Nanoscale Graphene Platelets – a New Class of Nanomaterials

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History of Graphene and the Scotch-tape cleavage

Graphene is a relatively new material. In the 1930’s, physicists believed that a two-dimensional plane was not stable enough to exist independently [8]. Microscopy
observation of atomically thin graphitic
fragments (possibly even monolayers of
graphite oxide) was cited as early as 1962 [9] with graphitic epitaxial growth reported in 1975 [10]. Dr. R. S. Ruoff and his research group reported thin sections of highly
ordered pyrolytic graphite plates (HOPG) and promised that future work would include trying to obtain single-layer graphene [11].

To grasp the full history of graphene,
understanding activities surrounding the material outside the scientific literature is essential. Dr. Bor Z. Jang, co-founder of
Angstron Materials, Inc., isolated single-layer and multi-layer graphene structures from partially graphitized polymeric
carbons. This class of nano-material is now commonly referred to as nano graphene
platelets (NGP). In 2002, Jang submitted the world's first patent application on single-layer graphene, which was also the first
patent in the world for graphene reinforced metal-, glass-, carbon-, and ceramic-matrix composites and single layer graphene-
reinforced polymer composites.

In October 2004, Andre Geim and Kostya Novoselov, both at Manchester University, published a paper in Science that led to them being awarded a Nobel Prize in 2010 [12]. Geim and Novoselov isolated graphene using “Scotch tape” and observed the significant electron mobility of the carbon lattice [13]. Since 2004, Geim and Novoselov, along with thousands of other researchers, have helped unravel the mysteries of graphene.
Furthermore, researchers with corporations around the world have filed hundreds of
patents and are seeking to commercialize graphene-enhanced products.

Various Methods to Obtain Graphene

In 2004, Geim and Novoselov obtained graphene by using tape to repeatedly peel off graphene sheets from graphite crystals [14]. Researchers have also explored epitaxial growth on silicon carbide by heating silicon carbide (SiC) to high temperatures to reduce it to graphene. Additionally, researchers
have grown graphene from metal-carbon melts through a process that dissolves carbon atoms inside a transition metal melt allowing the dissolved carbon to precipitate out at lower temperatures as single layer graphene.

Researchers have also produced gram quantities of graphene by the reduction of ethanol by sodium metal followed by
pyrolysis of the ethoxide product and
washing with water to remove sodium salts. While these methods do produce graphene, they are also expensive and are not practical for large scale production.

Jang and his team focused on the
properties of graphite and found it was less expensive to take natural graphite and peel it off billion of layers at a time. “By physically inserting chemicals such as nitric acid in between layers of graphite you can peel away countless layers,” says Jang. The exfoliation process is an economically viable approach that results in graphene being available in large quantities and at competitive prices. Since its founding, Angstron has worked to scale-up the production process of the raw materials and has recently achieved a
capacity of approximately 300 metric
tons per year.

Graphene is also now available to
manufacturers in a variety of forms,
including powders, nano-intermediates (pre-dispersions and masterbatches), and enhanced nanocomposites. Platelets can also be mixed with other nano materials, such as CNFs, CNTs, and nano clay platelets, to produce hybrid materials.

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