Home – Home – Jornals – Chemistry for Sustainable Development 2011 number 4

By introducing α-Al₂O₃ powder with particle size 25 nm, in the amount of 1–10 mass %, into the solution of aluminium nitrate or into dry aluminium hydroxide, the kinetics of the formation of the stable α-phase during subsequent heating of the precursor gets accelerated substantially. Depending on the amount and method of introducing the seeding agent, the complete transformation of the precursor into α-Al₂O₃ occurs at a temperature within the range 800 to 930 °С. The powder formed at such a low temperature is composed of porous aggregates 10–20 mm in size; the size of crystallites comprising the aggregates is independent of the amount of seeding agent introduced and is equal to approximately 50–60 nm. Grinding under soft conditions leads to the destruction of aggregates and to the formation of nanopowder which is active towards caking. Later on, a ceramic material with the porosity at a level of 1 % is obtained from the powder at 1450 °С.