JP2023060939A - ceramic structure - Google Patents

Abstract

To provide a ceramic structure capable of improving strength without increasing pressure loss.SOLUTION: A ceramic structure 10 has a ceramic skeleton 2 and communication pores, with a porosity of 60-97%. The skeleton is mainly composed of Al oxide, and contains one or more kinds of divalent elements selected from a group of Mg, Ca, Sr, Ba in 0.05-3.0 mass% in total.SELECTED DRAWING: Figure 2

Description

TECHNICAL FIELD The present invention relates to a ceramic structure that can be suitably used, for example, as a filter for exhaust pipes such as drafts, pipes and ducts.

BACKGROUND ART Conventionally, porous sintered bodies using ceramic powder have been used for applications such as sound absorbing materials and catalysts (Patent Document 1). In general, such porous sintered bodies are equipped with interconnected pores having countless fine pores.

JP-A-2000-264753

However, there is a problem that the ceramic porous body is weak in strength and easily broken.
On the other hand, if the porosity of the ceramic porous body is reduced, the strength is improved, but the pressure loss of the fluid passing through the ceramic porous body increases, which is not suitable.
SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a ceramic structure capable of improving strength without increasing pressure loss.

In order to solve the above problems, the ceramic structure of the present invention has a ceramic skeleton and has a porosity of 60 to 97% with continuous pores, wherein the skeleton is mainly composed of Al oxide. and containing 0.05 to 3.0 mass % in total of one or more divalent elements selected from the group of Mg, Ca, Sr and Ba.

According to this ceramic structure, since the skeleton contains a divalent element, the grain boundary strength of the Al oxide in the skeleton is improved, and the strength of the ceramic structure is also improved. As a result, there is no need to reduce porosity, and strength can be improved without increasing pressure loss.

In the ceramic structure of the present invention, an average aspect ratio of the divalent element region may be 3 or more when the cross section of the skeleton is viewed.
According to this ceramic structure, since the grains having an aspect ratio of 3 or more are present in the grains, the progress of cracks is suppressed, so that the grain boundary strength of the skeleton Al oxide is further improved.

In the ceramic structure of the present invention, the divalent element may form an aluminate phase.
According to this ceramic structure, the grain boundary strength of the Al oxide of the framework 2 is further improved.

In the ceramic structure of the present invention, when the cross section of the skeleton is viewed, the porosity in the skeleton may be 10% or less.
According to this ceramic structure, the strength of the skeleton is further improved.

In the ceramic structure of the present invention, the average aspect ratio of the divalent element region may be 3 or more when the surface of the skeleton is viewed.
According to this ceramic structure, the grain boundary strength of the Al oxide of the framework 2 is further improved.

According to the present invention, it is possible to obtain a ceramic structure whose strength can be improved without increasing pressure loss.

1 is a schematic diagram of a ceramic structure according to an embodiment of the present invention; FIG. 1 is a schematic cross-sectional view of a ceramic structure according to an embodiment of the invention; FIG. It is a figure which shows the EDS image of the cross section of an actual ceramic structure.

Below, the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic diagram of a ceramic structure 10 according to an embodiment of the present invention, and FIG. 2 is a schematic cross-sectional view of the ceramic structure 10. As shown in FIG.

As shown in FIG. 1, a ceramic structure 10 has a skeleton 2 and a divalent element, and has interconnecting pores in which gaps V in the skeleton 2 are voids.
The ceramic structure 10 can be suitably used, for example, as filters for exhaust pipes such as drafts, pipes and ducts. In particular, it can be suitably used in applications where large stress is applied, and where high-temperature fluids and chemicals flow. The fluid flows through the gap V.

The ceramic structure 10 (skeleton 2) is formed by using, for example, a urethane sponge having continuous pores as a mold, impregnating the sponge with a slurry containing ceramic particles, an organic solvent, etc., drying it, and then baking it to burn off the sponge. It can be manufactured by a manufacturing template method. By burning off the sponge, it becomes a porous ceramic having a three-dimensional network structure with communicating pores having substantially the same shape as the communicating pores of the sponge.

The porosity of the ceramic structure 10 is 60-97%, more preferably 80-95%.
If the porosity of the ceramic structure 10 is less than 60%, the pressure loss increases and the fluid flow becomes insufficient. If the porosity of the ceramic structure 10 exceeds 97%, it is difficult to manufacture the ceramic structure 10, and the skeleton 2 becomes thin, which reduces the strength of the ceramic structure 10.
The porosity of the ceramic structure 10 is calculated by cutting out a part of a predetermined size (for example, 30 mm×30 mm×30 mm, but if the ceramic structure 10 is smaller than this, the size is smaller), measuring the mass, and calculating the density. and calculate the porosity. More specifically, the theoretical density is calculated by composition analysis of the ceramic structure 10 (skeleton 2), and the porosity is calculated based on the calculated theoretical density and the measured density.

The skeleton 2 is mainly composed of Al oxide and contains 0.05 to 3.0 mass % in total of one or more divalent elements selected from the group of Mg, Ca, Sr and Ba. A main component means more than 50 mass %. Further, the framework 2 may substantially consist of Al oxide and a divalent element 4 .
Here, as shown in FIG. 1, many divalent elements are present on the surface of the skeleton 2 as regions 4 . In addition, as shown in FIG. 2, a large number of divalent elements are also present in the cross section of the skeleton 2 as regions 4 .

Since the skeleton 2 contains a divalent element in this way, the grain boundary strength of the Al oxide of the skeleton 2 is improved, and the strength of the ceramic structure 10 is also improved. If the content of divalent elements is less than 0.05% by mass, the strength is not improved. When the content of the divalent element exceeds 3.0% by mass, the growth of abnormal grains of Al oxide in the skeleton 2 is promoted, and the strength is lowered.
The total content of divalent elements contained in the skeleton 2 can be measured by ICP (Inductively Coupled Plasma).

Looking at the cross section of the skeleton 2 shown in FIG. 2, when the average aspect ratio of the divalent element region 4 is 3 or more, the presence of grains with a high aspect ratio in the grains suppresses the progress of cracks. Therefore, the grain boundary strength of the Al oxide of the skeleton 2 is further improved.
Here, the average aspect ratio is obtained as follows. First, as shown in FIG. 2, in a 300×300 μm field of view AR in the EDS (energy dispersive X-ray spectroscopy) image of the cross section of the skeleton 2, the region 4 indicating the composition of the divalent element is discriminated. At least one field of view AR is obtained. Then, based on the contour of each region 4 of the divalent element in the field of view AR, the long side and short side are obtained by image analysis software (for example, image analysis/image measurement/image processing software WinROOF), and the aspect ratio is calculated. do. An average aspect ratio is obtained by averaging the aspect ratios of the regions 4 .

For example, the upper right portion of the field of view AR in FIG. 2 includes a part of the region 4 of the divalent element. exclude. For example, in FIG. 2, the aspect ratios are calculated only for five areas 4 that are completely included in the field of view AR.

When the divalent element forms an aluminate phase, the grain boundary strength of the Al oxide of the skeleton 2 is further improved.
Whether or not the divalent element forms an aluminate phase is determined by detecting the peak of the aluminate phase by XRD (X-ray diffraction: for example, Rigaku's product name Smart Lab) of the powder obtained by pulverizing the skeleton 2. It can be determined by
The aluminate phase includes BaO.6Al ₂ O ₃ (barium hexaaluminate), BaAl ₂ Si ₂₈ (celsian), BaAl ₁₂ O ₁₉ and the like.

Further, as shown in FIG. 2, when the cross section of the skeleton 2 is viewed, the porosity in the skeleton 2 is preferably 10% or less, since the strength of the skeleton 2 is further improved.
The porosity in the skeleton 2 was determined by setting the matrix (Al oxide of the skeleton 2) and the darker part in a field of view of 100 × 100 µm in the backscattered electron image of the cross-sectional SEM of the skeleton 2. is binarized. Then, the area ratio of the dark portion in the field of view is calculated and taken as the porosity. This is because portions darker than the matrix can be regarded as voids G of the skeleton 2 .

Furthermore, when viewing the surface of the framework 2 shown in FIG. 1, if the average aspect ratio of the divalent element regions 4 is 3 or more, the grain boundary strength of the Al oxide of the framework 2 is further improved.
The calculation of the average aspect ratio of the divalent element region 4 on the surface of the skeleton 2 is performed in the same manner as the calculation of the average aspect ratio of the cross section of the skeleton 2 in the 300×300 μm field of view AR in the EDS image of the surface of the skeleton 2 .

In addition, in the EDS image of the cross section of the actual ceramic structure 10 shown in FIG.

It goes without saying that the present invention is not limited to the above-described embodiments, but extends to various modifications and equivalents within the spirit and scope of the present invention.
The shape of the ceramic structure is not limited, and may be a polygonal column, a polygonal cylinder, an ellipse, or an irregular shape.

EXAMPLES The present invention will be described in more detail below with reference to Examples, but the present invention is not limited to these.

A urethane sponge having continuous pores is used as a mold, and this sponge is impregnated with a slurry containing ceramic particles (alumina), particles or colloidal particles containing a divalent element shown in Table 1, a complex and an organic solvent, and then baked. Burned out the sponge. As a result, a ceramic structure 10 made of an oxide ceramic having a predetermined porosity and having continuous pores was manufactured. The dimensions of the ceramic structure 10 were a rectangular parallelepiped with a thickness of 30×30×7 mm.
The porosity of the ceramic structure 10 was adjusted to the values shown in Table 1 by changing the urethane sponge. Moreover, the aspect ratio of the cross section and the aspect ratio of the surface were adjusted by changing the firing conditions (the firing temperature, the time for holding at a predetermined temperature, etc.) for each sample. In addition, the presence or absence of the aluminate phase was adjusted by changing the firing conditions.

The porosities of the ceramic structure 10 and skeleton 2 were measured by the method described above.
The aspect ratios of the divalent elements in the cross section and surface of the skeleton 2 were measured by the method described above.
Whether or not the divalent element forms an aluminate phase was determined by the method described above.

The compressive strength of the ceramic structure 10 was measured by compressing it in the thickness direction with an autograph (AGX-X manufactured by Shimadzu Corporation) and breaking it. If the compressive strength exceeds 0.5 MPa, it can be said that the strength is high.
The pressure loss of the ceramic structure 10 was measured as the pressure loss when room temperature air was allowed to flow at a constant flow rate (within the range of 5 to 25 L/min) into the circulating constant temperature liquid bath. If the pressure loss is 3.0 Pa or less, it can be said that the pressure loss is small.

Table 1 shows the results obtained.

As is clear from Table 1, in each example in which the porosity of the ceramic structure is 60% or more and the total amount of divalent elements is 0.05 to 3.0% by mass, the strength is increased without increasing the pressure loss. I was able to improve.
In particular, in Examples 13 to 20 in which the average aspect ratio of divalent elements in the cross section of the skeleton was 3 or more, the strength was further improved compared to Example 2 in which the porosity and the composition of divalent elements were the same.
In Examples 16 to 20 in which the divalent element formed an aluminate phase, the strength was further improved compared to Example 13 in which the porosity, the composition of the divalent element and the average aspect ratio of the cross section were the same.
In Examples 18 to 20, in which the porosity in the skeleton was 10% or less, the strength was further improved compared to Example 16, in which other conditions were equivalent.

On the other hand, in the case of Comparative Example 1 in which the porosity of the ceramic structure is less than 60%, the pressure loss increased compared to each example.
In Comparative Example 2, in which the total content of divalent elements is less than 0.05% by mass, the strength was lower than that of each example.

2 skeleton 4 region of divalent element 10 ceramic structure

Claims (5)

A ceramic structure having a ceramic skeleton and a porosity of 60 to 97% with continuous pores,
A ceramic characterized in that the skeleton contains Al oxide as a main component and contains 0.05 to 3.0% by mass in total of one or more divalent elements selected from the group of Mg, Ca, Sr, and Ba. Structure. 2. The ceramic structure according to claim 1, wherein an average aspect ratio of said divalent element region is 3 or more when viewed in cross section of said skeleton. 3. The ceramic structure according to claim 1, wherein said divalent element forms an aluminate phase. 4. The ceramic structure according to claim 1, wherein the skeleton has a porosity of 10% or less when viewed in cross section. 5. The ceramic structure according to any one of claims 1 to 4, wherein the divalent element region has an average aspect ratio of 3 or more when the surface of the skeleton is viewed.

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