Abstract
A facile and cheap surfactant-assisted hydrothermal method was used to prepare mesoporous cobalt ferrite nanosystems with BET surface area up to 151 m2/g. These mesostructures with high BET surface areas and pore sizes are made from assemblies of nanoparticles (NPs) with average sizes between 7.8 and 9.6 nm depending on the initial pH conditions. The pH proved to be the key factor for controlling not only NP size, but also the phase purity and the porosity properties of the mesostructures. At pH values lower than 7, a parasite hematite phase begins to form. The sample obtained at pH = 7.3 has magnetization at saturation Ms = 38 emu/g at 300 K (54.3 emu/g at 10 K) and BET surface area SBET = 151 m2/g, whereas the one obtained at pH = 8.3 has Ms = 68 emu/g at 300 K (83.6 emu/g at 10 K) and SBET = 101 m2/g. The magnetic coercive field values at 10 K are high at up to 12,780 Oe, with a maximum coercive field reached for the sample obtained at pH = 8.3. Decreased magnetic performances are obtained at pH values higher than 9. The iron occupancies of the tetrahedral and octahedral sites belonging to the cobalt ferrite spinel structure were extracted through decomposition of the Mössbauer patterns in spectral components. The magnetic anisotropy constants of the investigated NPs were estimated from the temperature dependence of the hyperfine magnetic field. Taking into consideration the high values of BET surface area and the magnetic anisotropy constants as well as the significant magnetizations for saturation at ambient temperature, and the fact that all parameters can be adjusted through the initial pH conditions, these materials are very promising as recyclable anti-polluting agents, magnetically separable catalysts, and targeted drug delivery vehicles.
Highlights
IntroductionAn important candidate among the ferrite-type materials which is useful for various applications is cobalt ferrite (CoFe2O4)
We describe a cheap and facile surfactant-assisted hydrothermal method to prepare mesoporous CoFe2O4 structures with high BET surface area and significant magnetization at saturation at ambient temperature starting from non-ionic block copolymer PluronicTM P123 environmentally friendly surfactant
There is a significant decrease in the magnetization at saturation from 10 to 300 K due to both changing of the population of electron orbitals and thermal fluctuations of the magnetic moment
Summary
An important candidate among the ferrite-type materials which is useful for various applications is cobalt ferrite (CoFe2O4). It has an inverse spinel structure with Fe3+ ions occupying both tetrahedral A positions and octahedral B positions in the AB2O4 formula unit and Co2+ occupying the remaining octahedral B position. The magnetic moment of the ions belonging to the octahedral positions is oppositely oriented towards one of the ions from the tetrahedral positions, leading usually to a total uncompensated magnetic moment per formula unit. Other properties such as significant magnetization at saturation, high coercive field and Curie temperature, and good chemical and magnetic stability make this material very interesting for a wide range of applications. Besides the excellent absorber properties in the microwave range, CoFe2O4 has a wide energy bandgap, with semiconductor behavior, providing electrocatalytic effect, making it suitable for energy harvesting and conversion
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.