MORPHOLOGICAL FORMS OF ALPHA-ALUMINA PARTICLES SYNTHESIZED IN 1,4-BUTANEDIOL SOLUTION

Phase-pure, monodispersed, hexagonal plates of single-crystal alpha-al umina (approximate to 2 mu m wide and approximate to 0.5 mu m thick) h ave been prepared Fia precipitation by treating an aluminum hydrous ox ide precursor in 1,4-butanediol at 300 degrees C under autogenous vapo r pressure, Present work shows that KOH is the only reagent that preci pitates an aluminum hydrous oxide precursor suitable to synthesize or- alumina in 1,j-butanediol solution, In contrast, the use of NaOH or NH 4OH as the precipitating reagent for the precursor material does not y ield the alpha phase, The solution pH at which the precursor materials are precipitated is also a critical factor for the formation of alpha -Al2O3,. Phase-pure or-alumina powders were also only synthesized from the aluminum hydrous oxide precursors precipitated in the pH range fr om 10 to 10.5. The results of X-ray diffraction and scanning electron microscopy indicate that longer reaction times promote the phase trans formation from the intermediate boehmite phase to alpha-alumina. The c omplete transformation from boehmite to alpha-alumina requires reactio n times of about 12 h.