Milling is the reduction of larger sized solid substances into smaller sizes by the use of various mechanisms. Size reduction occurs through particle-particle interactions, particle-wall interactions, and particle-milling media interactions depending on the milling machine used. The different types of mill include ball mills, air jet mills, impact mills, and roller mills. The typical particle breakage methods involved are impact, shearing, crushing, attrition or a combination of them.

The main problems associated with milling are the inefficient use of energy, and the effect of milling on the material properties. A very small amount of the input energy goes into the breakage of the substance. Energy is lost through heat, friction, noise, and plastic deformation. Material properties such as hardness, reflectivity, composition, and flowability can all be changed through the course of milling.

Within the research group we currently have access to the following types of mills:

  • Planetary ball mill
  • Vibrating ball mill
  • Vibrating disc mill
  • Spiral jet mill
  • Stirred media mill

We are currently investigating the grindability of crystalline and amorphous solids, associated structural changes and physical, chemical and mechanical transformation that are induced. The energy utilisation of planetary ball mills is being investigated using silica, with there being further investigation into the final structure of the silica after milling. We are also carrying out numerical simulation of a spiral jet mill by DEM and CFD method.

Related Projects

Current Projects

Recent Projects

Past Projects

  • Milling of Pharamaceutical Powders
  • Effect of Mechanical Properties on the Milling Behaviour of Pharmaceutical Powders

Recent Publications


  • Olusanmi, D., Roberts, K., Ghadiri, M., Ding, Y. 2011. “The Breakage of Aspirin under Quasi-Static Indentation and Single Particle Loading: Effect of Crystallographic Anisotropy“, International Journal of Pharmaceutics, 411(1-2), 49-63.
  • Olusanmi, D., Wang, C., Ghadiri, M., Ding, Y. and Roberts, K.J., 2010, “Effect of Temperature and Humidity on the Breakage Behaviour of Aspirin and Sucrose Particles“, Powder Technology, 201(3), 248-252.
  • Yang, W., Kwan, C.C., Ding, Y.L., Ghadiri, M., Roberts, K.J. , 2007, “Milling of Sucrose“, Powder Technology, 174, 14-17.
  • Kwan, C.C., Mio, H., Chen, Y.Q., Ding, Y.L., Saito, F., Papadopoulos, D.G., Bentham, A.C., Ghadiri, M. , 2005, “Analysis of the Milling Rate of Pharmaceutical Powders using the Distinct Element Method (DEM)“, Chemical Engineering Science, 60, pp. 1441-1448.
  • Bentham, A.C., Kwan, C.C., Ghadiri, M., Boerefijn, R. , 2004, “Fluidised Bed jet Milling of Pharmaceutical Powders“, Powder Technology, 141, pp. 233-238.
  • Chen, Y.Q., Ding, Y.L., Papadopoulos, D.G., Ghadiri M. , 2004, “Energy Base Analysis of Milling α-Lactose Monohydrate“, Journal of Pharmaceutical Science, 93, pp. 886-895.
  • Kwan, C.C., Chen, Y.Q., Ding, Y.L., Papadopoulos, D.G., Bentham, A. C., Ghadiri, M. , “Development of a Novel Approach Towards Predicting the Milling Behaviour of Pharmaceutical Powders“, European Journal of Pharmaceutical Sciences, 23, pp. 327-336.
  • Kwan, C.C., Ghadiri, M., Papadopoulos, D.G., Bentham, A.C. , 2003, “The Effects of Operating Conditions on the Milling of Microcrystalline Cellulose“, Chemical Engineering and Technology, 26, pp. 185-190.
  • Mio, H., Saito, F., Ghadiri, M., Eastman, R., Stephen, R. , “Analysis of Media Motion and Behaviour of Particles in a Stirring-Type Mill“, Invited Lecture: SPTJ Symposium, Japan, July 2004.
  • Ghadiri, M., Kwan, C.C., Ding, Y. , “Analysis of Milling and the Role of Feed Properties“, Handbook of Partice Breakage, A.D. Salman, M. Ghadiri and M.J. Hounslow (Eds), Elsevier in Print, 2007.