It’s taken more than three decades, but scientists believe they have created a material that’s almost impossible to break and could rival diamond as the hardest substance on the planet.
An international team led by researchers from the Center for Science at Extreme Conditions at the University of Edinburgh have made a breakthrough, synthesizing carbon and nitrogen precursors to create carbon nitrides, which are tougher than cubic boron nitride – currently the second hardest material behind diamond.
"Upon the discovery of the first of these new carbon nitride materials, we were incredulous to have produced materials researchers have been dreaming of for the last three decades,” said Dominique Laniel from the University of Edinburgh. “These materials provide strong incentive to bridge the gap between high-pressure materials synthesis and industrial applications.”
While scientists recognized the potential of carbon nitrides back in the 1980s, including their high heat resistance, creating them was another story. In fact, no credible studies into their synthesis have been produced – until now.
“Carbon nitrides featuring three-dimensional frameworks of CN4 tetrahedra are one of the great aspirations of materials science,” the researchers noted in the study.
The team, which also included materials experts from the University of Bayreuth, Germany, and Linköping University, Sweden, achieved the feat by subjecting different forms of carbon nitrogen precursors to pressures of 70-135 gigapascals (or a million times our atmospheric pressure) while simultaneously heating them to more than 1,500 °C (2732 °F).
The atomic arrangement was then examined via X-ray beam at the European Synchrotron Research Facility in France, the Deutsches Elektronen-Synchrotron in Germany and the Advanced Photon Source in the US.
This analysis revealed that three of the synthesized carbon nitride compounds had structures required for the breakthrough super-hard material. The scientists were then pleasantly surprised to see that the trio of compounds retained their ultra-hard qualities when they cooled off and returned to ambient pressure.
The team believes this breakthrough paves the way for a multitude of uses, including protective coatings for vehicles and spacecraft, powerful cutting tools and photodetectors.
"These materials are not only outstanding in their multi-functionality but show that technologically relevant phases can be recovered from a synthesis pressure equivalent to the conditions found thousands of kilometers in the Earth's interior,” said Florian Trybel, assistant professor at Linköping University. “We strongly believe this collaborative research will open up new possibilities for the field.”
While yet unclear the extent of its capabilities, the incompressible carbon nitride compounds were also found to have photoluminescence, piezoelectric and high energy density, able to store a large amount of energy in a small amount of mass.
“Physical properties investigations show that these strongly covalently bonded materials, ultra-incompressible and super-hard, also possess high energy density, piezoelectric, and photoluminescence properties,” the researchers noted in the study. “The novel carbon nitrides are unique among high-pressure materials, as being produced above 100 GPa they are recoverable in air at ambient conditions.”
The research was published in the journal Advanced Materials.
Source: University of Edinburgh
