Scientists have developed a groundbreaking technique to synthesize diamonds at normal atmospheric pressure without the need for a starter gem. This innovation could simplify the process of growing diamonds in laboratories.
Typically, natural diamonds form deep within Earth’s mantle under extreme pressures and temperatures. The conventional method for creating artificial diamonds, known as high-pressure and high-temperature (HPHT) growth, mimics these conditions. It involves high pressures and temperatures to convert carbon in liquid metals like iron into diamonds around a small seed diamond.
However, HPHT is challenging due to the difficulty in maintaining the necessary extreme conditions. Additionally, the method limits the size of the diamonds produced, with the largest being about the size of a blueberry. The process also takes one to two weeks to produce small gems. Another method, chemical vapor deposition (CVD), reduces some of HPHT’s requirements but still needs seed diamonds.
The new technique, developed by Rodney Ruoff and his team at the Institute for Basic Science in South Korea, overcomes several limitations of both HPHT and CVD methods. Their findings were published on April 24 in the journal Nature.
Ruoff explained that he had been exploring new ways to grow diamonds for over a decade. The researchers used electrically heated gallium with a bit of silicon in a graphite crucible. This setup was chosen because previous studies showed gallium could catalyze the formation of graphene from methane. Graphene, like diamond, is pure carbon, but arranged differently.
The team used a custom-built chamber to house the crucible at sea-level atmospheric pressure, through which they flushed superhot, carbon-rich methane gas. This chamber, designed by co-author Won Kyung Seong, allowed rapid experimentation with different concentrations of metals and gases.
The optimal mixture for catalyzing diamond growth was found to be gallium-nickel-iron with a pinch of silicon. With this blend, the researchers produced diamonds from the crucible’s base in just 15 minutes, forming a more complete diamond film within two and a half hours. Spectroscopic analyses confirmed the film was mostly pure with minimal silicon contamination.
While the exact mechanism remains unclear, the researchers believe a temperature drop drives carbon from the methane to the crucible’s center, where it forms diamonds. Silicon appears to act as a seed for crystallization, as no diamonds form without it.
Despite the success, the new method faces challenges. The diamonds produced are extremely small, much smaller than those created with HPHT, making them unsuitable for jewelry. Potential uses for these tiny diamonds in technology, such as polishing and drilling, are still uncertain. However, Ruoff noted that the low-pressure process might significantly scale up diamond synthesis.
“In about a year or two, the world might have a clearer picture of things like possible commercial impact,” he said.