Lamellar reaction phenomena: from intercalation to nanomaterials formation

Lamellar reaction processes govern the formation and properties of a wide range of materials of fundamental and technological interest, offering the potential to control the structure, composition and dimension of materials down to the nanoscale. Environmental transmission electron microscopy, complementary investigations, and atomistic modeling have been combined to explore the mechanisms that control these processes. Model transition metal disulfide (e.g. TS₂, T=Ti,Ta) intercalation/deintercalation and lamellar hydroxide (e.g. Mg(OH)₂) dehydroxylation/rehydroxylation reaction processes are compared to probe the effect of relatively strong and weak/transitory intralayer bonding on lamellar reaction processes. Intriguing similarities are observed even though the hydroxide lamella are destroyed and reform during dehydroxylation and rehydroxylation processes, respectively. Deintercalation and dehydroxylation occur via analogous empty gallery and oxide layer formation. Both processes generally progress via lamellar nucleation and growth, with growth progressing away from the lamellar nucleation site. Similarities extend to stage formation, with random/'stage-2-like' oxide and hydroxide layer ordering occurring in the lamellar oxyhydroxide regions that form. In contrast to stable host layers associated with intercalation processes, relatively weak/transitory intralayer bonding associated with lamellar dehydroxylation/rehydroxylation processes facilitates layer delamination, shearing, cracking, and nanoreconstruction during dehydroxylation, and, nanocrystal formation, intergrowth and the rapid 'annealing out' of lamellar defects that form during rehydroxylation.