Graphene sheets exfoliated

One synthesis approach that does not rely on CNT formation from the gas phase is molten salt synthesis. The reactor consists of a vertically oriented quartz tube that contains two graphite electrodes (i.e. anode is also the crucible) and is filled with ionic salts (e.g. LiCl or LiBr). An external furnace keeps the temperature at around 600 °C, which leads to the melting of the salt. Upon applying an electric field the ions penetrate and exfoliate the graphite cathode, producing graphene-type sheets that wrap up into CNTs on the cathode surface. Subsequently, the reactor is allowed to cool down, washed with water, and nanocarbon materials are extracted with toluene [83]. This process typically yields 20-30 % MWCNTs of low purity. 

Graphene, exfoliated single sheets of atoms with sp bonds... 

The relatively low cost of graphite in comparison to CNTs makes exfoliated graphite an attractive material (20). The use of graphite nanoplatelets is advantageous because of the chemistry of the graphene and graphene-Uke sheets compared to clay nanoplates. 

Choi E-K, Jeon I-Y, Bae S-Y, Lee H-J, Shin HS, Dai L, Back J-B (2010) High-yield exfoliation of three-dimensional graphite into two-dimensional graphene-Uke sheets. Chem Commun 46(34) 6320-6322... 

Loryuenyong V, Totepvimarn K, Eimburanapravat P, Boonchompoo W, Buasri A. Preparation and characterization of reduced graphene oxide sheets via water-based exfoliation and reduction methods. Adv Mater Sci Eng 2013 2013(923403) l-5. 

H. Wang, J.T. Robinson, X. Li, H. Dai, Solvothermal reduction of chemically exfoliated graphene sheets, Journal of the American Chemical Society, 131 (2009) 9910-9911. 

This technique involves the dispersion of a nanomaterial in a monomer (Fig. 4.8). This step requires a certain amount of time that depends on the polarity of the monomer molecules, the surface treatment of the nanomaterial, and the swelling temperature. For thermoplastics, the polymerization can be initiated either by the addition of an agent or by an increase in temperature. For thermosets such as epoxies or unsaturated polyesters, a curing agent or peroxide can be added in order to initiate the polymerization. Functionalized nanomaterials can improve their initial dispersion in the monomer and consequently in the composites. In the case of layered materials, such as clays or graphene, the most important step is the penetration of the monomer between the sheets, thus allowing the polymer chains to exfoliate the material. The... 

It often becomes necessary to prepare dispersions of graphene in organic or aqueous media [73-74]. For this purpose, different approaches have been successfully employed for few-layer graphene. The two main approaches for obtaining this type of graphene are covalent functionalization or by means of noncovalent interactions. There has been some recent effort to carry out covalent and noncovalent functionalization of graphene with aromatic molecules, which help to exfoliate and stabilize the individual graphene sheets and to modify their electronic properties [75 84]. 

Actually, in our work, it can be imagined PVDF chains which are trapped between graphen sheets and are in close contact with PMMA chains, crystallize in the confined spaces that are provided by graphen sheets and PMMA chains. It is demonstrated that exfoliated graphene-based materials are often compliant, and when dispersed in a polymer matrix are typically not observed as rigid disks, but rather as bent or crumpled platelets 0. R. Potts, 2011). Consequently, as can be seen in TEM image of 70 30 sample (Fig. 7), the wrinkled surface of... 

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