Honeycomb structure, electric heating type carrier and exhaust gas purification device

Abstract

To provide a honeycomb structure capable of obtaining an electrode layer having an electric resistivity suitable for an electric resistivity of a honeycomb structure part, and capable of making heating distribution of the honeycomb structure part more uniform.SOLUTION: A honeycomb structure according to the present invention satisfies one or both of the following conditions (1) and (2): (1) a substrate silicon in a honeycomb structure part and an electrode layer silicon in an electrode layer contain P, and a ratio (Pe / Pb) of a P concentration (Pb) in the substrate silicon to a P concentration (Pe) in the electrode layer silicon is 0.80 to 6.0; (2) a substrate silicon carbide in the honeycomb structure part and an electrode layer silicon carbide in the electrode layer contain Al, and a ratio (Ale / Alb) of an Al concentration (Alb) in the substrate silicon carbide to an Al concentration (Ale) in the electrode layer silicon carbide is 0.20 to 6.0.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a honeycomb structure, an electrically heated carrier including the honeycomb structure, and an exhaust gas purification device including the electrically heated carrier. [Background technology]

[0002] Generally, an electrically heated catalyst (EHC) is known in which electrodes are arranged on a honeycomb structure made of conductive ceramics, and the honeycomb structure itself is heated by passing electricity through it, thereby raising the temperature of the catalyst supported on the honeycomb structure to its activation temperature before the engine starts, thereby purifying the exhaust gas emitted immediately after the internal combustion engine starts.

[0003] Since various voltage power supplies are used for the electrically heated carrier, it is necessary to adjust the resistance value of the electrically heated carrier to a predetermined value in order to match the voltage used.

[0004] The following Patent Document 1 proposes improving the heat distribution in the honeycomb structure by controlling the amount of P and B doped into the silicon of the ceramics in the honeycomb structure, and the amount of Al and N doped into the silicon carbide of the ceramics.

[0005] The following Patent Document 2 explains a preferable ratio between the electrical resistivity of the honeycomb structure (honeycomb structure portion) and the electrical resistivity of the electrode layer. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 7320154 [Patent Document 2] Patent No. 7225470 Summary of the Invention [Problem to be solved by the invention]

[0007] It is known that poor heat distribution within the honeycomb structure surface tends to make the honeycomb structure more susceptible to cracks. This is because the silicon (Si) and silicon carbide (SiC) used in the honeycomb structure have NTC characteristics (resistance decreases as the temperature increases), and more current flows in locally heated areas, making those areas more susceptible to heat generation. It is thought that cracks occur due to the difference in thermal stress that occurs between the locally heated area and the surrounding area.

[0008] As shown in Patent Documents 1 and 2, in order to uniformly distribute heat, it is important to balance the electrical resistivity between the honeycomb structure portion and the electrode layer. However, while prior art has examined the control of the electrical resistivity of the honeycomb structure portion, it has not clarified how to control the electrical resistivity of the electrode layer.

[0009] The present invention has been made to solve the above-mentioned problems, and one of its objects is to provide a honeycomb structure, an electrically heated carrier, and an exhaust gas purification device that can obtain an electrode layer having an electrical resistivity that is suitable for the electrical resistivity of the honeycomb structure part, and can make the heat generation distribution of the honeycomb structure part more uniform. [Means for solving the problem]

[0010] Item 1. In one embodiment, the present invention relates to a honeycomb structure comprising: an outer peripheral wall; and partition walls disposed inside the outer peripheral wall to separate a plurality of cells that form a fluid flow path from a first end face to a second end face; and a pair of electrode layers provided on the outer surface of the outer peripheral wall, extending in strip shapes in the extension direction of the cells, and disposed opposite each other across the central axis of the honeycomb structure, wherein the honeycomb structure and the pair of electrode layers are made of ceramics containing at least silicon and silicon carbide, and which satisfies one or both of the following conditions (1) and (2): (1) The substrate silicon in the honeycomb structure and the electrode layer silicon in the electrode layer contain P, and the P concentration in the substrate silicon (P b ) and the P concentration in the electrode layer silicon (P e ) and the ratio (P e / Pb ) is 0.80 to 6.0. (2) The substrate silicon carbide in the honeycomb structure and the electrode layer silicon carbide in the electrode layer contain Al, and the Al concentration in the substrate silicon carbide (Al b ) and the Al concentration in the silicon carbide electrode layer (Al e ) and the ratio (Al e / Al b ) is 0.20 to 6.0.

[0011] Item 2. The present invention may relate to the honeycomb structure according to Item 1, which satisfies both of the above conditions (1) and (2).

[0012] Item 3. In one embodiment, the present invention relates to an electrically heated carrier including the honeycomb structure according to Item 1 or 2, and metal terminals joined to the outer surfaces of the pair of electrode layers, respectively.

[0013] Item 4. In one embodiment, the present invention relates to an exhaust gas purification device including the electrically heated carrier according to Item 3 and a metal tube that houses the electrically heated carrier. [Effects of the Invention]

[0014] According to one embodiment of the honeycomb structure, electrically heated carrier, and exhaust gas purification device of the present invention, one or both of the above conditions (1) and (2) are satisfied, so that an electrode layer having an electrical resistivity suitable for the electrical resistivity of the honeycomb structure part can be obtained, and the heat generation distribution of the honeycomb structure part can be made more uniform. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a schematic diagram of an electrically heated carrier according to an embodiment of the present invention, observed from a first end surface. [Figure 2] 1 is a schematic perspective view of an electrically heated carrier according to an embodiment of the present invention; [Figure 3] 1 is a schematic cross-sectional view showing an exhaust gas purification device according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The present invention is not limited to each embodiment, and the components can be modified and embodied without departing from the spirit of the present invention. Furthermore, various inventions can be formed by appropriately combining multiple components disclosed in each embodiment. For example, some components may be omitted from all the components shown in the embodiments. Furthermore, components of different embodiments may be appropriately combined.

[0017] (1. Electrically heated carrier) Fig. 1 is a schematic view of an electrically heated carrier 100 according to one embodiment of the present invention when viewed from a first end surface 116. Fig. 2 is a schematic perspective view of the electrically heated carrier 100 according to one embodiment of the present invention.

[0018] The electrically heated carrier 100 includes a honeycomb structure 110 and a metal terminal 130. By supporting a catalyst on the electrically heated carrier 100, the electrically heated carrier 100 can be used as a catalyst body. Examples of the catalyst include noble metal catalysts and other catalysts. Noble metal catalysts include three-way catalysts and oxidation catalysts in which noble metals such as platinum (Pt), palladium (Pd), and rhodium (Rh) are supported on the surface of alumina pores and contain promoters such as ceria and zirconia, or alkaline earth metals and platinum are used to convert nitrogen oxides (NO x ) as a storage component of NO x Examples of catalysts that do not use precious metals include NOx storage reduction catalysts (LNT catalysts) containing copper-substituted or iron-substituted zeolites. x Examples include selective catalytic reduction catalysts (SCR catalysts). Two or more catalysts selected from these catalysts may be used. There are no particular limitations on the method for supporting the catalyst, and any known method for supporting a catalyst on a honeycomb structure may be used.

[0019] (1-1. Honeycomb structure) In one embodiment, the honeycomb structure 110 comprises: a ceramic honeycomb structure having an outer peripheral wall 114 and partition walls 113 disposed inside the outer peripheral wall 114 and partitioning a plurality of cells 115 that form a fluid flow path from a first end surface 116 to a second end surface 118; a pair of electrode layers 112a and 112b provided on the outer surface of the outer peripheral wall 114, extending in a strip shape in the extending direction of the cells 115, and facing each other across the central axis O of the honeycomb structure portion; The pair of electrode layers 112a, 112b may also be referred to as the first electrode layer 112a and the second electrode layer 112b.

[0020] The outer shape of the honeycomb structure 110 is not particularly limited, and may be, for example, a columnar body having rounded end faces such as circular, oval, elliptical, racetrack, and oval, a columnar body having polygonal end faces such as triangular and rectangular, and a columnar body having end faces with other irregular shapes. The honeycomb structure 110 shown in the figure has circular end faces and is cylindrical as a whole.

[0021] There is no particular limitation on the height of the honeycomb structure 110 (the length from one end face to the other end face) and it may be set appropriately depending on the application and required performance. There is also no particular limitation on the relationship between the height of the honeycomb structure 110 and the maximum diameter of each end face (the maximum length of the diameters passing through the center of gravity of each end face of the honeycomb structure). Therefore, the height of the honeycomb structure 110 may be longer than the maximum diameter of each end face, or the height of the honeycomb structure 110 may be shorter than the maximum diameter of each end face.

[0022] The size of the honeycomb structure 110 is set so that the area of ​​one end face is 2000 to 20000 mm2 in order to increase the heat resistance (to suppress cracks in the circumferential direction of the outer peripheral wall). 2 It is preferable that the thickness is 5000 to 15000 mm 2 It is more preferable that:

[0023] <Honeycomb structure> The ceramic honeycomb structure portion has a higher volume resistivity than the electrode layers 112a and 112b, but is conductive. The volume resistivity of the honeycomb structure portion is not particularly limited as long as it can generate heat by Joule heating when current is applied, and can be set appropriately depending on the applied voltage. For example, when measured at 25°C, the volume resistivity can be 0.001 to 500 Ω·cm. For high voltages greater than 60 V, the volume resistivity can be 2 to 100 Ω·cm, typically 5 to 100 Ω·cm. For low voltages of 60 V or less, such as 48 V, the volume resistivity can be 0.001 to 2 Ω·cm, typically 0.001 to 1 Ω·cm, and more typically 0.01 to 1 Ω·cm.

[0024] In one embodiment, the volume resistivity (ρ v50 ) versus volume resistivity at 500°C (ρ v500 ) ratio (ρ v500 / ρ v50 ) is 0.30 or more. v500 / ρ v50 A ρ of 0.30 or more means that the NTC thermistor characteristics are relaxed, and the uniformity of heat generation distribution is significantly improved. v500 / ρ v50 is preferably 0.35 or more, more preferably 0.40 or more. In addition, since a silicon-silicon carbide composite material or a ceramic material containing silicon carbide as a main component is used in the honeycomb structure, ρ v500 / ρ v50 The upper limit of is preferably 0.80 or less, more preferably 0.75 or less, and even more preferably 0.70 or less. v500 / ρ v50 is, for example, preferably 0.30 to 0.80, more preferably 0.35 to 0.75, and even more preferably 0.40 to 0.70.

[0025] In this specification, the volume resistivity of a honeycomb structure part is measured by the following procedure. A total of five partition wall samples, each measuring 5 mm × 5 mm × 50 mm (in the cell extension direction), are taken from the honeycomb structure part, and the volume resistivity of each is measured at 25°C by the four-terminal method unless otherwise specified, and the average value of the five samples is taken as the volume resistivity of the honeycomb structure part. The partition wall samples are taken from near the center in the height direction and radial direction of the honeycomb structure part.

[0026] In one embodiment, the ceramic constituting the honeycomb structure portion having the outer peripheral wall 114 and the partition walls 113 contains at least (metallic) silicon and silicon carbide, and preferably the total content of silicon and silicon carbide in the ceramic is 80 to 95 mass%. Typically, the ceramic contains a silicon carbide-silicon composite. From the viewpoint of achieving both heat resistance and electrical conductivity, the ceramic preferably contains a silicon carbide-silicon composite as its main component. When the ceramic contains a silicon carbide-silicon composite as its main component, it means that the silicon carbide-silicon composite (total mass) in the ceramic accounts for 70 mass% or more of the total, preferably 80 to 95 mass%. From the viewpoint of alleviating the NTC thermistor characteristics, it is advantageous to adjust the contents of silicon and silicon carbide in the ceramic constituting the honeycomb structure portion.

[0027] Here, the silicon carbide-silicon composite material contains silicon carbide particles as an aggregate and (metallic) silicon as a binder that binds the silicon carbide particles. The ceramic may contain, in addition to silicon carbide particles, one or two aggregates selected from silicon nitride particles and aluminum nitride particles. It may also contain one or more other aggregates. Examples of other aggregates include oxide ceramics such as alumina, mullite, zirconia, and cordierite.

[0028] However, if the main component of the aggregate is silicon carbide, it is preferable because it has a higher thermal conductivity and a smaller difference in thermal expansion coefficient from silicon. When the main component of the aggregate is silicon carbide, it means that silicon carbide (total mass) accounts for 80 mass% or more of the aggregate, and more preferably 90 mass% or more of the aggregate.

[0029] From the viewpoint of alleviating the NTC thermistor characteristics, it is preferable to also control the silicon oxide content in the ceramics constituting the honeycomb structure portion. The silicon oxide content in the ceramics is preferably 5 to 20 mass %, for example, 10 to 15 mass %.

[0030] The contents of Si (silicon), SiC (silicon carbide), and SiO2 (silicon oxide) in the ceramics constituting the honeycomb structure can be measured by the following method. The following method describes a calculation method when (doped) silicon and silicon carbide are used as ceramic raw materials. When silicon and silicon carbide are used as ceramic raw materials, the ceramics constituting the honeycomb structure are composed of silicon (Si), silicon carbide (SiC), and silicon oxide (SiO2). The contents of Si (silicon), SiC (silicon carbide), and SiO2 (silicon oxide) in the ceramics can be measured by measuring the amounts of silicon and oxygen using an X-ray fluorescence method, and the amount of carbon using a resistance heating infrared absorption method. Measurement samples are taken from near the center of the honeycomb structure in the height direction and radial direction. The mass of one sample is 10 g. The average value of the content of each component in the five samples is taken as the content of Si (silicon), SiC (silicon carbide), and SiO2 (silicon oxide) in the ceramic.

[0031] Regarding the amount of SiC (silicon carbide), all carbon elements are assumed to be SiC, and the amount of SiC in the ceramic is calculated by molecular weight calculation. Regarding the amount of SiO2 (silicon oxide), all oxygen elements are assumed to be SiO2, and the amount of SiO2 in the ceramic is calculated by molecular weight calculation. The amount of Si (silicon) can be calculated by subtracting the total amount of Si (the amount of Si in SiC and the amount of Si in SiO2) from the total amount of silicon element from the amounts of SiC and SiO2 calculated above. When using ceramic raw materials other than silicon carbide, the composition of the ceramics that make up the honeycomb structure portion can be confirmed based on the ceramic raw materials, and then the amount of elements can be measured using X-ray fluorescence or resistance heating infrared absorption spectroscopy, and the amount can be calculated in the same way.

[0032] The partition walls 113 of the honeycomb structure portion may be dense, such as in the form of Si-impregnated SiC, but are preferably porous. If the porosity of the partition walls 113 is 30% or more, deformation during firing is more easily suppressed. Furthermore, if the porosity of the partition walls 113 is 60% or less, the strength of the honeycomb structure portion is sufficiently maintained. Therefore, the porosity of the partition walls 113 is preferably, for example, 30% or more, more preferably 35 to 60% in order to keep the thermistor characteristics within a predetermined range, and even more preferably 37 to 45%. The porosity is a value measured using a mercury porosimeter. Note that dense refers to a porosity of 5% or less.

[0033] The thickness of the partition walls 113 that define the cells 115 is preferably 0.1 to 0.3 mm, and more preferably 0.1 to 0.2 mm. When the thickness of the partition walls 113 is 0.1 mm or more, it is possible to prevent a decrease in the strength of the honeycomb structure portion. When the thickness of the partition walls 113 is 0.3 mm or less, it is possible to prevent an increase in pressure loss when exhaust gas flows through the honeycomb structure portion when the honeycomb structure portion is used as a catalyst carrier and a catalyst is carried thereon. In the present invention, the thickness of the partition walls 113 is defined as the length of the portion of a line segment that connects the centers of gravity of adjacent cells 115 and that passes through the partition walls 113 in a cross section perpendicular to the extension direction of the cells 115.

[0034] Providing the honeycomb structure with the peripheral wall 114 is useful from the viewpoint of ensuring the structural strength of the honeycomb structure and suppressing leakage of the fluid flowing through the cells 115 from the peripheral wall 114. In this regard, the thickness of the peripheral wall 114 is preferably 0.1 mm or more, more preferably 0.15 mm or more, and even more preferably 0.2 mm or more. However, if the peripheral wall 114 is made too thick, it will have too high strength, which will disrupt the strength balance with the partition walls 113 and reduce thermal shock resistance. Therefore, the thickness of the peripheral wall 114 is preferably 1.0 mm or less, more preferably 0.7 mm or less, and even more preferably 0.5 mm or less. Therefore, the thickness of the peripheral wall 114 is preferably, for example, 0.1 to 1.0 mm, more preferably 0.15 to 0.7 mm, and even more preferably 0.2 to 0.5 mm. Here, the thickness of the outer peripheral wall 114 is defined as the thickness in the direction normal to the tangent to the outer surface of the outer peripheral wall 114 at the measurement point when the portion of the outer peripheral wall 114 where the thickness is to be measured is observed in a cross section perpendicular to the extension direction of the cell 115. preferable.

[0035] The honeycomb structure has a cell density of 40 to 150 cells / cm in a cross section perpendicular to the extension direction of the cells 115. 2 It is preferable that the number of cells is 70 to 100. 2 By setting the cell density in this range, it is possible to increase the purification performance of the catalyst while reducing the pressure loss when exhaust gas flows through the honeycomb structure. 2 If the cell density is 150 cells / cm or more, a sufficient catalyst carrying area is ensured. 2 When the honeycomb structure 110 is used as a catalyst carrier and a catalyst is carried thereon, excessive pressure loss during the flow of exhaust gas is suppressed if the honeycomb structure 110 is used as a catalyst carrier and the cell density is equal to or less than the above. The cell density is a value obtained by dividing the number of cells by the area of ​​one end face of the honeycomb structure part on the inner peripheral side of the outer peripheral wall 114.

[0036] Although there are no limitations on the shape of the cells in a cross section perpendicular to the extension direction of the cells 115, a square, a hexagon, an octagon, or a combination thereof is preferred. Among these, a square and a hexagon are more preferred. By using such a cell shape, the pressure loss when exhaust gas flows through the honeycomb structure 110 is reduced, and the purification performance of the catalyst is improved. From the viewpoint of easily achieving both structural strength and heating uniformity, a hexagon is particularly preferred.

[0037] The cells 115 may penetrate from the first end face 116 to the second end face 118. In this case, the cells 115 may be open at both the first end face 116 and the second end face 118. Alternatively, first cells having plugged first end faces 116 and openings at the second end faces 118 and second cells having openings at the first end faces 116 and plugged second end faces 118 may be alternately arranged adjacent to each other with the partition wall 113 interposed therebetween.

[0038] <Electrode layer> A first electrode layer 112a and a second electrode layer 112b facing the first electrode layer 112a across the central axis O of the honeycomb structure section can be provided on the outer surface of the outer peripheral wall 114. By providing the electrode layers 112a, 112b having a volume resistivity lower than that of the outer peripheral wall 114, current is more likely to spread in the circumferential direction of the honeycomb structure 110 and in the extension direction of the cells 115, thereby improving the uniform heat generation of the honeycomb structure 110. Referring to FIG. 1 , in a cross section perpendicular to the extension direction of the cells 115, the angle θ (0°≦θ≦180°) formed by two line segments extending from the circumferential centers of the pair of electrode layers 112a, 112b to the central axis O (center of gravity) of the honeycomb structure 110 is preferably 150°≦θ≦180°, more preferably 160°≦θ≦180°, even more preferably 170°≦θ≦180°, and most preferably 180°.

[0039] Although there are no particular restrictions on the formation regions of the pair of electrode layers 112a, 112b, from the viewpoint of improving the uniform heat generation of the honeycomb structure 110, it is preferable that the pair of electrode layers 112a, 112b are each provided in a strip-like shape extending on the outer surface of the outer peripheral wall 114 in the circumferential direction of the honeycomb structure 110 and in the extension direction of the cells 115. Specifically, in a cross section perpendicular to the extension direction of the cells 115, the central angle α formed by two line segments connecting both circumferential ends of each electrode layer 112a, 112b to the central axis O (center of gravity) is preferably 30° or more, more preferably 40° or more, and even more preferably 60° or more, from the viewpoint of spreading the current in the circumferential direction and improving the uniform heat generation (see FIG. 1). However, if the central angle α is too large, the current passing through the interior of the honeycomb structure 110 will be reduced and the current passing near the outer peripheral wall 114 will be increased. Therefore, from the viewpoint of uniform heat generation of the honeycomb structure 110, the central angle α is preferably 140° or less, more preferably 130° or less, and even more preferably 120° or less. Furthermore, it is desirable that each of the electrode layers 112a and 112b extends over 80% or more of the length between both end faces of the honeycomb structure 110, preferably over 90% or more, and more preferably over the entire length. The electrode layers 112a and 112b may be composed of a single layer, or may have a laminated structure in which multiple layers are stacked.

[0040] The thickness of the electrode layers 112a, 112b is preferably 0.01 to 5 mm, and more preferably 0.01 to 3 mm. Setting the thickness within this range can improve uniform heat generation. When the thickness of the electrode layers 112a, 112b is 0.01 mm or more, the electrical resistance is appropriately controlled, allowing for more uniform heat generation. When the thickness of the electrode layers 112a, 112b is 5 mm or less, the risk of breakage during canning is reduced. The thickness of the electrode layers 112a, 112b is defined as the thickness in the direction normal to the tangent to the outer surface of the electrode layers 112a, 112b at the measurement location when the location of the electrode layers 112a, 112b where the thickness is to be measured is observed in a cross section perpendicular to the extension direction of the cell 115.

[0041] By making the volume resistivity of the electrode layers 112a, 112b lower than the volume resistivity of the partition walls 113 and the outer peripheral wall 114, electricity flows preferentially through the electrode layers 112a, 112b, and when energized, electricity spreads more easily in the circumferential direction of the honeycomb structure 110 and in the extension direction of the cells 115. The volume resistivity of the electrode layers 112a, 112b is preferably 1 / 10 or less, more preferably 1 / 20 or less, and even more preferably 1 / 30 or less of the volume resistivity of the partition walls 113 and the outer peripheral wall 114. However, if the difference in volume resistivity between the electrode layers 112a and 112b becomes too large, current will concentrate between the ends of the opposing electrode layers 112a and 112b, resulting in uneven heat generation in the honeycomb structure 110. Therefore, the volume resistivity of the electrode layers 112a and 112b is preferably 1 / 200 or more, more preferably 1 / 150 or more, and even more preferably 1 / 100 or more of the volume resistivity of the partition walls 113 and the outer peripheral wall 114. Therefore, the volume resistivity of the electrode layers 112a and 112b is, for example, preferably 1 / 200 to 1 / 10 of the volume resistivity of the partition walls 113 and the outer peripheral wall 114, more preferably 1 / 150 to 1 / 20, and even more preferably 1 / 100 to 1 / 30. The volume resistivities of the electrode layers, partition walls, and outer peripheral wall herein are values ​​measured at 25°C by a four-terminal method.

[0042] The material of the electrode layers 112a and 112b is not limited to, but may be a composite (cermet) of metal and ceramic (especially conductive ceramic). Examples of metals include, for example, Cr, Fe, Co, Ni, Si, or Ti, or alloys containing at least one metal selected from these metals. Examples of ceramics include, but are not limited to, silicon carbide (SiC), as well as metal compounds such as metal silicides, such as tantalum silicide (TaSi2) and chromium silicide (CrSi2). Specific examples of composites (cermets) of metal and ceramic include composites of silicon and silicon carbide, composites of metal silicides, such as tantalum silicide or chromium silicide, and silicon and silicon carbide, as well as composites of one or more of the above metals to which one or more insulating ceramics, such as alumina, mullite, zirconia, cordierite, silicon nitride, and aluminum nitride, are added to reduce thermal expansion. As the material for the electrode layers 112a, 112b, among the various metals and ceramics mentioned above, a composite material of a metal silicide such as tantalum silicide or chromium silicide, silicon, and silicon carbide is preferred because it can be fired simultaneously with the partition wall and the outer peripheral wall, thereby contributing to simplifying the manufacturing process.

[0043] <Dopant> Silicon and silicon carbide in the ceramics that make up the honeycomb structure portion and the electrode layers 112a and 112b can contain one or more dopants. The dopant in silicon and silicon carbide may be, for example, one or more elements selected from elements in Group 13 and Group 15 of the periodic table. Examples of Group 13 elements include boron (B), aluminum (Al), gallium (Ga), and indium (In), and examples of Group 15 elements include nitrogen (N), phosphorus (P), arsenic (As), antimony (Sb), and bismuth (Bi).

[0044] It is known that poor heat distribution within the honeycomb structure surface tends to cause cracks in the honeycomb structure. This is because the silicon (Si) and silicon carbide (SiC) used in the honeycomb structure have NTC characteristics (resistance decreases with increasing temperature), and more current flows in locally heated areas, making those areas more likely to generate heat. It is thought that cracks occur due to the difference in thermal stress between the locally heated area and the surrounding area.

[0045] In order to make the heat generation distribution uniform, it is important to balance the electrical resistivity between the honeycomb structure portion and the electrode layers. The present inventors have found that when P is doped into silicon in the honeycomb structure portion (hereinafter referred to as "substrate silicon") and silicon in the electrode layers 112a, 112b (hereinafter referred to as "electrode layer silicon"), and / or P is doped into silicon carbide in the honeycomb structure portion (hereinafter referred to as "substrate silicon carbide") and silicon carbide in the electrode layers 112a, 112b (hereinafter referred to as "electrode layer silicon carbide"), the P concentration in the substrate silicon (P b ) (mass ppm) and the P concentration in the electrode layer silicon (P e ) (mass ppm) and the ratio (P e / P b ) and / or the Al concentration in the substrate silicon carbide (Al b ) (mass ppm) and the Al concentration in the silicon carbide electrode layer (Al e ) (mass ppm) e / Al b ) can provide electrode layers 112a and 112b having an electrical resistivity suitable for that of the honeycomb structure portion, thereby making the heat generation distribution in the honeycomb structure portion more uniform.

[0046] That is, the honeycomb structure 110 of the present embodiment satisfies one or both of the following conditions (1) and (2): It is preferable that both conditions (1) and (2) are satisfied. (1) The substrate silicon in the honeycomb structure and the electrode layer silicon in the electrode layers 112a and 112b contain P, and the P concentration in the substrate silicon (P b ) and the P concentration in the electrode layer silicon (P e ) and the ratio (Pe / P b ) is 0.80 to 6.0. (2) The silicon carbide substrate in the honeycomb structure portion and the silicon carbide electrode layers in the electrode layers 112a and 112b contain Al, and the Al concentration in the silicon carbide substrate (Al b ) and the Al concentration in the silicon carbide electrode layer (Al e ) and the ratio (Al e / Al b ) is 0.20 to 6.0.

[0047] Regarding the P concentration in the substrate silicon, a total of five partition wall samples, each weighing 10 g, were taken from near the center in the height direction and the diameter direction of the honeycomb structure part, and the P concentration in the silicon of each was measured using the following procedure, and the average value was calculated to be the measured value.

[0048] The method for measuring the P concentration in silicon (Si) in a partition wall sample is as follows. According to the silicon separation ICP atomic emission spectroscopy specified in JIS G1322-3:2010 "Metallic Silicon Analysis Method," the partition wall sample is decomposed with nitric acid and hydrofluoric acid, perchloric acid is added, and the sample is heated to generate white fumes of perchloric acid. The silicon is volatilized and separated as silicon tetrafluoride, and the salts are then dissolved in water. The P contained in the solution is then measured using ICP atomic emission spectroscopy, and the concentration in the silicon is calculated.

[0049] The P concentration in the electrode layer silicon was measured by taking five electrode layer samples, each weighing 1 g, from the center (near the center) of the pair of electrode layers 112a and 112b in the thickness direction and circumferential direction. The P concentration in the silicon for each was measured using the following procedure, and the average value was calculated. The P concentration in the silicon (Si) of the electrode layer samples was measured as follows: According to the silicon separation ICP atomic emission spectroscopy method specified in JIS G1322-3:2010 "Metallic Silicon Analysis Method," the electrode layer sample was decomposed with nitric acid and hydrofluoric acid, perchloric acid was added, and the mixture was heated to generate white perchloric acid fumes. The silicon was then volatilized and separated as silicon tetrafluoride, and the salts were dissolved in water. The P content in the solution was then measured using ICP atomic emission spectroscopy, and the concentration in the silicon was calculated.

[0050] The Al concentration in the silicon carbide substrate can be measured by the following method. First, a total of five partition wall samples are taken from the honeycomb structure part near the center in the height direction and the diameter direction of the honeycomb structure part. The size of one sample is 1 cm 3 The size of the sample is determined (cubic shape, 1 cm x 1 cm x 1 cm). The sample is observed under a scanning electron microscope (SEM) (magnification 1000x), and the dark contrast areas are visually identified as silicon carbide parts. The silicon carbide parts are then analyzed using secondary ion mass spectrometry (SIMS) to determine the Al concentration in the silicon carbide. The average Al concentration of the five samples is taken as the Al concentration in the silicon carbide substrate.

[0051] The Al concentration in the silicon carbide electrode layers was measured by cutting each of the pair of electrode layers 112a, 112b near the center (near the center) in the thickness direction and circumferential direction to expose the cross section of each electrode layer 112a, 112b. The unevenness of the cross section of the electrode layers 112a, 112b was then filled with resin and polished to obtain a sample. The sample was observed with a scanning electron microscope (SEM) (magnification 1000x), and dark contrast areas were visually identified as silicon carbide portions. The silicon carbide portions were then analyzed by secondary ion mass spectrometry (SIMS). The average Al concentration in the cross section of each of the pair of electrode layers 112a, 112b was determined to be the Al concentration in the silicon carbide.

[0052] (1-2. Metal terminal) The metal terminals 130 can be directly or indirectly bonded to the outer surfaces of the pair of electrode layers 112a, 112b. When a voltage is applied to the honeycomb structure 110 via the metal terminals 130, electricity flows and the honeycomb structure 110 can generate heat by Joule heat. Therefore, the honeycomb structure 110 can be suitably used as a heater. This makes it possible to improve the uniform heat generation of the honeycomb structure 110. The applied voltage is preferably 12 to 900 V, more preferably 48 to 600 V, but the applied voltage can be changed as appropriate.

[0053] The metal terminal 130 and the electrode layers 112a, 112b may be directly bonded to each other, or may be bonded via one or more base layers 120 in order to reduce the difference in thermal expansion between the electrode layers 112a, 112b and the metal terminal 130 and thereby improve the bonding reliability of the metal terminal 130. Therefore, in a preferred embodiment, the honeycomb structure 110 has a first electrode layer 112a and a second electrode layer 112b disposed on the outer peripheral wall 114 so as to face each other across the central axis O (center of gravity) of the honeycomb structure 110, and one or more metal terminals 130 are bonded to each of the electrode layers 112a, 112b via the base layer 120.

[0054] From the viewpoint of improving bonding reliability, it is preferable that the thermal expansion coefficient gradually decreases in the order of metal terminal 130 → (underlying layer 120) → electrode layers 112a, 112b → outer peripheral wall 114. Note that the "thermal expansion coefficient" here refers to the linear expansion coefficient measured in accordance with JIS R1618:2002 when the temperature is changed from 25°C to 800°C.

[0055] The material of the metal terminal 130 is not particularly limited as long as it is a metal, and simple metals and alloys can be used, but from the viewpoints of corrosion resistance, volume resistivity, and linear expansion coefficient, an alloy containing at least one selected from the group consisting of Cr, Fe, Co, Ni, and Ti is preferable, and stainless steel and an Fe-Ni alloy are more preferable. The number, shape, and size of the metal terminal 130 are not particularly limited, and can be designed appropriately depending on the size, electrical conductivity, etc. of the honeycomb structure 110.

[0056] The material of the base layer 120 is not limited, but a composite material (cermet) of metal and ceramic (especially conductive ceramic) can be used. The thermal expansion coefficient of the base layer 120 can be controlled by adjusting the compounding ratio of the metal and ceramic, for example.

[0057] The underlayer 120 preferably contains, but is not limited to, one or more metals selected from Ni-based alloys, Fe-based alloys, Ti-based alloys, Co-based alloys, silicon, and Cr.

[0058] The underlayer 120 preferably contains one or more ceramics selected from, but not limited to, oxide ceramics such as alumina, mullite, zirconia, glass, and cordierite, and non-oxide ceramics such as silicon carbide, silicon nitride, and aluminum nitride.

[0059] The thickness of the base layer 120 is not particularly limited, but is preferably 0.1 to 1.5 mm, and more preferably 0.3 to 0.5 mm, from the viewpoint of crack suppression. The thickness of the base layer 120 is defined as the thickness in the direction normal to the tangent to the outer surface of the base layer 120 at the measurement point when the base layer 120 whose thickness is to be measured is observed in a cross section perpendicular to the extension direction of the cells.

[0060] The method for joining the metal terminal 130 to the electrode layers 112a and 112b or the base layer 120 is not particularly limited, but examples thereof include thermal spraying, welding, and brazing.

[0061] (2. Exhaust gas purification device) An electrically heated carrier according to one embodiment of the present invention can be used in an exhaust gas purification device. Referring to Fig. 3, an exhaust gas purification device 200 includes an electrically heated carrier 100 and a metal tube 220 that houses the electrically heated carrier 100. An electric wire 240 for power supply can be connected to a metal terminal 130 of the electrically heated carrier 100. Metals constituting the metal tube 220 include, but are not limited to, various stainless steels such as chromium-based stainless steel. The use of these metals results in an exhaust gas purification device with high heat resistance and corrosion resistance.

[0062] In the exhaust gas purification device 200, the electrically heated carrier 100 can be installed midway through the flow path of a fluid such as automobile exhaust gas. The electrically heated carrier 100 can be fixed inside the metal tube 220, for example, by push-in canning, in which the electrically heated carrier 100 is pushed into the metal tube 220 and fitted into it in a positional relationship in which the extension direction of the cells and the extension direction of the metal tube 220 coincide. It is preferable to dispose a retaining material (mat) 260 between the metal tube 220 and the electrically heated carrier 100. The material constituting the retaining material (mat) 260 is not limited, but examples include ceramics such as alumina fiber, mullite fiber, and ceramic fiber mainly composed of alumina-silica.

[0063] (3. Manufacturing method) Next, a method for manufacturing a honeycomb structure according to one embodiment of the present invention will be described. The honeycomb structure can be manufactured by a manufacturing method including step 1 of preparing a clay, step 2 of molding the clay to obtain a honeycomb molded body, step 3 of applying a pair of electrode layer forming pastes to the outer surface of the peripheral wall so that the pastes extend in strips in the cell extension direction across the central axis of the honeycomb molded body to prepare a honeycomb molded body with the electrode layer forming pastes, and step 4 of firing the honeycomb molded body to prepare a honeycomb fired body.

[0064] (Process 1) In step 1, a forming raw material containing silicon carbide powder and (metallic) silicon powder is kneaded to produce a paste. One or both of the silicon carbide powder and silicon powder can be appropriately doped with a dopant such as B, Al, N, or P. The dopant concentrations in the silicon carbide powder and silicon powder can be adjusted, for example, by adding a trace amount of dopant element during the production of the forming raw material, or by mixing forming raw materials with different dopant amounts in any desired ratio. Another method for doping silicon with P and B is to knead an aqueous solution containing a predetermined amount of dopant source (such as a water-soluble inorganic salt or a water-soluble organic compound) with the forming raw material to incorporate the dopant source into the paste, and then doping during firing.

[0065] The mass of the metal silicon powder in the forming raw material is preferably 20 to 80 parts by mass, more preferably 25 to 60 parts by mass, and even more preferably 25 to 45 parts by mass, when the total mass of the silicon carbide powder and metal silicon powder is 100 parts by mass. The average particle size of the silicon carbide particles in the silicon carbide powder is preferably 3 to 50 μm, more preferably 3 to 40 μm. The average particle size of the metal silicon particles in the metal silicon powder is preferably 2 to 35 μm, more preferably 2 to 25 μm. The average particle sizes of the silicon carbide particles and metal silicon particles refer to the arithmetic mean diameter on a volume basis when the particle size frequency distribution is measured by laser diffraction. The silicon carbide particles are fine particles of silicon carbide that constitute the silicon carbide powder, and the metal silicon particles are fine particles of metal silicon that constitute the metal silicon powder.

[0066] The content of water in the forming raw material is, for example, preferably 20 to 60 parts by mass, and more preferably 25 to 50 parts by mass, when the total mass of the silicon carbide powder and the metallic silicon powder is taken as 100 parts by mass.

[0067] In step 1, the forming raw materials are kneaded to prepare a paste. Any appropriate device or mechanism can be used as the kneading means. Specific examples include a kneader and a vacuum kneader.

[0068] The forming raw material may contain a binder, a surfactant, and a pore former in addition to the silicon carbide powder and the silicon powder.

[0069] Examples of binders include methyl cellulose, hydroxypropyl methyl cellulose, hydroxypropoxyl cellulose, hydroxyethyl cellulose, carboxymethyl cellulose, polyvinyl alcohol, etc. 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 silicon powder is 100 parts by mass.

[0070] Examples of surfactants that can be used include ethylene glycol, dextrin, fatty acid soap, and polyalcohol. These may be used alone or in combination of two or more. The content of the surfactant is preferably 0.1 to 2.0 parts by mass when the total mass of the silicon carbide powder and silicon powder is 100 parts by mass.

[0071] The pore-forming material is not particularly limited as long as it forms pores after firing, and examples thereof include graphite, starch, foamed resin, water-absorbent resin, silica gel, etc. The content of the pore-forming material is preferably 0.5 to 10.0 parts by mass when the total mass of the silicon carbide powder and silicon powder is 100 parts by mass. The average particle diameter of the pore-forming material is preferably 10 to 30 μm. The average particle diameter of the pore-forming material refers to the arithmetic mean diameter on a volume basis when the frequency distribution of particle size is measured by laser diffraction. When the pore-forming material is a water-absorbent resin, the average particle diameter of the pore-forming material refers to the average particle diameter after water absorption.

[0072] (Process 2) In step 2, the paste produced in step 1 is molded to obtain a honeycomb molded body. Specifically, the paste is extrusion molded to produce a columnar honeycomb molded body having an outer peripheral wall and partition walls. A die having the desired overall shape, cell shape, partition wall thickness, cell density, etc. can be used during extrusion molding. Next, it is preferable to dry the obtained honeycomb molded body. If the length of the honeycomb molded body in the cell extension direction is not the desired length, both ends of the honeycomb molded body can be cut to obtain the desired length. The honeycomb molded body after drying is called a dried honeycomb body.

[0073] The honeycomb formed body may be fired once as a modified example of step 2. That is, in this modified example, the honeycomb formed body is fired to prepare a honeycomb fired body, and step 3 is then carried out on the honeycomb fired body.

[0074] (Step 3) Step 3 is a step of applying a pair of electrode layer forming pastes to the outer surface of the peripheral wall of the honeycomb formed body so that the pastes extend in bands in the cell extension direction across the central axis of the honeycomb formed body, thereby producing a honeycomb formed body with electrode layer forming pastes. The electrode layer forming paste can be formed by adding various additives appropriately to raw material powders (metal powders, ceramic powders, etc.) blended according to the required characteristics of the electrode layer, and kneading the mixture. The average particle diameter of the raw material powders is not limited, but is preferably, for example, 5 to 50 μm, and more preferably 10 to 30 μm. The average particle diameter of the raw material powders refers to the arithmetic mean diameter on a volume basis when the particle size frequency distribution is measured by laser diffraction.

[0075] Next, the obtained electrode layer forming paste is applied to required locations on the outer surface of the peripheral wall of a honeycomb formed body (typically a dried honeycomb body) to obtain a honeycomb formed body with the electrode layer forming paste. The method of preparing the electrode layer forming paste and the method of applying the electrode layer forming paste to the honeycomb formed body can be performed in accordance with known methods for manufacturing honeycomb structures, but in order to give the electrode layer a lower volume resistivity than the peripheral wall and partition walls, it is possible to increase the metal content ratio compared to the peripheral wall and partition walls, or to reduce the particle size of the metal particles in the raw material powder. After application, it is preferable to dry the electrode layer forming paste.

[0076] (Step 4) Step 4 is a step of firing the honeycomb formed body with the electrode layer forming paste to obtain a honeycomb fired body, i.e., the desired honeycomb structure. Before firing, degreasing may be performed to remove binders and the like. The degreasing and firing methods are not particularly limited, and firing can be performed using an electric furnace, a gas furnace, or the like. Firing conditions vary depending on the material of the honeycomb structure, but are preferably heating at 1400 to 1500°C for 1 to 20 hours in an inert atmosphere such as nitrogen or argon.

[0077] An electrically heated carrier can be manufactured by joining a metal terminal to the electrode layer of the honeycomb structure obtained in this way. The joining method is not particularly limited, but examples thereof include thermal spraying, welding, and brazing. In order to improve the bonding between the electrode layer and the metal terminal, a base layer may be formed by a method such as thermal spraying.

[0078] An appropriate catalyst may be supported on the electrically heated carrier depending on the application. As a method for supporting a catalyst on a honeycomb structure, for example, a catalyst slurry is introduced into cells by a conventionally known suction method or the like, and is allowed to adhere to the surfaces and pores of the partition walls, and then high-temperature treatment is performed to bake the catalyst contained in the catalyst slurry onto the partition walls and support the catalyst.

[0079] Although the preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, the present invention is not limited to these examples. It is clear that a person skilled in the art to which the present invention pertains can conceive of various modifications and alterations within the scope of the technical ideas set forth in the claims, and it is understood that these also naturally fall within the technical scope of the present invention. [Example]

[0080] The following examples are provided to provide a better understanding of the present invention and its advantages, but the present invention is not limited to these examples.

[0081] Example 1 (1. Preparation of cylindrical paste) 30 g of phosphate ester salt was added to 30 kg of pure water and stirred for 20 minutes to obtain an aqueous solution containing P. Next, Al-doped silicon carbide (SiC) powder and silicon (Si) powder were mixed in a mass ratio of 65:35 to prepare a ceramic raw material. The amount of Al doped into the SiC (silicon carbide) was adjusted by mixing SiC (silicon carbide) with different Al doping amounts. Hydroxypropyl methylcellulose as a binder, a water-absorbent resin as a pore-forming material, and the aforementioned aqueous solution containing P were added to this ceramic raw material to prepare a molding raw material. Next, the molding raw material was kneaded in a vacuum kneader to produce a cylindrical paste.

[0082] In the molding raw materials, the binder content was 7 parts by mass when the total of the silicon carbide (SiC) powder and silicon (Si) powder was 100 parts by mass. The pore-forming material content was 3 parts by mass when the total of the silicon carbide (SiC) powder and silicon (Si) powder was 100 parts by mass. The aqueous solution content was 30 parts by mass when the total of the silicon carbide (SiC) powder and silicon (Si) powder was 100 parts by mass. The average particle diameter of the silicon carbide powder was 20 μm, and the average particle diameter of the silicon powder was 6 μm. The average particle diameter of the pore-forming material was 20 μm. The average particle diameters of the silicon carbide powder, silicon powder, and pore-forming material refer to the arithmetic mean diameter on a volume basis when the particle size frequency distribution is measured by laser diffraction.

[0083] (2. Preparation of dried honeycomb body) The obtained cylindrical paste was molded using an extruder with a predetermined die structure to obtain a cylindrical honeycomb molded body in which each cell shape in the cross section perpendicular to the cell extension direction is hexagonal. This honeycomb molded body was dried by high-frequency dielectric heating, and then further dried in an air atmosphere at 120°C for 2 hours using a hot air dryer, and both end faces were cut by a predetermined amount to produce a dried honeycomb body.

[0084] (3. Preparation of electrode layer forming paste) 30 g of phosphate ester salt was added to 30 kg of pure water and stirred for 20 minutes to obtain an aqueous solution containing P. Silicon (Si) powder, silicon carbide (SiC) powder, methyl cellulose, glycerin, and water were mixed using a planetary centrifugal mixer to prepare an electrode layer-forming paste. The amount of Al doped into SiC (silicon carbide) was adjusted by mixing SiC (silicon carbide) with different Al doping amounts. The Si powder and SiC powder were blended at a volume ratio of Si powder:SiC powder = 40:60. Furthermore, when the total amount of Si powder and SiC powder was 100 parts by mass, the amount of methyl cellulose was 0.5 parts by mass, the amount of glycerin was 10 parts by mass, and the amount of water was 38 parts by mass. The average particle diameter of the silicon powder was 6 μm. The average particle diameter of the silicon carbide powder was 35 μm. These average particle diameters refer to the arithmetic mean diameters based on volume when measuring the particle size frequency distribution using a laser diffraction method.

[0085] (4. Application of electrode layer forming paste) The electrode layer forming paste was applied to two locations on the outer surface of the outer wall of the dried honeycomb body using a curved surface printing machine, facing each other across the central axis. Each application area was formed in a strip shape over the entire length between both end faces of the dried honeycomb body (angle θ = 180°, central angle α = 127°). Next, the electrode layer forming paste applied to the dried honeycomb body was dried to obtain a dried honeycomb body with the electrode layer forming paste. The drying temperature was 70°C.

[0086] (5. Firing) The obtained dried honeycomb body with the electrode layer forming paste was degreased in an air atmosphere at 550°C for 3 hours. Next, the degreased dried honeycomb body was fired in an argon atmosphere at 1450°C for 2 hours to obtain a cylindrical honeycomb structure. The number of honeycomb structures required for the following tests was manufactured.

[0087] (6. Honeycomb structure specifications) The honeycomb structure obtained above had a circular end face with a diameter of 80 mm, a height (length in the cell extension direction) of 80 mm, a partition wall thickness of 125 mm, a peripheral wall thickness of 0.5 mm, and a cell density of 90 cells / cm. 2The porosity of the partition walls was 38%.

[0088] (7. Dopant Concentration in Silicon) The P concentration in silicon (Si) in the ceramics constituting the honeycomb structure portion and electrode layer of the honeycomb structure obtained above was measured according to the method described above. The ICP (inductively coupled plasma) analyzer used was a Hitachi High-Technologies Corporation model PS3510DD. The results are shown in Table 1.

[0089] 8. Dopant Concentration in Silicon Carbide The Al concentration in silicon carbide (SiC) in the ceramics constituting the honeycomb structure portion and electrode layer of the honeycomb structure obtained above was measured according to the method described above. The SEM used was a Hitachi High-Technologies S-3400N, and the SIMS used was a CAMECA NanoSIMS 50L. The results are shown in Table 1.

[0090] (9. Volume Resistivity Measurement) The volume resistivity of the honeycomb structure portion of the honeycomb structure obtained above was measured at 25° C. according to the method described above. The results are shown in Table 1.

[0091] (10. Heat Distribution) A voltage of 400 V was applied to the center of each surface of the pair of electrode layers of the honeycomb structure obtained above for 20 seconds, and the temperature distribution on both end faces and the outer wall of the honeycomb structure was observed by thermography to evaluate the uniformity of the heat generation distribution. The evaluation criteria were as follows. The results are shown in Table 1. A: When electricity is applied to the honeycomb structure, the difference between the maximum and minimum temperatures is within +150°C compared to the difference between the maximum and minimum temperatures in Example 1. B: When electricity is applied to the honeycomb structure, the difference between the maximum and minimum temperatures is greater than +150°C and within +250°C compared to the difference between the maximum and minimum temperatures in Example 1. C: When electricity is applied to the honeycomb structure, the difference between the maximum and minimum temperatures is more than +250°C compared to the difference between the maximum and minimum temperatures in Example 1, and the region where the temperature exceeds +250°C is concentrated without spreading in the circumferential direction from the electrode layer. This state results in an increase in the resistance of the electrode layer, which deteriorates the spread of current in the desired circumferential direction, and the deterioration of heat generation distribution raises concerns about the impact on cracks. D: When electricity is applied to the honeycomb structure, the difference between the maximum and minimum temperatures is more than +250°C compared to the difference between the maximum and minimum temperatures in Example 1, and the area where the temperature exceeds +250°C is concentrated at the electrode ends of the honeycomb structure. This is a state in which the resistance of the electrode layer is low, current is concentrated at the electrode ends of the honeycomb structure, heat is concentrated at the ends of the honeycomb structure, and heat distribution deteriorates, which may affect cracks.

[0092] <Comparative Examples 1 to 3 and Examples 2 to 22> The honeycomb structure was fabricated in the same manner as in Example 1, except that the amount of P doped into Si (silicon) in the honeycomb structure portion and electrode layer of the honeycomb structure was changed by changing the P concentration in the P-containing aqueous solution, and the amount of Al doped into SiC (silicon carbide) was changed by mixing SiC (silicon carbide) with different Al doping amounts. The obtained honeycomb structure was subjected to the same characteristic evaluation as in Example 1. The results are shown in Table 1.

[0093] [Table 1]

[0094] In Comparative Example 1, the volume resistivity of the electrode layer was low, and the heat generation distribution was evaluated as D. In Comparative Examples 2 and 3, the volume resistivity of the electrode layer was high, and the heat generation distribution was evaluated as C. Examples 1 to 22 are examples that satisfy one or both of the following conditions (1) and (2), and the heat generation distribution was evaluated as B or A. (1) The substrate silicon in the honeycomb structure and the electrode layer silicon in the electrode layer contain P, and the P concentration in the substrate silicon (P b ) and the P concentration in the electrode layer silicon (P e ) and the ratio (Pe / P b ) is 0.80 to 6.0. (2) The substrate silicon carbide in the honeycomb structure and the electrode layer silicon carbide in the electrode layer contain Al, and the Al concentration in the substrate silicon carbide (Al b ) and the Al concentration in the silicon carbide electrode layer (Al e ) and the ratio (Al e / Al b ) is 0.20 to 6.0.

[0095] These results show that by satisfying one or both of the conditions (1) and (2), an electrode layer having an electrical resistivity suitable for the electrical resistivity of the honeycomb structure part can be obtained, and the heat generation distribution in the honeycomb structure part can be made more uniform.

[0096] In particular, Examples 8 to 22 are examples that satisfy both conditions (1) and (2), and the heat generation distribution was evaluated as A. This result shows that it is preferable to satisfy both conditions (1) and (2). [Explanation of symbols]

[0097] 100: Electrically heated carrier 110: Honeycomb structure 112a, 112b: Electrode layer 113: Bulkhead 114:Outer wall 115: Cell 116: First end surface 118: Second end face 130: Metal terminal 220: Metal tube O: Central axis

Claims

1. a honeycomb structure having an outer peripheral wall and partition walls disposed inside the outer peripheral wall and partitioning a plurality of cells that form a fluid flow path from a first end face to a second end face; a pair of electrode layers provided on the outer surface of the outer peripheral wall, extending in a strip shape in the extending direction of the cells, and facing each other across the central axis of the honeycomb structure section; Equipped with The honeycomb structure has the honeycomb structure portion and the pair of electrode layers made of ceramics containing at least silicon and silicon carbide, and satisfies one or both of the following conditions (1) and (2): (1) The substrate silicon in the honeycomb structure and the electrode layer silicon in the electrode layer contain P, and the P concentration in the substrate silicon (P b ) and the P concentration in the electrode layer silicon (P e ) and the ratio (P e / P b ) is 0.80 to 6.

0. (2) The substrate silicon carbide in the honeycomb structure portion and the electrode layer silicon carbide in the electrode layer contain Al, and the Al concentration in the substrate silicon carbide (Al b ) and the Al concentration in the silicon carbide of the electrode layer (Al e ) and the ratio (Al e / Al b ) is 0.20 to 6.

0.

2. 2. The honeycomb structure according to claim 1, wherein both of the conditions (1) and (2) are satisfied.

3. The honeycomb structure according to claim 1 or 2, a metal terminal joined to each outer surface of the pair of electrode layers; An electrically heated carrier comprising:

4. An electrically heated carrier according to claim 3; a metal tube containing the electrically heated carrier; An exhaust gas purification device comprising:

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