Japan scientists have discovered a new material that contracts when heated, a rarity. The metal-ceramic composite material is composed of calcium, ruthenium and oxygen atoms. When heated, it shrinks 6.7 percent. It’s a new record for negative thermal expansion, or NTE.
In many modern industries — whether electronics, aeronautics or medical equipment — devices and the machinery used to build them must maintain precision and predictability while enduring harsh conditions. Temperature changes can diminish these qualities, cause materials to degrade and deform as they contract and expand. Because most materials expand upon heating, NTE materials can help industrial engineers more precisely manage cycles of contraction and expansion.
By mixing normal materials with NTE materials, engineers can create new composite materials with a thermal expansion value close to zero. X-ray images suggest the new material is atomically altered by heat, triggering unique changes to its microstructure and resulting in a loss in volume. Scientists discovered voids surrounding the material’s unique arrangement of crystal grains.
“The non-uniform changes in the atomic structure seem to deform the microstructure of the material, which means that the voids collapse and the material shrinks,” Koshi Takenaka, a material scientist at Nagoya University in Japan, said in a news release. “This is a new way of achieving negative thermal expansion, and it will allow us to develop new materials to compensate for thermal expansion.”
