and Applications of Fullerenes, Carbon Dots, Nanotubes, Graphene, Nanodiamonds, and Combined Superstructures Vasilios Georgakilas,† Jason A. Perman,‡ Jiri Tucek,‡ and Radek Zboril*,‡ †Material Science Department, University of Patras, 26504 Rio Patras, Greece ‡Regional Centre of Advanced Technologies and Materials, Department of Physical Chemistry, Faculty of Science, Palacky University in Olomouc, 17 listopadu 1192/12, 771 46 Olomouc, Czech Republic

Broad family of carbon nanoallotropes: classification, chemistry, and applications of fullerenes, carbon dots, nanotubes, graphene, nanodiamonds, and combined superstructures.

▪ Abstract The synthesis of the two currently used superhard materials, diamond and cubic boron nitride, is briefly described with indications of the factors influencing the quality of the crystals obtained. The physics of hardness is discussed and the importance of covalent bonding and fixed atomic positions in the crystal structure, which determine high hardness values, is outlined. The materials investigated to date are described and new potentially superhard materials are presented. No material that is thermodynamically stable under ambient conditions and composed of light (small) atoms will have a hardness greater than that of diamond. Materials with hardness values similar to that of cubic boron nitride (cBN) can be obtained. However, increasing the capabilities of the high-pressure devices could lead to the production of better quality cBN compacts without binders.

Synthesis and Design of Superhard Materials

High-pressure torsion (HPT) method currently receives much attention as a severe plastic deformation (SPD) technique mainly because of the reports of Prof. Ruslan Z. Valiev and his co-workers in 1988. They reported the efficiency of the method in creating ultrafine-grained (UFG) structures with predominantly high-angle grain boundaries, which started the new age of nanoSPD materials with novel properties. The HPT method was first introduced by Prof. Percy W. Bridgman in 1935. Bridgman pioneered application of high torsional shearing stress combined with high hydrostatic pressure to many different kinds of materials such as pure elements, metallic materials, glasses, geological materials (rocks and minerals), biological materials, polymers and many different kinds of organic and inorganic compounds. This paper reviews the findings of Bridgman and his successors from 1935 to 1988 using the HPT method and summarizes their historical importance in recent advancement of materials, properties, phase transformations and HPT machine designs.

A review on high-pressure torsion (HPT) from 1935 to 1988

Analysis of correlations between various physical properties of solids provides a formulation of simple criteria applicable to the search for new superhard materials. The prospects for the synthesis of new substances with the key elastic moduli, whose values approach or even exceed those of diamond are also discussed. We introduce the concept of ideal hardness and strength, which relates the elastic properties of materials to the corresponding mechanical characteristics, the concepts that are less unambiguously determined and that depend on the conditions of measurements. The control of material nanostructure makes it possible to approach the ideal hardness. The formulation of trends interrelating physical properties is expected to allow an essential guidance in the synthesis of new classes of superhard materials.

Harder than diamond: Dreams and reality

Fullerene polymers: synthesis and properties.

Ultrahard and superhard carbon phases produced from C60 by heating at high pressure: structural and Raman studies

Is C60 fullerite harder than diamond

http://www.tisnum.ru/research-departments/tg_pdf/reference/1.pdf

Phase transformations in solid C60 at high-pressure-high-temperature treatment and the structure of 3D polymerized fullerites

in the pressure range 
\rangeunit{8}{13}{GPa}
 and the temperature range 
\rangeunit{600}{2100}{K}
 were studied These properties are the specific gravity, specific heat in the range 
\rangeunit{400}{600}{K}
 , sound velocities, elastic moduli, electrical properties, resistance to uniaxial stress and stability against oxidation These properties are different from those of diamond and other carbon forms The hardness of ultrahard fullerites exceed the hardness of diamond The structures of the samples are described on the basis of X-ray data

S.G. Buga

Papers

Ultrahard and superhard carbon phases produced from C60 by heating at high pressure: structural and Raman studies

Is C60 fullerite harder than diamond

Phase transformations in solid C60 at high-pressure-high-temperature treatment and the structure of 3D polymerized fullerites

Physical properties of superhard and ultrahard fullerites created from solid C60 by high-pressure-high-temperature treatment

Hard disordered phases produced at high-pressure–high-temperature treatment of C60