Composite Layers, Methods for Their Manufacture and Uses Thereof

Abstract

A composite layer of carbon nanotubes and metal such as copper is formed by electrodeposition. The layer has a thickness of at least 10 μm. The carbon nanotubes are distributed through the layer and are present in the layer at a volume fraction of at least 0.001 vol % and at most 65 vol %. The volume fraction is based on the total volume of the metal and carbon nanotubes and not including any pore volume. The carbon nanotubes are substantially uniformly plated with the metal. The composite layer has a density ratio satisfying P layer P metal ≤0.35 where p layer is the bulk density of the composite layer of thickness of at least 10 μm, including any voids that are present in the composite layer and pmetal is the volumetric mass density material property of the metal. The composite layer is of use in evaporation-condensation apparatus, as an active material layer in an electrochemical device or in an electroforming process.

1 . A composite layer of carbon nanotubes and metal, the layer having thickness of at least 10 μm, the carbon nanotubes being distributed through the layer and being present in the layer at a volume fraction of at least 0.001 vol % and at most 65 vol %, the volume fraction being based on the total volume of the metal and carbon nanotubes and not including any pore volume. 
     
     
         2 . The composite layer according to  claim 1  wherein the carbon nanotubes are substantially uniformly plated with the metal. 
     
     
         3 . The composite layer according to  claim 1  wherein the metal is at least one selected from the group consisting of: Antimony, Arsenic, Bismuth, Cadmium, Chromium, Cobalt, Copper, Gold, Indium, Iridium, Iron, Lead, Manganese, Nickel, Osmium, Palladium, Platinum, Rhenium, Rhodium, Ruthenium, Selenium, Silver, Tellurium, Thallium, Tin, Zinc, and alloys thereof, including alloys containing Cerium, Gadolinium, Lanthanum, Neodymium, Praseodymium, Samarium, Yttrium. 
     
     
         4 . The composite layer according to  claim 1  wherein the composite layer has a density ratio satisfying: 
       
         
           
             
               
                 
                   ρ 
                   layer 
                 
                 
                   ρ 
                   metal 
                 
               
               ≤ 
               0.35 
             
           
         
         where ρ layer  is the bulk density of the composite layer of thickness of at least 10 μm, including any voids that are present in the composite layer and ρ metal  is the volumetric mass density material property of the metal. 
       
     
     
         5 . A process for manufacturing a composite layer of carbon nanotubes and metal, the process comprising the steps:
 providing carbon nanotubes;   dispersing the carbon nanotubes in an electrolyte solution;   providing a working electrode and a counter electrode comprising the metal, each in contact with the electrolyte; and   electroplating the working electrode with the carbon nanotubes and metal to grow the composite layer at a rate of change of thickness of the composite layer of at least 10 μm/min to a thickness of at least 10 μm;   wherein, for at least a part of the process, the composite layer of thickness of at least 10 μm has a density ratio satisfying:   
       
         
           
             
               
                 
                   ρ 
                   layer 
                 
                 
                   ρ 
                   metal 
                 
               
               ≤ 
               0.35 
             
           
         
       
       where ρ layer  is the bulk density of the composite layer of thickness of at least 10 am, including any voids that are present in the composite layer and ρ metal  is the volumetric mass density material property of the metal. 
     
     
         6 . The process according to  claim 5  wherein, during electroplating the working electrode with the carbon nanotubes and metal to grow the composite layer at a rate of change of thickness of the composite layer of at least 10 μm/min, the rate of change of area density is at most 0.8 kg/m 2 /min. 
     
     
         7 . The process according to  claim 5  wherein the carbon nanotubes are functionalised with at least one selected from the group consisting of: Hydroxyl, Phenol, Carbonyl, Carboxylate, Carboxyl, Phosphate, Phosphono, Sulfonic acid, Sulfhydryl, Sulfide, Disulfide, Amino, Quaternary ammonium. 
     
     
         8 . The process according to  claim 7  wherein the degree of functionalisation of the carbon nanotubes is at least 1 wt %. 
     
     
         9 . The process according to  claim 5 , wherein the electrolyte, at least at the start of deposition, contains at least 0.0001 wt % carbon nanotubes. 
     
     
         10 . The process according to  claim 5  wherein the electrolyte, at least at the start of deposition, contains not more than 0.2 wt % carbon nanotubes. 
     
     
         11 . The process according to  claim 5  wherein the electrolyte, at least at the start of deposition, has a concentration of the metal in the range 0.05-1.2 M. 
     
     
         12 . An evaporation-condensation apparatus for the transfer of heat,
 the apparatus comprising a closed container having an evaporator region and a condenser region, the container having a wicking layer formed on an internal surface of the container and a working fluid contained in the container, wherein the wicking layer comprises a composite layer of carbon nanotubes and metal, the composite layer having thickness of at least 10 μm, the carbon nanotubes being distributed through the composite layer and being present in the composite layer at a volume fraction of at least 0.001 vol % and at most 65 vol %, the volume fraction being based on the total volume of the metal and carbon nanotubes and not including any pore volume,   wherein evaporation of the working fluid at the evaporator region, the mass transport of the evaporated working fluid from the evaporator region to the condenser region and the condensation of the working fluid at the condenser region contribute to the transfer of heat, the condensed working fluid being transported back to the evaporator region along the wicking layer.   
     
     
         13 . The evaporation-condensation apparatus according to  claim 12  in the form of a heat pipe. 
     
     
         14 . The evaporation-condensation apparatus according to  claim 12  in the form of a vapour chamber. 
     
     
         15 . An electrochemical device comprising an anode, electrolyte and cathode, wherein at least one of the anode and cathode includes an active material layer and a current collecting layer, wherein the current collecting layer is a composite layer of carbon nanotubes and metal, the composite layer having thickness of at least 10 μm, the carbon nanotubes being distributed through the composite layer and being present in the composite layer at a volume fraction of at least 0.001 vol % and at most 65 vol %, the volume fraction being based on the total volume of the metal and carbon nanotubes and not including any pore volume. 
     
     
         16 . An electroforming process comprising the steps:
 (i) providing a composite layer of carbon nanotubes and metal, the composite layer having thickness of at least 10 μm, the carbon nanotubes being distributed through the composite layer and being present in the composite layer at a volume fraction of at least 0.001 vol % and at most 65 vol %, the volume fraction being based on the total volume of the metal and carbon nanotubes and not including any pore volume; or   carrying out a process to manufacture a composite layer of carbon nanotubes and metal, the process comprising the steps:
 providing carbon nanotubes; 
 dispersing the carbon nanotubes in an electrolyte solution; 
 providing a working electrode and a counter electrode comprising the metal, each in contact with the electrolyte; and 
 electroplating the working electrode with the carbon nanotubes and metal to grow the composite layer at a rate of change of thickness of the composite layer of at least 10 μm/min to a thickness of at least 10 μm; 
 wherein, for at least a part of the process, the composite layer of thickness of at least 10 μm has a density ratio satisfying: 
   
       
         
           
             
               
                 
                   ρ 
                   layer 
                 
                 
                   ρ 
                   metal 
                 
               
               ≤ 
               0.35 
             
           
         
         
           where ρ layer  is the bulk density of the composite layer of thickness of at least 10 μm, including any voids that are present in the composite layer and ρ metal  is the volumetric mass density material property of the metal; and 
         
         (ii) carrying out additional electroplating of a metal into the composite layer to produce an electroformed product.