Comparative Study of Carbon Nanotubes and Carbon Nanofibers

By AZoNano Editors

Table of Contents

Introduction

Carbon nanotubes (CNT) and carbon nanofibers (carbon nanofibers) (also known as stacked-cup carbon nanotubes) share many similarities. They are produced using the same techniques, are both hollow and their sizes are at the nanoscale level. When it comes to differences, their size, morphology, processing techniques and prices vary from each other. In the subsequent sections, these differences will be discussed in more detail.

Comparison of carbon nanofiberss and CNTs

As mentioned above, carbon nanofibers and CNTs differ mainly in their morphology, processing method, price and size. Let us now deal with each of the points individually.

Morphology

Carbon nanofibers have a unique structure called stacked-cup carbon nanotubes (CSCNT). The graphene plane surface is canted from the fiber axis, which exposes the plane edges present on the interior and exterior surfaces of the carbon nanofibers. CNTs have a structure that appears like concentric cylinders. Figure 1 depicts the differences pictorially by comparing multi-walled carbon nanotubes and stacked-cup carbon nanotubes.

Figure 1. A) Multi-wall CNTs are composed of concentric cylinders of graphene where the basal planes form an inert surface. B) The stacked-cup structure of carbon nanofibers has exposed graphitic edge planes along its length, providing opportunities for chemical modification of the surface for covalent bonding directly with the matrix.

Size

The diameter of the fibers of CNT ranges from 1 to 30 nm. On the other hand. carbon nanofibers come with diameters of 50 to 200 nm; the diameter depends on the type of the carbon fiber. CNTs and carbon nanofibers can be several hundred micrometers in length. The length is determined by the production method and the feedstock.

Processing Methods

CNTs experience a greater magnitude of Van der Waals forces due to their smaller size, while these forces are less in carbon nanofibers. Due to this difference in forces, CNTs need the intervention of chemical dispersants or functionalization techniques to help and maintain dispersion. However, stacked-cup nanofobers are able to stay in the dispersed manner for a longer time and do not require costly processing methods. The cost of processing carbon nanofibers is much lesser when compared to CNTs.

The graphene edges are exposed in carbon nanofibers and hence this structure can be easily changed to enable chemical bonding with any matrix through chemical functionalization or thermal treatment methods. CNTs on the other hand require complex processing methods that involve creation of defect sites along the fiber’s side walls and then bonding with functional groups.

Pricing

Carbon nanofibers are generally priced much lower than CNTs. Carbon nanofibers are available in bulk volumes that are priced in the range of 100 to 500 dollars per pound. On the other hand, the prices of CNTs vary with their quality and purity. The lower price range is around 100 dollars per pound and for high-quality CNTs the price can go upto 750 dollars per gram or even more sometimes. As mentioned in the above paragraph, CNTs require complex processing techniques for functionalization, which increases their cost.

About Pyrograf

Pyrograf Products, Inc. (PPI) is one of the leading producers of carbon nanofibers worldwide

Pyrograf Products focuses on manufacturing high- quality, low-cost carbon nanofibers utilizing the proprietary and patented vapor grown carbon fiber (VGCF) process. Pyrograf-III, developed Applied Sciences, Inc. (ASI), is a versatile vapor grown carbon nanofiber with a wide range of applications.

This information has been sourced, reviewed and adapted from materials provided by Pyrograf.

For more information on this source, please visit Pyrograf.