CN116103703A - Rare earth metal deoxidizing method and deoxidizing device - Google Patents
Rare earth metal deoxidizing method and deoxidizing device Download PDFInfo
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- CN116103703A CN116103703A CN202310072267.0A CN202310072267A CN116103703A CN 116103703 A CN116103703 A CN 116103703A CN 202310072267 A CN202310072267 A CN 202310072267A CN 116103703 A CN116103703 A CN 116103703A
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Abstract
The embodiment of the invention relates to a rare earth metal deoxidizing method and deoxidizing device, wherein the method comprises the following steps: placing rare earth metal material rods in a molten salt system; heating to make the molten salt system reach a preset temperature for melting, and keeping the rare earth metal bar in a solid state; connecting a rare earth metal material rod to a solid-state electromigration power supply, and starting and slowly increasing direct current of the electromigration direct current power supply at the preset temperature; adjusting the temperature of the rare earth metal rod to be kept at a preset temperature, and starting to calculate the electrotransport time t; starting an electrochemical deoxidizing direct current power supply while calculating the electromigration time; after a first predetermined time, the voltage remains unchanged; after a second predetermined time, the solid state electromigration power supply and the electrochemical deoxidation power supply are turned off. According to the technical scheme provided by the embodiment of the invention, three methods of solid electromigration, molten salt extraction and electrochemical deoxidation are organically combined, so that the three methods are mutually promoted, the deoxidation limit is reduced, and the deoxidation efficiency is improved.
Description
Technical Field
The embodiment of the invention relates to the technical field of rare earth materials, in particular to a rare earth metal deoxidizing method and a rare earth metal deoxidizing device.
Background
Because of its unique electronic structure, rare earth elements have rich and excellent electric, magnetic, optical and thermal properties, and become strategic resources which are indispensable for developing modern high-precision technology, optimizing traditional industry and promoting low carbon and environmental protection, and are called as industrial vitamins and new material treasury in the 21 st century. With the development of new technology and new materials, higher requirements are put forward on the purity of rare earth metals. As a key raw material, high-purity rare earth metal is a substance guarantee for researching and developing high-performance functional materials, for example TbDyFe magnetostriction performance loss can be caused by low-purity Tb and Dy, and a magnetic refrigeration material Gd 5 Si 2 Ge 2 The impurities in (a) may cause deterioration of its refrigerating effect, etc. Impurities in rare earth metals are classified into substitutional impurities and interstitial impurities according to occurrence states, wherein the former mainly comprises metal impurities and partial nonmetallic impurities, and the latter mainly comprises oxygen impurities and the like which are dissolved in a rare earth metal matrix in an atomic form. Because of the active chemical nature of rare earth metals, the problem of removing oxygen gap impurity atoms is always that rare earth workers research ultra-high purity rare earth goldBelonging to a road blocking tiger. The deoxidization technology which is commonly used in the rare earth field at present comprises solid state electromigration, molten salt extraction, electrochemical deoxidization and the like.
The Solid State Electromigration (SSE) method is to place a metal material rod to be purified between two electrodes and apply direct current, and most of gap impurity atoms (C, O, N, etc.) migrate to one end of the anode of the material rod under the action of the direct current, and the purity of the other end is correspondingly improved. The disadvantage of solid electromigration is that the purity requirement of the metal raw material is high, the shape requirement is bar-shaped, the vacuum requirement of equipment is strict, the purification period is long, generally about several days to one month are needed, the yield is low, and the disadvantage of the method greatly restricts the application of ultra-high purity rare earth metal in the aspect of high and new technology.
Molten salt extraction (Molten Salt Extrartinn) is a method of purifying metals. The method is characterized in that specific molten salt is mixed with rare earth metal to be purified, and impurities enter the molten salt from the metal through chemical diffusion due to the fact that the concentration difference of the impurities exists between the metal and the molten salt, so that the rare earth metal is purified. The method has the defects that the extraction agent is selected and the molten salt ratio is required to be high, the purification effect is poorer than that of solid electromigration, and meanwhile, the total yield of rare earth metals is reduced.
Electrochemical deoxidation is carried out, and a carbon rod is used as an anode, metal to be purified is used as a cathode, halogen salt is used as electrolyte, and direct current is conducted between the anode and the cathode to generate electrochemical reaction. The difficulty faced by the method is mainly that the design of the reaction device needs to consider temperature control, environmental air tightness, current control range, fluidity of molten salt, personal safety and the like, in addition, as the electrolytic deoxidation is carried out, the oxygen impurity content is reduced, the electrolytic efficiency is gradually reduced, and if deep deoxidation is achieved, a very long time is required.
Disclosure of Invention
Based on the above situation of the prior art, the embodiment of the invention aims to provide a rare earth metal deoxidizing method and deoxidizing device, which are based on the electromigration principle, and a molten salt extraction method and an electrochemical deoxidizing method are introduced on the basis of electromigration to achieve the effect of deep deoxidization, thereby overcoming the defects of high vacuum requirement, long purification period and low efficiency of the existing solid electromigration deoxidizing technology equipment, and further breaking through the limit of traditional solid electromigration deoxidization.
To achieve the above object, according to one aspect of the present invention, there is provided a rare earth metal deoxidizing method comprising:
placing a rare earth metal rod in a molten salt system, wherein the molten salt system comprises alkaline earth metal and a chloride system thereof;
heating to make the molten salt system reach a preset temperature for melting, and keeping the rare earth metal bar in a solid state;
connecting a rare earth metal material rod to a solid-state electromigration power supply, and starting and slowly increasing direct current of the electromigration direct current power supply at the preset temperature;
adjusting the temperature of the rare earth metal rod to be kept at a preset temperature, and starting to calculate the electrotransport time t;
starting an electrochemical deoxidizing direct current power supply while calculating the electromigration time, and adjusting the voltage of the electrochemical deoxidizing direct current power supply along with the electromigration time t;
after a first predetermined time, the voltage remains unchanged;
after a second predetermined time, the solid state electromigration power supply and the electrochemical deoxidation power supply are turned off.
Further, the rare earth metal includes one of Y, sc, la, ce, pr, nd, gd, tb, dy, ho, er, and Lu.
Further, the method further comprises:
the voltage range of the electrochemical deoxidizing power source is set to be 0-10V according to the type of rare earth metal.
Further, the adjusting the temperature of the rare earth metal rod to be kept at a predetermined temperature includes:
the temperature of the rare earth metal bar is maintained at the predetermined temperature by adjusting the heating temperature.
Further, the voltage of the electrochemical deoxidizing direct current power supply is adjusted along with the electromigration time t, and the voltage is adjusted according to the following formula:
wherein t is in minutes.
Further, the method further comprises: argon is introduced before heating to maintain the micro-positive pressure state in the deoxidizing device.
Further, the molten salt system is a calcium-metal fluoride composite system or a metal fluoride binary system or an alkaline earth metal and halide composite system thereof.
According to another aspect of the present invention, there is provided a deoxidizing apparatus for deoxidizing rare earth by the deoxidizing method of rare earth according to the first aspect of the present invention, comprising: the device comprises a rare earth metal bar to be deoxidized, an electromigration direct current power supply, an electrochemical deoxidization direct current power supply, a first electrode, a second electrode and a reaction container with a sealing cover;
a molten salt system is arranged in the reaction container;
the first electrode comprises a cathode made of molybdenum and an anode made of graphite, and is connected to an electromigration direct current power supply;
two ends of the rare earth metal bar are connected to the positive electrode and the negative electrode of the electromigration direct current power supply through a second electrode, and the rare earth metal bar is integrally immersed into a molten salt system;
the first electrode and the second electrode are connected to corresponding direct current power sources through the sealing cover.
Further, an alumina gasket is arranged at the bottom of the reaction vessel.
Further, an air inlet and an air outlet are formed in the sealing cover.
In summary, the embodiment of the invention provides a rare earth metal deoxidizing method and deoxidizing device, the method includes: placing a rare earth metal rod in a molten salt system, wherein the molten salt system comprises alkaline earth metal and a chloride system thereof; heating to make the molten salt system reach a preset temperature for melting, and keeping the rare earth metal bar in a solid state; connecting a rare earth metal material rod to a solid-state electromigration power supply, and starting and slowly increasing direct current of the electromigration direct current power supply at the preset temperature; adjusting the temperature of the rare earth metal rod to be kept at a preset temperature, and starting to calculate the electrotransport time t; starting an electrochemical deoxidizing direct current power supply while calculating the electromigration time, and adjusting the voltage of the electrochemical deoxidizing direct current power supply along with the electromigration time t; after a first predetermined time, the voltage remains unchanged; after a second predetermined time, the solid state electromigration power supply and the electrochemical deoxidation power supply are turned off. According to the technical scheme, three methods of solid electromigration, molten salt extraction and electrochemical deoxidation are organically combined, and a setting mode of specific reaction conditions is provided in the combining process, so that the three methods are organically combined and mutually promoted, the deoxidation limit is reduced, the deoxidation efficiency is improved, the defects of high vacuum environment requirement, high deoxidation limit and low electrochemical deoxidation efficiency of the traditional solid electromigration equipment are avoided, the defects of high raw material quality requirement, strict equipment vacuum environment requirement and long purification period of the traditional solid electromigration are overcome, and the beneficial effect of deep deoxidation is achieved.
Drawings
FIG. 1 is a schematic view of a rare earth deoxidizing apparatus provided by an embodiment of the present invention;
fig. 2 is a flow chart of a rare earth deoxidation method provided by an embodiment of the invention.
Detailed Description
The objects, technical solutions and advantages of the present invention will become more apparent by the following detailed description of the present invention with reference to the accompanying drawings. It should be understood that the description is only illustrative and is not intended to limit the scope of the invention. In addition, in the following description, descriptions of well-known structures and techniques are omitted so as not to unnecessarily obscure the present invention.
It is noted that unless otherwise defined, technical or scientific terms used in one or more embodiments of the present invention should be given the ordinary meaning as understood by one of ordinary skill in the art to which this disclosure belongs. The use of the terms "first," "second," and the like in one or more embodiments of the present invention does not denote any order, quantity, or importance, but rather the terms "first," "second," and the like are used to distinguish one element from another. The word "comprising" or "comprises", and the like, means that elements or items preceding the word are included in the element or item listed after the word and equivalents thereof, but does not exclude other elements or items. The terms "connected" or "connected," and the like, are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. "upper", "lower", "left", "right", etc. are used merely to indicate relative positional relationships, which may also be changed when the absolute position of the object to be described is changed.
The technical scheme of the invention is described in detail below with reference to the accompanying drawings. The embodiment of the invention provides a rare earth metal deoxidizing method, which reduces deoxidizing limit and realizes deep deoxidization of rare earth metal by organically combining solid electromigration, molten salt extraction and electrochemical deoxidization. The deoxidizing device used in the rare earth deoxidizing method according to the embodiment of the present invention is shown in fig. 1, and includes two sets of constant dc power supplies, an electromigration dc power supply 5 and an electrochemical deoxidizing dc power supply 4, which are respectively used as a power supply for a solid state electromigration process and a power supply for an electrochemical deoxidizing process. The rare earth metal to be deoxidized is a rare earth metal bar 8, the length dimension range is 150-200mm, the diameter is 10-20mm, wherein the oxygen content is not particularly required, and the rare earth comprises Y, sc, la, ce, pr, nd, gd, tb, dy, ho, er, lu and the like. The two ends of the rare earth metal bar 8 are connected to the positive electrode and the negative electrode of the electromigration direct current power supply 5 through a stainless steel electrode bar 7, and the current density of the electromigration direct current power supply 5 is 100-600A/cm 2 The voltage was 12V. In 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 the two ends of the deoxidation device are connected with an electrochemical deoxidation direct current power supply 4, and the voltage range is 0-10V. The device also comprises a molten salt system 9 for molten salt extraction process, which can adopt alkaline earth metal and chloride system thereof, such as calcium-metal fluoride compound system or metal fluoride binary system or alkaline earth metal and halide compound system, wherein the melting temperature is kept below the melting point of rare earth metal material rod to be purified to prevent the rare earth metal from melting. The device also comprises an alumina gasket 10 arranged at the bottom of the device and provided withAn air inlet 3 and an air outlet 6 on the sealing cover. The whole material of the deoxidizing device can be stainless steel.
Fig. 2 is a flowchart of a rare earth metal deoxidizing method according to an embodiment of the present invention, and in combination with fig. 1 and fig. 2, the rare earth metal deoxidizing method includes the following steps:
molten salt system is filled in the deoxidizing device, two ends of the rare earth metal bar 8 are connected by a stainless steel electrode rod 7 (the connecting part of the stainless steel electrode rod 7 and the rare earth metal bar 8 is connected by a tantalum joint, and molybdenum wires are used as electrode wires). Before electrifying, argon can be introduced first to maintain the micro-positive pressure state in the deoxidizing device, and a thermocouple protected by a corundum tube is used for measuring the temperature of molten salt in the deoxidizing device.
After the preparation is finished, the resistance furnace is started to heat, and after the molten salt system 9 reaches a preset temperature to melt, the rare earth metal bar 8 is kept in a solid state. The predetermined temperature is preferably 800-1500 ℃.
After the temperature is stable, the temperature is started, the direct current of the electromigration direct current power supply 5 is slowly increased, and the rare earth metal bar 8 can generate heat due to Joule heat, so that the temperature is increased, and the external heating temperature is correspondingly reduced until the temperature returns to the set temperature. After the molten salt reaches the preset temperature and is melted, the temperature of the rare earth metal material rod to be purified is kept solid, namely the temperature is visually stable, and the temperature floating range is +/-10 ℃. And after the temperature is stabilized, the current is continuously increased, the external heating temperature is reduced until the current is increased to the set target current, and the existing external heating temperature is maintained, so that the electromigration temperature is stabilized, the electromigration time is calculated at the moment, the electromigration time is calculated to be the temperature when the molten salt is just in a molten state and the rare earth metal rod to be purified is in a solid state, and the temperature difference exists between the inner wall temperature and the outer wall temperature because the molten salt is melted to increase the current, so that the electromigration time is calculated to be the time with consistent inner and outer temperatures. In the electromigration process, the voltage of the electromigration direct current power supply 5 and the change of the molten salt temperature need to be monitored, the molten salt temperature is the temperature reaching the eutectic point of the phase diagram according to the mixture ratio of the used molten salt materials, and can be determined according to the type of the molten salt actually used. In the step, the solid electromigration of oxygen impurity atoms is realized, the oxygen impurity atoms in the rare earth metal are enriched towards the anode end by the action of the electromigration direct current power supply 5, and the concentration difference of the oxygen impurity atoms in the molten salt system 9 at the anode end and near the anode end is increased. After solid state electromigration, a molten salt extraction process occurs, and oxygen impurity atoms are moved from the anode to the molten salt system 9 under the action of concentration difference by utilizing the property that the oxygen impurity atoms have larger affinity with components in the molten salt system 9.
After the electromigration is started (i.e. the electromigration time is calculated at the same time), the electrochemical deoxidizing direct current power supply 4 is started, and the voltage of the electrochemical deoxidizing direct current power supply 4 is set to be 0-10V according to the type of the rare earth metal to be purified. In the step, oxygen impurity atoms in a molten salt system near rare earth metal migrate to the surface of a graphite anode 2 under the action of an electrochemical deoxidization direct current power supply 4 by utilizing the principle of electrochemical deoxidization and react with the graphite anode 2 to generate CO/CO 2 And (3) precipitation. The process makes oxygen impurity atoms difficult to enrich in the molten salt system 9, the oxygen impurity concentration in the molten salt system 9 always keeps a lower level, and conversely, the molten salt extraction process is promoted, the oxygen impurity atom concentration at the metal anode end can be continuously reduced in the molten salt extraction process, the solid electromigration process is effectively promoted, and the purpose of deep deoxidation is realized along with the continuous progress of the whole reaction. In the whole process, the dynamic balance is maintained between the diffusion rate of oxygen impurity atoms from the anode end into molten salt and the escape rate of oxygen impurities on the graphite anode. Thus, the whole deoxidizing process can be continuously carried out. Therefore, the voltage of the electrochemical deoxidized dc power source 4 needs to be adjusted over time, and as the oxygen impurity content becomes lower and deoxidization becomes more difficult, the voltage can be adjusted according to the following formula:
after a first predetermined time (e.g., 120min-480 min), the voltage remains unchanged until the deoxidization process is completed.
After the solid electromigration is started and the molten salt temperature is kept floating by +/-10 ℃ and begins to time for a second preset time (for example, 10-30 h), the solid electromigration direct current power supply 5 and the electrochemical deoxidization direct current power supply 4 are turned off, after the molten salt is cooled, the rare earth metal bar 8 is taken out, surface treatment and sampling are carried out in a glove box, and metal impurity detection and gas impurity detection analysis are respectively carried out.
Specific examples and experimental data are given below.
Comparative example:
using molten CaCl 2 As electrolyte, yttrium metal was used as cathode and carbon rod was used as anode. In the electrochemical process, ca 2+ And (3) separating out at a cathode, reacting with oxygen in yttrium metal to generate CaO, and then dissolving in molten salt. Under the action of direct-current voltage, caO is decomposed again, generated oxygen ions move to the anode and react at the anode to generate CO/CO 2 And (3) separating out the gas, thereby removing oxygen impurities in the yttrium metal.
The results show that the oxygen content in the purified yttrium metal cathode end is less than 100ppm (and greater than 50 ppm).
Example 1:
step 01: processing metal Y into bars with the length of 150mm and the diameter of 10 mm;
step 02: in a glove box, treating the surface of a metal Y rod, removing pollutants generated in the processing process, sampling and analyzing the content of oxygen impurities in the metal Y rod, wherein the test result is 3581ppm;
step 03: two ends of a metal Y rod are connected by using tantalum joints, and two electrode rods are respectively led out of the two ends of the metal Y rod, and the metal Y rod is made of stainless steel;
step 04: caCl is put into a graphite crucible 2 Powder, caCl before 2 The powder is subjected to vacuum heat treatment at 600 ℃ for 10 hours to remove the water contained in the powder;
step 05: two ends of the metal Y rod are connected with a solid electromigration power supply, and an electrochemical deoxidization power supply is connected between the molybdenum wire and the graphite rod;
step 06: starting a resistance furnace heating power supply, observing the thermocouple temperature to display, stabilizing the thermocouple temperature at 950 ℃, and observing molten salt melting; then sinking the metal Y rod, the molybdenum wire and the graphite rod until the molten salt completely submerges the metal Y rod;
step 07: and (3) starting an electrochemical deoxidizing power supply, adding about 1.5V voltage between the molybdenum wire and the graphite rod, and carrying out pre-electrolysis for about 0.5h to remove residual impurities in the molten salt. Subsequently, the power supply is turned off;
step 08: turning on solid electromigration power supply, controlling current density at 600A/cm 2 The metal Y rod generates heat under the action of Joule heat, the temperature of the thermocouple is observed, and when the temperature of the thermocouple is stabilized at 950 ℃, the electromigration time is calculated;
step 09: starting the electromigration timing, starting an electrochemical deoxidizing direct current power supply, setting a voltage initial value of 3.3V, and enabling the voltage to be according to a formula along with time
After 480min, the voltage remained unchanged until the deoxidation process ended, and the whole deoxidation process continued for 30h. Then, the electromigration power supply and the electrochemical deoxidization power supply are turned off, after the molten salt is cooled to room temperature, the metal Y rod is taken out, the metal surface is polished in a glove box, and sampling analysis is carried out, so that the oxygen content in the cathode end of the purified metal Y is 46ppm.
Example 2:
step 01: processing metal La into bars with the length of 150mm and the diameter of 15 mm;
step 02: in a glove box, treating the surface of a metal La rod, removing pollutants generated in the processing process, sampling and analyzing the content of oxygen impurities in the metal La rod, wherein the test result is 1642ppm;
step 03: connecting two ends of a metal La rod by using tantalum joints, and leading out an electrode rod respectively from the two ends, wherein the metal La rod is made of stainless steel;
step 04: caCl is put into a graphite crucible 2 Powder, caCl before 2 The powder is subjected to vacuum heat treatment at 600 ℃ for 10 hours to remove the water contained in the powder;
step 05: two ends of the metal La rod are connected with a solid-state electromigration power supply, and an electrochemical deoxidization power supply is connected between the molybdenum wire and the graphite rod;
step 06: starting a resistance furnace heating power supply, observing the thermocouple temperature to display, stabilizing the thermocouple temperature at 850 ℃, and observing molten salt melting; then, sinking the metal La rod, the molybdenum wire and the graphite rod until the molten salt completely submerges the metal La rod;
step 07: and (3) starting an electrochemical deoxidizing power supply, adding about 1.5V voltage between the molybdenum wire and the graphite rod, and carrying out pre-electrolysis for about 0.5h to remove residual impurities in the molten salt. Subsequently, the power supply is turned off;
step 08: turning on solid electromigration power supply, controlling current density at 400A/cm 2 The metal La rod generates heat under the action of Joule heat, the temperature of the thermocouple is observed, and when the temperature of the thermocouple is stabilized at 850 ℃, the electromigration time is calculated;
step 09: starting the electromigration timing, starting an electrochemical deoxidizing direct current power supply, setting an initial value of 3.3V, and enabling the voltage to be according to a formula along with time
After 380min, the voltage is kept unchanged until the deoxidation process is finished, and the whole deoxidation process lasts for 20h. Then, the electromigration power supply and the electrochemical deoxidization power supply are turned off, after the molten salt is cooled to room temperature, the metal La rod is taken out, the metal surface is polished in a glove box, and sampling analysis is carried out, so that the oxygen content in the purified metal La is 33ppm.
Example 3:
step 01: processing metal Ce into bars with the length of 150mm and the diameter of 20 mm;
step 02: in a glove box, treating the surface of a metal Ce rod, removing pollutants generated in the processing process, sampling and analyzing the content of oxygen impurities in the metal Ce rod, wherein the test result is 1832ppm;
step 03: connecting two ends of a metal Ce rod by using tantalum joints, and leading out an electrode rod respectively from the two ends, wherein the material is stainless steel;
step 04: caCl is put into a graphite crucible 2 And NaCl powder in a molar ratio of 3:17, before which CaCl 2 And NaCl powder are subjected to vacuum heat treatment at 600 ℃ for 10 hours to remove the water contained in the NaCl powder;
step 05: two ends of the metal Ce rod are connected with a solid electromigration power supply, and an electrochemical deoxidization power supply is connected between the molybdenum wire and the graphite rod;
step 06: starting a heating power supply of the resistance furnace, observing the temperature display of the thermocouple, stabilizing the thermocouple at 750 ℃, and observing molten salt melting; then, sinking the metal Ce rod, the molybdenum wire and the graphite rod until the molten salt completely submerges the metal Ce rod;
step 07: and (3) starting an electrochemical deoxidizing power supply, adding about 1.5V voltage between the molybdenum wire and the graphite rod, and carrying out pre-electrolysis for about 0.5h to remove residual impurities in the molten salt. Subsequently, the power supply is turned off;
step 08: starting a solid electromigration power supply, controlling the current density to be 500A/cm < 2 >, generating heat by a metal Ce rod under the action of Joule heat, observing the temperature of a thermocouple, and calculating electromigration time when the temperature of the thermocouple is stabilized at 850 ℃;
step 09: starting the electromigration timing, starting an electrochemical deoxidizing direct current power supply, setting an initial value of 3.3V, and enabling the voltage to be according to a formula along with time
After 420min, the voltage is kept unchanged until the deoxidation process is finished, and the whole deoxidation process lasts for 20h. Then, the electromigration power supply and the electrochemical deoxidization power supply are turned off, after the molten salt is cooled to room temperature, the metal Ce rod is taken out, the metal surface is polished in a glove box, and sampling analysis is carried out, so that the oxygen content in the purified metal Ce is 32ppm.
Example 4:
step 01: processing metal Tb into bars with the length of 150mm and the diameter of 10 mm;
step 02: in a glove box, treating the surface of a metal Tb rod, removing pollutants generated in the processing process, sampling and analyzing the content of oxygen impurities in the metal Tb rod, wherein the test result is 1541ppm;
step 03: connecting two ends of a metal Tb rod by using tantalum connectors, and leading out an electrode rod respectively from the two ends, wherein the material of the electrode rod is stainless steel;
step 04: caCl is put into a graphite crucible 2 Powder, caCl before 2 Vacuum heat treatment at 600 deg.C for 10 hrRemoving moisture contained in the water;
step 05: two ends of the metal Tb rod are connected with a solid electromigration power supply, and an electrochemical deoxidization power supply is connected between the molybdenum wire and the graphite rod;
step 06: starting a resistance furnace heating power supply, observing the thermocouple temperature to display, stabilizing the thermocouple temperature at 950 ℃, and observing molten salt melting; then sinking the metal Tb rod, the molybdenum wire and the graphite rod until the molten salt completely submerges the metal Tb rod;
step 07: and (3) starting an electrochemical deoxidizing power supply, adding about 1.5V voltage between the molybdenum wire and the graphite rod, and carrying out pre-electrolysis for about 0.5h to remove residual impurities in the molten salt. Subsequently, the power supply is turned off;
step 08: starting a solid electromigration power supply, controlling the current density at 400A/cm < 2 >, generating heat by a metal Tb rod under the action of Joule heat, observing the temperature of a thermocouple, and calculating the electromigration time when the temperature of the thermocouple is stabilized at 950 ℃;
step 09: starting the electromigration timing, starting an electrochemical deoxidizing direct current power supply, setting an initial value of 3.3V, and enabling the voltage to be according to a formula along with time
After 320min, the voltage remained unchanged until the deoxidation process ended, and the whole deoxidation process continued for 20h. Then, the electromigration power supply and the electrochemical deoxidization power supply are turned off, after the molten salt is cooled to room temperature, the metal Tb rod is taken out, the metal surface is polished in a glove box, and sampling analysis is carried out, so that the oxygen content in the purified metal Tb is 35ppm.
Example 5:
step 01: processing metal Lu into bars with the length of 150mm and the diameter of 10 mm;
step 02: in a glove box, treating the surface of a metal Lu rod, removing pollutants generated in the processing process, sampling and analyzing the content of oxygen impurities in the pollutants, wherein the test result is 2836ppm;
step 03: two ends of a metal Lu rod are connected by using tantalum joints, and two electrode rods are led out of the two ends respectively, and the metal Lu rod is made of stainless steel;
step 04: caCl is put into a graphite crucible 2 Powder, caCl before 2 Vacuum heat treatment at 600 deg.c for 10 hr to eliminate water;
step 05: two ends of the metal Lu rod are connected with a solid electromigration power supply, and an electrochemical deoxidization power supply is connected between the molybdenum wire and the graphite rod;
step 06: starting a resistance furnace heating power supply, observing the thermocouple temperature to display, stabilizing the thermocouple temperature at 950 ℃, and observing molten salt melting; subsequently, sinking the metal Lu rod, the molybdenum wire and the graphite rod until the molten salt completely submerges the metal Lu rod;
step 07: and (3) starting an electrochemical deoxidizing power supply, adding about 1.5V voltage between the molybdenum wire and the graphite rod, and carrying out pre-electrolysis for about 0.5h to remove residual impurities in the molten salt. Subsequently, the power supply is turned off;
step 08: starting a solid electromigration power supply, controlling the current density at 300A/cm < 2 >, generating heat by a metal Lu rod under the action of Joule heat, observing the temperature of a thermocouple, and calculating electromigration time when the temperature of the thermocouple is stabilized at 950 ℃;
step 09: starting the electromigration timing, starting an electrochemical deoxidizing direct current power supply, setting an initial value of 3.3V, and enabling the voltage to be according to a formula along with time
After 320min, the voltage remained unchanged until the deoxidation process ended, and the whole deoxidation process continued for 10h. Then, the electromigration power supply and the electrochemical deoxidization power supply are turned off, after the molten salt is cooled to room temperature, the metal Lu rod is taken out, the metal surface is polished in a glove box, and sampling analysis is carried out, so that the oxygen content in the purified metal Lu is 31ppm.
In summary, the embodiment of the invention relates to a rare earth metal deoxidizing method and deoxidizing device, the method comprising: placing a rare earth metal rod in a molten salt system, wherein the molten salt system comprises alkaline earth metal and a chloride system thereof; heating to make the molten salt system reach a preset temperature for melting, and keeping the rare earth metal bar in a solid state; connecting a rare earth metal material rod to a solid-state electromigration power supply, and starting and slowly increasing direct current of the electromigration direct current power supply at the preset temperature; adjusting the temperature of the rare earth metal rod to be kept at a preset temperature, and starting to calculate the electrotransport time t; starting an electrochemical deoxidizing direct current power supply while calculating the electromigration time, and adjusting the voltage of the electrochemical deoxidizing direct current power supply along with the electromigration time t; after a first predetermined time, the voltage remains unchanged; after a second predetermined time, the solid state electromigration power supply and the electrochemical deoxidation power supply are turned off. According to the technical scheme, three methods of solid electromigration, molten salt extraction and electrochemical deoxidation are organically combined, and a setting mode of specific reaction conditions is provided in the combining process, so that the three methods are organically combined and mutually promoted, the deoxidation limit is reduced, the deoxidation efficiency is improved, the defects of high vacuum environment requirement, high deoxidation limit and low electrochemical deoxidation efficiency of the traditional solid electromigration equipment are avoided, the defects of high raw material quality requirement, strict equipment vacuum environment requirement and long purification period of the traditional solid electromigration are overcome, and the beneficial effect of deep deoxidation is achieved.
It is to be understood that the above-described embodiments of the present invention are merely illustrative of or explanation of the principles of the present invention and are in no way limiting of the invention. Accordingly, any modification, equivalent replacement, improvement, etc. made without departing from the spirit and scope of the present invention should be included in the scope of the present invention. Furthermore, the appended claims are intended to cover all such changes and modifications that fall within the scope and boundary of the appended claims, or equivalents of such scope and boundary.
Claims (10)
1. A rare earth metal deoxidizing method, comprising:
placing a rare earth metal rod in a molten salt system, wherein the molten salt system comprises alkaline earth metal and a chloride system thereof;
heating to make the molten salt system reach a preset temperature for melting, and keeping the rare earth metal bar in a solid state;
connecting a rare earth metal material rod to a solid-state electromigration power supply, and starting and slowly increasing direct current of the electromigration direct current power supply at the preset temperature;
adjusting the temperature of the rare earth metal rod to be kept at a preset temperature, and starting to calculate the electrotransport time t;
starting an electrochemical deoxidizing direct current power supply while calculating the electromigration time, and adjusting the voltage of the electrochemical deoxidizing direct current power supply along with the electromigration time t;
after a first predetermined time, the voltage remains unchanged;
after a second predetermined time, the solid state electromigration power supply and the electrochemical deoxidation power supply are turned off.
2. The method of 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:
the voltage range of the electrochemical deoxidizing power source is set to be 0-10V according to the type of rare earth metal.
4. The method of claim 1, wherein said adjusting the temperature of the rare earth metal bar to be maintained at a predetermined temperature comprises:
the temperature of the rare earth metal bar is maintained at the predetermined temperature by adjusting the heating temperature.
5. The method of claim 1, wherein adjusting the voltage of the electrochemical deoxygenation dc power source with the electromigration time t comprises adjusting according to the following equation:
wherein t is in minutes.
6. The method according to claim 1, wherein the method further comprises: argon is introduced before heating to maintain the micro-positive pressure state in the deoxidizing device.
7. The method of claim 1, wherein 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 deoxidizing apparatus for deoxidizing rare earth by the rare earth metal deoxidizing method as claimed in any one of claims 1 to 7, comprising: the device comprises a rare earth metal bar to be deoxidized, an electromigration direct current power supply, an electrochemical deoxidization direct current power supply, a first electrode, a second electrode and a reaction container with a sealing cover;
a molten salt system is arranged in the reaction container;
the first electrode comprises a cathode made of molybdenum and an anode made of graphite, and is connected to an electromigration direct current power supply;
two ends of the rare earth metal bar are connected to the positive electrode and the negative electrode of the electromigration direct current power supply through a second electrode, and the rare earth metal bar is integrally immersed into a molten salt system;
the first electrode and the second electrode are connected to corresponding direct current power sources through the sealing cover.
9. The deoxidizing device of claim 8, wherein the bottom of the reaction vessel is provided with an alumina gasket.
10. The deoxidizing device of claim 9, wherein the sealing cover is provided with an air inlet and an air outlet.
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