COPPER(II) OXIDE AS A MORPHOLOGY DIRECTING AGENT IN THE HYDROTHERMAL CRYSTALLIZATION OF MAGNETITE

Magnetite crystals with unique morphological characteristics have been grown from hematite under hydrothermal conditions at 150 and 175 degr ees C in the presence of hydrazine and copper (II) oxide. In the absen ce of CuO, octahedral crystals of magnetite with a distribution of par ticle sizes were grown in accordance with literature procedures. In th e presence of CuO, magnetite crystals with distorted morphology were p repared in which the [111] crystal faces were absent, leaving a framew ork structure of corners and edges. Examples of crystal intergrowths w ere observed, as well as the partial collapse of the framework structu re of the magnetite. The results are discussed with reference to the p ossible effect of copper redox couples on the hematite reduction react ion.