JP6401433B2 - Honeycomb structure - Google Patents

Description

  The present invention relates to a honeycomb structure. More specifically, the present invention relates to a honeycomb structure in which when bonded to a metal member, the bonding strength of the bonded portion is good, the electrical resistance change rate of the bonded portion is low, and the contact thermal resistance of the bonded portion is low.

  Conventionally, a honeycomb-like ceramic body (honeycomb structure) made of ceramic has been used as a base material for an electric heating catalytic converter (EHC) for exhaust gas purification, a ceramic heater, a heat exchanger, and the like. In this ceramic body, a metal member is bonded to the outer peripheral surface. Thereafter, the ceramic body to which the metal member is bonded is used as the EHC or the like.

  For example, an EHC or a ceramic heater is heated by applying a voltage. The EHC is an exhaust purification device that is provided on an exhaust path of an automobile or the like and purifies exhaust gas exhausted from an engine. A catalyst is supported on the EHC, and the catalyst can be heated to a temperature required for activation by heating the EHC (see Patent Documents 1 to 3).

  These EHC and ceramic heater are used by being electrically connected to a power source such as a battery via a metal wire harness or the like. And the method of using a brazing material, welding, etc. are employ | adopted as a method of joining EHC, the said wire harness, etc. (refer patent document 4).

  The heat exchanger performs heat transfer between a high temperature fluid and a low temperature fluid by using a heat exchange member that conducts heat. The heat exchanger includes, for example, a metal covering member (metal member) that covers the side surface of the ceramic body. The ceramic body and the metal covering member are joined by brazing or the like (see Patent Document 5).

JP 2011-106308 A JP 2011-246340 A JP 2011-230971 A Japanese Patent No. 4210417 Japanese Patent No. 3813654

  However, the EHC and heat exchanger described in Patent Documents 1 to 5 are still improved in the “electrical resistance change rate” and “contact thermal resistance” at the joint portion between the ceramic ceramic body and the metal metal member. There was room. Therefore, when bonded to a metal member such as a wire harness or a cylindrical metal tube, the bonding strength of the bonded portion is good, and the rate of change in electrical resistance of the bonded portion is low (that is, the ohmic contact property is high). Therefore, development of a honeycomb structure having a low contact thermal resistance at the joined portion has been desired.

  The present invention has been made in view of such problems of the prior art. The problem is that when bonded to a metal member such as a wire harness or a cylindrical metal tube, the bonding strength of the bonded portion is good, the rate of change in electrical resistance of the bonded portion is low, and the bonded portion A honeycomb structure having a low contact thermal resistance is provided.

  According to the present invention, the following honeycomb structure is provided.

[1] A pair of partition walls that form a plurality of cells extending from one end face to the other end face that serve as a fluid flow path, and an outer peripheral wall that is positioned on the outermost periphery, and are further disposed on the outer peripheral wall. A honeycomb-shaped ceramic body containing metal Si having a plurality of electrodes, and a joint portion joined to the outer peripheral surface of the pair of electrodes of the ceramic body, wherein the joint portion of the pair of electrodes of the ceramic body A diffusion layer having metal silicide as a main component located on the outer peripheral surface side; and a metal layer formed on the diffusion layer, wherein the metal layer includes a metal component as a main component and has a thermal expansion coefficient of 5 A honeycomb structure in which a compound of 0.0 × 10 ⁻⁶ / ° C. or less is dispersed.

[1] A pair of partition walls that form a plurality of cells extending from one end face to the other end face that serve as a fluid flow path, and an outer peripheral wall that is positioned on the outermost periphery, and are further disposed on the outer peripheral wall. A honeycomb-shaped ceramic body containing metal Si having a plurality of electrodes, and a joint portion joined to the outer peripheral surface of the pair of electrodes of the ceramic body, wherein the joint portion of the pair of electrodes of the ceramic body A diffusion layer having metal silicide as a main component located on the outer peripheral surface side; and a metal layer formed on the diffusion layer, wherein the metal layer includes a metal component as a main component and has a thermal expansion coefficient of 5 are those .0 × ^{10 -6} / ℃ following compounds were dispersed, the pair of electrodes, porosity observed contains a is and metal Si 30 to 55% metal Si is the entire electrode 15 mass % Honeycomb structure.

[3] The honeycomb structure according to [1] or [2], wherein the thickness of the diffusion layer is 0.1 mm or less.

[4] The honeycomb structure according to [2] or [3], wherein a content ratio of SiC dispersed in the metal layer of the joint is 10 to 50%.

[5] The honeycomb structure according to any one of [2] to [4], wherein an average particle diameter of SiC dispersed in the metal layer of the joint is 1 to 50 μm.

[6] The honeycomb structure according to any one of [2] to [5], wherein a content ratio of cordierite dispersed in the metal layer of the joint portion is 10 to 50%.

[7] The honeycomb structure according to any one of [2] to [6], wherein an average particle diameter of cordierite dispersed in the metal layer of the joint portion is 1 to 50 μm.

[8] The honeycomb structure according to any one of [1] to [7], wherein the metal component is at least one selected from the group consisting of Cr, Fe, and Ni.

[9] Any of [1] to [8], wherein the metal silicide is formed by a reaction between the metal Si contained in the ceramic body and a metal component contained in a raw material for forming the joint. A honeycomb structure according to any one of the above.

A honeycomb structure of the present invention has a partition wall that partitions and forms a plurality of cells serving as fluid flow paths, an outer peripheral wall positioned at the outermost periphery , and a metal having a pair of electrodes disposed on the outer peripheral wall A honeycomb-shaped ceramic body containing Si and a bonding portion bonded on a pair of electrodes of the ceramic body are provided. The joining portion includes a diffusion layer mainly composed of metal silicide located on the outer peripheral surface (side surface) side of the ceramic body, and a metal layer formed on the diffusion layer. This joint is a member for favorably joining the ceramic body and a metal material such as a wire harness. The joint (specifically, the diffusion layer) and the ceramic body are firmly joined. And the main component which comprises the metal layer of a junction part is a metal component. Therefore, the metal member and the joint portion (particularly the metal layer) are favorably joined. Therefore, the honeycomb structure of the present invention has good bonding strength (bonding reliability) with the metal member. Furthermore, in the honeycomb structure of the present invention, the metal layer of the joint portion contains “a compound having a thermal expansion coefficient of 5.0 × 10 ⁻⁶ / ° C. or less” in addition to the metal component, and this is dispersed in the metal layer. Is. Therefore, the honeycomb structure of the present invention has a low rate of change in electrical resistance at the joint portion and a contact thermal resistance at the joint portion. Therefore, when a voltage is applied to the honeycomb structure of the present invention, “desired heat generation” can be obtained with respect to the applied voltage. With the conventional honeycomb structure, less heat generation than “desired heat generation” was obtained. In the honeycomb structure of the present invention, when fluids are respectively flowed outside and inside the honeycomb structure, heat exchange is favorably performed between the fluid flowing inside the honeycomb structure and the fluid flowing outside the honeycomb structure.

1 is a perspective view schematically showing an embodiment of a honeycomb structure of the present invention. It is sectional drawing which shows typically the cross section parallel to the cell extending direction of one embodiment of the honeycomb structure of the present invention. The implementation form of honeycomb structure is a perspective view schematically showing. The section parallel to the cell extension direction of the implementation form of honeycomb structure is a cross-sectional view schematically showing.

  Embodiments of the present invention will be described below with reference to the drawings. The present invention is not limited to the following embodiments, and appropriate modifications and improvements are added to the following embodiments on the basis of ordinary knowledge of those skilled in the art without departing from the spirit of the present invention. It should be understood that what has been described also falls within the scope of the invention.

[1] Honeycomb structure:
As an embodiment of the honeycomb structure of the present invention, a honeycomb structure 100 shown in FIG. 1 can be cited. The honeycomb structure 100 has a porous partition wall 1 and an outer peripheral wall 3 located at the outermost periphery, and further includes a honeycomb-like ceramic body containing metal Si having a pair of electrodes 21 disposed on the outer peripheral wall 3. 20 and a joint portion 30 joined on the pair of electrodes 21 of the ceramic body 20. The partition wall 1 partitions and forms a plurality of cells 2 extending from one end face 11 to the other end face 12 to be a fluid flow path. As shown in FIG. 2, the joint portion 30 is located on the outer peripheral surface (side surface) 5 side of the ceramic body 20 (that is, in contact with the side surface 5 of the ceramic body 20), and a diffusion layer 31 mainly composed of metal silicide. And a metal layer 32 formed on the diffusion layer 31. The metal layer 32 is a layer in which a compound containing a metal component as a main component and having a thermal expansion coefficient of 5.0 × 10 ⁻⁶ / ° C. or less is dispersed. FIG. 1 is a perspective view schematically showing one embodiment of a honeycomb structure of the present invention. FIG. 2 is a cross-sectional view schematically showing a cross section parallel to the cell extending direction of one embodiment of the honeycomb structure of the present invention.

As described above, the honeycomb structure 100 includes the partition walls 1 and the outer peripheral wall 3, and includes the honeycomb-shaped ceramic body 20 containing metal Si and the joint portion 30 joined to the outer peripheral wall 3 of the ceramic body 20. As shown in FIG. 2, the bonding portion 30 includes a diffusion layer 31 mainly composed of metal silicide located on the outer peripheral surface (side surface) 5 side of the ceramic body 20, and a metal layer 32 formed on the diffusion layer 31. And. The joint portion 30 is a member for joining the ceramic body 20 and a metal material (not shown) such as a wire harness. The metal silicide is formed by reacting with metal Si contained in the ceramic body and a metal component contained in the raw material for forming the junction. Specifically, the metal silicide is in a layer in which the metal Si contained in the ceramic body 20 and the metal component contained in the raw material for forming the joint are mixed (interface region between the ceramic body 20 and the raw material). The metal Si and metal component diffuse and react with each other. The main component constituting the metal layer 32 of the joint portion 30 is a metal component, and “a compound having a thermal expansion coefficient of 5.0 × 10 ⁻⁶ / ° C. or less” is dispersed in the metal layer 32. Since the main component which comprises the metal layer 32 is a metal component, metal members, such as a wire harness, and the junction part 30 (metal layer 32 of the junction part 30) join favorably. Therefore, the honeycomb structure 100 has good bonding strength (bonding reliability) with the metal member. Further, in the honeycomb structure 100, the metal layer 32 of the joint portion 30 includes “a compound having a thermal expansion coefficient of 5.0 × 10 ⁻⁶ / ° C. or less” in addition to the metal component, and this is dispersed in the metal layer 32. It is a thing. Therefore, since the thermal expansion of the metal layer 32 is moderately suppressed as compared with the case where only the metal component is contained, the honeycomb structure 100 has a low rate of change in electrical resistance at the joined portion and a contact thermal resistance at the joined portion. Become. Therefore, when a voltage is applied to the honeycomb structure 100, “desired heat generation” is obtained with respect to the applied voltage. With the conventional honeycomb structure, less heat generation than “desired heat generation” was obtained. In the honeycomb structure 100, when a fluid flows in and out of the honeycomb structure 100, between the fluid flowing in the honeycomb structure 100 (cell 2 of the ceramic body 20) and the fluid flowing outside the honeycomb structure 100. Heat exchange is performed well.

  Thus, the honeycomb structure 100 can be used as an EHC or a heater because a desired heat generation is obtained with respect to the applied voltage when a voltage is applied.

  The “main component” means a component occupying 50.0% or more of all components in each layer. Here, in this specification, the content ratio (%) of each component is a value calculated as follows. That is, first, a cross-section in the thickness direction of each layer is observed using a scanning electron microscope (SEM), and a plurality (three places) of arbitrary fields (100 μm in length × 100 μm in width) are selected and photographed. To do. The observation magnification is 1000 times. Next, the ratio of the area of each component in the captured image is calculated for each field of view. Next, the average value of the calculated “area ratio” is calculated and used as the content ratio of each component.

The thermal expansion coefficient of 5.0 × ^{10 -6} / ℃ following compounds, for example, SiC, etc. can be mentioned cordierite, thermal expansion coefficient of 5.0 × ^{10 -6} / ℃ following compounds , SiC and cordierite are preferred. By being at least one of SiC and cordierite, the effect of the present invention is exhibited well. Here, “a compound having a thermal expansion coefficient of 5.0 × 10 ⁻⁶ / ° C. or less” means that a sample is prepared by using the compound alone, and an average of room temperature (20 ° C.) to 800 ° C. according to JIS R1618. The measured value obtained when the linear thermal expansion coefficient is measured refers to a compound having a value of 5.0 × 10 ⁻⁶ / ° C. or less.

[1-1] Joint part:
The content ratio of SiC dispersed in the metal layer 32 of the joint portion 30 (the SiC content ratio in the metal layer) is preferably 10 to 50%. The lower limit value of the SiC content ratio in the metal layer is preferably 15%, and more preferably 20%. On the other hand, the upper limit value of the SiC content ratio in the metal layer is preferably 45%, and more preferably 40%. When the SiC content ratio in the metal layer is within the above range, the thermal expansion coefficient of the metal layer is lowered. Therefore, even if a thermal stress is applied, there is an advantage that the joint is difficult to peel off from the ceramic body. Moreover, the strength (joining strength) for joining the ceramic body and the metal member is increased. In addition, the strength (impact strength) of the metal layer 32 against an external impact is increased. When the SiC content ratio in the metal layer is less than the lower limit value, the metal component content ratio in the metal layer is relatively increased, so that the thermal expansion coefficient of the metal layer is increased. As a result, the degree of shrinkage of the metal layer during sintering increases, and the thermal stress increases. Therefore, the ceramic body may be broken by this thermal stress. Moreover, there exists a possibility that a junction part may peel from a ceramic body by this thermal stress. On the other hand, if it exceeds the upper limit, sintering may be hindered. As a result, since the neck becomes thin, the impact strength of the metal layer may be lowered.

  The average particle diameter of SiC dispersed in the metal layer 32 of the joint portion 30 is preferably 1 to 50 μm. The lower limit value of the average particle diameter of SiC is preferably 2 μm, and more preferably 5 μm. On the other hand, the upper limit of the average particle size of SiC is preferably 40 μm, and more preferably 30 μm. When the average particle size of SiC in the metal layer is within the above range, there is an advantage that homogeneity of thermal expansion coefficient is generated, thermal stress is not partially generated, and strong bonding is possible. is there. If it is less than the lower limit of the average particle size of SiC, the joint 30 may be broken at the interface region between the diffusion layer 31 and the metal layer 32, and the metal layer 32 may be peeled off. If it exceeds the upper limit, the thermal expansion coefficient in the metal layer 32 is not uniform, and the generated thermal stress may be increased. As a result, there is a possibility that the joint 30 is peeled off from the ceramic body due to thermal stress. In addition, the average particle diameter of SiC is a value calculated as follows. That is, first, a cross-section in the thickness direction of each layer is observed using a scanning electron microscope (SEM), and a plurality (three places) of arbitrary fields (100 μm in length × 100 μm in width) are selected and photographed. To do. The observation magnification is 1000 times. Next, in each field of view, the longest diameter of a plurality (three) of SiC in the photographed image is measured, and an average value is calculated to obtain the average particle diameter of SiC. For the SiC for measuring the longest diameter, three particles having the largest longest diameter are selected from the particles having the entire image in the observation field.

  The content ratio of cordierite dispersed in the metal layer 32 of the joint portion 30 (cordierite content ratio in the metal layer) is preferably 10 to 50%. The lower limit of the cordierite content in the metal layer is preferably 12%, and more preferably 15%. On the other hand, the upper limit of the cordierite content in the metal layer is preferably 45%, and more preferably 40%. When the cordierite content ratio in the metal layer is within the above range, the thermal expansion coefficient of the metal layer is lowered. Therefore, even if a thermal stress is applied, there is an advantage that the joint is difficult to peel off from the ceramic body. Moreover, the strength (joining strength) for joining the ceramic body and the metal member is increased. In addition, the strength (impact strength) of the metal layer 32 against an external impact is increased. When the cordierite content ratio in the metal layer is less than the lower limit value, the metal component content ratio in the metal layer is relatively increased, so that the thermal expansion coefficient of the metal layer is increased. As a result, the degree of shrinkage of the metal layer during sintering increases, and the thermal stress increases. Therefore, the ceramic body may be broken by this thermal stress. Moreover, there exists a possibility that a junction part may peel from a ceramic body by this thermal stress. On the other hand, if it exceeds the upper limit, sintering may be hindered. As a result, since the neck becomes thin, the impact strength of the metal layer may be lowered.

  The average particle size of cordierite dispersed in the metal layer 32 of the joint portion 30 is preferably 1 to 50 μm. The lower limit value of the average particle size of the cordierite is preferably 2 μm, and more preferably 5 μm. On the other hand, the upper limit of the average particle size of the cordierite is preferably 40 μm, and more preferably 30 μm. When the average particle size of cordierite in the metal layer is within the above range, the thermal expansion coefficient is homogenized, the occurrence of partial thermal stress is suppressed, and strong bonding is possible. There are advantages. If the average particle size of the cordierite is less than the lower limit, the joint portion 30 may be broken at the interface region between the diffusion layer 31 and the metal layer 32, and the metal layer 32 may be peeled off. If it exceeds the upper limit, the thermal expansion coefficient in the metal layer 32 is not uniform, and the generated thermal stress may be increased. As a result, the joint 30 may be peeled off from the ceramic body. In addition, the average particle diameter of cordierite is measured by the same method as that for measuring the average particle diameter of SiC.

The metal component is not particularly limited as long as it is composed of one or more metals (metal simple substance). However, the “thermal expansion coefficient of 5.0 × 10 ⁻⁶ / ° C. or less” is not included in the metal component in the present specification. It is preferable that the metal contains Cr, Fe, and Ni. By including Fe, it is possible to sinter at a low temperature, and furthermore, since the strength is increased, the diffusion layer can be formed thin. Further, since Fe is inexpensive, the manufacturing cost is reduced. By including Ni, the strength of the metal layer is increased. Further, the addition of Ni and Cr increases the corrosion resistance of the metal layer and improves the heat resistance.

  The diffusion layer is substantially made of metal silicide, and specifically contains 99% or more of metal silicide. Here, whether or not the diffusion layer is formed is confirmed as follows. That is, when the cross section in the thickness direction of the joint portion is observed by SEM, it is confirmed that the joint portion has two layers, and the layer on the ceramic body side is subjected to energy dispersive X-ray spectroscopic analysis (EDS) to detect metal silicide. When it is confirmed, it can be determined that “a diffusion layer is formed”. The type of metal silicide can be confirmed by microscopic X-ray diffraction. In addition, according to the “joint forming step” described later, a diffusion layer containing 99% or more of metal silicide can be easily formed.

  It is preferable that the content rate (content rate of the metal component in a metal layer) of the metal component contained in the metal layer 32 of the junction part 30 is 50 to 90%. The lower limit of the content ratio of the metal component in the metal layer is preferably 55%, and more preferably 60%. On the other hand, the upper limit value of the content ratio of the metal component in the metal layer is preferably 88%, and more preferably 85%. When the content ratio of the metal component in the metal layer is within the above range, the thermal expansion coefficient of the metal layer is lowered. Therefore, even if a thermal stress is applied, there is an advantage that the joint is difficult to peel off from the ceramic body. Moreover, the strength (joining strength) for joining the ceramic body and the metal member is increased. In addition, the strength (impact strength) of the metal layer 32 against an external impact is increased. When the cordierite content ratio in the metal layer is less than the lower limit value, the metal component content ratio in the metal layer is relatively increased, so that the thermal expansion coefficient of the metal layer is increased. As a result, the degree of shrinkage of the metal layer during sintering increases, and the thermal stress increases. Therefore, the ceramic body may be broken by this thermal stress. Moreover, there exists a possibility that a junction part may peel from a ceramic body by this thermal stress. On the other hand, if it exceeds the upper limit, sintering may be hindered. As a result, since the neck becomes thin, the impact strength of the metal layer may be lowered.

  The thickness of the joint portion 30 is preferably 0.05 to 1.0 mm. The lower limit value of the thickness of the joint portion 30 is preferably 0.75 mm, and more preferably 0.1 mm. On the other hand, the upper limit value of the thickness of the joint portion 30 is preferably 0.7 mm, and more preferably 0.5 mm. By setting the thickness of the joint portion 30 within the above range, the thermal stress is reduced and the joint strength is increased. If the thickness of the joint portion 30 is less than the lower limit value, the joint strength when the metal member is joined to the ceramic body via the joint portion 30 is low, and thus the joint portion 30 may be peeled off after joining. On the other hand, if it exceeds the upper limit value, the joining portion 30 becomes too thick, so that the thermal stress increases. Therefore, when a thermal stress is generated, the ceramic body may be broken or the joint portion 30 may be peeled off from the ceramic body. In addition, when the thickness of a junction part is not uniform, "the thickness of a junction part" is the thickness of the thickest part of a junction part.

  The thickness of the diffusion layer is preferably 0.1 mm or less. The lower limit value of the thickness of the diffusion layer is preferably 0.01 mm, more preferably 0.015 mm, and particularly preferably 0.02 mm. On the other hand, the upper limit is more preferably 0.07 mm, and particularly preferably 0.06 mm. By setting the thickness of the diffusion layer in the above range, the thermal stress generated in the diffusion layer is reduced, so that the bonding strength is increased (that is, the bonded portion is hardly peeled off from the ceramic body). The thickness of the diffusion layer is preferably 0.1 mm or less, but if it is less than 0.01 mm, the diffusion layer is too thin, the bonding strength is lowered, and the bonded portion may be peeled off from the ceramic body. On the other hand, if it exceeds the upper limit value, the joining portion 30 becomes too thick, so that the thermal stress increases. Therefore, when a thermal stress is generated, the ceramic body may be broken or the joint portion may be peeled off from the ceramic body. When the thickness of the diffusion layer is not uniform, the “thickness of the diffusion layer” is the thickness of the thickest portion of the diffusion layer.

  The ratio of the thickness of the metal layer 32 to the thickness of the diffusion layer 31 is preferably 1-10. The lower limit of the ratio value is preferably 1.1, and more preferably 1.2. On the other hand, the upper limit is preferably 7, and more preferably 5. By setting the value of the ratio within the above range, the thermal stress generated between the diffusion layer and the metal layer is reduced, so that the strength (joining strength) at which the ceramic body and the joined portion are joined is increased. If the value of the ratio is less than the lower limit value, the bonding strength for bonding the ceramic body and the bonding portion is lowered, and the bonding portion may be peeled off from the ceramic body. On the other hand, if the value exceeds the upper limit value, the thermal stress generated between the diffusion layer and the metal layer becomes large, so that the ceramic body may be broken or the joint may be peeled off from the ceramic body. The thickness of the metal layer was a value obtained by calculating the difference of the “thickness of the diffusion layer” from the “thickness of the junction”.

  The size of the joint portion 30 is not particularly limited. For example, when it has the electrode part 21 like the honeycomb structure 100 of this embodiment, it is preferable that it is smaller than the electrode part 21.

[1-2] Ceramic body:
The ceramic body 20 includes a cylindrical honeycomb structure portion 4 having a porous partition wall 1 and an outer peripheral wall 3 located on the outermost periphery, and a pair of electrode portions 21 disposed on the side surface 5 of the honeycomb structure portion 4. 21. That is, in the present embodiment, the “ceramic body” includes the honeycomb structure portion 4 and the pair of electrode portions 21 and 21. The partition wall 1 partitions and forms a plurality of cells 2 extending from one end face 11 to the other end face 12 to be a fluid flow path.

  The ceramic body 20 has conductivity. Therefore, the ceramic body 20 generates heat when a voltage is applied between the pair of electrode portions 21 and 21.

Ceramic body 20 and the electrode portion 21, Monodea containing metal Si is, metallic Si is the electrode portions 21 total 15% by mass or more.

  The partition wall thickness, cell density, outer peripheral wall thickness and the like of the honeycomb structure portion 4 can be appropriately determined according to the use of the honeycomb structure.

  The electrode portion 21 preferably has a porosity of 30 to 55%, more preferably 35 to 50%. When the porosity of the electrode portion 21 is in such a range, a suitable electrical resistivity can be obtained. When the porosity of the electrode part 21 is lower than 30%, the specific resistance becomes small, and an electric current may flow excessively when energized. Therefore, the electric circuit or the like may be damaged. In addition, when the porosity of the electrode portion 21 is lower than 30%, the heat capacity increases, so that the rate of temperature increase during energization may be slow. When the porosity of the electrode part 21 is higher than 55%, the electrical resistivity may become too high. The porosity is a value measured by Archimedes method. In the present specification, the “porosity of the ceramic body” means “porosity of the electrode portion” when the electrode portion is provided like EHC or a heater.

The thermal expansion coefficient of the ceramic body 20 is preferably 3.5 to 5.0 × 10 ⁻⁶ / ° C. The lower limit value of the thermal expansion coefficient of the ceramic body 20 is preferably 3.7 × 10 ⁻⁶ / ° C., and more preferably 4.0 × 10 ⁻⁶ / ° C. On the other hand, the upper limit value of the ceramic body 20 is preferably 4.8 × 10 ⁻⁶ / ° C., more preferably 4.6 × 10 ⁻⁶ / ° C. When the thermal expansion coefficient of the ceramic body 20 is within the above range, a ceramic body with low thermal stress and excellent heat resistance can be obtained. If the thermal expansion coefficient of the ceramic body 20 is less than the lower limit value, the thermal expansion coefficient with the joint portion is increased, and a large thermal stress is generated during the cooling / heating cycle, and the joint portion may be peeled off. On the other hand, if it exceeds the upper limit value, the ceramic body may be cracked by thermal stress generated by expansion and contraction of the ceramic body itself during the cooling / heating cycle.

[2] Manufacturing method of honeycomb structure:
Next, the manufacturing method of the honeycomb structure of the present invention will be described. Hereinafter, a method for manufacturing the honeycomb structure 100 as an embodiment of the honeycomb structure of the present invention will be described.

[2-1] Manufacturing process of ceramic body:
First, a ceramic body 20 including the honeycomb structure portion 4 and the pair of electrode portions 21 and 21 is manufactured. Specifically, first, a forming raw material is prepared by adding a binder, a surfactant, a pore former, water and the like to silicon carbide powder and metal Si powder.

  Examples of the binder include methyl cellulose, hydroxypropyl methyl cellulose, hydroxypropoxyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, and polyvinyl alcohol. Among these, it is preferable to use methyl cellulose and hydroxypropoxyl cellulose in combination. The content of the binder is preferably 2.0 to 10.0 parts by mass when the total mass of the silicon carbide powder and the metal silicon (metal Si) powder is 100 parts by mass.

  The water content is preferably 20 to 60 parts by mass when the metal Si is 100 parts by mass.

  As the surfactant, ethylene glycol, dextrin, fatty acid soap, polyalcohol and the like can be used. These may be used individually by 1 type and may be used in combination of 2 or more type.

  The pore former is not particularly limited as long as it becomes pores after firing, and examples thereof include graphite, starch, foamed resin, water absorbent resin, and silica gel.

  Next, the forming raw material is kneaded to form a clay. There is no restriction | limiting in particular as a method of kneading | mixing a shaping | molding raw material and forming a clay, For example, the method of using a kneader, a vacuum clay kneader, etc. can be mentioned.

  Next, the kneaded material is extruded to form a honeycomb formed body. In extrusion molding, it is preferable to use a die having a desired overall shape, cell shape, partition wall thickness, cell density and the like. As the material of the die, a cemented carbide which does not easily wear is preferable. The honeycomb formed body has a structure having partition walls that form a plurality of cells that serve as fluid flow paths and an outer peripheral wall that is positioned on the outermost periphery.

  Next, it is preferable to dry the obtained honeycomb formed body. The drying method is not particularly limited, and examples thereof include an electromagnetic heating method such as microwave heating drying and high-frequency dielectric heating drying, and an external heating method such as hot air drying and superheated steam drying.

  Note that the partition wall thickness, cell density, outer peripheral wall thickness, etc. of the honeycomb molded body can be appropriately determined in accordance with the structure of the honeycomb structure of the present invention to be manufactured in consideration of shrinkage during drying and firing. it can.

  Next, a paste-like electrode part forming raw material for forming the electrode part is prepared. This electrode part forming raw material can be prepared by adding a binder, a surfactant, a pore former, water and the like to silicon carbide powder (silicon carbide) and metal silicon (metal Si) powder and kneading them. The method of kneading is not particularly limited, and for example, a vertical stirrer can be used.

  Examples of the binder include methyl cellulose, hydroxypropyl methyl cellulose, hydroxypropoxyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, and polyvinyl alcohol. Among these, it is preferable to use methyl cellulose and hydroxypropoxyl cellulose in combination.

  As the surfactant, ethylene glycol, dextrin, fatty acid soap, polyalcohol and the like can be used. These may be used individually by 1 type and may be used in combination of 2 or more type.

  The pore former is not particularly limited as long as it becomes pores after firing, and examples thereof include graphite, starch, foamed resin, water absorbent resin, and silica gel.

  Next, the produced electrode part forming raw material is applied to the side surface of the dried honeycomb formed body. The method for applying the electrode part forming raw material to the side surface of the honeycomb formed body is not particularly limited, and for example, a printing method can be used. The electrode part forming raw material is formed so that one electrode part of the pair of electrode parts is disposed on the opposite side of the center of the honeycomb formed body with respect to the other electrode part of the pair of electrode parts. Apply to the side of the body.

  Next, it is preferable to dry the electrode part forming raw material applied to the side surface of the honeycomb formed body to obtain a dried honeycomb body. The drying conditions are preferably 50 to 100 ° C.

  Next, the obtained honeycomb dried body can be fired to obtain the ceramic body 20. The firing conditions are preferably 1400 to 1500 ° C. for 1 to 20 hours in an inert atmosphere such as nitrogen or argon. In addition, it is preferable to perform temporary baking in order to remove a binder etc. before baking. Pre-baking is preferably performed at 400 to 500 ° C. for 0.5 to 20 hours in an air atmosphere.

[2-2] Step of forming the joint:
Next, the joint portion 30 is formed on the side surface 5 of the obtained ceramic body 20. Specifically, the bonding portion 30 is formed on the pair of electrode portions 21 and 21.

First, a metal component and at least one of SiC and cordierite (a compound having a thermal expansion coefficient of 5.0 × 10 ⁻⁶ / ° C. or less) are mixed to prepare a raw material for forming a joint. Next, the prepared raw material is formed into a predetermined shape (for example, a plate shape) by a method such as press working. Next, the formed raw material (molded raw material) is disposed on the side surface 5 of the ceramic body 20 (specifically, on the one electrode portion 21 and the other electrode portion 21). Next, in this state (that is, in a state in which the molded raw material is disposed on one electrode portion 21 and the other electrode portion 21), pressure in the thickness direction of the molded raw material is applied to each of the molded raw materials. While firing under the following conditions. The pressure applied to the shaped raw material is preferably 0.01 to 10 MPa. Firing conditions are preferably 10 minutes to 2 hours at 900 to 1300 ° C. in an Ar atmosphere. In this way, the honeycomb structure 100 shown in FIG. 1 can be manufactured. In addition, when baking a shaping | molding raw material, it is not necessary to apply a pressure, However, The diffusion layer is easy to be formed when the pressure is applied.

  As described above, the pressure applied to the shaped raw material is preferably 0.01 to 10 MPa. The lower limit value of the pressure applied to the shaped raw material is more preferably 0.05 MPa, and particularly preferably 0.1 MPa. On the other hand, the upper limit value of the pressure applied to the shaped raw material is more preferably 7 MPa, and particularly preferably 5 MPa. By setting the pressure applied to the shaped raw material within the above range, the reaction between the metal component and the metal Si is likely to occur. As a result, the diffusion layer is more easily formed. Further, the ceramic body 20 and the joint portion 30 are strongly joined. If the pressure applied to the molded raw material is less than the lower limit value, it is difficult to form a diffusion layer, and the bonding force between the ceramic body 20 and the bonding portion 30 may be weakened. On the other hand, if it exceeds the upper limit value, a large pressure is applied to the ceramic body 20, which may cause the ceramic body 20 to break.

  Firing conditions are preferably 10 minutes to 2 hours at 900 to 1300 ° C. in an Ar atmosphere. By baking under such conditions, the diffusion layer and the metal layer are formed with a good thickness (0.1 mm or less in the diffusion layer). The lower limit of the firing temperature is more preferably 920 ° C, and particularly preferably 950 ° C. On the other hand, the upper limit of the firing temperature is more preferably 1250 ° C, and particularly preferably 1200 ° C. By setting the firing temperature in the above range, the diffusion layer and the metal layer are formed with a good thickness. Therefore, the bonding strength between the ceramic body and the bonding portion is increased, and in particular, the thermal stress generated in the diffusion layer is decreased. Therefore, it becomes difficult for the joint portion to be peeled off from the ceramic body. When the firing temperature is less than the lower limit value, the metal component and the metal Si are difficult to diffuse, and the reaction between the metal component and the metal Si is difficult to occur, so that there is a possibility that the joint portion having the diffusion layer and the metal layer is not formed. On the other hand, when the value exceeds the upper limit, the reaction between the metal component and the metal Si occurs excessively, and the diffusion layer may be formed thick. Therefore, there is a possibility that the diffusion layer (bonding part) is cracked when thermal stress is generated.

  The lower limit of the firing time is more preferably 7 minutes, and particularly preferably 10 minutes. On the other hand, the upper limit of the firing time is more preferably 1 hour and a half, and particularly preferably 1 hour. By setting the firing time in the above range, the diffusion layer and the metal layer are formed with a good thickness. For this reason, the bonding strength between the ceramic body and the bonding portion is increased, and in particular, the thermal stress generated in the diffusion layer is decreased. Therefore, it becomes difficult for the joint portion to be peeled off from the ceramic body. When the firing time is less than the lower limit, the thickness of the diffusion layer and the metal layer is difficult to be in a favorable range, and in particular, the diffusion layer is thinner than the range of the favorable thickness, so the bonding strength between the ceramic body and the joint portion May be low. Therefore, there exists a possibility that a junction part may peel from a ceramic body. On the other hand, if the value exceeds the upper limit, the thickness of the diffusion layer and the metal layer is unlikely to be within a favorable range, and in particular, the diffusion layer is thicker than the preferable thickness, and thus the thermal stress generated in the diffusion layer may be increased. is there. Therefore, when a thermal stress is applied, the joint may be peeled off from the ceramic body.

  Note that, as described above, by firing in a state where pressure is applied, a joining portion having a diffusion layer and a metal layer formed on the diffusion layer is easily formed. Specifically, when heated while applying pressure, the metal component in the molded raw material is first melted in a predetermined temperature range. Thereafter, when the temperature is further increased, the metal Si in the ceramic body is melted, and the metal component and the metal Si are mixed and reacted. In this way, a diffusion layer is formed.

[3] Honeycomb structure:
Figure 3 is a perspective view schematically showing another embodiment of a honeycomb structure. A honeycomb structure 101 shown in FIG. 3 includes a ceramic body 40 and a joint portion 30 formed so as to cover the entire outer peripheral surface (side surface) 5 (see FIG. 4) of the ceramic body 40. The joint portion 30 is joined to the ceramic body 40. As shown in FIG. 4, the joint portion 30 includes a diffusion layer 31 on the side surface 5 side of the ceramic body 40 and a metal layer 32 formed on the diffusion layer 31. The ceramic body 40 has a cylindrical shape having a partition wall 1 that partitions and forms a plurality of cells 2 extending from one end surface 11 serving as a fluid flow path to the other end surface 12 and an outer peripheral wall 3 positioned at the outermost periphery. . That is, the “ceramic body” in the present embodiment is different from the above-described one embodiment in that it does not include an electrode portion. The ceramic body 40 has thermal conductivity. Such a honeycomb structure 101 can be used as a base material of a heat exchanger. That is, what was obtained by fitting the honeycomb structure 101 into a cylindrical metal tube can be used as a heat exchanger. Such a heat exchanger causes the first fluid and the second fluid to flow by flowing the first fluid in the cell 2 of the ceramic body 40 and flowing the second fluid outside the honeycomb structure 101. The heat exchange can be performed. Figure 4 is a cross-sectional view schematically showing a cross section parallel to the cell extension direction of another embodiment of a honeycomb structure.

  The porosity of the ceramic body 40 in the present embodiment is preferably 0 to 0.1%, and more preferably 0 to 0.05%. When the porosity of the ceramic body 40 is within such a range, the ceramic body 40 has a dense structure. That is, the partition wall and the outer peripheral wall are dense walls. By having a dense structure in this way, it has good thermal conductivity. The porosity is a value measured by Archimedes method.

  The partition wall thickness, the cell density, the outer peripheral wall thickness, and the like of the ceramic body 40 can be appropriately determined.

  As the joint portion 30, a joint portion similar to the joint portion 30 of the honeycomb structure 100 shown in FIG. 1 can be used. Therefore, when the honeycomb structure 101 is bonded to a metal member, the rate of change in electrical resistance at the bonded portion is low. Therefore, when a voltage is applied to the honeycomb structure 101, desired heat generation is obtained with respect to the applied voltage. In addition, the honeycomb structure 101 has a low contact thermal resistance at the joint portion. Therefore, in the honeycomb structure 101, heat exchange between the fluid flowing in the honeycomb structure 101 (the cell 2 of the ceramic body 40) and the fluid flowing outside the honeycomb structure 101 is favorably performed.

[4] Manufacturing method of honeycomb structure:
Next, a method for manufacturing a honeycomb structure 101 which is another embodiment of the honeycomb structure of the present invention will be described.

  First, the ceramic body 40 is produced. Specifically, first, a forming raw material is prepared by adding a binder, a surfactant, water, and the like to silicon carbide powder and metal Si powder.

  Examples of the binder include methyl cellulose, hydroxypropyl methyl cellulose, hydroxypropoxyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, and polyvinyl alcohol. Among these, it is preferable to use methyl cellulose and hydroxypropoxyl cellulose in combination.

  As the surfactant, ethylene glycol, dextrin, fatty acid soap, polyalcohol and the like can be used. These may be used individually by 1 type and may be used in combination of 2 or more type.

  Next, the forming raw material is kneaded to form a clay. There is no restriction | limiting in particular as a method of kneading | mixing a shaping | molding raw material and forming a clay, For example, the method of using a kneader, a vacuum clay kneader, etc. can be mentioned.

  Next, the kneaded material is extruded to form a honeycomb formed body. In extrusion molding, the shape and thickness of the outer peripheral wall, the thickness of the partition walls, the shape of the cells, the cell density, and the like can be made desired by selecting an appropriate form of die and jig. It is preferable to use a die made of a cemented carbide that hardly wears.

  Next, it is preferable to dry the obtained honeycomb formed body. The drying method is not particularly limited, and examples thereof include an electromagnetic heating method such as microwave heating drying and high-frequency dielectric heating drying, and an external heating method such as hot air drying and superheated steam drying.

  Note that the partition wall thickness, cell density, outer peripheral wall thickness, etc. of the honeycomb molded body can be appropriately determined in accordance with the structure of the honeycomb structure of the present invention to be manufactured in consideration of shrinkage during drying and firing. it can.

  Next, a lump of metal Si is placed on the honeycomb formed body and fired in a vacuum or in an inert gas under reduced pressure. By firing, the lump of metal Si placed on the honeycomb formed body can be melted, and the outer peripheral wall and partition walls can be impregnated with metal Si. In this way, the ceramic body 40 having a dense structure can be produced.

Next, the joint portion 30 is formed so as to cover the entire side surface 5 of the obtained ceramic body 40. Specifically, first, a metal component and at least one of SiC and cordierite (a compound having a thermal expansion coefficient of 5.0 × 10 ⁻⁶ / ° C. or less) are mixed to form “a junction part for forming”. "Raw material" is prepared. Next, the prepared raw material is applied so as to cover the entire side surface 5 of the ceramic body 40 by a method such as thermal spraying, cold spraying, printing, or brush application to form a coating layer. Thereafter, the “ceramic body 40 on which the coating layer is formed” is heated at 900 to 1300 ° C. for 10 minutes to 2 hours. In this way, a layer in which at least one of the metal component and SiC and cordierite is diffused is formed in the interface region between the coating layer and the ceramic body 40. The metal component in this layer reacts with “at least one of SiC and cordierite” to form a diffusion layer. In this way, the honeycomb structure 101 having the joint can be manufactured. In addition, when heating the “ceramic body 40 on which the coating layer is formed”, it is preferable to apply a pressure in the thickness direction of the coating layer to the coating layer. By applying pressure, the diffusion layer is easily formed. This pressure can be a pressure under the same conditions as the “pressure applied to the shaped raw material” described above.

  The obtained honeycomb structure 101 can be used as a heat exchanger by being integrated with a metal tube (metal member) (not shown) as follows. That is, first, the honeycomb structure 101 is inserted into a metal tube. Thereafter, the temperature is raised to about 1000 ° C. by a high-frequency heater or the like. If it does in this way, the honeycomb structure 101 and the metal pipe will be joined by the junction part 30, and will be integrated.

  EXAMPLES Hereinafter, although this invention is demonstrated concretely based on an Example, this invention is not limited to these Examples.

Example 1
First, silicon carbide (SiC) powder and metal silicon (metal Si) powder were mixed at a mass ratio of 80:20. To this, hydroxypropylmethylcellulose as a binder and a water-absorbing resin as a pore former were added, and water was added to form a molding raw material. Thereafter, this forming raw material was kneaded using a kneader to obtain a kneaded product. The kneaded material was put into a vacuum kneader to produce a plate-shaped clay. Next, this plate-shaped clay was dried to obtain a plate-shaped dry body . In the following, it was sintered for 2 hours forming a firing temperature of 1500 ° C. under an argon atmosphere. Thus, to prepare a plate-like fired body mainly composed of S iC. The plate-like fired body had a square with a side of 20 mm and a thickness of 5 mm. This plate-like fired body was used as a test piece of a ceramic body. The porosity of the ceramic body was 30.2%. The porosity of the ceramic body is a value measured by Archimedes method.

Next, as raw materials for constituting the joint, Fe powder (average particle size 5 μm), Cr powder (average particle size 5 μm), SiC powder (average particle size 5 μm, thermal expansion coefficient 4.1 × 10 ⁻⁶ / ° C) was prepared. In addition, the average particle diameter of these powder raw materials is the value measured with the laser diffraction type particle size distribution apparatus. Next, the above powders were mixed and stirred for 10 minutes so that the Fe powder was 78.4% by mass, the Cr powder was 17.2% by mass, and the SiC powder was 4.4% by mass. Thereafter, the mixed powder was press-molded into a square shape with a side of 20 mm and a thickness of 5 mm to obtain a “plate-shaped raw material”. Then, it arrange | positioned on both surfaces of the said test piece so that the said test piece may be pinched | interposed with this "plate-shaped raw material", and the laminated body was obtained. Next, a surface pressure of 0.1 MPa was applied to the laminate by placing a weight on one surface of the laminate. Thereafter, with the pressure applied, the laminate was heated at 1100 ° C. for 1 hour in an Ar atmosphere. In this way, the metal (Fe powder, Cr powder) in the “plate-shaped raw material” is sintered to form a metal layer, and Si constituting the above-mentioned test piece made of ceramic and “plate-shaped raw material” The metal (metal component) inside was reacted to form a diffusion layer. In this manner, a test structure including a ceramic body and a joint portion joined to the ceramic body was obtained. The average particle size of SiC in the obtained test structure was calculated as follows. First, a cross section in the thickness direction of the test structure was observed using a scanning electron microscope (SEM), and three arbitrary fields (100 μm in length × 100 μm in width) in this observation field were selected and photographed. The observation magnification was 1000 times. Next, in each field of view, the diameter of SiC (three pieces) in the photographed image was measured, and the average value was calculated. The calculated value was defined as the average particle diameter of SiC. In Table 1, it is simply referred to as “particle size”. The SiC for measuring the diameter was selected as large as possible in the visual field.

  Next, the junction was observed with a scanning electron microscope (SEM) and subjected to energy dispersive X-ray spectroscopic analysis (EDS) to confirm the presence or absence of a diffusion layer and the presence or absence of a metal layer. In the honeycomb structure of the present example, a diffusion layer and a metal layer were formed at the joint. In the diffusion layer, silicide of Fe and Cr was formed. The thickness of the diffusion layer was 0.04 mm. In the metal layer, SiC was dispersed in an alloy of Fe and Cr. The content ratio of “SiC” in the metal layer was 10.2%. The results are shown in Table 3. In Table 3, the case where the diffusion layer is formed is described as “present”. The case where the diffusion layer is not formed is described as “none”.

Specifically, when it is confirmed by SEM that the joint portion is two layers and the layer on the ceramic body side is subjected to energy dispersive X-ray spectroscopic analysis, it is confirmed that metal silicide is formed. A diffusion layer is formed (with a diffusion layer) ”. In addition, the content ratio of the “compounds (SiC and cordierite) having a thermal expansion coefficient of 5.0 × 10 ⁻⁶ / ° C. or less” in the metal layer is determined by analyzing the SEM image. The total area of the compound (SiC and cordierite) of 0.0 × 10 ⁻⁶ / ° C. or less ”and the area of the metal component were calculated. Specifically, an arbitrary field of view (100 μm in length × 100 μm in width) in the SEM image is selected, and “a compound having a thermal expansion coefficient of 5.0 × 10 ⁻⁶ / ° C. or less (SiC and cordierite) ”And the area of the metal component were measured, and the average value was calculated. The observation magnification was 1000 times. In addition, the content ratio of the metal silicide in the diffusion layer is similar to the content ratio of the “compound having a thermal expansion coefficient of 5.0 × 10 ⁻⁶ / ° C. or less (SiC and cordierite)” in the metal layer. The area of the metal silicide was measured and calculated by image analysis. And about the kind of metal silicide, it confirmed by micro part X-ray diffraction.

  Next, each evaluation was performed by the following method about the produced test structure.

[Omic contact properties]:
A voltage of 0.01 to 1 V is sequentially applied to the manufactured test structure, and the current value at this time is measured. Thereafter, it is confirmed whether or not the graph showing the relationship between the current and voltage drawn is a straight line. Specifically, the difference between the current value at 0.5V and the current value at 0.01V is calculated. This value is defined as “current I1”. The difference between 0.5V and 0.01V (0.5V) is defined as voltage V1. The resistance R1 (R1 = voltage V1 ÷ current I1) is obtained from these values. Thereafter, the difference between the current value at 1 V and the current value at 0.5 V is calculated. This value is defined as “current I2”. The difference between 1V and 0.5V (0.5V) is defined as voltage V2. Thereafter, the resistance R2 (R2 = voltage V2 ÷ current I2) is obtained from these values. Thereafter, “resistance R2 ÷ resistance R1” is calculated. The case where the calculated value is 0.95 to 1.05 is “A”, and the case where the calculated value is outside this range is “B”.

[Joint reliability]:
First, the prepared test structure was “held at 950 ° C. for 2 minutes and then held at room temperature (about 25 ° C. for 2 minutes)” as a cooling cycle, and this cooling cycle was performed 1000 times (cooling cycle test) ). Next, it observes using a magnifier microscope, a metal microscope, and SEM, and confirms generation | occurrence | production of the crack in a peeling of a junction part and a joined body and a ceramic body. Thereafter, evaluation is performed according to the following criteria. The case where the peeling and the generation of the crack are not recognized is referred to as “A”. The case where large peeling or a crack is recognized is set to "B".

[Electric resistance]:
First, the electrical resistance of the test structure before the [Joint Reliability] test is measured. Next, the electrical resistance of the test structure after the [Joint Reliability] test is measured. Thereafter, the resistance change rate is calculated by the following equation. Thereafter, evaluation is performed according to the following criteria. A case where the resistance change rate is less than 3% is defined as “A”. A case where the resistance change rate is 3% or more and less than 5% is defined as “B”. A case where the resistance change rate is 5% or more and less than 100% is defined as “C”. A case where the resistance change rate is 100% or more is defined as “D”.
Formula: (Electric resistance of test structure after [Joint reliability] test / Electric resistance of test structure before [Joint reliability] test) × 100

[Thermal Resistance] (Reference Example 2) :
First, silicon carbide (SiC) powder and metal silicon (metal Si) powder are mixed at a mass ratio of 80:20. To this, hydroxypropylmethylcellulose as a binder and a water-absorbing resin as a pore former are added, and water is added to form a molding raw material. Thereafter, this forming raw material is kneaded using a kneader to obtain a kneaded product. This kneaded product is put into a vacuum kneader to prepare a honeycomb-shaped clay. Next, the honeycomb-shaped clay is dried to obtain a honeycomb-shaped honeycomb dried body. Metal Si is loaded on the end face of the obtained honeycomb dried body. Next, impregnation firing is performed for 2 hours at 1500 ° C. in an argon atmosphere. In this way, a honeycomb-shaped honeycomb fired body mainly composed of Si-impregnated SiC is manufactured. The obtained honeycomb fired body had a diameter of 42 mm and a length in the central axis direction of 100 mm.

  Next, heat exchange is performed by flowing 300 ° C. air into the center of the obtained honeycomb fired body at 10 g / second and flowing water at 20 ° C. at 10 L / min into the outer peripheral portion. And the heat exchange amount W1 in this case is calculated | required. Specifically, the heat exchange amount W1 is obtained from the temperature difference between water before and after heat exchange.

  Next, Fe powder (average particle size 5 μm), Cr powder (average particle size 5 μm), and SiC powder (average particle size 5 μm) are prepared as raw materials for forming the joint. In addition, the average particle diameter of these powder raw materials is the value measured with the laser diffraction type particle size distribution apparatus. Next, the above powders are mixed and stirred for 10 minutes so that the Fe powder is 78.4% by mass, the Cr powder is 17.2% by mass, and the SiC powder is 4.4% by mass. Thereafter, the mixed powder is press-molded into a square shape with a side of 20 mm and a thickness of 5 mm to obtain a “plate-shaped raw material”. Thereafter, this “plate-shaped raw material” is heated at 1100 ° C. for 1 hour in an Ar atmosphere while being placed on the side surface of the honeycomb fired body. In this way, a test honeycomb structure including a honeycomb fired body and a joint portion (a diffusion layer thickness of 0.04 mm) joined to the side surface of the honeycomb fired body is obtained.

  Next, for the obtained test honeycomb structure, a heat exchange amount W2 is obtained by the same method as that for the honeycomb fired body.

Thereafter, a value calculated by the formula: (heat exchange amount W2 / heat exchange amount W1 × 100) −100 is obtained. The case where the calculated value is 0 to 5% is “ C ”, the case where it is over 5% and 15% or less is “B”, and the case where it is over 15% is “ A ”. In this way, the contact thermal resistance of the test honeycomb structure is evaluated. Note that the greater the value calculated by the above equation, the better the heat transfer between the ceramic body and the joint. Therefore, it can be evaluated that the larger the value calculated by the above equation, the better the contact thermal resistance.

  In the honeycomb structure of the present example, the evaluation of [ohmic contact property] was “A”. The evaluation of “joining reliability” was “A”. The evaluation of “electric resistance” was “B”. The evaluation of “thermal resistance” was “A”. The results are shown in Table 4.

(Examples 5, 7, 9, 11, 13, and 14, Reference Examples 2 to 4, 6, 8, 10, and 12, Comparative Examples 1 to 7)
Table 1, using the raw materials shown in Table 2, Table 1, a raw material composition was prepared at the mixing ratio shown in Table 2, except that to produce a joint by using the raw material composition, Example 1, Reference A test piece and a honeycomb fired body were produced in the same manner as in Example 2 . Thereafter, the porosity of the ceramic body was measured in the same manner as in Example 1 for the prepared test piece . Moreover, the presence or absence of the diffusion layer and the presence or absence of the metal layer were confirmed, and the content ratio of “SiC and cordierite” in the metal layer was calculated. Further, in the same manner as in Example 1, “ohmic contact property”, “junction reliability”, “electric resistance”, and “thermal resistance” were evaluated in the same manner as in Reference Example 2 . The “content ratio of the compound dispersed in the metal layer” is referred to as “content ratio of the compound in the metal layer” in Table 3.

As is apparent from Table 4 , the honeycomb structures of Examples 1 , 5, 7, 9, 11, 13, and 14 all had an evaluation of “ohmic contact” of “A”. That is, it was confirmed that the honeycomb structures of Examples 1 , 5, 7, 9, 11, 13, and 14 had a low rate of change in electrical resistance at the joint. In addition, the honeycomb structures of Examples 1 , 5, 7, 9, 11, 13, and 14 all have an evaluation of “joining reliability” of “A”, and Examples 1 , 5, 7, 9, and 11 , 13 and 14 had a better evaluation of “electrical resistance” than the honeycomb structures of Comparative Examples 1 to 7. In other words, it was confirmed that the ceramic body and the metal member were favorably joined by the joining portion, and the joining strength of the joining portion was good. Furthermore, it was confirmed that the honeycomb structures of Examples 1 , 5, 7, 9, 11, 13, and 14 had a good evaluation of “thermal resistance” and a low contact thermal resistance at the joint portion. When a ceramic body having a porosity of less than 0.1% was used, the electrical resistance was about 0.05 to 0.5 Ωcm. When a ceramic body having a porosity of 0.1 or more and about 60% was used, the electric resistance was about 2 to 20 Ωcm. The thermal expansion coefficient of Si is 3.3 × 10 ⁻⁶ / ° C., and the thermal expansion coefficient of SiO ₂ is 30 × 10 ⁻⁶ / ° C. When Si is contained in the metal layer, Si reacts with the metal, the coefficient of thermal expansion of the metal layer becomes high, and the metal layer becomes brittle. That is, the bonding strength is lowered. Further, when Si is added, the diffusion layer becomes thick. Therefore, sufficient results cannot be obtained in the above evaluation. SiO ₂ is the thermal expansion coefficient of the SiO ₂ itself is high, to include SiO ₂ in the metal layer, the thermal expansion coefficient of the metal layer is increased. Therefore, sufficient results cannot be obtained in the above evaluation.

  The honeycomb structure of the present invention can be used as a base material for an electrically heated catalytic converter (EHC), a ceramic heater, a heat exchanger and the like for exhaust gas purification.

1: partition wall, 2: cell, 3: outer peripheral wall, 4: honeycomb structure portion, 5: outer peripheral surface (side surface), 11: one end surface, 12: the other end surface, 20, 40: ceramic body, 21: electrode portion , 30: junction, 31: diffusion layer, 32: metal layer, 100, 101: honeycomb structure.

Claims (9)

A partition wall for partitioning a plurality of cells extending from one end face to the other end face to be a fluid flow path; and an outer peripheral wall positioned at the outermost periphery; and a pair of electrodes disposed on the outer peripheral wall. A honeycomb-shaped ceramic body containing metal Si, and a bonding portion bonded to the outer peripheral surface of the pair of electrodes of the ceramic body,
The junction includes a diffusion layer mainly composed of metal silicide located on the outer peripheral surface side of the pair of electrodes of the ceramic body, and a metal layer formed on the diffusion layer,
The metal layer contains a metal component as a main component and a compound having a thermal expansion coefficient of 5.0 × 10 ⁻⁶ / ° C. or less is dispersed.
The pair of electrodes, porosity observed containing a and metallic Si is 30 to 55%, metal Si may honeycomb structure is at least 15 wt% of the total electrode. 2. The honeycomb structure according to claim 1, wherein the compound having a thermal expansion coefficient of 5.0 × 10 ⁻⁶ / ° C. or less is at least one of SiC and cordierite.   The honeycomb structure according to claim 1 or 2, wherein the diffusion layer has a thickness of 0.1 mm or less.   The honeycomb structure according to claim 2 or 3, wherein a content ratio of SiC dispersed in the metal layer of the joint portion is 10 to 50%.   The honeycomb structure according to any one of claims 2 to 4, wherein an average particle diameter of SiC dispersed in the metal layer of the joint portion is 1 to 50 µm.   The honeycomb structure according to any one of claims 2 to 5, wherein a content ratio of cordierite dispersed in the metal layer of the joint portion is 10 to 50%.   The honeycomb structure according to any one of claims 2 to 6, wherein an average particle size of cordierite dispersed in the metal layer of the joint portion is 1 to 50 µm.   The honeycomb structure according to any one of claims 1 to 7, wherein the metal component is at least one selected from the group consisting of Cr, Fe, and Ni.   The metal silicide is formed by a reaction between the metal Si contained in the ceramic body and the metal component contained in a raw material for forming the junction. Honeycomb structure.

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