Formation of a magnetic composite by reduction of Co-Nd doped strontium hexaferrite in a hydrogen gas flow

Co-Nd strontium hexaferrite nanoparticles synthesized by the self-combustion method were treated in a hydrogen flow at different temperatures and times. The samples were characterized structurally by scanning electron microscopy and X-ray diffraction and magnetically with a vibrating sample magnetometer. Phase identification showed decomposition of the hexaferrite structure into Fe 3O 4 and different strontium mixed oxides. The sample treated at 500 °C for 30 minutes shows good magnetic properties due to the formation of a magnetite/hexaferrite composite. In this case magnetization is very close to the original sample while the coercivity slightly diminishes. The hexagonal phase is almost completely transformed into different oxides at a reducing temperature of 500 °C for 120 minutes. The obtained results are analyzed in terms of the phase composition and of the magnetic susceptibility of the studied samples.Fil: Herme, Carlos Alberto. Universidad de Buenos Aires. Facultad de Ingeniería; ArgentinaFil: Bercoff, Paula Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; ArgentinaFil: Jacobo, Silvia Elena. Universidad de Buenos Aires. Facultad de Ingeniería; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Corrosion of steel alloys with ferrite coating

Ponencia presentada en el Congreso Internacional de Metalurgia y Materiales 14º SAM-CONAMET/IBEROMAT/MATERIA. Santa Fe, Argentina, 21 al 24 de octubre de 2014The corrosion protection offered by coatings of hexagonal Sr ferrites on steel samples in the presence of chloride was evaluated by electrochemical techniques. Different samples were prepared using Nd-Co doped and un-doped strontium hexaferrite coatings, and tested in sodium chloride (NaCl) solutions during 45 days. Time variation of the corrosion potential and polarization resistance measurements were carried out for each of the tested steel samples at different immersion times. All the samples were characterized by scanning electronic microscopy and energy dispersive X-ray analysis (SEM/EDX). All the tested ferrite coatings offered good protection and corrosion resistance, which increased as the samples remained immersed in the chloride solution. When a concentrated NaCl solution was employed as corrosive agent, the coatings continued offering protection and the currents increased one order of magnitude, while remaining constant with the variation of the immersion time. The samples coated with doped ferrite showed the highest resistance to the aggressive environment, with low corrosion rates even after 48 hours of immersion in NaCl 0.5 M.Fil: Herme, Carlos Alberto. Universidad de Buenos Aires. Facultad de Ingeniería. Laboratorio de Fisicoquímica de Materiales Cerámicos Electrónicos; Argentina.Fil: Herme, Carlos Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Tecnologías y Ciencias de la Ingeniería; Argentina.Fil: Herme, Carlos Alberto. Universidad de Buenos Aires. Instituto de Tecnologías y Ciencias de la Ingeniería; Argentina.Fil: Cicileo, Gabriela Perla. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones Científicas y Técnicas para la Defensa. Unidad de Investigación y Desarrollo Estratégico para la Defensa. Centro de Investigaciones en Sólidos. División Corrosión; Argentina.Fil: Cicileo, Gabriela Perla. Ministerio de Defensa de la Nación. Instituto de Investigaciones Científicas y Técnicas para la Defensa. Unidad de Investigación y Desarrollo Estratégico para la Defensa. Centro de Investigaciones en Sólidos. División Corrosión; Argentina.Fil: Bercoff, Paula Gabriela. Universidad Nacional de Córdoba. Facultad de Matemática, Astronomía y Física; Argentina.Fil: Bercoff, Paula Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Física Enrique Gaviola; Argentina.Fil: Jacobo, Silvia Elena. Universidad de Buenos Aires. Facultad de Ingeniería. Laboratorio de Fisicoquímica de Materiales Cerámicos Electrónicos; Argentina.Fil: Jacobo, Silvia Elena. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Tecnologías y Ciencias de la Ingeniería; Argentina.Fil: Jacobo, Silvia Elena. Universidad de Buenos Aires. Instituto de Tecnologías y Ciencias de la Ingeniería; Argentina.Otras Ciencias Física

Sr hexaferrite/Ni ferrite nanocomposites: Magnetic behavior and microwave absorbing properties in the X-band

Nickel ferrite nanoparticles were synthesized by a self-combustion method over nanocrystalline powders of Nd-Co substituted strontium hexaferrite with nominal composition Sr0.5Nd0.5Co0.5Fe10.5O19, at different mass relations. The samples were structurally characterized by X-ray diffractometry (XRD), scanning electron microscopy (SEM), and energy dispersive X-ray analysis (EDX). The M vs. H loops of the composites were determined with a vibrating sample magnetometer (VSM) and the interaction with the X-band microwave radiation of the nanocomposites dispersed in epoxy resin was measured with a vector network analyzer (VNA). The hysteresis loops showed strong exchange-coupling between the two magnetic phases for the 30:70 and 50:50 Sr0.5Co0.5Nd0.5Fe10.5O19/NiFe2O4 nanocomposites, while a weak interaction was observed for the 70:30 mass ratio. The nanocomposite with an equal amount of hard and soft phase shows the highest performance both in reflectivity and in bandwidth, reaching a maximum in reflectivity of -34.4 dB at 11.1 GHz while the bandwidth below -10 dB is 3.5 GHz.Fil: Jacobo, Silvia Elena. Universidad de Buenos Aires. Facultad de Ingeniería; ArgentinaFil: Bercoff, Paula Gabriela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; ArgentinaFil: Herme, Carlos Alberto. Universidad de Buenos Aires. Facultad de Ingeniería; ArgentinaFil: Vives, Leandro A.. Ministerio de Defensa. Instituto de Investigaciones Científicas y Técnicas para la Defensa; Argentin