FRITSCH introduced the Planetary Micro Mill PULVERISETTE 7 premium line in 2006. The production of very fine particle sizes down to the nanometer range was transformed by this high-energy planetary mill by reaching rotational speeds of 1100 rpm. From then on, the PULVERISETTE 7 has become indispensable for research into new fuel cells, mechanical alloying and developing new lithium batteries
The sample volume of this instrument is very small, resulting in increased demand for a mill with the same performance but a larger volume. At ACHEMA in 2012, FRITSCH introduced the new Planetary Mill PULVERISETTE 5 premium line that meets perfectly customer demands.
Figure 1. Planetary Mill PULVERISETTE 5 premium line
Planetary Ball Mills
Planetary ball mills are the most commonly used ball mills in laboratories for preparing samples ranging from soft to hard to brittle and fibrous materials. The mill derives its name from the unique kinematics wherein the grinding bowls are mounted on a rotating "sun" disk that rotate in the opposite direction around the disk centre. Because of this, the samples are quickly and effectively comminuted by impact, frictional and shear forces resulting from ball-to-wall and ball-to-ball collisions.
Due to the planetary movement, the grinding bowl filling is not just subject to the gravitational force as with traditional ball mills, coriolis and centrifugal forces further improve the kinetic energy of the grinding components up to 100 times the gravitational force. At increased rotational fields the impact of these forces on the grinding components and the material being ground produces a high load intensity and grinding performance. The energy transmission density is 10 times that of vibratory mills and 50 times conventional ball mills.
Figure 2. Function diagram of planetary ball mill
The grinding result is influenced by a number of parameters, especially by the rotational speed of the mill, the grinding time, the ball size, the ratio of the sample quantity to the ball filling as well as the material of the grinding parts.
Grinding into the Nano Range
There is a growing demand for fine particles with a fine size distribution especially in the pharmaceutical and chemical industries. It is possible to produce fine particles down to the nanometre range by chemical synthesis or by communition of existing coarse particles in a top-down mill. Even particles obtained through crystallization are too coarse and need to be processed in mills.
It is possible to explain industry interest in nanoparticles as these particles exhibit completely new chemical and physical properties because of their large specific surface. For example, non-conductive particles become conductors suddenly and opaque metal oxides become transparent.
When compared to the previous model PULVERISETTE 6 classic line, there is a doubling in drive power for the premium line version. A maximum rotational speed of up to 850 rpm is enabled by the powerful 1.5 kW version resulting in an increased energy application. Figure 3 shows the sample of aluminium oxide ground to particles in the nano range.
Figure 3. Comparison of Planetary Mill PULVERISETTE 5 premium line with Planetary Mill PULVERISETTE 6 classic line
After just 30 mins the d50 value of the ground sample is already below 200 nm and after 60 minutes it is below 100 nm. A significantly long grinding time is necessary to receive similar results with the classic line.
Along with the considerably high drive power the mill operation is also premium. All major parameters, such as rotational speed, grinding time, pause function, number of grinding cycles, etc. are entered through a 4.3-inch touch screen with colour display and can be saved as a grinding program.
Until now, users of planetary mills had to adjust manually the needed compensation for imbalance with a counterweight. This new equipment enables imbalance compensation to be done in a fully automatic manner due to a patented technology by FRITSCH. The new grinding bowl clamping mechanism ServoLOCK (Figure 4) is also patented.
Figure 4. Especially safe: Automatic grinding bowl clamping ServoLOCK
The bowl is reproducibly tensioned with a clamping force of 16 kN thanks to the motor-driven ServoLOCK.
The distinct functions of the Planetary Mill PULVERISETTE 5 premium line are:
- Motor-driven grinding bowl clamping (ServoLOCK)
- Convenient touch screen with colour display
- Doubled drive power for fast, powerful, high-performance grinding
- Fully automatic grinding bowl imbalance compensation
Truly the new planetary mill is the new high technology standard for the modern laboratory.
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.