A nano rare earth alloy prepared by low-temperature molten salt electrolysis and its preparation method

Abstract

The present invention belongs to the technical field of the preparation of nanoalloys. The present invention provides a nano rare earth alloy prepared by low-temperature molten salt electrolysis and a preparation method thereof. After mixing molten salt and rare earth chloride, the temperature is raised to the electrolysis temperature and kept at the electrolysis temperature to obtain a molten salt electrolyte. The molten salt electrolyte is electrolyzed by using a three-electrode system under an inert atmosphere to obtain a nano rare earth alloy. The rare earth chloride is lanthanum chloride, samarium chloride or cerium chloride. Among the three electrodes, the metal rod is the cathode, the metal rod is a nickel rod, an iron rod or a copper rod, the glassy carbon rod is the anode, and Ag / AgCl is the reference electrode. The method for directly preparing a nano rare earth alloy by low-temperature molten electrolysis of the present invention has simple operation, low reaction temperature, low required cost, strong feasibility, can significantly reduce energy consumption, reduce carbon emissions during the electrolysis process, and has better environmental and economic benefits compared with the traditional preparation method.

Description

Technical Field

[0001] The present invention relates to the technical field of nano-alloy preparation, and particularly to a nano rare-earth alloy prepared by low-temperature molten salt electrolysis and a preparation method thereof. Background Art

[0002] During the process of metal ions being reduced to neutral atoms at the cathode, there is an ion discharge process. The ion discharge process will release a large amount of heat. The heat released by each metal ion during discharge and reduction to a neutral atom can reach several electron volts (eV), which is equivalent to the atom experiencing a high temperature of tens of thousands of degrees Celsius. Therefore, in theory, metal ions can be reduced to liquid metal at very low temperatures. At the same time, low-temperature electrolysis can cause the liquid metal formed by reduction to solidify rapidly, and in principle, spherical or quasi-spherical metal particles on the micron / nano scale can be formed.

[0003] In the actual electrolysis process, it is very difficult to directly prepare metal particles on the micron or nano scale through electrolysis because the entire process is affected by factors such as temperature, overpotential, and nucleation rate. If the temperature is too high, the nucleation rate is too fast, and the overpotential is too large, the formed metal particles will grow and aggregate rapidly to form large pieces of metal; if the temperature is too low, the nucleation rate is too slow, and the overpotential is too small, the formed metal particles will be too small to fall off the electrode surface. Not only are they very difficult to collect, but also due to their high surface activity, they are easily dissolved into the electrolyte or diffuse to the anode and are directly electrochemically oxidized.

[0004] Hydrogen energy has a wide range of application fields and plays a crucial role in transportation, industrial production, construction, military, energy storage, and supply systems. The storage of hydrogen energy is also a key topic in the research of the hydrogen energy industrial chain. La-Ni alloy is currently the most mature solid hydrogen storage material, and Sm-Fe and Ce-Cu alloys are also excellent magnetic materials and hydrogen storage materials at present. There are many methods for preparing these rare-earth alloys, such as traditional melting methods, mechanical alloying methods, combustion synthesis methods, coprecipitation reduction methods, diffusion methods, molten salt electro-deoxidation methods, and molten salt electrolysis methods, etc. Molten salt electrolysis is a metallurgical process that uses electrical energy to convert into chemical energy, melts certain metal salts and uses them as electrolytes for electrolysis to extract and purify metals. Compared with other traditional methods, it has the advantages of low heating temperature, low cost, energy conservation and environmental protection, and simple process conditions. However, the current molten salt electrolysis method still has defects such as high reaction temperature, high cost, and complex process, and needs to be further optimized.

[0005] Therefore, it is of great economic value and environmental value to research and obtain a method for preparing nano-alloys by molten salt electrolysis with low reaction temperature, low cost, and simple process. Summary of the Invention

[0006] The purpose of the present invention is to provide a nano rare earth alloy prepared by low-temperature molten salt electrolysis and a preparation method thereof in order to overcome the deficiencies of the prior art.

[0007] In order to achieve the above-mentioned invention purpose, the present invention provides the following technical solutions:

[0008] The present invention provides a method for preparing a nano rare earth alloy by low-temperature molten salt electrolysis, comprising the following steps:

[0009] 1) Mix the molten salt and rare earth chloride, then heat to the electrolysis temperature and keep warm at the electrolysis temperature to obtain a molten salt electrolyte;

[0010] 2) Electrolyze the molten salt electrolyte with three electrodes under an inert atmosphere to obtain a nano rare earth alloy;

[0011] The rare earth chloride is lanthanum chloride, samarium chloride or cerium chloride;

[0012] Among the three electrodes, the metal rod is the cathode, the metal rod is a nickel rod, an iron rod or a copper rod, the glassy carbon rod is the anode, and Ag / AgCl is the reference electrode.

[0013] Preferably, the molten salt in step 1) is a potassium chloride-lithium chloride molten salt. In the potassium chloride-lithium chloride molten salt, the molar fraction of potassium chloride is 31-48%, and the molar fraction of lithium chloride is 52-69%.

[0014] Preferably, the mass ratio of the molten salt to the rare earth chloride in step 1) is 65-75:0.8-3.8.

[0015] Preferably, after the molten salt is electrochemically purified, it is mixed with the rare earth chloride. The method of electrochemical purification is to sequentially heat the molten salt to the drying temperature and the electrolysis temperature.

[0016] Preferably, the heating in step 1) is to sequentially heat to the drying temperature and the electrolysis temperature.

[0017] Preferably, the drying temperature is 280-320 °C, the electrolysis temperature is 358-450 °C, the holding time at the drying temperature is 1.5-12 h, and the holding time at the electrolysis temperature is 0.5-2.5 h.

[0018] Preferably, the heating rate to the drying temperature is 1-3 °C / min, and the heating rate to the electrolysis temperature is 4-6 °C / min.

[0019] Preferably, the inert atmosphere in step 2) is an argon atmosphere or a nitrogen atmosphere, the electrolysis time is 50-220 min, and the electrolysis voltage is -1.4 to -2.2 V.

[0020] Preferably, the metal rod is the one that has been polished, buffed, washed with water, and then washed with absolute ethanol successively.

[0021] The present invention also provides a nano rare earth alloy prepared by the method described above, and the particle size of the nano rare earth alloy is 80 - 480 nm.

[0022] The beneficial effects of the present invention include:

[0023] 1) The principle of preparing the nano rare earth alloy by low-temperature molten salt electrolysis in the present invention is as follows: By means of the heat released during the discharge of the reduction process of rare earth ions such as lanthanum ions, samarium ions, or cerium ions, a liquid lanthanum-nickel alloy, samarium-iron alloy, or cerium-copper alloy can be formed with a nickel electrode, an iron electrode, or a copper electrode at a relatively low temperature; then, by controlling process parameters such as electrolysis temperature, electrolysis time, and voltage, the critical nucleation radius of the alloy is controlled, so that the formed alloy grows into alloy particles at the nanoscale.

[0024] 2) The method for directly preparing the nano rare earth alloy by low-temperature molten salt electrolysis in the present invention is simple in operation, low in reaction temperature, low in required cost, and strong in feasibility, which can significantly reduce energy consumption and reduce carbon emissions during the electrolysis process, and has better environmental and economic benefits compared with traditional preparation methods. Description of the Drawings

[0025] Figure 1 It is a schematic diagram of the heating furnace used for preparing the nano rare earth alloy by low-temperature molten salt electrolysis in the present invention. Among them, 1 is the cathode, 2 is the anode, 3 is the reference electrode, 4 is the corundum tube, 5 is the corundum tube, 6 is the boron nitride sling, 7 is the glassy carbon crucible, 8 is the water-cooled flange, 9 is the constant temperature zone, and 10 is the tubular furnace;

[0026] Figure 2 It is the SEM image of the nano La-Ni alloy prepared in Example 1;

[0027] Figure 3 It is the SEM image of the nano La-Ni alloy prepared in Example 2;

[0028] Figure 4 It is the SEM image of the nano La-Ni alloy prepared in Example 3;

[0029] Figure 5 It is the SEM image of the nano La-Ni alloy prepared in Example 4;

[0030] Figure 6 It is the SEM image of the nano La-Ni alloy prepared in Example 5;

[0031] Figure 7 It is the SEM image of the nano Sm-Fe alloy prepared in Example 8;

[0032] Figure 8 SEM image of the nano Ce-Cu alloy prepared in Example 9. Detailed implementation mode

[0033] The present invention provides a method for preparing nano rare earth alloy by low-temperature molten salt electrolysis, which comprises the following steps:

[0034] 1) Mix the molten salt and rare earth chloride, and then heat up to the electrolysis temperature and keep warm at the electrolysis temperature to obtain a molten salt electrolyte;

[0035] 2) Electrolyze the molten salt electrolyte with three electrodes under an inert atmosphere to obtain a nano rare earth alloy;

[0036] The rare earth chloride is lanthanum chloride, samarium chloride or cerium chloride;

[0037] Among the three electrodes, the metal rod is the cathode, the metal rod is a nickel rod, an iron rod or a copper rod, the glassy carbon rod is the anode, and Ag / AgCl is the reference electrode.

[0038] In the present invention, the molten salt in step 1) is preferably potassium chloride-lithium chloride molten salt. In the potassium chloride-lithium chloride molten salt, the molar fraction of potassium chloride is preferably 31-48%, more preferably 35-45%, and even more preferably 38-40%; the molar fraction of lithium chloride is preferably 52-69%, more preferably 55-65%, and even more preferably 58-60%; when the molar fraction of potassium chloride is 41% and the molar fraction of lithium chloride is 59%, the eutectic point temperature of the molten salt is 352 °C.

[0039] The potassium chloride-lithium chloride molten salt of the present invention is a low-temperature water-soluble molten salt.

[0040] In the present invention, the mass ratio of the molten salt to the rare earth chloride in step 1) is preferably 65-75:0.8-3.8, more preferably 68-72:1.0-3.5, and even more preferably 70:1.5-3.0.

[0041] In the present invention, the molten salt is preferably subjected to electrochemical impurity removal and then mixed with rare earth chloride. The method of electrochemical impurity removal is preferably to heat the molten salt sequentially to the drying temperature and the electrolysis temperature.

[0042] In the present invention, the heating in step 1) is preferably to heat up sequentially to the drying temperature and the electrolysis temperature.

[0043] In the present invention, the drying temperature is preferably 280 - 320°C, more preferably 290 - 310°C, and even more preferably 300°C; the electrolysis temperature is preferably 358 - 450°C, more preferably 372 - 446°C, and even more preferably 379 - 392°C; the holding time at the drying temperature is preferably 1.5 - 12 h, more preferably 2 - 10 h, and even more preferably 4 - 8 h; the holding time at the electrolysis temperature is preferably 0.5 - 2.5 h, more preferably 0.8 - 2.2 h, and even more preferably 1 - 2 h.

[0044] In the present invention, the heating rate for raising the temperature to the drying temperature is preferably 1 - 3°C / min, more preferably 1.5 - 2.5°C / min, and even more preferably 2°C / min; the heating rate for raising the temperature to the electrolysis temperature is preferably 4 - 6°C / min, more preferably 4.5 - 5.5°C / min, and even more preferably 5°C / min.

[0045] In the present invention, the molten salt and rare earth chloride are held at the electrolysis temperature to fully transform the molten salt electrolyte into a molten state.

[0046] In the present invention, the inert atmosphere in step 2) is preferably an argon atmosphere or a nitrogen atmosphere, the electrolysis time is preferably 50 - 220 min, more preferably 60 - 200 min, and even more preferably 90 - 120 min; the electrolysis voltage is preferably -1.4 - -2.2 V, more preferably -1.5 - -2.0 V, and even more preferably -1.8 - -1.9 V.

[0047] In the present invention, the metal rod is preferably a metal rod that has been polished, polished, washed with water, and washed with absolute ethanol in sequence; the polishing is preferably carried out by polishing with sandpapers of 200 mesh, 400 mesh, 600 mesh, 800 mesh, 1000 mesh, 1200 mesh, and 1500 mesh in sequence; the power of the water washing and the absolute ethanol washing is independently preferably 90 - 110 W, more preferably 95 - 105 W, and even more preferably 100 W; the washing time is independently preferably 8 - 12 min, more preferably 9 - 11 min, and even more preferably 10 min.

[0048] In the present invention, the device used for the low-temperature molten salt electrolysis to prepare the nano rare earth alloy is a conventional heating furnace, and the structural schematic diagram of the heating furnace is as Figure 1 shown, where 1 is the cathode, 2 is the anode, 3 is the reference electrode, 4 is the corundum tube, 5 is the corundum tube, 6 is the boron nitride sling, 7 is the glassy carbon crucible, 8 is the water-cooled flange, 9 is the constant temperature zone, and 10 is the tube furnace.

[0049] The present invention also provides the nano rare earth alloy prepared by the method described above, and the particle size of the nano rare earth alloy is 80 - 480 nm.

[0050] The technical solution provided by the present invention will be described in detail below in conjunction with embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0051] In the embodiment, the diameters of the metal rods (nickel rods, iron rods, and copper rods) are 6 mm, and the purity is 99%. The metal rods are successively polished with sandpapers of 200 mesh, 400 mesh, 600 mesh, 800 mesh, 1000 mesh, 1200 mesh, and 1500 mesh, polished by a polishing machine, washed with deionized water and anhydrous ethanol. The washing with deionized water and anhydrous ethanol is carried out in an ultrasonic cleaning machine with an ultrasonic power of 100 W, and each is washed for 10 min. After the cleaning is completed, the lower half of the nickel rod, iron rod, or copper rod is sleeved in a hollow boron nitride sleeve with an outer diameter of 8 mm and an inner diameter of 6 mm to ensure that the contact area between the metal rod and the molten salt electrolyte remains unchanged.

[0052] Example 1

[0053] 38.524 g of potassium chloride and 31.476 g of lithium chloride are fully mixed and put into a glassy carbon crucible. Then the glassy carbon crucible is put into a boron nitride sling and heated in a heating furnace at a heating rate of 2 °C / min to 300 °C, and kept warm and dried at 300 °C for 2 h. Then it is heated at a heating rate of 5 °C / min to 358 °C and kept warm at 358 °C for 2 h to carry out electrochemical purification of the molten salt, and then cooled to room temperature. The molten salt is mixed with 0.84 g of lanthanum chloride and heated at a heating rate of 2 °C / min to 300 °C, kept warm and dried at 300 °C for 2 h, and then heated at a heating rate of 5 °C / min to 358 °C and kept warm at 358 °C for 2 h to obtain a molten salt electrolyte.

[0054] Using a nickel rod as the cathode, a glassy carbon rod as the anode, and Ag / AgCl as the reference electrode, the molten salt electrolyte is electrolyzed at a constant voltage of -1.5 V under an argon atmosphere for 200 min. After the electrolysis is completed, the nickel rod electrode is taken out, and the melt is slowly cooled with the furnace. The chloride molten salt adhering to the nickel rod is washed off with deionized water, and a nano-La-Ni alloy is obtained at the top of the nickel rod electrode.

[0055] The SEM image of the nano-La-Ni alloy prepared in this example is as Figure 2 shown. Through EDS analysis, the atomic ratio of La and Ni in the La-Ni alloy is 1:5, and the obtained alloy is a LaNi5 alloy, and the alloy particle size is 450 ± 11 nm.

[0056] Example 2

[0057] Mix 39.224 g of potassium chloride and 30.776 g of lithium chloride thoroughly, place them in a glassy carbon crucible, then put the glassy carbon crucible into a boron nitride sling, and heat it in a heating furnace at a heating rate of 2 °C / min to 300 °C. Keep it warm and dry at 300 °C for 4 h, then heat it at a heating rate of 5 °C / min to 372 °C, and keep it warm at 372 °C for 1 h to perform electrochemical purification on the molten salt, and then cool it down to room temperature. Mix the molten salt with 0.84 g of lanthanum chloride, heat it at a heating rate of 2 °C / min to 300 °C, keep it warm and dry at 300 °C for 2 h, then heat it at a heating rate of 5 °C / min to 372 °C, and keep it warm at 372 °C for 1 h to obtain a molten salt electrolyte.

[0058] Using a nickel rod as the cathode, a glassy carbon rod as the anode, and Ag / AgCl as the reference electrode, electrolyze the molten salt electrolyte at a constant voltage of -1.9 V in an argon atmosphere for 90 min. After the electrolysis is completed, take out the nickel rod electrode, slowly cool the melt in the furnace, rinse off the chloride molten salt adhering to the nickel rod with deionized water, and obtain a nano-La-Ni alloy at the top of the nickel rod electrode.

[0059] The SEM image of the nano-La-Ni alloy prepared in this example is as Figure 3 shown. Through EDS analysis, the atomic ratio of La and Ni in the La-Ni alloy is 1:5, and the obtained alloy is the LaNi5 alloy, and the particle size of the alloy is 100 ± 7 nm.

[0060] Example 3

[0061] Mix 38.524 g of potassium chloride and 31.476 g of lithium chloride thoroughly, place them in a glassy carbon crucible, then put the glassy carbon crucible into a boron nitride sling, and heat it in a heating furnace at a heating rate of 2 °C / min to 300 °C. Keep it warm and dry at 300 °C for 6 h, then heat it at a heating rate of 5 °C / min to 379 °C, and keep it warm at 379 °C for 1 h to perform electrochemical purification on the molten salt, and then cool it down to room temperature. Mix the molten salt with 0.84 g of lanthanum chloride, heat it at a heating rate of 2 °C / min to 300 °C, keep it warm and dry at 300 °C for 2 h, then heat it at a heating rate of 5 °C / min to 379 °C, and keep it warm at 379 °C for 1 h to obtain a molten salt electrolyte.

[0062] Using a nickel rod as the cathode, a glassy carbon rod as the anode, and Ag / AgCl as the reference electrode, electrolyze the molten salt electrolyte at a constant voltage of -1.8 V in an argon atmosphere for 120 min. After the electrolysis is completed, take out the nickel rod electrode, slowly cool the melt in the furnace, rinse off the chloride molten salt adhering to the nickel rod with deionized water, and obtain a nano-La-Ni alloy at the top of the nickel rod electrode.

[0063] The SEM image of the nano-La-Ni alloy prepared in this example is as Figure 4As shown. Through EDS analysis, the atomic ratio of La and Ni in the La-Ni alloy is 1:5, and the obtained alloy is LaNi5 alloy, and the alloy particle size is 119±8nm.

[0064] Example 4

[0065] Mix 43.263 g of potassium chloride and 26.73 g of lithium chloride evenly, put them into a glassy carbon crucible, then put the glassy carbon crucible into a boron nitride sling, heat it in a heating furnace at a heating rate of 2 °C / min to 300 °C, keep it warm and dry at 300 °C for 8 h, then heat it at a heating rate of 5 °C / min to 446 °C, keep it warm at 446 °C for 1 h, carry out electrochemical impurity removal on the molten salt, and then cool it down to room temperature. Mix the molten salt with 0.84 g of lanthanum chloride, heat it at a heating rate of 2 °C / min to 300 °C, keep it warm and dry at 300 °C for 2 h, then heat it at a heating rate of 5 °C / min to 446 °C, keep it warm at 446 °C for 1 h to obtain a molten salt electrolyte.

[0066] Using a nickel rod as the cathode, a glassy carbon rod as the anode, and Ag / AgCl as the reference electrode, electrolyze the molten salt electrolyte at a constant voltage of -2.0 V under an argon atmosphere for 60 min. After the electrolysis is completed, take out the nickel rod electrode, slowly cool the melt with the furnace, rinse off the chloride molten salt adhering to the nickel rod with deionized water, and obtain a nano-La-Ni alloy at the top of the nickel rod electrode.

[0067] The SEM image of the nano-La-Ni alloy prepared in this example is as Figure 5 shown. Through EDS analysis, the atomic ratio of La and Ni in the La-Ni alloy is 2:7, and the obtained alloy is La2Ni7 alloy, and the alloy particle size is 350±8nm.

[0068] Example 5

[0069] Mix 38.524 g of potassium chloride and 31.476 g of lithium chloride evenly, put them into a glassy carbon crucible, then put the glassy carbon crucible into a boron nitride sling, heat it in a heating furnace at a heating rate of 2 °C / min to 300 °C, keep it warm and dry at 300 °C for 2 h, then heat it at a heating rate of 5 °C / min to 392 °C, keep it warm at 392 °C for 1 h, carry out electrochemical impurity removal on the molten salt, and then cool it down to room temperature. Mix the molten salt with 0.84 g of lanthanum chloride, heat it at a heating rate of 2 °C / min to 300 °C, keep it warm and dry at 300 °C for 2 h, then heat it at a heating rate of 5 °C / min to 392 °C, keep it warm at 392 °C for 1 h to obtain a molten salt electrolyte.

[0070] Using a nickel rod as the cathode, a glassy carbon rod as the anode, and Ag / AgCl as the reference electrode, electrolyze the molten salt electrolyte at a constant voltage of -1.8 V in an argon atmosphere for 90 min. After the electrolysis is completed, take out the nickel rod electrode, slowly cool the melt in the furnace, rinse off the chloride molten salt adhering to the nickel rod with deionized water, and obtain a nano-La-Ni alloy at the top of the nickel rod electrode.

[0071] The SEM image of the nano-La-Ni alloy prepared in this example is as Figure 6 shown. Through EDS analysis, the atomic ratio of La and Ni in the La-Ni alloy is 1:5, and the obtained alloy is LaNi5 alloy, and the particle size of the alloy is 151 ± 8 nm.

[0072] Example 6

[0073] Fully mix 38 g of potassium chloride and 32 g of lithium chloride evenly, put them into a glassy carbon crucible, then place the glassy carbon crucible in a boron nitride sling, heat it to 290 °C in a heating furnace at a heating rate of 1.5 °C / min, keep it warm and dry at 290 °C for 2.5 h, then heat it to 385 °C at a heating rate of 4.5 °C / min, keep it warm at 385 °C for 2 h, perform electrochemical impurity removal on the molten salt, and then cool it to room temperature. Mix the molten salt with 0.82 g of lanthanum chloride, heat it to 290 °C at a heating rate of 1.5 °C / min, keep it warm and dry at 290 °C for 2.5 h, then heat it to 385 °C at a heating rate of 4.5 °C / min, and keep it warm at 385 °C for 2 h to obtain the molten salt electrolyte.

[0074] Using a nickel rod as the cathode, a glassy carbon rod as the anode, and Ag / AgCl as the reference electrode, electrolyze the molten salt electrolyte at a constant voltage of -1.7 V in a nitrogen atmosphere for 130 min. After the electrolysis is completed, take out the nickel rod electrode, slowly cool the melt in the furnace, rinse off the chloride molten salt adhering to the nickel rod with deionized water, and obtain a nano-La-Ni alloy at the top of the nickel rod electrode.

[0075] In the nano-La-Ni alloy prepared in this example, the atomic ratio of La and Ni is 1:5, the obtained alloy is LaNi5 alloy, and the particle size of the alloy is 115 ± 7 nm.

[0076] Example 7

[0077] Mix 39 g of potassium chloride and 31 g of lithium chloride thoroughly, place them in a glassy carbon crucible, then put the glassy carbon crucible into a boron nitride sling, and heat it in a heating furnace at a heating rate of 2.5 °C / min to 310 °C. Keep it warm and dry at 310 °C for 2 h, then heat it at a heating rate of 5.5 °C / min to 415 °C, and keep it warm at 415 °C for 1 h. Carry out electrochemical purification on the molten salt, and then cool it down to room temperature. Mix the molten salt with 0.86 g of lanthanum chloride, heat it at a heating rate of 2.5 °C / min to 310 °C, keep it warm and dry at 310 °C for 2 h, then heat it at a heating rate of 5.5 °C / min to 415 °C, and keep it warm at 415 °C for 1 h to obtain a molten salt electrolyte.

[0078] Use a nickel rod as the cathode, a glassy carbon rod as the anode, and Ag / AgCl as the reference electrode. Electrolyze the molten salt electrolyte at a constant voltage of -2.1 V under a nitrogen atmosphere for 100 min. After the electrolysis is completed, take out the nickel rod electrode, slowly cool the melt with the furnace, rinse off the chloride molten salt adhering to the nickel rod with deionized water, and obtain a nano-La-Ni alloy at the top of the nickel rod electrode.

[0079] In the nano-La-Ni alloy prepared in this example, the atomic ratio of La to Ni is 7:16, and the obtained alloy is La7Ni 16 alloy, and the particle size of the alloy is 111 ± 6 nm.

[0080] Example 8

[0081] Mix 39 g of potassium chloride and 31 g of lithium chloride thoroughly, place them in a glassy carbon crucible, then put the glassy carbon crucible into a boron nitride sling, and heat it in a heating furnace at a heating rate of 2.5 °C / min to 300 °C. Keep it warm and dry at 300 °C for 2 h, then heat it at a heating rate of 5 °C / min to 400 °C, and keep it warm at 400 °C for 1 h. Carry out electrochemical purification on the molten salt, and then cool it down to room temperature. Mix the molten salt with 1.0 g of samarium chloride, heat it at a heating rate of 2.5 °C / min to 300 °C, keep it warm and dry at 300 °C for 2 h, then heat it at a heating rate of 5 °C / min to 400 °C, and keep it warm at 400 °C for 1 h to obtain a molten salt electrolyte.

[0082] Use an iron rod as the cathode, a glassy carbon rod as the anode, and Ag / AgCl as the reference electrode. Electrolyze the molten salt electrolyte at a constant voltage of -1.6 V under a nitrogen atmosphere for 60 min. After the electrolysis is completed, take out the iron rod electrode, slowly cool the melt with the furnace, rinse off the chloride molten salt adhering to the iron rod with deionized water, and obtain a nano-Sm-Fe alloy at the top of the iron rod electrode.

[0083] The SEM image of the nano-Sm-Fe alloy prepared in this example is as Figure 7As shown, where the atomic ratio of Sm and Fe is close to 1:5, the resulting alloy is the SmFe5 alloy, and the alloy particle size is 222 ± 11 nm.

[0084] Example 9

[0085] Mix 39 g of potassium chloride and 31 g of lithium chloride evenly, place them in a glassy carbon crucible, then put the glassy carbon crucible into a boron nitride sling, heat it in a heating furnace at a heating rate of 2.5 °C / min to 300 °C, keep it warm and dry at 300 °C for 2 h, then heat it at a heating rate of 5 °C / min to 400 °C, keep it warm at 400 °C for 2 h, perform electrochemical impurity removal on the molten salt, and then cool it down to room temperature. Mix the molten salt with 1.0 g of cerium chloride, heat it at a heating rate of 2.5 °C / min to 300 °C, keep it warm and dry at 300 °C for 2 h, then heat it at a heating rate of 5 °C / min to 380 °C, keep it warm at 380 °C for 2 h to obtain the molten salt electrolyte.

[0086] Using a copper rod as the cathode, a glassy carbon rod as the anode, and Ag / AgCl as the reference electrode, electrolyze the molten salt electrolyte at a constant voltage of -2.1 V in a nitrogen atmosphere for 90 min. After the electrolysis is completed, take out the copper rod electrode, slowly cool the melt with the furnace, rinse off the chloride molten salt adhering to the copper rod with deionized water, and obtain a nano Ce-Cu alloy at the top of the copper rod electrode.

[0087] The SEM image of the nano Ce-Cu alloy prepared in this example is as Figure 8 shown, where the atomic ratio of Ce and Cu is close to 1:2, the resulting alloy is the CeCu2 alloy, and the alloy particle size is 313 ± 15 nm.

[0088] The present invention controls the nucleation rate, growth rate, and alloy particle size of the nano alloy by controlling the electrolysis temperature, overpotential, and electrolysis time, so as to directly prepare a rare earth alloy at the nanoscale by low-temperature molten electrolysis on a metal electrode.

[0089] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing nano rare earth alloy by low-temperature molten salt electrolysis, characterized in that It includes the following steps: 1) Mix molten salt and rare earth chloride, then heat up to the electrolysis temperature and keep it at the electrolysis temperature to obtain molten salt electrolyte; 2) Electrolyze the molten salt electrolyte with three electrodes under an inert atmosphere to obtain nano rare earth alloy; The rare earth chloride is lanthanum chloride, samarium chloride or cerium chloride; Among the three electrodes, the metal rod is the cathode, the metal rod is a nickel rod, an iron rod or a copper rod, the glassy carbon rod is the anode, and Ag / AgCl is the reference electrode; The molten salt in step 1) is potassium chloride-lithium chloride molten salt; The molten salt is subjected to electrochemical impurity removal and then mixed with rare earth chloride. The method of electrochemical impurity removal is that the molten salt is heated up to the drying temperature and the electrolysis temperature in sequence; The heating up in step 1) is to heat up to the drying temperature and the electrolysis temperature in sequence; The drying temperature is 280~320°C, the electrolysis temperature is 358~450°C, the holding time at the drying temperature is 1.5~12h, and the holding time at the electrolysis temperature is 0.5~2.5h; The electrolysis time in step 2) is 50~220min, and the electrolysis voltage is -1.4~-2.2V.

2. The method according to claim 1, wherein In the potassium chloride-lithium chloride molten salt, the molar fraction of potassium chloride is 31~48%, and the molar fraction of lithium chloride is 52~69%.

3. The method according to claim 1 or 2, wherein The mass ratio of the molten salt to the rare earth chloride in step 1) is 65~75:0.8~3.

8.

4. The method according to claim 3, wherein The heating rate to the drying temperature is 1~3°C / min, and the heating rate to the electrolysis temperature is 4~6°C / min.

5. The method according to claim 4, wherein The inert atmosphere in step 2) is an argon atmosphere or a nitrogen atmosphere.

6. The method according to claim 5, wherein The metal rod is a metal rod that has been polished, polished, washed with water, and washed with absolute ethanol in sequence.

7. The nano rare earth alloy prepared by the method according to any one of claims 1 to 6, characterized in that, The particle size of the nano rare earth alloy is 80~480nm.

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