Method for preparing metal niobium through thermal reduction of lanthanum

Abstract

The invention belongs to the field of metal niobium preparation, and particularly relates to a method for preparing metal niobium through lanthanum thermal reduction, and the method comprises the following steps: S1, mixing niobium oxide with metal lanthanum chippings; s2, putting the mixed raw materials into a crucible, and paving lanthanum powder; and S3, the crucible is heated in a high vacuum environment, a reaction is conducted for 15-30 min under the condition that the temperature ranges from 950 DEG C to 1200 DEG C, and the elemental metal niobium is obtained. The prepared metal niobium is high in purity, the preparation technology is simple, the processing cost is low, the equipment structure is simple, the reaction period is short, the reaction condition is mild, energy consumption is low, and mass production can be achieved.

Description

Technical Field

[0001] The invention belongs to the field of metal niobium preparation, and particularly relates to a method for preparing metal niobium by thermal reduction of lanthanum. Background Art

[0002] Niobium is an important rare metal with relatively abundant resources. Niobium has significant ductility, excellent oxidation resistance, excellent impact resistance, high thermal conductivity, good corrosion resistance, high melting point and high superconducting transition temperature, and is widely used in the fields of nuclear industry, aerospace, high energy transmission and steel materials.

[0003] At present, niobium powder is mainly obtained by reducing high-purity niobium compounds (oxides, fluorine complexes, chlorides) at high temperatures. This method has a long process flow, high energy consumption, and side reactions that pollute the environment. At the same time, the crude niobium prepared contains a large amount of impurities, such as the embedding of divalent or trivalent impurity elements. The energy consumption when refining crude niobium by electron beam melting, vacuum sintering, etc. is high, and the niobium obtained has low precision, resulting in high cost and low supply of niobium, which limits its application in various fields. Therefore, the development of a short process, low cost, and environmentally friendly process for producing niobium has become a hot topic in recent years.

[0004] Currently, sodium thermal reduction method and carbon reduction method and molten salt electrolysis method have been developed to replace the above-mentioned high-temperature reduction method for preparing metallic niobium. However, the sodium thermal reduction method for preparing metallic niobium has a high reaction temperature, high energy consumption, serious equipment corrosion, and involves strong acid during washing, which makes the operation difficult. The carbon reduction method for preparing metallic niobium requires a relatively expensive vacuum graphite carbon tube furnace, which has a complex equipment structure, harsh reaction conditions, a long reduction cycle, high temperature, high power consumption, and relatively difficult operation. The molten salt electrolysis method for preparing metallic niobium has low current efficiency and small output, which are bottlenecks restricting its expansion and development. Before electrolysis, niobium oxide must be prepared into niobium fluoride, which increases production costs and production cycles. Summary of the invention

[0005] In order to improve the deficiencies of the prior art, the present invention provides a method for preparing metallic niobium by thermal reduction of lanthanum, which uses high-purity metallic lanthanum as a reducing agent, controls the embedding of divalent or trivalent impurity elements, and provides relatively high-purity metallic niobium for subsequent electron beam remelting.

[0006] To achieve the above objectives, in a first aspect, the present invention provides a method for preparing metallic niobium by thermal reduction of lanthanum, comprising the following steps:

[0007] S1, mixing niobium oxide and metal lanthanum chips;

[0008] S2, putting the mixed raw materials into a crucible and covering it with lanthanum powder;

[0009] S3. The crucible is heated in a high vacuum environment, and reacted at a temperature of 950 to 1200° C. for 15 to 30 minutes to obtain elemental metallic niobium.

[0010] According to an embodiment of the present invention, the niobium oxide in step S1 is selected from at least one of niobium dioxide, niobium trioxide and niobium pentoxide, for example, niobium pentoxide.

[0011] According to an embodiment of the present invention, the niobium oxide is in powder form, and the purity is ≥ 99.5%, for example, 99.9%.

[0012] According to an embodiment of the present invention, the lanthanum metal chips are in the form of fragments, flakes or powders, and the size of the fragments is 1 to 3 cm, preferably 1 to 1.5 cm.

[0013] According to an embodiment of the present invention, the purity of the lanthanum metal scraps is ≥ 99.5%, for example 99.9%.

[0014] According to an embodiment of the present invention, the mass ratio of niobium oxide to metal lanthanum fragments is (1-5):1, preferably the mass ratio of niobium oxide to metal lanthanum fragments is (1-3):1, and further preferably, the mass ratio of niobium oxide to metal lanthanum fragments is (1.5-2):1, for example, 1.9:1.

[0015] According to an embodiment of the present invention, the mixing in step S1 comprises the following steps: adding niobium oxide and metal lanthanum chips into a mixing device for mixing, wherein the mixing device is a ball mill, a mixer, a grinding mechanism, etc. commonly used in the art, such as a ball mill.

[0016] As an example, the mixing in step S1 includes the following steps: adding niobium oxide and metal lanthanum chips into a ball mill, and grinding for 2 to 8 hours at a ball-to-material ratio of 1: (1 to 4) and a rotation speed of 20 to 100 r / min.

[0017] According to an embodiment of the present invention, the ball-to-material ratio of the ball mill is 1:(1-3), the rotation speed is 30-60 r / min, and the grinding time is 3-5 h.

[0018] According to an embodiment of the present invention, the mass ratio of the lanthanum powder to niobium oxide in step S2 is 1:(2-3).

[0019] According to an embodiment of the present invention, the spreading of lanthanum powder in step S2 refers to spreading lanthanum powder evenly above and below the mixture.

[0020] According to the embodiment of the present invention, the high vacuum environment in step S3 refers to a vacuum degree less than or equal to 10 -1 Pa, preferably the vacuum degree is less than or equal to 10 -2Pa.

[0021] According to an embodiment of the present invention, the reaction in step S3 is carried out under inert conditions, such as under an argon, helium or nitrogen environment.

[0022] According to an embodiment of the present invention, the reaction temperature in step S3 is 1000-1100° C., and the reaction time is 20-25 min.

[0023] According to an embodiment of the present invention, step S3 is followed by the following step: surface treatment and pickling of the reduced metal niobium to remove surface residues, which include part of lanthanum, lanthanum oxide and niobium oxide.

[0024] According to an embodiment of the present invention, the step of surface treating metal niobium includes: removing metal lanthanum, lanthanum oxide powder and niobium oxide on the surface of metal niobium, then cleaning the surface with anhydrous ethanol, polishing the surface with sandpaper, and ultrasonic cleaning.

[0025] According to an embodiment of the present invention, after the surface treatment of the metal niobium, the following step is further included: drying the surface-treated metal niobium, for example, placing the surface-treated metal niobium in a vacuum drying oven with a vacuum degree of 5Pa to 10Mpa, and drying it at a temperature of 100°C to 150°C for 10 to 20 minutes.

[0026] Beneficial Effects

[0027] 1) The present invention adopts lanthanum thermal reduction reaction to prepare high-purity metallic niobium. Since the raw materials niobium oxide and lanthanum are both of high purity, and the entire lanthanum thermal reduction reaction is carried out in a high vacuum environment in a high vacuum furnace, the method avoids the problems of oxidation and pollution that may occur in the traditional preparation process. The prepared metallic niobium has high purity, and the preparation process is simple, the processing cost is low, the equipment structure is simple, the reaction cycle is short, the reaction conditions are mild, the energy consumption is small, and it can be mass-produced. In addition, rare earth oxides are more active than traditional metal oxides, which is conducive to removal in the subsequent pickling process, reducing the use of pickling solution. Compared with the traditional aluminum thermal reduction method, it is more energy-saving and emission-reducing, and more environmentally friendly.

[0028] 2) The method of the present invention prepares niobium metal with high purity, and can control the embedding of divalent or trivalent impurity elements, providing high-purity niobium metal for subsequent refining, distillation and electron beam remelting, thereby reducing the difficulty of refining, saving refining costs, and obtaining 4N-6N high-purity niobium metal. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a surface morphology of the metal niobium prepared in Example 2 of the present invention;

[0030] Figure 2This is a surface morphology of the metal niobium prepared in Example 2 of the present invention after a 24-hour corrosion test;

[0031] Figure 3 This is a process diagram for preparing metallic niobium according to Example 2 of the present invention. DETAILED DESCRIPTION

[0032] The preparation method of the present invention will be described in further detail below in conjunction with specific examples. It should be understood that the following examples are only exemplary illustrations and explanations of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are included in the scope that the present invention is intended to protect.

[0033] Unless otherwise specified, the raw materials and reagents used in the following examples are commercially available or can be prepared by known methods.

[0034] Example 1

[0035] The present invention provides a method for preparing metallic niobium by thermal reduction of lanthanum, comprising the following steps:

[0036] S1. Cut 100 g of metallic lanthanum into pieces of 1-1.5 cm in length, and mix them evenly with 150 g of Nb2O5 powder in a ball mill at a weight ratio of 1:1.9 to obtain a mixed raw material. The purity of metallic lanthanum and Nb2O5 powder are both 99.9%.

[0037] S2. Put the mixed raw materials into a crucible covered with lanthanum powder, and then spread lanthanum powder on the surface of the mixed raw materials to make the lanthanum powder fully contact with the mixed raw materials. The mass ratio of the total amount of lanthanum powder to niobium oxide is (2-3):1.

[0038] S3, in high vacuum environment (10 -2 ~10 -3 The crucible was heated at 200 °C (500 °C) to start the reaction. When the temperature reached 950 °C, the metal La began to melt and came into contact with the niobium pentoxide powder, causing a reduction reaction while releasing a large amount of heat. The reaction lasted for 20 minutes to obtain a crude elemental metal niobium product.

[0039] S4. Surface treatment and pickling of the crude niobium metal product are performed to remove some of the lanthanum metal, lanthanum oxide powder and niobium oxide on the surface of the crude niobium metal product, and then the surface is cleaned with anhydrous ethanol, and the surface is polished with sandpaper to make it bright, and then ultrasonic cleaning is performed.

[0040] S6. Put the crude metal niobium after surface treatment into a vacuum drying oven with a vacuum degree of 5Pa to 10Mpa, and dry it at 100°C to 150°C for 10 to 20 minutes to obtain metal niobium.

[0041] Example 2

[0042] S1: Weigh the reaction raw materials: 100 g of metal lanthanum powder and 190 g of niobium pentoxide powder. The purity of the powders used is 99.9%.

[0043] S2: Add the reaction materials in step S1 into a planetary ball mill for mixing. The rotation speed of the ball mill is 50 r / min, the ball-to-material ratio is 1:2, the ball milling time is 4 h, and the direction of the ball mill is changed every 1 h to ensure that the raw materials are mixed evenly to obtain a mixed raw material.

[0044] S3: Put the mixed raw material of step S2 into a crucible evenly paved with at least 150g of lanthanum powder, wherein the mixed raw material is evenly paved on the lanthanum powder, and then at least 150g of lanthanum powder is evenly paved on the paved mixed raw material, and then the vacuum pump is turned on to evacuate the air in the furnace body so that the pressure in the furnace is reduced to 10 -2 Pa, turn off the vacuum pump, introduce argon, and start heating to 950°C. The metallic lanthanum begins to melt and undergoes a lanthanum thermal reduction reaction with the contacting niobium pentoxide. After reacting for 20 minutes, stop heating and cool to obtain a crude metallic niobium product.

[0045] S4: Acid pickling is used to remove part of the metal lanthanum, lanthanum oxide powder and niobium oxide on the surface of the crude metal niobium product, and then it is cleaned with anhydrous ethanol, and then the surface is polished with sandpaper to make it bright, and then ultrasonic cleaning is performed.

[0046] S5: placing the crude metal niobium after the surface treatment into a vacuum drying oven with a vacuum degree of 5 Pa, and drying at 100° C. for 10 minutes to obtain metal niobium.

[0047] The purity of the metal niobium prepared in this example was 99.9% as tested by ICP (atomic emission spectrometry).

[0048] Test Example 1

[0049] The metal niobium prepared in Example 2 was polished to a bright surface, washed with water, degreased with acetone, dried, added into a 3 mol / L hydrochloric acid solution, and immersed at a temperature of 150° C. for 24 h. Figure 2 As shown, after the 24-hour corrosion test, a small amount of black spots exist on the surface of the metal niobium prepared in Example 2, but most of it remains intact, indicating that it has good corrosion resistance.

[0050] Example 3

[0051] S1: Weigh the reaction raw materials: 100 g of metal lanthanum powder and 200 g of niobium dioxide powder. The purity of the powders used is 99.9%.

[0052] S2: Add the reaction materials in step S1 into a planetary ball mill for mixing. The speed of the ball mill is 100 r / min, the ball-to-material ratio is 1:1.5, the ball milling time is 2 h, and the direction of the ball mill is changed every 1 h to ensure that the raw materials are evenly mixed to obtain a mixed raw material.

[0053] S3: Put the mixed raw material of step S2 into a crucible evenly paved with 200g lanthanum powder, wherein the mixed raw material is evenly paved on the lanthanum powder, and then 200g lanthanum powder is evenly paved on the paved mixed raw material, and then the vacuum pump is turned on to evacuate the air in the furnace body so that the pressure in the furnace is reduced to 10 -3 Pa, turn off the vacuum pump, introduce argon, and start heating to 1000℃. The metallic lanthanum begins to melt and undergoes a lanthanum thermal reduction reaction with the contacting niobium pentoxide. After reacting for 15 minutes, stop heating and cool to obtain a crude metallic niobium product.

[0054] S4: Acid pickling is used to remove part of the metal lanthanum, lanthanum oxide powder and niobium oxide on the surface of the crude metal niobium product, and then it is cleaned with anhydrous ethanol, and then the surface is polished with sandpaper to make it bright, and then ultrasonic cleaning is performed.

[0055] S5: placing the crude metal niobium after the surface treatment into a vacuum drying oven with a vacuum degree of 5 Pa, and drying at 100° C. for 10 minutes to obtain metal niobium.

[0056] The purity of the metal niobium prepared in this embodiment is 99.9% as tested by ICP.

[0057] The above examples are used to illustrate the specific implementation of the present invention. However, the protection scope of the present invention is not limited to the above exemplary implementation. Any modification, equivalent substitution, improvement, etc. made by those skilled in the art within the spirit and principle of the present invention shall be included in the protection scope of the claims of the present invention.

Claims

1. A method for preparing metallic niobium by thermal reduction of lanthanum, characterized in that: The following steps are involved: S1, mixing niobium oxide and metal lanthanum chips; S2, putting the mixed raw materials into a crucible and covering it with lanthanum powder; S3. The crucible is heated in a high vacuum environment, and reacted at a temperature of 950 to 1200° C. for 15 to 30 minutes to obtain elemental metallic niobium.

2. The method for preparing metallic niobium by thermal reduction of lanthanum according to claim 1, characterized in that: The niobium oxide in step S1 is at least one selected from niobium dioxide, niobium trioxide and niobium pentoxide.

3. The method for preparing metallic niobium by thermal reduction of lanthanum according to claim 1, characterized in that: The niobium oxide is in powder form with a purity of ≥99.5%, and the purity of the metal lanthanum scraps is ≥99.5%.

4. The method for preparing metallic niobium by thermal reduction of lanthanum according to any one of claims 1 to 3, characterized in that: The mass ratio of the niobium oxide to the metal lanthanum fragments is (1-5):

1.

5. The method for preparing metallic niobium by thermal reduction of lanthanum according to any one of claims 1 to 3, characterized in that: The ball-to-material ratio of the ball mill is 1:(1-3), the rotation speed is 30-60 r / min, and the grinding time is 3-5 hours.

6. The method for preparing metallic niobium by thermal reduction of lanthanum according to any one of claims 1 to 3, characterized in that: The mass ratio of the lanthanum powder to niobium oxide in step S2 is 1:(2-3).

7. The method for preparing metallic niobium by thermal reduction of lanthanum according to any one of claims 1 to 3, characterized in that: The step S2 of spreading lanthanum powder means spreading lanthanum powder evenly on the top and bottom of the mixture.

8. The method for preparing metallic niobium by thermal reduction of lanthanum according to any one of claims 1 to 3, characterized in that: The reaction temperature in step S3 is 1000-1100° C., and the reaction time is 20-25 min.

9. The method for preparing metallic niobium by thermal reduction of lanthanum according to any one of claims 1 to 3, characterized in that: The following steps are also included after step S3: surface treatment and pickling of the metal niobium obtained by reduction to remove surface residues, which include part of lanthanum, lanthanum oxide and niobium oxide.

10. The method for preparing metallic niobium by thermal reduction of lanthanum according to claim 9, characterized in that: After the surface treatment of the metal niobium, the following step is further included: drying the surface treated metal niobium, for example, placing the surface treated metal niobium in a vacuum drying oven with a vacuum degree of 5Pa to 10Mpa, and drying it at a temperature of 100°C to 150°C for 10 to 20 minutes.

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