Cu-cr alloy inert anode and its preparation method and application

Abstract

The application discloses a Cu-Cr alloy inert anode and a preparation method and application thereof, and belongs to the technical field of electrode preparation. According to the preparation method, a mixture formed by 3.74-15.42% of Cr, 69.38-79.94% of CuO, 9.02-10.33% of Al and 5.99-6.17% of CaF2 is subjected to a self-propagating reaction under the excitation of an external heat source, heat released by the reaction is used for self-sustaining the reaction and forming an alloy, and after the self-propagating reaction is completed, the Cu-Cr alloy inert anode is obtained. The process adopts the self-propagating reaction, and has the advantages of simple operation, high efficiency and reliable material forming. The prepared Cu-Cr alloy inert anode has excellent oxidation resistance and corrosion resistance, does not participate in the reaction to generate CO2 when applied to the electrolysis field, optimizes the industrial production environment and reduces environmental pollution.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of electrode preparation, in particular to a Cu-Cr alloy inert anode and a preparation method and application thereof. BACKGROUND

[0002] Metallic aluminum and aluminum alloy materials have excellent ductility, electrical conductivity, corrosion resistance and high specific strength, and are widely used in space, navigation, automobile, household appliances, building materials, metallurgy, daily necessities, food packaging and other fields. The electrolytic aluminum industry has developed rapidly, and the industrial production of aluminum metal mainly adopts the cryolite-aluminum oxide molten electrolysis method (also known as the Hall-Heroult molten salt electrolysis method). However, the carbon anode of this method will generate a large amount of CO2 gas during the reaction, resulting in a poor industrial production environment and polluting the natural environment.

[0003] In order to reduce the use of carbon anodes, research on inert anode materials has been increasingly in-depth. The inert anode materials currently studied more include ceramics, cermet, metal alloy materials, etc. Among them, ceramics and cermet materials have good inertness, but relatively poor electrical conductivity, and are extremely brittle, which can easily be damaged during use; they are difficult to prepare and have high cost. Metal alloy inert anodes have high strength, good electrical conductivity and excellent processing performance, and have higher research and application value.

[0004] Chinese patent CN113215429A discloses a preparation method of a high-density cermet inert anode material for aluminum electrolysis. Oxide ceramic powder, metal powder, single-phase oxide ceramic powder and additives are mixed to obtain raw powder, which is added to a solvent to obtain a mixed slurry, a binder is added, ball milling, spray granulation, and the cermet green body is obtained by compression molding, degreasing, and sintering under oxygen partial pressure to obtain the inert anode material. The preparation method, on the one hand, adds single-phase oxides to the raw material, and on the other hand, sintering in a certain oxygen partial pressure atmosphere, effectively improves the wettability of the metal phase and the spinel-type oxide ceramic, effectively improves the spreading and distribution of the metal phase between the ceramic phases, and effectively inhibits the coalescence and growth of the ceramic grains, realizes the network-like distribution of the metal phase, and obtains an aluminum electrolysis cermet inert anode material with a sintered relative density of more than 97%. The inert anode prepared by the process has excellent corrosion resistance, but the preparation process is very complex, and the content of the added ceramic phase is relatively high, which makes it difficult to ensure the electrical conductivity of the inert anode.

[0005] Chinese patent CN113308713A provides a cermet anode and its preparation method and application, which includes a through-hole foam metal substrate and a ceramic. The ceramic includes a filling ceramic filled in the pores of the through-hole foam metal substrate and a ceramic outer layer located on the outer surface of the through-hole foam metal substrate. The material of the through-hole foam metal substrate is copper or nickel. The material of the ceramic is doped NiO-NiFe2O4 ceramic, which includes a NiO-NiFe2O4 ceramic substrate and a doped oxide. In this invention, the through-hole foam metal substrate forms a metal phase with a connected network structure, and the filling ceramic filled in the pores of the through-hole foam metal substrate also forms a ceramic phase with a connected network structure, which is beneficial to improve the electrical conductivity, thermal shock resistance and mechanical strength of the cermet anode. Similarly, the preparation method is difficult, the forming quality is difficult to guarantee, and the finished product has a network gap, which can cause the molten aluminum to enter during use, damage the internal structure, and result in poor stability. SUMMARY

[0006] In view of the above-mentioned defects of the prior art, in the first aspect of the present application, a preparation method of Cu-Cr alloy inert anode with simple process operation, high efficiency and reliable material forming is provided, which adopts self-propagating reaction (SHS) process, including the following steps:

[0007] A mixture of 3.74% to 15.42% Cr, 69.38% to 79.94% CuO, 9.02% to 10.33% Al and 5.99% to 6.17% CaF2 is subjected to self-propagating reaction under the excitation of an external heat source. The heat released by the reaction maintains the reaction and forms an alloy. After the self-propagating reaction is completed, a Cu-Cr alloy inert anode is obtained.

[0008] This process utilizes the principle of self-propagating reaction, which is a self-sustaining reaction based on aluminum thermal reaction. It is started by an external heat source. After the reaction starts, a large amount of heat is released, which induces the reaction in the surrounding area. After the reaction in the surrounding area, a large amount of heat is released, which induces the reaction in a more distant area. The whole system is activated by energy, and the complete reaction is achieved by chain transmission of released energy, without the need for external energy to maintain it. The self-propagating reaction is essentially an aluminum thermal reaction of CuO. The raw materials are CuO, Cr and Al, and CaF2 can not only significantly reduce the surface tension of the metal liquid, but also react with alumina to obtain a low-melting-point eutectic, greatly reducing the melting point of alumina from more than 2,000 degrees to more than 1,300 degrees, enhancing the fluidity of the alumina slag, facilitating its separation from the alloy ingot, playing a role in slagging and deoxidizing, and improving the purity of the prepared alloy composition.

[0009] Cr, CuO, Al, and CaF2 are used as raw materials in this invention, and their physical forms can be diverse. The key is that each raw material should have sufficient reaction surface area to allow for a self-propagating reaction under the stimulation of an external heat source. Under conditions suitable for achieving a self-propagating reaction, appropriate forms of raw materials, such as granules or powders, can be selected according to actual conditions. Preferably, to improve reaction efficiency, the Cr, CuO, Al, and CaF2 are in powder form.

[0010] In the process of forming a mixture of Cr, CuO, Al, and CaF2, thorough mixing is beneficial for the smooth progress of the self-propagating reaction and results in a product with superior properties. It is important to note that Al and CuO may react and explode at high temperatures during mixing; therefore, the mixing process must be strictly controlled. While extending the mixing time helps improve the homogeneity of the raw materials, the time should not be excessive. Overly long mixing times can cause the raw materials to overheat, creating a potential hazard. If overheating or other phenomena are observed, the process must be stopped immediately. To achieve a balance between operational safety and raw material homogeneity, preferably, the mixing time for each batch in the formation of the mixture is 50–70 minutes, and the mixing rate is 40–60 r / min.

[0011] After the self-propagating reaction, heat treatment can be used to homogenize the alloy, making the element distribution more uniform, reducing voids, and improving the density and uniformity of the alloy ingot. Preferably, after the self-propagating reaction, the alloy is heated to a predetermined temperature in a vacuum environment and held at that temperature for heat treatment to homogenize it. Subsequently, it is cooled to room temperature in an inert gas atmosphere to complete the heat treatment. The inert gas is a gas that does not react with either the raw materials or the alloy substrate. To achieve the best homogenization effect, it is further preferred that the heating rate is 8–12 °C / min, the predetermined heat treatment temperature is 1000–1200 °C, and the holding time is 9–12 h.

[0012] In addition, after heat treatment, the high heat of the heat source can be used to rapidly heat the alloy surface and then cool it to form a remelted alloy layer on the alloy surface, improving the density and uniformity of the alloy ingot, while also increasing its surface hardness, wear resistance, and corrosion resistance. More preferably, after heat treatment, the alloy is remelted to form a remelted alloy layer on the alloy surface, with a thickness of 2-4 mm. The type of heat source for remelting is not unique; various forms can be used. To achieve the purpose of forming a remelted alloy layer, a suitable type and parameters can be selected according to the actual process conditions. More preferably, the heat source for remelting is one of laser, plasma, or induced current.

[0013] Oxidation treatment of remelted alloy ingots forms an oxide layer containing Cu and Cr on the surface, ensuring good corrosion resistance of the anode material during electrolysis. More preferably, after remelting, the resulting alloy is treated at a specific temperature and in an oxygen atmosphere to form the oxide layer, followed by cooling to room temperature to complete the oxidation process. Controlling the oxidation parameters allows for the formation of a suitable oxide layer, achieving optimal corrosion resistance. Furthermore, the oxidation treatment temperature is 900–980°C, the oxygen partial pressure is 0.2–1.2 MPa, and the treatment time is 10–12 hours.

[0014] In a second aspect of the present invention, a Cu-Cr alloy inert anode with excellent oxidation and corrosion resistance is provided, which is prepared by the method of the first aspect of the present invention.

[0015] In a third aspect of the present invention, an application of a Cu-Cr alloy inert anode is provided, specifically the application of a Cu-Cr alloy inert anode as an electrode in the field of electrolysis or battery manufacturing.

[0016] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0017] This invention provides a method for preparing Cu-Cr alloy inert anodes, which adopts a self-propagating reaction process. Compared with the prior art, it has the advantages of simple operation, high efficiency and reliable material forming.

[0018] This invention provides a Cu-Cr alloy inert anode with good oxidation resistance and corrosion resistance.

[0019] This invention provides an application of a Cu-Cr alloy inert anode, which is carbon-free and will not participate in the reaction to generate CO2 when used in the electrolysis field, thus optimizing the industrial production environment and reducing environmental pollution. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the self-propagating reaction process of the present invention;

[0021] Figure 2 Metallographic image of the Cu-Cr alloy prepared in Example 1;

[0022] Figure 3 Metallographic image of the Cu-Cr alloy prepared in Example 2. Detailed Implementation

[0023] The present invention is further illustrated below by way of embodiments, but the invention is not limited to the scope of the embodiments described herein. Experimental methods in the following embodiments that do not specify specific conditions were performed according to conventional methods and conditions, or as selected according to the product instructions.

[0024] Example 1

[0025] Preparation method of Cu-Cr alloy inert anode:

[0026] Weigh the following raw material powders according to their mass: Cr 10.0g (7.56wt.%), CuO 101.2g (76.49wt.%), Al 13.1g (9.90wt.%), and CaF2 8.0g (6.05wt.%). Then, add the weighed raw material powders to the ball mill jar and add 20mL of anhydrous ethanol as a control agent to lubricate, assist in heat dissipation, and prevent powder oxidation. Argon gas with a purity of 99.99% is introduced as a protective gas. Adjust the speed of the ball mill to 50r / min. To prevent the risk of overheating during mixing, the ball milling time is 60min per cycle, with a 30min interval before the next ball milling. Control the total ball milling time to 4h. Transfer the resulting mixed powder to a drying oven at 70℃ and dry for 8h to ensure that the mixed powder is completely dry.

[0027] The dried mixed powder was added to a reaction apparatus consisting of a graphite crucible and a graphite plate. Before preparation began, the reaction apparatus was preheated in a 500°C preheating chamber for 8 hours to ensure complete drying. Figure 1 As shown, after the mixed powder is added, it is ignited to start a self-propagating reaction under the excitation of an external heat source. As the reaction proceeds automatically, the desired Cu-Cr alloy is obtained.

[0028] Figure 2 The image shows the metallographic image of the Cu-Cr alloy obtained using a metallographic microscope. Cu-Cr alloys are immiscible, meaning Cr cannot completely dissolve into Cu. The bright dots in the image represent the Cr phase, while the substrate is the Cu-Cr phase. The granular Cr particles are dispersed on the Cu matrix, providing dispersion strengthening to the alloy. Microhardness testing revealed that the average hardness of the prepared Cu-Cr alloy is 131.5 HV.

[0029] The Cu-Cr alloy was homogenized by heat treatment. The Cu-Cr alloy was heated to 1000°C at a rate of 10°C / min in a vacuum furnace and held at that temperature for 12 hours. Then, an inert gas was introduced and the furnace was cooled to room temperature in the atmosphere to complete the heat treatment.

[0030] After heat treatment, plasma is used to rapidly heat the alloy surface using the high heat input of the plasma heat source, followed by cooling. Due to the relatively large plasma current, to ensure sufficient remelting of the alloy and a greater improvement in surface density, the scanning speed cannot be too fast. Therefore, the main parameters for plasma remelting in this embodiment are as follows: remelting current 150A, scanning speed 250mm / min, argon as the working gas, protective gas flow rate 300L / h, ion gas flow rate 300L / h, and nozzle distance from the substrate surface 10mm. After remelting, the surface is allowed to cool naturally to room temperature, forming a remelted alloy layer, thus completing the remelting process.

[0031] Finally, the alloy ingot that has undergone surface remelting is subjected to further surface oxidation. It is placed in an oxygen atmosphere at 900℃ with an oxygen partial pressure of 1MPa for 12 hours. Then it is cooled in the furnace to form an oxide layer containing Cu and Cr elements on the surface of the alloy ingot, thus completing the oxidation process and obtaining a Cu-Cr alloy inert anode.

[0032] Example 2

[0033] This embodiment uses a preparation method similar to that of Example 1. The difference in this embodiment is that the raw material powder used is as follows: Cr 20.0g (15.42wt.%), CuO 89.96g (69.38wt.%), Al 11.7g (9.02wt.%), CaF 28.0g (6.17wt.%). Other preparation steps and processing conditions are consistent with those of Example 1.

[0034] In this embodiment, the duration of the self-propagating reaction is relatively longer than in Example 1, approximately 15 seconds. This is because the increased Cr content reduces the intensity of the self-propagating reaction. The metallographic image of the Cu-Cr alloy in this embodiment was obtained using the same method, as shown below. Figure 3 As shown, compared to Example 1, the alloy ingot obtained in this example has more dispersed Cr particles, and their size is also slightly larger. Therefore, its strengthening effect is better, and its hardness is relatively higher, with an average hardness of 162.2 HV. A higher Cr content can further refine the alloy grains, thereby improving the overall strength and hardness. However, when the Cr content increases, since the solidification points of Cu (1085℃) and Cr (1875℃) are very different, it can be assumed that Cr with the higher solidification point precipitates from the melt first during solidification, resulting in a decrease in the density of the alloy ingot obtained through the self-propagating reaction.

[0035] Example 3

[0036] This embodiment employs a similar preparation method to Example 1, the difference being the remelting process. This embodiment uses laser remelting, with the following main parameters: laser power 2200W, argon as the working gas, protective gas flow rate 300-400L / h, laser distance from substrate (defocusing amount) 13mm, spot diameter 4mm, multiple overlapping fusion depositions on the substrate from left to right, and a scanning speed of 300mm / min. Because lasers differ from plasmas in their heat concentration, spot diameter, and energy penetration, the more concentrated and rapid heat input means a relatively faster cooling rate. Therefore, the laser-remelted alloy has finer internal grains, a more uniform precipitate distribution, and superior overall performance.

[0037] Example 4

[0038] An inert anode of Cu-Cr alloy is prepared by the following method:

[0039] Weigh the following raw material powders according to their mass: Cr 10.0g (7.56wt.%), CuO 101.2g (76.49wt.%), Al 13.1g (9.90wt.%), and CaF2 8.0g (6.05wt.%). Then, add the weighed raw material powders to the ball mill jar, and add 20mL of anhydrous ethanol as a control agent to lubricate, assist in heat dissipation, and prevent powder oxidation. Argon gas with a purity of 99.99% is introduced as a protective gas. Adjust the speed of the ball mill to 60r / min. To prevent the risk of overheating during mixing, the ball milling time is 50min per cycle, with a 30min interval before the next ball milling. Control the total ball milling time to 4h. Transfer the resulting mixed powder to a drying oven at 70℃ and dry for 8h to ensure that the mixed powder is completely dry.

[0040] The dried mixed powder was added to a reaction apparatus consisting of a graphite crucible and a graphite plate. Before preparation began, the reaction apparatus was preheated in a 500°C preheating chamber for 8 hours to ensure complete drying. Figure 1 As shown, after the mixed powder is added, it is ignited to start a self-propagating reaction under the excitation of an external heat source. As the reaction proceeds automatically, the desired Cu-Cr alloy is obtained.

[0041] The Cu-Cr alloy was homogenized by heat treatment. The Cu-Cr alloy was heated to 1100°C at a rate of 10°C / min in a vacuum furnace and held at that temperature for 10 hours. Then, an inert gas was introduced and the furnace was cooled to room temperature in the atmosphere to complete the heat treatment.

[0042] Subsequently, under an argon atmosphere, remelting was performed on the Cu-Cr alloy surface using induced current as a heat source. The main parameters for induced current remelting included: induction heating frequency of 170 kHz, gap between the coil and the sample of 4 mm, and cooling water flow rate of 2.5 mL / min·mm. 2 The heating power is 12kW, the surface moving speed is 550mm / min, and after remelting, it is allowed to cool to room temperature to form a remelted alloy layer.

[0043] Unlike laser and plasma heat sources, induction remelting primarily utilizes electromagnetic induction to generate current within the heated material, relying on the energy of these eddy currents to achieve heating. Therefore, it has a larger heating range and deeper influence, while also exhibiting a faster heating rate. Although its scanning speed is faster than laser, the resulting remelted layer thickness is close to 2.5 mm.

[0044] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A method for preparing a Cu-Cr alloy inert anode, employing a self-propagating reaction process, characterized in that, Includes the following steps: By mass percentage, a mixture of 3.74%~15.42% Cr, 69.38%~79.94% CuO, 9.02%~10.33% Al and 5.99%~6.17% CaF2 undergoes a self-propagating reaction under the excitation of an external heating source. The heat released by the reaction sustains the reaction and forms an alloy. After the self-propagating reaction is completed, a Cu-Cr alloy inert anode is obtained. After the self-propagating reaction is completed, the alloy is heated to a predetermined temperature in a vacuum environment and held at that temperature. The alloy is then heat-treated at this temperature to homogenize it. After that, it is cooled to room temperature in an inert gas atmosphere to complete the heat treatment. After the heat treatment, the alloy is remelted to form a remelted alloy layer on the alloy surface. After the remelting treatment, the resulting alloy is treated at a certain temperature and in an oxygen atmosphere to form an oxide layer. Then it is cooled to room temperature to complete the oxidation treatment. The Cr, CuO, Al, and CaF2 are in powder form; the heating rate is 8~12℃ / min; the predetermined temperature for the heat treatment is 1000~1200℃; the holding time is 9~12h; the oxidation treatment temperature is 900~980℃; the oxygen partial pressure is 0.2~1.2MPa; and the treatment time is 10~12h.

2. The method according to claim 1, characterized in that: During the formation of the mixture, the single mixing time is 50-70 min and the mixing rate is 40-60 r / min.

3. The method according to claim 1, characterized in that: The thickness of the remelted alloy layer is 2~4mm.

4. The method according to claim 1, characterized in that: The heat source for the remelting process is one of laser, plasma, or induced current.

5. A Cu-Cr alloy inert anode, characterized in that: It is prepared by the method described in any one of claims 1 to 4.

6. An application of the Cu-Cr alloy inert anode as described in claim 5, characterized in that: Applications of Cu-Cr alloy inert anodes as electrodes in the fields of electrolysis or battery manufacturing.

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