In a pre-print research article, scientists, mostly from China but also from the U.S., Sweden, Germany, and Russia, detailed what they called an “ultrahard, ultrastrong, semiconducting” synthetic carbon.
The team say the material, known as an amorphous material (AM) referred to as “glassy,” is the hardest of its type yet discovered.
A pre-print of the article was made available online in November 2020, and it was published in the National Science Review journal on Thursday, August 5.
The researchers created the material by crushing a carbon molecule known as buckminsterfullerene, or C60, at high pressures and exposing it to very high temperatures.
Samples of C60 were taken and put under a pressure of 25 gigapascals, or GPa. This is equal to more than 246,000 times more pressure than standard atmospheric pressure. Then, the samples were heated to well over 1,000 degrees Celsius.
At temperature milestones of 1,000, 1,100, and 1,200, three different categories of material were created, termed AM-I, AM-II, and AM-III.
This third material, AM-III, had the highest hardness of around 113 GPa, measured using the Vickers hardness method. The scientists said that a plane of natural single crystaline diamond has a hardness of around 62 GPa by comparison, “thus hardness of the synthesized amorphous carbons can rival that of diamond.”
The pre-print article states: “Such extreme hardness allows the AM-III sample scratch [sic] the face of synthetic diamond crystal with Vickers hardness of 103 GPa.
“The emergence of this type of ultrahard, ultrastrong, semiconducting AM carbon material offers excellent candidates to most demanding practical applications and calls-up for further experimental and theoretical exploration of the AM carbon allotropes.”
It’s important to note that not all diamond types have the same hardness, so while AM-III may be harder than some samples, it is not necessarily harder than other types.
It is unclear exactly what sort of applications the material could be used in, but the pre-print research article states it may be useful in electronics that must withstand tough environments.
Creating super-hard materials is nothing new, and materials harder than diamond have been synthesized before. But creating hard materials that also display other useful properties such as conductivity is more difficult.
For example, lonsdaleite, also called hexagonal diamond, is another carbon-based material that has been measured to be stronger than diamond in lab tests.
However, the material was only synthesized for a few nanoseconds and was created by smashing pieces of graphite together at 15,000 miles per hour.
