Freedericksz transition in Ferronematic Liquid Crystal under weak anchoring conditions

Freedericksz effect is investigated theoretically for a ferronematic liquid crystal, which is a colloidal suspension of ferromagnetic nanoparticles in a nematic fluid. Considering a splay type Freedericksz geometry, weak anchoring conditions are assumed at the cell boundaries. The specific nature of this anchoring reveals a rich variety of stable ferronematic phases, which include uniform, distorted and saturated states. Apart from weak anchoring conditions at the cell boundaries, soft planar anchoring is assumed for the mesogenic molecules at the surface of a nanoparticle. The interplay between these two anchoring phenomena along with Frank type elastic theory determine the values of Freedericksz threshold between various ferronematic states. It is found that compared to relatively strong anchoring for the mesogens both at the cell boundaries and at the surface of the nanoparticles, weak anchoring significantly reduces the Freedericksz threshold field. Landau theory is then utilized to understand the nature of transition between different ferronematic states. Based on the phenomenon of segregation effect, these transitions are found to be either first order or second order in nature. The present theory is also extended to non-ferromagnetic nanoparticles and significant reduction in Freedericksz threshold is obtained. Finally, these results are corroborated with experimental findings.

Application of ferromagnetic nanoparticles and rotating electromagnetic fields for oil desulfurization

An innovative technology for desulfurization of hydrocarbon raw materials, based on the effect of a rotating electromagnetic field of high power and ferromagnetic nanoparticles located in the working area of the device on oil or fuel oil, has been developed and implemented on a pilot scale. The basis of the technology is the device named “electromagnetic process activator”, which is based on the principle of converting the energy of the electromagnetic field into other types of energy. The reduction of sulfur in oil by 2.5 times and fuel oil by 3 times was achieved at energy costs of up to 1.0 kW per ton of processed raw materials, which allows us to conclude that the developed technology is highly efficient and productive.

Simulating the Self-Assembly and Hysteresis Loops of Ferromagnetic Nanoparticles with Sticking of Ligands

The agglomeration of ferromagnetic nanoparticles in a fluid is studied using nanoparticle-level Langevin dynamics simulations. The simulations have interdigitation and bridging between ligand coatings included using a computationally-cheap, phenomenological sticking parameter c. The interactions between ligand coatings are shown in this preliminary study to be important in determining the shapes of agglomerates that form. A critical size for the sticking parameter is estimated analytically and via the simulations and indicates where particle agglomerates transition from well-ordered (c is small) to disordered (c is large) shapes. Results are also presented for the hysteresis loops (magnetization versus applied field) for these particle systems in an oscillating magnetic field appropriate for hyperthermia applications. The results show that the clumping of particles has a significant effect on their macroscopic properties, with important consequences on applications. In particular, the work done by an oscillating field on the system has a nonmonotonic dependence on c.

Effect Magneto – Optic on Ferromagnetic Nanoparticle Polymer Composite Films

Optical properties of a composite material made of ferromagnetic matel nanoparticles embedded in dielectric host are studied. A nonlinear dependence of the optical rotation on magnetic field resulting from the reorientation of nanoparticles is demonstrated. The data of optical properties finding were applied to the magneto – optic experimental data of nickel ferrite (NiFe2 O4) ferromagnetic nanoparticles embedded in polymer (PMMA) host. The magneto – optic is applied at wavelength (540 nm) and magnetic field intensity (450 m T), from result we found the affect magneto – optical on samples.