Jan 30, 2017

Team including Lankan invents metallic hydrogen (video)

For the first time in history, physicists from Harvard University turned hydrogen into metal.

The team, which includes a Sri Lankan, proves a concept that was first predicted over 80 years ago by physicists who won the Nobel prize for their work.

Thomas D. Cabot Professor of the Natural Sciences Professor Isaac Silvera and postdoctoral fellow Dr Ranga Dias have long sought the material, called atomic metallic hydrogen.

Changing state

Hydrogen, the tiniest element on the periodic table, These molecules like to quickly bounce around and take up a lot of space—which is what makes them a gas.

But it’s possible to change the state of any element by speeding up or slowing down their molecules, or by giving them more or less room to bounce around. The lower the temperature, the slower molecules move.

Experiment

In this case, the researchers slowed these molecules way down to the point where they were barely moving by cooling them to 5.5 Kelvins (-267.65 °C). At that point, the hydrogen molecules arrange themselves in a lattice structure. Then, they squashed the molecules together to 495 gigapascals, which is nearly 5 million times the pressure we feel at sea level.

“Eventually [the molecules] get so close that two atoms that are in a molecule can’t distinguish whether they should be in that molecule or the adjacent one,” says Isaac Silvera, the lead author of the paper published on Jan. 26 in the journal Science. Instead of having separate molecules in the lattice, the atoms form a tightly packed mass that all share their electrons—just like a metal.

To make the metallic hydrogen, Silvera and his colleague, Ranga Dias, used an apparatus called a diamond anvil cell, which, as its name suggests, uses diamonds to apply pressure to chemical samples. “Diamonds are the hardest material we know,” says Silvera. They can withstand a lot of pressure, and are transparent to light and X-rays, which makes the smooshed sample inside the anvil cell easier to study. In this case, they used synthetic diamonds, which have no impurities. They were also coated with a thin layer of aluminum oxide to prevent the hydrogen molecules from seeping into the gemstones.

Superconductor

Silvera thinks that because of the way molecules rearrange themselves in metallic hydrogen, there’s a possibility that when warmed up again it could maintain its structure and be a superconductor, which can transport electricity without losing any energy,

However they only existed at very low temperatures so far, making them impractical for most uses, since keeping things that cold requires lots of energy.

In the near future, Silvera plans to conduct research to figure out if, in fact, metallic hydrogen is a room-temperature superconductor.

A room temperature superconductor, Dias said, could change our transportation system, making magnetic levitation of high-speed trains possible, as well as making electric cars more efficient and improving the performance of many electronic devices. The material could also provide major improvements in energy production and storage. Because superconductors have zero resistance, superconducting coils could be used to store excess energy, which could then be used whenever it is needed.

Metallic hydrogen could also play a key role in helping humans explore the far reaches of space, as a more powerful rocket propellant.

(Excerpts : harvard.edu / qz.com)

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