JPS63146400A - Plasma torch - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a plasma torch, and particularly to an apparatus that utilizes reactions in plasma.

[Conventional technology]

Plasma torches can utilize chemical species such as heat, ions, and radicals in plasma. Therefore, plasma chemical reactions using active species and high temperatures (>5,0
It is applied to the processing of high melting point substances using OOK). In particular, those that generate plasma using high frequencies or microwaves (hereinafter referred to as (Radio Frequency)
1lave Induced Plasma (hereinafter simply referred to as RF plasma) is often used for the synthesis of high-purity substances because there is no contamination from electrodes.However, when applying an RF plasma torch to chemical reactions, it is especially important to When a solid raw material is used, there is a problem in that plasma instability increases.

Therefore, as proposed in Japanese Patent Application Laid-Open No. 55-32317, an arc plasma torch has been provided and the arc plasma generated by the arc plasma torch is used as a pilot light for a high-frequency flame. Even if the RF flame becomes unstable due to the reactants supplied into the torch, the RF plasma is stabilized by the supply of electrons and ions from the arc plasma.

In addition, we have developed a plasma chemical reaction device that is an improved version of this method.
An apparatus has been proposed in which different materials are introduced into the DC arc jet and RF plasma generated by a DC arc plasma torch, and the DC arc jet and RF plasma are superimposed.

(Unexamined Japanese Patent Publication No. 6O-19034).

[Problem that the invention seeks to solve]

In all of the above-mentioned conventional devices, instability of the plasma accompanying the introduction of raw materials into the plasma is improved by supplying electrons and ions from the arc plasma generated by the arc plasma torch.

However, when the arc electrode (anode copper, cathode tungsten, etc.) is heated by the heat of the plasma, the metal components that make up the electrode evaporate, and the evaporated metal components mix into the products of the plasma reaction, resulting in high-purity substances. The problem is that it cannot be obtained. Further, when a corrosive gas such as HCI NHz or an oxidizing gas such as 02 or N2 is used as a raw material, the electrodes are corroded or oxidized by these raw material gases.

As a result, new problems arise, such as increased instability of the arc due to corrosion of the electrodes and deterioration of conductivity due to oxidation of the electrodes.

The purpose of the present invention is to solve the problems of the prior art described above,
It is an object of the present invention to provide a plasma torch capable of stabilizing plasma and obtaining a highly pure substance regardless of the raw material such as corrosive gas or oxidizing gas.

[Means for solving problems]

The above object is achieved by installing an electron emitter inside the torch at a position that is at least spaced apart from the plasma formed in the plasma torch, in which plasma is formed within the torch using high frequency waves or microwaves. Ru.

[Effect]

If a raw material is introduced into the plasma torch while plasma is being generated, the temperature of the plasma will drop and RF or microwaves will not be efficiently introduced due to the difference in dielectric constant between the raw material and the plasma gas ( (a condition in which matching cannot be achieved) occurs. Therefore, the temperature of the plasma further decreases, making it impossible to maintain the plasma. Therefore, when a raw material is introduced into plasma, electrons are introduced into the plasma as a means to excite, ionize, and dissociate the raw material.

Electrons introduced into the plasma are accelerated by RF or microwaves and become electrons in a high energy state. These high-energy electrons greatly increase the number of collisions with the raw material, and can excite, ionize, and dissociate the raw material. and,
Fluctuations in the dielectric constant and temperature within the plasma can be suppressed to a level that allows the plasma to exist stably, and an increase in instability of the plasma can be prevented. The electron emitter is plasma)
The electron emitter material can be selected depending on the type of raw material, and the electron emitter material is installed at a location separated from the plasma in the chamber, and the electron emitter material is not corroded, oxidized, and the substances that cause these are mixed into the product. can be ignored.

[Embodiments of the invention]

In the present invention, the electron emitter is disposed within the plasma torch, but the temperature of the plasma is in an extremely high temperature region of almost 10.0 OOK or higher, and it cannot be disposed within the plasma. Therefore, the electron emitter may be installed in a region where the temperature near the plasma on the inner wall of the torch is about 1.000 to 2.0 OOK.

When a thermionic emitter or an electron emitter is used, oxidation of the electron emitter is not a problem because it is installed in a part that does not receive heat from plasma. The photoelectron emitter is used as a condition (
a) Wavelength between 2,000 and 7,000 (especially 4,0
It is desirable to have the maximum photoelectric efficiency (A/1m) for light (nearly 0.00 people).The reason for this is that plasma emission
This is because there is a maximum peak around 00 people. Further, it is desirable that the maximum photoelectric efficiency is 40 uA/1 m or more.

In the present invention, photoelectron emitters that can be used include C
Typical examples include compounds consisting of components such as sSb, AgCs, and B1Cs, or compounds containing these compounds as a main component.

The thermionic emitter preferably has a melting point of 1,250° C. or higher and a work constant of 3.5 eV or higher, and it is desirable to install the thermionic emitter in a temperature range that is 0.8 times or lower than the melting point. In the present invention, typical examples of thermionic emitters that can be used include compounds consisting of components such as Th0z, BaO1SrO, etc., or compounds having these compounds as main components.

Hereinafter, the effects of the plasma torch of the present invention will be explained in detail with reference to the following examples.

Example 1 When the entire apparatus shown in FIG. 1 was evacuated, A gas was flowed from the plasma gas nozzle 1, and the RF coil 9 connected to the RF power source 3 was energized to ignite the plasma. Cooling Ar gas was flowed from the cooling gas nozzle 2 to localize the plasma inside the plasma torch by a thermal pinch effect.At this time, the flow rate of the Ar gas introduced from the plasma gas nozzle 1 and the cooling gas nozzle 2 was was set to 1:1, and the pressure inside the plasma torch was set to 160 Torr.

As shown in FIG. 2, a thermionic emitter 11 made of BaO formed into a film with a film thickness of about 10 μm by the ion plating method was attached to a plasma torch. RF power supply 3 output to 800W
As a result of temperature measurement using an optical pyrometer (not shown), the temperature of the BaO film was 800 to 850°C.

Under the above conditions, trichloromethylsilane (CIIsSiCl*) was introduced into the plasma from the raw material gas nozzle 4 using A' gas as a carrier. No change in the optical shape of the plasma was observed by visual inspection.
The surface temperature of the BaO film was 760 to 810°C, which was fairly stable. After the experiment was completed, a product as shown in Figure 3 was obtained. This product was a B-3iC single phase according to X-ray diffraction, and Ba was not detected according to EPMA analysis.

Next, in order to compare with the above experimental results, among the above experimental conditions, the shape of the plasma torch was
The experiment was conducted under the same conditions as the case with a built-in plasma torch, except that the plasma torch was changed to a plasma torch without a thermionic emitter installed.

When the source gas was introduced from the source gas nozzle 4, the plasma clearly showed a change in optical shape, and the plasma, which was in a stable state as shown in FIG. 4, changed to an unstable state as shown in FIG. When such an experiment was repeated five times, a phenomenon in which plasma was completely reduced occurred twice. Further, due to the unstable plasma state, no products could be recovered.

Example 2 In the apparatus shown in FIG. 6, Cs,
The following experiment was conducted using the plasma torch shown in FIG. 6 using sb foil ring material No. 12. The internal dimensions of the torch are the same as the torch of Example 1. In addition, all conditions other than the torch structure were the same as in Example 1. When the raw material was introduced into the plasma, there was no visual change in the optical shape of the plasma.The maximum value of the optical wavelength-electron emission rate for scs and sb was around the wavelength of 4,000, and for Ar, the maximum value of the optical wavelength - electron emission rate was around 4,000.
AI with a spectrum close to that of humans (4,200 people)
The intensity was measured with a spectrum analyzer before and after introducing the raw material.
As a result of repeated measurements, the strength of AI decreased after the introduction of raw materials, but the same product as in Example 1 was obtained, and according to EPMA analysis, no Cs or sb was detected. The impact was negligible.

If the electron emitter is built into the plasma torch as described above, the unused energy emitted from the plasma can be recovered and the plasma itself can be formed more stably. Moreover, the stability of the plasma can be made high. Furthermore, since the stability of the plasma is increased, the plasma torch itself can withstand continuous use on an industrial scale, and it is possible to obtain a highly pure product free from contamination with electrode materials.

Furthermore, even in a plasma reactor that utilizes thermal plasma, it is possible to prevent an increase in plasma instability due to the introduction of raw materials, and to obtain a highly pure product free from contamination with electrode materials.

Example 3 As shown in FIG. 7, a photoelectron emitter 12 was installed and an Ar
An experiment was conducted in which the photoelectron emitter 12 was irradiated with laser light using a gas laser. Stow powder as raw material (particle size 1μ
A mixed gas of NH3 (30%) and Ar (70%) was introduced into the torch from the source gas nozzle 4 shown in FIG. At this time, Sin.

10 g/h of powder, 500 m 1 / m of mixed gas
A is introduced from cooling gas nozzle 2 and plasma gas nozzle l in Fig. 1, and the ratio of the flow rates is lO.
:1, and the pressure inside the plasma torch is 160 To.
The respective flow rates were also adjusted so that rr.

The test was carried out at an RF specific output of 800W. At that time, when the photoelectron emitting material was irradiated with a 1 mW Ar gas laser, the optical shape of the plasma was stabilized as shown in FIG. 4.

On the other hand, when the irradiation of the photoelectron emitter 12 with the laser was stopped, the optical shape of the plasma changed to an unstable optical shape as shown in FIG. Further, when the electron emitter 12 was irradiated with a laser, a product (sisNa) was obtained after the experiment.

However, if the above irradiation was not performed, the product would be Si
ng, and Si and N were not detected by X-ray diffraction. Further, in product analysis by EPMA, neither Cs nor sb was detected in either case with or without laser irradiation.

Example 4 In Fig. 8, BaO was added to the tungsten ring in a thickness of Q, 1 mm.
Using the thermionic emitter 15 coated to a thickness of
A heating element 16 is fixed to this electron emitter 15. The experimental conditions were exactly the same as in Example 3 (type of raw material, flow rate, pressure, RF specific output) except that the experiment was conducted using the plasma torch shown in Fig. 8 and the apparatus shown in Fig. 1. The tungsten ring is set to generate heat due to Joule heat. After adjusting the voltage so that the tungsten ring reaches 870 to 920°C, raw materials are introduced as shown in Example 3, and Ar is also Introduce the torch internal pressure to 160
Adjusted to Torr. In this case, the plasma shape is stable as shown in FIG. On the other hand, when the tungsten ring was not heated and an experiment was conducted under the same conditions as above, the plasma shape became unstable as shown in FIG.

In addition, as for the product in each case, when the tungsten ring was heated, 3t3Na was produced, but when the tungsten ring was not heated, a mixture of Sin and 5isFJ・a was produced. .

Ba was not detected in the analysis by EPMA (both by X diffraction) and EPMA.

As mentioned above, from Examples 3 and 4, when using a solid and/or liquid as the raw material, the electron emitter can be given energy from another energy source in addition to the energy from the plasma. By increasing the electron concentration in the plasma, the plasma can be stabilized without the introduction of impurities.

The same comparison as that made with the RF plasma was made using the microwave plasma torch shown in FIG. 9 with a microwave output of 800 W. In FIG. 9, the coil 18 is powered by the power source 17.
Example 5. corresponding to Example 1.2.3.4 was conducted under the same conditions except that the RF plasma was replaced with microwave plasma.
6,7°8 was performed. The results obtained were exactly the same, and no difference was observed depending on the plasma generation method.

〔Effect of the invention〕

As described above, according to the present invention, plasma can be stabilized by installing an electron emitter near the plasma in a plasma torch, and the electron emitter is an arc plasma electrode installed in a conventional plasma torch. Since it is not exposed to ultra-high temperatures, there is no oxidation phenomenon that occurs in arc plasma electrodes, and it is also possible to change the electron emitter to match the raw material, making it possible to stabilize the plasma and obtain high-purity materials. I can do it.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram showing one embodiment of the plasma torch of the present invention, FIG. 2 is an explanatory diagram showing the arrangement of thermionic emitters in the plasma torch of FIG. 1, and FIG. 3 is Embodiment 1.
An electron micrograph showing the state of the particles obtained at a magnification of 10,000 times, Figure 4 is an illustration of the optical shape of plasma in a stable state, and Figure 5 is an illustration of the optical shape of plasma in an unstable state. FIG. 6 is a sectional view of a main part of a plasma torch with a built-in photoelectron emitter showing another embodiment of the present invention, and FIG. 7 is a plasma torch of a light irradiation method from outside the torch, showing still another embodiment of the present invention. 8 is a schematic configuration diagram of a plasma torch with a built-in thermionic emitter showing still another embodiment of the present invention, and FIG. 9 is a schematic diagram of a plasma torch equipped with a microwave power source according to the present invention. It is a configuration diagram. l...Plasma gas nozzle, 2...
Cooling gas nozzle, 3...RF power supply, 4...
... Raw material gas nozzle, 5... Filter, 6.
...Plasma gas inlet, 7...Cooling gas inlet, 8...Raw material gas inlet, 9...
...RF coil, 10...Recovery section, 11...
...Plasma, 12...Photoelectron emitter, 13
......Cooling water, 14...Water-cooled quartz tube,
15... Thermionic emitter, 16... Heating body, 17... Power source for microwave, 18...
...Microwave coil. Agent Patent Attorney Masaru Nishimoto - Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6

Claims (8)

[Claims] (1) A plasma torch that forms plasma within the torch using high frequency waves or microwaves, characterized in that an electron emitter is installed inside the torch at a position that is at least spaced apart from the plasma formed in the plasma torch. plasma torch. (2) The plasma according to claim (1), wherein the electron emitter is a thermionic emitter, and its heating source is the heat of plasma formed within the plasma torch. torch. (3) The electron emitter is a thermionic emitter, and a heat source separate from the heat of the plasma formed in the plasma torch is installed in the heat source of the electron emitter. ) Plasma torch described in section. (4) The plasma torch according to claim 1, wherein the electron emitter is a photoelectron emitter, and its light source is plasma formed in the plasma torch. (5) The plasma torch according to claim 1, wherein the electron emitter is a photoelectron emitter, and its light source is plasma formed within the plasma torch. (6) A patent characterized in that the electron emitter is a photoelectron emitter, and the photoelectron emitter is irradiated with light from a light source different from the light of the plasma formed in the plasma torch. A plasma torch according to claim (1). (7) The thermionic emitter is made of a compound selected from the group of ThO_2, BaO, and SrO, or has the compound as a main component, or The plasma torch according to item (3). (8) The photoelectron emitter may include CsSb, AgCs and B.
The plasma torch according to claim 4 or 5, characterized in that it consists of a compound selected from the group of iCs or has the compound as its main component.