Appaaratus for generating low temperature plasma at atmospheric pressure

Abstract

Disclosed is an apparatus for generating low-temp plasma at atmospheric pressure, comprising: a couple of electrodes facing each other at a distance, one of them being connected to a power supply, the other being grounded; a couple of dielectrics with a thickness of 25 mum-10 mm, positioned on the facing surfaces of the electrodes in such a way as to face each other, one of them having at least one discharge gap therein; and a conductor electrode having at least one tip positioned within the discharge gap, in which an electric field is applied at an intensity of 1-100 KV / cm through the power supply across the electrodes by use of a pulse direct current or an alternating current in a frequency bandwidth of 50 Hz-10 GHz while a reaction gas is fed between the electrodes, so as to induce a hollow cathode discharge, a capillary discharge or the high accumulation of charges from the discharge gap. With this structure, the apparatus prevents the conversion of the plasma to arcs and thus gives stable, low-temp plasma in a high density, and utilizes a broad bandwidth of frequencies in addition to being low in electricity consumption and being manufactured at a low cost. At low voltages, it can generate and maintain stable, low-temperature plasma over a large area. The plasma is suitable to form radicals of high energy and can be used for bonding, polishing, cleaning, thin films deposition, sterilization, ozone generation, printing, dyeing, etching, purification of water and air, complete combustion of fuels, manufacture of highly luminous lamps.

Description

[0001] 1. Field of the invention[0002] The present invention relates to an apparatus for generating low-temperature plasma in a high density at atmospheric pressure with low discharge initiation and maintenance voltages.[0003] 2. Description of the Prior Art[0004] Generally, plasma is defined as a partially ionized gas composed of a nearly equal number of positive and negative free charges so that it is electrically neutral. Subgrouped into high-temperature and low-temperature plasma according to the temperature at which it undergoes ionization, plasma is of very high reactivity, chemically and physically.[0005] Low-temperature plasma is used to synthesize various materials, such as metals, semiconductors, polymers, nylon, plastic, paper, fiber, and ozone, or to modify surface properties of materials with a concomitant improvement in various physical and chemical properties such as junction strength, dyeing properties, printability, etc. Accordingly, low-temperature plasma finds num...

AI Technical Summary

Benefits of technology

[0014] It is another object of the present invention to provide a plasma-generating apparatus, which is so low in discharge voltage as to greatly reduce the operating and installment cost and electricity consumption of the power supply equipped.

[0016] It is still a further object of the present invention to provide a plasma-generating apparatus, which can discharge in gases of high discharge initiation potentials, such as nitrogen, oxygen and the air.

[0017] It is still another object of the present invention to provide a plasma-generating apparatus, which can generate a homogeneous, high-density, low-temperature plasma at a low discharge voltage over a large area.

Problems solved by technology

In order to maintain such a vacuum, there is needed an apparatus, which is expensive on the whole.

Additionally, if materials to be treated are large in size, it is difficult to apply plasma to them.

Another problem with plasma treatment is difficulty in automation of plasma processes.

Further to these, plasma has difficulty in treating materials which show high vapor pressures or are degassed, such as rubber, biomaterials, etc.

Additionally, because the gap between two electrodes is narrow, a corona discharge is difficult to apply to targets of three-dimensional shape.

Also, other problems with the coronal discharge include noise generation and a short electrode lifetime.

Although providing homogenous plasma, the dielectric barrier discharge does not ensure the generation of homogenous, diffused plasma over a large area, as in the corona discharge.

However, the power supply is difficult to operate and manage because of its being expensive and high in electricity consumption.

Limitations in the size and number of the tips are attributed to the fact that, when the size and number are out of the ranges, the accumulation of charges at the tips is too inefficient to lower the discharge initiation and maintenance voltages, to obtain high-density plasma, and to generate homogeneous plasma.

The plasma generated is, however, low in density.

If the width and height are out of the limit ranges, no capillary and hollow cathode discharges are generated so that discharge initiation and maintenance potentials cannot be reduced to desired values.

In addition, stable highdensity plasma cannot be generated, nor can plasma be prevented from being converted to an arc.

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