title: AlM2B2(M  =  Cr, Mn, Fe, Co, Ni): a group of nanolaminated materials.
abstract: Combining theory with experiments, we study the phase stability, elastic properties, electronic structure and hardness of layered ternary borides AlCr2B2, AlMn2B2, AlFe2B2, AlCo2B2, and AlNi2B2. We find that the first three borides of this series are stable phases, while AlCo2B2and AlNi2B2are metastable. We show that the elasticity increases in the boride series, and predict that AlCr2B2, AlMn2B2, and AlFe2B2are more brittle, while AlCo2B2and AlNi2B2are more ductile. We propose that the elasticity of AlFe2B2can be improved by alloying it with cobalt or nickel, or a combination of them. We present evidence that these ternary borides represent nanolaminated systems. Based on SEM measurements, we demonstrate that they exhibit the delamination phenomena, which leads to a reduced hardness compared to transition metal mono- and diborides. We discuss the background of delamination by analyzing chemical bonding and theoretical work of separation in these borides.
authors.affiliation: Division of Materials Theory, Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20, Uppsala, Sweden.
authors.forename: K
authors.initials: K
authors.lastname: Kádas
authors.forename: D
authors.initials: D
authors.lastname: Iuşan
authors.forename: J
authors.initials: J
authors.lastname: Hellsvik
authors.forename: J
authors.initials: J
authors.lastname: Cedervall
authors.forename: P
authors.initials: P
authors.lastname: Berastegui
authors.forename: M
authors.initials: M
authors.lastname: Sahlberg
authors.forename: U
authors.initials: U
authors.lastname: Jansson
authors.forename: O
authors.initials: O
authors.lastname: Eriksson