Special features for functionalization of carbon nanotubes nanopowders

Abstract

Physical and mechanical properties of carbon nanotube (CNT) powders depend on the method of their synthesis and chemical refinement. In order to create new composite materials that contain CNT powders as a filler, it is necessary to achieve functionalization of powder surface. Functionalization of MWCNT-A brand CNT powder surface using pulse processing by high voltage electric discharges (HVED) in liquid leads to changes in distribution of its particles by size, a decrease in amorphous carbon content and in powder thermostability. Sedimentation separation of powder after HVED processing leads to formation of powder in three size ranges (0.118-0.139, 2.639-20.895 and 2.44-33.701 µm). Thermochemical modification of CNT powders leads to an increase in specific surface area, total volume of pores and micropores, their mean radii, a decrease in impurities content, changes in distribution of its particles by size, a decrease in amorphous carbon content and in powder thermostability. Electrochemical reconstruction of the surface of specimens of initial MWCNT-A brand CNT powder allows decreasing impurities content, free energy of surface saturation by water vapor, specific magnetic susceptibility, electrokinetic potential as well as increasing specific surface area, pores total volume and hydrogen adsorption. Consecutive application of these methods leads to a decrease in impurities content in MWCNT-A brand CNT powder and to changes of its physical and chemical characteristics. Mass share of impurities decreases 3.7 times, mass share of soluble impurities decreases 7 times, specific magnetic susceptibility increases 5.2 times, electrokinetic potential increases 7.8 times. Specific electric resistivity increases 1.3 times, which leads to changes of adsorption and structural characteristics of powder: specific surface area increases 1.4 times and free energy of surface saturation by water vapor decreases by 11.9 %, which means that surface becomes more hydrophobic. As a result of such changes, rate of hydrogen adsorption on powders surface increases by 46 % and the current density at the potential of-0.6 V increases by 50 %.