Ellen Phiddian
Cosmos science journalist
Researchers have made a material capable of cooling substances down to -253°C – enough to liquefy hydrogen – using magnets.
They say their research, published in Nature Communications, could provide a cheaper and more sustainable way to supercool hydrogen fuel for storage and transport.
The researchers tapped into the “magnetocaloric effect”: applying magnetic fields to certain substances can change their temperature.
A magnetic field causes atoms to align in the substance, heating up. The heat is transferred to a heat sink, but the substance remains in its magnetised state. Then, the magnetic field is turned off, and the substance cools as the atoms fall out of alignment.
If the temperature change is dramatic enough, these substances can be used to cool other things.
Magnetic refrigeration has been touted as a possible alternative to the vapour technology that powers most modern coolers, which is a source of potent greenhouse gases.
But while scientists have known about the phenomenon and have been able to get it to work at near-room temperature since 1976, it’s typically needed expensive rare earth.
In this new research, the team investigated a polymer made from cobalt and an organic (carbon-containing) material.
The pink crystals could cool to 20 Kelvin, or -253°C. Just 20°C above absolute zero, this is cool enough to prompt the condensation of hydrogen, rendering it a liquid.
“Our material, or a future variant of it, could probably reduce the cost and improve the environmental friendliness of this cooling technology,” says senior author Dr Graeme Blake, an assistant professor of inorganic chemistry at the University of Groningen, in the Netherlands.
“We expect that there is still room for improving the magnetocaloric properties,” write the researchers in their paper, suggesting that iron or manganese might work even better than cobalt.
