Honeycomb structure and electric heating element

Abstract

To provide a honeycomb structure that is less susceptible to dielectric breakdown and damage at high temperatures. [Solution] A honeycomb structure comprising a ceramic honeycomb structure having an outer periphery wall and partition walls disposed inside the outer periphery wall and forming a plurality of cells extending from a first end face to a second end face, a pair of electrode parts disposed on the outer periphery wall, one or more slits provided in the honeycomb structure, and a filler material filling at least a part of the space of the slit. The filler material has an electrical resistivity of 10.0 × 10 at 900°C. 3 A thermal expansion coefficient of 9.0 × 10⁻¹⁰ or greater, at temperatures of 40 to 800°C. -6 The temperature is below / ℃, and the Young's modulus is 0.10 GPa or higher.

Description

[Technical Field]

[0001] This invention relates to a honeycomb structure and an electric heating heater. [Background technology]

[0002] Industrial heaters are used to heat objects in various products and production equipment, and one type known is the electric heating heater using a honeycomb structure. For example, Patent Document 1 proposes a honeycomb structure comprising a columnar honeycomb structure having porous partition walls that divide a plurality of cells extending from a first end face to a second end face, which serve as fluid flow paths, and an outer peripheral wall located on the outermost periphery, and a pair of electrode parts disposed on the side surface of the honeycomb structure. In this honeycomb structure, one or more slits opening on the side surface are formed in the honeycomb structure, and the honeycomb structure has a filler material filled in at least one of the slits, with the filler material disposed in at least a part of the space of the slit. The filler material contains aggregate and neck material, and the ratio (α2 / α1) of the thermal expansion coefficient α2 of the filler material at 25 to 800°C to the thermal expansion coefficient α1 of the honeycomb structure at 25 to 800°C is 0.6 to 1.5. Furthermore, this honeycomb structure can suppress the unevenness of the temperature distribution when a voltage is applied and has excellent thermal shock resistance. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2015-174011 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] The honeycomb structure described in Patent Document 1 is primarily used as a catalyst support for purifying automobile exhaust gases and is not suitable for other applications. For example, when using the honeycomb structure described in Patent Document 1 for various applications, the honeycomb structure may be exposed to high temperatures (e.g., around 900°C). However, the filler material filling the slits may not provide sufficient insulation due to its low electrical resistivity at high temperatures. Therefore, when the applied voltage is increased, leakage current may increase in the areas where the filler material is filled in the slits, potentially leading to dielectric breakdown. Furthermore, the filler material used in the honeycomb structure described in Patent Document 1 is mainly composed of silicon carbide (SiC), and therefore is prone to oxidation to silicon dioxide (SiO2) and expansion in a high-temperature oxygen atmosphere. As a result, there is a risk that the honeycomb structure may be damaged due to the expansion of the filler material packed into the slits. Furthermore, the portion of the slit filled with filler material is subjected to the weight of the honeycomb structure itself, which can cause damage to that portion.

[0005] This invention was made to solve the above-mentioned problems, and aims to provide a honeycomb structure and an electric heating heater that are less prone to dielectric breakdown and damage at high temperatures. [Means for solving the problem]

[0006] The inventors of this invention have diligently researched electric heating heaters using honeycomb structures and have found that the above problems can be solved by filling the slit spaces of the honeycomb structure with a specific filler material, thus completing the present invention. That is, the present invention is illustrated as follows.

[0007] <1> A ceramic honeycomb structure having an outer perimeter wall and partition walls disposed inside the outer perimeter wall, which divide and form a plurality of cells extending from a first end face to a second end face, A pair of electrode portions disposed on the outer peripheral wall, One or more slits provided in the aforementioned honeycomb structure, A filler material that fills at least a portion of the space in the slit and Equipped with, The aforementioned filler has an electrical resistivity of 10.0 × 10 at 900°C. 3A honeycomb structure having a specific resistance of 1 Ω·cm or more, a thermal expansion coefficient of 9.0 × 10 -6 / °C or less in the range of 40 to 800 °C, and a Young's modulus of 0.10 GPa or more.

[0008] <2> The honeycomb structure according to <1>, wherein the filler is composed of an oxide.

[0009] <3> The honeycomb structure according to <2>, wherein the oxide contains Al2O3.

[0010] <4> The honeycomb structure according to <3>, wherein the oxide further contains MgO and / or SiO2.

[0011] <5> The honeycomb structure according to <3> or <4>, wherein the content of Al2O3 in the filler is 30% by mass or more.

[0012] <6> The honeycomb structure according to any one of <1> to <5>, wherein the porosity of the outer peripheral wall and the partition wall is less than 30%.

[0013] <7> The honeycomb structure portion is quadrangular prism-shaped, the pair of electrode portions are disposed on one plane of the outer peripheral wall, the slit includes a first slit extending from the outer peripheral wall between the pair of electrode portions to the inside, and is the honeycomb structure according to any one of <1> to <6>.

[0014] <8> The honeycomb structure according to <7>, wherein the slit further includes a second slit extending from two of the outer peripheral walls orthogonal to the outer peripheral wall on which the pair of electrode portions are provided to the inside, and a third slit intersecting the first slit and not reaching the outer peripheral wall.

[0015] <9> The honeycomb structure according to <8>, wherein the second slit and the third slit are provided so as to be alternately positioned.

[0016] <10> <1> ~ <9> An electric heating heater having a honeycomb structure as described in any one of the following. [Effects of the Invention]

[0017] According to the present invention, it is possible to provide a honeycomb structure and an electric heating heater that are less susceptible to dielectric breakdown and damage at high temperatures. [Brief explanation of the drawing]

[0018] [Figure 1] This is a perspective view of a honeycomb structure according to an embodiment of the present invention. [Figure 2] This is a front view of a plane perpendicular to the direction in which the cells of another honeycomb structure according to an embodiment of the present invention extend. [Figure 3] This is a perspective view illustrating the method for measuring the four-point bending strength of a filler material. [Modes for carrying out the invention]

[0019] The honeycomb structure of the present invention comprises: a ceramic honeycomb structure having an outer periphery wall and partition walls disposed inside the outer periphery wall and forming a plurality of cells extending from a first end face to a second end face; a pair of electrode parts disposed on the outer periphery wall; one or more slits provided in the honeycomb structure; and a filler material filling at least a portion of the space of the slit. The filler material has an electrical resistivity of 10.0 × 10 at 900°C. 3 A thermal expansion coefficient of 9.0 × 10⁻¹⁰ or greater, at temperatures of 40 to 800°C. -6 The temperature is below / ℃, and the Young's modulus is 0.10 GPa or higher. Because the honeycomb structure of the present invention has the above-mentioned predetermined filler material provided in at least a part of the slit space, dielectric breakdown and damage are less likely to occur at high temperatures.

[0020] The embodiments of the present invention will be described in detail below with reference to the drawings. The present invention is not limited to the following embodiments, and it should be understood that modifications, improvements, etc., to the following embodiments, based on the ordinary knowledge of those skilled in the art, without departing from the spirit of the invention, also fall within the scope of the present invention.

[0021] Figure 1 is a perspective view of a honeycomb structure according to an embodiment of the present invention. As shown in Figure 1, the honeycomb structure according to an embodiment of the present invention comprises a honeycomb structure portion 10, a pair of electrode portions 20, a slit 30, and a filler material 40. The honeycomb structure 10 has an outer periphery wall 11 and partition walls 15 disposed inside the outer periphery wall 11, which divide and form a plurality of cells 14 extending from a first end face 12 to a second end face 13. The plurality of cells 14 serve as fluid flow paths. The honeycomb structure 10 is made of ceramics. A pair of electrode parts 20 are disposed on the outer periphery wall 11. One or more slits 30 are provided in the honeycomb structure 10. At least a portion of the space of the slit 30 is filled with a filler material 40. In Figure 1, an example is shown in which the entire space of the slit 30 is filled with the filler material 40, but the filler material 40 may be filled only in a portion of the space of the slit 30. A honeycomb structure having the above-described structure can generate heat in the honeycomb structure 10 by Joule heating when an electric current is passed from a pair of electrode parts 20 to the honeycomb structure 10.

[0022] The filler material 40 has an electrical resistivity of 10.0 × 10 at 900°C. 3 Ω·cm or more, preferably 15.0 × 10 3 Ω·cm or more, more preferably 30.0 × 10 3 It is Ω·cm or greater. By controlling the electrical resistivity of the filler material 40 at 900°C within this range, the insulating properties of the filler material 40 can be ensured even when the honeycomb structure is exposed to high temperatures, thereby suppressing dielectric breakdown due to leakage current. The upper limit of the electrical resistivity at 900°C is not particularly limited, but for example, 2000.0 × 10 3 It is Ω·cm. Here, the electrical resistivity of the filler 40 at 900 °C in this specification means the value measured by the four-terminal method.

[0023] The filler 40 has a coefficient of thermal expansion of 9.0×10 -6 / °C or less, preferably 8.0×10 -6 / °C or less, more preferably 5.0×10 -6 / °C or less in the range of 40 to 800 °C. By controlling the coefficient of thermal expansion of the filler 40 in this range, even when exposed to high temperatures, the expansion of the filler 40 can be reduced, so that damage to the honeycomb structure can be suppressed. The lower limit value of the coefficient of thermal expansion in the range of 40 to 800 °C is not particularly limited. For example, it is 0.5×10 -6 / °C.

[0024] Here, the coefficient of thermal expansion of the filler 40 in the range of 40 to 800 °C in this specification is measured by the following method. A measurement sample measuring 1 mm in length, 3 mm in width, and 50 mm in length is prepared from the filler material 40 that fills the slits 30 of the honeycomb structure. Hereinafter, the direction from one end to the other of the portion of the measurement sample that has a length of 50 mm may be referred to as the "length direction of the measurement sample." The measurement sample is prepared by cutting it out from the honeycomb structure so that the direction in which the cells 14 of the honeycomb structure extend is the length direction of the measurement sample. Specifically, the direction in which the length of the measurement sample is 50 mm (length direction) corresponds to the direction in which the cells 14 of the honeycomb structure extend. If it is difficult to prepare a measurement sample of the above size, a separate test piece of the same material and form as the filler material 40 to be measured may be prepared, and each measurement sample may be prepared by cutting out the respective test piece. The test piece is larger than the size required for the measurement sample. Furthermore, if the length of the cells 14 of the honeycomb structure is short and a measurement sample length of 50 mm cannot be secured, the thermal expansion coefficient may be measured by supplementing the measurement with a sample made from a material whose thermal expansion properties are known in advance, applied to the direction of extension of the cells 14 of the honeycomb structure. For example, if the length of the cells 14 of the honeycomb structure is 25 mm, it is preferable to apply a 25 mm sample (with known thermal expansion properties) to the filler material 40 to measure the thermal expansion coefficient. The thermal expansion coefficient of the prepared measurement sample is measured from 40 to 800°C using a method compliant with JIS R1618:2002. The thermal expansion coefficient from 40 to 800°C is measured along the length of the measurement sample. A BrukerAXS "TD5000S (product name)" can be used as the thermal expansion meter.

[0025] The filler material 40 has a Young's modulus of 0.10 GPa or higher, preferably 0.50 GPa or higher, and more preferably 0.80 GPa or higher. By controlling the Young's modulus of the filler material 40 within this range, it is possible to suppress damage to the filler material 40 filled in the slit 30 due to the weight of the honeycomb structure. The upper limit of Young's modulus is not particularly limited, but for example, it is 200 GPa.

[0026] Here, the Young's modulus of the filler 40 in this specification can be calculated from the stress and strain at a stress load of 20-50% during the four-point bending strength measurement. Figure 3 is a perspective view illustrating the method for measuring the four-point bending strength of the filler 40. The four-point bending strength measurement sample can be prepared by cutting out a plate-shaped measurement sample 100 from the honeycomb structure as shown in Figure 3. The part indicated by reference numeral 40 in the measurement sample 100 is part of the filler 40, and the part indicated by reference numeral 10 is part of the honeycomb structure 10. In the four-point bending strength measurement, the measurement sample 100 is supported by two outer supports 120, and a load is applied to two inner supports 110 to measure the bending strength of the measurement sample 100. In the four-point bending strength measurement as shown in Figure 3, as long as the ratio of the thickness 140 to the width 130 of the measurement sample 100 and the width 150 of the filler 40 are fixed, the size of the measurement sample 100 has almost no effect on the measurement value. Therefore, the measurement sample 100 should be a sample of a size suitable for strength measurement. The ratio of the thickness 140 to the width 130 of the measurement sample 100 shall be thickness:width = 1:2. The thickness 140 of the measurement sample 100 is preferably 1 to 3 mm. The width 150 of the filler material 40 shall be the width of one cell formed in the honeycomb structure 10. If it is difficult to produce a measurement sample 100 of the predetermined size from the honeycomb structure 10, a test piece of the same material and shape as the honeycomb structure 10 to be measured may be separately produced, and the measurement sample 100 may be cut out from the produced test piece. The test piece shall be larger than the size required for the measurement sample 100. The ratio of the thickness 140 to the width 130 of the measurement sample 100 produced from the test piece shall be thickness:width = 1:2. The thickness 140 of the measurement sample 100 produced from the test piece is preferably 7 mm. The width 150 of the packing material 40 of the measurement sample 100 from the measurement test piece is set to the width of one cell formed in the honeycomb structure 10.

[0027] The filler material 40 is preferably composed of an oxide. By composing the filler material 40 from an oxide, expansion due to oxidation does not occur even in a high-temperature oxygen atmosphere, thus preventing damage to the honeycomb structure due to expansion of the filler material 40 filled in the slit 30.

[0028] The oxides constituting the filler 40 are not particularly limited, but it is preferable that they include Al2O3. In addition, the oxides constituting the filler 40 may further include MgO and / or SiO2. By including such oxides, it becomes easier to control the above-mentioned properties of the filler 40 (electrical resistivity at 900°C, coefficient of thermal expansion from 40 to 800°C, and Young's modulus) within a predetermined range.

[0029] The Al2O3 content in the filler 40 (total oxide) is not particularly limited, but is preferably 30% by mass or more, more preferably 40% by mass or more, and even more preferably 50% by mass or more. By controlling the Al2O3 content within this range, it becomes easier to stably control the above-mentioned properties of the filler 40 (electrical resistivity at 900°C, coefficient of thermal expansion at 40-800°C, and Young's modulus) within a predetermined range. Furthermore, there is no particular upper limit to the Al2O3 content, and it may be 100% by mass (i.e., it may consist only of Al2O3).

[0030] When the oxide contains MgO, the MgO content in the filler 40 (total oxide) is not particularly limited, but is preferably 50% by mass or less, more preferably 40% by mass or less, and even more preferably 30% by mass or less. Also, when the oxide contains SiO2, the SiO2 content in the filler 40 (total oxide) is not particularly limited, but is preferably 70% by mass or less, more preferably 60% by mass or less, and even more preferably 50% by mass or less. Furthermore, the lower limits for MgO and SiO2 are not particularly limited and may be 0% by mass (i.e., MgO and SiO2 may not be present at all).

[0031] Here, the content of each oxide (Al2O3, MgO, and SiO2) in the filler 40 can be measured by X-ray fluorescence analysis.

[0032] The honeycomb structure 10 has a columnar shape and thickness in the direction in which the cells 14 extend. The ratio (aspect ratio) of the length of the cells 14 in the direction in which the honeycomb structure 10 extends to the width or diameter of each end face (first end face 12, second end face 13) is not particularly limited. Furthermore, the columnar shape may include a shape (flattened shape) in which the length of the cells 14 in the direction in which the honeycomb structure 10 extends is shorter than the width or diameter of each end face (first end face 12, second end face 13).

[0033] The external shape of the honeycomb structure 10 is not particularly limited, and can be other shapes such as a columnar shape with circular end faces (cylindrical), a columnar shape with oval end faces, or a columnar shape with polygonal end faces (square, pentagon, hexagon, heptagon, octagon, etc.). Note that the external shape of the honeycomb structure 10 in Figure 1 shows a columnar shape with square (rectangular) end faces as an example. Furthermore, the size of the honeycomb structure 10 is such that the area of ​​each end face is 2000 to 65000 mm², in order to improve heat resistance (suppress cracks entering the circumferential direction of the outer wall 11). 2 Preferably, it is 5000~25000mm 2 It is preferable that it be so.

[0034] The shape of the cell 14 on a plane perpendicular to the direction in which the cell 14 extends (the end face or cross-section of the honeycomb structure 10) is not particularly limited, but examples include a square, hexagon, octagon, or a combination thereof. Among these, the shape of the cell 14 is preferably a square or hexagon. With such a cell 14 shape, the pressure loss when a fluid such as exhaust gas flows through the honeycomb structure 10 can be reduced.

[0035] The thickness of the outer peripheral wall 11 is not particularly limited, but from the viewpoint of ensuring the structural strength of the honeycomb structure 10 and suppressing leakage of the fluid flowing through the cell 14 from the outer peripheral wall 11, it is preferably 0.05 mm or more, more preferably 0.10 mm or more, and even more preferably 0.15 mm or more. However, if the outer peripheral wall 11 is made too thick, it will become too strong, which may disrupt the strength balance with the partition wall 15 and reduce thermal shock resistance. For this reason, the thickness of the outer peripheral wall 11 is preferably 1.0 mm or less, more preferably 0.7 mm or less, and even more preferably 0.5 mm or less. The thickness of the outer perimeter wall 11 refers to the thickness in the direction normal to the tangent of the outer perimeter wall 11 at the measurement point, when the location of the outer perimeter wall 11 to be measured is observed on a plane perpendicular to the direction in which the cell 14 extends.

[0036] The thickness of the partition wall 15 is not particularly limited, but is preferably 0.05 to 0.8 mm, and more preferably 0.1 to 0.6 mm. By making the thickness of the partition wall 15 0.05 mm or more, it is possible to suppress a decrease in the strength of the honeycomb structure 10. By making the thickness of the partition wall 15 0.8 mm or less, it is possible to suppress an increase in pressure loss when exhaust gas is passed through, such as when the honeycomb structure 10 is used as a catalyst carrier. In this specification, the thickness of the partition wall 15 means the length of the portion of the line segment that passes through the partition wall 15, which connects the centroids of adjacent cells 14 in a plane perpendicular to the direction in which the cells 14 extend.

[0037] The cell density of the honeycomb structure 10 is not particularly limited, but is preferably 4 to 150 cells / cm². 2 Comfortably 7-100 cells / cm 2 By controlling the cell density within this range, pressure loss can be reduced when fluids such as exhaust gas flow through it. In this specification, cell density refers to the value obtained by dividing the number of cells by the area of ​​one end face of the honeycomb structure 10 excluding the outer periphery wall 11.

[0038] The honeycomb structure 10 (outer wall 11 and partition wall 15) is made of ceramics, and more preferably, conductive ceramics are the main component. Here, "conductive ceramics as the main component" means that the proportion of conductive ceramics in the total components is 50% by mass or more. The proportion of conductive ceramics is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more.

[0039] Conductive ceramics are not particularly limited, but include oxide ceramics such as alumina, mullite, zirconia, and cordierite; non-oxide ceramics such as silicon carbide, silicon nitride, and aluminum nitride; silicon-silicon carbide composites; and silicon carbide / graphite composites. These can be used individually or in combination of two or more. Among these, from the viewpoint of achieving both heat resistance and conductivity, the conductive ceramic is preferably a silicon-silicon carbide composite or silicon carbide. The silicon-silicon carbide composite contains silicon carbide particles as aggregate and silicon as a binder to bind the silicon carbide particles, and it is preferable that multiple silicon carbide particles are bound together by silicon so as to form pores between the silicon carbide particles. The silicon content in the silicon-silicon carbide composite is not particularly limited, but is preferably 10 to 40% by mass, more preferably 15 to 35% by mass.

[0040] The volume resistivity of the honeycomb structure 10 (outer wall 11 and partition wall 15) is not particularly limited, but is preferably 0.001 to 200 Ω·cm, and more preferably 0.001 to 100 Ω·cm. In this specification, the volume resistivity of the honeycomb structure 10 refers to the value measured at 25°C using the four-terminal method.

[0041] The porosity of the honeycomb structure 10 (outer wall 11 and partition wall 15) is not particularly limited, but is preferably less than 30%, more preferably 25% or less, even more preferably 20% or less, and particularly preferably 10% or less. A honeycomb structure 10 having such a porosity tends to be more susceptible to damage to the filler material 40 filling the slit 30 due to its own weight compared to a honeycomb structure 10 with a porosity of 30% or more. However, by using a filler material 40 having the above characteristics, damage to the honeycomb structure 10 due to its own weight can be suppressed. In this specification, the porosity of the honeycomb structure 10 refers to the value measured by a mercury porosimeter.

[0042] The average pore diameter of the honeycomb structure 10 (outer peripheral wall 11 and partition wall 15) is not particularly limited, but is preferably 2 to 15 μm, more preferably 4 to 8 μm. In this specification, the average pore size refers to the value measured using a mercury porosimeter.

[0043] The slits 30 provided in the honeycomb structure 10 are formed by removing or eliminating the outer peripheral wall 11 and / or partition wall 15. The slits 30 may extend from the first end face 12 to the second end face 13 of the honeycomb structure 10.

[0044] The pair of electrode portions 20 are formed from a conductive material. The conductive material used for the pair of electrode portions 20 is not particularly limited, but it is preferably an oxide ceramic or a mixture of a metal or metal compound and an oxide ceramic. The metal may be either a single metal or an alloy, and for example, silicon, aluminum, iron, stainless steel, titanium, tungsten, Ni-Cr alloy, etc. can be suitably used. The metal compound may be anything other than an oxide ceramic, such as a metal oxide, metal nitride, metal carbide, metal silicide, metal boride, or composite oxide, and for example, FeSi2, CrSi2, alumina, silica, titanium oxide, etc. can be suitably used. The metal and metal compound may be a single type or two or more types may be used in combination. Specific examples of oxide ceramics include glass, cordierite, and mullite. The glass may further contain an oxide consisting of at least one component selected from the group consisting of B, Mg, Al, Si, P, Ti, and Zr.

[0045] The thickness of the pair of electrode portions 20 is not particularly limited, but is preferably 0.01 to 5 mm, more preferably 0.01 to 3 mm. By controlling it within this range, the honeycomb structure can be heated uniformly. If the thickness of the pair of electrode portions 20 is 0.01 mm or more, the electrical resistance is appropriately controlled, and heating can be achieved more uniformly. If the thickness of the pair of electrode portions 20 is 5 mm or less, the risk of damage is reduced. In this specification, the thickness of the pair of electrode portions 20 refers to the thickness of the outer surface of the pair of electrode portions 20 in the direction normal to the tangent at the measurement location, when the location of the pair of electrode portions 20 whose thickness is to be measured is observed in a plane perpendicular to the direction in which the cell 14 extends.

[0046] The electrical resistivity of the pair of electrode portions 20 is not particularly limited, but is preferably 1 × 10⁻⁶. -7 ~5×10 -1 Ω·m, more comfortable 5×10 -7 ~2.5×10 -1 Ω·m, more preferably 1 × 10 -6 ~1.25×10-1 It is Ω·m. In particular, the electrical resistivity of the pair of electrode parts 20 is 5 × 10 -1 By setting the resistance to Ω·m or less, the resistance during electric heating can be reduced. In this specification, the electrical resistivity of the pair of electrode portions 20 refers to the value measured at 400°C using the four-terminal method.

[0047] The position of the pair of electrode portions 20 is not particularly limited as long as it is on the outer peripheral wall 11 of the honeycomb structure portion 10. Similarly, the position of the slit 30 provided in the honeycomb structure portion 10 is not particularly limited. For example, in one embodiment, as shown in Figure 1, the honeycomb structure has a pair of electrode portions 20 arranged on one plane of the outer peripheral wall 11 of the rectangular prism-shaped honeycomb structure portion 10, and the slit 30 may include a first slit 31 extending inward from the outer peripheral wall 11 between the pair of electrode portions 20. By controlling the positions of the pair of electrode portions 20 and the first slit 31 in this way, the heat distribution of the honeycomb structure can be adjusted.

[0048] As shown in Figure 1, the slit 30 may further include a second slit 32 extending inward from two outer peripheral walls 11 perpendicular to the outer peripheral wall 11 on which a pair of electrode portions 20 are provided, and a third slit 33 that intersects with the first slit 31 and does not reach the outer peripheral wall 11. In this case, it is preferable that the second slit 32 and the third slit 33 are arranged alternately. With this configuration, the current flows while bypassing along the second slit 32 and the third slit 33 as indicated by the arrows in the honeycomb structure portion 10 shown in Figure 1, making it easier to heat the honeycomb structure uniformly.

[0049] Furthermore, the honeycomb structure may have multiple honeycomb structural parts 10, and the multiple honeycomb structural parts 10 may be connected by conductive connectors 50. Figure 2 shows a front view of a plane perpendicular to the direction in which the cells of such a honeycomb structure extend. The honeycomb structure shown in Figure 2 has a first honeycomb structure 10A and a second honeycomb structure 10B, and the first honeycomb structure 10A and the second honeycomb structure 10B are connected by a conductive connector 50. Even with this structure, the current flows while bypassing along the second slit 32 and the third slit 33 of the first honeycomb structure 10A and the second honeycomb structure 10B, making it easier to heat the honeycomb structure uniformly.

[0050] Two conductive connectors 50 are provided on the outer peripheral wall 11 where the first honeycomb structure 10A and the second honeycomb structure 10B face each other. Specifically, the two conductive connectors 50 are each partially provided on the outer peripheral wall 11 at a position perpendicular to the first slit 31 and without straddling the first slit 31.

[0051] Various materials can be used for the conductive connector 50, but for example, Si-SiC composite materials, Si metal-impregnated Si-SiC composite materials, etc., may be used.

[0052] Electrode terminals (not shown) may be connected to the pair of electrode sections 20 as needed. The shape of the electrode terminals is arbitrary, but they may be columnar. By applying a voltage to the honeycomb structure through the electrode terminals, the honeycomb structure can be easily heated by Joule heating. The applied voltage is preferably 12 to 900V, and more preferably 48 to 600V, but the applied voltage can be changed as appropriate.

[0053] The electrode terminals can be made of ceramics or carbon. If the electrode terminals are made of ceramics, electrical connection to the honeycomb structure becomes possible. Alternatively, metal terminals may be joined to the tips of the electrode terminals. The joining of ceramic or carbon electrode terminals to metal terminals can be done by crimping, welding, conductive adhesive, etc. The metal terminals can be made of conductive metals such as iron alloys or nickel alloys.

[0054] The ceramics constituting the electrode terminals are not particularly limited, but examples include silicon carbide (SiC); metallic compounds such as tantalum silicide (TaSi2) and chromium silicide (CrSi2); and composite materials (cermets) containing one or more metals. Specific examples of cermets include composite materials of metallic silicon and silicon carbide, composite materials of metallic silicon and silicon carbide with metallic silicides such as tantalum silicide and chromium silicide, and composite materials in which one or more insulating ceramics such as alumina, mullite, zirconia, cordierite, silicon nitride, and aluminum nitride are added to one or more of the above metals from the viewpoint of reducing thermal expansion. It is preferable that the carbon constituting the electrode terminals is mainly composed of carbon. Mainly composed of carbon means that the carbon content is 50% by mass or more of the total components constituting the electrode terminals. More preferably, the carbon content is 80% by mass or more, and even more preferably 90% by mass or more.

[0055] Furthermore, a catalyst may be supported on the outer peripheral wall 11 facing the partition wall 15 or cell 14 of the honeycomb structure 10, as needed. Various catalysts can be used, but examples include a three-way catalyst and / or nickel oxide. By supporting the catalyst, purification performance can be obtained when exhaust gas or the like is flowed into the cell 14 as a fluid.

[0056] The honeycomb structure according to the embodiment of the present invention can be used in an electric heater because it can generate heat when electricity is applied. This electric heater comprises the honeycomb structure and may further include various other components as needed.

[0057] The method for manufacturing a honeycomb structure according to the embodiment of the present invention is not particularly limited as long as it can manufacture a honeycomb structure having the above-described features. An example of a method for manufacturing a honeycomb structure according to the embodiment of the present invention will be described below. A method for manufacturing a honeycomb structure according to an embodiment of the present invention comprises the steps of: S1 for obtaining a honeycomb molded body with electrode material attached; S2 for forming slits; S3 for firing the honeycomb molded body; and S4 for filling with filler material.

[0058] Step S1 is a step in which an electrode-forming raw material is applied to a honeycomb molded body, which is a precursor of the honeycomb structure 10, to obtain a honeycomb molded body with electrode-forming raw material. Here, the honeycomb molded body is the honeycomb structure 10 before firing, which is used to produce the honeycomb structure 10 described above.

[0059] The honeycomb molded body can be manufactured in accordance with the honeycomb molded body manufacturing method in known methods for manufacturing honeycomb structures. For example, first, a molding material is prepared by adding a binder, surfactant, pore-forming agent, water, etc. to a ceramic raw material such as silicon carbide powder (silicon carbide) or metallic silicon powder (metallic silicon). Examples of binders include methylcellulose, hydroxypropylmethylcellulose, hydroxypropoxylcellulose, hydroxyethylcellulose, carboxymethylcellulose, and polyvinyl alcohol. Among these, it is preferable to use methylcellulose and hydroxypropoxylcellulose in combination. The binder content is preferably 2.0 to 10.0 parts by mass when the mass of the ceramic powder (ceramic raw material) is 100 parts by mass. The water content is preferably 20 to 60 parts by mass when the mass of the ceramic powder (ceramic raw material) is 100 parts by mass. As surfactants, ethylene glycol, dextrin, fatty acid soap, polyalcohol, etc., can be used. These may be used individually or in combination of two or more. The surfactant content is preferably 0.1 to 2.0 parts by mass when the mass of ceramic powder (ceramic raw material) is 100 parts by mass. Examples of por-forming materials include starch, foamed resins, and water-absorbent resins.

[0060] Next, the obtained molding material is kneaded to form a clay base. Then, the clay base is extruded to produce a honeycomb molded body. When extruding, it is preferable to use a die having the desired overall shape, cell shape, outer wall thickness, partition wall thickness, cell density, etc. Next, it is preferable to dry the obtained honeycomb molded body. Hereinafter, the honeycomb molded body after drying may be referred to as a "dried honeycomb body". If the axial length of the honeycomb molded body (or dried honeycomb body) in the central axis direction is not the desired length, it is preferable to cut both ends of the honeycomb molded body to the desired length.

[0061] Next, electrode-forming raw materials for forming a pair of electrode portions 20 are prepared. When the main components of the pair of electrode portions 20 are silicon carbide and silicon, it is preferable to prepare the electrode-forming raw materials by adding predetermined additives to silicon carbide powder and silicon powder and kneading them together. Next, the obtained electrode-forming raw materials are applied to predetermined positions on the outer peripheral wall 11 of the dried honeycomb molded body (honeycomb dried body) to obtain a honeycomb molded body with electrode-forming raw materials. The method for preparing the electrode-forming raw materials and the method for applying the electrode-forming raw materials to the honeycomb molded body can be carried out in accordance with known methods for manufacturing honeycomb structures.

[0062] As an alternative method for manufacturing the honeycomb structure, in step S1, the honeycomb molded body may be fired before applying the electrode-forming material. That is, in the alternative manufacturing method, the honeycomb molded body is fired to produce a honeycomb fired body, and the electrode-forming material is applied to the honeycomb fired body to obtain a honeycomb fired body with electrode material attached instead of a honeycomb molded body with electrode material attached.

[0063] Step S2 is a step in which slits are formed at predetermined positions in the honeycomb molded body with electrode material attached. It is preferable to form the slits using a rotary tool or the like. The slits are formed so as to open at predetermined positions in the honeycomb molded body with electrode material attached.

[0064] Step S3 is a process of firing the honeycomb molded body with electrode material attached to obtain a fired honeycomb body. Before firing, the honeycomb molded body with electrode material attached may be dried. Alternatively, pre-firing may be performed before firing to remove binders and other substances from the filler material. Preferably, the firing conditions are heating at 1350 to 1600°C for 0.25 to 5 hours in a reduced-pressure inert atmosphere or vacuum. After firing, it is preferable to perform oxidation treatment at 1200 to 1350°C for 1 to 300 hours to improve durability. The pre-firing and firing methods are not particularly limited and can be performed using an electric furnace, gas furnace, etc.

[0065] Furthermore, in step S3, the honeycomb molded body with electrode material attached may be heat-treated at 300 to 1500°C. This heat treatment may be included in the calcination and firing processes described above, or it may be performed separately from the calcination and firing processes.

[0066] Step S4 is the process of filling the slits formed in the honeycomb calcined body with filler material. In step S4, first, the filler material is prepared. The filler material is the raw material for producing the filler described above. For example, the filler material can be obtained by kneading a mixture obtained by mixing an inorganic compound such as the oxide described above as the main raw material with a binder, surfactant, pore-forming agent, water, etc. The filler material is preferably in slurry form. Examples of inorganic compounds include cordierite, alumina, mullite, kaolin, silicon carbide, montmorillonite, talc, boehmite, feldspar, colloidal silica, etc.

[0067] Examples of binders used in filler raw materials include methylcellulose, hydroxypropylmethylcellulose, hydroxypropoxylcellulose, hydroxyethylcellulose, carboxymethylcellulose, and polyvinyl alcohol. Among these, it is preferable to use methylcellulose and hydroxypropoxylcellulose in combination. The binder content is preferably 0 to 25 parts by mass when the mass of the main raw material is 100 parts by mass.

[0068] The water content is preferably 15 to 75 parts by mass when the mass of the main raw material is 100 parts by mass.

[0069] Surfactants that can be used as raw materials for fillers include ethylene glycol, dextrin, fatty acid soap, and polyalcohol. These may be used individually or in combination of two or more. The surfactant content is preferably 0 to 15 parts by mass when the mass of the main raw material is 100 parts by mass.

[0070] The pore-forming material used as a raw material for the filler is not particularly limited as long as it becomes pore after firing, and examples include graphite, starch, foamed resin, superabsorbent resin, and silica gel. The content of the pore-forming material is preferably 0 to 85 parts by mass when the mass of the main raw material is 100 parts by mass.

[0071] There are no particular restrictions on the method of filling the slits formed in the honeycomb molded body with electrode material attached with the filler material, but one method is to fill the slits with the filler material using a syringe or the like. With this method, the filler material can be evenly filled into the slits. Of course, the filler material may also be filled into the slits using a spatula or the like.

[0072] After filling with the filler material, the binder and other contaminants in the filler material are removed by heat treatment. The heat treatment conditions are not particularly limited, but it is preferable to heat at 300 to 600°C for 0.5 to 5 hours in an atmospheric environment. Alternatively, the binder removal process may be performed simultaneously with the oxidation treatment of the honeycomb calcined body described above, in which case it is preferable to perform the heat treatment at 1200 to 1350°C for 1 to 300 hours. [Examples]

[0073] The present invention will be described in more detail below with reference to examples, but the present invention is not limited in any way by these examples.

[0074] A molding material was prepared by adding methylcellulose and hydroxypropylmethylcellulose as binders and a water-absorbing resin as a pore-forming agent to silicon carbide (SiC) powder, along with water. The molding material was then kneaded in a vacuum clay mixer to produce clay. The binder content was 8 parts by mass when the silicon carbide (SiC) powder was 100 parts by mass. The pore-forming agent content was 4 parts by mass when the silicon carbide (SiC) powder was 100 parts by mass. The water content was 45 parts by mass when the silicon carbide (SiC) powder was 100 parts by mass. Next, the clay was molded using an extrusion molding machine to obtain a rectangular prism-shaped honeycomb molded body as shown in Figure 1. The obtained honeycomb molded body was dried using high-frequency dielectric heating, and then dried in a hot air dryer at 120°C for 2 hours.

[0075] Next, silicon carbide (SiC) powder and metallic silicon (Si) powder were mixed in a mass ratio of 60:40. Hydroxypropyl methylcellulose was added as a binder, a surfactant as a dispersant, and water was added and mixed. The mixture was kneaded to form the electrode material. The binder content was 0.5 parts by mass when the total amount of silicon carbide (SiC) powder and metallic silicon (Si) powder was 100 parts by mass. The surfactant content was 0.3 parts by mass when the total amount of silicon carbide (SiC) powder and metallic silicon (Si) powder was 100 parts by mass. The water content was 42 parts by mass when the total amount of silicon carbide (SiC) powder and metallic silicon (Si) powder was 100 parts by mass. Kneading was performed using a vertical stirrer.

[0076] Next, as shown in Figure 1, electrode-forming material was applied to two locations on one of the outer walls 11 of the rectangular prism-shaped honeycomb structure 10, and then dried to obtain a honeycomb dried body with electrode material attached. The drying temperature was 70°C. Next, a first slit, a second slit, and a third slit were formed in the honeycomb dried body with the electrode material attached, as shown in Figure 1. Each slit was formed using a rotary tool. Next, the honeycomb dried material with the electrode portion having formed slits was degreased, impregnated with metallic Si, and fired to obtain a honeycomb structure with slits. The degreasing conditions were 550°C for 3 hours. The firing conditions were 1450°C for 2 hours in a vacuum.

[0077] Next, the filler material was prepared. First, the main ingredients (Al2O3, SiO2, MgO, SiC) in the proportions shown in Table 1 were mixed, hydroxypropyl methylcellulose was added as a binder, then a surfactant and a pore-forming agent were added as dispersants, and water was further added and mixed. The mixture was kneaded to obtain the filler material. The binder content was 1 part by mass when the total amount of main ingredients was 100 parts by mass. The surfactant content was 0.3 parts by mass when the total amount of main ingredients was 100 parts by mass. The water content was 20 parts by mass when the total amount of main ingredients was 100 parts by mass. The pore-forming agent content was 6 parts by mass for Example 11, 12 parts by mass for Comparative Example 4, and 0 parts by mass for all others, when the total amount of main ingredients was 100 parts by mass. Kneading was performed using a vertical stirrer.

[0078] Next, the filler material was filled into the slits of the slitted honeycomb structure to obtain a honeycomb structure filled with the filler material. When filling with the filler material, the filler material was introduced into a syringe and then used to fill (inject) it into the slits. The filler material was filled into all of the slits. The amount of filler material filled was equal to the volume of the slits. Next, the honeycomb structure filled with the filler material was heat-treated at a temperature of 1225°C. The heat treatment was carried out in an air atmosphere. The heat treatment time was 24 hours. In Comparative Example 1, to prevent damage to the honeycomb structure due to oxidation of the main raw material SiC, a heat treatment was performed at a temperature of 600°C for 1 hour.

[0079] The porosity of the septa of the honeycomb structure obtained above was 2%. The porosity was measured by the Archimedes method. The thickness of the septa of the honeycomb structure was 200 μm, and the cell density was 16 cells / cm³. 2Furthermore, the end faces of the honeycomb structure were square with sides of 140 mm, and the length in the direction in which the cells of the honeycomb structure extend was 150 mm. In addition, the shape of the cells in the honeycomb structure in a cross section perpendicular to the direction in which the cells extend was square.

[0080] Furthermore, Table 1 shows the results for the electrical resistivity at 900°C, the coefficient of thermal expansion from 40 to 800°C, and the Young's modulus of the filler material in the honeycomb structure obtained above. These were measured using the method described above.

[0081] [Table 1]

[0082] The honeycomb structure obtained above was subjected to high-temperature insulation performance evaluation tests using the method described below. The results are shown in Table 2.

[0083] [High-temperature insulation performance evaluation test] Based on actual operating conditions, the voltage at which leakage current begins to increase significantly (defined as withstand voltage) was determined by applying voltage at 900°C. In this evaluation, if the withstand voltage is 4kV / mm or higher, it can be said that dielectric breakdown is unlikely to occur at high temperatures. In Table 2, the withstand voltage evaluation symbols are as follows: ◎: 6kV / mm or higher, ○: 5kV / mm or higher but less than 6kV / mm, △: 4kV / mm or higher but less than 5kV / mm, ×: less than 4kV / mm. Furthermore, after the test, we checked for any damage to the honeycomb structure and the filling material.

[0084] [Table 2]

[0085] As shown in Table 2, the electrical resistivity at 900°C is 10.0 × 10⁻⁶. 3 A thermal expansion coefficient of 9.0 × 10⁻¹⁰ or greater, at temperatures of 40 to 800°C. -6In Examples 1 to 14, honeycomb structures were used in which the slits were filled with a filler material having a temperature of 0.7°C or lower and a Young's modulus of 0.10 GPa or higher. These structures were less prone to dielectric breakdown at high temperatures and did not suffer any damage. In contrast, the honeycomb structures of Comparative Examples 1 and 3 had insufficient dielectric strength because they used fillers with low electrical resistivity at 900°C. Furthermore, in Comparative Example 2, the honeycomb structure was damaged due to the difference in thermal expansion between the honeycomb structure and the filler material, as a filler material with a high coefficient of thermal expansion of 40-800°C was used. Furthermore, the honeycomb structure in Comparative Example 4 used a filler with a low Young's modulus, which was insufficient to support its own weight. As a result, the filler was damaged by deformation due to the honeycomb structure's own weight before the high-temperature insulation performance evaluation could be conducted.

[0086] As can be seen from the above results, the present invention provides a honeycomb structure and an electric heating heater that are less susceptible to dielectric breakdown and damage at high temperatures. [Explanation of Symbols]

[0087] 10 Honeycomb structure 10A First honeycomb structure 10B Second honeycomb structure 11 Peripheral wall 12 First end surface 13 Second end face 14 cells 15 Bulkhead 20 Pair of electrode sections 30 slits 31. First Slit 32. Second Slit 33 Third Slit 40 Filler 50 Conductive connector 100 measurement samples 110 Inside fulcrum 120 External fulcrum 130 width 140 thickness 150 width

Claims

1. A ceramic honeycomb structure having an outer perimeter wall and partition walls disposed inside the outer perimeter wall, which divide and form a plurality of cells extending from a first end face to a second end face, A pair of electrode portions disposed on the outer peripheral wall, One or more slits provided in the honeycomb structure, A filler material that fills at least a portion of the space in the slit and Equipped with, The aforementioned filler has an electrical resistivity of 10.0 × 10 at 900°C. 3 A thermal expansion coefficient of 9.0 × 10⁻¹⁰ Ω·cm or greater, at temperatures between 40 and 800°C. -6 A honeycomb structure having a temperature of 0.7°C or less and a Young's modulus of 0.10 GPa or more.

2. The honeycomb structure according to claim 1, wherein the filler is composed of an oxide.

3. The aforementioned oxide is Al 2 O 3 The honeycomb structure according to claim 2, including the following:

4. The oxide is MgO and / or SiO 2 The honeycomb structure according to claim 3, further comprising:

5. Al in the aforementioned filler 2 O 3 The honeycomb structure according to claim 3 or 4, wherein the content of is 30% by mass or more.

6. The honeycomb structure according to any one of claims 1 to 4, wherein the porosity of the outer peripheral wall and the partition wall is less than 30%.

7. The aforementioned honeycomb structure is in the shape of a rectangular prism, The pair of electrode portions are arranged on one of the planes of the outer peripheral wall. The honeycomb structure according to any one of claims 1 to 4, wherein the slit includes a first slit extending inward from the outer peripheral wall between the pair of electrode portions.

8. The honeycomb structure according to claim 7, wherein the slit further includes a second slit extending inward from two outer peripheral walls perpendicular to the outer peripheral wall on which the pair of electrode portions are provided, and a third slit intersecting the first slit and not reaching the outer peripheral wall.

9. The honeycomb structure according to claim 8, wherein the second slit and the third slit are arranged to alternate positions.

10. An electric heating heater comprising a honeycomb structure according to any one of claims 1 to 4.

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