Microstructural features of nanocomposite of alumina@carbon nanotubes/alumina nanoparticles synthesized by a solvothermal method

The present study focuses on the synthesis of nanocomposite gamma alumina (γ-Al2O3), boehmite and multi- walled carbon nanotubes (MWCNTs) via a solvothermal procedure. The method is based on the ex situ filling of opened CNTs by liquid reactants. The microstructure and morphology of the synthesized nanocomposite Al2O3@CNTs/Al2O3 was characterized by high resolution transmission electron microscopy (HRTEM), transmission electron microscopy (TEM), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) and N2 adsorption–desorption analysis.Based on the experimental results, it was determined that the volume ratio of γ-Al2O3/MWCNTs and the surface tension of the solvent both greatly influence the morphology of the nanocomposite. The resultant MWCNTs were coated and filled by homogeneous and uniform boehmite and γ-Al2O3 layers and nanoparticles with thicknesses of 1–3 nm and diameters of 20–40 nm, when the volume ratio of γ-Al2O3/MWCNTS is 1 and the surface tension of the solvent is approximately 26 mN m−1 at 20 °C, far below the maximum value (100–200 mN m−1) for MWCNT filling.