Catalytic materials based on aluminium hydroxide, for the large scale production of bundles of multi-walled (MWNT) carbon nanotubes

Abstract

Finding out a material with a right combination of a support and the catalyst for the synthesis of carbon nanotubes in good quantity and quality, is an active field of research. In an attempt to achieve this goal, in the present work aluminium hydroxide obtained from different routes was used as a support for a mixture of iron/cobalt catalysts and investigated their activity in the production of carbon nanotubes (CNTs). The CNTs synthesis reactions were carried out by catalytic chemical vapour deposition (CCVD) method in a horizontal furnace at 700 °C, in the presence of nitrogen as a carrier gas and acetylene as the source of carbon. The yield and the nature of the CNTs produced were greatly influenced by the method of preparation of the support and the catalyst-support mixture. The yield of the carbon deposit obtained varied from 24% to 319% of the initial weight of the catalyst. Scanning electron microscope analysis of the carbon product revealed that the CNTs were produced either as dense bundles or as a network. Transmission electron micrograph analysis of the carbon product indicated that the CNTs formed are multiwall in nature. Powder X-ray diffraction and Thermogravimetric analysis profiled made on the support-catalyst mixtures provided useful information on the interpretation of the results on the nature of the CNTs produced. A method for the purification of the as synthesised carbon deposit is described. The purity of the nanotubes was followed, analysing the carbon deposit by 27Al MASNMR for the remaining traces of support, proton induced X-ray emission for the Fe and Co content and proton induced gamma emission experiments for the Al content.