Polymer composites with highly tunable thermal and mechanical properties and methods of manufacture

Abstract

A method of forming an polymer composites is disclosed herein that includes infiltrating CNT sponges with a polymer or metal to form a composite. The method uses a relatively easy, scalable, and low-cost synthesis process that makes the composites attractive as TIM. CNTs in the sponge structure are covalently bonded, resulting in a low Young's modulus while at the same time maintaining a good thermal conductivity. This strategy makes it possible to obtain both high deformability and high thermal conductivity, which are difficult to have simultaneously due to their adverse correlation.

1 . A composite material that can be used as a thermal interface material, aerogel, lightweight material, comprising covalently-bonded carbon nanotubes (CNT) embedded in a matrix comprising a polymer or a metal. 
     
     
         2 . The composite material of  claim 1 , wherein the polymer comprises at least one of polyvinylidene fluoride, polyurethane, epoxy or polydimethylsiloxane. 
     
     
         3 . The composite material of  claim 1 , wherein the metal comprises at least one of indium, tin, zinc, gallium, an indium alloy, a tin alloy, and a zinc alloy. 
     
     
         4 . The composite material of  claim 1 , wherein the covalent bonds comprise bonds formed between junctions of the CNTs. 
     
     
         5 . The composite material of  claim 1 , wherein the covalent bonding results in a thermal conductivity of at least 1 W/(m−K) and a Young's modulus of ˜50 MPa or lower. 
     
     
         6 . The composite material of  claim 5 , wherein the thermal conductivity and Young's modulus allow the thermally deformable interface material to deform upon surfaces. 
     
     
         7 . The composite material of  claim 1 , wherein polymer is coated on the surface of CNT, maintaining a highly porous structure. 
     
     
         8 . The composite material of  claim 7 , wherein the porous structure results in a low thermal conductivity of ˜0.25 W/(m−K) even after 1000 cycles of repeated deformation. 
     
     
         9 . The composite material of  claim 7 , wherein the strengthened structure with the polymer coating provide high resilience, showing invariable compressive stress over 8000 cycles of repeated deformation. 
     
     
         10 . The composite material of  claim 7 , wherein the resistance of the aerogel consistently varies as a function of deformation. 
     
     
         11 . A method for producing CNT sponges comprising:
 producing CNT sponges in a tube furnace;   slicing the produced CNT sponges into a shape with a desired dimensions;   treating the sliced CNT sponges with ozone plasma to make the sliced CNT sponges more hydrophilic;   soaking the treated CNT sponges in a polymer to solution to infiltrate the treated CNT sponges with the polymer solution;   degassing the soaked CNT sponges in a vacuum; and   drying the degassed CNT sponges.   
     
     
         12 . The method of  claim 11 , wherein producing the CNT sponges comprises producing CNTs having covalently bonded tubular structures. 
     
     
         13 . The method of  claim 12 , wherein the tube furnace comprises three zones and the producing step comprises:
 using ferrocene in a first zone to deliver iron as a CNT catalyst to a third zone; and   flowing hydrogen gas, ethylene gas, and argon gas through the tube furnace.   
     
     
         14 - 15 . (canceled) 
     
     
         16 . A method of preparing a carbon nanotube-polydimethylsiloxane (CNT-PDMS) composite, the method comprising:
 soaking a CNT sponge in a mixture comprising at least one of a polymer and at least one of a solvent to dissolve the polymer to form a layer of polydimethylsiloxane on walls of CNTs in the CNT sponge;   exposing the soaked CNT sponge to multiple microwave radiation treatments with cooling steps between each treatment; and   wherein the exposing forms bonds between the CNTs due to the layer of polydimethylsiloxane on the walls of the CNTs.   
     
     
         17 . The method of  claim 16 , wherein the polymer is polydimethylsiloxane and the solvent is hexane. 
     
     
         18 . The method of  claim 17 , wherein the concentration of polymer can be changed or multiple deposition processes can be carried out to fill the voids created in the composite up to 100%. 
     
     
         19 - 20 . (canceled) 
     
     
         21 . A method of manufacturing polymer-CNT composites, the method comprising:
 placing a slurry comprising CNTs and liquid-phase polymers on a conveyor;   conveying the slurry to a first pulse-microwave radiation location and irradiating the slurry;   monitoring in situ the irradiated slurry with at least one sensor; and   conveying the slurry to a second pulse-microwave radiation location and irradiating the slurry.   
     
     
         22 . The method of  claim 21 , wherein the irradiating at the second pulse-microwave radiation location comprises adjusting one or more irradiating parameters based upon the monitoring. 
     
     
         23 . The method of  claim 21 , wherein the monitoring comprises at least one of a manufacturing status, a curing status of the slurry, a thickness of the slurry, a rheology of the slurry, and cylinder orientation of the CNTs. 
     
     
         24 . The method of  claim 21 , further comprising adjusting an orientation of the CNTs by adjusting at least one of a roller pressure of a roller, tiling a roller stage, and a magnetic field. 
     
     
         25 . The method of  claim 21 , wherein hollow fillers are added to make lightweight composites. 
     
     
         26 . The method of claim  19 , wherein hollow fillers are oriented along a desired direction to achieve desired mechanical properties along a particular orientation. 
     
     
         27 - 37 . (canceled)