Bamboo-shaped carbon nanotubes generated by methane thermal decomposition using Ni nanoparticles synthesized in water-oil emulsions

► Two systems of Ni nanoparticles between 3 and 12 nm were synthesized in water-oil emulsions. ► The reactivity toward methane decomposition was studied into a thermobalance. ► Ni nanoparticles were reactive to methane decomposition above 480 °C. ► Bamboo-shaped carbon nanotubes with diameters between 30 and 60 nm were obtained at the end of the runs.