A new planetary ball mill PULVERISETTE 7 premium line has been launched by FRITSCH GmbH. The company uses this comminution concept to consider the needs of customers who wish to comminute small samples up into the nano range (1 nm = 10-9 m).
An example is the pharmaceutical industry, where there is interest in new medications that contain active ingredients in the nanoscale. The human body absorbs active ingredients in the nanoscale much faster than standard compounds. Due to better bioavailablity, it is possible to significantly reduce medication dosages.
In addition to achieving the same therapeutic effects with less active ingredients, unwanted side effects can also be reduced. Nanoparticles are also in demand within the chemical industry, as their significantly enlarged specific surface demonstrates new catalytic attributes.
Principle of the Planetary Mills
In a planetary mill, the sample and the grinding balls are placed into the grinding bowl. The bowls are then fastened onto the 'sun dial,' and the grinding bowls counter-rotate around the center of this disk. The sample is effectively comminuted after beating, crushing, and grinding.
For standard planetary mills, the maximum possible speed range is limited to approximately 800 rpm. The clamping of the grinding bowls distinguishes the premium line from a regular mill. In the premium line the bowls are sunken into the sun disk (SelfLOCK Technology), instead of being clamped onto the disk.
Planetary Micro Mill PULVERISETTE 7 premium line
This arrangement raises the maximum rotational speed in the premium line to 1100 rpm, providing a 150% increase in the kinetic energy of the grinding bodies. The comminution of nanoparticles for certain materials becomes possible as a result of a drastic reduction in the grinding time into the nanoscale.
Nano Grinding of Aluminum Oxide
Here, the comminution of aluminum oxide (Al2O3) is shown as a testing system. The d50 value of the base material is 20 µm. 0.5 mm zirconium oxide (ZrO2) balls and 5 ml Al2O3 are ground together with water for 60 minutes to approximately 300 nm. It is necessary to utilize even smaller grinding pearls to reach the range of <100 nm. In this case, ZrO2 pearls with a diameter of 0.1 mm were used.
After an additional 180 minutes of grinding, the following results were obtained:
|d value [%]
||grain size [nm]
Considering the corresponding Mie parameters, the illustrated grain size distribution was measured using the FRITSCH Laser Particle Sizer ANALYSETTE 22 NanoTec. A certain abrasion on the grinding bodies is unavoidable if a ball mill is used for comminution. The resulting abrasion was measured by deducting from the original.
Comparable results can also be obtained with other, hard fibrous metal oxides. With these oxides, the comminution is always in a suspension, and a dry comminution is not possible. As nanoparticles have a very large specific surface, the suspension is unstable at the end of the comminution - the particles re-agglomerate quickly.
Special additives need to be used for stabilization. Corresponding tests are carried out in the Fritsch application laboratory.
The safety of the process during comminution is improved as the grinding bowls are sunk using the new SelfLOCK-Technology. The bowls are clamped into the mill with just two hand motions, and the clamping mechanism improves the safety process during grinding as the possibility of faulty operation is eliminated.
The grinding bowls used are automatically identified by the RFID-chip integrated into the lid of the bowl. Optimal rotation speed is achieved, and impermissible grinding settings are eliminated. If the mill is loaded incorrectly, an integrated balance check prevents startup.
The newly developed special bowls enables secure sealing. A built-in valve in the lid is used for the controlled release of any overpressure arising during grinding, ensuring the best conditions to achieve reproducible and precise grinding results in the nano-range.
The premium line is capable of generating and saving various grinding programs for routine operations. The variable parameters are grinding time, speed, pause times, and reverse mode. Standard operating procedures (SOP) can be generated and can be password-protected.
Integration of the ball mill into the IT structure of the laboratory is enabled though a USB interface. Special software allows the grinding parameters to be recorded and saved, enabling validation of the grinding process.
Accessories for Each Specific Application
Various sizes of the grinding bowl are available for the new FRITSCH PULVERISETTE 7 premium line, including 20 ml, 45 ml, and 80 ml. The bowls are made in a variety of materials and are available for a wide range of applications. From agate to zirconium oxide, from steel to hard metal tungsten carbide, the right material exists for every application.
Additionally, balls are available in an extensive range of sizes. Increasingly small grinding balls are also available to achieve even smaller particle sizes.
The FRITSCH PULVERISETTE 7 premium line is the new standard for the creation of nanopowders on a laboratory scale.
This information has been sourced, reviewed and adapted from materials provided by FRITSCH GMBH - Milling and Sizing.
For more information on this source, please visit FRITSCH GMBH - Milling and Sizing.