JP2015063455A - Method for producing vanadium dioxide fine particle having thermochromic properties - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing vanadium dioxide fine particles capable of obtaining high purity vanadium dioxide particles having thermochromic properties and a small average particle diameter without requiring high temperature and high pressure conditions and to provide vanadium dioxide fine particles produced using the production method of the vanadium dioxide fine particles.SOLUTION: There is provided a method for producing vanadium dioxide fine particles having thermochromic properties, which includes a step of irradiating a raw material liquid comprising a compound containing a pentavalent vanadium atom (V) and a solvent containing an organic solvent with a laser beam, where the laser beam has a fluence of 0.2 to 5 J/cmper pulse.

Description

The present invention relates to a method for producing vanadium dioxide fine particles capable of obtaining vanadium dioxide fine particles that do not require high-temperature and high-pressure conditions, have thermochromic properties, a small average particle diameter, and high purity. The present invention also relates to vanadium dioxide fine particles produced using the method for producing vanadium dioxide fine particles.

Vanadium dioxide exhibits a monoclinic crystal structure below the phase transition temperature and exhibits semiconducting properties. On the other hand, above the phase transition temperature, it changes to a rutile crystal structure and exhibits metallic properties. Along with this phase transition phenomenon, vanadium dioxide has attracted attention as a switching material, a thermal sensor, and a thermochromic material because its resistance and transmittance in the infrared region change greatly. Among them, application research to thermochromic materials based on changes in infrared (heat ray) transmittance is most actively conducted. For example, using the thermochromic properties of vanadium dioxide, an “automatic temperature control material” that transmits heat rays in winter and blocks heat rays in summer has been proposed. When such a temperature automatic adjustment material is applied to a window of an automobile or a building, an effect of suppressing an increase in the temperature of the inside of the vehicle or the room and improving the cooling / heating efficiency is expected.

When applying a vanadium dioxide thermochromic material to windows of automobiles or buildings, transparency is required in addition to thermochromic properties. In order to maintain transparency, it is necessary to produce nanometer-order vanadium dioxide fine particles.

As a method of obtaining fine particles of vanadium dioxide, for example, a method in which a material obtained by synthesizing vanadium oxide and tungsten oxide by a melting method is pulverized with a bead mill (see Patent Document 1), a vanadium compound is oxidized with hydrogen peroxide water, There has been proposed a method in which a porous vanadium oxide is deposited at a predetermined temperature and pulverized and then subjected to a reduction treatment (see Patent Document 2).
However, in the method described in Patent Document 1, the vanadium oxide material is made into fine particles by mechanical pulverization, and although particles having a size of several hundred nanometers are obtained, severe pulverization conditions are necessary. In the method described in Patent Document 2, the porous vanadium oxide is precipitated to facilitate the pulverization and the pulverization conditions are eased. However, the contamination and particles are not changed into the fine particles by mechanical pulverization. In this case, there is a problem that the thermochromic property is lowered.
Furthermore, the methods described in Patent Documents 1 and 2 are complicated because they require multistage production processes such as synthesis and pulverization of vanadium dioxide.

Non-Patent Document 1 synthesizes a complex such as (NH ₄ ) ₅ [(VO) ₆ (CO ₃ ) ₄ (OH) ₉ ] · 10H ₂ O from a solution containing vanadium ions, A method for producing vanadium dioxide particles by firing at 500 ° C. or higher in an atmosphere of an active gas (for example, nitrogen) is disclosed.
However, in the method described in Non-Patent Document 1, since a baking process at a high temperature is necessary to form vanadium dioxide particles having thermochromic properties, sintering between particles occurs, and the average particle size is small. There was a problem that particles could not be obtained.

Further, Patent Document 3 discloses a method for producing vanadium dioxide particles by a hydrothermal synthesis method.
However, in the method described in Patent Document 3, particles having a size of 100 nm or less can be obtained. However, conditions of high temperature and high pressure are necessary at the time of synthesis. Was necessary.

JP 2000-233929 A JP 2011-136873 A JP2011-178825A

Z. Peng et al. , J .; Phys. Chem. C. , Vol. 111 (2007), pp. 1119-1115.

In view of the above situation, the present invention provides a method for producing vanadium dioxide fine particles that does not require high-temperature and high-pressure conditions, has thermochromic properties, has a small average particle diameter, and can obtain high-purity vanadium dioxide fine particles. The purpose is to provide. Another object of the present invention is to provide vanadium dioxide fine particles produced using the method for producing vanadium dioxide fine particles.

The present invention relates to a method for producing thermochromic vanadium dioxide fine particles, wherein a raw material liquid containing a compound containing a pentavalent vanadium atom (V ⁵⁺ ) and a solvent containing an organic solvent is irradiated with laser light. And the laser beam is a method for producing vanadium dioxide fine particles having a fluence per pulse of 0.2 to 5 J / cm ² .
Hereinafter, the present invention will be described in detail.

As a result of intensive studies, the present inventors started a compound of vanadium (for example, valence of vanadium atom: +5) having a valence higher than that of the target product, vanadium dioxide (valence of vanadium atom: +4). The valence of vanadium atoms becomes tetravalent by irradiating the dispersion liquid in which the starting material is dispersed in an organic solvent with a laser beam having a fluence per pulse of 0.2 to 5 J / cm ^2. The inventors have found that fine particles of vanadium dioxide can be obtained, and have completed the present invention.

Using a compound of vanadium atoms (valence of vanadium atoms: +5) having higher valence than vanadium dioxide (valence of vanadium atoms: +4) as a starting material, a desired valence (+4) is obtained after laser irradiation. Vanadium oxide can be obtained.
In addition, since a vanadium atom having a lower valence than vanadium dioxide (vanadium valence: +2 or +3) is used as a starting material, it does not use impurities such as an oxidizing agent, rather than oxidizing it to obtain vanadium dioxide. Purity can be increased, and vanadium dioxide fine particles that are the target can be efficiently obtained.

Since vanadium atoms are most stable in pentavalence, when trying to obtain vanadium dioxide having tetravalent vanadium atoms from a compound containing pentavalent vanadium atoms, it is described in, for example, Patent Document 2 above. As described above, it is necessary to perform reduction treatment under severe conditions at 300 to 400 ° C. for about 1 to 6 hours. In addition, it is necessary to adjust the conditions of the reduction process so that the reduction does not proceed excessively. The method for producing vanadium dioxide fine particles of the present invention does not require such a reduction treatment, and the valence per pulse of laser light is set within a predetermined range, so that the valence of vanadium atoms is changed from pentavalent to tetravalent. In addition, it is possible to prevent the valence from deteriorating too much.
Moreover, in the method for producing vanadium dioxide fine particles of the present invention, fine particles having a small average particle diameter can be produced simultaneously with the production of vanadium dioxide. Therefore, vanadium dioxide fine particles can be obtained by a simple method in a short time without requiring a reaction under high temperature and high pressure conditions for a long time.
Furthermore, unlike a mechanical grinding method such as a bead mill, contamination and particle defects are unlikely to occur.

The method for producing vanadium dioxide fine particles of the present invention includes a laser irradiation step of irradiating a raw material solution containing a compound containing a pentavalent vanadium atom (V ⁵⁺ ) and a solvent containing an organic solvent with a laser beam.

The laser irradiation step is performed in a liquid phase. Compared to the conventional synthesis method of fine particles by laser irradiation in the gas phase (gas phase laser ablation method), the synthesis method by laser irradiation in the liquid phase (liquid phase laser ablation method) is a simple operation in a non-vacuum process. It has features such as being able to.
In liquid phase laser ablation, laser light is irradiated toward a target material that has been precipitated or dispersed in the liquid phase. When the target is irradiated with light having a very high photon density, such as laser light, both in space and in time, a local high-temperature and high-pressure state called a cavitation bubble is generated near the interface between the target material and the solvent. It has been reported that plasma can be generated at the same time that is formed. As a result, phenomena such as ionization of target material, breakage of chemical bonds, melting, or evaporation occur. Since the laser irradiation step can be performed without increasing the temperature of the raw material solution, the resulting vanadium dioxide fine particles are unlikely to aggregate, coalesce and sinter, and vanadium dioxide fine particles having excellent dispersibility can be obtained. .

The laser beam has an energy density (fluence) per pulse of 0.2 to 5 J / cm ² . The laser beam is a pulse laser.
Note that the fluence means an energy density (J / cm ² ) obtained by dividing the energy per one pulse of the laser light by the irradiation area.
It is known that the vanadium atom has an [Ar] 3d ³ 4s ² electron configuration in the ground state and mainly takes a valence of +2, +3, +4, and +5 when forming a compound with other atoms. By irradiating a laser beam to a raw material liquid containing a compound containing a pentavalent vanadium atom and a solvent containing an organic solvent, electrons are transferred between the compound and the organic solvent, and the value of the vanadium atom is increased. The number can be lower than pentavalent.
In particular, by setting the energy density (fluence) per pulse to 0.2 to 5 J / cm ² , the valence of the vanadium atom can be kept tetravalent.
When the fluence per pulse of the laser beam M is less than 0.2 J / cm ² , the energy of the irradiated laser beam is low, so that the ablation phenomenon does not occur and the valence of the vanadium atom is changed from pentavalent to tetravalent. If the energy exceeds 5 J / cm ² , the energy of the irradiated laser beam is too high, and the valence of the vanadium atom does not remain tetravalent, and may be divalent or trivalent. is there. Further, since the energy of the laser beam is too high, high heat is generated during the irradiation process, which may increase the risk of experiments.
A preferable lower limit of the fluence per pulse of the laser beam M is 0.5 J / cm ² , and a preferable upper limit is 3 J / cm ² . When the fluence per pulse of the laser beam M is within the above preferable range, tetravalent vanadium oxide can be efficiently formed.

As the organic solvent, hydrocarbons, ketones, alcohols, glycols and derivatives thereof, amines, ionic liquids, or the like can be used.
Among them, it is preferable to contain at least one selected from ketones, alcohols, glycols and derivatives thereof, and since the content of vanadium dioxide other than tetravalent can be reduced, alcohols, glycols and their It is more preferable to contain at least one selected from derivatives.
Examples of ketones include acetone, methyl ethyl ketone, diethyl ketone, methyl propyl ketone, methyl isobutyl ketone, and amyl methyl ketone. Examples of alcohols include ethanol, methanol, 1-propanol, 2-propanol, butanol, and pen. Examples of the glycols include ethylene glycol, propylene glycol, diethylene glycol, and triethylene glycol. Examples of these derivatives include triethylene glycol di-2- Ethyl hexanoate (3GO), triethylene glycol di-2-ethylbutyrate (3GH), dihexyl adipate (DHA), tetraethylene glycol diheptanoate (4G7), or Tiger ethylene glycol di-2-ethylhexanoate (4GO), and the like.
By using a solvent containing an organic solvent, the obtained vanadium dioxide fine particles can have very excellent dispersion stability compared to particles produced by a conventional method without adding a dispersant. .
The present inventors have also found that the organic solvent is indispensable for converting a compound containing a pentavalent vanadium atom into a tetravalent vanadium oxide. Although its mechanism of action is not yet clear, the high energy of the laser light activates the organic solvent at the interface between the solvent and the target material, resulting in the formation of an active intermediate that is easy to emit electrons. Conceivable. It is assumed that a compound containing a pentavalent vanadium atom forms a tetravalent vanadium oxide as a result of the donation of electrons from such an active intermediate.
It is preferable that the content rate of the organic solvent in the said solvent is 30 mass% or more. If content of the organic solvent in the said solvent is 30 mass% or more, the vanadium oxide which has desired valence (+4) can fully be formed. As for the content rate of the organic solvent in the said solvent, it is more preferable that it is 40 mass% or more. Moreover, the upper limit of content of the organic solvent in the said solvent is although it does not specifically limit, It is preferable that it is 100 mass% or less. If content of the organic solvent in the said solvent is 100 mass% or less, the vanadium oxide which has a desired valence (+4) can fully be formed.
Examples of the solvent other than the organic solvent used as the solvent include water. Of these, water is preferably used.
As the solvent, highly pure vanadium dioxide fine particles can be obtained efficiently, and therefore an organic solvent or a mixed solution of an organic solvent and water is preferable, and at least one selected from ketones, alcohols, glycols and derivatives thereof Or a mixed solution of these with water is more preferable, at least one kind selected from alcohols, glycols and derivatives thereof or a mixed solution of these with water is more preferable, and an alcohol or a mixed solution of these with water is particularly preferable. preferable.

An example of a liquid phase laser ablation apparatus for carrying out the method for producing vanadium dioxide fine particles of the present invention is shown in FIG. The liquid phase laser ablation apparatus includes a laser oscillator 100, a mirror 101, a processing vessel 102, a compound 103 containing pentavalent vanadium atoms, a solvent 104 containing an organic solvent, a stirrer table 105, a stirrer 106, a gas cylinder. 107. In FIG. 1, the symbol M indicates laser light.

The method for producing vanadium dioxide fine particles of the present invention includes a step of irradiating a raw material liquid containing a compound 103 containing a pentavalent vanadium atom and a solvent 104 containing an organic solvent with laser light.
The raw material liquid containing the compound 103 containing a pentavalent vanadium atom and the solvent 104 containing an organic solvent is orange. However, when laser light is irradiated, cavitation bubbling occurs, and the color change of the raw material liquid starts. When the valence of a compound containing a pentavalent vanadium atom is changed and converted to a divalent, trivalent or tetravalent vanadium oxide, the liquid color becomes black.

Specifically, in the step of irradiating the laser beam, as shown in FIG. 1, the laser beam M generated from the laser oscillator 100 is reflected by a mirror 101 and contains pentavalent vanadium atoms in the processing vessel 102. The compound 103 to be irradiated is irradiated.
In addition, by rotating the mirror 101, the angle of the reflecting surface is changed, and the irradiation position of the laser beam M can be moved so that the compound 103 containing pentavalent vanadium atoms is not repeatedly irradiated to the same position. it can.

The laser oscillator 100 is not particularly limited as long as it can generate the laser light M. For example, the laser oscillator 100 includes a YAG laser device and an excimer laser device, and among these, the YAG laser device is used. Those are preferred.

The mirror 101 is not particularly limited, and a known reflector or the like (for example, a mirror) can be used as appropriate. The mirror 101 is preferably used in a rotatable state so that the angle of the reflecting surface can be changed from the viewpoint of more uniformly irradiating the target with laser light.

The processing container 102 is not particularly limited as long as it can transmit the laser light M, and examples of the material include quartz, sapphire, and glass. As the shape of the processing container 102, for example, a cup-shaped one, a round bottom flask, an eggplant-shaped flask, a pear-shaped flask, a test tube, or the like can be used as appropriate.

Examples of the compound 103 containing a pentavalent vanadium atom include oxides and metavanadates containing a pentavalent vanadium atom.
Examples of the oxide containing a pentavalent vanadium atom include vanadium pentoxide (V ₂ O ₅ ).
Examples of the metavanadate include ammonium metavanadate (NH ₄ VO ₃ ) and sodium metavanadate (NaVO ₃ ).

The compound 103 containing a pentavalent vanadium atom may be in the form of powder or particles, or may be in the form of a rod, plate or pellet. From the viewpoint of reducing the particle size, powders and particles are preferable. In the case of powder and particles, a compound containing a pentavalent vanadium atom may be dispersed throughout the solvent as shown in FIG. 1, and in the case of a plate or pellet, the compound is disposed on the inner surface of the processing vessel. That's fine. FIG. 2 shows a case where a plate-like compound 103 is used as the compound 103 containing a pentavalent vanadium atom. The compound 103 containing a pentavalent vanadium atom is arrange | positioned at the inner surface of the processing container.

The size of the compound 103 containing a pentavalent vanadium atom is not particularly limited. However, in order to efficiently obtain vanadium dioxide fine particles having a small average particle diameter, those having an average particle diameter of 500 μm or less are preferable. More preferably, it is 250 μm or less.
The amount of the compound 103 containing a pentavalent vanadium atom is preferably 0.001 to 10% by mass of the raw material liquid. If it is 0.001% by mass or more, the productivity can be improved, and if it is 10% by mass or less, the laser beam required to pulverize the compound 103 containing pentavalent vanadium atoms to the nanometer order. Irradiation time can be shortened.

The raw material liquid containing the compound 103 containing a pentavalent vanadium atom and the solvent 104 containing an organic solvent may contain an appropriate dispersant. Examples of the dispersant include amine-based dispersants, carboxylic acid-based dispersants, and sulfonic acid-based dispersants.

The preferable lower limit of the wavelength of the laser beam M is 250 nm, and the preferable upper limit is 2500 nm.
If the wavelength of the laser beam M is within the above preferred range, the efficiency of laser ablation can be increased.
The more preferable lower limit of the wavelength of the laser beam M is 300 nm, the more preferable upper limit is 2000 nm, the still more preferable upper limit is 1100 nm, the particularly preferable upper limit is 1064 nm, and the most preferable upper limit is 550 nm.

The laser beam M preferably has a pulse width of 100 femtoseconds to 100 nanoseconds. If the pulse width is within the preferable range, tetravalent vanadium dioxide can be efficiently formed.

The minimum with the preferable irradiation time of the said laser beam M is 1.0 minute, and a preferable upper limit is 300 minutes.
If the irradiation time of the laser beam M is 1.0 minute or more, the valence of the vanadium atom can be sufficiently changed from pentavalent to tetravalent, and the average particle diameter of the obtained vanadium dioxide fine particles is small. It can be made uniform.
If the irradiation time of the laser beam M is 300 minutes or less, it is possible to suppress the valence of the vanadium atom from becoming divalent or trivalent, and the vanadium dioxide fine particles formed by heating the raw material liquid. Aggregation can be suppressed. The more preferable lower limit of the irradiation time of the laser beam M is 3.0 minutes, the more preferable upper limit is 200 minutes, the still more preferable lower limit is 5.0 minutes, and the further preferable upper limit is 150 minutes.

The temperature of the raw material liquid when irradiating the laser beam M is not particularly limited, but may be room temperature or a controlled constant temperature. From the viewpoint of suppressing increase in the liquid temperature due to heat generation during laser light irradiation, the latter is preferable. Although the upper limit with preferable liquid temperature is based also on the kind of solvent used and the atmosphere at the time of irradiation, normally 50 degrees C or less is preferable and 30 degrees C or less is especially preferable. Moreover, the minimum with a preferable liquid temperature is not specifically limited, What is necessary is just the temperature more than the freezing point of a raw material liquid. From the viewpoint of the difficulty of temperature control and the cost of equipment, −10 ° C. is an appropriate lower limit temperature. The temperature control of the raw material liquid can be performed by installing the processing container 102 in FIG. 1 in a thermostatic chamber capable of controlling the temperature.

The method for producing vanadium dioxide fine particles of the present invention may have a gas replacement step of replacing the compound 103 containing pentavalent vanadium atoms and the raw material liquid with an inert gas.
The gas replacement step may be performed before the laser light irradiation step or may be performed during the laser light irradiation step.
Specifically, after the inert gas is passed from the gas cylinder 107 through the gas pipe 108 to the raw material liquid containing the compound 103 containing pentavalent vanadium atoms and the solvent 104 containing an organic solvent in the processing vessel 102. A method of discharging through the exhaust port 109 can be used.

By performing such a gas replacement step, dissolved oxygen in the raw material liquid is removed, and oxidation of the resulting vanadium dioxide fine particles can be suppressed. Further, when an organic solvent is used, the risk of ignition or explosion during laser irradiation can be reduced by removing dissolved oxygen.

Although the time which performs the said gas replacement process is not specifically limited, 1-120 minutes are preferable, More preferably, it is 5-60 minutes. When the time for performing the gas replacement step is within the preferable range, oxidation of the obtained vanadium dioxide fine particles can be further suppressed.
Further, the gas flow rate during the gas replacement step is preferably 10 to 1000 ml / min. If the gas flow rate when performing the gas replacement step is within the preferred range, oxidation of the resulting vanadium dioxide fine particles can be further suppressed.

Examples of the inert gas include noble gases such as helium, neon, argon, krypton, and xenon, and nitrogen, and a mixed gas thereof may be used. Especially, it is preferable to use argon from a viewpoint of reducing oxygen content and a viewpoint of cost.

Specific examples of the gas replacement step include a method of directly introducing the inert gas described above.
Moreover, it is preferable to perform the said gas substitution process in the state which disperse | distributed the compound containing the said pentavalent vanadium atom.
Thereby, dissolved oxygen can be removed efficiently. Specifically, a method of introducing an inert gas while stirring using the stirrer 106 may be used.

By using the method for producing vanadium dioxide fine particles of the present invention, vanadium dioxide fine particles having thermochromic properties and a small average particle diameter can be obtained.
Vanadium atoms constituting the obtained vanadium dioxide fine particles are tetragonal (rutile type) or monoclinic (M type), both of which have thermochromic properties.

The preferable lower limit of the average particle diameter of the vanadium dioxide fine particles is 1 nm, the preferable upper limit is 300 nm, the more preferable lower limit is 5 nm, the more preferable upper limit is 200 nm, the still more preferable lower limit is 10 nm, and the further preferable upper limit. Is 100 nm. The average particle diameter of the vanadium dioxide fine particles can be measured using, for example, a particle size distribution meter (manufactured by NICOMP, NICOMP 380DLS). The average particle size is preferably a volume average particle size.

In the vanadium dioxide constituting the vanadium dioxide fine particles, a part of vanadium atoms may be substituted with at least one atom selected from tungsten, molybdenum, niobium and tantalum (hereinafter also referred to as substituted vanadium dioxide). .
The vanadium dioxide has various crystal phases, but a monoclinic crystal and a tetragonal crystal (rutile type) undergo a phase transition reversibly. Its phase transition temperature is about 68 ° C., but the phase transition temperature is adjusted by replacing some of the vanadium atoms in vanadium dioxide with at least one atom selected from tungsten, molybdenum, niobium and tantalum. be able to. Therefore, the performance of the obtained thermochromic film can be controlled by appropriately selecting the vanadium dioxide fine particles or the substituted vanadium dioxide fine particles, or appropriately selecting the atomic species and the substitution rate to be substituted in the substituted vanadium dioxide fine particles. it can.

The substituted vanadium dioxide can be obtained by adding the compound of the substituted metal element to the raw material liquid in the laser irradiation step and causing it to coexist.

The substituted vanadium dioxide preferably has a metal atom substitution rate of 0.1 atomic% at the lower limit and 10 atomic% at the upper limit. When the substitution rate is within this range, the phase transition temperature of the substituted vanadium dioxide can be easily adjusted, and excellent thermochromic properties can be exhibited. The metal atom substitution rate is a value indicating the percentage of the number of substituted atoms in the total of the number of vanadium atoms and the number of substituted atoms.

Vanadium dioxide fine particles obtained by using the method for producing vanadium dioxide fine particles of the present invention, the content of vanadium atoms having a valence other than tetravalent in the measurement using X-ray photoelectron spectroscopy (XPS), Vanadium dioxide fine particles that are 10 mol% or less of all vanadium atoms are also one aspect of the present invention.
If the content of vanadium atoms having a valence other than tetravalent with respect to all the vanadium atoms is 10 mol% or less, sufficient thermochromic properties can be obtained.

Since the vanadium dioxide fine particles of the present invention are extremely excellent in dispersibility and a highly transparent film is obtained when formed, an intermediate film for laminated glass having excellent thermochromic properties, a coating solution, A film can be produced.

The interlayer film for laminated glass containing the vanadium dioxide fine particles of the present invention is also one aspect of the present invention.
The interlayer film for laminated glass of the present invention can be produced, for example, by mixing the vanadium dioxide fine particles of the present invention, a thermoplastic resin, a plasticizer, and a dispersant, forming a film, and then drying.
For the mixing, an extruder, a plastograph, a kneader, a Banbury mixer, a calendar roll, or the like can be used.
For the film formation, a spin coating method, an extrusion method, a calendar method, a pressing method, or the like can be used.

The coating liquid containing the vanadium dioxide fine particles of the present invention is also one aspect of the present invention.
The coating liquid of the present invention is prepared by, for example, mixing the vanadium dioxide fine particles of the present invention, a plasticizer, and a dispersant using a planetary stirrer, a wet mechanochemical device, a Henschel mixer, a homogenizer, an ultrasonic irradiator, or the like. It is obtained by doing.

The film containing the vanadium dioxide fine particles of the present invention is also one aspect of the present invention.
The film of the present invention can be produced, for example, by mixing the vanadium dioxide fine particles of the present invention, a thermoplastic resin, a plasticizer, and a dispersant, forming a film, and then drying. As the mixing method and the film forming method, for example, the method exemplified for the interlayer film for laminated glass of the present invention can be used.

ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the vanadium dioxide microparticles | fine-particles which can obtain the vanadium dioxide microparticles which do not require high temperature / high pressure conditions, have thermochromic property, a small average particle diameter, and high purity can be provided. be able to. Moreover, the vanadium dioxide fine particle manufactured using the manufacturing method of this vanadium dioxide fine particle can be provided.

It is a schematic diagram which shows an example of the liquid phase laser ablation apparatus for performing the manufacturing method of the vanadium dioxide microparticles | fine-particles of this invention. It is a schematic diagram which shows another example of the liquid phase laser ablation apparatus for performing the manufacturing method of the vanadium dioxide microparticles | fine-particles of this invention. ₂ is a SEM photograph taken of the V ₂ O ₅ powder before the laser irradiation process used in Example 1. 2 is a SEM photograph taken of vanadium dioxide fine particles after the laser irradiation step in Example 1. FIG. And V ₂ O ₅ powder before the laser irradiation process in Example 1, is a graph comparing the X-ray photoelectron spectrum of the fine particles in suspension after laser irradiation step (XPS).

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples.

Example 1
(Gas replacement process)
After weighing 20 mg of vanadium pentoxide (V ₂ O ₅ ) powder having an average particle diameter of 80 μm into a glass vial with a volume of 30 ml, 20 g of ethanol was added. Thereafter, the rubber stopper of the vial was sealed with an aluminum cap and sealed. Subsequently, an injection needle was inserted into the rubber stopper, and the gas was replaced by introducing argon gas in a gas cylinder into the vial for 10 minutes while stirring.

(Laser irradiation process)
The solution subjected to gas replacement was irradiated with Nd: YAG laser light (wavelength 1064 nm, pulse width 10 nanoseconds, fluence per pulse: 1.5 J / cm ² ) generated from a laser oscillator for 15 minutes. The liquid temperature of the raw material liquid was 20 ° C. The color of the V ₂ O ₅ / ethanol suspension before laser light irradiation was orange, but the color change started 30 seconds after laser irradiation and became black after 5 minutes.
Since V ₂ O ₅ particles are orange and divalent, trivalent, or tetravalent vanadium oxide is black, the change in the valence of the vanadium atom can be easily confirmed by checking the color tone. can do.

FIG. 3 is an SEM photograph obtained by photographing the V ₂ O ₅ powder before the laser irradiation process used in Example 1, and FIG. 4 is an SEM photograph obtained by photographing the vanadium dioxide fine particles after the laser irradiation process in Example 1. is there. As shown in FIG. 3, the V ₂ O ₅ powder before the laser irradiation step was a large particle having an average particle diameter of 80 μm. On the other hand, as shown in FIG. 4, the black fine particles contained in the dispersion after irradiating the laser beam for 15 minutes were spherical particles having an average particle diameter of about 29.3 nm. The SEM photograph was taken with a scanning electron microscope (manufactured by Hitachi High-Tech, S-4800).

(Example 2)
A black suspension was obtained in the same manner as in Example 1 except that the solvent was changed from ethanol to acetone in Example 1 (gas replacement step).
The color of the V ₂ O ₅ / acetone suspension before the laser irradiation was orange, but the color change started about 30 seconds after the laser irradiation and became completely black after 5 minutes.

(Example 3)
A black suspension was obtained in the same manner as in Example 1 except that the solvent was changed from ethanol to ethylene glycol in Example 1 (gas replacement step).
The color of the V ₂ O ₅ / ethylene glycol suspension before the laser irradiation was orange, but the color change started 40 seconds after the laser irradiation and became completely black after 5 minutes.

Example 4
A black suspension was obtained in the same manner as in Example 1, except that the solvent was changed from ethanol to triethylene glycol di-2-ethylhexanoate (3GO) in Example 1 (gas replacement step).
The color of the V ₂ O ₅ / 3GO suspension before laser light irradiation was orange, but the color change started 20 seconds after laser irradiation and became completely black after 5 minutes.

(Example 5)
In the same manner as in Example 1 except that the compound containing a pentavalent vanadium atom was changed from vanadium pentoxide to ammonium metavanadate (NH ₄ VO ₃ ) in (gas replacement step) of Example 1, A suspension was obtained.
The color of the NH ₄ VO ₃ / ethanol suspension before laser light irradiation was pale yellow, but the color change started 2 minutes after laser irradiation and became black 10 minutes later.

(Example 6)
Example 1 (Laser irradiation process) Same as Example 1 except that the wavelength of the laser beam was changed from 1064 nm to 532 nm and the irradiation fluence was changed from 1.5 J / cm ² to 0.75 J / cm ^2. As a result, a black suspension was obtained.
The color of the V ₂ O ₅ / ethanol suspension before laser light irradiation was orange, but the color change started 40 seconds after laser irradiation and became completely black after 10 minutes.

(Example 7)
Example 1 (Laser irradiation step) In the same manner as in Example 1 except that the wavelength of the laser beam was changed from 1064 nm to 355 nm and the irradiation fluence was changed from 1.5 J / cm ² to 0.75 J / cm ^2. As a result, a black suspension was obtained.
The color of the V ₂ O ₅ / ethanol suspension before the laser light irradiation was orange, but the color change started 30 seconds after the laser irradiation and became completely black after 10 minutes.

(Example 8)
A black suspension was obtained in the same manner as in Example 1 except that the laser light irradiation fluence was changed from 1.5 J / cm ² to 0.25 J / cm ² in Example 1 (laser irradiation step). It was.
The color of the V ₂ O ₅ / ethanol suspension before laser light irradiation was orange, but the color change started 60 seconds after laser irradiation and became completely black after 10 minutes.

Example 9
A black suspension was obtained in the same manner as in Example 1 except that the laser light irradiation fluence was changed from 1.5 J / cm ² per pulse to 4.5 J / cm ² in Example 1 (laser irradiation step). A liquid was obtained.
The color of the V ₂ O ₅ / ethanol suspension before laser light irradiation was orange, but the color change started 10 seconds after laser irradiation and became completely black after 4 minutes.

(Example 10)
A black suspension was obtained in the same manner as in Example 1 except that the gas replacement step was not performed and the solvent was changed from ethanol to ethylene glycol in Example 1 (laser irradiation step).
The color of the V ₂ O ₅ / ethylene glycol suspension before laser light irradiation was orange, but the color change started 30 seconds after laser irradiation and became completely black after 5 minutes.

(Example 11)
A black suspension was obtained in the same manner as in Example 1 except that the solvent was changed from ethanol to an ethanol / water mixture having an ethanol concentration of 40% by mass in Example 1 (gas replacement step).
The color of the V ₂ O ₅ / ethanol / water suspension before the laser light irradiation was orange, but the color change started about 60 seconds after the laser irradiation and became completely black after 15 minutes.

(Example 12)
A black suspension was obtained in the same manner as in Example 1 except that the solvent was changed from ethanol to an ethanol / water mixture having an ethanol concentration of 70% by mass in Example 1 (gas replacement step).
The color of the V ₂ O ₅ / ethanol / water suspension before laser light irradiation was orange, but the color change started about 45 seconds after laser irradiation and became completely black after 10 minutes.

(Comparative Example 1)
The experiment was performed in the same manner as in Example 1 except that the solvent was changed from ethanol to water in Example 1 (gas replacement step). Even when the laser beam was irradiated for 15 minutes, the color of the mixed solution did not become black but remained orange.

(Comparative Example 2)
Experiments were performed in the same manner as in Example 1 except that the laser irradiation fluence was changed from 1.5 J / cm ² per pulse to 0.1 J / cm ² in Example 1 (laser irradiation step). Even when the laser beam was irradiated for 15 minutes, the color of the mixed solution did not become black but remained orange.

(Comparative Example 3)
A black suspension was obtained in the same manner as in Example 1 except that the laser irradiation fluence was changed from 1.5 J / cm ² per pulse to 5.5 J / cm ² in Example 1 (laser irradiation step). Got.
The color of the V ₂ O ₅ / ethanol suspension before laser light irradiation was orange, but the color change started 5 seconds after laser irradiation and became black 3 minutes later.

(Evaluation)
(Average particle size)
The average particle diameter of the fine particles in the suspensions obtained in Examples and Comparative Examples was measured using a particle size distribution meter (NICOMP 380DLS, manufactured by NICOMP).

(Content of vanadium atoms having a valence other than tetravalent)
After the suspensions obtained in Examples and Comparative Examples were vacuum-dried, the obtained powder was put into an aluminum cap having a diameter of 5 mm, and pellets were produced by pressurization. The pellet was measured for binding energy of 2p electrons of vanadium atoms (hereinafter also referred to as V2p) by X-ray photoelectron spectroscopy (XPS) using PHI5000 VersaProbe manufactured by ULVAC-PHI.

The binding energy of the V2p electron shifts to the higher energy side as its valence increases. The valence of the vanadium atom can be determined from the value of the binding energy. By performing curve fitting on the obtained V2p spectrum, the peak area corresponding to the vanadium atom of each valence can be obtained. The content (%) of vanadium atoms other than tetravalent (V ²⁺ , V ³⁺ or V ⁵⁺ ) was evaluated by the ratio of the sum of the peak areas of vanadium atoms other than tetravalent to the total area of V2p. The detection sensitivity of the device was 0.1%.

FIG. 5 is a graph comparing the V ₂ O ₅ powder before the laser irradiation process in Example 1 with the X-ray photoelectron spectrum (XPS) of the fine particles in the suspension after the laser irradiation process.
Taking Example 1 as an example, in FIG. 5, the peak near the binding energy of 530 eV is the 1s peak of the oxygen atom, the peak near the binding energy of 523 eV is the V2p1 / 2 peak, and the peak near the binding energy of 517 eV is V2p3. / 2 peak. The V2p3 / 2 binding energy when the valence of the vanadium atom is pentavalent is 516.5 eV to 517.5 eV, and the binding energy of V2p3 / 2 when the valence of the vanadium atom is tetravalent is 515. 0.0 eV to 516.2 eV.

As can be seen from FIG. 5, it can be seen that the binding energy of the V2p3 / 2 peak of the V ₂ O ₅ powder before laser light irradiation is 517.04 eV, and the valence of the vanadium atom is +5. On the other hand, the V2p3 / 2 peak of the fine particles in the suspension after laser light irradiation shifts to the low energy side (516.05 eV), and the valence of vanadium atoms in the V ₂ O ₅ powder is +5 by laser irradiation. It changed to +4 and it was confirmed that the vanadium dioxide fine particle was obtained.

(With or without phase transition)
The suspensions obtained in the examples and comparative examples were centrifuged, and the precipitates were vacuum dried to obtain powder. 10 mg of the obtained powder was weighed, and its phase transition energy and phase transition temperature were measured using a thermal analyzer (Seiko Instruments Inc., DSC 6220).

The presence or absence of phase transition was evaluated according to the following criteria.
○: When the sample was heated from 10 ° C. to 110 ° C. at a temperature rising rate of 10 ° C./min, a heat dissipation peak derived from the phase transition was observed.
X: When the sample was heated from 10 ° C. to 110 ° C. at a heating rate of 10 ° C./min, no heat dissipation peak derived from the phase transition was observed.

ADVANTAGE OF THE INVENTION According to this invention, the manufacturing method of the vanadium dioxide microparticles | fine-particles which can obtain the vanadium dioxide microparticles which do not require high temperature / high pressure conditions, have thermochromic property, a small average particle diameter, and high purity can be provided. be able to. Moreover, the vanadium dioxide fine particle manufactured using the manufacturing method of this vanadium dioxide fine particle can be provided.

DESCRIPTION OF SYMBOLS 100 Laser oscillator 101 Mirror 102 Processing container 103 Compound containing pentavalent vanadium atom 104 Solvent containing organic solvent 105 Stirrer stand 106 Stirrer 107 Gas cylinder 108 Gas pipe (In)
109 Exhaust port

Claims (10)

A method for producing vanadium dioxide fine particles having thermochromic properties,
A laser irradiation step of irradiating with a laser beam a raw material liquid containing a compound containing a pentavalent vanadium atom (V ⁵⁺ ) and a solvent containing an organic solvent;
The method for producing vanadium dioxide fine particles, wherein the laser beam has a fluence per pulse of 0.2 to 5 J / cm ² . The compound containing a pentavalent vanadium atom (V ⁵⁺ ) is vanadium pentoxide (V ₂ O ₅ ), ammonium metavanadate (NH ₄ VO ₃ ), or sodium metavanadate (NaVO ₃ ). The method for producing vanadium dioxide fine particles according to claim 1. The method for producing vanadium dioxide fine particles according to claim 1 or 2, wherein the organic solvent contains at least one selected from ketones, alcohols, glycols and derivatives thereof. The method for producing vanadium dioxide fine particles according to claim 1, 2 or 3, wherein the content of the organic solvent in the solvent is 30% by mass or more. The method for producing vanadium dioxide fine particles according to claim 1, 2, 3, or 4, wherein the wavelength of the laser light is 300 nm or more. 6. The method for producing vanadium dioxide fine particles according to claim 5, wherein the wavelength of the laser light is 300 nm or more and 2000 nm or less. Vanadium dioxide fine particles obtained by using the method for producing vanadium dioxide fine particles according to claim 1, 2, 3, 4, 5 or 6,
Vanadium dioxide fine particles, characterized in that the content of vanadium atoms having a valence other than tetravalence in the measurement using X-ray photoelectron spectroscopy (XPS) is 10 mol% or less of all vanadium atoms. A laminated glass comprising the vanadium dioxide fine particles obtained by using the method for producing vanadium dioxide fine particles according to claim 1, 2, 3, 4, 5 or 6, or the vanadium dioxide fine particles according to claim 7. Interlayer film. A coating solution comprising the vanadium dioxide fine particles obtained by using the method for producing vanadium dioxide fine particles according to claim 1, 2, 3, 4, 5 or 6, or the vanadium dioxide fine particles according to claim 7. . A film comprising the vanadium dioxide fine particles obtained using the method for producing vanadium dioxide fine particles according to claim 1, 2, 3, 4, 5 or 6, or the vanadium dioxide fine particles according to claim 7.