Mechanical property of Pyro-Carbon coated SiC fibers fabricated by continuous chemical vapor deposition method

Abstract

PurposeA continuous chemical vapor deposition (CVD) method has been used to fabricate pyro-carbon (PyC) coating on continuous silicon carbide (SiC) fibers. The paper aims to evaluate these coated fibers by testing filament tensile and using microstructure characterization.Design/methodology/approachThe continuous SiC fiber-reinforced SiC matrix (SiC/SiC) composite is widely studied in aerospace and nuclear applications. The PyC is the probable option in fusion and fast reactor. However, the conventional fabrication method of PyC coating has some drawbacks influencing performance and efficiency.FindingsThe results showed that PyC-coated SiC fibers with continuous CVD method are more straight than conventional ones and residual deformations could not be observed, and these PyC coatings have complete geometry and uniform thickness. In different process conditions, the thickness of PyC coating could control from ∼100 to ∼1,000 nm.Originality/valueThe coated SiC fibers in a lower gas ratio (1:7 to 1:3), lower pressure (500–1,000 Pa) and appropriate winding speed (3 to 5 rpm) have relative high filament tensile strength (∼3.5 to ∼3.9 GPa). And the strength of coated SiC fibers has a negative correlation with the measured thickness of PyC coating. A distinctive growth process was discovered in the continuous CVD method. In a certain range, the quicker growing rate of PyC is obtained in shorter deposition time which means an efficient and quality method could be applied to fabricate coatings.