Molten salt synthesis and formation mechanisms of ternary V‐based MAX phases by V–Al alloy strategy. Issue 3 (5th November 2021)

• Record Type: Journal Article
• Authors: Zhong, Yi; Liu, Ying; Ye, Jinwen; Jin, Na; Lin, Zifeng
• Is Part Of: Journal of the American Ceramic Society. Volume 105:Issue 3(2022)
• Page Start: 2277
• Page End: 2287
• Publication Date: 2021-11-05
• Subjects: Formation mechanism -- MAX phases -- phase transition -- synthesis -- transmission electron microscopy; Ceramics -- Periodicals; 620.1405
• DOI: 10.1111/jace.18198
• Languages: English
• ISSNs: 0002-7820

Abstract

Abstract: V2 AlC and V4 AlC3 are obtained in much milder conditions by a new facile approach using low‐cost V–Al alloys and carbon black with the assistance of molten salts. Density functional theory (DFT) calculations show that our strategy is feasible and thermodynamically superior to the traditional method, with the following X‐ray diffraction and Scanning Electron Microscopy fully revealing the phase and morphology evolutions of both reaction processes. Unreported formation mechanisms are revealed for the first time. Al8 V5 transforms directly into V2 AlC with both lattices perfectly overlapped due to the existence of multiple parallel planes between V2 AlC and Al8 V5 with consistent interplanar spacings, which leads to the overlapped phenomenon of the diffraction spots as well. For V4 AlC3, an embedded structure of V2 AlC–VC is first formed through an aluminum removing behavior in V2 AlC layers, causing the increase of the VC content, and V4 AlC3 is transformed by the embedded V2 AlC–VC structure through diffusion and interface migration with a possible climb behavior of Frank partial dislocation. Abstract :