Аннотация:Nanocrystalline alpha-iron (III) oxide powders with
different morphology and particle size (25-100 nm) were
prepared under hydrothermal conditions from both iron
nitrate solutions and amorphous hydroxide gel. Prepared
samples were investigated by XRD, TEM, SEM, TGA and IR
spectroscopy. High temperature hydrolysis of aqueous
iron (III) nitrate solution at the temperature range
150-250шC and concentration 0.01-1 mole/l leads to the
intensive formation of hematite. At low concentrations
(0.01-0.1 mole/l) only dense particles of iron oxide
were observed. Increasing concentration up to 0.15-0.25
mole/l result in the formation of porous particles
containing non-intersecting 5-20 nm pores. Heating of
porous iron oxide at 450шC is accompanied by substantial
coalescence of pores followed by particle agglomeration
and sintering at 700-800шC. The formation mechanism of
mesoporous iron oxide particles is suggested. In the
case of hydrothermal treatment of amorphous iron
hydroxide no pores formation was observed. The particle
size of the synthesized hematite powders increases with
the concentration, temperature, and time of hydrothermal
treatment. Decreasing of particle size is accompanied by
substantial enhancement of its reactivity in solid state
processes, demonstrated in reaction with lithium
carbonate.