(a) Please describe the structure of small-angle grain boundaries. (b) Given a small angle tilt boundary, whose angle of tilt is 0.1 deg., find the spacing between dislocations in the boundary if the Burgers vector of the dislocations is 0.33 nm. (c) On the assumption that the dislocations conform to the conditions involved in Eq. 4.20, that ′ = , = . × and = . ⁄ , determine an approximate value for the surface energy of the tilt boundary. Give your answer in ⁄