Tubular ceramic support body for solid oxide fuel cell and preparation method of tubular ceramic support body

Abstract

The invention discloses a tubular ceramic support body for a solid oxide fuel cell and a preparation method of the tubular ceramic support body, and belongs to the technical field of solid oxide fuel cells. The method solves the problems that when the tubular SOFC supporting body is prepared through an extrusion molding method, a green body is greatly influenced by environment temperature and humidity, the green body is prone to cracking and deformation, the consumption of raw materials is large, and secondary utilization of remaining green bodies is difficult. The preparation method comprises the following steps: firstly preparing a powder material, then mixing the powder material with wax to form slurry, or mixing the powder material with NiO and then mixing with wax to form slurry, cooling and kneading the slurry to obtain a blank, performing extrusion molding on the blank under heating to obtain a green body, and de-waxing and sintering the green body to obtain the tubular ceramic support. The preparation method provided by the invention has the advantages of high yield, small influence by environmental temperature and humidity, small raw material consumption, difficult cracking and deformation of the blank, and reutilization of the residual blank, and the prepared tubular support has proper compactness and porosity, has certain hardness, and is suitable for industrial production and application.

Description

Technical Field

[0001] The invention belongs to the technical field of solid oxide fuel cells, and in particular relates to a tubular ceramic support for a solid oxide fuel cell and a preparation method thereof. Background Art

[0002] Solid Oxide Fuel Cells (SOFC) are highly efficient electrochemical conversion devices that convert chemical energy in fuels (hydrogen and other forms of hydrocarbons) into electrical energy through various electrochemical reactions. Compared with mechanical generators that work at the Carnot cycle efficiency, SOFC has higher efficiency because it does not involve a combustion process. Compared with traditional generators, SOFC has higher power efficiency. SOFC also has a wide range of fuel flexibility and can use hydrocarbons such as hydrogen, natural gas, coal gas, biomass gas, hydrocarbons, alcohols, etc. as fuels for power generation. At present, in the field of solid oxide fuel cells (SOFC), the structure of the battery is mainly determined by the support body. There are two common battery structures, namely flat and tubular. The structure of the flat SOFC is relatively simple, with the advantages of high power density, low manufacturing cost, and easy integration, but there are shortcomings. First, the thermal cycle stability of the SOFC system is poor, and second, for large-area flat SOFCs, sealing work is quite difficult. In comparison, tubular SOFC has demonstrated its unique advantages. It can present different diameter and length specifications, is easy to seal, and has good thermal cycle stability. Not only that, tubular SOFC can also effectively shorten the startup time, can achieve higher volume output density, and has the characteristic of portability. Based on these advantages and characteristics, tubular SOFC has a broader application prospect.

[0003] At present, the main preparation methods of tubular SOFC supports are impregnation, grouting, phase transformation and extrusion. The impregnation method is to mix the raw materials with a binder and a solvent into a suspended slurry, immerse the mold and pull it up at a uniform speed, and form a liquid film by adhesion and gravity. Repeat the operation, and wait for the solvent to evaporate and solidify to obtain a green body of the desired thickness. The impregnation method is simple to operate and low in cost. The support obtained has high mechanical strength, small deformation and uniform microstructure, but the green body has a high shrinkage rate, it is difficult to accurately control the battery size, and the thickness is uneven in the length direction of the tube; the grouting method is to mix the raw material powder with a surfactant to form a stable water-based suspension and inject it into the gypsum mold. As the water penetrates, the ceramic powder is formed on the mold wall due to physical and chemical effects. Aggregation and deposition to obtain a green body of a specific shape. This method is simple to operate, has strong applicability, a small amount of organic additives, and low cost. It can produce a variety of support bodies, but the production efficiency and recycling rate of gypsum molds are low, the green body has low mechanical strength, and it is easy to deform during sintering; the phase inversion method is to dissolve the polymer in a solvent and mix it into the ceramic raw material to make it cross-linked into a network structure, and then use a non-solvent liquid to extract the solvent to solidify the polymer to obtain a green body. The green body has a special straight pore structure and rich pores. The preparation process is simple and the production efficiency is high. However, when sintered at high temperature, the green body will be severely deformed. Based on the defects of the above methods, the researchers continued to study the preparation method of tubular SOFC and developed an extrusion molding method. This method is to mix the powder raw material with water and additives such as a binder to refine it into an extruded green body, and use an extrusion molding device to apply pressure so that the green body is extruded into a green body of a specific shape through an extrusion die. This method has high production efficiency, relatively low equipment cost, and simple process, but it is greatly affected by the temperature and humidity factors of the environment. The green body is easy to crack and deform, the raw material consumption is large, and the remaining green body is difficult to reuse. Summary of the invention

[0004] In order to solve the technical problems in preparing a tubular SOFC support by extrusion molding, such as the green body is greatly affected by the ambient temperature and humidity, the green body is easy to crack and deform, the raw material consumption is large, and the remaining green body is difficult to recycle, the present invention provides a tubular ceramic support for a solid oxide fuel cell and a preparation method thereof.

[0005] In order to solve the above technical problems, the present invention is implemented through the following technical solutions:

[0006] The object of the present invention is to provide a method for preparing a tubular ceramic support for a solid oxide fuel cell, comprising:

[0007] (1) Preparation of powder material: placing raw material powder containing metal elements into a ball mill, adding grinding balls and a ball milling solvent for the first ball milling to obtain a slurry, drying and compacting the slurry, and then sequentially performing high-temperature calcination, secondary ball milling and secondary drying steps, and sequentially performing re-sintering, tertiary ball milling, tertiary drying and sieving on the powder after the secondary drying to obtain a powder material;

[0008] (2) Mixing: Put wax into a stirring tank, increase the temperature, and after the wax is completely melted, add the preheated powder material or mixed powder, stir to obtain a mixed slurry, transfer the mixed slurry to a slow speed slurry bucket, stir under vacuum, and then cool the mixed slurry into a block material, and process the block material through a kneader to obtain a blank;

[0009] (3) Extrusion molding: Extruding the blank at a certain temperature to obtain a blank, and cutting the blank;

[0010] (4) Drying and sintering: drying the cut green body, dewaxing and sintering the dried green body to obtain a tubular ceramic support body;

[0011] The mixed powder consists of powder material and NiO.

[0012] It is further defined that the mass ratio of the powder material to NiO is (1-3):2.

[0013] It is further defined that the raw material powder containing metal elements in (1) is a mixture of barium carbonate, zirconium oxide, cerium oxide, ytterbium oxide and yttrium oxide.

[0014] It is further defined that the molar ratio of the barium element, the zirconium element, the cerium element, the ytterbium element and the yttrium element in the mixture is 1:0.1:0.7:0.1:0.1.

[0015] It is further defined that the mass ratio of the grinding balls to the raw material powder containing the metal element in (1) is (1-5):1.

[0016] It is further defined that the ball milling solvent in (1) is one of anhydrous ethanol, methanol, butanone, benzene and xylene.

[0017] It is further defined that the ball milling speed in (1) is 200 to 500 r / min and the time is 12 to 36 h.

[0018] It is further defined that (1) the medium-high temperature calcination temperature is 1000-1400°C and the time is 6-12 hours.

[0019] It is further defined that the re-firing temperature in (1) is 1000-1400°C and the time is 6-12 hours.

[0020] Further, the chemical formula of the powder material in (1) is BaZr 0.1 Ce 0.7 Yb 0.1 Y 0.1 O 3-δ .

[0021] It is further defined that δ is the oxygen vacancy concentration, and 3-δ ranges from 2.5 to 2.9.

[0022] It is further defined that: (2) the mass ratio of the medium wax to the powder material or the mixed powder is (1-3): 20.

[0023] It is further defined that the preheating temperature in (2) is 60-80°C and the time is 2-5 hours.

[0024] It is further defined that the stirring speed under medium vacuum in (2) is 100 to 200 r / min and the time is 2 to 4 h.

[0025] It is further defined that the extrusion molding temperature in (3) is 60 to 100°C.

[0026] It is further defined that the drying time in (4) is 1 to 3 days.

[0027] It is further defined that the sintering process in (4) is: heating to 1000°C at a rate of 3-10°C / min, then heating to 1050-1450°C at a rate of 1-3°C / min, and keeping the temperature for 6-12h.

[0028] A second object of the present invention is to provide a tubular ceramic support for a solid oxide fuel cell prepared by the above method.

[0029] The beneficial effects of the present invention are:

[0030] (1) The traditional tubular solid oxide fuel cell ceramic support uses water or solution mixed with powder to prepare the ceramic body. During the long drying process of the body, the volatilization of water or solution is greatly affected by the ambient temperature and humidity, resulting in different drying speeds on the surface and inside of the body, causing uneven shrinkage of the body and changes in the internal structure, which leads to cracking of the body. The present invention uses wax mixed with powder to prepare the body. Compared with water or solution, wax is stable at room temperature, avoiding the cracking of the body caused by the influence of ambient temperature and humidity. At the same time, the wax substance is mixed with the powder more evenly, and the density of the body is improved.

[0031] (2) The present invention performs extrusion molding under heating conditions, which is conducive to the wax flowing in the extrusion head without sticking to the inside of the extrusion head, so that the blank is cooled and shaped outside the extrusion head after extrusion, which is conducive to blank molding.

[0032] (3) Compared with the hot injection extrusion molding method, the preparation method provided by the present invention is not limited by the mold size because no mold is required in the molding process. Large-sized tubular ceramic supports can be manufactured, and the product application range is wider. The preparation method provided by the present invention breaks the problem that the traditional hot injection molding process cannot prepare large-sized supports and requires the use of molds.

[0033] (4) The preparation method provided by the present invention has a high yield rate, is less affected by ambient temperature and humidity, consumes less raw materials, the green body is not easy to crack and deform, the remaining green body can be reused, and the prepared tubular ceramic support has appropriate density and porosity, has strong hardness, and is suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is a physical photo of the extruded body obtained in (3) of Example 1;

[0035] Figure 2 This is a photo of the tubular ceramic support obtained after sintering in (4) of Example 1;

[0036] Figure 3 This is a SEM image of the tubular ceramic support obtained after sintering in (4) of Example 1;

[0037] Figure 4 This is a physical photo of the extruded body obtained in (3) of Example 2;

[0038] Figure 5 This is a photo of the tubular ceramic support obtained after sintering in (4) of Example 2;

[0039] Figure 6 This is a SEM image of the tubular ceramic support obtained after sintering in (4) of Example 2;

[0040] Figure 7 This is a physical photo of the extruded body obtained in (3) of Comparative Example 1;

[0041] Figure 8 This is a photo of the tubular ceramic support obtained after sintering (4) in Comparative Example 1;

[0042] Fig. 9 This is a SEM image of the tubular ceramic support body obtained after sintering (4) in Comparative Example 1. DETAILED DESCRIPTION

[0043] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the embodiments of the specification.

[0044] In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0045] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

[0046] The experimental methods used in the following examples are conventional methods unless otherwise specified. The materials, reagents, methods and instruments used are conventional materials, reagents, methods and instruments in the art unless otherwise specified, and can be obtained through commercial channels by those skilled in the art.

[0047] Example 1

[0048] (1)BaZr 0.1 Ce 0.7 Yb 0.1 Y 0.1 O 3-δ Preparation of powder materials: 789.36 g of BaCO3 (Aladdin), 49.288 g of ZrO2 (Aladdin), 481.908 g of CeO2 (Aladdin), 45.162 g of Y2O3 (Sigma) and 78.816 g of Yb2O3 (Sigma) were weighed according to the molar ratio and put into a 5 L nylon ball mill, 1 kg of grinding balls with a diameter of 12 mm, 2 kg of grinding balls with a diameter of 10 mm and 8 mm, 1200 mL of anhydrous ethanol was added, and the ball mill speed was set to 300 r / min for grinding. After 24 hours, the slurry was taken out and dried at 70 ° C for 12 hours. The dried powder was put into a crucible and compacted. Then, it was placed in a muffle furnace and heated to 1100 ° C at a rate of 3 ° C / min and calcined for 10 hours. The calcined powder was taken out and ball-milled for a second time for 24 hours. The conditions of the second ball milling were the same as those of the first ball milling. The ball-milled slurry was dried and then heated to 1150 ° C at a rate of 3 ° C / min for re-firing for 10 hours. After re-firing, the third ball milling was performed. The conditions of the third ball milling were the same as those of the first ball milling. The ground slurry was dried and then passed through an 80-mesh sieve to obtain BaZr 0.1 Ce 0.7 Yb 0.1 Y 0.1 O 3-δ Powder material, sealed for standby use;

[0049] Among them, δ is the oxygen vacancy concentration, and the range of 3-δ is 2.5 to 2.9. In the chemical formula of the final material powder, Ce may have a valence of +3 or +4, and Yb may have a valence of +2 or +3. The valence states of the two elements cannot be determined, so the exact value of δ cannot be calculated, but it does not affect the preparation of the material powder and the microstructure and performance of the support.

[0050] (2) Mixing: weigh BaZr 0.1 Ce 0.7 Yb 0.1 Y 0.1 O 3-δ Powder material and 56# semi-refined paraffin, the mass ratio of paraffin to powder material is 1:20, put 56# semi-refined paraffin into the stirring tank, set the stirring tank temperature to 100℃ and the speed to 120r / min, after 56# semi-refined paraffin is completely melted, put BaZr 0.1 Ce 0.7 Yb 0.1 Y 0.1 O 3-δ The powder material (preheated at 60°C for 2h) was evenly added to the stirring tank three times to mix it with No. 56 semi-refined paraffin. The mixed slurry was released and transferred to a slow slurry bucket. The slurry bucket was started to stir slowly at a speed of 120r / min for 2h. During the stirring process, the bubbles in the slurry were slowly floated out by vacuuming. The slurry was cooled into blocks and processed with a kneading machine to form a blank to make it have a certain plasticity. The blank was soft and uniform to the touch without obvious granularity and was placed in a sealed container.

[0051] (3) Extrusion molding: The kneaded billet is placed in the hopper of a single-screw extruder. The screw diameter of the extruder is 20 mm and the aspect ratio is 16:1. The extruder is started and the screw speed is 5 r / min. The billet is gradually allowed to enter the conveying area of ​​the screw. The heating extrusion head is set to 80°C and extrusion molding is performed at this temperature. When the billet extrusion length is 8 cm, the billet is cut with a wire cutter. When cutting, the cut is made to be smooth to avoid damage to the billet. The actual photo of the extruded billet is shown in the figure. Figure 1 As shown;

[0052] (4) Drying and sintering: The cut green body is placed in a well-ventilated environment for drying for 3 days, and the dried green body is dewaxed. After dewaxing, the green body is fixed to prevent deformation during sintering. The fixing method is: two alumina plates with grooves are placed face to face, and the grooves on the two plates form a hole. The green body is placed in the formed hole, placed in a muffle furnace, and heated to 1000°C at a rate of 3°C / min, and then heated to 1450°C at a rate of 2°C / min and sintered for 10 hours to obtain a tubular ceramic support body;

[0053] The wax removal process is as follows: use 300-mesh alumina powder to fill the interior of the green body, then place the green body vertically in a crucible, fill the gap between the green body and the crucible with alumina powder, and vibrate the powder in the gap to make it dense, then put the green body and the crucible into a debinding furnace for wax removal, first raise the temperature to 100°C at a rate of 0.125°C / min and keep it for 2 hours to soften the paraffin, then raise the temperature to 300°C at a rate of 0.2°C / min and keep it for 4 hours to make the paraffin evaporate initially, finally raise the temperature to 600°C at a rate of 0.3°C / min and keep it for 8 hours to make the paraffin completely evaporate, thus completing the wax removal process.

[0054] The digital photo of the tubular ceramic support prepared in this example is as follows: Figure 2 As shown, SEM images are Figure 3 As shown, there is no NiO in this embodiment, which is an electrolyte support. The preparation of SOFC with it requires a dense structure. Figure 3 It can be seen that the tubular support has a high density; the porosity test of the tubular ceramic support prepared in this embodiment is 5%, indicating that the support is conducive to the rapid transmission and migration of protons. The characterization and test results show that the method provided in this embodiment has good ceramic powder molding characteristics, and the prepared tubular ceramic support has a strong hardness and can meet the needs of subsequent processing of the support.

[0055] Example 2

[0056] (1) The steps and process parameters are the same as those in (1) of Example 1;

[0057] (2) Mixing: weigh BaZr 0.1 Ce 0.7 Yb 0.1 Y 0.1 O 3-δ The powder material and NiO were mixed by ball milling (the ball milling solvent was anhydrous ethanol, the mass ratio of the sum of the powder material and NiO to anhydrous ethanol was 1:1, the ball-to-material ratio was 3.46:1, and the ball milling speed was 120 r / min), and then dried to obtain a mixed powder. NiO and BaZr 0.1 Ce 0.7 Yb 0.1 Y 0.1 O 3-δThe mass ratio of the powder is 3:2. Weigh 56th semi-refined paraffin and put it into the stirring tank. The mass ratio of paraffin to mixed powder is 3:20. Set the temperature of the stirring tank to 100℃ and the speed to 120r / min. After the 56th semi-refined paraffin is completely melted, add the mixed powder (preheated at 60℃ for 2h) into the stirring tank three times to mix it with the 56th semi-refined paraffin. Release the mixed slurry and transfer it to a slow slurry bucket. Start the slurry bucket and stir slowly at a speed of 120r / min for 2h. During the stirring process, vacuumize the slurry to slowly float out the bubbles in the slurry. Cool the slurry into blocks and use a kneading machine to form a blank to make it have a certain plasticity. Put it into a sealed container until the blank feels soft and uniform without obvious granularity.

[0058] (3) Extrusion molding: The steps and process parameters are the same as those in (3) of Example 1. The actual photo of the extruded blank is as follows: Figure 4 As shown;

[0059] (4) Drying and sintering: The steps and process parameters are the same as those in (4) of Example 1.

[0060] The digital photo of the tubular ceramic support prepared in this example is as follows: Figure 5 As shown, SEM images are Figure 6 As shown, NiO is added in this embodiment, which is an anode support. The preparation of SOFC with it needs to have a porous structure. Figure 6 It can be seen that the pores of the tubular support are evenly distributed, mainly large pores, which are mainly derived from the volatilization of paraffin wax; the porosity of the tubular ceramic support prepared in this embodiment was tested, and the porosity was measured to be 55%, indicating that the support is conducive to gas transmission. The characterization and test results show that the method provided in this embodiment has good ceramic powder molding characteristics, and the prepared tubular ceramic support has strong hardness and can meet the needs of subsequent processing of the support.

[0061] Comparative Example 1

[0062] The difference between this comparative example and Example 1 is that: (2) No. 56 semi-refined paraffin and BaZr 0.1 Ce 0.7 Yb 0.1 Y 0.1 O 3-δ The mass ratio of powder materials is 7:100, and the remaining steps and process parameters are the same.

[0063] The actual photo of the extruded body obtained in this comparative example (3) is as follows Figure 7 The actual photograph of the tubular ceramic support prepared in this comparative example is shown in Figure 8 As shown, SEM images are Fig. 9 As shown, from Fig. 9It can be seen that there are large particles in the tubular support, and the void distribution is relatively uniform; the porosity test of the tubular ceramic support prepared in this comparative example is 15%, indicating that the support has neither a dense arrangement nor a uniform porous structure, and the transmission efficiency of protons and gases is low, and it can neither be used as an electrolyte support nor as an anode support. The tubular ceramic support prepared in this comparative example has high strength and hardness, but the transmission efficiency of protons and gases is low, and it cannot meet the needs of the subsequent preparation of solid oxide fuel cells by the support.

[0064] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for preparing a tubular ceramic support for a solid oxide fuel cell, characterized in that: include: (1) Preparation of powder material: placing raw material powder containing metal elements into a ball mill, adding grinding balls and a ball milling solvent for the first ball milling to obtain a slurry, drying and compacting the slurry, and then sequentially performing high-temperature calcination, secondary ball milling and secondary drying steps, and sequentially performing re-sintering, tertiary ball milling, tertiary drying and sieving on the powder after the secondary drying to obtain a powder material; (2) Mixing: Put wax into a stirring tank, increase the temperature, and after the wax material is completely melted, add the preheated powder material or mixed powder, stir to obtain a mixed slurry, transfer the mixed slurry to a slurry bucket, stir under vacuum, and then cool the mixed slurry into a block material, and process the block material through a kneader to obtain a blank; (3) Extrusion molding: Extruding the blank at a certain temperature to obtain a blank, and cutting the blank; (4) Drying and sintering: drying the cut green body, dewaxing and sintering the dried green body to obtain a tubular ceramic support body; The mixed powder in (2) is composed of powder material and NiO.

2. The preparation method according to claim 1, characterized in that: (1) the raw material powder containing metal elements is a mixture of barium carbonate, zirconium oxide, cerium oxide, ytterbium oxide and yttrium oxide; The molar ratio of barium element, zirconium element, cerium element, ytterbium element and yttrium element in the mixture is 1:0.1:0.7:0.1:0.

1.

3. The preparation method according to claim 1, characterized in that: (1) The mass ratio of the grinding balls to the raw material powder containing the metal element is (5-15):1; the ball milling speed is 200-500 r / min, and the time is 12-36 h.

4. The preparation method according to claim 1, characterized in that: (1) The medium-high temperature calcination temperature is 1000-1400°C for 6-12 hours; the re-firing temperature is 1000-1400°C for 6-12 hours.

5. The preparation method according to claim 1, characterized in that: (1) The chemical formula of the powder material is BaZr 0.1 Ce 0.7 Yb 0.1 Y 0.1 O 3-δ ; The δ is the oxygen vacancy concentration, and the range of 3-δ is 2.5 to 2.

9.

6. The preparation method according to claim 1, characterized in that: (2) The mass ratio of the medium wax to the powder material or the mixed powder is (1-3):

20.

7. The preparation method according to claim 1, characterized in that: The mass ratio of the powder material to NiO in the mixed powder of (2) is (1-3):

2.

8. The preparation method according to claim 1, characterized in that: (3) The extrusion molding temperature is 60-100°C.

9. The preparation method according to claim 1, characterized in that: (4) The drying time is 1 to 3 days; the sintering process is: heating to 1000°C at a rate of 3 to 10°C / min, then heating to 1050 to 1450°C at a rate of 1 to 3°C / min, and keeping warm for 6 to 12 hours.

10. A tubular ceramic support for a solid oxide fuel cell, characterized in that: The method is prepared by any one of claims 1 to 9.

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