Síntese sol-gel protéica e propriedades magnéticas de ni/nio com estrutura core-shell

Abstract

This work was the result of an experimental activity initiated in the discipline of Particulate Materials, offered by the Department of Materials Engineering at the UFPB Technology Center. This is the first report on the magnetic characterization of Ni/NiO powders with core-shell structure synthesized by a proteic sol-gel method that uses gelatin (of animal origin) as a chelating and polymerizing agent. Commercial gelatin and nickel nitrate were used as starting materials. The synthesized material was calcined at 500 °C in air and later analyzed by DRX, VSM and MET. In order to investigate the effects of structure on magnetic properties, NiO powders were synthesized by three other methods for comparison purposes: citrate method, nitrate calcination method and combustion method. The DRX results revealed that the material with core-shell structure is composed of 84.8% by weight of NiO and 15.2% by weight of Ni, while samples from other methods are single-phase (NiO). The hysteresis cycle at room temperature showed a strong ferromagnetic behavior for samples prepared by the proteic sol-gel and citrate methods. Powders that were synthesized by nitrate calcination and combustion methods showed weak ferromagnetic behavior, probably attributed to unpaired moments in their nanoparticles. The general results showed that the proteic sol-gel method is a versatile chemical route to obtain Ni/NiO ferromagnetic powders with core-shell structure.