Groundbreaking Discovery: Harder Than Diamond Material Created by Chinese Physicists
China's scientific community is celebrating a major breakthrough: the creation of a variant of diamond, known as hexagonal diamond, that is even harder than the naturally occurring cubic diamond. This feat has been regarded as a first in the world of physics. Diamonds, due to their incredible hardness, have always been placed at the top of the Mohs hardness scale, which measures a mineral's resistance to being scratched.
The standard diamond is called a cubic diamond because of the arrangement of its carbon atoms, which form a cubic structure. On the other hand, the hexagonal diamond has a different structure, where carbon atoms are arranged in a honeycomb pattern, forming a hexagonal lattice.
The Mysterious Mineral
In the early 1960s, scientists speculated that the carbon atoms in diamonds could be arranged in a hexagonal pattern, instead of the usual cubic pattern. This theory was based on the unique way carbon atoms bond with each other. By the late 1960s, hexagonal diamond, or lonsdaleite, was created in a laboratory setting. It was believed to be even harder than the cubic diamond.
Scientists began to search for natural examples of hexagonal diamonds within specific meteorites, known as ureilites. These meteorites originate from the mantle of destroyed dwarf planets. The first recorded detection of hexagonal diamonds in nature was in 1967, in fragments of meteorites found in Arizona and Assam, India. These fragments contained a combination of both hexagonal and cubic diamond structures.
However, the existence of these natural hexagonal diamonds, known as Canyon Diablo lonsdaleite, has been a subject of debate among scientists. Some believe that the supposed hexagonal diamond could simply be flawed cubic diamonds with chaotic layering. Despite this skepticism, several recent studies have successfully identified lonsdaleite within meteorites and lab samples.
The Challenge of Identifying Lonsdaleite
One of the biggest hurdles in studying lonsdaleite is the lack of pure samples. Most often, it is found mixed with cubic diamond, graphite, and other minerals. This mixture makes it incredibly difficult to test and measure the unique properties of lonsdaleite.
A recent study has made significant progress by creating several pure hexagonal diamond samples. These samples were large enough to measure the material properties. The study found that hexagonal diamond is not only stiffer but also harder than cubic diamond. Additionally, it resists oxidation much more than its cubic counterpart. This resistance to oxidation means that the hexagonal diamond can withstand high temperatures without reacting with oxygen. This property is crucial for high-temperature applications like drilling.
Is Hexagonal Diamond Real?
The recent study offered substantial evidence supporting the existence of hexagonal diamond as a distinct material. Through a series of structural and spectroscopic analyses, along with large-scale molecular dynamical simulations, the study confirmed the identity of hexagonal diamond.
To create the hexagonal diamond samples, the scientists compressed highly organized graphite for 10 hours at a pressure about 200,000 times that of Earth's atmospheric pressure at sea level. They also exposed the graphite to temperatures between 2,300 and 3,450 degrees Fahrenheit. At these extreme conditions, the hexagonal diamond began to transform into cubic diamond.
The Potential of Hexagonal Diamond
The potential applications of hexagonal diamond are boundless. It could enhance the performance of tools and processes that currently rely on cubic diamond, such as drilling and cutting tools, polishing abrasive coatings, and heat dissipation from electronics. The presence of hexagonal diamond in meteorites can provide valuable insights into the formation and origin of these celestial bodies, contributing to our understanding of our solar system.
The recent study also presents a practical method for producing hexagonal diamond in large quantities. This discovery paves the way for larger samples, further scientific exploration, and industrial applications that are not limited by the hardness of cubic diamond.