| Abstract |
| Ferromagnetic Mn-Al nanoparticles were prepared using a plasma arc discharge method. The influence of the process parameters on the vaporization rate, composition, particle size, and magnetic properties of the as-produced nanoparticles was investigated. The Mn content was found to be higher in the nanoparticles than in the corresponding mother materials, although the difference diminished with the reaction time. As the H2 content in the reaction gas increased, both the vaporization rate and the particle size increased. With 30 at.% Mn, the average particle diameter was 35.2 nm under a pure Ar gas condition, whereas it was 95.4 nm at a Ar:H2 ratio of 60:40. With the addition of a small amount of carbon, ε-phase nanoparticles were successfully synthesized. After a heat treatment in a vacuum for 30 min at 500°C, the nonmagnetic ε-phase was transformed into the ferromagnetic τ-phase, and a very high coercivity of nearly 5.6 kOe was achieved. (Received October 26, 2009) |
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| Key Words |
| plasma arc-discharge, ferromagnetic materials, phase transformation, annealing, nanoparticles |
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