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Graphene

Nanoscale Graphene Platelets – a New Class of Nanomaterials

| Author / Editor: Ron Beech * / Johann Wiesböck

"Bird's nest": Unlike graphene, Carbon Nanotubes (CNTs) can easily entangle in one another.
"Bird's nest": Unlike graphene, Carbon Nanotubes (CNTs) can easily entangle in one another. (Bild: Angstron Materials Inc.)

Graphene is making the transition from research journals to commercial applications. This article discusses a new class of nano- material and their commercialization in wide ranging applications.

Graphene’s popularity with researchers has risen dramatically. In 2000, the number of scientific papers that
included graphene as a topic was less than 100 [1]. That number has risen to more than 9,000 articles in 2013 [2]. Further sparking worldwide interests in using graphene in commercial applications was the awarding of the 2010 Nobel Prize in Physics to Andre Geim and Konstantin Novoselov "for
groundbreaking experiments regarding the two-dimensional material graphene.” [3].

Graphene is particularly commercially
valuable because it has exceptional
electrical, mechanical, thermal, optical, and barrier properties suited to applications in a broad range of industries ranging from
aerospace, automotive, composites, energy, marine and electronics to construction,
biomedical and telecommunications [4]. In the last decade, fundamental research has prompted corporations to work with
graphene manufactures to provide practical modifications to existing products and
create new products capable of capturing the performance advantages of this material.

The basics of graphene and its two-dimensional properties

Ideal graphene is a composed of a single atom thick sheet of carbon atoms. Well-known forms of carbon include graphite and diamond. Graphene’s properties are the
result of carbon atoms occupying a two-
dimensional hexagonal lattice. These carbon atoms are bonded together through strong covalent bonds at an atomic level and
resemble a chicken wire lattice. While there are many potential commercial applications for the graphene materials, some of the key properties useful in real-world applications are illustrated in the image on the right.

Comparing graphene to other nanomaterials

Both carbon nanotubes (CNT) and carbon nanofiber (CNF) are effective materials for exciting applications. CNTs and graphene share similarities like low density, a low
percolation threshold for electrical
conduction, and high purity. However, as recently demonstrated by Mohammad Rafiee and colleagues, graphene outperforms CNT when measuring mechanical properties in an epoxy [5].

These properties included Young’s modulus, ultimate tensile strength, fracture toughness, fractured energy, and the
resistance to fatigue crack propagation [6]. Rafiee et al. concluded that the high specific surface area, enhanced matrix adhesion
arising from the wrinkled surface of
graphene and the twodimensional geometry of the material contributed to the results [7].

Beyond the science of graphene is the practical ability of manufacturers to process a nonmaterial into a manufactured product. Unlike graphene, CNTs are long and thin and can easily entangle with one another to form a “birds nest” structure in applications. The loading of these nano-fillers dramatically increases the viscosity of a matrix.

In contrast, graphene is a twodimensional platelet that has the capability to slide over one another, allowing for higher loading and lower viscosities. In some applications, the properties of both CNT and graphene are
optimized by combining both materials. The graphene acts as a lubricant and bridge
between the CNTs and the matrix. Angstron Materials’s chief technical officer, Dr. Aruna Zhamu noted that manufacturers familiar with CNTs have found the transition to
graphene to be straightforward.

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