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Production of Fine Powders for Permanent Magnets Using a D.C. Arc Plasma,

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Powdered feeds of iron-100 mesh and -325 mesh Crumac Mn3A1C, various sieved fractions entrained in argon were fed into a D.C. arc through a Forced Convection Cathode. The arc effluent was quenched with argon and the products collected in a cyclone and Pulsaire baghouse. The baghouse products from the iron runs are frequently pyrophoric, igniting in air. The object was to prepare rapidly quenched, submicron powders of high coercive force for use in permanent magnets. The electrical conductivity of the feed and products proved to be the major source of difficulty in this work. The products and unvaporized feed would collect on the arc chamber walls and never reach the cyclone and baghouse. This problem was partially solved by applying a negative potential -100 v to the chamber. Useful product was obtainable in only five runs three with iron, two with Crumac, near the end of this project. The products from the three iron runs were combined into two samples, one cyclone product and one baghouse product. These two samples, along with the baghouse products from the two Crumac runs were shipped to Crucible Research Division of Colt Industries. The highest surface areas of the baghouse products were 27 sq mg for Iron and 42 sq. mg for Crumac. The surface area was measured on samples that had been exposed to air and undoubtedly oxidized. All samples appeared to be heterogeneous, at least after exposure to air.

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  • Metallurgy and Metallography
  • Electricity and Magnetism

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