Titre :	Influence de l’aluminium sur les processus physicochimiques de frittage des éléments de transition : Cu – Ni – Co et l’oxydation du nickel.
Type de document :	texte imprimé
Auteurs :	Zohra Halem, Auteur ; Said Chekroud, Directeur de thèse
Editeur :	جامعة الإخوة منتوري قسنطينة
Année de publication :	2018
Format :	30 cm.
Note générale :	2 copies imprimées disponibles
Langues :	Français (fre)
Catégories :	Français - Anglais Physique
Tags :	Cristaux de NiO non dopés et dopés au Al ou au Cr  La diffusion  Conductivité électrique  Défauts ponctuels  Démixage cinétique de cation  Cinétique d'oxydation  Undoped and Al-or Cr doped NiO single crystals  Diffusion  Electrical conductivity  Point defects  Cation kinetic demixing  Oxidation kinetics
Index. décimale :	530 Physique
Résumé :	Sintering is based on the consolidation of solid alloyed particles and does not necessarily require the melting of the metal, representing an economic advantage of material and energy for the refractory metals, allowing, thus, to obtain the finished products with a much higher homogeneity than those made by classical techniques. In this study, we are interested in the influence of Al on the physico-chemical sintering processes of alloys (Co-X% Al), (Ni-X% Al) and (Cu-X% Al) with X = 4-8% mass. of intermetallic Al using different experimental techniques (isothermal dilatometry, ATD, ...) to define the type of sintering. The addition of Al is likely to give corrosion-resistant alloys at high temperature by substantially forming a higher Al2O3 protective layer than NiO or Cr2O3. Al which can be easily incorporated into the nickel network, because of the existence of the Ni-Al alloy, could play a role in the microstructure forming a layer of alumina. The surface condition of each particle, related to the porosity of the material, is a factor likely to affect the mechanism of the reaction and to modify the kinetics of oxidation. This thesis is structured in five chapters: • the 1st chapter is relative to the bibliographical reminders, • the experimental and analysis techniques used to carry out this thesis are presented in the 2nd chapter. • the third chapter is dedicated to the characterization of starting powders. • the elaboration and study of the alloys (Co-X% Al), (Ni-X% Al) and (Cu-X% Al) with X = 4-8% mass. Al are the subject of the 4th chapter. • the kinetics of oxidation and demixing occurring in the oxidation products obtained during the oxidation of the low alloy (Ni-0.5% mass.Al) sintered are transcribed in the 5th chapter. For the pure materials (Co-Ni and Cu), it is a purely solid phase sintering. Al increase from 4 to 8% mass. in the Co + Al and Ni + Al systems shows that all the results obtained during sintering are consistent following the formation of an aluminum-rich transient liquid phase rapidly soluble in the solid phase of nickel and cobalt. The coupling of the results obtained by the two techniques (dilatometry and DTA) shows that the sintering of the three alloys is a solid phase reactive sintering with the presence of a transient liquid phase (Self Heat-propagating Sintering). As for the influence of low Al contents (0.5% mass.Al) on the growth and adhesion of NiO layers on nickel polycrystals, the oxidation is carried out between 700 and 1200 ° C, under PO2 = 1 atm. Beyond 900 ° C, the addition of Al to nickel generates an increase in the rate of oxidation. However, the kinetics remains parabolic. The oxide formed on the surface of the alloys (Ni-0.5%Al) has a duplex structure. In the vicinity of the metal / oxide interface, the layer is porous, slightly adherent to the metal and consists of two NiO and NiAl2O4 phases. As a result of the kinetic demixing processes taking place in the corrosion layer, Al enrichment in the vicinity of the metal / oxide interface has been attributed to the difference in cation diffusivity, with: DAl
Diplôme :	Doctorat en sciences
En ligne :	../theses/physique/HAL7344.pdf
Format de la ressource électronique :	pdf
Permalink :	index.php?lvl=notice_display&id=10994

Influence de l’aluminium sur les processus physicochimiques de frittage des éléments de transition : Cu – Ni – Co et l’oxydation du nickel. [texte imprimé] / Zohra Halem, Auteur ; Said Chekroud, Directeur de thèse . - جامعة الإخوة منتوري قسنطينة, 2018 . -  ; 30 cm.
2 copies imprimées disponibles

Langues : Français (fre)

Catégories :	Français - Anglais Physique
Tags :	Cristaux de NiO non dopés et dopés au Al ou au Cr  La diffusion  Conductivité électrique  Défauts ponctuels  Démixage cinétique de cation  Cinétique d'oxydation  Undoped and Al-or Cr doped NiO single crystals  Diffusion  Electrical conductivity  Point defects  Cation kinetic demixing  Oxidation kinetics
Index. décimale :	530 Physique
Résumé :	Sintering is based on the consolidation of solid alloyed particles and does not necessarily require the melting of the metal, representing an economic advantage of material and energy for the refractory metals, allowing, thus, to obtain the finished products with a much higher homogeneity than those made by classical techniques. In this study, we are interested in the influence of Al on the physico-chemical sintering processes of alloys (Co-X% Al), (Ni-X% Al) and (Cu-X% Al) with X = 4-8% mass. of intermetallic Al using different experimental techniques (isothermal dilatometry, ATD, ...) to define the type of sintering. The addition of Al is likely to give corrosion-resistant alloys at high temperature by substantially forming a higher Al2O3 protective layer than NiO or Cr2O3. Al which can be easily incorporated into the nickel network, because of the existence of the Ni-Al alloy, could play a role in the microstructure forming a layer of alumina. The surface condition of each particle, related to the porosity of the material, is a factor likely to affect the mechanism of the reaction and to modify the kinetics of oxidation. This thesis is structured in five chapters: • the 1st chapter is relative to the bibliographical reminders, • the experimental and analysis techniques used to carry out this thesis are presented in the 2nd chapter. • the third chapter is dedicated to the characterization of starting powders. • the elaboration and study of the alloys (Co-X% Al), (Ni-X% Al) and (Cu-X% Al) with X = 4-8% mass. Al are the subject of the 4th chapter. • the kinetics of oxidation and demixing occurring in the oxidation products obtained during the oxidation of the low alloy (Ni-0.5% mass.Al) sintered are transcribed in the 5th chapter. For the pure materials (Co-Ni and Cu), it is a purely solid phase sintering. Al increase from 4 to 8% mass. in the Co + Al and Ni + Al systems shows that all the results obtained during sintering are consistent following the formation of an aluminum-rich transient liquid phase rapidly soluble in the solid phase of nickel and cobalt. The coupling of the results obtained by the two techniques (dilatometry and DTA) shows that the sintering of the three alloys is a solid phase reactive sintering with the presence of a transient liquid phase (Self Heat-propagating Sintering). As for the influence of low Al contents (0.5% mass.Al) on the growth and adhesion of NiO layers on nickel polycrystals, the oxidation is carried out between 700 and 1200 ° C, under PO2 = 1 atm. Beyond 900 ° C, the addition of Al to nickel generates an increase in the rate of oxidation. However, the kinetics remains parabolic. The oxide formed on the surface of the alloys (Ni-0.5%Al) has a duplex structure. In the vicinity of the metal / oxide interface, the layer is porous, slightly adherent to the metal and consists of two NiO and NiAl2O4 phases. As a result of the kinetic demixing processes taking place in the corrosion layer, Al enrichment in the vicinity of the metal / oxide interface has been attributed to the difference in cation diffusivity, with: DAl
Diplôme :	Doctorat en sciences
En ligne :	../theses/physique/HAL7344.pdf
Format de la ressource électronique :	pdf
Permalink :	index.php?lvl=notice_display&id=10994