Formation Mechanism of High-Purity Ti2AlN Powders under Microwave Sintering

Abstract

In the present study, high-purity ternary-phase nitride (Ti2AlN) powders were synthesized through microwave sintering using TiH2, Al, and TiN powders as raw materials. X-ray diffraction (XRD), differential scanning calorimetry (DSC), transmission electron microscopy (TEM), and scanning electron microscopy (SEM) were adopted to characterize the as-prepared powders. It was found that the Ti2AlN powder prepared by the microwave sintering of the 1TiH2/1.15Al/1TiN mixture at 1250 °C for 30 min manifested great purity (96.68%) with uniform grain size distribution. The formation mechanism of Ti2AlN occurred in four stages. The solid-phase reaction of Ti/Al and Ti/TiN took place below the melting point of aluminum and formed Ti2Al and TiN0.5 phases, which were the main intermediates in Ti2AlN formation. Therefore, the present work puts forward a favorable method for the preparation of high-purity Ti2AlN powders.

Processing of MAX phases: From synthesis to applications

“…The reduction of the sintering temperature is associated with the enhanced diffusion of species by their interaction with the microwaves, and the reported decrease of the activation energy, 233 KJ/mol for the formation of Ti 3 SiC 2 174 . The synthesized pellets exhibit high purity, with values up to 97.5%, 171 and grain size in the range between 1 and 10 µm 169,173 . Synthesized pellets are typically porous, although relative densities up to 95% have been reported for Ti 3 SiC 2 doped with aluminum 173 .…”

“…It is the least explored process of SSR methods, although reported for V 2 AlC, 168 Cr 2 AlC, 169 Ti 2 AlN, 166 Ti 2 AlC, 170 Ti 3 AlC 2 , 171 Ti 2 SC, 172 , and Ti 3 SiC 2 173,174 . Starting precursors are heated under argon atmosphere with heating rates up to 200°C/min, maximum temperatures between 850°C and 1480°C, 170,173 and dwell times up to 30 minutes 168,171 . The reduction of the sintering temperature is associated with the enhanced diffusion of species by their interaction with the microwaves, and the reported decrease of the activation energy, 233 KJ/mol for the formation of Ti 3 SiC 2 174 .…”

Synthesis and high temperature corrosion behaviour of nearly monolithic Ti3AlC2 MAX phase in molten chloride salt

“…Some MAX phases, such as V2AlC and Nb2AlC have been reported to possess higher bonding energy; as a result, longer time is required to remove the A-atoms [44]. As the M-A bond energies in MAX phases are different, it is conceivable that the weak M-Al bonding in Ti3AlC2 [48] favoured the ease of extraction of Al atoms from the two-dimensional A-site plane which was then subsequently dissolved in the molten salt. The formation of AlCl3 vapour is also probable as its boiling point is 180 °C.…”

Kinetic role of C/Zr ratio in the reaction process, combustion behavior, and synthetic product of 70 wt.% (xC–Zr)–30 wt.% Cu

“…As these ceramic particles are mainly derived from the combustion synthesis reaction, understanding the kinetic characteristics is vital to achieving a desired microstructure. Conventionally, the influence of the kinetic parameters on the combustion behaviors and synthesized products was predicted by thermodynamic calculations and/or reaction mechanism 31–34 . These methods are helpful but not entirely accurate.…”