NOVELTY - Making a carbon fiber, involves extruding a solution of a primary component and a solution of a secondary component through a bi-component extrusion apparatus to form a bi-component polymer fiber comprising a primary component and a secondary component; and drawing the bi-component polymer fiber to form a drawn bi-component polymer fiber. The primary component comprises an acrylonitrile-containing polymer.    USE - For making carbon fiber (claimed) useful in a variety of applications, including, but not limited to, material reinforcement (e.g., in tire cord and in cement), aircraft parts, body panels for high-performance vehicles (e.g., formula one race cars and motorcycles), sporting equipment (e.g., bikes, golf clubs, tennis rackets, and skis), and other demanding mechanical applications. Can also used in electronic devices, fuel cells, and electrochemical capacitors.    ADVANTAGE - The carbon fiber has an average diameter of 10 nanometers to 10 micrometers. The carbon fibers and/or films can be tailored to exhibit high strength, high modulus, high electrical conductivity, high thermal conductivity, and optical transparency, depending on the desired application for the fibers or films.    DETAILED DESCRIPTION - Making a carbon fiber, involves extruding a solution of a primary component and a solution of a secondary component through a bi-component extrusion apparatus to form a bi-component polymer fiber comprising a primary component and a secondary component; and drawing the bi-component polymer fiber to form a drawn bi-component polymer fiber. The primary component comprises an acrylonitrile-containing polymer. The method further involves stabilizing the drawn bi-component polymer fiber under tension or in oxidizing environment at 200-400 degrees C for less than or equal to 36 hours; separating the primary component from the secondary component; carbonizing the primary component of the bi-component polymer fiber under tension or in an inert environment at 500-1800 degrees C for less than or equal to 2 hours; and graphitizing the carbonized primary component of the bi-component polymer fiber under tension in a non-nitrogen-containing inert environment at 1800-2800 degrees C for less than or equal to 1 hour. The extruding comprises gel-extruding or solution-extruding. The drawn bi-component polymer fiber has an average diameter of 100 nanometers to 1 millimeter. The primary and secondary components are separated by dissolving the secondary component from drawn or stabilized bi-component polymer fiber, sonicating the drawn or stabilized bi-component polymer fiber to reduce any interfacial interactions between primary and secondary component, heating to melt the second component away from the drawn or stabilized bi-component polymer fiber and/or heating to burn the second component away from the drawn or stabilized bi-component polymer fiber. The method further involves contacting carbon nanotubes (CNT) with an acrylonitrile-containing polymer to form a primary component solution. The CNT comprise single wall nanotubes, double wall nanotubes and/or triple wall nanotubes. The CNT have an average diameter of 0.5-25 nanometers. The carbon fiber is optically transparent. An INDEPENDENT CLAIM is included for a carbon fiber formed from carbon nanotubes (CNT) and an acrylonitrile-containing polymer, comprising an average diameter of 10 nanometers to 10 micrometers; and a crystallized graphitic region radially extending 0.34 nanometers to 50 nanometers from a wall of each CNT.    DESCRIPTION OF DRAWING(S) - The figure shows a process flow diagram of the method for making a carbon fiber.