Preparation method of nano indium tin oxide powder

Abstract

The invention provides a preparation method of nano indium tin oxide powder, and belongs to the technical field of preparation of electronic ceramic transparent oxide functional inorganic materials. The preparation method comprises the following steps: in an oxygen-containing environment, performing electric arc gasification on an indium tin metal melt, and oxidizing metal steam generated by the electric arc gasification to obtain the nano indium tin oxide powder, the current applied for generating the electric arc is 500 to 1200 A, and the voltage is 50 to 120 V. The preparation method provided by the invention is simple, the oxidation reaction time is short, no exhaust gas is discharged, and meanwhile, the problems of wastewater and waste acid discharge and difficult impurity removal caused by addition of strong acid are avoided. The preparation method provided by the invention can realize continuous production and is high in production efficiency; and the particle size D50 of the prepared nano indium tin oxide powder can be kept to be less than 0.5 mu m and D90 is less than 1 mu m.

Description

Technical Field

[0001] The invention belongs to the technical field of preparation of electronic ceramic transparent oxide functional inorganic materials, and in particular relates to a method for preparing nano indium tin oxide powder. Background Art

[0002] ITO (Indium Tin Oxide) target is a kind of indium oxide (In 2 O 3 ) and tin oxide (SnO 2 ) are mixed in a certain proportion to prepare a composite material. This special combination gives ITO targets unique physical and chemical properties, with advantages such as high transmittance, low resistivity, strong mechanical hardness, and good chemical stability, making ITO targets widely used in optoelectronic fields such as panels and photovoltaics.

[0003] The conventional preparation method of ITO targets is to prepare indium oxide and tin oxide powders separately, then mix the two powders into ITO powder or slurry, and then form and sinter them into ITO targets. The process is long and the efficiency is low. In order to improve the production efficiency of ITO targets, it is considered to optimize the process from each process part of the production process. Among them, the forming and sintering parts are the key processes for preparing ceramic products. In order to ensure the performance of ceramic targets, it is necessary to retain the necessary forming and sintering time. The optimization space for improving efficiency is very limited. Therefore, people focus on the preparation of indium tin oxide (ITO) powder to improve the production efficiency of ITO targets.

[0004] In the prior art, ITO powder is generally prepared by preparing a mixed salt solution of indium and tin, generating an indium tin precursor at a suitable pH, and then sintering it at high temperature, or by dissolving indium in a strong acid, preparing an indium tin mixed salt solution, and reacting it at high pressure and low temperature in a reactor to prepare ITO powder.

[0005] However, the above methods have many preparation steps, long processes, and a large amount of waste gas emissions. In addition, due to the addition of strong acid, a large amount of waste water and waste acid are discharged, and the introduced impurities (such as some anions, etc.) are difficult to completely remove. Summary of the invention

[0006] In view of this, the purpose of the present invention is to provide a method for preparing nano indium tin oxide powder. The preparation method provided by the present invention is simple, has a short oxidation reaction time, has no waste gas emission, and avoids the problem of waste water and waste acid emission caused by the addition of strong acid and the difficulty in removing impurities.

[0007] In order to achieve the above object, the present invention provides the following scheme:

[0008] The present invention provides a method for preparing nano indium tin oxide powder, comprising the following steps:

[0009] In an oxygen-containing environment, arc gasification is performed on the indium tin metal melt, and the metal vapor generated by the arc gasification is oxidized to obtain the nano indium tin oxide powder;

[0010] The electric arc is generated by applying a current of 500-1200A and a voltage of 50-120V.

[0011] Preferably, the electric arc is generated by energizing an anode and a cathode; the anode comprises a conductive container and a molten indium tin metal placed in the conductive container; and the cathode comprises a graphite electrode.

[0012] Preferably, the indium tin metal melt is conveyed to the arc gasification step by inert gas pressure, and the preparation of the indium tin metal melt comprises the following steps:

[0013] Under the protection of protective gas, the indium ingot and the tin ingot are melted to obtain an indium-tin metal melt;

[0014] The indium tin metal melt is kept warm.

[0015] Preferably, the inert gas includes argon, and the pressure of the inert gas is 0.1-0.6 MPa.

[0016] Preferably, the transport is carried out through a heat-insulating conduit, and the temperature of the heat-insulating conduit is 200-400°C.

[0017] Preferably, the mass ratio of the indium ingot to the tin ingot is (80-100):(0.5-20).

[0018] Preferably, the smelting temperature is 300-500°C.

[0019] Preferably, the protective gas includes nitrogen or argon, and the protective gas flow rate is 5 to 100 L / min.

[0020] Preferably, the insulation temperature is 150-300°C.

[0021] Preferably, the nano-indium tin oxide powder has a D50 of less than 0.5 μm and a D90 of less than 1 μm.

[0022] The present invention provides a method for preparing nano indium tin oxide powder, comprising the following steps: arc gasification of indium tin metal melt in an oxygen-containing environment, oxidation of metal vapor generated by the arc gasification, and obtaining the nano indium tin oxide powder; the current applied to generate the arc is 500-1200A, and the voltage is 50-120V. The preparation method provided by the present invention is simple, has a short oxidation reaction time, has no waste gas emission, and avoids the problem of waste water and waste acid emission caused by the addition of strong acid and the difficulty in removing impurities, and belongs to an environmentally friendly technology.

[0023] The indium tin oxide nanoparticles prepared by the present invention have controllable size, complete crystallization, uniform morphology, and can be directly used for ITO target material preparation to improve target material production efficiency. The present invention controls the current at 500-1200A and the voltage at 50-120V, so that the particle size of the prepared nano indium tin oxide powder can be maintained at D50<0.5μm and D90<1μm. Specifically, the change of current and voltage values ​​affects the powder because as the current and voltage values ​​passed increase, the heat provided also increases. When the current and voltage values ​​exceed a certain limit (current>1200A, voltage>120V), the powder particle size begins to gradually increase, resulting in D50>0.3μm. The reason is that the indium tin metal melt evaporates into indium tin atoms and then reacts with oxygen atoms in the air to oxidize to form indium tin oxide powder. The indium tin oxide grains grow under the influence of ambient temperature, and the growth stops after the air cools the powder to a certain temperature. When the heat provided is higher, the grain growth rate is also faster, and the powder cannot be cooled in time, causing it to grow excessively, thus affecting the particle size results.

[0024] The prior art also uses metal indium ingots and tin ingots as raw materials, obtains metal melt after pre-melting, and then introduces oxygen for oxidation during the heating ball milling process, and the process is simple. However, this method performs oxidation reaction when the metal indium and tin are in the liquid phase, and relies on ball milling to reduce their particle size. The effect of refining the particle size is limited, and the average particle size of the powder is greater than 1μm, which is not conducive to the improvement of the performance of the ITO target material. The present invention heats the indium tin metal melt, and then transports the heat-insulated indium tin metal melt to the arc gasification step under inert gas pressure. The method can achieve continuous production with high production efficiency; the present invention can obtain nanoscale indium tin oxide powder with small particle size (D50<0.5μm, D90<1μm) in large quantities, and the powder particle size distribution is uniform, which is conducive to improving the performance of the indium tin oxide target material, such as density, and is conducive to the production of indium tin oxide targets.

[0025] Furthermore, the present invention controls the inert gas pressure at 0.1-0.6 MPa, which can speed up the transmission speed of the indium tin melt and improve the output to a certain extent. However, after the inert gas pressure is further increased, it is limited by the arc heat and the output is not significantly improved. Further increasing the pressure will result in a large waste of inert gas.

[0026] The present invention exhibits significant advantages in terms of manufacturing cost, product performance, large-scale production and environmental friendliness. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0028] Figure 1 Schematic diagram of the process of the present invention; in the figure: 1-smelting furnace, 2-insulating furnace, 3-insulating conduit, 4-vaporization furnace, 5-powder destination;

[0029] Figure 2 This is a scanning electron microscope image (SEM image) of the nano indium tin oxide powder prepared in Example 1;

[0030] Figure 3 This is the XRD spectrum of the nano indium tin oxide powder prepared in Example 1. DETAILED DESCRIPTION

[0031] The present invention provides a method for preparing nano indium tin oxide powder, comprising the following steps:

[0032] In an oxygen-containing environment, the indium tin metal melt is arc-gasified, and the metal vapor generated by the arc gasification is oxidized to obtain the nano indium tin oxide powder; the current applied to generate the arc is 500-1200A and the voltage is 50-120V.

[0033] Unless otherwise specified, the materials and equipment used in the present invention are commercially available products.

[0034] In the present invention, the electric arc is preferably generated by energizing an anode and a cathode; the anode preferably includes a molten metal and a conductive container; the cathode preferably includes a graphite electrode; and the conductive container preferably includes a graphite crucible.

[0035] In the present invention, the indium tin metal melt is preferably conveyed to the arc gasification step by inert gas pressure, and the preparation of the indium tin metal melt preferably includes the following steps:

[0036] The present invention melts indium ingots and tin ingots under the protection of protective gas to obtain indium tin molten liquid;

[0037] The indium tin metal melt is kept warm.

[0038] In the present invention, the protective gas preferably includes nitrogen or argon; the protective gas flow rate is preferably 5 to 100 L / min. In an embodiment of the present invention, it can be 5 L / min, 10 L / min, 20 L / min, 30 L / min, 40 L / min, 50 L / min, 60 L / min, 70 L / min, 80 L / min or 100 L / min.

[0039] In the present invention, the mass ratio of the indium ingot and the tin ingot is preferably (80-100): (0.5-20), and in the embodiment of the present invention, it can be 80:0.5, 80:5, 80:10, 35.10:1, 80:20, 90:5, 90:15, 90:20, 100:5, 100:10 or 100:20. In the present invention, the purity of the indium ingot and the tin ingot is ≥4N. In the present invention, the smelting temperature is preferably 300-500°C, and in the embodiment of the present invention, it can be 300°C, 350°C, 400°C, 450°C or 500°C.

[0040] In the present invention, the insulation temperature is preferably 150-300° C., and in the embodiment of the present invention, it can be 150° C., 180° C., 200° C., 220° C., 250° C. or 300° C. In the present invention, the inert gas pressure is preferably 0.1-0.6Mpa, and in the embodiment of the present invention, it can be 0.1Mpa, 0.2Mpa, 0.3Mpa, 0.4Mpa, 0.5Mpa or 0.6Mpa; the inert gas preferably includes argon.

[0041] The present invention controls the inert gas pressure at 0.1-0.6 MPa, which can speed up the transmission of the indium tin melt and improve the yield to a certain extent. However, after the inert gas pressure is further increased, it is limited by the arc heat and the yield is not significantly increased. Further increasing the pressure will waste a lot of inert gas.

[0042] In the present invention, the transportation is preferably carried out through an insulated conduit, and the temperature of the insulated conduit is preferably 200-400°C. In the embodiments of the present invention, it can be 200°C, 220°C, 250°C, 300°C, 350°C or 400°C.

[0043] After the transportation is completed, the present invention performs arc gasification on the indium tin metal melt in an oxygen-containing environment, and the metal vapor generated by the arc gasification is oxidized to obtain the nano indium tin oxide powder.

[0044] In the present invention, the oxygen-containing environment preferably includes air at room temperature or oxygen. In the present invention, the arc gasification is preferably performed in a gasification furnace. The present invention has no special requirements for the gasification furnace, as long as it can implement the solution of the present invention.

[0045] In the present invention, the current applied to generate the arc is 500-1200A, and in the embodiment of the present invention, it can be 500A, 600A, 700A, 800A, 900A, 1000A, 1100A or 1200A; the voltage applied to generate the arc is 50-120V, and in the embodiment of the present invention, it can be 50V, 60V, 70V, 80V, 90V, 100V, 110V or 120V. In the present invention, the D50 of the nano-indium tin oxide powder is less than 0.5μm and the D90 is less than 1μm.

[0046] The present invention controls the current at 500-1200A and the voltage at 50-120V, and can keep the particle size of the prepared nano indium tin oxide powder at D50<0.5μm and D90<1μm. Specifically, the change of current and voltage values ​​affects the powder because as the current and voltage values ​​increase, the heat provided also increases. When the current and voltage values ​​exceed a certain limit (current>1200A, voltage>120V), the powder particle size begins to gradually increase, resulting in D50>0.3μm. The reason is that after the indium tin melt evaporates into indium tin atoms, it reacts with oxygen atoms in the air to oxidize to form indium tin oxide powder. The indium tin oxide grows grains under the influence of ambient temperature, and stops growing after the air cools the powder to a certain temperature. When the heat provided by the vaporization furnace is higher, the grain growth rate is also faster, and the powder cannot be cooled in time, resulting in excessive growth, thereby affecting the particle size result.

[0047] The present invention preferably cools the generated powder rapidly under the action of air; the air is transported by a fan (the air is sucked into the device by the fan from the environment), and the processing air volume of the fan is preferably 3000-7000m 3 / h, which can be 3000m / h in the embodiment of the present invention. 3 / h、3500m 3 / h、4000m 3 / h、4500m 3 / h、5000m 3 / h、6000m 3 / h or 7000m 3 In the present invention, a small air volume affects the cooling effect of the powder, and a large air volume places high demands on the powder collecting device, resulting in a waste of investment cost and floor space.

[0048] The present invention preferably collects the indium tin oxide powder through a multi-stage powder collection system under the action of a fan. The present invention has no special requirements for the multi-stage powder collection system, and any system familiar in the art can be used.

[0049] The present invention sequentially heats the indium tin metal melt, and then transports the heat-insulated indium tin metal melt to an arc gasification step under an inert gas pressure. The method can realize continuous production with high production efficiency.

[0050] The preparation method provided by the present invention is simple, the oxidation reaction time is short, and no waste water or waste acid is discharged during the process, which belongs to environmentally friendly technology; the indium tin oxide nanoparticles prepared by the present invention are controllable in size, complete in crystallization, and uniform in morphology, and can be directly used for ITO target material preparation to improve the target material production efficiency. The present invention can obtain nanoscale indium tin oxide powder with small particle size (D50 < 0.5 μm, D90 < 1 μm) in large quantities, and the powder particle size distribution is uniform, which is beneficial to improving the performance of indium tin oxide target material, such as density, and is beneficial to the production of indium tin oxide target material. The present invention shows significant advantages in terms of manufacturing cost, product performance, large-scale production and environmental friendliness.

[0051] In order to further illustrate the present invention, a method for preparing a nano indium tin oxide powder provided by the present invention is described in detail below in conjunction with the accompanying drawings and examples, but they should not be construed as limiting the scope of protection of the present invention.

[0052] Example 1

[0053] like Figure 1 The process schematic diagram of the present invention is shown in FIG. Indium ingot and tin ingot are weighed at a weight ratio of 35.10:1, placed in a crucible of a smelting furnace, 50 L / min of argon gas is introduced into the smelting furnace, the smelting furnace is started, heated to 400°C, and kept warm, so that the indium ingot and the tin ingot are melted into liquid and kept in a stirring state, forming a uniform indium-tin metal melt;

[0054] The holding furnace and the holding conduit are heated to 300° C. and kept warm, the indium tin metal melt is poured into the crucible of the holding furnace, the holding furnace cover is closed, and argon gas at a pressure of 0.4 MPa is filled into the crucible of the holding furnace, so that the indium tin metal melt is input into the crucible of the vaporization furnace through the holding conduit under the argon pressure;

[0055] The powder collection system is turned on, and the working parameters of the vaporization furnace are set to 1000A current and 80V voltage to generate an arc. The anode is the insulated indium tin metal melt, and the cathode is the graphite electrode. Under the high temperature of the arc, the indium tin metal melt quickly evaporates and gasifies, and reacts with oxygen atoms under the action of air to generate ITO powder, which is quickly cooled under the action of air. The air is sucked into the equipment by the fan, and the processing air volume of the fan is 4500m 3 / h, and then the nano-indium tin oxide powder is collected by a multi-stage powder collection system under the action of a fan.

[0056] Example 2

[0057] The same as Example 1, except that the operating parameters of the vaporization furnace are set to current 1000A and voltage 50V.

[0058] Example 3

[0059] The same as Example 1, except that the operating parameters of the vaporization furnace are set to current 1000A and voltage 100V.

[0060] Example 4

[0061] The same as Example 1, except that the working parameters of the vaporization furnace are set to current 1000A and voltage 120V.

[0062] Example 5

[0063] The same as Example 1, except that the operating parameters of the vaporization furnace are set to current 600A and voltage 80V.

[0064] Example 6

[0065] The same as Example 1, except that the operating parameters of the vaporization furnace are set to current 800A and voltage 80V.

[0066] Example 7

[0067] The same as Example 1, except that the operating parameters of the vaporization furnace are set to current 1200A and voltage 80V.

[0068] Example 8

[0069] The same as Example 1, except that the pressure of the argon gas introduced into the crucible of the holding furnace is changed to 0.2 MPa.

[0070] Example 9

[0071] The same as Example 1, except that the pressure of the argon gas introduced into the crucible of the holding furnace is changed to 0.6 MPa.

[0072] Comparative Example 1

[0073] The same as Example 1, except that the operating parameters of the vaporization furnace are set to current 1000A and voltage 150V.

[0074] Comparative Example 2

[0075] The same as Example 1, except that the operating parameters of the vaporization furnace are set to current 1500A and voltage 100V.

[0076] The particle size and specific surface area of ​​the nano-indium tin oxide powder obtained in Examples 1 to 9 and Comparative Examples 1 to 2 were tested. The specific results are shown in Table 1.

[0077] Table 1 Test results of nano indium tin oxide powder obtained in Examples 1 to 9 and Comparative Examples 1 to 2

[0078] - D10(μm) D50(μm) D90(μm) <![CDATA[BET(m 2 / g)]]> Output (kg / h) Example 1 0.104 0.195 0.478 13.856 25.2 Example 2 0.104 0.194 0.477 13.857 18.8 Example 3 0.109 0.210 0.505 11.575 27.4 Example 4 0.115 0.260 0.585 10.285 30.6 Example 5 0.102 0.194 0.477 13.857 17.7 Example 6 0.104 0.194 0.475 13.855 21.1 Example 7 0.106 0.209 0.499 12.025 26.4 Example 8 0.105 0.196 0.479 13.850 22.5 Example 9 0.104 0.192 0.474 13.868 26.0 Comparative Example 1 0.122 0.302 0.652 9.166 35.2 Comparative Example 2 0.121 0.310 0.660 9.023 35.6

[0079] The results of the embodiment show that as the current and voltage values ​​input to the vaporizer change, the particle size and output of the powder change. As the argon pressure input to the crucible of the holding furnace changes, the main change is the output of the powder, and the powder properties (such as particle size and specific surface area) are basically not affected. The change in current and voltage values ​​affects the powder because as the current and voltage values ​​passed into the vaporizer increase, the heat provided by the vaporizer also increases, which accelerates the volatilization rate of the indium tin melt, resulting in an increase in output; and when the current and voltage values ​​exceed a certain limit (current>1200A, voltage>120V), the powder particle size begins to gradually increase, resulting in D50>0.3μm, because the indium tin melt evaporates into indium tin atoms and then reacts with oxygen atoms in the air to oxidize to form indium tin oxide powder, and the indium tin oxide grains grow under the influence of ambient temperature, and the growth stops after the air cools the powder to a certain temperature. When the heat provided by the vaporization furnace is higher, the grain growth rate is also faster, and the powder cannot be cooled in time, causing it to grow excessively, thus affecting the particle size results.

[0080] The effect of the argon pressure introduced into the crucible of the holding furnace on the output is that the increase in argon pressure speeds up the transmission speed of the molten liquid, which increases the output to a certain extent. However, when the argon pressure is further increased, the output is limited by the arc heat and the increase in output is not obvious. Further increasing the pressure will result in a large waste of argon.

[0081] In summary, taking into account the powder performance, output, cost and other factors, in Example 1, the operating parameters of the vaporization furnace are 1000A current, 80V voltage, and the argon pressure introduced into the crucible of the insulation furnace is 0.4Mpa, which is the optimal result of the present invention. The powder has a small particle size and is evenly distributed, and has a large specific surface area.

[0082] Figure 2 This is a scanning electron microscope image (SEM image) of the nano indium tin oxide powder prepared in Example 1; Figure 3 This is the XRD spectrum of the nano indium tin oxide powder prepared in Example 1 (where the ordinate is Intensity (Counts), the blue line on the figure shows the standard diffraction peak position of cubic indium oxide, and the blue small characters indicate the standard PDF card number of cubic indium oxide #06-0416). It can be seen from the SEM image that the indium tin oxide powder prepared in Example 1 is all nanometer-scale particles, and the XRD results show that it is cubic indium oxide, no tin oxide phase is detected, and the lattice parameters of indium oxide change, indicating that tin oxide has been uniformly mixed into indium oxide, which is beneficial to the preparation of ITO target material.

[0083] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention, not all of the embodiments. People can also obtain other embodiments based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for preparing nano indium tin oxide powder, characterized in that: The following steps are involved: In an oxygen-containing environment, arc gasification is performed on the indium tin metal melt, and the metal vapor generated by the arc gasification is oxidized to obtain the nano indium tin oxide powder; The electric arc is generated by applying a current of 500-1200A and a voltage of 50-120V.

2. The preparation method according to claim 1, characterized in that: The electric arc is generated by energizing an anode and a cathode; the anode comprises a conductive container and a molten indium tin metal placed in the conductive container; and the cathode comprises a graphite electrode.

3. The preparation method according to claim 1 or 2, characterized in that: The indium tin metal melt is transported to the arc gasification step by inert gas pressure. The preparation of the indium tin metal melt includes the following steps: Under the protection of protective gas, the indium ingot and the tin ingot are melted to obtain an indium-tin metal melt; The indium tin metal melt is kept warm.

4. The preparation method according to claim 3, characterized in that: The inert gas includes argon, and the pressure of the inert gas is 0.1-0.6 MPa.

5. The preparation method according to claim 3 or 4, characterized in that: The transportation is carried out through a heat-insulating conduit, and the temperature of the heat-insulating conduit is 200-400°C.

6. The preparation method according to claim 3, characterized in that: The mass ratio of the indium ingot to the tin ingot is (80-100):(0.5-20).

7. The preparation method according to claim 3 or 6, characterized in that: The smelting temperature is 300-500°C.

8. The preparation method according to claim 3, characterized in that: The protective gas includes nitrogen or argon, and the flow rate of the protective gas is 5 to 100 L / min.

9. The preparation method according to claim 3, characterized in that: The insulation temperature is 150-300°C.

10. The preparation method according to claim 1, 2, 4 or 6, characterized in that: The nano-indium tin oxide powder has a D50 of less than 0.5 μm and a D90 of less than 1 μm.

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