Crystallinity, Crystalline Quality, and Microstructural Ordering in Boron Nitride Fibers
A qualitative and quantitative analysis of the microtexture/microstructure in several experimental boron nitride fibers was investigated by X-ray diffraction and electron microscopy according to their mechanical properties. Young's modulus was controlled by grain orientation. The disordered microstructure of low modulus fibers consisted of amorphous regions and nanometer-sized crystallites arranged in a wide range of orientation. In contrast, high modulus samples showed a coarse-grained microtexture in which crystallites were ordered in a meso-hexagonal arrangement along the fiber-axis. Cracks were easily propagated as crystallinity increased, leading to decreased failure strain. The strength-microstructure relationship was obscured by the fiber porosity and defects.
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Document Type: Research Article
Affiliations: Laboratoire des Multimatériaux et Interfaces, UMR CNRS 5615, Université Claude Bernard Lyon 1, F-69622 Villeurbanne, France
Publication date: 2005-06-01