Method and apparatus for producing metallic ultrafine particles

Abstract

An object of the present invention is to efficiently produce ultrafine particles having such a small diameter as 50 nm or less, a narrow range of size distribution, and a non-oxidation surface. According to the present invention, the metallic ultrafine particles are produced by dropping a raw metallic powder onto a controllably heated evaporating surface in a decompressed inert gas; instantly evaporating the raw metallic powder to form the ultrafine particle; and condensing and depositing the ultrafine particle on a trapping surface arranged above the evaporating surface. The raw metallic powder is any one of a single metal, an alloy and an intermetallic compound, preferably has an average particle diameter controlled to 500 μm or smaller so that the powder can be instantly evaporated, and is preferably supplied by a minute amount.

1 . A method for producing metallic ultrafine particles comprising: dropping a raw metallic powder onto a controllably heated evaporating surface in a decompressed inert gas; instantly evaporating the raw metallic powder to form ultrafine particles; and condensing and depositing the ultrafine particles on a trapping surface arranged above the evaporating surface.  
     
     
         2 . The method for producing the metallic ultrafine particles according to  claim 1 , wherein the raw metallic powder is any one of a single metal, an alloy and an intermetallic compound, having an average particle diameter of 500 μm or smaller.  
     
     
         3 . An apparatus for producing the metallic ultrafine particles comprising: a vessel for forming a space of an inert gas; a heating device which is placed in a lower part in the vessel and has an evaporating surface on the top face thereof; a trapping portion of the ultrafine particle, which spreads above the heating device and is provided with cooling means; and a raw powder-feeding device for gradually dropping a raw metallic powder to the evaporating surface.  
     
     
         4 . The apparatus for producing metallic ultrafine particles according to  claim 3 , wherein the evaporating surface of the heating device is made from a highly corrosion-resistant material, and has a detachable structure from a main body of the heating device.  
     
     
         5 . The apparatus for producing the metallic ultrafine particles according to  claim 3 , wherein the trapping portion of the ultrafine particle has a structure that permits cooling water to pass inside the portion, and has a trapping surface of a hemispheric shape with its concave portion facing downward, and a through-hole for dropping the raw metallic powder therethrough, which is formed in the top center of the trapping surface.  
     
     
         6 . The apparatus for producing the metallic ultrafine particles according to  claim 3 , wherein the trapping portion of the ultrafine particle permits cooling water to pass into the portion and has a trapping surface having a cylindrical inner surface.  
     
     
         7 . The apparatus for producing the metallic ultrafine particles according to  claim 4 , wherein the trapping portion of the ultrafine particle has a structure that permits cooling water to pass inside the portion, and has a trapping surface of a hemispheric shape with its concave portion facing downward, and a through-hole for dropping the raw metallic powder therethrough, which is formed in the top center of the trapping surface.  
     
     
         8 . The apparatus for producing the metallic ultrafine particles according to  claim 4 , wherein the trapping portion of the ultrafine particle permits cooling water to pass into the portion and has a trapping surface having a cylindrical inner surface.