Not just another pretty rock, diamonds are a scientist's best friend - for studying outer planets

Diamonds are a scientist's best friend, at least for studying atmospheric pressure on the outer planets, like Pluto.

Oak Ridge National Laboratory scientists have teamed up with Maryland-based WD Lab Grown Diamonds to test atmospheric pressure in Oak Ridge.

Setting a new scientific record

ORNL researchers set a new scientific record when one of the company's 6 mm lab-grown diamonds withstood about 600,000 atmospheres of pressure during a study on how light elements like water and ice react under extreme pressure on other planets.

"Outer planets like Pluto and Neptune are mainly water and ice at very high pressures, so we try to understand the properties of these planets, like magnetism, said ORNL senior scientist Reinhard Boehler.

Boehler's background is in geophysics, which means he uses pressure to simulate the interiors of planets.

"We take matter that we think is down there at a very high pressure and study the properties," Boehler said. He spent a decade studying the melting behavior at very high pressures of iron, which makes up much of the earth's core.

"From those measurements, you can derive the temperature of the earth's center," Boehler said.

He is studying outer planets because of their magnetic fields. "They must generate pressure on water and water becomes metallic."

He uses neutrons to probe the crystals of metallic ices from water and heavy water to probe the ice crystals and see their atomic structure.

To do that, he needs to be able to simulate those high pressures.

That's where the diamonds come in.

Twice the pressure of the earth's core

"They can generate pressures of around six megabars, twice the pressure of the center of the earth," Boehler said."Diamonds are by far the hardest material and diamonds are transparent through a lot of radiation: neutrons, X-Rays, even infrared."

To do the experiments, ORNL scientists sandwich other materials between the flat sides of diamond anvils that are as many as 10 carats in weight. They use a pocket-sized device shaped like an hourglass frame to put extreme pressure behind the anvils.

Despite their hardness, the extreme experiments can still prove too much for one of nature's hardest elements.

Boehler said he has actually broken a diamond before in a pressure experiment.

"That hurt," he laughed. "It makes a lot of noise. If you put 10 tons of pressure on it and it breaks, it collapses into dust and makes a noise like a rifle shot."

Aaron West, WD Lab Grown Diamonds spokesman, said such experiments are only possible with lab-grown diamonds that can withstand greater pressure than natural ones.

Now they use smaller, single-crystal, lab-grown diamonds for experiments done in a specialized beam line at the laboratory's Spallation Neutron Source.

“Our company is proud to be growing these diamonds to help researchers break scientific barriers," said Yarden Tsach, chief technology officer for WD Lab Grown Diamonds. "We see great promise in both our gemstone markets as well as in the high pressure and scientific fields."

One of the latest experiments set a new record when a diamond withstood about 600,000 atmospheres of pressure.

"In order to go to say a million atmospheres, we need about 20 tons of force," Boehler said. At that pressure, steel would flow like peanut butter.

Peanut butter to diamonds to new materials

Speaking of peanut butter, scientists can turn almost any carbon-containing material into more diamonds.

"It's actually not known how diamonds form in the earth; one doesn't know how deep they form, or under what conditions," Boehler said. "It's still a mystery. Definitely, you need pressure. You need about 50,000 atmospheres at about 1,500 degrees centigrade to convert coal or organics into a diamond."

"We did a lot of research in the lab, you can take anything that's carbon-containing, from peanut butter to candle wax, you put it under high pressure and you make diamonds."

At ORNL, you could even turn a human fingernail into a diamond.

Boehler said the real applications of the research come from what they will discover doing "basic science," to understand materials' matter.

"Understanding the structure of matter, the behavior of matter under pressure - the application comes later. Once we understand the atomic behavior of something, we can make materials that are unique, and we have done this in the past a lot."

Through the same kind of pressure exertion, ORNL scientists have created silicon and germanium nitrides that have applications in orthopaedic medicine, the automotive industry and in creating more durable electronics.