem, 1982
The electrochemical oxidation of maleic acid on tungsten anodes has been investigated. Glyoxal an... more The electrochemical oxidation of maleic acid on tungsten anodes has been investigated. Glyoxal and carbon dioxide were the main products together with tartaric acid and acetaldehyde. Glyoxal is also obtained as the main product from the oxidation ofd-tartaric acid. Under the same conditions succinic acid is completely oxidized to carbon dioxide and water. The anodic dissolution of tungsten and the
Electrochimica Acta, Sep 30, 2003
The electrochemical fabrication of alumina membranes by anodizing of aluminium in phosphoric acid... more The electrochemical fabrication of alumina membranes by anodizing of aluminium in phosphoric acid and oxalic acid solutions, in the temperature interval from (/1 to 16 8C, was investigated in order to study the influence of different parameters (initial treatment of aluminium surface, nature and composition of electrolyte, temperature) on the final characteristics of the membranes. Porous layers were grown using a linear potential scan at 0.2 V s (1 up to 160 V in H 3 PO 4 solution and 70 V in oxalic acid solution. The efficiency of porous layer formation was calculated by using Faraday's law and weight measurements. Pore size distribution and porosity of membranes prepared in 0.4 M H 3 PO 4 were found to be dependent on temperature, while in 0.04 M smaller pore size and lower porosity were obtained, independent of temperature. Highly ordered structures were formed by aluminium anodizing in 0.15 M oxalic acid solution at 70 V. A uniform pore diameter of about 90 nm was found, independent of temperature. A porosity value of about 26% was achieved and it was found to be independent of temperature for membranes prepared in oxalic acid. Porous layers grown either in H 3 PO 4 or oxalic acid solution crystallized at temperatures around 870 Á/890 8C. For membranes formed in oxalic acid the pyrolysis of oxalate anions also occurs. #
Electrochim Acta, 1993
ABSTRACT