Plasma enhanced growth of carbon nanotubes with in-situ catalyst generation for multifunctional basalt fabrics

Hierarchical reinforcements offer the opportunity to produce high-performance composite materials with multifunctional properties. In this work, the growth of carbon nanotubes (CNTs) is achieved on basalt fabrics at low temperatures (400-600 °C) without the addition of any external catalyst by combining in-situ catalyst generation and plasma assistance. First, an alkaline etching pre-treatment is performed to promote the segregation of the native iron oxides of basalt to be exploited as catalysts upon thermal annealing in H2 atmosphere. Afterwards, a plasma-enhanced chemical vapour deposition (PE-CVD) technique is employed for the synthesis of CNTs at low temperatures to mitigate the well-known degradation of the fibre strength following high-temperature exposure in traditional thermal CVD. As a result, SEM investigation revealed an abundant growth of vertically aligned CNTs at 585 °C, with catalyst activation through H2-annealing pre-treatment at temperatures as low as 485 °C. At lower temperatures (440-500 °C), only short and sparse CNTs were obtained. Moreover, the CNT-modified basalt fabric, in combination with a conductive polymer, showed promising responses in the electrochemical characterization, opening for possible applications as electrochemical devices, such as energy harvesting devices, to be further investigated in future research.