The Developing And Application Of Nano-Magnetic Fluid Using Plasma Technique

The application field and range of magnetic fluids, a nanometer composite fuctional materials, depend on its properties. For the preparation of magnetic fluids with high charcter and high quality, the technology is complicated, and technological process is long, which hinders the application and the development of the magnetic fluid. Considering that beside high temperature and high density, the plasma technique can induce some physical changes and chemical reactions that are impossible at normal conditions, and therefore can be used in preparation of nitride oxide magnetic fluid. This thesis consists of two parts, one is, based on reviewing the earlier work, to investigate the new technology of manufacturing nitride magnetic fluid using plasma activation mathod; the other part is to make a fundamental research on the application of the nitride magnetic fluid by plasma techniques.For the preparation of magnetic fluid, different methods, according to different applications, were adopted to develop magnetic fluid of ferrate and nitride. By using chemical co-deposition and gas-liquid phase, and plasma activation methods, researches on practically preparing nano-magnetic liquid were performed. It is discovered in the experiment that for preparing nitride oxide magnetic fluid the plasma activation is a new method. It is also find in comparison experiment that gas-liquid phase method is complex in processing technology, time consuming, and that tens hours are needed for multi-time heating and cooling before the magnetic fluid is obtained. But if plasma activation is adopted, combining with the special pulse discharge configuration on the self-made plasma reaction device, nano-magnetic fluid can be prepared through the activation and ionization of the gas-liquid phases media, accelerating the bond breaking of the gas-liquid molecules to form magnetic particles withnano-grain size, and through wrapping the particle with mono layer of surfactant. It is also determined through experimental researches that the highest pulse frequency should be controlled at 62 kHz, the highest pulse voltage 15 kV, the temperature inside the reaction chamber around 200℃, and the reaction time around two hours. Although the reaction inside the chamber varied rapidly, and the complicated influence factors were correlated one another, the magnetic fluid of nitride with higher quality can be produced if the pulsed frequency, pulsed voltage, reaction temperature and time were well controlled. The saturated magnetic-field strength of the prepared magnetic fluid was as high as 800 Gs (before concentrated); the average grain size of its constituents was around 10 nm; and the preparation period was reduced about 80% compared with gas-liquid method. This technique has realized the controlling of the reaction rate of two phases through physical method at normal temperature, and exploited a new way of producing nitride magnetic fluid. So far there is not such a kind of relevant report.At the same time, through a pulse interleaving method a special electric power supply, more suitable for the preparation of magnetic fluid of nitride using the method of plasma activation, was developed which realized the increment of frequency and the enlargement of capacity for the IGBT with the small volume and rapidity. The output frequency of the power supply is continuously tunable over the range from 9-65kHz; its output voltage is continuously tunable from 0-30kV; output power reaches 5 kVA; the surface activator, produced through the reaction between ethylene amic and unsaturated fatty acid (with ratio 1:4) using the solvent method, is successfully applied for the development of nitride magnetic fluid; as far as the stability is concerned, it is comparable to that of the PBSI made in Japan.In the foundamental investigation on the application of the nitride magneticfluid, the property of the magnetic fluid of ferrate and nitride prepared by plasma activation method and the practical requirement of industry was combined during the research. Taking into account the d...