| Preparation and Phase Changes of
Amorphous Alumina |
S. G. SAMDANI, J. LAXMINARASIMHAIAH AND ABDE Au
Pages : 57-60
DOI : 10.1080/0371750X.1972.10840800 |
| Abstract |
| Amorphous alumina was prepared (i) from aluminium nitrate solution at pH 6.0 and
9.0 and (ii) by coprecipitationfrom aluminium nitrate solution containing 5% magnesium
and chromium nitrate at pH 9. Phase changes taking place in them during calcination were
compared with those of aluminium hydroxide by DTA and X-ray diffraction techniques.
DT A of the prepared samples generally showed a sharp endothermic peak at
325°C, corresponding to the dehydration of the possible traces of fine gibbsite and an
exothermic peak at 345°C which could be considered as characteristic of amorphous
phase. Aluminium hydroxide, however, showed three endothermic peaks at 240°, 325°
and 540°C corresponding to the coarse gibbsite to boehmite conversion, gibbsite
dehydration and boehmite dehydration respectively.
The X-ray diffraction study of the prepared samples showed mostly amorphous
patterns. When calcined to 750°, 950° and 1450°C respectively the gamma, delta and
alpha phases were formed. |
| Full text : Subscribe to Download Full Text |
| [Go Back] |
|
