Skip to Main content Skip to Navigation
Theses

Simulations 2D et 3D de microstructure d'alumine projetée plasma pour l'étude de ses propriétés mécaniques et électriques

Abstract : Alumina coating can ensure electrical insulation in a mechanical assembly. It is used in geologic probes which measure borehole resistivity. The oil context encourages companies such as Schlumberger to develop advanced coatings among which some are made of alumina. They are achieved by the plasma spraying which, however, generates interconnected pores and cracks in the microstructure. The resulting network, which characterizes the ceramic porosity, impairs coating properties. This thesis is based on the study of a range of plasma-sprayed alumina coating. Alumina coating microstructure can therefore be considered as exhibiting two phases: the ceramic matrix and the porosity. First, a classical two-dimensional (2D) analysis using SEM was compared with a three-dimensional (3D) analysis using microtomography to determine the type, the orientation and the distribution of the phases: -the 2D analysis of the coating microstructure was suitable for discriminating materials depending on their processing method. Different microstructures with various surface densities of pores and cracks were studied. Co-spraying led to coatings with an alumina-glass matrix. A post-treatment by excimer laser could generate materials with various surface properties. Lastly, impregnation techniques led to alumina microstructure with porosity filled with resin or aluminium phosphates. -the analysis by synchrotron microtomography was shown to be powerful only to characterize the pores in the coating. The study showed their orientation parallel to the spraying direction and their morphology. In addition, this technique could show changes of morphology and distribution of pores in a matrix of alumina-glass after thermal or laser treatment. All these results were used to simulate mechanical and electric properties as a function of microstructure characteristics. Impedance measurements in a liquid environment could characterize the interconnected porosity through an equivalent electric circuit. This showed to be an experimental method to exhibit connections in the microstructure, which allowed to compare the different materials. In a final stage, from 2D and 3D images, finite element simulation of the real microstructures resulted in the calculation of the Young's modulus and electrical permittivity of the coating. These simulations (i.e. both experimental and numerical) allowed to establish links between microstructure and properties of the coating.
Complete list of metadatas

Cited literature [71 references]  Display  Hide  Download

https://pastel.archives-ouvertes.fr/tel-00331802
Contributor : Bibliothèque Umr7633 <>
Submitted on : Friday, October 17, 2008 - 4:20:37 PM
Last modification on : Wednesday, October 14, 2020 - 4:02:05 AM
Long-term archiving on: : Monday, June 7, 2010 - 6:54:54 PM

Identifiers

  • HAL Id : tel-00331802, version 1

Citation

Olivier Amsellem. Simulations 2D et 3D de microstructure d'alumine projetée plasma pour l'étude de ses propriétés mécaniques et électriques. Mécanique [physics.med-ph]. École Nationale Supérieure des Mines de Paris, 2008. Français. ⟨NNT : 2008ENMP1550⟩. ⟨tel-00331802⟩

Share

Metrics

Record views

805

Files downloads

2187