KR102300880B1 - Process for producing indium hydroxide powder, and cathode - Google Patents

Abstract

The present invention provides a method for producing an indium hydroxide powder that suppresses an increase in the liquid temperature and pH between electrodes, has excellent particle size uniformity, and has a narrow particle size distribution width. In the method for producing indium hydroxide powder in which an indium hydroxide powder is produced by electrolysis in an electrolytic solution using a plurality of anodes and cathodes made of metallic indium, the main surface portion of the cathode used for electrolysis is formed in a network.

Description

Manufacturing method and negative electrode of indium hydroxide powder

The present invention relates to a method for producing an indium hydroxide powder by an electrolytic method, and to a negative electrode used in a method for producing an indium hydroxide powder. This application claims priority on the basis of Japanese Patent Application No. 2014-014405 for which it applied in Japan on January 29, 2014, This application is used for this application by being referred.

In recent years, the use of a transparent conductive film is increasing as a solar cell use or a touchscreen use, and the demand of the material for transparent conductive film formation, such as a sputtering target, is increasing with it. Indium oxide-based sintered materials are mainly used for these materials for forming a transparent conductive film, and indium oxide powder is used as the main raw material thereof.

Patent Document 1 describes a method for producing indium oxide powder by electrolytically treating metal indium to cause precipitation of indium hydroxide powder and calcining this to produce indium oxide powder, a so-called electrolytic method.

In the electrolytic method, as described in Patent Document 2, a method of increasing the electrode area by alternately arranging a plurality of positive and negative electrode plates may be used.

In patent document 2, in an Example, the distance between electrodes is set to 25 mm - 50 mm. However, the distance between the electrodes and the electrolysis voltage have a close relationship, and from the viewpoint of controlling the liquid temperature and pH between the electrodes due to the voltage rise, the distance between the electrodes is preferably as close as possible.

The chemical reaction formulas of the cathode and the anode in the electrolytic crystallization method of In(OH) _{3 are as shown in Formula 1-1, Formula 1-2, and Formula 2.}

Cathode: (Note) 6 NO ₃ ^- + 24 H ⁺ +18 e ^- → 6 NO + 12 H ₂ O (Formula 1-1)

(Part) 18 H ₂ O + 18 e ^- → 9 H ₂ + 18 OH ^- (Formula 1-2)

Anode: 6 In + 18 OH ^- → 6 In(OH) ₃ + 18 e ^- (Equation 2)

In the main reaction in the vicinity of the cathode, ^{the pH rises because H +} is consumed, but in the vicinity of the anode, the pH decreases because ^{OH − is consumed. For this reason, an increase in the H +} concentration, ie, the pH value, occurs from the negative electrode to the positive electrode. In order to make the pH value between the electrodes uniform, it is necessary to stir the electrolytic solution to make the H ⁺ concentration uniform. However, since the movement of ions becomes difficult as the distance between electrodes increases, there is a problem that the effect cannot be obtained unless the stirring is sufficiently strong.

On the other hand, since the movement of ions becomes easy when the distance between electrodes is shortened, even if the stirring intensity is the same, the H ⁺ concentration becomes more uniform. For this reason, it becomes easier to control the pH value uniformly when the distance between electrodes is shortened.

However, when the distance between the electrodes is too short, contact between the electrodes and a short circuit are likely to occur, and the electrolyte solution between the electrodes is not sufficiently stirred and remains there, and there is a fear that the pH between the electrodes rises.

Further, when the distance between the electrodes is increased, the voltage between the electrodes rises, so that the liquid temperature rises due to the liquid resistance. In Chemical Reaction Formula 1-2 at the cathode, since the standard electrode potential is lower than that of Formula 1-1, the rate at which the reaction of Formula 1-2 occurs is low compared to the reaction of Formula 1-1. However, when the inter-electrode voltage rises, since the surface potential of the cathode shifts in the negative direction, the rate at which the reaction of Equation 1-2 occurs increases.

For this reason, the pH value in the vicinity of the cathode tends to rise. On the other hand, ^{since the consumption amount of OH -} in Formula 2 does not change, the pH value of the whole liquid rises as a result.

That is, by increasing the distance between the electrodes, the liquid temperature and the pH rise, and in order to cope with the liquid temperature control, the cost of a large-capacity chiller facility or the like is required.

In general, in the crystallization of hydroxide particles, the higher the pH, the easier the nucleation of the particles. However, in the crystallization reaction in a region where the pH value is high, nucleation tends to occur, whereas dissolution and re-crystallization of the nuclei once formed do not occur easily. For this reason, it becomes a result that many small microparticles|fine-particles which are easy to aggregate remain|survive, the particle size and particle size distribution of a secondary particle coarsen, and the width|variety of a particle size distribution becomes wide.

On the other hand, in the crystallization reaction in a region where the pH value is low, OH ⁻ around the nucleus is consumed by nucleation, so the pH value is lowered, whereby small nuclei are dissolved, and growth of the remaining nuclei is promoted.

As described above, in the crystallization reaction, it is preferable to perform the reaction in a region where the liquid temperature and the pH value are low, but it is difficult to suppress the increase in the liquid temperature and the pH while maintaining an appropriate distance between the electrodes.

Patent Document 1: Japanese Patent No. 2829556 Patent Document 2: Japanese Patent Laid-Open No. 2013-36074

The present invention has been proposed in view of the conventional situation as described above, and suppresses the rise of the liquid temperature and pH between the electrodes, the indium hydroxide powder has excellent uniformity of particle size of the indium hydroxide powder, and the indium hydroxide powder has a narrow particle size distribution width It is to provide a method for producing an indium hydroxide powder capable of obtaining

In the method for producing indium hydroxide powder according to the present invention, in the method for producing indium hydroxide powder in which indium hydroxide powder is produced by electrolysis in an electrolytic solution using a plurality of anodes and cathodes made of metal indium, a cathode used for electrolysis It is characterized in that the main surface portion of the network is formed.

In addition, in the method for producing indium hydroxide powder according to the present invention, the liquid temperature between the anode and the cathode is controlled in the range of ±2° C. with respect to the set temperature of the electrolysis device, and the pH of the electrolyte between the anode and the cathode is 3.2 to 4.0. It is desirable to control in a range.

Moreover, the negative electrode which concerns on this invention is a negative electrode used in the manufacturing method of indium hydroxide powder, Comprising: It is a negative electrode which forms the main surface part of a negative electrode in a network.

In the present invention, it is possible to obtain an indium hydroxide powder that suppresses an increase in the liquid temperature and pH between the electrodes, is excellent in the uniformity of the particle size, and has a narrow particle size distribution.

1 is a view showing an example of the shape of a mesh cathode to which the present invention is applied. Fig. 1 (A) is a diagram showing an example of a net negative electrode when lath processing is performed, and Fig. 1 (B) is a diagram showing an example of a network negative electrode when punching processing is performed.
It is a figure which showed the transition of the liquid temperature between an anode and a cathode at the time of electrolysis in an Example and a comparative example.
It is a figure which showed the transition of the pH of the electrolyte solution between an anode and a cathode at the time of electrolysis in an Example and a comparative example.
4 is a view showing the particle size of the indium hydroxide powder obtained by Examples and Comparative Examples.

Below, the negative electrode used by the manufacturing method of the indium hydroxide powder and the manufacturing method of the indium hydroxide powder to which this invention is applied is demonstrated in the following procedure.

1. Manufacturing method of indium hydroxide powder

2. Structure of the cathode

<1. Manufacturing method of indium hydroxide powder>

In the manufacturing method of an indium hydroxide powder, the indium hydroxide powder is obtained using the electrolytic reaction using the electrolyte solution which adjusted the density|concentration, pH, solubility, etc. In this manufacturing method, a metal indium as a raw material is used as an anode (anode), a conductive metal is used for a cathode (cathode) as a counter electrode, and both are immersed in an electrolyte to generate a potential difference between the anodes to generate a current. Dissolution of the metal proceeds at the anode. Moreover, in the manufacturing method of an indium hydroxide powder, in electrolyte solution, by adjusting pH so that the solubility of the indium hydroxide powder produced|generated may become a low state, an indium hydroxide slurry crystallizes and causes precipitation.

Although the metal indium used for an anode is not specifically limited, In order to suppress mixing of impurities with respect to the indium oxide powder obtained by calcining indium hydroxide powder, it is preferable that it is high purity. As metal indium, a purity of 99.9999% (common name 6N product) is mentioned as a suitable product.

The cathode may be any material that is not corroded by the electrolytic solution, and a conductive metal or the like is used. For the negative electrode, for example, an insoluble titanium plate or the like can be used, and an insoluble electrode in which the titanium plate is coated with platinum, a stainless steel (SUS) plate, an In plate, or the like can be used. Moreover, as for the negative electrode, the main surface part is formed in the network.

The interelectrode distance between the anode and the cathode is not particularly specified, but is preferably 10 to 25 mm. When it exceeds 25 mm, since a voltage rises by liquid resistance, the liquid temperature and pH between electrodes rise, the particle size of indium hydroxide powder becomes non-uniform|heterogenous, and the width|variety of a particle size distribution spreads. Moreover, in the case of less than 10 mm, it becomes easy to generate|occur|produce contact between electrodes and a short circuit.

As the electrolyte solution, an aqueous solution of a general electrolyte salt such as a water-soluble nitrate, sulfate, or chloride salt can be used. As the electrolytic solution, an aqueous solution of ammonium nitrate using ammonium nitrate in which nitrate ions and ammonium ions are removed as nitrogen compounds and do not remain as impurities after drying and calcining after precipitating the indium hydroxide powder is preferable.

The electrolyte solution preferably has a solubility of 10 ^-6 to 10 ^-3 mol/ml of the produced indium hydroxide powder. The solubility of indium hydroxide powder ¹⁰ is lower than ⁶ mol / ℓ, since they are easy to be an indium ion is eluted from the anode to the nucleation, the primary particle diameter becomes too fine. Since the separation and recovery of the indium hydroxide powder in the subsequent step of recovering the indium hydroxide powder becomes difficult when the primary particle diameter is too fine, it is not preferable.

On the other hand, when the solubility of indium hydroxide powder ^{is higher than 10 - 3} mol/L, since particle growth is accelerated|stimulated, a primary particle diameter becomes large. For this reason, as the particles grow, the difference in particle diameter between the growing particles and the non-growing particles increases. Since the difference in particle diameter affects the degree of aggregation, as a result, the width of the particle size distribution of the indium hydroxide powder is widened. When the width of the particle size distribution of the indium hydroxide powder is wide, the width of the particle size distribution of the indium oxide powder obtained by calcining the indium hydroxide powder also increases, and the density of the sputtering target obtained by sintering this is not preferable because it is difficult to achieve high density.

Therefore, in the electrolyte solution, the solubility of the indium hydroxide powder should just be in ^{the range of 10 -6} to 10 ^-3 mol/L, and the solubility can be controlled according to the concentration, pH, liquid temperature, and the like of ammonium nitrate.

Although it does not specifically limit about the density|concentration of electrolyte solution, 0.1-2.0 mol/L is preferable. When it is thinner than 0.1 mol/L, the voltage rise during electrolysis becomes large, and the amount of heat generated increases in places with high contact resistance, such as the contact part of the electrode. Accordingly, it is not preferable because problems such as an increase in the temperature of the electrolyte solution or an increase in electric power cost occur due to heat generation of the electrode. When it thickens more than 2.0 mol/L, since the indium hydroxide particle coarsens by electrolysis and the dispersion|variation in particle size becomes large, it is unpreferable.

Although it does not specifically limit about the pH of the electrolyte solution between an anode and a cathode, 3.2-4.0 are preferable. When the pH of the electrolyte solution is less than 3.2, it is difficult to precipitate the hydroxide, and when it is greater than 4.0, the hydroxide precipitation rate is too high and the precipitate is formed in a state of non-uniform concentration, so the particle size becomes non-uniform, and the particle size distribution width becomes It is undesirable to widen. Moreover, it is preferable that the pH of the whole electrolyte solution also becomes 3.2-4.0. When the main surface portion of the negative electrode is formed in a network, the electrolyte is easily circulated through the holes in the network of the negative electrode, and the increase in pH between the electrodes can be suppressed by uniformly mixing the electrolyte as a whole.

The electrolyte between the anode and the cathode, for example, by adjusting the concentration of ammonium nitrate to 0.1 to 2.0 mol/L, the pH to 3.2 to 4.0, and the liquid temperature between the electrodes to the range of 20 to 60° C., the solubility of the indium hydroxide powder is increased to 10 It can be controlled in the range of ^-6 to 10 ^{- 3 mol/L.} pH can be adjusted according to the addition amount of ammonium nitrate.

When the liquid temperature of the electrolyte between the anode and the cathode is lower than 20 ° C, the precipitation rate is too slow, and when it is higher than 60 ° C, the precipitation rate is too fast and the precipitate is formed in a concentration non-uniform state, so the particle size becomes non-uniform, and the hydroxide Since the particle size distribution width of indium powder becomes wide, it is unpreferable. Moreover, it is preferable to control the liquid temperature between electrodes in the range of +/-2 degreeC with respect to the set temperature of an electrolysis apparatus. When the temperature range of the electrolyte between the electrodes is wider than ±2°C, the particle size distribution width of the indium hydroxide powder becomes wider. By controlling the liquid temperature of the electrolytic solution between the electrodes within a range of ±2°C with respect to the set temperature of the electrolysis device, it is possible to obtain an indium hydroxide powder having excellent uniformity in particle size and a narrow particle size distribution. When the main surface of the negative electrode is formed in a network, the electrolyte is easily circulated through the network holes in the negative electrode, and the electrolyte is uniformly mixed as a whole, thereby suppressing an increase in the liquid temperature between the electrodes.

In addition, in order to improve the dissolution stability of indium hydroxide powder, you may add oxygen-containing chelate compounds, such as citric acid, tartaric acid, glycolic acid, and nitrogen-containing chelates, such as EDTA, to electrolyte solution as needed.

Although the electrolysis conditions are not specifically limited, It is preferable to perform a ^{current density at 3 A/dm 2 -} 24 A/dm ^{2 .} When a current density is ^{lower than 3 A/dm<2>} , the production efficiency of indium hydroxide powder will fall. When a current density is ^{higher than 24 A/dm<2>} , the liquid temperature and pH between electrodes will rise by an electrolysis voltage rising, the particle size of indium hydroxide powder becomes non-uniform|heterogenous, and the width|variety of a particle size distribution spreads.

As mentioned above, in the manufacturing method of indium hydroxide powder, the main surface part of the negative electrode used for electrolysis is formed in the mesh|network, so that electrolyte solution becomes easy to circulate through the mesh|network hole of a negative electrode. Accordingly, in the method for producing indium hydroxide powder, the electrolyte solution is uniformly mixed as a whole, suppressing an increase in the liquid temperature and pH between the electrodes, and obtaining an indium hydroxide powder having excellent uniformity of particle size and narrow particle size distribution. . In addition, by controlling the liquid temperature between the electrodes in the range of ±2° C. with respect to the set temperature of the electrolysis device and controlling the pH of the electrolyte between the electrodes in the range of 3.2 to 4.0, the uniformity of the particle size is more excellent and the particle size distribution A narrow indium hydroxide powder can be obtained.

<2. Structure of Cathode>

In the manufacturing method of the above-mentioned indium hydroxide powder, the negative electrode demonstrated below is used. The negative electrode is formed by forming a main surface portion in a network. In addition, the cathode is mainly an insoluble electrode.

For example, the cathode 1A as shown in FIG. 1A. The cathode 1A has a contact portion 2A electrically connected to a power supply portion and a main surface portion 3A mainly in contact with an electrolytic solution and in which an electrolytic reaction occurs. And the cathode 1A has a network shape by forming the hole 4A by lath processing in the main surface part 3A of the cathode.

The cathode 1A is formed into a mesh by alternately forming a number of slits on a Ti plate having a thickness of 1.0 mm, and lathing the plate material in a direction perpendicular to the slits. By processing the cathode 1A into a mesh, the electrolyte solution existing between the electrodes does not stay and circulates between the electrodes.

In the case of lath processing, the mesh shape is not particularly limited, but when a Ti plate having a thickness of 1.0 mm is used, a mesh shape with rhombic holes having a vertical dimension of 3 mm to 4 mm and a horizontal dimension of 6 mm to 7 mm is preferable.

Further, the cathode may be, for example, a cathode 1B as shown in FIG. 1B. The cathode 1B has a contact portion 2B that is electrically connected to a power supply portion of a power source, and a main surface portion 3B that mainly comes in contact with the electrolyte and undergoes an electrolytic reaction. And the negative electrode 1B has a network shape by forming the hole 4B by a punching process in the main surface part 3B of a negative electrode.

In addition, in the cathode, the hole processing by a punching board or etching is also effective, since the electrolyte solution contained between electrodes may circulate without stagnation.

In addition, the cathodes 1A and 1B shown in FIG. 1 are examples, and the shape, size, number, spacing, and the like of the holes are not limited thereto.

The network cathode as described above performs electrolysis by arranging a plurality of sheets alternately in an electrolytic solution together with the anode made of metallic indium, for example. In this electrolysis, by making the shape of the negative electrode a network, the electrolyte solution is circulated through the network negative electrode without staying between the positive electrode and the negative electrode. As a result, the electrolyte is uniformly mixed as a whole, and an increase in the liquid temperature and pH between the electrodes can be suppressed, and an indium hydroxide powder having an excellent particle size uniformity and a narrow particle size distribution can be obtained.

Example

Hereinafter, specific examples to which the present invention is applied have been described, but the present invention is not limited to these examples.

As a condition common to Examples and Comparative Examples, an aqueous solution of 1 mol/L ammonium nitrate was used for the electrolyte. Further, the liquid temperature between the electrodes was set to 40° C., the pH was set to 3.5, and at a current density of 12 A/dm ² , 14 metal indium sheets (size 30 cm×30 cm×4 mm thickness) were electrolytically applied as an anode. Electrolysis was carried out to prepare an indium hydroxide slurry. In addition, the liquid temperature between electrodes was measured by immersing a thermometer in the electrolyte solution between electrodes, and the pH between electrodes took the electrolyte solution between electrodes, and immediately measured the pH of electrolyte solution with a pH meter.

(Example 1)

In Example 1, as a negative electrode for the positive electrode, a 1 mm thick Ti plate was lathed with a mesh pitch of 1 mm to form a rhombic hole with a vertical dimension of 3.2 mm and a horizontal dimension of 6 mm, and 30 cm × 30 cm × A net negative plate having a thickness of 1 mm was used. Electrolysis was performed with the distance between the electrodes of the anode and the cathode being 17 mm, and the transition of the liquid temperature and pH between the electrodes at the time of electrolysis and the particle size distribution of the obtained indium hydroxide powder were confirmed.

As a result, the liquid temperature between the electrodes was almost constant at about 40°C. In addition, the pH of the electrolyte was also approximately constant at about 3.5.

In the cumulative distribution of the particle size of the obtained indium hydroxide powder, 10% particle size (D10): 0.626 µm, 50% particle size (D50): 1.176 µm, and 90% particle size (D90): 1.864 µm.

(Example 2)

In Example 2, as a negative electrode for the positive electrode, a 1 mm thick Ti plate was lathed with a mesh pitch of 1 mm to form a rhombic hole with a vertical dimension of 3.2 mm and a horizontal dimension of 6 mm, and 30 cm × 30 cm × A net negative plate having a thickness of 1 mm was used. Electrolysis was performed with the distance between the electrodes of the anode and the cathode being 25 mm, and the transition of the liquid temperature and pH between the electrodes during electrolysis and the particle size distribution of the obtained indium hydroxide powder were confirmed.

As a result, the liquid temperature between the electrodes was almost constant at about 40°C. In addition, the pH of the electrolyte was also approximately constant at about 3.5.

In the cumulative distribution of the particle size of the obtained indium hydroxide powder, it was 10% particle size (D10): 0.647 µm, 50% particle size (D50): 1.345 µm, and 90% particle size (D90): 2.204 µm.

(Comparative Example 1)

In Comparative Example 1, a flat plate having a thickness of 30 cm × 30 cm × 1 mm was used as the negative electrode for the positive electrode, not the mesh negative electrode. Electrolysis was performed by setting the distance between the electrodes of the anode and the cathode to be 17 mm, and the transition of the liquid temperature and pH between the electrodes during electrolysis and the particle size distribution of the obtained indium hydroxide powder were confirmed.

As a result, the liquid temperature between the electrodes increased with the passage of time. In addition, the pH of the electrolytic solution also increased with the passage of time.

In the cumulative distribution of the particle size of the obtained indium hydroxide powder, 10% particle size (D10): 0.796 µm, 50% particle size (D50): 2.023 µm, and 90% particle size (D90): 3.624 µm.

(Comparative Example 2)

In Comparative Example 2, a flat plate having a thickness of 30 cm × 30 cm × 1 mm was used as the negative electrode for the positive electrode, not the mesh negative electrode. Electrolysis was performed with the distance between the electrodes of the anode and the cathode being 25 mm, and the transition of the liquid temperature and pH between the electrodes during electrolysis and the particle size distribution of the obtained indium hydroxide powder were confirmed.

As a result, the liquid temperature between the electrodes increased with the passage of time. In addition, the pH of the electrolytic solution also increased with the passage of time.

In the cumulative distribution of the particle size of the obtained indium hydroxide powder, 10% particle size (D10): 0.814 µm, 50% particle size (D50): 2.369 µm, and 90% particle size (D90): 4.432 µm.

The integration of these results is shown in FIGS. 2 to 4 . The particle size of the obtained indium hydroxide powder is shown in FIG. 2, the transition of the liquid temperature between electrodes, the transition of the pH in the electrolyte solution between electrodes in FIG. 3, and FIG.

In Fig. 2, in Examples 1 and 2 using a mesh negative electrode, the liquid temperature between the electrodes was almost constant at about 40 ° C., whereas in Comparative Examples 1 and 2 using a flat negative electrode, the liquid temperature increased with the lapse of time. have. Therefore, it turns out that the rise of the liquid temperature between electrodes can be suppressed by using a meshed cathode.

In addition, in FIG. 3, the pH of the electrolyte solution is also approximately constant in Examples 1 and 2 at about 3.5, whereas in Comparative Examples 1 and 2, the pH value is increasing with the passage of time. Therefore, it turns out that the raise of the pH between electrodes can be suppressed by using a meshed cathode.

In addition, in FIG. 4 , in Examples 1 and 2 and Comparative Examples 1 and 2 at 10% particle size, there was no difference as much, whereas at 90% particle size, Comparative Examples 1 and 2 were compared with Examples 1 and 2 It is about twice as large. That is, it can be seen that in the case of applying Example 1 or 2, it is possible to obtain an indium hydroxide powder having an excellent particle size uniformity and a narrow particle size distribution width, compared to the case where Comparative Example 1 or 2 is applied.

As described above, when the present invention is applied, it is possible to obtain an indium hydroxide powder having an excellent uniformity of particle size and a narrow particle size distribution by suppressing an increase in the liquid temperature and pH between the electrodes.

1A, 1B: negative electrode
2A, 2B: contact
3A, 3B: main surface part
4A, 4B: hole

Claims (3)

In the manufacturing method of indium hydroxide powder which produces|generates an indium hydroxide powder by electrolysis in electrolyte solution using the anode and the cathode which consist of metallic indium alternately,
Controlling the liquid temperature between the positive electrode and the negative electrode in the range of 20 ~ 40 ℃,
Controlling the liquid temperature between the anode and the cathode in the range of ±2° C. with respect to the set temperature of the electrolysis device, and controlling the pH of the electrolyte between the anode and the cathode in the range of 3.2 to 4.0,
The main surface part where the electrolytic reaction of the cathode used for the electrolysis occurs is formed in a network,
The method for producing indium hydroxide powder, characterized in that the distance between the electrodes between the anode and the cathode is 10 to 25 mm. delete delete

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