Superlubricity coating containing carbon nanotubes
A method for producing a structure containing an array of MWCNTs on a metal substrate, comprising: (i) subjecting a metal substrate to a surface oxidation process at a first elevated temperature in an oxygen-containing atmosphere and under a first reduced pressure; (ii) subjecting the metal substrate to a surface reduction process at a second elevated temperature in a reducing atmosphere and under a second reduced pressure of at least 0.01 atm and less than 1 atm to result in reduction of the surface of said metal substrate, wherein the reducing atmosphere contains hydrogen gas; (iii) subjecting the metal substrate to a third reduced pressure of no more than 0.1 atm; and (iv) contacting the metal substrate, while at the third reduced pressure and under an inert or reducing atmosphere, with an organic substance at a third elevated temperature for suitable time to produce the MWCNTs on the metal substrate.
1. A method for producing a structure containing an array of multi-walled carbon nanotubes on a metal substrate, the method comprising:
(i) subjecting a metal substrate to a surface oxidation process in which the metal substrate is subjected to a first temperature of 600-1000° C. in an O 2 -containing atmosphere and under a first reduced pressure of at least 0.01 atm and less than 1 atm to result in oxidation of a surface of said metal substrate, wherein said first temperature is at least 100° C. below the melting point of the metal;
(ii) subjecting the metal substrate to a surface reduction process in which the metal substrate is subjected to a second temperature of 600-1000° C. in a reducing atmosphere and under a second reduced pressure of at least 0.01 atm and less than 1 atm to result in reduction of the surface of said metal substrate, wherein said reducing atmosphere contains hydrogen gas;
(iii) subjecting the metal substrate to a third reduced pressure of no more than 0.1 atm; and
(iv) contacting the metal substrate, while at the third reduced pressure and under an inert or reducing atmosphere, with an organic substance at a third temperature of 700-900° C. for at least 1 minute, to result in production of said structure containing an array of multi-walled carbon nanotubes on said metal substrate.
2. The method of claim 1 , further comprising: (v) cooling the metal substrate to room temperature under an inert or reducing atmosphere after completion of step (iv).
3. The method of claim 1 , wherein an externally provided metallic, metal salt, or metal oxide catalyst is excluded.
4. The method of claim 1 , wherein step (i) comprises subjecting the metal substrate to a surface oxidation process in which the metal substrate is elevated in temperature from room temperature to said first temperature of 600-1000° C. at a temperature ramp rate of no more than 50° C./min in an O 2 -containing atmosphere and under a first reduced pressure of at least 0.1 atm and less than 1 atm to result in oxidation of a surface of said metal substrate, wherein said first temperature is at least 100° C. below the melting point of the metal.
5. The method of claim 4 , wherein said temperature ramp rate is no more than 40° C./min.
6. The method of claim 4 , wherein said temperature ramp rate is no more than 30° C./min.
7. The method of claim 4 , wherein said temperature ramp rate is within a range of 5-50° C/min.
8. The method of claim 1 , wherein the organic substance in step (iv) has a molecular weight of up to 500 g/mol.
9. The method of claim 1 , wherein the organic substance in step (iv) is an alcohol or hydrocarbon.
10. The method of claim 1 , wherein said metal substrate has an iron-based composition.
11. The method of claim 1 , wherein said iron-based composition is steel.
12. The method of claim 11 , wherein said steel is stainless steel.
13. The method of claim 11 , wherein said steel is tool steel.
14. The method of claim 11 , wherein said steel is an alloy steel.
15. The method of claim 1 , wherein the multi-walled carbon nanotubes are aligned substantially perpendicular to said metal substrate and substantially parallel to each other.