Synthesis And Properties Of Electro-Magneto-Rheological Double Functional Nanocomposites

Electrorheological Fluids (ER) and Magnetorheological Fluids (MR), composed of dielectric particles dispersed in a noconducting or weakly conducting liquid, undergo dramatic, reversible changes when apply to an external electric or magnetic field. Apparent suspension viscosities and shear stress can increase several orders of magnitude. Similar to the electrorheological fluid (ERF) and magethorheological fluid (MRF), the electro-magneto-rheological fluid (EMRF) is one kind of controllable suspension with micron-sized particles dispersed in a carrier medium. In the absence of external electric or magnetic field, EMRF presents a Newtonian behavior and abruptly transforms into high viscosity plastic-like solid from low viscosity fluid within milliseconds under an applied electric or magnetic field. Moreover, the Theological property of EMRF exhibits synergistic effect under the combination of electric and magnetic field, which is stronger than that under external electric or magnetic field. The bentonite/polyaniline nanofibers hybrid, Fe3O4@TiO2core-shell particles, BaTiO3/Fe3O4hierarchical structure particles and a-Fe2O3/TiO2core-shell composite particles are synthesized by different approach and characterized by the means of X-ray powder diffraction (XRD), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), et al.The main contents and major results are given as follows:1. A modified interfacial polymerization was used to prepare polyaniline (PANI) nanofibers. The nanofibers have an average diameter ranging from30to50nm with characteristic lengths of200-300nm. Then, the hexadecyl trimethyl ammonium bromide (CTAB) was used to modify the surface of bentonite, which was helpful in hybridizing with PANI for its hydrophobic properties. The results show that both the intercalation and coating structure could be found in the PANI/bentonite nanohybrid. TEM and SEM images verified that the surface of the bentonite plate was coated by the PANI nanofiber. The d001interlayer space increased0.236nm. The PANI nanofibers have three peaks at340,440, and800nm in UV-vis pattern. However, the spectrum intensity of the serial of PANI/bentonite obtained decreased with the enhanced concentration of bentonite. After hydrophobization treatment by CTAB, the ultraviolet visible absorption peak position change. With and without the electric field, electrorheological fluid appears obvious rheological properties change. When the electric field was not applied, it was found to be a Newtonian fluid. However, when an electric field was applied, it changed to a Bingham fluid with big apparent viscosity and high electrorheological effect.2. One pot of a simple solvothermal method has been demonstrated for the preparation of bifunctional Fe3O4@TiO2core/shell nanoparticles. In a typical procedure, tetra-alkoxyl titanium Ti(OC4H9)4and FeCl3as precursor was added to ethylene glycol and further solvothermal treatment were used to syntheses the core/shell particles. The morphological results shown that TiO2with100-200nm length and10-20nm, diameter coated on the surface of200-300nm Fe3O4submicrosphere. The results show that the ER composed of Fe3O4@TiO2core/shell particles had excellent electrorheological property.3. Other Fe3O4@TiO2core/shell particles were synthesized and characterized by changing the experimental conditions. The results showed that the morphology of product under Ti/Fe=38%ratio was better than Ti/Fe=63%. The diffraction peak intensity of Fe3O4was decreased with increasing the Ti/Fe ratio after coated by TiO2. The saturation magnetization (Ms) values of Fe3O4are72emu/g-1(at300K). After being coated by TiO2, the Ms values of the sample are28emu/g-1(Ti/Fe=38%) and 11emu/g-1(Ti/Fe=63%) at300K, respectively. In addition, the study for reaction time reasonably explains the formation mechanism of the core-shell structure.4. Flower-like BaTiO3/Fe3O4hierarchical structure particles were synthesized by a simple solvothermal approach. Magnetic testing results show that the samples have strong magnetism and they exhibit a superparamagnetic behavior, as evidenced by no coercivity and the remanence at room temperature on the M-H loop. The saturation magnetization (Ms) value can achieve to18.3emu g-1.The electrorheological (ER) effect was investigated using a suspension of the flower-like BaTiO3/Fe3O4hierarchical structure particles dispersed in silicone oil. The BaTiO3/Fe3O4suspensions exhibit a dramatic reorganization when submitted to a strong DC electric field and the particles aggregate to forms chain-like structures along the direction of applied electric field. A slight shear-thinning behavior of shear viscosity can be observed at a low shear rate region even at zero electric field applied and a Newtonian fluid behavior at high shear rate regions.5.α-Fe2O3/TiO2core-shell composite particles with uniform morphology were synthesised by boiling reflux hydrolysis and situ controlled hydrolysis. In this article, several factors have been researched. The results showed that monodisperse a-Fe2O3/TiO2core-shell composite particles were prepared when less water is added. However, with the increase of water, TiO2is reunioned on the surface of a-Fe2O3due to the hydrolysis rate of tetrabutyl titanate accelerated. So the spindle-shaped particles are completely wrapped and stuck together. The agglomeration of particles is serious when less surfactant is added. With the increase of surfactant, the coated environment is better, so the a-Fe2O3/TiO2core-shell composite particles are more likely to be spindle-shaped monodisperse particles, and the coating effect is good. In fact, the best concentration of tetrabutyl titanate is0.75mL. If the concentration of the tetrabutyl titanate is too low, the coating phenomenon can hardly observed. However, the concentration of the tetrabutyl titanate is too much, solid bulk with irregularly morphology is synthesised and will be coated seriously.