Synthesis of Hercynite at very Mild Condition

• Main Authors: M. Daghetta, M. Dapiaggi, L. Pellegrino, B. Pastore, L. Pagliari, C. Mazzocchia
• Format: Article
• Language: English
• Published: AIDIC Servizi S.r.l. 2015-05-01
• Series: Chemical Engineering Transactions
• Online Access: https://www.cetjournal.it/index.php/cet/article/view/5058

Hercynite, Fe(II)Al2O4, is a double oxide with the spinel structure, found in rocks of various origin and composition. Due to its high hardness and thermal stability, it is exploited as an abrasive, in polishing/cutting tools and in refractories, such as in magnesia-hercynite refractory bricks. Hercynite is not easily obtained as a monophasic material, and its synthesis is usually a highly energy demanding process. In fact, the two main methods of preparation, electro-fusion and traditional solid state route from the composing oxides, need very high temperatures (1450-1650 °C). To make matter more complex, the presence of Fe2+ ions requires any heating process to be performed under oxygen-free conditions. In this work a method for obtaining hercynite at 490-600 °C is reported. The synthesis involves a sol-gel reaction, followed by dehydration of the gel and calcination of the solid under nitrogen or nitrogen/hydrogen atmosphere. Different iron precursors have been tested. Hercynite percentage in the products ranged from 80 (wt) % to 100 (wt) %, depending on the experimental parameters. The products have been characterized by X-ray powder diffraction, thermogravimetric and elemental analyses, and scanning electron microscopy investigations.