Improvement of Hydrogen Absorption and Desorption Kinetics ... Springer
At the same time, 2 kg stainless steel balls with a diameter of 3 mm were put into the ball mill. The balltomaterial ratio was constant at 20:1, and the ball mill speed was set at 900/1000 rpm. To prevent contact between powder and air during ball milling, the chamber was vacuumed before ball milling, and then, argon was filled.