Application of γ-alumina as catalyst support for the synthesis of CNTs in a CVD reactor

Kariim Ishaq, Abdulkareem Ambali Saka, Abubakre Oladiran Kamardeen, Abdulkareem Abdulrahman, Ibrahim Kabir Adekunle and Ayo Samuel Afolabi

Abstract

The continuous search for effective and efficient engineered materials towards solving human challenges is in continuous needs. This study reports the preparation of γ-alumina from kaolin as catalyst support using methanol as precipitant for the synthesis of multiwalled carbon nanotubes (MWCNTs) in a horizontal chemical vapour deposition (CVD) reactor. The process involved thermal treatment of kaolin in a static air furnace, leaching of the treated kaolin in tetraoxosulphate(VI) acid (H₂SO₄), precipitation in methanol medium, washing in distilled water and calcination at 900 °C. The alumina in the kaolin was successfully leached and a cubic structure γ-alumina of high thermal stability was synthesized. The alumina was then characterised and utilised as support for the bimetallic catalyst (Fe-Ni) using wet impregnation method. The produced catalyst was used to produce CNTs in a CVD reactor. The thermal properties, surface morphologies, surface functional groups, crystallinity, elemental analyses, and surface areas of the starting kaolin, γ-alumina, prepared bimetallic catalyst (Fe-Ni/γ-alumina) and the synthesized MWCNTs were determined using TGA/DTA, HRSEM, FTIR, XRD, EDX, and BET respectively. The XRD analysis of the bimetallic catalyst was employed to determine its average crystalline particle size to be 26.23 nm using Scherer equation. Tip growth mechanism of MWCNTs was observed during the MWCNTs nucleation process with 41.2 nm external diameters, 13.01 μm length and 340 aspect ratio using dynamic light scattering (DLS) technique. The purified MWCNTs showed high antibacterial activities at long exposure time. The results of the various analysis conducted show that the synthesized γ-alumina has potential properties as catalyst support for MWCNTs growth via CVD technique