Orientation Distribution of Vertically Aligned Multiwalled Carbon Nanotubes

Abstract

Carbon nanotube “forests” show great promise in a variety of applications, from supercapacitors to fuel cells, but the realization of such materials for functional devices relies on a better control over processing routes such that targeted structures and associated properties can be reproducibly obtained. The orientation distribution of the nanotubes is a critical structural property affecting both electrical and mechanical response, yet it remains a challenging characteristic to quantify. Small-angle X-ray scattering (SAXS) is a technique well suited to investigate the vertical alignment of nanotubes. Here we show that the orientation distribution obtained from SAXS is not satisfactorily represented by the normal distribution or the Lorentzian, which have been used until now. Instead, an excellent agreement between model and data is found with the generalized normal distribution (GND). Such quantification of the carbon nanotube alignment can be used as direct input in simulations for optimizing structure–property relations.