Ceramic material for aluminum electrolysis inert anodes and method for its preparation

Abstract

The application belongs to the technical field of electrolytic aluminum anode materials, and particularly relates to a ceramic material for an inert anode of aluminum electrolysis and a preparation method thereof. The metal ceramic phase powder provided by the application comprises a metal inner core and a metal coating layer coated on the surface of the metal inner core; the number of layers of the metal coating layer is n=1-4; and the metal elements in the metal inner core and the metal coating layer independently comprise one or more of iron, nickel, cobalt, manganese, copper, chromium, aluminum, magnesium and zinc. The metal ceramic phase powder provided by the application is a nano-particle with fine and uniform particles, high purity, stable performance, uniform size, good electrical conductivity and electrochemical stability. When the metal ceramic phase powder is applied to electrolytic aluminum, the performance of the electrolytic aluminum as an anode material can be effectively improved.

Description

Technical Field

[0001] This invention belongs to the technical field of electrolytic aluminum anode materials, specifically relating to a ceramic material for aluminum electrolysis inert anodes and its preparation method. Background Technology

[0002] Currently, the internationally accepted aluminum electrolysis technology uses carbon anodes to reduce alumina to primary aluminum in high-temperature molten salt, while simultaneously emitting CO2. This process consumes approximately 13,000 kWh of electricity and about 0.4 tons of carbon materials per ton of aluminum. In contrast, inert anode aluminum electrolysis technology releases oxygen during the production of primary aluminum, eliminating the emission of greenhouse gases such as CO2 and CO. Therefore, inert anode aluminum electrolysis technology is a disruptive technology that will fundamentally transform the aluminum electrolysis industry and is a core strategic technology for achieving carbon neutrality. Inert anode materials are one of the core components of inert electrode aluminum electrolysis technology, and their material types mainly encompass three systems: ceramics, alloys, and cermets.

[0003] Ceramic metals are heterogeneous composite materials composed of metals or alloys and one or more ceramic phases. They combine the excellent thermochemical stability, strong corrosion resistance, and oxidation resistance of ceramics with the good electrical conductivity and thermal shock resistance of metals, and have long been considered a promising inert anode material for aluminum electrolysis. However, the cermet materials currently used as inert anodes for aluminum electrolysis have irregular particle shapes and unstable electrochemical performance. Summary of the Invention

[0004] In view of this, the purpose of the present invention is to provide a metal-ceramic phase powder, its preparation method and application, and a ceramic material for aluminum electrolysis inert anode and its preparation method. The metal-ceramic phase powder has good electrical conductivity and electrochemical stability, which can effectively improve the performance of the ceramic material for aluminum electrolysis inert anode.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] This invention provides a metal-ceramic phase powder, comprising a metal core and a metal coating layer covering the surface of the metal core; wherein the number of layers of the metal coating layer is n = 1 to 4;

[0007] The metal elements in the metal core and metal cladding layer independently include one or more of iron, nickel, cobalt, manganese, copper, chromium, aluminum, magnesium, and zinc.

[0008] Preferably, the metal core and the metal cladding layer are metal oxides.

[0009] Preferably, the diameter of the metal core is 0.5 to 100 μm; the thickness of each metal cladding layer is independently 10 to 500 μm.

[0010] The present invention also provides a method for preparing the metal-ceramic phase powder described in the above technical solution, comprising the following steps:

[0011] (1) The precursor solution of the metal core is subjected to a first coprecipitation to obtain the metal core precursor system;

[0012] (2) In the metal core precursor system, the precursor liquid with metal coating layer is added n times to perform n co-precipitation to obtain a metal core precursor system with n layers of metal coating layer.

[0013] (3) The metal core precursor system with n layers of metal coating is sequentially filtered, dried and calcined to obtain metal ceramic phase powder;

[0014] The precursor solution for the metal core and the precursor solution for the metal coating layer each independently comprise: metal salt, complexing agent, precipitant, and water;

[0015] The metal salts include one or more of the following: iron salts, nickel salts, cobalt salts, manganese salts, copper salts, chromium salts, aluminum salts, magnesium salts, and zinc salts.

[0016] Preferably, the iron salt includes one or more of ferric sulfate, ferric chloride, ferric nitrate, and ferric acetate;

[0017] The nickel salt includes one or more of nickel sulfate, nickel chloride, nickel nitrate, and nickel acetate;

[0018] The cobalt salt includes one or more of cobalt sulfate, cobalt chloride, cobalt nitrate, and cobalt acetate;

[0019] The manganese salt includes one or more of manganese sulfate, manganese chloride, manganese nitrate, and manganese acetate;

[0020] The copper salt includes one or more of copper sulfate, copper chloride, copper nitrate, and copper acetate;

[0021] The chromium salts include one or more of chromium sulfate, chromium chloride, chromium nitrate, and chromium acetate;

[0022] The aluminum salts include one or more of aluminum sulfate, aluminum chloride, aluminum nitrate, and aluminum acetate;

[0023] The magnesium salt includes one or more of magnesium sulfate, magnesium chloride, magnesium nitrate, and magnesium acetate;

[0024] The zinc salts include one or more of zinc sulfate, zinc chloride, zinc nitrate, and zinc acetate.

[0025] Preferably, the complexing agent includes one or more of EDTA, ammonia, ammonium chloride, ammonium sulfate, ammonium nitrate, ammonium citrate, ethylenediamine, acetic acid, ammonium acetate, sodium fluoride, tartaric acid, maleic acid, succinic acid, citric acid, and malonic acid.

[0026] Preferably, the precipitant includes one or more of ammonia, sodium hydroxide, potassium hydroxide, and ammonium hydroxide.

[0027] The present invention also provides the application of the metal-ceramic phase powder described in the above technical solution or the metal-ceramic phase powder prepared by the preparation method described in the above technical solution in ceramic materials for aluminum electrolysis inert anodes.

[0028] The present invention also provides a ceramic material for an inert anode in aluminum electrolysis, the raw materials for which include a metal-ceramic phase powder, a metal phase powder and a binder; the metal-ceramic phase powder is the metal-ceramic phase powder described in the above technical solution or the metal-ceramic phase powder prepared by the preparation method described in the above technical solution.

[0029] The present invention also provides a method for preparing the ceramic material for the aluminum electrolysis inert anode described in the above technical solution, comprising the following steps:

[0030] Metal-ceramic phase powder, metal phase powder and binder are mixed and pressed into shape. The resulting pressed blank is then sintered and oxidized in sequence to obtain the ceramic material for aluminum electrolysis inert anode.

[0031] This invention provides a metal-ceramic phase powder, comprising a metal core and a metal coating layer covering the surface of the metal core; the number of layers in the metal coating layer is n = 1 to 4; the metal elements in the metal core and the metal coating layer independently include one or more of iron, nickel, cobalt, manganese, copper, chromium, aluminum, magnesium, and zinc. The metal-ceramic phase powder provided by this invention consists of fine, uniform, and high-purity nanoparticles with stable performance, uniform size, and good electrical conductivity and electrochemical stability. When applied to electrolytic aluminum, it can effectively improve the performance of the anode material.

[0032] This invention also provides a method for preparing the aforementioned metal-ceramic phase powder. This invention uses a complexing agent and metal ions for complexation, controlling the concentration of free total metal salt ions in the reaction system at an appropriate level. When the free total metal salt ions at an appropriate concentration level react with OH-... - When ionic reactions generate precipitates, uniform spherical or near-spherical bodies can form. These bodies serve as cores, and by adding salt solutions, complexing agents, and precipitating agents of different formulations to their surfaces, new coating layers are deposited on the spherical surfaces of the cores. This method can achieve one to multiple layers of coating. Finally, the multi-component precursor is calcined in an oxygen atmosphere to obtain ceramic powder with a spherical or near-spherical multilayered coating structure. This method is simple, requires minimal equipment (no expensive equipment is needed), allows for controllable particle size, and produces fine, uniform, and high-purity particles. It is also economical and environmentally friendly. Detailed Implementation

[0033] This invention provides a metal-ceramic phase powder, comprising a metal core and a metal coating layer covering the surface of the metal core; wherein the number of layers of the metal coating layer is n = 1 to 4;

[0034] The metal elements in the metal core and metal cladding layer independently include one or more of iron, nickel, cobalt, manganese, copper, magnesium, and zinc.

[0035] Unless otherwise specified, the present invention does not have special requirements on the source of raw materials used, and commercially available products well known to those skilled in the art can be used.

[0036] The metal-ceramic phase powder provided by this invention includes a metal core. In this invention, the metal core is preferably a metal oxide; the metal element in the metal core preferably includes one or more of iron, nickel, cobalt, manganese, copper, chromium, aluminum, magnesium, and zinc, more preferably iron. When there are multiple metal elements, this invention does not have a special limitation on the ratio of different types of metal elements; any ratio is acceptable.

[0037] In this invention, the diameter of the metal core is preferably 0.5 to 100 μm, more preferably 1 to 20 μm.

[0038] The metal-ceramic phase powder provided by this invention includes a metal coating layer covering the surface of a metal core. In this invention, the metal coating layer is preferably a metal oxide; the number of layers n is 1 to 4, preferably 1 to 3; the metal element in the metal coating layer preferably includes one or more of iron, nickel, cobalt, manganese, copper, chromium, aluminum, magnesium, and zinc, more preferably nickel, iron, or cobalt. When there are multiple metal elements, this invention does not have a special limitation on the ratio of different types of metal elements; any ratio is acceptable.

[0039] In this invention, the thickness of each metal cladding layer is preferably 10 to 500 μm, more preferably 10 to 40 μm.

[0040] In this invention, the particle size of the metal-ceramic phase powder is preferably 200-400 mesh, more preferably 250-300 mesh.

[0041] The metal-ceramic phase powder provided by this invention consists of fine, uniform, and high-purity nanoparticles with stable performance, uniform size, and good electrical conductivity and electrochemical stability. When applied to electrolytic aluminum, it can effectively improve the performance of the anode material. The anode material prepared with it has excellent conductivity and strong corrosion resistance, and has excellent application prospects in industry.

[0042] The present invention also provides a method for preparing the metal-ceramic phase powder described in the above technical solution, comprising the following steps:

[0043] (1) The precursor solution of the metal core is subjected to a first coprecipitation to obtain the metal core precursor system;

[0044] (2) In the metal core precursor system, the precursor liquid with metal coating layer is added n times to perform n co-precipitation to obtain a metal core precursor system with n layers of metal coating layer.

[0045] (3) The metal core precursor system with n layers of metal coating is sequentially filtered, dried and calcined to obtain metal ceramic phase powder;

[0046] The precursor solution for the metal core and the precursor solution for the metal coating layer each independently comprise: metal salt, complexing agent, precipitant, and water;

[0047] The metal salts include one or more of the following: iron salts, nickel salts, cobalt salts, manganese salts, copper salts, chromium salts, aluminum salts, magnesium salts, and zinc salts.

[0048] The present invention involves a first co-precipitation of the precursor liquid of the metal core to obtain a metal core precursor system.

[0049] In this invention, the precursor solution of the metal core comprises: a metal salt, a complexing agent, a precipitant, and water; the metal salt comprises one or more of iron salt, nickel salt, cobalt salt, manganese salt, copper salt, chromium salt, aluminum salt, magnesium salt, and zinc salt, preferably an iron salt.

[0050] In this invention, the iron salt preferably includes one or more of ferric sulfate, ferric chloride, ferric nitrate, and ferric acetate, more preferably ferric chloride; the nickel salt preferably includes one or more of nickel sulfate, nickel chloride, nickel nitrate, and nickel acetate; the cobalt salt includes one or more of cobalt sulfate, cobalt chloride, cobalt nitrate, and cobalt acetate, more preferably cobalt nitrate; the manganese salt preferably includes one or more of manganese sulfate, manganese chloride, manganese nitrate, and manganese acetate, more preferably manganese nitrate; the copper salt preferably includes one or more of copper sulfate, copper chloride, copper nitrate, and copper acetate, more preferably copper nitrate; the chromium salt preferably includes one or more of chromium sulfate, chromium chloride, chromium nitrate, and chromium acetate, more preferably chromium nitrate; the aluminum salt preferably includes one or more of aluminum sulfate, aluminum chloride, aluminum nitrate, and aluminum acetate, more preferably aluminum chloride; the magnesium salt preferably includes one or more of magnesium sulfate, magnesium chloride, magnesium nitrate, and magnesium acetate, more preferably magnesium chloride; and the zinc salt preferably includes one or more of zinc sulfate, zinc chloride, zinc nitrate, and zinc acetate, more preferably zinc nitrate.

[0051] In this invention, the complexing agent preferably includes one or more of EDTA, ammonia, ammonium chloride, ammonium sulfate, ammonium nitrate, ammonium citrate, ethylenediamine, acetic acid, ammonium acetate, sodium fluoride, tartaric acid, maleic acid, succinic acid, citric acid, and malonic acid, more preferably ethylenediamine.

[0052] In this invention, the precipitant preferably includes one or more of ammonia, sodium hydroxide, potassium hydroxide and ammonium hydroxide, and more preferably sodium hydroxide.

[0053] In this invention, the molar ratio of each metal salt to the complexing agent is preferably (0.1-1):(2-4), more preferably (0.1-1):(2-3); the molar ratio of each metal salt to the precipitant is preferably (0.1-1):(2-4), more preferably (0.1-1):(3-4); the molar ratio of each metal salt to the volume of water is preferably (0.1-1) mol:(1-2) L, more preferably 1 mol:1 L.

[0054] In this invention, the preferred method for preparing the precursor liquid of the metal core is to mix the metal salt, complexing agent, precipitant and water under the protection of an inert gas, more preferably to mix them under the protection of an inert gas; the inert gas is preferably nitrogen or argon, more preferably nitrogen.

[0055] In this invention, the pH value of the precursor solution of the metal core is preferably 9 to 12, and more preferably 10 to 11.

[0056] In this invention, the first coprecipitation is preferably carried out under water bath heating conditions; the temperature of the first coprecipitation is preferably 40-100°C, more preferably 50-60°C; and the time of the first coprecipitation is preferably 1-10 hours, more preferably 2-8 hours.

[0057] After obtaining the metal core precursor system, the present invention repeatedly adds the precursor liquid with metal coating layer n times to the metal core precursor system for n co-precipitation to obtain a metal core precursor system with n metal coating layers.

[0058] In this invention, the precursor solution for the metal coating layer includes: a metal salt, a complexing agent, a precipitant, and water.

[0059] In the process of n co-precipitation, the types and amounts of metal salts, complexing agents and precipitants in the precursor solution of the metal coating layer added each time can be the same as or different from those in the precursor solution of the metal core.

[0060] In this invention, the metal salt includes one or more of iron salts, nickel salts, cobalt salts, manganese salts, copper salts, chromium salts, aluminum salts, magnesium salts, and zinc salts, more preferably iron or nickel salts.

[0061] In this invention, the iron salt preferably includes one or more of ferric sulfate, ferric chloride, ferric nitrate, and ferric acetate, more preferably ferric chloride; the nickel salt preferably includes one or more of nickel sulfate, nickel chloride, nickel nitrate, and nickel acetate; the cobalt salt includes one or more of cobalt sulfate, cobalt chloride, cobalt nitrate, and cobalt acetate, more preferably cobalt nitrate; the manganese salt preferably includes one or more of manganese sulfate, manganese chloride, manganese nitrate, and manganese acetate, more preferably manganese nitrate; the copper salt preferably includes one or more of copper sulfate, copper chloride, copper nitrate, and copper acetate, more preferably copper nitrate; the chromium salt preferably includes one or more of chromium sulfate, chromium chloride, chromium nitrate, and chromium acetate, more preferably chromium nitrate; the aluminum salt preferably includes one or more of aluminum sulfate, aluminum chloride, aluminum nitrate, and aluminum acetate, more preferably aluminum chloride; the magnesium salt preferably includes one or more of magnesium sulfate, magnesium chloride, magnesium nitrate, and magnesium acetate, more preferably magnesium chloride; and the zinc salt preferably includes one or more of zinc sulfate, zinc chloride, zinc nitrate, and zinc acetate, more preferably zinc nitrate.

[0062] In this invention, the complexing agent preferably includes one or more of EDTA, ammonia, ammonium chloride, ammonium sulfate, ammonium nitrate, ammonium citrate, ethylenediamine, acetic acid, ammonium acetate, sodium fluoride, tartaric acid, maleic acid, succinic acid, citric acid, and malonic acid, more preferably ethylenediamine.

[0063] In this invention, the precipitant preferably includes one or more of ammonia, sodium hydroxide, potassium hydroxide and ammonium hydroxide, and more preferably sodium hydroxide.

[0064] In this invention, the molar ratio of each metal salt to the complexing agent is preferably (0.1-1):(2-4), more preferably (0.1-1):(2-3); the molar ratio of each metal salt to the precipitant is preferably (0.1-1):(2-4), more preferably (0.1-1):(3-4); the molar ratio of each metal salt to the volume of water is preferably (0.1-1) mol:(1-2) L, more preferably 1 mol:1 L.

[0065] In this invention, the preferred method for preparing the precursor liquid of the metal core is to mix the metal salt, complexing agent, precipitant and water under the protection of an inert gas, more preferably to mix them under the protection of an inert gas; the inert gas is preferably nitrogen or argon, more preferably nitrogen.

[0066] In this invention, the pH value of the precursor solution of the metal coating layer is preferably 9 to 12, and more preferably 10 to 11.

[0067] In this invention, the co-precipitation is preferably carried out under water bath heating conditions; the temperature of each co-precipitation is preferably 40-100°C, more preferably 50-60°C; and the time of each co-precipitation is preferably 1-10 hours, more preferably 2-8 hours.

[0068] After obtaining the metal core precursor system coated with n metal layers, the present invention sequentially filters, dries and calcines the metal core precursor system coated with n metal layers to obtain metal-ceramic phase powder.

[0069] The present invention does not impose any particular limitation on the filtration process; any filtration process well known in the art can be used.

[0070] In this invention, the drying temperature is preferably 40-150°C, more preferably 80°C; the drying time is preferably 2-10 hours, more preferably 2-8 hours.

[0071] In this invention, the calcination temperature is preferably 600–1500°C, more preferably 800–1200°C; the calcination holding time is preferably 1–10 h, more preferably 2–8 h; the calcination is preferably carried out in an oxygen atmosphere; this invention does not have a special limitation on the oxygen atmosphere, and an oxygen atmosphere well known in the art can be used.

[0072] After the calcination is completed, the present invention preferably further includes: crushing and sieving the calcined product in sequence; the crushing is preferably grinding; the mesh size of the sieve used for sieving is preferably 200-400 mesh, more preferably 250-300 mesh.

[0073] This invention utilizes a complexing agent and metal ions to complex, controlling the concentration of free total metal salt ions in the reaction system at an appropriate level. When the appropriate concentration of free total metal salt ions reacts with OH-... - When ionic reactions generate precipitates, uniform spherical or near-spherical bodies can form. These bodies serve as cores, and by adding salt solutions, complexing agents, and precipitating agents of different formulations to their surfaces, new coating layers are deposited on the spherical surfaces of the cores. This method can achieve one to multiple layers of coating. Finally, the multi-component precursor is calcined in an oxygen atmosphere to obtain ceramic powder with a spherical or near-spherical multilayered coating structure. This method is simple, requires minimal equipment (no expensive equipment is needed), allows for controllable particle size, and produces fine, uniform, and high-purity particles. It is also economical and environmentally friendly.

[0074] The present invention also provides the application of the metal-ceramic phase powder described in the above technical solution or the metal-ceramic phase powder prepared by the preparation method described in the above technical solution in ceramic materials for aluminum electrolysis inert anodes.

[0075] The present invention also provides a ceramic material for an inert anode in aluminum electrolysis, the raw materials for which include a metal-ceramic phase powder, a metal phase powder and a binder; the metal-ceramic phase powder is the metal-ceramic phase powder described in the above technical solution or the metal-ceramic phase powder prepared by the preparation method described in the above technical solution.

[0076] In this invention, the metallic phase powder preferably includes one or more of Co powder, Cr powder, Fe powder, Ni powder, Mn powder, Al powder, Ti powder, Zn powder, and Cu powder, more preferably Cu powder or Ni powder; the particle size of the metallic phase powder is preferably 300 mesh. This invention does not impose any special limitation on the proportions of the various metals in the metallic phase powder; any proportion is acceptable.

[0077] The preferred mass ratio of the metal phase powder to the metal-ceramic phase powder is (10-60):(40-90), more preferably (30-40):(60-70); the preferred particle size of the metal phase powder is less than the particle size of the metal-ceramic phase powder.

[0078] In this invention, the binder is preferably polyvinyl alcohol; the mass of the binder is preferably 1 to 6% of the total mass of the metal-ceramic phase powder and the metal phase powder, more preferably 2 to 4%.

[0079] The present invention also provides a method for preparing the ceramic material for the aluminum electrolysis inert anode described in the above technical solution, comprising the following steps:

[0080] Metal-ceramic phase powder, metal phase powder and binder are mixed and pressed into shape. The resulting pressed blank is then sintered and oxidized in sequence to obtain the ceramic material for aluminum electrolysis inert anode.

[0081] This invention involves mixing metal-ceramic phase powder, metal phase powder, and binder, and then pressing them into a compact.

[0082] In this invention, the mixing is preferably wet ball milling; the dispersant used in the wet ball milling is preferably anhydrous ethanol; the mass of the dispersant is preferably 2 to 5 times the total mass of the metal-ceramic phase powder and the metal phase powder, more preferably 3 to 4 times; the ball-to-material ratio of the wet ball milling is preferably (10 to 20):1, more preferably (10 to 15):1; the rotation speed of the wet ball milling is preferably 250 to 300 r / min, more preferably 250 r / min; the time of the wet ball milling is preferably 10 to 20 h, more preferably 10 to 15 h.

[0083] After wet ball milling, the present invention preferably dries the mixture obtained by wet ball milling; the drying temperature is preferably 60-80℃, more preferably 60-70℃; the drying time is preferably 8-10h, more preferably 8-9h.

[0084] In this invention, the pressing pressure is preferably 20-200 MPa, more preferably 50-200 MPa; the pressing time is preferably 1-20 min, more preferably 1-10 min.

[0085] After obtaining the pressed blank, the present invention preferably sinters the pressed blank.

[0086] In this invention, the sintering temperature is preferably 1200–1800℃, more preferably 1200–1700℃, and most preferably 1200℃, 1300℃, 1400℃, 1500℃, 1600℃, or 1700℃; the sintering holding time is preferably 1–7h, more preferably 1–5h, and most preferably 1h, 2h, 3h, 4h, or 5h; the sintering is preferably carried out under inert gas protection; the inert gas is preferably nitrogen or argon, more preferably nitrogen; and the purity of the nitrogen is preferably 99%.

[0087] After sintering, the present invention preferably performs an oxidation treatment on the sintered product to obtain a ceramic material for aluminum electrolytic inert anode.

[0088] In this invention, the oxidation treatment temperature is preferably 800–1300°C, more preferably 800°C, 900°C, 1000°C, 1100°C, 1200°C, or 1300°C; the holding time for the oxidation treatment is preferably 1–4 hours, more preferably 2–3 hours; the oxidation treatment is preferably carried out in a mixture of oxygen and inert gas; the partial pressure of oxygen in the mixture of oxygen and inert gas is preferably 200–1,000,000 ppm, more preferably 200,000–500,000 ppm, and most preferably 200,000 ppm, 300,000 ppm, 400,000 ppm, or 500,000 ppm; the total pressure of the mixture of oxygen and inert gas is preferably 5–20 MPa, more preferably 10–15 MPa.

[0089] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention, but they should not be construed as limiting the scope of protection of the present invention.

[0090] Example 1

[0091] A metal-ceramic phase powder comprising a metal core ((Co) 0.2 Ni 0.2 Mn 0.2 Cu 0.2 Zn 0.2 )O), and a first metal cladding layer ((Co) sequentially coated on the surface of the metal core. 0.2 Ni 0.2 Mn 0.2 Cu 0.2Mg 0.2 O), second metal cladding layer ((Zn) 0.2 Ni 0.2 Mn 0.2 Cu 0.2 Mg 0.2 )O);

[0092] The preparation method is as follows:

[0093] Cobalt chloride, nickel chloride, manganese chloride, copper chloride, and zinc chloride were dissolved in a molar ratio of 0.2:0.2:0.2:0.2:0.2 to obtain a metal salt solution of 1 mol / L for each metal element. Then, 3 mol / L ammonia water was prepared as a complexing agent and 3 mol / L sodium hydroxide solution was prepared as a precipitating agent. These solutions were added to the reaction vessel in parallel streams and heated in a water bath at 60°C. The pH of the reaction was controlled at 12 and co-precipitation was carried out for 2 hours. The resulting precipitate flowed into reaction vessel 1 as the core.

[0094] Cobalt chloride, nickel chloride, manganese chloride, copper chloride, and magnesium chloride were dissolved in a molar ratio of 0.2:0.2:0.2:0.2:0.2 to obtain a metal salt solution with each metal element having a concentration of 1 mol / L. Then, 3 mol / L ammonia water was prepared as a complexing agent and 3 mol / L sodium hydroxide solution was prepared as a precipitating agent. The salt solution, ammonia water, and sodium hydroxide solution were added to reaction vessel 1 in a parallel stream. The mixture was heated in a water bath at 60°C, and the pH of the reaction was controlled at 12 to co-precipitate for 2 hours, so that the first metal coating layer could grow on the surface of the core. The resulting precipitate flowed into reaction vessel 2.

[0095] Zinc chloride, nickel chloride, manganese chloride, copper chloride, and magnesium chloride were dissolved in a molar ratio of 0.2:0.2:0.2:0.2:0.2 to obtain a metal salt solution with each metal element having a concentration of 1 mol / L. Then, 3 mol / L ammonia water was prepared as a complexing agent and 3 mol / L sodium hydroxide solution was prepared as a precipitating agent. The salt solution, ammonia water, and sodium hydroxide solution were added to reaction vessel 2 in a parallel stream. The mixture was heated in a water bath at 60°C, and the pH of the reaction was controlled at 12 for co-precipitation for 2 hours to grow a second metal coating layer on the core surface. After the reaction, the product was filtered, washed, and dried to obtain a multi-element ceramic precursor with a coating layer number of n=2. The precursor was placed in a muffle furnace, oxygen was introduced, and it was calcined at 1500°C for 8 hours to obtain a metal-ceramic phase powder.

[0096] Example 2

[0097] A metal-ceramic phase powder includes a metal core (NiFe2O4) and a first metal coating layer (Co) covering the surface of the metal core. 0.5 Mn 0.5 )O);

[0098] The preparation method is as follows:

[0099] Prepare a 1 mol / L nickel chloride and a 2 mol / L ferric chloride metal salt solution, use 3 mol / L ammonia water as a complexing agent and 3 mol / L sodium hydroxide solution as a precipitant. Add these solutions together into the reaction vessel in parallel streams, heat in a water bath at 50°C, control the pH of the reaction to 12, and co-precipitate for 2 hours. The resulting precipitate flows into reaction vessel 1 as the core.

[0100] Cobalt chloride and manganese chloride were dissolved in a molar ratio of 0.5:0.5 to obtain a metal salt solution with each metal element at a concentration of 1 mol / L. This solution was added to reaction vessel 1 in parallel with ammonia and sodium hydroxide solution. The mixture was heated in a water bath at 50°C, and the pH of the reaction was controlled at 12 for co-precipitation for 2 hours to allow a coating layer to grow on the core surface. After the reaction, the product was filtered, washed, and dried to obtain a multi-element ceramic precursor with a coating layer number of n=1. The precursor was placed in a muffle furnace, oxygen was introduced, and the mixture was calcined at 1000°C for 8 hours. The obtained product was crushed, ground, and passed through a 200-mesh sieve to obtain a metal-ceramic phase powder.

[0101] Example 3

[0102] A metal-ceramic phase powder includes a metal core (NiFe2O4) and a first metal coating layer (Co) covering the surface of the metal core. 0.32 Ni 0.42 Mn 0.26 )O);

[0103] The preparation method is as follows:

[0104] Prepare a 1 mol / L nickel chloride and a 2 mol / L ferric chloride metal salt solution, use 3 mol / L ammonia water as a complexing agent and 3 mol / L sodium hydroxide solution as a precipitant. Add these solutions together into the reaction vessel in parallel streams, heat in a water bath at 50°C, control the pH of the reaction to 12, and co-precipitate for 2 hours. The resulting precipitate flows into reaction vessel 1 as the core.

[0105] Cobalt chloride, nickel chloride, and manganese chloride were dissolved in a molar ratio of 0.32:0.42:0.26 to obtain a 1 mol / L metal salt solution. This solution was then added to reaction vessel 1 in parallel with 3 mol / L ammonia and 3 mol / L sodium hydroxide solutions. The mixture was heated in a water bath at 50°C, and the pH of the reaction was controlled at 12 for co-precipitation for 2 hours to allow a coating layer to grow on the core surface. The resulting product was filtered, washed, and dried to obtain a multi-element ceramic precursor with n=1 coating layers. The precursor was placed in a muffle furnace, oxygen was introduced, and the mixture was calcined at 1000°C for 8 hours. The resulting product was crushed, ground, and passed through a 200-mesh sieve to obtain a metal-ceramic phase powder.

[0106] Comparative Example 1

[0107] Compared to Example 2, Comparative Example 1 differs only in that it does not use a coating structure and uses NiFe2O4 as the ceramic phase; otherwise, it is the same as Example 2.

[0108] Application Example 1

[0109] A method for preparing a ceramic material for an inert anode in aluminum electrolysis is as follows:

[0110] Metal phase powder (Ni and Co with an atomic ratio of 70:30 and a particle size of 300 mesh) and metal-ceramic phase powder prepared in Example 1 were mixed at a mass ratio of 30:70. Polyvinyl alcohol (3% of the total mass of metal-ceramic phase powder and metal phase powder) and anhydrous ethanol (4 times the total mass of metal-ceramic phase powder and metal phase powder) were added to the ball mill jar and the ball mill jar was installed on the ball mill for wet grinding. The grinding was carried out under the conditions of ball-to-material ratio of 20:1, rotation speed of 300 r / min and time of 20 h. After wet grinding, the mixed slurry was placed in a drying oven at 80°C and dried for 10 h. The dried material was then placed in a hydraulic press for pressing and molding. The pressing pressure was 200 MPa and the pressing time was 1 min to obtain a pressed green.

[0111] The pressed blank is placed in a sintering furnace for sintering at a temperature of 1600°C for 3 hours. The atmosphere used is high-purity argon (99% purity). After sintering, an oxidation treatment is performed at a temperature of 1100°C for 3 hours. The atmosphere is a mixture of oxygen and argon, with an oxygen partial pressure of 400,000 ppm and a total gas pressure of 20 MPa. After the oxidation treatment, a ceramic material for aluminum electrolysis inert anodes is obtained.

[0112] Application Example 2

[0113] A method for preparing a ceramic material for an inert anode in aluminum electrolysis is as follows:

[0114] Metal phase powder (Ni and Fe with an atomic ratio of 70:30 and a particle size of 300 mesh) and metal-ceramic phase powder prepared in Example 2 were mixed at a mass ratio of 40:60. Polyvinyl alcohol (3% of the total mass of metal-ceramic phase powder and metal phase powder) and anhydrous ethanol (4 times the total mass of metal-ceramic phase powder and metal phase powder) were added to the ball mill jar and the ball mill jar was installed on the ball mill for wet grinding. The grinding was carried out under the conditions of ball-to-material ratio of 10:1, rotation speed of 250 r / min and time of 10 h. After wet grinding, the mixed slurry was placed in a drying oven at 60°C and dried for 8 h. The dried material was then placed in a hydraulic press for pressing and molding. The pressing pressure was 150 MPa and the pressing time was 2 min to obtain a pressed green.

[0115] The pressed blank is placed in a sintering furnace for sintering at a temperature of 1400°C for 2 hours. The atmosphere used is high-purity argon (99% purity). After sintering, an oxidation treatment is performed at a temperature of 1000°C for 2 hours. The atmosphere is a mixture of oxygen and argon, with an oxygen partial pressure of 500,000 ppm and a total gas pressure of 12 MPa. After the oxidation treatment, a ceramic material for aluminum electrolysis inert anodes is obtained.

[0116] Application Example 3

[0117] A method for preparing a ceramic material for an inert anode in aluminum electrolysis is as follows:

[0118] Metal phase powder (Cu, Fe, and Cr with an atomic ratio of 60:30:10 and a particle size of 300 mesh) and the metal-ceramic phase powder prepared in Example 3 were mixed at a mass ratio of 40:60. Polyvinyl alcohol (3% of the total mass of the metal-ceramic phase powder and the metal phase powder) and anhydrous ethanol (4 times the total mass of the metal-ceramic phase powder and the metal phase powder) were added to the ball mill jar and the ball mill jar was installed on the ball mill for wet grinding. The grinding was carried out under the conditions of a ball-to-material ratio of 10:1, a rotation speed of 250 r / min, and a grinding time of 10 h. After the wet grinding was completed, the mixed slurry was placed in a drying oven at 60 °C and dried for 8 h. The dried material was then placed in a hydraulic press for pressing and molding. The pressing pressure was 150 MPa and the pressing time was 2 min to obtain a pressed green.

[0119] The pressed blank is placed in a sintering furnace for sintering at a temperature of 1400°C for 2 hours. The atmosphere used is high-purity argon (99% purity). After sintering, an oxidation treatment is performed at a temperature of 1000°C for 2 hours. The atmosphere is a mixture of oxygen and argon, with an oxygen partial pressure of 500,000 ppm and a total gas pressure of 12 MPa. After the oxidation treatment, a ceramic material for aluminum electrolysis inert anodes is obtained.

[0120] Performance testing

[0121] The performance of the ceramic materials used for aluminum electrolysis inert anodes prepared in corresponding use cases 1-3 and comparative application example 1 was tested, and the results are shown in Table 1. The specific test methods are as follows:

[0122] (1) Detection of conductivity

[0123] In this experiment, the conductivity of the inert anode material was determined using the probe method.

[0124] (2) Testing of flexural strength

[0125] Bending strength refers to a material's ability to resist bending without fracturing. To examine the strength of inert anode materials, the three-point method was used to determine it on an electronic universal testing machine.

[0126] (3) Corrosion resistance test

[0127] Corrosion resistance is one of the important criteria for selecting inert anode materials for aluminum electrolysis. The thermal corrosion rate of inert anode materials in molten cryolite electrolyte is determined by the weight loss method. The specific test procedure includes weighing the sample, measuring dimensions and calculating the surface area, simulating aluminum electrolysis test conditions, cooling after electrolysis, and immersing in an aluminum trichloride aqueous solution for heating.

[0128] This experiment uses 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:

[0129] First, weigh the inert anode material sample m1 (mg), then measure the dimensions of the sample and calculate the surface area s (cm²) of the inert anode material. 2 Next, the inert anode material was subjected to aluminum electrolysis testing under simulated industrial conditions. These simulated conditions included an electrolyte system of cryolite molten salt (composed of 90 wt% cryolite, 5 wt% calcium fluoride, and 5 wt% aluminum oxide), an electrolysis temperature of 960°C, and an electrolysis time of 20 hours. After electrolysis, the sample was removed and cooled, then immersed in a 30 wt% aluminum chloride aqueous solution and heated to dissolve the molten salt adhering to the sample surface. After all residues on the sample surface had completely detached, the sample surface was washed with clean water, boiled in clean water, and then dried.

[0130] During the recording process, it is necessary to:

[0131] (4-1) Record the cell voltage (V) during the electrolysis process;

[0132] (4-2) Observe whether corrosion occurs on the surface of the sample after drying;

[0133] (4-3) Weigh the dried sample, m2 (mg). Calculate the corrosion rate of the inert anode material using the formula f = (m2 - m1) / s.

[0134]

[0135] (4-4) Finally, inductively coupled plasma atomic emission spectrometry (ICP) is used to determine the content of impurities in the molten aluminum to ensure product quality and production efficiency.

[0136] Table 1 shows the properties of ceramic materials for aluminum electrolysis inert anodes prepared in Application Examples 1-3 and Comparative Application Example 1.

[0137]

[0138] As shown in Table 1, the inert anode material of this disclosure possesses good electrical conductivity, high-temperature mechanical properties, and corrosion resistance. 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 the aluminum electrolytic cell using a conventional carbon anode.

[0139] By comparing Application Example 1 and Comparative Application Example 1, it can be seen that obtaining ceramic phase raw materials first by co-precipitation and then sintering the ceramic phase raw materials with metal phase raw materials can improve the corrosion resistance, high-temperature mechanical properties and electrical conductivity of inert anode materials.

[0140] By comparing application examples 1 to 3, it can be seen that when the particle size of the ceramic phase raw material is less than or equal to the particle size of the metallic phase raw material, the corrosion resistance and high-temperature mechanical properties of the inert anode material can be improved.

[0141] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention and not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A ceramic material for use as an inert anode in aluminum electrolysis, characterized in that, The raw materials for its preparation include metal-ceramic phase powder, metal phase powder and binder; the metal-ceramic phase powder includes a metal core and a metal coating layer covering the surface of the metal core; the number of layers of the metal coating layer n=1~4; The metal elements in the metal core and metal cladding layer independently include one or more of iron, nickel, cobalt, manganese, copper, chromium, aluminum, magnesium, and zinc; the metal core and metal cladding layer are metal oxides. The method for preparing the ceramic material for the inert anode of aluminum electrolysis includes the following steps: Metal-ceramic phase powder, metal phase powder and binder are mixed and pressed into shape. The resulting pressed blank is then sintered and oxidized in sequence to obtain the ceramic material for aluminum electrolysis inert anode. The sintering temperature is 1200~1800℃; the sintering holding time is 1~7h; the sintering is carried out under inert gas protection; The oxidation treatment temperature is 800~1300℃; the holding time of the oxidation treatment is 1~4h; the oxidation treatment is carried out in a mixed gas of oxygen and inert gas; The metallic phase powder includes one or more of Co powder, Cr powder, Fe powder, Ni powder, Mn powder, Al powder, Ti powder, Zn powder, and Cu powder; The method for preparing the metal-ceramic phase powder includes the following steps: (1) The precursor solution of the metal core is subjected to a first coprecipitation to obtain the metal core precursor system; (2) In the metal core precursor system, the precursor liquid with metal coating layer is added n times to perform n co-precipitation to obtain a metal core precursor system with n layers of metal coating layer. (3) The metal core precursor system with n layers of metal coating is sequentially filtered, dried and calcined to obtain metal ceramic phase powder; The precursor solution for the metal core and the precursor solution for the metal coating layer each independently comprise: metal salt, complexing agent, precipitant, and water; The metal salts include one or more of the following: iron salts, nickel salts, cobalt salts, manganese salts, copper salts, chromium salts, aluminum salts, magnesium salts, and zinc salts.

2. The ceramic material for inert anodes in aluminum electrolysis according to claim 1, characterized in that, The diameter of the metal core is 0.5~100μm; the thickness of each metal cladding layer is independently 10~500μm.

3. The ceramic material for inert anodes in aluminum electrolysis according to claim 1, characterized in that, The iron salts include one or more of ferric sulfate, ferric chloride, ferric nitrate, and ferric acetate; The nickel salt includes one or more of nickel sulfate, nickel chloride, nickel nitrate, and nickel acetate; The cobalt salt includes one or more of cobalt sulfate, cobalt chloride, cobalt nitrate, and cobalt acetate; The manganese salt includes one or more of manganese sulfate, manganese chloride, manganese nitrate, and manganese acetate; The copper salt includes one or more of copper sulfate, copper chloride, copper nitrate, and copper acetate; The chromium salts include one or more of chromium sulfate, chromium chloride, chromium nitrate, and chromium acetate; The aluminum salts include one or more of aluminum sulfate, aluminum chloride, aluminum nitrate, and aluminum acetate; The magnesium salt includes one or more of magnesium sulfate, magnesium chloride, magnesium nitrate, and magnesium acetate; The zinc salts include one or more of zinc sulfate, zinc chloride, zinc nitrate, and zinc acetate.

4. The ceramic material for inert anodes in aluminum electrolysis according to claim 1, characterized in that, The complexing agent includes one or more of EDTA, ammonia, ammonium chloride, ammonium sulfate, ammonium nitrate, ammonium citrate, ethylenediamine, acetic acid, ammonium acetate, sodium fluoride, tartaric acid, maleic acid, succinic acid, citric acid, and malonic acid.

5. The ceramic material for inert anodes in aluminum electrolysis according to claim 1, characterized in that, The precipitant includes one or more of ammonia, sodium hydroxide, potassium hydroxide, calcium hydroxide, and ammonium hydroxide.

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