| AVS 54th International Symposium | |
| Advanced Surface Engineering | Tuesday Sessions |
| Session SE-TuA |
| Session: | Naturally and Artificially Nanolaminated Coatings |
| Presenter: | J.M. Schneider, RWTH Aachen University, Germany |
| Authors: | J.M. Schneider, RWTH Aachen University, Germany D. Music, RWTH Aachen University, Germany |
| Correspondent: | Click to Email |
Mn+1AXn phases (space group P63/mmc), where M is a transition metal, A is mostly IIIA or IVA group element, X is either C or N and n = 1–3, can be referred to as nanolaminates, where MX layers are interleaved with A layers. We have investigated the valence electron concentration induced changes in the elastic properties of M2AlC phases (M = Sc, Y, La, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, W) using ab initio calculations.1,2 In terms of bulk moduli [1], we have suggested that M2AlC phases can be classified into two groups based on the coupling between MC and Al layers: M2AlC phases with M = VB and VIB are strongly coupled, while M2AlC with M = IVB are weakly coupled. In terms of shearing,2 we have proposed that these phases can also be classified into two groups: one group comprises M = VB and VIB, where the C44 values are independent of the corresponding MC. The other group includes M = IIIB and IVB, where the C44 shows a linear dependency with the corresponding MC. This may be understood based on the electronic structure: shear resistant bands are filled in M2AlC phases with M = VB and VIB, while they are not completely filled when M = IIIB and IVB. These classification proposals exhibit identical critical valence electron concentration values for the group boundary. Experimental efforts have been dedicated towards exploring the correlation between the valence electron concentration, constitution, and the elastic properties of M2AlC phases (M = Ti, V, Cr). Ti2AlC can be deposited onto sapphire substrates at a growth temperature of 800 °C using a compound target and an additional source of Ti.3 V2AlC was grown at a substrate temperature of 850 °C. We report that 450 °C is sufficient to grow crystalline Cr2AlC thin films. This is the lowest deposition temperature ever reported for a MAX phase and is significantly lower than the crystallization temperature of an amorphous Cr2AlC thin film based on our differential scanning calorimetry data.4
1D. Music, Z. Sun, R. Ahuja, J.M. Schneider, Phys. Rev. B 73 (2006) 134117.
2D. Music, Z. Sun, A.A. Voevodin, J.M. Schneider, Solid State Commun. 139 (2006) 139.
3C. Walter, C. Martinez, T. El-Raghy, J.M. Schneider, Steel Research Int. 76 (2005) 225.
4C. Walter, D.P. Sigumonrong, T. El-Raghy, J.M. Schneider, Thin Solid Films 515 (2006) 389.