Low friction coatings
A low friction, wear-resistant surface operable at high temperatures and high loads with a low coefficient of friction including boron nitride and graphene-oxide on steel or nanodiamonds and graphene on aluminum. The low friction, wear-resistant surface remains with a coefficient of friction in the superlubric regime at temperatures in between about 200° C. and 970° C.
1. A method comprising:
preparing graphene-oxide by chemical exfoliation of polycrystalline graphite or highly-oriented pyrolytic graphite;
suspending the prepared graphene-oxide in a solvent to form a mixture of at least 50 mg/L;
adding at least 50 mg/L of boron nitride to the mixture;
adding a functionalizer comprising polydopamine (“PDA”);
sonicating the mixture to form a homogenous mixture; and
disposing the homogeneous mixture by:
spraying the homogeneous mixture on a substrate via a process of air-spray coating, wherein the substrate has a temperature of at least 110° C.,
forming a wet film on the substrate, and
evaporating the solvent to form a dry coating layer, the dry coating layer reducing the friction of the substrate by greater than or equal to 50%.
2. The method of claim 1 , wherein the graphene oxide and the boron nitride are in a range of ratios of about 1:1.
3. The method of claim 1 , wherein the solvent is water.
4. The method of claim 1 , wherein the solvent is oil-free.
5. The method of claim 1 , wherein the substrate is boron steel.
6. The method of claim 1 , wherein the temperature is about 275° C.
7. The method of claim 1 , wherein the functionalizer is added prior to sonicating the mixture.
8. The method of claim 7 , wherein the functionalizer further comprises Polyether ether ketone (“PEEK”).
9. A method comprising:
preparing a functionalizer solution comprising polydopamine;
forming a solid lubricant mixture;
sonicating the solid lubricant mixture to form a homogenous mixture;
adding the functionalizer solution to the homogenous mixture, forming a liquid spray mixture; and
disposing the liquid spray mixture by:
spraying the liquid spray mixture on a substrate via a process of air-spray coating,
forming a wet film on the substrate, and
evaporating the solvent component to form a dry coating layer, the dry coating layer reducing the friction of the substrate by greater than or equal to 50%;
wherein the dry coating layer comprises polydopamine and the solid lubricant.
10. The method of claim 9 , wherein preparing a functionalizer solution comprises:
mixing PDA powder with ethanol and water;
adjusting the pH to 8.3; and
polymerizing PDA.
11. The method of claim 10 , wherein the polydopamine and solid lubricant are present in a substantially 1:1 ratio.
12. The method of claim 9 , wherein the solid lubricant is selected from the group consisting of boron nitride and graphene oxide, nanodiamonds, molybdenum sulfide, graphene, and tungsten sulfide.
13. The method of claim 9 , further comprising diluting the solid lubricant mixture with water.
14. The method of claim 9 , wherein the substrate has a temperature at least about 110° C.
15. The method claim 9 , wherein the substrate is boron steel.
16. The method claim 9 , wherein the substrate is aluminum.