Experimental investigation of milling regimes in planetary ball mill and their influence on structure and reactivity of gasless powder exothermic mixtures

• In-situ validation of different high energy ball milling regimes
• Correlations: milling regimes–microstructure–reactivity of powder mixtures
• Domination of the share deformation in the structure transformation mechanism
• Effectiveness of the cascading regime for tuning the properties of reactive media

The dynamics of ball motion during high energy planetary ball milling was investigated in-situ using high speed video recording. The trajectories and velocities of the balls were determined for different milling conditions. Correlations of these parameters, with both microstructure and reactivity of various as-milled powder mixtures (Ni–Al, Ti–Si, Si–C), were revealed. It was shown that all of the main theoretically predicted milling regimes – cascading, cataracting and centrifugal – can be achieved by varying the rotation speed of the vial. The conclusion is made that shear deformation plays a major role in the transformation of the microstructure and reactivity of these powder mixtures. According to this observation, the cascading regime appears to be the most effective for controlling the properties of the mixtures.

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