| 摘要 |
PROBLEM TO BE SOLVED: To provide magnetite particle having fixed specific surface area or above, and its particle shape is octahedral or hexahedral and having a specific coercive force, and a producing method thereof. SOLUTION: The magnetite particles are composed of octahedral particles having a specific surface area of 5m<2> /g by BET method and coercive force of 40-100Oe, or hexahedral particles having a specific surface area of 6m<2> /g by BET method and a coercive force of 40-80Oe. There particles are produced by mixing a ferrous salt aq. solution with a silicate aq. solution, further mixing an alkali aq. solution with the mixed aq. solution, then carrying out oxidation reaction and heating so as FeO to be >=18wt.%, in the resultant magnetite particles. |
