TW202408685A - Method for producing microparticles, and colloidal solution - Google Patents

Abstract

To provide: a method for producing microparticles, whereby it becomes possible to improve the purity of the microparticles; and a colloidal solution. Provided is a method for producing microparticles using a femtosecond pulse laser, the method being characterized by comprising an irradiation step for irradiating a powdery material 5 in a solvent 6 with a femtosecond pulse laser to produce microparticles each containing a metal atom, in which the powdery material 5 has a median diameter larger than the microparticles and contains a metal atom. For example, the powdery material 5 comprises a first powdery material containing a first metal atom and a second powdery material containing a second metal atom that is different from the first metal atom, and the microparticles comprise an alloy containing the first metal atom and the second metal atom.

Description

Manufacturing method of microparticles and colloidal solution

This invention relates to a method for producing microparticles and a colloidal solution.

Conventionally, as a method of generating microparticles using lasers, a method for producing microparticles disclosed in Patent Document 1 has been proposed.

Patent document 1 discloses a method of generating metal nanoparticles by irradiating a basic solvent containing one or more metal ions with a femtosecond pulse laser. [Prior art document] [Patent document]

[Patent Document 1] Japanese Patent Application Publication No. 2021-017622

[Problems to be solved by the invention]

Here, Patent Document 1 discloses that a basic solvent in which metal ions are dissolved is irradiated with a femtosecond pulse laser to decompose water molecules in the basic solvent to reduce metal ions with radicals (for example, hydrogen radicals) generated to generate Metal nanoparticle approach. According to this generation method, during the reduction reaction of metal ions, in addition to the metal nanoparticles as the target substance, for example, chloride ions bound to the metal ions are oxidized, and impurities other than the target substance may be generated. For this reason, the generated impurities may have an influence on the metal nanoparticles such as adhesion, and may degrade the quality of the metal nanoparticles.

Here, the present invention has been proposed in view of the above-mentioned problems, and an object thereof is to provide a method for producing fine particles and a colloidal solution that can suppress degradation in quality of the fine particles. [To solve the problem]

The method for producing microparticles according to the first invention is a method for generating microparticles using a femtosecond pulse laser, and includes an irradiation process of irradiating a powder material in a solvent with a femtosecond pulse laser to generate microparticles containing metal atoms. The powder material has a central diameter larger than that of the microparticles and is characterized by containing metal atoms.

According to the method for producing fine particles in the second invention, in the first invention, the powder material includes a first powder material containing a first metal atom, and a second powder material containing a second metal atom different from the first metal atom. The second powder material is characterized in that the fine particles are an alloy containing the first metal atoms and the second metal atoms.

According to the method for producing fine particles in the third invention, in the second invention, the melting point of the second powder material is higher than the melting point of the first powder material.

According to the method for producing microparticles of the fourth invention, in the second invention or the third invention, the microparticles are characterized by being a solid solution of a combination of the first metal atoms and the second metal atoms.

According to the colloidal solution of the fifth invention, it is characterized by comprising the aforementioned microparticles produced by the microparticle production method described in any one of the first invention to the third invention, and a solvent for dispersing the aforementioned microparticles. [Effect of the invention]

According to the first to fourth inventions, there is an irradiation process for irradiating a powder material in a solvent with a femtosecond pulse laser to generate fine particles containing metal atoms, and the powder material has a larger central diameter than the fine particles. Therefore, compared with the method of producing fine particles using reduction of metal ions, the generation of impurities that affect the fine particles can be suppressed. This can prevent the quality of the generated fine particles from deteriorating.

In particular, according to the second invention, the powder material includes a first powder material containing a first metal atom and a second powder material containing a second metal atom different from the first metal atom, and the fine particles contain the first metal. An alloy of atoms and atoms of a second metal. Therefore, the ratio of the first powder material to the second powder material can be adjusted, and the composition ratio of each metal atom contained in the fine particles can be easily controlled. This can suppress variation in the composition ratio of each metal atom contained in the fine particles.

In particular, according to the third invention, the melting point of the second powder material is higher than the melting point of the first powder material. That is, fine particles having the characteristics of the first powder material and a higher melting point than the first powder material are generated. Therefore, compared with the case of producing fine particles without using the second powder material, the temperature range in which the fine particles are stable can be expanded. This can improve the stability of the generated microparticles.

In particular, according to the fourth invention, the fine particles are a solid solution in which the first metal atoms and the second metal atoms are combined. For this reason, partial state changes or chemical changes of the particles are less likely to occur compared to fine particles that are not solid solutions. As a result, the stability of the generated microparticles can be further improved.

In particular, according to the fifth invention, the colloid solution includes a solvent in which fine particles are dispersed. Therefore, compared with the case where fine particles are stored without using a solvent, aggregation of fine particles can be easily suppressed. Thus, fine particles with maintained quality can be provided.

Hereinafter, an example of a method for producing fine particles, fine particles, and a colloid solution as an embodiment of the present invention will be described with reference to the drawings.

(Embodiment: microparticles, colloidal solution) The fine particles in this embodiment are used in fields such as medical treatment and food, in addition to electronic devices such as power generation elements. The fine particles may contain, in addition to metal fine particles, metal atoms and non-metal atoms. The fine particles can be used in the energy field such as power generation components, or in the electronic device field such as conductive parts. In addition to the above, the microparticle system can be used in the medical field as pharmaceuticals or cosmetics, the material field as a part of composite materials, food, and other fields. In particular, by subjecting the surface of the microparticles to arbitrary surface treatment (for example, formation of a film), microparticles with additional functions can be produced, and are expected to be used in various applications.

The fine particles include plural particles having a particle diameter of, for example, 1 nm or more and 100 nm or less. The fine particles may include, for example, particles having a median diameter (central diameter: D50) of not less than 1 nm and not more than 10 nm, but also particles having an average particle diameter of not less than 1 nm and not more than 10 nm. The median diameter or the average particle diameter can be measured, for example, by using a particle size distribution meter. As a particle size distribution measuring device, for example, a particle size distribution measuring device using a dynamic light scattering method (for example, Zetasizer Ultra manufactured by Malvern Panalytical, etc.) may be used.

In addition to a particle group generated from a single atom, a particle group generated from, for example, a plurality of metal particles can be referred to as a microparticle. A microparticle can be referred to as a particle group generated from, for example, an alloy.

The colloidal solution in this embodiment is used in the same field as microparticles. A colloidal solution represents a state in which two or more substances containing fine particles are mixed, for example. The colloidal solution system contains, for example, a solvent 6 in which fine particles are dispersed.

The colloidal solution system includes a solvent 6 in which fine particles are dispersed. At this time, compared with the case of storing the fine particles without using the solvent 6, it is easier to suppress the aggregation of the fine particles. This makes it possible to provide fine particles with maintained quality.

Examples of fine particles include known metal atoms such as nickel, platinum, gold, and titanium. The microparticle system only needs to contain metal atoms. For example, any of pure metals, non-metal-free alloys, or metal oxides may be contained. However, when producing a colloidal solution in which fine particles containing no pure metal or non-metal alloy are dispersed, factors that promote oxidation of the fine particles can be reduced by using alcohol as the solvent 6 . This makes it possible to provide fine particles with maintained quality.

The microparticle system represents, for example, a perovskite structure. The microparticle system may include, for example, barium titanate (BaTiO ₃ ), strontium titanate (SrTiO ₃ ), calcium titanate (CaTiO ₃ ), lead titanate (PbTiO ₃ ), tin titanate (SnTiO ₃ ), cadmium titanate (CdTiO ₃ ), and at least one of strontium zirconate (SrZrO ₃ ).

The fine particles are generated using, for example, a first powder material and a second powder material. The first powder material contains first metal atoms (first metal atoms), and the second powder material contains second metal atoms (second metal atoms). The fine particles are, for example, an alloy containing first metal atoms and second metal atoms. The fine particles contain, for example, a second powder material (second powder material) whose melting point is higher than the melting point of the first powder material (first powder material). That is, fine particles having the characteristics of the first powder material and having a higher melting point than the first powder material are generated. In this case, compared with the case of producing fine particles without using the second powder material, the temperature range in which the fine particles are stable can be expanded. As a result, the stability of the fine particles can be improved. The fine particle system may contain an alloy of two different metal atoms, or may contain an alloy of three or more different metal atoms.

The microparticles are, for example, a solid solution of a first metal atom and a second metal atom. At this time, compared with microparticles that are not solid solutions, partial state changes or chemical changes of the microparticles are difficult to occur, and the microparticles as a whole tend to exist stably. As a result, the stability of the generated microparticles can be improved. As examples of combinations of metal atoms contained in microparticles representing solid solutions, there can be listed combinations of nickel and platinum, nickel and ruthenium, nickel and rhodium, nickel and palladium, nickel and iridium, etc. The microparticles of the solid solution may also contain more than three metal atoms. As examples of combinations of metal atoms contained in microparticles of the solid solution, for example, metal atoms with a mixing enthalpy of less than 0 may be selected.

The microparticles are, for example, eutectic particles formed by combining the first metal atom and the second metal atom. In this case, the stability of the microparticles can be improved compared to microparticles that are not eutectic particles.

The microparticles contain, for example, two or more materials showing the same crystal structure. In this case, the alloy microparticles as a whole show the same tendency of crystal structure. This can improve the stability of the generated microparticles.

(Manufacturing device 100) Next, an example of the production apparatus 100 used in the method of producing fine particles according to this embodiment will be described. FIG. 1 is a schematic perspective view showing an example of the manufacturing apparatus 100 in this embodiment.

1 , the manufacturing apparatus 100 includes a laser device 1, a lens 2, a container 3, and a solution 4. The manufacturing apparatus 100 may include, for example, a plurality of containers 3 and solutions 4 for one laser device 1.

<Laser device 1> The laser device 1 emits a pulse laser having a time width of about ^10-15 seconds. As the laser device 1, for example, the following characteristics are exhibited, and for example, a femtosecond pulse laser such as Astrella manufactured by COHERENT can be used. Oscillation wavelength: 800nm±20nm Pulse width: 100fs Energy: 5-9mJ Repetition frequency: 100Hz (output 0.5-0.9W)

In addition to the above, the laser device 1 may be Spitfire Pro manufactured by Spectra Physics, etc., and may be selected arbitrarily according to the application. However, the laser emitted from the laser device 1 has an energy of several mJ, and it is difficult to effectively generate microparticles with an energy of several μJ used in laser processing, etc.

＜Lens 2＞ The lens 2 condenses the laser emitted from the laser device 1 . By using the lens 2, the light intensity can be increased with respect to a specific area. In particular, by using the lens 2 , the laser can be focused into the interior of the solution 4 , which is closer to the interface of the solution 4 . As the lens 2, a known lens such as a condenser lens can be used. By irradiating the solution 4 with laser light condensed through the lens 2, the production efficiency of microparticles can be improved.

The position at which the lens 2 focuses the laser light into the inside of the solution 4 can be adjusted, for example, by adjusting the shape of the lens 2 or the distance from the solution 4 . For example, a focus variable lens may be used as the lens 2 , and the position of the lens 2 to focus the laser light into the inside of the solution 4 may be adjusted while the position of the lens 2 is fixed.

＜Container 3＞ The container 3 contains the solution 4 . As the container 3, a transparent material, such as a quartz absorption cell, is used. As the container 3 , for example, a material whose absorbance at a wavelength near 800 nm is lower than the absorbance at a wavelength near 400 nm is used. In this case, when laser is irradiated through the container 3, it is possible to suppress a decrease in the production efficiency of fine particles.

<Solution 4> Solution 4 includes powder material 5 and solvent 6. Solvent 6 suspends powder material 5. Microparticles in this embodiment are generated by irradiating the powder material 5 suspended in solvent 6 with laser light emitted from laser device 1.

<Powder material 5> Powder material 5 has, for example, a larger central diameter than fine particles. Powder material 5 includes, for example, a plurality of particles having a particle diameter of a finite value of 500 μm or less. Powder material 5 includes, for example, particles having a central diameter of 50 nm or more and 100 μm or less.

Since the powder material 5 directly reflects the composition of the generated microparticles, it can be arbitrarily set according to the type of the generated microparticles. For example, when gold is used as the powder material 5, the generated microparticles contain gold. In this case, compared with the method of producing microparticles by reducing gold (III) chloride acid hydrate, for example, it is possible to suppress the generation of impurities that may adhere to the microparticles. As a result, it is possible to suppress the degradation of the quality of the generated microparticles.

The powder material 5 contains, for example, one or more types of materials. For example, when the powder material 5 contains two or more materials, fine particles containing an alloy of each material can be generated. The powder material 5 contains, for example, known metal atoms such as nickel, platinum, gold, and titanium. The powder material 5 series only contains metal atoms. For example, any of pure metals, non-metal-free alloys, or metal oxides may be contained.

The powder material 5 contains, for example, a first powder material and a second powder material. The first powder material contains first metal atoms. The second powder material contains second metal atoms different from the first metal atoms. The first powder material has a different composition from the second powder material, for example. In this case, the ratio of the first powder material to the second powder material can be adjusted, and the composition ratio of each metal atom contained in the fine particles can be easily controlled. This can suppress variation in the composition ratio of each metal atom contained in the fine particles. For example, when the powder material 5 in which the molar ratio of nickel to platinum is 8:2 is used, fine particles with a composition close to nickel:platinum=8:2 are easily generated.

The second powder material has a higher melting point than the first powder material, for example. That is, microparticles having the characteristics of the first powder material and a higher melting point than the first powder material are generated. In this case, the temperature range in which the microparticles are stable can be expanded compared to the case where the microparticles are produced without using the second powder material. Thus, the stability of the generated microparticles can be improved.

The powder material 5 contains, for example, two or more materials showing the same crystal structure. At this time, the entire fine particles of the produced alloy tend to have the same crystal structure. As a result, it is possible to suppress the stability of fine particles and improve them.

For example, the crystal structure of iron, sodium and potassium shows a body-centered cubic lattice. Therefore, by containing at least two or more materials among iron, sodium and potassium as the powder material 5, the crystal structure shows the same tendency on the whole of the generated alloy particles. Also, for example, the crystal structure of nickel, aluminum and calcium shows a face-centered cubic lattice. Therefore, by containing at least two or more materials among nickel, aluminum and calcium as the powder material 5, the crystal structure shows the same tendency on the whole of the generated alloy particles.

(Embodiment: Method for producing fine particles) Next, an example of the method for producing fine particles according to this embodiment will be described.

The method for producing microparticles includes an irradiation process. The method for producing microparticles includes at least one of a conditioning process and a stirring process.

<Irradiation process> The irradiation process is to focus the femtosecond pulse laser and irradiate the powder material 5 suspended in the solvent 6. The irradiation process is, for example, to emit a femtosecond pulse laser from the laser device 1 to irradiate the powder material 5 suspended in the solvent 6. At this time, since the pulse width of the femtosecond pulse laser is shorter than the time for the heat of the laser to be transferred to the inside of the powder material 5, the heat will not diffuse to objects other than the irradiated object. At this time, the energy of the laser is not easily consumed by reactions other than the generation of microparticles. As a result, the generation efficiency of microparticles can be improved.

The irradiation process is a process of focusing a femtosecond pulse laser and irradiating the powder material 5, for example, the solvent 6 may also be irradiated. At this time, although free radicals are generated in the solvent 6, the method for producing microparticles in this embodiment does not require a process of chemically reacting the free radicals with the powder material 5. At this time, the amount of microparticles generated is not easily affected by the reaction rate of the free radicals with the powder material 5 or the amount of free radicals generated.

In the irradiation process, for example, the powder material 5 having a larger central diameter than the fine particles is irradiated with femtosecond pulse laser. Therefore, compared with the method of producing fine particles using reduction of metal ions, it is possible to suppress the generation of impurities that are generated by the reduction reaction of metal ions and affect the fine particles. This makes it possible to produce fine particles whose quality is unlikely to deteriorate.

The irradiation process is, for example, irradiating a powder material 5 including a first powder material containing a first metal atom and a second powder material containing the first metal atom with a femtosecond pulse laser. In this case, microparticles of an alloy containing the first metal atom and the second metal atom are generated. In this case, the ratio of the first powder material to the second powder material can be adjusted, and the composition ratio of each metal atom contained in the microparticle can be easily controlled. In this way, microparticles in which the deviation of the composition ratio of each metal atom contained can be suppressed can be generated.

In the irradiation process, for example, the powder material 5 containing the first powder material and the second powder material having a higher melting point than the first powder material may be irradiated with femtosecond pulse laser. That is, fine particles having the characteristics of the first powder material and a higher melting point than the first powder material are generated. In this case, compared with the case of producing fine particles without using the second powder material, the temperature range in which the fine particles are stable can be expanded. This makes it possible to produce highly stable microparticles.

In the irradiation process, for example, the powder material 5 containing the first metal atoms and the second metal atoms may be irradiated with a femtosecond pulse laser to generate fine particles of a solid solution combining the first metal atoms and the second metal atoms. At this time, compared with fine particles that are not solid solutions, partial state changes or chemical changes of the particles are less likely to occur. This makes it possible to produce highly stable microparticles.

The irradiation process may be, for example, irradiating the powder material 5 containing the first metal atoms and the second metal atoms with a femtosecond pulse laser to generate eutectic microparticles combining the first metal atoms and the second metal atoms. In this case, microparticles with higher stability can be produced compared to microparticles that are not eutectic.

<Adjustment process> In this embodiment, the powder material 5 contains metal atoms. At this time, according to the wavelength of the laser irradiated on the powder material 5, it is assumed that before the laser reaches the focus, it is absorbed by the surface of the metal atoms contained in the powder material 5, and the laser irradiated on the powder material 5 cannot be effectively consumed in the generation of microparticles. That is, by adjusting the wavelength of the irradiated laser, the generation efficiency of microparticles can be improved.

The adjustment process is, for example, adjusting the oscillation wavelength of the laser emitted from the laser device 1 to a wavelength that avoids the wavelength range absorbed by the metal atoms contained in the powder material 5 . At this time, the energy of the laser is difficult to be absorbed by the metal atoms contained in the powder material 5 and is easily and effectively consumed in the generation of fine particles. This can improve the production efficiency of fine particles.

In the adjustment process, for example, the wavelength conversion function of the laser device 1 may be used to adjust the oscillation wavelength of the laser emitted from the laser device 1 . The adjustment process may be performed during the irradiation process, at least before or after the irradiation process, or may be performed in a plurality of times.

＜Mixing process＞ In this embodiment, the powder material 5 is irradiated with laser. At this time, although the focus of the laser needs to be aimed at the powder material 5, it is conceivable that the powder material 5 settles into the solvent 6 over time, making it difficult to irradiate the laser. That is, by stirring the solvent 6 and causing the powder material 5 to pass through the focus of the laser, the generation efficiency of fine particles can be improved.

The stirring process is to stir the solvent 6 in which the powder material 5 is suspended. The stirring process system can also stir the solvent 6 while performing the irradiation process. At this time, it is easy to irradiate the powder material 5 with laser uniformly. This can improve the production efficiency of fine particles. In the stirring process, a known mixer such as a stirrer can be used to stir the solvent 6 . The stirring process can be performed at least either before or after the irradiation process.

The stirring process makes it easy to maintain the dispersed state of the powder material 5 in the solvent 6, for example. That is, it prevents the powder material 5 in the solvent 6 from settling over time. Therefore, the laser can be easily irradiated onto the powder material 5. As a result, the generation efficiency of fine particles can be improved.

The stirring process makes it easy to maintain a state in which the first powder material containing the first metal atoms and the second powder material containing the second metal atoms are uniformly dispersed in the solvent 6 . For this reason, in the case of fine particles containing a solid solution of first metal atoms and second metal atoms, the composition ratio of each metal contained in the fine particles can be easily made uniform. As a result, fine particles with higher uniformity can be produced.

Thus, microparticles and a colloidal solution in the present embodiment are produced.

According to the present embodiment, a femtosecond pulse laser is irradiated to a powder material 5 in a solvent 6 to generate fine particles containing metal atoms, and the powder material 5 has a central diameter larger than the fine particles. Therefore, compared with the method for producing fine particles involving the reduction of metal ions, the generation of impurities that affect the fine particles can be suppressed. Thus, the quality of the generated fine particles can be suppressed from being degraded.

Furthermore, according to this embodiment, the powder material 5 includes, for example, a first powder material containing a first metal atom and a second powder material containing a second metal atom different from the first metal atom, and the fine particles contain An alloy of first metal atoms and second metal atoms. Therefore, the ratio of the first powder material to the second powder material can be adjusted, and the composition ratio of each metal atom contained in the fine particles can be easily controlled. This can suppress variation in the composition ratio of each metal atom contained in the fine particles.

Furthermore, according to this embodiment, the melting point of the second powder material is higher than the melting point of the first powder material. That is, microparticles having the characteristics of the first powder material and a higher melting point than the first powder material are generated. Therefore, the temperature range in which the microparticles are stable can be expanded compared to the case where the microparticles are produced without using the second powder material. Thus, the stability of the generated microparticles can be improved.

Furthermore, according to this embodiment, the fine particles are a solid solution in which the first metal atoms and the second metal atoms are combined. For this reason, partial state changes or chemical changes of the particles are less likely to occur compared to fine particles that are not solid solutions. As a result, the stability of the generated microparticles can be further improved.

Furthermore, according to this embodiment, the colloidal solution system includes the solvent 6 in which fine particles are dispersed. For this reason, compared with the case of storing the fine particles without using the solvent 6, it is easier to suppress the aggregation of the fine particles. This makes it possible to provide fine particles with maintained quality.

Although several embodiments of the present invention are described, these embodiments are provided as examples and are not intended to limit the scope of the invention. These innovative embodiments can be implemented in various other forms, and various omissions, substitutions, or changes can be made without departing from the scope of the gist of the invention. These embodiments or modifications are included in the scope or gist of the invention, and are also included in the invention described in the scope of the patent claim and its equivalent.

1: Laser device 2: Lens 3: Container 3a: Opening 4: Solution 5: Powder material 6: Solvent 100: Manufacturing device

[Fig. 1] Fig. 1 is a schematic perspective view showing an example of a production apparatus used in the method of producing fine particles according to this embodiment.

1:Laser device

2: Lens

3:Container

4: solution

5: Powder material

6: Solvent

100: Manufacturing device

Claims (5)

A method of manufacturing microparticles using femtosecond pulse laser to generate microparticles, which has the following characteristics: An irradiation process that irradiates powder materials in a solvent with femtosecond pulse laser to generate microparticles containing metal atoms. The powder material has a larger central diameter than the fine particles and contains metal atoms. The method for producing microparticles as described in claim 1, wherein the powder material includes a first powder material containing a first metal atom and a second powder material containing a second metal atom different from the first metal atom, and the microparticles are alloys containing the first metal atom and the second metal atom. The method for producing microparticles as recited in claim 2, wherein the melting point of the second powder material is higher than the melting point of the first powder material. The method for producing fine particles according to claim 2 or 3, wherein the fine particles are a solid solution in which the first metal atoms and the second metal atoms are combined. A colloidal solution characterized by comprising the aforementioned microparticles produced by the method for producing microparticles as described in any one of claim 1 to claim 3, and a solvent for dispersing the aforementioned microparticles.

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