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This paper presents a dielectric and magneto-dielectric study of magnetic fluids made of three different, partially substituted, manganese ferrite particles dispersed in kerosene. Measurements were performed using a wholly automated spectrometer in the frequency range 1 mHz–10 MHz and a temperature range from −200°C up to 100°C. We can distinguish the two phases (solid and liquid) in pure kerosene and three phases for all the magnetic fluid samples. We observed the effect of anisotropy constant and domain magnetization of the particles on magneto-dielectric measurements. We also observed the temperature sensitivity of these fluids.

We have measured the susceptibility of two ferrofluids in the frequency range 0.1–20 GHz. We confine the liquid under test in a coaxial line cell and we use the reflection/transmission method to obtain χ ∗ . If we add a constant axial magnetic field to the microwave field we evidence an increase of the gyromagnetic resonance phenomenon appearing as a consequence of the artificial increase of anisotropy.

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.

We studied the complex permittivity of alkylhydrazines/water mixtures from room temperature down to − 120°C between 50 mHz and 2 MHz, in the mole fraction range 0.1 ≤ x ≤ 1. The addition of a second suitable component decreases and even eliminates, at sufficient concentration, the anomalies of pure water and allows, according to Oguni and Angell, to separate the “normal” and the “anomalous” parts of water physical properties. The static permittivity of alkylhydrazines - water mixtures (with monomethylhydrazine and 1,1-dimethylhydrazine) leads to estimate, by extrapolation at x = 0, the static permittivity of normal supercooled water below its homogeneous nucleation temperature, in spite of chemical associations present in the solutions. The values calculated by this method are in good agreement with our previous results obtained on alcohol/water mixtures and the data predicted by the random network model of Sceats and Rice.

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.

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.

This paper presents a dielectric study of a ferrofluid Fe2CoO4 in dibutyl phthalate at different concentrations from room temperature down to low temperature less than -100°C. With results from our spectrometer we discuss, for a large interval of temperature, the homogeneity of the ferrofluid solutions when a continuous magnetic field is applied perpendicularly to the electric field.

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.

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.