The biggest challenge when developing a high energy ball mill is controlling the temperature. The very high energy produced by ball milling leads to an extreme heat increase inside the grinding jars. RETSCH solved this problem by creating an innovative integrated water-cooling system. Grinding breaks for cooling, which are unavoidable in conventional ball mills even after only 30 minutes grinding at moderate speed, are usually not necessary when using the High Energy Ball Mill Emax.
How are nano particles produced? The “Bottom-Up” method synthesizes particles from atoms or molecules. The “Top-Down” method involves reducing the size of larger particles to nanoscale, for example with laboratory mills. Due to their significantly enlarged surface in relation to the volume, small particles are drawn to each other by their electrostatic charges. Nano particles are produced by colloidal grinding which involves dispersion of the particles in liquid to neutralize the surface charges. Both water and alcohol can be used as dispersion medium, depending on the sample material. Factors such as energy input and size reduction principle make ball mills the best choice for the production of nanoparticles.
The Emax is an entirely new type of ball mill which was specifically designed by RETSCH for high energy milling. The impressive speed of 2,000 min-1, so far unrivaled in a ball mill, in combination with the special grinding jar design generates a vast amount of size reduction energy. The unique combination of impact, friction and circulating grinding jar movement results in ultrafine particle sizes in the shortest amount of time. Thanks to the new liquid cooling system, excess thermal energy is quickly discharged preventing both sample and mill from overheating, even after long grinding times.
Alloys such as amalgam in dental medicine or stainless steel are universally known and used. The traditional way to produce alloys is to fuse the components at very high temperatures. If only small quantities are required or if the alloys cannot be fused by melting mechanical alloying is an alternative. For this application ball mills are ideally suited. They provide a high energy input due to the impact and friction effects which occur during grinding.