Samira Touhtouh

Mechanical characterization of an electrostrictive polymer for actuation and energy harvesting

Electroactive polymers have been widely used as smart material for actuators in recent years. Electromechanical applications are currently focused on energy harvesting and actuation, including the development of wireless portable electronic equipment autonomous and specific actuators such as artificial muscles. The problem to be solved is to make its devices the most efficient, as possible in terms of harvested energy and action. These two criteria are controlled by the permittivity of the electrostrictive polymer used, the Young’s modulus, and their dependence on frequency and level of stress. In the present paper, we presented a model describing the mechanical behaviour of electrostrictive polymers with taking into account the mechanical losses. Young’s modulus follows a linear function of strain and stress. However, when the elongation becomes higher, the data obtained from this strain linear trend and significant hysteresis loops appear the reflections on the existence of mechanical losses. In this wo...

Nonlinearity and scaling behavior in a soft lead zirconate titanate piezoceramic

Lead oxide-based ferroelectrics, represented by lead zirconate titanate [Pb(Zr,Ti)O3] or PZT), are the most widely used materials for piezoelectric actuators, sensors, and transducers due to their excellent piezoelectric properties. Most of these piezoelectric materials are employed under a variety of strains (stress, electrical field, and temperature). It would thus be interesting to predict their behaviors under different excitations without having to perform too much experimental work, i.e., just carry out a single experiment and still be able to provide the other experimental values. The purpose of this paper has thus been to propose several behavioral laws linking the electrical field, temperature and mechanical stress. The first law rendered it possible to express the mechanical stress by an equivalent electric field [ΔE≡αΔT×P(E,T0)]. Subsequently, a law linking the electrical field and temperature {ΔE≡[2β×P(E,θ0)]×Δθ} was proposed. From these two laws, a third law was identified reflecting the mech...

Magnetoelectricity in polyurethanes nanocomposites

ABSTRACT Magnetoelectric (ME) effect, triggered much interests because of its potential of the cross correlation between the electric and magnetic properties of matter for technical applications such as magnetic field sensors, transducers, actuators. Magnetoelectric (ME) effect represents the coupling between a change in electric polarization in a solid when a magnetic field is applied. This study reports on the magnetoelectric (ME) effect observed in nanocomposite polymer consisting of polyurethane (PU) filled with 2.5wt% and 5wt% of Fe3C magnetic nanoparticles. In general, the electric response to an applied magnetic field (H) on polymer composites filled by magnetic particles is not well known. That is the reason why our study aims to show the influence of the magnetic fillers (Fe3C) in PU matrix. Our experimental findings are discussed for different situations.

Investigation of structural and physical properties of xSrO-(100-x)P2O5 glasses

ABSTRACT The structural and physical properties for xSrO-(100-x)P2O5 glasses, with x = 30, 35, 40, 45, and 50, were investigated. The amorphous state of samples was verified by X-ray diffraction (XRD). Substitution of P2O5 for SrO in the binary SrO–P2O5 glass decreases the molar volume and increase the density measurements from 1.98 to 4.01 g/cm3. The Infra-Red (IR) and Raman spectra allow us to identify the network modifier role of Sr2+ ions and the structural network of these phosphate glasses which consists of branching (Q3), middle phosphate tetrahedra (Q2) and pyrophosphate (Q1).

Synthesis of nanosized TiO2 powder by sol gel method at low temperature

ABSTRACT Nanotechnology is all about making products from very small constituents, components or subsystems to gain greatly enhanced material properties and functionality. Nanocrystalline anatase TiO2 was prepared by a facile sol–gel route at a temperature of 50°C under mild conditions. Titanium tetraisopropoxide (TTIP) was used as a titanium precursor, and 2-propanol was used as a solvent. XRD, TEM, SEM, FT-IR and BET were applied to characterize the crystal phase. The Crystalline size of TiO2 powder has been obtained with diameter < 30 nm for anatase at 500°C using an acid.

Synthesis and vibrational analysis of new bismuth phosphate glasses

ABSTRACT Bismuth phosphate glasses were prepared using the conventional melt quenching technique with a mixture of Bismuth(III) oxide and hydrogen ammonium phosphate. The amorphous state of the samples was verified by X-ray diffraction. The physical parameters like molar volume and oxygen packing density were evaluated from the measured density values. It is found that the density increased from 5.45 g/cm3 to 6.12 g/cm3, while the values of the molar volume increased from 34,97 to 39.08 cm3/mol, and whereas the oxygen packing density decreased with the gradual increase of the of bismuth content. The structure of the glasses was determined using Infrared Spectroscopy. The Fourier Transform Infrared Spectroscopy spectra were recorded in the spectral range from 400 to 1400 cm−1. The structural investigations based on these spectra show the rapid depolymerization of phosphate chains with an increase in bismuth oxide. Also, this investigation highlights that the glassy-matrix contains various phosphate and bismuth structural units. The results indicate that Bismuth oxide plays a network modifier role and stabilizes the structure of the vitreous matrix.