Method for Making Ultra-Fine Carbon Fibers and Activated Ultra-Fine Carbon Fibers

Abstract

A method for making ultra-fine carbon fibers and activated ultra-fine carbon fibers includes core-sheath melt-spinning to produce a core-sheath fiber including a sheath made of polyolefin and a carbon-containing polymer, and a core made of a polyolefin polymer. Under control of temperature, the core-sheath fiber is stabilized as a carbon-containing precursor fiber. The stabilized core-sheath fiber is carbonized in nitrogen at 600 to 1500 degrees Celsius and converted into ultra-fine carbon fibers with a diameter of 20 to 800 nm. Then, the ultra-fine carbon fibers are activated in carbon dioxide, steam, air or any combination thereof at 600 to 1500 degrees Celsius to form activated ultra-fine carbon fibers.

1 . A method for making ultra-fine carbon fibers comprising:
 providing a core-sheath fiber with a core made of a polyolefin polymer, and a sheath made of a polyolefin polymer and a carbon-containing polymer, with the carbon-containing polymer being at least one selected from the group consisting of phenol-formaldehyde, thermoplastic polyacrylonitrile, thermoplastic polyvinyl alcohol, polyvinyl chloride and mesophase pitch;   stabilizing the core-sheath fiber into carbon-containing precursor fiber; and   carbonizing the carbon-containing precursor fiber at 600 to 1500 degrees Celsius to get ultra-fine carbon fibers with a diameter of 20 to 800 nm.   
     
     
         2 . The method according to  claim 1 , wherein the polyolefin polymer is at least one selected from the group consisting of polystyrene, polyethylene, polypropylene, polymethylpentene and an olefin-containing co-polymer. 
     
     
         3 . The method according to  claim 1 , wherein the weight ratio of the core to the sheath is in a range between 20:80 and 80:20. 
     
     
         4 . The method according to  claim 1 , wherein the weight ratio of the carbon-containing polymer of the sheath to the polyolefin polymer of the sheath is in a range between 1:5 and 3:2. 
     
     
         5 . The method according to  claim 1 , further comprising graphitizing the ultra-fine carbon fibers in Argon at 1500 to 3000 degrees Celsius. 
     
     
         6 . The method according to  claim 1 , further comprising activating the ultra-fine carbon fibers in at least one selected from the group consisting of carbon dioxide, steam and air to get activated ultra-fine carbon fibers with a diameter of 20 to 800 nm.