Method for preparing shape-controllable high-purity zirconium through pulse electrolysis

Abstract

The embodiment of the invention discloses a method for preparing shape-controllable high-purity zirconium through pulse electrolysis. The method comprises the following steps: forming an electrolysis system by taking crude metal zirconium as an anode, copper as a cathode and eutectic salt electrolyte containing K2ZrF6 as molten salt electrolyte; and carrying out pulse electrolysis on the electrolysis system in different pulse forms to obtain high-purity zirconium with different morphologies. According to the method for preparing the shape-controllable high-purity zirconium through pulse electrolysis, pulse electrolysis waveforms such as square waves, triangular waves and sawtooth waves in the pulse electrolysis process are regulated and controlled, optimization of the period, the duty ratio and the like in the pulse electrolysis process is combined, the product shape of molten salt electrolysis refined zirconium can be reasonably regulated and controlled, and shape controllability is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of electrochemical metallurgy, and particularly relates to a method for preparing morphology-controllable high-purity zirconium by using pulse electrolysis. Background Art

[0002] Molten salt electrolysis has always been a promising metal smelting method that can replace the Kroll process. It has a simple process, relatively low reaction temperature and is environmentally friendly.

[0003] At present, the product morphology cannot be well controlled in the process of preparing metallic zirconium by molten salt electrolysis. Summary of the Invention

[0004] In view of this, some embodiments disclose a method for preparing morphology-controllable high-purity zirconium by pulse electrolysis, comprising:

[0005] An electrolysis system is formed with crude metal zirconium as an anode, copper as a cathode, and a eutectic salt electrolyte containing K2ZrF6 as a molten salt electrolyte;

[0006] The electrolysis system performs pulse electrolysis under different pulse forms to obtain high-purity zirconium with different morphologies.

[0007] Furthermore, some embodiments disclose a method for preparing high-purity zirconium with controllable morphology by pulse electrolysis, wherein the pulse form is a square wave pulse, and high-purity zirconium with uniform morphology and uniform thickness distribution is obtained.

[0008] Some embodiments disclose a method for preparing high-purity zirconium with controllable morphology by using pulse electrolysis, wherein the pulse form is a triangular wave pulse, and high-purity zirconium with relatively uniform morphology and relatively uniform thickness is obtained.

[0009] Some embodiments disclose a method for preparing high-purity zirconium with controllable morphology by pulse electrolysis, wherein the pulse form is a sawtooth pulse, and high-purity zirconium with a rough morphology, loose structure, or containing dendrites is obtained.

[0010] Some embodiments disclose a method for preparing morphology-controllable high-purity zirconium by pulse electrolysis, wherein the eutectic salt electrolyte is a eutectic sodium-potassium salt electrolyte or a eutectic lithium-potassium salt electrolyte, and the mass content of K2ZrF6 is 1 to 20 wt.%.

[0011] Some embodiments disclose a method for preparing morphology-controllable high-purity zirconium by pulse electrolysis, wherein the pulse period is 2 to 20 minutes, wherein the duty cycle is 0.1 to 0.9.

[0012] In some embodiments of the present invention, the method for preparing morphology-controllable high-purity zirconium by pulse electrolysis is disclosed, wherein the molten salt electrolysis temperature is set at 450-850°C.

[0013] Some embodiments disclose a method for preparing morphology-controlled high-purity zirconium by pulse electrolysis, wherein the current density of the pulse electrolysis is 0.1 to 1 A / cm 2 .

[0014] The method for preparing high-purity zirconium with controllable morphology by pulse electrolysis disclosed in an embodiment of the present invention utilizes the control of the pulse electrolysis waveform, such as square wave, triangle wave, sawtooth wave, etc., during the pulse electrolysis process, combined with the optimization of the period, duty cycle, etc. during the pulse electrolysis process, to reasonably control the product morphology of molten salt electrolytic refined zirconium and achieve morphological control. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 Schematic diagram of electrolysis current waveform disclosed in some embodiments;

[0016] Figure 2 Schematic diagram of a square wave disclosed in some embodiments. DETAILED DESCRIPTION

[0017] The term "embodiment" is used herein specifically to describe any embodiment as "exemplary," and should not be construed as superior or preferable to other embodiments. Performance indicators in the embodiments of the present invention were tested using conventional testing methods in the art, unless otherwise specified. It should be understood that the terms used in the embodiments of the present invention are intended solely to describe specific implementations and are not intended to limit the disclosure of the embodiments of the present invention.

[0018] Unless otherwise specified, the technical and scientific terms used herein have the same meanings as commonly understood by those skilled in the art to which the embodiments of the present invention pertain; any experimental methods and technical means not otherwise specified in the embodiments of the present invention refer to experimental methods and technical means commonly used by those skilled in the art.

[0019] As used herein, the terms "substantially" and "approximately" are used to describe small fluctuations. For example, they can refer to less than or equal to ±5%, such as less than or equal to ±2%, such as less than or equal to ±1%, such as less than or equal to ±0.5%, such as less than or equal to ±0.2%, such as less than or equal to ±0.1%, such as less than or equal to ±0.05%. Numerical data expressed or presented in range format herein are used for convenience and brevity only and should therefore be interpreted flexibly to include not only the values ​​explicitly listed as the limits of the range, but also all independent values ​​or subranges contained within the range. For example, a numerical range of "1-5%" should be interpreted to include not only the explicitly listed values ​​of 1% to 5%, but also the independent values ​​and subranges within the indicated range. Thus, included in this numerical range are independent values ​​such as 2%, 3.5%, and 4%, and subranges such as 1% to 3%, 2% to 4%, and 3% to 5%, etc. This principle also applies to ranges that only list a single value. Furthermore, this interpretation applies regardless of the width of the range or the characteristics described.

[0020] Throughout this document, including in the claims, transitional terms such as "comprises," "includes," "with," "having," "contains," "involving," and "accommodating" are understood to be open-ended, meaning "including but not limited to." Only the transitional terms "consisting of" and "composed of" are closed transitional terms.

[0021] In order to better illustrate the present invention, numerous specific details are provided in the following specific examples. It should be understood by those skilled in the art that the present invention can be practiced without certain specific details. In the examples, some methods, means, instruments, and equipment well known to those skilled in the art are not described in detail in order to highlight the main purpose of the present invention.

[0022] Under the premise of no conflict, the technical features disclosed in the embodiments of the present invention can be arbitrarily combined, and the resulting technical solutions belong to the contents disclosed in the embodiments of the present invention.

[0023] In some embodiments, a method for preparing morphology-controlled high-purity zirconium by pulse electrolysis includes:

[0024] An electrolysis system is formed with crude metal zirconium as an anode, copper as a cathode, and a eutectic salt electrolyte containing K2ZrF6 as a molten salt electrolyte;

[0025] The electrolysis system performs pulse electrolysis under different pulse forms to obtain high-purity zirconium with different morphologies.

[0026] Generally, according to the nucleation theory, the morphology of electrochemical deposition products is mainly determined by the relationship between the nucleation current (nucleation rate) and the crystal nucleus growth current (crystal nucleus growth rate). Under the premise that the total current I remains unchanged, the nucleation current I n and the crystal nucleus growth current I g The following relationship exists:

[0027] I = I n + I g (1)

[0028] From formula (1), it can be seen that during the electrolysis process, if the nucleation current I n If it is too large, the crystal nucleus growth current I g It will inevitably decrease, resulting in fine particles of the deposited product.

[0029] On the other hand, the nucleation rate is proportional to the number of nuclei per unit time, and the number of nuclei mainly depends on the metal ion concentration on the electrode surface:

[0030] N n = a + blg(J k / c Me ) (2)

[0031] In formula (2), N n is the nucleation number; a and b are constants related to metal properties and temperature; J k is the current density, A / cm 2 ;c Me is the metal ion concentration on the electrode surface, mol / L.

[0032] According to formula (2), at the beginning of electrolysis, the metal ion concentration on the electrode surface is the highest, close to the concentration in the molten salt bulk; at this time, the number of nuclei is the smallest, and larger grains can be obtained. However, as electrolysis proceeds, the metal ions on the electrode surface are consumed, and the metal ions in the molten salt bulk cannot be replenished to the electrode surface in time due to diffusion limitations. This causes the metal ion concentration on the electrode surface to decrease, the number of nuclei to increase, and the product to become finer. This is the fundamental reason why the products of constant current electrolysis are finer. With pulse electrolysis, the metal ions in the molten salt bulk have enough time to diffuse to the electrode surface during power outages, maintaining a stable metal ion concentration on the electrode surface, thereby obtaining larger grains, inhibiting dendrite growth, improving morphological stability, and making the thickness of the deposited product more uniform.

[0033] Some embodiments disclose a method for preparing high-purity zirconium with controllable morphology by pulse electrolysis, wherein the electrolysis pulse is in the form of a square wave pulse, and high-purity zirconium with uniform morphology and uniform thickness distribution is obtained.

[0034] Some embodiments disclose a method for preparing high-purity zirconium with controllable morphology by pulse electrolysis, wherein the electrolysis pulse is in the form of a triangular wave pulse, and high-purity metallic zirconium with relatively uniform morphology and thickness is obtained.

[0035] Some embodiments disclose a method for preparing high-purity zirconium with controllable morphology by pulse electrolysis, wherein the electrolysis pulse is in the form of a sawtooth pulse, and high-purity zirconium with a rough morphology, loose structure, or containing dendrites is obtained.

[0036] Some embodiments disclose a method for preparing morphology-controllable high-purity zirconium by pulse electrolysis, wherein the eutectic salt electrolyte is a eutectic sodium-potassium salt electrolyte or a eutectic lithium-potassium salt electrolyte, and the mass content of K2ZrF6 is 1 to 20 wt.%.

[0037] Some embodiments disclose a method for preparing morphology-controllable high-purity zirconium by pulse electrolysis, wherein the pulse period is 2 to 20 minutes, wherein the duty cycle is 0.1 to 0.9.

[0038] In some embodiments of the present invention, the method for preparing morphology-controllable high-purity zirconium by pulse electrolysis is disclosed, wherein the molten salt electrolysis temperature is set at 450-850°C.

[0039] In some embodiments, a method for preparing morphology-controlled high-purity zirconium by pulse electrolysis includes:

[0040] A thick zirconium rod serves as the anode and a copper sheet serves as the cathode. A eutectic salt electrolyte containing K2ZrF6 is selected as the molten salt electrolyte. Typically, a eutectic sodium-potassium salt or a eutectic lithium-potassium salt containing K2ZrF6 is used as the molten salt electrolyte, placed in the electrolytic cell to provide a reaction site. The cathode and anode are typically placed at the same depth within the electrolyte to facilitate current calculation. Pulse waveforms include square, triangular, and sawtooth waves, involving control of the period and duty cycle. During pulse electrolysis, the period is 2 to 20 minutes, with a duty cycle (the ratio of electrolysis time to period) of 0.1 to 0.9.

[0041] In some embodiments, a method for preparing morphology-controlled high-purity zirconium by pulse electrolysis is used, wherein a crude metal zirconium rod is used as an anode and a copper sheet is used as a cathode. The anode and cathode are placed at the same depth in a molten salt electrolyte in an electrolytic cell; the anode and cathode are connected to the positive and negative electrodes of a pulse power supply, respectively, and the electrolysis time is t on , power off stop time t off A single cycle of pulse electrolysis is formed; the cycle is repeated many times to complete the overall pulse electrolysis process. During the electrolysis process, by changing the pulse electrolysis waveform, such as square wave, triangle wave, sawtooth wave, different electrolysis modes are provided for the electrolysis system, and different electrolysis product morphologies can be obtained. Figure 1 、 2 As shown, Figure 1 The conventional constant current waveform, the square wave pulse, sawtooth wave pulse and triangle wave pulse waveform used in the present invention are listed in FIG; For the square wave pulse, such as Figure 2 As shown, t on Indicates the electrolysis time, t off Indicates the power-off non-electrolysis time, t on , t off The sum is the electrolysis period T, t on The ratio of T to duty cycle is the ratio of electrolysis time to cycle.

[0042] The technical details are further illustrated below with reference to embodiments.

[0043] Example 1

[0044] In Example 1, the method for preparing morphology-controllable high-purity zirconium by pulse electrolysis comprises:

[0045] Crude zirconium metal is used as the anode and copper sheet is used as the cathode;

[0046] The eutectic sodium-potassium salt NaCl-KCl containing 10 wt% K2ZrF6 was used as the molten salt electrolyte, and the cathode and anode were set at the same depth in the molten salt electrolyte. The molten salt electrolyte was heated to 750°C for pulse electrolysis. The pulse electrolysis waveforms were square wave, triangle wave, and sawtooth wave. In a single pulse, the electrolysis time was 2 minutes, the power-off time was 2 minutes, the cycle was 4 minutes, the duty cycle was 0.5, and the current density was 0.1 A / cm 2 .

[0047] The experimental results show that the electrolytically refined zirconium product under square wave pulses presents the most uniform morphology, low surface roughness, and stable thickness distribution; the product deposition uniformity under triangular wave pulses is inferior to that under square wave pulses, but better than that under sawtooth wave pulses, and there are local thickness fluctuations in the deposited layer; while the deposited layer under sawtooth wave pulses is significantly non-uniform, with high roughness, and is prone to forming loose structures or dendrites.

[0048] Example 2

[0049] In Example 2, a method for preparing morphology-controlled high-purity zirconium by pulse electrolysis is described with reference to Example 1; wherein the pulse electrolysis waveform is a square wave; in a single pulse, the duty cycle is 0.5, and the period is 2 to 20 minutes.

[0050] The experimental results show that when the cycle is short (T = 2-10min), the Zr 4+ The periodic fluctuation amplitude of the concentration is small, which can achieve a faster recovery of the concentration gradient, thereby effectively suppressing the generation of concentration polarization; when the period is long (T = 16min), it will cause Zr 4+ The concentration of Zr decreased significantly within a single cycle. 4+ Insufficient diffusion replenishment speed aggravates concentration polarization and increases cathode potential. Under the same duty cycle, for example, when both are 0.5, shorter cycle pulse electrolysis can stabilize the electrode interface microenvironment, promote uniform Zr deposition, and make the thickness distribution of deposited Zr more uniform, with lower surface roughness and steady growth over time. When the cycle is too long, the interface Zr 4+ Periodic imbalance in concentration leads to fluctuations in deposition rate, which can easily lead to dendrite formation or local delamination.

[0051] Example 3

[0052] In Example 3, a method for preparing morphology-controllable high-purity zirconium by pulse electrolysis is described with reference to Example 1; wherein the pulse electrolysis waveform is a square wave; in a single pulse, the duty cycle is 0.1 to 0.9, and the period is 8 minutes.

[0053] The experimental results show that under low duty cycle (such as R = 0.2), shorter electrolysis time significantly reduces the Zr 4+The consumption at the cathode interface is reduced, and a longer power-off time is beneficial to ion diffusion and replenishment, which suppresses concentration polarization and promotes uniform deposition. Under high duty cycle (such as R = 0.8), the prolonged electrolysis time leads to the 4+ Continuous consumption and insufficient power-off time significantly reduce the interface concentration, exacerbating concentration polarization and triggering dendritic growth or powdery deposition. At low duty cycles, the thickness of the electrolytically refined zirconium cathode deposit is uniform, and the surface roughness remains stable within a low range. However, at high duty cycles, the deposit thickness fluctuates greatly, edge effects are significant, and the roughness continues to increase, accompanied by localized zirconium shedding, resulting in a decrease in current efficiency.

[0054] The method for preparing high-purity zirconium with controllable morphology by pulse electrolysis disclosed in an embodiment of the present invention utilizes the control of the pulse electrolysis waveform, such as square wave, triangle wave, sawtooth wave, etc., during the pulse electrolysis process, combined with the optimization of the period, duty cycle, etc. during the pulse electrolysis process, to reasonably control the product morphology of molten salt electrolytic refined zirconium and achieve morphological control.

[0055] The technical solutions and technical details disclosed in the embodiments of the present invention are merely illustrative of the inventive concept of the present invention and do not constitute a limitation on the technical solutions of the embodiments of the present invention. Any conventional changes, replacements or combinations of the technical details disclosed in the embodiments of the present invention have the same inventive concept as the present invention and are within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing morphology-controlled high-purity zirconium by pulse electrolysis, characterized in that: include: An electrolysis system is formed with crude metal zirconium as an anode, copper as a cathode, and a eutectic salt electrolyte containing K2ZrF6 as a molten salt electrolyte; The electrolysis system performs pulse electrolysis under different pulse forms to obtain high-purity zirconium with different morphologies.

2. The method for preparing morphology-controlled high-purity zirconium by pulse electrolysis according to claim 1, characterized in that: The pulse form is a square wave pulse, which can obtain high-purity zirconium with uniform morphology and uniform thickness distribution.

3. The method for preparing morphology-controlled high-purity zirconium by pulse electrolysis according to claim 1, characterized in that: The pulse form is a sawtooth wave pulse, which can obtain high-purity zirconium with a rough morphology, loose structure or containing dendrites.

4. The method for preparing morphology-controlled high-purity zirconium by pulse electrolysis according to claim 1, characterized in that: The pulse form is a triangular wave pulse, which can obtain high-purity zirconium with relatively uniform morphology and relatively uniform thickness.

5. The method for preparing morphology-controlled high-purity zirconium by pulse electrolysis according to claim 1, characterized in that: The eutectic salt electrolyte is a eutectic sodium potassium salt electrolyte or a eutectic lithium potassium salt electrolyte, and the mass content of the K2ZrF6 is 1 to 20 wt.%.

6. The method for preparing morphology-controlled high-purity zirconium by pulse electrolysis according to claim 1, characterized in that: The pulse period is 2 to 20 minutes, wherein the duty cycle is 0.1 to 0.

9.

7. The method for preparing morphology-controlled high-purity zirconium by pulse electrolysis according to claim 1, characterized in that: The molten salt electrolysis temperature is set at 450-850°C.

8. The method for preparing morphology-controlled high-purity zirconium by pulse electrolysis according to claim 1, characterized in that: The current density of pulse electrolysis is 0.1~1A / cm 2 .

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