Preparation method of a SOFC ceramic support material

Abstract

The present invention provides a magnesium-aluminum composite ceramic material, a preparation method thereof and an application thereof, belonging to the technical field of solid oxide fuel cells. Instead of using a pore-forming agent, the present invention uses a precursor of a magnesium-aluminum composite ceramic material containing a large amount of anions as a raw material, and uses MgO and Al2O3 powders to regulate the composition ratio of the finally obtained magnesium-aluminum composite ceramic material. Then, through co-grinding, blank forming and sintering, the volume change generated by the phase structure transformation of the Mg-Al-O system in the ceramic is fully utilized to in-situ self-assemble pores to obtain a porous magnesium-aluminum composite ceramic material. The magnesium-aluminum composite ceramic material prepared by the present invention can be directly used for the production of a ceramic outer support of an SOFC. The prepared ceramic outer support has the characteristics of controllable composition and adjustable thermal expansion coefficient, can be adapted to most of the SOFC battery materials on the market, and can effectively reduce the production cost of SOFCs.

Description

Technical Field

[0001] The present invention belongs to the technical field of solid oxide fuel cells, and particularly relates to a magnesium-aluminum composite ceramic material, a preparation method thereof, and an application thereof. Background Art

[0002] A solid oxide fuel cell (SOFC) is a device that directly converts chemical energy into electrical energy and heat energy through an electrochemical method. Compared with traditional generators, there is no combustion process, so it is not restricted by the Carnot cycle, and the efficiency can reach 80% when waste heat is fully utilized. At present, SOFC has broad application prospects in the fields of cogeneration, ship shipping, and automotive range extension.

[0003] Traditional solid oxide fuel cells adopt a sandwich structure of anode - electrolyte - cathode. In order to ensure good catalytic activity, the cathode and anode must have sufficient effective porosity and good pore structure.

[0004] At present, the method of creating pores in industry generally adopts adding pore-forming agents. For example, Chinese invention patent CN108947568B discloses a method for preparing alumina hollow sphere bricks using a pore-forming agent, which uses a spherical pore-forming agent as any one of PS (polystyrene), PMMA (polymethyl methacrylate), or any combination of the two for pore formation; Chinese invention patent CN 111504105 B discloses that two co-crystals of sodium chloride / sodium sulfate with different particle sizes of thick and thin are mixed in a certain mass ratio to obtain a composite pore-forming agent, and the composite pore-forming agent is mixed uniformly with copper powder, added to a mold for roasting to obtain a liquid-absorbing core containing the composite pore-forming agent, and the composite pore-forming agent therein is dissolved and removed for pore formation; Chinese invention patent CN 100419012C discloses a composite pore-forming agent and a method for preparing an anode support using the same, and the organic pore-forming agent and the elemental carbon pore-forming agent are mixed in a ratio of (0.5 - 50) : (0 - 30) by mass; Chinese invention patent CN 111850338 B discloses a composite pore-forming agent mainly composed of water, soluble inorganic salts, kaolin, and bentonite, which is used for pore formation of foam metal.

[0005] The above patents all use adding pore-forming agents to create pores, and this process generally has the following disadvantages: (1) As a second phase is added, the pore-forming agent is difficult to be completely mixed evenly with the matrix material, which easily causes uneven pores in the material; (2) Some pore-forming agents or pore-forming methods will significantly reduce the bonding strength of the matrix. Summary of the Invention

[0006] In view of this, the purpose of the present invention is to provide a magnesium-aluminum composite ceramic material, a preparation method thereof, and an application thereof. The magnesium-aluminum composite ceramic material provided by the present invention creates pores through in-situ self-assembly, has uniform pores, and has good mechanical strength.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] The present invention provides a method for preparing a magnesium-aluminum composite ceramic material, comprising the following steps:

[0009] According to the composition of magnesium-aluminum oxides in the target magnesium-aluminum composite ceramic material, MgO powder, Al 2 O 3 powder and the precursor of the magnesium-aluminum composite ceramic material are mixed and ball-milled to obtain a co-milled powder;

[0010] The co-milled powder is formed to obtain a preform;

[0011] The preform is sintered to obtain a magnesium-aluminum composite ceramic material;

[0012] The composition of the precursor of the magnesium-aluminum composite ceramic material includes magnesium element, aluminum element, oxygen element and anions; the anions include at least NO 3 - , OH - , CO 3 2- , CH 3 COO - , HCO 3 - , SO 4 2- and PO 4 3- in one of them.

[0013] Preferably, in terms of the mass percentage content of oxides, the magnesium-aluminum composite ceramic material includes: MgO 30-90%; Al 2 O 3 10-70%; SiO 2 <1%.

[0014] Preferably, the molar ratio of magnesium element to aluminum element in the precursor of the magnesium-aluminum composite ceramic material is (1-5):1.

[0015] Preferably, the mass of the precursor of the magnesium-aluminum composite ceramic material accounts for 20-70% of the total mass of MgO powder, Al 2 O 3 powder and the precursor of the magnesium-aluminum composite ceramic material.

[0016] Preferably, the precursor of the magnesium-aluminum composite ceramic material is prepared by an aqueous phase reaction method.

[0017] Preferably, the aqueous phase reaction method includes co-precipitation method, hydrothermal method, sol-gel method or ion exchange method.

[0018] Preferably, before forming, it further includes mixing a binder with the co-ground powder; the binder includes one or more of starch, urea, glucose, alcohol binders, aldehyde binders, ester binders, and ketone binders; the mass of the binder accounts for less than 10% of the total mass of the binder and the co-ground powder.

[0019] Preferably, the sintering temperature is 1200 - 1600 °C; the heat preservation time for sintering is 2 - 10 h.

[0020] The present invention provides a magnesium-aluminum composite ceramic material prepared by the preparation method described in the above solution. The fracture strength of the magnesium-aluminum composite ceramic material is 100 - 180 MPa, the pore diameter is 5 - 25 μm, and the porosity is 30 - 50%.

[0021] The present invention provides an application of the magnesium-aluminum composite ceramic material described in the above solution in an SOFC ceramic support.

[0022] The present invention provides a preparation method of a magnesium-aluminum composite ceramic material, including the following steps: According to the composition of magnesium-aluminum oxides in the target magnesium-aluminum composite ceramic material, mix MgO powder, Al 2 O 3 powder with a magnesium-aluminum composite ceramic material precursor by ball milling to obtain co-ground powder; form the co-ground powder to obtain a preform; sinter the preform to obtain a magnesium-aluminum composite ceramic material; the composition of the magnesium-aluminum composite ceramic material precursor includes magnesium element, aluminum element, oxygen element, and anions; the anions include at least NO 3 - , OH - , CO 3 2- , CH 3 COO - , HCO 3 - , SO 4 2- and PO 4 3- in one kind. The present invention does not use a pore-forming agent, but uses a magnesium-aluminum composite ceramic material precursor as the raw material. The magnesium-aluminum composite ceramic material precursor is a structure with a large number of anion groups. During the high-temperature sintering process, the loss of anions achieves the purpose of in-situ pore formation, avoiding uneven pores caused by the use of a pore-forming agent. By adding MgO powder and Al 2 O 3 powder, using it as the initial skeleton support, it can regulate the composition ratio of the finally prepared magnesium-aluminum composite ceramic material and avoid the collapse of the structure; if only the magnesium-aluminum composite ceramic material precursor is used, it will collapse during the sintering process due to the lack of skeleton support and cannot achieve the purpose of in-situ pore formation. On the other hand, MgO, Al2 O 3 The magnesium-aluminum composite ceramic material precursor will undergo a solid-phase reaction at high temperatures to form a new phase, MgAl 2 O 4 , causing the Mg-Al-O framework to undergo reconstruction sintering, thereby improving the strength of the ceramic phase while retaining the original pore structure.

[0023] The magnesium-aluminum composite ceramic material prepared by the present invention will not react with the electrode material interface, has good compatibility, uniform pores, and has good porosity and mechanical strength. Moreover, by adjusting the amounts of MgO powder, Al 2 O 3 powder and the magnesium-aluminum composite ceramic material precursor, the composition ratio of MgO and Al 2 O 3 in the finally prepared ceramic material can be adjusted, and its thermal expansion coefficient can be changed to adapt to different electrode materials.

[0024] Furthermore, by adjusting the amount of the magnesium-aluminum composite ceramic material precursor, the porosity of the magnesium-aluminum composite ceramic material can be adjusted, and a magnesium-aluminum composite ceramic material with a porosity between 30% and 50% can be obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0026] Figure 1 XRD spectrum of the magnesium-aluminum composite ceramic material prepared in Example 1;

[0027] Figure 2 SEM image of the magnesium-aluminum composite ceramic material prepared in Example 1;

[0028] Figure 3 SEM image of the interface between the magnesium-aluminum composite ceramic material prepared in Example 1 and NiO-YSZ;

[0029] Figure 4 XRD patterns of the magnesium-aluminum composite ceramic material prepared in Example 1 and NiO-YSZ, and the mixture of the two sintered at 1450°C for 4 h;

[0030] Figure 5 Appearance of the tubular magnesium-aluminum composite ceramic material prepared in Example 1. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0031] The present invention provides a method for preparing a magnesium-aluminum composite ceramic material, comprising the following steps:

[0032] According to the composition of magnesium-aluminum oxides in the target magnesium-aluminum composite ceramic material, mix MgO powder, Al 2 O 3 powder with the precursor of the magnesium-aluminum composite ceramic material by ball milling to obtain a co-milled powder;

[0033] Mold the co-milled powder to obtain a preform;

[0034] Sinter the preform to obtain a magnesium-aluminum composite ceramic material;

[0035] The composition of the precursor of the magnesium-aluminum composite ceramic material includes magnesium element, aluminum element, oxygen element and anions; the anions include at least NO 3 - , OH - , CO 3 2- , CH 3 COO - , HCO 3 - , SO 4 2- and PO 4 3- one of them.

[0036] According to the composition of magnesium-aluminum oxides in the target magnesium-aluminum composite ceramic material, mix MgO powder, Al 2 O 3 powder with the precursor of the magnesium-aluminum composite ceramic material by ball milling to obtain a co-milled powder.

[0037] In the present invention, based on the mass percentage content of oxides, the target magnesium-aluminum composite ceramic material preferably includes: 30-90% of MgO; Al 2 O 3 10-70%; SiO 2 <1%. The content of MgO is further preferably 40-80%, more preferably 50-70%. The content of Al 2 O 3 is further preferably 20-60%, more preferably 30-50%.

[0038] In the present invention, the particle sizes of the MgO powder and Al 2 O 3 powder are independently preferably ≤10 μm, further preferably ≤5 μm, and more preferably ≤1 μm. By adding MgO powder and Al 2 O 3The powder is used as the initial skeleton support, which can regulate the composition ratio of the finally prepared magnesium-aluminum composite ceramic material and avoid the collapse of the structure. If the precursor of the magnesium-aluminum composite ceramic material is completely used, it will collapse during sintering due to the lack of skeleton support, and the purpose of in-situ pore formation cannot be achieved.

[0039] In the present invention, the molar ratio of magnesium element to aluminum element in the precursor of the magnesium-aluminum composite ceramic material is preferably (1-5):1, more preferably (2-4):1, and still more preferably (2.5-3.5):1. In the present invention, the mass of the precursor of the magnesium-aluminum composite ceramic material preferably accounts for 20-70% of the total mass of MgO powder, Al 2 O 3 powder and the precursor of the magnesium-aluminum composite ceramic material, further preferably 30-60%, and still more preferably 40-50%. By adjusting the dosage of the precursor, the porosity of the magnesium-aluminum composite ceramic material can be adjusted, and a ceramic material with a porosity between 30-50% can be obtained. In addition, by adjusting the dosages of MgO powder, Al 2 O 3 powder and the precursor of the magnesium-aluminum composite ceramic material, the composition ratio of MgO to Al 2 O 3 in the finally prepared ceramic material can be adjusted, and its thermal expansion coefficient can be changed, so as to adapt to different electrode materials.

[0040] In the present invention, the time of the mixed ball milling is preferably 2-12 h, more preferably 4-10 h, and still more preferably 5-7 h. In the present invention, the mixed ball milling is preferably carried out in an agate ball mill; the medium of the mixed ball milling is preferably zirconium beads; the mass ratio of the balls to the materials is preferably (1-20):1, more preferably (2-15):1, and still more preferably (3-10):1.

[0041] In the present invention, the precursor of the magnesium-aluminum composite ceramic material is preferably prepared by an aqueous phase reaction method; the aqueous phase reaction method preferably includes a co-precipitation method, a hydrothermal method, a sol-gel method or an ion exchange method.

[0042] In the present invention, the preparation method of the precursor of the magnesium-aluminum composite ceramic material preferably includes the following steps:

[0043] Dissolve the magnesium compound and the aluminum compound in water to obtain a magnesium-aluminum mixed solution;

[0044] Mix the alkaline solution or the anion exchanger with the magnesium-aluminum mixed solution, and carry out the corresponding reaction to obtain the precursor of the magnesium-aluminum composite ceramic material.

[0045] In the present invention, the magnesium compound preferably includes magnesium chloride, sulfate, phosphate, nitrate or organic salt; the magnesium chloride preferably includes magnesium chloride; the magnesium sulfate preferably includes magnesium sulfate; the magnesium phosphate preferably includes magnesium phosphate; the magnesium nitrate preferably includes magnesium nitrate; the magnesium organic salt preferably includes magnesium acetate, magnesium formate or magnesium picolinate. In the present invention, the aluminum compound preferably includes aluminum chloride, sulfate, phosphate, nitrate or organic salt; the aluminum chloride preferably includes aluminum chloride; the aluminum sulfate preferably includes aluminum sulfate; the aluminum phosphate preferably includes aluminum phosphate; the aluminum nitrate preferably includes aluminum nitrate; the aluminum organic salt preferably includes aluminum acetate, aluminum formate or aluminum tricarboxylate. In the present invention, the molar ratio of Mg in the magnesium compound to Al in the aluminum compound is preferably (1 to 5):1, more preferably (2 to 4):1, and still more preferably (2.5 to 3.5):1.

[0046] In the present invention, the alkaline solution preferably includes one or more of LiOH solution, NaOH solution, KOH solution, ammonia water, NaHCO 3 solution and Na 2 CO 3 solution; the concentration of the alkaline solution is preferably 0.5 to 3 mol / L, more preferably 0.8 to 2.5 mol / L, and still more preferably 1.2 to 2.2 mol / L.

[0047] Specifically, when preparing the precursor of the magnesium-aluminum composite ceramic material by the coprecipitation method, the preparation method of the precursor of the magnesium-aluminum composite ceramic material preferably includes the following steps:

[0048] Dissolve the magnesium compound and the aluminum compound in water to obtain a magnesium-aluminum mixed solution;

[0049] Add an alkaline solution to the magnesium-aluminum mixed solution, adjust and maintain the pH value of the mixed solution at 8 to 12, and precipitate in the mixed solution to obtain the precursor of the magnesium-aluminum composite ceramic material.

[0050] For the types and amounts of the magnesium compound and the aluminum compound and the types and amounts of the alkaline solution, refer to the above, and will not be elaborated here.

[0051] In the present invention, the alkaline solution is preferably added under stirring conditions, and after the addition is completed, stirring is continuously maintained. As a further preferred solution, the present invention preferably adjusts and maintains the pH value of the mixed solution at 9 to 11, and more preferably at 10 to 11.

[0052] After the precipitation no longer occurs, the present invention preferably filters, washes and dries the obtained precipitate to obtain the precursor of the magnesium-aluminum composite ceramic material. The present invention has no special requirements for the processes of stirring, filtering, washing and drying, and the well-known processes in the art can be adopted.

[0053] When preparing the precursor of the magnesium-aluminum composite ceramic material by the hydrothermal method, the preparation method of the precursor of the magnesium-aluminum composite ceramic material preferably includes the following steps:

[0054] Dissolve the magnesium compound and the aluminum compound in water to obtain a magnesium-aluminum mixed solution;

[0055] Add an alkaline solution to the magnesium-aluminum mixed solution, adjust the pH value of the magnesium-aluminum mixed solution to 8-12, and carry out a hydrothermal reaction on the magnesium-aluminum mixed solution with the adjusted pH value to obtain a precursor of the magnesium-aluminum composite ceramic material.

[0056] In the present invention, for the types and dosages of the magnesium compound and the aluminum compound and the types and dosages of the alkaline solution, refer to the above, and will not be elaborated here.

[0057] The present invention preferably adds the alkaline solution under stirring conditions, and keeps stirring continuously before carrying out the hydrothermal reaction after the addition is completed. As a further preferred scheme, the present invention preferably adjusts the pH value of the magnesium-aluminum mixed solution to 9-11, more preferably to 10-11.

[0058] In the present invention, the hydrothermal reaction is preferably carried out in a reaction kettle; the temperature of the hydrothermal reaction is preferably 100-230 °C, further preferably 110-210 °C, and more preferably 130-180 °C; the time of the hydrothermal reaction is preferably 1-4 h, and specifically can be 1 h, 2 h, 3 h or 4 h.

[0059] After completing the hydrothermal reaction, the present invention preferably filters, washes and dries the obtained precipitate to obtain the precursor of the magnesium-aluminum composite ceramic material. The present invention has no special requirements for the processes of filtration, washing and drying, and the processes well-known in the art can be adopted.

[0060] When preparing the precursor of the magnesium-aluminum composite ceramic material by the sol-gel method, the preparation method of the precursor of the magnesium-aluminum composite ceramic material preferably includes the following steps:

[0061] Dissolve the magnesium compound and the aluminum compound in water to obtain a magnesium-aluminum mixed solution;

[0062] Add an alkaline solution to the magnesium-aluminum mixed solution, adjust the pH value of the magnesium-aluminum mixed solution to 8-12, and heat the magnesium-aluminum mixed solution with the adjusted pH value to obtain a gel-like product, thereby obtaining a precursor of the magnesium-aluminum composite ceramic material.

[0063] In the present invention, for the types and dosages of the magnesium compound and the aluminum compound and the types and dosages of the alkaline solution, refer to the above, and will not be elaborated here.

[0064] The present invention preferably adds an alkaline solution under stirring conditions. After the addition is completed and before heating, stirring is continuously maintained. The present invention preferably adjusts the pH value of the magnesium-aluminum mixed solution to 9-11, more preferably 10-11.

[0065] In the present invention, the heating temperature is preferably 70-90 °C, further preferably 75-85 °C, and more preferably 78-82 °C; the heating time is preferably 4-12 h, further preferably 5.5-10.5 h, and more preferably 7-10 h.

[0066] After heating is completed, the present invention preferably filters, washes, and dries the obtained gel-like product to obtain the precursor of the magnesium-aluminum composite ceramic material. The present invention has no special requirements for the processes of filtration, washing, and drying, and the processes well-known in the art can be adopted.

[0067] When preparing the precursor of the magnesium-aluminum composite ceramic material by the ion exchange method, the preparation method of the precursor of the magnesium-aluminum composite ceramic material preferably includes the following steps:

[0068] Dissolve a magnesium compound and an aluminum compound in water to obtain a magnesium-aluminum mixed solution;

[0069] Add an anion exchanger to the magnesium-aluminum mixed solution, conduct ion exchange, and adjust the pH value of the exchanged solution to 3 to form a gel-like product, thereby obtaining the precursor of the magnesium-aluminum composite ceramic material.

[0070] In the present invention, the types and dosages of the magnesium compound and the aluminum compound are as described above and will not be elaborated here.

[0071] In the present invention, the anion exchanger preferably includes organic acids; the organic acids preferably include acetic acid, glutamic acid, or ethylenediaminetetraacetic acid.

[0072] After forming the gel-like product, the present invention preferably centrifuges, filters, washes, and dries the gel-like product to obtain the precursor of the magnesium-aluminum composite ceramic material. The present invention has no special requirements for the processes of centrifugation, filtration, washing, and drying, and the processes well-known in the art can be adopted.

[0073] In the present invention, the composition of the precursor of the magnesium-aluminum composite ceramic material preferably includes magnesium element, aluminum element, oxygen element, and anions; the anions preferably include at least NO 3 - , OH - , CO 3 2- , CH 3 COO - , HCO 3 - , SO 42- and PO 4 3- One of them. The precursor of the magnesium-aluminum composite ceramic material prepared in the present invention is a structure with a large number of anionic groups. During the high-temperature sintering process, the loss of anions achieves the purpose of in-situ pore formation and avoids uneven pores caused by the use of pore-forming agents.

[0074] After obtaining the co-ground powder, the present invention forms the co-ground powder to obtain a preform.

[0075] In the present invention, the forming is preferably extrusion forming or pressing forming; when extrusion forming is adopted, the forming is preferably carried out in an extruder; when pressing forming is adopted, the forming is preferably carried out in a mold, and the shape of the mold preferably includes flat shape, round tubular shape or corrugated shape. In the present invention, the pressure of the extrusion forming is preferably 50-100 MPa, further preferably 60-90 MPa, and more preferably 65-80 MPa; the time of the extrusion forming is preferably 3-5 min, specifically it can be 3 min, 4 min or 5 min. In the present invention, the pressure of the pressing forming is preferably 10-30 MPa, further preferably 15-30 MPa, and more preferably 20-30 MPa.

[0076] In the present invention, before the forming, it is also preferably to mix a binder with the co-ground powder; the binder preferably includes one or more of starch, urea, glucose, alcohol binders, aldehyde binders, ester binders and ketone binders. In the present invention, the alcohol binder preferably includes one or more of glycerol and ethylene glycol; the aldehyde binder preferably includes one or more of valeraldehyde and furfural; the ester binder preferably includes one or more of phenyl acetate and butyl acetate; the ketone binder preferably includes one or more of aliphatic ketones, alicyclic ketones and aromatic ketones; the aliphatic ketone preferably includes acetone, acetophenone, diethyl ketone, methyl isopropyl ketone, 2-pentanone or 2-nonanone; the alicyclic ketone preferably includes cyclohexanone, tolylcyclohexanone, cyclopentanone or cyclobutanone; the aromatic ketone preferably includes dibenzopyrone, phenanthrenone or fluorenone. In the present invention, the mass of the binder preferably accounts for less than 10% of the total mass of the binder and the co-ground powder, further preferably ≤7%, and more preferably ≤5%. The present invention can make the co-ground powder easier to be pressed into shape by adding a binder.

[0077] In the present invention, when the forming is carried out in a mold, it also preferably includes demolding.

[0078] After the forming is completed, it is preferable to dry the obtained green body. In the present invention, the drying temperature is preferably 75 to 85 °C, more preferably 78 to 83 °C, and still more preferably 80 °C; the drying time is preferably 12 to 36 h, more preferably 15 to 30 h, and still more preferably 20 to 28 h.

[0079] After obtaining the preform, the present invention sinters the preform to obtain a magnesium-aluminum composite ceramic material.

[0080] In the present invention, the sintering temperature is preferably 1200 to 1600 °C, more preferably 1300 to 1500 °C, and still more preferably 1400 to 1500 °C; the holding time for sintering is preferably 2 to 10 h, more preferably 3 to 8 h, and still more preferably 4 to 6 h. In the present invention, the heating rate to the sintering temperature is preferably 1 to 10 °C / min, more preferably 2 to 8 °C / min, and still more preferably 4 to 6 °C / min. In the present invention, the sintering is preferably carried out in an electric resistance furnace. The precursor of the magnesium-aluminum composite ceramic material prepared in the present invention has a structure with a large number of anionic groups. During the high-temperature sintering process, non-metal ions other than oxygen ions will vaporize and dissipate, so as to achieve the purpose of in-situ pore formation; at the same time, MgO, Al 2 O 3 and the magnesium-aluminum composite ceramic material precursor will undergo a solid-phase reaction during sintering to generate a new phase MgAl 2 O 4 .

[0081] In the present invention, after the sintering is completed, it is preferable to cool the obtained magnesium-aluminum composite ceramic material to room temperature.

[0082] The present invention provides a magnesium-aluminum composite ceramic material prepared by the above preparation method. The fracture strength of the magnesium-aluminum composite ceramic material is 100 to 180 MPa, the pore diameter is 5 to 25 μm, and the porosity is 30 to 50%.

[0083] In the present invention, the fracture strength of the magnesium-aluminum composite ceramic material is preferably 110 to 170 MPa, more preferably 120 to 150 MPa; the pore diameter of the magnesium-aluminum composite ceramic material is preferably 8 to 22 μm, more preferably 10 to 18 μm; the porosity of the magnesium-aluminum composite ceramic material is preferably 35 to 45%, more preferably 38 to 42%.

[0084] The present invention uses a magnesium-aluminum composite ceramic material precursor containing a large amount of anions as a raw material, and obtains a porous magnesium-aluminum composite ceramic material through in-situ pore formation, avoiding the use of pore-forming agents, and the obtained magnesium-aluminum composite ceramic material has uniform pores; in addition, during the sintering process, MgO, Al 2 O 3The precursor of the magnesium-aluminum composite ceramic material will undergo a solid-phase reaction at high temperatures to form a new phase, MgAl 2 O 4 , causing the Mg-Al-O framework to undergo reconstructive sintering, thereby improving the strength of the ceramic phase while retaining the original pore structure.

[0085] In addition, the porosity of the magnesium-aluminum composite ceramic of the present invention can be adjusted. By adjusting the amount of the precursor of the magnesium-aluminum composite ceramic material, the porosity of the magnesium-aluminum composite ceramic material can be adjusted, and a magnesium-aluminum composite ceramic material with a porosity between 30% and 50% can be obtained.

[0086] The present invention provides the application of the magnesium-aluminum composite ceramic material described in the above solution in the preparation of an SOFC ceramic support. The magnesium-aluminum composite ceramic material provided by the present invention does not react with the electrode material at the interface, has good compatibility, uniform pores, and has good porosity and mechanical strength. Moreover, the thermal expansion coefficient can be changed by adjusting the composition ratio of the finally prepared ceramic material, so as to adapt to different electrode materials.

[0087] In order to further illustrate the present invention, the preparation method and application of the magnesium-aluminum composite ceramic material provided by the present invention will be described in detail below with reference to the drawings and embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0088] Example 1

[0089] Using the coprecipitation method, Mg(NO 3 ) 2 and Al(NO 3 ) 3 were weighed according to a molar ratio of 3:1 and dissolved in water to obtain a Mg-Al-NO 3 mixed solution;

[0090] 1 mol / L of NaOH solution was added to the Mg-Al-NO 3 mixed solution, and continuous stirring was carried out to adjust and maintain the pH value of the mixed solution at 10-11, and precipitation occurred in the mixed solution;

[0091] After the precipitation no longer occurred, the precipitate was filtered, washed, and dried to obtain the precursor of the magnesium-aluminum composite ceramic material;

[0092] According to the composition of 85 wt% MgO and 15 wt% Al 2 O 3 in the target magnesium-aluminum composite ceramic material, MgO powder with a particle size ≤ 10 μm and Al 2 O 3 powder were mixed with the precursor of the magnesium-aluminum composite ceramic material (the mass of the precursor of the magnesium-aluminum composite ceramic material accounts for MgO powder, Al2 O 3 (50% of the total mass of the powder and the precursor of the magnesium-aluminum composite ceramic material), and add it to an agate ball mill. Use zirconium beads as the ball milling medium, and the mass ratio of the balls to the material is 3:1. After ball milling for 12 h, the co-ground powder is obtained;

[0093] Mix 5 wt% of starch with the co-ground powder, and extrude it into a tubular support in an extrusion machine. The extrusion pressure is 100 MPa, and the extrusion time is 3 min. Then place it in an oven at 80 ± 5 °C and dry for 24 h. Place the qualified dried green body in a resistance furnace, heat it to 1450 °C at a rate of 2 °C / min, and keep it for 4 h, and then naturally cool it to room temperature to obtain the magnesium-aluminum composite ceramic material.

[0094] For the magnesium-aluminum composite ceramic material prepared in this example, the coefficient of thermal expansion at 800 °C is 12.81×10 -6 / °C, which is basically compatible with NiO-YSZ.

[0095] Example 2

[0096] Adopt the hydrothermal method. Weigh MgCl 2 and AlCl 3 according to the molar ratio of 2:1, and dissolve them in water to obtain a Mg-Al-Cl mixed solution;

[0097] Add 1 mol / L ammonia water and Na 2 CO 3 solution to the Mg-Al-Cl mixed solution, and continuously stir to adjust the pH value of the mixed solution to 10 - 11. Then pour the magnesium-aluminum mixed solution with adjusted pH value into a reaction kettle for hydrothermal reaction, and keep it at 120 °C for 4 h;

[0098] Filter, wash and dry the obtained precipitate to obtain the precursor of the magnesium-aluminum composite ceramic material;

[0099] According to the composition of 70 wt% MgO and 30 wt% Al 2 O 3 in the target magnesium-aluminum composite ceramic material, mix the MgO powder with a particle size ≤ 5 μm and Al 2 O 3 powder with the precursor of the magnesium-aluminum composite ceramic material (the mass of the precursor of the magnesium-aluminum composite ceramic material accounts for 40% of the total mass of the MgO powder, Al 2 O 3 powder and the precursor of the magnesium-aluminum composite ceramic material), and add it to an agate ball mill. Use zirconium beads as the ball milling medium, and the mass ratio of the balls to the material is 8:1. After ball milling for 3 h, the co-ground powder is obtained;

[0100] Mix 6 wt% of polyvinylpyrrolidone with the co-ground powder, and place it in an extrusion tube machine to extrude a tubular support. The extrusion pressure is 100 MPa, and the extrusion time is 3 min. Then place it in an oven at 80 ± 5 °C and dry for 24 h. Place the qualified dried blank in an electric resistance furnace, heat it to 1200 °C at a rate of 4 °C / min, hold for 10 h, and then cool it naturally to room temperature to obtain the magnesium-aluminum composite ceramic material.

[0101] For the magnesium-aluminum composite ceramic material prepared in this example, the coefficient of thermal expansion at 800 °C is 7.42×10 -6 / °C.

[0102] Example 3

[0103] Using the sol-gel method, weigh Mg(CH 3 COO) 2 ·4H 2 O and Al(CH 3 COO) 3 in a molar ratio of 3.5:1, and dissolve them in water to obtain a Mg-Al-CH 3 COO mixed solution;

[0104] Add 1 mol / L KOH and NaHCO 3 solution to the mixed solution, and continuously stir to adjust the pH value of the mixed solution to 8 - 12. Keep the magnesium-aluminum mixed solution after adjusting the pH value at 90 °C for 6 h to obtain a gel-like product;

[0105] Filter, wash, and dry the gel-like product to obtain a precursor of the magnesium-aluminum composite ceramic material;

[0106] According to the composition of 65 wt% MgO and 35 wt% Al 2 O 3 in the target magnesium-aluminum composite ceramic material, mix MgO powder with a particle size ≤ 1 μm and Al 2 O 3 powder with the precursor of the magnesium-aluminum composite ceramic material (the mass of the precursor of the magnesium-aluminum composite ceramic material accounts for 30% of the total mass of the MgO powder, Al 2 O 3 powder and the precursor of the magnesium-aluminum composite ceramic material), and add it to an agate ball mill. Use zirconium beads as the ball milling medium, and the ball-to-material mass ratio is 10:1. After ball milling for 2 h, obtain the co-ground powder;

[0107] Mix 8 wt% glycerol with the co-ground powder, place it in an extrusion tube machine to extrude a circular tubular support, with an extrusion pressure of 80 MPa and an extrusion time of 4 min. Then place it in an oven at 80 ± 5 °C and dry for 24 h. The qualified green body after drying is placed in a resistance furnace, heated to 1400 °C at a rate of 6 °C / min, held for 8 h, and then naturally cooled to room temperature to obtain the magnesium-aluminum composite ceramic material.

[0108] The magnesium-aluminum composite ceramic material prepared in this example has a thermal expansion coefficient of 8.66×10 -6 / °C at 800 °C.

[0109] Example 4

[0110] Using the ion exchange method, weigh MgSO 4 and Al 2 (SO 4 ) 3 in a molar ratio of 4:1 and dissolve them in water to obtain a Mg-Al-SO 4 mixed solution;

[0111] Add glutamic acid as an anion exchanger to the Mg-Al-SO 4 mixed solution for ion exchange, adjust the pH value of the mixed solution to 3, and a gel-like product appears;

[0112] Centrifuge, filter, wash, and dry the gel-like product to obtain the precursor of the magnesium-aluminum composite ceramic material;

[0113] According to the composition of 80 wt% MgO and 20 wt% Al 2 O 3 in the target magnesium-aluminum composite ceramic material, mix MgO powder with a particle size ≤ 5 μm and Al 2 O 3 powder with the precursor of the magnesium-aluminum composite ceramic material (the mass of the precursor of the magnesium-aluminum composite ceramic material accounts for 60% of the total mass of the MgO powder, Al 2 O 3 powder and the precursor of the magnesium-aluminum composite ceramic material), and add it to an agate ball mill. Use zirconium beads as the ball milling medium, with a ball-to-material mass ratio of 6:1. After ball milling for 4 h, obtain the co-ground powder;

[0114] Mix 7 wt% glucose with the co-ground powder, place it in an extrusion tube machine to extrude a circular tubular support, with an extrusion pressure of 80 MPa and an extrusion time of 4 min. Then place it in an oven at 80 ± 5 °C and dry for 24 h. The qualified green body after drying is placed in a resistance furnace, heated to 1500 °C at a rate of 8 °C / min, held for 6 h, and then naturally cooled to room temperature to obtain the magnesium-aluminum composite ceramic material.

[0115] The magnesium-aluminum composite ceramic material prepared in this example has a thermal expansion coefficient of 10.17×10 -6 / °C at 800 °C and can be adapted to LST.

[0116] Example 5

[0117] Using the hydrothermal method, weigh Mg(NO 3 ) 2 and AlCl 3 in a molar ratio of 2.5:1, and dissolve them in water to obtain a Mg-Al-Cl mixed solution;

[0118] Add 1 mol / L ammonia water and NaHCO 3 solution to the mixed solution, and continuously stir to adjust the pH value of the mixed solution to 9-11. Then pour the magnesium-aluminum mixed solution with adjusted pH value into a reaction kettle for hydrothermal reaction and maintain it at 120 °C for 4 h;

[0119] Filter, wash, and dry the obtained precipitate to obtain a precursor of the magnesium-aluminum composite ceramic material;

[0120] According to the composition of 50 wt% MgO and 50 wt% Al 2 O 3 in the target magnesium-aluminum composite ceramic material, mix MgO powder with a particle size ≤1 μm and Al 2 O 3 powder with the precursor of the magnesium-aluminum composite ceramic material (the mass of the precursor of the magnesium-aluminum composite ceramic material accounts for 70% of the total mass of the MgO powder, Al 2 O 3 powder and the precursor of the magnesium-aluminum composite ceramic material), and add it to an agate ball mill. Use zirconium beads as the ball milling medium, and the ball-to-material mass ratio is 4:1. After ball milling for 8 h, obtain a co-milled powder;

[0121] Mix 9 wt% urea with the co-milled powder, place it in an extrusion tube machine to extrude a tubular support, the extrusion pressure is 70 MPa, and the extrusion time is 4 min. Then place it in an oven at 80±5 °C for drying for 24 h. The qualified green body after drying is placed in a resistance furnace, heated to 1300 °C at a rate of 10 °C / min, and kept warm for 7 h and then naturally cooled to room temperature to obtain the magnesium-aluminum composite ceramic material.

[0122] The magnesium-aluminum composite ceramic material prepared in this example has a thermal expansion coefficient of 11.52×10 -6 / °C at 800 °C and can be adapted to YSZ.

[0123] Example 6

[0124] Using the co-precipitation method, Mg3 (PO 4 ) 2 and AlPO 4 are weighed in a molar ratio of 1:1 and dissolved in water to obtain a Mg-Al-PO 4 mixed solution;

[0125] Add 1 mol / L NaOH solution to the mixed solution and continuously stir to adjust and maintain the pH value of the mixed solution at 9-10, and a precipitate will form in the mixed solution;

[0126] After the precipitate no longer forms, filter, wash, and dry the precipitate to obtain a precursor of the magnesium-aluminum composite ceramic material;

[0127] According to 40 wt% MgO and Al 2 O 3 60 wt% in the target magnesium-aluminum composite ceramic material for batching, mix MgO powder with a particle size ≤ 10 μm and Al 2 O 3 powder with the precursor of the magnesium-aluminum composite ceramic material (the mass of the precursor of the magnesium-aluminum composite ceramic material accounts for 20% of the total mass of the MgO powder, Al 2 O 3 powder and the precursor of the magnesium-aluminum composite ceramic material), and add it to an agate ball mill. Use zirconium beads as the ball milling medium, with a ball-to-material mass ratio of 2:1. After ball milling for 12 h, a co-milled powder is obtained;

[0128] Mix 10 wt% ethylene glycol with the co-milled powder, place it in an extrusion tube machine to extrude a tubular support, with an extrusion pressure of 50 MPa and an extrusion time of 5 min. Then place it in an oven at 80 ± 5 °C for drying for 24 h. The qualified green body after drying is placed in a resistance furnace and heated to 1600 °C at a rate of 5 °C / min, and kept at this temperature for 9 h and then naturally cooled to room temperature to obtain the magnesium-aluminum composite ceramic material.

[0129] The magnesium-aluminum composite ceramic material prepared in this example has a thermal expansion coefficient of 13.68×10 -6 / °C at 800 °C.

[0130] Example 7

[0131] Using the sol-gel method, weigh MgCl 2 and Al(NO 3 ) 3 in a molar ratio of 5:1 and dissolve them in water to obtain a Mg-Al-NO 3 mixed solution;

[0132] Add 1 mol / L NaOH and Na 2CO 3 The solution was continuously stirred, and the pH value of the mixed solution was adjusted to 8 - 10. The magnesium-aluminum mixed solution with adjusted pH value was maintained at 90 °C for 6 h, and a gel-like product appeared;

[0133] The gel-like product was filtered, washed, and dried to obtain a precursor of magnesium-aluminum composite ceramic material;

[0134] According to 30 wt% of MgO and 70 wt% of Al 2 O 3 in the target magnesium-aluminum composite ceramic material for batching, MgO powder with a particle size ≤ 5 μm and Al 2 O 3 powder were mixed with the precursor of magnesium-aluminum composite ceramic material (the mass of the precursor of magnesium-aluminum composite ceramic material accounted for 45% of the total mass of MgO powder, Al 2 O 3 powder and the precursor of magnesium-aluminum composite ceramic material), and it was added to an agate ball mill. Zirconium beads were used as the ball milling medium, and the ball-to-material mass ratio was 5:1. After ball milling for 6 h, a co-milled powder was obtained;

[0135] 6% furfural was mixed with the co-milled powder, and it was placed in an extrusion tube machine to extrude a circular tubular support. The extrusion pressure was 60 MPa, and the extrusion time was 5 min. Then it was placed in an oven at 80 ± 5 °C for drying for 24 h. The qualified green body after drying was placed in a resistance furnace, heated to 1300 °C at a rate of 7 °C / min, and kept warm for 8 h and then naturally cooled to room temperature to obtain a magnesium-aluminum composite ceramic material.

[0136] For the magnesium-aluminum composite ceramic material prepared in this example, the thermal expansion coefficient at 800 °C was 14.11×10 -6 / °C and it could be adapted to LSCF-GDC.

[0137] Comparative Example 1

[0138] MgO powder with a particle size ≤ 10 μm and Al 2 O 3 powder were batched according to a mass ratio of 85:15, and 10% of the total mass of activated carbon was added as a pore-forming agent, and 5 wt% of starch was used as a binder. Mixing was carried out using an agate ball mill, zirconium beads were used as the ball milling medium, and the ball-to-material mass ratio was 3:1. After ball milling for 12 h, it was placed in an extrusion tube machine to extrude a circular tubular support. The extrusion pressure was 100 MPa, and the extrusion time was 3 min. Then it was placed in an oven at 80 ± 5 °C for drying for 24 h. The qualified green body after drying was placed in a resistance furnace, heated to 1450 °C at a rate of 2 °C / min, and kept warm for 4 h and then naturally cooled to room temperature to obtain a magnesium-aluminum composite ceramic material.

[0139] Performance testing and structural characterization

[0140] Table 1 shows the test results of the thermal expansion coefficient, porosity, and fracture strength of the magnesium-aluminum composite ceramic materials prepared in Examples 1 to 7 and Comparative Example 1.

[0141] (1) The test of the thermal expansion coefficient was carried out using a PCY-G high-precision thermal dilatometer from Hunan Xiangyi (specifically refer to the instrument operation manual). Its working principle is that one end of the push rod touches the long strip sample, and the other end touches the displacement sensor. When the sample undergoes a length change due to the temperature increase in the tube furnace, the change situation is transmitted by the displacement sensor to the intelligent instrument and recorded by the intelligent instrument. Then, the system calculates and gives the thermal expansion coefficient (TEC) of the sample based on the recorded sample length change data.

[0142] (2) The test of porosity: The test of porosity was completed using an MDJ-300A1 density balance from Xiamen Ouyin. Its working principle is the Archimedes drainage method. First, weigh the dry weight of the sample to be measured, denoted as m 0 ; then, place the weighed sample in a clean water tank, pour distilled water into the beaker until the sample is submerged and add an appropriate amount of zeolite; then place the sample in a constant temperature heating box and heat and boil for 2 h to allow the distilled water to fully penetrate into the pores of the sample. Stop heating, and after cooling, take out the sample and place it on the hanging basket of the density balance (immersed in the water tank), and weigh the floating weight of the sample in water, denoted as m 1 ; then take out the sample, use a wet cloth to wipe off the water stained on the surface of the sample, and quickly weigh the mass of the sample at this time, denoted as m 2 .

[0143] (3) The fracture strength was tested by the three-point bending method. During the test, place the sample to be measured on the sample stage with a spacing of 16 - 20 mm, and the external load is applied by a universal testing machine. The fracture strength of the sample is obtained by calculating according to formula (1).

[0144]

[0145] In the formula: F—the maximum fracture load applied to the sample measured (N)

[0146] L—the span between the two supports (mm)

[0147] a—the width of the cross-section of the specimen (mm)

[0148] h—the thickness of the specimen (mm)

[0149] σ—the flexural strength of the sample measured (Mpa)

[0150] The magnesium-aluminum composite ceramic material prepared in Example 1 was characterized by XRD, and the results are shown in Figure 1 . From Figure 1It can be seen that the main phases of the prepared magnesium-aluminum composite ceramic material include MgAl 2 O 4 and MgO.

[0151] The magnesium-aluminum composite ceramic material prepared in Example 1 was observed by SEM, and the results are shown in Figure 2 . It can be seen from Figure 2 that the pore distribution of the prepared magnesium-aluminum composite ceramic material is uniform and has a good porosity. After testing, its porosity is 45.63%, meeting the working requirements of SOFC.

[0152] The interface between the magnesium-aluminum composite ceramic material prepared in Example 1 and NiO-YSZ was observed by SEM, and the results are shown in Figure 3 . The interface is formed by bonding the magnesium-aluminum composite ceramic material and NiO-YSZ materials together by brushing or spraying, and they are firmly bonded together after sintering. However, an obvious boundary line can be observed under the electron microscope. It can be seen from Figure 3 that the compatibility between the two is good, the combination is tight and there is an obvious boundary layer, indicating that there will be no significant chemical reaction between them and they can coexist stably for a long time.

[0153] Figure 4 is the XRD pattern of the magnesium-aluminum composite ceramic material prepared in Example 1, NiO-YSZ, and their mixture sintered at 1450 °C for 4 h. It can be seen from Figure 4 that no new phases are formed, indicating that there will be no chemical reaction between them.

[0154] Figure 5 is the appearance of the tubular magnesium-aluminum composite ceramic material extruded by an extruder in Example 1. It can be seen from Figure 5 that through the preparation method described in the above scheme, a tubular magnesium-aluminum composite ceramic material can be prepared. Combining the properties described in other figures, it shows that the magnesium-aluminum composite ceramic material prepared by the present invention can be used as a support for SOFC.

[0155] Table 1 Performance test results

[0156]

[0157] It can be seen from Table 1 that with different formulation ratios, the thermal expansion coefficients of the prepared magnesium-aluminum composite ceramic materials at 800 °C are in the range of 7.42×10 -6 ~13.68×10 -6Between / ℃, covering all current SOFC cathode and anode materials, indicating that with the formula of the present invention, by adjusting the proportion, a support body formula can be provided for any SOFC; the porosity is between 32.16% and 45.63%, indicating that any formula meets the requirements of SOFC for the support body; on the premise that the porosity is not lower than that of Comparative Example 1, the fracture strength of the magnesium-aluminum composite ceramic material prepared by the present invention is higher than that of the porous composite ceramic currently using pore-forming agents, indicating that the formula of the present invention is superior to the formula for preparing porous composite ceramics currently using pore-forming agents.

[0158] Although the above embodiments have described the present invention in detail, they are only a part of the embodiments of the present invention, rather than all embodiments. People can also obtain other embodiments based on this embodiment without creative efforts, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A preparation method of a magnesium-aluminum composite ceramic material, characterized in that, it comprises the following steps: According to the composition of magnesium-aluminum oxides in the target magnesium-aluminum composite ceramic material, MgO powder, Al 2 O 3 powder and the precursor of the magnesium-aluminum composite ceramic material are mixed and ball-milled to obtain a co-milled powder; Form the co-ground powder to obtain a preform; Sinter the preform to obtain a magnesium-aluminum composite ceramic material; The composition of the precursor of the magnesium-aluminum composite ceramic material includes magnesium element, aluminum element, oxygen element and anions; the anions include at least NO 3- , OH - , CO 3 2- , CH 3 COO - , HCO 3- , SO 4 2- and PO 4 3- ; the porosity of the magnesium-aluminum composite ceramic material is 30-50%; The molar ratio of magnesium element to aluminum element in the precursor of the magnesium-aluminum composite ceramic material is (1-5):

1.

2. The preparation method according to claim 1, characterized in that, Based on the mass percentage of the oxides, the magnesium-aluminum composite ceramic material comprises: 30 to 90% of MgO; Al 2 O 3 10 to 70%; SiO 2 < 1%.

3. The preparation method according to claim 1, characterized in that, The mass of the precursor of the magnesium-aluminum composite ceramic material accounts for 20-70% of the total mass of the MgO powder, Al 2 O 3 powder and the precursor of the magnesium-aluminum composite ceramic material.

4. The preparation method according to claim 1, characterized in that, The precursor of the magnesium-aluminum composite ceramic material is prepared by an aqueous phase reaction method.

5. The preparation method according to claim 4, characterized in that, The aqueous phase reaction method includes co-precipitation method, hydrothermal method, sol-gel method or ion exchange method.

6. The preparation method according to claim 1, characterized in that, Before forming, it further includes mixing a binder with the co-ground powder; the binder includes one or more of starch, urea, glucose, alcohol binders, aldehyde binders, ester binders and ketone binders; the mass of the binder accounts for less than 10% of the total mass of the binder and the co-ground powder.

7. The preparation method according to claim 1, characterized in that, The sintering temperature is 1200-1600 °C; the sintering holding time is 2-10 h.

8. The magnesium-aluminum composite ceramic material prepared by the preparation method according to any one of claims 1-7, the fracture strength of the magnesium-aluminum composite ceramic material is 100-180 MPa, the pore size is 5-25 μm, and the porosity is 30-50%.

9. Application of the magnesium-aluminum composite ceramic material according to claim 8 in an SOFC ceramic support.

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