A method for deoxidizing rare earth metals and a deoxidizing device

Abstract

An embodiment of the present invention relates to a method and a device for deoxidizing rare earth metals. The method includes: placing a rare earth metal rod in a molten salt system; heating to make the molten salt system reach a predetermined temperature and melt, while the rare earth metal rod remains in a solid state; connecting the rare earth metal rod to a solid-state electromigration power supply, and turning on and slowly increasing the direct current of the electromigration direct current power supply at the predetermined temperature; adjusting the temperature of the rare earth metal rod to remain at the predetermined temperature, and starting to calculate the electromigration time t; while calculating the electromigration time, turning on the electrochemical deoxidation direct current power supply; after a first predetermined time, the voltage remains unchanged; after a second predetermined time, turning off the solid-state electromigration power supply and the electrochemical deoxidation power supply. The technical solution of the embodiment of the present invention organically combines the three methods of solid-state electromigration, molten salt extraction, and electrochemical deoxidation, enabling the three methods to promote each other, reducing the deoxidation limit, and improving the deoxidation efficiency.

Description

Technical Field

[0001] The embodiments of the present invention relate to the technical field of rare earth materials, and particularly to a method and a device for deoxidizing rare earth metals. Background Art

[0002] Due to their unique electronic structures, rare earth elements possess rich and excellent electrical, magnetic, optical, and thermal properties, becoming strategic resources indispensable for the development of modern high-tech and sophisticated technologies, the optimization of traditional industries, and the promotion of low-carbon environmental protection, and are reputed as the "industrial vitamins" and the "treasure house of new materials in the 21st century". With the development of new technologies and new materials, higher requirements are put forward for the purity of rare earth metals. As a key raw material, high-purity rare earth metals are the material guarantee for the research and development of high-performance functional materials. For example, low-purity Tb and Dy will cause the loss of magnetostrictive properties of TbDyFe, and impurities in the magnetocaloric material Gd5Si2Ge2 will lead to a deterioration of its refrigeration effect. Impurities in rare earth metals are classified into substitutional impurities and interstitial impurities according to their occurrence states. The former mainly includes metal impurities and some non-metal impurities, and the latter mainly includes oxygen impurities that are dissolved in the rare earth metal matrix in atomic form. Due to the active chemical properties of rare earth metals, the removal of oxygen interstitial impurity atoms has always been a stumbling block for rare earth researchers in the study of ultra-high-purity rare earth metals. Currently, relatively common deoxidation technologies in the rare earth field include solid-state electromigration, molten salt extraction, electrochemical deoxidation, etc.

[0003] The solid-state electromigration method (SSE) is to place the metal rod to be purified between two electrodes and apply direct current. Under the action of direct current, most interstitial impurity atoms (C, O, N, etc.) migrate to one end of the anode of the rod, and the purity of the other end is correspondingly improved. The disadvantage of solid-state electromigration is that the purity requirement of the metal raw material is high, the shape requirement is rod-shaped, the vacuum requirement of the equipment is strict, the purification period is long, generally taking about several days to a month, and the yield is low. Its disadvantages greatly restrict the application of ultra-high-purity rare earth metals in high-tech fields.

[0004] The molten salt extraction method (Molten Salt Extrartinn) is a method for purifying metals. That is, a specific molten salt is mixed with the rare earth metal to be purified. Due to the impurity concentration difference between the metal and the molten salt, impurities diffuse from the metal into the molten salt through chemical diffusion to achieve the purification of the rare earth metal. The disadvantage of this method is that the selection of the extractant and the molten salt ratio require high requirements, the purification effect is worse than that of solid-state electromigration, and at the same time, the total output of rare earth metals will decrease.

[0005] Electrochemical deoxidation, as a means of deoxygenation, specifically uses a carbon rod as the anode, the metal to be purified as the cathode, and a halogen salt as the electrolyte. A direct current is passed between the anode and cathode to generate an electrochemical reaction. The main difficulties faced by this method are mainly the design of the reaction device, which requires consideration of temperature control, environmental airtightness, current control range, fluidity of the molten salt, and personal safety. In addition, as the electrolytic deoxidation progresses and the oxygen impurity content decreases, the electrolysis efficiency gradually decreases. If deep deoxidation is to be achieved, it requires an extremely long time. Summary of the Invention

[0006] Based on the above situation of the prior art, the purpose of the embodiments of the present invention is to provide a rare earth metal deoxidation method and a deoxidation device. Based on the principle of electromigration, a molten salt extraction method and an electrochemical deoxidation method are introduced on the basis of electromigration to achieve the effect of deep deoxidation, overcoming the disadvantages of the existing solid-state electromigration deoxidation technology, such as high vacuum requirements, long purification cycle, and low efficiency. At the same time, it further breaks through the traditional solid-state electromigration deoxidation limit.

[0007] To achieve the above object, according to one aspect of the present invention, a rare earth metal deoxidation method is provided, including:

[0008] Placing a rare earth metal rod in a molten salt system, where the molten salt system includes an alkaline earth metal and its chloride system;

[0009] Heating to make the molten salt system reach a predetermined temperature and melt, while the rare earth metal rod remains solid;

[0010] Connecting the rare earth metal rod to a solid-state electromigration power supply, and turning on and slowly increasing the direct current of the electromigration direct current power supply at the predetermined temperature;

[0011] Adjusting the temperature of the rare earth metal rod to remain at the predetermined temperature, and starting to calculate the electromigration time t;

[0012] While calculating the electromigration time, turning on the electrochemical deoxidation direct current power supply, and adjusting the voltage of the electrochemical deoxidation direct current power supply with the electromigration time t;

[0013] After the first predetermined time, the voltage remains unchanged;

[0014] After the second predetermined time, turning off the solid-state electromigration power supply and the electrochemical deoxidation power supply.

[0015] Further, the rare earth metal includes one of Y, Sc, La, Ce, Pr, Nd, Gd, Tb, Dy, Ho, Er, and Lu.

[0016] Further, the method further includes:

[0017] Setting the voltage range of the electrochemical deoxidation power supply to 0 - 10V according to the type of rare earth metal.

[0018] Further, maintaining the temperature of the adjusted rare earth metal rod at a predetermined temperature includes:

[0019] Maintaining the temperature of the rare earth metal rod at the predetermined temperature by adjusting the heating temperature.

[0020] Further, adjusting the voltage of the electrochemically deoxidized DC power supply with the electromigration time t includes adjusting according to the following formula:

[0021] wherein, the unit of t is minutes.

[0022] Further, the method further includes: introducing argon before heating to maintain a slightly positive pressure state inside the deoxidation device.

[0023] Further, the molten salt system is a calcium-metal fluoride composite system or a metal fluoride binary system or an alkaline earth metal and its halide composite system.

[0024] According to another aspect of the present invention, there is provided a deoxidation device for rare earth deoxidation using the rare earth metal deoxidation method described in the first aspect of the present invention, including: a rare earth metal rod to be deoxidized, an electromigration DC power supply, an electrochemically deoxidized DC power supply, a first electrode, a second electrode, and a reaction vessel with a sealing cover;

[0025] A molten salt system is provided inside the reaction vessel;

[0026] The first electrode includes a cathode made of molybdenum and an anode made of graphite, and the first electrode is connected to the electromigration DC power supply;

[0027] Both ends of the rare earth metal rod are connected to the positive and negative poles of the electromigration DC power supply through the second electrode, and the rare earth metal rod is integrally immersed in the molten salt system;

[0028] The first electrode and the second electrode pass through the sealing cover and are connected to the corresponding DC power supplies.

[0029] Further, an alumina gasket is provided at the bottom of the reaction vessel.

[0030] Further, an air inlet and an air outlet are provided on the sealing cover.

[0031] In summary, the embodiments of the present invention provide a rare earth metal deoxidation method and a deoxidation device. The method includes: placing a rare earth metal rod in a molten salt system, where the molten salt system includes an alkaline earth metal and its chloride system; heating to make the molten salt system reach a predetermined temperature and melt, while the rare earth metal rod remains solid; connecting the rare earth metal rod to a solid-state electromigration power supply, and turning on and slowly increasing the direct current of the electromigration direct current power supply at the predetermined temperature; adjusting the temperature of the rare earth metal rod to remain at the predetermined temperature, and starting to calculate the electromigration time t; while calculating the electromigration time, turning on the electrochemical deoxidation direct current power supply, and adjusting the voltage of the electrochemical deoxidation direct current power supply with the electromigration time t; after a first predetermined time, the voltage remains unchanged; after a second predetermined time, turning off the solid-state electromigration power supply and the electrochemical deoxidation power supply. The technical solution of the embodiments of the present invention organically combines the three methods of solid-state electromigration, molten salt extraction, and electrochemical deoxidation, and gives the setting method of specific reaction conditions during the combination process, so that the three methods are organically combined and promote each other, reducing the deoxidation limit, improving the deoxidation efficiency, avoiding the disadvantages of the high vacuum environmental requirements of traditional solid-state electromigration equipment, the high deoxidation limit of the molten salt extraction method, and the low electrochemical deoxidation efficiency, overcoming the disadvantages of high requirements for raw material quality, strict equipment vacuum environment requirements, and long purification cycle of traditional solid-state electromigration, and achieving the beneficial effect of deep deoxidation. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 is a schematic diagram of the rare earth metal deoxidation device provided by the embodiment of the present invention;

[0033] Figure 2 is a flowchart of the rare earth metal deoxidation method provided by the embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0034] To make the objectives, technical solutions, and advantages of the present invention clearer and more understandable, the present invention will be further described in detail below in conjunction with the specific embodiments and with reference to the accompanying drawings. It should be understood that these descriptions are merely exemplary and are not intended to limit the scope of the present invention. In addition, in the following description, the descriptions of well-known structures and technologies are omitted to avoid unnecessarily confusing the concepts of the present invention.

[0035] It should be noted that, unless otherwise defined, the technical terms or scientific terms used in one or more embodiments of the present invention should have the ordinary meaning understood by those of ordinary skill in the art to which the present disclosure pertains. The "first", "second" and similar terms used in one or more embodiments of the present invention do not denote any order, quantity or importance, but are only used to distinguish different components. Words such as "comprising" or "including" mean that the elements or items appearing before this word cover the elements or items listed after this word and their equivalents, without excluding other elements or items. Words such as "connected" or "coupled" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "Upper", "lower", "left", "right", etc. are only used to represent relative positional relationships, and when the absolute position of the object being described changes, the relative positional relationship may also change accordingly.

[0036] The technical solutions of the present invention will be described in detail below with reference to the accompanying drawings. An embodiment of the present invention provides a method for deoxidizing rare earth metals. This method combines solid-state electromigration, molten salt extraction and electrochemical deoxidation organically, reduces the deoxidation limit, and realizes deep deoxidation of rare earth metals. Figure 1 The deoxidation device adopted in the rare earth metal deoxidation method of this embodiment of the present invention is shown. It includes two sets of steady DC power supplies, an electromigration DC power supply 5 and an electrochemical deoxidation DC power supply 4. These two sets of power supplies serve as the power supply for the solid-state electromigration process and the power supply for the electrochemical deoxidation process respectively. The rare earth metal to be deoxidized is a rare earth metal rod 8, with a length dimension range of 150 - 200 mm and a diameter of 10 - 20 mm. The oxygen content is not specifically required, and the rare earth types involved include Y, Sc, La, Ce, Pr, Nd, Gd, Tb, Dy, Ho, Er, and Lu, etc. Both ends of the rare earth metal rod 8 are connected to the positive and negative electrodes of the electromigration DC power supply 5 through stainless steel electrode rods 7. The current density of this electromigration DC power supply 5 is 100 - 600 A / cm 2 , and the voltage is 12V. During the electrochemical deoxidation process, the cathode material of the deoxidation device is molybdenum wire 1, the anode material of the deoxidation device is graphite 2, and both ends are connected to the electrochemical deoxidation DC power supply 4, with a voltage range of 0 - 10V. This device also includes a molten salt system 9 for the molten salt extraction process, which can adopt an alkaline earth metal and its chloride system, such as a calcium-metal fluoride composite system or a metal fluoride binary system or an alkaline earth metal and its halide composite system. The melting temperature is kept below the melting point of the rare earth metal feed rod to prevent the rare earth metal from melting. This device also includes an alumina gasket 10 arranged at the bottom of the device, an air inlet 3 and an air outlet 6 arranged on the sealing cover. The overall material of this deoxidation device can be stainless steel.

[0037] Figure 2The flowchart of the rare earth metal deoxidation method provided by the embodiment of the present invention, in combination with Figure 1 and Figure 2 , the rare earth metal deoxidation method includes the following steps:

[0038] Fill the molten salt system in the deoxidation device. The two ends of the rare earth metal rod 8 are connected by stainless steel electrode rods 7 (the connection part between the stainless steel electrode rod 7 and the rare earth metal rod 8 is connected with a tantalum joint, and molybdenum wire is used as the electrode wire). Before energization, argon can be introduced first to maintain a slightly positive pressure state in the deoxidation device, and the temperature of the molten salt in the deoxidation device is measured by a thermocouple protected by a corundum tube.

[0039] After the above preparations are completed, first turn on the resistance furnace for heating. After the molten salt system 9 reaches the predetermined temperature and melts, the rare earth metal rod 8 remains solid. The predetermined temperature is preferably 800 - 1500 °C.

[0040] After the temperature is stable, turn on and slowly increase the direct current of the electromigration DC power supply 5. Due to Joule heat, the rare earth metal rod 8 will generate heat, resulting in a temperature rise. Therefore, the external heating temperature should be correspondingly reduced until the temperature returns to the set temperature. That is, after the molten salt reaches the above-mentioned predetermined temperature and melts, the temperature at which the rare earth metal material rod to be purified remains solid can be regarded as the stable temperature, and the floating range of this temperature is ±10 °C. After the temperature is stable, continue to increase the current and reduce the external heating temperature until the current increases to the set target current, and maintain the existing external heating temperature to make the electromigration temperature stable. At this time, start calculating the electromigration time. Starting to calculate the electromigration time means the temperature when the molten salt is just in a molten state and the rare earth metal material rod to be purified is solid. Because the current increases when the molten salt melts, there will be a temperature difference between the inside and the outer wall. The electromigration time should be calculated when the internal and external temperatures are the same. During the electromigration process, it is necessary to monitor the changes in the voltage of the electromigration DC power supply 5 and the temperature of the molten salt. The temperature of the molten salt is the temperature at the eutectic point of the phase diagram according to the material ratio of the molten salt used, and can be determined according to the type of molten salt actually used. In this step, solid-state electromigration of oxygen impurity atoms is realized. Through the action of the electromigration DC power supply 5, the oxygen impurity atoms in the rare earth metal are enriched towards the anode end, increasing the concentration difference of oxygen impurity atoms in the molten salt system 9 near the anode end. After solid-state electromigration, a molten salt extraction process occurs. Utilizing the property that the oxygen impurity atoms have a greater affinity with the components in the molten salt system 9, the oxygen impurity atoms move from the anode to the molten salt system 9 under the action of the concentration difference.

[0041] After the electromigration starts (i.e., while starting to calculate the electromigration time), turn on the electrochemically deoxidized DC power supply 4, and set the voltage of the electrochemically deoxidized DC power supply 4 to 0 - 10 V according to the type of rare earth metal to be purified. In this step, based on the principle of electrochemically deoxidizing, the oxygen impurity atoms in the molten salt system near the rare earth metal migrate to the surface of the graphite anode 2 under the action of the electrochemically deoxidized DC power supply 4 and react with the graphite anode 2 to generate CO / CO2 and precipitate. This process makes it difficult for oxygen impurity atoms to accumulate in the molten salt system 9, and the oxygen impurity concentration in the molten salt system 9 always remains at a relatively low level, which in turn promotes the occurrence of the molten salt extraction process. The molten salt extraction process can continuously reduce the concentration of oxygen impurity atoms at the metal anode end, effectively promoting the occurrence of the solid-state electromigration process. As the entire reaction progresses continuously, the purpose of deep deoxidation is achieved. During the whole process, the rate of oxygen impurity atoms diffusing from the anode end to the molten salt is in dynamic equilibrium with the rate of oxygen impurity escaping from the graphite anode. In this way, the entire deoxidation process can proceed continuously. Therefore, the voltage of the electrochemically deoxidized DC power supply 4 needs to be adjusted over time. Since the oxygen impurity content is getting lower and lower and deoxidation becomes more and more difficult, the voltage can be adjusted according to the following formula:

[0042]

[0043] After the first predetermined time (e.g., 120 min - 480 min), the voltage remains unchanged until the deoxidation process ends.

[0044] After the above process (starting to time when the molten salt temperature fluctuates by ±10 °C after the solid-state electromigration starts) continues for the second predetermined time (e.g., 10 - 30 h), turn off the solid-state electromigration DC power supply 5 and the electrochemically deoxidized DC power supply 4. After the molten salt cools down, take out the rare earth metal rod 8 and perform surface treatment and sampling in the glove box, and conduct metal impurity detection and gas impurity detection and analysis respectively.

[0045] The following gives specific examples and experimental data.

[0046] Comparative example:

[0047] Use molten CaCl2 as the electrolyte, metallic yttrium as the cathode, and a carbon rod as the anode. During the electrochemical process, Ca 2+ precipitates at the cathode, reacts with the oxygen in the metallic yttrium to form CaO, and then dissolves in the molten salt. Under the action of the DC voltage, CaO decomposes again, and the generated oxygen ions move towards the anode and react at the anode to generate CO / CO2 gas and precipitate, thereby removing the oxygen impurities in the metallic yttrium.

[0048] The results show that the oxygen content at the cathode end of the purified metallic yttrium is less than 100 ppm (and greater than 50 ppm).

[0049] Example 1:

[0050] Step 01: Process metal Y into a rod with a length of 150 mm and a diameter of 10 mm;

[0051] Step 02: In the glove box, treat the surface of the metal Y rod to remove contaminants generated during the processing, and take a sample to analyze the oxygen impurity content. The test result is 3581 ppm;

[0052] Step 03: Connect both ends of the metal Y rod with tantalum joints, and lead out an electrode rod at each end, with the material being stainless steel;

[0053] Step 04: Put CaCl2 powder in a graphite crucible. Before that, the CaCl2 powder needs to be heat-treated under vacuum at 600 °C for 10 h to remove the moisture contained therein;

[0054] Step 05: Connect both ends of the metal Y rod to a solid-state electromigration power supply, and connect an electrochemical deoxidation power supply between the molybdenum wire and the graphite rod;

[0055] Step 06: Turn on the heating power supply of the resistance furnace, observe the temperature display of the thermocouple, and make it stable at 950 °C. It can be observed that the molten salt melts; subsequently, lower the metal Y rod, the molybdenum wire and the graphite rod until the molten salt completely submerges the metal Y rod;

[0056] Step 07: Turn on the electrochemical deoxidation power supply, apply a voltage of about 1.5 V between the molybdenum wire and the graphite rod, and perform pre-electrolysis for about 0.5 h to remove residual impurities in the molten salt. Subsequently, turn off this power supply;

[0057] Step 08: Turn on the solid-state electromigration power supply, control the current density at 600 A / cm 2 , the metal Y rod will generate heat under the action of Joule heat. Observe the thermocouple temperature, and when it is stable at 950 °C, calculate the electromigration time;

[0058] Step 09: At the same time as the electromigration timing starts, turn on the electrochemical deoxidation DC power supply, set the initial voltage value to 3.3 V, and with time, the voltage is adjusted according to the formula . After 480 min, the voltage remains unchanged until the deoxidation process ends. The entire deoxidation process lasts for 30 h. Then, turn off the electromigration power supply and the electrochemical deoxidation power supply. After the molten salt cools to room temperature, take out the metal Y rod, polish the metal surface in the glove box, and take a sample for analysis. The result shows that the oxygen content in the cathode end of the purified metal Y is 46 ppm.

[0059] Example 2:

[0060] Step 01: Process metal La into a rod with a length of 150 mm and a diameter of 15 mm;

[0061] Step 02: In the glove box, the surface of the La metal rod was treated to remove the pollutants generated during the processing, and a sample was taken to analyze the oxygen impurity content. The test result was 1642 ppm;

[0062] Step 03: Both ends of the La metal rod were connected using tantalum joints, and an electrode rod was led out from each end, with the material being stainless steel;

[0063] Step 04: CaCl2 powder was placed in a graphite crucible. Before that, the CaCl2 powder needed to be heat-treated under vacuum at 600 °C for 10 h to remove the moisture contained therein;

[0064] Step 05: Solid-state electromigration power supplies were connected to both ends of the La metal rod, and an electrochemical deoxidation power supply was connected between the molybdenum wire and the graphite rod;

[0065] Step 06: The heating power supply of the resistance furnace was turned on, and the temperature display of the thermocouple was observed to stabilize at 850 °C. It could be observed that the molten salt melted; subsequently, the La metal rod, molybdenum wire, and graphite rod were lowered until the molten salt completely submerged the La metal rod;

[0066] Step 07: The electrochemical deoxidation power supply was turned on, and a voltage of approximately 1.5 V was applied between the molybdenum wire and the graphite rod for approximately 0.5 h of pre-electrolysis to remove the residual impurities in the molten salt. Subsequently, this power supply was turned off;

[0067] Step 08: The solid-state electromigration power supply was turned on, and the current density was controlled at 400 A / cm 2 , and the La metal rod would generate heat under the action of Joule heat. The temperature of the thermocouple was observed, and when it stabilized at 850 °C, the electromigration time was calculated;

[0068] Step 09: Simultaneously with the start of electromigration timing, the electrochemical deoxidation DC power supply was turned on, and the initial value was set at 3.3 V. Over time, the voltage was adjusted according to the formula After 380 min, the voltage remained unchanged until the deoxidation process ended. The entire deoxidation process lasted for 20 h. Then, the electromigration power supply and the electrochemical deoxidation power supply were turned off. After the molten salt cooled to room temperature, the La metal rod was taken out. In the glove box, the surface of the metal was polished and sampled for analysis. The result showed that the oxygen content in the purified La metal was 33 ppm.

[0069] Example 3:

[0070] Step 01: The Ce metal was processed into a rod with a length of 150 mm and a diameter of 20 mm;

[0071] Step 02: In the glove box, the surface of the Ce metal rod was treated to remove the pollutants generated during the processing, and a sample was taken to analyze the oxygen impurity content. The test result was 1832 ppm;

[0072] Step 03: Connect both ends of the metal Ce rod with tantalum joints, and lead out an electrode rod at each end, with the material being stainless steel;

[0073] Step 04: Put CaCl2 and NaCl powders in a graphite crucible, with a molar ratio of 3:17. Before that, both CaCl2 and NaCl powders need to be heat-treated under vacuum at 600 °C for 10 h to remove the moisture contained therein;

[0074] Step 05: Connect both ends of the metal Ce rod to a solid-state electromigration power supply, and connect an electrochemical deoxidation power supply between the molybdenum wire and the graphite rod;

[0075] Step 06: Turn on the heating power supply of the resistance furnace, observe the temperature display of the thermocouple, and make it stable at 750 °C. It can be observed that the molten salt melts; subsequently, lower the metal Ce rod, molybdenum wire and graphite rod until the molten salt completely submerges the metal Ce rod;

[0076] Step 07: Turn on the electrochemical deoxidation power supply, apply a voltage of about 1.5 V between the molybdenum wire and the graphite rod, and perform pre-electrolysis for about 0.5 h to remove the residual impurities in the molten salt. Then, turn off this power supply;

[0077] Step 08: Turn on the solid-state electromigration power supply, control the current density at 500 A / cm2. The metal Ce rod will generate heat under the action of Joule heat. Observe the thermocouple temperature, and calculate the electromigration time when it is stable at 850 °C;

[0078] Step 09: At the same time as the electromigration timing starts, turn on the electrochemical deoxidation DC power supply, set the initial value at 3.3 V, and with time, the voltage is adjusted according to the formula After 420 min, the voltage remains unchanged until the deoxidation process ends. The entire deoxidation process lasts for 20 h. Then, turn off the electromigration power supply and the electrochemical deoxidation power supply. After the molten salt cools to room temperature, take out the metal Ce rod, polish the metal surface in a glove box, and take samples for analysis. The results show that the oxygen content in the purified metal Ce is 32 ppm.

[0079] Example 4:

[0080] Step 01: Process the metal Tb into a rod with a length of 150 mm and a diameter of 10 mm;

[0081] Step 02: In a glove box, treat the surface of the metal Tb rod to remove the pollutants generated during the processing, and take samples to analyze the oxygen impurity content therein. The test result is 1541 ppm;

[0082] Step 03: Connect both ends of the metal Tb rod with tantalum joints, and lead out an electrode rod at each end, with the material being stainless steel;

[0083] Step 04: Place CaCl2 powder in a graphite crucible. Before this, CaCl2 needs to be vacuum heat-treated at 600 °C for 10 h to remove the moisture contained therein;

[0084] Step 05: Connect both ends of the metal Tb rod to a solid-state electromigration power supply, and connect an electrochemical deoxidation power supply between the molybdenum wire and the graphite rod;

[0085] Step 06: Turn on the heating power supply of the resistance furnace, observe the temperature display of the thermocouple, and make it stable at 950 °C. It can be observed that the molten salt melts; subsequently, lower the metal Tb rod, molybdenum wire, and graphite rod until the molten salt completely submerges the metal Tb rod;

[0086] Step 07: Turn on the electrochemical deoxidation power supply, apply a voltage of about 1.5 V between the molybdenum wire and the graphite rod, and perform pre-electrolysis for about 0.5 h to remove the residual impurities in the molten salt. Subsequently, turn off this power supply;

[0087] Step 08: Turn on the solid-state electromigration power supply, control the current density at 400 A / cm2. The metal Tb rod will generate heat under the action of Joule heat. Observe the temperature of the thermocouple. When it is stable at 950 °C, calculate the electromigration time;

[0088] Step 09: At the same time as the electromigration timing starts, turn on the electrochemical deoxidation DC power supply, set the initial value to 3.3 V. Over time, the voltage is adjusted according to the formula After 320 min, the voltage remains unchanged until the deoxidation process ends. The entire deoxidation process lasts for 20 h. Then, turn off the electromigration power supply and the electrochemical deoxidation power supply. After the molten salt cools to room temperature, take out the metal Tb rod, polish the metal surface in a glove box, and sample and analyze. The result shows that the oxygen content in the purified metal Tb is 35 ppm.

[0089] Example 5:

[0090] Step 01: Process the metal Lu into a rod with a length of 150 mm and a diameter of 10 mm;

[0091] Step 02: In a glove box, treat the surface of the metal Lu rod to remove the pollutants generated during the processing, and sample and analyze the oxygen impurity content therein. The test result is 2836 ppm;

[0092] Step 03: Connect both ends of the metal Lu rod with tantalum connectors, and lead out an electrode rod at each end, with the material being stainless steel;

[0093] Step 04: Place CaCl2 powder in a graphite crucible. Before this, CaCl2 needs to be vacuum heat-treated at 600 °C for 10 h to remove the moisture contained therein;

[0094] Step 05: Connect a solid-state electromigration power supply to both ends of the metallic Lu rod, and connect an electrochemical deoxidation power supply between the molybdenum wire and the graphite rod;

[0095] Step 06: Turn on the heating power supply of the resistance furnace, observe the temperature display of the thermocouple, and keep it stable at 950 °C. It can be observed that the molten salt melts; subsequently, lower the metallic Lu rod, the molybdenum wire and the graphite rod until the molten salt completely submerges the metallic Lu rod;

[0096] Step 07: Turn on the electrochemical deoxidation power supply, apply a voltage of about 1.5 V between the molybdenum wire and the graphite rod, and perform pre-electrolysis for about 0.5 h to remove the residual impurities in the molten salt. Then, turn off this power supply;

[0097] Step 08: Turn on the solid-state electromigration power supply, control the current density at 300 A / cm2. The metallic Lu rod will generate heat under the action of Joule heat. Observe the temperature of the thermocouple. When it is stable at 950 °C, calculate the electromigration time;

[0098] Step 09: At the same time when the electromigration timing starts, turn on the electrochemical deoxidation DC power supply, set the initial value at 3.3 V. As time goes by, the voltage is adjusted according to the formula After 320 min, the voltage remains unchanged until the deoxidation process ends. The entire deoxidation process lasts for 10 h. Then, turn off the electromigration power supply and the electrochemical deoxidation power supply. After the molten salt cools down to room temperature, take out the metallic Lu rod, polish the metal surface in the glove box, and take samples for analysis. The results show that the oxygen content in the purified metallic Lu is 31 ppm.

[0099] In summary, the embodiments of the present invention relate to a method and a device for deoxidizing rare earth metals. The method includes: placing a rare earth metal rod in a molten salt system, where the molten salt system includes an alkaline earth metal and its chloride system; heating to make the molten salt system reach a predetermined temperature and melt, while the rare earth metal rod remains solid; connecting the rare earth metal rod to a solid-state electromigration power supply, and turning on and slowly increasing the direct current of the electromigration direct current power supply at the predetermined temperature; adjusting the temperature of the rare earth metal rod to remain at the predetermined temperature, and starting to calculate the electromigration time t; while calculating the electromigration time, turning on the electrochemical deoxidation direct current power supply, and adjusting the voltage of the electrochemical deoxidation direct current power supply with the electromigration time t; after a first predetermined time, the voltage remains unchanged; after a second predetermined time, turning off the solid-state electromigration power supply and the electrochemical deoxidation power supply. The technical solution of the embodiments of the present invention organically combines the three methods of solid-state electromigration, molten salt extraction, and electrochemical deoxidation, and gives the setting method of specific reaction conditions during the combination process, so that the three methods are organically combined and promote each other, reducing the deoxidation limit, improving the deoxidation efficiency, avoiding the disadvantages of the high vacuum environmental requirements of traditional solid-state electromigration equipment, the high deoxidation limit of the molten salt extraction method, and the low deoxidation efficiency of electrochemical deoxidation, overcoming the disadvantages of high requirements for raw material quality, strict requirements for the vacuum environment of the equipment, and long purification cycle of traditional solid-state electromigration, and achieving the beneficial effect of deep deoxidation.

[0100] It should be understood that the above specific embodiments of the present invention are only used for exemplary illustration or explanation of the principle of the present invention, and do not constitute a limitation to the present invention. Therefore, any modifications, equivalent replacements, improvements, etc. made without departing from the spirit and scope of the present invention shall be included within the protection scope of the present invention. In addition, the appended claims of the present invention are intended to cover all changes and modifications that fall within the scope and boundaries of the appended claims, or equivalent forms of such scope and boundaries.

Claims

1. A method for deoxidizing rare earth metals, characterized in that, Comprising: Placing a rare earth metal rod in a molten salt system, the molten salt system comprising an alkaline earth metal and its chloride system; Heating to cause the molten salt system to reach a predetermined temperature and melt, while the rare earth metal rod remains in a solid state; Connecting a first electrode to an electrochemically deoxidizing DC power source, connecting both ends of the rare earth metal rod to an electromigration DC power source through a second electrode, and turning on and slowly increasing the DC current of the electromigration DC power source at the predetermined temperature; Adjusting the temperature of the rare earth metal rod to remain at the predetermined temperature, and starting to calculate the electromigration time t; While calculating the electromigration time, turning on the electrochemically deoxidizing DC power source, and adjusting the voltage of the electrochemically deoxidizing DC power source with the electromigration time t; After a first predetermined time, the voltage remains unchanged; After a second predetermined time, turning off the electromigration DC power source and the electrochemically deoxidizing DC power source; Wherein, the first electrode and the second electrode pass through the sealing cover of the deoxidizing device and are connected to the corresponding DC power sources, and the first electrode comprises a cathode made of molybdenum and an anode made of graphite.

2. The method according to claim 1, wherein The rare earth metal comprises one of Y, Sc, La, Ce, Pr, Nd, Gd, Tb, Dy, Ho, Er, and Lu.

3. The method according to claim 1, wherein The method further comprises: According to the type of rare earth metal, setting the voltage range of the electrochemically deoxidizing DC power source to 0 - 10V.

4. The method according to claim 1, wherein The adjusting the temperature of the rare earth metal rod to remain at the predetermined temperature comprises: Adjusting the heating temperature to make the temperature of the rare earth metal rod remain at the predetermined temperature.

5. The method according to claim 1, characterized in that, The adjusting the voltage of the electrochemically deoxidizing DC power source with the electromigration time t includes adjusting according to the following formula: Wherein, the unit of t is minutes.

6. The method according to claim 1, characterized in that The method further comprises: Passing argon before heating to maintain a slightly positive pressure state inside the deoxidizing device.

7. The method according to claim 1, characterized in that, The molten salt system is a calcium-metal fluoride composite system or a metal fluoride binary system or an alkaline earth metal and its halide composite system.

8. A deoxidation device for rare earth deoxidation using the rare earth metal deoxidation method described in any one of claims 1-7, characterized in that, Comprising: A rare earth metal rod to be deoxidized, an electromigration DC power source, an electrochemically deoxidizing DC power source, a first electrode, a second electrode, and a reaction vessel with a sealing cover; A molten salt system is arranged inside the reaction vessel; The first electrode is connected to the electrochemically deoxidizing DC power source; Both ends of the rare earth metal rod are connected to the positive and negative electrodes of the electromigration DC power source through the second electrode, and the entire rare earth metal rod is immersed in the molten salt system; The first electrode and the second electrode pass through the sealing cover and are connected to the corresponding DC power sources.

9. The deoxidation device according to claim 8, characterized in that An alumina gasket is arranged at the bottom of the reaction vessel.

10. The deoxidation device according to claim 9, characterized in that, An air inlet and an air outlet are arranged on the sealing cover.

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