Nanomullite powders were successfully prepared from activated kaolin and gibbsite. Kaolin activation was performed by the thermal treatment at 800 oC and sulfuric acid treatment. The activation process has changed kaolin structure to produce alumina, silica, and aluminosilicate phases, as given by XRD result. The XRD result was corroborated and was proved by the result of electron diffraction TEM analysis, the activated kaolin consisted of a-Al2O3, quartz, and mullite phases. Nanomullite was prepared from the activated kaolin, gibbsit, and sulfuric acid and was calcined at 400 o, 600 o, 800 o, and 1200 oC. Crystallization of the as-prepared mullite in the temperature range of 400 o-1200 oC produced mullite, α-Al2O3, and spinel phases at 400 oC. A further phase transformation of the mullite sample maintained mullite and α-Al2O3 phases at 1200 oC. The grain sizes of mullite powders are found to be less than 100 nm at a calcination temperature of 1200 oC. The electron diffraction (ED) patterns of the calcined mullite are indexed to the mullite phase with the crystal plane orientations of (310), (030), (101), (001), (201), (040) and (121). These results are in agreement with the XRD result for the calcined mullite at 1200 oC.

Keywords: nanomullite, kaolin, gibbsite, H2SO4, activation process, calcination.