Comminution of powders in the planetary centrifugal mill II. Some milling characteristics

Conclusions

• 1. A systematic study was made of the milling of materials in the planetary centrifugal mill, and the optimum milling conditions, enabling powders with a specific surface of 40–50 m²/cm³ and a moderate iron impurity content (under 3 vol.%) to be produced in 30–40 min, were determined.

• 2. It is shown that, in a general case, the process of comminution under PCM conditions is described by Rebinder's two-term equation, although in the milling of brittle refractory compounds only the second term of the equation is in fact operative. The comminutability of materials is determined by their physicomechanical properties; in milling in the PCM, it generally increases with increasing E, G, Hμ, and brittleness (i.e., with decreasing % and (ū²)^1/2), just as it does in vibratory milling.

• 3. Milling in the PCM is not suited to the comminution of ductile materials susceptible to cold welding, since these exhibit agglomeration.

• 4. Pickup of impurities markedly grows with increasing abrasive power of powders, which is determined by both the nature of the material and the size and shape of its particles.