Organic / Inorganic Hybrid Change Materials And Self-assembly Current Study

Electrorheological(ER) fluids, composed of nonconducting or weakly conducting particles dispersed in an insulating liquid, undergo dramatic, reversible changes when exposed to an external electric field. Apparent viscosities and shear stress increase several orders of magnitude. Such excellent characteristics will result in a revolution in the field of electrics-mechanics transfer.The organic/inorganic hybide compound is a new material with good properties both of inorganic and organic materials. In this paper, we integrate properties of titanium dioxide colloides and carboxylmethyl starch, proposing a novel way to improve electrorheological effect by hybriding and self-assembly. The experimental results are given as follows:1 Carboxylmethyl starch / titanium dioxide hybrids were synthesized using a modified in-situ sol-gel method and characterized by chemical dying and FTIR. IR analysis shows that there is somewhat strong interaction between carboxylmethyl starch (CMS) and titanium oxide, whose disperion was almost up to nanometre level. Due to highly active surface of hybrid particles and their proper dielectric behaviors in accordance with the previous theoretic calculation, the suspensions of CMS/TiO₂ hybrids in silicone oil display a remarkable ER effect. The static yield stress can be up to above 16 k Pa (shear rate 5 S-1) in a direct current field of 4 kV/mm at room temperature, much higher than that of pure starch and pure titanium dioxide ERF. In the meanwhile, their temperature dependence and sedimentation stability were optimized. Based on experimental results, we propose that dielectric properties and surface (interface) activity are two necessary conditions fulfilling the requirement of high ER activity. The combination of both factors can effectively reduce theactivation energy needed for ERF restructuring. The dielectric and rheological properties of ER fluid were measured. The experiment shows that at 1kHz and 20 ℃, the dielectric constant of CMS/TiO2 hybrid (1:3) can be up to 21, which is 5.25 times than that of pure titanium dioxide and 2.33 times than that of CMS. The conductivity and dielectric loss of CMS/TiO2 hybrid (1:3) is 13 X 10"7 S/m and 2.55, respectively. In the meanwhile, the antisedimentation and stability of this ERF is excellent (sedimentation ratio=20% for 63 days). The hybrid ERF's operational temperature range has been broadened (10-90 ℃). The intrinsic reason for enhancing the rheological property is the improvement of dielectric property of the hybrids.2 We exploited self-assembly mould technique to get porous nanometercompound particle. Many of caves of nanometer size on the surface provide this material with adsorpting organic molecular with strong polarity. Various surfactants coating such as dimethylsulfoxide, urea, etc, greatly improve the mechanic property of nano compound ERF. Especially, PVP/TiO2/Starch has huge shear stress of 37kPa (E=4kV/mm DC, γ =5S-1) . The experimental results showed that porous coating procedure improves the ER effect. For example, the static shear stress of porous TiO2/Starch nanocomposites ERF is 21kPa, after coating the yield stress could further improve. The dielectric properties of PVP/Starch/TiO2 is 60(1 kHz, T=25 ℃), 15 times as large as that of the pure titanium dioxide, and 4 times as largr as non-porous hybride. The conductivity of PVP/Starch/TiO2 is 38 X 10-7 S/m, and the dielectric loss is 1.1.