Sodium-Catalyzed Growth Of Carbon Nanotubes For Interlaminar Reinforcement Of Unidirectional Hierarchical Laminates

摘要

A new catalyst for the growth of carbon nanotubes (CNTs) is identified and demonstrated on aerospace grade carbon fibers to produce hierarchical aerospace composites with the potential for mechanical and multifunctional improvements without degrading fiber strengths. As an element in a region of the periodic table not previously identified to catalyze CNT growth, sodium was recently found to grow CNTs on carbon (micro) fibers (CFs) at temperatures as low as 390 °C using a wide range of sodium-containing precursor compounds. Sodium hydroxide, sodium carbonate, sodium bicarbonate, and sodium chloride were all found to yield successful and similar growth on both sized and desized carbon fiber fabrics. Unlike traditional transition metal catalysts, sodium results in conformal CNT growths without clear and encapsulated catalyst particles when observed through transmission electron microscopy (TEM). Scanning electron microscopy (SEM) studies with energy dispersive x-ray spectroscopy (EDS) was used to confirm the identity of the catalyst particles formed on the surface of carbon fibers prior to growth. TEM analyses reveal a hollow CNT structure that is similar across all attempted Na-based compounds, and supports the role of Na in catalyzing CNT growth. Moreover, the growth process was transitioned to an environmental TEM (ETEM) environment for in situ studies to confirm the catalyst identity. Leveraging the recent developments in CNT synthesis and composites manufacturing from unidirectional (UD) carbon fabrics that result in increased CNT fill-fraction, facile and direct CNT growth is demonstrated on UD fabrics to enable the fabrication of UD CNT-reinforced "fuzzy" CFRPs that can be characterized for interlaminar reinforcement.