Abstract
The fibrous crystalline habit observed in isothermally heated glasses of approximately metasilicate composition is due to the formation of spherulitic β-CaSiO3 (wollastonite). By using the technique of hot-stage cine-micrography to measure crystallization kinetics, several 3-component systems have been selected in which growth rates are sufficiently high for the orientation of crystallization to be controlled by zone melting vitreous specimens. A development of this process has enabled β-CaSiO3 filaments to be crystallized by continuous drawing from a melt contained in a resistance-heated platinum crucible, whereby the temperature of crystallization is determined primarily by the speed of drawing. X-ray and microscopic examination of these filaments has confirmed that their polycrystalline microstructure is highly oriented, with the crystallographic b-axis (which corresponds to the chain direction of the [SiO4]3 tetrahedra) aligned longitudinally. They possess mechanical strength and elastic modulus significantly higher than filaments of the parent glass and, as a consequence of their fibrous fracture behaviour, may be crushed into fine acicular fragments suitable for composite reinforcement.
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Maries, A., Rogers, P.S. Continuous unidirectional crystallization of fibrous metasilicates from melts. J Mater Sci 13, 2119–2130 (1978). https://doi.org/10.1007/BF00541665
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DOI: https://doi.org/10.1007/BF00541665