Russian scientists create ultrahard ‘Fullerite’ material at room temperature and lower pressure

"Ultrahard" materials are harder than diamond
September 22, 2014

Photo of a Vickers indenter made of ultrahard fullerite (credit: Mikhai lPopov)

A method for synthesis of an ultrahard material called Fullerite (exceeding diamond in hardness) at room temperature and lower pressure has been developed by Russian researchers from the Technological Institute for Superhard and Novel Carbon Materials in Troitsk, Moscow Institute of Physics and Technology (MIPT), MISiS, and MSU.

The research is described in a recently published paper in the journal Carbon.

Fullerite is a polymer composed of fullerenes, or spherical molecules made of carbon atoms. It has become first on the list of ultra hard materials (harder than diamond),  with values that range from 150 to 300 GPa.

Diamond anvils malformed during synthesis of ultrahard fullerite. Note the dent in the center. (Credit: MIPT)

Creating an ultrahard material

What makes synthesizing fullerite in large quantities so difficult is the high pressure required for the reaction to begin. Formation of the three-dimensional polymer begins at a pressure of 13 GPa, or 130,000 atm (atmospheres). But modern equipment cannot provide such pressure on a large scale.

The scientists in the current study have shown that adding carbon disulfide (CS2) to the initial mixture of reagents can accelerate fullerite synthesis, even if the pressure is only 8GPa. In addition, while previous efforts to synthesize fullerite at a pressure of 13 GPa required heating up to 1100K (more than 820 degrees Celsius), in the new research, it occurs at room temperature.

“The discovery will create a new research area in materials science because it substantially reduces the pressure required for synthesis and allows for manufacturing the material and its derivatives on an industrial scale,” explained Mikhail Popov, lead author of the research paper and head of the laboratory of functional nanomaterials at FSBI TISNCM.

Abstract of Carbon paper

3D polymerization of C60 realizes under conditions of large plastic deformation at pressure 6–7 GPa and room temperature in the presence of CS2. The phase of 3D-polymerized C60 is identical to ultrahard fullerite synthesized from pure C60 at 18 GPa pressure: in both cases, the samples plough diamond during the rotation of the sample in a shear diamond anvil cell, bulk module is 585 GPa, and a sequence of phase transitions preceding to ultrahard phase is also the same in both cases (in the presence of CS2, the phase transitions take place at lower pressures than in pure C60). Raman and transmission microscope studies confirm the structure equivalence of samples of both types. The absence of sulfur in the structure of ultrahard fullerite synthesized in the presence of CS2 proves the catalysis role of CS2 in the 3D polymerization of C60.