STRESS- AND NANOSTRUCTURE-IMAGING OF CERAMIC FIBERS AND ABRADABLE THERMAL BARRIER COATINGS BY RAMAN MICROSPECTROMETRY-STATE OF THE ART AND PERSPECTIVES

摘要

Raman scattering is a unique tool providing information on the structure and short-range order of matter, whatever its physical state (liquid. amorphous or crystalline), through the intensity, wavenumber and bandwidth of the Raman peaks. Stress-induced Raman shifts can be used to determine the stress strain in films. fibers. Particulates, and. more generally, in any phase a few micron in scale, either bv it salt or dispersed in a matrix. Quantitative results follow from wavenumber calibration as a function of tensile strains or pressures applied to fibers or crystals. Furthermore, if the material is colored, (near) resonant Raman scattering occurs, which enhances the scattered light intensity and simplifies the spectra, especially for harmonics, but drastically reduces the analyzed volume (in-depth penetration approx 10-100 nm). This paper gives an overview of die effective and potential advantages and drawbacks of the Raman microspectrometry technique. The procedures to improve the sensitivity, the legibility and the reliability will be addressed. Examples will be chosen among (C. SiC) fiber reinforced ceramic or metal matrix composites, and an abradable zirconia-based engine case coating impacted with various coated blades.