Florida State University Research Foundation (Tallahassee, FL) engineers have developed a method and machine for mechanically chopping carbon nanotube and nanoscale fibrous materials. The cutting is done using one or more conventional blades (e.g., diamond, ceramic, or metal) mechanically driven through a portion of a macroscale article of carbon nanotubes.
According to U.S. Patent 7,641,829, the method includes forming a macroscale article which include the nanoscale fibers, and then mechanically cutting the macroscale article into a finely divided form. In one embodiment, these steps are repeated. The nanoscale fibers may be carbon nanotubes, which optionally are aligned in the macroscale article. The macroscale article may be in the form of buckypapers or carbon fiber yarns.
According to inventors, Florida State Industrial and Manufacturing Engineering Professor Zhiyong Liang, Zhi Wang, Ben Wang and Chun Zhang, the macroscale article includes a solid matrix material in which the nanoscale fibers are contained or dispersed. The forming step can include making a suspension of nanoscale fibers dispersed in a liquid medium and then solidifying the liquid medium to form the macroscale article. After the mechanical cutting step, the medium can be dissolved or melted to enable separation of the chopped nanoscale fibers from the medium.
Nanotube materials chopped by Florida States apparatus can be widely used for development of nanotubes, nanofibers and other nanoscale fibrous-based materials and functional devices. Examples of applications include nanotube and nanofiber-reinforced composites, electrical conducting plastic and rubber materials, nanotube containers for drug delivery, and tips of atomic force microscopes. More particular examples include lightweight, exceptionally strong materials for aerospace structural and functional composites, lightning strike protection, EMI shielding, and directional thermal and electrical conducting applications in materials and devices.
FIG. 1 is a process flow diagram illustrating one embodiment of the process for mechanically chopping carbon nanotubes.
FIG. 2 is a plan view of an illustration of a pristine nanotube and a chopped nanotube, which has been mechanically cut near one end. The chopped tubes demonstrate good dispersion and interfacial bonding in SWNT/epoxy nanocomposites, which are critical properties in the development of both high performance structural and multifunctional composites using nanotubes.
In the chopping process, the source single wall carbon nanotube (SWNT) can be pristine, in which the carbon fullerene tube has fullerene end caps, or the source SWNT can be non-pristine, for example, where the SWNT has already been chemically or mechanically chopped and then optionally functionalized to convert dangling carbon atoms to carbonyl or other oxygen containing functional groups.
The methods can be applied to other nanoscale fibrous materials besides nanotubes, including carbon nanofibers and various nanoscale rods and fibrous materials, which generally have a diameter less than 500 nm. For instance, carbon nanofibers (CNFs) are filamentous fibers that resemble whiskers of multiple graphite sheets or MWNTs.
The methods can be applied to other nanoscale fibrous materials besides nanotubes, including carbon nanofibers and various nanoscale rods and fibrous materials, which generally have a diameter less than 500 nm. For instance, carbon nanofibers (CNFs) are filamentous fibers that resemble whiskers of multiple graphite sheets or MWNTs.
The macroscale article can be formed essentially entirely of the nanoscale fibers, e.g., as a continuous network of interwoven or entangled or glued nanoscale fibers, formed of a solid matrix material in which the nanoscale fibers are embedded, or a combination of the materials.
