Preparation method and application of nickel ferrite-based eutectic cermet inert anode material

Abstract

The application discloses a preparation method and application of a nickel ferrite-based eutectic cermet inert anode material. The disclosed method melts a nickel ferrite-based cermet pre-sintered body through high-temperature melting, controls the cooling solidification and heat treatment process, and regulates the microstructure of the cermet, so that a eutectic cermet inert anode with good performance is prepared. The overall performance of the cermet inert anode is greatly improved, including conductivity, thermal shock resistance, molten salt corrosion resistance and the like. The preparation process is simple, can be easily combined with other materials, and is convenient for industrialization.

Description

TECHNICAL FIELD

[0001] The present application relates to aluminum electrolysis related technology, in particular to a eutectic metal ceramic inert anode material and a preparation method and application thereof. BACKGROUND

[0002] Nickel ferrite ceramic has become a hot ceramic material in the field of electrolytic aluminum industry in recent decades due to its good electrical conductivity and certain high-temperature molten salt corrosion resistance. The main reason is that this kind of ceramic inert anode can reduce carbon emissions in the process of electrolytic aluminum electrolysis.

[0003] In order to achieve the balance of density, mechanical properties and electrical conductivity and high-temperature molten salt corrosion resistance, different metal components are often added to improve the electrical conductivity of the nickel ferrite-based ceramic inert anode to form a large class of metal ceramic anode materials.

[0004] According to the actual production condition test research, through the high-temperature molten salt corrosion experiment, the metal and the grain boundary of the ceramic inert anode are preferentially corroded in the electrolysis process, so that micropores are easily generated on the surface of the metal ceramic inert anode, which provides a penetration channel for the high-temperature molten salt electrolyte, and the metal ceramic inert anode is further electrochemically and chemically corroded.

[0005] In order to improve the corrosion resistance of the metal ceramic anode, many methods and measures for improving the sintering density of the ceramic are proposed in the prior art, but the effect of improving the corrosion resistance of the metal ceramic material is not good. In addition, according to the traditional metal ceramic sintering process, it is very difficult to sinter a large metal ceramic anode, and the industrial manufacturing of this kind of anode material is extremely difficult, and the forming and sintering process technology is complex, which limits the application of the metal ceramic anode in the electrolytic aluminum industry. SUMMARY

[0006] In view of the defects or deficiencies of the prior art, the present application provides a preparation method of a nickel ferrite-based eutectic metal ceramic inert anode material.

[0007] Therefore, the preparation method of the nickel ferrite-based eutectic metal ceramic inert anode material provided by the present application comprises:

[0008] Step 1, preparing a pre-sintered body:

[0009] The mixed powder of the NiFe2O4-based spinel powder, the nickel pyrochlore powder, the non-oxide ceramic powder and the metal powder is mixed with a binder to form 10-30 mesh granules, and then the granules are pressed into green bodies under a pressure of 100-200 MPa; and then the green bodies are pre-sintered in an inert gas protective atmosphere at 1200-1400℃ for 3-5 hours to obtain a metal ceramic pre-sintered body;

[0010] The non-oxide ceramic powder contains MXene, ZrB2, TiB2, TiN and VN; the metal powder is selected from a mixture of two or more of Co powder, Fe powder, Ni powder, Ti powder and Cu powder;

[0011] The total mass of the NiFe2O4-based spinel powder, the nickel pyrochlore powder and the non-oxide ceramic powder accounts for 50wt% to 90wt% and the mass of the metal powder accounts for 10wt% to 50wt% based on 100% of the mass ratio;

[0012] The mass of the NiFe2O4-based spinel powder accounts for 40wt% to 70wt%, the mass of the nickel pyrochlore powder accounts for 10wt% to 20wt% and the mass of the non-oxide ceramic powder accounts for 20wt% to 40wt% based on 100% of the mass ratio;

[0013] The binder is selected from one or a mixture of both of polyvinyl alcohol and polyethylene glycol, and the mass of the binder is 0.5wt% to 2wt% of the total mass of the NiFe2O4-based spinel powder, the nickel pyrochlore powder, the non-oxide ceramic powder and the metal powder;

[0014] Step 2, melting and solidification of the pre-sintered body:

[0015] The pre-sintered body is heated and melted in an inert gas protection gas so that the pre-sintered body is in a molten state; then it is cooled and solidified at a cooling rate of 1-100℃ / min, or it is cast after being in a molten state and cooled and solidified at a cooling rate of 1-100℃ / min to obtain a ceramic solidified body;

[0016] Step 3, heat treatment:

[0017] The ceramic solidified body obtained in Step 2 is treated at a temperature of 1250-1500℃ for 2-6 hours to adjust the microstructure and eliminate stress, and then cooled to room temperature at a cooling rate of 1-50℃ / min to obtain a nickel ferrite-based eutectic metal ceramic inert anode material.

[0018] Optionally, the particle size of the mixed powder is less than 100 mesh.

[0019] Optionally, in Step 1, the NiFe2O4-based spinel powder, the nickel pyrochlore powder, the non-oxide ceramic powder, the metal powder, the dispersant and water are mixed and ball milled for 12-24 hours to obtain a metal ceramic slurry with a particle size of less than 200 mesh, and then the slurry is dried at a temperature of 150℃ and ground to obtain a mixed powder with a particle size of less than 100 mesh;

[0020] The dispersant is selected from one or a mixture of two or more of ethanol, ethylene glycol and glycerol, and the mass of the dispersant is 1wt%-5wt% of the total mass of the NiFe2O4-based spinel powder, the nickel pyrochlore powder, the non-oxide ceramic powder and the metal powder;

[0021] The mass of the water is 3-5 times the total mass of the NiFe2O4-based spinel powder, the nickel pyrochlore powder, the non-oxide ceramic powder and the metal powder.

[0022] Optionally, in step 2, the pre-sintered body is melted at a temperature of 1700-2300°C for 1-2 hours in an argon protective gas, so that the pre-sintered body is in a molten state.

[0023] Optionally, in the NiFe2O4-based spinel, the proportion of NiFe2O4 is 20wt%-80wt%, the proportion of ZnFe2O4 is 0wt%-20wt%, the proportion of CuFe2O4 is 0wt%-20wt%, the proportion of CoFe2O4 is 0wt%-20wt%, and the proportion of MnFe2O4 is 0wt%-20wt%, excluding the end point value 0.

[0024] Optionally, in the nickel pyrochlore, the proportion of NiO is 20wt%-80wt%, the proportion of BaO is 0wt%-20wt%, the proportion of CeO2 is 0wt%-20wt%, the proportion of ZrO2 is 0wt%-20wt%, the proportion of Yb2O3 is 0wt%-20wt%, and the proportion of V2O5 is 0wt%-20wt%, excluding the end point value 0.

[0025] Optionally, in the non-oxide ceramic phase, the proportion of MXene is 20wt%-80wt%, the proportion of ZrB2 is 0wt%-20wt%, the proportion of TiB2 is 0wt%-20wt%, the proportion of TiN is 0wt%-20wt%, the proportion of VN is 0wt%-20wt%, excluding the end point value 0.

[0026] Optionally, the metal powder comprises Co powder, Fe powder, Ni powder, Ti powder and Cu powder, and the proportion of Ni powder is 20wt%-80wt%, the proportion of Cu powder is 0wt%-20wt%, the proportion of Ti powder is 0wt%-20wt%, the proportion of Co powder is 0wt%-20wt%, the proportion of Fe powder is 0wt%-20wt%, excluding the end point value 0.

[0027] Optionally, in step 2, the pre-sintered body is melted by one or a combination of several of arc melting, discharge plasma melting, laser floating zone melting, optical floating zone melting, electron beam melting, high-frequency electromagnetic induction melting and electrically heated Joule heat melting.

[0028] The prepared material has a density of 98%-100%; a thermal shock resistance of 90%-100%; a mechanical property of 80-120MPa; a high-temperature corrosion resistance of 10-60 microns; and an electrical conductivity of 150-1000S / cm.

[0029] The application also provides an application scheme of the material, which is specifically used for preparing a composite anode.

[0030] The metal ceramic pre-sintered body is prepared by the above step 1;

[0031] Then, the pre-sintered body is heated and melted in an inert gas atmosphere, so that the pre-sintered body is in a molten state; then the molten material is cast on the outer surface of the carbon anode, and then cooled and solidified at a cooling rate of 1-100℃ / min to obtain a composite anode solidification body;

[0032] Subsequently, the obtained composite anode solidification body is treated at a temperature of 1250-1500℃ for 2-6 hours to adjust the microstructure and eliminate stress, and then cooled to room temperature at a cooling rate of 1-50℃ / min to obtain a composite anode.

[0033] The application can greatly improve the density of the nickel ferrite-based metal ceramic material, eliminate the grain boundary defects existing in the traditional sintering process of the metal ceramic, and improve the overall performance of the metal ceramic material, including corrosion resistance, electrical conductivity and mechanical properties; at the same time, by increasing the amount of non-oxide ceramic with good electrical conductivity and reducing the amount of metal powder, the corrosion resistance of the material is increased. The process of the application is easy to form, the process flow is simple, easy to be combined with other materials, and is beneficial to the shape and size control of the ceramic, and is easy to be industrialized.

[0034] The composite anode prepared by the application can be used in an electrolytic aluminum cell for electrolyzing aluminum oxide to obtain metallic aluminum and oxygen. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 It is a structural schematic diagram of the composite anode prepared in the examples. DETAILED DESCRIPTION

[0036] Unless otherwise specified, the scientific and technical terms in this document are understood according to the understanding of the ordinary skilled in the art.

[0037] The present application adds non-oxide ceramic components on the basis of traditional metal and oxide ceramic components, reduces the amount of metal, after pre-sintering of the powder, further implements high-temperature melting (the melting temperature can be determined according to the composition and properties of the material, so as to heat and melt the pre-sintered body in a reasonable time), and casting process, by controlling the cermet chemical composition, melting temperature and melting atmosphere and cooling speed, a nickel ferrite-based eutectic cermet with uniform microstructure and excellent performance is obtained.

[0038] It should be explained that the temperature and the amount of the substance involved herein are approximate values for illustrative purposes. Although methods and materials similar or equivalent to those described herein can be used in the implementation of the present disclosure, some suitable methods and raw materials are described below. In addition, the raw materials, amounts and examples are only exemplary and are not intended to be limiting. In a specific scheme, the person skilled in the art can optimize the raw materials, amounts of substances and operation parameters involved in the method according to the disclosed content of the present application by using conventional experimental period to achieve the purpose of the present application.

[0039] The raw materials used in the following examples are commercially available products, and the composition of the material is analytical pure.

[0040] The NiFe2O4-based spinel composition used in the following examples is as follows: NiFe2O4 accounts for 79.6wt%; ZnFe2O4 accounts for 5.8%; CuFe2O4 accounts for 2.6wt%; CoFe2O4 accounts for 0.9wt%; MnFe2O4 accounts for 10.4wt%;

[0041] The nickel pyrochlore used is composed of: NiO accounts for 68.5wt%; BaO accounts for 11.0wt%; CeO2 accounts for 9.5wt%; ZrO2 accounts for 3.9wt%; Yb2O3 accounts for 4.8wt%; V2O5 accounts for 2.1wt%.

[0042] The non-oxide ceramic phase used in the present application is composed of: MXene (Ti4N3 MXene nitride material in this example) accounts for 77.9wt%, ZrB2 accounts for 5.5wt%, TiB2 accounts for 11.4wt%; TiN accounts for 2.4wt%, VN accounts for 2.6wt%.

[0043] The metal powder used is composed of: Ni accounts for 55.0wt%, Cu accounts for 15.0wt%; Ti accounts for 5.0wt%; Co accounts for 7.0wt%; Fe accounts for 18wt%.

[0044] The performance detection method of the material described herein is as follows:

[0045] The density is measured by Archimedes drainage method, which is the ratio of actual density and theoretical density.

[0046] Thermal shock resistance: the material is put into a high temperature furnace at 960℃ from room temperature, and kept for 10 minutes, then taken out and cooled to room temperature in air, which is one thermal shock, then the material after one thermal shock is tested for bending strength, the strength ratio after thermal shock to that before thermal shock is the strength residual rate (representing thermal shock resistance), the greater the strength residual rate, the better the thermal shock resistance of the material.

[0047] Mechanical property: the mechanical property is represented by bending strength, and the bending strength is detected according to GB / T4741-1999.

[0048] High temperature corrosion resistance: the NiFe2O4 eutectic ceramic inert anode material sintered at different temperatures is subjected to high temperature molten salt static corrosion experiment, the inert anode material is placed in a high-purity graphite crucible containing sufficient electrolyte, the electrolyte composition is 90% industrial cryolite (molecular ratio is 2.2), 5% CaF2 and 5% Al2O3 (mass ratio); after being immersed at 960℃ for 8h, it is taken out and cooled; the immersed inert anode material is heated in an AlCl3 solution with a mass percentage concentration of 30% in a water bath, so that the residues on the surface of the material are dissolved and fall off, then the material surface is washed with water; the surface of the immersed material is subjected to SEM and EDS element analysis. The corrosion layer thickness of the material is measured under a microscope, which represents the high temperature corrosion resistance of the material.

[0049] Electrical conductivity: at 960℃, the current through the unit area and unit length of the sample is measured under constant voltage, and the electrical conductivity of the sample is calculated according to Ohm's law.

[0050] Based on the above detection methods, the density of the material prepared by the application is between 98% and 100%; the thermal shock resistance is 90%-100% of the strength after one thermal shock; the mechanical property is 80-120MPa; the high temperature corrosion resistance is 10-60 microns; the electrical conductivity is 150-1000S / cm.

[0051] Example 1:

[0052] 1) Preparation of pre-sintered body: the formula amount of NiFe2O4 spinel powder, non-oxide ceramic powder, nickel pyrochlore powder, metal powder, ethanol and water are mixed and ball milled for 20 hours to obtain a metal ceramic slurry with a particle size of less than 200 mesh, the slurry is dried at a temperature of 150±10℃ and then ground to obtain a mixed powder of less than 100 mesh, then 1.8wt% of polyvinyl alcohol as a binder is added, and then granulated into 10-30 mesh granules, the granulated granules are pressed into green bodies under a pressure of 150MPa, and then pre-sintered in a nitrogen protective atmosphere at 1300±100℃ for 4 hours to obtain a metal ceramic pre-sintered body;

[0053] The total mass of the NiFe2O4-based spinel powder, the nickel garnet powder and the non-oxide ceramic powder accounts for 50wt% of 100% by mass, and the mass of the metal powder accounts for 50wt% of 100% by mass;

[0054] The mass of the NiFe2O4-based spinel powder accounts for 40wt% of 100% by mass, the mass of the nickel garnet powder accounts for 20wt% of 100% by mass, and the mass of the non-oxide ceramic powder accounts for 40wt% of 100% by mass;

[0055] The mass of the polyvinyl alcohol is 1wt% of the total mass of the NiFe2O4-based spinel powder, the nickel garnet powder, the non-oxide ceramic powder and the metal powder;

[0056] The mass of the ethanol is 3.5wt% of the total mass of the NiFe2O4-based spinel powder, the nickel garnet powder, the non-oxide ceramic powder and the metal powder;

[0057] The mass of the water is 4 times of the total mass of the NiFe2O4-based spinel powder, the nickel garnet powder, the non-oxide ceramic powder and the metal powder;

[0058] 2) The pre-sintered body is melted and solidified by melting the pre-sintered body in an SPS (spark plasma sintering) device under the protection of argon gas at a temperature of 1700-1900℃ for 1-2 hours, and then solidified by cooling at a cooling rate of 20±5℃ / min to obtain a ceramic solidified body;

[0059] 3) The ceramic solidified body is subjected to a crystallization and annealing treatment at a temperature of 1250-1350℃ for 5 hours to adjust the microstructure and eliminate stress, and then cooled to room temperature at a cooling rate of 20±5℃ / min to obtain a high-performance eutectic metal ceramic inert anode material.

[0060] The density of the material prepared in this embodiment is 99.1%, the thermal shock resistance is 96.6%, the mechanical property is 90MPa, the high-temperature corrosion resistance is 23 microns, and the electrical conductivity is 984S / cm.

[0061] Embodiment 2:

[0062] The difference between this embodiment and embodiment 1 is that the raw materials used are:

[0063] The total mass of the NiFe2O4-based spinel powder, the nickel garnet powder and the non-oxide ceramic powder accounts for 90wt% of 100% by mass, and the mass of the metal powder accounts for 10wt% of 100% by mass;

[0064] The mass of the NiFe2O4-based spinel powder accounts for 70wt% of 100% by mass, the mass of the nickel garnet powder accounts for 10wt% of 100% by mass, and the mass of the non-oxide ceramic powder accounts for 20wt% of 100% by mass.

[0065] The density of the material prepared in this example is 99.7%; the thermal shock resistance is 94.3% for the first thermal shock strength ratio; the mechanical property is 170 MPa; the high temperature corrosion resistance is 57 microns; and the electrical conductivity is 157 S / cm.

[0066] Example 3:

[0067] In this example, the molten material prepared in Example 1 is cast into a sand mold 5 provided with a carbon anode (the carbon anode uses an existing anode, including a metal guide rod 1, a phosphorus iron 2, and a carbon body 4), so that the molten material 3 fills the surface of the carbon anode (see Figure 1 After cooling at the same cooling rate as in Example 1, a cermet and carbon material composite anode is obtained.

Claims

1. A method for preparing a nickel ferrite-based eutectic metal-ceramic inert anode material, characterized in that the method... The application relates to a preparation method of a nickel ferrite-based eutectic cermet inert anode material. Step 1, preparation of a pre-sintered body: The mixed powder of the NiFe2O4-based spinel powder, the nickel pyrochlore powder, the non-oxide ceramic powder and the metal powder is mixed with a binder, granulated into 10-30 mesh granules, and then the granules are pressed into green bodies under a pressure of 100-200 MPa; subsequently, the green bodies are pre-sintered in an inert gas protective atmosphere at 1200-1400 DEG C for 3-5 hours to obtain a cermet pre-sintered body; The non-oxide ceramic powder contains MXene, ZrB2, TiB2, TiN and VN; and the metal powder is selected from a mixture of two or more of Co powder, Fe powder, Ni powder, Ti powder and Cu powder; In the NiFe2O4-based spinel, the proportion of NiFe2O4 is 20wt%-80wt%; the proportion of ZnFe2O4 is 0wt%-20wt%; the proportion of CuFe2O4 is 0wt%-20wt%; the proportion of CoFe2O4 is 0wt%-20wt%; and the proportion of MnFe2O4 is 0wt%-20wt%, without the end point value 0; In the nickel pyrochlore, the proportion of NiO is 20wt%-80wt%; the proportion of BaO is 0wt%-20wt%; the proportion of CeO2 is 0wt%-20wt%; the proportion of ZrO2 is 0wt%-20wt%; the proportion of Yb2O3 is 0wt%-20wt%; and the proportion of V2O5 is 0wt%-20wt%, without the end point value 0; The total mass proportion of the NiFe2O4-based spinel powder, the nickel pyrochlore powder and the non-oxide ceramic powder is 50wt%-90wt% based on 100% of the mass ratio, and the mass proportion of the metal powder is 10wt%-50wt%; The mass proportion of the NiFe2O4-based spinel powder is 40wt%-70wt%, the mass proportion of the nickel pyrochlore powder is 10wt%-20wt%, and the mass proportion of the non-oxide ceramic powder is 20wt%-40wt% based on 100% of the mass ratio; The binder is selected from one or a mixture of both of polyvinyl alcohol and polyethylene glycol, and the mass of the binder is 0.5wt%-2wt% of the total mass of the NiFe2O4-based spinel powder, the nickel pyrochlore powder, the non-oxide ceramic powder and the metal powder; Step 2, melting and cooling solidification of the pre-sintered body: The pre-sintered body is melted at a temperature of 1700-2300 DEG C in an argon protective gas for 1-2 hours to make the pre-sintered body into a molten state; then the molten material is cooled and solidified at a cooling speed of 1-100 DEG C / min, or the molten material is cast and cooled and solidified at a cooling speed of 1-100 DEG C / min to obtain a ceramic solidified body; Step 3, heat treatment: The ceramic solidified body obtained in step 2 is treated at a temperature of 1250-1500 DEG C for 2-6 hours, and then cooled to room temperature at a cooling speed of 1-50 DEG C / min to obtain a nickel ferrite-based eutectic cermet inert anode material.

2. The method for preparing nickel ferrite-based eutectic metal-ceramic inert anode material according to claim 1, characterized in that, The particle size of the mixed powder is less than 100 mesh.

3. The method for preparing nickel ferrite-based eutectic metal-ceramic inert anode material according to claim 1, characterized in that, In step 1, the NiFe2O4-based spinel powder, nickel pyrochlore powder, non-oxide ceramic powder, metal powder, dispersant and water are mixed and ball milled for 12-24 hours to obtain a metal ceramic slurry with a particle size of less than 200 mesh, and then the slurry is dried at a temperature of 150°C and then ground to obtain a mixed powder with a particle size of less than 100 mesh; The dispersant is selected from one or a mixture of two or more of ethanol, ethylene glycol and glycerol, and the mass of the dispersant is 1 wt%-5 wt% of the total mass of the NiFe2O4-based spinel powder, nickel pyrochlore powder, non-oxide ceramic powder and metal powder; The mass of the water is 3-5 times the total mass of the NiFe2O4-based spinel powder, nickel pyrochlore powder, non-oxide ceramic powder and metal powder.

4. The method for preparing nickel ferrite-based eutectic metal-ceramic inert anode material according to claim 1, characterized in that, The proportion of MXene in the non-oxide ceramic phase is 20wt%-80wt%, the proportion of ZrB2 is 0wt%-20wt%, the proportion of TiB2 is 0wt%-20wt%, the proportion of TiN is 0wt%-20wt%, and the proportion of VN is 0wt%-20wt%, without the endpoint value 0.

5. The method for preparing nickel ferrite-based eutectic metal-ceramic inert anode material according to claim 1, characterized in that, The metal powder comprises Co powder, Fe powder, Ni powder, Ti powder and Cu powder, and the proportion of Ni powder is 20wt%-80wt%, the proportion of Cu powder is 0wt%-20wt%, the proportion of Ti powder is 0wt%-20wt%, the proportion of Co powder is 0wt%-20wt%, the proportion of Fe powder is 0wt%-20wt%, and the endpoint value 0 is not included.

6. The method for preparing nickel ferrite-based eutectic metal-ceramic inert anode material according to claim 1, characterized in that, In step 2, the pre-sintered body is melted by one or a combination of several of arc melting, discharge plasma melting, laser floating zone melting, optical floating zone melting, electron beam melting, high-frequency electromagnetic induction melting and electrically heated Joule heat melting.

7. A method of preparing a composite anode, characterized in that the method The method comprises the following steps: Preparation of the metal ceramic pre-sintered body according to any one of claims 1-6; Then, the pre-sintered body is heated and melted in an inert gas atmosphere to form a molten state, and then the molten material is cast on the outer surface of the carbon anode, and then cooled and solidified at a cooling rate of 1-100°C / min to obtain a composite anode solidification body; Subsequently, the obtained composite anode solidification body is treated at a temperature of 1250-1500°C for 2-6 hours to adjust the microstructure and eliminate stress, and then cooled to room temperature at a cooling rate of 1-50°C / min to obtain a composite anode.

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