Influence of Si addition on thermal conductivity of unidirectional CF/Al-Si composites fabricated by low pressure infiltration process

Abstract

Unidirectional CF/Al-Si composites were fabricated by low pressure infiltration, permeating molten Al into porous CF-Si preform. In this study, the influences of Si addition in the preforms on the thermal conductivity of obtained CF/Al-Si composites were investigated in terms of the degradation of high thermal conductive CFs by chemical reactions in Si-C and Al-C systems. Comparing with theoretical value, the thermal conductivity of CF/Al-Si composites was extremely low. Although the Si-C reaction led to the decrease of the thermal conductivity, the sintered Si around CF surfaces protected from the significant decrease of the thermal conductivity being attributed to the severe Al and CF reaction. The surface damage of high thermal conductive CFs by Al-C reaction became a main reason for the decrease in the thermal conductivity of CF/Al-Si composites. Especially, the active Al-C reaction in the region of extremely low Si content around CF surfaces affected significant degradation of the CFs.