JP2010121193A - Apparatus for producing nanoparticle and method for producing nanoparticle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To extend the life of a plasma source in a solution by preventing the fracture of a sealing member due to heat. <P>SOLUTION: This apparatus 1 for forming nanoparticles in the solution by excited plasma includes: a container 30 in which the solution is stored; an electrode 42 for supplying a microwave to the solution; a hole 43-7 which is arranged in a side face 32 of the container 30 while being in the lower part of the water surface of the solution, and passes the electrode 42 therethrough; the sealing member 44 which is arranged between the electrode 42 and the hole 43-7; and an insulating member 45 which is arranged at the solution side of the sealing member 44. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a nanoparticle production apparatus and a nanoparticle production method for generating nanoparticles by exciting plasma in a solution, and in particular, the end of an electrode is formed in a conical shape and the tip contacts the solution. The present invention relates to a nanoparticle production apparatus and a nanoparticle production method for generating plasma.

Examples of generally known methods for producing nanoparticles include a gas phase method, a liquid phase method, a crushing method, and a laser ablation method.
Among them, the vapor phase method generates nanoparticles in vacuum or in gas, so that high-purity and high-quality nanoparticles can be obtained, but the production rate is slow and the production cost is high.
In the liquid phase method, a metal salt is reduced by reducing a metal salt in a solution. However, a reducing agent or the like may be mixed as an impurity.
In the crushing method, a large lump is crushed using a tool or a grindstone to obtain nanoparticles, but contamination of impurities such as the cutting edge of the tool is inevitable during the crushing process.
In the laser ablation method, the laser oscillator is expensive and has a short life, and it is dangerous if the laser beam leaks to the outside.

  Thus, each production method has advantages and disadvantages, but from the viewpoint of producing nanoparticles at high speed, a process in a liquid phase is more advantageous than a gas phase. Moreover, in the liquid phase, if the in-liquid plasma is used as an energy source, the reaction can proceed without adding extra chemicals, so that no impurities are mixed.

When using plasma in liquid as an energy source, there are two methods for obtaining nanoparticles.
One is a method of obtaining a nanoparticle by obtaining a metal atom from an atomic or molecular level by oxidation or reduction reaction, and crystal-growing it.
The other is a method in which large particles are generated in advance by such a method or other processes and then pulverized by the energy of plasma in liquid to obtain nanoparticles. The pulverization by submerged plasma does not have the possibility of mixing impurities as in the case of using tools and grindstones.

Various techniques for generating a plasma in liquid by applying a microwave have been proposed (see, for example, Patent Documents 1 and 2).
A technique for generating a plasma in liquid by applying a direct current pulse has also been proposed (see, for example, Patent Document 3).
Japanese Patent Laid-Open No. 2006-179211 No. 2006/059808 JP 2008-013810 A

However, the apparatus for generating submerged plasma has a problem that its life is short due to thermal degradation of the electrode and its surroundings.
In order to explain this problem, FIG. 12 shows the configuration of an in-liquid plasma source used in the nanoparticle production apparatus.
As shown in the figure, the in-liquid plasma source 100 includes an electrode 110 having a conical end, and a support 120 that supports the electrode 110.
Here, the support 120 is formed in a cap shape having a top plate portion 121 and a skirt portion 122, and a small hole 123 is formed in the center of the top plate portion 121.
The electrode 110 is disposed in the hollow portion 124 of the support 120, and its tip is exposed from the hole 123.
And between the inner surface of this hollow part 124 and the electrode 110, the sealing member 130 for preventing inflow of a solution is embedded.
The sealing member 130 needs to be in close contact with the inner surface of the hollow portion 124 and the electrode 110 so that the solution does not leak. Therefore, deformable soft materials such as rubber, polytetrafluoroethylene (Poly Tetra Fluoro Ethylene; hereinafter abbreviated as “PTFE”), and plastics including polyamide have been used.

However, these materials generally have a low heat-resistant temperature. For this reason, if they are used, they are destroyed in a short time due to radiant heat from plasma, creeping discharge running on the surface, high temperature of the electrode 110, etc., resulting in water leakage and contamination of the nanoparticles.
Moreover, the submerged plasma source 100 itself cannot be used due to the destruction of the sealing member 130. For this reason, the proposal of the technique which prevents destruction of the sealing member 130 and implement | achieves the lifetime improvement of the plasma source 100 in a liquid was calculated | required.

  The present invention has been made to solve the above-mentioned problems, and a nanoparticle production apparatus and a nanoparticle production method capable of preventing the destruction of the sealing member due to heat and extending the life of the plasma source in liquid. The purpose is to provide.

  In order to achieve this object, a nanoparticle production apparatus of the present invention is a nanoparticle production apparatus that generates nanoparticles in a solution by excitation of plasma, and provides a container in which the solution is stored and a microwave to the solution. An electrode, and has a hole through which the electrode passes on the side of the container and below the water surface of the solution. A sealing member is disposed between the electrode and the hole, and the solution side of the sealing member is disposed on the solution side. In this configuration, an insulating member is arranged.

  The nanoparticle production method of the present invention is a nanoparticle production method in which plasma is generated in a solution to generate nanoparticles, and the solution is placed in a container and disposed inside a hole formed on a side surface of the container. An annular sealing member, an annular insulating member disposed on the solution side of the sealing member, and an electrode disposed inside the sealing member and the insulating member. This is a method of generating nanoparticles by supplying plasma-like microwaves and exciting plasma with microwaves at the tips of electrodes protruding into the solution.

  According to the nanoparticle production apparatus and the nanoparticle production method of the present invention, since the insulating member is disposed between the sealing member and the solution, thermal destruction of the sealing member can be prevented. As a result, the life of the sealing member can be extended and the life of the plasma source in liquid can be extended.

  Hereinafter, preferred embodiments of a nanoparticle production apparatus and a nanoparticle production method according to the present invention will be described with reference to the drawings.

[First embodiment]
First, a first embodiment of a nanoparticle production apparatus and a nanoparticle production method of the present invention will be described with reference to FIG.
The figure is a front view showing the configuration of the nanoparticle production apparatus of the present embodiment.

(Nanoparticle production equipment)
As shown in the figure, the nanoparticle manufacturing apparatus 1 a includes a microwave oscillator 10, a waveguide 20, a container 30, and a submerged plasma source 40.
Here, the microwave oscillator 10 includes a magnetron box 11, a microwave power supply 12, and a microwave power supply controller 13.
The magnetron box 11 generates and outputs a microwave.
The microwave power source 12 supplies power for generating microwaves to the magnetron box 11.
The microwave power supply controller 13 sends a signal to the microwave power supply 12 to adjust and control the output of the microwave.
In FIG. 1, the magnetron box 11, the microwave power source 12, and the microwave power source controller 13 are shown as separate configurations, but are not limited to different configurations, and can be integrated.

The waveguide 20 propagates the microwave output from the microwave oscillator 10 to the container 30.
A solid circuit such as an isolator 21, a power meter 22, and a tuner 23 can be attached to the waveguide 20.
The isolator 21 absorbs it with a dummy load and converts it into heat so that the microwave reflected from the load does not return to the magnetron again.
The power meter 22 measures the output and reflected microwave power.

The tuner 23 performs load impedance matching.
The tuner 23 includes a three tab tuner and an EH tuner.
The three tab tuner adjusts the three stubs to maximize the power consumption of the load.
The EH tuner performs tuning by providing plungers at the E branch and the H branch of the waveguide and taking them in and out.
In addition, when implementing the nanoparticle manufacturing apparatus 1a, you may use any of a sleeving tuner and an EH tuner.

The waveguide 20 can be a corner waveguide 24, a terminal plunger 25, or the like.
Furthermore, the waveguide 20 has a coaxial waveguide converter 26.
The structure of the coaxial waveguide converter 26 will be described in detail later in (Liquid plasma source).

The container 30 is a container for storing a solution. Plasma is generated in the solution stored in the container 30.
A hole 31 for attaching a support 43 (described later) of the in-liquid plasma source 40 is formed in a part of the side surface of the container 30.
As described later, the support body 43 is formed in a cap shape, and includes a skirt portion 43-1 and a top plate portion 43-2. The hole 31 is drilled to a size that allows the top plate portion 43-2 and a part of the skirt portion 43-1 (the vicinity of the top plate portion 43-2) to be fitted.
When the support body 43 is fitted into the hole 31, the electrode 42 located inside the support body 43 is located on the side surface of the container 30 and below the water surface of the solution contained in the container 30. Become.

The container 30 can be formed of acrylic, for example. The solution is often acid or alkaline. In this case, if the container is made of metal, it may become a battery and cause electrolysis, so glass or resin is preferable.
A stainless steel container can be provided outside the acrylic container 30. Thereby, leakage of the microwave can be prevented.

(Power supplied to the solution)
Next, the power supplied to the solution will be described.
The solution is supplied with power for exciting the plasma into the solution to generate nanoparticles.
This power is not a direct current pulse but a microwave having a single frequency spectrum such as 2.45 GHz, 5.8 GHz, and 9.5 GHz band. For this reason, high power supply efficiency becomes possible by optimizing the resonance structure and transmission line impedance.

In the liquid plasma, there is an example of discharge by direct current pulse as a conventional technique.
Since the DC pulse contains a fundamental frequency and an extremely wide range of frequency components that are odd multiples thereof, perfect matching with the transmission line and the load (impedance of the solution) is difficult. As a result, the reflected power is large and the power supply efficiency to the load is high. Becomes lower.
On the other hand, the load on the electrode 42 can be reduced by making the driving power microwave.
That is, since the microwave has a single frequency, it becomes possible to supply power very efficiently and to eliminate the electrode such as covering the electrode with a dielectric.
The microwave can theoretically be made non-reflective. In this case, the power supply efficiency to the load is only the greatest loss of the oscillation efficiency of the magnetron, so the power efficiency is close to 70%. Become. This number is very high compared to other methods.

Further, in the direct current pulse, it is necessary to control the conductivity of the liquid. This means that if the conductivity is low, it is necessary to mix an extra electrolyte in the liquid, or if the conductivity is already higher than necessary, plasma cannot be obtained.
On the other hand, since microwaves generate plasma by absorbing energy due to a large relative dielectric constant of water (about 80) and a large dielectric loss tangent (about 10), it is not necessary to control the conductivity. Therefore, it can be applied to many substances without introducing impurities. The fact that water is appropriate as a solution is also a feature for other systems.

As shown in FIG. 2, the microwave power is preferably in the form of a pulse having a plurality of cycles as one pulse.
When microwave power capable of steady plasma discharge is input to the plasma source, intense heat is generated by the power and the electrode 42 is destroyed. However, the electric power for generating plasma is high, and the prototype required a peak power of 2 kW or more. In order to simultaneously realize these conflicting requirements, the power supply needs to be a microwave pulse.
On the other hand, if the pulse width of the microwave pulse is shorter than 1 μsec, the plasma becomes non-thermal equilibrium plasma, the temperature rise is suppressed, and the wear of the electrode 42 is remarkably reduced. However, since the energy given to the solution is small, the reaction rate may be slow or may not be generated depending on conditions.
Regardless of which is used, it is possible to produce nanoparticles, but the particle size distribution, production rate, and the like differ depending on conditions.

The microwave power may be any power as long as it generates plasma, but there is power optimal for the process.
The microwave power source 12 is not necessarily limited to a plasma power source that can constantly obtain power, and may be a power source that generates power in pulses.
When power is generated in the form of pulses, corona discharge, that is, non-thermal equilibrium plasma can be obtained by making the pulse width extremely short, that is, about 1 μsec.

(Liquid plasma source)
Next, the configuration of the in-liquid plasma source will be described with reference to FIGS.
FIG. 3 is a cross-sectional view showing the configuration of the in-liquid plasma source. FIG. 4 is a perspective view showing a support member constituting the in-liquid plasma source. FIG. 5 is an enlarged view of the electrodes constituting the plasma source in liquid and the surroundings thereof.
In the present embodiment, it is assumed that the coaxial tube 41 of the coaxial waveguide converter 26 is included in the in-liquid plasma source 40.

The in-liquid plasma source 40 is an apparatus for supplying the microwave that has propagated through the waveguide 20 to the solution.
As shown in FIG. 3, the submerged plasma source 40 includes a coaxial tube 41, an electrode 42, a support 43, a sealing member 44, and an insulating member 45.
The coaxial tube 41 constitutes a part of the coaxial waveguide converter 26 and receives and propagates microwaves from the waveguide 20.
Generally, in the coaxial waveguide converter 26, the waveguide (tube body 26-1) and the coaxial tube 41 are connected vertically. For this reason, when the microwave is transmitted from the tube body 26-1 to the coaxial tube 41, the propagation direction is changed to the vertical direction.

The coaxial pipe 41 is formed in a coaxial pipe structure, and includes a coaxial pipe outer conductor 41-1 and a coaxial pipe inner conductor 41-2.
The coaxial pipe outer conductor 41-1 is a tubular member that protrudes outward from the surface of the pipe body 26-1 of the coaxial waveguide converter 26. The central axis direction of the coaxial pipe outer conductor 41-1 is perpendicular to the central axis of the pipe body 26-1 of the coaxial waveguide converter 26.
The inner diameter of the coaxial pipe outer conductor 41-1 is sized such that the characteristic impedance is 50Ω.
The characteristic impedance can be changed according to the inner / outer diameter ratio of the tube. It is also possible to adjust to match the load (plasma).

The coaxial pipe inner conductor 41-2 is a rod-like or cylindrical member, and is disposed coaxially with the coaxial pipe outer conductor 41-1 in the hollow of the coaxial pipe outer conductor 41-1.
One end of the coaxial tube inner conductor 41-2 is on the inner surface of the tube 26-1 of the coaxial waveguide converter 26 (the surface facing the portion where the coaxial tube outer conductor 41-1 is attached). It is in contact. An electrode 42 extends from the other end.
The diameter of the coaxial pipe inner conductor 41-2 is 10 mm in the prototype, but 10 mm is not necessarily optimal, and can be changed as appropriate as described above.

A support member 50 is attached to a portion where the coaxial pipe inner conductor 41-2 is in contact with the pipe body 26-1.
As shown in FIGS. 3 and 4, the support member 50 includes a first support member 51 and a second support member 52.
The first support member 51 is formed in the shape of a truncated cone whose top is cut off, and the bottom 51-1 is fitted in the hole 26-2 of the tube 26-1. Further, a through hole 51-3 is formed in a straight line from the center of the bottom portion 51-1 toward the center of the top ridge cross section (the pier surface 51-2). One end of the coaxial waveguide inner conductor 41-2 is fitted in the through hole 51-3.

The reason why the first support member 51 is formed in the shape of a truncated cone is as follows.
The transmission fundamental mode of the rectangular waveguide is a TE mode or a TM mode. On the other hand, the transmission basic mode of the coaxial line is a TEM mode. As described above, although the transmission modes are different between the rectangular waveguide and the coaxial line, the coaxial waveguide converter 26 is able to propagate microwaves by matching them.
Although there are various matching methods, the coaxial waveguide converter 26 according to the present embodiment is matched according to the shape of the first support member 51.
There is a wine glass shape as a known shape for the first support member, but there is a drawback that the processing is difficult because the curved shape is complicated. On the other hand, the 1st support member 51 of this embodiment is a truncated cone, and a process is easy.

The wine glass type is used for a high power converter having an average power of 1 MW and a peak power of 1 MW. However, when the high power up to that point is not handled, the shape of the truncated cone does not generate heat. , Practical alignment can be taken. This was found from the fact that the inventor conducted an electromagnetic field simulation at an average power of 500 W to 1 kW and a peak power of 5 kW, and as a result, an electromagnetic field distribution equivalent to that of a wine glass type was obtained.
Furthermore, as another advantage, since there is no edge on the surface of the first support member 51, discharge can be prevented.
In addition, by providing the three tab tuner 23, further alignment can be achieved.

The second support member 52 has a truncated cone part 52-1 and a screw part 52-2.
The truncated cone part 52-1 is formed in the shape of a truncated cone having a truncated top part, and is linearly formed from the center of the bottom part 52-3 toward the center of the top truncated section (the truncated surface). A through hole 52-4 is formed.
In addition, the truncated cone portion 52-1 is formed with a plurality of slits 52-5 along an inclination (taper), which is a kind of collet chuck. The tooth portion 52-6 between the slits supports the coaxial waveguide inner conductor 41-2 fitted in the through hole 52-4.

The screw part 52-2 is a cylindrical member extending from the bottom part 52-3 of the truncated cone part 52-1, and a male screw 52-7 is formed on the outer periphery. Further, the hollow 52-8 of the screw part 52-2 and the through hole 52-4 of the conical part 52-1 communicate with each other.
On the other hand, a through hole 51-3 is formed in the center of the truncated surface 51-2 of the first support member 51, and a female screw 51-4 is formed in the through hole 51-3. Thereby, the male screw 52-5 of the second support member 52 can be screwed into the female screw 51-4 of the first support member 51, and by this screwing, the through-hole 52- of the second support member 52 is obtained. 4 and the hollow 52-8 communicate with the through hole 51-3 of the first support member 51.

  The diameter of the outer edge of the truncated surface 51-2 of the first support member 51 is the same as the diameter of the outer edge of the bottom 52-3 of the second support member 52. Thereby, even if the screw portion 52-2 of the second support member 52 is screwed into the female screw 51-4 of the first support member 51, an edge does not appear, so that discharge can be prevented.

As shown in FIG. 5, the electrode 42 has a barrel portion formed in a columnar shape, one end portion formed in a conical shape, and the other end portion of the other end of the coaxial tube inner conductor 41-2. The end is attached. By making one end of the electrode 42 conical, the electric field can be concentrated on the tip 46 and the electric field strength can be increased.
This electrode 42 is passed through the hollow portion (hole) 43-6 of the support 43. At this time, the tip 46 of the electrode 42 is exposed to the solution, and plasma is generated in this portion.

The electrode 42 is made of a conductor such as metal. In particular, the tip 46 is formed of a heat-resistant material (high melting point material) such as tungsten because it may be damaged by the heat of plasma. However, it is not necessarily made of metal, and can be made using a dielectric. If the electrode 42 is made of a dielectric, the metal is not exposed to the solution, so that the mixing of metal impurities can be reduced.
When using a dielectric, it is necessary to pay attention to the dielectric constant of the liquid. For example, since the relative dielectric constant of water is 80, a material having a dielectric constant larger than this and mechanical thermal strength is not common.

The support 43 is a cap-like member attached so as to cover one end of the coaxial tube outer conductor 41-1 (the end of the coaxial waveguide converter 26 not connected to the tube 26-1). is there.
The support body 43 has a skirt portion 43-1 and a top plate portion 43-2.
The skirt part 43-3 of the skirt part 43-1 is connected to one end of the coaxial pipe outer conductor 41-1.
Of the skirt portion 43-1, the vicinity of the top plate portion 43-2 is exposed to the inside of the container 30 together with the top plate portion 43-2 when fitted into the hole 31 of the container 30. A screw groove 43-4 is formed on the outer periphery of the exposed skirt portion 43-1. The support body 43 is fixed to the side surface 32 of the container 30 by screwing the stop ring 43-5 here.
The top plate portion 43-2 and a part of the skirt portion 43-1 exposed from the hole 31 are immersed in the solution.

Moreover, the support body 43 has the hollow part 43-6. The hollow portion 43-6 communicates with the hollow of the coaxial waveguide outer conductor 41-1.
The hollow portion 43-6 is formed in a tapered shape so that the inner diameter gradually decreases from the inner surface of the skirt portion 43-1 toward the center of the top plate portion 43-2. And the small hole 43-7 is drilled in the center of the top-plate part 43-2. The tip 46 of the electrode 42 slightly protrudes from the hole 43-7.

Further, a heat resistant member 43-7 is attached to the surface of the top plate portion 43-2 of the support body 43.
The heat-resistant member 43-7 prevents the support 34 from being worn out by the plasma heat and increasing the diameter of the hole 43-7.

The sealing member 44 is an annular member provided between the inner surface of the support body 43 (side surface of the hollow portion 43-6) and the electrode 43.
The sealing member 44 supports the electrode 43 and prevents the solution from flowing into the coaxial tube 41.
The insulating member 45 is between the side surface of the hollow portion 43-6 of the support 43 and the electrode 42, and between the sealing member 44 and the hole 43-7 of the top plate portion 43-2 (that is, the container 30). It is a ring-shaped member provided between the sealing member 44 and the solution when the solution is put into the container.
The insulating member 45 has a function of supporting the electrode 42, a function of sealing so that the solution does not enter the coaxial tube 41 and the waveguide 20, and a function of preventing the sealing member 44 from being directly exposed to plasma. And have.

Here, the sealing member 44 and the insulating member 45 will be further described.
The material of the sealing member 44 needs to be a material that is elastic enough to be deformed and in close contact with the surrounding metal and has a small dielectric loss so as not to generate heat by the microwave. In addition, it is desirable to have a certain degree of heat resistance in order to receive some heat from the plasma.
Therefore, for example, rubber, PTFE, or a soft plastic material can be considered as an elastic soft material. However, these materials generally have a low heat resistant temperature. If these heat-resistant materials are used for this purpose, they will be destroyed in a short time due to radiant heat from plasma, creeping discharge running on the surface, high temperature of the center electrode, etc., resulting in water leakage, contamination of nanoparticles, etc. . On the other hand, materials having a high heat-resistant temperature are typically hard materials such as glass and ceramic, and are not suitable for sealing water by being in close contact with metal.

Further, it may be possible to braze the insulating member 45 using ceramic or the like, but this is not suitable for this purpose.
The reason is that the center electrode 42 has a high thermal expansion due to a high temperature, and is destroyed due to strain in normal brazing. In order to absorb this shape change due to thermal expansion, a complicated structure is required. However, since the center electrode 42 becomes a consumable item, this is not suitable for this purpose.
Furthermore, if PTFE is used as the sealing member 44 and is retracted from the discharge part to the waveguide side, the thermal problem can be alleviated. However, the microwave propagates through the surface of the electrode 42 due to the skin effect, and as a result also propagates to water, and therefore attenuates before propagating to the tip 46 of the electrode 42.

Therefore, the inventor has created a double structure in which plastic is used as the sealing member 44 and the solution side is covered and protected with ceramic as the insulating member 45.
As the plastic, PTFE is used. This is because the dielectric loss in the microwave band is small, there is no excessive dielectric constant, and the heat resistance is as high as possible. However, the material is not limited to PTFE as long as it satisfies these conditions.
As the ceramic, alumina (Al ₂ 0 ₃ ) is used. This is because, like PTFE, there is little dielectric loss in the microwave band, there is no excessive dielectric constant, and there is high heat resistance and mechanical strength. By adopting such a structure, it is possible to realize a heat resistant structure in which only the electrode tip is exposed to the solution and the plasma can be maintained for a long time. However, the material is not limited to alumina as long as it satisfies these conditions.

(Nanoparticle production method)
Next, a method for producing nanoparticles will be described.
A microwave power source 12 supplies power to the magnetron box 11.
The magnetron box 11 receives the supply of electric power from the microwave power source 12 and generates and outputs a microwave. This microwave indicates a value adjusted by the microwave power supply controller 13. Further, as shown in FIG. 2, the microwave is formed in a pulse shape having a plurality of cycles as one pulse.

The waveguide 20 conveys the microwave output from the magnetron box 11 and sends it to the coaxial tube 41 provided inside the coaxial waveguide exchanger 26.
The microwave electric field concentrates on the tip 46 of the electrode 42 attached to the end of the coaxial pipe inner conductor 41-2. Thereby, the in-liquid plasma is excited in the solution stored in the container 30.
The excited plasma generates nanoparticles in the solution.

There are the following two generation principles of nanoparticles.
One is that the plasma generates hydrogen radicals, hydroxyl radicals, electrons, etc. in the liquid, and reduces and oxidizes the ion particles. This produces nanoparticles.
The other is to pulverize relatively large particles by plasma energy and impact to produce nanoparticles. In many cases, this interaction allows particle size control.

In addition, the inventors of the present application operated the nanoparticle manufacturing apparatus 1a according to the nanoparticle manufacturing method, and observed how underwater plasma was generated. FIG. 6 shows how the underwater plasma is generated.
When 1 kW of electric power is applied to the solution (water), as shown in the figure, small bubbles begin to appear immediately after the introduction (the figure (i)), and a very bright and pale flame-like length of about 50 mm. Plasma was blown into the water ((ii) in the figure, 2 seconds after the start of injection).
The plasma gradually increased with time, and became a constant magnitude in about 4 seconds ((iii) in the figure, 4 seconds after the start of injection). Since the sealing member was formed of plastic and the insulating member was formed of ceramic, continuous discharge for 1 hour or more was possible.

(Example)
Next, an example of producing nanoparticles will be described.
Here, an example of production of nanoparticles by the reduction method is shown.

(First Example) Production of Gold Nanoparticles 500 mg of “HAuC1 ₄ 3.6H ₂ O” and 5 g of “PolyVinylPyrrolidone (PVP) K-30” were dissolved in 500 mL of ion-exchanged water and placed in a container 30.
A microwave with a frequency of 2.45 GHz, an average power of 500 to 1 kW, and a peak power of 5 kW with a 100 Hz pulse output is supplied from the microwave oscillator 10, and the solution in the container 30 is irradiated with plasma in liquid for 60 to 90 seconds. .

Immediately after the irradiation, the color of the solution began to change from nearly colorless yellow to red, and after about 30 minutes, the color changed to red overall. The red color of the gold nanoparticles is due to plasmon emission.
In addition, bubbles appeared from the plasma in liquid. The liquid surface has been gradually covered with bubbles. This foam is generated because PVP is added as a dispersant.
An electron microscope (SEM) image of the gold nanoparticles taken out from this solution is shown in FIG.

(Second Example) Production of Silver Nanoparticles 1 g of “AgNO ₃ ” and 5 g of “polyvinylpyrrolidone PVD K-30” were dissolved in 500 mL of ion-exchanged water and put into a container 30.
A microwave with a frequency of 2.45 GHz, an average power of 500 to 1 kW, and a peak power of 5 kW with a 100 Hz pulse output is supplied from the microwave oscillator 10, and the solution in the container 30 is irradiated with plasma in liquid for 60 to 90 seconds. .
After irradiation, the color of the liquid changed from colorless to yellow. FIG. 7 (ii) shows an electron microscope (SEM) image of the silver nanoparticles taken out from this solution.

  In these first and second examples, the yield of nanoparticles per device by each process was 20-60 g per hour. Compared to other methods, it is faster and mass production is possible.

  As described above, according to the nanoparticle manufacturing apparatus and the nanoparticle manufacturing method of this embodiment, thermal damage to the sealing member can be prevented by providing the insulating member between the sealing member and the solution. . As a result, the life of the sealing member is extended and the life of the in-liquid plasma source can be extended.

[Second Embodiment]
Next, 2nd embodiment of the nanoparticle manufacturing apparatus and nanoparticle manufacturing method of this invention is described with reference to FIGS.
The figure is a diagram showing the configuration of the nanoparticle production apparatus of the present embodiment.
This embodiment differs from the first embodiment in the configuration of the in-liquid plasma source. That is, in the first embodiment, an ordinary coaxial tube is used, whereas in this embodiment, the coaxial tube is provided with a cooling means. Other components are the same as those in the first embodiment.
Therefore, in FIGS. 8 to 10, the same components as those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.

As shown in FIGS. 8 to 10, the nanoparticle manufacturing apparatuses 1 b to 1 d include a cooling means 60 in the coaxial tube 41.
Here, as the cooling means 60, as shown in FIG. 8, for example, a radiator (heat sink) 61 can be used.
The radiator 61 is attached to the end of the coaxial waveguide inner conductor 41-2 and a portion protruding from the tubular body 26-1 of the coaxial waveguide converter 26.
The coaxial waveguide inner conductor 41-2 is made of a metal material having a high thermal conductivity such as copper, for example.
Thereby, the heat | fever of the electrode 42 can be discharge | released from the heat radiator 61 to external air using the heat conduction of the coaxial pipe | tube inner conductor 41-2.
In addition, in the same figure, although the air-cooling type which radiates heat to the outside air as it is from the radiator 61 is shown, it is not limited to the air-cooling type, and for example, a water-cooled heat sink can also be used.

Further, as shown in FIG. 9, the cooling unit 60 can use a heat pipe 62.
The heat pipe 62 is a heat transfer means that transfers heat to a distant place at a high speed. In the present embodiment, the coaxial pipe inner conductor 41-2 is used as the heat pipe 62.
The heat pipe 62 includes a metal tube, a wick (a material having a capillary action), and a working fluid. As an operation principle, the working fluid evaporates in the heating portion (portion where the electrode 42 is in contact), and the vapor of the working fluid moves to the cooling portion (portion where the radiator 61 is attached) and condenses. Here, the latent heat of vaporization is transferred, and the condensed working fluid is returned to the heating portion by the capillary action of the wick in the tube. By repeating this, heat is transferred from the heating section to the cooling section.
In addition, the heat pipe 62 can also be used in combination with the heat radiator 61, as shown in FIG. Thereby, it is also possible to improve the heat dissipation efficiency.

Further, as shown in FIG. 10, the cooling means 60 can use, for example, a refrigerant 63.
The refrigerant 63 is passed through the hollow portion of the tubular coaxial waveguide inner conductor 41-2. Thereby, the heat transmitted from the electrode 42 is absorbed and the temperature rise is suppressed.
The refrigerant 63 has a large heat capacity such as water because the amount of heat to be transported is larger than the pipe diameter.
Although the microwave is absorbed by water, the microwave current flows only to the outer skin side of the coaxial pipe inner conductor 41-2 due to the skin effect, and thus even if water passes through the inner side of the coaxial pipe inner conductor 41-2 in this way. There is no loss.
The refrigerant 63 may be circulated through the hollow portion of the coaxial waveguide inner conductor 41-2 or may be stored.

As described above, by providing the cooling means 60 in the coaxial tube 41, thermal destruction of the electrode 42 can be prevented.
In the liquid plasma, bubbles are generated at the interface with the liquid, and plasma is generated therein. Therefore, the center electrode 42 is heated, and cooling with the liquid cannot be expected, resulting in a high temperature. For this reason, the center electrode 42 needs to use a high-temperature point metal such as tungsten, and further requires positive cooling to the atmosphere side.
Further, although the diameter of the coaxial pipe inner conductor is 10 mm, it can be easily analogized that the heat radiation from the tip that generates heat can be improved by increasing the cross-sectional area of the inner conductor. It is preferable for heat dissipation that the angle of the electrode tip is an obtuse angle.

[Third embodiment]
Next, 3rd embodiment of the nanoparticle manufacturing apparatus and nanoparticle manufacturing method of this invention is described with reference to FIG.
This figure is a block diagram showing the configuration of the nanoparticle production apparatus of this embodiment.
This embodiment is different from the first embodiment in the configuration of an apparatus for storing a solution. That is, in the first embodiment, the solution is stored and retained in a rectangular container, whereas in the present embodiment, the solution is stored in the circulation device and circulated. Other components are the same as those in the first embodiment.
Therefore, in FIG. 11, the same components as those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.

As shown in FIG. 11, the nanoparticle manufacturing apparatus 1 e includes a circulation system 70.
Here, the circulation system 70 includes a nanoparticle production container 71, an extraction path 72, an exchange container 73, a raw material input valve 74, a nanoparticle extraction valve 75, a solution supply path 76, and a pump 77. ing.
The nanoparticle generation container 71 corresponds to the container 30 in the first embodiment, and stores a solution. The nanoparticle generation container 71 is excited by microwaves supplied from the in-liquid plasma source 40 to generate plasma, thereby generating nano particles. Generate particles.
The take-out path 72 takes out the solution (nanoparticles) from the nanoparticle production container 71 and sends it to the exchange container 73.

The exchange container 73 is a storage container for receiving and storing the solution (nanoparticles) sent from the take-out path 72 and supplying a new solution to the nanoparticle generation container 71.
The raw material input valve 74 is a valve attached to a supply path for supplying a new solution to the exchange container 73.
The nanoparticle extraction valve 75 is a valve attached to an extraction path for extracting the nanoparticles from the exchange container 73.
The solution supply path 76 supplies a new solution from the exchange container 73 to the nanoparticle generation container 71.
The pump 77 provides moving power so that the solution circulates in the circulation system 70, and can be provided in the solution supply path 76, the extraction path 72, and the like.

  As described above, according to the nanoparticle production apparatus and the nanoparticle production method of the present embodiment, the solution can be circulated by the circulation system. For this reason, plasma can be irradiated evenly on the solution.

As mentioned above, although preferred embodiment of the nanoparticle manufacturing apparatus and nanoparticle manufacturing method of the present invention was described, the nanoparticle manufacturing apparatus and nanoparticle manufacturing method according to the present invention are not limited to the above-described embodiments, It goes without saying that various modifications can be made within the scope of the present invention.
For example, in the above-described embodiment, only one container is provided. However, the number of containers is not limited to one, and two or more containers may be provided.
In the above-described embodiment, the configuration of the waveguide is the configuration shown in FIG. 1, but the configuration is not limited to this configuration, and any configuration can be used as long as microwaves can propagate to the solution. be able to.

  The nanoparticle production apparatus and nanoparticle production method of the present invention may be an arbitrary combination of the nanoparticle production apparatuses in the first embodiment, the second embodiment, and the third embodiment.

  Since the present invention relates to a technology for generating nanoparticles in a solution using in-liquid plasma excited by microwaves, the present invention can be used for an apparatus or an apparatus for generating nanoparticles using in-liquid plasma. is there.

It is a schematic side view which shows the structure of the nanoparticle manufacturing apparatus in 1st embodiment of this invention. It is a wave form diagram which shows the waveform of a microwave electric power. It is side surface sectional drawing which shows the structure of a coaxial waveguide and a plasma source in a liquid. It is a perspective view which shows the structure of a supporting member among plasma sources in a liquid. It is side surface sectional drawing which shows the structure of an electrode vicinity among submerged plasma sources. It is an image showing a state in which underwater plasma is generated, (i) is a state immediately after the start of power-on, (ii) is a state two seconds after the start of power-on, and (iii) is a start of power-on. 4 seconds after. It is the image which image | photographed the nanoparticle, Comprising: (i) is a gold nanoparticle and (ii) is an image of a silver nanoparticle. It is sectional drawing which shows the shape of the plasma source in a liquid provided with the heat radiator. It is sectional drawing which shows the shape of the in-liquid plasma source provided with the heat pipe. It is sectional drawing which shows the shape of the plasma source in a liquid using a refrigerant | coolant. It is a figure which shows the structure of the nanoparticle manufacturing apparatus provided with the circulation system. It is sectional drawing which shows the structure of the related plasma source in a liquid.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1a-1e Nanoparticle manufacturing apparatus 10 Microwave oscillator 20 Waveguide 30 Container 40 In-liquid plasma source 41 Coaxial tube 43 Support body 44 Sealing member 45 Insulation member 46 Tip 50 Support member 60 Cooling means 61 Radiator 62 Heat pipe 63 Refrigerant 70 Circulation system 71 Nanoparticle production container 72 Extraction path 73 Exchange container 76 Solution supply path 77 Pump

Claims (9)

A nanoparticle production apparatus that generates nanoparticles in a solution by excitation of plasma,
A container containing the solution;
An electrode for applying a microwave to the solution,
A hole through which the electrode passes on the side of the container and below the water surface of the solution;
A sealing member is disposed between the electrode and the hole,
An insulating member is disposed on the solution side of the sealing member. The nanoparticle production apparatus according to claim 1, wherein the sealing member is made of plastic, and the insulating member is made of ceramic. The nanoparticle production apparatus according to claim 1, further comprising a cooling unit that suppresses a temperature rise of the electrode. The said cooling means contains any one or more of a heat conductor, a refrigerant | coolant, a heat radiator, and a heat pipe. The nanoparticle manufacturing apparatus of Claim 3 characterized by the above-mentioned. The nanoparticle manufacturing apparatus according to any one of claims 1 to 4, wherein the microwave is formed in a pulse shape having a plurality of cycles as one pulse. The said electrode was formed using the metal or a dielectric material. The nanoparticle manufacturing apparatus in any one of Claims 1-5 characterized by the above-mentioned. The said electrode was formed with the heat resistant material. The nanoparticle manufacturing apparatus in any one of Claims 1-6 characterized by the above-mentioned. An extraction path for removing the solution from the container;
An exchange container for storing the solution sent from the take-out path;
A solution supply path for sending the solution from the exchange container to the container;
The nanoparticle production apparatus according to claim 1, further comprising a pump that circulates the solution through the solution supply path and / or the extraction path. A nanoparticle manufacturing method for generating nanoparticles by generating plasma in a solution,
Placing the solution in a container;
An annular sealing member disposed inside a hole formed in a side surface of the container, an annular insulating member disposed on the solution side of the sealing member, and an inner side of the sealing member and the insulating member An electrode disposed on the electrode, supplying a pulsed microwave to the electrode,
A nanoparticle production method, wherein plasma is excited by the microwave at the tip of the electrode protruding into the solution to generate the nanoparticle.