JP2019137900A - Method for producing nanoparticles and its use - Google Patents

Abstract

To provide a more efficient method for producing nanoparticles, and to provide an apparatus for producing the nanoparticles for implementing the method.SOLUTION: An apparatus 100 for producing nanoparticles includes: a charged particle-producing apparatus (a sputtering apparatus 30) for producing charged particles by a sputtering method; and an electrical mobility-classifier (DMA 40), wherein a charged particle-extracting port in the charged particle-producing apparatus is connected to a charged particle-extracting port in the electrical mobility-classifier.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for producing nanoparticles, an apparatus for producing nanoparticles, nanoparticles, products containing the nanoparticles, and the like.

  It has been reported that new properties of a substance can be brought out by making the substance into nanoparticles. Therefore, attempts have been made to produce nanoparticles in various materials.

  The method for producing nanoparticles is appropriately selected according to the type of the substance, but industrially, mechanical pulverization methods such as ball milling have become the mainstream (Non-Patent Document 1).

In addition, as a method for producing nanoparticles, a metal (substance) is heated and evaporated in an inert gas, and metal nanoparticles are produced by colliding and rapidly cooling the evaporated metal atoms with the inert gas. The middle evaporation method is also a general method (Non-Patent Document 2).
Moreover, the method of nonpatent literature 3 is known as a method of producing | generating a nanocluster.

“Size effects on the hydrogen storage properties of nanostructured metal hydrides: A review”, Vincent Berube et al., Int. J. Energy Res. 31 (2007) 637-663. "Ultrafine particles" Solid physics and metal physics seminar 1984, special issue special edition Edit: Ultrafine particle editorial committee, Agne Technology Center “Performance of a size-selected nanocluster deposition facility and in situ characterization of grown films by x-ray photoelectron spectroscopy”, Mondal S. and Bhattacharyya SR1., Review of Scientific Instrument., 2014 Jun; 85 (6): 065109.

  However, the ball milling method is limited because it is a mechanical grinding method. That is, the ball milling method has a limit from the viewpoint of miniaturization of nanoparticles, and it is theoretically extremely difficult to produce particles of less than 15 nm (actually less than 30 nm). Furthermore, the ball milling method cannot avoid the problem of contamination of the obtained nanoparticles and the problem of non-uniformity of the size of the nanoparticles.

  In addition, the vaporization method in gas (especially, the method using arc discharge heating for metal heating) can generally avoid the problem of contamination of nanoparticles, but generally the problem of nonuniformity of the size of the obtained nanoparticles Is likely to occur. In order to solve the problem of non-uniformity, it is conceivable to attempt classification for each size after charging the nanoparticles in the obtained aerosol. However, in order to charge the nanoparticles in the aerosol, an additional treatment such as using a radioactive substance such as Am or using a corona discharge in the aerosol is required. Furthermore, there is a problem that the charging efficiency of the nanoparticles can be reduced by various factors. For example, the charging efficiency of nanoparticles tends to decrease when the particle size of the nanoparticles is small or under a low pressure environment. However, there are also cases where a smaller particle size is being investigated in search of a more reactive nanoparticle, or operation under a low pressure environment suitable for handling a highly reactive nanoparticle. Reality.

  One embodiment of the present invention has been made in view of the above problems, and provides a more efficient method for producing nanoparticles, a nanoparticle production apparatus for performing the method, and the like. It is aimed.

  In order to solve the above-mentioned problems, the inventors of the present application have conducted intensive studies. As a result, it has been found that the above problems can be solved by combining sputtering and nanoparticle classification based on electric mobility, and the present invention has been achieved.

That is, the present invention provides any of the following.
1) A method for producing nanoparticles, comprising: a step A for producing charged particles by a sputtering method; and a step B for classifying the charged particles based on the electric mobility of the charged particles.
2) The method according to 1), wherein the step B is performed using a differential electric mobility classifier (DMA).
3) The method according to 1) or 2), wherein the particle size of the charged particles is in the range of 1 nm to 100 nm.
4) The method according to any one of 1) to 3), wherein the charged particles are metal particles having hydrogen storage properties.
5) The method according to any one of 1) to 4), wherein the atmosphere in which the step A is performed is cooled.
6) A nanoparticle manufacturing apparatus, comprising a charged particle manufacturing apparatus that manufactures charged particles by a sputtering method, and an electric mobility classifying device, and a charged particle extraction port of the charged particle manufacturing apparatus, and the electric transfer An apparatus for producing nanoparticles, in which the charged particle inlet of the degree classifier is connected.
7) The nanoparticle production apparatus according to 6), wherein the operation pressure of the charged particle production apparatus and the operation pressure of the electric mobility classification apparatus are both in the range of 300 Pa to 2000 Pa.
8) The apparatus according to 6), wherein the charged particle manufacturing apparatus includes a cooling unit for cooling an atmosphere in which charged particles are manufactured.
9) Nanoparticles produced by the method according to any one of 1) to 5) above.
10) The nanoparticles according to 9), which are particles of a single metal selected from the group consisting of alkali metals and alkaline earth metals, or particles of an alloy containing at least one of these metals.
11) A product comprising the nanoparticles according to 9) or 10) above.

  According to one embodiment of the present invention, it is possible to provide a more efficient method for producing nanoparticles, a nanoparticle production apparatus for performing the method, and the like.

It is a figure which shows the whole structure of the manufacturing apparatus of the nanoparticle based on one Embodiment of this invention. It is a figure which shows the principal part structure of the manufacturing apparatus of the nanoparticle shown in FIG. It is a figure which shows the measurement result of particle size distribution regarding one Example of this invention. It is a figure which shows the measurement result of particle size distribution regarding the other Example of this invention. It is a figure which shows the measurement result of particle size distribution regarding the further another Example of this invention. It is a figure which shows the measurement result of particle size distribution regarding the further another Example of this invention.

Embodiment 1
Hereinafter, an embodiment of the present invention will be described in detail.

(Outline of nanoparticle production method)
In the method for producing nanoparticles according to an embodiment of the present invention, a charged particle is produced by a sputtering method, and the charged particle obtained in the step A is classified based on the electric mobility of the charged particle. Step B.

(Charged particles and nanoparticles)
In the present specification, the “charged particle” refers to the charged particle obtained in the above step A unless otherwise specified. In this specification, “nanoparticles” refer to those obtained by classifying the charged particles in the step B. However, the nanoparticles may be charged or uncharged.

  The charged particles and nanoparticles are, for example, metal particles, and a preferred example is metal particles having hydrogen storage properties. Specific examples of metal particles having hydrogen storage properties include lithium, sodium, potassium, rubidium, cesium, magnesium, calcium, strontium, barium, scandium, yttrium, lanthanum, titanium, zirconium, hafnium, vanadium, niobium, and tantalum. , Particles of a single metal selected from the group of metals consisting of palladium, nickel, cobalt, and aluminum, or particles of an alloy containing at least one of these metals.

  Other preferable examples of the charged particles and nanoparticles include particles of simple metals selected from the group consisting of alkali metals and alkaline earth metals, which have been conventionally difficult to form into nanoparticles, or these metals. And alloy particles containing at least one of the above. Preferred examples of the alkali metal include lithium, sodium, and potassium, and preferred examples of the alkaline earth metal include magnesium and calcium.

  The charged particles and the nanoparticles may be metal particles having hydrogen storage properties, particles of a single metal containing metal other than alkali metal and alkaline earth metal, or alloy particles.

  Although not necessarily limited, there may be a case where it is preferable to obtain charged particles and nanoparticles that are not subjected to treatment such as nitridation and oxidation by performing Step A and Step B under, for example, vacuum or low-pressure conditions close to vacuum. is there.

  The particle size of the charged particles and nanoparticles is, for example, in the range of 1 nm to 100 nm, preferably in the range of 1 nm to 50 nm, more preferably in the range of 1 nm to 10 nm, or 5 nm or more. In the range of 50 nm or less, and more preferably in the range of 1 nm or more and 10 nm or less. In one example, the particle size of the charged particles and nanoparticles may be in the range of 5 nm to 20 nm, in the range of 5 nm to 15 nm, or in the range of 5 nm to 10 nm. It may be within.

  Compared with the group of charged particles obtained in the process A, the group of nanoparticles obtained in the process B is subjected to size selection based on the particle size. In one example, a group of nanoparticles is a population of nanoparticles having substantially the same particle size. In another example, the group of nanoparticles is formed by mixing a group of nanoparticles having substantially the same particle diameter A1 and a group of nanoparticles having substantially the same particle diameter A2. Here, the particle size A1 and the particle size A2 are different particle sizes. In addition, as long as it satisfies the premise that size selection based on the particle size is performed as compared with the group of charged particles obtained in step A, the group of nanoparticles is a group of nanoparticles having three or more particle sizes. It may be a mixture.

(Example of nanoparticle production equipment)
Hereinafter, based on an example of the nanoparticle production apparatus whose outline is shown in FIGS. 1 and 2, the method for producing nanoparticles will be described in more detail.

<Outline of configuration>
The nanoparticle manufacturing apparatus 100 includes a sputtering apparatus (charged particle manufacturing apparatus) 30 and a DMA (electric mobility classification apparatus) 40, and a particle extraction port (charged particle extraction port) 35 of the sputtering apparatus 30; The particle introduction port (charged particle introduction port) 43a of the DMA 40 is connected.

<Sputtering device>
The sputtering apparatus 30 is an apparatus that manufactures charged particles by a sputtering method. As shown in FIG. 2, an example of the sputtering apparatus 30 includes a double cylindrical structure in which an outer cylinder 37b and an inner cylinder 37a are arranged so as to share a central axis, and an inner space 34 of the inner cylinder 37a is formed. It functions as a reaction space for sputtering. In the internal space 34, a sputtering target 33 is provided on one end side (lower side) of the central axis of the inner cylinder 37a, and a particle outlet 35 is provided on the other end side (upper side) of the central axis. The target 33 is connected to a moving mechanism 31 attached to the lower end of the double cylindrical structure. By operating the moving mechanism 31, the target 33 can move up and down along the central axis of the inner cylinder 37 a, and by this up and down movement, the aggregation length L <b> 1 can be changed to a desired length.

  The plurality of supply ports 32a for supplying refrigerant and gas are supply ports for supplying the refrigerant and various gases into the double cylindrical structure from the outside.

  The outer cylinder 37b is provided with a mounting port 36 for a vacuum pump (not shown). As a preliminary exhaust before operating the sputtering apparatus 30, the space between the outer cylinder 37b and the inner cylinder 37a and the inner space 34 are maintained at a high vacuum by evacuation using a vacuum pump. .

  A refrigerant tank (cooling means) 32b is provided on the side wall of the inner cylinder 37a, and the refrigerant tank 32b communicates with a refrigerant supply port 38. The refrigerant tank 32b accumulates the refrigerant, thereby introducing the inner cylinder 37a and the gas introduced into the inner space 34 that exchanges heat with the inner cylinder 37a (atmosphere: indicates at least one of sputtering gas, reaction adjusting gas, and the like). Is for cooling. The refrigerant is, for example, cold water or liquid nitrogen. The refrigerant tank 32b may be provided in contact with the outside of the side wall of the inner cylinder 37a or may be provided inside the side wall. However, from the viewpoint of cooling the gas introduced into the internal space 34, the refrigerant tank 32b It is preferable to be provided in contact with at least the inside of the side wall.

  A pipe (not shown) that communicates with any of the supply ports 32 a is provided upstream (downward) of the target 33. This pipe is for supplying a sputtering gas to the vicinity of the target 33 from the gap between the target 33 and the inner cylinder 37a. The sputtering gas is an inert gas such as argon or neon.

  Further, a flow path 39b is provided for supplying a reaction adjusting gas from the particle outlet 35 side toward the target 33 side. The flow path 39b communicates with the reaction control gas supply port 39a. The flow path 39b is for controlling the growth of charged particles generated by sputtering by blowing a reaction adjusting gas into the internal space 34. The reaction control gas is, for example, a gas such as helium or neon.

  The sputtering gas and the reaction adjusting gas are supplied to the sputtering apparatus 30 through the mass flow controller (only one is shown) 11 while controlling the flow rate.

  In the sputtering apparatus 30, the above-described step A is performed. In the sputtering apparatus 30, a voltage is applied to the target 33 to generate glow discharge, and the atoms of the sputtering gas are ionized. Then, ionized gas atoms collide with the surface of the target 33 at a high speed, thereby ejecting particles of the material constituting the target 33 from the target 33. The ejected particles agglomerate with each other before reaching the particle outlet 35, and charged particles are obtained.

  As shown in FIG. 2, it may be preferable that the center axis of the inner cylinder 37 a is along the vertical direction from the viewpoint of more uniformly agglomerating the particles ejected from the target 33.

  The aggregation length L1 is one of the factors affecting the particle size of the obtained charged particles. The aggregation length L1 is not particularly limited as long as desired charged particles can be obtained, but it may be preferably 1 cm or more and 40 cm or less, and may be 20 cm or more and 30 cm or less, or 1 cm or more and 10 cm or less. May be more preferred.

  The operating pressure of the sputtering apparatus 30 (pressure in the internal space 34 during sputtering) is not particularly limited as long as desired charged particles can be obtained. From the viewpoint of obtaining sputtering efficiency and clean charged particles, the operating pressure is 300 Pa or more and 2000 Pa. It may be preferable to be within the following range, may be more preferably within a range of 350 Pa or more and 1100 Pa or less, and may be further preferably within a range of 400 Pa or more and 1000 Pa or less. It may be particularly preferable that the pressure is in the range of 600 Pa or less. In particular, when the charged particles are highly reactive particles such as hydrogen-occlusion particles, such a low-pressure environment is preferable.

  In the case of obtaining charged particles of an alloy, the target 33 itself may be the alloy, but each single metal constituting the alloy may be disposed as the target 33. One of the advantages of using the sputtering method is that if the single metals constituting the alloy are arranged at a ratio constituting the alloy, charged particles of the alloy can be obtained.

  Although the temperature at the time of performing the process A is not particularly limited as long as desired charged particles can be produced, it may be preferable to perform the process while cooling the internal space 34. The temperature of the internal space 34 after being cooled is, for example, 25 ° C. or less. Note that when manufacturing charged particles containing at least one metal selected from the group consisting of alkali metals and alkaline earth metals, the temperature condition for performing step A is extremely important. In this case, the step A is preferably performed at a temperature at which it grows into nanoparticles according to the concentration of atoms ejected from the material constituting the target 33 by sputtering, and more preferably at a temperature of −190 ° C. or lower. It may be preferable.

  As the sputtering apparatus 30, a commercially available apparatus can be used. As the sputtering apparatus 30, for example, an apparatus sold under a trade name such as a sputter type cluster ion source can be used (for example, supplied by Mantis Deposition). However, devices available on the market are usually used as devices for synthesizing high-concentration ions of extremely small clusters and are evaluated only in combination with a mass selector. Not too much. There are no reports of synthesizing nanoparticles having a size of about 5 nm or more, or about 10 nm or more, using an apparatus available on the market.

  The particle take-out port 35 of the sputtering apparatus 30 is connected to the particle introduction port 43 a of the DMA 40 via a pipe 91. A pressure gauge 61 is attached to the pipe 91, and the pressure gauge 61 monitors the pressure of the aerosol containing charged particles flowing in the pipe 91.

  As described above, since the ionization of particles can be performed simultaneously with the production of particles by using the sputtering apparatus 30 (charged particles with clusters grown are produced), even in a low pressure environment such as a vacuum, In this latter stage, particle size measurement and classification using the DMA 40 can be performed efficiently.

  Further, by using the sputtering apparatus 30, the charged particles are contained in a high concentration while enjoying the advantages of the evaporation method by the sputtering method such as the composition of the obtained charged particles, the low temperature growth process, and the clean synthesis environment. You can get an aerosol.

<DMA>
The DMA 40 (differential type electric mobility classification device) is a device that performs the step B of classifying the charged particles obtained in the above step A based on the electric mobility of the charged particles. The DMA 40 has a double cylindrical structure in which a cylindrical outer electrode 41a and an inner electrode 41b are arranged so as to share a central axis. The central axis of this double cylindrical structure is along the horizontal direction. The aerosol containing charged particles supplied from the sputtering apparatus 30 is introduced into the space 42 between the outer electrode 41a and the inner electrode 41b through the particle inlet 43a.

  When classifying charged particles, a sheath gas flows in the space 42 along the direction of the arrow in FIG. The sheath gas is an inert gas such as argon or nitrogen. The sheath gas is supplied to the DMA 40 via the mass flow controller 12 while controlling the flow rate.

  When classifying charged particles, a predetermined voltage is applied between the outer electrode 41a and the inner electrode 41b by the voltage application device 46. The charged particles introduced into the space 42 are classified based on their electric mobility. More specifically, the charged particles 45 (corresponding to the nanoparticles obtained in the step B) having the desired electric mobility pass through the slit 43b of the inner electrode 41b, which is located downstream in the sheath gas flow direction. The particles are selectively taken out into the particle take-out tube 44.

  The DMA 40 is connected to the vacuum dry pump 21 via a double valve structure 81a / 81b. By vacuuming using the vacuum dry pump 21, the space 42 is maintained at a high vacuum. In addition, from the viewpoint of efficiently taking in the aerosol containing charged particles from the sputtering apparatus 30 to the DMA 40, the operating pressure of the DMA 40 is equal to the operating pressure of the sputtering apparatus, or a pressure at which desired flow rates of the sheath gas and the aerosol gas are obtained. May be preferred. As the DMA 40, a commercially available device can be used.

  In the DMA 40, the aerosol containing the charged particles at a high concentration produced by the sputtering apparatus 30 is directly taken in and classified, so that the size-selected nanoparticles can be efficiently obtained (see also the examples). .

<Analysis Department>
The nanoparticles selectively extracted into the particle extraction tube 44 of the DMA 40 are sent to an analysis unit for analysis as necessary. The manufacturing apparatus shown in FIG. 1 includes a Faraday cup ammeter (FC) 71 and a crystal resonator microbalance (QCM) 51 as analysis units. The Faraday cup ammeter 71 is for accurately measuring the particle charge amount concentration of the nanoparticles. The quartz crystal microbalance 51 enables analysis of the hydrogen storage capacity when the obtained nanoparticles are hydrogen storage nanoparticles. The quartz crystal microbalance 51 is connected to the DMA via a valve 82 in order to switch use / nonuse. The quartz crystal microbalance 51 is connected to the vacuum dry pump 22 via double valve structures 83a and 83b. In order to realize highly accurate analysis, the quartz crystal microbalance 51 is maintained at an extremely low pressure by evacuation using the vacuum dry pump 22.

(Product comprising the resulting nanoparticles)
One aspect of the present invention includes nanoparticles produced by the above-described method and products comprising the nanoparticles. Although the kind of product is not specifically limited, For example, the catalyst which carry | supported the nanoparticle; Hydrogen filter (when a nanoparticle has hydrogen storage property); etc. are mentioned.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

  The features of the present invention will be described more specifically with reference to examples. The scope of the present invention should not be construed as being limited by the specific examples shown below.

[Example 1]
A nanoparticle production apparatus 100 having the same configuration as shown in FIGS. 1 and 2 was used. In the sputtering apparatus 30 in this apparatus, an Mg gas disk is used as a target 33, and argon gas (gas pressure 480 Pa, flow rate 0.55 slm) is introduced into the evacuated internal space 34 via a mass flow controller (only one shown) 11. Then, sputtering was performed by direct current discharge (input power 50 W). Thus, magnesium charged particles were generated in the internal space 34 where the sputtering cathode is located. The aggregation length L1 shown in FIG. 2 was 25 cm. The operating pressure of the sputtering apparatus 30 can be regarded as being equivalent to the gas pressure of argon gas.

  DMA40 is used for charged particles obtained when the temperature in the refrigerant tank is 1) room temperature (25 ° C.), 2) immediately after the start of cooling with liquid nitrogen, and 3) liquid nitrogen temperature (−196 ° C.). The particle size distribution was measured.

  In the size distribution measurement by the DMA 40, the aerosol containing charged particles discharged from the particle extraction port 35 of the sputtering apparatus 30 was introduced from the particle introduction port 43a of the DMA 40. The size distribution measurement by the DMA 40 is performed by using a DMA 40 operated under the conditions of a classification length of 18 mm and a sheath gas (argon gas) flow rate of 5 (std L / min), and an aerosol gas flow rate including charged particles of 0.55 (std L / min). ). In order to capture charged particles having a particle size of approximately 0 to 25 nm, the voltage applied between the outer electrode 41a and the inner electrode 41b was variable, and scanning was performed from 0 to 25 nm. The operating pressure of DMA40 was kept at 480 Pa.

The results are shown in FIG. In addition, approximately 10 ng of nanoparticles (charged particles classified by DMA) were obtained in one minute after starting sputtering with the sputtering apparatus 30.
The number of nanoparticles was counted using a Faraday cup ammeter 71.

[Example 2]
As a target 33, a disk having an area ratio of Mg: Ni = 2: 1 was used, and sputtering was performed under the conditions of an argon gas pressure of 500 Pa, an argon gas flow rate of 0.8 slm, and an input power of 70 W. Were the same as in Example 1 to produce magnesium-nickel alloy charged particles. The operating pressure of DMA 40 was maintained at 500 Pa.

  The particle size distribution was measured in the same manner as in Example 1 for the charged particles obtained when the temperature in the refrigerant tank was room temperature (25 ° C.) and the liquid nitrogen temperature (−196 ° C.). The results are shown in FIG.

Example 3
As the target 33, a Cu disk was used, and the sputtering was performed under the conditions of argon gas pressure of 430 Pa, argon gas flow rate of 0.5 slm, and input power of 40 W. Copper charged particles were generated. The operating pressure of DMA40 was kept at 430 Pa.

  For the charged particles obtained when the temperature in the refrigerant tank was room temperature (25 ° C.), the particle size distribution was measured in the same manner as in Example 1. The results are shown in FIG.

Example 4
As the target 33, an Al disk was used, and the sputtering was performed under the conditions of argon gas pressure of 430 Pa, argon gas flow rate of 0.5 slm, and input power of 30 W. Aluminum charged particles were generated. The operating pressure of DMA40 was kept at 430 Pa.

  For the charged particles obtained when the temperature in the refrigerant tank was room temperature (25 ° C.), the particle size distribution was measured in the same manner as in Example 1. The results are shown in FIG.

  The present invention can be used for more efficient production of nanoparticles.

12 Mass flow controllers 21 and 22 Vacuum dry pump 30 Sputtering device 31 Moving mechanism 32a Supply port 32b Refrigerant tank 91 Pipe 33 Target 34 Internal space 37a Inner cylinder 37b Outer cylinder 38 / 39a Supply port 39b Flow path 40 DMA
41a outer electrode 41b inner electrode 42 space 43a particle introduction port 43b slit 44 particle take-out tube 45 charged particle 46 voltage application device 51 crystal oscillator microbalance 61 pressure gauge 71 Faraday cup ammeter 81a / 81b double valve structure 83a / 83b double valve Structure 100 Manufacturing equipment

Claims (11)

Step A for producing charged particles by sputtering,
A process B for classifying the charged particles based on the electric mobility of the charged particles;   The method according to claim 1, wherein step B is performed using a differential electric mobility classifier (DMA).   The method according to claim 1 or 2, wherein the particle size of the charged particles is in the range of 1 nm to 100 nm.   The method according to claim 1, wherein the charged particles are metal particles having hydrogen storage properties.   The method as described in any one of Claims 1-4 with which the atmosphere which performs the said process A is cooled. An apparatus for producing nanoparticles,
A charged particle production apparatus for producing charged particles by a sputtering method;
An electric mobility classification device,
The charged particle outlet of the charged particle manufacturing apparatus is connected to the charged particle inlet of the electric mobility classifier,
Nanoparticle production equipment.   The nanoparticle production apparatus according to claim 6, wherein an operation pressure of the charged particle production apparatus and an operation pressure of the electric mobility classification apparatus are both within a range of 300 Pa to 2000 Pa.   The said charged particle manufacturing apparatus is an apparatus of Claim 6 which has a cooling means for cooling the atmosphere where manufacture of a charged particle is performed.   Nanoparticles produced by the method according to any one of claims 1-5.   The nanoparticle according to claim 9, wherein the nanoparticle is a single metal particle selected from the group consisting of an alkali metal and an alkaline earth metal, or an alloy particle containing at least one of these metals.   A product comprising the nanoparticles according to claim 9 or 10.

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