RESUMEN
The electrorheological properties of colloidal dispersions of aluminum oxide nanotubes and nanoparticles in silicone oil were investigated. The shear storage modulus of colloidal dispersions containing 5 wt% of aluminum oxide nanotubes increased by four orders of magnitude upon the application of an external electric field of as low as 400 V/mm. The storage modulus of the nanotube systems increased further by increasing the concentration of nanotubes. The electrorheological response of aluminum oxide nanoparticles dispersions was significantly lower than that of the dispersions containing the same weight fraction of aluminum oxide nanotubes at the same external electric field. This result reflects the effect of shape anisotropy on the electrorheological features of colloidal dispersions.
RESUMEN
The grafting of polybutylene oxide onto purified and functionalized carbon nanofibers is reported. Grafting was possible after the insertion of 2-(formyloxy)ethyl 2-bromo-2-methylpropanoate onto the carbon nanofibers. The polymerization of tetrahydrofuran was mediated by copper(I) bromide and 1,1,4,7-pentamethyl diethylenetriamine. The polymer-grafted carbon nanofibers were characterized by Raman spectrsocopy, Transmission Electron Microscopy, and Thermogravimetric Analysis. TEM images of CNF-COOH (A), CNF-PBO (B), completely open tip of CNF-COOH, and coated tip of CNF-PBO (D) are shown in the left panel. The right panel depicts the distribution of bromine (blue), and carbon (red) atoms inside and in the vicinity of CNF-Br (as obtained by Electron Energy Loss Spectroscopy). The bottom shows the actual doped CNF. Preliminary data showed that these modified fibers have potential applications as smart (electrorheological) fluids.