What is the difference between carbon fiber, carbon nanofiber, carbon nanotubes, and "buckyballs"?

Buckyballs, nanotubes, and nanofibers form a continuum of carbon nanomaterials. Buckyballs are single fullerene molecules of carbon, such as C60, C70, etc. Single wall nanotubes (SWNT) are effectively the cylindrical
version of buckyballs - a tube of carbon atoms with a diameter equal to that of a corresponding spherical buckyball (~1.2 nm), and which may have buckyball hemispheres as end caps. A nanotube may have additional concentric cylinders of carbon, in which case it is a multiwall nanotube
 (MWNT, typically ~3-10 nm). Some nanotubes are formed by a process that involves growth from a metal catalyst particle. In some cases, particularly smaller diameter nanotubes, the catalyst particle is thought to dance around
 the end of the nanotube, adding carbon atoms to the structure as it goes. In larger nanotubes, the catalyst particle remains static at the end of the tube, and adds to the entire rim of the cylinder at once, and a MWNT is usually formed. For smaller nanotubes, the allowed diameters are determined by the
 energetics of the curved carbon structure. For the larger nanotubes, the diameter is determined by the diameter of the catalyst particle (which sets the inner diameter of the core), the number of layers of catalytically grown carbon (which set the outer diameter of the core), and the amount of extra
 vapor deposited carbon that may form on them (which sets the final total diameter). These larger structures (~ 80 - 200 nm) are what we at ASI term nanofibers. Once a nanofiber is formed, it is possible to increase its diameter, through chemical vapor deposition, to the diameter of conventional carbon fibers (~ 5 -10 mms). ASI's Pyrograf®-III material is a nanofiber. The Pyrograf®-I material is a full size carbon fiber.

In terms of performance how does it differ from PAN and Pitch based fibers?

PAN and Pitch derived carbon fiber are most frequently used as a continuous reinforcement for structural applications. Carbon nanofibers have a much smaller diameter, and are discontinuous. Such reinforcements will initially be used in applications where milled or chopped carbon fiber is used today, or in applications where PAN or Pitch carbon fiber are not suitable for use. For example, chopped and milled PAN fibers are used as an electrical conductivity additive. Carbon nanofiber can provide equal electrical conductivity with only 20% of the loading needed to achieve a selected
conductivity in a polymer with milled PAN fiber. For other applications, such as providing conductivity or stiffness in rubber, conventional carbon fiber is typically not suitable because of its size.

How is Pyrograf® I produced?

Pyrograf I is produced by growing the carbon fibers on a solid substrate containing the catalyst at elevated temperatures.  Methane is used as the carbon source.  Carbon in the methane is used to grow the fiber; hydrogen gas is produced as a byproduct.  Once the fiber is grown, it is harvested for either sale or use in composites.

How is Pyrograf® III produced?

Pyrograf III is produced in the vapor phase by decomposing either methane, ethane, other aliphatic hydrocarbons, or coal gas in the presence of a metal catalyst, hydrogen sulfide and ammonia.  Once produced the fiber is debulked for either sale or additional processing.  The additional processing can include pyrolytic stripping to remove tars and other hydrocarbons from the surface of the fiber.  As required by customers the fibers can be heat treated at temperatures up to 3,000°C for use in their applications. 

In what forms can I buy Pyrograf®?

Pyrograf I is sold as a fiber, carbon pre-form or metal matrix composite.

Pyrograf III is sold as a raw fiber, in pellet form or blended in resin matrices.