TWI508351B - Growing method of layers for protecting metal interconnects of solid oxide fuel cells - Google Patents

Description

Method for forming film layer for protecting solid oxide fuel cell metal connecting plate

A method for forming a film layer for protecting a metal oxide connecting plate of a solid oxide fuel cell, in particular to a film layer forming method capable of slowing the increase of the ohmic resistance of the surface of the connecting plate and reducing the poisoning phenomenon of the cathode, thereby prolonging the solid oxide fuel cell power generation system The service life.

An existing solid oxide fuel cell stack structure includes a plurality of metal interconnectors and a plurality of solid oxide fuel cell sheets. The metal connecting plate connects the solid oxide fuel cell sheets in series.

The working environment of the metal connecting plate is a high temperature and a specific environmental atmosphere. One side of the metal connecting plate is oxygen, and the other side of the metal connecting plate is hydrogen and moisture. Therefore, the material of the metal connecting plate needs to be a high-temperature corrosion-resistant and oxidation-resistant material, and the expansion coefficient thereof must be matched with the solid oxide fuel cell sheet, and the metal connecting plate also needs to have high conductivity, that is, low resistance loss. The material of the existing metal connecting plate is a chromium-containing (Cr) ferrite-based stainless steel such as Crofer 22, ZM232 or SS441.

In the working environment of the solid oxide fuel cell, although the metal connecting plate has the ability of corrosion resistance and oxidation resistance, the surface of the metal connecting plate still forms an oxide layer, such as a chromium oxide (Cr ₂ O ₃ ) layer. Although the chromium oxide layer is an electron conductor, the conductivity of the chromium oxide layer is not good at the operating temperature of the solid oxide fuel cell sheet. The conductivity of the lanthanum strontium manganite (LSM) cathode of the perovskite structure is about 65 S/cm at 800 ° C, and the conductivity of Crofer 22 is about 8700 S/cm at 800 ° C, but the conductivity of the chromium oxide layer The rate is about 1.5 S/cm at 800 °C.

The chromium oxide layer increases the surface ohmic resistance of the metal connecting plate, resulting in an increase in stack ohmic resistance of the solid oxide fuel cell stack when stacking the solid oxide fuel cell stack, and increasing the solid oxide fuel cell stack The resistance energy is lost and the power generation efficiency of the solid oxide fuel cell stack is reduced.

As the use time of the solid oxide fuel cell stack increases, the chromium oxide layer on the surface of the metal connection plate also thickens with time of use. As a result, the ohmic resistance of the solid oxide fuel cell stack increases with the use time, which is one of the main causes of the power generation efficiency degradation of the solid oxide fuel cell power generation system.

In addition, on the air side of the metal connecting plate, that is, the side facing the cathode, if wet air is used, the chromium (Cr)-containing metal connecting plate generates a gas phase chromium-containing (Cr) substance such as CrO ₂ (OH). ₂ , the gas phase containing chromium (Cr) material will be deposited in the porous cathode, causing serious reduction of the three-phase interface (Triple Phase Boundaries) in the cathode, reducing the reaction efficiency of cathode conversion O ₂ to O ^- , causing cathode poisoning to the cathode (Cathode Poisoning) phenomenon.

The vapor phase material containing chromium (Cr) may also interact with the cathode containing manganese (Mn) to form manganese chrome spinel, thereby changing the material and performance of the cathode; in addition, the gas phase material containing chromium (Cr) It may also interact with the strontium (Sr) element in the cathode to form a non-conductive material of SrCrO ₄ and increase the cathode resistance. Chromium (Cr) ions can also diffuse into the cathode of a solid oxide fuel cell via solid diffusion into the crystal lattice of the metal interconnector, causing cathodic poisoning.

The existing method for reducing the ohmic resistance or area specific resistance (ASR) of the metal connecting plate surface to increase or reduce the toxic phenomenon of the chromium (Cr) in the metal connecting plate to the cathode of the solid oxide fuel cell is based on the metal connecting plate. The surface forms a layer of perovskite or spinel or a protective film of a perovskite and spinel bilayer structure.

The protective film layer is formed by radio frequency plasma magnetron sputtering, electrophoresis, plasma spraying, sol-gel method or ion beam sputtering. The RF plasma magnetron sputtering method requires a vacuum device, so the cost of manufacturing the protective film layer is increased. The aforementioned sputtering method, package Including RF plasma magnetron sputtering or ion beam sputtering, the protective film layer usually contains a part of the amorphous phase, so it needs high temperature treatment to completely crystallize, but in the process of complete crystallization, it often leads to protective film. Layer cracking.

The RF plasma magnetron sputtering method, electrophoresis method, sol-gel method or ion beam sputtering method requires high temperature treatment to crystallize the protective film layer into a pure phase. The protective film layer prepared by the electrophoresis method and the sol-gel method has poor adhesion. Plasma spraying can directly form the protective film layer of the crystalline phase on the surface of the metal connecting plate, without the need for post-high temperature treatment, and does not require expensive vacuum equipment, but the protective film layer of the existing plasma spraying is often porous. The structure or the heterophase exists, so the structure of the protective film layer is not dense, and the protection function at high temperatures often does not meet the requirements of the solid oxide fuel cell power generation system.

"Pan Yang, et al", "Effects of pre-oxidation on the microstructural and electrical properties of La0.67Sr0.33MnO3-δ coated ferritic stainless steels," Journal of Power Sources, 213, 63, 2012 and China No. I329378 of the Republic of China, which discloses a method for fabricating a protective film layer by a radio frequency plasma magnetron sputtering method, but the protective film layer is amorphous due to the operating temperature of the solid oxide fuel cell stack. The component is recrystallized into a perovskite structure of cerium manganese oxide to cause cracking. Yang Pengzhi's journal paper reveals the surface morphology of a protective film layer produced by radio frequency plasma magnetron sputtering using a scanning electron microscope. The protective film layer is cracked and is about 500 times of solid oxide fuel cell stack work. After a child, the manganese-chromium spinel will grow from the crack of the protective film layer, and the manganese-chromium spinel penetrates the protective film layer, so that the protective film layer cannot reliably protect the metal connecting plate and prevent cathodic poisoning. Similarly, if the protective film layer made by the other methods described above is caused by the phenomenon that the manganese chrome spinel grows from the crack of the protective film layer, the protective film layer cannot achieve the function of protection.

In addition, the manganese chrome spinel grown from the crack is a spinel containing less chromium (Cr) and high manganese (Mn), and its conductivity is usually inferior to that of lanthanum manganese oxide. The value of the ohmic resistance that makes contact with the surface of the metal connecting plate is increased. The conductivity described above, unless otherwise specified, refers to the conductivity of the conductors.

For example, U.S. Patent Application Publication No. US20130230792 and Marian Palcut et. "Improved oxidation resistance of ferritic steels with LSM coating for high temperature electrochemical applications", International Journal of Hydrogen Energy, 37, 8087, 2012, which discloses a method for producing a protective film layer by plasma spraying, but According to the scanning electron microscope image disclosed in the publication and the journal article, the protective film layer is a porous non-dense structure, and has many cracks which are approximately perpendicular to the metal connecting plate, and the protective film layer has a poor protective effect and cannot be satisfied. The functional requirements of the protective film layer.

Regardless of the method described above, the protective film layer itself must be a good conductive sub-conductor and a poor oxygen-conducting ion conductor, and must be dense and free of through cracks. When such a protective film layer is plated on the surface of the ferrite-iron metal substrate, the protective film layer which is dense and has no through cracks can more effectively prevent or reduce chromium (Cr) or manganese (Mn) or chromium (Cr) and manganese ( The loss of Mn) element and the formation of a spinel structure film containing chromium (Cr), manganese (Mn) and oxygen (O) on the surface of the metal connecting plate under the protective film layer for further prevention or reduction A phenomenon in which chromium (Cr) or manganese (Mn) or chromium (Cr) and manganese (Mn) elements leak outward from the metal connecting plate. On the other hand, if the protective film layer has a through crack, the chromium (Cr) and manganese (Mn) elements are easily lost from the through crack, and the manganese chromium spinel is also elongated from the crack gap, which is unfavorable for the metal connection under the protective film layer. A conductive, dense and continuous layer of manganese chrome spinel is formed on the surface of the board.

The prior art, regardless of the method, uses only a protective film layer plated on the surface of the metal connecting plate, such as a LSM or spinel layer of a perovskite structure to prevent or reduce chromium (Cr) or manganese (Mn) or chromium. Loss of (Cr) and manganese (Mn) elements diffused from the metal connecting plate.

The object of the present invention is to provide a method for forming a film layer for protecting a metal oxide connecting plate of a solid oxide fuel cell, which is capable of forming a dense, continuous and non-penetrating protective film layer on the surface of the metal connecting plate under an atmospheric environment. And the intermediate film layer, through the double protection of the protective film layer and the intermediate film layer, is more favorable for forming a conductive, dense and continuous spinel containing chromium (Cr) and manganese (Mn) on the surface of the metal connecting plate. stone The layer is combined with the spinel layer to further prevent or reduce the problem that the chromium (Cr) element leaks from the metal connecting plate in the high temperature working environment of the solid oxide fuel cell, and the ohmic resistance of the surface of the connecting plate is slowed down. Rate and reduce the poisoning phenomenon of the cathode in order to extend the service life of the solid oxide fuel cell power generation system.

In the present invention, the protective film layer and the intermediate film layer plated on the surface of the metal connecting plate are used together to prevent or reduce the loss of chromium (Cr) or manganese (Mn) or chromium (Cr) and manganese (Mn) elements, and the present invention The protective film layer and the intermediate film layer are dense and continuous without cracks, which are more favorable for preventing or reducing the loss of chromium (Cr) or manganese (Mn) or chromium (Cr) and manganese (Mn) elements, thus contributing more to A conductive, dense and continuous spinel structure film composed of chromium (Cr), manganese (Mn) and oxygen (O) is formed on the surface of the metal connecting plate, and the spinel layer is combined to further prevent or reduce the length. The problem of chromium (Cr) element leaking out of the metal connecting plate in the high temperature working environment of the solid oxide fuel cell.

In order to achieve the above object, the technical means of the present invention is to provide a method for forming a film layer for protecting a solid oxide fuel cell metal connecting plate, comprising: a metal connecting plate for preheating or pre-oxidizing and preheating. a program; providing a plurality of powder groups, each powder group having a specific particle size range, optionally a powder group, and feeding the powder group into a high-speed plasma flame; the high-speed electricity The slurry flame heats the powder mass to a molten state, and the molten powder group impacts the surface of the metal connecting plate at a high speed, and immediately forms a protective film layer and an intermediate film layer on the surface of the metal connecting plate. The intermediate film layer is located between the protective film layer and the metal connecting plate.

The method for forming a film layer for protecting a metal oxide connecting plate of a solid oxide fuel cell according to the present invention, which is formed in an atmosphere, and a protective film layer and an intermediate film layer are formed on a surface of the metal connecting plate, the intermediate film A layer is between the protective film layer and the metal connecting plate. By the double-layer protection of the protective film layer and the intermediate film layer, the initial area specific resistance of the surface of the metal connecting plate on the air side and the fuel side at the operating temperature of the solid oxide fuel cell and the time value thereof The rate of increase can be significantly reduced to meet the long-term operation of the solid oxide fuel cell. The ohmic resistance of the contact surface of the air side and the fuel side of the metal connecting plate can reach a relatively low area ratio resistance value, thereby extending the solid oxide fuel cell. The service life of the power generation system. In addition, based on the double protection of the protective film layer and the intermediate film layer, it is easier to form a continuous, dense and conductive (conducting) spinel layer above the metal connecting plate at the operating temperature of the solid oxide fuel cell. To achieve further and more effective blocking of chromium (Cr) elements from the metal connecting plate to avoid cathode poisoning.

S1~S4‧‧‧ steps

10‧‧‧Metal connection plate

20‧‧‧Plate heater

30‧‧‧Powder

31‧‧‧Injection tube

40‧‧‧Plastic spray torch device

400‧‧‧High speed plasma flame

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a flow chart of a method for forming a film layer for protecting a metal oxide connecting plate of a solid oxide fuel cell.

Fig. 2 is a schematic view showing the processing action of forming a protective film layer and an intermediate film layer on the surface of a metal connecting plate by a high-speed plasma flame.

Fig. 3 is a scanning electron microscope cross-sectional view of a test piece (without heat treatment) in which a protective film layer is formed by the method of the present invention.

Figure 4 is an Energy-dispersive X-ray spectroscopy (EDX) of an intermediate film layer (point A of Figure 3).

Fig. 5 is a line scan EDX signal intensity distribution diagram of iron (Fe) and chromium (Cr) elements in the intermediate film layer of Fig. 3.

Fig. 6 is a cross-sectional view of a scanning electron microscope of a test piece prepared by the method of the present invention after heat treatment at 800 ° C for 800 hours.

Figure 7 is an EDX spectrum elemental analysis of a manganese-chromium spinel layer.

Figure 8 is an elemental analysis of the EDX spectrum of the lower edge of a manganese-chromium spinel layer.

Fig. 9 is an X-ray diffraction pattern of the protective film layer which has just been subjected to plasma spraying without heat treatment and heat treatment in air at 800 °C for 600 hours.

Figure 10 is a long-term measurement of the ASR of the metal connection plate without a pre-oxidation treatment.

Figure 11 is a long-term measurement of the ASR of a metal connecting plate subjected to a pre-oxidation treatment.

The embodiments of the present invention are described below by way of specific embodiments, and those skilled in the art can readily understand the other advantages and advantages of the present invention.

Referring to FIG. 1 and FIG. 2 together, the present invention is a method for forming a film layer for protecting a metal oxide connecting plate of a solid oxide fuel cell, and the steps thereof include:

S1, the protective film layer material powder is granulated, and a plurality of powder groups are formed.

The protective film layer material powder is a perovskite-structured yttrium-manganese oxide (LSM, La _1-x Sr _x MnO _3-δ , x=0.2-0.4) powder or spinel having poor conductivity and conductivity. Powder, the spinel powder is manganese cobalt or manganese cobalt iron or manganese cobalt copper spinel powder. The perovskite structure powder or the spinel powder may be a nano or submicron or micron powder having a particle size of less than or equal to 10 μm .

The granulation step is discussed below to illustrate the invention and not to limit it.

The powder of the protective film layer material may have a particle size of nanometer or submicron or micron before granulation, and the powder of the protective film layer material has a particle diameter of less than or equal to 10 μm , and the shape of the powder is not limited, and then the powder obtained is obtained. Granulated into a plurality of powders with good fluidity and near spherical shape, the particle size range is 10~90 μ m, and the binder in granulation is polyvinyl alcohol (PVA) or hydroxypropyl methylcellulose. (hydroxypropyl methylcellulose, HPMC). First, a small amount of the above-mentioned binder and dispersing agent are dissolved in water, and then the powder of the protective film layer material obtained by weighing is poured into a slurry, and then the slurry is granulated into a plurality of powder granules by a spray dryer.

If discussed further, the powdering step can be divided into two steps, one for slurry preparation and the other for slurry atomization. The slurry prepared below is mainly LSM powder, but is not intended to limit the present invention.

Slurry preparation: take 80 g of LSM powder of sub-micron (<1 μ m), 200 g of oxidized ball, and 120-160 g of deionized water, put into plastic PE jar, and carry out ball milling process at 100~300 rpm. Lasts 4 to 6 hours. 12 grams of PVA aqueous solution (15 to 45 wt% PVA) was placed in the plastic PE jar described above, and subjected to a ball milling procedure at a speed of 100 to 300 rpm for 30 to 50 minutes. 2.6 g of a polyethylin glycohol (PEG) aqueous solution (PEG 60-80 wt%) was placed in the above-mentioned plastic PE jar, and subjected to a ball milling process at a speed of 100 to 300 rpm for 30 to 50 minutes. The preparation of the LSM slurry was completed.

Slurry atomization: the atomizer is a rotating disc (disc), rotating disc speed: 8000~20000rpm; the liquid feeder is a peristaltic pump, the liquid feeding speed is 8~20g/min; the drying temperature is set to the drying tower inlet temperature: 200~300°C and the cyclone collector outlet temperature: 100~130°C. Exhaust fan speed: 20~60Hz (frequency control).

S2, providing a plurality of powder clusters, each powder cluster having a specific particle size range.

As described above, if further described, the above plurality of powder clusters are divided into a plurality of powder clusters, each of which has a specific particle size range, which is a granulation with good fluidity. The powder sieve is divided into a plurality of particle size groups having a specific particle size range of 5 to 20 μm , 20 to 45 μm , 45 to 63 μm, and 63 to 90 μm .

S3, a metal connecting plate 10 performs a preheating or a pre-oxidation and a preheating process.

According to the material properties of the metal connecting plate 10 and the effect of reducing the ASR increase rate after pre-oxidation, the pre-oxidation procedure is determined or not. The pre-oxidation procedure of the metal connecting plate 10 is to place the metal connecting plate 10 in an air high-temperature furnace, heat up to a specific high temperature, and perform heating for a predetermined time to perform the pre-oxidation process. The specific high temperature is 600~ 850 ° C, the predetermined time is 8 to 20 hours.

As shown in FIG. 2, after the metal connecting plate 10 to be pre-oxidized is cooled, the metal connecting plate 10 can be placed in a flat heating furnace 20 to be preheated to a specific temperature of 600 to 850 ° C. The surface temperature of the metal connecting plate 10 is confirmed by a non-contact thermometer, and is ready to be subjected to the atmospheric plasma spraying process of the present invention. When the metal connecting plate 10 in the preheating process of the flat heating furnace 20 is covered, a heat insulating cotton blanket may be covered thereon to reduce heat loss, and then removed before the plasma spraying is performed. The details of the plasma spray coating are discussed later.

Since the metal connecting plate 10 is preheated or pre-oxidized and preheated in the air, the surface of the metal connecting plate 10 is oxidized.

S4, take any powder group and put it into a powder feeder. The powder feeder sends the powder group 30 of the selected powder group into a powder injection tube 31 at a feeding rate in an externally injected horizontal manner.

A plasma spray torch assembly 40 produces a high speed plasma flame 400 in the atmosphere. The powder injection tube 31 injects the powder group 30 into the high-temperature high-speed plasma flame 400. The high temperature is as high as 10000 ° C or above. High-speed plasma flame 400 can be injected into the flame The adhesive of the multi-powder 30 is burned off and the remaining powder is heated to a molten state, and the remaining powder is also accelerated to a high speed, which can be as high as 650 m/s, and then hits the preheated metal connecting plate 10, which is in a molten state. After the plurality of powder balls 30 are solidified by cooling, they are formed on the metal connecting plate 10 to form a protective film layer 11, as shown in Fig. 2. The test piece (without heat treatment) of the LSM protective film layer formed on the Crofer 22 H metal connecting plate is subjected to the embedding treatment and the cross-section grinding, and the cross section is observed by a scanning electron microscope to obtain the protective film layer 11 and the An intermediate film layer is formed between the metal connecting plates 10, and the intermediate film layer is a continuous, dense and non-penetrating structure, as shown by the arrow in Fig. 3, that is, the point A.

The electric power of the torch for plasma spraying needs to be adjusted according to the particle size range and size of the powder group. The small particle size group uses a small torch electric power, and the large particle size group uses a large torch electric power. The use of the powder group of the sifted powder group is narrower than the powder group before the sieving, which is advantageous for the plasma flame to evenly heat the injected powder to a molten state without generating a small powder group. The plasma flame is heated to cause overheating deterioration or the excessively large powder group is not heated enough due to insufficient heating of the plasma flame.

The high temperature and high temperature preheating effect of high-power plasma spraying in the atmosphere makes the oxygen in the air and the surface elements of the metal connecting plate produce mutual diffusion effect, and when the protective film layer is formed by plasma spraying, An intermediate film layer is simultaneously produced on the surface of the metal connecting plate under the protective film layer. The purpose of preheating the metal connecting plate is that when a plurality of powder groups in a molten state strike the surface of the metal connecting plate, each of the powder groups can be solidified and combined to form a continuous, dense and non-penetrating protective film layer.

The intermediate film layer is a film layer having no through cracks, and its main elements are iron, chromium, oxygen and manganese. The upper and middle portions of the intermediate film layer are rich in iron, and the lower portion of the intermediate film layer is rich in chromium. The portion of the intermediate film layer that is in contact with the metal connection plate begins to gradually transform into a continuous dense manganese chrome spinel film layer composed of manganese, chromium and oxygen at the operating temperature of the solid oxide fuel cell.

The steps of the plasma spraying are discussed below to illustrate the invention and not to limit it.

The powder group 30 injected into the plasma flame 400 is a granulated powder group, and a powder group having a size of 20 to 45 μm is taken. The powder group 30 is a micron-sized powder group prepared by mixing a submicron La _0.8 Sr _0.2 MnO _3-δ powder and a polyvinyl alcohol (PVA) adhesive, and the powder injection method is a horizontal injection type, as shown in Fig. 2 Shown. The plasma spraying parameters are plasma gas: argon gas 49~55slpm, helium gas 20~27slpm, nitrogen gas 2~5slpm, and the working pressure of each gas is 4~6kg/cm2. Spray electric power: 45~53kW (current 400~500A/voltage 100~110V). Spraying distance: 8~10cm. Spray gun scanning speed: 800~1200mm/sec.

Feeding rate: 2~6g/min. The preheating temperature of the metal connecting plate 10 on which the protective film layer is to be plated is: 600 to 850 °C.

The above plasma gas system uses a composition of argon (Ar) helium (He) and nitrogen (N2) instead of a hydrogen-containing plasma gas. The heat enthalpy value of the high-temperature high-speed plasma flame containing hydrogen is higher than the heat enthalpy of the high-temperature high-speed plasma flame containing nitrogen, so that the powder in the molten state hits the surface of the metal connecting plate, due to the powder in each molten state. When the temperature of the mass is too high, a protective film layer which is liable to be cracked when solidified and combined. In addition, the high-temperature high-speed plasma flame containing hydrogen also deteriorates the molten powder in the molten state due to the reduction effect of hydrogen, resulting in the presence of impure heterophase in the protective film layer.

Please refer to the scanning electron microscope cross-sectional view of the test piece prepared by the above-mentioned method for forming a film layer for protecting a solid oxide fuel cell metal connecting plate, as shown in FIG. The protective film layer is an LSM protective film layer of a perovskite structure, and the metal connecting plate material is Crofer 22 H. As shown, the protective film layer is quite detailed, with only a few tiny holes and no through cracks. The few tiny holes may be created when the cross section is ground. The thickness of the protective film layer is 8 to 15 μm , but is not limited.

As shown in Fig. 3, the metal connecting plate of this figure is not pre-oxidized, and the arrow in the figure refers to an intermediate film layer, that is, the position of point A in the figure, which is located in the metal connecting plate and the LSM protective film layer. between. Please refer to Figure 4, which is the result of EDS spectrum analysis (EDX) of the A-point of the interlayer film shown in Figure 3, which shows that the main elements of the interlayer film are Iron (Fe), chromium (Cr), oxygen (O) and manganese (Mn). Referring to Figure 5, the middle and upper portions of the intermediate film layer are rich in iron (Fe), and the lower portion of the intermediate film layer (close to or in contact with the metal connecting plate) is rich in chromium (Cr). )Area.

Please refer to the picture shown in Figure 6, which is the above test piece in the air environment 600 A cross-sectional view of the scanning electron microscope was made after heat treatment at 800 ° C. As shown, the LSM protective film layer has only a few tiny holes and no through cracks. Please refer to Figure 7 for the EDX spectrum elemental analysis of the position at point B of Figure 6, which shows only the elements of manganese (Mn), chromium (Cr) and oxygen (O). The lower part has been transformed into a manganese chrome spinel film layer which is uniform and has no through cracks and contains manganese (Mn), chromium (Cr) and oxygen (O).

Please refer to Figure 8 for the EDX spectrum elemental analysis of the position at point C of Figure 6, which shows only the elements of manganese (Mn), chromium (Cr) and oxygen (O), but chromium ( The signal of Cr) is much stronger than the signal of manganese (Mn). Combining the chromium (Cr) and manganese (Mn) signal ratio analysis of Figures 7 and 8, it shows that the chromium (Cr) content in the intermediate film layer decreases as the distance from the metal connecting plate increases, and also represents the protection of the present invention. The film layer and the intermediate film layer have a function of blocking chromium (Cr) from the metal connecting plate. Please refer to Figure 9 for the X-ray diffraction pattern of the protective film layer of the test piece before heat treatment and after 600 hours of heat treatment at 800 ° C. The figure shows that the perovskite structure before and after heat treatment is not Changed to a pure perovskite structure without other miscellaneous phases.

If the test piece made by the present invention is subjected to an area specific resistance (ASR) for a long time (~2250 hours), the measurement condition is 800 ° C and the air environment, and the metal connecting plates are Crofer 22H and Crofer 22 APU. . Please refer to Figure 10 and Figure 11. The metal connection plate of Figure 10 is not pre-oxidized, and the metal connection plate of Figure 11 is pre-oxidized. The pre-oxidation conditions are 800 ° C and 12 hours. . Comparing the results of the above two figures, the pre-oxidized metal connecting plate has a relatively small average ASR final value and long time (less than or equal to 2250 hours) after a long time (less than or equal to 2250 hours). For solid oxide fuel cell power generation systems, a pre-oxidized metal connection plate provides a lower surface ohmic resistance, which is beneficial to reducing the energy consumption of the solid oxide fuel cell power generation system and extending the solid oxide fuel cell power generation system. Service life. According to the data in Figure 10 and Figure 11, if the metal connecting plate material is Crofer 22 APU, the difference in ASR data without pre-oxidation and pre-oxidation is not very large, and the pre-oxidation step can be omitted to save manufacturing costs; The plate material is Crofer 22 H, and the combined pre-oxidation step can effectively reduce the average rise rate of ASR.

In summary, the present invention directly uses a plasma spraying method without an additional vacuum device, and a protective film layer and an intermediate film layer which are dense and non-penetrating cracks can be formed on the surface of the metal connecting plate in an atmospheric environment. Under the protection of the double protective film layer structure (ie, the protective film layer and the intermediate film layer), the pre-oxidation step can be used to effectively suppress chromium (Cr) or manganese (Mn) or chromium according to the material difference of the metal connecting plate. The leakage of (Cr) and manganese (Mn) elements from the metal connecting plate helps to form a conductive, dense and continuous spinel containing chromium (Cr) and manganese (Mn) on the surface of the metal connecting plate. The layer is bonded to the spinel layer to further prevent or reduce the problem that the chromium (Cr) element leaks from the metal connecting plate in the high temperature working environment of the solid oxide fuel cell for a long time, so that the surface area of the metal connecting plate The specific resistance value and its increase rate with time become smaller, slowing the increase rate of contact surface ohmic resistance of the connecting plate and prolonging the service life of the solid oxide fuel cell power generation system to meet the long-term operation of the solid oxide fuel cell power generation system. Demand. The protective film layer structure of the invention can also effectively block chromium (Cr) from separating from the metal connecting plate to avoid cathode poisoning.

The specific embodiments described above are only used to exemplify the features and functions of the present invention, and are not intended to limit the scope of the present invention, and may be used without departing from the spirit and scope of the invention. Equivalent changes and modifications made to the disclosure of the invention are still covered by the scope of the following claims.

S1~S4‧‧‧ steps

Claims (16)

A method for forming a film layer for protecting a solid oxide fuel cell connecting plate, comprising: a preheating or a pre-oxidation and a preheating process of a metal connecting plate; providing a plurality of powder groups, each powder group having a specific particle size range, optionally a powder group, and feeding the powder group of the powder group into a high-speed plasma flame; the high-speed plasma flame heats the powder group to a molten state, The powder group in a molten state strikes the surface of the metal connecting plate at a high speed, and immediately forms a protective film layer and an intermediate film layer on the surface of the metal connecting plate, and the intermediate film layer is located on the protective film layer and the metal connecting plate between. The method for forming a film layer for protecting a solid oxide fuel cell connecting plate according to claim 1, wherein the pre-oxidation step of the metal connecting plate is to place the metal connecting plate in an air high temperature furnace, and Warm to a specific high temperature for a predetermined time of heating. The method for forming a film layer for protecting a solid oxide fuel cell connecting plate according to claim 2, wherein the pre-oxidation specific high temperature is 600 to 850 ° C, and the predetermined time is 8 to 20 hours. The method for forming a film layer for protecting a solid oxide fuel cell connecting plate according to claim 1, wherein the metal connecting plate is preheated by placing the metal connecting plate in a flat heating furnace to preheat Specific temperature. The method for forming a film layer for protecting a solid oxide fuel cell connecting plate according to claim 4, wherein the specific temperature of the preheating is 600 to 850 °C. The method for producing a film layer for protecting a solid oxide fuel cell connecting plate according to claim 1, wherein the powder group of the specific particle size range is obtained by a sieving method, and the specific particle size range It is 5~20μm, 20~45μm, 45~63μm and 63~90μm. The method for forming a film layer for protecting a solid oxide fuel cell connecting plate according to claim 1, wherein the powder group is fed into the high speed by a horizontal injection type with a powder feeding rate and a powder feeding rate. In the plasma flame. Protecting solid oxide fuel cell connecting plate as described in claim 1 a method for forming a film layer, wherein the powder group is formed by a granulation method, wherein the oxidizing agent is a poorly oxygen-conducting ion but a conductive material is a perovskite structure powder or a spinel powder. It is caused by a fluidity and a nearly spherical powder. The method for producing a film layer for protecting a solid oxide fuel cell connecting plate according to claim 8, wherein the approximately spherical powder group has a diameter of 10 to 90 μm ; and the bonding agent is polyvinyl alcohol or hydroxypropyl Methyl cellulose. The method for producing a film layer for protecting a solid oxide fuel cell connecting plate according to claim 8, wherein the perovskite structure powder is lanthanum manganese oxide (LSM, La _1-x Sr _x MnO _3-δ , x = 0.2 ~ 0.4) powder, the spinel powder is manganese cobalt or manganese cobalt iron or manganese cobalt copper spinel powder. The method for producing a film layer for protecting a solid oxide fuel cell connecting plate according to claim 10, wherein the perovskite structure powder or the spinel powder may be nano or submicron or micron powder. The powder has a particle size of less than or equal to 10 μm . The method for forming a film layer for protecting a solid oxide fuel cell connecting plate according to claim 1, wherein the protective film layer is a film layer having no through crack. The method for forming a film layer for protecting a solid oxide fuel cell connecting plate according to claim 1, wherein the intermediate film layer is a film layer having no through crack, and the main elements thereof are iron, chromium, oxygen and manganese. The method for producing a film layer for protecting a solid oxide fuel cell connecting plate according to claim 1, wherein the upper film layer has iron in the upper and middle portions, and the lower portion of the intermediate film layer contains chromium. The method for forming a film layer for protecting a solid oxide fuel cell connecting plate according to claim 1, wherein the portion of the intermediate film layer in contact with the metal connecting plate starts to gradually transform at a working temperature of the solid oxide fuel cell. A continuous layer of manganese chrome spinel film consisting of manganese, chromium and oxygen. The method for forming a film layer for protecting a solid oxide fuel cell connecting plate according to the first aspect of the invention, wherein the high-speed plasma flame is generated by a plasma spraying torch device under the atmosphere, the plasma spraying torch device Argon, helium and nitrogen are used.