Ferroelastic composites are smart materials with unique properties including large magnetodeformational effects, strong field enhancement of the elastic modulus and magnetic shape memory. On basis mechanical tests, direct microscopy observations measurements we conclude that all these effects caused by reversible motion particles inside polymeric matrix in response to an applied field. The basic points a model accounting for particle structuring magnetoactive elastomer under external presented.

The origin of the so called magnetostriction effect, i.e., deformation a soft magnetic elastomer (SME) in response to uniform field is discussed. We note that up now there exists number cases, where theory unable explain facts well established for real SMEs. In our view, essential issue, formerly not adequately accounted for, type structural short-range order microparticle assembly. Two-dimensional model problems are formulated and solved, which demonstrate validity hypothesis.

The interaction between two particles made of an isotropic linearly polarizable magnetic material and embedded in elastomer matrix is studied. In this case, when external field imposed, the attraction particles, contrary to point dipoles, almost wraparound. exact solution problem linear polarization although existing, not practical; circumvent its use, interpolation formula proposed. One more expression developed for resistance elastic field-induced particle displacements. Minimization total...

A problem of the equilibrium orientation an elongated solid particle put inside a uniformly aligned nematic liquid crystal is studied. The assumed to be sufficiently large so that orientational distortions it causes may treated in framework continuum theory. Three kinds anchoring material on surface are considered: two planar, and one homeotropic type. We prove that, depending strength, stable major axis either perpendicular (weak anchoring) or parallel (strong unperturbed director...

The theory of ferromagnetic resonance (FMR) in an assembly single-domain uniaxially anisotropic particles is being applied to suspensions. approach used has, as its basis, the independent-grain model once proposed for description FMR polycrystals. We surmise that basic assumptions this are also appropriate composites fine magnetic particles. With regard specific properties systems question, we extend taking into account (i) thermofluctuational effects (superparamagnetism) and (ii)...

Abstract The Brochard-de Gennes continuum model of ferronematics—magnetic suspensions with the nematic liquid-crystalline carrier—is modified to take into account finiteness energy molecules anchoring on particle surface. developed approach is specified be capable describe equilibrium properties real thermotropic ferronematics.

On the basis of Brown's kinetic equation a consistent study regimes cyclic magnetization reversal single-domain particles with uniaxial anisotropy is performed. The applied field harmonic and linearly polarized, its amplitude equals maximal coercive force Stoner-Wohlfarth particle. dynamic magnetic hysteresis loops are obtained for particle (oriented ensemble), whose easy-magnetization axis tilted to direction under an arbitrary angle. It shown that regime (often termed as quasistatic) able...

Field-induced magnetostatic interaction in a pair of identical particles made magnetically soft ferromagnet is studied. It shown that due to saturation the magnetization, this case differs significantly from (super)paramagnetic one. A numerical solution given, discussed, and compared with provided by simpler model (nonlinear mutual dipoles). We show for multidomain ferromagnetic embedded an elastomer matrix, as paramagnetic ones same environment, clusters may form or break hysteresis...

This work describes the use of mesoporous SBA-15 silicas as hard templates for size-controlled synthesis oxide nanoparticles, with pores acting nanoscale reactors. fundamental is mainly aimed at understanding unresolved issues concerning occurrence and size dependence phase transitions in nanocrystals. Aqueous solutions Fe(NO3)3*9H2O are deposited inside mesopore diameters 4.3, 6.6, 9.5 nm. By calcination, nitrate salt transforms into FeOx oxides. The XRD peaks nanocrystals broad...

We analyze theoretically the field-induced microstructural deformations in a hybrid elastomer, that consists of polymer matrix filled with mixture magnetically soft and hard spherical microparticles. These composites were introduced recently order to obtain material allows tuning its properties by both, active passive control. Our theoretical analysis puts forward two complementary models: continuum magnetomechanical model bead-spring computer simulation model. use both approaches describe...

The mechanical response of a cantilever made magnetoactive elastomer (MAE) that is positioned on solid plane surface and subjected to uniform magnetic field studied. MAE the magnetically soft type, i.e., its filler particles become magnetized only in presence external field. Test observations with applied normal reveal two possible perturbed configurations cantilever: either free end just bends upward or folds into an arc, so does not detach from supporting plane. tests evidence under cyclic...

Abstract The magnetoelectric (ME) effect in composites consisting of a piezopolymer matrix (PVDF or akin) filled with the ferrite particles possessing weak zero magnetostriction (barium hexaferrite, BFO is considered. A theoretical model proposed that takes into account contribution mechanical stresses arising due to magnetic torques applied on part external field. composite film constructed as layer adjoined identical representative cells each which made PVDF polymer surrounding...

Numerical modeling of the direct magnetoelectric (ME) effect in a PVDF–cobalt ferrite (CFO) composite film has been performed. The problem is solved within framework mesoscopic RVE approach, where each elementary cell contains three particles with varying mutual positions. Both modes mechanical stress generation are taken into account: magnetostrictive and magnetorotational, i.e., changes shape rotation particle as whole. Depending on sign magnetostriction constants, these sources...

New ionic ferrofluids containing NiFe2O4 nanoparticles of size ⩽10 nm are investigated. The crystalline structure the particles is probed by transmission electron microscopy and x-ray scattering. Static magnetization field-induced birefringence measurements performed on three samples differing particle volume fraction. Cross analyzing results those two types macroscopic tests completely rejects a simple single-domain model but readily supports two-component scheme as consisting core with...

The theory of Brownian motion a particle in viscoelastic Jeffreys fluid is extended for the case rotational motion. employed rheological model combines two viscous mechanisms (instantaneous and retarded) and, contrast to Maxwell model, does not produce artifacts works robustly when applied diffusion tracer particles real complex fluids. With aid this specific features dynamic susceptibility magnetic suspension power losses induced by an ac field are analyzed conclusions derived that valid...