Inert anode material, method for its production and use

Abstract

The present disclosure relates to the field of electrolytic aluminum anode material, and particularly discloses an inert anode material, a preparation method and use thereof. The preparation method of the inert anode material comprises the following steps: S1, mixing metal oxide powder for the first time, and then performing solid phase synthesis to obtain ceramic phase raw materials; S2, mixing the ceramic phase raw materials, metal phase raw materials and a binder for the second time, and then performing compression molding to obtain a green body; S3, the green body is sequentially subjected to sintering and pre-oxidation treatment to obtain the inert anode material. The inert anode material is prepared by the preparation method. The inert anode material is used in electrolytic aluminum. The inert anode material provided by the present disclosure has good corrosion resistance, high temperature mechanical properties and electrical conductivity.

Description

Technical Field

[0001] This disclosure relates to the field of electrolytic aluminum anode materials, specifically to an inert anode material, its preparation method, and its uses. Background Technology

[0002] Aluminum has a melting point of 660℃ and a boiling point of 2327℃. It possesses good ductility and malleability and is an excellent conductor of electricity and heat. Aluminum constitutes 8% of the Earth's crust, ranking first among metallic elements. In metal products, aluminum products play an increasingly important role in the construction, aerospace, and automotive industries due to their superior properties such as light weight, abundant resources, and recyclability. It is a widely used, high-demand, and highly competitive metallic material.

[0003] Generally, based on the purity of aluminum, it is classified into three categories both domestically and internationally: primary aluminum, refined aluminum, and high-purity aluminum. Currently, primary aluminum is still extracted from alumina using the Hall-Héroult method, in which the aluminum electrolysis process is an electrochemical reaction that occurs in a Na3AlF6-Al2O3 melt at 940–970℃.

[0004] When aluminum is produced by electrolysis using carbon anodes, the carbon anode participates in the reaction, and the electrolysis reaction is as follows:

[0005] 2Al₂O₃ + 3C = 4Al + 3CO₂

[0006] If we calculate based on a current efficiency of 100% (i.e., all anode gas is CO2) and assume that the carbon anode contains 100% carbon, theoretically, each ton of aluminum consumes 333 kg of carbon. However, the actual carbon consumption is much greater than this, accounting for 5% to 20% of the primary aluminum production cost.

[0007] In cryolite-alumina molten salt electrolysis, the anode that is not consumed or is consumed in minimal quantities is called an inert anode. When using an inert anode to electrolyze aluminum, the inert anode does not participate in the reaction, the anode gas is O2, and the electrolysis reaction is:

[0008] 2Al₂O₃=4Al+3O₂

[0009] The application of inert anode materials has two advantages: economic and environmental. Economically, it replaces carbon anodes, saving a significant amount of high-quality carbon material, reducing labor costs associated with electrode replacement, and lowering the electrode spacing. Especially when using both inert anodes and cathodes simultaneously, it can greatly reduce energy consumption in aluminum electrolysis production. Furthermore, oxygen, as a byproduct of the anode process, contributes up to 3% of the economic benefits of aluminum electrolysis. Environmentally, the use of inert anodes can eliminate CO2 emissions (which contribute to the greenhouse effect) and other harmful gases emitted during aluminum electrolysis, such as CF4 and C2F6.

[0010] Therefore, inert anode materials have a significant impact on the advancement of electrolytic aluminum production technology and the improvement of economic benefits.

[0011] Since inert anode materials need to be used for a long time in Na3AlF6-Al2O3 melt at 940-970℃, such a high working environment and strong corrosive environment require inert anode materials to have good corrosion resistance, high temperature mechanical properties and electrical conductivity. Summary of the Invention

[0012] In order to enable inert anode materials to have good corrosion resistance, high-temperature mechanical properties and electrical conductivity, this disclosure provides an inert anode material, its preparation method and its uses.

[0013] Firstly, this disclosure provides a method for preparing an inert anode material, employing the following technical solution:

[0014] A method for preparing an inert anode material, the method comprising the following steps:

[0015] S1. After the metal oxide powder is first mixed, it is then synthesized in a solid phase to obtain a ceramic phase raw material.

[0016] The metal oxide powder is selected from at least five of the following: Fe2O3, FeO, Co3O4, Co2O3, CoO, NiO, Cr2O3, CuO, CuO2, MnO2, MnO, Al2O3, TiO2, ZnO, MgO, Nb2O5, NbO, Ta2O5, La2O3, Nd2O3, Sm2O3, Eu2O3, CeO2, ZrO2, and HfO2.

[0017] S2. After the ceramic phase raw material, the metal phase raw material, and the binder are mixed for the second time, the mixture is pressed and molded to obtain a pressed blank.

[0018] The metal phase raw material is selected from at least two of the following metal powders: Co, Cr, Fe, Ni, Mn, Al, Ti, Zn and Cu;

[0019] The weight ratio of the metallic phase raw material to the ceramic phase raw material is (10-50):(50-90);

[0020] Based on a total amount of 100 parts by weight of the metallic phase raw material and the ceramic phase raw material, the amount of the binder is 1 to 5 parts;

[0021] S3. The pressed blank is subjected to sintering and pre-oxidation treatment in sequence to obtain the inert anode material.

[0022] In some optional embodiments of this disclosure, the metal oxide powder is selected from at least five of the following: Fe2O3, Co3O4, CoO, NiO, Cr2O3, CuO, MnO2, TiO2, ZnO, MgO, Nb2O5, La2O3, Nd2O3, Sm2O3, Eu2O3, CeO2, ZrO2, and HfO2.

[0023] In some optional embodiments of this disclosure, the metal oxide comprises La2O3, Nd2O3, Sm2O3, Eu2O3 and ZrO2; wherein the molar ratio of La2O3, Nd2O3, Sm2O3, Eu2O3 and ZrO2 is (0.8~1.2):(0.8~1.2):(0.8~1.2):(0.8~1.2):(3.6~4.4); for example 1:1:1:1:4.

[0024] In some optional embodiments of this disclosure, the metal oxide comprises MgO, CoO, NiO, CuO and ZnO; wherein the molar ratio of MgO, CoO, NiO, CuO and ZnO is (0.8-1.2):(0.8-1.2):(0.8-1.2):(0.8-1.2):(0.8-1.2); for example 1:1:1:1:1.

[0025] In some optional embodiments of this disclosure, the metal raw materials comprise TiO2, ZrO2, HfO2, Nb2O5, CeO2, and La2O3; wherein the molar ratio of TiO2, ZrO2, HfO2, Nb2O5, CeO2, and La2O3 is (0.8–1.2):(0.8–1.2):(0.8–1.2):(0.8–1.2):(4.5–5.5); for example, 1:1:1:1:1:5.

[0026] In some optional embodiments of this disclosure, the metal oxide comprises Fe2O3, Co3O4, NiO, Cr2O3 and MnO2; wherein the molar ratio of Fe2O3, Co3O4, NiO, Cr2O3 and MnO2 is (2.8-3.2):(1.8-2.2):(5.8-6.2):(2.8-3.2):(5.8-6.2); for example 3:2:6:3:6.

[0027] In some alternative embodiments of this disclosure, the metallic phase raw material is selected from at least two of Ni, Fe, Co, Cu, and Cr.

[0028] In some alternative embodiments of this disclosure, the metallic phase raw material includes Ni, and at least one of Fe, Co, Cu and Cr.

[0029] In some optional embodiments of this disclosure, the metal raw material comprises Ni and Fe; wherein the metal atomic ratio Ni:Fe = (95-50):(5-50).

[0030] In some optional embodiments of this disclosure, the metal raw material comprises Ni and Co; wherein the metal atomic ratio Ni:Co = (95-70):(5-30).

[0031] In some optional embodiments of this disclosure, the metal raw material comprises Cu, Ni and Fe; wherein the metal atomic ratio Cu:Ni:Fe = (70-40):(25-40):(5-20).

[0032] In some optional embodiments of this disclosure, the metal raw material comprises Ni, Fe and Cr; wherein the metal atomic ratio Ni:Fe:Cr = (50-45):(45-35):(5-20).

[0033] In some optional embodiments of this disclosure, the weight ratio of the metallic phase raw material to the ceramic phase raw material is (20-50):(50-80); for example, 30:70, 40:60, 50:50, 20:80, etc.

[0034] In some optional embodiments of this disclosure, the particle size of the metal oxide is 50 to 350 mesh; for example, 200 mesh, 300 mesh, etc.

[0035] In some alternative embodiments of this disclosure, the particle size of the metal oxide is 200-300 mesh.

[0036] In some optional embodiments of this disclosure, the particle size of the ceramic phase raw material is 200-350 mesh.

[0037] In some alternative embodiments of this disclosure, the particle size of the metallic phase raw material is less than or equal to the particle size of the ceramic phase raw material.

[0038] In some optional embodiments of this disclosure, the particle size of the ceramic phase raw material is 200-300 mesh.

[0039] In some optional embodiments of this disclosure, the particle size of the metallic phase raw material is 100-200 mesh.

[0040] In some alternative embodiments of this disclosure, the particle size of the metallic phase raw material is 200 mesh.

[0041] In some specific embodiments of this disclosure, the particle size of the ceramic phase raw material is 300 mesh, and the particle size of the metallic phase raw material is 200 mesh.

[0042] In some specific embodiments of this disclosure, the particle size of the ceramic phase raw material is 200 mesh, and the particle size of the metallic phase raw material is 200 mesh.

[0043] In some optional embodiments of this disclosure, the solid-phase synthesis temperature is 750–1200°C; for example, 800°C, 900°C, 1000°C, 1100°C, 1200°C, etc.

[0044] In some optional embodiments of this disclosure, the solid-phase synthesis time is 2 to 7 hours; for example, 3 hours, 4 hours, 5 hours, 6 hours, etc.

[0045] In some optional embodiments of this disclosure, the solid-phase synthesis is carried out in a mixture of oxygen and an inert protective gas, wherein the partial pressure of oxygen is 100 to 1,000,000 ppm (e.g., 200,000 ppm, 300,000 ppm, 400,000 ppm or 500,000 ppm, etc.), and the total pressure of the mixture is 10 to 15 MPa (e.g., 10 MPa, 11 MPa, 12 MPa, 13 MPa, 14 MPa or 15 MPa, etc.).

[0046] In some optional embodiments of this disclosure, the specific steps of the first mixing are: dispersing the metal oxide powder in a first dispersant, followed by a first wet grinding and a first drying.

[0047] In some alternative embodiments of this disclosure, the total weight of the first dispersant is 3 to 5 times the total weight of the metal oxide powder, for example, 3 times, 3.5 times, 4 times, 4.5 times or 5 times.

[0048] In some optional embodiments of this disclosure, the first dispersant is selected from anhydrous ethanol. In some optional embodiments of this disclosure, the ball-to-particle ratio of the first wet milling is (5-20):1 (e.g., 5:1, 10:1, 15:1 or 20:1, etc.), the rotation speed is 100-400 r / min (e.g., 100 r / min, 150 r / min, 200 r / min, 250 r / min, 300 r / min, 350 r / min or 400 r / min, etc.), and the time is 1-24 hours (e.g., 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, 17 hours, 18 hours, 19 hours, 20 hours or 24 hours, etc.).

[0049] In some optional embodiments of this disclosure, the first drying temperature is 50–80°C (e.g., 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, or 80°C, etc.) and the time is 5–10 hours (5 hours, 6 hours, 7 hours, 8 hours, 9 hours, or 10 hours, etc.). In some optional embodiments of this disclosure, in step S2, the adhesive is selected from polyvinyl alcohol.

[0050] In some optional embodiments of this disclosure, in step S2, the specific steps of the second mixing are: dispersing the ceramic phase raw material, the metal phase raw material and the binder in a second dispersant, followed by a second wet grinding and a second drying.

[0051] In some optional embodiments of this disclosure, the total weight of the second dispersant is 3 to 5 times the total weight of the ceramic phase raw material and the metal phase raw material, for example, 3 times, 3.5 times, 4 times, 4.5 times or 5 times.

[0052] In some alternative embodiments of this disclosure, the second dispersant is selected from anhydrous ethanol.

[0053] In some optional embodiments of this disclosure, the ball-to-material ratio of the second wet grinding is (5-20):1 (e.g., 5:1, 10:1, 15:1 or 20:1, etc.), the rotation speed is 100-400 r / min (e.g., 100 r / min, 150 r / min, 200 r / min, 250 r / min, 300 r / min, 350 r / min or 400 r / min, etc.), and the time is 1-24 hours (e.g., 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, 17 hours, 18 hours, 19 hours, 20 hours or 24 hours, etc.).

[0054] In some optional embodiments of this disclosure, the temperature of the second drying is 50-80°C (e.g., 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, or 80°C) and the time is 5-10 hours (5 hours, 6 hours, 7 hours, 8 hours, 9 hours, or 10 hours).

[0055] In some optional embodiments of this disclosure, the compression molding pressure is 10–500 MPa (e.g., 100 MPa, 150 MPa, 200 MPa, 250 MPa, 300 MPa, 400 MPa, or 500 MPa, etc.), and the time is 1–30 minutes (e.g., 1 minute, 2 minutes, 3 minutes, 4 minutes, 5 minutes, 10 minutes, 15 minutes, 20 minutes, 25 minutes, or 30 minutes, etc.).

[0056] In some optional embodiments of this disclosure, in step S3, the sintering temperature is 1000–1700°C (e.g., 1000°C, 1500°C, 1200°C, 1250°C, 1300°C, 1350°C, 1400°C, 1450°C, 1500°C, 1550°C, 1600°C, 1650°C, or 1700°C, etc.) and the time is 2–6 hours (e.g., 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, 5.5 hours, or 6 hours, etc.).

[0057] In some alternative embodiments of this disclosure, in step S3, the sintering is carried out in an inert atmosphere, such as a nitrogen atmosphere or a helium atmosphere.

[0058] In some optional embodiments of this disclosure, the pre-oxidation treatment is carried out in a mixture of oxygen and an inert protective gas, wherein the partial pressure of oxygen is 100 to 1,000,000 ppm (e.g., 200,000 ppm, 300,000 ppm, 400,000 ppm or 500,000 ppm, etc.), and the total pressure of the mixture is 10 to 15 MPa (e.g., 10 MPa, 11 MPa, 12 MPa, 13 MPa, 14 MPa or 15 MPa, etc.);

[0059] In some optional embodiments of this disclosure, the pre-oxidation treatment is carried out at a temperature of 850–1200°C (e.g., 850°C, 900°C, 950°C, 1000°C, 1050°C, 1100°C, 1150°C, or 1200°C) for a time of 1–3 hours (e.g., 1 hour, 1.5 hours, 2 hours, 2.5 hours, or 3 hours).

[0060] In a second aspect of this disclosure, an inert anode material prepared by the preparation method described in the first aspect is provided.

[0061] In a third aspect of this disclosure, the inert anode material described in the second aspect is provided for use in electrolytic aluminum.

[0062] This disclosure has the following beneficial effects:

[0063] First, metal oxide powder is first synthesized in a solid state to obtain ceramic phase raw materials, and then the ceramic phase raw materials are sintered with the metal phase raw materials, which can improve the corrosion resistance, high-temperature mechanical properties and electrical conductivity of inert anode materials.

[0064] Secondly, when the particle size of the metallic phase raw material is less than or equal to that of the ceramic phase raw material, the corrosion resistance and high-temperature mechanical properties of the inert anode material can be improved. Attached Figure Description

[0065] Figure 1This is a scanning electron microscope image of the inert anode material of Embodiment 1 of this disclosure;

[0066] Figure 2 This is a scanning electron microscope image of the inert anode material of Embodiment 4 of this disclosure;

[0067] Figure 3 This is a scanning electron microscope image of the inert anode material of Embodiment 7 of this disclosure. Detailed Implementation

[0068] The present disclosure will be further described in detail below with reference to the accompanying drawings and embodiments.

[0069] This disclosure provides a method for preparing an inert anode material, the method comprising the following steps:

[0070] S1. After the metal oxide powder is first mixed, it is then subjected to solid-phase synthesis and grinding to obtain ceramic phase raw material;

[0071] The metal oxide powder is selected from at least five of the following: Fe2O3, FeO, Co3O4, Co2O3, CoO, NiO, Cr2O3, CuO, CuO2, MnO2, MnO, Al2O3, TiO2, ZnO, MgO, Nb2O5, NbO, Ta2O5, La2O3, Nd2O3, Sm2O3, Eu2O3, CeO2, ZrO2, and HfO2.

[0072] S2. After the ceramic phase raw material, the metal phase raw material, and the binder are mixed for the second time, the mixture is pressed and molded to obtain a pressed blank.

[0073] The metal phase raw material is selected from at least two of the following metal powders: Co, Cr, Fe, Ni, Mn, Al, Ti, Zn and Cu;

[0074] The weight ratio of the metallic phase raw material to the ceramic phase raw material is (10-50):(50-90);

[0075] Based on a total amount of 100 parts by weight of the metallic phase raw material and the ceramic phase raw material, the amount of the binder is 1 to 5 parts;

[0076] S3. The pressed blank is subjected to sintering and pre-oxidation treatment in sequence to obtain the inert anode material.

[0077] The following performance tests were conducted on the inert anode material in this disclosure:

[0078] (1) Scanning electron microscopy (SEM) detection

[0079] The inert anode material is cut using a cutting machine, and the cut sample is fixed in an inlay machine. Then, it is polished using a polishing machine with a gradient of sandpaper grit, from 500 grit to 5000 grit. Conductive adhesive is applied to the cross-section of the polished sample, and gold is sprayed on. Finally, scanning electron microscopy is used for measurement.

[0080] (2) Detection of conductivity

[0081] This experiment uses the probe method to determine the conductivity of inert anode materials.

[0082] (3) Testing of flexural strength

[0083] Flexural strength refers to a material's ability to resist bending without fracturing, and is mainly used to assess the strength of brittle materials such as ceramics. This experiment uses the three-point method to determine the flexural strength of inert anode materials on an electronic universal testing machine.

[0084] (4) Corrosion resistance test

[0085] Corrosion resistance is one of the fundamental criteria for selecting inert anode materials for aluminum electrolysis. During the electrolysis process, inert anode materials undergo electrochemical corrosion and chemical dissolution corrosion in high-temperature cryolite molten salt. Anode components corrode into the electrolyte, which not only reduces the grade of the aluminum product but also affects the anode's service life, production continuity, and increases costs.

[0086] This experiment used the weight loss method to determine the thermal corrosion rate of inert anode materials in molten cryolite electrolyte. The specific experimental procedure is as follows:

[0087] Weigh the inert anode material sample (m1, mg), measure the dimensions of the sample, and calculate the surface area (s, cm²) of the inert anode material. 2 An inert anode material was tested for aluminum electrolysis under simulated industrial conditions. Simulated industrial conditions: the electrolyte was a cryolite molten salt system (specifically composed of 90 wt% cryolite, 5 wt% calcium fluoride, and 5 wt% aluminum oxide); the electrolysis temperature was 960℃; and the electrolysis time was 20 hours. After electrolysis, the sample was removed and cooled. The cooled sample was then immersed in a 30 wt% aluminum chloride aqueous solution and heated to gradually dissolve the molten salt adhering to the sample surface. Once all residues on the sample surface were completely removed, the sample surface was first washed with clean water, then boiled in clean water, and finally dried.

[0088] (4-1) Record the cell pressure (V) during the electrolysis process.

[0089] (4-2) Observe whether the surface of the sample is corroded after drying.

[0090] (4-3) Weigh the dried sample m2 (mg).

[0091] The corrosion rate f (mg·cm) of the inert anode material is calculated using the following formula. -2 ).

[0092]

[0093] (4-4) The content of impurities in molten aluminum was determined using inductively coupled plasma atomic emission spectrometry (ICP).

[0094] Examples 1-3 and Comparative Example 1

[0095] Example 1

[0096] In this embodiment, metal oxide powders La2O3, Nd2O3, Sm2O3, Eu2O3, and ZrO2 were weighed according to a molar ratio of 1:1:1:1:4. The purity of each metal oxide powder was not less than 99.9%, and the particle size was 300 mesh.

[0097] In this embodiment, Ni and Co metal powders were weighed according to a metal atomic ratio of Ni:Co = 80:20 to obtain the metal phase raw material. The purity of each metal powder was not less than 99.9%, and the particle size was 200 mesh.

[0098] In this embodiment, the preparation method of the inert anode material specifically includes the following steps:

[0099] S1. The above-mentioned metal oxide powder and dispersant anhydrous ethanol (weight ratio of metal oxide powder to anhydrous ethanol is 1:4) are placed in a ball mill jar, and then the ball mill jar is installed on a ball mill for wet grinding (ball-to-material ratio is 10:1, rotation speed is 250 r / min, time is 10 hours). After ball milling, the mixed slurry is placed in a 60℃ drying oven for 8 hours. The dried material is then placed in an agate mortar for grinding and sieved to obtain a powder with a particle size of 300 mesh. The powder is then subjected to solid-phase synthesis (temperature is 1100℃; time is 2 hours; atmosphere is a mixed gas composed of oxygen and argon, wherein the oxygen partial pressure is 500,000 ppm and the total gas pressure of the mixed gas is 12 MPa). After solid-phase synthesis, the material is placed in an agate mortar for grinding and sieved to obtain a ceramic phase raw material with a particle size of 300 mesh.

[0100] S2. Place the metallic phase raw material, ceramic phase raw material, binder polyvinyl alcohol, and dispersant anhydrous ethanol into a ball mill jar, and then install the ball mill jar onto a ball mill for wet grinding (ball-to-material ratio of 10:1, rotation speed of 250 r / min, and time of 10 hours). After ball milling, place the mixed slurry in a 60℃ drying oven to dry for 8 hours. Place the dried material under a hydraulic press for pressing and molding (pressing pressure of 150 MPa and pressing time of 2 minutes) to obtain a pressed blank.

[0101] The weight ratio of the metallic phase raw material to the ceramic phase raw material is 40:60; the amount of binder is 3% of the total weight of the metallic phase raw material and the ceramic phase raw material; and the amount of dispersant is 4 times the total weight of the metallic phase raw material and the ceramic phase raw material.

[0102] S3. The pressed blank is placed in a sintering furnace for sintering (temperature 1400℃, time 2 hours, atmosphere is high-purity argon), followed by pre-oxidation treatment (temperature 1000℃; time 2 hours; atmosphere is a mixture of oxygen and argon, where the oxygen partial pressure is 500000ppm and the total pressure of the mixture is 12MPa) to obtain inert anode material.

[0103] Example 2

[0104] Compared to Example 1, the only difference in Example 2 is that the particle size of each metal oxide powder is 200 mesh, and in step S1, the particle size of the powder is 200 mesh, and the particle size of the ceramic phase raw material is 200 mesh.

[0105] Example 3

[0106] Compared to Example 1, the only difference in Example 3 is that the particle size of each metal powder in the metal phase raw material is 300 mesh.

[0107] Comparative Example 1

[0108] Compared to Example 1, the only difference in Comparative Example 1 is that the metal oxide powder did not go through step S1, the five metal oxide powders directly participated in step S2, and the total amount of the five metal oxide powders used in step S2 was in a weight ratio of 60:40 to the metal phase raw material.

[0109] Table 1 shows the performance test results of the inert anode materials in Examples 1-3 and Comparative Example 1.

[0110]

[0111]

[0112] As can be seen from Table 1, the inert anode material of this disclosure possesses good corrosion resistance, high-temperature mechanical properties, and electrical conductivity. Furthermore, the voltage of the aluminum electrolytic cell using the inert anode material of this disclosure during the electrolysis process is 3.414–3.501 V, which is lower than the voltage (3.8–4.0 V) of a conventional carbon anode used in an aluminum electrolytic cell.

[0113] By comparing Example 1 and Comparative Example 1, it can be seen that the ceramic phase raw material is obtained by first performing solid-state synthesis of metal oxide powder, and then the ceramic phase raw material is sintered with the metal phase raw material, which can improve the corrosion resistance, high-temperature mechanical properties and electrical conductivity of the inert anode material.

[0114] Comparing Examples 1 to 3, it can be seen that when the particle size of the metallic phase raw material is less than or equal to the particle size of the ceramic phase raw material, the corrosion resistance and high-temperature mechanical properties of the inert anode material can be improved.

[0115] The inert anode material from Example 1 was used for scanning electron microscopy measurements, and the results are as follows: Figure 1 As shown. In this embodiment, after the metal dispersed phases Ni and Co are pre-oxidized, a dense oxide film (Ni,Co)O is formed on the surface of the inert anode material.

[0116] Examples 4-6 and Comparative Example 2

[0117] Example 4

[0118] In this embodiment, metal oxide powders MgO, CoO, NiO, CuO, and ZnO are weighed in a molar ratio of 1:1:1:1:1. The purity of each metal oxide powder is not less than 99.9%, and the particle size is 200 mesh.

[0119] In this embodiment, metal powders Cu, Ni, and Fe were weighed according to a metal atomic ratio of Cu:Ni:Fe = 60:30:10 to obtain the metal phase raw material. The purity of each metal powder was not less than 99.9%, and the particle size was 200 mesh.

[0120] In this embodiment, the preparation method of the inert anode material specifically includes the following steps:

[0121] S1. The above-mentioned metal oxide powder and dispersant anhydrous ethanol (weight ratio of metal oxide powder to anhydrous ethanol is 1:4) are placed in a ball mill jar, and then the ball mill jar is installed on a ball mill for wet grinding (ball-to-material ratio is 10:1, rotation speed is 300 r / min, time is 5 hours). After ball milling, the mixed slurry is placed in a 70℃ drying oven for 7 hours. The dried material is then placed in an agate mortar for grinding and sieved to obtain a powder with a particle size of 200 mesh. The powder is then subjected to solid-phase synthesis (temperature is 1000℃; time is 6 hours; atmosphere is a mixed gas composed of oxygen and argon, wherein the oxygen partial pressure is 300,000 ppm and the total gas pressure of the mixed gas is 12 MPa). After solid-phase synthesis, the material is placed in an agate mortar for grinding and sieved to obtain a ceramic phase raw material with a particle size of 200 mesh.

[0122] S2. Place the metallic phase raw material, ceramic phase raw material, binder polyvinyl alcohol, and dispersant anhydrous ethanol into a ball mill jar, and then install the ball mill jar onto a ball mill for wet grinding (ball-to-material ratio of 10:1, rotation speed of 300 r / min, and time of 5 hours). After ball milling, place the mixed slurry in a 70℃ drying oven to dry for 7 hours. Place the dried material under a hydraulic press for pressing and molding (pressing pressure of 200 MPa and pressing time of 1 minute) to obtain a pressed blank.

[0123] The weight ratio of the metallic phase raw material to the ceramic phase raw material is 50:50; the amount of binder is 3% of the total weight of the metallic phase raw material and the ceramic phase raw material; and the amount of dispersant is 4 times the total weight of the metallic phase raw material and the ceramic phase raw material.

[0124] S3. The pressed blank is placed in a sintering furnace for sintering (temperature 1000℃, time 2.5 hours, atmosphere is high-purity argon), and then pre-oxidation treatment is performed (temperature 900℃, time 3 hours, atmosphere is a mixed gas composed of oxygen and argon, wherein the partial pressure of oxygen is 300000ppm, and the total pressure of the mixed gas is 12Mpa) to obtain inert anode material.

[0125] Example 5

[0126] Compared to Example 4, the only difference in Example 5 is that the particle size of each metal oxide powder is 300 mesh, and in step S1, the particle size of the powder is 300 mesh, and the particle size of the ceramic phase raw material is 300 mesh.

[0127] Example 6

[0128] Compared to Example 4, the only difference in Example 6 is that the particle size of each metal powder in the metal phase raw material is 300 mesh.

[0129] Comparative Example 2

[0130] Compared to Example 4, the only difference in Comparative Example 2 is that the metal oxide powder did not go through step S1, the five metal oxide powders directly participated in step S2, and the total amount of the five metal oxide powders used in step S2 was in a weight ratio of 50:50 to the metal phase raw material.

[0131] Table 2 shows the performance test results of the inert anode materials in Examples 4-6 and Comparative Example 2.

[0132]

[0133]

[0134] As can be seen from Table 2, the inert anode material of this disclosure possesses good corrosion resistance, high-temperature mechanical properties, and electrical conductivity. Furthermore, the voltage of the aluminum electrolytic cell using the inert anode material of this disclosure during the electrolysis process is 3.303–3.405 V, which is lower than the voltage (3.8–4.0 V) of a conventional carbon anode used in an aluminum electrolytic cell.

[0135] By comparing Example 4 and Comparative Example 2, it can be seen that the ceramic phase raw material is first obtained by solid-state synthesis of metal oxide powder, and then the ceramic phase raw material is sintered with the metal phase raw material, which can improve the corrosion resistance, high-temperature mechanical properties and conductivity of the inert anode material.

[0136] Comparative examples 4-6 show that when the particle size of the metallic phase raw material is less than or equal to the particle size of the ceramic phase raw material, the corrosion resistance and high-temperature mechanical properties of the inert anode material can be improved.

[0137] The inert anode material from Example 4 was subjected to scanning electron microscopy measurements, and the results are as follows: Figure 2 As shown. In this embodiment, after the metal dispersed phases Fe, Ni, and Cu are pre-oxidized, a dense oxide film is formed on the surface of the inert anode material. The oxide film, from the outside to the inside, is (CuO)-(CuO2)-(NiFe2O4+NiO).

[0138] Examples 7-10 and Comparative Example 3

[0139] Example 7

[0140] In this embodiment, metal oxide powders TiO2, ZrO2, HfO2, Nb2O5, CeO2, and La2O3 were weighed out in a molar ratio of 1:1:1:1:1:5. The purity of each metal oxide powder was not less than 99.9%, and the particle size was 300 mesh.

[0141] In this embodiment, metal powders Ni, Fe, and Cr were weighed according to a metal atomic ratio of Ni:Fe:Cr = 50:40:10 to obtain the metal phase raw material. The purity of each metal powder was not less than 99.9%, and the particle size was 200 mesh.

[0142] In this embodiment, the preparation method of the inert anode material specifically includes the following steps:

[0143] S1. The above-mentioned metal oxide powder and dispersant anhydrous ethanol (weight ratio of metal oxide powder to anhydrous ethanol is 1:4) are placed in a ball mill jar, and then the ball mill jar is installed on a ball mill for wet grinding (ball-to-material ratio is 15:1, rotation speed is 350 r / min, time is 4 hours). After ball milling, the mixed slurry is placed in a 60℃ drying oven for 10 hours. The dried material is then placed in an agate mortar for grinding and sieved to obtain a powder with a particle size of 300 mesh. The powder is then subjected to solid-phase synthesis (temperature is 1100℃; time is 2 hours; atmosphere is a mixed gas composed of oxygen and argon, wherein the oxygen partial pressure is 400000 ppm and the total gas pressure of the mixed gas is 12 MPa). After solid-phase synthesis, the material is placed in an agate mortar for grinding and sieved to obtain a ceramic phase raw material with a particle size of 300 mesh.

[0144] S2. Place the metallic phase raw material, ceramic phase raw material, binder polyvinyl alcohol, and dispersant anhydrous ethanol into a ball mill jar, then install the ball mill jar onto a ball mill for wet grinding (ball-to-material ratio of 10:1, rotation speed of 300 r / min, time of 5 hours). After ball milling, place the mixed slurry in a 60℃ drying oven to dry for 10 hours. Place the dried material under a hydraulic press for pressing and molding (pressing pressure of 200 MPa, pressing time of 10 minutes) to obtain a pressed blank.

[0145] The weight ratio of the metallic phase raw material to the ceramic phase raw material is 20:80; the amount of binder is 3% of the total weight of the metallic phase raw material and the ceramic phase raw material; and the amount of dispersant is 4 times the total weight of the metallic phase raw material and the ceramic phase raw material.

[0146] S3. The compact is placed in a sintering furnace for sintering (temperature 1400℃, time 2 hours, atmosphere is high-purity argon), followed by pre-oxidation treatment (temperature 1200℃, time 1 hour, atmosphere is a mixture of oxygen and argon, where the oxygen partial pressure is 400000ppm and the total pressure of the mixture is 12MPa) to obtain inert anode material.

[0147] Example 8

[0148] Compared to Example 7, the only difference in Example 2 is that the particle size of each metal oxide powder is 200 mesh, and in step S1, the particle size of the powder is 200 mesh, and the particle size of the ceramic phase raw material is 200 mesh.

[0149] Example 9

[0150] Compared to Example 7, the only difference in Example 3 is that the particle size of each metal powder in the metal phase raw material is 300 mesh.

[0151] Example 10

[0152] Compared to Example 7, the only difference in Example 10 is that the metal phase raw materials include Fe and Cr, wherein the metal powder is weighed according to the metal atomic ratio Fe:Cr = 80:20. Comparative Example 3

[0153] Compared to Example 7, the only difference in Comparative Example 3 is that the metal oxide powder did not go through step S1, the five metal oxide powders directly participated in step S2, and the total amount of the five metal oxide powders used in step S2 was 80:20 in weight ratio to the metal phase raw material.

[0154] Table 3 shows the performance test results of the inert anode materials in Examples 7-10 and Comparative Example 3.

[0155]

[0156] As can be seen from Table 3, the inert anode material of this disclosure possesses good corrosion resistance, high-temperature mechanical properties, and electrical conductivity. Furthermore, the voltage of the aluminum electrolytic cell using the inert anode material of this disclosure during the electrolysis process is 3.450V, which is lower than the voltage (3.8–4.0V) of aluminum electrolytic cells using conventional carbon anodes.

[0157] By comparing Example 7 and Comparative Example 3, it can be seen that the ceramic phase raw material is first obtained by solid-state synthesis of metal oxide powder, and then the ceramic phase raw material is sintered with the metal phase raw material, which can improve the corrosion resistance, high-temperature mechanical properties and electrical conductivity of the inert anode material.

[0158] Comparative examples 7-9 show that when the particle size of the metallic phase raw material is less than or equal to the particle size of the ceramic phase raw material, the corrosion resistance and high-temperature mechanical properties of the inert anode material can be improved.

[0159] By comparing Examples 7 and 10, it can be seen that the metallic raw material Ni mainly affects the corrosion resistance and high-temperature mechanical properties of the inert anode material.

[0160] The inert anode material from Example 7 was subjected to scanning electron microscopy measurements, and the results are as follows: Figure 3As shown. Since the metal dispersed phases in this embodiment are Fe, Ni, and Cr, a dense oxide film is formed on the surface of the inert anode material after pre-oxidation treatment. The oxide film, from the outside to the inside, is (Ni, Fe)3O4-(Ni, Fe, Cr)3O4-Cr2O3.

[0161] Example 11 and Comparative Example 4

[0162] In this embodiment, metal oxide powders Fe2O3, Co3O4, NiO, Cr2O3, and MnO2 were weighed according to a molar ratio of 3:2:6:3:6. The purity of each metal oxide powder was not less than 99.9%, and the particle size was 200 mesh.

[0163] In this embodiment, Ni and Fe metal powders were weighed according to a metal atomic ratio of Ni:Fe = 70:30 to obtain the metal phase raw material. The purity of each metal powder was not less than 99.9%, and the particle size was 200 mesh.

[0164] In this embodiment, the preparation method of the inert anode material specifically includes the following steps:

[0165] S1. The above-mentioned metal oxide powder and dispersant anhydrous ethanol (weight ratio of metal oxide powder to anhydrous ethanol is 1:4) are placed in a ball mill jar, and then the ball mill jar is installed on a ball mill for wet grinding. The ball-to-powder ratio is 10:1, and the mixture is mixed at 200 r / min for 15 hours. After ball milling, the mixed slurry is placed in a 60℃ drying oven and dried for 8 hours. The dried material is then placed in an agate mortar for grinding and sieved to obtain a powder with a particle size of 200 mesh. The powder is then subjected to solid-phase synthesis (solid-phase synthesis temperature is 1200℃, solid-phase synthesis time is 5 hours, and the atmosphere for solid-phase synthesis is a mixed gas composed of oxygen and argon, wherein the oxygen partial pressure is 200,000 ppm, and the total pressure of the mixed gas is 12 MPa). After solid-phase synthesis, the material is placed in an agate mortar for grinding and sieved to obtain a ceramic phase raw material with a particle size of 200 mesh.

[0166] S2. Place the metallic phase raw materials, ceramic phase raw materials, binder polyvinyl alcohol, and dispersant anhydrous ethanol into a ball mill jar, then install the ball mill jar onto a ball mill for wet grinding. The ball-to-material ratio is 10:1, and the mixture is mixed at 200 r / min for 15 hours. After ball milling, place the mixed slurry in a 60℃ drying oven to dry for 8 hours. Place the dried material under a hydraulic press for pressing and molding (pressing pressure 100 MPa, pressing time 5 minutes) to obtain a pressed blank.

[0167] The weight ratio of the metallic phase raw material to the ceramic phase raw material is 30:70; the amount of binder is 3% of the total weight of the metallic phase raw material and the ceramic phase raw material; and the amount of dispersant is 4 times the total weight of the metallic phase raw material and the ceramic phase raw material.

[0168] S3. The pressed blank is placed in a sintering furnace for sintering (sintering temperature is 1200℃, sintering time is 3 hours, sintering atmosphere is high-purity argon), and then pre-oxidation treatment is performed (pre-oxidation temperature is 850℃, pre-oxidation time is 2 hours, pre-oxidation atmosphere is a mixture of oxygen and argon, wherein the oxygen partial pressure is 200000ppm, and the total pressure of the mixture is 12MPa) to obtain inert anode material.

[0169] Comparative Example 4

[0170] Compared to Example 11, the only difference in Comparative Example 4 is that the metal oxide powder did not go through step S1, the five metal oxide powders directly participated in step S2, and the total amount of the five metal oxide powders used in step S2 was 70:30 in weight ratio to the metal phase raw material.

[0171] Table 4. Performance test results of the inert anode materials in Example 11 and Comparative Example 4.

[0172] Testing items Example 11 Comparative Example 4 Conductivity (S / cm) 103.21 103.50 Bending strength (MPa) 215 166 Voltage (V) in the aluminum electrolysis cell during electrolysis. 3.426 3.757 Is there any obvious peeling on the surface? No obvious peeling No obvious peeling <![CDATA[Corrosion rate f (mg·cm -2 )]]> 4.42 5.05 Impurity content (wt%) in molten aluminum 0.24 0.37

[0173] As can be seen from Table 4, the inert anode material of this disclosure possesses good corrosion resistance, high-temperature mechanical properties, and electrical conductivity. Furthermore, the voltage of the aluminum electrolytic cell using the inert anode material of this disclosure during the electrolysis process is 3.426V, which is lower than the voltage (3.8–4.0V) of aluminum electrolytic cells using conventional carbon anodes.

[0174] By comparing Example 11 and Comparative Example 4, it can be seen that the ceramic phase raw material is first obtained by solid-state synthesis of metal oxide powder, and then the ceramic phase raw material is sintered with the metal phase raw material, which can improve the corrosion resistance, high-temperature mechanical properties and conductivity of the inert anode material.

[0175] The metal dispersed phases are Fe and Ni. After pre-oxidation treatment, a dense oxide film is formed on the surface of the inert anode material. The outermost layer of the oxide film is composed of NiFe2O4, and the innermost layer is composed of NiO.

[0176] It is understood that the above embodiments are merely exemplary implementations used to illustrate the principles of the present invention, and the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also considered to be within the scope of protection of the present invention.

Claims

1. A method for preparing an inert anode material, characterized in that, The preparation method includes the following steps: S1. After the metal oxide powder is first mixed, it is then subjected to solid-phase synthesis and grinding to obtain ceramic phase raw material; The metal oxides are La2O3, Nd2O3, Sm2O3, Eu2O3, and ZrO2; and the molar ratio of La2O3, Nd2O3, Sm2O3, Eu2O3, and ZrO2 is (0.8–1.2):(0.8–1.2):(0.8–1.2):(0.8–1.2):(3.6–4.4). Alternatively, the metal oxide may be MgO, CoO, NiO, CuO, and ZnO; wherein the molar ratio of MgO, CoO, NiO, CuO, and ZnO is (0.8–1.2):(0.8–1.2):(0.8–1.2):(0.8–1.2):(0.8–1.2). Alternatively, the metal oxide may be TiO2, ZrO2, HfO2, Nb2O5, CeO2, and La2O3; wherein the molar ratio of TiO2, ZrO2, HfO2, Nb2O5, CeO2, and La2O3 is (0.8–1.2):(0.8–1.2):(0.8–1.2):(0.8–1.2):(4.5–5.5). Alternatively, the metal oxide may be Fe2O3, Co3O4, NiO, Cr2O3, and MnO2; wherein the molar ratio of Fe2O3, Co3O4, NiO, Cr2O3, and MnO2 is (2.8–3.2):(1.8–2.2):(5.8–6.2):(2.8–3.2):(5.8–6.2). The solid-phase synthesis temperature is 750–1200℃; The solid-phase synthesis time is 2 to 7 hours; The solid-phase synthesis is carried out in a mixture of oxygen and an inert protective gas, wherein the partial pressure of oxygen is 100 to 1,000,000 ppm and the total pressure of the mixture is 10 to 15 MPa. S2. After a second mixing of the ceramic phase raw material, the metal phase raw material, and the binder, the mixture is pressed into a compact; wherein the metal phase raw material is Ni and Fe; wherein the metal atomic ratio Ni:Fe = (95~50):(5~50); or The metallic phase raw materials are Ni and Co; wherein the atomic ratio of the metals Ni:Co = (95-70):(5-30); or The metal phase raw materials are Cu, Ni and Fe; wherein the metal atomic ratio Cu:Ni:Fe = (70-40):(25-40):(5-20); or the metal phase raw materials are Ni, Fe and Cr; wherein the metal atomic ratio Ni:Fe:Cr = (50-45):(45-35):(5-20); The weight ratio of the metallic phase raw material to the ceramic phase raw material is (10-50):(50-90); the particle size of the metallic phase raw material is less than or equal to the particle size of the ceramic phase raw material; wherein, the particle size of the ceramic phase raw material is 200-300 mesh; the particle size of the metallic phase raw material is 100-200 mesh; and the particle size of the metal oxide is 200-300 mesh. Based on a total amount of 100 parts by weight of the metallic phase raw material and the ceramic phase raw material, the amount of the binder is 1 to 5 parts; S3. The pressed blank is subjected to sintering and pre-oxidation treatment in sequence to obtain the inert anode material.

2. The preparation method according to claim 1, characterized in that, In step S2, the adhesive is selected from polyvinyl alcohol; the compression molding pressure is 10-500 MPa and the time is 1-30 minutes.

3. The preparation method according to claim 1, characterized in that, In step S3, the sintering temperature is 1100-1700℃ and the time is 2-6 hours; the sintering is carried out in an inert atmosphere.

4. The preparation method according to claim 1, characterized in that, In step S3, the pre-oxidation treatment is carried out in a mixture of oxygen and an inert protective gas, wherein the partial pressure of oxygen is 100 to 1,000,000 ppm and the total pressure of the mixture is 10 to 15 MPa; the temperature of the pre-oxidation treatment is 850 to 1200°C and the time is 1 to 3 hours.

5. An inert anode material prepared by the preparation method according to any one of claims 1 to 4.

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