Elongated Mullite Crystals Obtained from High Temperature Transformation of Sillimanite

A.G. TOMBA MARTINEZ; CAMERUCCI, MA; GUILLERMINA URRETAVIZCAYA; CAVALIERI, A.L.; SAINZ M.A.; CABALLERO, A.

CERAMICS INTERNATIONAL

ELSEVIER SCI LTD

Lugar: Amsterdam; Año: 1999 vol. 25 p. 245 - 252

0272-8842

The high temperature transformation of sillimanite to mullite has been studied by means of dilatometry, X-ray diffraction, FT-IR and scanning electron microscopy (SEM-EDS) techniques. The results obtained showed that total transformation of sillimanite to mullite takes place between 1550 and 1600_C. A rapid nucleation occurs above 1550_C due to the resemblance of sillimanite and mullite structures. As a consequence of the high temperature of mullitization of sillimanite, the grain growth of elongated mullite crystals takes place almost simultaneously with the nucleation stage. Finally, a step of acid leaching was employed to remove the glassy phase and high-grade purity mullite powders were obtained.