Nanostructured Materials Synthesized by Mechanical Means
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A variety of mechanical milling devices have been developed for different purposes. Powder particles with typical particle diameters of about 20–100 µm are placed together with a number of hardened steel or WC-coated balls in a sealed container, which is shaken violently. Consequently, plastic deformation at high strain rates (∼ 103–104 sec− 1) occurs within the particles and the average grain size can be reduced to a few nanometers after extended milling. The temperature rise during this process is modest and is generally estimated to be ≤ 100 to 200°C. The collision time corresponds to typically 2 msec.