High Energy Mechanical Milling- Parameters for Optimizing Milling Efficiency

Milling is a method to reduce solid particles to micron size level. It can also be used for mixing, blending and mechanical synthesis. Planetary ball mill is the most commonly used equipment for milling, but it is not easy to reduce particle size to nano size level by planetary ball mill. Various factors can affect milling performance, and it requires optimization. Typically, wet grinding performance can be better than dry grinding. The main factors affecting milling efficiency and performance include the followings:

1. Materials of the milling jars and media.
2. Milling media size
3. Milling time
4. Grinding speed
5. Ball to powder ratio

MSE Supplies offers various high-energy ball mills, milling jars and media. The selections of the milling tool set depend on the sample characteristics. Below are the guidelines.

Materials of milling jars and media selection

Selections of milling jars and media depend on sample properties. In general, milling jar material must be harder than the sample to be milled. Common milling jars and media materials include stainless steel, zirconia, alumina, tungsten carbide and agate.

MSE Supplies offer milling jars and media. We also provide customized products.

Milling media size selection

The diameter of the milling balls is critical in the optimization and improvement of the milling efficiency. The size of the milling balls used are related to the size of the initial sample. Small balls are used for feed material with small sizes while larger balls are used for larger sized feed material. For chemical synthesis, the effective mixing and high stress frequency is crucial, which can be achieved by using  small balls¹¹.

The size selection requires optimization. It highly depends on the sample particle size and properties. Every application can have a very different optimal milling media size. It is also very common to use mix size.

MSE Supplies offers various size of milling media as well as media set. If you do not know which size of the milling media you should choose, using our milling media set is a good start. You can further optimize the size from there.

Grinding speed

If the milling speed is too high, it can lead to increased contamination by milling jars and/or media caused by high wear. High speed can also result in increasing jar temperature and pinning the ball to the inner wall. Speed control is one of the important factors for efficient milling process.

Ball to powder ratio

High-energy mechanical milling is one of the major methods to produce nano-crystalline materials via mechano-chemical synthesis. Ball size distribution and ball to powder ratio (BPR) can affect milling efficiency. There are no generic rules for choosing optimal BPR. Several parameters can influence each other. Many researchers used simulation model and statistical analysis of variance (ANOVA) to determine effects of the ball-to-powder ratio on milling efficiency and identify the statistically significant parameters.

(Kim et al., 2022)¹²

MSE Supplies (msesupplies.com) is a major global supplier of high energy milling tools. Both standard and customized products are available from MSE Supplies. If you need something not listed on our website, please email us at sales@msesupplies.com and we will prepare a quote for the customized products for you.  If you have any questions, please email us at tech@msesupplies.com.

Reference

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2. Kubota, K.; Seo, T.; Ito, H., Solid-state cross-coupling reactions of insoluble aryl halides under polymer-assisted grinding conditions. Faraday Discuss 2022.
3. Sawama, Y.; Niikawa, M.; Sajiki, H., Stainless Steel Ball Milling for Hydrogen Generation and its Application for Reduction. J. Synth. Org. Chem., Jpn 2019, 77 (11).
4. Saghir, M.; Umer, M. A.; Ahme, A.; Monir, N. B.; Manzoor, U.; Razzaq, A.; Xian, L.; Mohammad, K.; Shahid, M.; Park, Y.-K., Effect of high energy ball milling and low temperature densification of plate-like alumina powder. Powder Technology 2021, 383, 84-92.
5. Peterson, S. C.; A.Jackson, M.; Kima, S.; E.Palmquist, D., Increasing biochar surface area: Optimization of ball milling parameters. Powder Technology 2012, 228, 115-120.
6. Wood, M.; Gao, X.; Shi, R.; Heo, T. W.; Espitia, J. A.; Duoss, E. B.; C.Wood, B.; JianchaoYe, Exploring the relationship between solvent-assisted ball milling, particle size, and sintering temperature in garnet-type solid electrolytes. Journal of Power Sources 2021, 484, 229252.
7. Castrillo, P. D.; D.Olmos; D.R.Amador; J.González-Benito, Real dispersion of isolated fumed silica nanoparticles in highly filled PMMA prepared by high energy ball milling. Journal of Colloid and Interface Science 2007, 308 (2), 318-324.
8. Jung, H. J.; Sohn, Y.; Sung, H. G.; Hyun, H. S.; Shin, W. G., Physicochemical properties of ball milled boron particles: Dry vs. wet ball milling process. Powder Technology 2015, 269, 548-553.
9. T.Rojac; M.Kosec; B.Malič; J.Holc, The application of a milling map in the mechanochemical synthesis of ceramic oxides. Journal of the European Ceramic Society 2006, 26 (16), 3711-3716.
10. Pierard, N.; Fonseca, A.; Konya, Z.; Willems, I.; Tendeloo, G. V.; B.Nagy, J., Production of short carbon nanotubes with open tips by ball milling. Chemical Physics Letters 2001, 335 (1-2), 1-8.
11. Burmeister, C. F.; Kwade, A., Process engineering with planetary ball mills. Chem. Soc. Rev 2013, 42, 7660-7667.
12. Kim, K.-C.; Jiang, T.; Kim, N.-I.; Kwon, C., Effects of ball-to-powder diameter ratio and powder particle shape on EDEM simulation in a planetary ball mill. Journal of the Indian Chemical Society 2022, 99 (1), 100300.