| Ti-O electrorheological fluid (ERF) system is a Ti-O particle dispersed in the oil phase to form one kind of liquid material. According to the principle that high dielectric polarity molecular orientation at electric field, which would greatly enhance the shear strength, the ERF system is expected to be used for semi-active damping system, clutch brakes, fluid valves, and many others. However, some problems were still need to overcome such as the ERF was easy to reunion and settlement, and the performance of ERF is still unstable. The integration of cellulose nanowhisker (CNW) and cellulose nanofiber (CNF) prepared from forestry residues and Ti-O system is a new way to improve the performance of ERF. Nano-cellulose has a fine shape and size, large specific surface area, high surface energy and dielectric properties. Hydroxyl groups at the side chain can effectively adsorption of polar molecules in the oil, leading to the easy chain polymerization in the electric field. The similar density with the oil contribute to the good anti-settling property. In this paper, we prepare the titanium dioxide/CNW composites by the sol-gel method and prepare the Anatase/CNF composites by the hydrothermal method. The proportion of nano-cllulose/TiO2 can be tailered at 10%,20% and 30% by adjusting the addition ratio of the raw material. Analyzed by transmission electron microscopy, X-ray diffraction, infrared spectroscopy and ER performance test, we got the conclusions as follows:(1) the diameter of nanowhiskers/TiO2 composite which is obtained by sol-gel method is about 10nm and 200-300nm long, the nanowhiskers is covered uniformly by the TiO2 particles, when the ratio of TiO2 is increased, amorphous TiO2 will make a number of fibers linked each other. The diameter of Nanofiber prepared by hydrothermal method/TiO2 composites range 10-50nm, the length is several microns, the particles of TiO2 coated on the nanowhiskers surface. With the increase of TiO2, the diameter of the composite increased. Both of materials are meet the demand of the new ER fluid.(2) In the test of the shear strength-the electric field strength and shear strength-polar molecule, the shear strength of TiO2 was impacted by the amount of Ti-OH and TiO2 cannot play an effective role of polar molecule, and adsorption constraints can not give full place to the role of polar molecules, the existence of nano-cellulose provide a solution to the above problem, The polar molecules play an effective role in electrorheological fluid and expand the upper limit adsorption of polar molecules. The shear strength is six times higher than befor.(3) in the shear strength-shear rate test, compared withTiO2 ER fluids (17%,22%), ER fluids take full advantage of high aspect ratio of nanocellulose, maintained a high shear strength (58.9%,48.8%), which was affected by the fiber form of the composite. In this case there is a difference between materials, Nanowhisker add the composites have higher shear strength retention ratio, the nanofiber is held on the shear strength stability.(4) in the shear strength-temperature test, the morphology of nanocellulose and the crystals form of TiO2 donnot have an impact on the thermal property of the composites. When the ratio of nanocellulose in the composites from 10% to 20%, the ER fluid thermal property changed.(5) In electrorheological repeatability tests, when theTiO2 ER fluids have appeared breakdown (4kV · mm-1) or the deterioration of the case, the shear strength of the composite essentially unaffected (less than 4%). This shows that the composite nano-cellulose makes ER fluids ER fluids can still work under various conditions and environment, and broaden the range of applications and extended the life of its ER fluid. Nanofiber composites after in electrorheological repeatability tests the current density is less than it of whisker composites, indicating that the nanofiber enhance more evident in this regard.(6) anti-sedimentation test, nano-cellulose is added to improve the overall performance of the anti-sedimentation HO2. On the one hand a significant reduction in sedimentation rate, the sedimentation rate of TiO2 ranged from 50% to 10%, On the other hand, it slows the settling velocity of ER materials from one day to reach the final settlement value is extended to five days. Nanofibrillar performed more excellent in reduce sedimentation rate and sedimentation rate.The results confirmed that the addition of nano-cellulose making the Ti-O system ERF reduce loss of polar molecules. A significant improvement of shear strength and service life in the electric field strength, temperature and other environmental changes were achieved. The major electrorheological effects have been significantly improved. Nanofiber performs better at stability enhancement. |
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