CN116505000A - A kind of preparation method of Ni-Al intermetallic compound negative contact layer - Google Patents

Abstract

The invention relates to the field of electrochemical energy materials, in particular to a preparation method of a Ni-Al intermetallic compound negative contact layer, which comprises the following steps: s1, mixing powder: at atomic ratio 1.5:1, weighing nickel powder and aluminum powder, and grinding to obtain mixed powder; s2, preparing an adhesive: mixing ethyl cellulose and terpineol, and stirring to obtain transparent viscous gelatinous substance to obtain adhesive; s3, preparing a sintered sample; s4, atmosphere sintering: and (3) calcining the dried sample, and cooling to room temperature to obtain the Ni-Al intermetallic compound cathode contact layer. The invention provides a novel cathode contact layer material, namely a Ni-Al intermetallic compound, which has excellent conductivity and high-temperature oxidation resistance.

Description

A kind of preparation method of Ni-Al intermetallic compound negative contact layer

technical field

The invention relates to the field of chemical coating preparation, in particular to a preparation method of a Ni-Al intermetallic compound negative contact layer.

Background technique

The contact between the cell electrodes and the metal connector is a "hard" contact between ceramic or cermet and metal. In order to reduce the interface contact resistance (expressed as ASR, area specific resistance) and voltage loss, during the stack assembly process, a relatively "soft" and compressible conductive contact material is usually used at the interface to collect and conduct electrons on the one hand (collector layer), on the other hand, it enhances the interface contact and reduces the interface resistance. Therefore, at the operating temperature of the stack, the contact material should have compressibility, adhesion to cathode/anode, good electronic conductivity, resistance to high temperature oxidation, and maintain a porous structure (proper sintering activity and porosity) , to facilitate the diffusion of reactant gases into the electrodes and participate in electrochemical reactions. Considering that the anode and cathode of each single cell in the stack are exposed to reducing fuel atmosphere and air atmosphere respectively, nickel foam (Ni) is usually used as the gas diffusion layer material for the anode, and Ni slurry is used as the material between the nickel foam and the anode. On the cathode side, the commonly used diffusion layer material is mostly ferritic stainless steel, its structure is a channel or fin integrated with the metal connector, and the contact material is often compressible porous noble metal or conductive ceramics powder material.

The contact resistance produced by the cathode/metal connector interface is much higher than that of the anode, and the two show an order of magnitude difference; therefore, the performance of the cathode/metal connector interface is a constraint on the medium temperature solid oxide fuel cell (expressed as SOFC, Solid OxideFuel Cell) technology One of the bottlenecks of development. Cathode contact materials need to meet the conditions of high electronic conductivity, stable chemical properties, stable mechanical structure, matching coefficient of thermal expansion (CTE) with cathode and connector materials, and low cost. Generally, they are perovskite materials, noble metal materials, sharp Spar coating material. Among them, precious metals have good electrical conductivity, but are more expensive. The main problem of perovskite materials as the contact layer is that there is no way to perfectly integrate conductivity, CTE, sinterability and other properties. For example, lanthanum strontium cobalt has good electrical conductivity, but its CTE is much higher than other components; lanthanum strontium manganese has a CTE compatible with other components, but its conductivity is low, so how to balance the various properties of the material is a problem . However, spinel materials require a higher sintering temperature to obtain the spinel phase, which may lead to severe oxidation of the interconnect during the sintering process.

Contents of the invention

In order to solve the existing technical problems, the invention proposes a method for preparing a Ni-Al intermetallic compound negative contact layer.

A method for preparing a Ni-Al intermetallic compound negative contact layer, comprising the steps of:

S1, powder mixing: after weighing nickel powder and aluminum powder with an atomic ratio of 1.5:1, grinding to obtain a mixed powder;

S2, preparation of viscous agent: after mixing ethyl cellulose and terpineol, stirring into a transparent viscous jelly-like substance, the viscous agent is prepared;

S3, prepare the sintered sample: Weigh the mixed powder prepared in S1 and the adhesive prepared in S2 in proportion, mix them, and grind to obtain Ni-Al slurry, and then apply the Ni-Al slurry to ferritic stainless steel After connecting the body surface, dry;

S4, atmosphere sintering: after the dried sample is calcined, cooled to room temperature, the Ni-Al intermetallic compound cathode contact layer can be prepared.

Further, in S1, the grinding process is as follows: after mixing nickel powder, aluminum powder and grinding media at a speed of 200r/min, after mixing for 8 hours, a mixed powder is obtained.

Further, the grinding medium is a mixture of zirconia balls of φ10mm and φ5mm with a mass ratio of 1:1, and the mass of the grinding medium is three times the total amount of nickel powder and aluminum powder.

Further, in S2, in terms of weight percentage, ethyl cellulose: terpineol=96wt.%: 4wt.%.

Further, in S2, the stirring temperature condition is 80°C, and the stirring time condition is 5h.

Further, in S3, in terms of weight percentage, mixed powder: adhesive = 65wt.%: 35wt.%, the grinding time condition is 30min, and the Ni-Al slurry is applied to the ferrite by screen printing Body stainless steel connecting body surface.

Further, in S3, the drying temperature condition is 80° C., and the drying time condition is 3 hours.

Further, in S4, the specific process of calcination is as follows: put the dried sample into a tube furnace, pass in pure argon, raise the temperature to 550°C at a rate of 5°C/min and keep it at this temperature for 30min , and then continue to heat up to 900 ° C and keep at this temperature for 2 hours.

The Ni-Al intermetallic compound negative contact layer prepared by the above preparation method.

Application of the above-mentioned Ni-Al intermetallic compound negative contact layer in electrocatalyzing carbon dioxide to produce carbon monoxide.

Compared with the prior art, the present invention has the following advantages:

1. The present invention provides a new cathode contact layer material, Ni-Al intermetallic compound, which has excellent electrical conductivity and high temperature oxidation resistance.

2. The Ni-Al intermetallic compound cathode contact layer provided by the present invention can maximize the service life and electrical performance of the SOFC stack when applied.

3. The preparation method of the Ni-Al intermetallic compound cathode contact layer provided by the present invention has less process flow, simple equipment required, easy control of the preparation process, and is suitable for large-scale industrial production.

Description of drawings

Fig. 1 is a flow chart of the preparation of a Ni-Al intermetallic compound negative contact layer according to the present invention.

FIG. 2 is an experimental result diagram of the area specific resistance (ASR) of the Ni—Al intermetallic compound cathode contact layer prepared in Example 1. FIG.

FIG. 3 is a graph showing the variation of ASR with temperature at different temperatures for the Ni—Al intermetallic compound cathode contact layer prepared in Example 1. FIG.

Fig. 4 is the oxidation XRD spectrum of the Ni-Al intermetallic compound cathode contact layer prepared in Example 1 in the ASR test.

Fig. 5(a) is a SEM spectrum of the surface morphology of the Ni-Al intermetallic compound cathode contact layer prepared in Example 1 under a 500-fold mirror.

Figure 5(b) is the SEM spectrum of the surface morphology of the Ni-Al intermetallic compound cathode contact layer prepared in Example 1 under a 10k magnification lens.

Figure 5(c) is the EDS point scan spectrum of point A in Figure 5(b).

Figure 5(d) is the EDS point scan spectrum of point B in Figure 5(b).

Fig. 6(a) is a cross-sectional view of the Ni-Al intermetallic compound cathode contact layer prepared in Example 1 after ASR test oxidation.

Fig. 6(b) is the EDS surface scan pattern of Fig. 6(a).

Fig. 6(c) is the EDS point-scan pattern of Fig. 6(a).

Fig. 6(d) is the EDS point-scan pattern of Fig. 6(a).

7 is a comparative XRD pattern of the Ni-Al intermetallic compound negative contact layer prepared in Example 1 and the Ni-Al intermetallic compound negative contact layer prepared in Comparative Example 1.

Detailed ways

The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention. Unless otherwise specified, the equipment and reagents used in the present invention are conventional commercial products in the technical field.

Porous intermetallic compounds are a new type of inorganic porous materials between porous ceramics and porous metals. Due to their excellent performance and promising development prospects, they have attracted much attention in recent years. Ni-Al-based intermetallic compounds are a new generation of intermetallic compound porous materials, which have good electrical conductivity and high-temperature oxidation resistance, and can be used as high-temperature structural and functional materials, and have been widely used in the field of porous materials. Ni3Al and NiAl with a high melting point in the Ni-Al binary system not only have good electrical conductivity, thermal conductivity and high-temperature plasticity (compressibility) of metal materials, but also have excellent properties such as high-temperature resistance, corrosion resistance and oxidation resistance of ceramic materials; The excellent physical and chemical properties make it a good SOFC cathode contact material. Therefore, the present invention proposes a porous Ni-Al intermetallic compound as the cathode/metal connector interface contact material, which provides a new idea for the research and development of SOFC cathode contact materials, and lays the foundation for solving the bottleneck key technology of SOFC stacks.

<Example 1>

Please refer to FIG. 1, an embodiment of the present invention provides a method for preparing a Ni-Al intermetallic compound negative contact layer, comprising the following steps:

S1, powder mixing: Weigh nickel powder and aluminum powder at an atomic ratio of 1.5:1, put them into a mixing tank together with three times the mass of grinding media, put on a V-shaped mixer, and at a speed of 200r/min, Mixing materials for 8h, wherein the grinding medium is a mixture of φ10mm and φ5mm zirconia balls with a mass ratio of 1:1;

S2, preparation of viscous agent: pour 96wt.% ethyl cellulose and 4wt.% terpineol into a beaker, stir and heat in a magnetic stirrer at 80°C for 5 hours, until the two are completely mixed into a transparent and viscous colloid ;

S3, preparation of sintered samples: Weigh 65wt.% mixed powder and 35wt.% adhesive and pour them into natural agate grinding body, grind at a constant speed for 30min to obtain Ni-Al slurry, and use screen printing method to make Ni-Al slurry The material is applied to the surface of the SUS430 ferritic stainless steel connector, and placed in a drying oven at 80°C for 3 hours.

S4, Atmosphere sintering: Put the dried sample into a tube furnace, pass high-purity argon (99.9%), use a heating rate of 5°C/min to rise to 550°C and keep it at this temperature for 30min, and then continue The temperature was raised to 900° C. and kept at this temperature for 2 hours. After the sample was cooled to room temperature, the Ni-Al intermetallic compound cathode contact layer could be prepared.

The Ni-Al intermetallic compound cathode contact layer prepared by the present invention is different from the traditional noble metal or conductive oxide cathode contact material. The Ni-Al intermetallic compound not only has good electrical conductivity and high temperature oxidation resistance, but also meets the performance of the cathode contact material Requirements, and can form a porous contact layer through in-situ reaction sintering of Ni and Al mixed powder, and form a good interface bond with the cathode and the metal connector.

The preparation method of the present invention, the common conductive oxide cathode contact material, is applied between the cathode and the metal connector by screen printing after phase formation, and the interface between them is a physical combination under SOFC working conditions. easy to break. In this patent, the mixed powder of Ni and Al is applied between the cathode and the metal connector, and is kept warm (higher than the melting point of Al) during the heating process of the SOFC stack, and the porous Ni-Al intermetallic compound contact is formed by in-situ reaction sintering. layer. The heat released by the transient liquid (Al)-solid (Ni) reaction will cause the interdiffusion of the interface to form a chemical bond, thereby improving the bonding strength and reducing the contact resistance.

Fig. 2 is a graph showing the experimental results of testing the area specific resistance (ASR) of the Ni-Al intermetallic compound cathode contact layer prepared by the method of this embodiment in air at 750° C. for 300 hours. It can be seen from Figure 2 that the entire graph seems to fluctuate greatly, but in fact the fluctuation of the ASR value is very small, and the overall value is in the range of 8.4-9.2mΩ·cm ² . In the first 250h, the ASR value has not stabilized, but in the period of 250-300h, a plateau area appeared, and the ASR was stable at 8.67mΩ·cm ² . The ASR value is small, indicating that the Ni-Al intermetallic compound contact layer has good electrical conductivity, which fully meets the actual use of the cathode contact layer.

Fig. 3 is a graph showing the variation of ASR with temperature at different temperatures of 550-850°C for the Ni-Al intermetallic compound cathode contact layer prepared by the method of this embodiment. It can be seen from Figure 3 that the ASR value has been increasing with the increase of temperature. At 550°C, the ASR value was 1.51mΩ·cm ² , and then increased to 4.50mΩ·cm ² at 850°C, and the increase was relatively slow. Uniform, the graph approximates a straight line. The characteristic that the ASR value of the Ni-Al contact layer increases with the increase of temperature is very similar to that of metals. The conductivity of metal materials will decrease with the increase of temperature, and the ASR will increase with the increase of temperature. High, indicating that the conductive properties of Ni-Al intermetallic compounds are also similar to those of metals. Although the ASR value of the Ni-Al cathode contact layer has been increasing with the increase of temperature, its overall value is very small, and the maximum value at 850 ° C is also lower than 5mΩ·cm ² , indicating that the contact layer is different The electrical properties at high temperature are good.

Fig. 4 is an XRD spectrum of the Ni-Al intermetallic compound cathode contact layer prepared by the method of this example after being oxidized for 300 hours by ASR test at 750°C. It can be seen from the figure that the main components of the Ni-Al cathode contact layer before oxidation are NiAl, NiFe and a small amount of single-phase Ni, and the NiAl phase is the most content. The newly produced NiFe should be produced by the interdiffusion of Fe in the Fe-Cr alloy junction and Ni in the Ni-Al contact layer. It can be seen from the spectrum after ASR test oxidation at 750°C for 300h that its main components are: NiAl, NiFe, a small amount of single-phase Ni and very little NiO, and the strongest peak belongs to NiAl, followed by NiFe, and The contents of both Ni and NiO are very small. The diffraction peaks of the spectra before and after oxidation are very similar. The only difference is that a very small amount of NiO appears after oxidation, which also shows that the cathode contact layer has good oxidation resistance. After 300 hours of oxidation, there is no large amount of oxides. .

Figure 5 is the SEM spectrum of the surface morphology of the Ni-Al intermetallic compound cathode contact layer prepared by the method of this example, and the point scanning of the energy spectrum is carried out at points A and B, as shown in Figure 5 (a) , The Ni-Al cathode contact layer is a porous structure, and the spherical material with uniform distribution on the surface is formed by agglomeration of many small particles. Figure 5(b) is a photo of the surface of the Ni-Al cathode contact layer further enlarged to 10k times, and the EDS point scanning with two points A and B on it, the results are shown in Figure 5(c), (d) shown. According to the energy spectrum analysis in Figure 5(c), the elements at point A are Pt, Ni, and Al. There are platinum elements because a layer of platinum will be sprayed on the surface of the sample before taking the SEM photo to increase the conductivity of the sample. The photos taken are clearer. The atomic percentage of Pt is very small and negligible. Its main elements are Ni and Al. Ni and Al atomic ratio is close to 1:1, point A is likely to be NiAl. It can be seen from Figure 5(d) that the elements detected at point B are Pt, Ni, and Al, among which Pt can be ignored, the weight ratio of Ni to Al is 50.17:46.40, and the atomic ratio is 32.97:66.37. This substance may be Ni ₂ Al ₃ .

Figure 6 is a cross-sectional view of the Ni-Al intermetallic compound cathode contact layer prepared by the method of this example after being oxidized for 300 h by ASR test, the left part in Figure 6 (a) is the connector and the right side is the contact layer, the contact The layer is porous, but the pores of the contact layer are filled with acrylic resin due to the preparation of the mosaic. It can be seen that the thickness of the contact layer is more than 50 μm, and it is closely combined with the connector. No obvious cracks and oxide layers can be seen from the naked eye, but the interface position of 20-25 μm can be analyzed from the element spectrum of O The content of oxygen element is extraordinarily high, so it can be inferred that oxides are formed at this position, and an oxide layer may be formed. Figure 6(b) is the EDS surface scan pattern of Figure 6(a), where the red dots represent Fe particles, the green dots represent Al particles, and the yellow dots represent Ni particles. Figure 6(c) and Figure 6(d) are all EDS line scans of the position of the white line in Figure 6(a), and Figure 6(b) shows the elements and content contained on the line (d) shows this The distribution and content of elements at different positions on the line. It can be known from Figure 6(c) that the line contains C, O, Al, Cr, Mn, Fe, Ni, among which the atomic ratio of C element is the highest due to the presence of acrylic resin, followed by Ni and Al Elements, the atomic percentage of which accounts for 14.83% and one accounts for 14.08%, and the two are approximately one to one. Most of the particles that should be formed are NiAl particles, and the content of the remaining Cr, Mn, and Fe elements is relatively low. From the spectrum of Fe, Cr, O, Ni, and Al elements in Figure 6(d), it can also be inferred that the content of Fe and Cr elements in the first 20 μm is high, which is the connecting part, and a small amount of O appears in the 20-25 μm element and Ni element, indicating that an oxide layer of about 5 μm may be formed at this position, which should be NiO. The content of Ni and Al elements after 25 μm is extremely high, indicating that it is the contact layer part, and no accumulation of Cr element is found in the contact layer part, indicating that the contact layer can effectively block the volatilization of Cr element.

<Comparative example 1>

A method for preparing a Ni-Al intermetallic compound negative contact layer, comprising the following steps:

S1, powder mixing: Weigh nickel powder and aluminum powder with an atomic ratio of 3:1, put them into a mixing tank together with three times the mass of grinding media, put on a V-shaped mixer, and at a speed of 200r/min, Mixing materials for 8h, wherein the grinding medium is a mixture of φ10mm and φ5mm zirconia balls with a mass ratio of 1:1;

S2, preparation of viscous agent: pour 96wt.% ethyl cellulose and 4wt.% terpineol into a beaker, stir and heat in a magnetic stirrer at 80°C for 5 hours, until the two are completely mixed into a transparent and viscous colloid ;

S3, preparation of sintered samples: Weigh 65wt.% mixed powder and 35wt.% adhesive and pour them into natural agate grinding body, grind at a constant speed for 30min to obtain Ni-Al slurry, and use screen printing method to make Ni-Al slurry The material is applied to the surface of the SUS430 ferritic stainless steel connector, and placed in a drying oven at 80°C for 3 hours.

S4, Atmosphere sintering: Put the dried sample into a tube furnace, pass high-purity argon (99.9%), use a heating rate of 5°C/min to rise to 550°C and keep it at this temperature for 30min, and then continue The temperature was raised to 900° C. and kept at this temperature for 2 hours. After the sample was cooled to room temperature, the Ni-Al intermetallic compound cathode contact layer (Ni3Al cathode contact layer) could be prepared.

The Ni1.5Al cathode contact layer prepared in Example 1 was compared with the Ni3Al cathode contact layer prepared in Comparative Example 1, and the results are shown in FIG. 7 . It can be seen from the figure that the main phase of the Ni3Al contact layer is that Ni contains only a small amount of NiAl, which shows that when the atomic ratio of Ni and Al becomes 3:1, the atomic ratio of Ni is too high, resulting in the overflow of single Ni. The main components of the N1.5Al contact layer are NiAl and NiFe. From the point of view of the phase, the phase of the N1.5Al cathode contact layer is better.

The descriptions of the above embodiments are only used to help understand the technical solutions and core ideas of the present invention. It should be pointed out that for those skilled in the art, some improvements can also be made to the present invention without departing from the principles of the present invention. and modifications, these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims (10)

1. a preparation method of Ni-Al intermetallic compound negative contact layer, is characterized in that, comprises the steps: S1, powder mixing: after weighing nickel powder and aluminum powder with an atomic ratio of 1.5:1, grinding to obtain a mixed powder; S2, preparation of viscous agent: after mixing ethyl cellulose and terpineol, stirring into a transparent viscous jelly-like substance, the viscous agent is prepared; S3, prepare the sintered sample: Weigh the mixed powder prepared in S1 and the adhesive prepared in S2 in proportion, mix them, and grind to obtain Ni-Al slurry, and then apply the Ni-Al slurry to ferritic stainless steel After connecting the body surface, dry; S4, atmosphere sintering: after the dried sample is calcined, cooled to room temperature, the Ni-Al intermetallic compound cathode contact layer can be prepared. 2. the preparation method of a kind of Ni-Al intermetallic compound negative contact layer according to claim 1 is characterized in that, in S1, the process of grinding is: after nickel powder, aluminum powder and grinding medium are mixed, with At a speed of 200r/min, after mixing for 8 hours, a mixed powder was obtained. 3. the preparation method of a kind of Ni-Al intermetallic compound negative contact layer according to claim 2 is characterized in that, grinding medium is the mixture of the zirconia ball of φ 10mm and φ 5mm of mass ratio 1:1, and the grinding medium The mass is three times the total amount of nickel powder and aluminum powder. 4. the preparation method of a kind of Ni-Al intermetallic compound negative contact layer according to claim 1 is characterized in that, in S2, by weight percent, ethyl cellulose: terpineol=96wt.% : 4wt.%. 5 . The method for preparing a Ni-Al intermetallic compound negative contact layer according to claim 1 , characterized in that, in S2 , the stirring temperature condition is 80° C., and the time condition is 5 hours. 6. the preparation method of a kind of Ni-Al intermetallic compound negative contact layer according to claim 1, it is characterized in that, in S3, in weight percent, mixed powder: tackifier=65wt.%: 35wt %, the grinding time condition is 30min, and the Ni-Al slurry is applied to the surface of the ferritic stainless steel connecting body by screen printing. 7. The method for preparing a Ni-Al intermetallic compound negative contact layer according to claim 1, characterized in that, in S3, the drying temperature condition is 80°C and the drying time condition is 3h. 8. the preparation method of a kind of Ni-Al intermetallic compound negative contact layer according to claim 1 is characterized in that, in S4, the specific process of calcining is: put the sample that has dried into tube furnace, Infuse pure argon, raise the temperature to 550°C at a rate of 5°C/min and keep at this temperature for 30 minutes, then continue to heat up to 900°C and keep at this temperature for 2 hours. 9. The Ni-Al intermetallic compound negative contact layer prepared according to the preparation method described in any one of claims 1-8. 10. The application of the Ni-Al intermetallic compound cathode contact layer as claimed in claim 9 in electrocatalyzing carbon dioxide to produce carbon monoxide.