Formation of Ti2AlNx MAX phase by “Hydride Cycle” and SHS methods

Abstract

In the present work a new approach is proposed for Ti2AlNx MAX phase synthesis using highly efficient methods: self-propagating high-temperature synthesis (SHS) and Hydride Cycle (HC). Two ways of synthesis were developed, which differ in the use of different precursors and methods for the forming of Ti2AlNx MAX phase. The synthesis in Way 1 was carried out according to the following scheme: step 1− synthesis of a solid solution of N2 in Ti (TiN0.18) and titanium hydridonitride (TiN0.18H1.34) by SHS method. Step 2: synthesis of Ti2AlNx Max phase by HC method according to the reaction: 2TiN0.18H1.34 +Al → Ti2AlN0.25+ H2↑. The synthesis in Way 2 follows the scheme: step 1 – synthesis of Ti2Al intermetallic compound by HC method according to the reaction: 2TiH2 ​+ ​Al→ Ti2Al + H2↑. Step 2: synthesis of Ti2AlNx Max phase by SHS method according to reaction: Ti2Al ​+ ​N2 → Ti2AlN0.63. The peculiarities of structure and formation processes were studied by step-by-step analysis of the intermediate products using XRF, DTA, and chemical analysis methods. The synthesized Ti2AlN0.63 and Ti2AlN0.25 compounds were identified as single-phase MAX phases with hcp crystal structure and the same lattice parameters a = 0.29892 nm; c = 1.36540 nm, c/a = 4.57. It has been established that in both cases the formation of Ti2AlN0.25 and Ti2AlN0.67 MAX phases proceeded according to solid-phase mechanism. Taking into account all the advantages of SHS and HC methods, the developed ways for the synthesis of Ti2AlNx MAX phases can be recommended as fundamentally new, resource-saving, economical, and “low cost” technologies.