Effects of multilayer hydrothermal carbon interphases on mechanical properties and thermal shock resistance of CF/ZrB2-SiCBN

Multilayer hydrothermal carbon coatings (HTCCs) with various thicknesses were constructed on CFs using alternating hydrothermal carbonization and heat treatment approach. Well-established CF/ZrB2-SiCBN composites with distinct multilayer interphases were processed via slurry injection and precursor infiltration pyrolysis method. The multilayer HTCCs with suitable thickness would be pulled-out stepwise from the matrix, which could absorb the impact energy and toughen the composites effectively. Although the outer HTCC would still react with the matrix to form a strong interface, the moderate interfacial binding force between CF and inner HTCC could effectively transfer the load and assure the fiber debonding when the composites deformed drastically. Moreover, the increasing of coating thickness could alleviate the damage of fibers in oxidation environment and improve the critical thermal shock temperature difference of composites, while the excessive thick coating would weaken the fiber strength and limit toughening abilities of the CFs.