X-ray refraction is analogous to visible light deflection by matter, in particular discontinuities within materials. Trivially but importantly, deflection of X-rays is also sensitive to the orientation of the object boundaries. These features make X-ray refraction techniques extremely suitable to a) detect defects such as pores and microcracks, and quantify their densities in bulk materials, and b) evaluate porosity and particle properties such as orientation, size, and spatial distribution (by mapping).
While X-ray refraction techniques cannot in general image single defects, their detectability is simply limited by the wavelength of the radiation, i.e. crack opening above 1 nm can be detected. Such defects are on the contrary invisible even to advanced imaging techniques such as high-resolution X-ray computed tomography.
We will show the application of X-ray refraction 2D mapping (topography) and tomography to different sorts of problems in ceramic science and technology: 1) Sintering of SiC green bodies; 2) Porosity analysis in diesel particulate filter (with focus on silicates); 3) fiber de-bonding in metal and polymer matrix composites; 4) micro-cracking of glass-precursor b-eucryptite. We will see that the use of X-ray refraction analysis yields quantitative results, also directly usable in available models.