$($c$)$ Shown below are a set of scanning electron micrographs of ZnO tetrapodal

particles produced by flame transport synthesis, i$.$e$.,$ the controlled combustion

of metallic Zn microparticles. Briefly, a slurry of zinc microparticles in poly

$($vinyl butyral$)$ and ethanol is loaded into crucible and placed in a muffle

furnace. The slurry is heated to $900C$ for varied durations, with products

collected on substrates placed near the crucible.

$($i$)$ Describe the mechanism of formation of tetrapodal nano$-$ and

microparticles.

$($ii$)$ Suggest three other materials which may generate tetrapodal particles.

$($iii$)$ Describe a wet$-$chemical method which may be used to produce

tetrapodal particles of one of the materials chosen in$.$

$($iv$)$ One application envisaged for these ZnO tetrapods is in the formation of

hydrophobic materials. Why may these microstructures be suitable for

this purpose?