Grinding samples down to finer consistencies is an age-old process that has not changed much with time. Whether you are looking to achieve the ideal particle size for specific analytical methods, or to prepare homogenous powders for further downstream processing, the general principles of milling remain the same. Materials are broken-up using abrasion, by placing samples in a chamber packed with hard-wearing milling media and applying force.
The type of milling media used to crush and grind samples is one of the most important parameters to consider for abrasive applications. In this article, International Syalons will take a look at some of the different grinding setups before comparing specific milling media compositions.
Mill Configurations: Batch Vs. Continuous Processing
The main differentiating factors between one grinding method and another are: how that force is applied, how samples are loaded into the system, and the composition of the milling media used to physically break materials apart. These are largely determined on a market-to-market basis. Small-scale analytical grinding may be done by hand, while industrial-scale processing is typically mechanised. Some samples are placed into the milling chamber in batches, others are recirculated into the system in a continuous flow.
Key Properties of Milling Media
Selecting the right milling media is less about the scale of production and more about performance. Steel alloys are readily available with few manufacturing considerations to bear in mind when creating uniform spherical shapes. As a result, carbon, chrome, and stainless steel grades are among the most common materials used in the final stages of various grinding applications.
Sphericity is important is it guarantees the greatest uniformity in particle size distribution (PSD), ensuring high degrees of powder homogeneity. But the most important properties are density and hardness. Microscopic porous structures can cause volumes of sample media to be retained or represent a point of weakness which increased the rate of failure. Likewise, hardness also determines the wear-resistant properties of a part, thus its longevity in abrasive applications. Chemical composition is also important, particularly in applications where contamination is scrutinised at the lowest possible levels (chemicals, pharmaceuticals, etc.).
Though steels seem like the natural best fit for a wide cross-section of abrasive applications, advances in technical ceramics manufacturing have yielded superior products.
Benefits of Technical Ceramic Milling Media
At International Syalons, we have manufactured a wide range of grinding and milling media for both analytical and preparative applications. Based on a proprietary silicon nitride (Si3N4) derivative, our Syalon 101 abrasive media dramatically outperform steel alloys in terms of milling efficiency. They have also demonstrated significantly reduced weight losses over time compared to alternative technical ceramics, suggesting significantly extended service length and reduced sample contamination.