A method for preparing hafnium metal and electrolysis of molten salts to prepare hafnium metal

Abstract

The present invention provides a method for preparing hafnium metal by molten salt electrolysis of hafnium carbide, which includes: after uniformly mixing hafnium carbide raw materials and an appropriate amount of binder, granulating, and then subjecting to vacuum sintering treatment to obtain hafnium carbide particles; mixing alkali metal / alkaline earth metal chlorides with a small amount of hafnium salts, pre-melting and then cooling to obtain a molten salt electrolyte; adding the hafnium carbide particles to the bottom of a graphite crucible in an electrolytic furnace, and then adding the molten salt electrolyte into the graphite crucible, sealing the equipment and then carrying out electrolysis; after the electrolysis is completed, collecting the deposits attached to the cathode and extracting the hafnium metal from the deposits; the present invention uses hafnium carbide as the anode material, avoiding the problem of a large amount of chlorine gas being evolved at the anode during the direct electrolysis of hafnium powder in a high-temperature molten salt system, which causes equipment corrosion; in addition, the production cost of hafnium carbide is relatively low and can be obtained by carbon reduction method using hafnium oxide as the raw material, greatly saving costs compared with using hafnium sponge as the anode material.

Description

Technical Field

[0001] The present invention relates to the technical field of hafnium metal and its preparation, and particularly to a hafnium metal and a method for preparing hafnium metal by molten salt electrolysis. Background Art

[0002] Hafnium is widely used in many fields due to its unique physical and chemical properties. Hafnium has good neutron absorption characteristics and is commonly used in nuclear reactors as a neutron absorption material to help regulate and control nuclear reactions; hafnium is often used to manufacture nickel-based and cobalt-based superalloys, mainly for engine components in the aerospace field to improve high-temperature resistance and oxidation resistance; alloys formed by hafnium and other metals (such as tungsten, molybdenum, etc.) have excellent physical and chemical properties and are applied in some extreme working conditions. Hafnium oxide thin films prepared from hafnium metal are used as capacitor materials in microelectronics and integrated circuits due to their excellent dielectric properties. Hafnium is widely used in thin film technology and can be used as a coating material to enhance surface wear resistance and corrosion resistance; hafnium oxide thin films prepared from hafnium metal can be used to manufacture high-performance optical materials due to their high refractive index and excellent optical properties; in some chemical reactions, hafnium powder can be used as a catalyst or catalyst carrier to promote the reaction; at the same time, hafnium powder also plays an important role in the development and research of new materials, especially in the research and development of superconducting materials and new ceramic materials. The high-temperature oxidation-resistant coating prepared from hafnium powder has excellent properties and is applied in the aerospace field.

[0003] Currently, there are mainly three processes for preparing hafnium powder: The first is the hydrogenation-dehydrogenation method. This process requires using hafnium metal (sponge hafnium or hafnium chips) as raw materials. The hafnium metal is hydrogenated to obtain hafnium hydride, and after the hafnium hydride is crushed into powder, it is dehydrogenated to obtain hafnium powder. Using hydrogen in this process has certain safety risks, and the hafnium powder prepared by dehydrogenating hafnium hydride is prone to spontaneous combustion and there are potential safety hazards in production. The second method is the calcium (calcium hydride) reduction method. This process uses hafnium oxide and calcium (calcium hydride) as raw materials. This process can obtain hafnium powder with finer particle size, but the oxygen content of the hafnium powder is relatively high. If the process conditions are not well controlled, incomplete reduction of hafnium oxide will occur. At the same time, calcium and calcium hydride are also dangerous goods and there are certain safety hazards. The third method is the molten salt electrolysis method. This process uses potassium hafnium fluoride or hafnium tetrachloride as the hafnium source. Under the action of an electric field, hafnium metal powder is deposited on the cathode by controlling process conditions. This process uses an electric field to replace dangerous goods as reducing agents, ensuring the safety of production.

[0004] The molten salt electrolysis method is to melt salts at high temperature to form a melt, and then pass direct current through it, so that some ions in it undergo oxidation-reduction reactions on the electrodes, thereby achieving the purpose of preparing and refining metals or other substances. In the existing process for preparing hafnium powder by molten salt electrolysis, potassium hafnium fluoride or hafnium tetrachloride is used as the hafnium raw material, and sodium chloride and potassium chloride, the supporting electrolytes, are added for high-temperature molten salt electrolysis. Under the action of an electric field, metallic hafnium is deposited on the cathode, and after being washed with water, hafnium metal powder is obtained.

[0005] However, during the direct electrolysis process, chlorine gas is evolved at the anode. When the current density is too high or the concentration of hafnium ions is too low, an anode effect will be caused, resulting in the interruption of electrolysis. Due to the evolution of chlorine gas, the corrosion of equipment by chlorine gas at high temperature is serious, and at the same time, there are safety risks in the production process. To solve the problem of chlorine gas evolution at the anode, the existing process is to add hafnium sponge as the anode material to the anode to avoid the evolution of chlorine gas, and at the same time as the source of hafnium, but the production cost using hafnium sponge as the raw material is relatively high. Summary of the Invention

[0006] In view of the above problems existing in the prior art, the present invention provides a method for preparing metallic hafnium and molten salt electrolysis of metallic hafnium to solve the problems in the existing methods, such as the problem of chlorine gas evolution at the anode during direct electrolysis using potassium hafnium fluoride or hafnium tetrachloride as the hafnium source, or the high cost of using hafnium sponge as the anode raw material.

[0007] The specific content of the invention is as follows:

[0008] The present invention provides a method for preparing metallic hafnium by molten salt electrolysis, including:

[0009] Mix the hafnium carbide raw material and an appropriate amount of binder evenly, and then carry out granulation treatment to prepare granular materials with a size of 3-5 mm, and obtain hafnium carbide particles through vacuum sintering;

[0010] Mix an alkali metal / alkaline earth metal chloride salt with a small amount of hafnium salt, pre-melt and then cool to obtain a molten salt electrolyte;

[0011] Add the hafnium carbide particles to the bottom of the graphite crucible in the electrolysis furnace, and then add the molten salt electrolyte into the graphite crucible. After sealing the equipment, carry out electrolysis;

[0012] After the electrolysis is completed, collect the deposits attached to the cathode, and extract the metallic hafnium from the deposits;

[0013] Among them, the alkali metal / alkaline earth metal chloride salt is selected from one or a combination of more of sodium chloride, potassium chloride, lithium chloride, calcium chloride, rubidium chloride, cesium chloride, and calcium chloride;

[0014] The hafnium salt is selected from potassium hafnium fluoride and / or hafnium tetrachloride;

[0015] The oxygen content in the hafnium metal is 0.06 - 0.08%.

[0016] Optionally, the alkali metal / alkaline earth metal chloride is selected from NaCl-KCl, NaCl-CaCl 2 , NaCl-KCl-CsCl, NaCl-KCl-RbCl, LiCl-NaCl-KCl, LiCl-KCl-CsCl or LiCl-KCl-RbCl.

[0017] Optionally, the temperature of the electrolysis is 750 - 850 °C;

[0018] The cathode current density of the electrolysis is 0.1 - 5 A / cm 2 .

[0019] Optionally, the mass ratio of the hafnium carbide raw material to the binder is 4:1 - 7:1;

[0020] The binder is selected from one or a combination of polyvinyl acetate, polyvinyl alcohol, polyacrylate, polyurethane and phenolic resin;

[0021] The pressure of the vacuum sintering treatment is 0.1 MPa - 0.5 MPa, and the temperature is 1200 °C - 1500 °C.

[0022] Optionally, the mass ratio of the hafnium salt to the alkali metal / alkaline earth metal chloride is 3:7 - 4:6.

[0023] Optionally, the mass ratio of the hafnium carbide particles to the molten salt electrolyte is 1:3 - 1:5.

[0024] Optionally, the particle size of the hafnium carbide raw material is +500 mesh - -300 mesh.

[0025] Optionally, before mixing the alkali metal / alkaline earth metal chloride with a small amount of hafnium salt, the method further includes:

[0026] Vacuum dehydrating the alkali metal / alkaline earth metal chloride under the conditions of a temperature of 500 - 600 °C and 0.1 MPa - 0.5 MPa;

[0027] Vacuum dehydrating the potassium hafnium fluoride under the conditions of a temperature of 350 - 500 °C and 0.1 MPa - 0.5 MPa;

[0028] Vacuum dehydrating the hafnium tetrachloride under the conditions of a temperature of 200 - 300 °C and 0.1 MPa - 0.5 MPa.

[0029] Optionally, extracting the hafnium metal from the sediment includes:

[0030] Crush the cathode deposit into particles with a particle size of 1 - 3 mm, put them into deionized water at 50°C - 80°C and stir for cleaning. After all the molten salt electrolyte inclusions are dissolved in water, filter to obtain crude hafnium powder;

[0031] Immerse the crude hafnium powder in dilute hydrochloric acid and stir for cleaning. After sedimentation and filtration, wash it with deionized water 3 - 5 times, and then dry it at low temperature to obtain metal hafnium powder with a low oxygen content.

[0032] Optionally, the present invention provides a metal hafnium obtained by the method described in the first aspect above.

[0033] Compared with the prior art, the present invention has the following advantages:

[0034] The present invention provides a method for preparing metal hafnium by molten salt electrolysis, including: mixing hafnium carbide raw materials and an appropriate amount of binder evenly, then performing granulation treatment to prepare a granular material with a size of 3 - 5 mm, and obtaining hafnium carbide particles through vacuum sintering; adding an appropriate amount of hafnium salt to the electrolyte, pre-melting and then cooling to obtain a molten salt electrolyte; adding the hafnium carbide particles to the bottom of a graphite crucible in an electrolytic furnace, then adding the molten salt electrolyte into the graphite crucible, sealing the equipment, and performing electrolysis treatment; after electrolysis is completed, collect the deposits attached to the cathode, and extract metal hafnium powder with a low oxygen content from the deposits; the oxygen content in the metal hafnium powder is 0.06 - 0.08%.

[0035] In the preparation method provided by the present invention, hafnium carbide is used as the anode material, which avoids the problem of a large amount of chlorine gas being released at the anode during the direct electrolysis of hafnium powder in a high-temperature molten salt system (without anode material), resulting in equipment corrosion; in addition, the production cost of hafnium carbide is relatively low, and it can be obtained by carbon reduction method using hafnium oxide as the raw material, which greatly saves costs compared with using sponge hafnium as the anode material. Description of the Drawings

[0036] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0037] Figure 1 Shows the process flow chart of the method for preparing metal hafnium by molten salt electrolysis provided by the embodiments of the present invention;

[0038] Figure 2 Shows the metal hafnium obtained by molten salt electrolysis preparation in the embodiments of the present invention. Detailed Embodiments

[0039] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and in no way limits the present invention and its application or use. Based on the embodiments of the present invention, any product identical or similar to the present invention obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with other existing technologies falls within the protection scope of the present invention. And all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the protection scope of the present invention.

[0040] For the specific experimental steps or conditions not specified in the embodiments, the operations or conditions of the conventional experimental steps described in the existing technologies in the art can be followed. The reagents and other instruments not indicating the manufacturer can be obtained as conventional reagent products through commercial purchase. In addition, the accompanying drawings are only schematic illustrations of the embodiments of the present invention and are not necessarily drawn to scale. The same reference numerals in the drawings represent the same or similar parts, and thus the repeated description thereof will be omitted. Some of the block diagrams shown in the drawings are functional entities and do not necessarily correspond to physically or logically independent entities.

[0041] The technologies, methods, and equipment known to those of ordinary skill in the relevant fields may not be discussed in detail, but under appropriate circumstances, the said technologies, methods, and equipment should be regarded as part of the specification of the present invention.

[0042] In the description of the present invention, it should be understood that using words such as "first" and "second" to limit the components is only for the convenience of distinguishing the corresponding components. Without further statement, the above words have no special meaning, and thus cannot be construed as limiting the protection scope of the present invention.

[0043] In addition, the technical features involved in different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0044] Since there are problems in the preparation of hafnium metal by directly electrolyzing an electrolyte containing potassium hafnium fluoride or hafnium tetrachloride, such as chlorine gas being generated at the anode, deteriorating the production environment, and at the same time, the generation of chlorine gas seriously corrodes the equipment and causes a disproportionation reaction, resulting in a decrease in current efficiency. Therefore, the present invention uses hafnium carbide as the electrolytic anode material to provide a new method for preparing hafnium metal by molten salt electrolysis, realizing a method for preparing hafnium powder with a short process, low cost, environmental friendliness, and high safety. The specific implementation content is as follows:

[0045] In the first aspect, the present invention provides a method for preparing hafnium metal by molten salt electrolysis, Figure 1The flowchart of the method for preparing hafnium metal by molten salt electrolysis provided by the embodiment of the present invention is shown. As Figure 1 shown, the preparation method includes the following steps:

[0046] S1. After mixing hafnium carbide raw material and an appropriate amount of binder evenly, granulation treatment is carried out to prepare granular materials with a size of 3-5 mm. After vacuum sintering treatment, hafnium carbide particles are obtained.

[0047] Specifically in implementation, before hafnium carbide is used for electrolytic preparation of hafnium metal, hafnium carbide is granulated through this step first, that is, hafnium carbide and the binder are mixed evenly and put into a granulator to prepare granules with a particle size of 3-5 mm. After the granules are vacuum sintered, hafnium carbide particles with uniform and stable shapes are formed. Among them, the pressure of the vacuum sintering treatment is 0.1 MPa to 0.5 MPa, and the temperature is 1200 °C to 1500 °C.

[0048] Compared with directly using hafnium carbide powder for electrolysis, the specific surface area of the hafnium carbide particles formed by granulation is significantly increased, thereby increasing the contact area of the subsequent electrolysis reaction, promoting the reaction rate, and improving the yield and efficiency of hafnium metal; the granulated hafnium carbide has better fluidity, which is convenient for transportation and filling. At the same time, the granulated hafnium carbide can quickly sink to the bottom of the electrolyte anode after being added to the molten salt electrolyte, meeting the requirements of continuous electrolytic feeding.

[0049] In some embodiments, the mass ratio of the hafnium carbide raw material to the binder used for granulation is controlled at 4:1 to 7:1, and the binder is selected from one or a combination of polyvinyl acetate, polyvinyl alcohol, polyacrylate, polyurethane, phenolic resin, etc.

[0050] S2. Mix an alkali metal / alkaline earth metal chloride salt with a small amount of hafnium salt, pre-melt and then cool to obtain a molten salt electrolyte;

[0051] In this step, a mixture of an alkali metal / alkaline earth metal chloride salt and a hafnium salt is used to form an electrolyte system together. The presence of a small amount of hafnium salt in the electrolyte system helps to balance hafnium ions during electrolysis. In addition, the addition of hafnium salt can reduce the overall melting point of the electrolyte system, enabling the molten salt to be fully melted at a lower temperature, reducing the energy consumption and working temperature of the equipment.

[0052] In this step, the alkali metal / alkaline earth metal chloride salt and the hafnium salt are pre-melted and cooled. The pre-melting enables the alkali metal / alkaline earth metal chloride salt and the hafnium salt to interact with each other to form a composite molten salt electrolyte with specific structures and properties. The distribution of ions in the composite molten salt electrolyte is uniform, improving the conductivity of the molten salt and making it have better electrical conductivity and chemical stability.

[0053] In some embodiments, the alkali metal chloride salt may be selected from one or a combination of more than one of sodium chloride, potassium chloride, lithium chloride, calcium chloride, rubidium chloride, and cesium chloride, and the alkaline earth metal chloride salt is calcium chloride; the hafnium salt is selected from potassium hafnium fluoride and / or hafnium tetrachloride. The mass ratio of the added hafnium salt to the alkali metal / alkaline earth metal chloride salt is 3:7 to 4:6. When the alkali metal / alkaline earth metal chloride salt is a combination of two or more of the above, the alkali metal / alkaline earth metal chloride salts are mixed in equimolar amounts; the alkali metal / alkaline earth metal chloride salt may specifically be NaCl-KCl, NaCl-CaCl 2 , NaCl-KCl-CsCl, NaCl-KCl-RbCl, LiCl-NaCl-KCl, LiCl-KCl-CsCl, LiCl-KCl-RbCl.

[0054] In some embodiments, before the alkali metal / alkaline earth metal chloride salt and the hafnium salt participate in premelting, the alkali metal / alkaline earth metal chloride salt and the hafnium salt are respectively subjected to vacuum dehydration treatment to remove interfering impurities in the raw materials. Among them, the vacuum dehydration treatment procedure for the alkali metal / alkaline earth metal chloride salt includes: subjecting the alkali metal / alkaline earth metal chloride salt to vacuum dehydration under the conditions of a temperature of 500 to 600 °C and a pressure of 0.1 MPa to 0.5 MPa; and the vacuum dehydration treatment procedure for the hafnium salt includes: subjecting potassium hafnium fluoride to vacuum dehydration under the conditions of a temperature of 350 to 500 °C and a pressure of 0.1 MPa to 0.5 MPa; subjecting hafnium tetrachloride to vacuum dehydration under the conditions of a temperature of 200 to 300 °C and a pressure of 0.1 MPa to 0.5 MPa.

[0055] S3. Add the hafnium carbide particles to the bottom of the graphite crucible in the electrolytic furnace, then add the molten salt electrolyte into the graphite crucible, seal the equipment, and perform electrolysis treatment;

[0056] In this step, the hafnium carbide particles are placed in a graphite crucible and laid flat on the bottom of the graphite crucible. Then, the molten salt electrolyte is placed into the graphite crucible. After sealing the equipment, the assembly of the electrolysis equipment is completed. The hafnium carbide particles in direct contact with the bottom of the graphite crucible serve as part of the anode. During electrolysis, the hafnium ions in the hafnium carbide lose electrons and enter the electrolysis system, and finally metallic hafnium is deposited at the cathode, replacing the original chloride ions that lose electrons and avoiding the generation of chlorine gas.

[0057] During electrolysis, the hafnium carbide particle material obtained by granulation is convenient for continuous feeding. After granulation, the added hafnium carbide particles can sink to the bottom, avoiding suspension loss caused by the difficulty of sedimentation of powdered hafnium carbide materials, ensuring that more raw materials participate in the electrolysis reaction, and thus improving the utilization rate of the materials.

[0058] In some embodiments, the mass ratio of the added hafnium carbide particles to the molten salt electrolyte is 1:3 to 1:5, preferably 1:4. After sealing the electrolysis equipment, start the heating furnace to heat to the set temperature and keep it warm. After the molten salt electrolyte melts, start electrolysis. The electrolysis temperature is set at 750 - 850 °C, and the cathode current density of electrolysis is 0.1 - 5 A / cm 2 .

[0059] S4. After the electrolysis is completed, collect the deposits attached to the cathode and extract hafnium metal from the deposits.

[0060] Specifically, during implementation, after electrolysis for a certain period of time, lift the cathode electrode to the cooling chamber for cooling. After the electrode is cooled to room temperature, take out the deposits on the cathode. The deposits on the cathode are mainly molten salt electrolyte and hafnium metal powder inclusions. The operation of extracting hafnium metal powder from the deposits includes: crushing the cathode deposits into particles with a particle size of 1 - 3 mm, putting them into deionized water at 50 °C - 80 °C and stirring and washing. After all the molten salt electrolyte inclusions are dissolved in water, filter to obtain hafnium powder. Immerse the hafnium powder in dilute hydrochloric acid with a certain concentration and stir and wash. After sedimentation and filtration, wash with deionized water 3 - 5 times, and obtain electrolytic hafnium metal powder after low-temperature drying.

[0061] In the embodiments of the present invention, electrolyzing hafnium carbide as a raw material to prepare hafnium powder can replace using sponge hafnium prepared by the Kroll process (magnesium reduction of hafnium tetrachloride) as a raw material, reducing the cost and shortening the process flow. Because sponge hafnium needs to be prepared by chlorination of hafnium oxide to form hafnium tetrachloride, then purify hafnium tetrachloride, and then reduce hafnium tetrachloride with metallic magnesium and distill to separate magnesium, etc. before sponge hafnium can be obtained. The process flow is long and the cost is high. Hafnium carbide can be obtained by carbon reduction of hafnium oxide, with a short process and low cost. If no anode material is added and directly electrolyze an electrolyte containing potassium hafnium fluoride or hafnium tetrachloride, hafnium metal can also be prepared, but chlorine gas will be generated at the anode, deteriorating the production environment. At the same time, the generation of chlorine gas seriously corrodes the equipment and triggers a disproportionation reaction, resulting in a reduction in current efficiency. Therefore, using hafnium carbide as a raw material for electrolysis is a new process method for preparing hafnium powder with low oxygen content and has good application value.

[0062] Furthermore, for the method for preparing hafnium metal by molten salt electrolysis provided by the present invention, according to needs, by adopting the method of adding hafnium carbide particles at regular intervals, continuous production of hafnium metal can be achieved, and the production efficiency is greatly improved.

[0063] In the second aspect, the present invention provides a hafnium metal obtained by the method described in the first aspect above.

[0064] To make those skilled in the art understand the present invention more clearly, the following examples are now used to elaborate in detail on a hafnium metal and a method for preparing hafnium metal by molten salt electrolysis described in the present invention.

[0065] The following raw materials participating in electrolysis are pretreated in advance to remove moisture and volatile impurities:

[0066] Pretreatment of alkali metal chloride: Vacuum dehydration is carried out under the conditions of a temperature of 500 °C and a pressure of 0.1 MPa;

[0067] Pretreatment of potassium hafnium fluoride: Vacuum dehydration pretreatment is carried out under the conditions of a temperature of 350 °C and a pressure of 0.1 MPa;

[0068] Pretreatment of hafnium tetrachloride: Vacuum dehydration is carried out under the conditions of a temperature of 200 °C and a pressure of 0.1 MPa for dehydration pretreatment.

[0069] Example 1

[0070] Mix hafnium carbide raw materials (+500 mesh to -300 mesh) and polyvinyl acetate as a binder in a mass ratio of 4:1 evenly, and use a granulator to prepare particles with a size of 3 - 5 mm. Then, dehydrate under a vacuum of 0.1 MPa and sinter at 1500 °C to form hafnium carbide particles;

[0071] Mix sodium chloride and potassium chloride with an equimolar ratio and grind them for 30 min. Then, add them to a crucible and place it in a heating furnace. After evacuating, fill it with argon. Under a pressure of 0.1 MPa, heat it to 700 °C, keep it warm for 1 h, and cool it to room temperature to obtain a NaCl-KCl eutectic electrolyte;

[0072] Mix a mixed salt of sodium chloride and potassium chloride with an equimolar ratio accounting for 70% by mass and potassium hafnium fluoride accounting for 30% by mass, pre-melt and cool to obtain a molten salt electrolyte NaCl-KCl-K 2 HfF 6 for standby;

[0073] Take 20% by mass of hafnium carbide particles as the anode material and add them to the bottom of the crucible in the electrolysis furnace, and add 80% by mass of the pre-melted and cooled molten salt electrolyte. After sealing the electrolysis equipment, start the heating furnace to heat to the set temperature and keep it warm. After the molten salt electrolyte melts, start electrolysis. The electrolysis temperature is set at 750 °C, and the electrolysis cathode current density is 1 A / cm 2 . After electrolyzing for a certain period of time, lift the electrode to the cooling chamber for cooling. After the electrode cools to room temperature, take out the cathode and the deposits on the cathode together. The deposits on the cathode are mainly molten salt electrolyte and hafnium metal powder mixed in;

[0074] Crush the cathode deposits into particles with a particle size of 1 - 3 mm, put them into deionized water at 50 °C and stir for cleaning. After all the molten salt electrolyte mixed in dissolves in water, filter to obtain hafnium powder. Immerse the hafnium powder in dilute hydrochloric acid with a certain concentration and stir for cleaning. After sedimentation and filtration, wash it with deionized water 3 to 5 times, and dry it at a low temperature to obtain electrolytic hafnium metal powder;Figure 2 The metal hafnium prepared by molten salt electrolysis in an embodiment of the present invention is shown.

[0075] Table 1 shows the chemical composition analysis results of the metal hafnium provided in the embodiment of the present invention. As shown in Table 1, the oxygen content of the metal hafnium prepared by the molten salt electrolysis method provided in Example 1 is as low as 0.072%.

[0076] Table 1 Chemical composition analysis of metal hafnium

[0077]

[0078] Embodiment 2:

[0079] The hafnium carbide raw material (+500 mesh ~ -300 mesh) and the adhesive polyvinyl alcohol in a mass ratio of 4:1 are evenly mixed, and a granulator is used to prepare particles with a particle size of 3-5 mm, and then dehydrated and sintered under a vacuum of 0.5 MPa to form hafnium carbide particles as the raw material of electrolytic hafnium powder.

[0080] Sodium chloride and potassium chloride in equal molar ratios were ground for 30 min, added into a crucible and placed in a heating furnace. After evacuation, argon was filled into the crucible. The crucible was heated to 700°C at a pressure of 0.1 MPa, kept at this temperature for 1 h, and cooled to room temperature to obtain a NaCl-KCl eutectic electrolyte.

[0081] The NaCl-KCl eutectic electrolyte with a mass ratio of 65% and hafnium tetrachloride with a mass ratio of 35% were mixed and pre-melted and cooled to obtain NaCl-KCl-K 2 HfCl 6 Molten salt electrolyte is available for backup.

[0082] 20% by weight of hafnium carbide particles were used as anode material and added to the bottom of the crucible in the electrolytic furnace. 80% by weight of pre-melted and cooled NaCl-KCl-K 2 HfCl 6 Molten salt electrolyte. After the electrolysis equipment is sealed, the heating furnace is started to heat to the set temperature and then kept warm. After the molten salt electrolyte melts, electrolysis begins. The electrolysis temperature is set at 750°C and the electrolysis cathode current density is 2 A / cm 2 After a certain period of electrolysis, the electrode is lifted to a cooling chamber for cooling. After the electrode cools to room temperature, the cathode and the deposit on the cathode are taken out together. The deposit on the cathode is mainly mixed molten salt electrolyte and metal hafnium powder.

[0083] The cathode sediment is crushed into particles with a size of 1-3 mm, and then placed in deionized water at 80°C for stirring and cleaning. After all the mixed molten salt electrolyte is dissolved in water, the hafnium powder is filtered out, and the hafnium powder is immersed in a certain concentration of dilute hydrochloric acid for stirring and cleaning. After sedimentation and filtration, it is washed with deionized water for 3 to 5 times, and then dried at low temperature to obtain electrolytic metal hafnium powder.

[0084] Table 2 shows the chemical composition analysis results of hafnium metal provided in the embodiments of the present invention. As shown in Table 2, in the hafnium metal prepared by the molten salt electrolysis method provided in Example 2, the oxygen content is as low as 0.068%.

[0085] Table 2 Chemical Composition Analysis of Hafnium Metal

[0086]

[0087] Example 3

[0088] Mix hafnium carbide raw materials (+500 mesh to -300 mesh) and binder polyacrylate with a mass ratio of 4:1 evenly, and use a granulator to prepare particles with a particle size of 3 - 5 mm. Then dehydrate under a vacuum of 0.1 MPa and sinter at 1500 °C to form hafnium carbide particles;

[0089] After mixing sodium chloride - calcium chloride with an equimolar ratio and grinding for 30 min, add it to a crucible and place it in a heating furnace. After evacuating, fill it with argon. Under a positive pressure of 0.1 MPa, heat it to 700 °C, keep it warm for 1 h, and cool it to room temperature to obtain NaCl - CaCl 2 eutectic electrolyte;

[0090] Mix 60% by mass of NaCl - CaCl 2 and 40% by mass of potassium hafnium fluoride, pre - melt and cool to obtain molten salt electrolyte NaCl - CaCl 2 -K 2 HfF 6 for standby;

[0091] Add 20% by mass of hafnium carbide particles as anode material to the bottom of the crucible in the electrolysis furnace, and add 80% by mass of the pre - melted and cooled molten salt electrolyte. After sealing the electrolysis equipment, start the heating furnace to heat to the set temperature and keep it warm. After the molten salt electrolyte melts, start electrolysis. The electrolysis temperature is set at 750 °C, and the electrolysis cathode current density is 3 A / cm 2 . After electrolyzing for a certain time, lift the electrode to the cooling chamber for cooling. After the electrode cools to room temperature, take out the cathode and the deposits on the cathode together. The deposits on the cathode are mainly the molten salt electrolyte and hafnium metal powder mixed in;

[0092] Crush the cathode deposits into particles with a particle size of 1 - 3 mm, put them into deionized water at 50 °C and stir for cleaning. After all the molten salt electrolyte mixed in dissolves in water, filter to obtain hafnium powder. Immerse the hafnium powder in dilute hydrochloric acid with a certain concentration and stir for cleaning. After sedimentation and filtration, wash it with deionized water 3 - 5 times, and dry it at a low temperature to obtain electrolytic hafnium metal powder.

[0093] Table 3 shows the chemical composition analysis results of hafnium metal provided by the embodiments of the present invention. As shown in Table 3, in the hafnium metal prepared by the molten salt electrolysis method provided by Example 3, the oxygen content is as low as 0.065%.

[0094] Table 3 Chemical Composition Analysis of Hafnium Metal

[0095]

[0096] Example 4

[0097] Mix hafnium carbide raw materials (+500 mesh to -300 mesh) and binder phenolic resin with a mass ratio of 6:1 evenly, and use a granulator to prepare particles with a particle size of 3 - 5 mm. Then dehydrate under a vacuum of 0.1 MPa and sinter at 1500 °C to form hafnium carbide particles.

[0098] Mix equimolar ratios of NaCl - KCl - CsCl for 30 min, add them to a crucible and place it in a heating furnace. After evacuating, fill it with argon. Under a positive pressure of 0.1 MPa, heat it to 700 °C, keep it warm for 1 h, and cool it to room temperature to obtain the NaCl - KCl - CsCl eutectic electrolyte.

[0099] Mix 65% of the mass of NaCl - KCl - CsCl with 35% of HfCl 4 and perform mixing, pre - melting and cooling to obtain the molten salt electrolyte NaCl - KCl - Cs 2 HfCl 6 composite electrolyte for standby.

[0100] Take 20% of the mass of hafnium carbide particles as the anode material and add it to the bottom of the crucible in the electrolysis furnace, and add 80% of the mass of the pre - melted and cooled molten salt electrolyte. After sealing the electrolysis equipment, start the heating furnace to heat to the set temperature and keep it warm. Start electrolysis after the molten salt electrolyte melts. The electrolysis temperature is set at 750 °C, and the electrolysis cathode current density is 1.5 A / cm 2 . After electrolyzing for a certain time, lift the electrode to the cooling chamber for cooling. After the electrode cools to room temperature, take out the cathode and the deposits on the cathode together. The deposits on the cathode are mainly the molten salt electrolyte and hafnium metal powder mixed in.

[0101] Crush the cathode deposits into particles with a particle size of 1 - 3 mm, put them into deionized water at 50 °C and stir for cleaning. After all the molten salt electrolyte mixed in dissolves in water, filter to obtain hafnium powder. Immerse the hafnium powder in dilute hydrochloric acid with a certain concentration and stir for cleaning. After sedimentation and filtration, wash it with deionized water 3 - 5 times, and dry it at a low temperature to obtain electrolytic hafnium metal powder.

[0102] Table 4 shows the chemical composition analysis results of hafnium metal provided by the embodiments of the present invention. As shown in Table 4, in the hafnium metal prepared by the molten salt electrolysis method provided by Example 4, the oxygen content is as low as 0.06%.

[0103] Table 4 Chemical Composition Analysis of Hafnium Metal

[0104]

[0105] Example 5

[0106] Mix hafnium carbide raw materials (+500 mesh to -300 mesh) and binder polyurethane with a mass ratio of 5:1 evenly, and use a granulator to prepare particles with a particle size of 3 - 5 mm. Then dehydrate under a vacuum of 0.1 MPa and sinter at 1500 °C to form hafnium carbide particles;

[0107] Mix equimolar ratios of NaCl - KCl - RbCl for 30 min, add them to a crucible and place it in a heating furnace. After evacuating, fill it with argon. Under a positive pressure of 0.1 MPa, heat it to 700 °C, keep it warm for 1 h, and cool it to room temperature to obtain the NaCl - KCl - RbCl eutectic electrolyte;

[0108] Mix 65% of the mass of NaCl - KCl - RbCl with 35% of HfCl 4 and perform premelting and cooling to obtain the molten salt electrolyte NaCl - KCl - Rb 2 HfCl 6 composite electrolyte for standby;

[0109] Take 20% of the mass of hafnium carbide particles as the anode material and add it to the bottom of the crucible in the electrolysis furnace, and add 80% of the mass of the premelted and cooled molten salt electrolyte. After sealing the electrolysis equipment, start the heating furnace to heat to the set temperature and keep it warm. Start electrolysis after the molten salt electrolyte melts. The electrolysis temperature is set at 750 °C, and the electrolysis cathode current density is 2.5 A / cm 2 . After electrolyzing for a certain time, lift the electrode to the cooling chamber for cooling. After the electrode cools to room temperature, take out the cathode and the deposits on the cathode together. The deposits on the cathode are mainly the molten salt electrolyte and hafnium metal powder mixed in;

[0110] Crush the cathode deposits into particles with a particle size of 1 - 3 mm, put them into deionized water at 50 °C and stir for cleaning. After all the molten salt electrolyte mixed in dissolves in water, filter to obtain hafnium powder. Immerse the hafnium powder in dilute hydrochloric acid with a certain concentration and stir for cleaning. After sedimentation and filtration, wash it with deionized water 3 to 5 times, and dry it at a low temperature to obtain electrolytic hafnium metal powder.

[0111] Table 5 shows the chemical composition analysis results of hafnium metal provided by the embodiments of the present invention. As shown in Table 5, in the hafnium metal prepared by the molten salt electrolysis method provided in Example 5, the oxygen content is as low as 0.06%.

[0112] Table 5 Chemical Composition Analysis of Hafnium Metal

[0113]

[0114] Example 6

[0115] Mix hafnium carbide raw materials (+500 mesh to -300 mesh) and polyvinyl alcohol, an organic binder, with a mass ratio of 7:1 evenly, and use a granulator to prepare particles with a particle size of 3 - 5 mm. Then dehydrate under a vacuum of 0.1 MPa and sinter at 1500 °C to form hafnium carbide particles.

[0116] Mix equimolar LiCl - KCl - CsCl for 30 min, add it to a crucible and place it in a heating furnace. After evacuating, fill it with argon. Under a positive pressure of 0.1 MPa, heat it to 700 °C, keep it warm for 1 h, and cool it to room temperature to obtain the NaCl - KCl - CsCl eutectic electrolyte.

[0117] Mix 65% of the mass of LiCl - KCl - CsCl with 35% of HfCl 4 and perform premelting and cooling to obtain the molten salt electrolyte LiCl - KCl - Cs 2 HfCl 6 composite electrolyte for standby.

[0118] Take 20% of the mass of hafnium carbide particles as the anode material and add it to the bottom of the crucible in the electrolysis furnace, and add 80% of the mass of the premelted and cooled molten salt electrolyte. After sealing the electrolysis equipment, start the heating furnace to heat to the set temperature and keep it warm. Start electrolysis after the molten salt electrolyte melts. The electrolysis temperature is set at 750 °C, and the electrolysis cathode current density is 3.5 A / cm 2 . After electrolyzing for a certain time, lift the electrode to the cooling chamber for cooling. After the electrode cools to room temperature, take out the cathode and the deposits on the cathode together. The deposits on the cathode are mainly the molten salt electrolyte and hafnium metal powder mixed in.

[0119] Crush the cathode deposits into particles with a particle size of 1 - 3 mm, put them into deionized water at 50 °C and stir for cleaning. After all the molten salt electrolyte mixed in dissolves in water, filter to obtain hafnium powder. Immerse the hafnium powder in dilute hydrochloric acid with a certain concentration and stir for cleaning. After sedimentation and filtration, wash it with deionized water 3 - 5 times, and dry it at a low temperature to obtain electrolytic hafnium metal powder.

[0120] Table 6 shows the chemical composition analysis results of hafnium metal provided by the embodiments of the present invention. As shown in Table 6, in the hafnium metal prepared by the molten salt electrolysis method provided by Example 6, the oxygen content is as low as 0.061%.

[0121] Table 6 Chemical Composition Analysis of Hafnium Metal

[0122]

[0123] Example 7

[0124] Mix hafnium carbide raw materials (+500 mesh to -300 mesh) and polyvinyl alcohol, an organic binder, with a mass ratio of 4:1 evenly, and use a granulator to prepare particles with a particle size of 3 - 5 mm. Then dehydrate under a vacuum of 0.1 MPa and sinter at 1500 °C to obtain hafnium carbide particles.

[0125] Mix equimolar ratios of LiCl - KCl - RbCl for 30 min, add them to a crucible and place it in a heating furnace. After evacuating, fill it with argon. Under a positive pressure of 0.1 MPa, heat up to 700 °C, keep it warm for 1 h, and cool to room temperature to obtain the LiCl - KCl - RbCl eutectic electrolyte.

[0126] Mix 65% of the mass of LiCl - KCl - RbCl with 35% of HfCl 4 and perform premelting and cooling to obtain the molten salt electrolyte LiCl - KCl - Rb 2 HfCl 6 composite electrolyte for standby.

[0127] Take 20% of the mass of hafnium carbide particles as the anode material and add it to the bottom of the crucible in the electrolysis furnace, and add 80% of the mass of the premelted and cooled molten salt electrolyte. After sealing the electrolysis equipment, start the heating furnace to heat to the set temperature and keep it warm. Start electrolysis after the molten salt electrolyte melts. The electrolysis temperature is set at 750 °C, and the electrolysis cathode current density is 4 A / cm 2 . After electrolyzing for a certain time, lift the electrode to the cooling chamber for cooling. After the electrode cools to room temperature, take out the cathode and the deposits on the cathode together. The deposits on the cathode are mainly molten salt electrolyte inclusions and hafnium metal powder.

[0128] Crush the cathode deposits into particles with a particle size of 1 - 3 mm, put them into deionized water at 50 °C and stir for cleaning. After all the molten salt electrolyte inclusions dissolve in water, filter to obtain hafnium powder. Immerse the hafnium powder in dilute hydrochloric acid with a certain concentration and stir for cleaning. After sedimentation and filtration, wash it with deionized water 3 to 5 times, and dry it at a low temperature to obtain electrolytic hafnium metal powder.

[0129] Table 7 shows the chemical composition analysis results of hafnium metal provided by the embodiments of the present invention. As shown in Table 7, in the hafnium metal prepared by the molten salt electrolysis method provided by Example 7, the oxygen content is as low as 0.062%.

[0130] Table 7 Chemical Composition Analysis of Hafnium Metal

[0131]

[0132] In the description of this specification, the descriptions referring to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples", etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic descriptions of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, those skilled in the art can combine and combine the different embodiments or examples described in this specification.

[0133] For method embodiments, for the sake of simple description, they are all expressed as a series of action combinations. However, those skilled in the art should know that the present invention is not limited by the described action sequence, because according to the present invention, certain steps can be performed in other sequences or simultaneously. Secondly, those skilled in the art should also know that the embodiments described in the specification are all preferred embodiments, and the actions and components involved are not necessarily essential to the present invention.

[0134] The above has introduced in detail a method for preparing hafnium metal and a method for preparing hafnium metal by molten salt electrolysis provided by the present invention. Specific examples are used in this article to elaborate on the principle and implementation manner of the present invention. The description of the above embodiments is only used to help understand the method and its core idea of the present invention; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation to the present invention.

Claims

1. A method for preparing metallic hafnium by molten salt electrolysis, characterized in that: include: The hafnium carbide raw material and an appropriate amount of adhesive are uniformly mixed, and then granulated to prepare 3-5 mm granular materials, and then vacuum sintered to obtain hafnium carbide particles; Alkali metal / alkaline earth metal chloride salt is mixed with a small amount of hafnium salt, pre-melted and then cooled to obtain a molten salt electrolyte; Adding the hafnium carbide particles to the bottom of a graphite crucible in an electrolytic furnace, adding the molten salt electrolyte into the graphite crucible, sealing the equipment, and performing electrolysis; After the electrolysis is completed, collecting the sediment attached to the cathode, and extracting the metal hafnium from the sediment; Wherein, the alkali metal / alkaline earth metal chloride salt is selected from one or a combination of sodium chloride, potassium chloride, lithium chloride, calcium chloride, rubidium chloride, cesium chloride and calcium chloride; The hafnium salt is selected from potassium hafnium fluoride and / or hafnium tetrachloride; The vacuum sintering process is performed at a pressure of 0.1 MPa to 0.5 MPa and a temperature of 1200° C. to 1500° C. The mass ratio of the hafnium carbide raw material to the adhesive is 4:1-7:1; The adhesive is selected from one or a combination of polyvinyl acetate, polyvinyl alcohol, polyacrylate, polyurethane and phenolic resin.

2. The method for preparing metallic hafnium by molten salt electrolysis according to claim 1, characterized in that: The alkali metal / alkaline earth metal chloride salt is selected from NaCl-KCl, NaCl-CaCl2, NaCl-KCl-CsCl, NaCl-KCl-RbCl, LiCl-NaCl-KCl, LiCl-KCl-CsCl or LiCl-KCl-RbCl.

3. The method for preparing metallic hafnium by molten salt electrolysis according to claim 1, characterized in that: The electrolysis temperature is 750-850°C; The cathode current density of the electrolysis is 0.1 to 5 A / cm 2 .

4. The method for preparing metallic hafnium by molten salt electrolysis according to claim 1, characterized in that: The mass ratio of the hafnium salt to the alkali metal / alkaline earth metal chloride salt is 3:7-4:

6.

5. The method for preparing metallic hafnium by molten salt electrolysis according to claim 1, characterized in that: The mass ratio of the hafnium carbide particles to the molten salt electrolyte is 1:3 to 1:

5.

6. The method for preparing metallic hafnium by molten salt electrolysis according to claim 1, characterized in that: The particle size of the hafnium carbide raw material is +500 mesh to -300 mesh.

7. The method for preparing metallic hafnium by molten salt electrolysis according to claim 1, characterized in that: Before mixing the alkali metal / alkaline earth metal chloride salt with a small amount of hafnium salt, the method further comprises: Under the conditions of a temperature of 500-600° C. and a pressure of 0.1 MPa-0.5 MPa, vacuum dehydrating the alkali metal / alkaline earth metal chloride salt; The potassium hafnium fluoride is subjected to vacuum dehydration at a temperature of 350-500° C. and a pressure of 0.1 MPa-0.5 MPa; The hafnium tetrachloride is subjected to vacuum dehydration at a temperature of 200-300° C. and a pressure of 0.1 MPa-0.5 MPa.

8. The method for preparing metallic hafnium by molten salt electrolysis according to claim 1, characterized in that: The step of extracting the metallic hafnium from the sediment comprises: The cathode sediment is crushed into particles with a particle size of 1-3 mm, and placed in deionized water at 50°C to 80°C for stirring and cleaning. After the mixed molten salt electrolyte is completely dissolved in the water, the coarse hafnium powder is filtered out; The crude hafnium powder is immersed in dilute hydrochloric acid for stirring and cleaning, and after sedimentation and filtration, it is washed with deionized water for 3 to 5 times, and dried at low temperature to obtain metal hafnium powder with low oxygen content.

9. A metal hafnium, characterized in that: The hafnium metal is obtained by the method for preparing hafnium metal by molten salt electrolysis as claimed in any one of claims 1 to 8.

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