Factors in the precipitation medium governing morphology and structure of haematite particles in forced hydrolysis reaction

The effects of dioxane (DX) on morphology and texture of haematite particles produced from a forced hydrolysis reaction of FeCl3-HCl solution were investigated by TEM, XRD, XFS, FTIR, TG-DTA, N(2 )and H2O adsorption, and zeta potential measurements. The spherical shape of haematite particles produced below the DX concentration of 10 vol% (diameters: 600-1000 nm) was changed to cubic for particles produced at more than 12 vol% DX (mean edge lengths: 900-1200 nm). The rod-like beta-FeOOH particles were precipitated as cubic particles at the DX concentration greater than or equal to 28 vol%. TEM and XRD suggested that the haematite particles formed in the presence of DX are polycrystalline with an enlarged c dimension in a unit cell. TG and FTIR indicated that the haematite particles produced with DX are hydrohaematite possessing OH- ions in the lattice. The results obtained in the present study revealed that variation of the polarity of the medium with addition of DX is a determining factor of the particle size and shape rather than the interfacial tension of the medium and the particles. (C) 1998 Academic Press.