Predictions of attainable compositions of layered quaternary i-MAB phases and solid solution MAB phases

Abstract

MAB phases are layered materials combining metallic and ceramic attributes. Their ternary composition, however, have been limited to a few elemental combinations which makes controlled and tailored properties challenging. Inspired...

Chemical order or disorder – a theoretical stability expose for expanding the compositional space of quaternary metal borides

“…It was found that the bonding states are optimized in Ti 4 MoSiB 2 and that the electronegativity difference of Mo and Ti could, at least in part, explain the stability of both Ti 4 MoSiB 2 and Mo 5 SiB 2 compared to Ti 5 SiB 2 . Recently, we demonstrated that the preference for order or solid solution upon metal alloying in 212 MAB phases is dictated by for example the size difference between the alloying metal elements, 58 also shown for alloying of 211 MAX phases. 59 On the other hand, out-of-plane MAX phases, o -MAX, is possible when the atomic sizes of the alloying metals are similar while the difference in electronegativity between M′ and A is large.…”

MAB‐Phases and Beyond—A Tribological Success Story?

“…[65] This finding was accompanied by providing 39 chemically ordered (i-MAB) and 52 solid solution (MAB) phases that were predicted to be thermodynamically stable at typical synthesis temperatures of which a majority is yet to be reported experimentally. [36] Recent theoretical calculations performed for i-MAB-phases confirmed their high metallicity and conductivity irrespective of their chemical composition. In particular, d electrons originating from M′ and M″ metals dominate the proximity of the Fermi level, ranging from −4 up to +2 eV.…”

“…Most MAB-phases have an orthorhombic crystal structure, but with the recent addition of Ti 2 InB 2 , which is a hexagonal subgroup of P6 3 /mmc, the hexagonal symmetry has been introduced. [35,36] MAB-phases exhibit intrinsic energy-dissipating mechanisms, ductility, and machinability like metals, along with refractory and oxidative properties like those of conventional ceramic materials. Numerous MAB-phase compositions make them promising candidates for the establishment of tailored tribo-films for the specific matrix material or tribo-couple.…”

“…[ 65 ] This finding was accompanied by providing 39 chemically ordered ( i ‐MAB) and 52 solid solution (MAB) phases that were predicted to be thermodynamically stable at typical synthesis temperatures of which a majority is yet to be reported experimentally. [ 36 ]…”

“…Most MAB‐phases have an orthorhombic crystal structure, but with the recent addition of Ti 2 InB 2 , which is a hexagonal subgroup of P 6 3 / mmc , the hexagonal symmetry has been introduced. [ 35,36 ]…”