(a) What is meant by Frenkel defect and Schottky defect? ZnS has the FCC structure with lattice parameter of 0.5990 nm.

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(a) What is meant by Frenkel defect and Schottky defect? ZnS has
the FCC structure with lattice parameter of 0.5990 nm. Determine
the number of Schottky defects per unit cell of ZnS. Given the
molar mass for Zn and S are 65.00 g mol-1 and 32.00 g mol-1 ,
respectively. (8 marks)
(b) What are the functions of matrix and reinforcement phases in
composite materials? Briefly discuss the important advantages of
hybrid composites over ordinary composites. (6 marks)
(c) Based on the molecular structures, make comparisons between
thermoplastic and thermosetting polymers on their densities,
crystallinities and mechanical characteristics upon heating. (6
marks)