Mechanism and kinetics of zinc oxidation by sub- and supercritical water

Bulk solid (Zn)_S and liquid zinc (Zn)_L samples are oxidized by water with the formation of nanodimensional ZnO. The rate of this process, called chemical recondensation (CR) by water, increases with temperature and water density rise. The CR process begins with the formation of (ZnO)_n clusters via the reaction (Zn)_S,L + nH₂O = [(Zn)_S,Lmiddot(ZnO)_n] + nH₂, followed by their growth at n > 4. The CR of solid Zn leads predominantly to the formation of nanowires and nanorods, while the CR of liquid Zn practically always proceeds with the formation of nanoparticles. The complete CR of solid Zn cylinders results in the formation of highly porous nanostructural ceramics.