New Extremely Hard Carbon Nitride Compound Created

Materials scientists find compounds made from carbon and nitrogen particularly exciting because they can be superhard and very heat-resistant. Indeed, predictions suggest some carbon/nitrogen compounds could be harder than diamond. Such synthetic carbon nitrides could have a number of practical applications in materials machining and protective coatings; however, making them has proved elusive.

A team led by DCO scientist Alexander Goncharov (Carnegie Institution for Science, USA) has created a new extremely incompressible carbon nitride compound. They say it could represent a prototype for a whole new family of superhard materials, due to the unexpected ratio of carbon to nitrogen atoms. Their work is published in the journal Chemistry of Materials.

“It was long ago theorized that a certain structural form of carbon nitride composed of three carbons and four nitrogens would create the ultimate harder-than-diamond material, the Holy Grail of materials science,” Goncharov explained.

Goncharov and his team set out to synthesize a new ultra-incompressible form of carbon nitride using purely the component elements under intense pressure and high temperatures. They exposed the carbon-nitrogen mixture to more than 550,000 times normal atmospheric pressure and more than 6600 degrees Celsius. The resulting compound displayed a 1:1 ratio of carbon to nitrogen, rather than the long-sought-after 3:4 ratio. It satisfies all the conditions for superhardness, including a high number of bonds with very short distances between the component atoms.

“This work demonstrates that a good understanding of the laws of high pressure chemistry is crucial to discovering new chemical structures never seen under ambient conditions,” Goncharov said.

“We will see many more such novel materials with unusual compositions in near future,” stated co-author Elissaios Stavrou (Lawrence Livermore National Laboratory, USA).

The paper’s other authors are Sergey Lobanov (Carnegie Institution for Science, USA), Huafeng Dong and Artem Oganov (Stony Brook University, USA), Vitali Prakapenka (University of Chicago, USA), and Zuzana Konôpková (DESY Photon Science, Germany). 

Article adapted from source.

An illustration of chemical structures showing how elemental carbon and nitrogen under extreme pressures and temperature conditions (more than 550,000 times normal atmospheric pressure and heated to more than 12,000 degrees Fahrenheit) were synthesized into this new incompressible form of carbon nitride. Credit: Elissaios Stavrou.

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This work was supported by DARPA, the National Natural Science Foundation of China, the Deep Carbon Observatory, the Chinese Academy of Sciences, and the Ministry of Education and Science of the Russian Federation.

Part of the work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Security. GSECARS is supported by the U.S. NSF and DOE Geosciences. Use of the APS was supported by the DOE-BES.

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