Shao-Hua Zhang

Effect of microstructure, grain size, and rare earth doping on the electrorheological performance of nanosized particle materials

Nanosized particle materials with different structures and grain sizes were prepared by doping TiO2 or ZrO2 with rare earth (RE) elements, and by changing the method of treatment. Their microstructures were confirmed by X-ray diffraction (XRD) analyses and measurements of the surface areas, pore volumes, and pore sizes of the particles. The electrorheological (ER) performance and dielectric properties of these materials, and the relationship between ER activity, microstructure, and grain size of these particle materials were investigated. The results have shown that RE doping can either increase or decrease the ER activity of a material, which is related to the pore volume in the grain. Body-centered tetragonal TiO2 and tetragonal ZrO2 possess higher ER activity than tetragonal TiO2 and monoclinic ZrO2, respectively. The effect of grain size on ER performance should not be neglected for different materials in a system with identical crystal structure and composition, and the co-action of both larger grain size and larger pore volume can play a very important role in nanosized particle materials. Optimal matching between appropriate RE-doping, microstructure and particle size, which can be achieved by fine-tuning the production process of a material, may provide a basis for producing an ER material with high activity.

A HIGHLY ACTIVE ELECTRORHEOLOGICAL MATERIAL, NANO-SIZED BOEHMITE: INFLUENCE OF HYDROXYL ON ITS ELECTRORHEOLOGICAL PROPERTY

A highly active electrorheological (ER) material, nano-sized boehmite, AlO(OH), has been obtained. The relative shear stress (τr = τE/τ0, τ0 and τE are the shear stresses at the electric field strength of 0 kV/mm and 4.2 kV/mm, respectively) of the suspension (25 wt.%) in silicone oil reached 212 at a shear rate of 14.5 s−1 and a DC electric field. The dielectric property, conductivity, surface energy, microstructure, and composition of boehmite [AlO(OH)] and alkaline alumina containing both AlO(OH) and Al2O3 have been studied. The results showed that the hydroxyl group plays a critical role in influencing the ER activity of the material by changing the dielectric property and conductivity of the material.

Preparation and Electrorheological Property of NaNO3-Doped Y2O3 Material

Abstract A new class of electrorheological (ER) material using rare earth (RE = Y) oxide as the substrate, NaNO3doped Y2O3 materials, were synthesized using Na2CO3 and Y(NO3)3 as starting materials. Their ER performance, dielectric property, and crystal structure were studied. The results show that doping NaNO3 can markedly enhance the ER activity of the Y2O3 material. For the suspensions of these materials in dimethyl silicone oil, a clear dependence of the shear stress on the doping degree of NaNO3 was observed, and the optimal value of Na/Y molar ratio of 0.6 in doping degree was discovered, the relative viscosity ηr(ηE/ηO, E = 4.2 kV·mm−1) of the suspensions is nine times higher than that of pure Y2O3 material. The new results of the relationship between ER effect and the microstructure were obtained, which are helpful for further understanding the mechanism of ER effect and synthesizing a good ER material.

Preparation and Electrorheological Property of Y4O(OH)9(NO3)-NH4NO3 Materials

Abstract The new electrorheological (ER) material, a particle material composed of Y 4 O(OH) 9 (NO 3 ) and NH 4 NO 3 , was obtained. They display better ER performance. The shear stress of the suspension of Y 4 O(OH) 9 (NO 3 ) (NH 4 NO 3 ) 2.8 material in dimethyl silicone oil reaches 1469 Pa at an electric field strength ( E ) of 4.2 kV. mm −1 and the shear rate (γ) of 150s −1 . The relative shear stress, τ E /τ 0 (τ E and τ 0 are the shear stresses at E = 4.2 and O kV-mm −1 , respectively), is up to 29, which is 19 times that of pure Y 2 O 3 material. The dielectric and conductive property of the materials play important roles in the modification of the ER effect of the particle materials. The researches on these new ER materials are very useful for obtaining a better understanding on the mechanism of the ER effect and finding an ideal ER material.

MOLECULE-BASED ELECTRORHEOLOGICAL MATERIAL, ELECTRORHEOLOGICAL PERFORMANCE AND MOLECULE STRUCTURE

Molecule-based electrorheological (ER) materials as a novel type of ER materials, a series of compounds using melamine (C3N6H6) as the substrate, have been synthesized using orthophosphoric acid (H3PO4), oxalic acid (H2C2O4), 4-toluenesulfonic acid (PTA, C7H8O3S) and 5-sulfosalicylic acid (SSA, C7H6O6S), respectively as starting materials. The ER performance and dielectric property of materials have been studied. The results show that these materials have ER activity. The unusual relationship between dielectric property and ER property of these materials was found and discussed. The composition and structure of molecule are the dominant factors, the function group plays an important role, in influencing ER performance of the molecule-based ER material.

MICROSTRUCTURE AND ELECTRORHEOLOGICAL PROPERTY OF PURE TiO2 PARTICLE MATERIAL

JUAN WANG AND SHAO-HUA ZHANG School of Vehicle and Transmission Engineering, Beijing Institute of Technology, Beijing, 100081, China Pure titanium dioxide (Ti02) particle materials were prepared by hydrolyzing titanium tetrachloride (TiC14). The microstructures of these materials were determined by X-ray difiactometer (XRD) and accelerated surface area & porosimetry apparatus (BET) etc. The Ti02 materials obtained by calcinations under different temperatures revealed distinctly different microstructures in terms of crystal structure type, surface area, pore size, pore volume and grain size. The relationship between the microstructure of the Ti02 materials and their electrorheolagical (ER) activity was investigated.