Composite material comprising oriented carbon nanotubes in a carbon matrix and process for preparing same

Abstract

Fiber spinning of two polymer compositions wherein one of the compositions contains carbon nanotubes produces structures such as fibers, ribbons, yarns and films of carbon nanotubes. The polymers are removed and stabilization of the carbon nanotube material is achieved by post-spinning processes. The advances disclosed herein enable the carbon nanotube composites to be used in actuators, supercapacitors, friction materials and in devices for electrical energy harvesting.

1 . A structure comprising carbon nanotubes wherein the carbon nanotubes in the structure are aligned to give an f value of 0.590-1.00.  
     
     
         2 . The structure according to  claim 1 , wherein the carbon nanotubes in the structure are aligned to give an f value of 0.630-0.900.  
     
     
         3 . The structure according to  claim 1 , wherein the carbon nanotubes in the structure are aligned to give an f value of 0.630-0.750.  
     
     
         4 . The structure according to  claim 1 , wherein at least one of carbon, silicon and silicon carbide has been deposited on the carbon nanotubes.  
     
     
         5 . The structure according to  claim 2 , wherein the structure is a hollow macrotube comprising walls made of the carbon nanotubes.  
     
     
         6 . The structure according to  claim 2 , wherein the structure is an essentially flat film formed of the carbon nanotubes.  
     
     
         7 . A friction material for braking systems comprising the structure according to  claim 1 .  
     
     
         8 . An apparatus for preparing a structure comprising aligned carbon nanotubes according to  claim 1 , said apparatus comprising an upper spinneret having inner walls defining a cavity (A) through which a core polymer flows, a lower spinneret having inner walls defining a cavity (B) which is aligned with the cavity (A) so that the core polymer flowing from the upper spinneret flows directly into the cavity (B), the lower spinneret having an upper surface which is indented to form at least one cavity (C) for a mixture comprising a sheath polymer and carbon nanotubes, wherein the cavity (C) is defined by an inner wall, bottom wall and outer wall, the lower spinneret containing at least one annular space which connects cavity (C) with cavity (B) to allow flow of the sheath polymer/carbon nanotube mixture from cavity (C) to cavity (B) to coat the core polymer to form a carbon nanotube coated polymer mixture, the inner walls defining cavity (B) constrict at a constricting point to reduce the diameter of cavity (B) to a distance D i  thereby increasing the shear force on the carbon nanotube coated polymer mixture before exiting the apparatus through an exit hole in the lower spinneret.  
     
     
         9 . The apparatus according to  claim 8 , wherein multiple cavities (C) are concentrically located around cavity (B) and are each connected to cavity (B) with at least one annular space.  
     
     
         10 . The apparatus according to  claim 8 , wherein cavity (C) is a single cavity concentrically located around cavity (B).  
     
     
         11 . The apparatus according to  claim 9 , wherein a line D o  is a measurement of an average of twice the distance between the inner wall of cavity (C) and a center point of cavity, (B), wherein the line D o  is measured at an angle which is perpendicular to the flow of the core polymer through cavity (B), and wherein the ratio D o /D i  is 4-25.  
     
     
         12 . The apparatus according to  claim 10 , wherein the cavity (C) is a single concentric cavity which is connected to cavity (B) by multiple annular spaces, a line D o  is a measure of the diameter of the inner wall, and the ratio D o /D i  is 4-25.  
     
     
         13 . The apparatus according to  claim 11 , wherein the ratio D o /D i  is 6-10.  
     
     
         14 . The apparatus according to  claim 12 , wherein the ratio D o /D i  is 6-10.  
     
     
         15 . The apparatus according to  claim 8 , wherein the structure contains 2-30 capillaries.