阅读说明：本技术 电阻体、蜂窝结构体及电加热式催化剂装置 (Resistor, honeycomb structure, and electrically heated catalyst device ) 是由 德野刚大 平田和希 高山泰史 于 2018-12-12 设计创作，主要内容包括：电阻体(1)包含：硼硅酸盐粒子(10)、含Si粒子(11)、和气孔部(12)。气孔部(12)由硼硅酸盐粒子(10)与含Si粒子(11)之间的间隙构成,并包围硼硅酸盐粒子(10)以及含Si粒子(11)。蜂窝结构体(2)包含电阻体(1)而构成。电加热式催化剂装置(3)具有蜂窝结构体(2)。(The resistor (1) includes: borosilicate particles (10), Si-containing particles (11), and an air hole portion (12). The gas hole section (12) is formed by a gap between the borosilicate particles (10) and the Si-containing particles (11), and surrounds the borosilicate particles (10) and the Si-containing particles (11). The honeycomb structure (2) is configured to include a resistor (1). The electrically heated catalyst device (3) has a honeycomb structure (2).)

1. A resistor body (1) comprising:

borosilicate particles (10),

Si-containing particles (11), and

and a gas hole section (12) which is configured by a gap between the borosilicate particles and the Si-containing particles, and which surrounds the borosilicate particles and the Si-containing particles (12).

2. The resistor according to claim 1, wherein the cumulative pore volume is 0.05ml/g or more.

3. The resistor body according to claim 1 or 2, wherein the resistivity is 0.0001 Ω · m or more and 1 Ω · m or less, and the rate of increase in resistance is 0/K or more and 5.0 × 10 in a temperature range of 25 ℃ to 500 ℃^-4and/K is less than or equal to.

4. The resistor according to any one of claims 1 to 3, wherein the Si-containing particles are at least one selected from the group consisting of Si particles, Fe-Si-based particles, Si-W-based particles, Si-C-based particles, Si-Mo-based particles, and Si-Ti-based particles.

5. The resistor body according to any one of claims 1 to 4, wherein the B atom content in the borosilicate particles is 0.1 mass% or more and 5 mass% or less.

6. The resistor body according to any one of claims 1 to 5, wherein the borosilicate particles contain at least one alkali atom selected from the group consisting of Na, Mg, K, and Ca in a total content of 2 mass% or less.

7. The resistor body according to any one of claims 1 to 6, wherein the borosilicate particles are aluminoborosilicate particles.

8. The resistor according to any one of claims 1 to 7, wherein the resistor is configured to be used as a honeycomb structure in an electrically heated catalyst device.

9. A honeycomb structure (2) comprising the resistor according to any one of claims 1 to 7.

10. A honeycomb structure (2) comprising the resistor according to any one of claims 1 to 7 and having a particle-trapping function.

11. An electrically heated catalyst device (3) having the honeycomb structure according to claim 9 or 10.

Technical Field

The present invention relates to a resistor, a honeycomb structure, and an electrically heated catalyst device.

Background

Conventionally, in each field, a resistor is used for electrical heating. For example, in the field of vehicles, there is known an electrically heated catalyst device in which a catalyst-supporting honeycomb structure is made of a resistor such as SiC, and the honeycomb structure is heated by energization to generate heat.

Patent document 1 discloses a resistor containing 5 to 60 wt% of Si and 5 to 50 wt% of SiC in a ceramic structural material mainly containing an aluminum silicate. In addition, the following is described in this document: a glass component is added to the resistor, and the glass component is dissolved out on the surface of the resistor during firing at 1000 to 1400 ℃, thereby forming an insulating glass coating on the surface of the resistor.

Disclosure of Invention

In order to efficiently generate heat in the resistor by electrical heating, the resistance of the resistor has an optimum value of current and voltage. However, most resistors, as typified by SiC, have a large temperature dependence of resistivity, and the optimum value of current and voltage varies depending on the temperature of the resistor. Therefore, a resistor having a small temperature dependence of resistivity is required. In addition, in order to efficiently generate heat by the resistor by electrical heating, it is important that the heat capacity of the resistor is small.

In order to reduce the weight of the honeycomb structure, the volume density of the resistor is preferably small. In addition, it is also important that the resistor applied to the material of the honeycomb structure has excellent catalyst supporting properties.

The invention provides a resistor, a honeycomb structure using the resistor, and an electrically heated catalyst device using the honeycomb structure, wherein the resistor has small temperature dependence of resistivity, reduces volume density and heat capacity, and improves catalyst carrying performance.

One aspect of the present invention relates to a resistor including: the borosilicate particles, the Si-containing particles, and the pores that surround the borosilicate particles and the Si-containing particles are formed by gaps between the borosilicate particles and the Si-containing particles.

Another aspect of the present invention relates to a honeycomb structure including the resistor.

Another aspect of the present invention relates to an electrically heated catalyst device including the honeycomb structure.

Effects of the invention

Since the resistor has borosilicate particles and Si-containing particles, the temperature dependence of the resistivity can be reduced. Further, since the resistor has the gas hole portions which are formed by the gaps between the borosilicate particles and the Si-containing particles and surround the borosilicate particles and the Si-containing particles, the volume density and the heat capacity can be reduced as compared with a resistor in which the gaps between the borosilicate particles and the Si-containing particles are filled with glass. In addition, the resistor has irregularities formed on the surface thereof through the air hole. Therefore, the resistor can improve the carrying property of a catalyst such as an exhaust gas purifying catalyst.

The honeycomb structure includes the resistor. Therefore, the honeycomb structure described above is less likely to have a temperature distribution inside the structure and to have cracks due to a difference in thermal expansion when heated by energization. In addition, the honeycomb structure is likely to generate heat at an early stage at a low temperature when heated by energization. In addition, the above-described honeycomb structure is advantageous for weight reduction. In addition, the honeycomb structure described above easily carries an exhaust gas purification catalyst on the surface.

The electrically heated catalyst device has the honeycomb structure. Therefore, the electrically heated catalyst device described above is less likely to cause cracks in the honeycomb structure during electrical heating, and can improve reliability. In addition, the electrically heated catalyst device can generate heat at a low temperature at an early stage when electrically heated, and is advantageous for early activation of the catalyst. In addition, the electrically heated catalyst device is advantageous for weight reduction of the device due to weight reduction of the honeycomb structure.

In the claims, the parenthesized reference signs indicate correspondence with specific means described in the embodiments described later, and do not limit the technical scope of the present invention.

Drawings

The above and other objects, features and advantages of the present invention will become more apparent with reference to the accompanying drawings and the following detailed description. The drawings are as follows.

Fig. 1 is an explanatory view schematically showing a microstructure of a resistor according to embodiment 1;

fig. 2 is an explanatory view schematically showing a honeycomb structure of embodiment 2;

fig. 3 is an explanatory view schematically showing an electrically heated catalyst device according to embodiment 3;

fig. 4 is an SEM (scanning electron microscope) image of sample 1 in experimental example 1;

fig. 5 is an SEM (scanning electron microscope) image of sample 1C in experimental example 1;

FIG. 6 is a graph showing the relationship between the temperature and the resistivity of sample 1 and sample 1C in Experimental example 1;

FIG. 7 shows pore size distributions of sample 1 and sample 1C in Experimental example 1;

FIG. 8 is a graph showing the relationship between the temperature and the resistivity of sample 2 and sample 3(1250 ℃ C. fired product) in Experimental example 2;

FIG. 9 is a graph showing the relationship between the temperature and the resistivity of samples 4 to 6(1300 ℃ C. fired product) in Experimental example 2.

Detailed Description

(embodiment mode 1)

The resistor of embodiment 1 will be described with reference to fig. 1. As illustrated in fig. 1, the resistor of the present embodiment includes borosilicate particles 10, Si-containing particles 11, and pores 12.

The borosilicate particles 10 may be amorphous or crystalline. The borosilicate particles 10 may contain, for example, Al (aluminum) atoms in addition to atoms such as boron (B), Si (silicon), and O (oxygen). In this case, the borosilicate particles 10 become aluminoborosilicate particles. With this configuration, the resistor 1 having a small temperature dependence of resistivity, a reduced volume density and heat capacity, and an improved catalyst carrying property can be reliably formed. The borosilicate particles 10 may contain alkali metal atoms such as Na and K, and alkaline earth metal atoms such as Mg and Ca (hereinafter, the alkali metal atoms and the alkaline earth metal atoms may be collectively referred to as "alkali atoms"). They may contain one or two or more species.

The borosilicate particles 10 may contain 0.1 mass% to 5 mass% of B atoms. This structure has an advantage that temperature dependence of resistivity can be easily reduced.

The content of B atoms is preferably 0.2 mass% or more, more preferably 0.3 mass% or more, even more preferably 0.5 mass% or more, even more preferably 0.6 mass% or more, even more preferably 0.8 mass% or more, from the viewpoint of facilitating the reduction of the resistance of the resistor 1, and the like, and may be even more preferably 1 mass% or more from the viewpoint of reducing the temperature dependence of the resistivity, facilitating the display of the PTC characteristic (the characteristic in which the resistivity increases as the temperature increases), and the like. The content of B atoms has a limit to the amount of doping into the silicate, and in the case of undoped, B is an insulator₂O₃From the viewpoint of uneven distribution in the material, which causes a decrease in conductivity, etc., it is preferably 4% by mass or less, more preferably 3.5% by mass or less, and still more preferably 3% by mass or less.

The borosilicate particles 10 may contain 5 mass% to 40 mass% of Si atoms. According to this structure, the temperature dependence of the resistivity can be easily reduced.

From the viewpoint of securing the above-described effects, increasing the softening point of the borosilicate particles 10, and the like, the content of Si atoms may be preferably 7 mass% or more, more preferably 10 mass% or more, and still more preferably 15 mass% or more. In addition, from the viewpoint of securing the above-described effects, the content of Si atoms may be preferably 30 mass% or less, more preferably 26 mass% or less, and still more preferably 24 mass% or less.

The borosilicate particles 10 may contain 40 to 85 mass% of O atoms. According to this structure, the temperature dependence of the resistivity can be easily reduced.

From the viewpoint of securing the above-described effects, the content of the O atom may be preferably 45 mass% or more, more preferably 50 mass% or more, further preferably 55 mass% or more, and further preferably 60 mass% or more. In addition, from the viewpoint of securing the above-described effects, the content of the O atom may be preferably 82 mass% or less, more preferably 80 mass% or less, and still more preferably 78 mass% or less.

When the borosilicate particles 10 are aluminoborosilicate particles, they may contain 0.5 mass% to 10 mass% of Al atoms. According to this structure, the temperature dependence of the resistivity can be easily reduced.

From the viewpoint of securing the above-described effects, the content of Al atoms may be preferably 1 mass% or more, more preferably 2 mass% or more, and still more preferably 3 mass% or more. From the viewpoint of securing the above-described effects, the content of Al atoms may be preferably 8 mass% or less, more preferably 6 mass% or less, and still more preferably 5 mass% or less.

When the borosilicate particles 10 contain alkali atoms, the total content of at least one alkali atom selected from the group consisting of Na, Mg, K, and Ca in the borosilicate particles 10 may be 2 mass% or less. According to this structure, even when the firing is performed in an atmosphere containing oxygen, formation of an insulating glass coating film formed by reaction of alkali atoms dissolved and segregated on the surface side of resistor 1 with oxygen in the atmosphere can be easily suppressed without forming an oxygen-barrier film. When the resistor 1 is used as a material of a conductive honeycomb structure, there is an advantage that when an electrode is formed on the surface of the honeycomb structure, the insulating glass coating film does not need to be removed in advance, and the productivity of the honeycomb structure is improved. In this case, the total content of alkali atoms may be preferably 1.5% by mass or less, more preferably 1.2% by mass or less, and still more preferably 1% by mass or less, from the viewpoint of suppressing the formation of an insulating glass coating film or the like.

From the above viewpoint, the total content of alkali atoms is preferably as small as possible. However, the alkali atoms are elements that are relatively easily mixed from the material of the resistor 1. Therefore, in order to make the borosilicate particles 10 free of alkali atoms, it takes a cost and time to completely remove the alkali atoms from the raw material. Therefore, the total content of the alkali atoms may be preferably 0.01% by mass or more, more preferably 0.05% by mass or more, still more preferably 0.1% by mass or more, and still more preferably 0.2% by mass or more. In addition, in resistor 1, the alkali atoms can be reduced by using boric acid instead of borosilicate glass containing alkali atoms as a raw material. Details will be described later in the experimental examples. The "total content of alkali atoms" means "mass% of one kind of alkali atom" when the borosilicate contains the one kind of alkali atom. When the borosilicate particles 10 contain a plurality of alkali atoms, the term "total content (% by mass) obtained by adding the respective contents (% by mass) of the plurality of alkali atoms" means.

The content of each atom in the borosilicate particles 10 may be selected from the above range so as to be 100 mass% in total. Examples of the atoms that can be contained in the borosilicate particles 10 include, for example, Fe and C in addition to the above atoms. Among the atoms described above, the contents of Si, O, Al, and alkali atoms were measured using an electron beam microanalyzer (EPMA) analyzer. The content of B in each atom was measured by an Inductively Coupled Plasma (ICP) analyzer. In the ICP analysis, the measurement result obtained is converted to the B content in the borosilicate particles 10 in order to measure the B content in the entire resistor 1.

The Si-containing particles 11 are electron-conductive particles containing Si atoms. Therefore, the Si-containing particles 11 do not contain SiO₂Particles, and the like. Specific examples of the Si-containing particles include Si particles, Fe-Si-based particles, Si-W-based particles, Si-C-based particles, Si-Mo-based particles, and Si-Ti-based particles. They may contain one or two or more kinds. This structure has an advantage that Si-containing particles, which are electron conductive particles, are easily electrically bridged between the borosilicate particles 10. Among these, Si particles, Fe — Si-based particles, and the like are preferable from the viewpoint of relatively low melting point, less occurrence of a pasting phenomenon, and the like. The "gelatinization phenomenon" described above is caused in MoSi₂Or WSi₂The phenomenon of polycrystalline body pulverization by oxidation at a relatively low temperature of about 500 ℃ is observed.

The resistor 1 may contain, in addition to the Si-containing particles 11, one or more of a filler, a material for reducing a thermal expansion coefficient, a material for increasing a thermal conductivity, a material for improving a strength, kaolin, and the like, as necessary.

The gas hole portion 12 is formed by a gap between the borosilicate particles 10 and the Si-containing particles 11, and surrounds the borosilicate particles 10 and the Si-containing particles 11. That is, the pore portion 12 is formed by a gap formed at the interface between the borosilicate particles 10 and the Si-containing particles 11, and is different from a void that can be formed at the time of manufacturing the resistor 1. The voids having a maximum outer diameter of 5 μm or more are generally pores. The air hole portion 12 may be continuous or discontinuous. The pore portion 12 may not completely surround the borosilicate particles 10 and the Si-containing particles 11 all around. Fig. 1 shows an example in which a plurality of borosilicate particles 10 and a plurality of Si-containing particles 11 are surrounded by the pore portions 12.

The resistor 1 may have a cumulative pore volume of 0.05ml/g or more. According to this structure, a structure in which the gas hole portions 10 are present at the interface between the borosilicate particles 10 and the Si-containing particles 11 can be reliably formed. If the cumulative pore volume of the resistor 1 is less than 0.05ml/g, the volume density and the heat capacity are not easily reduced due to the shortage of the pore portion 10. Further, when the cumulative pore volume of the resistor 1 becomes less than 0.05ml/g, the anchor effect at the time of catalyst loading becomes weak, and there is a concern that the catalyst may be peeled off due to a cooling-heating cycle, for example, because most of the pore portions are filled with the molten glass component at the time of firing. The cumulative pore volume of the resistor 1 was measured according to JIS R1655: 2003 "method for testing pore size distribution of molded body by mercury intrusion method for purified ceramic". The measurement is performed on the surface of the resistor 1.

The average particle diameter of the borosilicate particles 10 may be preferably 0.5 μm or more, more preferably 1 μm or more, and still more preferably 2 μm or more, from the viewpoint of increase in particle size, increase in electrical resistance, and the like when the average particle diameter becomes too small. The average particle diameter of the borosilicate particles 10 is preferably 30 μm or less, more preferably 20 μm or less, and still more preferably 15 μm or less, from the viewpoint of, for example, being problematic when the thickness of the honeycomb structure is reduced when the average particle diameter is too large.

The average particle diameter of the Si-containing particles 11 may be preferably 0.5 μm or more, more preferably 1 μm or more, and even more preferably 2 μm or more, from the viewpoint of increase in grain boundary, increase in electrical resistance, and the like when it becomes too small. The average particle diameter of the Si-containing particles 11 may be preferably 30 μm or less, more preferably 20 μm or less, and still more preferably 15 μm or less, from the viewpoint of, for example, being problematic when the thickness of the honeycomb structure is reduced when the average particle diameter is too large.

The average particle diameters of the borosilicate particles 10 and the Si-containing particles 11 were measured as follows. EPMA observation was performed on a cross section perpendicular to the surface of the resistor 1, and the element map was measured with respect to the observation region to specify the positions of the borosilicate particles 10 and the Si-containing particles 11. The maximum outer diameters of the borosilicate particles 10 in the observation region were determined, and the average of the obtained maximum outer diameters was defined as the average particle diameter of the borosilicate particles 10. Similarly, the maximum outer diameters of the Si-containing particles 11 in the observation region are determined, and the average of the maximum outer diameters is defined as the average particle diameter of the Si-containing particles 11. The particle size can be calculated by analysis using image analysis software ("WinROOF", manufactured by sango corporation).

The volume density of the resistor 1 may preferably be 1g/cm from the viewpoint of easily ensuring the flexural strength necessary for maintaining the shape and the like³Above, more preferably 1.1g/cm³Above, more preferably 1.2g/cm³The above. The volume density of the resistor 1 may preferably be 2g/cm from the viewpoint of reduction in heat capacity and the like³Hereinafter, more preferably 1.8g/cm³Hereinafter, more preferably 1.6g/cm³The following.

The resistor 1 can be formed to have a resistivity of 0.0001 to 1 Ω · m and a resistance increase of 0/K to 5.0 × 10 in a temperature range of 25 to 500 ℃^-4A structure of:/K or less. According to this configuration, since the temperature dependency of the resistor 1 is small, a temperature distribution is less likely to occur inside during electrical heating, and the resistor 1 in which cracks due to a thermal expansion difference are less likely to occur can be reliably formed. Further, according to the above configuration, since the resistor 1 can be heated early at a lower temperature during the electrical heating, it is useful as a material for a honeycomb structure requiring early heating for early activation of a catalyst.

The resistivity of the resistor 1 varies depending on the required specifications of a system using the resistor 1, but from the viewpoint of lowering the resistance of the resistor 1, for example, it may be preferably 0.5 Ω · m or less, more preferably 0.3 Ω · m or less, further preferably 0.1 Ω · m or less, further preferably 0.05 Ω · m or less, further preferably 0.01 Ω · m or less, further preferably less than 0.01 Ω · m, and most preferably 0.005 Ω · m or less. The resistivity of the resistor 1 may be preferably 0.0002 Ω · m or more, more preferably 0.0005 Ω · m or more, and even more preferably 0.001 Ω · m or more, from the viewpoint of an increase in the amount of heat generated during electrical heating, for example. With this configuration, the resistor 1 suitable for the material of the honeycomb structure used in the electrically heated catalyst device can be obtained.

The resistance increase rate of the resistor 1 is preferably 0.001 × 10 from the viewpoint of facilitating suppression of the temperature distribution due to the electrical heating, and the like^-6More preferably 0.01 × 10K or more, and still more preferably 0.01 ×^-6More preferably 0.1 × 10K or more, and still more preferably 0.1 ×^-6The resistance increase rate of the resistor 1 is preferably 100 × 10, although it is preferable that the resistance increase rate does not change from the viewpoint that the resistance value most suitable for the energization heating exists in the circuit^-6A value of 10 × 10 or less, more preferably 10^-6A value of 1/K or less, more preferably 1 × 10^-6and/K is less than or equal to.

The resistivity of the resistor 1 is an average value of measured values (n is 3) measured by a four-terminal method. The rate of increase in resistance of the resistor 1 can be calculated by the following calculation method after measuring the resistivity of the resistor 1 by the above-described method. First, the resistivity was measured at 3 points of 50 ℃, 200 ℃ and 400 ℃. The resistance increase rate was calculated by dividing the value obtained by subtracting the resistivity at 50 ℃ from the resistivity at 400 ℃ by the temperature difference between 400 ℃ and 50 ℃ of 350 ℃.

The resistor 1 can be manufactured, for example, as described below, but is not limited thereto.

Boric acid, a substance containing a Si atom, and kaolin are mixed. By using boric acid containing almost no alkali atoms as a boron source, the amount of alkali atoms in the obtained resistor 1 can be reduced, and the doping of boron into silicate can be promoted. The mass ratio of boric acid may be 4 or more and 8 or less, for example. If the boric acid mass ratio is within the above range, the resistor 1 having a small temperature dependence of resistivity can be easily obtained. Further, by raising the firing temperature described later, the boron content in the borosilicate can be easily increased. The larger the amount of boron doped in the silicate, the more advantageous the resistance of the obtained resistor 1 is to be lowered.

Subsequently, a binder and water were added to the mixture. As the binder, for example, an organic binder such as methyl cellulose can be used. The content of the binder may be, for example, about 2% by mass.

Next, the obtained mixture is molded into a predetermined shape.

The obtained molded body is then fired under firing conditions of, for example, an inert gas atmosphere or an atmospheric atmosphere, at atmospheric pressure or less, at a firing temperature of 1150 to 1350 ℃, and for a firing time of 0.1 to 50 hours, or under an inert gas atmosphere, and at a firing pressure of, for example, normal pressure, in order to reduce the resistance of the resistor 1, it is preferable from the viewpoint of preventing oxidation that the residual oxygen is reduced, and the atmosphere in firing can be set to 1.0 × 10^-4After a high vacuum of Pa or more, inert gas is purged and fired. As the inert gas atmosphere, for example, N can be exemplified₂A gas atmosphere, a helium atmosphere, an argon atmosphere, and the like. Before the firing, the compact may be calcined, if necessary. The burn-in conditions may specifically be: and in the atmosphere or the inert gas atmosphere, the presintering temperature is 500-700 ℃, and the presintering time is 1-50 hours. According to the above conditions, the resistor 1 can be obtained.

Since the resistor 1 of the present embodiment includes the borosilicate particles 10 and the Si-containing particles 11, the temperature dependence of the resistivity can be reduced. In addition, since the resistor 1 has the gas holes 12 between the borosilicate particles 10 and the Si-containing particles 11, the volume density and the heat capacity can be reduced as compared with the case where the gaps between the borosilicate particles 10 and the Si-containing particles 11 are filled with glass. Further, the resistor 1 has irregularities formed on the surface thereof through the gas holes 12. Therefore, the resistor 1 can improve the carrying property of a catalyst such as an exhaust gas purifying catalyst.

(embodiment mode 2)

The honeycomb structure of embodiment 2 will be described with reference to fig. 2. Note that, of the symbols used in embodiment 2 and thereafter, the same symbols as those used in the above embodiment indicate the same components as those in the above embodiment and the like unless otherwise specified.

As illustrated in fig. 2, the honeycomb structure 2 of the present embodiment includes the resistor 1 of embodiment 1. In the present embodiment, specifically, the honeycomb structure 2 is constituted by the resistor 1 of embodiment 1. In fig. 2, specifically, in a honeycomb sectional view perpendicular to the central axis of the honeycomb structural body 2, a structure having a plurality of cells 20 adjacent to each other, cell walls 21 forming the cells 20, and an outer peripheral wall 22 provided at an outer peripheral portion of the cell walls 21 and integrally holding the cell walls 21 is exemplified. Note that a known structure may be applied to the honeycomb structure 2, and the structure is not limited to the structure of fig. 2. Fig. 2 shows an example in which the cells 20 are formed in a square shape in cross section, but the cells 20 may be formed in a hexagonal shape in cross section.

The honeycomb structure 2 of the present embodiment includes the resistor 1 of embodiment 1. Therefore, the honeycomb structure 2 of the present embodiment is less likely to cause temperature distribution in the structure and cracks due to a difference in thermal expansion when heated by energization. In addition, the honeycomb structure 2 is likely to generate heat early at low temperature when heated by energization. In addition, the honeycomb structure 2 is advantageous for weight reduction. In addition, the honeycomb structure 2 easily carries the exhaust gas purifying catalyst on the surface.

In addition, the honeycomb structure 2 may be formed to have a structure having a particulate trapping function. The particulate trapping function is a function of trapping the particulates contained in the exhaust gas in the pore portion 12. In recent years, in exhaust gas aftertreatment systems, in addition to the removal of normal NO_XIn addition to exhaust gases such as CO and HC, there is a need to remove particulate matter contained in the exhaust gas, and GPF (gasoline particulate filter) or DPF (diesel particulate filter) is mounted as a particulate filter. These trap fine particles by utilizing the pore structure of the honeycomb structure, and pore control is very important in the development of GPF and DPF. Therefore, in order to provide an electrically heated catalyst device having a honeycomb structure with a particulate trapping function, it is important to control the pore structure. In a honeycomb structure using a conventional resistor, since the gaps between borosilicate particles and Si-containing particles are filled with glass, it is difficult to control the pore portions, and it is difficult to apply the honeycomb structure to GPF or DPF. In addition, in general GPF or DPFIn the case where the honeycomb structure is clogged with the particulates trapped by long-term use, the clogging has to be eliminated by a combustion process using fuel injection. In contrast, the honeycomb structure 2 of the present embodiment is composed of the resistor 1 of embodiment 1, and has a fine particle trapping function. Therefore, according to this structure, the fine particles trapped in the pore portions 12 of the resistor 1 constituting the honeycomb structure 2 can be burned by electrical heating. Therefore, according to this configuration, not only application to GPF or DPF becomes easy, but also combustion processing of particulates by fuel injection becomes unnecessary and fuel saving is possible.

(embodiment mode 3)

An electrically heated catalyst device according to embodiment 3 will be described with reference to fig. 3. As illustrated in fig. 3, an electrically heated catalyst apparatus 3 of the present embodiment includes a honeycomb structure 2 of embodiment 3. In the present embodiment, specifically, the electrically heated catalyst device 3 includes: the honeycomb structure 2, an exhaust gas purification catalyst (not shown) supported on the cell walls 21 of the honeycomb structure 2, a pair of electrodes 31,32 arranged to face each other on the outer peripheral wall 22 of the honeycomb structure 2, and a voltage application unit 33 for applying a voltage to the electrodes 31, 32. Note that a known configuration may be applied to the electrically heated catalyst device 3, and the configuration is not limited to the configuration of fig. 3.

The electrically heated catalyst device 3 of the present embodiment has the honeycomb structure 2 of embodiment 2. Therefore, the electrically heated catalyst device 3 of the present embodiment is less likely to crack the honeycomb structure 2 during electrical heating, and can improve reliability. The electrically heated catalyst device 3 can generate heat early at a low temperature during energization and heating, and is advantageous for early activation of the catalyst. The electrically heated catalyst device 3 is advantageous for weight reduction of the device due to weight reduction of the honeycomb structure 2.

< Experimental example 1 >

(preparation of sample)

Sample 1-

Mixing boric acid and Si particles and kaolin in a ratio of 4: 42: 54 are mixed in a mass ratio of 54. Then, the process of the present invention is carried out,to this mixture was added 2 mass% of methylcellulose as a binder, and water was added to knead the mixture. Next, the obtained mixture was formed into pellets by an extruder and subjected to primary firing. The conditions of primary firing are as follows: the firing temperature is 700 ℃, the heating time is 100 ℃/h, the holding time is 1 h, the atmosphere is atmospheric and the normal pressure is normal. Subsequently, the primary fired body is fired twice. The conditions of the secondary sintering are as follows: n is a radical of₂Sample 1 having a shape of 5mm × 5mm × 18mm was obtained under atmospheric pressure, at a firing temperature of 1250 ℃, for a firing time of 30 minutes, and at a temperature rise rate of 200 ℃/hour, in accordance with the EPMA measurement, borosilicate particles in sample 1 contained 0.5 mass% in total of alkali atoms (Na, Mg, K, and Ca), 22.7 mass% of Si, 68.1 mass% of O, and 5.7 mass% of Al, and in accordance with the ICP measurement, borosilicate particles in sample 1 contained 0.9 mass% of B, and further, the EPMA analyzer used "JXA-8500F" manufactured by japan electronics, and the ICP analyzer used "SPS-3520 UV" manufactured by hitachi-techs science.

The same applies hereinafter.

Sample 1C-

Borosilicate glass fibers (average diameter of 10 μm and average length of 25 μm) containing Na, Mg, K, Ca, Si particles and kaolin were mixed in a ratio of 29: 31: 40, were mixed. Subsequently, 2 mass% of methylcellulose as a binder was added to the mixture, and water was added thereto to knead the mixture. Next, the obtained mixture was formed into pellets by an extruder and subjected to primary firing. The conditions of primary firing are as follows: the firing temperature is 700 ℃, the heating time is 100 ℃/h, the holding time is 1 h, the atmosphere is atmospheric and the normal pressure is normal. Subsequently, the primary fired body is fired twice. The conditions of the secondary sintering are as follows: n is a radical of₂Sample 1C having a shape of 5mm × 5mm × 18mm was obtained under atmospheric pressure, at a firing temperature of 1300 ℃, for a firing time of 30 minutes, and at a temperature rise rate of 200 ℃/hour, and the borosilicate particles in sample 1C contained 6.4 mass% in total of alkali atoms (Na, Mg, K, and Ca), 21.4 mass% of Si, 65.4 mass% of O, and 5.1 mass% of Al, as measured by EPMAThe borosilicate particles in sample 1C contained B: 0.9% by mass.

(SEM Observation)

The cross section of each sample obtained was observed by SEM. The sample for SEM observation was cut, polished with #800 polishing paper, and further polished with a cross-section polisher. This is because, when mechanical polishing is performed, fine powder blocks the pore portion, and it becomes difficult to appropriately observe the subsequent pore portion. The above observation results are shown in fig. 4 and 5. As shown in fig. 5, sample 1C contains aluminoborosilicate particles and Si particles, but no pore portion is observed which is constituted by gaps between the aluminoborosilicate particles and the Si particles and surrounds the aluminoborosilicate particles and the Si particles. The air hole portion was not formed because the borate glass used as the raw material was melted by firing, and the gap between the aluminoborosilicate particles and the Si particles was filled. In fig. 5, symbol B denotes a void. The pores are not surrounded by the aluminoborosilicate particles and the Si particles, and are large voids, unlike the pore portions.

In contrast, as shown in fig. 4, sample 1 contains aluminoborosilicate particles and Si particles. Further, in sample 1, a pore portion constituted by a gap between the aluminoborosilicate particles and the Si particle and surrounding the aluminoborosilicate particles and the Si particle was confirmed. Unlike sample 1C, the formation of the pores in sample 1 is caused by the use of boric acid as a boron source, which hardly contains alkali atoms such as Na, Mg, K, and Ca, in the raw material, and therefore, the gaps between the aluminoborosilicate particles and the Si particles are not filled with glass during firing. In addition, in sample 1, it was confirmed that the presence of the alkali atom is mainly caused by kaolin used in the raw material.

(measurement of pore diameter distribution)

As described above, according to JIS R1655: 2003, the pore size distribution of the surface of each sample was measured using a mercury porosimeter (manufactured by Shimadzu corporation, "AutoPorel V9500"). The measured pore size distribution of each sample is shown in fig. 7. Further, the pore diameter at the time of calculating the cumulative pore volume is in the range of 100nm to 100 μm. The cumulative pore volume of sample 1 was 0.220ml/g, and the cumulative pore volume of sample 1C was 0.032 ml/g. That is, the cumulative pore volume of sample 1 was increased by about 6.9 times as compared with sample 1C.

(measurement of bulk Density)

For each sample, the bulk density was measured. As a result, the bulk density of sample 1 was 1.51g/cm³Sample 1C had a bulk density of 1.93g/cm³. That is, the bulk density of sample 1 was reduced by about 21% as compared with sample 1C. From the results, it is found that sample 1 has a heat capacity reduced by about 21% in the same shape as sample 1C.

(measurement of resistivity)

Further, with respect to the resistivity, the thermoelectric property evaluation device (manufactured by U L VAC, Inc. 'ZEM-2') was used for a prism sample of 5mm × 5mm × 18mm, and the measurement was performed by the four-terminal method, and as shown in FIG. 6, it was found that the temperature dependence of the resistivity was significantly reduced and the resistivity showed PTC properties in all of the samples 1 as compared with SiC, and that the resistivity was 0.0001. omega. m or more and 1. omega. m or less and the increase rate of the resistance was 0/K or more and 5.0 × 10 or 5.0 × 10 in the temperature range of 25 ℃ to 500 ℃ in the sample 1^-4and/K is less than or equal to. In addition, sample 1 was fired at a lower temperature than sample 1C, but had predetermined characteristics. When the firing temperature of sample 1 is the same as that of sample 1C, it is estimated that doping of boron (B) into aluminoborosilicate in sample 1 can be promoted and the resistivity can be lowered. This point will be described later in experimental example 2.

< Experimental example 2 >

Sample 2-

Except that boric acid and Si particles and kaolin were mixed in a ratio of 6: 41: sample 2 was obtained in the same manner as in sample 1 of experimental example 1, except that the mixing was performed at a mass ratio of 53 and the firing temperature was 1250 ℃.

Sample 3-

Except that the boric acid and Si particles and kaolin were mixed in a ratio of 8: 40: sample 3 was obtained in the same manner as in sample 1 of experimental example 1, except that the mixing was performed at a mass ratio of 52 and the firing temperature was 1250 ℃.

Sample 4-

Except that the boric acid and Si particles and kaolin were mixed in a ratio of 4: 42: sample 4 was obtained in the same manner as in sample 1 of experimental example 1, except that the mixing was performed at a mass ratio of 54 and the firing temperature was 1300 ℃.

Sample 5-

Except that boric acid and Si particles and kaolin were mixed in a ratio of 6: 41: sample 5 was obtained in the same manner as in sample 1 of experimental example 1, except that the mixing was performed at a mass ratio of 53 and the firing temperature was 1300 ℃.

Sample 6-

Except that the boric acid and Si particles and kaolin were mixed in a ratio of 8: 40: sample 6 was obtained in the same manner as in sample 1 of experimental example 1, except that the mixing was performed at a mass ratio of 52 and the firing temperature was 1300 ℃.

The obtained samples were evaluated in the same manner as in experimental example 1. As a result, a structure having aluminoborosilicate particles, Si particles, and pores was observed in each sample. The cumulative pore volume of each sample was 0.05ml/g or more. In addition, the content of B contained in the borosilicate particles in sample 2 was 0.8 mass%, the content of B contained in the borosilicate particles in sample 3 was 1.3 mass%, the content of B contained in the borosilicate particles in sample 4 was 2.1 mass%, the content of B contained in the borosilicate particles in sample 5 was 1.4 mass%, and the content of B contained in the borosilicate particles in sample 6 was 2.0 mass%.

The resistivity of each sample was measured in the same manner as in experimental example 1. The results are shown in fig. 8 and 9. As shown in fig. 8 and 9, it was confirmed that the doping of boron into aluminum silicate was promoted and the resistivity was decreased as the amount of boric acid added was increased as the firing temperature was increased.

The present invention is not limited to the above embodiments and experimental examples, and various modifications may be made without departing from the scope of the invention. The structures shown in the embodiments and the experimental examples may be arbitrarily combined. That is, although the present invention has been described with reference to the embodiment, it is to be understood that the present invention is not limited to the embodiment, the structure, and the like. The present invention also includes various modifications and equivalent variations. In addition, various combinations and modes including only one element, and other combinations and modes not less than the element are also included in the scope or the spirit of the present invention.