Thermal and oxidation resistant barrier on carbon fiber with Si and Si–Ti based pre-ceramic coatings for high temperature application

Abstract

Carbon fiber (CF) must be protected from thermal oxidation for high temperature application because of its low thermo-oxidative stability above 450℃ in air. CF is now increasingly being used as a reinforcing material in the construction industry. A thermal and oxidation resistant coating is necessary for CF-reinforced concrete (CFRC) composites in order to satisfy a high level of safety standard in the case of fire. New types of pre-ceramic coatings, such as Tyranno® polymer (Si–Ti based pre-ceramic) and SiO2 sol–gel, have been deposited on CF filament yarn by means of a wet chemical continuous dip coating method. The results of surface analyses, e.g. scanning electron microscopy, X-ray photoelectron spectroscopy, and infrared spectroscopy, showed the changes in topographical properties of CF caused by the coatings. Thermogravimetric analysis proved that the high temperature (up to 800℃) oxidation stability of CF was considerably improved due to the coatings. Tensile test results indicated that the strength of CF yarn at 20℃ was increased by up to 80% with the coatings. Thermo-mechanical properties were also enhanced up to 600℃. CF yarn retains its original strength and elasticity modulus, i.e. the stiffness at 700℃, with a Tyranno® polymer coating.