Ali Siblini

Magneto-optical waveguides made of cobalt ferrite nanoparticles embedded in silica/zirconia organic-inorganic matrix

This paper describes a way to develop magneto-optical waveguides via sol-gel process. They are made of cobalt ferrite nanoparticles embedded in a silica/zirconia matrix. Thin films are coated on glass substrate using the dip-coating technique. Annealing and UV treatment are applied to finalize sample preparation. Therefore, planar waveguides combining magneto-optical properties with a low refractive index (≈1,5) are obtained. M-lines and free space ellipsometry measurements show a specific Faraday rotation of 250°/cm and a modal birefringence of 1×10−4 at 820 nm. Thus, the mode conversion efficiency can reach a maximum value around 56%.

Gravitational electrical generator on magnetic fluid cushion

The paper describes the possibility to capture the energy of the vertical movement of the ocean waves, using a gravitational electrical generator on magnetic fluid cushion. This is constructed from a permanent magnet in a magnetic fluid shell, which, under the ocean waves action, is moving by translation inside a hermetically sealed tube.

Influence of the magnetic permeability of materials used for the construction of inductive transducers with magnetic fluid

Abstract The paper presents the influence of relative magnetic permeability of the magnetic fluid ( μ r L ) on the sensitivity of the inductive transducers and the influence of relative magnetic permeability of the magnetic shell ( μ r E ) on its performances.

Aspects concerning the dimensioning of the inductive transducers with magnetic fluids

Abstract Using numerical simulation methods, the paper presents the influence of some geometrical dimensions (radius of the coil, radius and thickness of magnetic shell) on the performances of the inductive transducers with magnetic fluids. The conclusions of the paper allow the calculation of some geometrical tolerances of the transducer so that the assembly will be placed in a desired precision class.

Magneto dielectric behavior of the magnetic fluid manganese ferrite in carbon tetrachloride

Abstract This work concerns the research on ferrofluids or magnetic liquids. Fast changes of their dielectric properties, which may be induced by phase transitions of the carrier liquid or by aggregates or multi-layers forming, require the whole automation of the measurement process. Therefore, we have used a high impedance programmable adaptor working on shunt mode in the frequency range 1 mHz-10 kHz. It allowed us to characterize, between +50° C and −200° C , an ionic ferrofluid made from nanometric particles of manganese ferrite (Fe 2 MnO 4 ) diluted at different concentrations in carbon tetrachloride (CC1 4 ) used as carrier liquid. We have pointed out the different phases of pure CCI 4 (liquid, plastic and solid). In our experimental conditions, we have shown the lack of the ferrofluid stability at low temperature and high concentration. In addition, a magneto dielectric anisotropy is observed when a continuous magnetic field (parallel or perpendicular to the electric field) is applied.

Dielectric study of a ferrofluid Fe2CoO4 in dibutyl phthalate or diethylene glycol in the frequency range 1 mHz–10 MHz

Abstract We present a dielectric study on ferrofluid solutions of Fe 2 CoO 4 in diethylene glycol or dibutyl phthalate, from 50 mHz to 10 MHz, in the temperature range -160–+40°C. When a transversal magnetic field is applied, a magnetodielectric anisotropy is in evidence. Above a concentration limit the colloidal suspensions do not remain well dispersed at low temperature. Moreover it seems that the melting point of a solution could be affected.

Dielectric properties of supercooled binary mixtures of water and N,N-dimethylacetamide: Determination and modeling in terms of ideal associated solution

Abstract Dielectric relaxation times and static permittivity of the aqueous mixtures of N,N-dimethylacetamide (CH 3 ) 2 NCOCH 3 (DMAA) are investigated in supercooled conditions down to 150 K. The evolution of these properties as a function of the composition can be well described using a model of ideal associated solution involving a trihydrate and a monohydrate for DMAA.

Determination of Initial Magnetic Permeability of YIG Thin Films Using the Current Sheet Method

Abstract. A new technique of inductive measure to determine the initial magnetic permeability (r) of Yttrium Iron Garnet (YIG) thin films has been conceived and developed in our laboratory. The magnetic material is deposited by radio-frequency sputtering between two copper thin layers on alumina substrate. Because the as-deposited films are amorphous and non magnetic, thermal annealing is necessary to make the films crystallize and to obtain satisfactory magnetic properties. After different tests considering the geometrical, morphological and magnetic properties, we have established a protocol permitting to manufacture a prototype in an original design. The performance of the fabricated micro-inductor has been checked using a physical-chemistry characterization. To obtain accurate measurements, we have used a four-point probe test bench and a precision LCR meter. The current sheet method has been validated with thick layers of commercial YIG. The results obtained for thick and thin films of YIG have been compared to the simulation and theoretical ones. Several tests, made for different thickness and different number of loops, have permitted us to evaluate the magnetic permeability of YIG thin films to 32 ± 4.

Shear viscosity and dielectric relaxanon time of dibutyl phthalate down to glass transition temperature.

Abstract We studied the shear viscosity and the main dielectric relaxation time of dibutyl phthalate from 97°C down to −96°C (near its glass transition temperature Tg). A visco penetrometer and a dielectric spectrometer built in our laboratories allowed us to obtain experimental data in the ranges 10-109 Pa.s for viscosity and 1 mHz–2 MHz for dielectric relaxation time. All these data and those of different authors give viscosity and dielectric relaxation time versus temperature on twelve decades; they are well fitted by the Cohen and Grest relation. These fits obtained on a large temperature range show that there is a strong correlation between viscosity and dielectric relaxation time. Furthermore it appears that the dielectric relaxation time distribution is broadening in the vicinity of Tg.