Effect of an intermediate silicon carbide layer on the reaction of a carbon filter with nickel

Conclusions

• 1. A thin (about 40 Å thick) layer of silicon carbide on a carbon fiber in contact with nickel acts as a diffusion barrier inhibiting the processes of surface defect formation on the fiber and loss of strength of the fiber only up to temperatures of 700–800°C during exposure for up to 50 h.

• 2. Raising the temperature above 800°C brings about intense dissolution of the coating and fiber in the nickel, which is accompanied by activated recrystallization of the fiber and catastrophic loss of its strength. Under such conditions a silicon carbide coating no longer constitutes an effective diffusion barrier.

• 3. The application of a silicon carbide layer to a carbon fiber increases the latter's resistance to attack by oxidizing atmospheres, which may facilitate the process of formation of a nickel-carbon-fiber composite and raise the maximum permissible operating temperature of the material.