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

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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.