Abstract: Reactive diffusion study between NbC and Si are carried out at 1300℃under a vacuum of 10-5 torr and a uniaxial pressure of 1 MN /m2. The annealing time ranges from 8 to 100hours. The Si used is single crystal silicon; the NbC is hot-pressed powder compact. A NbSi2+SiC two-phase reaction product forms with NbSi2 as the matrix and SiC as the discontinuous particles. The microstructure of the reaction product is homogeneous, compact, and fine. The NbSi2 grain size and SiC particle size are at the micron range. The nucleation sites for the SiC partiales are at the voids of the NbC powder compact. The growth of the reaction products follows a parabolic kinetics. Extrapolation of the data to zero thickness suggests an incubation time of3.5 hours. However, for short annealing time (<60 hours), the thickness data can be represented by a linear kinetics with a growth rate of about 2 μm / hr.

Key words: in-situ composite, solid-state reaction, NbC, NbSi_2, SiC