Phase pure and well crystalline Cr2AlB2: A key precursor for two-dimensional CrB

Synthesis, characterization and first principle modelling of the MAB phase solid solutions: (Mn1-xCrx)2AlB2 and (Mn1-xCrx)3AlB4

“…The XRD patterns for the Cr-rich solid solutions show residual CrB peaks that increase in intensity as the Cr content increases. As shown in previous work [8,30], Cr 2 AlB 2 may require a second sintering, or excess Al, to fully react. As these compositions approach Cr 2 AlB 2 , the 20% excess Al is insufficient to react with all the CrB in a single reaction step, resulting in some impurity phases.…”

“…The ternaries, Cr 2 AlB 2 and Cr 3 AlB 4 were not synthesized until 1973 by Chaban and Kuz'ma [4]. Recently, there has been a renewed interest in these phases due to their unique magneto-caloric properties [5], high-temperature oxidation resistance [6] and their role as a precursor for 2-D, MXene-like borides [7,8]. A more complete history and summary of the MAB phases and their properties can be found in Ref.…”

Novel MAB phases and insights into their exfoliation into 2D MBenes

“…Experimentally, MoAlB with double layers of Al atoms has been partially etched into 2D MoB MBene [20,21] and Cr 2 AlB 2 has also been etched completely into 2D CrB MBene. [22,23] In the family of Cr-, Mo-, and W-based MAB phases, we find in Fig. 4(a) that the bonding between Al atoms and other atoms are very strong.…”

“…This is consistent with the experimental results that experimentalists succeeded to exfoliate Cr 2 AlB 2 into 2D CrB nanosheets. [22,23] Unfortunately, the experimental data on the exfoliation of MAB phases is still very limited. However, there are many on the exfoliation of MAX phases.…”

“…By ultrasonication, the multilayers can be separated into monolayers, named as MXenes. [4,5] For examples, Ti 2 AlC, Ti 2 AlN, V 2 AlC, Nb 2 AlC, Ti 3 [22,23,[46][47][48][49][50][51][52][53] As seen from Figure 1, the skeleton of MAlB, M 2 AlB 2 , and M 3 Al 2 B 2 contains isolated zigzag chains of boron atoms, while M 3 AlB 4 and M 4 AlB 6 contain double and triple chains of boron atoms, respectively, connected to form flat strips with hexagonal boron ring networks. In this paper, we extend the family members of MAB phases by studying the dynamic stability and the formation energy of MAlB, M 2 AlB 2 , M 3 Al 2 B 2 , M 3 AlB 4 , and M 4 AlB 6 (M = Sc, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W, Mn, Tc, Fe, Ru, Co, Rh, and Ni).…”