Heat tends to make the materials expand and gain volume, a volume that is then reduced when the temperature drops. This is a problem for architects and engineers since this effect is very noticeable in metals such as steel.
What if we could avoid this problem?
A new alloy. A group of scientists has created a new alloy that barely shows thermal expansion along a wide temperature fork. The key to development has been in invar, an alloy with similar properties that has previously been deciphered.
100 years of mystery. Invar is an alloy composed of iron, nickel and other elements with an extremely low thermal expansion coefficient, that is, an alloy that is barely dilated to an increase in temperatures. In a fork that covers more than 400 k (that is, more than 400º Celsius), invaria only expands 0.0001% of its length for each degree Celsius (or for each Kelvin).
This alloy was created at the end of the 19th century by Charles Édouard Guillaume, who I would receive the Nobel Prize in Physics In 1920 “for its discovery of anomalies in the steel and nickel alloys.” We have needed a century since the award concession to begin to understand the underlying science in this low thermal expansion.
Thermal expansion. The phenomenon of thermal expansion is an old acquaintance. As those responsible for the new work explain, this phenomenon is the result of the same movement of atoms (remember that the temperature is nothing other than that). When the atoms get hot, they move more and that makes more space need, then the material expands.
This phenomenon, they continue to point out, is inevitable, but understanding it in detail opens the door to create new materials that somehow balance this effect. To study it, the team resorted to computer simulations that allowed analyzing the behavior of magnetic materials on tiny scales.
“This allowed us to better understand the reason why invaria is hardly expanding,” said Segii Khmelevskyi, co -author of the new study. The effect is due to changes in the state of the electrons that occur as the temperature increases. These changes counteract “almost exactly” the thermal expansion of the material, adds Khmelevskyi.
From theory to practice. Knowing the theory opens the way to the creation of new alloys capable of overcoming thermal expansion. It is precisely what the study responsible for the study did, put their findings into practice. And the result is what they have called Pyrocloro magnet.
The new alloy combines more than two compounds: zirconium, niobium, iron and cobalt. “It is a material with an extremely under thermal coefficient above a range of unprecedented temperatures,” says Yili Cao, development co -author.
“The effect is because certain electrons change its status as the temperature increases. The magnetic order of the material decreases, which makes the material contract, ”explains CAO. This effect is precisely analogous to the one seen in invar.
The secret is irregularity. The team explains that the marked of the effect is also to the fact that the Pyroclloric magnet does not have a perfect network structure, that is, with the atoms arranged forming a regular and repeated pattern, but more heterogeneous. Some areas contain more or less cobalt which makes the material expand and contract in an almost identical proportion.
Development details were published In an article In the magazine National Science Review.
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