Nano-particles containing carbon and a ferromagnetic metal or alloy
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 process for the production of a nano-particle comprising a metal-carbon particle, wherein the metal-carbon particle comprises ferromagnetic metal particles at least partly encapsulated within graphitic carbon, wherein the process comprises:
impregnating a carbon containing body with an aqueous solution of a metal precursor;
drying the impregnated body; and
after drying the impregnated body, heating the impregnated body in a gas atmosphere at a temperature of above 700° C. to reduce a metal compound in the impregnated body to the ferromagnetic metal particles and to at least partly encapsulate the ferromagnetic metal particles within the graphitic carbon, wherein the gas atmosphere consists of inert gas.
2. The process according to claim 1 , wherein the ferromagnetic metal is iron.
3. The process according to claim 1 , 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.
4. The process according to claim 1 , wherein the carbon containing body is selected from the group consisting of microcrystalline cellulose, colloidal carbon, activated carbon bodies and mixtures thereof.
5. The process according to claim 1 , wherein the nano-particle comprises amorphous carbon, wherein the nano-particle is treated with an oxidizing agent, removing the amorphous carbon and producing carboxylic acid groups on the graphitic surfaces.
6. The process according to claim 1 , wherein the nano-particle is further treated in a flow comprising hydrogen and carbon containing molecules, wherein the nano-particle is completely encapsulated by graphitic carbon.