Exfoliated graphite nano-platelets (xGnP) are new types of

nanoparticles A nanoparticle or ultrafine particle is usually defined as a particle of matter that is between 1 and 100 nanometres (nm) in diameter. The term is sometimes used for larger particles, up to 500 nm, or fibers and tubes that are less than 1 ...

made from

graphite Graphite () is a crystalline form of the element carbon. It consists of stacked layers of graphene. Graphite occurs naturally and is the most stable form of carbon under standard conditions. Synthetic and natural graphite are consumed on large ...

. These nanoparticles consist of small stacks of

graphene Graphene () is an allotrope of carbon consisting of a single layer of atoms arranged in a hexagonal lattice nanostructure.

that are 1 to 15 nanometers thick, with diameters ranging from sub-micrometre to 100 micrometres. The X-ray diffractogram of this material would resemble that of graphite, in that the 002 peak would still appear at ~26^o 2 theta. However, the peak would appear considerably smaller and broader. These features indicate that the interplanar distance in exfoliated graphite is similar to that of the parent graphite, but the stack size (of graphene layers) is small. Since xGnP is composed of the same material as

carbon nanotubes A scanning tunneling microscopy image of a single-walled carbon nanotube Rotating single-walled zigzag carbon nanotube A carbon nanotube (CNT) is a tube made of carbon with diameters typically measured in nanometers. ''Single-wall carbon nan ...

, it shares many of the electrochemical characteristics, although not the tensile strength. The platelet shape, however, offers xGnP edges that are easier to modify chemically for enhanced dispersion in polymers. Composite materials made with

polymers A polymer (; Greek '' poly-'', "many" + ''-mer'', "part") is a substance or material consisting of very large molecules called macromolecules, composed of many repeating subunits. Due to their broad spectrum of properties, both synthetic an ...

, like

plastics Plastics are a wide range of synthetic polymers, synthetic or semi-synthetic materials that use polymers as a main ingredient. Their Plasticity (physics), plasticity makes it possible for plastics to be Injection moulding, moulded, Extrusion, e ...

nylon Nylon is a generic designation for a family of synthetic polymers composed of polyamides ( repeating units linked by amide links).The polyamides may be aliphatic or semi-aromatic. Nylon is a silk-like thermoplastic, generally made from petro ...

, or

rubber Rubber, also called India rubber, latex, Amazonian rubber, ''caucho'', or ''caoutchouc'', as initially produced, consists of polymers of the organic compound isoprene, with minor impurities of other organic compounds. Thailand, Malaysia, and ...

, can be made electrically or thermally conductive with the addition of small amounts of xGnP. These nanoparticles can change the fundamental properties of plastics, enabling them to perform more like metals with metallic properties. These new nanoparticles also improve barrier properties, modulus, and surface toughness when used in composites.

Properties

Graphene Graphene () is an allotrope of carbon consisting of a single layer of atoms arranged in a hexagonal lattice nanostructure.

is extremely electrically conductive material. In turn, xGnP has a percolation threshold for conductivity of 1.9 wt% in thermoplastic matrix. At densities of 2–5 wt%, conductivity reaches sufficient levels to provide electromagnetic shielding. xGnP can also be combined with glass fibers or other matrix materials to provide sufficient conductivity for electrostatic painting or other applications requiring electrical conductivity. xGnP significantly outperforms most other forms of carbon in terms of thermal conductivity when used at densities of 20 wt% in control resins. At these densities, xGnP also confers significant electrical conductivity as well as improved mechanical properties to most thermoplastic, thermoset, or elastomeric systems. At lesser densities, xGnP adds thermal stability to a variety of matrix materials. As opposed to materials like

carbon black Carbon black (subtypes are acetylene black, channel black, furnace black, lamp black and thermal black) is a material produced by the incomplete combustion of coal and coal tar, vegetable matter, or petroleum products, including fuel oil, fluid ...

, xGnP improves mechanical properties of most composites, particularly stiffness and tensile strength. Elastomeric compounds have been shown to experience increased life and reduced surface wear when reinforced with xGnP. Because of the platelet shape, xGnP significantly improves the impermeability of composites when used at densities of ~3 wt% or greater. xGnP particles can be aligned using electric field, although alignment is not necessary for use in most extrusion systems. Because xGnP also imparts electrical conductivity at these densities, the resulting composites offer attractive cost savings for applications like fuel lines or fuel tank linings.

References

{{reflist Allotropes of carbon Refractory materials