JP2022087696A - Honeycomb substrate having electrodes and manufacturing method thereof - Google Patents

Abstract

To provide a honeycomb substrate having electrodes capable of suppressing delay in temperature rise of a honeycomb substrate at electric heating even if a holding member has absorbed water, and a manufacturing method thereof.SOLUTION: A honeycomb substrate 1 having electrodes includes: a honeycomb substrate 2 configured to generate heat through energization; a pair of electrodes 30 arranged facing an outer peripheral surface of the honeycomb substrate 2; and a ceramic coating film 4 covering at least one of the honeycomb substrate 2 and the electrodes 30. In the honeycomb substrate 1 having electrodes, a water absorption rate of the ceramic coating film 4 is smaller than a water absorption rate of the honeycomb substrate 2. The honeycomb substrate 2, the electrodes 30 and the ceramic coating film 4 are formed through simultaneous sintering, or the honeycomb substrate 2 and the electrodes 30 are formed through simultaneous sintering and then the ceramic coating film 4 is formed through sintering.SELECTED DRAWING: Figure 1

Description

The present invention relates to a honeycomb substrate with electrodes and a method for producing the same.

Conventionally, in a catalyst device for purifying exhaust gas generated in an internal combustion engine such as an engine, a technique of generating heat by energizing a honeycomb base material carrying a catalyst is known. In this case, in order to apply a voltage to the honeycomb base material, a pair of electrodes are provided on the outer peripheral surface of the honeycomb base material. Further, the honeycomb base material with electrodes provided with a pair of electrodes on the honeycomb base material is usually housed in a case cylinder attached in the middle of the exhaust pipe, and has a mat-like shape arranged between the case cylinder and the case cylinder. It is held by a holding member.

The holding member described above usually functions as an insulating material in a dry state. Therefore, when the holding member is in a dry state, it is possible to secure insulation between the honeycomb base material with electrodes and the case cylinder. However, when the holding member is exposed to water by the condensed water generated by cooling the water vapor contained in the exhaust gas and absorbs water, the insulating property of the holding member is lowered. Deterioration of the insulating property of the holding member causes current leakage, and it becomes difficult to energize and heat the honeycomb base material.

In Patent Document 1 prior to the present application, a case is provided in order to secure insulation between the honeycomb base material and the case cylinder even if the holding member interposed between the honeycomb base material and the case cylinder absorbs moisture. A technique for providing an insulating layer formed of an insulating material containing a glass component and provided so as not to absorb water is disclosed between a cylinder and a holding member.

Japanese Patent No. 5408341

In the above-mentioned prior art of Patent Document 1, when the holding member absorbs water, the honeycomb base material in contact with the absorbed holding member easily absorbs water. When the honeycomb base material absorbs water, the heat capacity increases by that amount, and the temperature rise of the honeycomb base material is delayed during energization heating.

The present invention has been made in view of the above problems, and is a honeycomb base material with an electrode capable of suppressing a delay in temperature rise of the honeycomb base material during energization heating even when the holding member absorbs water, and a method for manufacturing the honeycomb base material. Is intended to provide.

One aspect of the present invention is a honeycomb base material (2) that generates heat when energized.
A pair of electrodes (30) provided facing the outer peripheral surface of the honeycomb base material, and
It has a honeycomb base material and a ceramic coating (4) covering at least one of the electrodes.
The water absorption rate of the ceramic film is smaller than the water absorption rate of the honeycomb base material.
It is on the honeycomb base material (1) with electrodes.

Another aspect of the present invention is the method for manufacturing a honeycomb base material with electrodes.
The honeycomb substrate, the electrodes, and the ceramic coating are formed by simultaneous sintering, or
After the honeycomb base material and the electrode are formed by simultaneous sintering, the ceramic film is formed by sintering.
It is in the method of manufacturing a honeycomb base material with electrodes.

The honeycomb substrate with electrodes has the above configuration. Therefore, the honeycomb substrate with electrodes can suppress the water absorption of the honeycomb substrate due to the holding member that has absorbed water, as compared with the honeycomb substrate with electrodes that is not covered with the ceramic coating by the ceramic coating. Therefore, according to the honeycomb base material with electrodes, an increase in heat capacity due to water absorption of the honeycomb base material can be suppressed, and a delay in temperature rise of the honeycomb base material during energization heating can be suppressed.

The method for manufacturing a honeycomb substrate with electrodes has the above configuration. Therefore, according to the method for manufacturing the honeycomb substrate with electrodes, the honeycomb substrate with electrodes can be obtained, which can suppress the delay in the temperature rise of the honeycomb substrate at the time of energization heating even when the holding member absorbs water.

The reference numerals in parentheses described in the scope of claims and the means for solving the problem indicate the correspondence with the specific means described in the embodiments described later, and limit the technical scope of the present invention. It's not a thing.

FIG. 1 is a diagram schematically showing an orthogonal cross section orthogonal to the substrate axial direction of the honeycomb substrate with electrodes according to the first embodiment. FIG. 2 is a diagram schematically showing an example of an electrically heated catalyst device to which a honeycomb substrate with electrodes according to the first embodiment is applied. FIG. 3 is a cross-sectional view taken along the line III-III in FIG. FIG. 4 is a diagram for explaining the action and effect of the honeycomb substrate with electrodes according to the first embodiment. FIG. 5 is a diagram for explaining a method of measuring the water absorption rate of the ceramic film. FIG. 6 is a diagram schematically showing an orthogonal cross section orthogonal to the substrate axial direction of the honeycomb substrate with electrodes according to the second embodiment. FIG. 7 is a diagram showing an example of a situation in which water is absorbed by the ceramic film when measuring the water absorption rate of the ceramic film in an experimental example.

The honeycomb substrate with electrodes of the first embodiment will be described with reference to FIGS. 1 to 5. As illustrated in FIGS. 1 to 3, the honeycomb base material 1 with electrodes of the present embodiment has a honeycomb base material 2 that generates heat by energization, a pair of electrodes 30, and a ceramic coating 4. ..

The exhaust gas F generated in an internal combustion engine (not shown) such as an engine, as illustrated in FIG. 2, in a state where the catalyst (platinum, palladium, rhodium, etc.) is supported on the honeycomb base material 1 with an electrode. Can be applied to the electric heating type catalyst device 9 provided in the exhaust pipe 91 for purifying. In FIG. 2, the direction of the arrow G is the gas flow direction G in the honeycomb substrate 1 with electrodes.

Specifically, in FIGS. 2 and 3, the case cylinder 92 of the electrically heated catalyst device 9 is attached in the middle of the exhaust pipe 91, and the honeycomb base material 1 with electrodes is housed in the case cylinder 92. An example is shown. A holding member 93 is arranged between the honeycomb base material 1 with electrodes and the case cylinder 92, and the honeycomb base material 1 with electrodes is held by the holding member 93. The holding member 93 is made of, for example, alumina fiber or the like in a matte shape, and has an insulating property in a dry state. The holding member 93 has water absorption. That is, the honeycomb base material 1 with electrodes is held and used by the holding member 93 having water absorption.

Further, FIGS. 2 and 3 show an example in which the electrode terminals 31 are electrically connected to each of the electrodes 30 in the honeycomb substrate 1 with electrodes. The end of the electrode terminal 31 opposite to the electrode 30 side protrudes to the outside of the holding member 93. The portion of the electrode terminal 31 protruding from the holding member 93 is arranged in the electrode chamber 921 provided in the case cylinder 92 and is protected from the outside. Further, FIG. 2 shows an example in which electric power from a power source 94 such as a battery is supplied to a pair of electrode terminals 31 via a switching circuit 95, a cutoff circuit 96, and a lead wire 97. There is. In the present embodiment, a voltage is applied between the pair of electrodes 30 via the pair of electrode terminals 31, and the honeycomb base material 2 can generate heat by energization by the voltage. The method of applying the external voltage may be any method such as a direct current method, an alternating current method, and a pulse method. A gas sealing material 98 for preventing leakage of the exhaust gas F is provided between the electrode chamber 921 and the lead wire 97. Examples of the material of the gas encapsulant 98 include ceramics and glass.

In the honeycomb base material 1 with electrodes, as illustrated in FIGS. 1 and 2, the honeycomb base material 2 has a partition wall 22 for partitioning a plurality of cells 21 and an outer peripheral wall 23 surrounding the outer periphery of the partition wall 22. It can be configured to be provided. The cell 21 is a flow path through which the exhaust gas F shown in FIG. 2 flows. For example, in FIG. 1, the partition wall 22 divides a plurality of square-shaped cells 21 in an orthogonal cross section (hereinafter, may be simply referred to as “orthogonal cross section”) orthogonal to the substrate axis of the honeycomb base material 2. An example of formation is shown. That is, in FIG. 1, the partition walls 22 are formed in a grid pattern. The partition wall 22 may also be configured to partition and form a plurality of cells 21 having a known shape, such as a plurality of hexagonal cells. In FIG. 1, the partition wall 22 is represented by a line for convenience, and the wall thickness and the like are omitted. Further, the substrate axis is in the same direction as the gas flow direction G shown in FIG.

The honeycomb base material 2 can have a cross-sectional shape such as a circular shape, an elliptical shape, a rectangular shape, or a race track shape when viewed in an orthogonal cross section. 1 and 2 show an example of a honeycomb base material 2 having a circular cross-sectional shape. In the race track shape, when viewed in an orthogonal cross section, the outer peripheral wall 23 has a pair of side surface portions (not shown) arranged in parallel in a state of being separated from each other, and an end edge on the same side of the pair of side surface portions. It is a shape having a pair of circular portions (not shown) connecting the spaces.

In the honeycomb base material 1 with electrodes, the electrodes 30 are provided so as to face the outer peripheral surface of the honeycomb base material 2. That is, the electrode 30 is provided so as to face the outer surface of the outer peripheral wall 23 of the honeycomb base material 2. Therefore, on the outer peripheral surface of the honeycomb base material 2, there are a surface portion on which the electrode 30 is formed and a surface portion on which the electrode 30 is not formed. In the honeycomb base material 2 having the above-mentioned cross-sectional shape of a race track, the electrodes 30 can be provided on the outer peripheral surface of each circular portion constituting the outer peripheral wall 23. As illustrated in FIG. 2, the electrode 30 can be formed so as to extend in the axial direction of the base material on the outer peripheral surface of the honeycomb base material 2. The electrode 30 can be bonded to the outer peripheral surface of the honeycomb base material 2. The electrode terminal 31 described above may or may not be bonded to the electrode 30. The electrode terminal 31 can be arranged at the center on the surface of the electrode 30. The electrode terminal 31 can be formed in a rod shape or the like, for example.

In the honeycomb base material 1 with electrodes, the ceramic coating 4 covers at least one of the honeycomb base material 2 and the electrodes 30. That is, the ceramic coating 4 may not cover the surface of the electrode 30, but may cover only the surface portion of the outer peripheral surface of the honeycomb base material 2 where the electrode 30 is not formed, or may cover only the surface of the electrode 30. Alternatively, the outer peripheral surface of the honeycomb base material 2 may cover both the surface portion on which the electrode 30 is not formed and the surface of the electrode 30. 1 and 2 show an example in which the ceramic coating 4 directly covers both the surface portion of the outer peripheral surface of the honeycomb base material 2 on which the electrode 30 is not formed and the surface of the electrode 30. According to this configuration, it becomes easier to suppress the water absorption of the honeycomb base material 2 caused by the water-absorbing holding member 93, as compared with the case where the ceramic coating 4 directly covers either the honeycomb base material 2 or the electrode 30. Further, FIGS. 1 to 3 show an example in which the ceramic coating 4 directly covers not only the honeycomb base material 2 and the electrode 30 but also the electrode terminal 31. Specifically, the ceramic coating 4 can cover the surface of the electrode terminal 31 except for the connection portion between the electrode terminal 31 and the lead wire 97. According to the configuration in which the ceramic coating 4 covers the honeycomb base material 2, the electrode 30, and the electrode terminal 31, the water-absorbing holding member 93 is caused as compared with the case where the ceramic coating 4 does not cover the electrode terminal 31. It becomes easy to suppress the water absorption of the honeycomb base material 2. As for each portion covered by the ceramic coating 4, the entire portion may be entirely covered by the ceramic coating 4, or each portion may be partially covered by the ceramic coating 4. The former is preferable. Further, the ceramic coating 4 may further cover the end face of the honeycomb base material 2, specifically, the surface of the partition wall 22 on the end face of the honeycomb base material 2.

Here, in the honeycomb base material 1 with electrodes, the water absorption rate of the ceramic film 4 is smaller than the water absorption rate of the honeycomb base material 2.

The honeycomb substrate with electrodes not covered with the ceramic coating 4 is used as the honeycomb substrate with electrodes of Comparative Form 1. Further, the honeycomb base material with electrodes having the water absorption rate of the ceramic film 4 equal to or higher than the water absorption rate of the honeycomb base material 2 is used as the honeycomb base material with electrodes of Comparative Form 2. In the honeycomb base material with electrodes of Comparative Form 1 and Comparative Form 2, when the holding member 93 absorbs water, the honeycomb base material 2 in contact with the water-absorbed holding member 93 absorbs water. When the honeycomb base material 2 absorbs water, the heat capacity increases by that amount, and the temperature rise of the honeycomb base material 2 is delayed during energization heating. That is, when the honeycomb base material 2 absorbs water, as shown in FIG. 4, the water absorbed by the honeycomb base material 2 and the time T1 for warming the honeycomb base material 2 and the honeycomb base material 2 absorb the water during energization heating. Extra time T2 is required to blow off the water. Therefore, the honeycomb base materials with electrodes of Comparative Forms 1 and 2 have a delay in the time required for energizing and heating to a predetermined temperature. On the other hand, according to the honeycomb base material 1 with electrodes of the present embodiment, the ceramic coating 4 can suppress the water absorption of the honeycomb base material 2 caused by the water-absorbing holding member 93. Therefore, according to the honeycomb base material 1 with electrodes of the present embodiment, the increase in heat capacity due to water absorption of the honeycomb base material 2 is suppressed, and as illustrated in FIG. 4, the temperature of the honeycomb base material 2 rises during energization heating. Delay can be suppressed.

Specifically, the water absorption rate of the ceramic film 4 can be 8% or less. According to this configuration, the highly dense ceramic film 4 makes it possible to reliably suppress the movement of water from the water-absorbing holding member 93 to the honeycomb base material 2. Therefore, according to this configuration, even when the holding member 93 absorbs water, it is possible to ensure that the delay in the temperature rise of the honeycomb base material 2 at the time of energization heating is suppressed.

The water absorption rate of the ceramic film 4 is preferably 7% or less, more preferably 6% or less, still more preferably 5% or less, still more preferably 4%, from the viewpoint of improving the denseness of the ceramic film 4. Below, even more preferably, it can be 3% or less.

The water absorption rate of the ceramic film 4 can be measured as follows. As shown in FIG. 5A, a sample S1 containing a part of the ceramic film 4 is cut out from the honeycomb substrate 1 with electrodes. For example, when the ceramic coating 4 directly covers the honeycomb base material 2, the sample S1 includes a part of the ceramic coating 4 and a part of the honeycomb base material 2. Although the ceramic coating 4 in the sample S1 is omitted in FIG. 5A, it is assumed that the ceramic coating 4 is formed on the upper surface side of the sample S1. Next, the mass of the sample S1 is measured. Next, as shown in FIG. 5B, distilled water W is dropped onto the upper surface of the sample S1 using a pipette P. Next, the distilled water W is spread over an area of 20 mm × 20 mm and left at room temperature for 10 minutes. Then, as shown in FIG. 5C, a paper waste K is used to wipe off the distilled water W remaining on the surface of the sample S1 without being absorbed. Then, the mass of the sample S1 is measured again. Then, the mass increase of the sample S1 is taken as the water absorption mass of the ceramic film 4. The water absorption rate (%) of the ceramic film 4 can be calculated from the formula of 100 × (mass of water absorption of ceramic film 4 by sample S1) / (mass of ceramic film 4 before water absorption by sample S1). The mass of the ceramic film 4 before water absorption can be calculated by the following formula. Mass of the ceramic film 4 before water absorption = true density of the ceramic film 4 × (1-porosity of the ceramic film 4 / 100) × coverage area of the ceramic film 4 on the sample S1 × average film thickness of the ceramic film 4. In this formula, the true density of the ceramic film 4 is a value measured by a pycnometer using a sample of a part of the ceramic film 4 peeled off from the sample S1. For the porosity of the ceramic coating 4, a value calculated from the pore volume obtained by the mercury intrusion method using the same sample is used. For the covering area of the ceramic coating 4 on the sample S1, a value calculated by geometric calculation is used. The average film thickness of the ceramic film 4 is an arithmetic average value of the film thicknesses at 9 points in each cross section obtained by performing microscope observation on the side 4 cross sections of the sample S1.

In the honeycomb base material 1 with electrodes, the water absorption rate of the honeycomb base material 2 can be 10% or more. In the honeycomb base material 1 with electrodes using the honeycomb base material 2 having a high water absorption rate as described above, the ceramic coating 4 is more effective than the honeycomb base material 1 with electrodes in which the water absorption rate of the honeycomb base material 2 is less than 10%. Easy to work. The water absorption rate of the honeycomb base material 2 can be preferably 12% or more, more preferably 15% or more, still more preferably 18% or more. The water absorption rate of the honeycomb base material 2 is preferably 30% or less, more preferably 28% or less, still more preferably 25% or less, from the viewpoint of suppressing a decrease in the strength of the honeycomb base material due to the increase in pores. Can be done.

The water absorption rate of the honeycomb base material 2 can be measured as follows. Specifically, a sample of the honeycomb base material 2 is cut out from the honeycomb base material 1 with electrodes. The mass of this sample is then measured. The sample is then immersed in pure water and degassed by ultrasonic waves for 2 minutes. The degassed sample is taken out from the water, and the water on the surface of the sample and the water aggregated in the capillaries inside the cell are removed by an air blow from a distance of about 10 cm. The mass of the sample is then measured again. Then, the mass increase of the sample is taken as the water absorption mass (measured value) of the honeycomb base material 2. After drying the sample in the oven at 110 ° C. for 24 hours, the same measurement is repeated twice. Then, the arithmetic mean value of the water absorption mass (measured value) obtained by the three measurements is taken as the water absorption mass of the honeycomb base material 2. The water absorption rate (%) of the honeycomb base material 2 can be calculated from the formula of 100 × (mass of water absorption of honeycomb base material 2 by sample) / (mass of honeycomb base material 2 before water absorption by sample).

In the honeycomb base material 1 with electrodes, the film thickness of the ceramic film 4 can be 100 μm or more. When the thickness of the ceramic film 4 is 100 μm or more, the thickening of the ceramic film 4 makes it possible to increase the diffusion distance when water diffuses into the honeycomb base material 2 inside the ceramic film 4. As a result, it becomes easier to suppress the water absorption of the honeycomb base material 2. The film thickness of the ceramic film 4 can be preferably 150 μm or more, more preferably 200 μm or more, still more preferably 250 μm or more, from the viewpoint of suppressing water absorption of the honeycomb base material 2 and ensuring impact strength. The film thickness of the ceramic film 4 can be preferably 500 μm or less, more preferably 450 μm or less, still more preferably 400 μm or less, from the viewpoint of suppressing cracking of the ceramic film 4 due to thermal stress. The film thickness of the ceramic coating 4 is an arithmetic mean value of the thickness measurement values of the ceramic coating 4 measured at arbitrary 10 points in an orthogonal cross section orthogonal to the substrate axis of the honeycomb base material 2.

In the honeycomb base material 1 with electrodes, the ceramic coating 4 can be specifically formed of insulating ceramics. According to this configuration, it is possible to suppress the leakage of current to the outside of the honeycomb base material 2, and it becomes difficult for the current to flow through the holding member 93 that has absorbed water. Therefore, according to this configuration, the honeycomb base material 1 with an electrode that does not easily impair the temperature raising function at the time of energization heating can be obtained.

The ceramic coating 4 may be, for example, SiO ₂ (including silica and fused silica), Al ₂ O ₃ (alumina), TiO ₂ (titania), cordierite, SiC (silicon carbide), mullite, ZrO ₂ (zirconia) and the like. Insulating ceramics can be included. These may be contained alone or in combination of two or more. It is preferable that the main component of the ceramic film 4 is SiO ₂ . Among many insulating ceramics, SiO ₂ has high meltability and easily forms a dense film. Therefore, according to this configuration, it is possible to form a dense ceramic film 4 having a lower water absorption rate, and it is possible to ensure the above-mentioned action and effect. The main component of the ceramic film 4 is a component having the highest content in mass% among the components constituting the ceramic film 4.

In the honeycomb base material 1 with electrodes, both the honeycomb base material 2 and the electrodes 30 can be configured to include a conductive material and an insulating material. Specifically, the honeycomb base material 2 and the electrode 30 can be formed of ceramics containing a conductive material and an insulating material. Further, the electrode terminal 31 may be configured to include a conductive material and an insulating material. Specifically, the electrode terminal 31 can be formed of ceramics containing a conductive material and an insulating material. In addition to the above, the electrode terminal 31 may be formed of, for example, a metal or the like.

The conductive material contained in the honeycomb base material 2, the electrode 30, and the electrode terminal 31 is doped with a conductive element such as Si (silicon), an oxide containing Si and B (boron), and Si. Examples thereof include various resistors such as silicide compounds such as SiC (silicon carbide) and metal silicide, nickel-chromium alloys, and the like. These may be contained alone or in combination of two or more. Examples of the insulating material contained in the honeycomb base material 2, the electrode 30, and the electrode terminal 31 include SiO ₂ (including silica and molten silica), Al ₂ O ₃ (alumina), and TIO ₂ (titania). Examples thereof include cordierite, MgO (magnesia), ZrO ₂ (zirconia), mullite, and SiC (silicon carbide). These may be contained alone or in combination of two or more. The honeycomb base material 2 and the electrode 30 may be made of the same material or may be made of different materials. Further, the electrode 30 and the electrode terminal 31 may be formed of the same material or may be formed of different materials.

As described above, when the main component of the ceramic coating 4 is SiO ₂ , the ceramic coating 4 may cover the honeycomb base material 2 and the honeycomb base material 2 may include SiO ₂ . According to this configuration, since the ceramic coating 4 and the honeycomb base material 2 contain the same kind of material, the SiO ₂ is covalently bonded between the ceramic coating 4 and the honeycomb base material 2 at the time of manufacturing the honeycomb base material 1 with an electrode. It can promote the formation. Therefore, according to this configuration, the bonding strength of the ceramic film 4 is increased, and it becomes easy to form the ceramic film 4 on the outer peripheral surface of the honeycomb base material 2.

Further, when the main component of the ceramic film 4 is SiO ₂ , the ceramic film 4 may cover the electrode 30 and the electrode 30 may include the SiO ₂ . According to this configuration, since the ceramic coating 4 and the electrode 30 contain the same kind of material, the formation of a covalent bond of SiO ₂ between the ceramic coating 4 and the electrode 30 is promoted at the time of manufacturing the honeycomb base material 1 with an electrode. Can be done. Therefore, according to this configuration, the bonding strength of the ceramic film 4 is increased, and it becomes easy to form the ceramic film 4 on the surface of the electrode 30.

In these configurations, the content of SiO ₂ contained in the electrode 30 is preferably 30% by mass or less, more preferably 25% by mass or less, still more preferably 20% by mass or less, still more preferably 15% by mass. % Or less, and even more preferably 10% by mass or less. In this case, it is advantageous for improving the bonding strength of the ceramic film 4, ensuring the film-forming property of the ceramic film 4, and heat generation of the honeycomb base material 2. Further, the content of SiO ₂ contained in the electrode 30 can be preferably 5% by mass or more from the viewpoint of current shunting property to the honeycomb base material 2 and energy efficiency. Further, the content of SiO ₂ contained in the honeycomb base material 2 is preferably 30% by mass or more, more preferably 40% by mass or more, still more preferably, from the viewpoint of improving the thermal impact resistance of the honeycomb base material 2. Can be 50% by mass or more. Further, the content of SiO ₂ contained in the honeycomb base material 2 is preferably 80% by mass or less, more preferably 70% by mass or less, still more preferably 60% by mass or less, from the viewpoint of ensuring electric resistance. can do. According to these configurations, it becomes easy to adjust the sum of the electric resistances of the honeycomb base material 2 and the electrode 30 to a range in which the temperature can be efficiently raised by the vehicle-mounted power supply mounted on the vehicle.

When the main component of the ceramic film 4 is SiO ₂ , the ceramic film 4 covers the honeycomb base material 2, the honeycomb base material 2 contains a conductive material, and the main component of the conductive material is Si. It can be configured. According to this configuration, it is possible to promote the formation of a covalent bond between the Si of the honeycomb base material 2 and the SiO ₂ of the ceramic coating 4 at the time of manufacturing the honeycomb base material 1 with electrodes. Therefore, according to this configuration, the bonding strength of the ceramic film 4 is increased, and it becomes easy to form the ceramic film 4 on the outer peripheral surface of the honeycomb base material 2. The main component of the conductive material contained in the honeycomb base material 2 is a component having the highest content in mass% among the components constituting the conductive material contained in the honeycomb base material 2.

When the main component of the ceramic film 4 is SiO ₂ , the ceramic film 4 covers the electrode 30, the electrode 30 contains a conductive material, and the main component of the conductive material is Si. Can be done. According to this configuration, it is possible to promote the formation of a covalent bond between the Si of the electrode 30 and the SiO ₂ of the ceramic coating 4 at the time of manufacturing the honeycomb base material 1 with an electrode. Therefore, according to this configuration, the bonding strength of the ceramic film 4 is increased, and it becomes easy to form the ceramic film 4 on the surface of the electrode 30. The main component of the conductive material contained in the electrode 30 is a component having the highest content in mass% among the components constituting the conductive material contained in the electrode 30.

In the honeycomb base material 1 with electrodes, the sum of the electric resistances of the honeycomb base material 2 and the electrodes 30 is preferably increased from the viewpoint that, for example, the temperature can be efficiently raised by the vehicle-mounted power supply mounted on the vehicle. It can be 1Ω or more and 100Ω or less, more preferably 1Ω or more and 80Ω or less, and further preferably 1Ω or more and 60Ω or less. The honeycomb base material 1 with electrodes having electrical resistance as described above can efficiently raise the temperature according to the voltage specifications of the vehicle-mounted power supply, so that it does not require a transformer or the like, and the catalyst is activated economically at an early stage. Can be planned.

(Embodiment 2)
The honeycomb substrate with electrodes of the second embodiment will be described with reference to FIG. In addition, among the reference numerals used in the second and subsequent embodiments, the same reference numerals as those used in the above-mentioned embodiments represent the same components and the like as those in the above-mentioned embodiments, unless otherwise specified.

As illustrated in FIG. 6, the honeycomb base material 1 with electrodes of the present embodiment is an example in which the ceramic coating 4 covers the honeycomb base material 2 and the electrodes 30 and does not cover the electrode terminals 31. Other configurations are the same as those in the first embodiment. Also in this case, it is possible to suppress the water absorption of the honeycomb base material 2 caused by the water-absorbing holding member 93. Therefore, according to the honeycomb base material 1 with electrodes of the present embodiment, the increase in heat capacity due to water absorption of the honeycomb base material 2 can be suppressed, and the delay in the temperature rise of the honeycomb base material 2 at the time of energization heating can be suppressed. Other effects are the same as in the first embodiment.

(Embodiment 3)
The method for manufacturing the honeycomb base material with electrodes according to the third embodiment will be described.

The method for manufacturing a honeycomb base material with electrodes according to the present embodiment is a manufacturing method capable of manufacturing the honeycomb base material with electrodes according to the first or second embodiment described above. In the method for manufacturing a honeycomb base material with electrodes of the present embodiment, the honeycomb base material, the electrodes, and the ceramic coating are formed by simultaneous sintering. This will be described in detail below. This will be described in detail below.

As a method of forming the honeycomb base material, the electrode, and the ceramic film by simultaneous sintering, for example, an electrode forming material is applied to the calcined (temporarily fired) honeycomb base material, and then the ceramic film forming material is applied. Examples thereof include a method of applying and then firing for degreasing as necessary, and then simultaneously sintering the calcined honeycomb base material, the electrode forming material, and the ceramic film forming material. can. The ceramic film forming material is applied to the exposed portion of the outer peripheral surface of the calcined honeycomb base material without the electrode forming material applied, and the surface of the applied electrode forming material. At least one of them. When forming a ceramic film on the surface of the electrode terminal, the molded electrode terminal forming material may be attached to the electrode forming material, and the ceramic film forming material may also be applied to the surface of the electrode terminal forming material. good. In this case, the honeycomb base material, the electrode, the ceramic coating, and the electrode terminal can be formed by simultaneous sintering. For details of the portion where the ceramic film is formed, the first and second embodiments can be referred to as appropriate.

The calcined honeycomb base material has been calcined, but has not yet been main sintered. For the pre-baked honeycomb base material, for example, a material for forming a honeycomb base material is molded into a honeycomb shape, the obtained honeycomb molded body is dried, and if necessary, fired for degreasing, and 1000 under an argon atmosphere. It can be prepared by calcining at a temperature of ° C. or higher and 1300 ° C. or lower, preferably 1250 ° C. or higher and 1300 ° C. or lower. The firing for degreasing is a firing performed to remove organic components (same below), for example, in an oxidizing atmosphere, at a temperature of 500 ° C. or higher and 800 ° C. or lower, preferably 600 ° C. or higher and 700 ° C. or lower. Can be carried out.

The material for forming the honeycomb base material is a material for forming the honeycomb base material. Specifically, the material for forming the honeycomb base material can be prepared in the form of a clay containing, for example, a conductive material, an insulating material, and a binder. The electrode forming material is a material for forming an electrode. Specifically, the electrode forming material can be prepared in the form of a paste containing, for example, a conductive material, an insulating material, and a binder. The electrode terminal forming material is a material for forming an electrode terminal. Specifically, the material for forming the electrode terminal can be prepared in the form of a clay containing, for example, a conductive material, an insulating material, and a binder. The material for forming a ceramic film is a material for forming a ceramic film. Specifically, the material for forming a ceramic film can be prepared in the form of a paste containing, for example, an insulating ceramic and a binder.

More specifically, the material for forming a ceramic film may contain SiO ₂ so that the main component of the ceramic film is SiO ₂ . Further, the material for forming the honeycomb base material may contain SiO ₂ so that the insulating material in the honeycomb base material containing the conductive material and the insulating material contains SiO ₂ . Further, the material for forming the honeycomb base material may contain Si so that the main component of the conductive material in the honeycomb base material including the conductive material and the insulating material is Si.

The simultaneous sintering can be performed at a temperature higher than the calcining temperature. The temperature of the simultaneous sintering can be preferably a temperature higher than the calcining temperature by 10 ° C. or more. Specifically, the simultaneous sintering can be carried out under an argon atmosphere at a temperature of 1300 ° C. or higher, preferably 1325 ° C. or higher and 1375 ° C. or lower.

According to the method for manufacturing a honeycomb base material with electrodes of the present embodiment, by simultaneous sintering, a bond between the honeycomb base material and the electrode covered with the ceramic coating and the ceramic coating is formed by mutual sintering. It is generated and the bonding strength of the ceramic film is increased. Therefore, according to the method for manufacturing the honeycomb substrate with electrodes of the present embodiment, it becomes easy to form a ceramic film. Further, according to the method for manufacturing a honeycomb substrate with electrodes of the present embodiment, the water absorption rate of the ceramic film formed by the simultaneous sintering can be further lowered.

(Embodiment 4)
The method for manufacturing the honeycomb substrate with electrodes according to the fourth embodiment will be described.

The method for manufacturing a honeycomb base material with electrodes according to the present embodiment is a manufacturing method capable of manufacturing the honeycomb base material with electrodes according to the first or second embodiment described above. In the method for manufacturing a honeycomb base material with electrodes of the present embodiment, the honeycomb base material and the electrodes are formed by simultaneous sintering, and then a ceramic film is formed by sintering. That is, in the present embodiment, the honeycomb base material and the electrode are first formed by simultaneous sintering, and then the ceramic film is formed by post-sintering. This will be described in detail below.

As a method of forming a ceramic film by sintering after forming a honeycomb base material and an electrode by simultaneous sintering, for example, a material for forming an electrode is applied to a temporarily fired honeycomb base material, and then, if necessary. After firing for degreasing, the calcined honeycomb substrate and the electrode forming material are simultaneously sintered, then the ceramic film forming material is applied, and then for degreasing as necessary. And then, a method of sintering a material for forming a ceramic film can be exemplified. For other configurations, the third embodiment can be referred to as appropriate.

According to the method for manufacturing a honeycomb base material with electrodes of the present embodiment, the bonding strength of the ceramic film is increased, and the ceramic film can be easily formed.

(Experimental example)
-Preparation of sample 1-
Silicon powder as a conductive material, boric acid, and silica powder as an insulating material were mixed at a mass ratio of 18: 6: 76, and 4% by mass of methyl cellulose was added as a binder to the obtained mixture, and water was added. , A material for forming a clay-like honeycomb base material was prepared by kneading sufficiently.

Further, silicon powder as a conductive material, boric acid, and silica powder as an insulating material were mixed at a mass ratio of 40:10:50, and 1.87% by mass of methyl cellulose was added as a binder to the obtained mixture. , Water was added and mixed thoroughly to prepare a paste-like material for forming an electrode.

Further, 1.87% by mass of methyl cellulose as a binder was added to silica powder as an insulating material, water was added, and the mixture was sufficiently mixed to prepare a paste-like material for forming a ceramic film.

A honeycomb molded body was obtained by molding the material for forming a honeycomb base material into a honeycomb shape by extrusion molding. Then, after the honeycomb molded body was dried, it was degreased and fired at a temperature of 600 ° C. in an atmospheric atmosphere. Next, the degreased and fired honeycomb molded body was calcined at a temperature of 1250 ° C. under an argon atmosphere to obtain a calcined honeycomb base material. Next, the electrode forming material was applied to the outer peripheral surface of the calcined honeycomb base material, and then the ceramic film forming material was further applied. In this example, the coating of the ceramic film forming material is applied to the exposed portion of the outer peripheral surface of the calcined honeycomb base material without the electrode forming material being applied, and the applied electrode forming material. Both surfaces. At this time, the coating of the ceramic film forming material was adjusted so that the formed ceramic film had a film thickness of 100 μm. In this example, the formation of the electrode terminals is omitted for the sake of simplification of the test. Next, the calcined honeycomb base material coated with the electrode forming material and the ceramic film forming material was degreased and fired at a temperature of 600 ° C. in an atmospheric atmosphere. Next, the degreased and fired honeycomb base material was main-baked at a temperature of 1350 ° C. under an argon atmosphere to obtain a honeycomb base material with an electrode of sample 1 (sum of electrical resistances of the honeycomb base material and the electrodes: 8.4 Ω). Got That is, in this example, the honeycomb base material, the electrode, and the ceramic coating were formed by simultaneous sintering.

-Preparation of sample 2-
Each material was prepared in the same manner as in the preparation of the honeycomb base material with electrodes of Sample 1, and a calcined honeycomb base material was formed. Next, after applying the electrode forming material to the outer peripheral surface of the calcified honeycomb base material, the honeycomb base material and the electrode were simultaneously sintered by firing at a temperature of 1350 ° C. in an argon atmosphere. Next, the ceramic film forming material was applied to both the exposed portion of the outer peripheral surface of the honeycomb base material without forming the electrode and the surface of the electrode. At this time, the coating of the ceramic film forming material was adjusted so that the formed ceramic film had a film thickness of 100 μm. Next, this was degreased and fired at a temperature of 600 ° C. under an atmospheric atmosphere, and then fired at a temperature of 1350 ° C. under an argon atmosphere to sinter the ceramic film, and the honeycomb substrate with electrodes of Sample 2 ( The sum of the electrical resistances of the honeycomb substrate and the electrodes: 8.1Ω) was obtained. That is, in this example, the honeycomb base material and the electrode were first formed by simultaneous sintering, and then the ceramic film was formed by post-sintering.

-Preparation of sample 1C-
A honeycomb substrate with electrodes (sum of electrical resistances of the honeycomb substrate and the electrodes: 8.6 Ω) with electrodes of sample 1C was obtained in the same manner except that the ceramic film was not formed in the preparation of sample 2.

-Measurement of water absorption of ceramic coating-
By the above-mentioned method, the water absorption rate of the ceramic coating in each honeycomb substrate with electrodes was measured. Note that FIG. 7 shows a state in which distilled water is spread over an area of 20 mm × 20 mm in sample S1 and left at room temperature for 10 minutes at the time of measuring the water absorption rate of the ceramic film.

-Measurement of water absorption of honeycomb base material-
By the method described above, the water absorption rate of the honeycomb base material in each honeycomb base material with electrodes was measured.

-Measurement of total water absorption of honeycomb substrate with electrodes-
The mass of the honeycomb substrate with electrodes was measured. Next, the honeycomb substrate with electrodes was immersed in pure water and degassed by ultrasonic waves for 2 minutes. The degassed honeycomb substrate with electrodes was taken out from the water, and the moisture on the surface of the honeycomb substrate with electrodes and the moisture aggregated in the capillaries inside the cell were removed by air blowing from a distance of about 10 cm. Then, the mass of the honeycomb substrate with electrodes was measured again. Then, the mass increase of the honeycomb base material with electrodes was taken as the total water absorption mass (measured value) of the honeycomb base material with electrodes. The honeycomb substrate with electrodes was dried at 110 ° C. for 24 hours in an oven, and then the same measurement was repeated twice. Then, the arithmetic mean value of the total water absorption mass (measured value) obtained by the three measurements was taken as the total water absorption mass of the honeycomb substrate with electrodes. The total water absorption rate (%) of the honeycomb substrate with electrodes was calculated from the formula of 100 × (total water absorption mass of the honeycomb substrate with electrodes) / (mass of the honeycomb substrate with electrodes before water absorption).

Table 1 summarizes the above test results.

According to Table 1, Sample 1C does not have a ceramic coating. Therefore, the sample 1C has a high total water absorption rate. That is, it can be said that it is difficult for the sample 1C to suppress the water absorption of the honeycomb base material due to contact with the water-absorbing holding member.

On the other hand, in Sample 1 and Sample 2, at least one of the honeycomb base material and the electrode is covered with a ceramic film having a water absorption rate smaller than that of the honeycomb base material. Therefore, Sample 1 and Sample 2 have a lower total water absorption rate than Sample 1C. That is, it can be said that the sample 1 and the sample 2 can suppress the water absorption of the honeycomb base material due to contact with the water-absorbing holding member as compared with the sample 1C. Therefore, according to Sample 1 and Sample 2, it can be said that the increase in heat capacity due to water absorption of the honeycomb base material is suppressed, and the delay in the temperature rise of the honeycomb base material during energization heating can be suppressed.

Further, when comparing the results of Sample 1 and Sample 2, the honeycomb base material, the electrode, and the ceramics are compared with the case where the honeycomb base material and the electrode are first formed by simultaneous sintering and then the ceramic film is formed by post-sintering. It was confirmed that a honeycomb substrate with an electrode having a ceramic coating having a lower water absorption rate could be obtained by forming the coating by simultaneous sintering.

The present invention is not limited to each of the above embodiments and experimental examples, and various modifications can be made without departing from the gist thereof. In addition, each configuration shown in each embodiment and each experimental example can be arbitrarily combined.

1 Honeycomb base material with electrodes 2 Honeycomb base material 30 Electrodes 4 Ceramic coating

Claims (9)

Honeycomb base material (2) that generates heat when energized,
A pair of electrodes (30) provided facing the outer peripheral surface of the honeycomb base material, and
It has a honeycomb base material and a ceramic coating (4) covering at least one of the electrodes.
The water absorption rate of the ceramic film is smaller than the water absorption rate of the honeycomb base material.
Honeycomb substrate with electrodes (1). The water absorption rate of the ceramic film is 8% or less.
The honeycomb substrate with electrodes according to claim 1. The thickness of the ceramic film is 100 μm or more.
The honeycomb substrate with electrodes according to claim 1 or 2. The water absorption rate of the honeycomb base material is 10% or more.
The honeycomb substrate with electrodes according to any one of claims 1 to 3. The main component of the ceramic film is SiO ₂ .
The honeycomb substrate with electrodes according to any one of claims 1 to 4. The ceramic coating covers the honeycomb substrate, and the ceramic coating covers the honeycomb base material.
The honeycomb substrate contains SiO ₂ .
The honeycomb substrate with electrodes according to claim 5. The ceramic coating covers the honeycomb substrate, and the ceramic coating covers the honeycomb base material.
The honeycomb base material contains a conductive material and contains
The main component of the conductive material is Si.
The honeycomb substrate with electrodes according to claim 5 or 6. The sum of the electrical resistances of the honeycomb substrate and the electrodes is in the range of 1Ω or more and 100Ω or less.
The honeycomb base material with an electrode according to any one of claims 1 to 7. The method for manufacturing a honeycomb substrate with electrodes according to any one of claims 1 to 8.
The honeycomb substrate, the electrodes, and the ceramic coating are formed by simultaneous sintering, or
After the honeycomb base material and the electrode are formed by simultaneous sintering, the ceramic film is formed by sintering.
A method for manufacturing a honeycomb base material with electrodes.

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