MXenes - 2D Nanomaterials
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- เผยแพร่เมื่อ 1 ธ.ค. 2024
- Transition metals carbides, nitrides, and carbonitrides known as MXenes (pronounced “maxenes”) [Ref 1, 2].
MXenes Chemical Formula
Mn+1XnTx (n = 1, 2, or 3), where M is early transition metals (Ti, V, Cr, Zr, Nb), X is carbon and/or nitrogen, and T refer to surface terminations (-O, -OH, -F, -Cl) [Ref 3]. The first MXenes (Ti3C2Tx) was discovered at Drexel University in 2011 [Ref 1].
MXenes are basically produce by etching A layer from MAX phases and the suffix ‘ene’ added in order to shows its similarity to graphene. Immersing a MAX phase in strong etching solutions at room temperature such as hydrofluoric acid (HF). 2D nanosheet Ti3C2 layers produced by exfoliation of Ti3AlC2 in hydrofluoric acid.
MAX phases can also be synthesized with different combinations, or solid solutions, of M atoms, such as (Ti0.5Nb0.5)2 AlC[Ref 4], A atoms, such as Ti3(Al0.5 Si0.5)C2 [Ref 5] and in the X sites such as Ti2 Al(C0.5N0.5)[Ref 6]
Carbide
It is usually describes a compound consist of carbon and a metal or semi-metallic elements. Example are calcium carbide (CaC2) and silicon carbide (SiC)
Nitrides
It is an inorganic compound of nitrogen. Example are boron nitride and phosphorus nitride, P3N5.
Hydrophilicity
A hydrophile is a molecule that is attracted to water molecules and tends to be dissolved by water. On the other hand, hydrophobes entity do not attracted to water and may seem to be repelled by it. The third type is Hygroscopics, which are attracted to water, but are not dissolved by it.
[Ref 1] Naguib, M.; Kurtoglu, M.; Presser, V.; Lu, J.; Niu, J.; Heon, M.; Hultman, L.; Gogotsi, Y.; Barsoum, M. W. Two-Dimensional Nanocrystals Produced by Exfoliation of Ti3AlC2. Adv. Mater. 2011, 23, 4248- 4253, DOI: 10.1002/adma.201102306
[Ref 2] Science 331, 568 (2011); DOI: 10.1126/science.1194975
[Ref 3] J. Mater. Chem. A, 2017,5, 24564-24579
[Ref 4] I. Salama , T. El-Raghy , M. W. Barsoum , J. Alloys Compd. 2002 , 347 , 271 .
[Ref 5] H. B. Zhang , Y. C. Zhou , Y. W. Bao , M. S. Li , J. Y. Wang , J. Eur. Ceram. Soc. 2006 , 26 , 2373
[Ref 6] M. W. Barsoum , T. El-Raghy , M. Ali , Metall. Mater. Trans. A 2000 , 31 , 1857 .
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Slam sir, are high entropy transition metal carbides and transition mono carbides (ZrC, HfC, TaC) in the category of MX phases?
Wsalm,
The *MAX* formula is *Mn+1AXn*, where *M* is early transition metals (Se, Te, V,....), *A* is group A elements (Al, Si,....) and *X* is only C or N.
For MAX phase, the following must be satisfied:
1• the ratio of M:X must be (n+1/n)
2• A should be 1
3• X must be C or N
otherwise, it will be not a MAX phase
why we remove A layer sir, what about M and X layer
Good question. There are two bonds M-A (Metallic in nature) and bond M-X ( which is covalent /ionic/metallic). The bonds between M-A is weaker than M-X and it is can be easily removed. The M can also be removed but then we get another structure that is called CDC, carbon derived carbon.,... Further I will make videos on this
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sir can u pls explain how to derive this formula M n+1 A n Xn , can you pls use any example to derive it sir
These are basically ternary carbide in most cases and the compound formed either Ti2SiC, Ti3Si2C2, Ti4Si3C3..... There are almost 1200 MAX phases confirmed by DFT.. Anyways I will explain this one too
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