Structured elastomer composites of CoFe2-xSmxO4 : effect of samarium substitution on the crystalline, elastic and magnetic properties

MARIANO M. RUIZ; P.SOLEDAD ANTONEL; OSCAR E PÉREZ ; GUILLERMO JORGE; MIREILLE PEREC ; MARTÍN NEGRI

Córdoba

Congreso; XVII Congreso Argentino de Fisicoquímica y Química Inorgánica; 2011

Asociación Argentina de Investigación Fisicoquímica (aaifq)

IntroductionThe generation of smart materials with magnetic properties modulated by rare earth substitution has potential applications for developing pressure and magnetic field sensors, actuators for microfluidic and high-density memory devices. This otivates to study the influence on the magnetorheological properties of CoFe2-xSmxO4-PDMS structured elastomers when substituting iron by samarium in the magnetic cobalt ferrites nanoparticles.ObjectivesThe first objective is the synthesis and characterization of magnetic CoFe2-xSmxO4 (x=0-0.5) nanoparticles. Then, we analyze the variation on the crystalline and magnetic properties of the particles as function of samarium doping. The next step is to disperse the nanoparticles in polydimethylsiloxane (PDMS), curing the nanoparticles-PDMS mixture in presence of a uniform magnetic field to introduce magnetic anisotropy. Finally, the magnetic and elastic properties of the composites are measured as function of the orientation.ResultsA Dewar reactor with controlled temperature was designed in order to make the synthesis by the co-precipitation method. Acid solutions of FeCl3.6H2O, CoCl2.6H2O and SmCl3 (aq) at defined stoichiometry were drop-by-drop added to a solution of NaOH (pH=12, T=80 °C) under permanent stirring. The obtained particles were washed by centrifugation and finally dried in a vacuum oven at 40ºC for 24 hours. XRD, SEM and TEM experiments were performed, indicating a continuous increase of thenanoparticle size when increasing samarium (around 30 nm). Magnetization curves of the nanoparticles at room temperature were recorded by VSM (Vibrating Sample Magnetometer), showing ferromagnetic behaviour. PDMS base and crosslinker agents were mixed in defined proportions and then loaded with the magnetic nanoparticles (10% w/w). This mixture, still fluid, was placed for curing inside a cylindrical mould which is part of a designed device that allows curing the samples at a given temperature (75 °C) in the presence of an applied magnetic field (0.3 Tesla) during 4 hours. Magnetic cycles, elastic curves and determinations of the Young´s modulus were performed as function of the composite orientation.ConclusionsThe substitution of iron by samarium modifies the properties of the nanoparticles. The polymerized composites display both magnetic and elastic anisotropic behaviour, whose variation with samarium content is under investigation at present.