The processing of Mg–Ti for hydrogen storage; mechanical milling and plasma synthesis

A study was carried out into the processing of Mg-10 vol.% Ti powder mixture for hydrogen storage purposes. Two processing routes were evaluated; mechanical milling and plasma synthesis. Mechanical milling, carried out with a high speed planetary mill, yielded a particulate structure made up of large Mg agglomerates, 90–100 μm, with embedded Ti fragments of approx. 1 μm in size with a uniform distribution. Mg agglomerates were made up of coherently diffracting volumes that were less than 50 nm in size. Plasma processing was carried out with an RF plasma torch of 25–27 kW applied power, the powder mixtures fed with 1–3 g/min axially into the torch. The mixture Mg-10 vol.% Ti after plasma processing comprised Mg powders which were extremely fine, <100 nm. Ti occurred as separate particles mixed with Mg nanopowders. The powders had a coherently diffracting volumes that were comparable to the size of the particles themselves indicating that the plasma processing yields relatively defect free crystals. The formation of the nano-size particulate structures is evaluated with regard to their possible implications on the hydrogenation of Mg–Ti alloys.