1. Sample feed particle size. The smaller the feed particle size of the sample, the easier it is to be ground finer, so we should reduce the size of the sample as much as possible before grinding, and methods such as primary crushing, shearing, and grinding can be used.
2. Sample properties. Some samples are spherical in appearance, which is not favorable for ball milling, because the grinding ball is also spherical, so the contact area is greatly reduced, the effect of friction is weakened, and the grinding effect is deteriorated, so for spherical samples, before grinding to smash it. In addition, for some viscous or soft samples, in order to achieve better results, they can be pre-frozen in a liquid nitrogen tank to improve their hardness so as to achieve a better grinding effect.
3. Grinding time. The longer the grinding time, the longer the grinding ball will act on the sample, and the easier the sample will be ground.
4. Ball material ratio. The so-called ball-to-material ratio is the volume ratio of the grinding ball to the sample material. Generally, in the case of initial grinding, the volume ratio between the grinding ball, the sample material and the reserved grinding space should be 1:1:1, that is, each occupies the volume of the ball mill tank. one-third. In the subsequent grinding, the ball-to-material ratio can be adjusted according to the previous grinding situation. If the expected grinding effect is not achieved, the sample amount can be appropriately reduced. If the grinding effect can be completely satisfied, the sample amount can be appropriately increased to improve the experimental efficiency.
5. Grinding ball configuration. The reasonable configuration of the grinding balls also has a great influence on the sample grinding, mainly the quantity ratio of grinding balls of different sizes. Because different sizes of grinding balls play different roles in ball milling, the large ball has a large mass and generates a large kinetic energy. It is mainly responsible for smashing large-volume samples. The small ball has a large specific surface area and a large contact area with the sample. It is mainly responsible for Grind the sample finely.
Therefore, when the grinding is completed, the particle size of the sample does not change greatly, and the number of large balls should be appropriately increased to help break the sample. If the particle size of the sample becomes smaller after grinding, but does not reach the required discharge particle size, the number of pellets can be appropriately increased to help grind the sample.
6. Grinding method. Grinding methods are mainly divided into dry grinding and wet grinding, and some require vacuum grinding. For samples to be ground to the nanoscale, wet grinding is easier than dry grinding to make the sample reach the nanoscale, because when the sample particles reach the nanoscale or even the submicron scale, the molecular forces between the particles will act. action to re-agglomerate the ground and dispersed particles. In wet grinding, a grinding aid solvent is added to the ball mill tank. When the particles are dispersed, the molecular force between them is reduced to achieve a predetermined grinding effect.
