Louise Affleck

The effect of large magnetic fields on solid state combustion reactions: novel microstructure, lattice contraction and reduced coercivity in barium hexaferrite

Combustion reactions of BaO2, Fe2O3 and Fe performed in large applied fields have revealed unexpected modifications in the microstructure of the multiphase combustion product, and in the lattice parameters and coercivity of monophase BaFe12O19 obtained by post-production grinding and sintering.

Combustion Synthesis of BaFe12O19 in an External Magnetic Field: Time-Resolved X-ray Diffraction (TRXRD) Studies

Time-resolved X-ray diffraction (TRXRD) experiments were performed on hexagonal BaFe12O19. The sample was synthesized from the self-propagating high-temperature synthesis (SHS) reaction of BaO2, Fe, and Fe2O3 in the presence of an external magnetic field. The reduction of coercivity in barium ferrite was normally achieved using chemical dopants.

Self propagating high temperature synthesis of magnesium zinc ferrites (MgxZn1-xFe2O3): thermal imaging and time resolved X-ray diffraction experiments

Spinel ferrites of the form MgxZn1-xFe2O4 ( x = 0. 0.25, 0.50, 0.75, 1.00) were prepared by self-propagating high-temperature synthesis (SHS) from reactions of iron(III), zinc and magnesium oxides, iron powder and sodium perchlorate. The driving force for the reactions is the oxidation of iron powder. Reactions were carried out in the presence of an external magnetic field of 0.2 or 1.1 T. Reaction velocity and temperatures were obtained by thermal imaging camera. The transformation of reactants to products was studied by time resolved X-ray diffraction using Rietveld refinement for determination of phase percentages. Reactions typically reached temperatures in excess of 1150 degreesC with a timescale of complete conversion of reactant to products of 20 s. All materials were characterised by X-ray powder diffraction (XRD), energy dispersive X-ray analysis (EDXA), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), Mossbauer spectroscopy and vibrating sample magnetometry (VSM).