JPH04293766A - Thin aluminum film having high corrosion resistance for fuel cell using molten carbonate - Google Patents

Abstract

PURPOSE:To provide a thin Al film having high corrosion resistance to molten carbonate for a fuel cell using molten carbonate. CONSTITUTION:A mixed layer consisting of Al and a base material 12 is formed by the vacuum deposition of Al as an evaporating material 14 and irradiation with ions 16 of inert gas and then a thin Al film is formed. The mixed layer almost hinders the flowing of electric current causing corrosion by the action of a local cell and prevents the exfoliation of the formed thin Al film, accordingly the thin Al film has high corrosion resistance even under severe corrosive conditions due to exposure to molten carbonate at a high temp. for a long time.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] This invention relates to a highly corrosion-resistant aluminum thin film for molten carbonate fuel cells, which is formed on the surface of a metal material used in molten carbonate fuel cells and has high corrosion resistance. .

0002

BACKGROUND OF THE INVENTION Research and development on various types of fuel cells have been carried out. Among these fuel cells, molten carbonate fuel cells are capable of operating at high current densities because the conductivity of the molten carbonate used as an electrolyte is much higher than that of aqueous solutions, and are called second-generation fuel cells. There are high expectations.

An example of this molten carbonate fuel cell will be explained based on FIG. 3. FIG. 3 is a schematic diagram illustrating the structure of a molten carbonate fuel cell. This molten carbonate fuel cell has 6
Li2CO3-Na2 in a molten state at a high temperature of 50℃
A cathode electrode 42 made of nickel oxide (NiO 2 ) is placed on one side of an electrolyte plate 41 impregnated with CO3-based molten carbonate.
, a corrugated separator material 43 and an anode electrode 44 made of nickel (Ni) are provided, and on the other side of the electrolyte plate 41,
An anode electrode 44 made of nickel (Ni), a corrugated separator material 43, and a cathode electrode 42 made of nickel oxide (NiO 2 ) are provided, and a wet seal is applied to seal between the end of each separator material 43 and the electrolyte plate 41. A member 45 is provided. Note that A is a fuel gas and B is an oxidizing gas.

[0004] In a molten carbonate fuel cell having such a structure, the separator material 4 is used in parts that particularly require corrosion resistance.
3. The wet seal member 45 etc. is made of a special metal material such as stainless steel or stainless steel, a special metal material such as stainless steel or stainless steel with a thin aluminum (Al) film coated on the surface by vacuum evaporation, or a special metal material such as aluminum (Al) on the surface. Special metal materials such as stainless steel or stainless steel materials in which a thin Al) film is provided by an ion plating method and then heat treated are in practical use.

[0005]

[Problem to be solved by the invention] However, 650
Separator material 43 used by being exposed to Li2CO3-Na2CO3-based molten carbonate at a high temperature of ℃
, Even if the wet seal member 45 is made of a special metal material such as corrosion-resistant stainless steel or stainless steel, the temperature will be high (650°C) while the molten carbonate fuel cell is in use (discharging/charging). Li2CO3-Na2CO
Exposure to three types of molten carbonate causes corrosion and molten carbonate leakage, making the molten carbonate fuel cell unusable.

Furthermore, when a special metal material such as stainless steel or stainless steel material on which a thin aluminum (Al) film is formed on the surface by vacuum evaporation is used as the separator material 43 and the wet seal member 45, the aluminum (Al) deposited on the surface may be Al) and molten carbonate lithium (Li) react to form LiAlO2 whose main component is aluminum (Al).
Although the aluminum (Al) thin film formed by vacuum evaporation has pinholes, corrosion occurs from these pinholes (pinhole corrosion). Because the adhesion between the aluminum (Al) thin film and the special metal material is low, the aluminum (Al) thin film easily peels off due to thermal stress, corrosion occurs on the surface and inside of the constituent materials, and the molten carbonate fuel cell becomes unusable.

Furthermore, when a special metal material such as stainless steel or stainless steel which has been heat-treated with an aluminum (Al) thin film formed on the surface by ion plating is used as the separator material 43 and the wet seal member 45,
Pinholes in aluminum (Al) thin films can be eliminated and pinhole corrosion can be prevented;
l) Since the degree of vacuum, which is one of the conditions for forming a thin film, is low, impurities are mixed in and local corrosion is likely to occur, and the formation of defects due to corrosion makes the molten carbonate fuel cell unusable. Furthermore, since the formation of an aluminum (Al) thin film and high-temperature heat treatment are performed, there are disadvantages in that the quality of the special metal material is limited, and productivity is poor and manufacturing costs are high.

It is an object of the present invention to provide a highly corrosion resistant aluminum thin film for molten carbonate fuel cells that exhibits high corrosion resistance properties even when exposed to high temperature molten carbonates for long periods of time. .

[0009]

[Means for solving the problem] Claim (1) of this invention
A highly corrosion-resistant aluminum thin film for molten carbonate fuel cells is produced by vacuum-depositing aluminum (Al) onto the surface of a substrate and simultaneously or alternately irradiating inert gas ions to bond the aluminum (Al) and the substrate. After forming a mixed layer of , an aluminum (Al) thin film was formed.

The highly corrosion-resistant aluminum thin film for a molten carbonate fuel cell according to claim (2) is the highly corrosion-resistant aluminum thin film for a molten carbonate fuel cell according to claim (1), in which aluminum (Al) The film is characterized in that the thin film is formed using a vacuum evaporation method. The highly corrosion-resistant aluminum thin film for molten carbonate fuel cells according to claim (3),
In the highly corrosion-resistant aluminum thin film for a molten carbonate fuel cell according to claim (1), the aluminum (Al) thin film is formed by a vacuum arc discharge deposition method.

[0011]

[Operation] The highly corrosion-resistant aluminum thin film for molten carbonate fuel cells according to claim (1) of the present invention is characterized by aluminum (A
A mixed layer of aluminum (Al) and the base material is formed by vacuum evaporation of l) and irradiation of inert gas ions, and an aluminum (Al) thin film is formed on the surface of the base material, so that the mixed layer forms a local battery. It is possible to make it difficult for corrosion current to flow due to the action of , and to prevent the aluminum (Al) thin film formed on the surface of the base material from peeling off.

The highly corrosion-resistant aluminum thin film for a molten carbonate fuel cell according to claim (2) forms a mixed layer of aluminum (Al) and a base material to make it difficult for corrosion current to flow and to prevent peeling. By forming an aluminum (Al) thin film on the surface of the base material using a vacuum evaporation method, the film thickness can be controlled in a fine order, resulting in a thin film with fewer defects such as pinholes.

The highly corrosion-resistant aluminum thin film for a molten carbonate fuel cell according to claim (3) forms a mixed layer of aluminum (Al) and a base material to make it difficult for corrosion current to flow and to prevent peeling. By forming an aluminum (Al) thin film on the surface of the base material using the vacuum arc discharge deposition method, it is possible to obtain a thin film that is even more dense and free of pinholes.

[0014]

EXAMPLE A first example of a highly corrosion-resistant aluminum thin film for a molten carbonate fuel cell according to the present invention will be described with reference to FIG. Figure 1 shows the IVD method (Ion Vapor De
1 is a schematic configuration diagram of an apparatus for forming a highly corrosion-resistant aluminum thin film by a method (positioning method).

In this device, a base material 12 is fixed to a holder 11 that can be water-cooled by circulating water in a vacuum device (not shown). An evaporation source 13 and an ion source 15 are arranged at positions facing the base material 12. This evaporation source 13 can be heated to a high temperature by an electron beam, laser beam, high frequency, or the like, and contains an evaporation substance 14 of aluminum (Al).

The ion source 15 is of the Kaufman type or a bucket type using a cusp magnetic field for confining plasma, and is supplied with at least one type of inert gas, which is ionized and released into the base material as ions 16. This device irradiates the surface of 12. Furthermore, a film thickness meter 17 and a current measuring meter 18 are arranged within the vacuum apparatus. This film thickness meter 17 measures aluminum (A) deposited on the surface of the base material 12.
It is used to measure the number of particles and film thickness of (l), and is, for example, a vibrating film thickness meter using a crystal resonator. Further, the current measuring meter 18 is for measuring the amount of inert gas ions 16 irradiated onto the base material 12, and is for example a cup-shaped structure having a secondary electron suppressing electrode such as a Faraday cup. These are ion beam current measuring meters, etc.

Note that the ions 1 supplied to the ion source 15
As the inert gas to be irradiated onto the base material 12, at least one of helium (He), neon (Ne), argon (Ar), krypton (Kr), and xenon (Xe) is supplied. In the apparatus having such a configuration, after fixing the base material 12 made of stainless steel material (SUS303) to the holder 11, aluminum (Al) is attached to the evaporated material 1.
4 in the evaporation source 13 and the inside of the vacuum device as 5×1
Maintain a high vacuum of 0-6 Torr or less. and,
The evaporation source 13 is heated with an electron beam to vacuum evaporate the evaporation material 14 onto the surface of the base material 12, and at the same time, argon (Ar) is heated.
An inert gas consisting of
), the irradiation energy value of the ions 16 was changed to 10 [KeV] to form a highly corrosion-resistant aluminum thin film with a thickness of 1 [μm].

Note that the mixed layer and aluminum (Al)
During the formation of the thin film, the number of particles of the evaporated substance 14 made of aluminum (Al) and the number of particles of the ions 16 reaching the base material 12 are constantly measured and monitored using the film thickness meter 17 and the current meter 18. The value is controlled to a predetermined value. FIG. 2 is a schematic diagram of an apparatus called a vacuum arc discharge type deposition apparatus for forming a highly corrosion-resistant aluminum thin film by a vacuum arc discharge deposition method.

This vacuum arc discharge type vapor deposition apparatus includes a gas introduction section 1a for introducing various gases and a vacuum pump (not shown).
An electrode 2 made of aluminum (Al) is provided on one side of the interior of the vacuum device 1 provided with a vacuum exhaust part 1b connecting the
A holder 3 is provided inside the vacuum device 1 on the other side, and a base material 4 made of stainless steel (SUS303) is supported and arranged in the holder 3 so as to face the electrode 2.

Then, an arc power source 5 having a trigger 5a is connected so that the vacuum device 1 becomes an anode and the electrode 2 becomes a cathode, so that a DC voltage can be applied between the vacuum device 1 and the electrode 2, and A bias power supply 6 that applies a negative bias voltage is connected to the base material 4 via the holder 3 . In a vacuum arc discharge type vapor deposition apparatus having such a configuration, the vacuum pump (not shown) is used to evacuate the evacuation part 1b of the vacuum apparatus 1, and the inside of the vacuum apparatus 1 is evacuated to 5×10 −
After holding at 6 [Torr], Ar is supplied from the gas introduction part 1a.
After introducing an inert gas consisting of 1 [mTorr],
50 [A] between the vacuum device 1 and the electrode 2 with the arc power source 5
An arc current of 1 is applied to cause an arc discharge, and a plasma of metal ions M of the metal of the electrode 2, that is, aluminum (Al) and electrons e is generated.

[0021] Then, 100 [V] which is more negative than the vacuum device 1
] is applied by the bias power supply 6 through the holder 3, the metal ions M of aluminum (Al) plasma are accelerated toward the base material 4, and the metal ions of aluminum (Al) are applied to the surface of the base material 4. M is deposited to form a highly corrosion-resistant aluminum thin film with a thickness of 5 [μm]. In this case, by appropriately controlling the bias voltage, a mixed layer of the base material 4 and the evaporated substance 14, that is, aluminum (Al) can be formed between the surface of the base material 4 and the aluminum thin film.

[0022] The corrosion-resistant metal material of the example thus obtained was coated with aluminum (Al) on the surface by vacuum deposition.
) The stainless steel material on which the thin film was formed is
(1983)), and the corrosion state of the surface after the corrosion test was visually observed, and cross-sectional observation and cross-sectional composition analysis were performed using a scanning electron microscope (SEM).
) and a wavelength dispersive X-ray analyzer.

As a result, aluminum (Al
) The aluminum (Al) thin film on the surface of the stainless steel material on which the thin film was formed mostly peeled off, pinholes were generated, and corrosion progressed to the inside of the stainless steel material, whereas the aluminum material in the example The corrosion-resistant metal material made of stainless steel on which the (Al) thin film was formed had no peeling of the thin film or pinholes, and it was confirmed that corrosion had not progressed to the inside of the metal material.

As described above, after forming a mixed layer of the evaporation material 14 (aluminum (Al)) and the base material 12 by vacuum deposition of the evaporation material 14 made of aluminum (Al) and irradiation with argon ions 16, , aluminum (Al
) By forming a thin film on the surface of the base material 12, the mixed layer makes it difficult for corrosion current due to the action of a local battery to flow, and also reduces the amount of aluminum (Al) formed on the surface of the base material 12.
It is possible to prevent the thin film from peeling off, and the film thickness can be controlled to a fine order to create a denser thin film without defects such as pinholes. It is possible to obtain a highly corrosion-resistant aluminum thin film for molten carbonate fuel cells that exhibits high corrosion-resistant properties even when used.

[0025] Furthermore, the IVD method (Ion Vapor D
The vacuum evaporation equipment and the vacuum arc discharge type evaporation equipment that form the highly corrosion-resistant aluminum thin films of each example are not only equipments that form highly corrosion-resistant aluminum thin films using a low-temperature and high-vacuum method. Since an aluminum (Al) thin film can be formed under certain conditions, the material of the base material 12 is not limited and contamination with impurities can be avoided.

In particular, the vacuum arc discharge type evaporation apparatus requires a short time to form an aluminum (Al) thin film, and uses a metal electrode as an evaporation source.
A thin metal film can be formed using multiple electrodes,
It is possible to handle base materials 4 with complex shapes and large surface areas, and it is possible to further improve productivity.

[0027]

Effects of the Invention The highly corrosion-resistant aluminum thin film for molten carbonate fuel cells according to claim (1) of the present invention is produced by vacuum deposition of aluminum (Al) and irradiation of inert gas ions. and the base material to form a mixed layer,
By forming an aluminum (Al) thin film on the surface of the base material, the mixed layer makes it difficult for corrosion current to flow due to the action of a local battery, and also prevents the peeling of the aluminum (Al) thin film formed on the surface of the base material. As a result, it exhibits high corrosion resistance even when exposed to high-temperature molten carbonates for long periods of time.

The highly corrosion-resistant aluminum thin film for a molten carbonate fuel cell according to claim (2) forms a mixed layer of aluminum (Al) and a base material to make it difficult for corrosion current to flow and to prevent peeling. By forming a thin aluminum (Al) film on the surface of the base material using a vacuum evaporation method, the film thickness can be controlled to a fine order, there are fewer defects such as pinholes, and it can be exposed to high-temperature molten carbonate for a long time. Even when used, a thin film can be obtained that exhibits high corrosion resistance.

The highly corrosion-resistant aluminum thin film for a molten carbonate fuel cell according to claim (3) forms a mixed layer of aluminum (Al) and a base material to make it difficult for corrosion current to flow and to prevent peeling. By forming an aluminum (Al) thin film on the surface of the base material using vacuum arc discharge deposition, it is more dense and free of pinholes, and has high resistance even when exposed to high-temperature molten carbonate for long periods of time. It can be a thin film that exhibits corrosive properties.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of an apparatus for forming a thin film by an IVD method.

FIG. 2 is a schematic configuration diagram of a vacuum arc discharge type deposition apparatus.

FIG. 3 is a schematic diagram illustrating the structure of a molten carbonate fuel cell.

[Explanation of symbols]

1 Vacuum equipment 2 Electrode 4 Base material 5 Arc power supply 6 Bias power supply M Metal ion e Electronic 12 Base material 14 Evaporation substances 16 Ion

Claims (3)

[Claims] 1. After vacuum-depositing aluminum (Al) on the surface of a base material and simultaneously or alternately irradiating inert gas ions to form a mixed layer of the aluminum (Al) and the base material, the aluminum (Al) A highly corrosion-resistant aluminum thin film for molten carbonate fuel cells. 2. Formation of the aluminum (Al) thin film comprises:
The highly corrosion-resistant aluminum thin film for a molten carbonate fuel cell according to claim 1, characterized in that the film is produced by a vacuum deposition method. 3. Forming the aluminum (Al) thin film,
The highly corrosion-resistant aluminum thin film for a molten carbonate fuel cell according to claim 1, characterized in that it is produced by a vacuum arc discharge deposition method.