Carbon-nanotube-based composite coating and production method thereof

Abstract

A first aspect of the invention relates to a carbon-nanotube-based composite coating, comprising a layer of carbon nanotubes (CNTs) that comprise metal oxide claddings sheathing them. Another aspect of the invention relates to a method for producing such CNT-based composite coatings using chemical vapour deposition (CVD).

1 . A carbon-nanotube-based composite coating, comprising a layer of carbon nanotubes, wherein the carbon nanotubes comprise metal oxide claddings that sheathe the carbon nanotubes. 
     
     
         2 . The carbon-nanotube-based composite coating as claimed in  claim 1 , wherein the carbon nanotubes are non-aligned. 
     
     
         3 . The carbon-nanotube-based composite coating as claimed in  claim 1 , wherein the carbon nanotubes have an average diameter in the range from 0.3 to 150 nm. 
     
     
         4 . The carbon-nanotube-based composite coating as claimed in  claim 1 , wherein the metal oxide claddings comprise or consist of MgO. 
     
     
         5 . The carbon-nanotube-based composite coating as claimed in  claim 1 , comprising a ceramic cap as a layer atop said sheathed carbon nanotubes and/or as an infiltration in said layer of carbon nanotubes. 
     
     
         6 . The carbon-nanotube-based composite coating as claimed in  claim 5 , wherein the ceramic cap layer consists of a different material than said metal oxide claddings. 
     
     
         7 . The carbon-nanotube-based composite coating as claimed in  claim 5 , wherein said ceramic cap layer consists of a material selected from the group comprising Al 2 O 3 , Si 2 O, Si 3 N 4 , MgF 2 , SiO x N x , AlN, AlNO, MgO, ZnO, SnO 2 , NiO, ZrO 2 , Cr 2 O 3 , MoO 2 , RuO 2 , CoO x , CuO x , VO x , FeO, x  MnO x , TiO 2 , CaF 2 , BaF 2 , ternary and complex oxides involving one or more elemental species of the foregoing, and mixtures thereof. 
     
     
         8 . An optical black coating, comprising a carbon-nanotube-based composite coating as claimed in  claim 1 . 
     
     
         9 . A method for producing carbon nanotubes by chemical vapour deposition, said method comprising:
 providing, in a reaction chamber, a substrate with metal and/or metal carbide nanoparticles on its surface, the metal and/or metal carbide nanoparticles comprising a first, CNT-growth-catalysing, metal selected from the group comprising Fe, Co, Ni and mixtures thereof;   introducing an inorganic, metalorganic or organometallic precursor into the reaction chamber, together with a precursor for CNTs, the inorganic, metalorganic or organometallic precursor selected for the deposition of a second metal;   growing CNTs from the precursor for CNTs, the second metal obtained from the inorganic, metalorganic or organometallic precursor enhancing CNT-growth-catalysing activity of the first metal.   
     
     
         10 . The method as claimed in  claim 9 , wherein the precursor for CNTs comprises a hydrocarbon. 
     
     
         11 . The method as claimed in  claim 9 , wherein the second metal forms an alloy or carbide phase with the first metal, the alloy or carbide phase causing the enhanced CNT-growth-catalysing activity. 
     
     
         12 . The method as claimed in  claim 9 , wherein the growth of the CNTs is carried out in the temperature range from 300 to 600° C. 
     
     
         13 . The method as claimed in  claim 12 , wherein the growth of the CNTs is neither plasma-induced nor radiation-induced. 
     
     
         14 . The method as claimed in  claim 9 , wherein the second metal forms a metal oxide cladding sheathing the CNTs. 
     
     
         15 . The method as claimed in  claim 9 , wherein the second metal is Mg. 
     
     
         16 . The method as claimed in  claim 9 , comprising depositing a ceramic cap layer atop the CNTs. 
     
     
         17 . The method as claimed in  claim 16 , wherein the cap layer consists of a material selected from the group comprising Al 2 O 3 , Si 2 O, Si 3 N 4 , SiO x N x , AlN, AlNO, MgO, ZnO, SnO 2 , NiO, ZrO 2 , Cr 2 O 3 , MoO 2 , RuO 2 , CoO x , CuO x , VO x , FeO x , MnO x , TiO 2 , CaF 2 , BaF 2 , MgF 2 , ternary and/or complex oxides involving one or more elemental species of the foregoing, and mixtures thereof. 
     
     
         18 . The method as claimed in  claim 9 , wherein the metal and/or metal carbide nanoparticles are deposited from a metalorganic or organometallic precursor for the first metal. 
     
     
         19 . The method as claimed in  claim 9 , wherein the chemical vapour deposition comprised pulsed spray evaporation chemical vapour deposition, the metal and/or metal carbide nanoparticles being deposited from a first precursor solution comprising a metalorganic or organometallic precursor for the first metal dissolved in a solvent, the second metal being deposited from a second precursor solution containing the metalorganic or organometallic precursor selected for the deposition of the second metal dissolved in alcohol serving as the precursor for the CNTs. 
     
     
         20 . The method as claimed in  claim 19 , wherein the precursor for the first metal comprises at least one of cobalt acetylacetonate, nickel acetylacetonate, and iron acetylacetonate, and wherein the precursor selected for the deposition of the second metal comprises magnesium acetylacetonate.