Continuous production of hybrid metal oxide fine particles

采用流动合成装置研究了超临界水（SCW）中混合金属氧化物微粒的合成。所使用的样品是有望作为高密度记录材料的钡六角铁氧体，实验表明，本发明的超临界水技术在一定的反应条件下可以在很短的时间内连续制备出钡六角铁氧体的细颗粒，并且产物颗粒的尺寸和形状强烈依赖于温度和压力。为了制备窄粒度分布的细颗粒（小于60 nm），应注意的是，首先通过Fe（NO_3）_2Ba（NO_3）_2水溶液和KOH的中和来制备溶液，然后必须控制成核和晶体生长阶段的速率。形核速率可以通过改变加热速率来控制。通过这项工作成功生产颗粒的条件是在280 ℃下进行成核的初始加热和在相当高的钡浓度下进行晶体生长的400 ℃。该技术在浓度范围、金属种类、温度和压力等方面的适用范围较广，可实现工业化生产。

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.