Nanolaminated 2-2-1 MAX-phase compositions

1. A crystalline solid having an empirical formula of M 2 A 2 X,

wherein M is Cr, Hf, Sc, Ti, Mo, Nb, Ta, V, Zr, or a combination thereof;

wherein A is Al, Ga, Ge, In, Pb, or Sn, or a combination thereof; and

each X is C x N y , where x+y=1.

2. The crystalline solid of claim 1 that is Cr 2 Ga 2 C, Cr 2 Ga 2 N, Mo 2 Ga 2 C, Mo 2 Ga 2 N, Nb 2 Ga 2 C, Nb 2 Ga 2 N, Ta 2 Ga 2 C, Ta 2 Ga 2 N, Ti 2 Ga 2 C, Ti 2 Ga 2 N, V 2 Ga 2 C, or V 2 Ga 2 N.

3. The crystalline solid of claim 1 that is Hf 2 In 2 C, Hf 2 In 2 N, Hf 2 Sn 2 C, Hf 2 Sn 2 N, Nb 2 In 2 C, Nb 2 In 2 N, Nb 2 Sn 2 C, Nb 2 Sn 2 N, Sc 2 In 2 C, Sc 2 In 2 N, Ti 2 In 2 C, Ti 2 In 2 N, Ti 2 Sn 2 C, Ti 2 Sn 2 N, Zr 2 In 2 C, Zr 2 In 2 N, Zr 2 Sn 2 C, or Zr 2 Sn 2 N.

4. The crystalline solid of claim 1 , wherein the empirical formula is defined by the unit cell stoichiometry of the crystalline solid.

5. The crystalline solid of claim 1 , having a unit cell stoichiometry of Mo 2 Ga 2 C.

6. The crystalline solid of claim 5 , in which two layers of Ga atoms are stacked between otherwise adjacent Mo 2 C layers.

7. The crystalline solid of claim 5 , wherein the Ga atoms are stacked in a simple hexagonal arrangement of atoms.

8. The crystalline solid of claim 1 , wherein A is Ga, In, or Sn, and in which two layers of Ga, In, or Sn atoms are stacked between layers of Cr 2 C, Cr 2 N, Hf 2 C, Hf 2 N, Mo 2 C, Mo 2 N, Nb 2 C, Nb 2 N, Sc 2 C, Sc 2 N, Ta 2 C, Ta 2 N, Ti 2 C, Ti 2 N, V 2 C, V 2 N, Zr 2 C, or Zr 2 N.

9. The crystalline solid of claim 1 comprising molybdenum, gallium, and carbon exhibiting at least five of the following characteristic X-ray powder diffraction peaks (Cu Kα radiation, expressed in degrees 2θ) at approximately 9.8, 34.1, 37.3, 39.9, 42.5, 53.4, 61.0, and 75.4 and optionally other one or more additional peaks at approximately 67.1, 73.7, 77.2, or 77.6 degrees 2θ.

10. The crystalline solid of claim 1 consisting essentially of molybdenum, gallium, and carbon exhibiting at least five of the following characteristic X-ray powder diffraction peaks (Cu Kα radiation, expressed in degrees 2θ) at approximately 9.8, 34.1, 37.3, 39.9, 42.5, 53.4, 61.0, and 75.4 and optionally other one or more additional peaks at approximately 67.1, 73.7, 77.2, or 77.6 degrees 2θ.

11. The crystalline solid of claim 1 comprising molybdenum, gallium, and carbon whose unit cell is characterized by a P63/mmc space group and having a and c-lattice parameters calculated to be about 3.04 Å and about 18.09 Å.

12. The crystalline solid of claim 1 comprising molybdenum, gallium, and carbon whose unit cell is characterized by the x, y, and z-positions and/or Wykcoff positions substantially as provided as:

Element

x

y

z

Wykcoff positions

Mo

⅓

⅔

0.06434 (10)

4f

Ga

⅓

⅔

0.68238 (10)

4f

C

0

0

0

2a.