Skip to Main content Skip to Navigation
Theses

Micro-pyrolyse de couches minces de polymères précurseurs de céramiques

Abstract : Polymer pyrolysis is one method to make ceramic coatings. Compared to classical methods (CVD, PVD), the principle is simple but there are important problems in its implementation. With this technique, uncracked and adhering coatings thicker than 0.5 micrometers cannot be obtained. The aim of this study is to understand spontaneous cracking phenomena during the transformation by pyrolysis of a thin polysilazane film into « SiCN » ceramic.
First, the analysis of the behaviour of coatings pyrolysed under various atmospheres is done with a micro-pyrolysis apparatus, specifically builts for this study. It allows in-situ observations of the surface by optical microscopy during pyrolysis heat treatment. The changes during heating are demonstrated. In particula, we show that craking during heating occurs at about 580°C under nitrogen or argon atmosphere. Chemical characterization shows that in these conditions, the coatings are SiCNO ceramic with an oxydized layer (SiO2) at their surface (around 100 nm thick).
Mechanical modelling from literature and the construction of a simple monodimensionnal model allow us to describe the cracking and decohesion phenomena more quantitatively.
The last part of this study consists of the characterization of the main parameters which control these cracking phenomena. Mechanical characterization of coatings at different stages of the pyrolysis treatments is done by nanoindentation. We show that the cracking occurs simultaneously with a large increase of the material ‘s mechanical properties (hardness and Young's modulus) between 550°C and 650°C, coupled with an important shrinkage at these temperatures. This shows that the cracking is due to polymer/ceramic transition.
Complete list of metadatas

https://tel.archives-ouvertes.fr/tel-00151134
Contributor : Sandrine Bec <>
Submitted on : Friday, June 1, 2007 - 4:35:00 PM
Last modification on : Wednesday, November 20, 2019 - 2:27:13 AM
Long-term archiving on: : Thursday, April 8, 2010 - 6:42:26 PM

Identifiers

  • HAL Id : tel-00151134, version 1

Collections

Citation

Sandrine Bec. Micro-pyrolyse de couches minces de polymères précurseurs de céramiques. Mécanique [physics.med-ph]. Ecole Centrale de Lyon, 1992. Français. ⟨tel-00151134⟩

Share

Metrics

Record views

511

Files downloads

256