[nanoPost] Mechanical preparation of phyllosilicate nanoparticles and nanocomposites

Research Centre Czech Rep

The nanoparticles and nanomaterials are extensively studied for many years. Increasing interest has focused on a variety
of nanostructured materials with clearly defined particle size. Size, shape and surface chemistry are determining factors
that are among key properties to the utilization of nanomaterials.
Modern technologies open the possibilities to fabricate the nanomaterials with various dimensionalities of
nanostructures. An attractive category of nanomaterials are nanoparticles. Nanoparticles become more and more
important in many areas, especially in development of new high-tech materials. Nanoparticles can be produced using
various processes such as wet milling, high-pressure homogenization, emulsification, precipitation, rapid expansion
or/and spray freezing. The milling methods represent one of the most popular approaches to produce nanoparticles by
the mechanical way. Generally are referred as a ‘ground’. The resulting particulate powders can exhibit nanostructural
characteristics on at least two types. At first, the natural particles are ‘nanoparticles’ if their average characteristic
dimension (diameter for spherical particles) is less than 100 nm. Secondly, many of the milled materials are highly
crystalline, such that the particle size after milling is often between 1 and 10 nm in diameter.
As mechanical preparation technique of defined particles we used jet mill (Sturtevant Micronizer®). This technique is
relatively simple preparation method for particles with defined size, although is energy consuming. The jet mill is widely
used in industries for grinding the solid materials (agricultural chemicals, minerals, metals, metal oxides - titanium and
iron oxides, pigments, ceramics etc.). Principle of grinding in jet mill is in regulation of feeding and grinding pressure
(kPa). The pressure of compressed air provides the grinding energy. The milling in jet mill consists of two stages:
1) the mixing of solid materials with compressed air;
2) the acceleration of compressed air and solid materials flow in the grinding chamber. High speed rotation of materials
in chamber causes the particle-on-particle collisions creating increasingly smaller particles.