| Electrorheological (ER) fluids, or suspensions, as a kind of smart materials, have very important and potential applications in electromechanical control due to their attractive features of rapid (with ms order), reversible, and controllable changes in rheological properties upon application of an external electric field with kv/mm order. Once ER fluids have met the engineering targets, they will bring revolution in several areas of industry and technology such as mechanics, transportation, hydraulics and so on.Upon the emergence of anhydrous ER fluids, the research of ER suspensions has been in wide progress. But the development of ER technology in industry is currently hindered by ER fluids for want of excellent properties such as high activity and low density. On the other hand, a lack of systematical analysis of ER fluids'or dispersing media's application properties, especially the want of tribological studies, has also slowed down the progress of application of ER fluids. Based on the establishment of ER measuring instrument in this dissertation, the design, properties and mechanism of ER fluids based on chitosan(CTS) or hollow cenosphere, the influence of the dispersing media and protection of chlorinated paraffin, the influence of additives(including water, surfactant) on ER fluids and the stability of ER fluids, were investigated.The ER suspensions containing CTS as dispersed particulatematerial, exhibited good ER effect. Factors influencing the ER effect and leak current density (J) were studied. The results showed that the shear stress( ) and J increased with the increasing field strength (E) and weight fraction of particles(C) respectively, and decreased with the increasing shear rate ( ). The phenomena were studied with the polarization mechanism and percolation model. It was found that with the increasing deacetylation degree, the ER effect and J of CTS-based ER fluids also increased. The viewpoint of moving ions was used to elucidate this phenomenon.The factors influencing properties of CTS-based ER fluids such as water, glycerol, some surfactants and dispersing media were studied in detail. The results showed that and J of CTS-based ER fluids increased with the increasing water content (Q). It was discussed upon the principles of moving ions and "hydrogen-bond bridges". The ER effect of the suspensions decreased with the increasing surfactant, such as T151 and T705. It was found that the longer the non-polar molecules and the bigger the space volume of the surfactants, the lower will be and J. Based on these experimental results, the viewpoint of "insulation film" was proposed. ER effect was typically affected with the dispersing media. For CTS-based ER fluids, the value of r decreased in the order of chlorinated paraffin oil, protected paraffin oil, castor oil or silicone. Polarization mechanism was used to explain this phenomenon.With the molecular design method, a series of CTS-Mn+ and iodine doped chitosan (CTS-I2 complex) have been prepared and characterized by IR, X-Ray and TGA or DSC. Their characteristicsas ER dispersed particles and influence factors have been investigated. The and J of CTS-Mn+ based ER fluids increased with the increasing of Mn+ content due to the increasing number of moving ions. It was found that CTS-I2 complex was an excellent anhydrous ER dispersed particulate material. The value of of CTS-I2 complex was about twice of that of CTS-based ER fluids (Q=10.0wt%, of particles).In investigating hollow cenosphere ER effect, it was shown that the hollow cenosphere particles had ER effect in silicone oil, but no effect in castor oil. It was also found that hollow cenosphere is an anhydrous ER dispersed particulate material because that r increased with the increasing pre-heated temperature. After heat treatment at 400 C for 2 hours, the hollow cenosphere particles show stronger ER effect than those pre-heated at 100 C.Hollow cenosphere composite particles with core-shell structure were prepared by surface modification of hollow cenosphere particles by ble...
|
PDF Full Text Request