Continuous production of hybrid metal oxide fine particles

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The synthesis of hybrid metal oxide fine particles in supercritical wate (SCW) were investigated by using a flow apparatus. The sample used was a barium hexaferrite, which is expected as a high density recording material.It was revealed from the experiments that the present technique with SCW can produce fine particles of barium hexaferrite continuously within a very short period under certain reaction conditions and that the size and shape of the product particles are strongly dependents on the temperature and pressure. For producing the fine particles (less than 60 nm) of narrow size distributions, it should be noted that the solution is firstly prepared via neutralization of Fe (NO_3) _2Ba (No3) 2 aqueous solutions and KOH and then the rate of the nucleation and crystal growth stages has to be controlled. The nucleation rate can be controlled by changing the heating rate. The conditions for successful producing particles through this work were the initial heating at 280 C for nucleation and 400 C for crystal growth at fairly high Barium concentrations. It was also suggested that the applicable range of this technique is very wide in concentration range, metal species, temperature and pressure and can be an industrial process.