Varied morphology carbon nanotubes

Abstract

The present invention describes the preparation of carbon nanotubes of varied morphology, catalyst materials for their synthesis. The present invention also describes reactor apparatus and methods of optimizing and controlling process parameters for the manufacture carbon nanotubes with pre-determined morphologies in relatively high purity and in high yields. In particular, the present invention provides methods for the preparation of non-aligned carbon nanotubes with controllable morphologies, catalyst materials and methods for their manufacture.

Description

RELATED APPLICATIONS[0001]This application is a divisional of U.S. application Ser. No. 10 / 151,382, filed May 20, 2002, which claims priority to U.S. Provisional Application Ser. No. 60 / 292,486, filed on May 21, 2001, and the entirety of these applications are hereby incorporated herein by reference for the teachings therein.STATEMENT AS TO FEDERALLY SPONSORED RESEARCH[0002]The present invention was made with partial support from The US Army Natick Soldier Systems Center (DAAD, Grant Number 16-00-C-9227), Department of Energy (Grant Number DE-FG02-00ER45805) and The National Science Foundation (Grant Number DMR-9996289)FIELD OF THE INVENTION[0003]The present invention relates generally to carbon nanotubes of varied morphology, catalyst materials for their synthesis, and apparatus and methods for controllably manufacturing carbon nanotubes with pre-determined morphologies. More particularly, the present invention concerns non-aligned carbon nanotubes with controllable morphologies, c...

AI Technical Summary

Benefits of technology

This approach enables the production of CNTs with controlled morphology and structure in high yields, making them suitable for applications in materials reinforcement, energy storage, and electronic devices, while reducing production costs and overcoming previous synthesis limitations.

Problems solved by technology

A major limitation to their large-scale commercialization however, has remained the need for large quantity, cost-effective production methods.

They however, require relatively expensive and complex reactor apparatus, and typically require a high vacuum (10−5 to 10−7 torr) environment.

Furthermore, such methods are only capable of providing a uniform flat surface layer of the metal catalyst on the substrate on which CNT formation and growth can occur.

Since CNT yield is directly related to surface area of the catalytic surface, substantially large areas of metal coated substrate is required to synthesize large quantities of CNTs, which is impractical in terms of existing limitations of the reaction apparatus.

According to Li et al., preparation of such large area catalytic substrate is hampered by the inherent tendency to shrink, crack and shatter during their preparation.

Imperfect catalyst preparation can severely limit yields of CNT product.

Also, CNT synthesis by the process of Li et al. requires a reaction temperature of 700° C., which is impractical for substrates such as flat panel glass.

Such methods however, require high vacuum conditions, which is difficult to achieve in large reactors in a commercially viable CNT manufacturing processes.

Although such methods are capable of providing highly pure, aligned CNTs, they are not best suited for large-scale production due to low volume (typically several milligrams to grams per batch), low yields based on amount of catalyst and high manufacturing cost.

Furthermore, existing methods do not allow control of nanotube morphology, tubule diameter, tubule wall thickness and other structural elements that are important in achieving desired material properties that may required for specific applications.

Such drawbacks are limiting factors that restrict the widespread use of CNTs in potential applications.

Although it is theoretically possible to introduce a wide range of structural defects with useful electronic properties in CNTs, synthetic limitations have precluded such introduction of systematic structural defects.

Furthermore, currently available methods do not allow controlled alteration of linear tubule structures during their growth.

Post growth modifications of CNTs have been difficult to implement and are prone to uncontrolled and random defects.

The branched Y-shaped CNTs obtained by the method however, are not symmetrical with respect to arm length, straightness and angles between arms, since their shape and symmetry is determined by limitations in fabrication of the aluminum mold in which they are formed.

Such processes are also not suited for large scale manufacture of CNTs and are, therefore, not economically viable for use in a commercial process.

Images