Magnetoelasticidad: elastómeros estructurado de nanopartículas ferromagnéticas (Ni0) y superparamagnéticas (Fe3O4) en PDMS, curados en presencia de un campo magnético.

P. SOLEDAD ANTONEL; ROMINA A. LANDA; JOSÉ LUIS MIETTA; OSCAR E. PEREZ; GUILLERMO JORGE ; MARTÍN NEGRI

Córdoba

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

Asociación Argentina de Investigación Fisicoquímica (aaifq)

Introduction: The preparation of materials with anisotropic properties modulated by external fields is of high relevance for the design of electronic devices. We explore the modulation of both elastic and magnetic properties in dispersions of magnetic nanoparticles in an elastomer matrix, using superparamagnetic and ferromagnetic nanoparticles, in the context of developing actuators and sensors (1).Aims - Synthesis of magnetic nanoparticles with different magnetic properties: superparamagnetism (Fe3O4) and ferromagnetism (Ni0).- Preparation of structured elastomeric composites of the nanoparticles in polydimethysiloxane (PDMS), by curing the composite in presence of a magnetic field.- Determination of the elastic and magnetic properties of the cured composites as function of the orientation with respect to the magnetic field applied during curing.Results: Superparamagnetic nanoparticles of Fe3O4 were obtained by standard acidbase co-precipitation. Ferromagnetic nickel nanoparticles were synthesized by reduction with sodium borohydride in micelar media. Magnetic properties at room temperature were determined by VSM. SQUID experiments were performed for Fe3O4,observing the paramagnetic-ferromagnetic transition at 260 K (blocking temperature at zero field). XRD, TEM and SEM results were consistent with average sizes of 13 nm for Ni and 16 nm for Fe3O4. Dispersions of nanoparticles-PDMS at defined proportions were placed in a specially designed device which allows curing at a given temperature in the presence of a uniform magnetic field (0.3 T), while rotating the sample at constant speed.Macroscopic chains (needles), formed by aggregation of nanoparticles, aligned in the direction of the field applied when curing, were obtained. Thus, the polymerized material appears as morphologically structured. The elastic and magnetic properties were studied as function of the orientation. The composites presented always elastic character, with low elastic hysteresis and Young´s modulus larger in the direction of the needles (dependent on nanoparticle`s nature and concentration). All systems presented magnetic anisotropy also, with larger magnetizations in the direction of the needles.ConclusionsAnisotropic effects were induced for both superparamagnetic and ferromagnetic systems, suggesting that the relevant magnitude is the absolute value of the magnetization at the applied field (20 and 40 emu/g for Ni0 and Fe3O4, respectively). This is supported by results obtained for CoFe2O4, where alignment was obtained for ferromagnetic nanoparticles with relative large magnetization (30-50 emu/g), but not for superparamagnetic nanoparticles with low magnetization (<2 emu/g) at the curing field.