(i) At a particular temperature, the coefficient DP describing diffusion through the perfect lattice differs by three orders of magnitude relative to that describing diffusion along grain boundaries (Dgb=21011m2s1) in a polycrystalline material. Stating any assumptions, calculate the net diffusion coefficient that represents both fluxes, given that the grain size of the material is 100m. [50%] (ii) On the basis of your answer, giving reasons, comment on whether the diffusion data represent measurements made at a very high temperature, or not. [20%] (iii) Why is it important to eliminate grain boundaries in a turbine blade that operates in the hottest part of the engine? Explain how the blade could be made into a single-crystal without any grain boundaries. [30%]