The effect of carbonization conditions on the properties of rayon-based carbon fibres

Abstract

The effect of carbonization temperature on the properties of prewoven carbon fibre made from a rayon precursor is examined. Bulk composition is contrasted with surface elemental analysis (XPS) which shows that low carbonization temperatures (2300F, 1260C) produce a fibre with up to 15 and 5 at.% of oxygen and sodium respectively on the surface. At higher firing temperatures (up to 3000, 1649 C), the surface O and Na levels are significantly reduced and the measured fibre surface area declines from 50 m² g-¹ to under 5 ml g-'. Atomic force microscopy (AFM) was used to examine the surface detail of fibres at magnifications over 250000 times. AFM micrographs reveal that the fibre surface after carbonization at low temperatures is covered with a crust believed to be the char residue from tars released during the precarbonization stage. Surface analysis by Auger spectroscopy has confirmed the high oxygen and sodium content of the char material. Use of higher carbonization temperatures results in fibre surface properties which are generally regarded as preferable for use in ablative applications.