We used microwave plasma enhanced chemical vapor deposition (MPECVD) to carbonize an electrospun polyacrylonitrile (PAN) precursor to form carbon fibers. Scanning electron microscopy, Raman spectroscopy, and Fourier transform infrared spectroscopy were used to characterize the fibers at different evolution stages. It was found that MPECVD-carbonized PAN fibers do not exhibit any significant change in the fiber diameter, whilst conventionally carbonized PAN fibers show a 33% reduction in the fiber diameter. An additional coating of carbon nanowalls (CNWs) was formed on the surface of the carbonized PAN fibers during the MPECVD process without the assistance of any metallic catalysts. The result presented here may have a potential to develop a novel, economical, and straightforward approach towards the mass production of carbon fibrous materials containing CNWs. V

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Alternating current field measurement (ACFM) probes are used to detect and size cracks in a range of engineering components. Crack sizing for this, and other electromagnetic (EM) based NDT systems, relies on relating the signal obtained to the actual crack length. For cracks that do not propagate vertically, such as rolling contact fatigue cracks in rails, predicting the crack depth, which determines the rail depth to be removed by grinding, requires an assumed propagation angle into the material as no method to determine crack vertical angle from the EM signals has been reported. This paper discusses the relationship between ACFM signals and propagation angles for surface-breaking cracks using a COMSOL model. The Bx signal accurately predicts the crack pocket length when the vertical angle is 30-90° but underestimates pocket length for shallower angles, e.g. a 50% underestimate is seen for a 3.2 mm pocket length crack propagating at a vertical angle of 10°. A new measure, the Bz trough-peak ratio, is proposed to determine the crack vertical angle. These are verified by experimental measurements using a commercial ACFM pencil probe for cracks with a range of vertical angles between 10° and 90°.

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Linking the ferrite fraction in a dual-phase (DP) steel microstructure and its electromagnetic properties is critical in the effort to develop on-line measurement techniques for phase transformation using electromagnetic (EM) sensors. This paper developed a seamlessly integrated method for generating 3D microstructures and evaluating their equivalent permeability values. Both the generation of 3D microstructures and evaluation of equivalent permeability have been achieved through custom modelling packages developed by the authors. Voronoi modelling based on the random close packing of spheres (RCPS-VM) was used to precisely control the ferrite fraction in DP steel microstructure, and an equivalent uniform field method for 3D finite element simulation was developed for efficient analysis.