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

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 (R) 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 (R) polymer coating.