Documents disponibles écrits par cet auteur

Corrosion behaviour in physiological fluids of surface films formed on titanium alloys / J. C. Mirza Rosca in Materials and corrosion, Vol. 63 N° 6 (Juin 2012) 

Public ISBD [article]  in Materials and corrosion > Vol. 63 N° 6 (Juin 2012) . - pp. 527–533 Titre : Corrosion behaviour in physiological fluids of surface films formed on titanium alloys Type de document : texte imprimé Auteurs : J. C. Mirza Rosca, Auteur ; E. Vasilescu, Auteur ; P. Drob, Auteur Année de publication : 2012 Article en page(s) : pp. 527–533 Note générale : Génie mécanique Langues : Anglais (eng) Mots-clés : Chemical  and  heat  treatments;  EIS;  microhardness;  open  circuit  potentials Résumé : The properties of the surface films formed on Ti and its Ti–5Al–4V and Ti–6Al–3.5Fe alloys by chemical (immersion in 10 M NaOH) and thermal treatment (500 °C) were studied in this paper. Their corrosion behaviour in Ringer solution was investigated. After treatments, the sample microhardness was measured. Also, the sample surfaces were observed by an optical microscope before and after immersion in Ringer solutions. The electrochemical behaviour of the surface films obtained by the chemical and thermal treatments was studied using the methods of the electrochemical impedance spectroscopy (EIS) and monitoring of open circuit potentials at different immersion periods (up to 60 days) in Ringer solution. Microhardness increased with the increasing loads for the studied materials, showing the existence of a compact protective layer. Microscopic observations exhibited more compact coatings after 60 days of exposure in Ringer solution, due to the formation of an apatite layer. EIS spectra revealed surface films with two layers: an inner, barrier protective layer and an outer, porous apatite layer. The impedance increases in time denoting that the films have grown by apatite nucleation. Also, EIS spectra showed that the complex treatment by chemical + heat method is the most efficiently. For the samples treated by the two processes (chemical + heat) the values of the open circuit potentials are nobler than of the chemical treated samples, denoting better protective, bioactive films. En ligne : http://onlinelibrary.wiley.com/doi/10.1002/maco.201106102/abstract [article] Corrosion behaviour in physiological fluids of surface films formed on titanium alloys [texte imprimé] / J. C. Mirza Rosca, Auteur ; E. Vasilescu, Auteur ; P. Drob, Auteur . - 2012 . - pp. 527–533. Génie mécanique Langues : Anglais (eng) in Materials and corrosion > Vol. 63 N° 6 (Juin 2012) . - pp. 527–533 Mots-clés : Chemical  and  heat  treatments;  EIS;  microhardness;  open  circuit  potentials Résumé : The properties of the surface films formed on Ti and its Ti–5Al–4V and Ti–6Al–3.5Fe alloys by chemical (immersion in 10 M NaOH) and thermal treatment (500 °C) were studied in this paper. Their corrosion behaviour in Ringer solution was investigated. After treatments, the sample microhardness was measured. Also, the sample surfaces were observed by an optical microscope before and after immersion in Ringer solutions. The electrochemical behaviour of the surface films obtained by the chemical and thermal treatments was studied using the methods of the electrochemical impedance spectroscopy (EIS) and monitoring of open circuit potentials at different immersion periods (up to 60 days) in Ringer solution. Microhardness increased with the increasing loads for the studied materials, showing the existence of a compact protective layer. Microscopic observations exhibited more compact coatings after 60 days of exposure in Ringer solution, due to the formation of an apatite layer. EIS spectra revealed surface films with two layers: an inner, barrier protective layer and an outer, porous apatite layer. The impedance increases in time denoting that the films have grown by apatite nucleation. Also, EIS spectra showed that the complex treatment by chemical + heat method is the most efficiently. For the samples treated by the two processes (chemical + heat) the values of the open circuit potentials are nobler than of the chemical treated samples, denoting better protective, bioactive films. En ligne : http://onlinelibrary.wiley.com/doi/10.1002/maco.201106102/abstract

Corrosion behaviour of a new Ti-6Al-2Nb-1Ta alloy in various solutions / C. Pirvu in Materials and corrosion, Vol. 62 N° 10 (Octobre 2011) 

Public ISBD [article]  in Materials and corrosion > Vol. 62 N° 10 (Octobre 2011) . - pp. 948–955 Titre : Corrosion behaviour of a new Ti-6Al-2Nb-1Ta alloy in various solutions Type de document : texte imprimé Auteurs : C. Pirvu, Auteur ; I. Demetrescu, Auteur ; P. Drob, Auteur Année de publication : 2012 Article en page(s) : pp. 948–955 Note générale : Génie Mécanique Langues : Anglais (eng) Mots-clés : Corrosion  rates  EIS  Neutral  corrosive  environment  Pitting  corrosion  Titanium  alloy Résumé : A new Ti-6Al-2Nb-1Ta alloy was obtained for to satisfy the mechanical and anticorrosion requirements in neutral corrosive environment. The corrosion behaviour of this new Ti-6Al-2Nb-1Ta alloy in 0.1 M Na2SO4, 3% NaCl solutions and synthetic sea water was studied in this paper, using potentiodynamic and linear polarisation method, electrochemical impedance spectroscopy (EIS) and monitoring of the open circuit potentials. The structure of the alloy represents an α + β uniform structure with un-oriented grains. From the potentiodynamic polarisation curves it resulted that the studied alloy is self-passivated in all three solutions having a very good and very easy tendency to passivation. The most favourable values of the electrochemical parameters were registered in 0.1 M Na2SO4 solution due to its reduced corrosivity. EIS measurements proved the improvement of the passive layer resistance with the immersion time. An electric equivalent circuit with two time constants was fitted. The values of the polarisation resistances showed very good protective capacities which improved in time. The open circuit potentials have the general tendency to ennoble in time, suggesting the thickening of the passive films and the increase of their protective capacities. DEWEY : 620.1 ISSN : 0947-5117 En ligne : http://onlinelibrary.wiley.com/doi/10.1002/maco.201006041/abstract [article] Corrosion behaviour of a new Ti-6Al-2Nb-1Ta alloy in various solutions [texte imprimé] / C. Pirvu, Auteur ; I. Demetrescu, Auteur ; P. Drob, Auteur . - 2012 . - pp. 948–955. Génie Mécanique Langues : Anglais (eng) in Materials and corrosion > Vol. 62 N° 10 (Octobre 2011) . - pp. 948–955 Mots-clés : Corrosion  rates  EIS  Neutral  corrosive  environment  Pitting  corrosion  Titanium  alloy Résumé : A new Ti-6Al-2Nb-1Ta alloy was obtained for to satisfy the mechanical and anticorrosion requirements in neutral corrosive environment. The corrosion behaviour of this new Ti-6Al-2Nb-1Ta alloy in 0.1 M Na2SO4, 3% NaCl solutions and synthetic sea water was studied in this paper, using potentiodynamic and linear polarisation method, electrochemical impedance spectroscopy (EIS) and monitoring of the open circuit potentials. The structure of the alloy represents an α + β uniform structure with un-oriented grains. From the potentiodynamic polarisation curves it resulted that the studied alloy is self-passivated in all three solutions having a very good and very easy tendency to passivation. The most favourable values of the electrochemical parameters were registered in 0.1 M Na2SO4 solution due to its reduced corrosivity. EIS measurements proved the improvement of the passive layer resistance with the immersion time. An electric equivalent circuit with two time constants was fitted. The values of the polarisation resistances showed very good protective capacities which improved in time. The open circuit potentials have the general tendency to ennoble in time, suggesting the thickening of the passive films and the increase of their protective capacities. DEWEY : 620.1 ISSN : 0947-5117 En ligne : http://onlinelibrary.wiley.com/doi/10.1002/maco.201006041/abstract

Corrosion resistance of the new Ti-25Ta-25Nb alloy in severe functional conditions / E. Vasilescu in Materials and corrosion, Vol. 61 N° 11 (Novembre 2010) 

Public ISBD [article]  in Materials and corrosion > Vol. 61 N° 11 (Novembre 2010) . - pp. 947–954 Titre : Corrosion resistance of the new Ti-25Ta-25Nb alloy in severe functional conditions Type de document : texte imprimé Auteurs : E. Vasilescu, Auteur ; P. Drob, Auteur ; C. Vasilescu, Auteur Année de publication : 2011 Article en page(s) : pp. 947–954 Note générale : Génie mécanique Langues : Anglais (eng) Mots-clés : Corrosion  tests;  EIS;  microstructure;  SEM;  titanium  alloy Résumé : In this study, a new Ti-25Ta-25Nb (mass%) β alloy was synthesised by cold crucible semi-levitation melting. After melting, each ingot was solution treated in the β-phase domain and water quenched in order to obtain a fully recrystallised homogeneous β-phase microstructure. To evaluate the bio-corrosion property of this new alloy, corrosion tests (cyclic potentiodynamic and linear polarisation, EIS) and surface analysis (SEM) were carried out in Ringer solution at different pH values (acid, neutral and basic). The results indicated that the corrosion resistance of the Ti-25Ta-25Nb alloy is quite higher than that of the commercially pure CP Ti alloy. These results show that this new alloy possesses all the characteristics necessary for its long-term use as medical implants. En ligne : http://onlinelibrary.wiley.com/doi/10.1002/maco.201005740/abstract [article] Corrosion resistance of the new Ti-25Ta-25Nb alloy in severe functional conditions [texte imprimé] / E. Vasilescu, Auteur ; P. Drob, Auteur ; C. Vasilescu, Auteur . - 2011 . - pp. 947–954. Génie mécanique Langues : Anglais (eng) in Materials and corrosion > Vol. 61 N° 11 (Novembre 2010) . - pp. 947–954 Mots-clés : Corrosion  tests;  EIS;  microstructure;  SEM;  titanium  alloy Résumé : In this study, a new Ti-25Ta-25Nb (mass%) β alloy was synthesised by cold crucible semi-levitation melting. After melting, each ingot was solution treated in the β-phase domain and water quenched in order to obtain a fully recrystallised homogeneous β-phase microstructure. To evaluate the bio-corrosion property of this new alloy, corrosion tests (cyclic potentiodynamic and linear polarisation, EIS) and surface analysis (SEM) were carried out in Ringer solution at different pH values (acid, neutral and basic). The results indicated that the corrosion resistance of the Ti-25Ta-25Nb alloy is quite higher than that of the commercially pure CP Ti alloy. These results show that this new alloy possesses all the characteristics necessary for its long-term use as medical implants. En ligne : http://onlinelibrary.wiley.com/doi/10.1002/maco.201005740/abstract