WO2021111869A1 - Electrical resistor, honeycomb structure, and electrically heated catalyst device - Google Patents

Electrical resistor, honeycomb structure, and electrically heated catalyst device Download PDF

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Publication number
WO2021111869A1
WO2021111869A1 PCT/JP2020/042884 JP2020042884W WO2021111869A1 WO 2021111869 A1 WO2021111869 A1 WO 2021111869A1 JP 2020042884 W JP2020042884 W JP 2020042884W WO 2021111869 A1 WO2021111869 A1 WO 2021111869A1
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Prior art keywords
electric resistor
electric
honeycomb structure
mass
increase
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PCT/JP2020/042884
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French (fr)
Japanese (ja)
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剛大 徳野
泰史 ▲高▼山
慎二 冨田
幸司 笠井
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株式会社デンソー
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Publication of WO2021111869A1 publication Critical patent/WO2021111869A1/en

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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01N—GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL COMBUSTION ENGINES
    • F01N3/00—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust
    • F01N3/08—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous
    • F01N3/10—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust
    • F01N3/18—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control
    • F01N3/20—Exhaust or silencing apparatus having means for purifying, rendering innocuous, or otherwise treating exhaust for rendering innocuous by thermal or catalytic conversion of noxious components of exhaust characterised by methods of operation; Control specially adapted for catalytic conversion ; Methods of operation or control of catalytic converters
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B3/00—Ohmic-resistance heating
    • H05B3/10—Heating elements characterised by the composition or nature of the materials or by the arrangement of the conductor
    • H05B3/12—Heating elements characterised by the composition or nature of the materials or by the arrangement of the conductor characterised by the composition or nature of the conductive material
    • H05B3/14—Heating elements characterised by the composition or nature of the materials or by the arrangement of the conductor characterised by the composition or nature of the conductive material the material being non-metallic

Definitions

  • the present disclosure relates to an electric resistor, a honeycomb structure, and an electric heating type catalyst device.
  • electric resistors have been used for energizing and heating in various fields.
  • an electric heating type catalyst device in which a honeycomb structure supporting a catalyst is composed of an electric resistor and the honeycomb structure is heated by energization heating.
  • Examples of this type of electric resistor include a mixture of silicon particles, boric acid, and kaolin in a mass ratio of 42: 4: 54 and a mass ratio of 40: 8: 52 in the preceding Patent Document 1.
  • An electric resistor formed by firing a mixed mixture is described.
  • the electric resistor that generates heat when energized and heated is required to have oxidation resistance when used at high temperatures.
  • the conventional electric resistor is exposed to a high temperature oxidizing atmosphere of 1000 ° C., the electric resistance increases and the electric characteristics deteriorate.
  • the present disclosure describes an electric resistor capable of suppressing an increase in electric resistance even when exposed to a high-temperature oxidizing atmosphere of 1000 ° C., a honeycomb structure using the electric resistance, and electric heating using the honeycomb structure. It is an object of the present invention to provide a type catalyst device.
  • One aspect of the present disclosure comprises silicon particles and oxides containing silicon and boron.
  • the Si / B ratio which is the mass ratio of silicon to boron in the entire material, is 280 or less.
  • the boron content in the whole material is 0.5% by mass or more. It is in the electric resistor.
  • Another aspect of the present disclosure is a honeycomb structure including the above electric resistor.
  • Yet another aspect of the present disclosure is in an electrically heated catalyst device having the honeycomb structure.
  • the electric resistor has the above configuration. Therefore, the electric resistor can suppress an increase in electric resistance even when exposed to a high temperature oxidizing atmosphere of 1000 ° C.
  • the honeycomb structure includes the electric resistor. Therefore, the honeycomb structure can suppress an increase in electrical resistance even when exposed to a high-temperature oxidizing atmosphere of 1000 ° C., and can realize a constant temperature rise rate. Therefore, the honeycomb structure is suitable as a honeycomb structure of an electrically heated catalyst device.
  • the electroheating catalyst device has the honeycomb structure. Therefore, the electric heating type catalyst device can suppress an increase in the electric resistance of the honeycomb structure even when exposed to a high temperature oxidizing atmosphere of 1000 ° C. in an exhaust gas environment, and realizes a constant temperature rising rate. be able to. Further, the electric heating type catalyst device is also advantageous in improving thermal durability.
  • FIG. 1 is an explanatory view schematically showing a cross section of the electric resistor according to the first embodiment.
  • FIG. 2 is a diagram for explaining an estimation mechanism of the action and effect of the electric resistor according to the first embodiment, in which (a) is the electric resistor according to the first embodiment and (b) is the comparative embodiment. It is a figure which showed the electric resistor, and is FIG. 3 is an explanatory view schematically showing the honeycomb structure according to the second embodiment.
  • FIG. 4 is an explanatory view schematically showing the electrically heated catalyst device according to the third embodiment.
  • FIG. 1 is an explanatory view schematically showing a cross section of the electric resistor according to the first embodiment.
  • FIG. 2 is a diagram for explaining an estimation mechanism of the action and effect of the electric resistor according to the first embodiment, in which (a) is the electric resistor according to the first embodiment and (b) is the comparative embodiment. It is a figure which showed the electric resistor, and is FIG. 3 is an explanatory view schematically showing
  • FIG. 5 is a diagram showing the relationship between the time (horizontal axis) held at 1000 ° C. in the air and the electrical resistivity (vertical axis) at 25 ° C. obtained in Experimental Example 1.
  • FIG. 6 is a diagram showing the relationship between the boron content (horizontal axis) measured by ICP and the electrical resistance increase rate (vertical axis) obtained in Experimental Example 1.
  • FIG. 7 is a diagram showing the relationship between the Si / B ratio (horizontal axis) obtained by ICP measurement and the electrical resistance increase rate (vertical axis) obtained in Experimental Example 1.
  • FIG. 8 is a diagram showing the relationship between the silicon / boric acid compounding ratio (horizontal axis) and the mass increase rate (vertical axis) obtained in Experimental Example 2.
  • FIG. 9 is a diagram showing the relationship between the silicon / boric acid compounding ratio (horizontal axis) and the electric resistance increase rate (vertical axis) obtained in Experimental Example 2.
  • the electric resistor 1 of the present embodiment has silicon particles 10 and an oxide containing silicon and boron (hereinafter, may be appropriately referred to as “Si / B-containing oxide”) 11. And are configured to include.
  • the silicon particles 10 and the Si / B-containing oxide 11 form a conductive path. That is, in the electric resistor 1, the silicon particles 10 and the Si / B-containing oxide 11 function as a conductive phase.
  • the electric resistor 1 can include a plurality of silicon particles 10 and include a silicon particle continuum 101 in which the silicon particles 10 are connected to each other.
  • the silicon particle continuum 101 can have a constricted portion 101a at a portion where the silicon particles 10 are connected to each other.
  • the Si / B-containing oxide 11 can exist so as to cover the surface of the silicon particle continuum 101.
  • the electric resistor 1 may contain a single silicon particle 10 in which the silicon particles 10 are not connected to each other, or a Si / B-containing oxide 11 that covers the surface of the single silicon particle 10.
  • the electric resistor 1 has a Si / B ratio of 280 or less, which is the mass ratio of silicon to boron in the entire material, and the boron content in the entire material is 0.5% by mass or more.
  • the Si / B ratio and the boron content can be measured by an ICP (Inductively Coupled Plasma) emission spectroscopic analyzer (hereinafter, the measurement may be appropriately referred to as "ICP measurement").
  • ICP emission spectroscopic analyzer an ICP emission spectroscopic analyzer manufactured by Hitachi High-Tech Science Co., Ltd. (ICP-AES, AES is an abbreviation for Atomic Emission Spectroscopy) can be used.
  • the boron content (mass%) and silicon content (mass%) contained in the entire material of the electric resistor 1 are measured by ICP measurement.
  • the Si / B ratio can be calculated by dividing the silicon content (mass%) by the boron content (mass%).
  • the electric resistor 1 contains silicon particles 10 and a Si / B-containing oxide 11 and is exposed to a high-temperature oxidizing atmosphere at 1000 ° C. by setting the Si / B ratio and the boron content within a specific range.
  • the increase in electrical resistance can be suppressed.
  • the reason for this will be described with reference to FIG.
  • the calorific value W is calculated by the following formula based on the current I, the voltage E, and the electric resistance R.
  • the conventional electric resistor 1 that does not satisfy the above regulation has a problem that the electric resistance increases when exposed to a high temperature oxidizing atmosphere of 1000 ° C. This is presumed to be due to the following reasons.
  • Oxidation of silicon proceeds by being exposed to an oxidizing atmosphere of about 1000 ° C. Therefore, when the above regulation is not satisfied, as shown in FIG. 2B, the film thickness of the Si / B-containing oxide 11 on the surface of the silicon particles 10 is thin, so that oxidation proceeds on the surface of the silicon particles 10. Then, a thick SiO 2 film grows. The grown SiO 2 film causes narrowing or cutting of the conductive path between the silicon particles 10. As a result, the conventional electric resistor 1 has an increased electric resistance when exposed to a high temperature oxidizing atmosphere of 1000 ° C. On the other hand, when the above regulation is satisfied, as shown in FIG.
  • the electric resistor 1 satisfying the above regulation can suppress an increase in electric resistance even when exposed to a high temperature oxidizing atmosphere of 1000 ° C.
  • boric acid can be used as a boron source in the production of the electric resistor 1.
  • the boron content corresponding to the boric acid blending amount at the time of production is not directly detected as the boron content of the electric resistor 1 by the ICP measurement, and the detected amount is smaller than the blending amount. It is considered that this is because when the amount of boric acid blended is small, the effect of boric acid evaporation during firing is large. Due to such a phenomenon, in order to form the Si / B-containing oxide 11 having a gas barrier property against oxygen gas around the silicon particles 10, the amount of boric acid blended should be increased in consideration of the amount of boron to evaporate. Is required.
  • the Si / B-containing oxide 11 is considered to be a borosilicate.
  • the Si / B-containing oxide 11 is preferably derived from at least silicon particles 10 and boric acid. According to this configuration, it becomes easier to suppress the mixing of the alkaline component as compared with the case where the Si / B-containing oxide 11 is derived from the silicon particles 10 and the borosilicate glass. Therefore, according to this configuration, it becomes easy to suppress the crystallization of the glass phase in the material, and the electric resistor 1 which is advantageous in reducing the coefficient of thermal expansion can be obtained.
  • the Si / B ratio of the electric resistor 1 exceeds 280, the rate of increase in electric resistance when exposed to a high-temperature oxidizing atmosphere of 1000 ° C. increases sharply. This is because the content of boron is smaller than that of the silicon particles 10, so that the gas barrier property is lowered, and the silicon particles 10 change to the insulating SiO 2 when exposed to a high temperature oxidizing atmosphere of 1000 ° C. This is because the electrical junction is broken.
  • the Si / B ratio is preferably 200 or less, more preferably 150 or less, and further, from the viewpoint of ensuring the effect of reducing the rate of increase in electrical resistance when exposed to a high-temperature oxidizing atmosphere of 1000 ° C. Preferably, it can be 100 or less.
  • the Si / B ratio is preferably 5 or more, more preferably 8 from the viewpoint that the amount of silicon particles 10, which are the key to the development of conductivity, is relatively small when the amount of boron is too large. Above, more preferably, it can be 10 or more.
  • the boron content of the electric resistor 1 is less than 0.5% by mass, the rate of increase in electrical resistance when exposed to a high-temperature oxidizing atmosphere of 1000 ° C. increases sharply.
  • the boron content is preferably 0.8% by mass or more, more preferably 1 from the viewpoint of ensuring the effect of reducing the rate of increase in electrical resistance when exposed to a high-temperature oxidizing atmosphere of 1000 ° C. It can be 0.0% by mass or more, more preferably 2.0% by mass or more. Further, the boron content is preferably 8.0% by mass or less, more preferably from the viewpoint that the amount of silicon particles 10, which are the key to the development of conductivity, is relatively small when the amount of boron is too large. Can be 6.0% by mass or less, more preferably 4.0% by mass or less.
  • the electric resistor 1 can further contain fused silica.
  • the molten silica melts during firing during the production of the electric resistor 1 to densify the material structure of the electric resistor 1. Therefore, according to this configuration, it becomes difficult for oxygen gas to permeate into the electric resistor 1, and the oxidation of the silicon particles 10 is suppressed. Therefore, according to this configuration, it becomes easy to reduce the rate of increase in electrical resistance when exposed to a high-temperature oxidizing atmosphere of 1000 ° C. Further, since the molten silica is produced by melting the raw material silica at a high temperature, it contains almost no alkaline component.
  • the alkaline component contained in the electric resistor 1 is reduced, and the crystallization of the glass phase is suppressed.
  • the molten silica has a low coefficient of thermal expansion (coefficient of thermal expansion of the molten silica: about 0.8 ppm / K). Therefore, according to this configuration, the coefficient of thermal expansion of the electric resistor 1 can be reduced, which is advantageous for improving the thermal shock resistance of the electric resistor 1.
  • the content of molten silica in the electric resistor 1 can be 85% by mass or less. According to this configuration, it becomes easy to secure the electrical conductivity, so that it becomes easy to obtain the electric resistor 1 suitable for the energization heating.
  • the content of the molten silica can be 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 the above effect. ..
  • the content of the molten silica is preferably 10% by mass or more, more preferably 20% by mass or more, still more preferably 30% by mass or more, from the viewpoint of the balance between oxidation resistance and low thermal expansion. can do.
  • the electric resistor 1 can further include cordierite. Cordierite melts during firing during the production of the electric resistor 1 to densify the material structure of the electric resistor 1. Therefore, according to this configuration, it becomes difficult for oxygen gas to permeate into the electric resistor 1, and the oxidation of the silicon particles 10 is suppressed. Therefore, according to this configuration, it becomes easy to reduce the rate of increase in electrical resistance when exposed to a high-temperature oxidizing atmosphere of 1000 ° C. Further, by adopting a configuration containing cordierite, it is possible to reduce or eliminate the amount of kaolin in the starting material.
  • Cordierite has a lower coefficient of thermal expansion than alumina and mullite produced by firing kaolin (coefficient of thermal expansion of cordierite: about 1.8 to 2.0 ppm / K). Therefore, according to this configuration, the coefficient of thermal expansion of the electric resistor 1 can be reduced, which is advantageous for improving the thermal shock resistance of the electric resistor 1.
  • the content of cordierite in the electric resistor 1 can be 75% by mass or less. According to this configuration, it becomes easy to secure the electrical conductivity, so that it becomes easy to obtain the electric resistor 1 suitable for the energization heating.
  • the content of cordierite is preferably 70% by mass or less, more preferably 68% by mass or less, still more preferably 60% by mass or less, still more preferably, from the viewpoint of ensuring the above effects. Can be 50% by mass or less.
  • the content of cordierite is preferably 30% by mass or more, more preferably 35% by mass or more, still more preferably 40% by mass or more, from the viewpoint of the balance between oxidation resistance and low thermal expansion. Can be.
  • the above-mentioned fused silica and cordierite can function as an insulating phase in the electric resistor 1.
  • Both the molten silica and cordierite can exist around the silicon particle continuum 101 whose surface is covered with the Si / B-containing oxide 11.
  • the electric resistor 1 contains a silicon particle continuum 101 whose surface is covered with a Si / B-containing oxide 11 in the matrix 12, and is described above.
  • Matrix 12 can be configured to contain at least one of fused silica and cordierite.
  • the electric resistor 1 can be configured such that the rate of increase in electrical resistance after holding at 1000 ° C. for 50 hours in the atmosphere is 250% or less. According to this configuration, it becomes easy to realize an electric resistor 1 capable of suppressing an increase in electric resistance even when exposed to a high-temperature oxidizing atmosphere of 1000 ° C.
  • the rate of increase in electrical resistance is preferably 230% or less, more preferably 200% or less, still more preferably 150% or less, still more preferably in an electrically heated catalyst device, from the viewpoint of improving oxidation resistance and the like. From the viewpoint of easy maintenance of the circuit element, it can be 135% or less, and even more preferably 130% or less.
  • the value measured as follows is used. For each sample of the electric resistor 1, the electrical resistivity before (that is, initial) holding at 1000 ° C. for 50 hours and after holding the sample are measured.
  • the electric resistor 1 can be configured to have an electric resistivity of 0.01 ⁇ ⁇ cm or more and 100 ⁇ ⁇ cm or less. According to this configuration, it becomes easy to select a circuit suitable for a hybrid car equipped with an electric heating type catalyst device, so that an electric resistor suitable as a honeycomb structure in the electric heating type catalyst device can be obtained.
  • the electrical resistivity of the electric resistor 1 is preferably 0.1 ⁇ ⁇ cm or more, more preferably 0., from the viewpoint of increasing the amount of heat generated during energization heating and making it easier to adopt a relatively simple electric circuit. It can be 3 ⁇ ⁇ cm or more, more preferably 0.5 ⁇ ⁇ cm or more.
  • the electrical resistivity of the electric resistor 1 can be preferably 50 ⁇ ⁇ cm or less, more preferably 30 ⁇ ⁇ cm or less, and further preferably 10 ⁇ ⁇ cm or less from the viewpoint of reducing the electric resistance.
  • the electric resistor 1 can be configured such that the rate of increase in electric resistance is 0% / ° C. or higher and 0.5% / ° C. or lower. According to this configuration, the electric resistor 1 does not have the NTC characteristic (the characteristic that the electrical resistivity decreases as the temperature rises). An electric resistor having NTC characteristics is disadvantageous from the viewpoint of uniform heat generation because a larger amount of current flows into a locally heated part, which causes a temperature distribution. On the other hand, according to the above configuration, since the electric resistor 1 does not have the NTC characteristic, the electric resistor 1 that can easily realize uniform heat generation can be obtained.
  • the electrical resistivity increase rate of the electric resistor 1 is preferably larger than 0% / ° C. from the viewpoint of PTC characteristics (characteristics in which the electrical resistivity increases as the temperature rises), and ensures the PTC characteristics. From this point of view, it can be more preferably 0.05% / ° C. or higher, further preferably 0.06% / ° C. or higher, and even more preferably 0.07% / ° C. or higher. Further, the rate of increase in electric resistance of the electric resistor 1 is preferably increased from the viewpoint that when used as a honeycomb structure in an electric heating type catalyst device, the change in electric resistance does not become too large and it is easy to correspond to a circuit. It can be 0.5% / ° C. or lower, more preferably 0.4% / ° C. or lower, still more preferably 0.3% / ° C. or lower, and even more preferably 0.2% / ° C. or lower.
  • the rate of increase in electrical resistance of the electrical resistor 1 is calculated as follows.
  • the electrical resistivity of the electric resistor 1 is measured at three points of 50 ° C., 200 ° C., and 400 ° C.
  • the rate of increase in electrical resistance [% / ° C.] is calculated by the following formula. Measuring the electrical resistivity at 200 ° C. in addition to the electrical resistivity at 50 ° C. and 400 ° C. is meaningful for confirming whether the temperature dependence of the electrical resistivity has linearity.
  • R 400 is the electrical resistivity [ ⁇ ⁇ cm] of the electrical resistor 1 at 400 ° C.
  • R 50 is the electrical resistivity [ ⁇ ⁇ cm] of the electrical resistor 1 at 50 ° C.
  • the honeycomb structure 2 of the present embodiment includes the electric resistor 1 of the first embodiment.
  • the honeycomb structure 2 is composed of the electric resistor 1 of the first embodiment.
  • FIG. 3 specifically, in a cross-sectional view of the honeycomb perpendicular to the central axis of the honeycomb structure 2, a plurality of cells 20 adjacent to each other, a cell wall 21 forming the cells 20, and an outer peripheral portion of the cell wall 21 are formed.
  • An example is a structure having an outer peripheral wall 22 provided and integrally holding the cell wall 21.
  • a known structure can be applied to the honeycomb structure 2, and the structure is not limited to the structure shown in FIG. FIG.
  • FIG. 3 shows an example in which the cell 20 has a quadrangular cross section, but in addition, for example, the cell 20 may have a hexagonal cross section. Further, FIG. 3 shows an example in which the honeycomb structure 2 has a cylindrical shape, but in addition, for example, the honeycomb structure 2 may have a cross-sectional track shape or the like.
  • the honeycomb structure 2 of the present embodiment is configured to include the electric resistor 1 of the first embodiment. Therefore, the honeycomb structure 2 of the present embodiment can suppress an increase in electrical resistance even when exposed to a high-temperature oxidizing atmosphere of 1000 ° C.
  • the calorific value increases in proportion to the electrical resistance. According to the honeycomb structure 2 of the present embodiment, the calorific value does not increase sharply, and a constant temperature rise rate can be realized. Therefore, the honeycomb structure 2 of the present embodiment is suitable as the honeycomb structure of the electric heating type catalyst device.
  • the electrically heated catalyst device 3 of the present embodiment has the honeycomb structure 2 of the second embodiment.
  • the electric heating type catalyst device 3 includes a honeycomb structure 2, an exhaust gas purification catalyst (not shown) supported on the cell wall 21 of the honeycomb structure 2, and the honeycomb structure 2. It has a pair of electrodes 31 and 32 arranged to face each other on the outer peripheral wall 22, and a voltage application unit 33 that applies and controls a voltage to the electrodes 31 and 32. A voltage is applied to the electrode 31 and the electrode 32, respectively, through the rod-shaped electrode terminal 310 and the rod-shaped electrode terminal 320, respectively.
  • the electric heating type catalyst device 3 can generate heat by energization through a pair of electrodes 31 and 32 provided to the outer peripheral wall 22.
  • the electrically heated catalyst device 3 can be heated to a temperature of, for example, 500 ° C. or higher from the viewpoint of fully exerting the function of the exhaust gas purification catalyst.
  • a known structure can be applied to the electrically heated catalyst device 3, and the structure is not limited to the structure shown in FIG. Further, the form of voltage application may be any form or combination such as direct current, alternating current, pulsed voltage application and the like.
  • the electrically heated catalyst device 3 of the present embodiment has the honeycomb structure 2 of the second embodiment. Therefore, the electric heating type catalyst device 3 of the present embodiment can suppress an increase in the electric resistance of the honeycomb structure 2 even when exposed to a high temperature oxidizing atmosphere of 1000 ° C. in an exhaust gas environment, and the increase is constant. A temperature rate can be achieved. Further, the electrically heated catalyst device 3 of the present embodiment is also advantageous in improving the thermal durability.
  • Example 1 ⁇ Preparation of sample> -Sample 1- Silicon particles (average particle size 7 ⁇ m), boric acid and cordierite (average particle size 1.7 ⁇ m) were mixed at a mass ratio of 30:20:50. Then, 4% by mass of methyl cellulose was added as a binder to this mixture, water was added, and the mixture was mixed. Next, the obtained mixture was molded into pellets by an extrusion molding machine, dried at 80 ° C. in a constant temperature bath, and then degreased. The degreasing conditions were air atmosphere / normal pressure, degreasing temperature 700 ° C., and degreasing time 3 hours.
  • the calcination conditions were an Ar gas atmosphere, normal pressure, a calcination temperature of 1250 ° C., and a calcination time of 30 minutes.
  • the obtained fired body was main fired.
  • the conditions for the main firing were an Ar gas atmosphere, normal pressure, a main firing temperature of 1350 ° C., and a main firing time of 30 minutes.
  • the obtained fired body was subjected to a preliminary oxidation treatment (oxidation aging treatment).
  • the conditions for pre-oxidation were atmospheric atmosphere / normal pressure, treatment temperature 1000 ° C., and treatment time 10 hours.
  • an electric resistor of Sample 1 having a shape of 5 mm ⁇ 5 mm ⁇ 25 mm was obtained.
  • sample 1C- An electric resistor of sample 1C was obtained in the same manner as in sample 1 except that a mixture of silicon particles, boric acid and cordierite in a mass ratio of 30: 4: 66 was used.
  • Example 2C- Sample 1 except that fused silica (average particle size 6.8 ⁇ m) was used instead of cordierite, and a mixture of silicon particles, boric acid, and fused silica mixed at a mass ratio of 30: 4: 66 was used. In the same manner as above, an electric resistor of sample 2C was obtained.
  • fused silica average particle size 6.8 ⁇ m
  • ⁇ Electrical resistivity, electrical resistance increase rate The electrical resistivity of each sample was measured.
  • the electrical resistivity of a prism sample having a size of 5 mm ⁇ 5 mm ⁇ 25 mm was measured by a four-terminal method using a thermoelectric characterization device (“ZEM-2” manufactured by ULVAC Riko Co., Ltd.). The measurement temperature in this measurement is 25 ° C.
  • the electrical resistors of each sample were held in the air at 1000 ° C. for 50 hours. The condition of holding the product in the atmosphere at 1000 ° C. for 50 hours simulates the usage state of being exposed to a high temperature oxidizing atmosphere of 1000 ° C.
  • the electrical resistivity of each electric resistor before the preliminary oxidation treatment was measured in the same manner as described above. Then, in the same manner as described above, the electrical resistivity of the electrical resistor of each sample after the holding was measured.
  • the electrical resistivity of the electrical resistivity of each sample after being subjected to the pre-oxidation treatment for 10 hours and before being held at 1000 ° C. for 50 hours is defined as the initial electrical resistivity.
  • the electrical resistivity of the electric resistor of each sample is calculated by the above formula. The rate of increase was measured.
  • Table 1 summarizes the production conditions of the electric resistors of each sample, various measurement results, and the like.
  • FIGS. 5 to 7 the following can be seen.
  • the electrical resistivity of Sample 1C and Sample 2C which did not have the configuration specified in the present disclosure, increased sharply when exposed to a high-temperature oxidizing atmosphere at 1000 ° C.
  • the electric resistors of Samples 1 to 4 having the configuration specified in the present disclosure suppress a rapid increase in electrical resistivity even when exposed to a high temperature oxidizing atmosphere of 1000 ° C. I was able to.
  • the honeycomb structure of the electric heating type catalyst device is constructed by using the electric resistance of this example, it is possible to suppress the increase of the electric resistance even when exposed to a high temperature oxidizing atmosphere of 1000 ° C. Therefore, it can be said that a constant temperature rise rate can be realized.
  • the electric heating type catalyst device having a honeycomb structure composed of the electric resistors of this example the electric resistance of the honeycomb structure increases even when exposed to a high temperature oxidizing atmosphere of 1000 ° C. in an exhaust gas environment. It can be said that a constant temperature rise rate can be realized because the temperature can be suppressed. Further, it can be said that such an electrically heated catalyst device is also advantageous in improving thermal durability.
  • the mass increase rate (%) was calculated from the formula of 100 ⁇ (mass of electric resistor after holding at 1000 ° C. for 50 hours) / (mass of electric resistor before pre-oxidation treatment).
  • the above-mentioned silicon / boric acid compounding ratio was changed to obtain the above-mentioned increase rate of electrical resistance. The results are shown in FIGS. 8 and 9.
  • the mass increase rate is large in the region where the silicon / boric acid compounding ratio is large, that is, the boric acid compounding amount is small with respect to the silicon compounding amount.
  • the boric acid compounding amount is small with respect to the silicon compounding amount.
  • the mass increase rate is small in the region where the silicon / boric acid compounding ratio is small, that is, the boric acid compounding amount is large relative to the silicon compounding amount.
  • the boric acid compounding amount is large relative to the silicon compounding amount.
  • the electric resistance increase rate is large and the silicon / boric acid compounding ratio is small. That is, it can be seen that the rate of increase in electrical resistance becomes smaller in the region where the boric acid compounding amount is larger than the silicon compounding amount. From this result, in order to suppress the increase in electric resistance when exposed to a high temperature oxidizing atmosphere of 1000 ° C., it is effective to increase the amount of boric acid compounded and increase the boron content contained in the electric resistor. It can be said that.

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Abstract

An electrical resistor (1) including silicon particles (10) and an oxide (11) including silicon and boron. The mass ratio of silicon to boron (Si/B) in the material overall is no more than 280 and the boron content in the material overall is at least 0.5% by mass. The electrical resistor (1) can also include fused silica or cordierite. A honeycomb structure (2) comprises the electrical resistor (1). An electrically heated catalyst device (3) has the honeycomb structure (2).

Description

電気抵抗体、ハニカム構造体、および、電気加熱式触媒装置Electric resistors, honeycomb structures, and electrically heated catalysts 関連出願の相互参照Cross-reference of related applications
　本出願は、２０１９年１２月６日に出願された日本出願番号２０１９－２２０８５５号に基づくもので、ここにその記載内容を援用する。 This application is based on Japanese Application No. 2019-220855 filed on December 6, 2019, and the contents of the description are incorporated herein by reference.
　本開示は、電気抵抗体、ハニカム構造体、および、電気加熱式触媒装置に関する。 The present disclosure relates to an electric resistor, a honeycomb structure, and an electric heating type catalyst device.
　従来、様々な分野において、通電加熱に電気抵抗体が用いられている。例えば、車両分野では、触媒を担持するハニカム構造体を電気抵抗体より構成し、通電加熱によってハニカム構造体を発熱させる電気加熱式触媒装置が公知である。 Conventionally, electric resistors have been used for energizing and heating in various fields. For example, in the vehicle field, there is known an electric heating type catalyst device in which a honeycomb structure supporting a catalyst is composed of an electric resistor and the honeycomb structure is heated by energization heating.
　この種の電気抵抗体としては、例えば、先行する特許文献１に、シリコン粒子とホウ酸とカオリンとを、４２：４：５４の質量比で混合した混合物や４０：８：５２の質量比で混合した混合物を焼成してなる電気抵抗体が記載されている。 Examples of this type of electric resistor include a mixture of silicon particles, boric acid, and kaolin in a mass ratio of 42: 4: 54 and a mass ratio of 40: 8: 52 in the preceding Patent Document 1. An electric resistor formed by firing a mixed mixture is described.
特開２０１９－１２６８２号公報Japanese Unexamined Patent Publication No. 2019-12682
　通電加熱によって発熱する電気抵抗体には、高温使用時における耐酸化性が要求される。しかしながら、従来の電気抵抗体は、１０００℃の高温酸化雰囲気に曝された場合に電気抵抗が増加し、電気特性が劣化する。 The electric resistor that generates heat when energized and heated is required to have oxidation resistance when used at high temperatures. However, when the conventional electric resistor is exposed to a high temperature oxidizing atmosphere of 1000 ° C., the electric resistance increases and the electric characteristics deteriorate.
　本開示は、１０００℃の高温酸化雰囲気に曝された場合でも電気抵抗の増加を抑制可能な電気抵抗体、当該電気抵抗体を用いたハニカム構造体、また、当該ハニカム構造体を用いた電気加熱式触媒装置を提供することを目的とする。 The present disclosure describes an electric resistor capable of suppressing an increase in electric resistance even when exposed to a high-temperature oxidizing atmosphere of 1000 ° C., a honeycomb structure using the electric resistance, and electric heating using the honeycomb structure. It is an object of the present invention to provide a type catalyst device.
　本開示の一態様は、シリコン粒子と、シリコンおよびホウ素を含む酸化物と、を含み、
　材料全体におけるホウ素に対するシリコンの質量比であるＳｉ／Ｂ比が２８０以下であり、
　材料全体に含まれるホウ素含有量が０．５質量％以上である、
　電気抵抗体にある。 One aspect of the present disclosure comprises silicon particles and oxides containing silicon and boron.
The Si / B ratio, which is the mass ratio of silicon to boron in the entire material, is 280 or less.
The boron content in the whole material is 0.5% by mass or more.
It is in the electric resistor.
　本開示の他の態様は、上記電気抵抗体を含んで構成されている、ハニカム構造体にある。 Another aspect of the present disclosure is a honeycomb structure including the above electric resistor.
　本開示のさらに他の態様は、上記ハニカム構造体を有する、電気加熱式触媒装置にある。 Yet another aspect of the present disclosure is in an electrically heated catalyst device having the honeycomb structure.
　上記電気抵抗体は、上記構成を有している。そのため、上記電気抵抗体は、１０００℃の高温酸化雰囲気に曝された場合でも電気抵抗の増加を抑制することができる。 The electric resistor has the above configuration. Therefore, the electric resistor can suppress an increase in electric resistance even when exposed to a high temperature oxidizing atmosphere of 1000 ° C.
　上記ハニカム構造体は、上記電気抵抗体を含んで構成されている。そのため、上記ハニカム構造体は、１０００℃の高温酸化雰囲気に曝された場合でも電気抵抗の増加を抑制することができ、一定した昇温速度を実現することができる。それ故、上記ハニカム構造体は、電気加熱式触媒装置のハニカム構造体として好適である。 The honeycomb structure includes the electric resistor. Therefore, the honeycomb structure can suppress an increase in electrical resistance even when exposed to a high-temperature oxidizing atmosphere of 1000 ° C., and can realize a constant temperature rise rate. Therefore, the honeycomb structure is suitable as a honeycomb structure of an electrically heated catalyst device.
　上記電気加熱式触媒装置は、上記ハニカム構造体を有する。そのため、上記電気加熱式触媒装置は、排ガス環境下にて１０００℃の高温酸化雰囲気に曝された場合でもハニカム構造体の電気抵抗の増加を抑制することができ、一定した昇温速度を実現することができる。また、上記電気加熱式触媒装置は、熱耐久性の向上にも有利である。 The electroheating catalyst device has the honeycomb structure. Therefore, the electric heating type catalyst device can suppress an increase in the electric resistance of the honeycomb structure even when exposed to a high temperature oxidizing atmosphere of 1000 ° C. in an exhaust gas environment, and realizes a constant temperature rising rate. be able to. Further, the electric heating type catalyst device is also advantageous in improving thermal durability.
　なお、請求の範囲に記載した括弧内の符号は、後述する実施形態に記載の具体的手段との対応関係を示すものであり、本開示の技術的範囲を限定するものではない。 Note that the reference numerals in parentheses described in the claims indicate the correspondence with the specific means described in the embodiments described later, and do not limit the technical scope of the present disclosure.
　本開示についての上記目的およびその他の目的、特徴や利点は、添付の図面を参照しながら下記の詳細な記述により、より明確になる。その図面は、
図１は、実施形態１に係る電気抵抗体の断面を模式的に示した説明図であり、 図２は、実施形態１に係る電気抵抗体が奏する作用効果の推定メカニズムを説明するための図であって、（ａ）は実施形態１に係る電気抵抗体、（ｂ）は比較形態に係る電気抵抗体を示した図であり、 図３は、実施形態２に係るハニカム構造体を模式的に示した説明図であり、 図４は、実施形態３に係る電気加熱式触媒装置を模式的に示した説明図であり、 図５は、実験例１にて得られた、大気中、１０００℃にて保持した時間（横軸）と、２５℃における電気抵抗率（縦軸）との関係を示した図であり、 図６は、実験例１にて得られた、ＩＣＰ測定によるホウ素含有量（横軸）と、電気抵抗増加率（縦軸）との関係を示した図であり、 図７は、実験例１にて得られた、ＩＣＰ測定によるＳｉ／Ｂ比（横軸）と、電気抵抗増加率（縦軸）との関係を示した図であり、 図８は、実験例２にて得られた、シリコン／ホウ酸配合比（横軸）と、質量増加率（縦軸）との関係を示した図であり、 図９は、実験例２にて得られた、シリコン／ホウ酸配合比（横軸）と、電気抵抗増加率（縦軸）との関係を示した図である。 The above objectives and other objectives, features and advantages of the present disclosure will be clarified by the following detailed description with reference to the accompanying drawings. The drawing is
FIG. 1 is an explanatory view schematically showing a cross section of the electric resistor according to the first embodiment. FIG. 2 is a diagram for explaining an estimation mechanism of the action and effect of the electric resistor according to the first embodiment, in which (a) is the electric resistor according to the first embodiment and (b) is the comparative embodiment. It is a figure which showed the electric resistor, and is FIG. 3 is an explanatory view schematically showing the honeycomb structure according to the second embodiment. FIG. 4 is an explanatory view schematically showing the electrically heated catalyst device according to the third embodiment. FIG. 5 is a diagram showing the relationship between the time (horizontal axis) held at 1000 ° C. in the air and the electrical resistivity (vertical axis) at 25 ° C. obtained in Experimental Example 1. FIG. 6 is a diagram showing the relationship between the boron content (horizontal axis) measured by ICP and the electrical resistance increase rate (vertical axis) obtained in Experimental Example 1. FIG. 7 is a diagram showing the relationship between the Si / B ratio (horizontal axis) obtained by ICP measurement and the electrical resistance increase rate (vertical axis) obtained in Experimental Example 1. FIG. 8 is a diagram showing the relationship between the silicon / boric acid compounding ratio (horizontal axis) and the mass increase rate (vertical axis) obtained in Experimental Example 2. FIG. 9 is a diagram showing the relationship between the silicon / boric acid compounding ratio (horizontal axis) and the electric resistance increase rate (vertical axis) obtained in Experimental Example 2.
（実施形態１）
　実施形態１の電気抵抗体について、図１および図２を用いて説明する。図１に例示されるように、本実施形態の電気抵抗体１は、シリコン粒子１０と、シリコンおよびホウ素を含む酸化物（以下、適宜「Ｓｉ・Ｂ含有酸化物」ということがある。）１１と、を含んで構成されている。 (Embodiment 1)
The electric resistor of the first embodiment will be described with reference to FIGS. 1 and 2. As illustrated in FIG. 1, the electric resistor 1 of the present embodiment has silicon particles 10 and an oxide containing silicon and boron (hereinafter, may be appropriately referred to as “Si / B-containing oxide”) 11. And are configured to include.
　電気抵抗体１において、シリコン粒子１０およびＳｉ・Ｂ含有酸化物１１は、導電パスを形成している。つまり、電気抵抗体１において、シリコン粒子１０およびＳｉ・Ｂ含有酸化物１１は、導電相として機能する。電気抵抗体１は、具体的には、図１に例示されるように、複数のシリコン粒子１０を含み、シリコン粒子１０同士が繋がってなるシリコン粒子連続体１０１を含むことができる。シリコン粒子連続体１０１は、シリコン粒子１０同士が繋がった部分にくびれ部１０１ａを有することができる。Ｓｉ・Ｂ含有酸化物１１は、シリコン粒子連続体１０１の表面を覆うように存在することができる。なお、電気抵抗体１は、シリコン粒子１０同士が繋がっていない単独のシリコン粒子１０や、単独のシリコン粒子１０の表面を覆うＳｉ・Ｂ含有酸化物１１を含んでいてもよい。 In the electric resistor 1, the silicon particles 10 and the Si / B-containing oxide 11 form a conductive path. That is, in the electric resistor 1, the silicon particles 10 and the Si / B-containing oxide 11 function as a conductive phase. Specifically, as illustrated in FIG. 1, the electric resistor 1 can include a plurality of silicon particles 10 and include a silicon particle continuum 101 in which the silicon particles 10 are connected to each other. The silicon particle continuum 101 can have a constricted portion 101a at a portion where the silicon particles 10 are connected to each other. The Si / B-containing oxide 11 can exist so as to cover the surface of the silicon particle continuum 101. The electric resistor 1 may contain a single silicon particle 10 in which the silicon particles 10 are not connected to each other, or a Si / B-containing oxide 11 that covers the surface of the single silicon particle 10.
　電気抵抗体１は、材料全体におけるホウ素に対するシリコンの質量比であるＳｉ／Ｂ比が２８０以下、材料全体に含まれるホウ素含有量が０．５質量％以上とされている。Ｓｉ／Ｂ比、ホウ素含有量は、ＩＣＰ（誘導結合プラズマ：Inductively Coupled Plasma）発光分光分析装置により測定することができる（以下、当該測定を、適宜「ＩＣＰ測定」ということがある。）。ＩＣＰ発光分光分析装置としては、日立ハイテクサイエンス社製、ＩＣＰ発光分光分析装置（ＩＣＰ－ＡＥＳ、ＡＥＳはAtomic Emission Spectroscopyの略）を用いることができる。ＩＣＰ測定により、電気抵抗体１の材料全体に含まれるホウ素含有量（質量％）、シリコン含有量（質量％）を測定する。Ｓｉ／Ｂ比は、シリコン含有量（質量％）をホウ素含有量（質量％）にて除すことにより算出することができる。 The electric resistor 1 has a Si / B ratio of 280 or less, which is the mass ratio of silicon to boron in the entire material, and the boron content in the entire material is 0.5% by mass or more. The Si / B ratio and the boron content can be measured by an ICP (Inductively Coupled Plasma) emission spectroscopic analyzer (hereinafter, the measurement may be appropriately referred to as "ICP measurement"). As the ICP emission spectroscopic analyzer, an ICP emission spectroscopic analyzer manufactured by Hitachi High-Tech Science Co., Ltd. (ICP-AES, AES is an abbreviation for Atomic Emission Spectroscopy) can be used. The boron content (mass%) and silicon content (mass%) contained in the entire material of the electric resistor 1 are measured by ICP measurement. The Si / B ratio can be calculated by dividing the silicon content (mass%) by the boron content (mass%).
　電気抵抗体１は、シリコン粒子１０とＳｉ・Ｂ含有酸化物１１とを含み、Ｓｉ／Ｂ比、ホウ素含有量が特定の範囲とされることにより、１０００℃の高温酸化雰囲気に曝された場合でも電気抵抗の増加を抑制することができる。以下、この理由について図２を用いて説明する。 When the electric resistor 1 contains silicon particles 10 and a Si / B-containing oxide 11 and is exposed to a high-temperature oxidizing atmosphere at 1000 ° C. by setting the Si / B ratio and the boron content within a specific range. However, the increase in electrical resistance can be suppressed. Hereinafter, the reason for this will be described with reference to FIG.
　通電加熱によって発熱する電気抵抗体１では、昇温速度の制御のために電気抵抗の制御が重要となる。発熱量Ｗは、電流Ｉ、電圧Ｅ、電気抵抗Ｒによって次の式にて計算される。
　Ｗ＝Ｅ×Ｉ＝Ｉ２×Ｒ
　このように発熱量は電気抵抗に比例するため、電気抵抗体１の使用時における発熱量の急激な増加を抑制するためには、電気抵抗を一定に保つ必要がある。しかしながら、上記規定を満たさない従来の電気抵抗体１は、１０００℃の高温酸化雰囲気に曝された場合に電気抵抗が増加する問題がある。これは、以下の理由によるものと推定される。シリコンの酸化は、１０００℃程度の酸化雰囲気下に曝されることにより進行する。そのため、上記規定を満たさない場合には、図２（ｂ）に示されるように、シリコン粒子１０表面におけるＳｉ・Ｂ含有酸化物１１の膜厚が薄いので、シリコン粒子１０表面にて酸化が進行し、厚いＳｉＯ２膜が成長する。成長したＳｉＯ２膜は、シリコン粒子１０間の導電パスの狭窄や切断を引き起こす。その結果、従来の電気抵抗体１は、１０００℃の高温酸化雰囲気に曝された場合に電気抵抗が増加する。これに対し、上記規定を満たす場合には、図２（ａ）に示されるように、Ｓｉ・Ｂ含有酸化物１１の膜厚が厚いので、シリコン粒子１０表面の酸化が抑制され、ＳｉＯ２が成長し難い。そのため、シリコン粒子１０間の導電パスの狭窄や切断が起こり難く、シリコン粒子１０間の電気抵抗変化が抑制される。その結果、上記規定を満たす電気抵抗体１は、１０００℃の高温酸化雰囲気に曝された場合でも電気抵抗の増加を抑制することができる。 In the electric resistor 1 that generates heat by energization heating, it is important to control the electric resistance in order to control the rate of temperature rise. The calorific value W is calculated by the following formula based on the current I, the voltage E, and the electric resistance R.
W = E x I = I 2 x R
Since the calorific value is proportional to the electric resistance in this way, it is necessary to keep the electric resistance constant in order to suppress a sudden increase in the calorific value when the electric resistor 1 is used. However, the conventional electric resistor 1 that does not satisfy the above regulation has a problem that the electric resistance increases when exposed to a high temperature oxidizing atmosphere of 1000 ° C. This is presumed to be due to the following reasons. Oxidation of silicon proceeds by being exposed to an oxidizing atmosphere of about 1000 ° C. Therefore, when the above regulation is not satisfied, as shown in FIG. 2B, the film thickness of the Si / B-containing oxide 11 on the surface of the silicon particles 10 is thin, so that oxidation proceeds on the surface of the silicon particles 10. Then, a thick SiO 2 film grows. The grown SiO 2 film causes narrowing or cutting of the conductive path between the silicon particles 10. As a result, the conventional electric resistor 1 has an increased electric resistance when exposed to a high temperature oxidizing atmosphere of 1000 ° C. On the other hand, when the above regulation is satisfied, as shown in FIG. 2A, since the film thickness of the Si / B-containing oxide 11 is thick, the oxidation of the surface of the silicon particles 10 is suppressed, and SiO 2 is formed. Hard to grow. Therefore, narrowing or cutting of the conductive path between the silicon particles 10 is unlikely to occur, and the change in electrical resistance between the silicon particles 10 is suppressed. As a result, the electric resistor 1 satisfying the above regulation can suppress an increase in electric resistance even when exposed to a high temperature oxidizing atmosphere of 1000 ° C.
　実験例にて後述するように、電気抵抗体１の製造には、ホウ素源としてホウ酸を用いることができる。この場合、製造時におけるホウ酸配合量に対応するホウ素含有量が、そのままＩＣＰ測定によって電気抵抗体１のホウ素含有量として検出されるわけではなく、検出量は、配合量よりも少なくなる。これは、ホウ酸配合量が少ない場合、焼成時にホウ酸が蒸発する影響が大きいためであると考えられる。このような現象があるため、酸素ガスに対するガスバリア性を有するＳｉ・Ｂ含有酸化物１１をシリコン粒子１０の周囲に形成するには、蒸発するホウ素量を加味してホウ酸配合量を多くすることが必要となる。なお、透過型電子顕微鏡（ＴＥＭ）のＥＤＸ測定と電子線回折測定の結果によれば、シリコン粒子１０の周囲にはＳｉ、Ｂ、Ｏの元素を含むアモルファス状の領域が見られる。そのため、Ｓｉ・Ｂ含有酸化物１１は、ホウケイ酸塩であると考えられる。Ｓｉ・Ｂ含有酸化物１１は、具体的には、少なくともシリコン粒子１０とホウ酸とに由来するものであるとよい。この構成によれば、Ｓｉ・Ｂ含有酸化物１１がシリコン粒子１０とホウケイ酸ガラスとに由来するものである場合に比べて、アルカリ成分の混入を抑制しやすくなる。そのため、この構成によれば、材料中におけるガラス相の結晶化を抑制しやすくなり、熱膨張率の低減に有利な電気抵抗体１が得られる。 As will be described later in the experimental example, boric acid can be used as a boron source in the production of the electric resistor 1. In this case, the boron content corresponding to the boric acid blending amount at the time of production is not directly detected as the boron content of the electric resistor 1 by the ICP measurement, and the detected amount is smaller than the blending amount. It is considered that this is because when the amount of boric acid blended is small, the effect of boric acid evaporation during firing is large. Due to such a phenomenon, in order to form the Si / B-containing oxide 11 having a gas barrier property against oxygen gas around the silicon particles 10, the amount of boric acid blended should be increased in consideration of the amount of boron to evaporate. Is required. According to the results of EDX measurement and electron diffraction measurement of a transmission electron microscope (TEM), an amorphous region containing elements of Si, B, and O can be seen around the silicon particles 10. Therefore, the Si / B-containing oxide 11 is considered to be a borosilicate. Specifically, the Si / B-containing oxide 11 is preferably derived from at least silicon particles 10 and boric acid. According to this configuration, it becomes easier to suppress the mixing of the alkaline component as compared with the case where the Si / B-containing oxide 11 is derived from the silicon particles 10 and the borosilicate glass. Therefore, according to this configuration, it becomes easy to suppress the crystallization of the glass phase in the material, and the electric resistor 1 which is advantageous in reducing the coefficient of thermal expansion can be obtained.
　電気抵抗体１において、Ｓｉ／Ｂ比が２８０を超えると、１０００℃の高温酸化雰囲気に曝された際の電気抵抗増加率が急激に大きくなる。これは、シリコン粒子１０に対してホウ素の含有量が少ないため、ガスバリア性が低下し、１０００℃の高温酸化雰囲気に曝されたときに、シリコン粒子１０が絶縁性のＳｉＯ２に変化することによって電気的接合が切断されるためである。Ｓｉ／Ｂ比は、１０００℃の高温酸化雰囲気に曝された際の電気抵抗増加率の低減効果を確実なものにするなどの観点から、好ましくは、２００以下、より好ましくは、１５０以下、さらに好ましくは、１００以下とすることができる。また、Ｓｉ／Ｂ比は、ホウ素量が多すぎる場合には導電性発現のキーとなるシリコン粒子１０の量が相対的に少なくなるなどの観点から、好ましくは、５以上、より好ましくは、８以上、さらに好ましくは、１０以上とすることができる。 When the Si / B ratio of the electric resistor 1 exceeds 280, the rate of increase in electric resistance when exposed to a high-temperature oxidizing atmosphere of 1000 ° C. increases sharply. This is because the content of boron is smaller than that of the silicon particles 10, so that the gas barrier property is lowered, and the silicon particles 10 change to the insulating SiO 2 when exposed to a high temperature oxidizing atmosphere of 1000 ° C. This is because the electrical junction is broken. The Si / B ratio is preferably 200 or less, more preferably 150 or less, and further, from the viewpoint of ensuring the effect of reducing the rate of increase in electrical resistance when exposed to a high-temperature oxidizing atmosphere of 1000 ° C. Preferably, it can be 100 or less. Further, the Si / B ratio is preferably 5 or more, more preferably 8 from the viewpoint that the amount of silicon particles 10, which are the key to the development of conductivity, is relatively small when the amount of boron is too large. Above, more preferably, it can be 10 or more.
　電気抵抗体１において、ホウ素含有量が０．５質量％未満になると、１０００℃の高温酸化雰囲気に曝された際の電気抵抗増加率が急激に大きくなる。ホウ素含有量は、１０００℃の高温酸化雰囲気に曝された際の電気抵抗増加率の低減効果を確実なものにするなどの観点から、好ましくは、０．８質量％以上、より好ましくは、１．０質量％以上、さらに好ましくは、２．０質量％以上とすることができる。また、ホウ素含有量は、ホウ素量が多すぎる場合には導電性発現のキーとなるシリコン粒子１０の量が相対的に少なくなるなどの観点から、好ましくは、８．０質量％以下、より好ましくは、６．０質量％以下、さらに好ましくは、４．０質量％以下とすることができる。 When the boron content of the electric resistor 1 is less than 0.5% by mass, the rate of increase in electrical resistance when exposed to a high-temperature oxidizing atmosphere of 1000 ° C. increases sharply. The boron content is preferably 0.8% by mass or more, more preferably 1 from the viewpoint of ensuring the effect of reducing the rate of increase in electrical resistance when exposed to a high-temperature oxidizing atmosphere of 1000 ° C. It can be 0.0% by mass or more, more preferably 2.0% by mass or more. Further, the boron content is preferably 8.0% by mass or less, more preferably from the viewpoint that the amount of silicon particles 10, which are the key to the development of conductivity, is relatively small when the amount of boron is too large. Can be 6.0% by mass or less, more preferably 4.0% by mass or less.
　電気抵抗体１は、さらに、溶融シリカを含むことができる。溶融シリカは、電気抵抗体１の製造時における焼成時に溶融し、電気抵抗体１の材料構造を緻密化する。そのため、この構成によれば、電気抵抗体１の内部に酸素ガスが浸透し難くなり、シリコン粒子１０の酸化が抑制される。それ故、この構成によれば、１０００℃の高温酸化雰囲気に曝された際の電気抵抗増加率の低減を図りやすくなる。また、溶融シリカは、原料シリカが高温で溶融されて作製されたものであるため、アルカリ成分をほとんど含まない。そのため、この構成によれば、電気抵抗体１に含まれるアルカリ成分が低減され、ガラス相の結晶化が抑制される。また、溶融シリカは、熱膨張率が低い（溶融シリカの熱膨張率：０．８ｐｐｍ／Ｋ程度）。それ故、この構成によれば、電気抵抗体１の熱膨張率を低下させることができ、電気抵抗体１の耐熱衝撃性の向上に有利である。 The electric resistor 1 can further contain fused silica. The molten silica melts during firing during the production of the electric resistor 1 to densify the material structure of the electric resistor 1. Therefore, according to this configuration, it becomes difficult for oxygen gas to permeate into the electric resistor 1, and the oxidation of the silicon particles 10 is suppressed. Therefore, according to this configuration, it becomes easy to reduce the rate of increase in electrical resistance when exposed to a high-temperature oxidizing atmosphere of 1000 ° C. Further, since the molten silica is produced by melting the raw material silica at a high temperature, it contains almost no alkaline component. Therefore, according to this configuration, the alkaline component contained in the electric resistor 1 is reduced, and the crystallization of the glass phase is suppressed. Further, the molten silica has a low coefficient of thermal expansion (coefficient of thermal expansion of the molten silica: about 0.8 ppm / K). Therefore, according to this configuration, the coefficient of thermal expansion of the electric resistor 1 can be reduced, which is advantageous for improving the thermal shock resistance of the electric resistor 1.
　電気抵抗体１に占める溶融シリカの含有量は、８５質量％以下とすることができる。この構成によれば、通電性を確保しやすくなるので、通電加熱に適した電気抵抗体１を得やすくなる。溶融シリカの含有量は、上記効果を確実なものとするなどの観点から、好ましくは、８０質量％以下、より好ましくは、７０質量％以下、さらに好ましくは、６０質量％以下とすることができる。なお、溶融シリカの含有量は、耐酸化性と低熱膨張性とのバランスなどの観点から、好ましくは、１０質量％以上、より好ましくは、２０質量％以上、さらに好ましくは、３０質量％以上とすることができる。 The content of molten silica in the electric resistor 1 can be 85% by mass or less. According to this configuration, it becomes easy to secure the electrical conductivity, so that it becomes easy to obtain the electric resistor 1 suitable for the energization heating. The content of the molten silica can be 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 the above effect. .. The content of the molten silica is preferably 10% by mass or more, more preferably 20% by mass or more, still more preferably 30% by mass or more, from the viewpoint of the balance between oxidation resistance and low thermal expansion. can do.
　電気抵抗体１は、さらに、コーディエライトを含むことができる。コーディエライトは、電気抵抗体１の製造時における焼成時に溶融し、電気抵抗体１の材料構造を緻密化する。そのため、この構成によれば、電気抵抗体１の内部に酸素ガスが浸透し難くなり、シリコン粒子１０の酸化が抑制される。それ故、この構成によれば、１０００℃の高温酸化雰囲気に曝された際の電気抵抗増加率の低減を図りやすくなる。また、コーディエライトを含む構成とすることにより、出発原料におけるカオリン量を低減、あるいは、無くすことが可能となる。カオリンが焼成されて生成するアルミナやムライトに比べ、コーディエライトは、熱膨張率が低い（コーディエライトの熱膨張率：１．８～２．０ｐｐｍ／Ｋ程度）。それ故、この構成によれば、電気抵抗体１の熱膨張率を低下させることができ、電気抵抗体１の耐熱衝撃性の向上に有利である。 The electric resistor 1 can further include cordierite. Cordierite melts during firing during the production of the electric resistor 1 to densify the material structure of the electric resistor 1. Therefore, according to this configuration, it becomes difficult for oxygen gas to permeate into the electric resistor 1, and the oxidation of the silicon particles 10 is suppressed. Therefore, according to this configuration, it becomes easy to reduce the rate of increase in electrical resistance when exposed to a high-temperature oxidizing atmosphere of 1000 ° C. Further, by adopting a configuration containing cordierite, it is possible to reduce or eliminate the amount of kaolin in the starting material. Cordierite has a lower coefficient of thermal expansion than alumina and mullite produced by firing kaolin (coefficient of thermal expansion of cordierite: about 1.8 to 2.0 ppm / K). Therefore, according to this configuration, the coefficient of thermal expansion of the electric resistor 1 can be reduced, which is advantageous for improving the thermal shock resistance of the electric resistor 1.
　電気抵抗体１に占めるコーディエライトの含有量は、７５質量％以下とすることができる。この構成によれば、通電性を確保しやすくなるので、通電加熱に適した電気抵抗体１を得やすくなる。コーディエライトの含有量は、上記効果を確実なものとするなどの観点から、好ましくは、７０質量％以下、より好ましくは、６８質量％以下、さらに好ましくは、６０質量％以下、さらにより好ましくは、５０質量％以下とすることができる。なお、コーディエライトの含有量は、耐酸化性と低熱膨張性とのバランスなどの観点から、好ましくは、３０質量％以上、より好ましくは、３５質量％以上、さらに好ましくは、４０質量％以上とすることができる。 The content of cordierite in the electric resistor 1 can be 75% by mass or less. According to this configuration, it becomes easy to secure the electrical conductivity, so that it becomes easy to obtain the electric resistor 1 suitable for the energization heating. The content of cordierite is preferably 70% by mass or less, more preferably 68% by mass or less, still more preferably 60% by mass or less, still more preferably, from the viewpoint of ensuring the above effects. Can be 50% by mass or less. The content of cordierite is preferably 30% by mass or more, more preferably 35% by mass or more, still more preferably 40% by mass or more, from the viewpoint of the balance between oxidation resistance and low thermal expansion. Can be.
　上述した溶融シリカ、コーディエライトは、電気抵抗体１において絶縁相として機能することができる。溶融シリカ、コーディエライトは、いずれも、Ｓｉ・Ｂ含有酸化物１１にて表面が覆われたシリコン粒子連続体１０１の周囲に存在することができる。電気抵抗体１は、具体的には、図１に例示されるように、マトリックス１２中に、Ｓｉ・Ｂ含有酸化物１１にて表面が覆われたシリコン粒子連続体１０１を含んでおり、上記のマトリックス１２が溶融シリカおよびコーディエライトのうちの少なくとも一方を含む構成とすることができる。 The above-mentioned fused silica and cordierite can function as an insulating phase in the electric resistor 1. Both the molten silica and cordierite can exist around the silicon particle continuum 101 whose surface is covered with the Si / B-containing oxide 11. Specifically, as illustrated in FIG. 1, the electric resistor 1 contains a silicon particle continuum 101 whose surface is covered with a Si / B-containing oxide 11 in the matrix 12, and is described above. Matrix 12 can be configured to contain at least one of fused silica and cordierite.
　電気抵抗体１は、大気中、１０００℃で５０時間保持した後の電気抵抗増加率が２５０％以下である構成とすることができる。この構成によれば、１０００℃の高温酸化雰囲気に曝された場合でも電気抵抗の増加を抑制可能な電気抵抗体１を実現しやすくなる。電気抵抗増加率は、耐酸化性の向上等の観点から、好ましくは、２３０％以下、より好ましくは、２００％以下、さらに好ましくは、１５０％以下、さらにより好ましくは、電気加熱式触媒装置における回路素子を維持しやすいなどの観点から、１３５％以下、さらにより一層好ましくは、１３０％以下とすることができる。 The electric resistor 1 can be configured such that the rate of increase in electrical resistance after holding at 1000 ° C. for 50 hours in the atmosphere is 250% or less. According to this configuration, it becomes easy to realize an electric resistor 1 capable of suppressing an increase in electric resistance even when exposed to a high-temperature oxidizing atmosphere of 1000 ° C. The rate of increase in electrical resistance is preferably 230% or less, more preferably 200% or less, still more preferably 150% or less, still more preferably in an electrically heated catalyst device, from the viewpoint of improving oxidation resistance and the like. From the viewpoint of easy maintenance of the circuit element, it can be 135% or less, and even more preferably 130% or less.
　なお、電気抵抗増加率は、次のようにして測定される値が用いられる。電気抵抗体１のサンプルにつき、大気中、１０００℃で５０時間保持する前（つまり、初期）と当該保持した後の電気抵抗率をそれぞれ測定する。なお、電気抵抗体１の電気抵抗率は、２５℃にて四端子法により測定される測定値（ｎ＝３）の平均値である。そして、１００×（１０００℃で５０時間保持した後の電気抵抗率）／（１０００℃で５０時間保持する前の初期の電気抵抗率）の計算式にて算出される値を、電気抵抗増加率（％）とする。 For the rate of increase in electrical resistance, the value measured as follows is used. For each sample of the electric resistor 1, the electrical resistivity before (that is, initial) holding at 1000 ° C. for 50 hours and after holding the sample are measured. The electrical resistivity of the electric resistor 1 is an average value of measured values (n = 3) measured by the four-terminal method at 25 ° C. Then, the value calculated by the formula of 100 × (electric resistivity after holding at 1000 ° C. for 50 hours) / (initial electrical resistivity after holding at 1000 ° C. for 50 hours) is the electric resistance increase rate. (%).
　電気抵抗体１は、電気抵抗率が０．０１Ω・ｃｍ以上１００Ω・ｃｍ以下である構成とすることができる。この構成によれば、電気加熱式触媒装置を搭載するハイブリッドカーに好適な回路を選択しやすくなるため、電気加熱式触媒装置におけるハニカム構造体として好適な電気抵抗体が得られる。なお、電気抵抗体１の電気抵抗率は、２５℃にて四端子法により測定される測定値（ｎ＝３）の平均値である。 The electric resistor 1 can be configured to have an electric resistivity of 0.01 Ω · cm or more and 100 Ω · cm or less. According to this configuration, it becomes easy to select a circuit suitable for a hybrid car equipped with an electric heating type catalyst device, so that an electric resistor suitable as a honeycomb structure in the electric heating type catalyst device can be obtained. The electrical resistivity of the electric resistor 1 is an average value of measured values (n = 3) measured by the four-terminal method at 25 ° C.
　電気抵抗体１の電気抵抗率は、通電加熱時の発熱量増大、比較的単純な電気回路を採用しやすくなるなどの観点から、好ましくは、０．１Ω・ｃｍ以上、より好ましくは、０．３Ω・ｃｍ以上、さらに好ましくは、０．５Ω・ｃｍ以上とすることができる。電気抵抗体１の電気抵抗率は、低電気抵抗化などの観点から、好ましくは、５０Ω・ｃｍ以下、より好ましくは、３０Ω・ｃｍ以下、さらに好ましくは、１０Ω・ｃｍ以下とすることができる。 The electrical resistivity of the electric resistor 1 is preferably 0.1 Ω · cm or more, more preferably 0., from the viewpoint of increasing the amount of heat generated during energization heating and making it easier to adopt a relatively simple electric circuit. It can be 3 Ω · cm or more, more preferably 0.5 Ω · cm or more. The electrical resistivity of the electric resistor 1 can be preferably 50 Ω · cm or less, more preferably 30 Ω · cm or less, and further preferably 10 Ω · cm or less from the viewpoint of reducing the electric resistance.
　電気抵抗体１は、電気抵抗上昇率が０％／℃以上０．５％／℃以下である構成とすることができる。この構成によれば、電気抵抗体１がＮＴＣ特性（温度が高くなるにつれて電気抵抗率が減少する特性）とならない。ＮＴＣ特性の電気抵抗体では、局所的に加熱された部位に電流がより多く流れ込むため、温度分布が生じ、均一発熱の観点から不利である。これに対して、上記構成によれば、電気抵抗体１がＮＴＣ特性とならないので、均一発熱を実現しやすい電気抵抗体１が得られる。 The electric resistor 1 can be configured such that the rate of increase in electric resistance is 0% / ° C. or higher and 0.5% / ° C. or lower. According to this configuration, the electric resistor 1 does not have the NTC characteristic (the characteristic that the electrical resistivity decreases as the temperature rises). An electric resistor having NTC characteristics is disadvantageous from the viewpoint of uniform heat generation because a larger amount of current flows into a locally heated part, which causes a temperature distribution. On the other hand, according to the above configuration, since the electric resistor 1 does not have the NTC characteristic, the electric resistor 1 that can easily realize uniform heat generation can be obtained.
　電気抵抗体１の電気抵抗上昇率は、ＰＴＣ特性（温度が高くなるにつれて電気抵抗率が増加する特性）とする観点から、０％／℃よりも大きいことが好ましく、ＰＴＣ特性を確実なものにする観点から、より好ましくは、０．０５％／℃以上、さらに好ましくは、０．０６％／℃以上、さらにより好ましくは、０．０７％／℃以上とすることができる。また、電気抵抗体１の電気抵抗上昇率は、電気加熱式触媒装置におけるハニカム構造体として用いた際に、電気抵抗変化が大きくなり過ぎず、回路対応が図りやすいなどの観点から、好ましくは、０．５％／℃以下、より好ましくは、０．４％／℃以下、さらに好ましくは、０．３％／℃以下、さらにより好ましくは、０．２％／℃以下とすることができる。 The electrical resistivity increase rate of the electric resistor 1 is preferably larger than 0% / ° C. from the viewpoint of PTC characteristics (characteristics in which the electrical resistivity increases as the temperature rises), and ensures the PTC characteristics. From this point of view, it can be more preferably 0.05% / ° C. or higher, further preferably 0.06% / ° C. or higher, and even more preferably 0.07% / ° C. or higher. Further, the rate of increase in electric resistance of the electric resistor 1 is preferably increased from the viewpoint that when used as a honeycomb structure in an electric heating type catalyst device, the change in electric resistance does not become too large and it is easy to correspond to a circuit. It can be 0.5% / ° C. or lower, more preferably 0.4% / ° C. or lower, still more preferably 0.3% / ° C. or lower, and even more preferably 0.2% / ° C. or lower.
　電気抵抗体１の電気抵抗上昇率は、次のように算出される。５０℃、２００℃、４００℃の３点で電気抵抗体１の電気抵抗率を測定する。各温度における電気抵抗体１の電気抵抗率は、四端子法により測定される測定値（ｎ＝３）の平均値である。そして、以下の計算式により、電気抵抗上昇率［％／℃］を算出する。なお、５０℃および４００℃における電気抵抗率に加えて２００℃における電気抵抗率を測定するのは、電気抵抗率の温度依存性が直線性を有するか確認する意義がある。
　電気抵抗上昇率［％／℃］
　＝｛１００×（Ｒ４００－Ｒ５０）／Ｒ５０［％］｝／（４００［℃］－５０［℃］）
　但し、上記式中、
　Ｒ４００は、４００℃における電気抵抗体１の電気抵抗率［Ω・ｃｍ］、
　Ｒ５０は、５０℃における電気抵抗体１の電気抵抗率［Ω・ｃｍ］である。 The rate of increase in electrical resistance of the electrical resistor 1 is calculated as follows. The electrical resistivity of the electric resistor 1 is measured at three points of 50 ° C., 200 ° C., and 400 ° C. The electrical resistivity of the electrical resistor 1 at each temperature is an average value of measured values (n = 3) measured by the four-terminal method. Then, the rate of increase in electrical resistance [% / ° C.] is calculated by the following formula. Measuring the electrical resistivity at 200 ° C. in addition to the electrical resistivity at 50 ° C. and 400 ° C. is meaningful for confirming whether the temperature dependence of the electrical resistivity has linearity.
Electrical resistance increase rate [% / ° C]
= {100 x (R 400- R 50 ) / R 50 [%]} / (400 [° C] -50 [° C])
However, in the above formula,
R 400 is the electrical resistivity [Ω · cm] of the electrical resistor 1 at 400 ° C.
R 50 is the electrical resistivity [Ω · cm] of the electrical resistor 1 at 50 ° C.
（実施形態２）
　実施形態２のハニカム構造体について、図３を用いて説明する。なお、実施形態２以降において用いられる符号のうち、既出の実施形態において用いた符号と同一のものは、特に示さない限り、既出の実施形態におけるものと同様の構成要素等を表す。 (Embodiment 2)
The honeycomb structure of the second embodiment will be described with reference to FIG. In addition, among the codes used in the second and subsequent embodiments, the same codes as those used in the above-described embodiments represent the same components and the like as those in the above-mentioned embodiments, unless otherwise specified.
　図３に例示されるように、本実施形態のハニカム構造体２は、実施形態１の電気抵抗体１を含んで構成されている。本実施形態では、具体的には、ハニカム構造体２は、実施形態１の電気抵抗体１より構成されている。図３では、具体的には、ハニカム構造体２の中心軸に垂直なハニカム断面視で、互いに隣接する複数のセル２０と、セル２０を形成するセル壁２１と、セル壁２１の外周部に設けられてセル壁２１を一体に保持する外周壁２２と、を有する構造が例示されている。なお、ハニカム構造体２には、公知の構造を適用することができ、図３の構造に限定されるものではない。図３は、セル２０を断面四角形状とした例であるが、他にも、例えば、セル２０を断面六角形状などとすることもできる。また、図３は、ハニカム構造体２を円柱形状とした例であるが、他にも、例えば、ハニカム構造体２を断面トラック形状などとすることもできる。 As illustrated in FIG. 3, the honeycomb structure 2 of the present embodiment includes the electric resistor 1 of the first embodiment. Specifically, in the present embodiment, the honeycomb structure 2 is composed of the electric resistor 1 of the first embodiment. In FIG. 3, specifically, in a cross-sectional view of the honeycomb perpendicular to the central axis of the honeycomb structure 2, a plurality of cells 20 adjacent to each other, a cell wall 21 forming the cells 20, and an outer peripheral portion of the cell wall 21 are formed. An example is a structure having an outer peripheral wall 22 provided and integrally holding the cell wall 21. A known structure can be applied to the honeycomb structure 2, and the structure is not limited to the structure shown in FIG. FIG. 3 shows an example in which the cell 20 has a quadrangular cross section, but in addition, for example, the cell 20 may have a hexagonal cross section. Further, FIG. 3 shows an example in which the honeycomb structure 2 has a cylindrical shape, but in addition, for example, the honeycomb structure 2 may have a cross-sectional track shape or the like.
　本実施形態のハニカム構造体２は、実施形態１の電気抵抗体１を含んで構成されている。そのため、本実施形態のハニカム構造体２は、１０００℃の高温酸化雰囲気に曝された場合でも電気抵抗の増加を抑制することができる。発熱量は、電気抵抗に比例して増加する。本実施形態のハニカム構造体２によれば、発熱量が急激に増加することがなく、一定した昇温速度を実現することができる。それ故、本実施形態のハニカム構造体２は、電気加熱式触媒装置のハニカム構造体として好適である。 The honeycomb structure 2 of the present embodiment is configured to include the electric resistor 1 of the first embodiment. Therefore, the honeycomb structure 2 of the present embodiment can suppress an increase in electrical resistance even when exposed to a high-temperature oxidizing atmosphere of 1000 ° C. The calorific value increases in proportion to the electrical resistance. According to the honeycomb structure 2 of the present embodiment, the calorific value does not increase sharply, and a constant temperature rise rate can be realized. Therefore, the honeycomb structure 2 of the present embodiment is suitable as the honeycomb structure of the electric heating type catalyst device.
（実施形態３）
　実施形態３の電気加熱式触媒装置について、図４を用いて説明する。図４に例示されるように、本実施形態の電気加熱式触媒装置３は、実施形態２のハニカム構造体２を有している。本実施形態では、具体的には、電気加熱式触媒装置３は、ハニカム構造体２と、ハニカム構造体２のセル壁２１に担持された排ガス浄化触媒（不図示）と、ハニカム構造体２の外周壁２２に対向配置された一対の電極３１、３２と、電極３１、３２に電圧を印加し、制御する電圧印加部３３とを有している。なお、電極３１、電極３２には、それぞれ、棒状電極端子３１０、棒状電極端子３２０を通じて電圧が印加される。電気加熱式触媒装置３は、外周壁２２に付与した一対の電極３１、３２を通じて通電発熱させることができる。電気加熱式触媒装置３は、排ガス浄化触媒の機能を十分に発揮させるなどの観点から、例えば、５００℃以上の温度に加熱されることができる。なお、電気加熱式触媒装置３には、公知の構造を適用することができ、図４の構造に限定されるものではない。また、電圧印加の形態も、直流、交流、パルス状の電圧印加等、いずれの形態、および組み合わせであってもよい。 (Embodiment 3)
The electrically heated catalyst device of the third embodiment will be described with reference to FIG. As illustrated in FIG. 4, the electrically heated catalyst device 3 of the present embodiment has the honeycomb structure 2 of the second embodiment. In the present embodiment, specifically, the electric heating type catalyst device 3 includes a honeycomb structure 2, an exhaust gas purification catalyst (not shown) supported on the cell wall 21 of the honeycomb structure 2, and the honeycomb structure 2. It has a pair of electrodes 31 and 32 arranged to face each other on the outer peripheral wall 22, and a voltage application unit 33 that applies and controls a voltage to the electrodes 31 and 32. A voltage is applied to the electrode 31 and the electrode 32, respectively, through the rod-shaped electrode terminal 310 and the rod-shaped electrode terminal 320, respectively. The electric heating type catalyst device 3 can generate heat by energization through a pair of electrodes 31 and 32 provided to the outer peripheral wall 22. The electrically heated catalyst device 3 can be heated to a temperature of, for example, 500 ° C. or higher from the viewpoint of fully exerting the function of the exhaust gas purification catalyst. A known structure can be applied to the electrically heated catalyst device 3, and the structure is not limited to the structure shown in FIG. Further, the form of voltage application may be any form or combination such as direct current, alternating current, pulsed voltage application and the like.
　本実施形態の電気加熱式触媒装置３は、実施形態２のハニカム構造体２を有している。そのため、本実施形態の電気加熱式触媒装置３は、排ガス環境下にて１０００℃の高温酸化雰囲気に曝された場合でもハニカム構造体２の電気抵抗の増加を抑制することができ、一定した昇温速度を実現することができる。また、本実施形態の電気加熱式触媒装置３は、熱耐久性の向上にも有利である。 The electrically heated catalyst device 3 of the present embodiment has the honeycomb structure 2 of the second embodiment. Therefore, the electric heating type catalyst device 3 of the present embodiment can suppress an increase in the electric resistance of the honeycomb structure 2 even when exposed to a high temperature oxidizing atmosphere of 1000 ° C. in an exhaust gas environment, and the increase is constant. A temperature rate can be achieved. Further, the electrically heated catalyst device 3 of the present embodiment is also advantageous in improving the thermal durability.
（実験例１）
＜試料の作製＞
－試料１－
　シリコン粒子（平均粒子径７μｍ）とホウ酸とコーディエライト（平均粒子径１．７μｍ）とを３０：２０：５０の質量比で混合した。次いで、この混合物にバインダーとしてメチルセルロースを４質量％添加し、水を加え、混合した。次いで、得られた混合物を押し出し成形機にてペレット状に成形し、恒温槽にて８０℃で乾燥させた後、脱脂した。脱脂の条件は、大気雰囲気・常圧、脱脂温度７００度、脱脂時間３時間とした。 (Experimental Example 1)
<Preparation of sample>
-Sample 1-
Silicon particles (average particle size 7 μm), boric acid and cordierite (average particle size 1.7 μm) were mixed at a mass ratio of 30:20:50. Then, 4% by mass of methyl cellulose was added as a binder to this mixture, water was added, and the mixture was mixed. Next, the obtained mixture was molded into pellets by an extrusion molding machine, dried at 80 ° C. in a constant temperature bath, and then degreased. The degreasing conditions were air atmosphere / normal pressure, degreasing temperature 700 ° C., and degreasing time 3 hours.
　次いで、脱脂した焼成体を仮焼した。仮焼条件は、Ａｒガス雰囲気下・常圧、仮焼温度１２５０℃、仮焼時間３０分とした。 Next, the degreased fired body was calcined. The calcination conditions were an Ar gas atmosphere, normal pressure, a calcination temperature of 1250 ° C., and a calcination time of 30 minutes.
　次いで、得られた焼成体を本焼成した。本焼成の条件は、Ａｒガス雰囲気下・常圧、本焼成温度１３５０℃、本焼成時間３０分とした。 Next, the obtained fired body was main fired. The conditions for the main firing were an Ar gas atmosphere, normal pressure, a main firing temperature of 1350 ° C., and a main firing time of 30 minutes.
　次いで、得られた焼成体を予備酸化処理（酸化エージング処理）した。予備酸化の条件は、大気雰囲気・常圧、処理温度１０００℃、処理時間１０時間とした。これにより、５ｍｍ×５ｍｍ×２５ｍｍの形状を有する試料１の電気抵抗体を得た。 Next, the obtained fired body was subjected to a preliminary oxidation treatment (oxidation aging treatment). The conditions for pre-oxidation were atmospheric atmosphere / normal pressure, treatment temperature 1000 ° C., and treatment time 10 hours. As a result, an electric resistor of Sample 1 having a shape of 5 mm × 5 mm × 25 mm was obtained.
－試料２－
　シリコン粒子とホウ酸とコーディエライトとを３０：１０：６０の質量比で混合した混合物を用いた点以外は、試料１と同様にして、試料２の電気抵抗体を得た。 -Sample 2-
An electric resistor of Sample 2 was obtained in the same manner as in Sample 1 except that a mixture of silicon particles, boric acid and cordierite was used at a mass ratio of 30:10:60.
－試料３－
　コーディエライトに代えて溶融シリカ（平均粒子径６．８μｍ）を用い、シリコン粒子とホウ酸と溶融シリカとを３０：２０：５０の質量比で混合した混合物を用いた点以外は、試料１と同様にして、試料３の電気抵抗体を得た。 -Sample 3-
Sample 1 except that fused silica (average particle diameter 6.8 μm) was used instead of cordierite, and a mixture of silicon particles, boric acid, and fused silica mixed at a mass ratio of 30:20:50 was used. In the same manner as above, the electric resistor of sample 3 was obtained.
－試料４－
　コーディエライトに代えて溶融シリカ（平均粒子径６．８μｍ）を用い、シリコン粒子とホウ酸と溶融シリカとを３０：１０：６０の質量比で混合した混合物を用いた点以外は、試料１と同様にして、試料４の電気抵抗体を得た。 -Sample 4-
Sample 1 except that fused silica (average particle diameter 6.8 μm) was used instead of cordierite, and a mixture of silicon particles, boric acid, and fused silica mixed at a mass ratio of 30:10:60 was used. In the same manner as above, the electric resistor of sample 4 was obtained.
－試料１Ｃ－
　シリコン粒子とホウ酸とコーディエライトとを３０：４：６６の質量比で混合した混合物を用いた点以外は、試料１と同様にして、試料１Ｃの電気抵抗体を得た。 -Sample 1C-
An electric resistor of sample 1C was obtained in the same manner as in sample 1 except that a mixture of silicon particles, boric acid and cordierite in a mass ratio of 30: 4: 66 was used.
－試料２Ｃ－
　コーディエライトに代えて溶融シリカ（平均粒子径６．８μｍ）を用い、シリコン粒子とホウ酸と溶融シリカとを３０：４：６６の質量比で混合した混合物を用いた点以外は、試料１と同様にして、試料２Ｃの電気抵抗体を得た。 -Sample 2C-
Sample 1 except that fused silica (average particle size 6.8 μm) was used instead of cordierite, and a mixture of silicon particles, boric acid, and fused silica mixed at a mass ratio of 30: 4: 66 was used. In the same manner as above, an electric resistor of sample 2C was obtained.
＜Ｓｉ／Ｂ比、ホウ素含有量＞
　各試料の電気抵抗体について、ＩＣＰ発光分光分析装置（日立ハイテクサイエンス社製、「ＳＰＳ－３５２０ＵＶ」）を用い、各材料全体に含まれるホウ素含有量（質量％）、シリコン含有量（質量％）を測定した。そして、各試料の電気抵抗体について、材料全体におけるホウ素に対するシリコンの質量比であるＳｉ／Ｂ比を算出した。 <Si / B ratio, boron content>
For the electrical resistors of each sample, use an ICP emission spectrophotometer (“SPS-3520UV” manufactured by Hitachi High-Tech Science Co., Ltd.), and the boron content (mass%) and silicon content (mass%) contained in each material as a whole. Was measured. Then, for the electric resistors of each sample, the Si / B ratio, which is the mass ratio of silicon to boron in the entire material, was calculated.
＜電気抵抗率、電気抵抗増加率＞
　各試料の電気抵抗体について、電気抵抗率を測定した。電気抵抗率は、５ｍｍ×５ｍｍ×２５ｍｍの角柱サンプルについて、熱電特性評価装置（アルバック理工社製、「ＺＥＭ－２」）を用い、四端子法で測定した。本測定における測定温度は、２５℃である。また、各試料の電気抵抗体を、大気中、１０００℃で５０時間保持した。なお、大気中、１０００℃で５０時間保持するという条件は、１０００℃の高温酸化雰囲気中に曝される使用状態を模擬したものである。なお、本例では、参考として、予備酸化処理を行う前の各電気抵抗体についても、上記と同様にして、電気抵抗率を測定した。次いで、上記と同様にして、当該保持後における各試料の電気抵抗体の電気抵抗率を測定した。本例では、１０時間の予備酸化処理が施された後、１０００℃で５０時間保持する前の各試料の電気抵抗体の電気抵抗率を初期の電気抵抗率とする。次いで、１０００℃で５０時間保持する前の初期の電気抵抗率と、１０００℃で５０時間保持した後の電気抵抗率とを用い、上述した計算式にて、各試料の電気抵抗体の電気抵抗増加率を測定した。 <Electrical resistivity, electrical resistance increase rate>
The electrical resistivity of each sample was measured. The electrical resistivity of a prism sample having a size of 5 mm × 5 mm × 25 mm was measured by a four-terminal method using a thermoelectric characterization device (“ZEM-2” manufactured by ULVAC Riko Co., Ltd.). The measurement temperature in this measurement is 25 ° C. In addition, the electrical resistors of each sample were held in the air at 1000 ° C. for 50 hours. The condition of holding the product in the atmosphere at 1000 ° C. for 50 hours simulates the usage state of being exposed to a high temperature oxidizing atmosphere of 1000 ° C. In this example, as a reference, the electrical resistivity of each electric resistor before the preliminary oxidation treatment was measured in the same manner as described above. Then, in the same manner as described above, the electrical resistivity of the electrical resistor of each sample after the holding was measured. In this example, the electrical resistivity of the electrical resistivity of each sample after being subjected to the pre-oxidation treatment for 10 hours and before being held at 1000 ° C. for 50 hours is defined as the initial electrical resistivity. Next, using the initial electrical resistivity before holding at 1000 ° C. for 50 hours and the electrical resistivity after holding at 1000 ° C. for 50 hours, the electrical resistivity of the electric resistor of each sample is calculated by the above formula. The rate of increase was measured.
＜電気抵抗上昇率＞
　各試料の電気抵抗体について、上述した電気抵抗率の測定方法に従い、５０℃における電気抵抗率（Ｒ５０）、２００℃における電気抵抗率（Ｒ２００）、４００℃における電気抵抗率（Ｒ４００）を測定した。そして、上述した計算式に基づいて、各試料の電気抵抗体の電気抵抗上昇率を算出した。 <Rate of increase in electrical resistance>
For the electrical resistivity of each sample, the electrical resistivity at 50 ° C. (R 50 ), the electrical resistivity at 200 ° C. (R 200 ), and the electrical resistivity at 400 ° C. (R 400 ) according to the method for measuring the electrical resistivity described above. Was measured. Then, based on the above-mentioned calculation formula, the rate of increase in electrical resistance of the electrical resistor of each sample was calculated.
　表１に、各試料の電気抵抗体の作製条件、各種測定結果等をまとめて示す。 Table 1 summarizes the production conditions of the electric resistors of each sample, various measurement results, and the like.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
　表１、図５～図７によれば、以下のことがわかる。本開示にて規定される構成を備えていない試料１Ｃ、試料２Ｃの電気抵抗体は、１０００℃の高温酸化雰囲気に曝された際に電気抵抗率が急激に増加した。これらに対し、本開示にて規定される構成を備えている試料１～試料４の電気抵抗体は、１０００℃の高温酸化雰囲気に曝された場合でも、電気抵抗率の急激な増加を抑制することができた。 According to Table 1, FIGS. 5 to 7, the following can be seen. The electrical resistivity of Sample 1C and Sample 2C, which did not have the configuration specified in the present disclosure, increased sharply when exposed to a high-temperature oxidizing atmosphere at 1000 ° C. On the other hand, the electric resistors of Samples 1 to 4 having the configuration specified in the present disclosure suppress a rapid increase in electrical resistivity even when exposed to a high temperature oxidizing atmosphere of 1000 ° C. I was able to.
　なお、表１によれば、試料１Ｃに対し、試料１は、ホウ酸の配合比が５倍になっているが、ＩＣＰ測定によるホウ素含有量の比は５倍にはなっていないことがわかる。つまり、ホウ酸の配合量とＩＣＰ測定によるホウ素含有量とは比例しないことがわかる。これは、ホウ酸配合量が少ない場合に焼成時にホウ酸が蒸発する影響が大きいためであると考えられる。 According to Table 1, it can be seen that the mixing ratio of boric acid in Sample 1 is 5 times higher than that in Sample 1C, but the ratio of the boron content measured by ICP is not 5 times higher. .. That is, it can be seen that the amount of boric acid blended is not proportional to the boron content measured by ICP. It is considered that this is because when the amount of boric acid blended is small, the effect of boric acid evaporation during firing is large.
　また、上記結果から、本例の電気抵抗体を用いて電気加熱式触媒装置のハニカム構造体を構成すれば、１０００℃の高温酸化雰囲気に曝された場合でも電気抵抗の増加を抑制することができるので、一定した昇温速度を実現することができるといえる。また、本例の電気抵抗体により構成したハニカム構造体を有する電気加熱式触媒装置によれば、排ガス環境下にて１０００℃の高温酸化雰囲気に曝された場合でもハニカム構造体の電気抵抗の増加を抑制することができるので、一定した昇温速度を実現することができるといえる。また、かかる電気加熱式触媒装置は、熱耐久性の向上にも有利であるといえる。 Further, from the above results, if the honeycomb structure of the electric heating type catalyst device is constructed by using the electric resistance of this example, it is possible to suppress the increase of the electric resistance even when exposed to a high temperature oxidizing atmosphere of 1000 ° C. Therefore, it can be said that a constant temperature rise rate can be realized. Further, according to the electric heating type catalyst device having a honeycomb structure composed of the electric resistors of this example, the electric resistance of the honeycomb structure increases even when exposed to a high temperature oxidizing atmosphere of 1000 ° C. in an exhaust gas environment. It can be said that a constant temperature rise rate can be realized because the temperature can be suppressed. Further, it can be said that such an electrically heated catalyst device is also advantageous in improving thermal durability.
（実験例２） (Experimental Example 2)
＜シリコン／ホウ酸配合比、質量増加率、電気抵抗増加率＞
　ホウ酸配合量を従来に比べて増量し、ＩＣＰ測定によるＳｉ／Ｂ比、ホウ素含有量を本開示にて規定される範囲とすることによって、１０００℃の高温酸化雰囲気に曝された際の電気抵抗率の増加を抑制することができた理由について、さらに調査した。具体的には、電気抵抗体の配合原料におけるホウ酸に対するシリコンの質量比であるシリコン／ホウ酸配合比を変化させ、大気中、１０００℃で５０時間保持した際の保持前後の電気抵抗体の質量から質量増加率を求めた。質量増加率（％）は、１００×（１０００℃で５０時間保持した後の電気抵抗体の質量）／（予備酸化処理を行う前の電気抵抗体の質量）の計算式より算出した。また、上記シリコン／ホウ酸配合比を変化させ、上述した電気抵抗増加率を求めた。その結果を、図８および図９に示す。 <Silicon / boric acid compounding ratio, mass increase rate, electrical resistance increase rate>
By increasing the boric acid content as compared with the conventional one and setting the Si / B ratio and the boron content as measured by ICP within the ranges specified in this disclosure, electricity when exposed to a high temperature oxidizing atmosphere at 1000 ° C. The reason why the increase in resistivity could be suppressed was further investigated. Specifically, the silicon / boric acid compounding ratio, which is the mass ratio of silicon to boric acid in the compounding raw material of the electric resistor, is changed, and the electric resistance before and after holding at 1000 ° C. for 50 hours in the air. The mass increase rate was calculated from the mass. The mass increase rate (%) was calculated from the formula of 100 × (mass of electric resistor after holding at 1000 ° C. for 50 hours) / (mass of electric resistor before pre-oxidation treatment). In addition, the above-mentioned silicon / boric acid compounding ratio was changed to obtain the above-mentioned increase rate of electrical resistance. The results are shown in FIGS. 8 and 9.
　図８に示されるように、シリコン／ホウ酸配合比が大きい、つまり、シリコン配合量に対してホウ酸配合量が少ない領域において、質量増加率が大きいことがわかる。これは、１０００℃の高温酸化雰囲気に曝された際にシリコン粒子の表面にて酸化が活発に生じたことにより、ＳｉＯ２膜が多く形成されて質量が増加したためである。その結果、シリコン粒子間の導電パスの狭窄や切断が生じ、実験例１の試料１Ｃ、試料２Ｃは、１０００℃の高温酸化雰囲気に曝された際に電気抵抗が増加したものと考えられる。一方、シリコン／ホウ酸配合比が小さい、つまり、シリコン配合量に対してホウ酸配合量が多い領域において、質量増加率が小さいことがわかる。これは、１０００℃の高温酸化雰囲気に曝された場合でもシリコン粒子表面の酸化が抑制され、ＳｉＯ２が成長し難かったためである。その結果、シリコン粒子間の導電パスの狭窄や切断が起こり難く、実験例１の試料１から試料４は、１０００℃の高温酸化雰囲気に曝された場合でも電気抵抗の増加が抑制されたものと考えられる。 As shown in FIG. 8, it can be seen that the mass increase rate is large in the region where the silicon / boric acid compounding ratio is large, that is, the boric acid compounding amount is small with respect to the silicon compounding amount. This is because when the silicon particles are exposed to a high-temperature oxidizing atmosphere at 1000 ° C., oxidation is actively generated on the surface of the silicon particles, so that a large number of SiO 2 films are formed and the mass is increased. As a result, the conductive path between the silicon particles was narrowed or cut, and it is considered that the electrical resistance of Sample 1C and Sample 2C of Experimental Example 1 increased when exposed to a high-temperature oxidizing atmosphere at 1000 ° C. On the other hand, it can be seen that the mass increase rate is small in the region where the silicon / boric acid compounding ratio is small, that is, the boric acid compounding amount is large relative to the silicon compounding amount. This is because oxidation of the surface of the silicon particles was suppressed even when exposed to a high-temperature oxidizing atmosphere of 1000 ° C., and SiO 2 was difficult to grow. As a result, narrowing or cutting of the conductive path between the silicon particles is unlikely to occur, and the samples 1 to 4 of Experimental Example 1 are said to have suppressed the increase in electrical resistance even when exposed to a high-temperature oxidizing atmosphere at 1000 ° C. Conceivable.
　また、図９によれば、シリコン／ホウ酸配合比が大きい、つまり、シリコン配合量に対してホウ酸配合量が少ない領域において、電気抵抗増加率が大きくなり、シリコン／ホウ酸配合比が小さい、つまり、シリコン配合量に対してホウ酸配合量が多い領域において、電気抵抗増加率が小さくなることがわかる。この結果から、１０００℃の高温酸化雰囲気に曝された際における電気抵抗の増加抑制のためには、ホウ酸配合量を多くし、電気抵抗体に含まれるホウ素含有量を高めることが有効であるといえる。 Further, according to FIG. 9, in the region where the silicon / boric acid compounding ratio is large, that is, the boric acid compounding amount is small with respect to the silicon compounding amount, the electric resistance increase rate is large and the silicon / boric acid compounding ratio is small. That is, it can be seen that the rate of increase in electrical resistance becomes smaller in the region where the boric acid compounding amount is larger than the silicon compounding amount. From this result, in order to suppress the increase in electric resistance when exposed to a high temperature oxidizing atmosphere of 1000 ° C., it is effective to increase the amount of boric acid compounded and increase the boron content contained in the electric resistor. It can be said that.
　本開示は、上記各実施形態、各実験例に限定されるものではなく、その要旨を逸脱しない範囲において種々の変更が可能である。また、各実施形態、各実験例に示される各構成は、それぞれ任意に組み合わせることができる。すなわち、本開示は、実施形態に準拠して記述されたが、本開示は、当該実施形態や構造等に限定されるものではないと理解される。本開示は、様々な変形例や均等範囲内の変形をも包含する。加えて、様々な組み合わせや形態、さらには、それらに一要素のみ、それ以上、あるいはそれ以下、を含む他の組み合わせや形態をも、本開示の範疇や思想範囲に入るものである。 The present disclosure is not limited to each of the above embodiments and experimental examples, and various changes 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. That is, although the present disclosure has been described in accordance with the embodiments, it is understood that the present disclosure is not limited to the embodiments, structures, and the like. The present disclosure also includes various modifications and modifications within an equal range. In addition, various combinations and forms, as well as other combinations and forms that include only one element, more, or less, are also within the scope of the present disclosure.

Claims (9)

  1. 　シリコン粒子（１０）と、シリコンおよびホウ素を含む酸化物（１１）と、を含み、
    　材料全体におけるホウ素に対するシリコンの質量比であるＳｉ／Ｂ比が２８０以下であり、
    　材料全体に含まれるホウ素含有量が０．５質量％以上である、
    　電気抵抗体（１）。     Containing silicon particles (10) and oxides containing silicon and boron (11),
    The Si / B ratio, which is the mass ratio of silicon to boron in the entire material, is 280 or less.
    The boron content in the whole material is 0.5% by mass or more.
    Electrical resistor (1).
  2. 　さらに、溶融シリカを含む、請求項１に記載の電気抵抗体。 The electric resistor according to claim 1, further comprising fused silica.
  3. 　さらに、コーディエライトを含む、請求項１または請求項２に記載の電気抵抗体。 The electrical resistor according to claim 1 or 2, further comprising cordierite.
  4. 　大気中、１０００℃で５０時間保持した後の電気抵抗増加率が２５０％以下である、請求項１から請求項３のいずれか１項に記載の電気抵抗体。 The electric resistor according to any one of claims 1 to 3, wherein the rate of increase in electrical resistance after holding at 1000 ° C. for 50 hours in the atmosphere is 250% or less.
  5. 　電気抵抗率が０．０１Ω・ｃｍ以上１００Ω・ｃｍ以下である、請求項１から請求項４のいずれか１項に記載の電気抵抗体。 The electric resistor according to any one of claims 1 to 4, wherein the electrical resistivity is 0.01 Ω · cm or more and 100 Ω · cm or less.
  6. 　電気抵抗上昇率が０％／℃以上０．５％／℃以下である、請求項１から請求項５のいずれか１項に記載の電気抵抗体。 The electric resistor according to any one of claims 1 to 5, wherein the rate of increase in electrical resistance is 0% / ° C. or higher and 0.5% / ° C. or lower.
  7. 　電気加熱式触媒装置におけるハニカム構造体に使用されるように構成されている、請求項１から請求項６のいずれか１項に記載の電気抵抗体。 The electric resistor according to any one of claims 1 to 6, which is configured to be used for a honeycomb structure in an electrically heated catalyst device.
  8. 　請求項１から請求項６のいずれか１項に記載の電気抵抗体を含んで構成されている、ハニカム構造体（２）。 A honeycomb structure (2) including the electric resistor according to any one of claims 1 to 6.
  9. 　請求項８に記載のハニカム構造体を有する、電気加熱式触媒装置（３）。 An electrically heated catalyst device (3) having the honeycomb structure according to claim 8.
PCT/JP2020/042884 2019-12-06 2020-11-18 Electrical resistor, honeycomb structure, and electrically heated catalyst device WO2021111869A1 (en)

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Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH02144874A (en) * 1988-11-28 1990-06-04 Tokai Konetsu Kogyo Co Ltd Conducting honeycomb ceramic
JP2000128637A (en) * 1998-10-29 2000-05-09 Kyocera Corp Ceramics heating element
JP2017170401A (en) * 2016-03-25 2017-09-28 トヨタ自動車株式会社 Catalytic converter
JP2019098302A (en) * 2017-12-07 2019-06-24 株式会社デンソー Honeycomb structure
WO2019124183A1 (en) * 2017-12-19 2019-06-27 株式会社デンソー Electrical resistor, honeycomb structure, and electrical heating-type ca- talytic device

Patent Citations (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH02144874A (en) * 1988-11-28 1990-06-04 Tokai Konetsu Kogyo Co Ltd Conducting honeycomb ceramic
JP2000128637A (en) * 1998-10-29 2000-05-09 Kyocera Corp Ceramics heating element
JP2017170401A (en) * 2016-03-25 2017-09-28 トヨタ自動車株式会社 Catalytic converter
JP2019098302A (en) * 2017-12-07 2019-06-24 株式会社デンソー Honeycomb structure
WO2019124183A1 (en) * 2017-12-19 2019-06-27 株式会社デンソー Electrical resistor, honeycomb structure, and electrical heating-type ca- talytic device

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