Effects of alumina coating on degradation, wettability and bonding ability of carbon fiber with aluminum.

Alumina coating on carbon fiber by ion-plating method was investigated in terms of a reaction barrier between PAN-based (ungraphitized) carbon fiber and aluminum. The carbon fiber coated directly with aluminum produced carbide (Al4C3) on the fiber-aluminum interface and degraded remarkably in strength at temperatures above 723K, while the carbon fiber coated first with alumina and then with aluminum produced less carbide and did not degrade in strength at temperatures up to 823K. These results indicated the availability of alumina coating as a reaction barrier. The alumina coating, however, had no good wettability and bonding ability with aluminum. The alumina coated carbon fiber was additionally coated with aluminum, nickel or titanium to improve these abilities. The aluminum coating improved these abilities without degrading in strength of the fiber after heating, but the nickel and titanium coating caused remarkable degradation in strength of the fibers after heating due to the formation of brittle intermetallic compounds such as Al3Ni and Al3Ti.