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

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.

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.

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.

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.