A ceramic composite sample has been fractured using standard tensile testing methods.

a) The overall fracture surface needs to be imaged to investigate the origin of the crack nucleation. What beam energy and working distance would you choose. Why?

b) After the crack origin is identified, the local area of the crack origin needs to be imaged with high resolution to better investigate the underlying fracture mechanisms. How would you change your beam energy and working distance to achieve high resolution imaging? Why?

c) After imaging at high resolutions, it is speculated that the crack originates from a phase formed as a result of heavy impurities segregating at the interface of the fiber-matrix composite. What imaging mode would you choose to identify if the phase is made of heavy impurities? Why?