Physical forms of MXene materials exhibiting novel electrical and optical characteristics
The present invention(s) is directed to novel conductive M n+1 X n (T s ) compositions exhibiting high volumetric capacitances, and methods of making the same. The present invention(s) is also directed to novel conductive M n+1 X n (T s ) compositions, methods of preparing transparent conductors using these materials, and products derived from these methods.
1. A method comprising,
(a) applying a MXene dispersion onto a substrate surface, said MXene dispersion comprising at least one type of MXene platelets dispersed in a solvent; and
(b) removing at least a portion of solvent so as to provide a coated film of at least one layer of MXene platelets oriented to be essentially coplanar with the substrate surface,
said MXene platelets comprising a M n+1 X n (T s ) composition having at least one layer, each layer having a first and second surface, each layer comprising
a substantially two-dimensional array of crystal cells,
each crystal cell having an empirical formula of M n+1 X n , such that each X is positioned within an octahedral array of M,
wherein M is at least one Group 3, 4, 5, 6, or 7,
wherein each X is C, N, or a combination thereof and
n=1, 2, or 3;
wherein at least one of said surfaces of the layers has surface terminations, T s , independently comprising alkoxide, alkyl, carboxylate, halide, hydroxide, hydride, oxide, sub- oxide, nitride, sub-nitride, sulfide, sulfonate, thiol, or a combination thereof;
said coated film being electrically conductive and exhibiting:
(i) a resistivity in a range of from about 0.01 to about 1000 micro-ohm-meters,
(ii) an ability to transmit at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, or at least about 95% of incident light of at least one wavelength in a range of from about 300 nm to about 2000 nm
(iii) a ratio of DC conductivity, measured in Siemens/meter, to light absorbance, (including visible light absorbance), measured as a decadic absorbance per meter, of at least 0 . 1 Siemens measured at at least one wavelength in the range of 300 to 2500 nm;
(iv) a value of the real dielectric permittivity less than negative one for wavelengths greater than a threshold wavelength, for example, 500 nm; or
(v) a combination of any two or more of (i), (ii), (iii), and (iv),
wherein the M n−1 X n (T s ) composition comprises a plurality of M n+1 X n (T s ) platelets having at least one mean lateral dimension in a range of from about 0.1 micron to about 50 microns.
2. The method of claim 1 wherein the MXene dispersion is applied dropwise onto an optionally rotating substrate surface, during or after which the optionally substrate surface is made to rotate at a rate in a range of from about 300 rpm (rotations per minute) to about 5000 rpm.
3. The method of claim 1 , wherein the MXene dispersion is an aqueous dispersion optionally comprising one or more surfactants.
4. The method of claim 1 , wherein the MXene dispersion comprising an organic solvent.
5. The method of claim 1 , wherein the substrate is rigid.
6. The method of claim 1 , wherein the substrate is flexible.
7. The method of claim 1 , wherein the film has surface electrical resistivity in a range of from about 1 micro-ohm-meters to about 10 micro-ohm-meters, from about 10 micro-ohm-meters to about 100 micro-ohm-meters, from about 100 micro-ohm-meters to about 1000 micro-ohm-meters, from about 1000 micro-ohm-meters to about 10,000 micro-ohm-meters, or any combination of two or more of these ranges.
8. The method of claim 1 , wherein M is at least one Group 4, 5, 6, or 7 metal.
9. The method of claim 1 , wherein M is at least one of Hf, Cr, Mn, Mo, Nb, Sc, Ta, Ti, V, W, or Zr.
10. The method of claim 1 , wherein M is Ti, and n is 1 or 2.
11. The method of claim 1 , wherein M n+1 X n comprises Sc 2 C, S c2 N, Ti 2 C, Ti 2 N, V 2 C, V 2 N, Cr 2 C, Cr 2 N, Zr 2 C, Zr 2 N, Nb 2 C, Nb 2 N, Hf 2 C, Hf 2 N, Ta 2 C, Mo 2 C, Ti 3 C 2 , Ti 3 N 2 , V 3 C 2 , Ta 3 C 2 , Ta 3 N 2 , Mo 3 C 2 , (Cr 2/3 Ti 1/2 ) 3 C 2 , Ti 4 C 3 , Ti 4 N 3 , V 4 C 3 , V 4 N 3 , Ta 4 C 3 , Ta 4 N 3 , Nb 4 C 3 , or a combination thereof.
12. The method of claim 1 , the crystal cells having an empirical formula Ti 3 C 2 or Ti 2 C and wherein at least one of said surfaces of each layer is coated with surface terminations, T s , comprising alkoxide, fluoride, hydroxide, oxide, sub-oxide, sulfonate, or a combination thereof.
13. The method of claim 1 , wherein the M n−1 X n (T s ) or M′ 2 M″ m X m+1 composition is formed by removing at least 90% the A atoms from a MAX-phase composition having an empirical formula of M n+1 AX n or M′ 2 M″ m AX m+1 , respectively;
wherein M is at least one Group 3, 4, 5, 6, or 7 metal,
wherein A is an A-group element;
each X is C, N, or a combination thereof; and
n=1, 2, or 3.
14. The method of claim 13 , wherein removing the A atoms is done in aqueous media.
15. The method of claim 13 , wherein M is at least one of Hf, Cr, Mn, Mo, Nb, Sc, Ta, Ti, V, W, or Zr.
16. The method of claim 13 , wherein A is at least one of Al, As, Ga, Ge, In, P, Pb, S, or Sn.
17. The method of claim 13 , wherein the A atoms are removed by a process comprising a treatment with a fluorine-containing acid.
18. The method of claim 17 , wherein the fluorine-containing acid is aqueous hydrofluoric acid.
19. The method of claim 17 , wherein the fluorine-containing acid comprises:
(a) aqueous ammonium hydrogen fluoride (NH 4 F.HF);
(b) an alkali metal bifluoride salt (i.e., QHF 2 , where Q is Li, Na, or K), or a combination thereof; or
(c) at least one fluoride salt in the presence of at least one mineral acid that is stronger than HF; or
(d) a combination of two or more of (a)-(c).
20. The method of claim 19 , wherein the fluorine-containing acid is derived from lithium fluoride and an aqueous mineral acid that is stronger than HF.
21. A method comprising,
(a) applying a MXene dispersion onto a substrate surface, said MXene dispersion comprising at least one type of MXene platelets dispersed in a solvent and
(b) removing at least a portion of solvent so as to provide a coated film of at least one layer of MXene platelets oriented to be essentially coplanar with the substrate surface,
said MXene platelets comprising a M n+1 X n (T s ) composition having at least one layer, each layer having a first and second surface, each layer comprising
a substantially two-dimensional array of crystal cells
each crystal cell having an empirical formula of M n+1 X n , such that each X is positioned within an octahedral array of M,
wherein M is at least one Group 3, 4, 5, 6, or 7,
wherein each X is C, N, or a combination thereof and p 1 n=1, 2, or 3,
wherein at least one of said surfaces of the layers has surface terminations, T s , independently comprising alkoxide, alkyl, carboxylate, halide, hydroxide, hydride, oxide, sub-oxide, nitride, sub-nitride, sulfide, sulfonate, thiol, or a combination thereof;
said coated film being electrically conductive and exhibiting:
(i) a resistivity in a range of from about 0.01 to about 1000 micro-ohm-meters,
(ii) an ability to transmit at least about 50%, at least about 55%, at least about 60%, at least about 65%, at least about 70%, at least about 75%, at least about 80%, at least about 85%, at least about 90%, or at least about 95% of incident light of at least one wavelength in a range of from about 300 nm to about 2000 nm
(iii) a ratio of DC conductivity, measured in Siemens/meter, to light absorbance, (including visible light absorbance), measured as a decadic absorbance per meter, of at least 0.1 Siemens measured at at least one wavelength in the range of 300 to 2500 nm;
(iv) a value of the real dielectric permittivity less than negative one for wavelengths greater than a threshold wavelength, for example, 500 nm; or
(v) a combination of any two or more of (i), (ii), (iii), and (iv),
further wherein M comprises at least two Group 4, 5, 6, or 7 metals, and the M n+1 X n (T s ) composition is represented by a formula M′ 2 M″ m X m+1 (T s ).
22. The method of claim 21 , wherein M′ comprises Ti, V, Cr, or Mo.
23. The method of claim 21 , wherein M″ comprises Ti, V, Nb, or Ta, and M′ is different than M″.
24. The method of claim 21 , wherein M′ 2 M″ m X m+1 , comprises Mo 2 TiC 2 , Mo 2 VC 2 , Mo 2 TaC 2 , Mo 2 NbC 2 , Mo 2 Ti 2 C 3 , Cr 2 TiC 2 , Cr 2 VC 2 , Cr 2 TaC 2 , Cr 2 NbC 2 , Ti 2 NbC 2 , Ti 2 TaC 2 , V 2 TaC 2 , V 2 TiC 2 , or a combination thereof.
25. The method of claim 21 , wherein M′ 2 M″ m X m+1 , comprises Mo 2 TiC 2 , Mo 2 VC 2 , Mo 2 TaC 2 , Mo 2 NbC 2 , Cr 2 VC 2 , Cr 2 TaC 2 , Cr 2 NbC 2 , Ti 2 NbC 2 , Ti 2 TaC 2 , V 2 TaC 2 , V 2 TiC 2 , or a combination thereof.
26. The method of claim 21 , wherein M′ 2 M″ m X m+1 , comprises Mo 2 Ti 2 C 3 , Mo 2 V 2 C 3 , Mo 2 Nb 2 C 3 , Mo 2 Ta 2 C 3 , Cr 2 Ti 2 C 3 , Cr2V 2 C 3 , Cr 2 Nb 2 C 3 , Cr 2 Ta 2 C 3 , Nb 2 Ta 2 C 3 , Ti 2 Nb 2 C 3 , Ti 2 Ta 2 C 3 , V 2 Ta 2 C 3 , V 2 Nb 2 C 3 , V 2 Ti 2 C 3 , or a combination thereof.
27. The method of claim 21 , wherein M′ 2 M″ m X m+1 , comprises Nb 2 VC 2 , Ta 2 TiC 2 , Ta 2 VC 2 , Nb 2 TiC 2 or a combination thereof.
28. The method of claim 21 , wherein the M′ 2 M″ m X m+1 is in a disordered state.