Nano-Particles Containing Carbon and a Ferromagnetic Metal or Alloy

Abstract

The invention relates to nano-particles comprising metallic ferromagnetic nanocrystals combined with either amorphous or graphitic carbon in which or on which chemical groups are present that can dissociate in aqueous solutions. According to the invention there is provided nano-particles comprising metal particles of at least one ferromagnetic metal, which metal particles are at least in part encapsulated by graphitic carbon. The nano-particles of the invention are prepared by impregnating carbon containing bodies with an aqueous solution of at least one ferromagnetic metal precursor, drying the impregnated bodies, followed by heating the impregnated bodies in an inert and substantially oxygen-free atmosphere, thereby reducing the metal compounds to the corresponding metal or metal alloy.

1 . A nano-particle comprising 3-100 metal particles of at least one ferromagnetic metal, and a graphitic carbon body, wherein said metal particles are at least in part encapsulated by said graphitic carbon body. 
     
     
         2 . The nano-particle according to  claim 1 , wherein the ferromagnetic metal comprises iron. 
     
     
         3 . The nano-particle according to  claim 2 , wherein the ferromagnetic particle further comprises a metal selected from the group of nickel, cobalt, precious metals and combinations thereof. 
     
     
         4 . The nano-particle according to  claim 1 , wherein the ferromagnetic particles are at least partly coated with graphitic carbon and at least partly by a gold layer. 
     
     
         5 . The nano-particle according to  claim 1 , wherein the ferromagnetic particles are completely encapsulated by graphitic carbon. 
     
     
         6 . The nano-particles according to  claim 1 , wherein said nano-particles further comprise substituted polynuclear aromatic compounds, which are adsorbed to the surface of said graphitic carbon body. 
     
     
         7 . A process for the production of a nano-particle comprising a metal-carbon body, wherein said metal-carbon body comprises ferromagnetic metal alloy particles at least partly encapsulated within graphitic carbon, which process comprises impregnating carbon containing body with an aqueous solution of at least one ferromagnetic metal precursor, drying the impregnated body, followed by heating the impregnated body in an inert and substantially oxygen-free atmosphere at a temperature of 450 to 600° C., thereby reducing the metal compounds to the corresponding metal alloy. 
     
     
         8 . A process for the production of a nano-particle comprising a metal-carbon particle, wherein said metal-carbon particle comprises ferromagnetic metal particles at least partly encapsulated within graphitic carbon, which process comprises impregnating a carbon containing body with an aqueous solution of a metal precursor, drying the impregnated body, followed by heating the impregnated body in an inert and substantially oxygen-free atmosphere at a temperature to above 700° C., thereby reducing the metal compound to the corresponding metal. 
     
     
         9 . The process according to  claim 7 , wherein the ferromagnetic metal is iron. 
     
     
         10 . The process according to  claim 7 , wherein the metal precursor is one or more salts of one or more organic acids selected from the group consisting of citric acid, acetic acid, formic acid, hydroxyl acids and ammonium citrate. 
     
     
         11 . The process according to  claim 7 , wherein said carbon containing body is selected from the group consisting of microcrystalline cellulose, colloidal carbon, and mixtures thereof. 
     
     
         12 . The process according to  claim 7 , wherein the metal alloy further comprises another metal selected from the group of nickel, cobalt, precious metals, and mixtures thereof. 
     
     
         13 . The process according to  claim 7 , wherein the nano-particle comprises amorphous carbon, wherein said nano-particle is treated with an oxidizing agent, removing said amorphous carbon and producing carboxylic acid groups on the graphitic surfaces. 
     
     
         14 . The process according to  claim 7 , wherein the nano-particle is treated in a flow comprising hydrogen and carbon containing molecules, wherein said nano-particle is completely encapsulated by graphitic carbon. 
     
     
         15 . The process according to  claim 7 , wherein the nano-particle is immersed in an aqueous solution comprising a gold compound, wherein said nano-particle is partly coated in a gold layer. 
     
     
         16 . The process according to  claim 8 , wherein the ferromagnetic metal is iron. 
     
     
         17 . The process according to  claim 8 , wherein the metal precursor is one or more salts of one or more organic acids selected from the group consisting of citric acid, acetic acid, formic acid, hydroxyl acids and ammonium citrate. 
     
     
         18 . The process according to  claim 8 , wherein said carbon containing body is selected from the group consisting of microcrystalline cellulose, colloidal carbon, and mixtures thereof. 
     
     
         19 . The process according to  claim 8 , wherein the nano-particle comprises amorphous carbon, wherein said nano-particle is treated with an oxidizing agent, removing said amorphous carbon and producing carboxylic acid groups on the graphitic surfaces. 
     
     
         20 . The process according to  claim 8 , wherein the nano-particle is treated in a flow comprising hydrogen and carbon containing molecules, wherein said nano-particle is completely encapsulated by graphitic carbon.