Gas-Phase Oxidation of Spark Plasma Sintered Products of Covalently Crosslinked Carbon Nanotubes

Abstract

Covalently crosslinked 3D structures of carbon nanotubes (CNTs) and CNTs with low-layer graphene fragments (LGFs) are obtained via the hydrolysis of 3-aminopropyltriethoxysilane with oxidized CNTs and/or LGFs. The resulting samples are consolidated into non-disintegrating pellets through spark plasma sintering at 1100°C and 30 MPa. Oxygen-containing groups are eliminated, and the LGF particles are transformed into a mixture of graphene sheets and onion-like carbon nanostructures. The resulting CNT consolidates and mixtures of CNTs with LGF have densities of 0.85 and 0.81 g cm−3 and conductivities of 42 and 57 S m−1, respectively. It is shown that the consolidated samples can be oxidized with nitric acid vapor without disturbing their 3D structure. When oxidative exposure time is increased from 3 to 6 h, the content of oxygen grows from 8.4 to 15.3 at % for 3D-crosslinked CNT structures, and from 14.0 to 16.1 at % for 3D-crosslinked CNT structures with LGFs.