This illustration shows hydrogen molecules (top) diffusing into a thin layer of palladium (purple), where they are separated into individual atoms that are then distributed in an underlying layer of yttrium. Image: Ranga Dias lab/University of Rochester.Towards the end of last year, researchers at the University of Rochester demonstrated superconducting materials at room temperatures (see Hydrogen-rich material pressured into superconducting at room temperature). Now, they report a new technique in the quest to create these materials at lower pressures.
In a paper published in Physical Review Letters, the lab of Ranga Dias, assistant professor of mechanical engineering and of physics and astronomy, describes separating individual hydrogen atoms with a thin film of palladium for transportation into yttrium. "This is a completely new technique that nobody has used before for high pressure superhydride synthesis," Dias says.
Hydrogen-rich materials are critical in the quest for room-temperature superconductors because, as Dias explains, "you want stronger bonds and light elements; those are the two very basic criteria. Hydrogen is the lightest material, and the hydrogen bond is one of the strongest."
Palladium is known to be a very good catalyst for "breaking down hydrogen molecules and diffusing them into whatever material you want to study", Dias says. In this case, a tiny layer of palladium protects the yttrium, a reactive transition metal, from oxidizing. At same time, it also breaks down the hydrogen into individual atoms, which are then transported into the yttrium. This is all done inside a diamond anvil, which is used to compress the materials.
The resulting yttrium superhydride is superconducting at 12°F and about 26 million pounds per square inch (psi). This is still too high for practical applications, but it is a significant improvement over the room temperature materials the researchers reported in a paper in Nature towards the end of last year.
In that paper, the researchers described combining hydrogen with carbon and sulfur to produce a material that was superconducting at about 36 million psi (pressure at sea level is about 15 psi.) "We will continue to use this new method to synthesize new superconducting materials at ambient pressure," Dias says.
The researchers used Raman spectroscopy, which they believe is more effective than the X-ray diffraction techniques that are traditionally used to measure the behavior of hydrogen atoms. To validate that, the researchers collaborated with Eva Zurek, professor of chemistry at the State University at Buffalo, who prepared theoretical simulations of how the hydrogen atoms could be expected to behave when transported into the yttrium. Those simulations were in "good agreement" with the lab's experimental data, Dias says.
First discovered in 1911, superconductivity gives materials two key properties: electrical resistance vanishes and any semblance of a magnetic field is expelled, due to a phenomenon called the Meissner effect. The magnetic field lines have to pass around the superconducting material, making it possible to levitate such materials, something that could be used for frictionless high-speed trains, known as maglev trains.
Superconducting materials could also have applications in medical imaging and scanning techniques such as MRI and magnetocardiography, as well as lead to faster, more efficient electronics for digital logic and memory device technology.
This story is adapted from material from the University of Rochester, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.