METAL-CERAMIC MATERIAL OF AN INERT ANODE WITH LOW METALLIC PHASE CONTENT AND A METHOD OF ITS MANUFACTURING

Abstract

A metal-ceramic inert anode material having low metal phase content and a preparation method. The metal-ceramic inert anode material comprises, by mass fraction: 3-5% of a metal phase and 95-97% of a ceramic phase, wherein metal elements of the metal phase include Cu, Ni and Fe; and the ceramic phase comprises NiFe2O4·10NiO, TiN, ZrB2, and an oxide additive.

Description

A metal ceramic inert anode material with low metal phase content and preparation method thereof

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to Chinese patent application No. 202410111989.7 filed on January 25, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present disclosure relates to the technical field of anode materials, and in particular to a metal-ceramic inert anode material with low metal phase content and a preparation method thereof. Background Art

[0004] The traditional prebaked carbon anode aluminum electrolysis production process has a high carbon emission intensity due to carbon anode consumption and the anode effect, resulting in an increasingly prominent problem of high carbon emissions. To address this issue, inert anode aluminum electrolysis technology is currently used to produce prebaked carbon anodes. Because the electrolysis process of inert anode aluminum electrolysis technology does not emit carbon dioxide, sulfur dioxide, and perfluorocarbons (PFCs), and the electrolysis process produces approximately 0.88 tons of oxygen per ton of aluminum, inert anode aluminum electrolysis technology has become a key technology for the aluminum smelting industry to continue to develop low-carbon and achieve carbon neutrality goals.

[0005] Currently available inert anode materials can be broadly categorized into three types: metal / alloy, oxide ceramic, and cermet. Metal / alloy anodes offer good conductivity but poor corrosion resistance, especially at high electrolysis temperatures. Oxide ceramic anodes offer good corrosion resistance but poor conductivity and thermal shock resistance. Cermet anodes are based on a NiFe2O4 ceramic matrix with a certain amount of metal added, combining the advantages of both metal and ceramic. They are considered the most promising inert anode material for aluminum electrolysis, potentially replacing the current carbon anode.

[0006] However, in actual implementation, it is difficult to strike a balance between the electrical conductivity, corrosion resistance, and thermal shock resistance of metal-ceramic inert anodes. For example, when the metal content of the metal ceramic is high, although its electrical conductivity and thermal shock resistance are good, the corrosion resistance and oxidation resistance of the metal phase are much lower than those of NiFe2O4 ceramics. This causes the metal phase to corrode preferentially during the electrolysis process, affecting the purity of the aluminum produced by aluminum electrolysis. When the metal content of the metal ceramic is low, although the corrosion resistance of the metal-ceramic inert anode is good, its electrical conductivity is weakened and its brittleness increases. Therefore, whether the comprehensive performance of the metal-ceramic inert anode is balanced will seriously restrict the industrial application of inert anode aluminum electrolysis technology.

[0007] Summary of the Invention

[0008] The present disclosure provides a metal ceramic inert anode material with low metal phase content and a preparation method thereof, so as to solve the technical problem in the prior art that the electrical conductivity, corrosion resistance and thermal shock resistance of the metal ceramic inert anode are difficult to be taken into account at the same time.

[0009] According to a first aspect of the present disclosure, a metal-ceramic inert anode material with a low metal phase content is provided. The metal-ceramic inert anode material comprises, by mass fraction, 3% to 5% of a metal phase and 95% to 97% of a ceramic phase. The metal elements of the metal phase include Cu, Ni, and Fe. The ceramic phase includes NiFe2O4·10NiO, TiN, ZrB2, and oxide additives.

[0010] In a second aspect, according to some embodiments of the present disclosure, a method for preparing the metal-ceramic inert anode material described in the first aspect is provided, the method comprising: mixing metal powder, NiFe2O4·10NiO ceramic powder, TiN ceramic powder, ZrB2 ceramic powder and oxide additives to obtain a first mixed powder; mixing an adhesive and the first mixed powder, and grinding them to obtain a second mixed powder; drying the second mixed powder, and then sieving it to obtain a metal-ceramic mixed powder; and, compression molding the metal-ceramic mixed powder, and then degreasing and sintering it to obtain a metal-ceramic inert anode material. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present disclosure and, together with the description, serve to explain the principles of the present disclosure.

[0012] In order to more clearly illustrate the embodiments of the present disclosure or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0013] FIG1 is a schematic diagram of the product structure of a cermet inert anode material with low metal phase content according to some embodiments of the present disclosure;

[0014] FIG2 is a schematic flow chart of a method for preparing a metal-ceramic inert anode material according to some embodiments of the present disclosure; and

[0015] FIG3 is a schematic diagram of a detailed process of preparing a metal-ceramic inert anode material according to some embodiments of the present disclosure. DETAILED DESCRIPTION

[0016] To make the objectives, technical solutions, and advantages of the embodiments of the present disclosure more clear, the technical solutions in the embodiments of the present disclosure will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are part of the embodiments of the present disclosure, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present disclosure without making any creative efforts shall fall within the scope of protection of the present disclosure.

[0017] Unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present disclosure can be purchased from the market or prepared by existing methods.

[0018] It should be noted that the current technologies related to ceramic inert anodes are:

[0019] (1) Ceramic alloy materials with high alloy content, whose alloy content is 30-70%. This material claims that the alloy phase can form a continuous and dense film layer with self-repairing film-forming function with the matrix oxide after oxidation during the electrolytic process, which makes the metal phase of this material relatively high.

[0020] (2) Non-carbon anode materials for oxygen-aluminum co-generation electrolysis or carbon-free aluminum electrolysis, with an alloy phase content of 21%-49%. The material claims that if the alloy phase contains iron, then the ceramic phase must have an oxide of an element more active than iron, which can be oxidized with iron to form a composite oxide; if the alloy phase does not contain iron or contains trace iron, then the ceramic phase must have excess iron oxide, which can be oxidized with the nickel element in the alloy phase to form a ferrite compound, which makes the metal phase of the material higher.

[0021] (3) Preparation method of nickel ferrite-based ceramic inert anode material for aluminum electrolysis, using titanium nitride to completely replace the metal phase, with titanium nitride accounting for 5%-20%, and sintering in an air atmosphere; in principle, titanium nitride and NiFe2O4 will be converted into titanium oxide when sintered in an air atmosphere, and will eventually be all oxide ceramic phases. Its thermal shock resistance, electrolytic application performance, and impact on impurities in electrolytic products need further evaluation.

[0022] (4) NiFe2O4-based metal ceramic inert anode material for aluminum electrolysis, wherein the metal phase accounts for 5-10% of the total mass, the titanium nitride phase accounts for 5-15% of the total mass, and the NiFe2O4-based composite ceramic accounts for 75-90% of the total mass. The preparation process is to first prepare a NiFe2O4-based composite ceramic sintered block, then crush and screen it into particles ≤74μm, and then mix and shape it with the metal phase composed of Cu and Ni and the titanium nitride phase, and sinter it in an argon protective atmosphere with an oxygen partial pressure of 10-50Pa. Although the metal phase of this material has been reduced, the maximum value is still 10%, and the oxygen partial pressure is low. The metal phase only contains Cu and Ni. Its long-term electrolysis application performance and its impact on the purity of the electrolysis product are still to be evaluated.

[0023] (5) ZrB2-based metal ceramic inert anode, in which ZrB2 as a ceramic phase accounts for 90-95%, and Cu and Ni as metallic phases account for 5-10%. After 120 hours of electrolysis experiment, aluminum with a purity of 99.1-99.5% was obtained. Although ZrB2 is the main material of the inert anode matrix, its performance in resisting the oxidation of hot oxygen generated by the inert anode electrolysis process during long-term electrolysis application needs further evaluation.

[0024] The description of the above-mentioned related technologies shows that it is difficult to balance the conductivity, corrosion resistance and thermal shock resistance of metal ceramic inert anodes. For example, when the metal phase content in the metal ceramic is high, although its conductivity and thermal shock resistance are good, the corrosion resistance and oxidation resistance of the metal phase are much lower than those of NiFe2O4 ceramics. This causes the metal phase to corrode preferentially during the electrolysis process, resulting in the purity of the aluminum produced by aluminum electrolysis being affected; and when the metal content in the metal ceramic is low, although the corrosion resistance of the metal ceramic inert anode is good, its conductivity is weakened and its brittleness is increased.

[0025] Therefore, in order to promote the advancement and industrial development of inert anode aluminum electrolysis technology, it is still necessary to further improve the comprehensive performance of inert anodes, especially for aluminum electrolysis applications. It is necessary to improve the corrosion resistance of inert anodes while taking into account electrical conductivity and thermal shock resistance.

[0026] Figure 1 exemplarily shows a schematic diagram of the product structure of a metal-ceramic inert anode material with low metal phase content according to some embodiments of the present disclosure. In Figure 1 , 1 is the metal-ceramic inert anode, and 2 is the reserved hole for connection with the metal guide rod.

[0027] As shown in FIG1 , an embodiment of the present disclosure provides a metal-ceramic inert anode material with a low metal phase content. The metal-ceramic inert anode material comprises, by mass fraction, 3% to 5% of a metal phase and 95% to 97% of a ceramic phase. The metal elements of the metal phase comprise Cu, Ni, and Fe. The ceramic phase comprises NiFe2O4·10NiO, TiN, ZrB2, and oxide additives.

[0028] In some optional embodiments, the metal phase comprises, by mass fraction, 5% to 8% Fe, 45% to 55% Cu, and the remainder Ni. It should be noted that if the Fe content in the metal phase is excessive, the excess Fe will reduce NiO in the ceramic phase of the cermet inert anode material during the subsequent sintering process. Furthermore, the excess Fe will cause the cermet inert anode material to preferentially corrode Fe during the electrolysis process in the application phase, leading to excessively high Fe impurities in the electrolysis product. In these embodiments, the Fe content in the metal phase can be 5% to 8%, which can prevent significant reduction of NiO in the ceramic phase of the cermet inert anode material during the subsequent sintering process. Furthermore, Fe will oxidize during the electrolysis process in the application phase, and the oxidized Fe can chemically react with the excess NiO in the ceramic phase of the cermet inert anode material to in-situ form a NiFe2O4 spinel corrosion-resistant layer. The Cu content in the metal phase can be 45% to 55%, as Cu is less likely to chemically react with NiO in the ceramic phase of the cermet inert anode material and less likely to produce harmful substances.

[0029] In some optional embodiments, the ceramic phase may include, by mass fraction, TiN: 15% to 20%, ZrB2: 0.5% to 5%, oxide additives: 0% to 3%, and the balance NiFe2O4·10NiO; in these embodiments, the mass fraction of TiN may be 15% to 20%, which may cause the TiN in the ceramic phase in the metal ceramic inert anode material to chemically react with the Fe2O3 and NiO in the ceramic phase NiFe2O4·10NiO in the metal ceramic inert anode material to respectively generate Ni3TiO5 and N2 and a small amount of Ni-Fe alloy phase. On the one hand, the generated Ni3TiO5 will be dispersed in the generated Ni-Fe alloy. Ni3TiO5 and the Ni-Fe alloy can pin the grain boundaries of the cermet inert anode material and enhance its conductivity. Furthermore, the generation of nitrogen (N2) creates micropores within the cermet, which enhance its thermal shock resistance and strength. Furthermore, since the solubility of Ni3TiO5 in the electrolyte melt generated during the electrolysis process during the application phase of the cermet does not significantly reduce the corrosion resistance of the ceramic phase NiFe2O4·10NiO. The mass fraction of ZrB2 can range from 0.5% to 5%. ZrB2 exhibits excellent electrical conductivity and can enhance the conductivity of the ceramic phase NiFe2O4·10NiO within the cermet.

[0030] In some optional embodiments, the oxide additives may include at least one of the following: MnO2, ZrO2, V2O5, CuO, TiO2, Y2O3, LaO, CeO2 and Nd2O5; in these embodiments, oxides such as MnO2, ZrO2, V2O5, CuO, TiO2, Y2O3, LaO, CeO2 and Nd2O5 can cover most of the existing oxide types. In addition, the above-mentioned oxide additives can, on the one hand, promote the sufficient sintering of metal ceramics to make the ceramic phase in the metal ceramic inert anode material denser, thereby improving the corrosion resistance of the metal ceramic inert anode material. On the other hand, the above-mentioned oxide additives can also avoid the generation of impurities in the metal ceramic inert anode material during the electrolysis process in the application stage.

[0031] FIG2 exemplarily shows a flow chart of a method for preparing a metal-ceramic inert anode material according to some embodiments of the present disclosure; as shown in FIG2 , the present disclosure provides a method for preparing the above-mentioned metal-ceramic inert anode material, the method comprising: step S1. mixing metal powder, NiFe2O4·10NiO ceramic powder, TiN ceramic powder, ZrB2 ceramic powder and oxide additives to obtain a first mixed powder; step S2. mixing an adhesive and the first mixed powder, and grinding them to obtain a second mixed powder; step S3. drying the second mixed powder, and then sieving it to obtain a metal-ceramic mixed powder; and step S4. molding the metal-ceramic mixed powder. forming, and then degreasing and sintering to obtain a metal ceramic inert anode material; in these embodiments, the raw materials of the metal ceramic inert anode material, such as metal powder, NiFe2O4·10NiO ceramic powder, TiN ceramic powder, ZrB2 ceramic powder and oxide additives, are first mixed to obtain a first mixed powder, and then a binder is added to the first mixed powder, and then the first mixed powder is ground to obtain a uniformly dispersed second mixed powder, and then the second mixed powder is dried and sieved to prepare a metal ceramic mixed powder, and then the metal ceramic mixed powder is sequentially subjected to compression molding and degreasing sintering to obtain a pure metal ceramic inert anode material.

[0032] This method is a method for preparing the above-mentioned metal ceramic inert anode material. The specific steps of the metal ceramic inert anode material can refer to the above-mentioned embodiment. Since the metal ceramic inert anode material adopts part or all of the technical solutions of the above-mentioned embodiment, it at least has all the beneficial effects brought by the technical solutions of the above-mentioned embodiment, which will not be repeated here.

[0033] It should be noted that the drying temperature may be 60° C. to 80° C., which can ensure that the mixed powder is completely dried and also control the moisture content of the second mixed powder to be 1 wt %.

[0034] It should be noted that the sieve aperture used for the screening may be 20 meshes.

[0035] It should be noted that the pressure used for compression molding can be 120MPa to 150MPa, and the device used for compression molding can be a hydraulic press or a cold isostatic press; wherein, the holding time during compression on the hydraulic press can be 1min to 3min, and the holding time during compression on the cold isostatic press can be 5s to 30s. The compression molding pressure can be 120MPa to 150MPa, and the holding time of different compression molding devices can be 5s to 30s, which can promote the complete molding of the metal-ceramic mixed powder, thereby obtaining a metal-ceramic mixed powder with sufficient bonding strength and dense distribution.

[0036] It should be noted that the first mixed powder refers to an overall mixed powder of solid phase materials, including solid phase powder components such as metal powder, NiFe2O4·10NiO ceramic powder, TiN ceramic powder, ZrB2 ceramic powder and oxide additives.

[0037] It should be noted that the second mixed powder refers to a mixture obtained by grinding after adding a binder, and may include a mixed powder component of a binder, metal powder, NiFe2O4·10NiO ceramic powder, TiN ceramic powder, ZrB2 ceramic powder and oxide additives. The second mixed powder has certain wettability.

[0038] It should be noted that the purity of the TiN ceramic powder, the ZrB2 ceramic powder and the oxide additive is respectively above 99.9%, and the particle size of the TiN ceramic powder, the ZrB2 ceramic powder and the oxide additive is 200 mesh to 500 mesh.

[0039] In some optional embodiments, the mass ratio of the adhesive to the mixed powder is 10% to 50%. In these embodiments, the mass ratio of the adhesive to the mixed powder can be 10% to 50%, and the mixed powder can be completely bonded by the adhesive to facilitate the subsequent compression molding in the preparation process of the metal ceramic inert anode material, thereby ultimately obtaining the metal ceramic inert anode material.

[0040] The mass ratio of the adhesive to the mixed powder can be 10%, 15%, 20%, 15%, 30%, 35%, 40%, 45% or 50%.

[0041] In some optional embodiments, the adhesive may include a polyvinyl alcohol solution, and the mass concentration of the polyvinyl alcohol solution is 8% to 12%; in these embodiments, the type of adhesive may include a polyvinyl alcohol solution, and the mass concentration of the polyvinyl alcohol solution may be 8% to 12%. The adhesive can further promote the complete bonding of the mixed powder, thereby facilitating the subsequent molding process of the metal ceramic inert anode material preparation process, thereby obtaining the metal ceramic inert anode material.

[0042] The mass concentration of the polyvinyl alcohol solution can be 8%, 9%, 10%, 11% or 12%.

[0043] In some optional embodiments, the metal powder includes single metal powders of Cu, Ni, and Fe or ternary alloy powder containing Cu, Ni, and Fe elements. The particle size of the Cu single metal powder, the Ni single metal powder, the Fe single metal powder, and the ternary alloy powder is 80 mesh to 300 mesh. In these embodiments, the metal powder may include single metal powders of Cu, Ni, and Fe or ternary alloy powder containing Cu, Ni, and Fe elements, and the particle size of the Cu single metal powder, the Ni single metal powder, the Fe single metal powder, and the overall metal powder may be 80 mesh to 300 mesh, respectively. These limiting conditions can facilitate the uniform mixing of the metal powder and the ceramic powder in the metal ceramic inert anode material.

[0044] It should be noted that if the metal powder in the metal ceramic inert anode material adopts a ternary alloy powder containing Cu, Ni and Fe elements, the metal ceramic inert anode material needs to be annealed at a temperature of 400°C to 600°C in an atmosphere of pure nitrogen or argon, and the annealing time can be 1h to 2h; after this annealing treatment, the activity of the ternary alloy powder of the metal powder in the metal ceramic inert anode material can be activated.

[0045] In some optional embodiments, the debinding and sintering includes a debinding stage and a high-pressure sintering stage, and the debinding stage includes debinding in an oxygen-free environment;

[0046] The high-pressure sintering stage includes sintering under conditions of a preset oxygen concentration, the preset oxygen concentration is 100ppm~500ppm, and the sintering temperature is 1200℃~1400℃; in these embodiments, the degreasing sintering can include a degreasing stage and a high-pressure sintering stage. In addition, the preset oxygen concentration of the high-pressure sintering stage can be 100ppm~500ppm and the high-pressure sintering temperature can be 1200℃~1400℃. The degreasing stage can be used first to fully remove impurities in the formed metal ceramic block, and then the high-pressure sintering stage can be used to transform the formed metal ceramic block into a metal ceramic inert anode material.

[0047] The preset oxygen concentration may be 100 ppm, 150 ppm, 200 ppm, 250 ppm, 300 ppm, 350 ppm, 400 ppm, 450 ppm or 500 ppm.

[0048] The sintering temperature may be 1200°C, 1250°C, 1300°C, 1350°C or 1400°C.

[0049] FIG3 exemplarily shows a detailed flow chart of a method for preparing a metal-ceramic inert anode material according to some embodiments of the present disclosure. As shown in FIG3 , in some optional embodiments, the steps for preparing the NiFe2O4·10NiO ceramic powder may include:

[0050] Step S101. Fe2O3 powder and NiO powder are mixed by wet grinding, and then dried to obtain NiFe2O4·10NiO ceramic powder precursor;

[0051] Step S102: calcining the NiFe2O4·10NiO ceramic powder precursor to obtain NiFe2O4·10NiO ceramic powder;

[0052] In the wet grinding of the above steps, the volume ratio of the dispersion medium to the precursor mixture is 1.5 to 2. In these embodiments, the preparation stage of the refined NiFe2O4·10NiO ceramic powder can include mixing, drying and calcining by wet grinding. The wet grinding method can be used to fully grind the Fe2O3 powder and NiO powder in the NiFe2O4·10NiO ceramic powder raw material, so that the Fe2O3 powder and NiO powder in the NiFe2O4·10NiO ceramic powder raw material in the subsequent preparation step are fully calcined to form NiFe2O4·10NiO ceramic powder. The volume ratio of the dispersion medium to the precursor mixture in the wet grinding stage can be 1.5 to 2. The Fe2O3 powder and NiO powder can be fully dispersed by the dispersion medium, so that the Fe2O3 powder and NiO powder in the NiFe2O4·10NiO ceramic powder raw material in the subsequent preparation stage are fully calcined to obtain NiFe2O4·10NiO ceramic powder.

[0053] It should be noted that the dispersion medium can be deionized water or ethanol, or a mixture of deionized water and ethanol.

[0054] It should be noted that the volume ratio of the dispersion medium to the precursor mixture may be 1.5, 1.6, 1.7, 1.8, 1.9 or 2.0.

[0055] It should be noted that the purity of the Fe2O3 powder and the NiO powder is respectively above 99.9%, and the particle sizes of the Fe2O3 powder and the NiO powder are respectively 200 mesh to 500 mesh.

[0056] The present disclosure will be further described below with reference to specific examples. It should be understood that these examples are intended to illustrate the present disclosure only and are not intended to limit the scope of the present disclosure. Experimental methods in the following examples where specific conditions are not specified are generally measured in accordance with industry standards. If no corresponding industry standards are available, the methods were performed in accordance with commonly used international standards, conventional conditions, or conditions recommended by the manufacturer.

[0057] Example 1

[0058] A method for preparing a cermet inert anode material with low metal phase content, comprising:

[0059] (1) Fe2O3 powder and NiO powder were weighed at 62% and 38% by mass, respectively. Deionized water was used as the dispersion medium, and the volume ratio of the dispersion medium to the powder was controlled to be 1.5. The Fe2O3 powder and NiO powder were ball-milled for 4 hours and then dried in a forced air drying oven to obtain a NiFe2O4·10NiO ceramic powder precursor. The particle size of the Fe2O3 powder and the NiO powder was 500 mesh, and the particle size of the NiO powder was 200 mesh.

[0060] (2) A NiFe2O4·10NiO ceramic powder precursor was placed in a corundum crucible and fired at 1000°C for 4 h in an electric furnace under air atmosphere to obtain NiFe2O4-10NiO ceramic powder.

[0061] (3) A metal-ceramic mixed powder is prepared according to a mass ratio of 5% of the metal phase to 95% of the ceramic phase to obtain a first mixed powder. In the first mixed powder, the metal phase is a mixture of three elemental powders of Cu, Ni and Fe, the mass proportion of 80-mesh Cu powder in the metal phase is 55%, the mass proportion of 300-mesh Fe powder in the metal phase is 8%, and the mass proportion of 300-mesh Ni powder in the metal phase is 37%; 500-mesh TiN powder accounts for 15% of the total weight of the metal ceramic, 300-mesh ZrB2 powder accounts for 0.5% of the total weight of the metal ceramic, NiFe2O4-10NiO ceramic powder accounts for 77% of the total weight of the metal ceramic, Y2O3 accounts for 1% of the total weight of the metal ceramic, and MnO2 accounts for 1.5% of the total weight of the metal ceramic; a polyvinyl alcohol solution with a mass fraction of 10% is used as a binder, and the addition amount is 30% of the total weight of the first mixed powder, and a small amount of deionized water is added to submerge the first mixed powder; the mixture of the binder and the first mixed powder is then ball-milled for 6 hours and then dried in an oven at 60°C to 80°C to control the moisture content to 1%, thereby obtaining a second mixed powder.

[0062] (4) Sieve the second mixed powder with a 20-mesh sieve, and the material under the sieve is used as the metal-ceramic mixed powder to be pressed into shape.

[0063] (5) Using a hydraulic press, the metal-ceramic mixed powder was pressurized at a pressure of 150 MPa for 1 minute to prepare disc-shaped and square-shaped sample green bodies, which were then degreased and sintered. The degreasing process was maintained at 600°C in a pure nitrogen atmosphere for 2 hours. The sintering process used a nitrogen atmosphere with an oxygen concentration of 100 ppm and was maintained at 1200°C for 6 hours to obtain a metal-ceramic inert anode material.

[0064] (6) The prepared metal ceramic inert anode material was subjected to thermal shock resistance test, conductivity measurement, static chemical corrosion and 20A electrolysis test respectively. The relevant detection methods in each experiment are as follows:

[0065] 1) The thermal shock resistance test method is as follows: place the inert anode sample in a furnace preheated to 800°C, keep it warm for 30 minutes, remove the sample, cool it to room temperature in air for 15 minutes, and then place it back in the furnace. Repeat the above steps until the circular sample breaks. The number of thermal cycles is used to indicate its thermal shock resistance.

[0066] 2) Conductivity measurement is performed by fixing a regularly shaped inert anode sample between two parallel plates, applying direct current, measuring the voltage across the sample, and calculating the conductivity σ (S / cm) using the formula: σ = (IL) / (US). Where S is the cross-sectional area of ​​the sample (cm²); L is the length of the sample (cm); I is the applied current (A); and U is the voltage across the sample (V).

[0067] 3) Static chemical etching method: Place an inert anode sample at the bottom of a corundum crucible filled with 200g of electrolyte; the electrolyte is a KF-NaF-AlF3 electrolyte system with a KF content of 15wt% and a NaF:AlF3 molar ratio of 1.0. Raise the furnace temperature to 800°C and hold for 24 hours. Remove the electrolyte and analyze the metal element content. The metal element content refers to all metal elements in the inert anode sample.

[0068] 4) 20A electrolysis experiment: The product structure shown in Figure 1 was used as an inert anode for the 20A electrolysis experiment. In Figure 1, 1 is a metal ceramic inert anode, and 2 is a reserved hole for connection to the metal guide rod. The reserved hole was machined using a hollow diamond drill bit, and the hollow diamond drill bit was a commercially available product.

[0069] 5) A crucible filled with electrolyte was preheated to 800°C in a pit furnace. The electrolyte was a KF-NaF-AlF3 system with a KF content of 15 wt% and a NaF to AlF3 molar ratio of 1.0. After the electrolyte was completely melted, an inert anode and two wettable cathodes made of TiB2-C hot-pressed ceramic were placed in parallel and spaced apart. The inert anode and wettable cathodes were connected by stainless steel rods. The inert anode was positioned between the two wettable cathodes, with the top of the inert anode slightly exposed above the electrolyte surface. A 20A DC current was applied from the anode to the cathode for 24 hours. After the experiment was completed and cooled, the aluminum block formed at the bottom of the crucible was removed and the impurity content in the block was measured.

[0070] The results show that the thermal shock resistance of the metal ceramic inert anode material is 6 times, the room temperature conductivity is 32.3S / cm, the total amount of Ni, Fe, Cu, Ti, and Zr elements in the electrolyte after 24 hours of static chemical corrosion is 0.0332%, and the total amount of Ni, Fe, Cu, Ti, and Zr elements in the aluminum produced after a 20A electrolysis experiment is 0.288%.

[0071] Example 2

[0072] A method for preparing a cermet inert anode material with low metal phase content, comprising:

[0073] (1) Fe2O3 powder and NiO powder were weighed at mass fractions of 62% and 38%, respectively. Deionized water was used as the dispersion medium, and the volume ratio of the dispersion medium to the powder was controlled to be 1.5. The Fe2O3 powder and NiO powder were ball-milled for 4 hours and then dried in a forced air drying oven to obtain a NiFe2O4·10NiO ceramic powder precursor. The Fe2O3 powder and NiO powder had a particle size of 500 mesh and a particle size of 200 mesh, respectively.

[0074] (2) A NiFe2O4·10NiO ceramic powder precursor was placed in a corundum crucible and fired at 900°C for 6 h in an electric furnace under air atmosphere to obtain NiFe2O4-10NiO ceramic powder.

[0075] (3) A metal-ceramic mixed powder is prepared according to a mass ratio of 5% of the metal phase and 95% of the ceramic phase to obtain a first mixed powder. In the first mixed powder, the metal phase is a Cu-Ni-Fe ternary alloy powder with a particle size of 300 meshes. The mass ratios of Cu, Ni, and Fe in the ternary alloy powder are 45%, 50%, and 5%, respectively. The ternary alloy powder is annealed at 400°C for 1 hour in a pure nitrogen atmosphere before use; 500-mesh TiN powder accounts for 15% of the total weight of the metal ceramic, 300-mesh ZrB2 powder accounts for 1% of the total weight of the metal ceramic, and NiFe2O4-10NiO ceramic powder accounts for 1% of the total weight of the metal ceramic. The weight of the first mixed powder is 76%, the weight of the 200-mesh MnO2 is 2.0%, and the weight of the ZrO2 as an additive is 1% of the total weight of the metal ceramic; a polyvinyl alcohol solution with a mass fraction of 10% is used as a binder, and the addition amount is 30% of the total weight of the first mixed powder, and a small amount of deionized water is added to submerge the first mixed powder; the mixture of the binder and the first mixed powder is ball-milled for 6 hours and then dried in an oven at 60°C to 80°C to control the moisture content to 1% to obtain a second mixed powder.

[0076] (4) Sieve the second mixed powder with a 20-mesh sieve, and the material under the sieve is used as the metal-ceramic mixed powder to be pressed into shape.

[0077] (5) A hydraulic press was used to pressurize the metal-ceramic mixed powder at a pressure of 120 MPa for 2 minutes to prepare disc-shaped and square-shaped sample green bodies, which were then degreased and sintered. The degreasing process was maintained at 600°C in a pure nitrogen atmosphere for 2 hours; the sintering process used a nitrogen atmosphere with an oxygen concentration of 300 ppm and was maintained at 1250°C for 4 hours to obtain a metal-ceramic inert anode material.

[0078] (6) The prepared metal ceramic inert anode material was subjected to the above-mentioned thermal shock resistance test, conductivity measurement, static chemical corrosion and 20A electrolysis test.

[0079] The results show that the thermal shock resistance of the metal ceramic inert anode material is 6 times, the room temperature conductivity is 31.2S / cm, the total amount of Ni, Fe, Cu, Ti, and Zr elements in the electrolyte after 24 hours of static chemical corrosion is 0.0312%, and the total amount of Ni, Fe, Cu, Ti, and Zr elements in the aluminum produced after a 20A electrolysis experiment is 0.291%.

[0080] Example 3

[0081] A method for preparing a cermet inert anode material with low metal phase content, comprising:

[0082] (1) Fe2O3 powder and NiO powder were weighed at 62% and 38% by mass, respectively. Deionized water was used as the dispersion medium, and the volume ratio of the dispersion medium to the powder was controlled to be 2. The Fe2O3 powder and NiO powder were ball-milled for 6 hours and then dried in a forced air drying oven to obtain a NiFe2O4·10NiO ceramic powder precursor. The particle size of the Fe2O3 powder and the NiO powder was 500 mesh, and the particle size of the NiO powder was 200 mesh.

[0083] (2) A NiFe2O4·10NiO ceramic powder precursor was placed in a corundum crucible and fired at 1000°C for 4 h in an electric furnace under air atmosphere to obtain NiFe2O4-10NiO ceramic powder.

[0084] (3) A metal-ceramic mixed powder is prepared according to a mass ratio of 4% of the metal phase and 96% of the ceramic phase to obtain a first mixed powder. In the first mixed powder, the metal phase is a Cu-Ni-Fe ternary alloy powder with a particle size of 300 mesh, and the mass ratios of Cu, Ni and Fe elements in the ternary alloy powder are 45%, 50% and 5% respectively. The ternary alloy powder is annealed at 400°C for 2 hours in a pure nitrogen atmosphere before use; 500 mesh TiN powder accounts for 18% of the total weight of the metal ceramic, 500 mesh ZrB2 powder accounts for 2% of the total weight of the metal ceramic, NiFe2O4-10NiO ceramic powder accounts for 73% of the total weight of the metal ceramic, and 200 mesh V2O5 as an additive accounts for 3.0% of the total weight of the metal ceramic; a polyvinyl alcohol solution with a mass fraction of 10% is used as a binder, and the addition amount is 10% of the total weight of the first mixed powder, and a small amount of deionized water is added to submerge the first mixed powder; the mixture of the binder and the first mixed powder is then ball-milled for 4 hours and then dried in an oven at 60°C to 80°C to control the moisture content to 1%, thereby obtaining a second mixed powder.

[0085] (4) Sieve the second mixed powder through a 20-mesh sieve, and the material under the sieve is used as the metal-ceramic mixed powder to be pressed into shape.

[0086] (5) A hydraulic press was used to pressurize the metal-ceramic mixed powder at a pressure of 120 MPa for 2 minutes to prepare disc-shaped and square-shaped sample green bodies, which were then degreased and sintered. The degreasing process was maintained at 600°C in a pure nitrogen atmosphere for 2 hours; the sintering process used a nitrogen atmosphere with an oxygen concentration of 400 ppm and was maintained at 1300°C for 4 hours to obtain a metal-ceramic inert anode material.

[0087] (6) The prepared metal ceramic inert anode material was subjected to the above-mentioned thermal shock resistance test, conductivity measurement, static chemical corrosion and 20A electrolysis test.

[0088] The results show that the thermal shock resistance of the metal ceramic inert anode material is 6 times, the room temperature conductivity is 34.5S / cm, the total amount of Ni, Fe, Cu, Ti, Zr, and V elements in the electrolyte after 24 hours of static chemical corrosion is 0.0287%, and the total amount of Ni, Fe, Cu, Ti, Zr, and V elements in the aluminum produced after a 20A electrolysis experiment is 0.284%.

[0089] Example 4

[0090] A method for preparing a cermet inert anode material with low metal phase content, comprising:

[0091] (1) Fe2O3 powder and NiO powder were weighed at mass fractions of 62% and 38%, respectively. Deionized water was used as the dispersion medium, and the volume ratio of the dispersion medium to the powder was controlled to be 1.5. The Fe2O3 powder and NiO powder were ball-milled for 4 hours and then dried in a forced air drying oven to obtain a NiFe2O4·10NiO ceramic powder precursor. The Fe2O3 powder and NiO powder had a particle size of 500 mesh and a particle size of 200 mesh, respectively.

[0092] (2) A NiFe2O4·10NiO ceramic powder precursor was placed in a corundum crucible and fired at 1000°C for 4 h in an electric furnace under air atmosphere to obtain NiFe2O4-10NiO ceramic powder.

[0093] (3) A metal-ceramic mixed powder is prepared according to a mass ratio of 5% of the metal phase to 95% of the ceramic phase to obtain a first mixed powder. In the first mixed powder, the metal phase is a Cu-Ni-Fe ternary alloy powder with a particle size of 300 mesh, and the mass ratios of Cu, Ni and Fe elements in the ternary alloy powder are 45%, 50% and 5% respectively. The ternary alloy powder is annealed at 400°C for 1 hour in a pure nitrogen atmosphere before use; 500-mesh TiN powder accounts for 20% of the total weight of the metal ceramic, 300-mesh ZrB2 powder accounts for 5% of the total weight of the metal ceramic, and NiFe2O4-10NiO ceramic powder accounts for 70% of the total weight of the metal ceramic, and no additives are added; a polyvinyl alcohol solution with a mass fraction of 12% is used as a binder, and the addition amount is 20% of the total weight of the first mixed powder, and a small amount of deionized water is added to submerge the first mixed powder; the mixture of the binder and the first mixed powder is then ball-milled for 6 hours and then dried in an oven at 60°C to 80°C to control the moisture content to 1%, thereby obtaining a second mixed powder.

[0094] (4) Sieve the second mixed powder with a 20-mesh sieve, and the material under the sieve is used as the metal-ceramic mixed powder to be pressed into shape.

[0095] (5) A hydraulic press was used to pressurize the metal-ceramic mixed powder at a pressure of 120 MPa for 2 minutes to prepare disc-shaped and square-shaped sample green bodies, which were then degreased and sintered. The degreasing process was maintained at 600°C in a pure nitrogen atmosphere for 2 hours; the sintering process used a nitrogen atmosphere with an oxygen concentration of 200 ppm and was maintained at 1250°C for 4 hours.

[0096] (6) The prepared metal ceramic inert anode material was subjected to the above-mentioned thermal shock resistance test, conductivity measurement, static chemical corrosion and 20A electrolysis test.

[0097] The results show that the thermal shock resistance of the metal ceramic inert anode material is 5 times, the room temperature conductivity is 35.3S / cm, the total amount of Ni, Fe, Cu, Ti, and Zr elements in the electrolyte after 24 hours of static chemical corrosion is 0.0291%, and the total amount of Ni, Fe, Cu, Ti, and Zr elements in the aluminum produced after a 20A electrolysis experiment is 0.298%.

[0098] Example 5

[0099] A method for preparing a cermet inert anode material with low metal phase content, comprising:

[0100] (1) Fe2O3 powder and NiO powder were weighed at mass fractions of 62% and 38%, respectively. Deionized water was used as the dispersion medium, and the volume ratio of the dispersion medium to the powder was controlled to be 2. The Fe2O3 powder and NiO powder were ball-milled for 6 hours and then dried in a forced air drying oven to obtain a NiFe2O4·10NiO ceramic powder precursor. The Fe2O3 powder and NiO powder had a particle size of 500 mesh and a particle size of 200 mesh, respectively.

[0101] (2) A NiFe2O4·10NiO ceramic powder precursor was placed in a corundum crucible and fired at 1100°C for 4 h in an electric furnace under air atmosphere to obtain NiFe2O4-10NiO ceramic powder.

[0102] (3) A metal-ceramic mixed powder is prepared according to a mass ratio of 3% metal phase to 97% ceramic phase to obtain a first mixed powder. In the first mixed powder, the metal phase is a Cu-Ni-Fe ternary alloy powder with a particle size of 300 mesh, and the mass ratios of Cu, Ni and Fe elements in the ternary alloy powder are 45%, 50% and 5% respectively. The ternary alloy powder is annealed at 600°C for 1 hour in a pure nitrogen atmosphere before use; 500 mesh TiN powder accounts for 20% of the total weight of the metal ceramic, 300 mesh ZrB2 powder accounts for 3% of the total weight of the metal ceramic, NiFe2O4-10NiO ceramic powder accounts for 71% of the total weight of the metal ceramic, and 200 mesh MnO2 as an additive accounts for 3% of the total weight of the metal ceramic; a polyvinyl alcohol solution with a mass fraction of 8% is used as a binder, and the addition amount is 50% of the total weight of the first mixed powder; the mixture of the binder and the first mixed powder is ball-milled for 4 hours and then dried in an oven at 60°C to 80°C to control the moisture content to 1%, thereby obtaining a second mixed powder.

[0103] (4) Sieve the second mixed powder with a 20-mesh sieve, and the material under the sieve is used as the metal-ceramic mixed powder to be pressed into shape.

[0104] (5) A hydraulic press was used to pressurize the metal-ceramic mixed powder at a pressure of 150 MPa for 3 minutes to prepare disc-shaped and square-shaped sample green bodies, which were then degreased and sintered. The degreasing process was maintained at 600°C in a pure nitrogen atmosphere for 2 hours; the sintering process used a nitrogen atmosphere with an oxygen concentration of 500 ppm and was maintained at 1400°C for 4 hours to obtain a metal-ceramic inert anode material.

[0105] (6) The prepared metal ceramic inert anode material was subjected to the above-mentioned thermal shock resistance test, conductivity measurement, static chemical corrosion and 20A electrolysis test.

[0106] The results show that the thermal shock resistance of the metal ceramic inert anode material is 5 times, the room temperature conductivity is 37.1S / cm, the total amount of Ni, Fe, Cu, Ti, Zr, and Mn elements in the electrolyte after 24 hours of static chemical corrosion is 0.0282%, and the total amount of Ni, Fe, Cu, Ti, Zr, and Mn elements in the aluminum produced after a 20A electrolysis experiment is 0.279%.

[0107] In summary, the embodiment of the present disclosure provides a metal ceramic inert anode material with low metal phase content, which controls the mass fraction of the metal phase to be 3% to 5%. Not only is its metal phase content lower than that of traditional inert anode materials, but its corrosion resistance is also significantly improved.

[0108] In addition, the metal ceramic inert anode material well takes into account the electrical conductivity, corrosion resistance and thermal shock resistance of the metal ceramic inert anode.

[0109] And in the electrolysis experiment, aluminum products with a total impurity content of less than 0.3% can be obtained.

[0110] The above technical solution provided by the embodiments of the present disclosure has the following advantages compared with the prior art:

[0111] According to some embodiments of the present disclosure, a metal-ceramic inert anode material with low metal phase content is provided: the overall proportion of the metal phase in the metal-ceramic inert anode material is controlled to be reduced to 3% to 5%. At this time, the role of the metal phase is no longer to improve the conductivity of the metal ceramic, but to achieve metal phase oxidation during the electrolysis process. After oxidation, the metal phase will expand in volume to block the pores of the anode substrate and the metal phase corrosion channels, and will also generate a dense corrosion-resistant layer mainly composed of spinels such as NiFe2O4 in situ with the ceramic phase. The dense corrosion-resistant layer can slow down or block the continuous corrosion of the metal phase, and improve the toughness and overall thermal shock resistance of the metal-ceramic anode; and, Ti is added to the ceramic phase. N and ZrB2, TiN reacts with Fe2O3 and NiO in the ceramic phase to produce Ni3TiO5, N2, and a small amount of Ni-Fe alloy phase. The Ni3TiO5 and Ni-Fe alloy dispersed at the grain boundaries act as pinning and enhance the conductivity of the cermet inert anode material. Furthermore, N2 escape leaves micropores within the cermet inert anode material. These processes enhance the thermal shock resistance and strength of the cermet. Furthermore, ZrB2 has good electrical conductivity and can enhance the conductivity of NiFe2O4 after sintering. Furthermore, the addition of oxide additives can assist in the thorough sintering process, making the ceramic phase denser and improving corrosion resistance. Therefore, by designing the composition of the cermet inert anode material, the difficult problem of balancing electrical conductivity, corrosion resistance, and thermal shock resistance in cermet inert anodes has been solved.

[0112] Various embodiments of the present disclosure may be presented in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of the present disclosure; therefore, the range description should be considered to have specifically disclosed all possible sub-ranges and single numbers within the range. For example, the description of a range from 1 to 6 should be considered to have specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. In addition, whenever a numerical range is indicated herein, it is meant to include any cited number (fractional or integer) within the indicated range.

[0113] In the present disclosure, unless otherwise specified, the directional words used, such as "upper" and "lower", specifically refer to the directions of the drawings in the accompanying drawings. In addition, in the description of the present disclosure, the terms "including", "comprising", etc. mean "including but not limited to". In this article, relational terms such as "first" and "second" are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply that there is any such actual relationship or order between these entities or operations. In this article, "and / or" describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. Wherein A and B can be singular or plural. In this article, "at least one" refers to one or more, and "plurality" refers to two or more. "At least one", "at least one of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, c can be single or multiple.

[0114] The foregoing description is intended only to provide specific embodiments of the present disclosure, intended to enable those skilled in the art to understand and implement the present disclosure. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present disclosure. Therefore, the present disclosure is not to be limited to the embodiments shown herein, but is to be construed in the broadest manner consistent with the principles and novel features claimed herein.

Claims

1. A low metallic phase inert anode metal-ceramic material containing by mass fraction: 3-5% metallic phase and 95-97% ceramic phase; wherein the metallic elements of the metallic phase comprise Cu, Ni and Fe; and the ceramic phase comprises NiFe₂O₄ 10NiO, TiN, ZrB₂ and an oxide additive.

2. The metal-ceramic material of the inert anode according to claim 1, in which the metallic phase contains by mass fraction: Cu: from 45% to 55%, Fe: from 5% to 8%, and the rest Ni.

3. The metal-ceramic material of the inert anode according to claim 1, wherein the ceramic phase contains by mass fraction: TiN: from 15% to 20%, ZrB₂: from 0.5% to 5%, oxide additive: from 0% to 3%, and the remainder NiFe₂O₄ 10NiO.

4. The metal-ceramic inert anode material according to claim 3, wherein the oxide additive contains at least one of the following: MnO₂, ZrO₂, V₂O₅, CuO, TiO₂, Y₂O₃, LaO, CeO₂ and Nd₂O₅.

5. A method for manufacturing a metal-ceramic material of an inert anode according to any of paragraphs 1-4, comprising: mixing the metal powder, the NiFe₂O₄·10NiO ceramic powder, the TiN ceramic powder, the ZrB₂ ceramic powder and the oxide additive to obtain the first mixed powder; mixing the binder and the first mixed powder and grinding the resulting mixture to obtain a second mixed powder; drying the second mixed powder and sieving the dried second mixed powder to obtain a metal-ceramic mixed powder; and forming a metal-ceramic mixed powder; followed by removal of the binder and sintering to obtain a metal-ceramic inert anode material.

6. The method according to claim 5, wherein the weight ratio between the binder and the mixed powder is from 10% to 50%.

7. The method according to claim 6, wherein the binder comprises a solution of polyvinyl alcohol, and the mass concentration of the solution of polyvinyl alcohol is from 8% to 12%.

8. The method according to claim 5, wherein the metal powder comprises powders of the metallic elements Cu, Ni and Fe or a powder of a three-component alloy containing the elements Cu, Ni and Fe; The Cu metallic element powder, Ni metallic element powder, Fe metallic element powder and ternary alloy powder have a particle size in the range of 80 mesh to 300 mesh.

9. The method of claim 5, wherein the debinding and sintering comprises a debinding step and an atmospheric sintering step, wherein the debinding step comprises performing the debinding in an oxygen-free environment; the atmosphere sintering step includes performing sintering under conditions of a predetermined oxygen concentration, wherein the predetermined oxygen concentration is from 100 ppm to 500 ppm, the sintering temperature is from 1200°C to 1400°C.

10. The method according to claim 5, wherein the production of the ceramic powder NiFe₂O₄·10NiO comprises: mixing Fe₂O₃ powder and NiO powder by wet milling followed by drying to obtain the starting material of NiFe₂O₄·10NiO ceramic powder; and firing the starting material of NiFe₂O₄·10NiO ceramic powder to produce NiFe₂O₄·10NiO ceramic powder; in which, during wet milling, the volume ratio between the dispersion medium and the mixture of the starting material is from 1.5 to 2.