Method for preparing ITO powder by using ITO waste target

Abstract

The invention discloses a method for preparing indium tin oxide (ITO) powder by using an ITO waste target, and belongs to the technical field of indium tin secondary resource recovery. Placing the ITO waste target powder in a double-temperature-zone tubular roasting furnace for roasting; the double-temperature-zone tubular roasting furnace comprises a first temperature zone and a second temperature zone, reducing gas is introduced into the first temperature zone, the temperature is set to be 875-1000 DEG C, oxidizing gas is introduced into the second temperature zone, and the temperature is set to be 1050-1150 DEG C; the ITO waste target powder is placed in the first temperature zone, and a graphite filter membrane is arranged at a gas outlet of the second temperature zone to collect the ITO powder. According to the method, the ITO waste target material is used as a raw material, the ITO powder product with high additional value is directly obtained through high-temperature roasting, efficient recycling and reutilization of the ITO waste target material are truly achieved, and the composition of the obtained ITO powder meets the standard YS / T 1353-2020.

Description

Technical Field

[0001] The invention relates to a method for recycling waste ITO targets, in particular to a method for preparing ITO powder by utilizing waste ITO targets based on hydrogen reduction, and belongs to the technical field of recycling indium tin secondary resources. Background Art

[0002] ITO (indium tin oxide) is a solid solution compound of indium oxide and tin oxide, of which the indium oxide content is about 80~90%, the tin oxide content is about 10~20%, and except for indium, tin and oxygen elements, the content of other impurities is extremely low. In the production and use of ITO targets, a large amount of waste ITO targets (i.e., ITO waste targets) will be generated due to low sputtering coating efficiency or other factors. These waste targets still contain incompletely utilized indium and tin oxides, and have the characteristics of high temperature resistance and corrosion resistance. However, due to the high loss rate of indium during sputtering (about 30%~70%), a large amount of ITO waste targets have accumulated, making it an important secondary resource that urgently needs to be recycled.

[0003] At present, existing patent technologies disclose some methods for remaking ITO powder using ITO waste targets. For example, Chinese patent (CN110498443B) discloses a method for remaking ITO powder using ITO waste targets, which specifically involves acid leaching and filtering the ITO waste target powder, adding nitrate to obtain an electrolyte, then collecting the ITO precursor through constant voltage electrolysis, and finally obtaining ITO powder through high-temperature calcination. Chinese patent (CN107129277B) discloses a method for preparing ITO target material from ITO waste target recycled powder, which specifically involves adding tin oxide or indium oxide powder to the ITO waste target recycled powder, mixing it, adding water to ball milling, spray drying it, putting it into a mold and gradually pressurizing it, and cold isostatic pressing it to form a green body, and the green body is heat-insulated and degreased, and then sintered in an oxygen atmosphere to form an ITO target material. A Chinese patent (CN111606353 B) discloses a method for recovering ITO powder from ITO target grinding waste liquid. The specific operation is to chemically deoil the ITO powder obtained after treating the ITO target grinding waste liquid to obtain a mixed powder of ITO and SiC, and then separate the mixed powder by specific gravity in a saturated sucrose aqueous solution to obtain a coarse ITO powder. Finally, the coarse ITO powder is washed and dried in sequence to obtain ITO powder. Although these methods can recover ITO powder, there are still some key problems, such as serious powder agglomeration and difficulty in accurately controlling the indium-tin ratio, which affect the quality and application value of the recovered products. Summary of the invention

[0004] In view of the technical problems existing in the existing methods for recycling ITO waste targets and re-preparing ITO powder, the purpose of the present invention is to provide a method for preparing ITO powder using ITO waste targets. This method uses ITO waste target materials as raw materials and directly obtains high-value-added ITO powder products through high-temperature roasting, truly realizing the efficient recycling and reuse of ITO waste targets, and the composition of the obtained ITO powder meets the standard YS / T 1353-2020.

[0005] In order to achieve the above technical objectives, the present invention provides a method for preparing ITO powder using ITO waste targets, the method comprising placing the ITO waste target powder in a double-temperature-zone tubular roasting furnace for roasting; the double-temperature-zone tubular roasting furnace comprises a first temperature zone and a second temperature zone, a reducing gas is introduced into the first temperature zone, and the temperature is set to 875-1000°C, an oxidizing gas is introduced into the second temperature zone, and the temperature is set to 1050-1150°C; the ITO waste target powder is placed in the first temperature zone, and a graphite filter membrane is arranged at the gas outlet of the second temperature zone to collect the ITO powder.

[0006] The key to the technical solution of the present invention is to make full use of the characteristics of low-priced indium / tin oxides having high and similar saturated vapor pressures, firstly by controlling the appropriate temperature and reducing atmosphere in the first temperature zone, reducing the ITO waste target to indium oxide and stannous oxide and volatilizing them, and then the volatilized indium oxide and stannous oxide enter the second temperature zone, and realize directional oxidation under appropriate oxidizing atmosphere and higher temperature conditions to generate stable ITO powder.

[0007] The technical solution of the present invention uses ITO waste targets as raw materials and directly obtains high-value-added ITO powder through high-temperature roasting, which meets the standard YS / T 1353-2020 and overcomes the technical problems of the existing technology that the ITO powder prepared using ITO waste target materials is seriously agglomerated and the indium-tin ratio is difficult to accurately control. The first temperature zone of the present invention performs reduction volatilization under a reducing atmosphere and relatively low temperature conditions, which can remove most of the non-volatile impurities in the ITO waste targets and reduce the surface activity of the volatiles, while the second temperature zone performs oxidation deposition under an oxidizing atmosphere and relatively high temperature conditions, which can quickly stabilize the surface structure of the volatiles, form a protective oxide layer, and deposit at the same time. The high-temperature coordinated treatment under two different atmospheres avoids the deviation of the composition caused by melting or excessive reduction caused by high-temperature oxidation in a single step. In the second temperature zone, the gas-phase low-valent oxides (stannous oxide, indium oxide) generated by reduction in the first temperature zone are re-oxidized to a stable oxidation state (SnO 2 、In 2 O 3 ), restore the stoichiometric ratio of ITO (In 2 O 3 :SnO 2≈9:1), while forming a dense oxide layer to inhibit physical contact and high-temperature diffusion between particles. The surface oxide layer generated in an oxidizing atmosphere can hinder grain boundary migration, reduce the driving force for sintering between particles, and thus inhibit agglomeration. At the same time, the high thermal conductivity and chemical inertness of the graphite filter membrane can be used to quickly cool the high-temperature powder at the outlet, shorten the time the particles are in a high-temperature state, reduce surface atomic migration and sintering tendencies, and the microporous structure of the graphite filter membrane can mechanically separate particles to prevent secondary agglomeration caused by airflow impact.

[0008] As a preferred solution, the indium grade of the ITO waste target is 70-75%, and the tin grade is 7-9%.

[0009] As a preferred solution, the particle size of the ITO waste target powder satisfies that the mass percentage of the particle size less than 200 mesh is 100%. The ITO waste target powder is obtained by crushing and grinding the TO waste target material. Its smaller particle size can significantly increase the specific surface area of ​​the particles, thereby improving its reaction activity and helping to improve its reaction efficiency. If the particle size of the ITO waste target is too large, it will lead to incomplete reduction, thereby affecting the stability of the recycling process and the quality of the final product.

[0010] As a preferred solution, the reducing gas is H 2 The concentration of the gas is in the range of 20~30vol%, and the carrier gas is a non-reactive gas. 2 The concentration can ensure the full reduction of indium oxide and prevent tin oxide from being over-reduced to metallic tin. Based on the reducing gas atmosphere, controlling the temperature within the range of 875~1000℃ helps indium oxide and tin oxide to be converted into indium oxide and stannous oxide and volatilize smoothly. If the temperature is too low, it will lead to incomplete volatilization, and if the temperature is too high, it will lead to over-reduction to generate metallic indium and metallic tin.

[0011] As a preferred embodiment, the oxidizing gas is O 2 The concentration of the gas is in the range of 7.5~12.5vol%, and the carrier gas is a non-reactive gas. 2 The concentration can ensure the full oxidation of indium oxide and stannous oxide in the gas phase, and avoid incomplete oxidation due to too low oxygen concentration. Based on the oxidizing gas atmosphere, the temperature is controlled within the range of 1050~1150℃. If the temperature is too low, it will trigger a disproportionation reaction, and avoid the oxidation of the disproportionation products during the transmission process to form impurities, thereby causing particle size segregation.

[0012] As a preferred solution, the calcination time is not less than 60 min. The calcination time is preferably more than 1 hour, which can ensure that indium oxide and tin oxide are fully volatilized, improve recovery efficiency and product quality, and at the same time ensure complete oxidation of indium oxide and tin oxide in the gas phase, thereby improving the uniformity and quality of the final product.

[0013] Compared with the prior art, the technical solution of the present invention brings the following beneficial technical effects:

[0014] (1) The method for preparing ITO powder using ITO waste targets provided by the present invention not only efficiently recovers indium tin secondary resources, but also successfully prepares ITO powder that meets industrial production requirements (meeting standard YS / T 1353-2020). Compared with the traditional method for recycling ITO waste targets, the present invention directly uses ITO waste targets to prepare ITO nanopowder, innovatively realizing short-process, high-value-added resource utilization, and providing an efficient and feasible new solution for the recycling of ITO waste targets.

[0015] (2) The method for preparing ITO powder using ITO waste targets provided by the present invention fully utilizes the characteristics of low-priced indium / tin oxides having high and similar saturated vapor pressures. By controlling the atmosphere and temperature, the indium oxide and tin oxide in the ITO waste targets are first volatilized in the form of indium oxide and stannous oxide with high selectivity, and then converted into indium oxide and tin oxide to generate stable ITO powder. This process realizes the efficient conversion of ITO waste targets into qualified ITO functional materials and realizes the comprehensive utilization of indium tin secondary resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a schematic diagram of a device for preparing ITO powder using ITO waste targets according to the present invention. DETAILED DESCRIPTION

[0017] The following examples are intended to further illustrate the present invention, rather than to limit the scope of protection of the claims of the present invention.

[0018] Comparative Example 1

[0019] Compared with Example 1, the only difference is that the H in the first stage atmosphere is controlled 2 The concentration is 5 vol%.

[0020] Since the first stage reducing atmosphere H 2 Too low a concentration is not conducive to the reduction of indium oxide and tin oxide to indium oxide and stannous oxide.

[0021] The experimental results show that the volatilization rate of indium component in ITO waste target is 71.2%, and the volatilization rate of tin component is 85.3%. 2When the concentration is too low, indium oxide and tin oxide are not fully reduced, and indium oxide is more difficult to reduce than tin oxide.

[0022] Comparative Example 2

[0023] Compared with Example 1, the only difference is that the H in the first stage atmosphere is controlled 2 The concentration is 35 vol%.

[0024] Since the first stage reducing atmosphere H 2 If the concentration is too high, indium oxide and tin oxide will be excessively reduced to metallic indium and metallic tin.

[0025] The experimental results show that the volatilization rate of indium component in ITO waste target is 95.4%, and the volatilization rate of tin component is 81.2%. 2 When the concentration is too high, tin oxide and indium oxide are over-reduced to metallic tin and metallic indium, and tin oxide is more easily over-reduced.

[0026] Comparative Example 3

[0027] Compared with Example 1, the only difference is that the first stage reduction temperature is controlled to be 800°C.

[0028] Since the reduction temperature in the first stage is too low, it is not conducive to the reduction of indium oxide and tin oxide to indium oxide and stannous oxide.

[0029] The experimental results show that the volatilization rate of indium component in ITO waste target is 84.2%, and the volatilization rate of tin component is 88.6%. Due to the low temperature, indium oxide and tin oxide are not fully reduced.

[0030] Comparative Example 4

[0031] Compared with Example 1, the only difference is that the O in the second oxidation atmosphere is controlled 2 The concentration is 5 vol%.

[0032] Since the second stage oxidizing atmosphere O 2 When the concentration is too low, it is not conducive to the oxidation of indium oxide and stannous oxide to indium oxide and tin oxide.

[0033] Analysis of the experimental results: In in the prepared ITO powder 2 O 3 The mass fraction of SnO is 86.11%, 2 The mass fraction of O is 9.52%, and its composition does not meet the standard YS / T 1353-2020. 2 The concentration is too low, and indium oxide and stannous oxide are not completely oxidized, resulting in a small amount of indium tin alloy.

[0034] Comparative Example 5

[0035] Compared with Example 1, the only difference is that the oxidation temperature of the second stage is controlled at 1000 °C.

[0036] Since the temperature of the second stage is too low, it is not conducive to the oxidation of indium oxide and tin oxide to indium oxide and tin oxide.

[0037] Analysis of the experimental results: In the prepared ITO powder, the mass fraction of In 2 O 3 is 82.53%, and the mass fraction of SnO 2 is 9.03%. Its composition does not meet the standard YS / T 1353-2020. Due to the low temperature, indium oxide and tin oxide are not completely oxidized, and a small amount of indium-tin alloy is formed.

[0038] Example 1

[0039] Using the ITO sputtering waste target corner materials of a certain factory (the metal In content is 72.9 wt.%, the In 2 O 3 content is 87.5 wt.%, the metal Sn content is 7.9 wt.%, and the SnO 2 content is 10.1 wt.%) as raw materials. First, 10 g of the ITO waste target is crushed and ground evenly (the particle size meets that the mass percentage of the particle size less than 200 mesh reaches 100%). The evenly ground ITO waste target powder is loaded into an alumina crucible and placed in the first temperature zone of a two-temperature zone tubular calcination furnace; then nitrogen is introduced to exhaust the excess air in the tube, and the atmosphere of the first temperature zone is controlled to be 20 vol% H 2 (the carrier gas is nitrogen), the temperature is 1000 °C, and the atmosphere of the second temperature zone is 10 vol% O 2 (the carrier gas is nitrogen), and calcination is carried out under the condition that the temperature is 1100 °C. The calcination time is about 70 min. Finally, the obtained ITO powder is collected by using the graphite filter membrane arranged at the gas outlet of the second temperature zone.

[0040] Analysis of the experimental results: In the prepared ITO powder, the mass fraction of In 2 O 3 is 89.86%, and the mass fraction of SnO 2 is 10.13%. Since the indium / tin components are basically completely volatilized during the volatilization process, the chemical stoichiometric ratio of In 2 O 3 :SnO 2 ≈9:1 can be restored, and its composition meets the standard YS / T 1353-2020.

[0041]

[0042] Example 2

[0043] The scraps of ITO sputtering targets from a certain factory (metal In content is 72.9 wt.%, In 2 O 3 The content is 87.5 wt.%, the metal Sn content is 7.9 wt.%, SnO 2 First, 10g of ITO waste target was crushed and ground evenly (the mass percentage of the particle size less than 200 mesh was 100%), and the evenly ground ITO waste target powder was put into an alumina crucible and placed in the first temperature zone of a double-temperature zone tubular roasting furnace; then nitrogen was introduced to exhaust the excess air in the furnace, and the atmosphere in the first temperature zone was controlled to be 30 vol% H 2 , the temperature is 875℃, and the atmosphere in the second temperature zone is 10 vol% O 2 The calcination was carried out at a temperature of 1100°C for about 70 minutes; finally, the obtained ITO powder was collected by using a graphite filter membrane set at the gas outlet of the second temperature zone.

[0044] Analysis of the experimental results: In in the prepared ITO powder 2 O 3 The mass fraction of SnO is 89.92%, 2 The mass fraction is 10.07%, and its composition meets the standard YS / T 1353-2020.

[0045]

[0046] Example 3

[0047] The scraps of ITO sputtering targets from a certain factory (metal In content is 72.9 wt.%, In 2 O 3 The content is 87.5 wt.%, the metal Sn content is 7.9 wt.%, SnO 2 First, 10g of ITO waste target was crushed and ground evenly (the mass percentage of particles with a particle size less than 200 mesh was 100%), and the evenly ground ITO waste target powder was put into an alumina crucible and placed in the first temperature zone of a double-temperature zone tubular roasting furnace; then nitrogen was introduced to exhaust the excess air in the furnace, and the atmosphere in the first temperature zone was controlled to be 25vol% H 2 , the temperature is 900℃, and the atmosphere in the second temperature zone is 12.5vol%O 2 , and calcined at a temperature of 1050° C.; finally, the obtained ITO powder was collected using a graphite filter membrane set at the gas outlet of the second temperature zone.

[0048] Analysis of the experimental results: In in the prepared ITO powder 2 O 3The mass fraction of SnO is 89.95%, 2 The mass fraction is 10.04%, and its composition meets the standard YS / T 1353-2020.

[0049]

[0050] Example 4

[0051] The scraps of ITO sputtering targets from a certain factory (metal In content is 72.9 wt.%, In 2 O 3 The content is 87.5 wt.%, the metal Sn content is 7.9 wt.%, SnO 2 First, 10g of ITO waste target was crushed and ground evenly (the mass percentage of particles with a particle size less than 200 mesh was 100%), and the evenly ground ITO waste target powder was put into an alumina crucible and placed in the first temperature zone of a double-temperature zone tubular roasting furnace; then nitrogen was introduced to exhaust the excess air in the furnace, and the atmosphere in the first temperature zone was controlled to be 25vol% H 2 , the temperature is 900℃, and the atmosphere in the second temperature zone is 7.5vol%O 2 , and calcined at a temperature of 1150° C.; finally, the obtained ITO powder was collected using a graphite filter membrane set at the gas outlet of the second temperature zone.

[0052] Analysis of the experimental results: In in the prepared ITO powder 2 O 3 The mass fraction of SnO is 89.96%, 2 The mass fraction is 10.03%, and its composition meets the standard YS / T 1353-2020.

[0053]

Claims

1. A method for preparing ITO powder using ITO waste target, characterized in that: The ITO waste target powder is placed in a double-temperature zone tubular roasting furnace for roasting; the double-temperature zone tubular roasting furnace comprises a first temperature zone and a second temperature zone, a reducing gas is introduced into the first temperature zone, and the temperature is set to 875-1000°C, an oxidizing gas is introduced into the second temperature zone, and the temperature is set to 1050-1150°C; the ITO waste target powder is placed in the first temperature zone, and a graphite filter membrane is set at the gas outlet of the second temperature zone to collect the ITO powder.

2. The method for preparing ITO powder using ITO waste target according to claim 1, characterized in that: The grade of indium in the ITO waste target powder is 70-75%, and the grade of tin is 7-9%.

3. The method for preparing ITO powder using ITO waste target according to claim 1 or 2, characterized in that: The mass percentage of the ITO waste target powder with a particle size less than 200 meshes reaches 100%.

4. The method for preparing ITO powder using ITO waste target according to claim 1, characterized in that: The reducing gas is a gas with a H2 concentration in the range of 20-30 vol%, and the carrier gas is a non-reactive gas.

5. The method for preparing ITO powder using ITO waste target according to claim 1, characterized in that: The oxidizing gas is a gas with an O2 concentration in the range of 7.5-12.5 vol%, and the carrier gas is a non-reactive gas.

6. The method for preparing ITO powder using ITO waste targets according to claim 1, characterized in that: The calcination time is not less than 60 min.

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