Dynamic Response of Polyindole Coated Zinc Ferrite Particle Suspension under an Electric Field

ZnFe2O4 particles initially synthesized through a simple solvothermal method were coated using polyindole (PIn) to prepare an actively controllable core-shell typed hybrid material under both electric and magnetic fields. An advantage of this process is not needing to add the stabilizers or surfactants commonly used for uniform coating when synthesizing core or shell-structured particles. The synthesized ZnFe2O4/PIn particles have a lower density than conventional magnetic particles and have suitable properties as electrorheological (ER) particles. The expected spherical shape of the particles was proven using both scanning electron microscopy and transmission electron microscopy. The chemical characterization was performed using Fourier-transform infrared spectroscopy and X-ray diffraction analysis. To analyze the rheological properties, a ZnFe2O4/PIn based suspension was prepared, and dynamic rheological measurements were performed for different electric field strengths using a rotary rheometer. Both dynamic and elastic yield stresses of the ER fluid had a slope of 1.5, corresponding to the conductivity model. Excellent ER effect was confirmed through rheological analysis, and the prepared ER fluid had a reversible and immediate response to repeated electric fields.

Preparation of Superparamagnetic Cobalt Ferrite Nanoparticles with High Saturation Magnetization by Temperature-Controlled Co-Precipitation Method

In this study, the effect of reaction temperature on the properties of cobalt ferrite nanoparticles was investigated. X-ray diffraction analysis and Fourier transform infrared spectroscopy confirmed that synthesized nanoparticles are cobalt ferrite. Particle sizes and shapes were determined by a transmission electron microscope, and magnetic measurements were done using a vibrating sample magnetometer. The average particle size varies in the range of 5.7 - 10.7 nm as the temperature is raised from 30 to 80°C. With that, there is a transition from ferrimagnetic to superparamagnetic behaviors at 40°C. The critical size of cobalt ferrite nanoparticles for the superparamagnetic limit with zero coercivity is found to be around 6 nm, and its saturation magnetization value is 25.4 emu/g. This value is impressive higher compared to that in the other studies with similar preparation conditions.

Electromagnetic Shielding for Buildings Using Hybrid Polymer Composites: A Life Cycle Assessment Study

In the present paper, we investigated a sandwich composite as a potential electromagnetic interference shielding wall panel for buildings. The panel was built using a ferrite-particle modified high density polyethylene in a sandwich assembly enabling electromagnetic shielding properties. The life cycle assessment (LCA) approach was employed here to assist in the production phase and in the materials selection, in order to obtain an environmental friendly final product. An optimization of the constituents of the sandwich structure is proposed by comparing the environmental impact of different potential solutions without influencing the EMI shielding properties.

Influence of annealing temperature on structural and magnetic properties of MnFe2O4 nanoparticles

Nanoparticles of manganese ferrite were obtained by the impregnation of highly ordered mesoporous MCM-41 silica support. The investigated sample contained 20% wt. Fe. The obtained nanocrystallites were strongly dispersed in silica matrix and their size was about 2 nm. The sample annealing at 500°C led to increase of particle size to about 5 nm. The Mössbauer spectroscopy investigations performed at room temperature show on occurrence of MnFe2O4 nanoparticle in superparamagnetic state for the sample annealed in all temperatures. The coexistence of superparamagnetic and ferromagnetic phase was observed at liquid nitrogen temperature. The sample annealed at 400°C and 500°C has bigger manganese ferrite particle and better crystallized structure. One can assign them the discrete hyperfine magnetic field components.