INFLUENCE OF LIQUID-PHASE OXIDATIVE TREATMENTS ON STRUCTURE AND HYDROPHILITY OF CARBON NANOTUBES

Abstract

Carbon nanotubes (CNTs) were synthesized by gas phase chemical deposition (CVD) using methane as a hydrocarbon reagent and using a catalyst of iron oxide deposited on fine aluminum oxide, as well as the same catalyst with the addition of molybdenum oxide deposited on fine magnesium oxide. The synthesized materials were treated with concentrated nitric acid (HNO3) or a mixture of concentrated nitric and sulfuric acids (HNO3 / H2SO4) in a volume ratio of 2: 1, at a temperature of 110-120 ° C for 1 h. Some of them were subjected to peroxide action (H2O2) before oxidative acid treatments for 1-2 h at a temperature of 100-110 ° C. Structural features, elemental compositions of synthesized CNTs were investigated before and after liquid-phase oxidative treatments by methods such as transmission electron microscopy, Raman spectroscopy, X-ray energy dispersive spectroscopy, X-ray phase analysis. In this work, the ability of CNTs that were undergone treatment in various oxidizing environments to form stable concentrated aqueous suspensions was studied. It was established that the initial defectity of the CNT molecules significantly affects the hydrophilic properties of oxidized CNT modifications. This causes their different ability to form concentrated, stable aqueous suspensions, predetermines the choice of combinations of oxidizing liquid-phase treatments that most contributing to this. It was revealed that HNO3 and HNO3 / H2SO4 mixture at the used temperature conditions of treatments and their duration do not have a strong destructive effect on the structure of CNT. The oxidative effect of these reagents on the molecules of this material is manifested mainly in defective places. The cleaning of the catalytic components of the synthesis from the catalytic components contributes to the more efficient purification of HNO3 / H2SO4 with the formation of stable aqueous suspensions from the molecules of this material, and this does not depend on the characteristics of the synthesis of the CNTs.