Dielectric Insulation Characteristics of Natural Ester Fluid Modified by Colloidal Iron Oxide Ions and Silica Nanoparticles

In this study, the dielectric characteristics of two types of natural esters modified into nanofluids are studied. The AC breakdown voltage was investigated for colloidal Fe2O3 and SiO2 nanoparticles effectively scattered in natural ester oil. The experimental results identify an increase in the breakdown voltage of the nanofluid with colloidal Fe2O3 conductive nanoparticles. In contrast, the breakdown voltage was reduced by adding SiO2 nanoparticles in the same matrix. The potential well distribution of the two different types of nanoparticles was also calculated in order for the results of the experiment to be explained. The dielectric losses of the colloidal nanofluid are compared with the matrix oil and studied at 25 °C and 100 °C in the frequency regime of 10−1–106 Hz. The experimental data and the theoretical study reveal that conductivity along with the permittivity of nanoparticles constitute a pivotal parameter in the performance of nanofluid. Specific concentrations of nanoparticles with different electrical conductivity and permittivity than those of matrix oil increase the breakdown voltage strength. Simultaneously, the addition of nanoparticles having electrical conductivity and permittivity comparable to the matrix oil results in reducing the breakdown voltage.

Assessing bioavailability levels of metals in effluent-affected rivers: effect of Fe(III) and chelating agents on the distribution of metal speciation

To assess the effects of Fe(III) and anthropogenic ligands on the bioavailability of Ni, Cu, Zn, and Pb, concentrations of bioavailable metals were measured by the DGT (diffusive gradients in thin films) method in some urban rivers, and were compared with concentrations calculated by a chemical equilibrium model (WHAM 7.0). Assuming that dissolved Fe(III) (<0.45 μm membrane filtered) was in equilibrium with colloidal iron oxide, the WHAM 7.0 model estimated that bioavailable concentrations of Ni, Cu, and Zn were slightly higher than the corresponding values estimated assuming that dissolved Fe(III) was absent. In contrast, lower levels of free Pb were predicted by the WHAM 7.0 model when dissolved Fe(III) was included. Estimates showed that most of the dissolved Pb was present as colloidal iron–Pb complex. Ethylene-diamine-tetra-acetic acid (EDTA) concentrations at sampling sites were predicted from the relationship between EDTA and the calculated bioavailable concentration of Zn. When both colloidal iron and predicted EDTA concentrations were included in the WHAM 7.0 calculations, dissolved metals showed a strong tendency to form EDTA complexes, in the order Ni > Cu > Zn > Pb. With the inclusion of EDTA, bioavailable concentrations of Ni, Cu, and Zn predicted by WHAM 7.0 were different from those predicted considering only humic substances and colloidal iron.

Straightforward phase-transfer route to colloidal iron oxide nanoparticles for protein immobilization

Removal of hydrophobic ligand enables a convenient phase-transfer route to aqueous magnetic nanocolloid that shows excellent protein immobilization capability.

Magnetic Field Induced Formation of Magnetic Wires into Thin Elastic Membranes with Controlled Properties

We present the fabrication of magnetic elastomeric membranes consisting of aligned superparamagnetic microwires embedded in a polymeric matrix. The wires are formed by the magnetic assembly of colloidal iron oxide nanoparticles (NPs) dispersed in the prepolymer matrix, during the curing of the polymer and the solvent evaporation. The appropriate combination of the NPs quantity and of the viscosity of the matrix results in the formation of thin membranes of about 10mm, containing few layers of aligned wires which after the polymer curing are blocked in fixed position into the matrix. The orientation and the dimensions of the magnetic wires depend on the direction and intensity of the external MF respectively.