Intermetallic compounds,such as NbSi2 and MoSi2,have recently attracted much attention as potential coating materials because of their high melting points and excellent oxidation resistance.In order to understand the oxidation and the durability of these intermetallics,studies of diffusion in these complex composites are needed.Recently,numerous investigations and theories on the diffusion behavior have been carried out regarding high temperature intermetallics.However,the parameters,restrictions and assumptions employed in these theories differ.So the large number of models and the different formalisms adopted can generate some confusion.The purpose of this investigation was to perform experiments on a system approximately satisfying the assumptions of the models,thereby supplying data suitable for a quantitative comparison of these theories.Diffusion experiments on Nb/Si couples were conducted at 1050℃,1150℃,1250℃ for annealing for 8h,10h and 15h.Two intermediate phases,NbSi2 and NbsSi3,were found to develop and grow as parallel layers in the Nb/Si couples,according to the parabolic rate law.Dayanandas analysis and Buscaglias analysis were applied to describe the diffusion properties of these Nb/Si couples.