Abstract
A critical overview of the various parameters, such as annealing atmospheres, pore microstructures, and pore sizes, that are critical in controlling the decomposition kinetics of Ti-based MAX phases is given in this paper. Ti-based MAX phases tend to decompose readily above 1400 °C during vacuum annealing to binary carbide (e.g., TiCx) or binary nitride (e.g., TiNx), primarily through the sublimation of A elements such as Al or Si, forming in a porous MXx surface layer. Arrhenius Avrami equations were used to determine the activation energy of phase decomposition and to model the kinetics of isothermal phase decomposition. Ironically, the understanding of phase decomposition via exfoliating or selective de-intercalation by chemical etching formed the catalyst for the sensational discovery of Mxenes in 2011. Other controlling parameters that also promote decomposition or degradation as reported in the literature are also briefly reviewed and these include effects of pressure and ion irradiations.
Highlights
MAX phases exhibit a unique combination of characteristics of both ceramics and metals and have unusual mechanical, electrical and thermal properties [1,2,3,4,5,6]
These conflicting results suggest that the thermochemical stability of MAX phases is still poorly understood, its susceptibility to thermal decomposition is strongly influenced by factors such as purity of powders and sintered materials, temperature, vapor pressure, atmosphere, and the type of heating elements used
We provide a critical overview of the various parameters, such as annealing atmospheres, pore microstructure, and pore size, that are critical in controlling the decomposition kinetics of MAX phases
Summary
MAX phases exhibit a unique combination of characteristics of both ceramics and metals and have unusual mechanical, electrical and thermal properties [1,2,3,4,5,6] These materials are nano-layered ceramics with the general formula Mn+1 AXn (n = 1–3), where M is an early transition metal, A is a group A element, and X is either carbon and/or nitrogen. Ti3 SiC2 was shown to be stable in a tungsten-heated furnace for 10 h at 1600 ◦ C and at 1800 ◦ C in an argon atmosphere but dissociated to TiCx under the same conditions when a graphite heater was used These conflicting results suggest that the thermochemical stability of MAX phases is still poorly understood, its susceptibility to thermal decomposition is strongly influenced by factors such as purity of powders and sintered materials, temperature, vapor pressure, atmosphere, and the type of heating elements used. Other parameters that cause decomposition or degradation as reported in the literature are briefly reviewed, and these include the effects of pressure and ion irradiations
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
