Carbon nanofiber materials and lubricants

Abstract

Nickel-containing carbon nanofiber (NiCNF) materials and lubricants comprising the nanofiber materials are described herein. The NiCNF materials comprise a plurality of elongate nickel-containing carbon nanofibers. Each NiCNF comprises a carbon nanofiber shaft that is capped at one end by a nickel nanoparticle encapsulated in multiple layers of graphitic carbon. The nanofibers typically have a generally circular cross-section (i.e., in the direction perpendicular to the length-axis of the fibers). The NiCNF materials as useful, e.g., in lubricant compositions, which also are described herein.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows: 
     
         1 . A nickel-containing nanofiber (NiCNF) material comprising a plurality of elongate nickel-containing carbon nanofibers, wherein individual nanofibers of the NiCNF material include a nickel nanoparticle encapsulated within multiple layers of graphitic carbon at one end of a carbon nanofiber shaft. 
     
     
         2 . The NiCNF material of  claim 1  wherein the individual nanofibers have a fiber diameter in the range of about of about 30 to about 100 nanometers (nm). 
     
     
         3 . The NiCNF material of  claim 1  wherein the individual nanofibers have a length in the range of about 100 nm to about 2 micrometers (μm). 
     
     
         4 . The NiCNF material of  claim 1  wherein the nickel nanoparticle has a diameter in the range of about 10 to about 30 nm. 
     
     
         5 . The NiCNF material of  claim 1  wherein the graphitic carbon encapsulating the nickel nanoparticle has a thickness in the range of about 4 to about 10 nm. 
     
     
         6 . The NiCNF material of  claim 1  wherein the NiCNF material contains not more than about 60 wt % of the carbon that is not part of the nickel-containing carbon nanofibers. 
     
     
         7 . The NiCNF material of  claim 1  wherein at least about 50% of the nickel in the NiCNF material is encapsulated at an end of a carbon nanofiber shaft. 
     
     
         8 . The NiCNF material of  claim 1  wherein the individual nanofibers have a fiber diameter in the range of about of about 30 to about 100 nm, and a length in the range of about 100 nm to about 2 μm; the nickel nanoparticle has a diameter in the range of about 10 to about 30 nm; and the graphitic carbon encapsulating the nickel nanoparticle has a thickness in the range of about 4 to about 10 nm. 
     
     
         9 . A lubricant composition comprising the NiCNF material of  claim 1  dispersed in a liquid medium. 
     
     
         10 . The lubricant composition of  claim 9  wherein the individual nanofibers have a fiber diameter in the range of about of about 30 to about 100 nm, and a length in the range of about 100 nm to about 2 μm; the nickel nanoparticle has a diameter in the range of about 10 to about 30 nm; and the graphitic carbon encapsulating the nickel nanoparticle has a thickness in the range of about 4 to about 10 nm. 
     
     
         11 . The lubricant composition of  claim 9  further comprising a surfactant. 
     
     
         12 . The lubricant composition of  claim 11  wherein the surfactant comprises a non-ionic surfactant. 
     
     
         13 . The lubricant composition of  claim 11  wherein the surfactant comprises sorbitan trioleate. 
     
     
         14 . The lubricant composition of  claim 11  wherein the surfactant is present in the composition at a concentration in the range of about 1000 to about 20000 parts-per-million (ppm). 
     
     
         15 . The lubricant composition of  claim 9  wherein the liquid carrier comprises a liquid hydrocarbon. 
     
     
         16 . The lubricant composition of  claim 15  wherein the liquid hydrocarbon comprises a poly alpha olefin. 
     
     
         17 . The lubricant composition of  claim 9  wherein the NiCNF material is present in the composition at a concentration in the range of about 0.01 to about 15 wt %. 
     
     
         18 . The lubricant composition of  claim 9  wherein the liquid carrier comprises a poly alpha olefin and the NiCNF material is present in the composition at a concentration in the range of about 0.5 to about 1 wt %. 
     
     
         19 . The lubricant composition of  claim 18  further comprising a non-ionic surfactant. 
     
     
         20 . A method of preparing a NiCNF material of  claim 1  comprising heating nickel(II) acetate neat in a sealed pressure reactor at a temperature of about 650 to about 800° C. at an autogenically produced pressure of about 300 to about 600 psi under an inert atmosphere.