In this study, nanostructured Fe powders were synthesized following 10 hours of high-energy ball milling with a superimposed dielectric barrier discharge plasma (DBDP). The mean size of the milled powder was approximately 100 nm with an average grain size of 16.2 nm. The influence of DBDP on the underlying grain refinement mechanisms during ball milling was investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and BET methods. Our results show that the Fe particles displayed an extraordinary plasticity during the early milling stages under the action of DBDP, and that the plastic deformation experienced by the Fe particles during this stage was more severe than that present in normal milling. A high concentration of spherical Fe particles, approximately 50-100 nm in diameter, was documented via TEM. We propose that these spherical particles were generated via high temperature disintegration as a result of DBDP electron bombardment during ball milling. Our results suggest that it may be possible to significantly refine metallic powders during milling via the superimposition of DBDP.
Nano-size aluminum nitride(AlN) powders have been successfully synthesized with a high efficiency method through annealing from milling assisted by discharge plasma(p-milling)alumina(Al_2O_3) precursors. The characterization of the p-milling Al_2O_3 powders and the synthesized AlN are investigated. Compared to conventional ball milling(c-milling), it can be found that the precursors by p-milling have a finer grain size with a higher specific surface area,which lead to a faster reaction efficiency and higher conversion to Al N at lower temperatures. The activation energy of p-milling Al_2O_3 is found to be 371.5 kJ/mol, a value that is much less than the reported value of the unmilled and the conventional milled Al_2O_3. Meanwhile, the synthesized Al N powders have unique features, such as an irregular lamp-like morphology with uniform particle distribution and fine average particle size. The results are attributed to the unique synergistic effect of p-milling, which is the effect of deformation, fracture, and cold welding of Al_2O_3 powders resulting from ball milling, that will be enhanced due to the introduction of discharge plasma.
