Magnetite/Poly(ortho-anisidine) Composite Particles and Their Electrorheological Response

Magnetic and semiconducting Fe3O4/poly(o-anisidine) (POA) core/shell composite particles were fabricated by an oxidation process using Fe3O4 synthesized separately. The dispersion stability in a liquid medium and the electrical conductivity of synthesized particles were improved because of the conductive POA polymeric shell. The morphological, microstructural, compositional/elemental, and thermal behaviors of the particles were characterized using SEM with energy dispersive X-ray spectroscopy, TEM, XRD, and thermogravimetric analysis, respectively. A smart electro-magneto-rheological suspension containing Fe3O4/POA particles with two functionalities, magnetism and conductivity, was prepared. Its electrorheological properties were investigated at different electric field strengths using a rotational rheometer. Without an electric field, the sample demonstrated typical Newtonian fluid behavior, as expected. However, while under the electric field, it exhibited a solid-like behavior, and the dynamic (or elastic) yield stress of the ER fluid increased linearly as a function of the electric field strength in a power-law function with an index of 2.0, following the polarization mechanism.

Experimental studies of electrorheological properties of lubricating oils containing ionic liquid. Part 3. Microscopic examination of the ER effect mechanism

The article presents the results of in situ microscopic observations of quasihomogenic mixtures of hydrocarbon oils containing ionic liquids. Observations were made using NIKON ECLIPSE LV 100 D optical microscope. The mechanism of generating the ER effect in two mixtures was observed, i.e., in silicone damping liquid GP-1, which is polimethylsiloksane mixture containing 2% (v/v) of ionic liquid CJ 001, i.e., tetrafluoroboran 1-methyl-3-octyloxymethylimidazolium and base polialfaolefine oil PAO-6 which containing 2% (v/v) of ionic liquid CJ 008, i.e., trihexyltertradecylfosfonium bis(trifluoromethylsulfonyl) imide as well as in the two-component standard liquid LID3354s. The ob-servations carried out showed that the prepared mixtures had generated the ER effect. At the threshold value E = 0.3 kV·mm–1, the ER effect disappeared. Photographs, presented in the paper, show changes in the structure of mixtures containing ionic liquids that occur under the influence of an external elec-tric field, consisting in the formation of „fibril chains and/or fibril streams” and then, their destruction and accumulation of ionic liquid particles at the electrodes. Keywords: electrorheological effect (ER), lubricating oils, ionic liquids, microscopy.

Electrorheological Properties of Polydimethylsiloxane/TiO2-Based Composite Elastomers

Electrorheological elastomers based on polydimethylsiloxane filled with hydrated titanium dioxide with a particle size of 100–200 nm were obtained by polymerization of the elastomeric matrix, either in the presence, or in the absence, of an external electric field. The viscoelastic and dielectric properties of the obtained elastomers were compared. Analysis of the storage modulus and loss modulus of the filled elastomers made it possible to reveal the influence of the electric field on the Payne effect in electrorheological elastomers. The elastomer vulcanized in the electric field showed high values of electrorheological sensitivity, 250% for storage modulus and 1100% for loss modulus. It was shown, for the first time, that vulcanization of filled elastomers in the electric field leads to a significant decrease in the degree of crosslinking in the elastomer. This effect should be taken into account in the design of electroactive elastomeric materials.

Interaction of titanium oxide with sodium hydroxide at hydrothermal conditions

Sodium titanates were obtained by hydrothermal treatment using titanium tetrabutoxide (ТBT), titanium tetroisopropoxide (TIPT), hydrated titanium dioxide (prepared by hydrolysis of titanium alkoxide) or air-dried TiO2 sol with a molar ratio of TBT/TIPT/TiO2: NaOH equal to 1:10–80, at the temperature 130–180 °C and treatment time 24–72 h. Samples were characterized by the adsorption method, X-ray phase analysis, scanning electron microscopy. The photocatalytic properties of nanostructured titanate in the H-form in the process of Rhodamine FL–BM photodegradation under UV-irradiation (K = 0.03–0.05 min–1), as well as the electrorheological properties, were evaluated. Partially hydrated sodium titanates as a filler of the electrorheological dispersion (the filler content of dispersion was 5 %) exhibited the shear stress of 50–60 Pa and the leakage current density of 1.0–1.5 μA/cm2 at an electric field strength of E = 4 kV/cm at a shear rate of 17.1 s–1.