Thermal transformation of synthetic bayerite and nordstrandite as studied by electron-optical methods

摘要

Bayerite and nordstrandite were prepared by the reaction of amalgamated aluminum foils with distilled water (bayerite) and ethylene glycol/water solution (nordstrandite) at room temperature. The Al-hydroxides were heated up to 1300℃ to change in the various alumina types. The Al-hydroxides and alumina powders were characterized by XRD, SAED, EDS/TEM, TEM and SEM.The morphological changes during growth of the bayerite somatoids and many-sides stars of nordstrandite are presented in details. Both hydroxides have the thermal sequence of transformation into eta (300℃), theta (900℃) and alpha-aluminas (1300℃).