Micro-waxs study of structural heterogeneity in single pan-precursor and subsequent carbon fiber

The crystallographic orientation distribution and micro-voids in polyacrylonitrile (PAN) based carbon fiber play a key role in controlling the fiber’s strength and modulus. The evolution of microstructure from polyacrylonitrile (PAN) precursor fibers throughout oxidation and subsequent carbon fiber, processed using a 100 ton carbon fiber pilot line (Carbon Nexus, Deakin University), was studied by synchrotron wide angle X-ray scattering (WAXS). A dedicated fiber testing capability has been developed on the X-ray Fluorescence Microscopy beamline at the Australian synchrotron facility, where spatially resolving measurements (Micro-WAXS patterns) were recorded as each single fiber was translated across the focused incident X-ray probe in 1 micron steps. Probing along the lateral fiber direction, (100) and (002) WAXS patterns for the PAN and subsequent carbon fibers respectively revealed a non-uniform distribution of crystallographic properties - quantified in terms of the lattice d-spacing, crystallite size and crystallographic orientation, indicating a skin-core-structure.