AMP_04_May_June_2021_Digital_Edition

A D V A N C E D M A T E R I A L S & P R O C E S S E S | M A Y / J U N E 2 0 2 1 1 3 FINE-TUNING SUPERALLOYS Scientists at KTH Royal Institute of Technology in Stockholm reported the discovery of a phenomenon relat- ed to the invar effect in paramagnetic high temperature alloys. According to the researchers, their discovery has great potential to advance the design of high-temperature alloys with excep- tional mechanical stability. Invar plasticity enables magnet- ically disordered nickel-iron alloys to show practically invariant deforma- tion behavior over a wide temperature range—making them ideal for turbines and other mechanical uses in extremely high temperatures. However, the invar effect has never been fully understood, and the researchers say these new findings help explain the peculiar high- temperature properties of special al- loys used in jet engines, such as nickel- based superalloys. Invar has two known effects— thermal expansion and elasticity. Be- cause both effects are linked with the interplay between tempera- ture and magnetic order, they are considered to be specific to magnetically ordered alloys. Using first-principles quantum mechanical modeling, the re- searchers identified how in- variant plasticity also occurs in nonmagnetic alloys when a structural balance exists at the atomic level between cubic and hexagonal close-packed structures. The new discovery emerges from a long-term col- laboration with industry to find alter- natives to carcinogenic cobalt in hard metals, such as cutting tools. The re- searchers say this finding broadens the palette of invar phenomena andmateri- al compositions with clear implications for new applications. They also say their findings create a new platform for tailoring high temperature properties of technologically relevant materials toward plastic stability at elevated tem- peratures. www.kth.se/en. STABILIZING BORON Borophane—atomically thin bo- ron that is stable at standard tempera- tures and air pressures—was synthe- sized for the first time by scientists from Northwestern University, Evanston, Ill. Researchers have long been inter- ested in the promise of borophene, a single-atom-thick sheet of boron, be- cause of its strength, flexibility, and electronics properties. Stronger, lighter, and more flexible than graphene, boro- phene could potentially revolutionize EMERGING TECHNOLOGY New research from Chalmers University of Technology, Sweden, offers key insights into fundamental questions about the correlation between the size of an atom and its other properties, such as electronegativity and energy. For the first time, it is possible under certain conditions to devise exact equations for such relationships—paving the way for advances in materials science. www.chalmers.se/en . BRIEF batteries, electronics, sensors, photo- voltaics, and quantum computing. Until now, scientists found boro- phene to be highly susceptible to fur- ther chemical reactions outside of a vacuum, such as oxidization. “Once it oxidizes,” explains the team, “it is no longer borophene and is no longer con- ductive.” By bonding borophene with atomic hydrogen, the Northwestern team created borophane, which has the same exciting properties as borophene and is stable outside of a vacuum. Although borophene is frequently compared to its super-material prede- cessor graphene, it is much more diffi- cult to create. To remove a two-dimen- sional layer from graphite, scientists simply peel it off. Boron, on the other hand, is not layered when in bulk form. Now that borophane can be taken out into the real world, the Northwestern team expects that its practical uses and applications will rapidly proliferate. northwestern.edu. Schematic depicting boron as teal balls and hydrogen as red balls. Courtesy of Northwestern University. A piece of alloy is stress tested at the KTH Royal Institute of Technology. Courtesy of Levente Vitos.