JPH04354543A - honeycomb structure ceramics - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to honeycomb structured ceramics that can be used as catalyst supports and various filters.

0002

[Prior Art] In order to improve the performance of catalyst supports and filters used to clean NOx, etc. contained in automobile exhaust gas, the honeycomb cell walls are made thinner and porous to increase the specific surface area. , further increasing the aperture ratio. For this reason, the mechanical strength is weak, and chipping and cracking are likely to occur particularly in the outer periphery, which is susceptible to external forces. To solve this problem, the outer periphery is coated with multiple sheets of ceramic dispersion paper to improve strength and thermal shock resistance. (For example, see Japanese Patent Application Laid-Open No. 49-31714)

0003

[Problems to be Solved by the Invention] However, in the above-mentioned conventional structure, deformation, distortion, and cracks occur due to the difference in density between the inside of the honeycomb structure and the covering part and the sinterability of the material, so the mechanical strength is weak. In particular, the outer periphery is susceptible to external forces and is prone to chipping and cracking, resulting in poor handling and durability. The present invention solves the above-mentioned conventional problems, and aims to provide a honeycomb structure ceramic having excellent handling properties and durability.

0004

[Means for Solving the Problems] In order to solve this problem, the honeycomb structure ceramic of the present invention has a structure in which a ceramic layer is provided on the outer periphery of a honeycomb structure sintered body made of fired ceramic sheets.

[0005]

[Operation] This structure makes the outer peripheral part dense and improves mechanical strength. Further, the outer peripheral portion is made of ceramics having various functions, thereby imparting various characteristics.

[0006]

EXAMPLE The honeycomb structured ceramic of the present invention is produced by the following steps.

[0007] ■ A process of integrating a corrugated sheet and a flat sheet made of a ceramic sheet mainly composed of heat-resistant inorganic fibers and ceramic powder for bonding the inorganic fibers to form a corrugated sheet.

[0008] ■ A step in which a molded body obtained by rolling up a corrugated sheet into a hollow cylindrical shape is fired to form a sintered body with a honeycomb structure.

[0009] ■ A step of thermally spraying ceramics onto the outer circumference of the sintered body while heating it. An embodiment of the present invention will be described in more detail below with reference to the drawings.

[0010] As the heat-resistant inorganic fiber, cordierite (
2MgO・2Al2O3・5SiO2), mullite (3
A material whose main component is one or more of Al2O3.2SiO2), silica (SiO2), alumina (Al2O3), or aluminum silicate (Al2O3-SiO2 system) is used. As the ceramic powder for bonding the inorganic fibers, aluminum-silicate clay powder is used. As the ceramic for thermal spraying, cordierite, mullite, silica, alumina, or aluminum silicate having the same composition as the heat-resistant inorganic fiber, ferrite as the magnetic material, or barium titanate ceramics as the dielectric material are used.

As shown in FIGS. 1 and 2, a corrugated sheet 1 and a flat sheet 2 made of ceramic sheets mainly composed of heat-resistant inorganic fibers and ceramic powder for bonding the inorganic fibers are made of corrugated cardboard. A corrugated sheet is formed as in the manufacturing process, and the corrugated sheet is rolled up into a hollow cylindrical shape to form a honeycomb-shaped molded body with a diameter of 200 mm and a height of 250 mm, and then fired at 1200 to 1800°C to form a sintered body 3 with a honeycomb structure. . A honeycomb structure in which a sprayed ceramic layer 4 is formed by uniformly spraying ceramics on the outer peripheral surface while heating the sintered body 3 at a temperature of 150 to 500°C to increase the bonding strength with the sprayed ceramics. Phase ceramics.

(Example 1) As an evaluation value of the mechanical strength of a honeycomb structure ceramic having a diameter of 200 mm and a height of 250 mm, in which mullite alone is used as a heat-resistant inorganic fiber and a sprayed ceramic layer 4 of mullite is formed, the mechanical strength is evaluated from the radial direction. The compressive strengths of the unsprayed and thermally sprayed products are compared and shown in Figure 3. As is clear from FIG. 3, the strength can be significantly improved by forming a dense thermal sprayed ceramic layer on the outer peripheral surface.

(Example 2) A honeycomb having the same shape as Example 1, in which a thermally sprayed ceramic layer 4 of mullite was formed using heat-resistant inorganic fibers and a mixture of cordierite and alumina in a weight ratio of 50:50. As shown in FIG. 3, the compressive strength of the structural ceramics is found to be significantly improved as in Example 1.

(Example 3) The compressive strength in the case where the coefficient of thermal expansion of the thermally sprayed ceramic layer 4 is different from that of the sintered body 3 having a honeycomb structure is measured for the case where the thermal expansion coefficient of the thermally sprayed ceramic layer 4 is The values measured after performing the impact test are shown in Figure 4 for the difference in thermal expansion coefficient. In the thermal shock test, one cycle consists of holding at a temperature of 600°C for 1 hour, then taking it out to room temperature, and holding it for 30 minutes.
0 cycles were performed.

As can be seen from FIG. 4, if the difference in coefficient of thermal expansion is large, even if the sprayed ceramic layer 4 is formed, the compressive strength will be lower than that of the unsprayed product. In other words, the difference in thermal expansion coefficient is more negative than -3 ppm/℃, or +2
It can be seen that when it exceeds 0 ppm/°C, it decreases. The reason why the coefficient of thermal expansion is more stable on the minus side is thought to be because compressive stress is acting on the thermal sprayed ceramic layer 4.

(Example 4) A sprayed ceramic layer 4 made of a dielectric or magnetic material is applied to the honeycomb-structured sintered body 3 of Example 1.
Microwave (2kW) was applied to the sprayed and unsprayed
, 2.45 GHz) is shown in FIG. 5. As can be seen from FIG. 5, by forming a sprayed ceramic layer suitable for microwave heating on the surface, the honeycomb structured ceramic can be used as a means of self-heating at the same time as mechanical protection. In this case, the thermal sprayed ceramic layer deviates from its original characteristics due to changes in crystal structure, introduction of oxygen defects, etc., and therefore is annealed in the atmosphere.

(Embodiment 5) A case where ceramics having different properties are formed by thermal spraying in multiple layers will be described. For example, if you want to form a sprayed ceramic layer suitable for microwave heating, but the difference in thermal expansion coefficient from the thermal expansion coefficient of the honeycomb-shaped fired body does not fall within the range of -3 ppm/℃ to +2 ppm/℃, the thermal expansion coefficient It can be used as a means to gradually alleviate the As an example, a honeycomb-shaped sintered body made of mullite fibers (the coefficient of thermal expansion is 6p
pm/℃) with a Ni-Zn ferrite layer (thermal expansion coefficient of 1
0 ppm/°C) on the outer periphery, Ba2Ti9O20 ceramic (thermal expansion coefficient: 8 ppm/°C) is formed as a first layer as a buffer material, and Ni--Zn ferrite is formed as a second layer thereon. Compressive strength after thermal shock test is 20kg/without buffer material.
cm2, but with buffer material, it was 9
It improved to 0 kg/cm2.

(Example 6) Drop impact test results of honeycomb structure ceramics in which a thermal spray ceramic layer 4 of 3 mol% Y2O3 partially stabilized zirconia was formed on the honeycomb structure sintered body 3 of Example 1 and unsprayed products , the results of honeycomb structure ceramics on which a sprayed ceramic layer of mullite or barium titanate ceramic was formed (Table 1)
It is shown in comparison to

[0019]

[Table 1]

As can be seen from this (Table 1), the honeycomb structured ceramics formed with the thermally sprayed ceramic layer of 3 mol % Y2O3 partially stabilized zirconia of this example have excellent mechanical impact resistance.

[0021] In the drop impact test, a honeycomb structure ceramic having the same shape as in Example 1 is naturally dropped onto hardwood from a height of 1 m, and judgment is made based on the damage state of n = 10 test pieces.

In the above-mentioned embodiment, the ceramics to be thermally sprayed were barium titanate ceramics as the dielectric material, ferrite ceramics as the magnetic material, or the same material as the heat-resistant inorganic fibers of the honeycomb structured sintered body. Depending on the function to be provided, glass, piezoelectric material, semiconductor, nitride, carbide, or boride, etc. may be used.

Further, although aluminum silicate was used as the ceramic powder for joining the inorganic fibers, other ceramic powders may be used as long as they have the same function.

[0024]

[Effects of the Invention] As is clear from the description of the embodiments above, the present invention has a structure in which a dense thermal sprayed ceramic layer is provided on the outer periphery, so it has high mechanical strength, excellent handling properties, and durability. , and can provide an excellent honeycomb structure ceramic that can provide effective functions (for example, as a heating medium for microwave heating).

[Brief explanation of drawings]

[Figure 1] Schematic diagram of the slope of the honeycomb structure ceramic of one example of the present example

[Fig. 2] A schematic cross-sectional view of a corrugated sheet of honeycomb structure ceramics according to an embodiment of the present invention.

FIG. 3 is a graph of the compressive strength of the honeycomb structure ceramics of the first example and the second example of the present invention.

FIG. 4 is a graph showing that the compressive strength after a thermal shock test differs depending on the difference in thermal expansion coefficient between the honeycomb structure ceramic of the third embodiment of the present invention and the thermally sprayed ceramic layer.

FIG. 5 is a graph showing the relationship between the microwave irradiation time of the honeycomb structure ceramic and the temperature of the honeycomb structure ceramic according to the fourth embodiment of the present invention.

[Explanation of symbols]

3 Sintered body 4 Sprayed ceramic layer

Claims (5)

[Claims] [Claim 1] A sintered body with a honeycomb structure made by molding and firing a corrugated sheet which is an integrated corrugated sheet and a flat sheet of a ceramic sheet mainly composed of ceramic powder for bonding heat-resistant inorganic fibers and inorganic fibers. Honeycomb structure ceramic with a dense thermal sprayed ceramic layer on the outer periphery. 2. The honeycomb structured ceramic according to claim 1, wherein the thermal expansion coefficient of the sprayed ceramic layer is within the range of -3 ppm/°C to 2 ppm/°C compared to the thermal expansion coefficient of the honeycomb structured sintered body. 3. The heat-resistant inorganic fiber according to claim 1,
Cordierite (2MgO・2Al2O3・5SiO2)
, mullite (3Al2O3・2SiO2), silica (S
Ham-kani structure ceramics that are one or a mixture of two or more of aluminum silicate (Al2O3-SiO2), alumina (Al2O3), or aluminum silicate (Al2O3-SiO2 system). 4. A honeycomb structure ceramic, wherein the sprayed ceramic layer according to claim 1 is partially stabilized zirconia, a magnetic material, or a dielectric material. 5. A honeycomb structure layered ceramic in which the sprayed ceramic layer according to claim 1 is formed of multiple layers of different materials.