Effect Of Cobalt Particle Morphology On Dynamic Viscoelasticity Of Magnetorheological Elastomers

Magnetorheological elastomer(MRE)is a new type of intelligent material,which is polymer matrix composite materials formed by magnetic particles and polymer materials.In the field of external magnetic field,due to the interaction of micron-type magnetically permeable particles in the non-magnetic polymer matrix,it has fast and reliable controllable mechanical properties and excellent damping performance.In the field of shock absorption and shock resistance,it has a wide range of application.Therefore,the development of magnetorheological elastomers with higher magnetorheological effects,better mechanical properties and damping properties has been the direction of research and exploration.Magnetic particles are one of the important factors that affect the performance of magnetorheological elastomers.The effects of particle-related factors such as volume fraction,particle size and particle type on the performance of MRE have been extensively studied,and the effect of particle morphology on the performance of MRE is rare studid,and the mechanism is also not clear.Therefore,to prepare the magnetorheological elastomer with better performance,explore the effect of particle morphology on the dynamic viscoelasticity of MRE is especially important.In this paper,we use solvothermal method for the preparation of spherical,chain-like,flower-like metal cobalt particles with different morphology.We used SEM and XRD characterize the morphology and structure of the metal cobalt particles.The results showed that the size of the spherical cobalt particles was 1-2?m,which was packed in hexagonal structure.The cobalt-like particles are composed of a combination of many spherical cobalt particles,which was also packed in hexagonal structure.The size of flower-like cobalt particles was 5-6?m,which had two structures: dense hexagonal and face-centered cubic.The preparation scheme and process of magnetorheological elastomers were explored and identified.We use silica rubber as the matrix and spherical,chain-like,flower-like cobalt particles for the function filling phase respectively.The magnetorheological elastomers were prepared under different oriented magnetic field strength: 0mT,480 mT and 1154 mT,respectively.We tested the dynamic viscoelasticity of magnetorheological elastomers under different working conditions which are frequency sweep test mode,strain amplitude sweep test mode,magnetic field sweep test mode.In the frequency sweep test mode,the constant strain amplitude was set to 0.01% and the frequency was increased in the range of 0.1-100 Hz.In the strain amplitude sweep test mode,the constant frequency was 10 Hz,the strain amplitude was in the range of 0.001%-100%.In the magnetic field sweep test mode,the constant strain amplitude was set at 0.01%,the constant frequency was 10 Hz,and the magnetic field intensity increased linearly in the range of 0 mT to 300 mT.The dynamic viscoelasticity of the isotropic magnetorheological elastomers with spherical,chain-like and flower-like cobalt particles as filling phase was summarized.And we also compared and analyzed the dynamic viscoelasticity of the anisotropic magnetorheological elastomers which use spherical,chain-like,flower-like cobalt particles as filling phrase directively.The experimental results show that,for isotropic magnetorheological elastomers,The energy storage modulus G' of the magnetorheological elastomer with spherical cobalt particles as filling phase is higher than the magnetorheological elastomers with chain-like cobalt particles as filling phase,With the increase of applied magnetic field,G' of the magnetorheological elastomers with flower-like cobalt particles as filling phase is fistly higher and then lower than magnetorheological elastomers with spherical cobalt particles as filling phase;As for the loss modulus G'' of the sample,the magnetorheological elastomers with chain-like cobalt particles as filling phases is the highest,and the magnetorheological elastomers with flower-like cobalt particles as filling phase is the lowest;the relative magnetorheological effect of the magnetorheological elastomer with spherical cobalt particles as filling phase is the highest.For anisotropic magnetorheological elastomers,the energy storage modulus G' and the loss modulus G'' of the magnetorheological elastomers with flower-like cobalt particles as filling phase are higher than the magnetorheological elastomer with spherical cobalt particles or chain-like cobalt particles as filling phase,It shows excellent stiffness controllabilityand Damping property.However for relative magnetorheological effect,the magnetorheological elastomers with flower-like cobalt particles as filling phase is the best.We also analyzed and summarized the influence of the orientation magnetic field strength on the magnetic rheological elastomers with different morphology of metal cobalt particles as the filling phase under zero applied magnetic field strength.The experimental results show that the orientation of microstructure of magnetorheological elastomers increases significantly with the increase of the orientation magnetic field strength,and the storage modulus G' and the loss modulus G'' also increase.When the intensity of the orientation magnetic field strength increases to a certain extent,the dynamic viscoelasticity tends to be stable due to the stable structure of the ordered structure.However,the effect of orientation magnetic field strength on relative magnetorheological effect isn't obvious.