Qualitative and quantitative analysis of the process chain: Wood polymer composite – C-template – C/Si/SiC-ceramic by means of X-ray computed tomography

The quality of a ceramic is defined by its homogenous and non-porous volume. These parameters determine the durability and failure probability of a component. By means of XCT, the structural changes within the samples over the whole manufacturing route were evaluated. In the qualitative evaluation at lower XCT resolutions (> (70 µm)³ voxel size) pores, cracks, and higher- and lower dense inclusions were compared within and between corresponding samples. Cracks in the wood polymer composite (WPC) tend to shrink in the C-template during carbonisation. In some WPCs no big cracks were visible while in the C-templates big cracks appeared due to carbonising and shrinkage – but these cracks are fully closed in the ceramic after the Si infiltration-step. For quantitative analysis of phase composition, high resolution XCT-measurements between (0.8 µm)³ and (3 µm)³ voxel size were applied. Due to the fact, that the absorption contrast between the wood and polymer matrix in the WPC and contrast between Si / SiC and C / Air in the ceramic is very limited, this quantification step is very challenging. For the C-templates, applying a simple threshold algorithm, the quantification by XCT leads to promising results and fits well to LOM and mercury porosimetry. With SEM/EDS higher dense inclusions, visible in XCT, were analyesed and mainly consist of the elements C-O and trace amounts of, for example, Fe, Zn, Si or Mg.