Electric discharge assisted mechanical milling can be applied to the synthesis of a range of fine powder products, including nanocrystalline powder particles and individual nano-particles and nano-fragments. Variables include the starting powder sample size; electric arc parameters, such as arc length and arc voltage/current; mechanical milling parameters and gas atmosphere. Recently, the new processing variable of electric discharge frequency (Hz and kHz range) has been added to the technique. In this presentation we describe the results of the current experimental program underway, to investigate phase transformations and/or particle fragmentation during discharge milling, and to optimise processing parameters required for the synthesis of particular high surface area particles, nanostructural powders and nano-particles. We describe microstructural, morphological, and phase changes induced during the often competing processes of fragmentation into nano-particles, agglomeration of powder particles, and particle melting and/or sintering. Specific investigations include; (i) the modification of carbon base materials, where discharge milling under controlled conditions has resulted in the transformation of graphite into amorphous carbon, and the formation of graphite nanostructures (nanotubes and exotic nanofragments), (ii) the transformation of silicon and boron into nanofragments by discharge milling and (iii) phase transformations and nanoparticle formation induced in inorganic oxides, including the transformation of hematite into nanostructural magnetite, and finally into nanoparticles of iron.

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1. Synthesis of nanoparticles using electrical discharges.
2. The effects of oxidized and non-oxidized boron on the Mg-B-H nanohydrides transformation in the nearly nanosized powders
3. Formation and Processing of Nanocrystalline Materials by Electrical Discharge Mechanical Milling