The penetrating diffusion of boron on the surface contact of cylindrical samples of type-GMZ graphite, one of which contained 0.1 to 0.3wt% of boron and the other less than 1 x 10-5wt%, was investigated by layer spectral analysis. At 2200 to 3000C, various equations were obtained for diffusion. Along the center of the samples:

D (cm2/s) = 6.3 x 10-3exp[-39900/RT]

while along their surface layer,

D (cm2/s) = 7.4 x 10-2exp[-39900/RT]

This was explained by the transport of boron, in the surface layer, through the gas phase.

Diffusion of Boron into Polycrystalline Graphite. Novak, Y.V., Pyrkova, T.V., Kuteinikov, A.F.: Solid Fuel Chemistry, 1982, 16[2], 121-5