A manganese-cobalt spinel coating and a method of making and using the same

Abstract

The present application relates to a kind of manganese cobalt spinel coating and its preparation method and application, belong to solid oxide fuel cell material technical field.The manganese cobalt spinel coating described in the present application is coated on the substrate containing Cr element, including the binding layer on substrate and the structural layer on the binding layer;The binding layer includes the following components: manganese cobalt spinel material, MnCr2O4, Cr2O3;The structural layer is manganese cobalt spinel material;The chemical formula of the manganese cobalt spinel material is Mn 1+ x Co 2‑x O4, wherein, -1

Description

Technical Field

[0001] The present invention belongs to the technical field of solid oxide fuel cell materials, and particularly relates to a manganese cobalt spinel coating, a preparation method thereof and an application thereof. Background Art

[0002] A solid oxide fuel cell (SOFC) is a power generation device that directly and efficiently converts the chemical energy in fuel into electrical energy in a clean manner. In order to obtain the required voltage and power, an SOFC power generation system usually contains more than one fuel cell unit. The fuel cell units are separated by a connecting component, and the connecting component also plays an electrical connection role. In order to meet the requirements of high-temperature strength and high-temperature oxidation resistance, heat-resistant alloys containing Cr are generally used for metal connecting components. However, as the use time of the above alloys increases, problems such as the thickening of the low-conductivity oxide film on the surface, an increase in the internal resistance of the battery, and the diffusion of Cr elements outside the metal component, poisoning the cathode and electrolyte materials will occur. Coating a protective coating on the surface of the interconnect is an effective method to control the growth of the alloy surface oxide layer and control Cr contamination, and has been widely adopted.

[0003] Currently, manganese cobalt spinel materials (Mn 1+x Co 2-x O4 (-1 < x < 2)) are one of the main coatings used for metal interconnects. Among them, the most commonly used composition ratio of manganese cobalt spinel is Mn 1.5 Co 1.5 O4. However, the spinel coatings in the prior art have uneven tissue structures, large porosities, poor bonding force with the metal matrix, low high-temperature conductivity, and long preparation time. These defects greatly affect the application of spinel coatings in SOFCs. Therefore, there is an urgent need to develop a manganese cobalt spinel coating with good high-temperature conductivity, good bonding force with the metal matrix, and effective control of Cr element diffusion. Summary of the Invention

[0004] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a manganese cobalt spinel coating with high-temperature conductivity, effective control of Cr element diffusion, and improved bonding force between the coating and the metal matrix.

[0005] In order to achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0006] In the first aspect, the present invention provides a manganese cobalt spinel coating coated on a matrix containing Cr elements, including a bonding layer on the matrix and a structural layer on the bonding layer;

[0007] The mass percentage content of Cr element in the matrix is 5-30%;

[0008] The bonding layer includes the following components: manganese cobalt spinel material, MnCr2O4 and Cr2O3;

[0009] The structural layer is made of manganese cobalt spinel material;

[0010] The chemical formula of the manganese cobalt spinel material is Mn. 1+x Co 2-x O4, where -1 <x<2。

[0011] The inventors of this invention have discovered that the laser cladding method can be used to prepare a manganese cobalt spinel coating with specific composition and structure. The manganese cobalt spinel coating has good electrical conductivity and good adhesion to the substrate. It can also effectively control the growth of the oxide layer on the alloy surface and the diffusion of Cr during the use of SOFC.

[0012] In a preferred embodiment of the manganese cobalt spinel coating of the present invention, the thickness ratio of the bonding layer to the structural layer is bonding layer: structural layer = 1:(5~20).

[0013] The inventors of this invention have discovered that when the thickness ratio of the bonding layer to the structural layer is within the aforementioned range, the conductivity of the manganese cobalt spinel coating and its adhesion to the substrate can be enhanced. When the thickness ratio of the bonding layer is relatively small, the adhesion between the manganese cobalt spinel coating and the substrate decreases; conversely, when the thickness ratio is relatively large, the conductivity of the manganese cobalt spinel coating decreases.

[0014] In a preferred embodiment of the manganese-cobalt spinel coating of the present invention, the XRD pattern of the structural layer satisfies: I 400 / I 200 ≥0.1 and I 440 / I 220 ≥0.05, where I 200 I represents the peak intensity of the crystal plane represented by peak (200). 400 I represents the peak intensity of the crystal plane represented by the (400) peak. 220 I represents the peak intensity of the crystal plane represented by peak (220). 440 The peak intensity of the crystal plane represented by peak (440) is given.

[0015] The inventors of this invention have discovered that the conductivity of the manganese-cobalt spinel coating described in this invention is related to the Mn content within the spinel. + / Mn (n+1)+ The concentration of octahedral structure is related, among which, Mn + / Mn (n+1)+ The octahedral structure corresponds to crystal planes (400) and (440) in the XRD pattern. Compared with the traditional wet process, the manganese cobalt spinel coating prepared by the laser cladding method of the present invention has higher peak intensity in crystal planes (400) and (440) in the XRD pattern, thus the manganese cobalt spinel coating has excellent conductivity.

[0016] In a preferred embodiment of the manganese-cobalt spinel coating of the present invention, the XRD pattern of the bonding layer satisfies: I MnCr2O4 / I Cr2O3 ≥1.5, where I MnCr2O4 2 θ The characteristic peak intensity of MnCr2O4 appearing in the range of 34.9–36.1°, I Cr2O3 2 θ The characteristic peak intensity of Cr2O3 appearing in the range of 32.9 to 34.5°.

[0017] The inventors of this invention have discovered that when a specific 2 in the XRD pattern... θ When the characteristic peak intensity ratio of MnCr2O4 and Cr2O3 is within the specified range, it indicates that the bonding layer contains more MnCr2O4, which can reduce the occurrence of undesirable chemical reactions, mainly preventing oxidation of the alloy substrate and enhancing the adhesion between the coating and the substrate. Simultaneously, controlling the laser cladding process parameters within a specific range can improve the Ig content in the bonding layer of the manganese cobalt spinel coating. MnCr2O4 / I Cr2O3 Within the aforementioned range, peeling measurements revealed that the adhesion between the manganese-cobalt spinel coating and the alloy substrate was at least 10 MPa and at most 38 MPa. However, conventional wet processes or laser cladding processes with parameters outside the specified range resulted in I... MnCr2O4 / I Cr2O3 If the value is less than 1.5, the bonding strength is less than 10 MPa.

[0018] In a preferred embodiment of the manganese cobalt spinel coating of the present invention, the molar ratio of Mn to Co in the structural layer is Mn:Co = 1:2 to 2:1.

[0019] The inventors of this invention have discovered that when the molar ratio of Mn to Co in the structural layer is within the aforementioned range, the coefficient of thermal expansion can be matched with that of the bonding layer and the substrate. If the Co content is too high, it will result in a large coefficient of thermal expansion, which can easily lead to cracking and peeling of the coating.

[0020] Secondly, the present invention also provides a method for preparing the above-mentioned manganese cobalt spinel coating, comprising the following steps:

[0021] S1. Mix manganese cobalt spinel powder, binder and solvent evenly, and ball mill to obtain precursor slurry;

[0022] S2. The precursor slurry described in step S1 is coated onto the substrate surface and laser cladding is performed to obtain the manganese cobalt spinel coating.

[0023] In step S2, the parameters of the laser cladding are as follows: laser power is 500-3000W, laser scanning speed is 10-500mm / s, beam diameter is 0.1-10mm, and wavelength is 0.5-5μm.

[0024] The inventors of this invention have discovered that by utilizing the rapid cooling characteristic of laser cladding in micro-areas, heat can be transferred at an extremely fast rate after laser scanning, allowing the scanned area to cool down quickly. This effectively avoids the phase transformation of manganese-cobalt spinel, resulting in a manganese-cobalt spinel coating with excellent surface density and thickness uniformity. This significantly improves the conductivity of the manganese-cobalt spinel coating and its adhesion to the metal substrate. In contrast, traditional wet processes require sintering manganese-cobalt spinel at temperatures around 800°C, which easily leads to phase transformation and volume shrinkage, resulting in internal cracks, a loose structure, and uneven coating thickness. Furthermore, the process parameters of the laser cladding method described in this invention can effectively control the volatilization and diffusion of Cr into the bonding layer and regulate the valence state of manganese. This facilitates the preparation of structural layers and bonding layers with specific thickness ratios and compositional structures, thereby improving the conductivity of the manganese-cobalt spinel coating and enhancing the adhesion between the coating and the substrate.

[0025] In addition, the manganese cobalt spinel coating prepared by the laser cladding method described in this invention can effectively control the diffusion of Cr elements, thus solving the problem of poisoning of cathode and electrolyte materials caused by the diffusion of Cr elements during the use of traditional SOFC connectors.

[0026] In a preferred embodiment of the preparation method of the present invention, in step S2, the surface roughness of the substrate is 0.05 to 0.5 μm.

[0027] The inventors of this invention have discovered that by controlling the surface roughness of the substrate within the aforementioned range, the substrate possesses higher surface energy, increasing interfacial energy and thereby enhancing the adhesion between the manganese cobalt spinel coating and the substrate. When the surface roughness of the substrate is low, the adhesion between the manganese cobalt spinel coating and the substrate is poor due to lower interfacial energy; conversely, when the surface roughness of the substrate is high, it leads to poorer assembly performance with the single cell and a decrease in interfacial conductivity.

[0028] In a more preferred embodiment of the preparation method of the present invention, in step S2, the surface roughness of the substrate is 0.3 to 0.4 μm.

[0029] The inventors of this invention have discovered that increasing the surface roughness of the substrate to the range described above is more conducive to enhancing the bonding force between the manganese cobalt spinel coating and the substrate.

[0030] In a preferred embodiment of the preparation method of the present invention, in step S1, the adhesive is selected from at least one of ethyl cellulose, polyvinyl butyral, polyvinyl formal, and polyvinylidene fluoride; the solvent is selected from at least one of ethylene glycol, isopropanol, isobutanol, terpineol, cyclohexane, and xylene.

[0031] In a preferred embodiment of the preparation method of the present invention, in step S1, the mass ratio of the binder to the manganese cobalt spinel powder is 0.03 to 0.07; and the mass ratio of the solvent to the manganese cobalt spinel powder is 0.75 to 0.85.

[0032] The inventors of this invention have discovered that adding the specific components and proportions of binder and solvent described above helps to keep the dispersibility and rheological properties of the precursor slurry within a suitable range, enabling it to be uniformly dispersed and thus preparing a uniform manganese cobalt spinel coating. When the amount of binder added is too small or the amount of solvent added is too large, the precursor slurry becomes thinner and will run off after being coated on the substrate surface, making laser cladding impossible. Conversely, when the amount of binder added is too large or the amount of solvent added is too small, the dispersion of the precursor slurry is poor, and the particles tend to agglomerate, resulting in an uneven distribution of the prepared manganese cobalt spinel coating.

[0033] In a preferred embodiment of the preparation method of the present invention, the parameters of the laser cladding in step S2 are as follows: laser power of 1350-1450W, laser scanning speed of 120-150mm / s, and beam diameter of 2-4mm.

[0034] The inventors of this invention have discovered that using the aforementioned laser power, laser scanning speed, and beam diameter to prepare a manganese cobalt spinel coating is more conducive to improving the conductivity of the manganese cobalt spinel coating and its bonding force with the substrate. At the same time, it can more effectively control the growth of the oxide layer on the alloy surface and inhibit the diffusion of Cr elements.

[0035] Furthermore, the various parameters in the laser cladding method described in this invention are interconnected. Since the heat required to form a manganese cobalt spinel coating without a phase transition is fixed, a manganese cobalt spinel coating with excellent surface density and thickness uniformity can only be prepared within the specific range of laser power, laser scanning speed, and beam diameter described in this invention. For example, the laser cladding method described in this invention can achieve the required heat received by the laser scanning plane by reducing the laser scanning speed at a lower laser power; and by increasing the laser scanning speed at a smaller beam diameter to avoid overheating.

[0036] In a preferred embodiment of the preparation method described in this invention, in step S2, the laser cladding parameters include a wavelength of 1–1.5 μm and a beam parameter product of 5–100 mm·mrad.

[0037] Thirdly, the present invention also provides an SOFC connector, the SOFC connector comprising the above-mentioned manganese cobalt spinel coating.

[0038] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0039] (1) The present invention uses laser cladding to prepare a manganese spinel coating with specific composition and structure. The manganese spinel coating has good conductivity and good adhesion to the substrate, which can effectively control the diffusion of Cr elements and solve the problem of poisoning of cathode and electrolyte materials caused by the diffusion of Cr elements to the outside of metal parts during the use of the coating of traditional SOFC connector.

[0040] (2) The present invention uses a laser cladding method. By setting specific laser cladding parameters, the micro-region rapid cooling characteristic can be utilized in the preparation of manganese cobalt spinel coating. After the laser sweeps, the heat can be transferred at an extremely fast speed, so that the swept area can be cooled down quickly, effectively avoiding the phase transformation of manganese cobalt spinel. Thus, a manganese cobalt spinel coating with excellent surface density and thickness uniformity is prepared, which effectively improves the conductivity of manganese cobalt spinel coating and its bonding force with the metal substrate. Attached Figure Description

[0041] Figure 1 The images show the morphology and cross-sectional views of the manganese cobalt spinel coatings prepared in Example 1 and Comparative Example 1 of the present invention; wherein, A1 is the morphology image of the manganese cobalt spinel coating prepared in Comparative Example 1 of the present invention, A2 is the cross-sectional view of the manganese cobalt spinel coating prepared in Comparative Example 1 of the present invention, B1 is the morphology image of the manganese cobalt spinel coating prepared in Example 1 of the present invention, and B2 is the cross-sectional view of the manganese cobalt spinel coating prepared in Example 1 of the present invention.

[0042] Figure 2 The images show XRD comparisons of the manganese cobalt spinel coatings prepared in Examples 1-3 and Comparative Example 1 of this invention, with the wet process corresponding to the manganese cobalt spinel coating prepared in Comparative Example 1.

[0043] Figure 3 XRD comparison images of manganese cobalt spinel coatings prepared by laser cladding and wet process;

[0044] Figure 4 This is a comparison diagram of the electrochemical impedance of the manganese cobalt spinel coatings prepared in Example 3 and Comparative Example 1 of the present invention;

[0045] Figure 5 This is a comparison diagram of the electrochemical impedance of the manganese cobalt spinel coatings prepared in Example 2 and Comparative Example 1 of the present invention;

[0046] Figure 6This is a comparison diagram of the electrochemical impedance of the manganese cobalt spinel coatings prepared in Example 1 and Comparative Example 1 of the present invention. Detailed Implementation

[0047] The technical solution of the present invention will be further described below with reference to the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention. Unless otherwise specified, the methods or operations used in the embodiments are conventional methods or operations in the art.

[0048] The manganese cobalt spinel powder used in the spinel coatings of the following embodiments and comparative examples of the present invention is (Mn,Co)3O4 spinel, wherein the molar ratio of Mn to Co is Mn:Co = 1:1.

[0049] The alloy matrix of the present invention can be selected from any one of lanthanum chromate, iron-based alloys, and chromium-based alloys, wherein the mass percentage of Cr in the alloy matrix can be 5-30%. The following embodiments and comparative examples of the present invention uniformly use stainless steel SUS441 (wherein the mass percentage of Cr is approximately 22%).

[0050] Examples 1-19 and Comparative Examples 1-3

[0051] Examples 1-19 and Comparative Examples 2-3 were all manganese-cobalt spinel coatings prepared by laser cladding. The manganese-cobalt spinel coatings of Examples 1-19 and Comparative Examples 2-3 were coated on a Cr-containing substrate and included a bonding layer on the substrate and a structural layer on the bonding layer; the bonding layer included the following components: Mn 1+x Co 2-x O4, MnCr2O4 and Cr2O3, the structural layer is Mn 1+x Co 2-x O4, where -1 <x<2。

[0052] The preparation methods of the manganese cobalt spinel coatings in Examples 1-15 and Comparative Examples 2-3 include the following steps:

[0053] S1. Weigh out manganese cobalt spinel powder, binder, and solvent, mix them evenly, and ball mill them to obtain a precursor slurry; the binder is ethyl cellulose, and the mass ratio of binder to manganese cobalt spinel powder is 0.05; the solvent is terpineol, and the mass ratio of solvent to manganese cobalt spinel powder is 0.8.

[0054] S2. The precursor slurry described in step S1 is coated onto the surface of a Cr-containing substrate and laser cladding is performed to obtain the manganese cobalt spinel coating.

[0055] The laser cladding method described in step S2 includes the following steps:

[0056] S21. Turn on the cooling water and start the laser equipment;

[0057] S22. The precursor slurry described in step S2 is uniformly coated onto the surface of the substrate and placed on the laser receiving mold stage.

[0058] S23. Program the laser path on the computer, with the laser scanning plane area being the sample area (the sample area in both the embodiment and the comparative example of this invention is 1*1cm). 2 The path can be set to vertical or horizontal (both the embodiments and comparative examples of this invention are vertical), and the laser parameters are set; among the laser cladding parameters, the wavelength is 1.5μm and the product of the beam parameters is 50mm·mrad;

[0059] S24. Start the laser emitter. The preparation time is (sample area / laser scanning speed * beam diameter). After the indicator light comes on at the end of the run, wait half an hour for the sample to cool down to obtain the manganese cobalt spinel coating.

[0060] The parameters for each step in the preparation methods of the manganese cobalt spinel coatings in Examples 1-15 and Comparative Examples 2-3 are shown in Table 1 below.

[0061] Table 1

[0062]

[0063]

[0064] This invention also includes Examples 16-19. Examples 16-19 all use laser cladding to prepare manganese cobalt spinel coatings. The only difference between Examples 16-19 and Example 1 is in step S2: the mass ratio of binder to manganese cobalt spinel powder and the mass ratio of solvent to manganese cobalt spinel powder are different, as shown in Table 2 below. The other steps and parameters of the preparation method of the manganese cobalt spinel coatings in Examples 16-19 are the same as those in Example 1.

[0065] Table 2

[0066] project Binder: Powder Solvent: Powder Example 1 0.05 0.80 Example 16 0.03 0.75 Example 17 0.06 0.71 Example 18 0.04 0.81 Example 19 0.07 0.88

[0067] The present invention also includes Comparative Example 1. Comparative Example 1 is a manganese cobalt spinel coating prepared using a conventional wet process.

[0068] The preparation method of the manganese cobalt spinel coating of Comparative Example 1 includes the following steps:

[0069] S1. Manganese powder and cobalt powder are added to ethanol at a mass ratio of 1:1 and mixed evenly to obtain a manganese-cobalt suspension; then the manganese-cobalt suspension is ball-milled to obtain a ball milling fluid; the ethanol in the ball milling fluid is then evaporated to obtain a manganese-cobalt mixed powder; the manganese-cobalt mixed powder is mixed with a solution to obtain a mixed slurry; the solution is obtained by compounding ethyl cellulose and terpineol, and the mass ratio of ethyl cellulose to terpineol in the solution is 10:90;

[0070] S2. The mixed slurry described in step S1 is applied to the surface of the ferritic stainless steel connector by screen printing and dried to obtain coating A on the surface of the ferritic stainless steel connector.

[0071] S3. The ferritic stainless steel connector with coating A on its surface is sintered at 800°C for 20 hours in a reducing atmosphere, and then sintered at 850°C for 48 hours with air introduced to obtain a manganese cobalt spinel coating.

[0072] Example of effect

[0073] To verify the performance of the manganese cobalt spinel coating described in this invention, the manganese cobalt spinel coatings of Examples 1-19 and Comparative Examples 1-3 were tested for adhesion, electrical resistance, Cr volatilization, and XRD performance. The specific test methods are as follows:

[0074] (1) The test method for bonding strength includes the following steps:

[0075] S1. Mix LSM powder and YSZ powder, add binder ethyl cellulose and solvent terpineol, cast into shape, and sinter at 1200℃ for 1 hour to form a simulated air electrode.

[0076] S2. Ferritic stainless steel with a Cr content of 22wt% is processed into the corresponding shape as a simulated connector.

[0077] S3. Using the simulated connector described in step S2 as the alloy substrate, manganese cobalt spinel coatings are prepared on the surface of the alloy substrate using the preparation methods of Examples 1-19 and Comparative Examples 1-3, respectively. The simulated air electrode described in step S1 is then bonded together with the simulated connector described in step S2. After drying at 100°C for 1 hour, the mixture is sintered at 900°C.

[0078] S4. Use commercially available epoxy resin adhesive to bond the above samples to the metal clamps, and test the bonding force of each connector through a tensile test; an average bonding force of 10MPa or more is considered qualified.

[0079] (2) The test method for ohmic impedance at 750℃ includes the following steps:

[0080] The manganese-cobalt spinel coatings prepared in Examples 1-19 and Comparative Examples 1-3 were assembled into single cells with cathodes, anodes, and electrolytes, respectively. Electrochemical impedance spectroscopy (EIS) was measured at 750 °C. Ohmic impedance was obtained from the value of the portion of the impedance curve coinciding with the horizontal axis in the Nyquist plot; the ohmic impedance at 750 °C was less than 0.15 Ω·cm. 2 It is considered qualified.

[0081] (3) The test method for Cr volatilization (ppm) over 500 hours includes the following steps:

[0082] S1. Ferritic stainless steel material with a Cr content of 22wt% is processed into the corresponding shape as a simulated connector;

[0083] S2. Using the simulated connector described in step S1 as the alloy substrate, manganese cobalt spinel coatings are prepared on the surface of the alloy substrate using the preparation methods of Examples 1-19 and Comparative Examples 1-3, respectively. Alumina material is placed around the simulated substrate with the coating to be tested and heated at 900°C for 500 hours.

[0084] S3. Subsequently, the alumina material described in step S2 is used to measure and evaluate the Cr volatilization amount using an inductively coupled plasma atomic emission spectrometer (ICP-AES); a Cr volatilization amount of less than 100 ppm is considered acceptable.

[0085] (4)XRD

[0086] The manganese cobalt spinel coatings prepared in Examples 1-19 and Comparative Examples 1-3 were tested using X-ray diffraction (XRD). The intensity ratio of the diffraction peaks on the (200) and (400) crystal planes was I. 400 / I 200 The intensity ratio of the diffraction peaks of the (220) and (440) crystal planes is I. 440 / I 220 The integral intensity ratio of the highest characteristic peaks of MnCr2O4 and Cr2O3 is I. MnCr2O4 / I Cr2O3 .

[0087] The test results are shown in Table 3 below. Figures 1-6 As shown.

[0088] Table 3

[0089]

[0090]

[0091] As can be seen from Table 3, the bonding strength between the manganese cobalt spinel coating and the alloy substrate prepared by the laser cladding method described in this invention and Examples 1 to 19 can reach more than 11 MPa, and it has a low ohmic impedance value and a Cr volatilization rate of 500 h, indicating that it has good conductivity and the ability to suppress Cr diffusion.

[0092] Comparing Examples 1-7, Examples 14-15, and Comparative Examples 2-3, it can be seen that the process parameters of the laser cladding method have a significant impact on the thickness of the manganese cobalt spinel coating and the composition of the structural layer and the bonding layer. Compared with Examples 14-15, the XRD patterns of the manganese cobalt spinel coatings prepared using the laser cladding process parameters of Examples 1-7 show that... 400 / I 200 I 440 / I 220 and I MnCr2O4 / I Cr2O3 The coating exhibits higher conductivity, stronger adhesion between the coating and the substrate, and superior electrical conductivity with less Cr volatilization. However, when the process parameters of the laser cladding method are outside the scope of this invention, resulting in excessively high or low heat output, the amount of Cr volatilization in the substrate cannot be effectively controlled. Consequently, the manganese-cobalt spinel coating with the specific structure and composition described in this invention cannot be prepared, and the adhesion and Cr diffusion inhibition performance of the manganese-cobalt spinel coating are poor.

[0093] Comparing Examples 8-13, it is evident that the surface roughness of the alloy substrate significantly affects the adhesion between the coating and the substrate, and also influences the amount of Cr volatilization. The manganese-cobalt spinel coatings prepared from the alloy substrates of Examples 8-9 exhibit both high adhesion and low Cr diffusion. When the surface roughness of the alloy substrate is high, although the manganese-cobalt spinel coating has high adhesion, its performance in controlling Cr diffusion decreases significantly, potentially leading to poisoning of the cathode and electrolyte materials over time. Conversely, when the surface roughness of the alloy substrate is low, the adhesion of the manganese-cobalt spinel coating is low.

[0094] The morphology and cross-sectional images of the manganese cobalt spinel coating prepared by laser cladding in Example 1 and the manganese cobalt spinel coating prepared by wet process in Comparative Example 1 are shown below. Figure 1 As shown. From Figure 1 It can be seen that the manganese cobalt spinel coating prepared by the wet process has uneven thickness distribution and poor surface density; while the manganese cobalt spinel coating prepared by the laser cladding method described in this invention has better surface density and thickness uniformity.

[0095] Figure 2 The XRD comparison images are of the manganese cobalt spinel coatings prepared in Examples 1-3 and Comparative Example 1 of this invention. Figure 3XRD patterns comparing manganese-cobalt spinel coatings prepared by laser cladding and wet processes. Figure 2 It can be clearly seen that, compared with the wet process of Comparative Example 1, the manganese cobalt spinel coatings prepared by the laser cladding method described in Examples 1 to 3 have obvious peaks on the (400) and (440) crystal planes, and the peak intensities are high, which is beneficial to improving the conductivity of the manganese cobalt spinel coating. As can be seen from Table 3, compared with the wet process, the integral intensity of the MnCr2O4 characteristic peak of the manganese cobalt spinel coating prepared by the laser cladding method of the present invention is higher than that of the wet process.

[0096] Figure 4 This is a comparison diagram of the electrochemical impedance of the manganese cobalt spinel coatings prepared in Example 3 and Comparative Example 1 of the present invention; Figure 5 This is a comparison diagram of the electrochemical impedance of the manganese cobalt spinel coatings prepared in Example 2 and Comparative Example 1 of the present invention; Figure 6 This is a comparison of the electrochemical impedance spectroscopy of the manganese-cobalt spinel coatings prepared in Example 1 and Comparative Example 1 of the present invention. Figures 4-6 It can be seen that the manganese cobalt spinel coatings prepared by laser cladding in Examples 1-3 of the present invention have lower impedance, indicating that they have excellent conductivity.

[0097] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the essence and scope of the technical solutions of the present invention.

Claims

1. A manganese-cobalt spinel coating, applied to a Cr-containing substrate, characterized in that, Includes a bonding layer on the substrate and a structural layer on the bonding layer; The bonding layer comprises the following components: manganese cobalt spinel material, MnCr2O4 and Cr2O3; The structural layer is made of manganese cobalt spinel material; The chemical formula of the manganese cobalt spinel material is Mn. 1+x Co 2-x O4, where -1 <x<2; The XRD patterns of the structural layer satisfy: I 400 / I 200 ≥0.78 and I 440 / I 220 ≥0.11, where I 200 I represents the peak intensity of the crystal plane represented by peak (200). 400 I represents the peak intensity of the crystal plane represented by the (400) peak. 220 I represents the peak intensity of the crystal plane represented by peak (220). 440 The peak intensity of the crystal plane represented by peak (440) is given.

2. The manganese-cobalt spinel coating as described in claim 1, characterized in that, The thickness ratio of the bonding layer to the structural layer is 1:(5~20).

3. The manganese-cobalt spinel coating as described in claim 1, characterized in that, The XRD pattern of the binding layer satisfies: I MnCr2O4 / I Cr2O3 ≥1.9, where I MnCr2O4 2 θ The peak intensity of MnCr2O4 appearing in the range of 34.9~36.1°, I Cr2O3 2 θ The peak intensity of Cr2O3 appearing in the range of 32.9~34.5°.

4. The manganese-cobalt spinel coating as described in claim 1, characterized in that, In the structural layer, the molar ratio of Mn to Co is Mn:Co = 1:2 to 2:

1.

5. The method for preparing the manganese-cobalt spinel coating according to any one of claims 1 to 4, characterized in that, Includes the following steps: S1. Mix manganese cobalt spinel powder, binder and solvent evenly, and ball mill to obtain precursor slurry; S2. The precursor slurry described in step S1 is coated onto the substrate surface and laser cladding is performed to obtain the manganese cobalt spinel coating. In step S2, the parameters of the laser cladding are as follows: laser power is 500~3000W, laser scanning speed is 10~500mm / s, beam diameter is 0.1~10mm, and wavelength is 0.5~5μm.

6. The preparation method according to claim 5, characterized in that, In step S2, the surface roughness of the substrate is 0.05~0.5μm.

7. The preparation method according to claim 6, characterized in that, In step S2, the surface roughness of the substrate is 0.3~0.4μm.

8. The preparation method according to claim 5, characterized in that, In step S1, the mass ratio of the binder to the manganese cobalt spinel powder is (0.03~0.07):1; the mass ratio of the solvent to the manganese cobalt spinel powder is (0.75~0.85):

1.

9. The preparation method according to claim 5, characterized in that, In step S2, the parameters of the laser cladding are as follows: laser power is 1350~1450W, laser scanning speed is 120~150mm / s, and beam diameter is 2~4mm.

10. An SOFC connector, characterized in that, The SOFC connector includes a manganese cobalt spinel coating as described in any one of claims 1 to 4.

Images