Researchers Create Pure Hexagonal Diamond
Researchers in China have reported the creation of the first pure samples of hexagonal diamond, also known as lonsdaleite. This theorized variant of diamond is believed to be exceptionally strong and has previously been identified in meteorites originating from shattered dwarf planets.
Understanding Diamond Structures
Natural diamond, or cubic diamond, is known for its carbon atoms arranged in a cubic structure. Hexagonal diamond, in contrast, features carbon atoms organized in a hexagonal lattice, similar to a honeycomb.
A History of Hexagonal Diamond
The concept of hexagonal diamond was first theorized in 1962. Laboratory creation of lonsdaleite occurred in 1967, and it was subsequently detected in specific diamond-rich meteorites, such as the Canyon Diablo and Goalpara meteorites.
Initial detections in natural samples were subject to debate, with some scientists suggesting the evidence could indicate flawed cubic diamond. However, recent studies have continued to identify lonsdaleite in meteorites and in laboratory-produced samples.
Overcoming Challenges: Pure Samples and New Discoveries
The primary challenge in studying hexagonal diamond has been the absence of pure samples, which hindered the precise measurement of its properties. The new study, published in Nature on March 4, addresses this by successfully creating several pure hexagonal diamond samples, each approximately 0.06 inches (1.5 millimeters) in diameter.
The research team found that hexagonal diamond is both stiffer and harder than cubic diamond. Additionally, it exhibits significantly higher resistance to oxidation, allowing it to tolerate elevated temperatures without surface degradation, which is beneficial for applications such as drilling.
The new study successfully created pure hexagonal diamond samples, revealing it to be stiffer, harder, and significantly more oxidation-resistant than cubic diamond.
Production Method
To produce the samples, researchers compressed highly organized graphite for 10 hours at 20 gigapascals (approximately 200,000 times Earth's atmospheric pressure at sea level).
These conditions were combined with temperatures ranging from 2,300 to 3,450 degrees Fahrenheit (1,300 to 1,900 degrees Celsius). The study noted that at higher temperatures and pressures, the lonsdaleite began to transform into cubic diamond.
Potential Applications and Future Impact
Hexagonal diamond holds potential for enhancing existing tools and processes that rely on cubic diamond, including cutting and drilling tools, abrasive coatings for polishing, and heat dissipation in electronics.
Its presence in meteorites can also provide information regarding the formation and origin of these extraterrestrial objects, offering insights into the solar system.
Chong-Xin Shan, a co-lead physicist on the Nature study, highlighted its potential applications in fields such as cutting tools, thermal management, and quantum sensing. The study also presents a practical strategy for producing hexagonal diamond in bulk, which could facilitate further scientific exploration and industrial uses beyond the limitations of cubic diamond's hardness.