Describe possible processes for preparing sintered compacts

Question

Describe possible processes for preparing sintered compacts with the following microstructures:

(a) fully densified compacts with different grain sizes (at least 10 times difference in size);

(b) compacts with the same grain and pore sizes but with different porosities, say 1-5 vol%;

(c) compacts with the same grain size and porosity but with different pore sizes, say 1-10 mm.