Magnetite-iron based composite powder, magnetite-iron based powder mixture, method for producing the same, method for remedying polluted soil, water or gases and electromagnetic wave absorber

Abstract

A magnetite-iron based composite powder includes magnetite with a ratio of X-ray diffraction intensity to that of α-Fe of about 0.001 to about 50 and has an average primary particle size of about 0.1 to about 10 μm. The composite powder can highly dehalogenate organic halogen compounds and exhibits satisfactory absorption power of high frequency electromagnetic waves after molding. An ultrafine nonferrous inorganic compound powder may adhere to the surface of the composite powder, or at least the composite powder may adhere to the surfaces of small particles of a nonferrous inorganic compound to thereby yield a composite powder composition. The composite powder can be produced by partial reduction of a material powder containing a hematite based powder or by complete reduction and subsequent partial oxidation of the material powder.

1 - 9 . (cancelled)  
     
     
         10 . (original) a method for producing a magnetite-iron based composite powder comprising: 
 reducing by heating a hematite based powder having an average primary particle size of from about 0.01 to about 10 μm in a reducing gas; and    stopping reduction at about midstream of reduction to yield a partially reduced powder which is a composite powder comprising magnetite and iron.    
     
     
         11 . A method for producing a magnetite-iron based composite powder mixture comprising: 
 reducing by heating a hematite based powder having an average primary particle size of from about 0.01 to about 10 μm in a reducing gas and in the presence of a nonferrous inorganic compound powder; and    stopping reduction at about midstream of reduction to yield a partially reduced powder which is a composite powder comprising magnetite and iron.    
     
     
         12 . A method for producing a magnetite-iron based composite powder comprising: 
 heating a hematite based powder having an average primary particle size of from about 0.01 to about 10 μm in a reducing gas to reduce the powder substantially completely; and    oxidizing a surface of resulting substantially completely reduced powder with an oxygen-containing gas to thereby yield a composite powder comprising magnetite and iron.    
     
     
         13 . A method for producing a magnetite-iron based composite powder mixture comprising: 
 heating a hematite based powder having an average primary particle size of from about 0.01 to about 10 μm in a reducing gas in the presence of a nonferrous inorganic compound powder to reduce the powder substantially completely; and    oxidizing a surface of resulting substantially completely reduced powder with an oxygen-containing gas to thereby yield a composite powder comprising magnetite and iron.    
     
     
         14 . A method for producing a magnetite-iron based composite powder comprising: 
 heating a hematite based powder having an average primary particle size of from about 0.01 to about 10 μm in a reducing gas to thereby partially reduce the powder;    stopping reduction at about midstream of reduction to yield a partially reduced powder; and    oxidizing a surface of the partially reduced powder with an oxygen-containing gas to thereby yield a composite powder comprising magnetite and iron.    
     
     
         15 . A method for producing a magnetite-iron based composite powder mixture comprising: 
 reducing by heating a hematite based powder having an average primary particle size of from about 0.01 to about 10 μm in a reducing gas in the presence of a nonferrous inorganic compound powder;    stopping reduction at about midstream of reduction to yield a partially reduced powder; and    oxidizing a surface of the partially reduced powder with an oxygen-containing gas to thereby yield a composite powder comprising magnetite and iron.    
     
     
         16 . A method for remedying polluted media comprising: 
 bringing a magnetite-iron based composite powder comprising magnetite and iron and having an average primary particle size of from about 0.01 to about 10 μm into contact with a media contaminated with an organic halogen compound; and    causing the organic halogen compound to decompose.    
     
     
         17 . A method for remedying polluted media comprising: 
 bringing a magnetite-iron based composite powder mixture comprising magnetite and iron and having an average primary particle size of from about 0.01 to about 10 μm and a nonferrous inorganic compound powder into contact with a media contaminated with an organic halogen compound; and    causing the organic halogen compound to decompose.    
     
     
         18 . An electromagnetic wave absorber comprising a compacted mixture of a magnetite-iron based composite powder comprising magnetite and iron and having an average primary particle size of from about 0.01 to about 10 μm and a rubber, a resin or a mixture thereof.  
     
     
         19 . An electromagnetic wave absorber comprising a compacted mixture of a magnetite-iron based composite powder mixture comprising magnetite and iron and having an average primary particle size of from about 0.01 to about 10 μm and a nonferrous inorganic compound powder and a rubber, a resin or a mixture thereof.  
     
     
         20 . The method according to  claim 16 , wherein the ratio of maximum diffraction intensity of magnetite to that of α-Fe in X-ray diffraction is from about 0.001 to about 50.  
     
     
         21 . The method according to  claim 16 , wherein the powder further comprises at least one component selected from the group consisting of nickel, cobalt, chromium, manganese and copper.  
     
     
         22 . The method according to  claim 16 , wherein the ratio of maximum diffraction intensity of magnetite to that of α-Fe in X-ray diffraction is from about 0.001 to about 50, and 
 the powder further comprises at least one component selected from the group consisting of nickel, cobalt, chromium, manganese and copper.  
 
     
     
         23 . The method according to  claim 16 , wherein the powder further comprises nickel.  
     
     
         24 . The method according to  claim 17 , wherein an average primary particle size of the nonferrous inorganic compound powder is less than or equal to about 0.1 μm and is less than that of the magnetite-iron based composite powder, and 
 wherein the nonferrous inorganic compound powder adheres to a surface of the magnetite-iron based composite powder.  
 
     
     
         25 . The method according to  claim 17 , wherein an average primary particle size of the nonferrous inorganic compound powder is greater than or equal to about 1 μm and less than or equal to about 100 μm and is greater than that of the magnetite-iron based composite powder, and 
 wherein the magnetite-iron based composite powder adheres to a surface of the nonferrous inorganic compound powder.  
 
     
     
         26 . The method according to  claim 17 , wherein the nonferrous inorganic compound powder comprises a first nonferrous inorganic compound powder and a second nonferrous inorganic compound powder, 
 wherein an average primary particle size of the first nonferrous inorganic compound powder is less than or equal to about 0.1 μm,    wherein the average primary particle size of the second nonferrous inorganic compound powder is greater than or equal to about 1 μm and less than or equal to about 100 μm and is greater than that of the magnetite-iron based composite powder, and    wherein the magnetite-iron based composite powder and the first nonferrous inorganic compound powder adhere to a surface of the second nonferrous inorganic compound powder.    
     
     
         27 . The composition according to  claim 18 , wherein the ratio of maximum diffraction intensity of magnetite to that of α-Fe in X-ray diffraction is from about 0.001 to about 50.  
     
     
         28 . The composition according to  claim 18 , further comprising at least one component selected from the group consisting of nickel, cobalt, chromium, manganese and copper.  
     
     
         29 . The composition according to  claim 18 , further comprising at least one component selected from the group consisting of nickel, cobalt, chromium, manganese and copper.  
     
     
         30 . The composition according to  claim 18 , further comprising nickel.  
     
     
         31 . The composition according to  claim 19 , wherein an average primary particle size of the nonferrous inorganic compound powder is less than or equal to about 0.1 μm and is less than that of the magnetite-iron based composite powder, and 
 wherein the nonferrous inorganic compound powder adheres to a surface of the magnetite-iron based composite powder.  
 
     
     
         32 . The composition according to  claim 19 , wherein an average primary particle size of the nonferrous inorganic compound powder is greater than or equal to about 1 μm and less than or equal to about 100 μm and is greater than that of the magnetite-iron based composite powder, and 
 wherein the magnetite-iron based composite powder adheres to a surface of the nonferrous inorganic compound powder.  
 
     
     
         33 . The composition according to  claim 19 , wherein the nonferrous inorganic compound powder comprises a first nonferrous inorganic compound powder and a second nonferrous inorganic compound powder, 
 wherein an average primary particle size of the first nonferrous inorganic compound powder is less than or equal to about 0.1 μm,    wherein the average primary particle size of the second nonferrous inorganic compound powder is greater than or equal to about 1 μm and less than or equal to about 100 μm and is greater than that of the magnetite-iron based composite powder, and    wherein the magnetite-iron based composite powder and the first nonferrous inorganic compound powder adhere to a surface of the second nonferrous inorganic compound powder.