The preparation of magnetic iron oxide


Sesigur H. , Acma E. , ADDEMIR O., TEKIN A.

MATERIALS RESEARCH BULLETIN, vol.31, no.12, pp.1573-1579, 1996 (Journal Indexed in SCI) identifier identifier

  • Publication Type: Article / Article
  • Volume: 31 Issue: 12
  • Publication Date: 1996
  • Doi Number: 10.1016/s0025-5408(96)00155-9
  • Title of Journal : MATERIALS RESEARCH BULLETIN
  • Page Numbers: pp.1573-1579

Abstract

Two methods for the preparation of magnetic iron oxide starting from FeSO4 . 7H(2)O are described. The traditional method involves preparation of Fe(OH)(2) seed material, conversion of the seed to acicular gamma-FeOOH crystals, dehydration of the crystals to alpha-Fe2O3, hydrogen reduction of Fe2O3 to magnetite, and finally reoxidation of magnetite particles to gamma-Fe2O3. Magnetic iron oxide particles thus obtained, after a total processing time of about 25 h, have a coercivity between 330 and 380 Oe. The other method, known as the direct method, involves fewer steps, a shorter overall processing time, and yields magnetic iron oxide having an equivalent or higher coercivity value. A sample from the seed preparation solution is recrystallized at 250 degrees C, yielding a product, gamma-Fe2O3, which has a coercivity value of 320 Oe. In another procedure the seed is prepared in the presence of H2O2 as the oxidizing agent and recrystallized at 300 degrees C for 2 h to yield gamma-Fe2O3 having 390 Oe coercivity.