Carbon nanotube foams with controllable mechanical properties

Abstract

Syntheses of carbon nanotubes (CNT) are disclosed. The syntheses can take place on a thermally oxidized silicon surface placed inside a furnace prior to a reaction. The setup can have many variables that could affect the resulting CNT arrays, including flow rate and composition of carrier gas, flow rate and composition of precursor solution, and temperature. By varying such variables the density of the resulting CNT arrays can be controlled.

1 . A method for controlling mechanical properties in a carbon nanotube foam structure, the method comprising:
 synthesizing the carbon nanotube foam structure by carrying a precursor solution comprising a catalyst and a carbon source in a reaction zone by way of a carrier gas; and   controlling or varying an input of precursor solution to affect the mechanical properties of the carbon nanotube foam structure.   
     
     
         2 . The method of  claim 1 , wherein controlling or varying an input of precursor solution includes controlling or varying an input rate of precursor solution. 
     
     
         3 . The method of  claim 2 , wherein controlling or varying an input rate of precursor solution determines a heterogeneous density distribution of the foam structure. 
     
     
         4 . The method of  claim 2 , further comprising increasing the input rate of the precursor solution to reduce average carbon nanotube diameter and to reduce density along a height of the structure. 
     
     
         5 . The method of  claim 1 , wherein controlling or varying an input of precursor solution includes controlling or varying an input flow direction of precursor solution. 
     
     
         6 . A method for controlling mechanical properties in a carbon nanotube foam structure, the method comprising:
 synthesizing the carbon nanotube foam structure by carrying a precursor solution comprising a catalyst and a carbon source in a reaction zone by way of a carrier gas including hydrogen to obtain the carbon nanotube foam structure; and   controlling or varying a concentration of hydrogen in the carrier gas to affect an average nanotube diameter in the foam structure and to control the mechanical properties of the carbon nanotube foam structure; and   controlling or varying an input rate of the precursor solution to affect an average carbon nanotube diameter in the foam structure and to control the mechanical properties of the carbon nanotube foam structure.   
     
     
         7 . The method of  claim 6 , further comprising increasing the input rate of the precursor solution to reduce density along a height of the structure and to reduce average carbon nanotube diameter. 
     
     
         8 . The method of  claim 7 , further comprising reducing a concentration of the hydrogen to increase number of walls of individual carbon nanotubes and to increase density of nominally-aligned arrays of carbon nanotubes. 
     
     
         9 . A method for synthesizing nominally-aligned arrays of carbon nanotubes (CNTs), the method comprising:
 synthesizing a foam structure of nominally-aligned arrays of carbon nanotubes (CNTs) by carrying a precursor solution comprising a catalyst and a carbon source in a reaction zone by way of a carrier gas to obtain the foam structure; and   determining a relationship between a flow direction of the carrier gas carrying the precursor solution and a density of the foam structure; and   synthesizing the CNTs by controlling the flow direction of the carrier gas in relation to a growth of the nominally-aligned arrays of carbon nanotubes to increase a density of the foam structure.   
     
     
         10 . The method of  claim 9 , wherein a foam structure density is higher in regions closer to a flow input of the carrier gas carrying the precursor solution than regions far from a flow input of the carrier gas carrying the precursor solution, and foam structure density decreases gradually as CNTs grow farther from the flow input.