1. Material selection
Material selection needs to consider the density, hardness and chemical properties of the material to be grinded, in general, we have to choose a grinding ball with a greater density and hardness than the sample, so as to achieve the effect of grinding; In addition, during the working process of the ball mill, a large amount of heat will be generated in the ball mill tank due to friction and impact, which requires good thermal stability of the grinding ball, and cannot undergo physical and chemical reactions with the material to be grinded, so as not to cause contamination to the sample.
2. Selection of volume size
Different volumes and sizes of grinding balls have different effects, and we have to configure them separately (commonly used are 3mm, 5mm, 10mm three sizes). The large ball has a large weight and a large impact force on the material, which can easily crush the material, but it is difficult to grind finely, and it is easy to have grinding dead angles; The small ball has a small volume and a large number of impacts, which has a great effect on the grinding of fine materials, but its impact force is small, and it is difficult to grind large materials. Generally speaking, we can choose three grinding balls of different volume sizes.
3. Configuration of quantity
Due to the different roles of large and small balls, we need to reasonably allocate their number, and for the number of quantities, we can use the principle of "equal surface area" for configuration. First calculate the surface area of different grinding balls according to their diameters, and then make the total surface area of different grinding balls roughly equal.
4. Spherical material assembly ratio
In the process of ball milling, we need to reserve a certain amount of space in the ball milling tank to play an effective role, so we can't fill too much. In addition, in order to achieve a good ball grinding effect, the quality ratio of the grinding ball to the sample material is recommended to be maintained between 0.9~1.1.