Improvement of Inter-face Layer Coating by Plasma Treatment of Carbon Fiber for Carbon Fiber Reinforced Silicon Carbide Composite Applications

Carbon fiber (CF) reinforced SiC (CF/SiC) composites are sought for high temperature application in areas of automobiles, aerospace and nuclear reactors due to their outstanding properties. However, CF/SiC composites have low durability owing to oxidation of CF upon air-exposure during high temperature applications. The inter-phase layer between fiber and SiC matrix is used in order to protect fiber from oxidation. Here, we have aimed to study the effect of air RF (13.56 MHz) plasma treatment on CF tow for improvement of SiO₂ inter-face layer coating by dip coating technique. The air RF (13.56 MHz) plasma treatments on CF tows and graphite proxy substrates (for 20, 40 and 60 min) have been analyzed by Scanning Electron Microscopy (SEM) and contact angle measurement, respectively confirmed the enhancement of wettability. Such plasma treated CF tows have been further used for deposition of SiO₂ coating and uniform deposition has been achieved for 20 min plasma treated CF as evident from SEM surface analysis. Whereas, Energy Dispersive X-ray Analysis (EDXA) and Fourier Transform Infra-Red spectroscopy (FTIR) measurements have been used to get elemental and bonding information of coated silicon substrates confirmed the high quality of SiO₂ coating. While tensile strength measurement verified the enhancement of tensile strength for plasma treated SiO2 coated CF tows as compare to untreated CF tow, and optimum strength (1449 MPa) has been obtained for 20 min plasma treated SiO₂ coated CF tow with uniform coating properties. Hence, 20 min plasma treatment on CF tow is confirmed the beneficial effect on SiO₂ inter-face layer coating for CF/SiC Composites Applications. (paper)