What Should Be Done If Grinding Fineness Cannot Reach the Nanometer Level?

If grinding fineness cannot reach the nanometer level, it is usually not a problem in a single link, but the combined result of equipment, media, separation system, pre-dispersion, temperature, and process parameters. To enter the nanometer range, these aspects need to be checked one by one and matched with one another.

First, look at equipment precision and energy density. If the rotor structure, chamber clearance, and drive capacity of an ordinary bead mill are limited, it will be difficult to further reduce particle size even if grinding time is extended. The RUCCA N series nano bead mill adopts a pin-type high-energy-density structure and can be equipped with ultra-fine grinding media of 0.03 mm or above. Through circulation grinding and parameter adjustment, it can stably achieve ultra-fine grinding with D50 ≤ 30 nm. The equipment linear speed, flow rate, media filling rate, and number of grinding passes should be set together; do not rely only on increasing rotational speed.

Next, look at the grinding media. When the media size is too large, the impact force is sufficient, but there are fewer shear zones, making it difficult to open small agglomerates. If the media size is too small and the equipment separation system does not match, it is easy to block the discharge port. Ordinary equipment cannot use ultra-fine beads often because the discharge separation system is not adapted to small beads. The RUCCA UM high energy vertical bead mill and DUM Typ bead mill, so that beads of 0.05 mm or even 0.03 mm can also operate stably. Media materials can be selected from zirconia or ceramics, depending on material hardness and purity requirements.

Pre-dispersion must also be sufficient. If the powder is not sufficiently wetted before entering the bead mill, the interior of the agglomerates remains dry, and subsequent grinding efficiency will decrease. Equipped with the Inline dispersing system-low viscosity IDS, powder can be sucked in under vacuum negative pressure, allowing the powder to be instantly wrapped by liquid and reducing “fish eyes” and secondary agglomeration. After uniform pre-dispersion, the initial particle size entering the bead mill is more consistent, the number of subsequent grinding passes can be reduced, and the particle size distribution is easier to narrow.

Temperature control is equally important. If the heat generated during grinding accumulates, the dispersant may fail, slurry viscosity may increase, and even re-coarsening may occur. RUCCA equipment can be equipped with an internal and external dual cooling system, with dual-channel heat exchange between the outer wall of the grinding chamber and the inner rotor, combined with adjustment of cooling water temperature, flow rate, and feed speed to help control temperature rise. For heat-sensitive systems, staged grinding or circulation cooling can also be used to reduce excessive residence time in a single pass.

In terms of process parameters, the feed speed should be stable to avoid interruption or blockage; the media filling rate should be appropriate—too high will increase friction heat, while too low will reduce grinding efficiency; the number of circulation passes should be gradually adjusted according to particle size changes, and it is not advisable to run for a long time in one go. Measure particle size distribution, D50, D90, span, and viscosity, and observe whether re-coarsening or agglomeration occurs.

If the fineness still cannot reach the nanometer level, it is recommended to send material samples for testing and verify with measured data. RUCCA can recommend equipment models, media specifications, separation systems, cooling solutions, and process parameters according to material characteristics. After confirming feasibility through laboratory or pilot tests, scale up to production models, which can reduce commissioning and adjustment time after going online.

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