Process and apparatus for producing metal nanoparticles

Abstract

A novel process and apparatus for producing metal nanoparticles by electro-explosion of wires is disclosed. The invention comprises placing a wire and a plate of the same material as two electrodes in a dense medium, preferably water, in such a manner so as to guide the wire in a straight line and applying a voltage of greater than 12V to said electrodes to cause the wire explode into nanoparticles.

Description

FIELD OF THE INVENTION [0001] The present invention relates to a novel process for producing metal nanoparticles by electro-explosion of wires. More particularly, the present invention provides a process for the production of nanoparticles comprising exploding wires into small fragments by application of suitable voltages, at low voltages in order to supply energy to the wires such that the nanoparticle size depends upon various controlling parameters such as applied voltages and current densities. The present invention provides a simple, repeatable process to achieve large production volumes for nanoparticles. BACKGROUND OF THE INVENTION [0002] Nanoparticles have been a source of great interest due to their novel electrical, optical, physical, chemical, magnetic etc. properties. They have significant potential for a wide range of applications including catalysis, magnetic recording media, optoelectronic materials, magnetic fluids, composite materials, fuel cells, pigments and senso...

AI Technical Summary

Benefits of technology

[0012] Still another object of the present invention is to use low voltages between 12V-50V DC, while also having the possibility of employing AC voltages for the purpose, thereby reducing the energy costs involved in production of nanoparticles.

[0015] The present invention provides a novel process for the production of metallic nanoparticles based on the electro-explosion of wires in a suitable medium. Particularly, the present invention relates to a novel process for the production of metallic nanoparticles by way of controlled explosion of the metal in a suitable medium applying voltages of about 12V and above, to two electrodes, one in the form of a wire and another in the form of a plate, so as to achieve a spark between the electrodes, thereby simulating a situation where the wire cross-section is pinched or reduced and whereby high current densities are achieved along the length of the wire, instantaneously exploding the electrodes by sending shock waves through the bulk of the material, melting them and dispersing them to form small fragments which are then collected by a suitable medium in which the process is initiated, not only for efficient recovery of the material but also to form a protective layer around the now highly reactive nanomaterial so to prevent the nanomaterials from coalescing into large particles by forming a cap, wherein the capping efficiency is determined by the combination of the metal and the medium in which the metal electrodes are exploded and the particle size can be modified by way of altering parameters such as applied voltage, explosion current density and wire diameters.

[0017] i. applying a voltage of greater than 12V to a first electrode and a second electrode, both said first and said second electrodes being formed of the metal whose nanoparticles are desired, said first electrode being in the form of a plate, and said second electrode being in the form of a wire, so as to achieve a spark between the said first and second electrodes, thereby simulating a situation where the second electrode cross-section is pinched or reduced and whereby high current densities are achieved along the length of the second electrode,

[0019] The present also provides an apparatus for the production of metallic nanoparticles by the controlled electro-explosion of a metallic wire in a suitable medium which comprises a reaction vessel containing said medium, a first and second electrodes mounted inside said vessel, submerged in said medium, said first and second electrodes being formed of a metal whose nanoparticles are desired, said first electrode being in the form of a plate, and said second electrode being in the form of a wire, so as to achieve a spark between the said first and second electrodes, thereby simulating a situation where the second electrode cross-section is pinched or reduced and whereby high current densities are achieved along the length of the second electrode, said electrodes being connected to a power source so that current is passed through said electrodes, instantaneously exploding both said first and second electrodes by sending shock waves through the bulk of the material, thereby melting the electrodes and dispersing them to form said nanoparticles of said metal.

[0024] The nanomaterials that have been realized are independent particles, comparable in size to other nanomaterials reported in the prior art literature. The process is very energy intensive since only relatively low voltages are applied, and also results in high volumes of nanoparticles being produced since both electrodes are consumed.

Problems solved by technology

However, industrial applications for such particles are limited due to the low production rates and high cost.

However, except for precious metals, chemical methods are generally not applied to the production of metallic nanoparticles.

The main drawback of this process is that it is time consuming.

The main drawbacks of this process are that it has to be operated in a vacuum environment and the product is a mixture of the metal and its oxide.

The drawback of this process is that it is used to enhance reactivity and does not result in the formation of nanoparticles.

The drawback of this process is that only an ionisable medium can be employed for this purpose together with the use of DC voltages high enough to achieve ionization of the medium.

Further, only one of the electrodes is consumed in the process to produce the nanoparticles.

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