Ball motions in a planetary ball mill with liquid media were simulated using the DEM. The distributions of ball impact energy were calculated from the simulation. Then, the cumulative value of the impact energy (E) and median of the impact energy at one collision (e1/2) were calculated. Grinding tests were examined and relationships between particle sizes and the specific impact energy multiplied by grinding time (Ewt) were evaluated. At higher acceleration, particle sizes of ground powders decreased faster. However, from the viewpoint of the impact energy, the energy efficiency got worse. With increase of ball sizes, e1/2 increased but the number of collisions decreased. As results, using the smaller balls, particle sizes decreased faster and the energy efficiency was also better. The amount of Ewt required to obtain 0.5 μm mean diameter (Ewt*(0.5 μm)) was calculated for each test condition. The fitting curve was applied for the relation of Ewt*(0.5 μm) vs e1/2.
Particle size of raw materials is one of the most important factors in granulation, a general particle processing method. Especially in the case of granulation of multiple materials, component uniformity depends on the particle size. Therefore, pulverizing raw materials to a smaller particle size before granulation is often selected as a preprocessing method. Currently, there is a direct granule producing apparatus, which produces granules direct from a suspension of raw materials. The granules produced from this apparatus have unique features such as content uniformity, spherical shape, and high content yield due to less addition of excipients. From these features, the granules have advantages-such as ease to swallow and downsizing of final dosage form if they used for drugs. Here, we describe the necessity of raw material pulverization by confirming the correlation between particle size of the pulverized raw material and component uniformity of the granules produced by direct granule producing apparatus.
This article explains a new concept of the room-temperature powder solidification process, named as the “non-firing solidification process”. Authors have recently introduced this method whose main concept is to activate the surface of particles by mechanical milling and consolidate the particles via the joining of activated surfaces. This method is shown to be effective for a wide range of materials including oxides and non-oxides. As a model, SiO2 (silica) is extensively studied and radical centers before and after surface activation are monitored by electron paramagnetic resonance (EPR). As an index of the activation, the amount of adsorbed water on the surface of silica is also measured. Finally, the wide application of the method from 3D printing to inorganic/organic composites is introduced.
Milling iron particles with a lubricant such as graphite deforms them into a platelet shape, and in the process, the (001) plane is oriented parallel to the platelet face. The (001) plane contains the <001> axis, which has excellent magnetic properties, making the particles ideal candidates for use as magnetic cores in motors. The effect of the graphite lubricant on the iron particles, i.e., the lubricity, depends on the milling atmosphere. X-ray absorption near edge structure (XANES) and transmission electron microscopy (TEM) observations reveal that this dependency is due to the difference in the orientation of the basal plane of graphite, where mechanochemically formed iron oxide at the graphite/iron interface most likely plays an important role in the orientation of the basal plane.