Rapid synthesis of magnetic ceramics powders from powder mixtures by using well-controlled thermal plasmas

1. 井控热等离子体反应器的研制该系统由强制收缩式等离子体射流发生器、进料环和真空容器组成。新设计的反应器采用浮动收缩喷嘴，可在各种工况下产生稳定的等离子体射流。快速合成铁氧体粉末成功地用Fe_2O_3、ZnO、NiO和CuO的粉末混合物合成了铁氧体薄膜和铁氧体粉末。不受加工时间和收集位置的限制，均可合成高纯度的铁氧体。CCD相机诊断系统的研制研制了利用CCD相机加滤光片对整个反应区等离子体射流进行处理的诊断系统。结果表明，采用该系统和二线法可以得到射流温度的二维分布。(1)用Al_2Q_3、Na_2CO_3和MgO的粉末混合物制备了热电材料（β”-氧化铝）。注氧也促进了β"-氧化铝的合成。Mo喷涂在常压下生成多孔膜，在减压下生成致密膜。(2)在某些实验条件下，MgO薄膜制备得很好，尽管由于其特殊的性质，MgO的喷涂通常被认为是困难的。为了阐明载气和粒子注入对等离子体射流热流体场的三维影响，建立了一个数值模型。

1. Development of the well controlled thermal plasma reactorThe system consists of the forced constricted type plasma jet generator, the feed ring and the vacuum vessel. With the use of the floating constriction nozzle, our newly designed reactor produces stable plasma jet for various operating conditions.2. Rapid synthesis of ferrite powdersFerrite films and ferrite powders are successfully synthesized from powder mixtures of Fe_2O_3, ZnO, NiO and CuO. Ferrite with high purity can be synthesized irrespective of processing duration time and collecting position.3. Development of the diagnostic system with CCD cameraDiagnostic system of processing plasma jet over the whole reaction region using the CCD camera with optical filters is developed. It is confirmed that with the present system and also two line method, two dimensional distribution of the jet temperature is obtained.4. Other two thermal plasma processings(1)Thermoelectric materials (β"- alumina) are well synthesized from powder mixtures of Al_2Q_3, Na_2CO_3 and MgO. Oxygen injection also enhances the synthesis of β"-alumina. Mo spraying produces porous films under atmospheric pressure and dense films under reduced pressure.(2)Under some experimental conditions, MgO films are well prepared although spraying of MgO is usually said to be difficult due to its particular properties.5. Modeling of RF thermal plasmaA numerical model is developed to clarify three-dimensional effects of carrier gas and particle injections on the thermo-fluid fields of plasma jets.