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Contribution à la caractérisation des propriétés mécaniques et microstructurales des liaisons céramique-métal utilisées pour les applications des matériaux dentaires

Abstract : The utility of dental porcelain, as a restorative, can be extended in the PFM technique, as a strengthening mechanism for porcelain. Several layers of dental porcelain are fused to a metal casting. The coefficient of thermal expansion of these porcelains must be suitably matched with that of the alloy and the melting range of the alloy must be raised sufficiently above the fusion temperature of the porcelain for a successful operation.
This study deals with the evaluation of the mechanical behaviour at the interface of a glassy-ceramic coated onto palladium alloy substrate. Microstructural characterisations and residual stresses evaluations are carried out in the different layers of the sample. Residual stress measurements have been realised by neutron diffraction and high-energy synchrotron radiation to characterise the mechanical state of the sample.
The mechanical properties of metallic layers greatly depend on the residual stresses induced by the manufacturing of the coating. It is therefore very important to characterise these stresses. Some general aspects of the evaluation of residual stress are reported. A micro-mechanical model used in the study and a quick theoretical calculus are also presented.
Diffraction measurements have been performed in different zones in the sample, in particular, neutron diffraction to analyse both the glassy ceramic surface and the bulk of the leucite and of the palladium alloy; high energy synchrotron radiation for the metal/ceramic interfaces. In this way, they have allowed to obtain the best information in different regions of the analysed sample. For these experimental techniques, measurements carried out at the interface between two different materials are difficult to analyse due to great parasitic peak shifts which are obtained in such condition.
Therefore, it is important to correct the parasitic peak shifts which appear in these cases and which are not linked to the stress state of the scanned volume. This effect can be much greater than the peak shifts induced by the stresses. To solve this problem a complete modelling of 2-axis spectrometers, based on Monte Carlo calculations, has been developed either for neutrons or for synchrotron radiation. It allows also to optimise the experimental conditions and to define precisely the true volume of the neutron gauge.
The microstructure of a leucite dental glass-ceramic and of the palladium alloy substrate were finally investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS). The Transmission Electron Microscope technique (TEM) was also employed to study the structural properties of both materials.
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Submitted on : Thursday, January 31, 2008 - 11:02:00 AM
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Adele Carrado. Contribution à la caractérisation des propriétés mécaniques et microstructurales des liaisons céramique-métal utilisées pour les applications des matériaux dentaires. Physique [physics]. Université de Reims - Champagne Ardenne, 2001. Français. ⟨tel-00229712⟩

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