The growth of carbon nanotubes in aluminum powders by the catalytic pyrolysis of polyethylene glycol

A simple approach based on the catalytic pyrolysis of polyethylene glycol (PEG) was developed to grow a uniform dispersion of carbon nanotubes (CNTs) in Al powders and thus supply raw material for the powder metallurgy fabrication of CNT/Al composites. Al nanoflake powders with quite a large surface area were used to adsorb a homogeneous PEG and citric acid film, and then were impregnated with a cobalt nitrate solution to anchor Co(II) by complexation with citric acid. Then the Al nanoflake powders were heated to 230 °C to form Co oxide nanoparticles, and then to 570 °C to induce the thermal decomposition of PEG. The pyrolytic products of PEG not only served as the reducing agent to reduce Co oxide to Co nanoparticle catalyst, but also as the carbon source for CNT growth. As a result, 2.13 wt.% graphitic CNTs, with diameters of 10–20 nm and length ranging from sub-micron to a few micrometers, were homogeneously grown in 500 nm thick Al nanoflakes. And the as-obtained CNT/Al composites fabricated by hot-pressing exhibited enhanced strength, which was almost two times that of the matrix.