JP5487949B2 - Electrode structure and manufacturing method thereof - Google Patents

Description

  The present invention relates to an electrode structure and a manufacturing method thereof, and more particularly, to an electrode structure including a ceramic substrate and a thermal spray electrode layer containing a Ni or Co-based metal material and a manufacturing method thereof.

  Conventionally, in a ceramic / metal bonded body in which a stress relaxation layer is provided between a ceramic and a metal, the stress relaxation layer has a low Young's modulus metal layer made of either nickel or copper as a base, A ceramic / metal joined body having a three-layer structure of a dispersion layer in which a metal such as tungsten or molybdenum having a low thermal expansion coefficient is dispersed in the center of the metal layer is known (for example, see Patent Document 1).

  Such a ceramic / metal bonded body described in Patent Document 1 does not cause peeling from the bonding interface or loosening of the bonded portion even when used in a high-temperature atmosphere, and can be used continuously for a long time. For the purpose of providing excellent durability, the above-described configuration is adopted.

JP-A-6-135774

  However, in the configuration described in Patent Document 1 described above, since the stress relaxation layer has a three-layer structure, the manufacturing process is complicated, and the number of joints increases, so there is a risk of peeling at the joint surface. There was a problem that occurred.

  Therefore, the present invention is an electrode structure that has a simple structure and a manufacturing method, relaxes the stress generated in the base material, prevents destruction of the base material, and has sufficient resistance under a high temperature use environment, and It aims at providing the manufacturing method.

In order to achieve the above object, an electrode structure according to the first invention comprises a ceramic substrate,
A sprayed electrode layer containing a Ni or Co-based metal material;
It consists of a porous body containing at least one metal material of Ni, Cr, or Co, and has an intermediate sprayed layer inserted between the ceramic substrate and the sprayed electrode layer.

  Thus, by providing an intermediate spray layer composed of a porous body between the ceramic substrate and the spray electrode layer, the stress caused by the difference in thermal expansion coefficient between the ceramic substrate and the spray electrode layer is alleviated, Breakage can be prevented and a heat resistant metal material is used for the intermediate sprayed layer, so that sufficient heat resistance can be provided.

A second invention is an electrode structure according to the first invention.
The intermediate sprayed layer is a sprayed layer containing graphite or resin.

  Thereby, a metal material can be comprised as a porous body, and the Young's modulus of an intermediate sprayed layer can be reduced and the function which relieve | moderates stress can be provided, without using a complicated structure and a process.

A third invention is an electrode structure according to the first or second invention,
The ceramic substrate is a carrier having a honeycomb structure.

  As a result, the electrode structure can be used as a carrier for an electrically heated catalyst that is easily destroyed by stress or the like, and chemical treatment such as rapid exhaust gas treatment can be performed by heating and electricity.

A fourth invention is an electrode structure according to any one of the first to third inventions,
The intermediate spray layer has a Young's modulus of 10 to 50 Pa.

  Thereby, a sufficient stress relaxation function can be given to the intermediate sprayed layer, and damage to the ceramic substrate can be surely prevented.

A fifth invention is an electrode structure according to any one of the first to fourth inventions,
The area ratio of the metal portion of the intermediate sprayed layer is 10 to 50%.

  Thereby, the ratio of the porous portion of the porous body can be sufficiently increased, and the intermediate sprayed layer can have a sufficient stress relaxation function.

A sixth invention is an electrode structure according to any one of the first to fifth inventions,
The intermediate sprayed layer has a thickness of 0.05 to 1 mm.

  Thereby, the thickness of the intermediate sprayed layer is set to a sufficient thickness, and the tensile stress generated from the sprayed electrode layer can be sufficiently absorbed.

The method for producing an electrode structure according to the seventh invention comprises a step of preparing a ceramic substrate,
A step of thermally spraying a material containing a composite powder of a combination of any one of Ni, Cr and Co and graphite or a resin on the ceramic substrate to form a porous intermediate sprayed layer;
And spraying a material containing a Ni or Co-based metal material on the intermediate sprayed layer to form a sprayed electrode layer.

  Thereby, a highly heat-resistant electrode structure can be manufactured by a simple process without damaging the ceramic substrate due to stress.

  ADVANTAGE OF THE INVENTION According to this invention, it can be set as the electrode structure which has high heat resistance, preventing a ceramic base material from being destroyed by stress.

It is sectional drawing which showed an example of the whole structure of the electrode structure which concerns on this embodiment. It is the figure which showed an example of the conventional electrode structure as a comparative reference example. FIG. 2A is a cross-sectional view of a conventional electrode structure. FIG. 2B is a view schematically showing a conventional electrode structure after the thermal spray electrode layer 130 is formed. It is the figure which showed an example of the manufacturing method of the electrode structure which concerns on this embodiment. FIG. 3A is a diagram showing an example of a ceramic substrate preparation process. FIG. 3B is a diagram showing an example of a thermal spray intermediate layer forming step. FIG. 3C is a diagram showing an example of the sprayed electrode layer forming step. It is the enlarged view which showed an example of the material of the thermal spraying intermediate | middle layer 20 of the electrode structure which concerns on a present Example. It is the enlarged view which showed an example of the state of the thermal spraying intermediate | middle layer 20 after the thermal spraying of the electrode structure which concerns on a present Example. FIG. 5A is an enlarged view showing an example of the surface texture of the sprayed intermediate layer 20. FIG. 5B is an enlarged view showing an example of a cross-sectional structure of the electrode structure.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings.

  FIG. 1 is a cross-sectional view showing an example of the overall configuration of an electrode structure according to an embodiment of the present invention. In FIG. 1, the electrode structure according to this embodiment includes a ceramic (SiC) substrate 10, a thermal spray intermediate layer 20, and a thermal spray electrode layer 30.

  The electrode structure according to this embodiment has a three-layer structure in which a thermal spray intermediate layer 20 is laminated on a ceramic substrate 10 and a thermal spray electrode layer 30 is further formed on the thermal spray intermediate layer 20.

  The ceramic substrate 10 is a substrate made of SiC (Silicon Carbide, silicon carbide). The ceramic substrate 10 is configured as a honeycomb structure and has a honeycomb-like structure in which hexagonal columnar porous bodies are arranged. With this honeycomb structure, the ceramic substrate 10 can carry the catalyst in the pores so as to be able to communicate with air, and can be used as a catalyst carrier. SiC itself is a material having sufficient strength against stress, but the ceramic substrate 10 has a porous honeycomb structure as described above, so that it is weak in stress and easily damaged. Become.

  The thermal spray electrode layer 30 is a conductive film formed by thermal spraying. The thermal spray electrode layer 30 is made of a metal material containing Co (cobalt) and Ni, and is made of a metal material such as a Ni alloy containing a Co alloy system or a Ni-high Cr alloy system, for example. The electrode structure according to the present embodiment is assumed to be used in an environment where a temperature change of about −40 ° C. to 950 ° C. occurs, and the thermal spray electrode layer 30 has such a high temperature of about 950 ° C. It is required to have the property that it can withstand and function as an electrode. Specifically, it is required to have heat resistance and oxidation resistance while having necessary electrical conductivity.

  The thermal spray electrode layer 30 may be formed with a thickness of 400 μm or more so that a terminal can be attached to the surface. The terminal may be provided by being joined to the surface of the thermal spray electrode layer 30 using, for example, a metal material such as stainless steel.

The thermal spray electrode layer 30 is formed by thermal spraying. In thermal spraying, a metal material is heated and melted to form fine particles, and the molten fine particle metal material is sprayed onto and collides with an object to be coated to form a coating by solidifying and depositing flattened fine particles. When the thermal spray electrode layer 30 is formed by thermal spraying, when the thermal spray electrode layer 30 is solidified, the volume becomes smaller than that at the time of melting, and tensile stress is generated in the direction in which the thermal spray electrode layer 30 contracts. Here, the linear expansion coefficient of Co and Ni alloy used as the material of the thermal spray electrode layer 30 is 13 × 10 ⁻⁶ / ° C., and the linear expansion coefficient of SiC used as the material of the ceramic substrate 10 is 4 × 10. ^Since it is ⁻⁶ / ° C., there is a large difference in linear expansion coefficient between the two.

  FIG. 2 is a diagram showing an example of a conventional electrode structure as a comparative reference example. FIG. 2A is a diagram showing a cross-sectional configuration of a conventional electrode structure. In FIG. 2A, a spray electrode layer 130 is formed on the ceramic substrate 110. As described above, the thermal spray electrode layer 130 is formed by being laminated on the ceramic substrate 110 by thermal spraying.

  FIG. 2B is a view schematically showing a conventional electrode structure after the thermal spray electrode layer 130 is formed. As described with reference to FIG. 2A, the thermal spray electrode layer 130 directly formed on the ceramic substrate 110 accumulates tensile internal stress and applies tensile stress to the ceramic substrate 130 in the process of rapid solidification. . In this case, if the thermal spray electrode layer 130 is not so thick, the ceramic substrate 130 can withstand the tensile stress, but the thermal spray electrode layer 130 is formed thick, for example, a thickness of 400 μm or more. In this case, the ceramic substrate 130 cannot withstand the applied tensile stress. In that case, as shown in FIG. 2 (B), the ceramic base material 130 is destroyed and cannot be manufactured as an electrode structure.

  Returning to FIG. Therefore, in the electrode structure according to the present embodiment, as shown in FIG. 1, the thermal spray intermediate layer 20 is inserted between the ceramic substrate 10 and the thermal spray electrode layer 30.

  The thermal spray intermediate layer 20 is a thermal spray layer configured as a porous body having a plurality of porous (holes or pores). Unlike the normal sprayed coating consisting of a dense continuous body, like the sprayed electrode layer 30, it has a low Young's modulus and has elasticity even though it is configured as a porous material, even if it is composed of a metal material. Can be configured.

  The thermal spray intermediate layer 20 can be made of a metal material having oxidation resistance and electrical conductivity that can withstand the above-mentioned high temperature of about 950 ° C., for example, Ni, Cr, Co-based alloy, or the like can be used. . By making these metal materials into composite powder or mixed powder with graphite or resin, it can be used as a thermal spray material. For example, Ni-graphite, Cr-graphite, Ni-polyester, Cr-polyester composite powder, Co-based alloy and polyester composite powder, or the like can be used as the thermal spray material. Further, a mixed powder of these composite powder and Co or Ni alloy used as the metal material of the thermal spray electrode layer 30 may be used as the thermal spray material.

  That is, the metal of the thermal spray layer is not a dense continuum like an ordinary thermal spray coating, and a material that has high deformability such as graphite and polyester and that sublimes at a high temperature (for example, 950 ° C.) is Ni, Cr, or Co. By thermal spraying by compounding with an alloy, a metal is not continuously deposited, and a coating containing porous material can be obtained. Then, by providing this film by inserting it between the ceramic substrate 10 and the sprayed electrode layer 30, stress relaxation between the ceramic substrate 10 and the sprayed electrode layer 30 is achieved not by the composition but by the coating structure. Can do.

  Here, the material that sublimes at a high temperature is selected as a composite material with Ni, Cr, and Co alloy because the material such as graphite and polyester may be extinguished after the thermal spraying intermediate layer 20 is configured in a porous structure. This is because it is preferable to eliminate it if possible. That is, the electrode structure according to the present embodiment may be used in a high temperature environment of about 950 ° C., but some of graphite, polyester, and the like are sublimated during use at such a high temperature. This is because it is preferable if it becomes a gas from a solid and disappears. Non-metallic materials such as graphite and polyester prevent the metal in the sprayed intermediate layer 20 from being densely arranged during the spraying and contribute to the formation of a porous structure. It does not add value to functions. Rather, since the thermal spray intermediate layer 20 has a role of supplying the current supplied from the thermal spray electrode layer 30 to the ceramic substrate 10, it is preferable that the electrical conductivity is high, and semi-metallic graphite or insulating resin. It is preferable to disappear rather than to remain. Therefore, a material that forms a composite powder with Ni, Cr, or Co alloy and later becomes the sprayed intermediate layer 20 may be selected from materials that sublime at high temperatures.

  In addition, Ni, Cr or Co-based alloys and graphite or polyester are combined to form a composite powder. It is difficult to obtain a thermal spray coating having a uniform porous due to the difference in specific gravity when the powder is simply mixed. Because. Therefore, in the electrode structure and the manufacturing method thereof according to the present embodiment, graphite or polyester particles are plated with Ni, Cr, or Co-based alloy, or granulated composite powder is used.

  The Young's modulus of the thermal spray intermediate layer 20 may be in the range of 10 to 50 GPa, for example. Since the Young's modulus of the thermal spray electrode layer 30 is often in the range of 100 to 200 GPa, the thermal spray intermediate layer 20 has a Young's modulus of 1/20 to 1/2 of the thermal spray electrode layer 30. The tensile stress generated at 30 can be greatly relieved.

  The area ratio of the metal portion of the sprayed intermediate layer 20 may be, for example, in the range of 10 to 50%. Since the thermal spray electrode layer 30 has a metal portion of almost 100%, the thermal spray intermediate layer 20 has a porous structure with more porous than the thermal spray electrode layer 30, and can sufficiently relieve the tensile stress. It has a structure.

  The film thickness of the sprayed intermediate layer 20 may be, for example, in the range of 0.05 to 1 mm, and preferably in the range of 0.1 to 1 mm. The thicker the thermal spray intermediate layer 20 is, the thicker the stress relaxation force can be surely increased. However, by using a material having a sufficiently low Young's modulus, the required film thickness can be reduced. Thus, the film thickness of the thermal spraying intermediate layer 20 may be determined in relation to the Young's modulus of the thermal spraying intermediate layer 20, and if the tensile stress applied to the thermal spraying electrode layer 30 can be set to a target value or less, depending on the application. In various thicknesses.

  Next, an example of the manufacturing method of the electrode structure according to the present embodiment will be described. FIG. 3 is a view showing an example of a method for manufacturing an electrode structure according to the present embodiment.

  FIG. 3A is a diagram showing an example of a ceramic substrate preparation process. In the ceramic base material preparation step, a ceramic base material 10 as an electrode formation target is prepared. For example, a ceramic carrier for EHC (Electrical Heated Catalyst) may be used as the ceramic substrate 10 and may be configured as a porous body. Further, the structure of the porous body may be various structures, for example, a honeycomb structure.

  FIG. 3B is a diagram showing an example of a thermal spray intermediate layer forming step. In the thermal spray intermediate layer forming step, the thermal spray intermediate layer 20 is laminated on the ceramic substrate 10. The material used for the thermal spraying intermediate layer 20 is a material containing a composite powder of any one of Ni, Cr and Co-based metals and a resin such as graphite or polyester. Specifically, for example, it may be a composite powder of any of Ni-graphite, Cr-graphite, Ni-polyester, and Cr-polyester, and these composite powders and Co that is a material of the thermal spray electrode layer 30 may be used. Or a mixed powder with Ni alloy may be sufficient.

  The EHC electrode structure requires Schottky characteristics (property of current flow between the semiconductor and the metal), and Ni is said to be effective for the SiC substrate 10. ing. However, in the case of pure Ni, since the high-temperature oxidation resistance is slightly inferior, Ni-high Cr alloy powder with improved oxidation resistance and Ni-graphite composite powder may be mixed and used as the material for the thermal spray intermediate layer 20. Here, the Ni-high Cr alloy is an alloy having a Cr content of 30% or more and has a property of improving oxidation resistance. It is also effective to use a Cr-graphite composite powder as the composite powder mixed with the Ni-high Cr alloy. In the case of such a mixed powder, the porosity and Young's modulus can be adjusted by the mixing ratio.

  Using such a material, the sprayed intermediate layer 20 is formed by thermal spraying. For example, the thermal spraying is performed by heating the material to 2000 ° C. to melt it, and colliding the melted material with the ceramic substrate 10 for cooling and solidification. Is done. Since the thermal spraying is performed in a very short time, the metal material plays a role of maintaining an appropriate interval without sublimation of graphite or polyester, and the porous thermal spray intermediate layer 20 is formed. The characteristics of the thermal spray intermediate layer 20 may be the characteristics described in FIG.

  By forming the sprayed intermediate layer 20, a conductive film having a sufficient stress relaxation force is formed on the ceramic substrate 10.

FIG. 3C is a diagram showing an example of the sprayed electrode layer forming step. In the thermal spraying electrode layer forming step, the thermal spraying electrode layer 30 is laminated on the thermal spraying intermediate layer 20. The thermal spray electrode layer 30 may be formed by ordinary thermal spraying using a Co or Ni alloy-based metal material. For example, the particle temperature at the time of thermal spraying may be about 2000 ° C. as in the formation of the thermal spraying intermediate layer 20. The coefficient of linear expansion of Co and Ni-based alloys is 13 × 10 ⁻⁶ / ° C., which is very different from the coefficient of linear expansion of SiC 4 × 10 ⁻⁶ / ° C. Although tensile stress is generated, since the thermal spray intermediate layer 20 is interposed, the stress is absorbed by the thermal spray intermediate layer 20 and the stress is hardly transmitted to the ceramic substrate 10. The Young's modulus of Co and Ni alloys is 100 to 200 GPa, but the Young's modulus of the porous thermal spray intermediate layer 20 is 10 to 50 GPa.

  Thus, according to the manufacturing method of the electrode structure according to the present embodiment, by adding a thermal spraying process in which only the material is changed without performing a complicated laminated structure or complicated processing, An electrode structure having high oxidation resistance can be easily manufactured.

  FIG. 4 is an enlarged view showing an example of the material of the thermal spray intermediate layer 20 of the electrode structure according to the embodiment of the present invention. In this example, Ni-25 wt% graphite composite powder was used as the material of the sprayed intermediate layer 20. In FIG. 4, an enlarged view of the Ni-graphite powder is shown. In addition, the same referential mark shall be attached | subjected to the referential mark of each component in a present Example to the component corresponding to embodiment described so far.

  FIG. 4 shows a state in which Ni 22 is coated around the particles of graphite 21 so as to cover the surface. A space 23 is shown in places other than the Ni-plated graphite 21. Thus, a Ni-graphite composite powder plated with Ni22 around the particles of graphite 21 was used as a material.

  FIG. 5 is an enlarged view showing an example of the state of the sprayed intermediate layer 20 after spraying of the electrode structure according to the present embodiment. FIG. 5A is an enlarged view showing an example of the surface structure of the thermal sprayed intermediate layer 20, and FIG. 5B is an enlarged view showing an example of a cross-sectional structure of the electrode structure.

  FIG. 5A shows a state in which Ni 22 and graphite 21 are present in a randomly dispersed state. Ni 22 and graphite 21 are dispersed almost uniformly, and a place where neither of them is present is a porous 24.

  Thus, it can be seen that the sprayed intermediate layer 20 has a structure including the porous 24, and thus has a structure capable of realizing a low Young's modulus.

  5B shows an enlarged cross-sectional configuration view of the electrode structure. Similarly to the configuration shown in FIG. 1, the ceramic substrate 10, the thermal spray intermediate layer 20, and the thermal spray electrode layer 30 are sequentially formed from the lower layer. Are stacked. When attention is paid to the coating of the thermal sprayed intermediate layer 20, the dispersed Ni 22 is shown by a white portion. The other portions are porous 24 and graphite 21, and it can be seen that the thermal spray intermediate layer 20 has a porous structure in which Ni 22 is dispersed. Thereby, the tensile stress resulting from the difference in the linear expansion coefficient between the thermal spray electrode layer 30 and the ceramic substrate 10 can be relaxed and absorbed by the thermal spray intermediate layer 20.

  In addition, as a result of measuring the Young's modulus of the coating of the thermal sprayed intermediate layer 20 shown in FIGS. 5A and 5B, it was about 30 GPa, and it was confirmed that it was effective as a stress relaxation layer.

  Further, a Co alloy and a Ni-high Cr alloy are formed on the coating of the thermal spray intermediate layer 20 by HVOF thermal spraying (High Velocity Oxygen Fuel, high-speed flame spraying) to 400 μm, and RT (Room Temperature, room temperature) is 950 ° C. As a result of the thermal cycle test, no abnormalities such as cracks were observed in the coating of the ceramic substrate 10 and the sprayed electrode layer 30.

  Thus, it was shown that the electrode structure according to this embodiment and the manufacturing method thereof can effectively prevent the ceramic substrate 10 from being broken by the electrode structure according to this example.

  In addition, in the present Example, it demonstrated taking the example of the composite powder of Ni-graphite, but also when using composite powder using resin, Cr, and Co system alloy, as shown in FIG. It becomes a composite powder material in which the periphery of the graphite or resin particles is coated like a metal material. Further, even after thermal spraying, a porous material structure in which the metal material is uniformly dispersed and the porous 24 and the graphite 21 or the resin are present as shown in FIGS.

  The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited to the above-described embodiments, and various modifications and substitutions can be made to the above-described embodiments without departing from the scope of the present invention. Can be added.

  INDUSTRIAL APPLICABILITY The present invention can be widely used for ceramic parts that require electrodes used in a high temperature environment, and can be suitably used for, for example, a ceramic carrier for an electrically heated catalyst.

10, 110 Ceramic substrate 20 Thermal sprayed intermediate layer 21 Graphite 22 Ni
23 Space 24 Porous 30, 130 Thermal spray electrode layer

Claims (7)

A ceramic substrate;
A sprayed electrode layer containing a Ni or Co-based metal material;
An electrode structure comprising a porous body containing at least one metal material of Ni, Cr, or Co, and having an intermediate sprayed layer inserted between the ceramic substrate and the sprayed electrode layer.   The electrode structure according to claim 1, wherein the intermediate sprayed layer is a sprayed layer containing graphite or resin.   The electrode structure according to claim 1 or 2, wherein the ceramic substrate is a carrier having a honeycomb structure.   4. The electrode structure according to claim 1, wherein a Young's modulus of the intermediate sprayed layer is 10 to 50 Pa. 5.   The electrode structure according to any one of claims 1 to 4, wherein an area ratio of a metal portion of the intermediate sprayed layer is 10 to 50%.   The electrode structure according to any one of claims 1 to 5, wherein a thickness of the intermediate sprayed layer is 0.05 to 1 mm. Preparing a ceramic substrate;
A step of thermally spraying a material containing a composite powder of a combination of any one of Ni, Cr and Co and graphite or a resin on the ceramic substrate to form a porous intermediate sprayed layer;
And a step of spraying a material containing a Ni or Co-based metal material on the intermediate sprayed layer to form a sprayed electrode layer.