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As of today, graphene, the thinnest one-atom-thick layer of carbon, is one of the most amazing materials. Measurements made in 2008 by researchers at Columbia University, proved that graphene was also the strongest and most elastic material among all known ones. However, the obtained data related to “ideal” graphene, which contains very few admixtures, its crystal structure being homogeneous. Apparently, defects in its structure should affect elastic properties and electronic features of the material.
Indeed, defects in structure have great impact on strength and electric properties of graphene. Researchers can learn to control the movement of these defects and, using them, “to sew together” carbon nanotubes or fullerenes. Such nanotubes or fullerenes connected to each other may be formed only owing to availability of defects, which possess sufficient mobility. Therefore, search for opportunities to connect such elements is the primary task in carbon electronics. For example, transistors running on nanotubes have already been created.
Researchers at the L.V. Kirensky Institute of Physics and Siberian Federal University carried out theoretical study of graphene structural defects influence on its elastic properties. The specialists considered vacancy as a defect. The word “vacancy” implies in this case disturbance of atomic arrangement periodicity in graphene structure. “Ideal” graphene is a highly-ordered structure, where each atom is “in its place”. If an atom is absent from the place assigned to it in the structure, then a defect is formed – a vacancy, a peculiar “blank space” in graphene crystal lattice.
To study elastic properties, the researchers determined the Young modulus. This coefficient characterizes the material’s ability to resist compression or extension: the higher Young modulus is, the stronger the material is. For reference: the Young modulus of aluminum is about 70 hPa, that of steel is 210 hPa, and that of “ideal” graphene is about 1,000 hPa! As a result of studies, the researchers came to the conclusion that the more defects in graphene structure are, the lower the Young modulus is. This dependence was expressed in strict inverse proportionality.
Besides this parameter, the researchers also assessed traverse speed of vacancies in graphene subject to direction the deformation is applied at. Obtained knowledge is extremely necessary to enable ordered motion of defects in graphene. It has turned out that traverse speed of vacancies changed significantly (both upward and downward) depending on whether the sample was compressed or extended.
Source of information:
A.S. Fedorov, D.A. Fedorov, Z.I. Popov, Yu.E. Ananieva, N.S. Eliseyeva, A.A. Kuzubov “Mobility of vacancies under deformation and their influence on elastic properties of graphene”. Experimental and Theoretical Physics Journal (Zhurnal Eksperimentalnoi i Teoreticheskoi Fiziki), 2011, Vol. 139, issue 5.
Azat Hadiev, published by STRF.ru