CVD on Iron Powder - Using Fluidising Bed Techniques

Abstract: Today's electrical energy conversion devices, such as motors, transformers, inductors and generators, are based on laminated magnetic cores for reduction of eddy current losses, imposing a two-dimensional magnetic flux distribution. Using a three-dimensional magnetic flux distribution while maintaining low magnetic losses requires new approaches to magnetic core materials. Soft Magnetic Composites, SMC's, are compounds consisting of magnetic iron particles coated with a thin and electrically insulating layer. Compacting and shaping such particles without reducing the effectiveness of the electrical insulation layer, while maintaining the magnetic characteristics, presents a major challenge. Furthermore, new motor designs taking into account the new possibilities of SMC's have been investigated only sparingly. The state-of-the-art SMC material today does not meet current requirements. Additional efforts are needed in the following three areas: CVD powder coating processes (for electrical insulation), bulk material characterisation methods (evaluation of magnetic, structural and mechanical bulk properties) and compaction/tooling processes (for bulk material/application production). The goals for the research study included an extensive literature research, the task to design and build a fluidising bed reactor CVD (FBRCVD) system and an exploration of the possibilities to deposit standard qualities of iron powder with various metal oxide films. In the literature research, it was concluded that the amount of published work pertaining to FBRCVD was rather scarce. It was shown that an FBRCVD apparatus could be designed and built. Furthermore, it was shown that TiO2 successfully could be deposited onto the iron powder in the CVD apparatus. Finally, it was concluded that the iron powder, when pressed into test rings, showed very interesting properties in regards to total loss and temperature stability.

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