From binary to ternary and back to binary: Transition of electromagnetic wave shielding to absorption among MAB phase Ni ₃ZnB ₂ and corresponding binary borides Ni _n+1 B _n ( n = 1, 3)

Abstract

Due to chemical inertness of nickel and boron, the preparation of nickel borides and corresponding layered ternary transition metal borides Ni 3 ZnB 2 (MAB phase) has always required high-temperature and/or high-pressure conditions. Yet, an innovative and efficient approach to preparing Ni 3 ZnB 2 at only 600 ℃ and without applied pressure is presented in this study. It is discovered that by simply adjusting the temperature, a phase transition from Ni 3 ZnB 2 to Ni 4 B 3 with a layered structure could be induced. This transition between the binary-component and the ternary-component brings about significant variation in electromagnetic wave (EMW) shielding/absorption performance of prepared borides. For instance, Ni 2 B has good EMW shielding performance (42.54 dB in X band) and Ni 3 ZnB 2 is of weak EMW shielding (13.43 dB in X band); Ni 3 ZnB 2 has poor EMW absorption performance (−5 dB) while Ni 4 B 3 has excellent EMW absorption performance (−45.19 dB) at a thickness of 2.7 mm with effective absorption bandwidth (10.4 GHz).