Fine-Milling to Create Nanoparticles from Large Substrates

A large broken stone

The FRITSCH Jaw Crusher PULVERISETTE 1 can be used to pre-crush medium-hard to hard materials with edge lengths up to 95 mm.

An additional fine comminution with other FRITSCH mills is possible.

These include:

  • Mortar Grinder PULVERISETTE 2
  • Disk Mill PULVERISETTE 13 classic line
  • Vibratory Micro Mill PULVERISETTE 0
  • Vibrating Cup Mill PULVERISETTE 9
  • Mini-Mill PULVERISETTE 23
  • Planetary Ball Mills like PULVERISETTE 4, PULVERISETTE 5, PULVERISETTE 6 and PULVERISETTE 7

Planetary Ball Mills

The material can be relatively quickly ground to “analytical fineness” - smaller than 63 µm - using any of these instruments. However, the first two instruments mentioned are no longer suitable to achieve significantly finer materials, which are used as the starting point for creating nanopowders.

Planetary ball mills were previously the only method used for the production of particles under 1 µm with mills from the Fritsch product range, and because of this, the company developed the Planetary Mono Mill PULVERISETTE 6 classic line. An appropriate test situation was the use of this line to grind quartz sand as the preferred "model" material, without any added liquid.

It is generally assumed that the “dry grinding” process is complete when the material adheres to the grinding balls and the bowl wall. For this test series, 20 mm grinding balls of zirconium oxide (ZrO2) and a 250 ml grinding bowl of the same material were used.

  1. 4 Quartz sand starting product for the tests for production of nanoparticles
  2. 2 quartz sand 5 minutes PULVERISETTE 6, dry grinding, 250 ml ZrO2 bowl, 20 mm balls, average
  3. 3 quartz sand 10 minutes PULVERISETTE 6, dry grinding, 250 ml ZrO2 bowl, 20 mm balls, average
  4. 31 quartz sand 15 minutes PULVERISETTE 6, dry grinding, 250 ml ZrO2 bowl, 20 mm balls, average
  5. 43 quartz sand 30 minutes PULVERISETTE 6, dry grinding, 250 ml ZrO2 bowl, 20 mm balls, average

The material is fine enough for normal analysis tasks after 10 minutes (curve 3) - the level of “analytical fineness” has been reached.

A material was produced after 30 minutes (curve 5) with x10 < 0.8 µm – x50 < 2.8 µm – x90 < 11.9 µm. This material has the appropriate particle size for further processing to produce nanopowders.

Tests using the Planetary Micro Mill PULVERISETTE 7 classic line show that extending the grinding time from 60 minutes to 240 minutes achieves practically no further increase in the fineness of the ground material. A significant increase in the fineness can be achieved in a short time by exchanging the 10 mm grinding balls used for this test with balls measuring approximately 1 mm in size.

The Planetary Mono Mill PULVERISETTE 6 classic line and a 250 ml bowl of ZrO2 was used again, and grinding beads of ZrO2 significantly smaller than 1 mm diameter were used in place of the 20 mm diameter grinding balls. The 20 mm grinding balls were weighed and an equivalent weight of grinding beads of 1 mm was used with 50 g of model substance from the first test and 100 ml of water in order to determine the quantity required.

After processing for 120 minutes, the particle size distribution was determined with the Laser-Particle-Sizer ANALYSETTE 22 NanoTec (curve 2).

  • 1-43 quartz sand 30 minutes PULVERISETTE 6, dry grinding, 250 ml ZrO2 bowl, 20 mm balls, average
  • 2 221 quartz sand 120 minutes PULVERISETTE 6, wet grinding, 2nd step, 250 ml ZrO2 bowl, 320 g of 0.4 mm ZrO2 balls
  • 3rd test series, average

A very convincing result was obtained with x10 < 140 nm - x50 < 180 nm - x90 < 240 nm. These test results show that Planetary Ball Mills from FRITSCH GmbH can be used to produce nanoparticles.

Using FRITSCH technology, a "boulder" can be turned into nanoparticles in just 1 hour, as an intermediate sample after 30 minutes yielded results of x10 < 180 nm - x50 < 250 nm and x90 < 580 nm.

Critical Factors for Production of Nanoparticles

  • physical properties of the grinding media
  • physical properties of the grinding sample
  • grinding ball size
  • ratio between the quantity of grinding materials to grinding balls and liquid
  • maximum possible energy application available with the mill

The Fritsch-patented Planetary Ball mill PULVERISETTE 6 classic line has an optimal speed ratio between the sun disk and the grinding set. This guarantees the maximum possible impact energy through the resulting trajectories of the grinding balls colliding radially with the grinding bowl walls, providing the best cost/performance ratio of any mill available.

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.

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