Metal hafnium and method for preparing metal hafnium through molten salt electrolysis

Abstract

The invention provides a method for preparing metal hafnium by electrolyzing metal hafnium and molten salt, which comprises the following steps: uniformly mixing a hafnium carbide raw material and a proper amount of adhesive, granulating, and sintering in vacuum to obtain hafnium carbide particles; mixing alkali metal / alkaline earth metal chlorine salt with a small amount of hafnium salt, pre-melting, and cooling to obtain molten salt electrolyte; adding hafnium carbide particles into the bottom of a graphite crucible in an electrolytic furnace, adding a molten salt electrolyte into the graphite crucible, sealing equipment, and carrying out electrolysis; after electrolysis is completed, sediment attached to the cathode is collected, and metal hafnium is extracted from the sediment; according to the invention, hafnium carbide is used as an anode material, so that the problem of equipment corrosion caused by a large amount of chlorine separated from an anode when a high-temperature molten salt system is directly electrolyzed to prepare hafnium powder is avoided; in addition, the production cost of hafnium carbide is relatively low, and hafnium carbide can be obtained by taking hafnium oxide as a raw material through a carbon reduction method, so that compared with sponge hafnium as an anode material, the cost is greatly saved.

Description

Technical Field

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

[0002] Hafnium is widely used in many fields due to its unique physical and chemical properties. Hafnium has excellent neutron absorption characteristics and is often 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 high-temperature alloys, mainly used in 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 used in some extreme working conditions. Hafnium oxide films prepared from metallic hafnium are used as capacitor materials in microelectronics and integrated circuits due to their excellent dielectric properties. Hafnium is widely used in thin film technology. It can be used as a coating material to enhance the surface wear resistance and corrosion resistance. Hafnium oxide thin films prepared with metallic hafnium as raw material can be used to manufacture high-performance optical materials due to its high refractive index and excellent optical properties. In certain 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. High-temperature anti-oxidation coatings prepared with hafnium powder as raw material have excellent performance and are used in the aerospace field.

[0003] At present, there are three main processes for preparing hafnium powder: the first is the hydrogenation-dehydrogenation method, which requires metal hafnium (hafnium sponge or hafnium chips) as raw material, hydrogenates metal hafnium to obtain hafnium hydride, crushes hafnium hydride into powder and then dehydrogenates to obtain hafnium powder. The use of hydrogen in this process has certain safety risks. The hafnium powder prepared by dehydrogenation of hafnium hydride is prone to spontaneous combustion and poses a safety hazard. The second method is the calcium (calcium hydride) reduction method, which uses hafnium oxide and calcium (calcium hydride) as raw materials. This process can obtain hafnium powder with finer particles, but the oxygen content of hafnium powder is high. If the process conditions are not well controlled, the reduction of hafnium oxide will not be complete. At the same time, calcium and calcium hydride are also dangerous goods, which poses certain safety hazards. The third method is the molten salt electrolysis method, which uses potassium hafnium fluoride or hafnium tetrachloride as the hafnium source. Under the action of the electric field, metal hafnium powder is precipitated at the cathode by controlling the process conditions. This process uses electric fields to replace dangerous goods reducing agents, ensuring production safety.

[0004] The molten salt electrolysis method is to melt salts at high temperature to form a melt, and then pass direct current to make some ions in it undergo redox reactions on the electrodes, thereby achieving the purpose of preparing and refining metals or other substances. The existing process of preparing hafnium powder by molten salt electrolysis is to use potassium hafnium fluoride or hafnium tetrachloride as the raw material of hafnium, and add supporting electrolytes such as sodium chloride and potassium chloride for high-temperature molten salt electrolysis. Under the action of the electric field, metallic hafnium is precipitated at the cathode, and after water washing, metallic hafnium powder is obtained.

[0005] However, chlorine is precipitated at the anode during direct electrolysis. When the current density is too high or the concentration of hafnium ions is too low, an anode effect will occur, interrupting the electrolysis. Chlorine precipitates cause serious corrosion to the equipment at high temperatures, and also lead to safety risks in the production process. In order to solve the problem of chlorine precipitating at the anode, the existing process is to add hafnium sponge to the anode as an anode material to avoid chlorine precipitating at the anode and as a source of hafnium. However, the production cost of hafnium sponge as a 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 metal hafnium and a method for preparing metal hafnium by molten salt electrolysis, so as to solve the problem of chlorine gas precipitation at the anode when potassium hafnium fluoride or hafnium tetrachloride is directly electrolyzed as the hafnium source in the prior art, or the problem of high cost when sponge hafnium is used as the anode raw material.

[0007] The specific content of the invention is as follows: The present invention provides a method for preparing metal hafnium by molten salt electrolysis, comprising: 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 oxygen content in the metal hafnium is 0.06-0.08%.

[0008] Optionally, 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.

[0009] Optionally, the electrolysis temperature is 750-850°C; The cathode current density of the electrolysis is 0.1 to 5 A / cm 2 .

[0010] Optionally, 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; 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.

[0011] Optionally, the mass ratio of the hafnium salt to the alkali metal / alkaline earth metal chloride salt is 3:7-4:6.

[0012] Optionally, the mass ratio of the hafnium carbide particles to the molten salt electrolyte is 1:3 to 1:5.

[0013] Optionally, the particle size of the hafnium carbide raw material is +500 mesh to -300 mesh.

[0014] Optionally, 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; Dehydrating the potassium hafnium fluoride in vacuum 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.

[0015] Optionally, 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 washing, and 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.

[0016] Optionally, the present invention provides metal hafnium obtained by the method described in the first aspect above.

[0017] Compared with the prior art, the present invention has the following advantages: The invention provides a method for preparing metal hafnium by molten salt electrolysis, comprising: mixing a hafnium carbide raw material and an appropriate amount of a binder uniformly, granulating the mixture to prepare a granular material of 3-5 mm, and vacuum sintering the mixture to obtain hafnium carbide particles; adding an appropriate amount of hafnium salt to an electrolyte, pre-melting the mixture, and cooling the mixture 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 to the graphite crucible, sealing the device, and performing an electrolysis treatment; after the electrolysis is completed, collecting the sediment attached to the cathode, and extracting metal hafnium powder with a low oxygen content from the sediment; the oxygen content of the metal hafnium powder is 0.06-0.08%.

[0018] In the preparation method provided by the present invention, hafnium carbide is used as the anode material, which avoids the problem of large amount of chlorine gas precipitated from the anode and causing equipment corrosion when hafnium powder is directly electrolyzed in a high-temperature molten salt system (without anode material); in addition, the production cost of hafnium carbide is relatively low, and it can be obtained by a carbon reduction method using hafnium oxide as a raw material, which greatly saves costs compared to using hafnium sponge as the anode material. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 A flow chart of a method for preparing metal hafnium by molten salt electrolysis provided by an embodiment of the present invention is shown; Figure 2 The metal hafnium prepared by molten salt electrolysis in an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0021] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is by no means a limitation on 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 prior arts falls within the scope of protection of the present invention. In addition, all other embodiments obtained by ordinary technicians in this field without carrying out creative work belong to the scope of protection of the present invention.

[0022] In the embodiment, no specific experimental steps or conditions are indicated, and the operation or conditions of the conventional experimental steps described in the prior art in this field can be carried out. The reagents used and other instruments that do not indicate the manufacturer are conventional reagent products that can be obtained commercially. In addition, the accompanying drawings are only schematic diagrams of the embodiments of the present invention and are not necessarily drawn to scale. The same reference numerals in the figures represent the same or similar parts, and thus their repeated description will be omitted. Some block diagrams shown in the accompanying drawings are functional entities and do not necessarily correspond to physically or logically independent entities.

[0023] Technologies, methods, and equipment known to ordinary technicians in the relevant field may not be discussed in detail, but where appropriate, the technologies, methods, and equipment should be considered as part of the description of the present invention.

[0024] In the description of the present invention, it should be understood that the use of terms such as "first" and "second" to limit components is only for the convenience of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore cannot be understood as limiting the scope of protection of the present invention.

[0025] In addition, the technical features involved in the different embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0026] Since the preparation of metallic hafnium is carried out by directly electrolyzing an electrolyte containing potassium hafnium fluoride or hafnium tetrachloride, there is a problem that the anode will produce chlorine gas, which will deteriorate the production environment. At the same time, the production of chlorine gas will cause serious corrosion to the equipment and induce disproportionation reaction, resulting in reduced current efficiency. Therefore, the present invention uses hafnium carbide as the electrolytic anode material to provide a new method for preparing metallic hafnium by molten salt electrolysis, realizing a short-process, low-cost, environmentally friendly and safe method for preparing metallic hafnium powder. The specific implementation content is as follows: In a first aspect, the present invention provides a method for preparing metallic hafnium by molten salt electrolysis. Figure 1The flowchart of the method for preparing metal hafnium by molten salt electrolysis provided by an embodiment of the present invention is shown as follows: Figure 1 As shown, the preparation method comprises the following steps: S1. After uniformly mixing the hafnium carbide raw material and an appropriate amount of adhesive, granulation is performed to prepare 3-5 mm granular materials, and after vacuum sintering, hafnium carbide particles are obtained.

[0027] In specific implementation, before the hafnium carbide is used for electrolytic preparation of metallic hafnium, the hafnium carbide is first granulated in this step, that is, the hafnium carbide is evenly mixed with a binder and put into a granulator to prepare particles with a particle size of 3-5 mm, and the particles are vacuum sintered to form hafnium carbide particles with uniform and stable shape. The vacuum sintering treatment pressure is 0.1MPa~0.5MPa and the temperature is 1200℃~1500℃.

[0028] Compared with direct electrolysis using hafnium carbide powder, 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 increasing the yield and efficiency of metal hafnium; the granulated hafnium carbide has better fluidity and is easy to transport and load. 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 electrolysis feeding.

[0029] In some embodiments, the mass ratio of the hafnium carbide raw material used for granulation to the binder is controlled at 4:1-7:1, and the binder is selected from one or a combination of polyvinyl acetate, polyvinyl alcohol, polyacrylate, polyurethane, and phenolic resin.

[0030] S2, mixing an alkali metal / alkaline earth metal chloride salt with a small amount of hafnium salt, pre-melting and then cooling to obtain a molten salt electrolyte; In this step, a mixture of alkali metal / alkaline earth metal chloride and hafnium salt is used to form an electrolyte system. The presence of a small amount of hafnium salt in the electrolyte system helps to balance the hafnium ions during the electrolysis process. In addition, the addition of hafnium salt can lower the melting point of the electrolyte system as a whole, so that the molten salt can be fully melted at a lower temperature, reducing the energy consumption and operating temperature of the equipment.

[0031] In this step, the alkali metal / alkaline earth metal chloride and the hafnium salt are pre-melted and cooled. The pre-melting allows the alkali metal / alkaline earth metal chloride to interact with the hafnium salt to form a composite molten salt electrolyte with a specific structure and properties. The ions in the composite molten salt electrolyte are evenly distributed, which improves the conductivity of the molten salt and makes it have better conductivity and chemical stability.

[0032] In some embodiments, the alkali metal chloride salt can be selected from one or more of sodium chloride, potassium chloride, lithium chloride, calcium chloride, rubidium chloride and cesium chloride, 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 3:7~4:6. 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 salt is mixed in equimolar amounts; the alkali metal / alkaline earth metal chloride salt can specifically be NaCl-KCl, NaCl-CaCl2, NaCl-KCl-CsCl, NaCl-KCl-RbCl, LiCl-NaCl-KCl, LiCl-KCl-CsCl, LiCl-KCl-RbCl.

[0033] In some embodiments, before the alkali metal / alkaline earth metal chloride and the hafnium salt are pre-melted, the alkali metal / alkaline earth metal chloride and the hafnium salt are respectively subjected to vacuum dehydration treatment to remove interfering impurities in the raw materials. The vacuum dehydration treatment procedure of the alkali metal / alkaline earth metal chloride includes: vacuum dehydration of the alkali metal / alkaline earth metal chloride at a temperature of 500-600°C and 0.1MPa-0.5MPa; and the vacuum dehydration treatment procedure for the hafnium salt includes: vacuum dehydration of potassium hafnium fluoride at a temperature of 350-500°C and 0.1MPa-0.5MPa; vacuum dehydration of hafnium tetrachloride at a temperature of 200-300°C and 0.1MPa-0.5MPa.

[0034] S3, 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; In this step, a graphite crucible is used to hold hafnium carbide particles, which are spread flat on the bottom of the graphite crucible, and then a molten salt electrolyte is placed in the graphite crucible. After the equipment is sealed, the assembly of the electrolysis equipment is completed. The hafnium carbide particles that are in direct contact with the bottom of the graphite crucible serve as part of the anode. During the electrolysis process, the hafnium ions in the hafnium carbide, as the party that loses electrons, enter the electrolysis system, and finally precipitate metallic hafnium at the cathode to replace the original chloride ions that lose electrons, thereby avoiding the generation of chlorine gas.

[0035] The hafnium carbide granular material obtained by granulation is convenient for continuous feeding during the electrolysis process. After granulation, the added hafnium carbide particles can sink to the bottom, avoiding the suspension loss caused by the hafnium carbide powder material not being easy to settle, ensuring that more raw materials participate in the electrolysis reaction, thereby improving the utilization rate of the material.

[0036] 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 the electrolysis equipment is sealed, the heating furnace is started to heat to the set temperature and then kept warm, and electrolysis begins after the molten salt electrolyte melts. The electrolysis temperature is set at 750-850°C, and the cathode current density of the electrolysis is 0.1~5A / cm 2 .

[0037] S4. After the electrolysis is completed, the sediment attached to the cathode is collected, and metal hafnium is extracted from the sediment.

[0038] In the specific implementation, after a certain period of electrolysis, the cathode electrode is lifted to the cooling chamber for cooling. After the electrode cools to room temperature, the deposit on the cathode is taken out. The deposit on the cathode is mainly mixed with molten salt electrolyte and metal hafnium powder. The operation of extracting metal hafnium powder from the sediment includes: crushing the cathode sediment into particles with a particle size of 1-3mm, putting it into deionized water at 50℃~80℃, stirring and washing, and filtering to obtain hafnium powder after the mixed molten salt electrolyte is completely dissolved in water. The hafnium powder is immersed in a certain concentration of dilute hydrochloric acid and stirred and washed. After sedimentation and filtration, it is washed with deionized water 3 to 5 times, and electrolytic metal hafnium powder is obtained after low-temperature drying.

[0039] In the embodiment of the present invention, hafnium carbide is used as a raw material for electrolysis to prepare hafnium powder, which can replace the use of sponge hafnium prepared by the Kroll method (magnesium reduction of hafnium tetrachloride) as a raw material, thereby reducing costs and shortening the process flow. Because sponge hafnium needs to be prepared into hafnium tetrachloride by chlorination of hafnium oxide, and then the hafnium tetrachloride is purified, and then the hafnium tetrachloride is reduced by metallic magnesium, and the magnesium is separated by distillation, the sponge hafnium can be obtained after other processes, and the process flow is long and the cost is high. Hafnium carbide can be obtained by carbon reduction using hafnium oxide as a raw material, which has a short process flow and low cost. If no anode material is added, the electrolyte containing potassium hafnium fluoride or hafnium tetrachloride is directly electrolyzed to prepare metallic hafnium, but the anode will produce chlorine gas, which will deteriorate the production environment. At the same time, the production of chlorine gas will seriously corrode the equipment and induce disproportionation reaction, resulting in a decrease in current efficiency. Therefore, using hafnium carbide as a raw material for electrolysis is a new process for preparing hafnium powder with low oxygen content, which has good application value.

[0040] Furthermore, the method for preparing metallic hafnium by molten salt electrolysis provided by the present invention can realize continuous production of metallic hafnium by regularly adding hafnium carbide particles as required, thereby greatly improving production efficiency.

[0041] In a second aspect, the present invention provides metal hafnium obtained by the method described in the first aspect.

[0042] In order to enable those skilled in the art to more clearly understand the present invention, the metal hafnium and the method for preparing the metal hafnium by molten salt electrolysis according to the present invention are now described in detail through the following examples.

[0043] The following raw materials involved in electrolysis are pre-treated to remove moisture and volatile impurities: Alkali metal chloride pretreatment: vacuum dehydration at 500°C and 0.1MPa; Potassium hafnium fluoride pretreatment: vacuum dehydration pretreatment at 350°C and 0.1MPa; Hafnium tetrachloride pretreatment: vacuum dehydration at a temperature of 200°C and a pressure of 0.1MPa for dehydration pretreatment.

[0044] Example 1 The hafnium carbide raw material (+500 mesh to -300 mesh) and the binder polyvinyl acetate in a mass ratio of 4:1 are mixed evenly, and prepared into 3-5 mm particles by a granulator, and then dehydrated under a vacuum of 0.1 MPa and sintered at 1500°C to form hafnium carbide particles; 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. Mix 70% by weight of a sodium chloride-potassium chloride mixed salt in an equal molar ratio and 30% by weight of potassium hafnium fluoride, pre-melt and cool, and obtain a molten salt electrolyte NaCl-KCl-K2HfF6 for use; 20% by weight of hafnium carbide particles are used as anode materials and added to the bottom of the crucible in the electrolytic furnace. 80% by weight of pre-melted and cooled molten salt electrolyte is added. 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 1 A / cm 2 After a certain period of electrolysis, the electrode is placed in 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 with molten salt electrolyte and metal hafnium powder. The cathode sediment is crushed into particles with a particle size of 1-3 mm, and then placed in deionized water at 50 °C for stirring and cleaning. After the mixed molten salt electrolyte is completely 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; Figure 2 The metal hafnium prepared by molten salt electrolysis in an embodiment of the present invention is shown.

[0045] 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%.

[0046] Table 1 Chemical composition analysis of metal hafnium

[0047] Embodiment 2: 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.

[0048] 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. Mix 65% by mass of NaCl-KCl eutectic electrolyte and 35% by mass of hafnium tetrachloride, pre-melt and cool to obtain NaCl-KCl-K2HfCl6 molten salt electrolyte for use.

[0049] 20% by weight of hafnium carbide particles are used as anode materials and added to the bottom of the crucible in the electrolytic furnace. 80% by weight of pre-melted and cooled NaCl-KCl-K2HfCl6 molten salt electrolyte is added. 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.

[0050] 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.

[0051] Table 2 shows the chemical composition analysis results of the metal hafnium provided in the embodiment of the present invention. As shown in Table 2, the oxygen content of the metal hafnium prepared by the molten salt electrolysis method provided in Example 2 is as low as 0.068%.

[0052] Table 2 Chemical composition analysis of metal hafnium

[0053] Example 3 The hafnium carbide raw material (+500 mesh to -300 mesh) and the adhesive polyacrylate are mixed evenly in a mass ratio of 4:1, and the particles with a particle size of 3-5 mm are prepared by a granulator, and then dehydrated under a vacuum of 0.1 MPa and sintered at 1500°C to form hafnium carbide particles; After mixing sodium chloride and calcium chloride in equal molar ratio for 30 min, the mixture was added into a crucible and placed in a heating furnace. After vacuuming, the mixture was filled with argon gas. The mixture was heated to 700°C under a positive pressure of 0.1 MPa and kept at this temperature for 1 h. After cooling to room temperature, the NaCl-CaCl2 eutectic electrolyte was obtained. 60% by mass of NaCl-CaCl2 and 40% by mass of potassium hafnium fluoride are mixed, pre-melted and cooled to obtain a molten salt electrolyte NaCl-CaCl2-K2HfF6 for standby use; 20% by weight of hafnium carbide particles are used as anode materials and added to the bottom of the crucible in the electrolytic furnace. 80% by weight of pre-melted and cooled molten salt electrolyte is added. 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 3 A / cm 2 After a certain period of electrolysis, the electrode is placed in 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 with molten salt electrolyte and metal hafnium powder. The cathode sediment is crushed into particles with a particle size of 1-3 mm, placed in 50 ℃ deionized water for stirring and cleaning, and after the mixed molten salt electrolyte is completely 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.

[0054] Table 3 shows the chemical composition analysis results of the metal hafnium provided by the embodiment of the present invention. As shown in Table 3, the oxygen content of the metal hafnium prepared by the molten salt electrolysis method provided by Example 3 is as low as 0.065%.

[0055] Table 3 Chemical composition analysis of metal hafnium

[0056] Example 4 The hafnium carbide raw material (+500 mesh to -300 mesh) and the adhesive phenolic resin are mixed evenly in a mass ratio of 6:1, and the particles with a particle size of 3-5 mm are prepared by a granulator, and then dehydrated under a vacuum of 0.1 MPa and sintered at 1500°C to form hafnium carbide particles; After grinding NaCl-KCl-CsCl in equal molar ratio for 30 min, the mixture was added into a crucible and placed in a heating furnace. After vacuuming, the mixture was filled with argon gas. The mixture was heated to 700°C under a positive pressure of 0.1 MPa and kept at this temperature for 1 h. After cooling to room temperature, the NaCl-KCl-CsCl eutectic electrolyte was obtained. Mix 65% of the mass of NaCl-KCl-CsCl and 35% of HfCl4, pre-melt and cool, and obtain a molten salt electrolyte NaCl-KCl-Cs2HfCl6 composite electrolyte for use; 20% by weight of hafnium carbide particles are added as anode material to the bottom of the crucible in the electrolytic furnace, and 80% by weight of pre-melted and cooled molten salt electrolyte is added. 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 1.5 A / cm 2 After a certain period of electrolysis, the electrode is placed in 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 with molten salt electrolyte and metal hafnium powder. The cathode sediment is crushed into particles with a particle size of 1-3 mm, placed in 50 ℃ deionized water for stirring and cleaning, and after the mixed molten salt electrolyte is completely 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.

[0057] Table 4 shows the chemical composition analysis results of the metal hafnium provided in the embodiment of the present invention. As shown in Table 4, the oxygen content of the metal hafnium prepared by the molten salt electrolysis method provided in Example 4 is as low as 0.06%.

[0058] Table 4 Chemical composition analysis of metal hafnium

[0059] Example 5 The hafnium carbide raw material (+500 mesh to -300 mesh) and the adhesive polyurethane in a mass ratio of 5:1 are uniformly mixed, and a granulator is used to prepare particles with a particle size of 3-5 mm, and then dehydrated under a vacuum of 0.1 MPa and sintered at 1500°C to form hafnium carbide particles; After grinding NaCl-KCl-RbCl in equal molar ratio for 30 min, the mixture was added into a crucible and placed in a heating furnace. After vacuuming, the mixture was filled with argon gas. The mixture was heated to 700°C under a positive pressure of 0.1 MPa and kept at this temperature for 1 h. After cooling to room temperature, the NaCl-KCl-RbCl eutectic electrolyte was obtained. Mix 65% of the mass of NaCl-KCl-RbCl and 35% of HfCl4, pre-melt and cool, and obtain a molten salt electrolyte NaCl-KCl-Rb2HfCl6 composite electrolyte for use; 20% by weight of hafnium carbide particles are added as anode material to the bottom of the crucible in the electrolytic furnace, and 80% by weight of pre-melted and cooled molten salt electrolyte is added. 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 2.5 A / cm 2 After a certain period of electrolysis, the electrode is placed in 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 with molten salt electrolyte and metal hafnium powder. The cathode sediment is crushed into particles with a particle size of 1-3 mm, placed in 50 ℃ deionized water for stirring and cleaning, and after the mixed molten salt electrolyte is completely 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.

[0060] Table 5 shows the chemical composition analysis results of the metal hafnium provided in the embodiment of the present invention. As shown in Table 5, the oxygen content of the metal hafnium prepared by the molten salt electrolysis method provided in Example 5 is as low as 0.06%.

[0061] Table 5 Chemical composition analysis of metal hafnium

[0062] Example 6 The hafnium carbide raw material (+500 mesh to -300 mesh) and the organic binder polyvinyl alcohol are mixed evenly in a mass ratio of 7:1, and the particles with a particle size of 3-5 mm are prepared by a granulator, and then dehydrated under a vacuum of 0.1 MPa and sintered at 1500°C to form hafnium carbide particles; After mixing LiCl-KCl-CsCl in equal molar ratio for 30 min, the mixture was added into a crucible and placed in a heating furnace. After evacuation, the crucible was filled with argon gas. The mixture was heated to 700 °C under a positive pressure of 0.1 MPa and kept at this temperature for 1 h. After cooling to room temperature, the NaCl-KCl-CsCl eutectic electrolyte was obtained. Mix 65% of the mass of LiCl-KCl-CsCl and 35% of HfCl4, pre-melt and cool, and obtain a molten salt electrolyte LiCl-KCl-Cs2HfCl6 composite electrolyte for standby use; 20% by weight of hafnium carbide particles are used as anode materials and added to the bottom of the crucible in the electrolytic furnace. 80% by weight of pre-melted and cooled molten salt electrolyte is added. 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 3.5 A / cm 2 After a certain period of electrolysis, the electrode is placed in 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 with molten salt electrolyte and metal hafnium powder. The cathode sediment is crushed into particles with a particle size of 1-3 mm, placed in 50 ℃ deionized water for stirring and cleaning, and after the mixed molten salt electrolyte is completely 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.

[0063] Table 6 shows the chemical composition analysis results of the metal hafnium provided in the embodiment of the present invention. As shown in Table 6, the oxygen content of the metal hafnium prepared by the molten salt electrolysis method provided in Example 6 is as low as 0.061%.

[0064] Table 6 Chemical composition analysis of metal hafnium

[0065] Example 7 The hafnium carbide raw material (+500 mesh to -300 mesh) and the organic binder polyvinyl alcohol are mixed evenly in a mass ratio of 4:1, and the particles with a particle size of 3-5 mm are prepared by a granulator, and then dehydrated under a vacuum of 0.1 MPa and sintered at 1500 ° C to form hafnium carbide particles; After mixing LiCl-KCl-RbCl in equal molar ratio for 30 min, the mixture was added into a crucible and placed in a heating furnace. After vacuuming, the crucible was filled with argon gas. The mixture was heated to 700 °C under a positive pressure of 0.1 MPa and kept at this temperature for 1 h. After cooling to room temperature, the LiCl-KCl-RbCl eutectic electrolyte was obtained. Mix 65% of the mass of LiCl-KCl-RbCl and 35% of HfCl4, pre-melt and cool, and obtain a molten salt electrolyte LiCl-KCl-Rb2HfCl6 composite electrolyte for standby use; 20% by weight of hafnium carbide particles are added as anode material to the bottom of the crucible in the electrolytic furnace, and 80% by weight of pre-melted and cooled molten salt electrolyte is added. 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 4 A / cm 2After a certain period of electrolysis, the electrode is placed in 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 with molten salt electrolyte and metal hafnium powder. The cathode sediment is crushed into particles with a particle size of 1-3 mm, placed in 50 ℃ deionized water for stirring and cleaning, and after the mixed molten salt electrolyte is completely 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.

[0066] Table 7 shows the chemical composition analysis results of the metal hafnium provided in the embodiment of the present invention. As shown in Table 7, the oxygen content of the metal hafnium prepared by the molten salt electrolysis method provided in Example 7 is as low as 0.062%.

[0067] Table 7 Chemical composition analysis of metal hafnium

[0068] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification.

[0069] For the method embodiments, for the sake of simplicity, they are all described as a series of action combinations, but those skilled in the art should know that the present invention is not limited by the order of the actions described, because according to the present invention, some steps can be performed in other orders 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 required by the present invention.

[0070] The above is a detailed introduction to a metal hafnium and a method for preparing metal hafnium by molten salt electrolysis provided by the present invention. Specific examples are used herein to illustrate the principle and implementation mode of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea. At the same time, for those skilled in the art, according to the idea of ​​the present invention, there will be changes in the specific implementation mode and application scope. In summary, the content of this specification should not be understood as limiting 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.

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 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; The vacuum sintering process has a pressure of 0.1 MPa to 0.5 MPa and a temperature of 1200° C. to 1500° C.

5. 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.

6. 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.

7. 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.

8. 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; Dehydrating the potassium hafnium fluoride in vacuum 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.

9. 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 washing, and 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.

10. 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 9.

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