Formation Of Manganese Ferrite Research Articles

Investigations on the MnO2-Fe2O3 system roasted in air atmosphere

Solid-state reaction method is a common and effective technique to synthesize ferrites. This work investigated the phase transformation of MnO2 and Fe2O3 system roasted at 500–1400°C in air atmosphere to understand the formation process of manganese ferrite. The results showed that the formation of manganese ferrite (MnxFe3−xO4) was derived from the reaction between Fe2O3 and Mn3O4 (the decomposition product of MnO2). Below 900°C, MnO2 firstly decomposed to Mn2O3 and then to Mn3O4, and Fe2O3 was seldom reacted with Mn2O3 and Mn3O4. When the temperature went up to 1000°C, Fe2O3 easily reacted with Mn3O4 to generate manganese ferrite. The reaction degree was enhanced dramatically with the rising of temperature. Moreover, the x value in the MnxFe3−xO4 increased from 0 to 1 from 900°C to 1400°C. In other words, the higher the temperature was, the closer the MnxFe3−xO4 was to MnFe2O4. Thermodynamic analysis of MnO2-Fe2O3 system under different O2 partial pressures was carried out to further explain the formation mechanism.

Role of polymeric surfactants on the growth of manganese ferrite nanoparticles

The growth kinetics of manganese ferrite (MnFe2O4) nanoparticles was studied by solvothermal reaction of iron and manganese salts in ethylene glycol as a solvent. To explore the mechanism of the nanoparticle formation and development, polyethylene glycol (PEG) with different molecular weights and polyvinyl pyrrolidone (PVP) were used as polymeric surfactants to investigate their effects on the formation of MnFe2O4 nanoparticles. The size evolution and the size distribution not only dependent on the kind of surfactant but also on the time and temperature of reaction process. In the presence of low molecular weight PEG (PEG300), nanoparticles with diameter of 180nm and narrow size distribution could be produced at 160°C during 12h of reaction while the nanoparticles with average size of 330nm were formed by using PEG300 at 200°C and 48h. Therefore, by increasing the temperature and the time of reaction, the size of nanoparticles was increased and finally reached a critical size and then collapsed. When a large molecular weight surfactant PEG10000 was used, the nanoparticles with average size of 230nm were formed at 180°C and 60h. In the case of PEG300 and PEG10000 as lower and higher molecular weights, the separation between building blocks occurred after 60h and 48h for 180°C and 200°C, respectively. However, more collapses between primary building blocks were observed by using PEG10000. The nanoparticles were composed of small building blocks and exhibited a spherical mesocrystal structure which was demonstrated from the TEM and scanning electron microscope (SEM) results. The investigation on the growth mechanism of the nanoparticles indicated that the formation of manganese ferrite was followed by the attachment and growth of primary building blocks and their Ostwald ripening process.

On the formation of manganese ferrite from MnO2 and FeSO47H2O aqueous solutions through coprecipitation

The formation and evolution of MnFe2O4 ferrite phase coprecipitated with NaOH from MnO2 and FeSO4·7H2O in aqueous solution are discussed, grounded on X-ray diffraction and derivatographic data, IR spectra and magnetic measurements. The results concerning the nature of the initial coprecipitates, their structural changes during ageing in the original solutions at temperatures in the range 25–95°C as well as the structure of the resulting ferritic phases are presented.

Formation of manganese ferrite by modified hydrothermal method

Formation of manganese ferrite by modified hydrothermal method