JP6934436B2 - A method for preparing a sample for cross-section observation of a collection filter and a method for evaluating the collection state of particulate matter in the collection filter. - Google Patents

Description

The present invention relates to a method for preparing a sample for cross-section observation of a collection filter and a method for evaluating the collection state of particulate matter in the collection filter.

Particulate matter in the exhaust gas discharged from an internal combustion engine or the like has a great influence on the human body, the environment, etc., so there is an increasing need to prevent it from being released into the atmosphere. In particular, PM (particulate matter) emitted from diesel engines and gasoline direct injection engines has a great influence as described above, and PM regulations are being tightened worldwide. Against this background, it is necessary to evaluate how the particulate matter is collected in the collection filter that collects the particulate matter. Therefore, the collection filter was cut using a cutter knife or the like, and the cross section of the filter was observed under a microscope to evaluate the collection state of particulate matter.

However, when the collection filter is cut using a cutter knife or the like, the cutting powder easily adheres to the cross section. Since it is difficult to distinguish the cut powder from the particulate matter when observed under a microscope, there is a problem that the collected state of the particulate matter cannot be accurately evaluated. In particular, this problem is remarkable when evaluating a collection filter formed of silicon carbide or the like.

The present invention has been made to solve the above problems, and provides a method for preparing a cross-section observation sample of a collection filter capable of accurately evaluating the collection state of particulate matter in the collection filter. The purpose is to provide. Another object of the present invention is to provide a method for accurately evaluating the collection state of particulate matter in the collection filter.

The present inventors have formed the above-mentioned problems by forming cut portions on at least two surfaces facing each other at the cross-sectional formation positions of the collection filter, and then applying a load to the cut portions to break the cut portions while supporting the collection filter. We have found that a collection filter cross-section observation sample capable of solving the above problems can be obtained, and have completed the present invention.

That is, the present invention is a method for preparing a sample for cross-section observation of a collection filter for evaluating the collection state of particulate matter, in which cut portions are formed on at least two opposing surfaces of the cross-section formation positions of the collection filter. This is a method for producing a cross-section observation sample of a collection filter, which comprises a step of performing the process and a step of applying a load to the cut portion to break the cut portion while supporting the collection filter.

Further, the present invention is a method for evaluating the collection state of particulate matter in the collection filter, and is a method for observing the cross section of the collection filter cross-sectional observation sample obtained by the production method with an optical microscope. ..

According to the present invention, it is possible to provide a method for preparing a cross-section observation sample of a collection filter capable of accurately evaluating the collection state of particulate matter in the collection filter. Further, according to the present invention, it is possible to provide a method for accurately evaluating the collection state of particulate matter in the collection filter.

It is a perspective view of the collection filter. It is a side view of the collection filter which shows the state which the cut part is formed on the two opposite surfaces of the cross-sectional formation position of the collection filter. It is a side view of the collection filter which shows the state which formed the cut part on the entire surface of the cross-section formation position of the collection filter. It is a side view of the collection filter which shows the state which supported the collection filter by using a tape. It is a figure which shows the state which applies the load by bending three points to the cut part of the collection filter. It is a figure which shows the state which applies the load by bending four points to the cut part of the collection filter. It is an optical micrograph of the cross-section observation sample of the collection filter of Example 1. It is an optical micrograph of the cross-section observation sample of the collection filter of Comparative Example 1.

Hereinafter, preferred embodiments of the method for preparing a sample for observing a cross section of a collection filter of the present invention and the method for evaluating the collection state of particulate matter in the collection filter will be specifically described. It should not be construed as being limited to the above, and various changes and improvements can be made based on the knowledge of those skilled in the art as long as it does not deviate from the gist of the present invention. The plurality of components disclosed in each embodiment can form various inventions by appropriate combinations. For example, some components may be deleted from all the components shown in the embodiment, or components of different embodiments may be combined as appropriate.

(Method of preparing a sample for cross-section observation of a collection filter)
The method for preparing the cross-section observation sample of the collection filter of the present embodiment includes a step of forming a notch on at least two surfaces facing each other at the cross-section formation position of the collection filter, and a load is applied to the notch while supporting the collection filter. In addition, it includes a step of breaking.

The collection filter used in the method for preparing a cross-section observation sample of the collection filter of the present embodiment is not particularly limited, and may be a DPF (diesel particulate filter), a GPF (gasoline particulate filter), or the like. The collection filter is preferably pre-cut to an appropriate size and shape from the viewpoint of facilitating the preparation of a collection filter cross-section observation sample. The size and shape of the collection filter are not particularly limited, but may be, for example, a square columnar having an axial length of 40 to 150 mm and a cross section orthogonal to the axial direction of 10 to 20 mm.

FIG. 1 is a perspective view showing an example of a collection filter used in the method for preparing a cross-sectional observation sample of the collection filter of the present embodiment. In FIG. 1, the collection filter 1 is a honeycomb structure having a partition wall 5 for partitioning a plurality of cells 4 that penetrate from the first end surface 2 to the second end surface 3 to form a fluid flow path.

The material constituting the collection filter 1 is not particularly limited, but is preferably made of ceramics. Examples of ceramics include silicon carbide, silicon-silicon carbide composite material, silicon nitride, corderite, mullite, alumina, spinel, corderite-silicon carbide composite material, lithium aluminum silicate, aluminum titanate and the like. Among these, the collection filter 1 formed of silicon carbide or a silicon-silicon carbide composite material is difficult to distinguish between the cut powder and the particulate matter when it is cut using a cutter knife or the like. It is suitable for use in preparing a cross-sectional observation sample of the collection filter of the embodiment. The "silicon-silicon carbide-based composite material" is a composite material formed by using silicon carbide as an aggregate and silicon as a binder. Here, the "main component" in the present specification means a component whose proportion in the total component exceeds 50% by mass.

The shape of the collection filter 1 is not particularly limited, but is a polygonal columnar shape such as a square columnar shape, a hexagonal columnar shape, or an octagonal columnar shape, a columnar shape, or an elliptical columnar shape.

In the method for producing a cross-section observation sample of a collection filter of the present embodiment, first, cut portions are formed on at least two opposing surfaces of the cross-section formation position 6 of the collection filter 1.
Here, in the present specification, the “cross-section forming position 6” means a position where a cross section should be formed.
The cross-section forming position 6 of the collection filter 1 is not particularly limited and can be appropriately selected by the observer. Typically, the cross-section forming position 6 of the collection filter 1 is in a direction orthogonal to the axial direction of the honeycomb structure. In this case, the cross section of the collection filter 1 is formed in a direction orthogonal to the axial direction of the honeycomb structure.

FIG. 2 is a side view of the collection filter showing a state in which cut portions 7 are formed on two opposing surfaces (upper surface and lower surface) of the cross-sectional formation position 6 of the collection filter 1. By forming the cut portions 7 on the two opposing surfaces, these cut portions 7 serve as the starting point and the ending point when the cut portion 7 is broken by a load, so that a flat cross section is easily formed. Since the flat cross section can be easily focused during microscopic observation, the cross section can be easily observed.
FIG. 3 is a side view of the collection filter 1 showing a state in which the cut portion 7 is formed on the entire surface of the cross-sectional formation position 6 of the collection filter 1. By forming the cut portion 7 on the entire surface, a flat cross section is more easily formed, so that the above effect can be stably obtained.

The method for forming the cut portion 7 is not particularly limited, and a method known in the art can be used. For example, the cutting portion 7 can be formed by using a cutting means such as a cutter knife or a laser.

The depth of the notch portion 7 is not particularly limited, and may be appropriately adjusted according to the size of the collection filter 1. Typically, the depth of the cut portion 7 is preferably 1/15 or more, preferably 1/13 or more of the length of the collection filter 1 in the cut direction from the viewpoint of forming a flat cross section. Is preferable. Further, the depth of the cut portion 7 is preferably 1/5 or less, preferably 1/8 or less, of the length of the collection filter 1 in the cut direction from the viewpoint of preventing the cut powder from adhering to the cross section. It is preferable to have.

The width of the cut portion 7 is not particularly limited, but is typically 0.1 mm to 3 mm, preferably 0.5 mm to 2 mm, and more preferably 0.5 to 1.5 mm from the viewpoint of forming a flat cross section. be.

Next, the collection filter 1 in which the cut portion 7 is formed is broken by applying a load to the cut portion 7 while supporting the collection filter 1. By forming the cross section in this way, it is possible to prevent the cutting powder from adhering to the cross section as in the case of cutting with a cutter knife or the like. Further, since the collecting filter 1 is broken while being supported, it is possible to prevent the particulate matter collected by the collecting filter 1 from moving due to the impact at the time of breaking. Therefore, the collection state of the particulate matter in the collection filter 1 can be accurately evaluated.

The method for supporting the collection filter 1 is not particularly limited, and a method known in the art can be used. For example, the collection filter 1 can be supported by using a supporting means such as a tape or an elastic member.
FIG. 4 is a side view of the collection filter 1 showing a state in which the collection filter 1 is supported by using the tape 10. In FIG. 4, the tape 10 is attached so as to cover the entire surface of the cross-section forming position 6, but it may be attached so as to cover only a part of the cross-section forming position 6.
When the collection filter 1 is supported by using an elastic member, the elastic member may be arranged at the bottom of the cross-section forming position 6. The elastic member is not particularly limited, but for example, a cushion member made of sponge may be used.

The method of applying the load to the cut portion 7 is not particularly limited, and a method known in the art can be used. For example, the load can be applied to the notch 7 by 3-point bending or 4-point bending.
Here, in the present specification, "three-point bending" means that, as shown in FIG. 5, both ends of the collection filter 1 are fulcrums 11, and one force point 12 is provided in the cut portion 7 to apply a load. means. Further, "four-point bending" means that, as shown in FIG. 6, both ends of the collection filter 1 are set as fulcrums 11, and two force points 12 are provided so as to sandwich the notch portion 7 to apply a load.

The load can be easily applied by using a commercially available universal testing machine. Here, the term "universal testing machine" as used herein means a testing device capable of performing various tests such as a tensile test, a compression test, and a bending test.

The load is preferably stopped at break. For example, when a universal testing machine is used, it may be set so that the load application is automatically stopped at the time of breakage. By doing so, it is possible to prevent the particulate matter collected by the collection filter 1 from moving after breaking.

(Method of evaluating the collection state of particulate matter in the collection filter)
In the method for evaluating the collection state of particulate matter in the collection filter of the present embodiment, the cross section of the collection filter cross-sectional observation sample obtained by the above-mentioned production method is observed with an optical microscope.
Observation of the cross section of the collection filter When observing the cross section of the sample with an electron microscope, it is necessary to create a vacuum inside the microscope, and at that time, the particulate matter collected by the collection filter moves, and the particulate matter It may not be possible to accurately evaluate the collection status.
On the other hand, in the evaluation method of the present embodiment, since the cross section of the collection filter cross-section observation sample is observed with an optical microscope, it is not necessary to evacuate the inside of the microscope, and the particulate matter collected by the collection filter is present. It can be prevented from moving. Therefore, according to the evaluation method of the present embodiment, the collection state of the particulate matter collected by the collection filter can be accurately evaluated.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.
(Example 1)
From the used DPF formed from silicon carbide, a rectangular columnar honeycomb structure having an axial length of 50 mm and a cross section orthogonal to the axial direction of 15 mm × 20 mm was obtained by cutting.
A cutter knife was used to form a cut portion having a width of 1 mm and a depth of 2 mm on the entire surface of the cross-sectional formation position of the honeycomb structure. Next, a tape was applied so as to cover the entire notch portion. After that, using a universal testing machine (3366 dual column tabletop testing machine manufactured by Instron), a load is applied to the notch by 4-point bending as shown in FIG. 6 to break the sample. Got The universal tester was set to automatically stop applying the load when it broke.

(Comparative Example 1)
A collection filter cross-section observation sample was obtained under the same conditions as in Example 1 except that the honeycomb structure was cut by a cutting process using a cutter knife.

The cross-sections of the collection filter cross-section observation samples obtained in Example 1 and Comparative Example 1 were observed using an optical microscope (VHX-1000 manufactured by KEYENCE CORPORATION). An optical micrograph of the collection filter cross-sectional observation sample of Example 1 is shown in FIG. 7, and an optical micrograph of the collection filter cross-section observation sample of Comparative Example 1 is shown in FIG. In FIGS. 7 and 8, (a) is a 30-fold optical micrograph and (b) is a 150-fold optical micrograph.
As shown in FIGS. 7 and 8, in the collection filter cross-section observation sample of Comparative Example 1, since a large amount of cut powder adhered to the cross section, it was difficult to distinguish between the collection filter and the particulate matter. On the other hand, in the collection filter cross-section observation sample of Example 1, the cut powder hardly adhered to the cross section, and it was easy to distinguish between the collection filter and the particulate matter.

As can be seen from the above results, according to the present invention, it is possible to provide a method for preparing a cross-section observation sample of a collection filter capable of accurately evaluating the collection state of particulate matter in the collection filter. Further, according to the present invention, it is possible to provide a method for accurately evaluating the collection state of particulate matter in the collection filter.

1 Collection filter 2 1st end face 3 2nd end face 4 cell 5 partition wall 6 cross-section formation position 7 notch 10 tape 11 fulcrum 12 point of effort

Claims (11)

A method for preparing a cross-section observation sample of a collection filter for evaluating the collection state of particulate matter.
A step of forming a notch on at least two opposite surfaces of the cross-section formation position of the collection filter, and
A method for producing a cross-section observation sample of a collection filter, which comprises a step of applying a load to the cut portion to break the cut portion while supporting the collection filter. The collection filter according to claim 1, wherein the collection filter is supported by a tape attached so as to cover at least a part of the cross-section forming position, or an elastic member arranged at the bottom of the cross-section forming position. A method for preparing a cross-section observation sample of a collecting filter. The method for preparing a cross-section observation sample of a collection filter according to claim 1 or 2, wherein the load is applied by 3-point bending or 4-point bending. The method for producing a cross-section observation sample of a collection filter according to any one of claims 1 to 3, wherein the cut portion is formed on the entire surface of the cross-section formation position of the collection filter. The method for producing a collection filter cross-section observation sample according to any one of claims 1 to 4, wherein the load is stopped at the time of breakage. The method for preparing a cross-section observation sample of a collection filter according to any one of claims 1 to 5, wherein the load is applied by a universal testing machine. Any one of claims 1 to 6, wherein the collection filter is a honeycomb structure having a partition wall for partitioning a plurality of cells forming a flow path of a fluid penetrating from a first end face to a second end face. A method for preparing a cross-section observation sample of a collection filter according to the above. The method for producing a collection filter cross-section observation sample according to claim 7, wherein the cross section of the collection filter is formed in a direction orthogonal to the axial direction of the honeycomb structure. The method for producing a cross-section observation sample of a collection filter according to any one of claims 1 to 8, wherein the collection filter is a DPF. The method for producing a cross-section observation sample of a collection filter according to any one of claims 1 to 9, wherein the collection filter is made of ceramics. It is a method of evaluating the collection state of particulate matter in the collection filter.
A method for observing the cross section of the collection filter cross-section observation sample obtained by the production method according to any one of claims 1 to 10 with an optical microscope.

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