CN112921362B - Method for preparing rare earth alloy by molten salt electrolysis - Google Patents
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Abstract
A method for preparing rare earth alloy by molten salt electrolysis, in the electrolysis process, valence-variable elements are introduced to participate in electrochemical reaction and form a compound (M) with carbon x C y ) Compound (M) x C y ) Carbon forms CO or CO at the anode 2 The gas escapes, and the cycle is repeated, so that the aim of reducing the carbon content in the product is fulfilled. The method is simple and convenient to use, simple to operate, low in investment cost and easy to industrially popularize and apply.
Description
Technical Field
The invention relates to the field of nonferrous metal electrolysis, in particular to a method for preparing rare earth alloy by molten salt electrolysis.
Background
Rare earth is an indispensable additive material due to its specific optical, electrical, magnetic and catalytic properties, and plays a great role in the field of functional materials such as luminescent materials, permanent magnetic materials, superconducting materials, hydrogen storage materials, magnetostrictive materials, catalytic materials and the like. The rare earth additive types comprise pure rare earth metals and rare earth alloys, wherein the rare earth alloys are increasingly applied in various fields due to the advantages of strong oxidation resistance, low melting point, less burning loss, difficult agglomeration in the adding process and the like. At present, the method for preparing the rare earth alloy mainly comprises a molten salt electrolysis method, a melting and matching method and a reduction method, wherein the molten salt electrolysis method has been applied to large-scale industry due to the advantages of short process flow, low preparation cost, low energy consumption, low oxygen content and the like, for example, the molten salt electrolysis method is used for producing Gd-Fe alloy, dyFe alloy, gd-Mg alloy and the like, and the single-furnace monthly yield reaches 3t to 5t.
At present, along with the fact that the rare earth is more and more widely applied to high-end application fields such as electronic information, high-performance magnetic materials and intelligent manufacturing, the purity requirement of rare earth alloy is higher and higher, and the content of carbon as a key impurity is required to be as low as possible. In industry, the carbon content of the rare earth alloy prepared by the molten salt electrolysis method can be controlled to be 0.03-0.05%, but the carbon content still can not meet the application requirements of some high-end fields.
The carbon impurities in the molten salt electrolysis process are derived from carbon-containing materials such as graphite anodes, graphite crucibles, ironware and the like. The formation of carbon impurities in rare earth metals needs two processes: (1) carbon impurities enter the molten salt from the carbonaceous material; (2) carbon in the molten salt reacts with the rare earth alloy obtained by electrolysis, and the carbon exists in the rare earth alloy in a solid solution state or a compound state. The methods for reducing the carbon content in the rare earth alloy are reported in the open, and mainly focus on the first process, namely reducing the carbon content in the rare earth alloy by reducing the content of carbon impurities entering the molten salt, for example, the method reduces the amount of the carbon impurities entering the molten salt by dipping the graphite anode in the Chinese patent [ CN102677100B ]; researches on troxacarb and the like show that the aim of reducing the content of carbon impurities is fulfilled by controlling the electrolysis temperature and reducing the carbon solubility and the graphite consumption rate in the molten salt. No carbon reduction method for the second process has been found.
Chinese patent CN 102361092A provides a molten carbonate electrolyte containing a valence-variable metal oxide, and the carbonate is Li 2 O 3 And K 2 CO 3 Oxidation of incorporated metal valuesThe substance being Fe 2 O 3 、Co 3 O 4 、NiO、Ni 2 O 3 、MnO 2 、CuO、V 2 O 5 、MoO 3 、SnO 2 、CeO 2 Or PbO 2 One or more than one of the mixture in (2), the weight ratio of the variable valence metal oxide is 3-5%. Anode is a graphite rod, reference electrode is 33% 2 -67％CO 2 Au, the counter electrode is a steel cylinder. Although the electrolyte solution of this patent incorporates a valence-variable metal compound, it is fundamentally different from the present invention and mainly includes the following two aspects: (1) the invention has different aims: the invention of Chinese patent CN 102361092A aims at improving the carbon anode electro-oxidation performance and further improving the power generation capacity of the carbon fuel cell, and the invention aims at reducing the carbon content in the molten salt electrolysis rare earth alloy; (2) the realization principle is different: the function of the valence-variable metal compound in Chinese patent CN 102361092A is catalytic action, the valence-variable ion does not directly react with carbon, and the electrochemical reaction (4M) n-1 →4M n +4e - ) Accelerating anodic oxidation reaction (C +2 CO) under the action 3 2- +4M n →3CO 2 +4M n-1 ) Thereby improving the discharge capability. In the process, the valence-variable ions mainly promote the movement of electrons and do not react with carbon; in the invention, valence-variable ions as reactants participate in cathode-anode reaction, and react with carbon in rare earth alloy at the cathode (M) n+ +e - +[C]→[M x C y ]) Forming low-valent carbides; the low-valence carbide reacts with oxygen ions ([ M ] at the anode x C y ]–e - +[O 2- ]→M n + +CO/CO 2 ℃.) to become high-valence compounds, and then the carbon element is combined with oxygen to form gas to escape. The variable valence element compound converted into the high valence state flows to the cathode along with the molten salt and reacts with carbon in the rare earth alloy again, and the process is repeated in such a circulating way, so that the aim of reducing the carbon content in the rare earth alloy is fulfilled. (3) The invention belongs to the technical field of different, and the Chinese patent CN 102361092A belongs to the chemical industry field, and the invention belongs to the non-ferrous metallurgy field.
Chinese patent CN 1986895A provides a method for enriching thulium and lutetium and simultaneously oxidizing cerium by electrolytic reduction of ytterbium, which is characterized in that: by utilizing the variable valence characteristics of ytterbium and cerium, the ytterbium is reduced to be bivalent in the cathode chamber, and the cerium is oxidized to be tetravalent in the anode chamber. Although this patent utilizes the valence change characteristics of ytterbium and cerium, it is fundamentally different from the present invention: (1) the invention aims at difference, chinese patent CN 1986895A utilizes the variable valence characteristics of cerium and ytterbium and the characteristic that the physical and chemical characteristics of ions with different valence states have larger difference to separate different rare earth ions, thereby obtaining thulium, lutetium, ytterbium oxide and cerium oxide or cerium hydroxide, the invention utilizes the cyclic reciprocating reaction of the variable valence ions and carbon between a cathode and an anode to convert carbon impurities into CO/CO2, and the aim is to reduce carbon impurities in rare earth metals; (2) the realization principle is different: chinese patent CN 1986895A reduces ytterbium into bivalent, cerium oxide quadrivalent, then separates them by using their different physical properties, the reaction is a one-way reaction; the invention utilizes the cyclic conversion of the valence-variable elements between the cathode and the anode in high and low valence states, so that carbon is converted into CO/CO2 to escape in the process.
Chinese patent No. 103337648B provides a low-temperature catalytic molten salt electrolyte for improving carbon electrooxidation performance, which is characterized in that: comprising a catalyst consisting of a powder of a valence-variable metal oxide and a salt capable of forming a eutectic with the valence-variable metal oxide, a carbonate, said catalyst being CsVO in a molar ratio of 3 3 -MoO 3 Or Cs 2 MoO 4 -V 2 O 5 (ii) a The carbonate is Li 2 CO 3 And K 2 CO 3 Or is Li 2 CO 3 、Na 2 CO 3 And K 2 CO 3 (ii) a In the electrolyte, the mass ratio of the catalyst to the carbonate is 5-20%. The implementation principle, the invention purpose and the technical field of the invention are the same as the Chinese patent CN 102361092A, so the invention has fundamental difference with the invention.
The Chinese patents CN 103952727B, CN 204702816U, CN 204702817U and CN 10169609B improve the uniformity, feeding accuracy and temperature stability of the furnace temperature by adding a stirring device, an accurate automatic feeding device, an automatic temperature control device, a radiator and the like, and avoid the over-standard carbon content in the product caused by furnace temperature fluctuation and inaccurate feeding, so as to achieve the purpose of reducing the carbon content in the product; chinese patents CN 103540961B, CN 1055140C, CN 204370008U and CN102677100B reduce the carbon content in molten salt or the carbide content at the bottom of a graphite cell by improving the structure of a graphite anode, changing the material of the graphite anode, changing the position of a cathode, coating a protective layer on the surface of the anode and the like, so as to achieve the purpose of reducing the carbon content in a product; the Lizonian, huhua industry, wanglinsheng, weixiaming, and Dongsui and the like enable an electrolysis flow field and a temperature field to be more reasonable by improving the composition structure of electrolysis equipment, electrolysis process conditions and the like, thereby achieving the purpose of reducing the carbon content in the product. All the reports above reduce the amount of carbon impurities entering the molten salt or reduce the solubility of carbon in the molten salt by methods such as structure improvement and process parameter control, so as to achieve the purpose of reducing the carbon content.
Disclosure of Invention
Aiming at the problem of high carbon content of rare earth alloy prepared by an electrolysis method, the invention provides a method for preparing the rare earth alloy by molten salt electrolysis, which takes part in electrochemical reaction through valence-variable elements and forms a compound (M) with carbon x C y ) Compound (M) x C y ) Carbon forms CO or CO at the anode 2 The gas escapes, and the aim of reducing the carbon content in the product is further achieved.
In order to achieve the aim, the invention provides a method for preparing rare earth alloy by molten salt electrolysis, which adopts an electrolytic cell to carry out electrolysis, wherein the electrolytic cell comprises a cathode, an anode, a cell body and a collecting container; the upper part of the electrolytic cell is provided with an opening, and electrolytic fused salt is filled in the cell body; the method comprises the following steps:
adding an electrolytic rare earth raw material from the opening;
adding a variable valence element, wherein the variable valence element is not a main alloy element of the rare earth alloy; the main alloy element is an element with the mass content not less than 5% in the alloy;
and stirring, discharging and charging in the electrolytic process by using an auxiliary operation tool. Further, the added variable valence elements are dissolved in the molten salt to form variable valence ions M n+ At the cathode, a reduction reaction takes place with carbon to form a compound M x C y ；
The compound M x C y Oxidation reaction takes place at the anode to make carbon react with CO or CO 2 Is released, the compound reforms a valence-variable ion M n+ 。
Furthermore, the added variable valence element can be in a simple substance state or a compound state; the single-state valence-variable elements comprise one or more of Yb, sm, fe, si, ni, ti, cr, cu, V, sn and Mn, and the compound state is the compound state of the single-state valence-variable elements and comprises Yb 2 O 3 、Sm 2 O 3 、Fe 2 O 3 、YbF 3 、SmF 3 、YbCl 3 Or SmCl 3 One or more of (a). Further, the step of adding the variable valence element comprises the following steps:
mixing a valence-variable element simple substance or a valence-variable element compound into a rare earth raw material, and feeding the rare earth raw material into electrolytic molten salt, wherein the mass percentage of the valence-variable element in the rare earth raw material is less than 30%;
or, adding a valence-variable element simple substance or a valence-variable element compound into the electrolytic molten salt, wherein the mass percentage of the valence-variable elements in the molten salt is less than 20%;
or, the valence-variable element simple substance or the valence-variable element compound is used as a material of a cathode in the electrolytic cell, and the mass ratio of the valence-variable element in the cathode is less than 80%;
or, mixing a valence-variable element simple substance or a valence-variable element compound into an anode material, wherein the mass percentage of the valence-variable element in the anode is less than 10%;
or, the variable valence element simple substance or the variable valence element compound is coated on the surface of the auxiliary operation tool or the collection container;
or, a variable price element is added in the operation tool or the collection container.
Further, the step of coating the variable valence element simple substance or the variable valence element compound on the surface of the auxiliary operation tool or the collection container comprises the following steps:
the thickness of a coating layer coated on the surface of the auxiliary operation tool is less than 10mm;
the thickness of the coating layer coated on the surface of the collecting container is less than 20mm.
Further, the adding of the variable-price element in the auxiliary operation tool or the collection container comprises:
the variable valence elements account for less than 10% of the auxiliary operation tool material by mass percent;
the variable valence elements account for less than 10% of the material quality of the collecting container. Furthermore, the rare earth alloy prepared by the method contains variable valence elements.
Further, the content of the variable valence elements is as follows: yb accounts for more than or equal to 0.01 percent of the mass percent of the prepared rare earth alloy; sm accounts for more than or equal to 0.01 percent of the mass percent of the prepared rare earth alloy; fe accounts for more than or equal to 0.40 percent of the mass percent of the prepared rare earth alloy; si accounts for more than or equal to 0.10 percent of the mass percent of the prepared rare earth alloy; ni accounts for more than or equal to 0.10 percent of the mass percent of the prepared rare earth alloy; ti accounts for more than or equal to 0.10 percent of the mass percent of the prepared rare earth alloy; the Cr accounts for more than or equal to 0.10 percent of the mass percent of the prepared rare earth alloy; cu accounts for more than or equal to 0.10 percent of the mass percent of the prepared rare earth alloy; v accounts for more than or equal to 0.10 percent of the mass percent of the prepared rare earth alloy; sn accounts for more than or equal to 0.10 percent of the mass percent of the prepared rare earth alloy; or Mn accounts for more than or equal to 0.08 percent of the mass of the prepared rare earth alloy.
Further, the rare earth alloy and the electrolytic molten salt obtained by the method both include valence-variable elements, and the mass contents of the valence-variable elements are respectively represented by omega (molten salt) And ω (rare earth alloy) And the following relationship exists between the two: omega (molten salt) /ω (rare earth alloy) ＞5。
The technical scheme of the invention has the following beneficial technical effects: through introducing the variable valence elements, the variable valence elements react at the cathode to generate a compound M x C y Compound M x C y Production of CO and CO in anodic reaction 2 The carbon content in the rare earth alloy can be effectively reduced by the cyclic reciprocating. The application method is simple and convenient, the operation is simple, the investment cost is low, and the industrial popularization and application are easy.
Drawings
FIG. 1 is a graph comparing the carbon content in rare earth alloys produced with different electrolyte compositions.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the accompanying drawings in combination with the embodiments. It is to be understood that these descriptions are only illustrative and are not intended to limit the scope of the present invention. Moreover, in the following description, descriptions of well-known structures and techniques are omitted so as to not unnecessarily obscure the concepts of the present invention.
At present, no related patent and literature report aiming at the method for reducing the carbon content in the rare earth alloy by adopting the variable valence element exists, and the variable valence element is introduced to react with carbon in the molten salt to form a compound (M) x C y ) And then removing the meta-compound (M) by anodic electrochemical reaction x C y ) The medium carbon impurities weaken the action of the rare earth alloy and carbon, and the purpose of reducing the carbon content in the rare earth alloy is achieved.
Aiming at the problem that the carbon content of the rare earth alloy prepared by an electrolysis method is higher, the invention provides a method for preparing the rare earth alloy by molten salt electrolysis, wherein an electrolysis bath is adopted for electrolysis, and the electrolysis bath comprises a cathode, an anode, a bath body and a collecting container; the upper part of the electrolytic cell is provided with an opening, and electrolytic fused salt is filled in the cell body; the cathode and the anode are electrically conductive through molten salt. During electrolysis, direct current is connected through the cathode and the anode, and electrolysis raw materials are added into the electrolysis molten salt through the upper opening of the electrolytic cell. Under the action of DC current, electrochemical reaction takes place to obtain rare earth alloy at cathode and CO at anode 2 A gas. The method comprises the following steps:
adding an electrolytic rare earth raw material from the opening;
adding a variable valence element, wherein the variable valence element is not a main alloy element of the rare earth alloy; the main alloy element is an element with the mass content not less than 5% in the alloy;
and stirring, discharging and charging in the electrolytic process by using an auxiliary operation tool.
It should be noted that the introduced valence-change element should not have negative influence on the application of the rare earth alloy product, for example, the valence-change element ytterbium, silicon and the like are introduced into the yttrium magnesium alloy, wherein the ytterbium has positive influence on the performance of the magnesium alloy, the silicon is an essential element in the magnesium alloy, and the introduced valence-change element does not have negative influence.
The carbon reduction principle of the invention is as follows: after the valence-variable element simple substance or compound is dissolved in the molten salt, valence-variable ions (M) are formed n + ) Under the action of direct current, electrons obtained at the cathode undergo a reduction reaction and are alloyed with carbon in the molten salt to form a compound (M) x C y ) The reaction equation is:
M n+ +e - +[C]→[M x C y ] (1)
formed Compound (M) x C y ) As the molten salt flows to the anode, electrons are lost at the anode to generate oxidation reaction, and carbon impurities are CO or CO 2 Is escaped, its reaction equation is:
[M x C y ]–e - +[O 2- ]→M n+ +CO/CO 2 ↑ (2)
generated valence-variable ion (M) n+ ) As the molten salt flows to the cathode, electrons are obtained again at the cathode to perform a reduction reaction and are alloyed with carbon in the molten salt to form a compound (M) x C y ) The above steps are repeated in a circulating way, and finally the purpose of reducing the carbon content in the rare earth alloy is achieved.
Further, the electrolytic molten salt and the rare earth raw material are a well-known molten salt system and a well-known raw material. Furthermore, the variable valence element introducing method adopted by the invention is simple, the operation is simple and convenient, the variable valence element introducing state is various and can be a single-substance state, and the single-substance variable valence element comprises one or more of Yb, sm, fe, si, ni, ti, cr, cu, V, sn and Mn; may also be in a compound state, such as an oxide, fluoride, chloride, etc., and specifically, the valence altering elements of the compound state include, but are not limited to Yb 2 O 3 、Sm 2 O 3 、Fe 2 O 3 、YbF 3 、SmF 3 、YbCl 3 Or SmCl 3 Can be based on electrolysisAnd (4) selecting a system. The variable valence elements are characterized in that in the process of electrolyzing the rare earth alloy: under the action of direct current, valence-variable elements can obtain electrons at the cathode to perform reduction reaction and form a compound (M) with carbon in the molten salt x C y ) The formed compound flows to the anode along with the molten salt, electrons are lost at the anode, oxidation reaction is carried out, and carbon impurities are CO or CO 2 The form of (a) escapes. The carbon reduction effect is obvious after the valence-variable elements are added, and the method can be popularized and applied in a large range in industry.
Further, the step of adding the variable valence element can comprise the following 1-6 modes:
1. mixing a valence-variable element simple substance or a valence-variable element compound into a rare earth raw material, and feeding the mixture into an electrolytic molten salt along with the rare earth raw material, wherein the mass percentage of the valence-variable element in the rare earth raw material is less than 30%. Specifically, during electrolysis, an electrolysis raw material is added through the upper opening of the electrolysis bath, one or more variable valence elements (such as Yb, sm and other rare earth variable valence elements, fe, si, mn and other non-rare earth variable valence elements) are mixed in the electrolysis raw material, the form of the mixed variable valence elements can be a single substance state or a compound state, and the mass of the variable valence elements in the electrolysis raw material is less than 30%.
2. Adding a valence-variable element simple substance or a valence-variable element compound into the electrolytic molten salt, wherein the mass percentage of the valence-variable elements in the molten salt is less than 20%. Specifically, during electrolysis, electrolytic molten salt is filled in the tank body, one or more variable valence elements (Yb, sm and other rare earth variable valence elements, fe, si, mn and other non-rare earth variable valence elements) are added into the electrolytic molten salt, the added variable valence elements can be in a single state or a compound state, and the mass of the variable valence elements in the electrolytic molten salt is less than 20%.
3. The valence-variable element simple substance or the valence-variable element compound is used as a material of a cathode in an electrolytic cell, and the mass ratio of the valence-variable element in the cathode is less than 80%. The cathode is the composition of electrolysis equipment, except the cathode material elements, one or more variable valence elements (rare earth variable valence elements such as Yb and Sm, and other non-rare earth variable valence elements such as Fe, si and Mn) are doped into the cathode, the doped variable valence elements can be in a single state or a compound state, and the mass proportion of the variable valence elements is less than 80%.
4. The valence-variable element simple substance or the valence-variable element compound is mixed into the anode material, and the mass percentage of the valence-variable element in the anode is less than 10%. Specifically, the anode is a component of the electrolysis equipment, besides the elements of the anode material, one or more variable valence elements (Yb, sm and other rare earth variable valence elements, fe, si, mn and other non-rare earth variable valence elements) are doped into the anode, the form of the doped variable valence elements can be a single substance state or a compound state, and the mass proportion of the variable valence elements in the anode material is less than 10%.
5. The variable valence element simple substance or the variable valence element compound is coated on the surface of the auxiliary operation tool or the collection container. Specifically, the collecting container is composed of electrolytic equipment, one or more variable valence elements (rare earth variable valence elements such as Yb and Sm, and other non-rare earth variable valence elements such as Fe, si and Mn) are coated on the surface of the collecting container, the form of the coated variable valence elements can be a simple substance layer or a compound layer, and the thickness of the coating layer is less than 20mm; or, the electrolysis process uses an auxiliary operation tool to carry out operations such as stirring, discharging, charging and the like, one or more variable valence elements (rare earth variable valence elements such as Yb and Sm, and other non-rare earth variable valence elements such as Fe, si and Mn) are coated on the surface of the used operation tool, the form of the coated variable valence gold element can be a simple substance layer or a compound layer, and the thickness of the coating layer is less than 10mm.
6. Adding variable-valence elements in an operation tool or a collection container. Specifically, an auxiliary operation tool is used for stirring, discharging, charging and the like in the electrolysis process, one or more variable valence elements (rare earth variable valence elements such as Yb and Sm, and other non-rare earth variable valence elements such as Fe, si and Mn) are doped into the material of the used operation tool, the doped variable valence elements can be in a single state or a compound state, and the variable valence elements account for less than 10 percent of the material of the operation tool; or the collecting container is a component of the electrolysis equipment, besides the elements of the material of the collecting container, one or variable valence elements (rare earth variable valence elements such as Yb and Sm, and other non-rare earth variable valence elements such as Fe, si and Mn) are doped into the material of the collecting container, the doped variable valence elements can be in a single substance state or a compound state, and the mass proportion of the variable valence elements in the material of the collecting container is less than 10%.
Furthermore, the rare earth alloy prepared by the method contains variable valence elements. If the contained variable valence elements are one or more variable valence elements in the table 2, the component mass content is less than or equal to 5 percent, and the component characteristics shown in the table 1 are met.
TABLE 1 VARIABLE VARIATION ELEMENTS AND THEIR CORRESPONDING MASS CONTENT IN RARE-EARTH ALLOY PRODUCTS
| Variable valence element | Yb | Sm | Fe | Si | Ni | Ti |
| Mass content/wt% | ≥0.01 | ≥0.01 | ≥0.40 | ≥0.10 | ≥0.10 | ≥0.10 |
| Variable valence element | Cr | Cu | V | Sn | Mn | Others |
| Mass content/wt% | ≥0.10 | ≥0.10 | ≥0.10 | ≥0.10 | ≥0.08 | ≥0.05 |
Furthermore, the rare earth alloy product prepared by the method of the invention contains a certain amount of variable valence elements in the electrolytic molten salt and the products, and the mass contents of the variable valence elements are respectively expressed as omega (molten salt) And omega (rare earth alloy) And the following relationship exists between the two: omega (molten salt) /ω (rare earth alloy) ＞5。
The method can further reduce the carbon content in the rare earth alloy by 20-70 percent, thereby achieving the purpose of preparing the low-carbon rare earth alloy.
The present invention will be further described with reference to the following specific examples.
The electrolysis equipment adopted by the embodiment of the invention is an industrial common electrolysis bath which comprises a tungsten cathode, a graphite anode, a graphite tank, a collecting crucible and the like.
Example 1
The electrolytic raw material is a mixture of yttrium oxide and magnesium oxide.
The electrolyte is a mixture of yttrium fluoride, lithium fluoride and ytterbium fluoride, and the mass content of ytterbium element is 1.0%.
The electrolysis temperature is 1000-1100 ℃, the average carbon content of the yttrium magnesium alloy obtained by electrolysis is 0.05wt%, and the ytterbium content is 0.04wt% -0.10 wt%.
For comparative analysis of the carbon reduction effect of the variable-valence elements, under the same electrolysis condition, the electrolyte composition is changed into a mixture of yttrium fluoride and lithium fluoride, and the average carbon content in the yttrium magnesium alloy obtained by electrolysis is 0.10wt%. Fig. 1 is a comparison result of the carbon content in the rare earth alloy under the condition that the electrolyte contains ytterbium fluoride, and it can be known from fig. 1 that the carbon content in the rare earth alloy is obviously reduced by 27% -67% after the valence-variable element ytterbium is added.
Example 2
The electrolytic raw material is a mixture of yttrium oxide, magnesium oxide and ytterbium oxide, wherein the content of ytterbium is 0.5wt%
The electrolyte comprises yttrium fluoride and lithium fluoride, and electrolysis is carried out at 1000-1100 ℃, so that the obtained yttrium magnesium alloy contains about 0.04wt% of carbon and 0.05-0.15 wt% of ytterbium;
example 3
The electrolytic raw material is a mixture of dysprosium oxide and ytterbium oxide, wherein the content of ytterbium is 0.1wt%;
dysprosium fluoride and lithium fluoride are formed in an electrolyte, and solid cathode (iron) consumable electrolysis is carried out at the temperature of 1080 +/-20 ℃, so that the obtained dysprosium-iron alloy has the carbon content of about 0.03wt% and the ytterbium content of 0.05-0.10 wt%;
example 4
The electrolysis raw material is a mixture of gadolinium oxide, magnesium oxide and samarium oxide, wherein the mass content of samarium is 0.1%;
the electrolyte is gadolinium fluoride and lithium fluoride, and electrolysis is carried out at 1050 +/-50 ℃, so that the obtained gadolinium-magnesium alloy has the carbon content of about 0.06wt% and the samarium content of 0.03-0.10 wt%.
Therefore, after the variable-valence elements are added, the carbon content in the obtained rare earth alloy product is obviously reduced. In summary, the present invention provides a method for preparing rare earth alloy by molten salt electrolysis, wherein during the electrolysis process, by introducing a valence-variable element, the valence-variable metal participates in the electrochemical reaction and forms a compound (M) with carbon x C y ) Compound (M) x C y ) Carbon forms CO or CO at the anode 2 The gas escapes, and the cycle is repeated, so that the aim of reducing the carbon content in the product is fulfilled.The method is simple and convenient to use, simple to operate, low in investment cost and easy to industrially popularize and apply.
It is to be understood that the above-described embodiments of the present invention are merely illustrative of or explaining the principles of the invention and are not to be construed as limiting the invention. Therefore, any modifications, equivalents, improvements and the like which are made without departing from the spirit and scope of the present invention shall be included in the protection scope of the present invention. Further, it is intended that the appended claims cover all such variations and modifications as fall within the scope and boundaries of the appended claims or the equivalents of such scope and boundaries.
Claims (6)
1. A method for preparing rare earth alloy by molten salt electrolysis adopts an electrolytic cell for electrolysis, wherein the electrolytic cell comprises a cathode, a graphite anode, a graphite cell body and a collection container; the upper part of the electrolytic cell is provided with an opening, and electrolytic fused salt is filled in the cell body; the method is characterized by comprising the following steps:
feeding an electrolysis raw material from the opening, wherein,
the electrolytic raw material is a mixture of yttrium oxide and magnesium oxide, the electrolyte is a mixture of yttrium fluoride, lithium fluoride and ytterbium fluoride, the mass content of ytterbium is 1.0%, the electrolytic temperature is 1000-1100 ℃, the average value of the carbon content in the yttrium magnesium alloy obtained by electrolysis is 0.05wt%, and the ytterbium content is 0.04-0.10 wt%; alternatively, the first and second liquid crystal display panels may be,
the electrolytic raw material is a mixture of yttrium oxide, magnesium oxide and ytterbium oxide, the ytterbium content is 0.5wt%, the electrolyte is yttrium fluoride and lithium fluoride, electrolysis is carried out at 1000-1100 ℃, and the carbon content and the ytterbium content in the obtained yttrium magnesium alloy are 0.04wt% and 0.05-0.15 wt%, respectively; alternatively, the first and second electrodes may be,
the electrolytic raw material is a mixture of dysprosium oxide and ytterbium oxide, the ytterbium content is 0.1wt%, electrolyte comprises dysprosium fluoride and lithium fluoride, solid cathode iron consumable electrolysis is carried out at 1080 +/-20 ℃, the carbon content of the obtained dysprosium iron alloy is 0.03wt%, and the ytterbium content is 0.05-0.10 wt%; alternatively, the first and second electrodes may be,
the electrolytic raw material is a mixture of gadolinium oxide, magnesium oxide and samarium oxide, wherein the mass content of samarium is 0.1%, the electrolyte comprises gadolinium fluoride and lithium fluoride, and the gadolinium fluoride and the lithium fluoride are electrolyzed at 1050 +/-50 ℃ to obtain the gadolinium-magnesium alloy with the carbon content of 0.06wt% and the samarium content of 0.03-0.10 wt%;
adding a variable valence element, wherein the variable valence element is not a main alloy element of the rare earth alloy; the main alloy element refers to an element with the mass content of not less than 5% in the rare earth alloy;
stirring, discharging and charging in an electrolytic process by using an auxiliary operation tool;
the added valence-variable elements are in a compound state; the compound state comprises Sm 2 O 3 、SmF 3 、YbCl 3 Or SmCl 3 One or more of (a); the added variable valence elements are dissolved in molten salt to form variable valence ions M n+ At the cathode, a reduction reaction takes place with carbon to form a compound M x C y (ii) a The compound is oxidized at the anode to make carbon react with CO or CO 2 Is released, the compound becomes a valence-variable ion M again n+ ；
The electrolytic molten salt and the rare earth alloy prepared by the method both comprise variable valence elements, and the mass content of the variable valence elements is respectively expressed as omega (molten salt) And ω (rare earth alloy) And the following relationship exists between the two: omega (molten salt) /ω (rare earth alloy) ＞ 5。
2. A method of molten salt electrolysis to produce rare earth alloys according to claim 1, wherein the step of adding a valence-variable element comprises:
mixing a valence-variable element compound into a rare earth raw material, and feeding the compound into electrolytic molten salt along with the rare earth raw material;
or, adding the valence-variable element compound into the electrolytic molten salt;
or, taking the variable valence element compound as the material of a cathode in the electrolytic cell;
or, mixing a valence-variable element compound into the anode material;
or, coating the variable valence element compound on the surface of the auxiliary operation tool or the collection container;
or, a variable-valence element is added to the operating tool or the collection container.
3. The method of molten salt electrolysis for producing rare earth alloys according to claim 2, wherein coating a surface of an auxiliary operating tool or a collecting container with a valence-variable element compound comprises:
the thickness of a coating layer coated on the surface of the auxiliary operation tool is less than 10mm;
the thickness of the coating layer coated on the surface of the collection container is less than 20mm.
4. The method of molten salt electrolysis for producing rare earth alloys according to claim 2, wherein the adding of a valence-changing element in an auxiliary operating tool or a collection vessel comprises:
the variable valence elements account for less than 10% of the auxiliary operation tool material by mass percent;
the variable valence elements account for less than 10% of the material quality of the collecting container.
5. A method for producing a rare earth alloy by molten salt electrolysis according to claim 1 or 2, wherein the rare earth alloy produced by the method contains a valence-changing element.
6. The method of molten salt electrolysis for producing rare earth alloys according to claim 5, wherein the content of the valence-variable elements is:
yb accounts for more than or equal to 0.01 percent of the mass percent of the prepared rare earth alloy;
sm accounts for more than or equal to 0.01 percent of the mass percent of the prepared rare earth alloy.
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