METHOD OF PRODUCING FERROMAGNETIC LIQUID Russian patent published in 2016 - IPC H01F1/28 B82B3/00 

FIELD: technological processes.

SUBSTANCE: method of producing ferromagnetic liquid involves dissolving in water double salt of iron-salt, followed by partial oxidation of hydrogen peroxide solution to ratio Fe³⁺:F²⁺=1.7-2:1 in an amount of 2.7-3 mol of Fe²⁺/mol H₂O₂, control is performed by means of redox electrode Fe²⁺/Fe³⁺. Then partially oxidised solution, with intense stirring, is mixed in droplets with aqueous ammonia solution. Then by means of magnet is precipitated fine particles of magnetite and separation of obtained mixture into solid and liquid phases. Solid phase is multiple washed with water to pH 7 and processing obtained in solid phase of magnetite particles with solution of mannitol stabilizer while stirring. Finished suspension is settled, solid phase is separated from liquid by means of magnet, mother solution is removed. Proposed method ensures production of ferromagnetic liquid with magnetic nano particles with average size of 7.1-9.7 nm and narrow distribution of their size.

EFFECT: said liquid has high specific saturation magnetisation and high stability for long period of time.

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