CN111370742A - SOFC power generation system, manganese-cobalt spinel coating and preparation method thereof - Google Patents
SOFC power generation system, manganese-cobalt spinel coating and preparation method thereof Download PDFInfo
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/24—Grouping of fuel cells, e.g. stacking of fuel cells
- H01M8/241—Grouping of fuel cells, e.g. stacking of fuel cells with solid or matrix-supported electrolytes
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C4/00—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge
- C23C4/04—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge characterised by the coating material
- C23C4/10—Oxides, borides, carbides, nitrides or silicides; Mixtures thereof
- C23C4/11—Oxides
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C4/00—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge
- C23C4/12—Coating by spraying the coating material in the molten state, e.g. by flame, plasma or electric discharge characterised by the method of spraying
- C23C4/134—Plasma spraying
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- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/24—Grouping of fuel cells, e.g. stacking of fuel cells
- H01M8/2465—Details of groupings of fuel cells
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/30—Hydrogen technology
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Abstract
The invention discloses an SOFC power generation system, a manganese-cobalt spinel coating and a preparation method thereof, and relates to the technical field of fuel cells. The preparation method comprises the following steps: preparing a manganese-cobalt spinel coating on the surface of the connector by atmospheric plasma spraying; the gas used in the spraying is mixed gas of hydrogen and inert gas, the total flow of the mixed gas is 60-90L/min, and the adopted spraying power is 30-60 kW. Under the conditions of the total gas amount for spraying and the spraying power provided by the invention, the control of the speed of the plasma jet and the temperature of the plasma jet can be realized, and the preparation of the manganese-cobalt spinel coating with higher conductivity, high density and low defect can be realized under the spraying process.
Description
Technical Field
The invention relates to the technical field of fuel cells, in particular to an SOFC power generation system, a manganese-cobalt spinel coating and a preparation method thereof.
Background
Solid Oxide Fuel Cells (SOFCs) are highly efficient energy converters that electrochemically convert the chemical energy of a fuel at relatively high temperatures into electrical and thermal energy, with only CO being released2And H2And O, no other sulfide, nitrogen oxide or particle dust is discharged, so that the method is a green and clean power generation technology. A plurality of flat SOFC monocells are stacked in series to form a SOFC cell stack with high power, so that modular application is achieved. During the assembly of an SOFC cell stack, a large number of connectors are required to connect two adjacent cells, i.e. one side of the connector is in contact with the anode of the cell and the other side is in contact with the cathode of the adjacent cell. Therefore, the connector is required to have high electrical conductivity and good thermal stability. Conventional connectors are made of conductive ceramics, such as LaCrO3. However, as the operating temperature of the battery becomes lower, the conductive ceramic connectors have been gradually replaced by metal connectors. Common interconnect metal materials are Cr alloys, Ni alloys, and ferritic stainless steels. Among them, ferritic stainless steel is widely used for connector forming and preparation due to its good workability, good thermal matching properties, low cost and good oxidation resistance.
However, long-term use under service conditions of SOFC causes Cr elements in ferritic stainless steel to diffuse to the surface and form an oxide layer (Cr) on the surface2O3). In an oxidizing environment, the presence of moisture can lead to Cr3+Further oxidation of the particles to Cr6+And form volatile CrO2(OH)2. The volatile component is easily reacted with cathode material (typically lanthanum strontium cobalt iron, LSCF) to form a low active phase (e.g., SrCrO)4) Leading to the reduction of cathode activity and the generation of poisoning phenomena. To prevent such phenomena, it is necessary to prepare a protective coating on the surface of the ferritic stainless steel connector. A commonly used protective coating material is a conductive ceramic. According to the requirements of protective performance and conductivity, the current mainstream protective material is conductive spinel which comprises (Mn, Co))3O4、(Mn，Cu)3O4And the like. Wherein (Mn, Cu)3O4The conductivity is highest, but the long-term stability is poor, and irreversible degradation is easy to generate in the using process. And (Mn, Co)3O4Although the conductivity is slightly lower than (Mn, Cu)3O4However, it has good long-term stability and is therefore widely used for protecting metal interconnects.
At present, (Mn, Co)3O4(or Mn)xCo3-xO4，0<x<1) The preparation of the protective coating can be realized by various modes, such as electroplating, high-temperature sintering, sol coating method, magnetron sputtering method, electroplating method, pulling and dipping method, high-energy micro-arc cold welding method and the like. The prior art and the prior method have obvious defects, such as serious pollution problem of an electroplating method, low density of a coating prepared by a sol coating method, low efficiency of a magnetron sputtering method and a pulling dipping method, and long-time post-treatment for oxidizing an alloy coating into a spinel coating by a high-energy micro-arc method, so that the prior art can not meet the large-scale preparation requirement of a metal connector protective coating brought by industrial application, and can not meet the requirements of high conductivity and low defect of the coating.
In view of this, the invention is particularly proposed.
Disclosure of Invention
The invention aims to provide an SOFC power generation system, a manganese-cobalt spinel coating and a preparation method thereof so as to solve the technical problems.
The invention is realized by the following steps:
a preparation method of a manganese cobalt spinel coating for an SOFC metal connector comprises the following steps: preparing a manganese-cobalt spinel coating on the surface of the connector by atmospheric plasma spraying;
the gas used in the spraying is the mixed gas of hydrogen and inert gas, the total flow of the mixed gas is 60-90L/min, and the adopted spraying power is 30-60 kW.
The invention provides a preparation method of a manganese cobalt spinel coating for an SOFC metal connector, which is characterized in that the manganese cobalt spinel coating is sprayed on the surface of the SOFC metal connector by a plasma spraying method, the control of the speed of plasma jet and the temperature of the plasma jet can be realized under the conditions of the total gas amount for spraying and the spraying power provided by the invention, and the preparation of the manganese cobalt spinel coating with higher conductivity, high density and low defect can be realized under the spraying process.
The plasma flame temperature is extremely high (>10000 ℃), and once the control is not good, the manganese cobalt spinel is easy to deoxidize and decompose and lose its property. The preparation method provided by the invention can be used for preparing the high-performance SOFC metal connector protective coating.
In the preferred embodiment of the present invention, the volume of hydrogen in the mixed gas is 5-12%.
In the preferred embodiment of the invention, the total flow of the mixed gas is controlled to be constant within the range of 60-90L/min, and the spraying power is controlled to be any point value within the range of 30kW-60 kW; or the spraying power is controlled to be constant at a fixed value within the range of 30-60kW, and the total flow of the mixed gas is controlled at any point within the range of 60-90L/min.
When the spraying power is not changed, the speed of the plasma jet can be regulated and controlled through the total flow of the mixed gas, so that the flight path of the powder particles is indirectly controlled.
In another embodiment, the total flow rate of the mixed gas is constant, and the temperature of the plasma jet can be regulated and controlled through the spraying power, so that the flight path of the powder particles is indirectly controlled.
In the preferred embodiment of the invention, the total flow of the mixed gas is constant within the range of 65-90L/min, and the spraying power is constant within the range of 30-50 kW.
In the preferred embodiment of the invention, the total flow rate of the mixed gas is 75L/min when the spraying power is constant within the range of 30-35 kW.
In the preferred embodiment of the invention, the total flow rate of the mixed gas is 65L/min when the spraying power is constant within the range of 36-44 kW.
In the preferred embodiment of the invention, when the spraying power is constant at a fixed value in the range of 45-50kW, the total flow rate of the mixed gas is 80L/min.
When the manganese-cobalt spinel coating is prepared by adopting a plasma spraying process, raw manganese-cobalt spinel powder enters plasma jet at a certain initial speed through a powder feeding port, and because the flow of carrier gas for powder feeding is only 2-6L/min and the inner diameter of a powder feeding pipe is generally 4-6mm, the maximum speed of carrier gas at the outlet of the powder feeding pipe (namely the powder feeding port) is only 8 m/s. In general, the plasma jet velocity is greater than 100m/s, and without optimization, raw manganese-cobalt spinel powder is difficult to enter the inner area of the plasma jet, and the surface of the raw manganese-cobalt spinel powder cannot reach a molten state, so that the formed coating has a large number of defects, such as cracks, pores, interlayer gaps and the like.
The inventor repeatedly researches and finds that three possible paths exist after spherical manganese-cobalt spinel raw powder is sent into plasma jet through a powder feeding port: the first path only passes through the outer low-temperature region of the plasma jet, the second path is located in the highest temperature region in the middle of the plasma jet, and the third path enters the region with lower outer temperature after passing through the highest temperature region in the middle of the plasma jet.
The particles on the first path collide with the surface of the connecting body to form a coating with more defects due to lower temperature when the particles do not completely reach a molten state; the particles on the second path enter the middle area of the plasma jet flow and are completely melted to form liquid drops, and the liquid drops are spread and solidified into a coating after impacting the surface of the connecting body, wherein the coating is compact and has fewer defects; the particles on the third path only pass through the hottest region in the middle of the plasma jet for a short time, the surface part of the particles is melted, the inner part of the particles is still solid, and the particles and the connecting body form a coating with certain density after being collided, but the defects are more.
The inventor artificially obtains a manganese cobalt coating with higher conductivity, and controls the conditions for preparing the coating to ensure that most particles form the coating through the second path.
The flight path of the particles in the plasma jet is determined by various factors, such as particle shape, particle size, location of the particles entering the plasma jet, plasma jet velocity and temperature, carrier gas type and flow rate, and the like. The inventor researches and discovers that when the factors such as the type and the flow of carrier gas, the shape and the particle size of particles and the like are kept constant, the temperature and the speed of plasma jet flow can be controlled to screen the conductivity of the manganese-cobalt spinel coating so as to obtain the optimal spraying parameters.
In plasma spraying, the amount of gas used for spraying affects primarily the velocity of the plasma jet, while the input power primarily regulates the temperature of the plasma jet. Thus, the temperature and velocity of the plasma jet can be indirectly controlled by the amount of gas used for plasma spraying and the input power.
The inventor repeatedly researches and discovers that if the spraying power and other parameters are kept unchanged, the spraying gas consumption is gradually increased, and the particle path is gradually changed from the path two to the path one, or from the path three to the path two and then to the path one. The optimal spraying gas consumption can be predicted when the manganese cobalt spinel coating is prepared by the process, and the prepared manganese cobalt spinel coating has optimal conductivity.
When the total gas amount of spraying is kept constant, the temperature of the plasma jet flow is lower than the temperature required by the state of complete melting of the particles, so that the coating has defects and poor conductivity. Increasing the spray power increases the temperature of the plasma jet, but the change in conductivity of the manganese cobalt spinel coating is limited due to the shorter time of flight (or exposure to the plasma flame stream) of the particles.
Under the optimal matching condition of the spraying gas amount and the input power provided by the invention, namely, when the power is kept constant, the optimal spraying gas amount exists, and the conductivity of the coating is reduced when the gas amount exceeds or is lower than the optimal spraying gas amount.
There is also an optimum input power to ensure optimum coating conductivity while maintaining a constant amount of spray air.
In the preferred embodiment of the present invention, the spraying distance is 90-150 mm.
In the preferred embodiment of the present invention, the spraying distance is 110-130 mm.
In the preferred embodiment of the present invention, the spraying speed is 300-600 mm/s.
In the preferred embodiment of the invention, the spraying speed is 400 mm/s.
The spraying distance is more than or less than the spraying distance provided by the invention, which easily causes the electric conductivity of the coating to be reduced.
The spraying speed refers to the translation speed of the spray gun, and the too high or too low spraying speed can cause the uneven sprayed coating and influence the actual conductivity of the metal connector.
In the preferred embodiment of the invention, the plasma jet is at an angle of 85-95 ° to the surface of the connector.
In the preferred embodiment of the invention, the plasma jet is at a 90 ° angle to the surface of the connector.
In a preferred embodiment of the invention, the interface is preheated prior to atmospheric plasma spraying.
In the preferred embodiment of the present invention, the preheating temperature for preheating the connector is 200-500 ℃.
The preheating treatment is used for reducing the solidification speed of the coating at the beginning of spraying, so that the stress of the coating is reduced, and the bonding strength of the coating and the connecting body is enhanced.
In the preferred embodiment of the present invention, the material of the connecting body is ferritic stainless steel, Cr-based alloy, alumina ceramic or Ni-based alloy.
In the preferred embodiment of the invention, the chemical formula of the sprayed manganese cobalt spinel is MnxCo3-xO4Wherein 0 is<x<3; preferably, x is 1 to 1.5.
In the preferred embodiment of the present invention, the raw material of manganese cobalt spinel is normal spinel, inverse spinel or mixed spinel.
In the preferred embodiment of the invention, the orthospinel is formed by manganese and cobalt occupying the tetrahedral and octahedral voids of the unit cell, respectively; inverse spinels are formed by cobalt and manganese occupying tetrahedral and octahedral voids of a unit cell, respectively; mixed spinels are formed by cobalt and manganese co-occupying the unit cell tetrahedral and octahedral voids.
In the preferred embodiment of the present invention, the raw material of the manganese cobalt spinel is spherical manganese cobalt spinel powder.
In the preferred embodiment of the invention, the spherical manganese cobalt spinel powder has an average particle size of 10-35 μm. Too large a particle size may result in a decrease in melting speed and cause non-uniformity in coating.
In the preferred embodiment of the present invention, the carrier gas for the raw material of manganese cobalt spinel is an inert gas.
In the preferred embodiment of the present invention, the carrier gas is argon. In addition, in other embodiments, the carrier gas may be adaptively replaced as desired.
In the preferred embodiment of the present invention, the flow rate of the carrier gas is 2-6L/min.
In the preferred embodiment of the present invention, the flow rate of the carrier gas is 2-4L/min; in the preferred embodiment of the present invention, the powder feeding amount of the carrier gas is 19-20 g/min.
The powder feeding amount of the carrier gas is matched with the spraying parameters, and the coating with low defect and high conductivity can be prepared under the powder feeding amount and the spraying parameters provided by the invention. The spraying frequency is 1-2 times, namely the coating which can meet the requirements of thickness and performance can be obtained only by spraying for 1 time or 2 times.
The manganese cobalt spinel coating prepared by the preparation method. The thickness of the coating is 20-26 μm.
An SOFC power generation system comprises at least two fuel cell units, wherein adjacent fuel cell units are electrically connected through a metal connector, and the surface of each metal connector is coated with a manganese cobalt spinel coating.
The invention has the following beneficial effects:
the invention provides an SOFC power generation system, a manganese-cobalt spinel coating and a preparation method thereof. Under the conditions of the total gas amount for spraying and the spraying power provided by the invention, the control of the speed of the plasma jet and the temperature of the plasma jet can be realized, and the preparation of the manganese-cobalt spinel coating with higher conductivity, high density and low defect can be realized under the spraying process. The preparation method provided by the invention effectively improves the preparation efficiency of the high-performance SOFC metal connector protective coating, reduces the preparation cost, is beneficial to the low-temperature development and application of SOFC metal, and is beneficial to the development of SOFC technology in China. The prepared manganese-cobalt spinel coating can be widely applied to an SOFC power generation system.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without inventive efforts.
FIG. 1 is a schematic diagram showing the relationship between the path of powder particles and the plasma beam current in atmospheric plasma spraying;
FIG. 2 is a graph showing the relationship (30kW) between the electrical conductivity of a manganese cobalt spinel coating and the amount of sprayed gas;
FIG. 3 is an electron micrograph of an unmelted particle from the powder particle of example 1 after the transition from route two to route one;
FIG. 4 is a graph showing the relationship (40kW) between the electrical conductivity of the manganese cobalt spinel coating and the amount of sprayed gas;
FIG. 5 is a graph showing the relationship (50kW) between the electrical conductivity of a manganese cobalt spinel coating and the amount of sprayed gas;
FIG. 6 is a graph showing the relationship between the conductivity of a manganese cobalt spinel coating and the spraying power (65L/min).
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.
The features and properties of the present invention are described in further detail below with reference to examples.
Example 1
In this example, alumina ceramic was used as a spray substrate (phi 18.5mmx2mm), which was cleaned to remove oil and then fixed on a jig. The alumina matrix is a non-conductive matrix and the conductivity of the alumina is less than 1mS/cm at the test temperature (750 ℃). Keeping the spraying input power 30kW unchanged, and respectively adopting the total spraying gas amount of 50L/min, 60L/min, 65L/min, 70L/min, 73L/min, 75L/min, 80L/min, 82L/min and 90L/min for coating preparation. Manganese cobalt raw powder (Mn) having an average particle diameter of 18.9. mu.m1.5Co1.5O4) The powder is sent into the plasma jet by argon with the flow rate of 4L/min, and the actually measured powder sending amount is 19 g/min. The spraying distance is fixed at 110mm, the spraying angle is 90 degrees, the average preheating temperature of the matrix is 250 ℃, and each sample is sprayed for 2 times. The coating thickness finally obtained was 22 μm. The conductivity of the coating at 700 c measured by the direct current four-electrode method is shown in figure 2. As can be seen from FIG. 2, when the total spraying gas amount is increased from 50L/min to 75L/min, the coating conductivity is increased from 5.4S/cm to 14.7S/cm; when the total spraying gas amount is continuously increased to 90L/min from 75L/min, the conductivity of the coating is reduced to 12.8S/cm from 14.7S/cm.
Referring to fig. 1, when the total spraying gas amount is increased from 50L/min to 75L/min, the path of the raw powder flying particles is gradually changed from the path three to the path two, the powder particles enter a complete melting area, and the conductivity of the prepared coating shows an increasing trend; when the total spraying gas amount continuously rises from 75L/min, the flight path of the powder particles is gradually changed from the path two to the path one, namely the powder particles are gradually changed from complete melting to partial melting, the prepared coating has more defects (shown in figure 3), and the conductivity of the prepared coating shows a descending trend.
Example 2
In this example, alumina ceramic was also used as a spray substrate (phi 18.5mmx2mm), which was cleaned to remove oil and then fixed on a jig. During spraying, the input power of spraying is kept unchanged at 40kW, and the total gas spraying amount is respectively 50L/min, 60L/min, 65L/min, 70L/min, 73L/min, 75L/min, 80L/min, 82L/min and 90L/min for coating preparation. Manganese cobalt raw powder (Mn) having an average particle diameter of 18.9. mu.m1.5Co1.5O4) Is sent into the plasma jet by argon with the flow rate of 4L/minAnd the actually measured powder feeding amount is 19 g/min. The spraying distance is fixed at 110mm, the spraying angle is 90 degrees, the average preheating temperature of the matrix is 250 ℃, and each sample is sprayed for 2 times. The final coating thickness was 24 μm.
The conductivity of the coating at 700 c measured by the direct current four-electrode method is shown in figure 4. As can be seen from FIG. 4, when the total spraying gas amount is increased from 50L/min to 65L/min, the coating conductivity is increased from 7.8S/cm to 14.2S/cm; when the total spraying air quantity is continuously increased to 90L/min from 65L/min, the conductivity of the coating is reduced to 12.6S/cm from 14.2S/cm.
As can be seen from FIG. 1, when the total spraying gas amount is increased from 50L/min to 65L/min, the flying particle path of the raw powder is gradually changed from the third path to the second path, the powder particles are in a good molten state, and the conductivity of the coating shows an increasing trend; and when the total spraying gas amount continuously rises from 65L/min, the flight path of the powder particles is gradually changed from the path two to the path one, the powder particles are not heated enough, the powder particles cannot be completely melted, and the conductivity of the coating shows a descending trend.
Example 3
In this example, alumina ceramic was also used as a spray substrate (phi 18.5mmx2mm), which was cleaned to remove oil and then fixed on a jig. During spraying, the input power of the spraying is kept unchanged at 50kW, and the total gas spraying amount is respectively 50L/min, 60L/min, 65L/min, 70L/min, 73L/min, 75L/min, 80L/min, 82L/min and 90L/min for coating preparation. Manganese cobalt raw powder (Mn) having an average particle diameter of 18.9. mu.m1.5Co1.5O4) The powder is sent into the plasma jet by argon with the flow rate of 4L/min, and the actually measured powder sending amount is 19 g/min. The spraying distance is fixed at 110mm, the spraying angle is 90 degrees, the average preheating temperature of the matrix is 250 ℃, and each sample is sprayed for 2 times. The coating thickness finally obtained was 25 μm.
The conductivity of the coating at 700 c measured by the direct current four-electrode method is shown in figure 5. As can be seen from FIG. 5, when the total spraying gas amount is increased from 50L/min to 80L/min, the coating conductivity is increased from 11.5S/cm to 19.9S/cm; when the total spraying gas amount is continuously increased to 90L/min from 80L/min, the conductivity of the coating is reduced to 18.3S/cm from 19.9S/cm.
As can be seen from FIG. 1, when the total spraying gas amount is increased from 50L/min to 80L/min, the flight particle path of the raw powder is gradually changed from the first path to the second path, and the conductivity of the coating shows an increasing trend; and when the total spraying gas amount continuously rises from 80L/min, the flight path of the powder particles is gradually changed from the second path to the third path, and the conductivity of the coating shows a descending trend.
Example 4
In this example, alumina ceramic was used as a spray substrate (phi 18.5mmx2mm), which was cleaned to remove oil and then fixed on a jig. During spraying, the spraying power is respectively controlled to be 39kW, 41kW, 47kW and 56kW, and the total spraying gas amount is kept to be 65L/min. Manganese cobalt raw powder (Mn) having an average particle diameter of 18.9. mu.m1.5Co1.5O4) The powder is sent into the plasma jet by argon with the flow rate of 4L/min, and the actually measured powder sending amount is 19 g/min. The spraying distance was 110mm, the average preheating temperature of the substrate was 250 ℃ and each sample was sprayed 2 times. The coating thickness finally obtained was 25 μm.
The conductivity of the coating at 700 c measured by the direct current four-electrode method is shown in figure 6. As can be seen from FIG. 6, the conductivity of the obtained coating showed a significant increase trend at spraying powers of 39kW and 41kW, which were 7.9S/cm and 14.2S/cm, respectively; at a spray power of 56kW, the coating obtained showed a marked decrease in conductivity, which was only 5.5S/cm.
The increase of the spraying power can greatly increase the temperature of the plasma jet, and the speed of the plasma jet also increases to a certain extent. As can be seen from fig. 1, when the spraying power is increased, the plasma jet velocity is increased, the flight path of the raw powder particles gradually approaches to the second path, and meanwhile, the increase of the plasma jet temperature also enables the powder particles to have a good molten state, which is beneficial to forming a compact coating, and the conductivity of the prepared coating shows a rising trend; when the spraying power is continuously increased, the temperature of the plasma jet is continuously increased greatly, the speed is only increased slightly, the powder particles are excessively heated in the plasma beam, the structure and the structure of the powder particles are denatured, the optimal element proportion is lost, and the conductivity of the coating shows a large descending trend.
Example 5
This example uses aluminaThe ceramic is a spraying substrate (phi 18.5mmx2mm), and is fixed on a clamp after being cleaned and deoiled. During spraying, the input power of spraying is controlled to be kept unchanged at 30kW, and the total gas flow of spraying is controlled to be 75L/min. Manganese cobalt raw powder (Mn) having an average particle diameter of 18.9. mu.m1.5Co1.5O4) The powder is sent into the plasma jet by argon with the flow rate of 4L/min, and the actually measured powder sending amount is 19 g/min. The spraying distance is fixed at 110mm, the spraying angle is 90 degrees, the average preheating temperature of the matrix is 250 ℃, and each sample is sprayed for 2 times. The coating thickness finally obtained was 22 μm. The conductivity of the coating at 700 ℃ was measured using the direct current four-electrode method. The coating conductivity was 14.7S/cm.
Example 6
In this example, alumina ceramic was also used as a spray substrate (phi 18.5mmx2mm), which was cleaned to remove oil and then fixed on a jig. During spraying, the spraying input power is kept unchanged at 40kW, and the total spraying gas amount is controlled to be 65L/min. Manganese cobalt raw powder (Mn) having an average particle diameter of 18.9. mu.m1.5Co1.5O4) The powder is sent into the plasma jet by argon with the flow rate of 4L/min, and the actually measured powder sending amount is 19 g/min. The spraying distance is fixed at 110mm, the spraying angle is 90 degrees, the average preheating temperature of the matrix is 250 ℃, and each sample is sprayed for 2 times. The final coating thickness was 24 μm.
The conductivity of the coating at 700 ℃ was measured using the direct current four-electrode method. The coating conductivity was 14.2S/cm.
Example 7
In this example, alumina ceramic was also used as a spray substrate (phi 18.5mmx2mm), which was cleaned to remove oil and then fixed on a jig. During spraying, the input power of the spraying is kept unchanged at 50kW, and the total gas of the spraying is respectively controlled at 80L/min. Manganese cobalt raw powder (Mn) having an average particle diameter of 18.9. mu.m1.5Co1.5O4) The powder is sent into the plasma jet by argon with the flow rate of 4L/min, and the actually measured powder sending amount is 19 g/min. The spraying distance is fixed at 110mm, the spraying angle is 90 degrees, the average preheating temperature of the matrix is 250 ℃, and each sample is sprayed for 2 times. The coating thickness finally obtained was 25 μm.
The conductivity of the coating at 700 ℃ was measured using the direct current four-electrode method. The coating conductivity was 19.9S/cm.
Comparative example 1
A preparation method (CN103194713A) of CoMn spinel coating on the surface of SOFC metal connector body is as follows: pure Mn and pure Co are sequentially deposited on the surface of a metal matrix by adopting a pulse electrodeposition method, and MnCo on the surface is converted into an oxide layer by high-temperature oxidation at 800 ℃ for 6 hours. The preparation method of the coating needs a plurality of steps and processes, although the cost is low, the process is multiple, the large-scale production is difficult, and the electrodeposition process has large pollution and is not beneficial to environmental protection. The thickness of the prepared MnCo oxide layer is 70-80 mu m, the influence on the air passage of the connector is large, and the prepared MnCo oxide layer only contains a certain amount of spinel phase, so that the requirement of the connector on the conductivity cannot be ensured.
Comparative example 2
Coating for metal connector of flat plate type intermediate temperature solid oxide fuel cell (CN 104878354A): a MnCu alloy layer with the thickness of about 20 mu m is sputtered on the surface of the connector in a magnetron sputtering mode, and then the connector is oxidized for 10 weeks at the high temperature of 800 ℃, and finally a double-layer structure with the surface being MnCu spinel and the bottom being Cr-rich oxide is formed. The preparation method of the spinel coating has long time consumption and extremely low efficiency, and is difficult to adapt to industrial requirements.
Comparative example 3
A preparation method of a conductive corrosion-resistant cobalt-manganese spinel coating (CN105332029A) comprises the following steps: plating a MnCo alloy and manganese hydroxide composite layer with the thickness of about 10 on the surface of the metal connector by adopting an electrochemical plating method, then carrying out high-temperature (750 ℃ and 800 ℃) conversion twice under vacuum, wherein the conversion time is 2 hours respectively, and finally obtaining a coating containing MnCo spinel on the surface. The preparation method of the conductive spinel disclosed by the patent is chemical plating, brings serious environmental problems when being applied in a large scale, and in addition, high-temperature conversion is required under vacuum, the required time and cost are high, the preparation efficiency is low, and the severe requirement of commercial application on productivity is difficult to meet.
Comparative example 4
A preparation method of a rare earth modified spinel coating (CN103695902A) comprises the following steps: according to the method, materials such as cobalt powder, manganese dioxide and lanthanum oxide are made into a composite electrode by adopting a hot-pressing sintering method, then the prepared electrode material is plated on the surface of a stainless steel substrate by adopting a high-energy micro-arc alloying method under a protective atmosphere to form a cobalt-containing composite oxide coating, and then the composite coating is converted into a manganese-cobalt spinel and lanthanum cobaltate composite oxide coating by carrying out thermal oxidation for a certain time under an oxidation environment. The preparation method of the coating needs multiple high-temperature heat treatment, the efficiency is low, and the preparation process cannot realize the preparation of the coating on the surface airway wall surface of the connector.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A method for preparing a manganese cobalt spinel coating for a SOFC metal interconnect, the method comprising the steps of: preparing a manganese-cobalt spinel coating on the surface of the connector by atmospheric plasma spraying;
the gas used in the spraying is mixed gas of hydrogen and inert gas, the total flow of the mixed gas is 60-90L/min, and the adopted spraying power is 30-60 kW.
2. The method according to claim 1, wherein the volume ratio of hydrogen in the mixed gas is 5-12%.
3. The production method according to claim 1, wherein the total flow rate of the mixed gas is controlled to be constant at a fixed value within a range of 60 to 90L/min, and the spraying power is controlled to be any point value within a range of 30kW to 60 kW; or the spraying power is controlled to be constant at a fixed value within the range of 30-60kW, and the total flow of the mixed gas is controlled at any point within the range of 60-90L/min.
4. The production method according to claim 1, wherein the total flow rate of the mixed gas is constant at a fixed value within a range of 65 to 90L/min, and the spraying power is constant at a fixed value within a range of 30 to 50 kW;
preferably, when the spraying power is constant within a fixed value within the range of 30-35kW, the total flow of the adopted mixed gas is 75L/min;
preferably, when the spraying power is constant within a fixed value range of 36-44kW, the total flow of the adopted mixed gas is 65L/min;
preferably, when the spraying power is constant at a fixed value within the range of 45-50kW, the total flow of the adopted mixed gas is 80L/min.
5. The production method according to claim 4, wherein the distance of spraying is 90 to 150 mm;
preferably, the spraying distance is 110-130 mm;
preferably, the spraying speed is 300-600 mm/s;
preferably, the spraying speed is 400 mm/s;
preferably, when spraying, the included angle between the plasma jet and the surface of the connector is 85-95 degrees;
preferably, the plasma jet is angled at 90 ° to the surface of the connector body.
6. The method of claim 1, wherein the linker is subjected to a preheating treatment before the atmospheric plasma spraying;
preferably, the preheating temperature for preheating the connector is 200-500 ℃;
preferably, the material of the interconnect is ferritic stainless steel, Cr-based alloy, alumina ceramic, or Ni-based alloy.
7. The method of claim 1, wherein the feedstock is a manganese cobalt spinel having a chemical formula of MnxCo3-xO4Wherein 0 is<x<3; preferably, x is 1 to 1.5;
preferably, the manganese-cobalt spinel raw material is normal spinel, inverse spinel or mixed spinel;
preferably, the orthospinel is formed by manganese and cobalt occupying the tetrahedral and octahedral voids, respectively, of the unit cell; the inverse spinel is formed by occupying tetrahedral and octahedral gaps of a unit cell by cobalt and manganese respectively; the mixed spinel is formed by cobalt and manganese occupying unit cell tetrahedral and octahedral voids together;
preferably, the raw material of the manganese-cobalt spinel is spherical manganese-cobalt spinel powder;
preferably, the spherical manganese cobalt spinel powder has an average particle size of 10 to 35 μm.
8. The preparation method according to claim 7, wherein the carrier gas of the manganese cobalt spinel raw material is an inert gas;
preferably, the carrier gas is argon;
preferably, the flow rate of the carrier gas is 2-6L/min;
more preferably, the flow rate of the carrier gas is 2-4L/min; more preferably, the powder feeding amount of the carrier gas is 19 to 20 g/min.
9. Manganese cobalt spinel coating obtainable by the process according to any one of claims 1 to 8.
10. An SOFC power generation system, comprising at least two fuel cell units, wherein adjacent fuel cell units are electrically connected by metal connectors, and the cathode side surface of each metal connector is coated with a manganese cobalt spinel coating according to claim 9.
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Cited By (2)
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| CN116023808A (en) * | 2022-12-30 | 2023-04-28 | 山东能源集团有限公司 | Protective coating and preparation method thereof |
| CN117778939A (en) * | 2024-02-28 | 2024-03-29 | 北矿新材科技有限公司 | Preparation method of connector coating, connector and battery or electrolytic cell group |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN116023808A (en) * | 2022-12-30 | 2023-04-28 | 山东能源集团有限公司 | Protective coating and preparation method thereof |
| CN117778939A (en) * | 2024-02-28 | 2024-03-29 | 北矿新材科技有限公司 | Preparation method of connector coating, connector and battery or electrolytic cell group |
| CN117778939B (en) * | 2024-02-28 | 2024-04-30 | 北矿新材科技有限公司 | Preparation method of connector coating, connector and battery or electrolytic cell group |
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