How to Make and Apply Nano Particles

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Posted in: , on 20. Dec. 2006 - 14:46

How to Make and Apply Nano Particles

by W. Pieper, NARA Machinery Europe

Brittle materials that turn to be plastically deformable or ductile, new properties that derive from directional atomic forces, functional surface textures – these are the reasons why many researchers focus on nano sized particles. At such small dimensions particles do no longer behave like big micron or millimetre sized blocks. For example Aluminium Silicate, a brittle material at micron size, can be bent from a size less than 100 nm.

Researchers and visionary people think of new functional powders for which a need already exists in highly specialized niches. The nano size is considered as one solution to many open questions. Therefore the interest for very fine powders transgresses all business field boundaries. It stretches across the pharmaceutical, electronic, powder metallurgy, cosmetics, ceramics, feed and fertilizer field.

The challenges with nano powders are many. Some major targets are: production of the powder, keeping the particles in a disperse state, applying them in a disperse state but also homogenous mixing of nano or nano and micron powders.

While nano application ideas exist in abundance throughout the industry it is the solving of the above challenges that is essential to manufacture highly functional products at reasonable cost.

A fairly straight forward method to generate nano particles is the laser ablation method also known as pulsed laser deposition (PLD). Very small nano particles are ablated from a target by laser light. Such a target can be any kind of material which means that any kind of nano particles can be produced by this methodIn order to keep the particles in a disperse state the laser deposition is executed either in the liquid phase or under vacuum in the gas phase.

Fig. 1:

Nano particles preparation


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How To Make And Apply Nano Particles (Continued)

Posted on 20. Dec. 2006 - 01:47

In the liquid phase process the particles that are deposited remain suspended in the liquid. Due to the very small size they will not settle in the liquid. The liquid itself immediately reduces the surface forces that exist after ablation. In this way the nano particles do not agglomerate but they remain in the disperse state. Such a suspension could be drunk as a drug or it may be used as an intermediate for further processing steps.

If an electric or magnetic field is activated in the nano-particle-liquid-suspension, the particles will migrate to one of the electrodes due to their charge. The anode or the cathode will then be covered by the nano particles. Choosing an electrode of application tailored shape and size one can produce and design coated substrates as needed in specific applications.

Depending on the vacuum, pulsed laser deposition in the gas phase yields different size disperse particles. The higher the vacuum the finer the particles will be. Producing uniform nano powders by this method is not feasible due to particle diffusion. But again coating of all kinds of substrates can readily be performed. Since it is free to choose the target material as well as the substrate, infinite combinations of substances are available. Even macromolecules can be deposited without destroying their chemical composition. Homogenous coating layers from 2 to 200 nanometers can be achieved by this method.

The plain set up of the ablation system furthermore allows multi layering of a substrate. Such coatings help to prevent chemical attack and degradation on the one hand it may improve substrate function like switching speed on the other hand. The shape of the substrate to coat can be the surface of a cuboid or powder. An example for powder coating is shown above. Extremely discrete Nano coatings on micron powders are a research field in the electronics and pharmaceutical industry.

Fig. 2:

Zincoxide coated Zincsulphate


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How To Make And Apply Nano Particles (Continued)

Posted on 20. Dec. 2006 - 01:49

Pulsed laser deposition allows its user to address and solve several of the above mentioned challenges in nano particle processing: nano powders production, keeping the particles in a disperse state as well as coating them on various shaped substrates including disperse micron particles.

However, most nano powders that are not suspended in a liquid exist as dry micron sized agglomerates that have a primary particle size of a few nanometer. This is due to the high surface energy of the single particles. In order to use the nano effects of the agglomerated powders it is necessary to disperse the particles and then immediately fix them on a substrate. Dispersing and coating should be one step. A solution to these requirements is Hybridization. In the Hybridization Process nano powders are coated on micron sized powders purely by mechanical forces. These mechanical forces not only lead to the coating of the core particles but it simultaneously effects the dispersion of the nano particles so that extremely fine, nano sized films are created on the core. No agglomeration of fine or core particles will take place during such a process.

The elimination of liquids and chemical reactions, that is the physical character of the process, makes the machine a highly flexible dry phase coater. Due to the fact that chemical properties can be neglected in this process, combinations of powders that are difficult to achieve by chemistry often are easy to establish by Hybridization. A product sample of a coated polymer is displayed above.

Production of quickly and easily designed, functional materials, that is materials with highly specific and reproducible properties, becomes increasingly crucial to sustain competitiveness. Dry phase coating by hybridization delivers such a processing route. Just throwing materials together and treating them is much simpler than developing a multi stage chemical process. By this method metals or polymers can be coated with inorganic powders like Aerosils or organic waxes, Waxes and polymers can be coated by metals, organic powders by inorganic or organic substances.

Fig. 3:

Resin coated polymer particle


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How To Make And Apply Nano Particles (Continued)

Posted on 20. Dec. 2006 - 01:52

Many Micron powder – nano powder combinations have been established already. Materials Hybridized range from pharmaceuticals for increased bioavailability, taste or smell masking to electronic parts where the conductivity needed to be changed.

Using a high mechanical energy/Volume ratio one can achieve dry phase/solid phase chemical reactions. The Nara Miralo offers this processing method using a rotor/rotor system. The inner rotor consists of rings that are radial accelerated so that the rings roll and scratch along the outer rotor (casing) surface. The material treated in the machine is subjected to high compression and shear forces. The energy transferred is transformed at a very limited level to fracture energy, to a larger extent to surface energy, to mixing energy and to the largest extent to heat energy as always is the case for grinding processes.

The high energy per volume can be applied for various purposes: uniform mixing of micron–nano or nano–nano powders, grinding, mechanical alloying and mechanochemical reaction. Homogenizing at nano size level can be crucial for sintering processes in the metallurgy and the polymer industry. Mechanical alloying helps to establish metal/metal combinations which are difficult or impossible to produce by a melting process. Furthermore nano powders can be added to adjust the ductility of the product. The field of highest impact for this technology is that of soft mechanochemical reaction or mechanochemistry. In soft mechanochemical processes components with functional groups that are liable to react are treated together. During the process the functional groups react with another due to the activation in the machine. The energy applied in such a process is by far lower than in solely chemical process. In metallurgy it was found that the activation of the particle surface by the Miralo leads to lower sintering temperatures or in other words the activated particle surface promotes sintering at lower temperatures.

Even though many nano particles are for sale on the market, producing and handling these still remains a challenge of producers as well as users. Especially when handling dry powders, dispersing and immediate applying on the requested surface or powder needs special technologies. Pulsed laser deposition, Hybridization and the Miralo processing are solutions to most of these problems.

For more information on NARA Machinery Co., Ltd. Europa, please visit:


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Fig. 4:

Operating principle Miralo


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Very Good Aricle

Posted on 6. Oct. 2008 - 06:52


Miralo Processor

Posted on 8. Oct. 2008 - 08:21

I would be interested to know a little more about the Miralo processor. I followed the link, but didn't find any information.

My involvement with mechanochemistry goes back to the 1990s when we were investigating its application to the destruction of toxic waste at the University of Western Australia. (Nature, 367: pp 223-223 (1994) , US 5648591, 1997-Donecker et al. Toxic material disposal).

Subsequently, we built the first pilot plant in Australia in Perth for the production of various nanoparticles in bulk using stirred ball mills. As Principal Process Engineer on that project, I looked at many options for the high intensity milling stage, I don't recall coming across your machine. As it turned out, we built our own mills and they were highly sucessful.

Peter Donecker Bulk Solids Modelling [url][/url] [url][/url]