A method for deoxidizing high-purity indium

Abstract

This invention discloses a method for deoxidizing high-purity indium. The method involves adding precipitated indium of grade 5N or higher to an indium melting vessel and immersing the precipitated indium in glycerol. The indium melting vessel is then heated to completely melt the precipitated indium into a liquid indium. The liquid indium is stirred thoroughly to allow indium oxides to float to the surface of the liquid indium. The liquid indium is then led out from the outlet at the bottom of the indium melting vessel using a conduit. The other end of the conduit is placed below the surface of the liquid glycerol in a mold containing glycerol. The liquid indium is transferred to the mold to cast indium ingots. The resulting ingots are then washed with acid, washed with ultrapure water, and dried sequentially. This method can prevent the high-purity precipitated indium sheets from oxidizing due to excessive contact with air during the melting and processing process. At the same time, it can transfer the generated indium oxides to the surface of the high-purity indium ingots, making them easy to clean and remove. This method effectively solves the technical problems of easy oxidation of electrolytic indium sheets and the difficulty in removing indium oxides.

Description

Technical Field

[0001] This invention relates to a method for deoxidizing metallic indium, and more particularly to a method for high-purity electrolytic deoxidation of indium, belonging to the field of metal purification technology. Background Technology

[0002] Indium is located in Group IIIA of Period 5 of the periodic table, with atomic number 49, relative atomic weight 114.82, melting point 156.61℃, and boiling point 2080℃. It is a soft, silvery-white metal. It possesses excellent physicochemical properties, including a strong metallic luster, good ductility, high plasticity, low melting point, high boiling point, good light penetration and electrical conductivity, and corrosion resistance.

[0003] High-purity indium refers to metallic indium with a purity exceeding 99.999% (5N). It is produced from industrial indium with a purity of 99.99% or higher through various purification processes such as electrolysis and refining. Material purity directly affects its physicochemical properties; increasing purity helps to further improve or enhance these properties. With the rapid development of high-tech fields such as new energy, optoelectronics, aerospace, and national defense, the purity requirements for indium materials are becoming increasingly stringent.

[0004] The indium industry is hailed as a "sunrise industry of the information age." Indium metal is widely used in high-tech fields such as electronics, aerospace, alloy manufacturing, and new materials for solar cells, holding a strategic position in electronics, telecommunications, optoelectronics, defense, and communications. With the development of these fields, the indium industry has broad prospects and its importance in the national economy is increasing. High-purity indium, with a purity of 99.999% (5N) or higher, can be transformed into different shapes and forms for various applications. High-purity indium ingots are commonly used to produce indium compounds; indium pellets are used for vapor deposition and electroplating; indium wire, indium strip, and indium foil are commonly used for soldering. High-purity indium is mainly used in ITO targets, solders and alloys, electronic components and semiconductors, photovoltaic solar cells, and research.

[0005] Currently, electrolysis is involved in various purification processes, and the melting and shaping of the high-purity indium precipitated sheets after electrolysis is crucial for further purification or application. Due to the large surface area of ​​the precipitated indium sheets, they are highly susceptible to oxidation during high-temperature melting due to full contact with air. Oxidized high-purity indium has a yellowish surface, affecting its appearance quality, and excessive oxides also reduce product purity, severely impacting the physical and chemical properties of subsequent products. Existing deoxidation technologies mainly include diffusion deoxidation and vacuum deoxidation, but these technologies require complex equipment and have very cumbersome processes, hindering large-scale production. Summary of the Invention

[0006] To address the technical problems in existing technologies, such as the presence of impure indium oxides in electrolytically deposited indium sheets and their susceptibility to oxidation during indium ingot processing, the present invention aims to provide a high-purity indium deoxidation method. This method avoids excessive contact with air during the melting and processing of high-purity indium sheets, thus preventing new oxidation. Simultaneously, it transfers the already generated indium oxides to the surface of the high-purity indium ingot, making them easy to clean and remove. This effectively solves the technical problems of easy oxidation of electrolytic indium sheets and difficulty in removing indium oxides.

[0007] To achieve the above-mentioned technical objectives, the present invention provides a method for deoxidizing high-purity indium. The method involves adding precipitated indium of grade 5N or higher to an indium melting vessel and immersing the precipitated indium in glycerol. The indium melting vessel is then heated to completely melt the precipitated indium into a liquid indium. The liquid indium is stirred thoroughly to allow indium oxides to float to the surface of the liquid indium. The liquid indium is then led out from the outlet at the bottom of the indium melting vessel using a conduit. The other end of the conduit is placed below the surface of the liquid glycerol in a mold containing glycerol. The liquid indium is transferred to the mold to cast indium ingots. The resulting indium ingots are then sequentially washed with acid, washed with ultrapure water, and dried.

[0008] The technical solution of this invention utilizes glycerol as an oxygen-isolated protective medium during the indium precipitation melting process. This effectively prevents the formation of new indium oxides during the melting of indium into liquid indium. After the indium is melted, taking advantage of the fact that the density of indium oxides is lower than that of metallic indium, the indium oxides can be accelerated to float to the surface of the liquid indium through stirring. The liquid indium is then transferred from the bottom of the indium melting vessel and used directly for ingot casting. This ensures that the indium oxides are transferred later than the liquid indium, thus retaining them on the surface of the indium ingot. The entire ingot casting process is also carried out in the glycerol protective medium, effectively avoiding the formation of new indium oxides. The indium oxides on the surface of the indium ingot are easily removed in subsequent washing to obtain metallic indium with higher purity.

[0009] As a preferred embodiment, the heating temperature is 160–180°C. Maintaining the heating temperature above the melting point of indium ensures that the precipitated indium is completely melted, while the heating temperature should not be too high, as this will cause the volatilization and decomposition of glycerol.

[0010] As a preferred embodiment, the acid washing process employs ultrasonic-assisted hydrochloric acid washing, wherein the hydrochloric acid concentration is 1–6 mol / L, the ultrasonic frequency is 30–50 kHz, and the acid washing time is 50–150 s. Under these preferred conditions, the removal of indium oxide from the surface of indium ingots can be achieved.

[0011] As a preferred embodiment, the ultrapure water washing process employs ultrasonic-assisted ultrapure water washing, wherein the resistivity of the ultrapure water is not less than 18.0 MΩ·cm, the frequency of the ultrasound is 30–50 kHz, and the ultrapure water washing time is 250–350 s.

[0012] As a preferred embodiment, the drying is performed by blowing with an inert gas and / or nitrogen, wherein the purity of the inert gas or nitrogen is above 99.999%.

[0013] The high-purity indium deoxidation method provided by this invention includes the following steps:

[0014] A. After cleaning the indium precipitate of 5N or higher, place it in an indium melting vessel and add analytical grade glycerol (glycerol) until it submerges the indium precipitate. Heat to 160-180℃ and hold until the indium precipitate is completely melted. Stir thoroughly to allow the oxide to float to the surface of the indium liquid.

[0015] B. Add analytical grade glycerol (glycerol) to the mold. Release the indium liquid obtained in step A from the outlet at the bottom of the indium melting vessel through the conduit. Insert the conduit below the glycerol liquid level in the mold. After casting one ingot, replace it with the next mold and repeat the above operation.

[0016] C. Place the high-purity indium ingot obtained in step B into a hydrochloric acid solution with a concentration of 1-6 mol / L for ultrasonic etching. The ultrasonic frequency is 30-50 kHz, and the etching time is 50-150 s. Ultrasonic etching can remove the oxide film on the surface of the high-purity indium ingot. Then, place the ultrasonically etched high-purity indium ingot into ultrapure water for ultrasonic cleaning. The resistivity of the ultrapure water is not less than 18.0 MΩ·cm, the ultrasonic frequency is 30-50 kHz, and the ultrapure water washing time is 250-350 s. Then, blow the ultrasonically cleaned high-purity indium ingot dry with an inert gas. The inert gas is argon or nitrogen with a purity of 99.999% or higher.

[0017] The glycerol of this invention is of analytical grade.

[0018] The hydrochloric acid used in this invention is of analytical grade.

[0019] Compared with existing technologies, the beneficial effects of the technical solution of this invention are as follows:

[0020] This invention can prevent high-purity indium precipitated sheets from coming into extensive contact with air and generating new oxidation during the melting and processing of the indium precipitated sheets. At the same time, it can transfer the indium oxides already generated in the precipitated indium sheets to the surface of high-purity indium ingots, making them easy to clean and remove. This invention effectively solves the technical problems of easy oxidation of electrolytic indium sheets and difficulty in removing indium oxides.

[0021] The present invention is simple to operate, low in cost, and requires no complex equipment or process, which is conducive to large-scale promotion and application. Detailed Implementation

[0022] The present invention will be further described in detail below with reference to the embodiments, but the scope of protection of the claims of the present invention is not limited to the specific embodiments.

[0023] Example 1

[0024] 40 kg of 5N indium precipitated sheets were cleaned and placed in an indium melting vessel. Analytical grade glycerol was added until it submerged the indium precipitate by 3 cm. The temperature was raised to 180°C and held until the indium precipitate was completely melted. Thorough stirring was performed to allow the oxide to float to the surface of the indium liquid. Analytical grade glycerol was added to a 5 kg mold. The indium liquid was discharged from the bottom outlet of the indium melting vessel through a conduit. The conduit was inserted below the glycerol surface in the mold. After casting one ingot, the mold was replaced, and the above operation was repeated until a total of 7 ingots of 5 kg each were cast. One ingot of high-purity indium was placed in a 1.0 mol / L hydrochloric acid solution and ultrasonically etched for 100 seconds to remove the oxide film on the surface of the ingot. Then, the ultrasonically etched ingot was placed in ultrapure water with a resistivity of 18.25 MΩ·cm and ultrasonically cleaned for 300 seconds. Finally, the ultrasonically cleaned ingot was dried with 99.999% nitrogen gas.

[0025] To examine the deoxidation effect, 5 kg of a cast 5N indium ingot was taken and remelted under glycerol protection to obtain 1.5 g of oxide slag with a slag ratio of 0.03%. 40 kg of 5N precipitated indium sheet raw material was melted under glycerol protection to obtain 0.81 kg of oxide slag with a slag ratio of approximately 2.0%.

[0026] Example 2

[0027] 30 kg of 6N indium precipitated sheets were cleaned and placed in an indium melting vessel. Analytical grade glycerol was added until it submerged the indium precipitate by 3 cm. The temperature was raised to 180°C and held until the indium precipitate was completely melted. Thorough stirring was performed to allow the oxide to float to the surface of the indium liquid. Analytical grade glycerol was added to a 3 kg mold. The indium liquid was discharged from the bottom outlet of the indium melting vessel through a conduit. The conduit was inserted below the glycerol surface in the mold. After casting one ingot, the mold was replaced, and the above operation was repeated until a total of 9 ingots of 3 kg each were cast. Two ingots of high-purity indium were ultrasonically etched in a 1.0 mol / L hydrochloric acid solution for 150 seconds to remove the oxide film on the surface of the ingots. Then, the ultrasonically etched ingots were ultrasonically cleaned in ultrapure water with a resistivity of 18.25 MΩ·cm for 300 seconds. Finally, the ultrasonically cleaned ingots were dried with 99.999% nitrogen gas.

[0028] To examine the deoxidation effect, two cast 6N indium ingots, totaling 6 kg, were taken and remelted under glycerol protection to obtain 0.95 g of oxide slag with a slag ratio of 0.016%. Meanwhile, 30 kg of 6N precipitated indium sheet raw material was melted under glycerol protection to obtain 0.52 kg of oxide slag with a slag ratio of approximately 1.7%.

Claims

1. A method for deoxidizing high-purity indium, characterized in that: Indium of grade 5N or higher is added to an indium melting vessel and analytical grade glycerol is added to immerse the indium. The indium melting vessel is then heated to completely melt the indium into indium liquid. The indium liquid is stirred thoroughly to allow indium oxide to float to the surface of the indium liquid. The indium liquid is then led out from the outlet at the bottom of the indium melting vessel through a conduit. The other end of the conduit is placed below the surface of the analytical grade glycerol in a mold containing analytical grade glycerol. The indium liquid is transferred to the mold to cast indium ingots. The resulting indium ingots are then washed with acid, washed with ultrapure water, and dried in sequence. The heating temperature is 160~180℃; the acid washing process uses ultrasonic-assisted hydrochloric acid washing, the hydrochloric acid concentration is 1~6mol / L, the ultrasonic frequency is 30~50kHz, and the acid washing time is 50~150s. The ultrapure water washing process employs ultrasonic-assisted ultrapure water washing, the resistivity of the ultrapure water is not less than 18.0 MΩ•cm, the frequency of the ultrasound is 30~50kHz, and the washing time of the ultrapure water is 250~350s. The drying process employs inert gas and / or nitrogen, with the purity of the inert gas or nitrogen exceeding 99.999%.