The evolution of carbon fibers with Fe3+ doping and effects on the mechanical properties of Cf/BAS composites

The barium aluminosilicate glass ceramic (BAS) is a potential material for high temperature application due to its high melting point and low thermal expansion coefficient. However, the low mechanical performance has limited its widely using in industry. A lot of effort has been made to reinforce the BAS matrix by incorporating carbon fibers, but the enhancement is limited by the strong interface bonding. In this work, the Fe3+ was employed to promote graphization of carbon fibers and increase mechanical properties by weakening the interface bonding. The evolution of carbon fibers with Fe3+ doping and effects on the mechanical properties of Cf/BAS composites were investigated. The results indicate that the incorporation of 1.35 wt.% Fe3+ could increase the flexural strength and fracture toughness of the composites by 28.11% and 37.10%, respectively. This is attributed to the formation of brick micro-crystalline graphite interface layer and carbon nano-sized grains in the matrix. When Fe3+ doping content is higher than 1.35 wt.%, the mechanical performance of composites undergo a gradually decrease, resulting from the excessive erosion of carbon fiber, accompanied by the growth of carbon nanofiber on the fiber surface. The mechanisms of the evolution of carbon fiber and the effects on mechanical properties are discussed.