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Microstructure and phase transformation of Ti 3 AC 2 (A = Al, Si) in hydrofluoric acid solution
Author(s) -
Chen Beibei,
Chang Fangyuan,
Yang Jin,
Tang Hua,
Li Changsheng
Publication year - 2014
Publication title -
crystal research and technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.377
H-Index - 64
eISSN - 1521-4079
pISSN - 0232-1300
DOI - 10.1002/crat.201400189
Subject(s) - hydrofluoric acid , hydrothermal circulation , microstructure , materials science , phase (matter) , hydrothermal synthesis , carbide , crystallography , covalent bond , chemical engineering , metallurgy , chemistry , organic chemistry , engineering
In this paper, Ti 3 AC 2 (A = Al, Si) were prepared by pressureless argon shielding synthesis technique. The microstructure and phase transformation of as‐prepared Ti 3 AC 2 (A = Al, Si) in hydrothermal hydrofluoric acid (HF) solution were investigated systematically. Results showed that the obtained Ti 3 AlC 2 and Ti 3 SiC 2 were closely aligned layered structure. In hydrothermal HF solution, Al or Si element was preferentially etched from the layered structure, inducing obvious transformation of microstructure and phase composition. For Ti 3 AlC 2 , Al atoms diffused out of the structure and reacted with HF to form AlF 3 •H 2 O, which induced the rearrangement of the Ti and C atoms, and finally resulted in the formation of TiC x cubic phase. With the hydrothermal temperature and reaction time increasing, the TiC x phase gradually disappeared and the grain size of AlF 3 •H 2 O gradually increased. When Ti 3 SiC 2 was immersed in hydrothermal HF solution, the main products were TiC and SiC. Interestingly, with the hydrothermal treatment temperature and reaction time increasing, TiC gradually disappeared, while SiC nearly kept unchanged. This can be explained that SiC was covalently bonded carbide, while TiC was metallically bonded, having relatively weak bond energy and consequently being unstable in hydrothermal HF solution.