A sample of Ni has a dislocation density of 5x10^12 dislocations/cm^2. The activation energy for self-diffusion in Ni by a vacancy mechanism is 280 kJ/mol, and the activation energy for pipe diffusion is 2/3 of this value for vacancy diffusion. Estimate the temperature where the contribution from pipe diffusion is the same as that from lattice diffusion. Assume that Doi = Dop and that the concentration gradients are the same. State any other assumptions you make.
Note that you should use crystal structure data for Ni to calculate areal density and do this for the (100) plane.