JP7459738B2 - Method for preparing resin-embedded samples and method for analyzing porous samples - Google Patents

Description

The present invention relates to a method for preparing a resin-embedded sample and a method for analyzing a porous sample.

For example, when analyzing granular samples, it has been disclosed that a powdered sample is embedded in resin to make it easier to introduce the powdered sample into an analytical device and analyze it (see, for example, Patent Document 1). The resin-embedded sample is subjected to analysis by exposing the analysis target on a cross section, for example by polishing or cutting. Such a resin-embedded sample allows the sample to be fixed with resin, making it possible to analyze the sample with high accuracy.

Unexamined Japanese Patent Publication No. 2016-50918

By the way, some samples to be analyzed are porous samples that have voids on the surface or inside. For porous samples, we need to know not only the elemental components that make up the sample, but also the size of each void, such as how large the void is and what its ratio (volume ratio, etc.) is. The abundance ratio may be analyzed.

However, even if a porous sample is embedded in resin and the voids are observed, for example, using an optical microscope, it may not be possible to obtain a clear difference in color between the resin filling the voids and the constituent components of the sample. On the other hand, when observing voids using an electron microscope, charge-up occurs due to the irradiation of the electron beam, and voids not filled with resin may be mistaken for other parts. In this way, it may not be possible to analyze porous samples accurately.

The present invention was made in consideration of the above problems, and aims to provide a technology for analyzing porous samples with high accuracy.

The first aspect of the present invention is
a preparation step of preparing a porous sample having voids;
a first embedding step of embedding the porous sample in a resin to form a solid body;
a cutting step of cutting the solid body so as to divide the porous sample to form a cut piece in which a cross section of the porous sample is exposed;
a second embedding step of embedding the cut piece in a resin and filling the voids existing in the cross section of the porous sample with the resin;
A method of making a resin-embedded sample is provided.

A second aspect of the present invention is a method for producing a composition comprising the steps of:
In the second embedding step, the cut piece is immersed in liquid resin with the cross section facing downward, and the liquid resin is hardened.

A third aspect of the present invention is, in the first or second aspect,
The porous sample has a size such that the maximum cross-sectional area is 2 mm ² or more and 700 mm ² or less.

The fourth aspect of the present invention is
a preparation step of preparing a porous sample having voids;
a first embedding step of embedding the porous sample in a resin to form a solid body;
a cutting step of cutting the solid body so as to divide the porous sample to form a cut piece in which a cross section of the porous sample is exposed;
a second embedding step of embedding the cut piece in a resin and filling the voids present in the cross section of the porous sample with the resin;
an acquisition step of irradiating an electron beam to a surface of the resin-embedded sample obtained in the second embedding step where the porous sample is exposed to obtain an electron image;
A method for analyzing a porous sample is provided, the method comprising: analyzing the porous sample based on the electron image.

A fifth aspect of the present invention is the fourth aspect,
The method further comprises, after the acquiring step, an image processing step of binarizing the electronic image,
In the analyzing step, the void is analyzed based on the binarized image.

A sixth aspect of the present invention is the fifth aspect,
In the binarization process, a gradation is set for the electronic image to distinguish between pixels corresponding to the porous sample and pixels corresponding to the resin, and each pixel is binarized using the set gradation as a threshold value.

A seventh aspect of the present invention is the method according to any one of the fourth to sixth aspects,
The electron image is a backscattered electron image.

The eighth aspect of the present invention is the method according to any one of the fourth to seventh aspects,
In the acquisition step, a fully automated mineral analysis device is used.

A ninth aspect of the present invention is any one of the fourth to eighth aspects,
In the analysis step, the volume ratio of each size of the void is measured.

According to the present invention, porous samples can be analyzed with high accuracy.

FIG. 1 is a perspective view showing a schematic configuration of a resin-embedded sample according to an embodiment of the present invention. FIG. 2 is a perspective view showing a schematic configuration of the solidified body. FIG. 3 is a perspective view showing the schematic structure of the cut piece. FIG. 4 is a diagram for explaining a method of arranging a cut piece in a container. FIG. 5 is a schematic diagram of a backscattered electron image of a cross section of a resin-embedded sample.

<One embodiment of the present invention>
An embodiment of the present invention will be described below with reference to the drawings. Fig. 1 is a perspective view showing a schematic configuration of a resin-embedded sample according to an embodiment of the present invention. Fig. 2 is a perspective view showing a schematic configuration of a solidified body. Fig. 3 is a perspective view showing a schematic configuration of a cut piece. Fig. 4 is a view for explaining a method of arranging the cut piece in a container.

(preparation process)
First, a porous sample to be measured is prepared.

The porous sample is not particularly limited as long as it has voids on its surface or inside. For example, a porous sample is a porous metal compound that contains metal elements and their oxides and sulfides.

The shape of the porous sample is, for example, spherical. Its size is not particularly limited, but it is preferable that the maximum value of the cross-sectional area is within the range of 2 mm ² to 700 mm ^2. The maximum diameter is, for example, 10 mm to 20 mm. The larger the porous sample, the more area is observed when the cross-section is taken, and there is a risk that the efficiency of evaluating the porous sample will decrease. In this regard, by using a fully automatic mineral liberation analyzer (hereinafter also referred to simply as MLA), it is possible to observe the entire cross-section at once even for porous samples having the above-mentioned size, and the evaluation efficiency can be maintained high.

(First embedding step)
Subsequently, the porous sample is embedded in resin. Specifically, a porous sample is placed in a container, a liquid resin is added into the container, and the porous sample is immersed in the liquid resin. Then, the liquid resin is cured to obtain a solid body. As shown in FIG. 2, the solidified body 14 has a porous sample 10 embedded in a hardened resin 13, and has, for example, a cylindrical shape. The size of the solid body 14 is not particularly limited as long as it can embed the porous sample 10, and may be changed as appropriate depending on the size of the porous sample 10.

As the liquid resin, for example, epoxy resin or acrylic resin can be used. Among these, epoxy resin is preferred because it can be easily cured.

(Cutting process)
Next, the cylindrical solidified body 14 is cut. At this time, for example, the solidified body 14 is cut along the dotted line in FIG. 2 so as to divide the porous sample 10. As a result, a cut piece 15 as shown in FIG. 3 is obtained. In the cut piece 15, the cross section 11 of the porous sample 10 is exposed on the cut surface. The cross section 11 of the porous sample 10 has voids 12 (or depressions caused by the voids). This is because the resin 13 is not embedded in the voids 12 of the cross section 11 because the liquid resin cannot penetrate into the inside of the porous sample 10 in the first embedding step. In FIG. 3, the cylindrical solidified body 14 is cut in the height direction, but the cutting direction is not particularly limited as long as the cross section of the porous sample 10 can be exposed. In addition, a conventionally known method may be used as a cutting method for the solidified body 14.

(Second embedding step)
In the cut piece 15, the resin 13 is not embedded in the voids 12 of the porous sample 10, so if you try to observe the cut piece 15 as it is, it will be difficult to clearly distinguish between the voids 12 and the parts that make up the porous sample 10. Can not. Therefore, in this embodiment, a second embedding step is provided separately from the first embedding step in order to embed the resin 13 into the voids 12 of the porous sample 10.

In the second embedding step, first, the cut piece 15 is placed in the container 20. At this time, the cut piece 15 is arranged so that the cut surface (the surface where the porous sample 10 is exposed) of the cut piece 15 faces upward. Thereafter, a liquid resin is added into the container 20, and the cut piece 15 is immersed in the liquid resin. Subsequently, defoaming treatment is performed. In the cut piece 15 immersed in the liquid resin, the liquid resin may not flow into the voids 12 and bubbles may remain. According to the defoaming process, the void 12 can be more reliably filled with the liquid resin. The defoaming treatment method is not particularly limited, and for example, vacuum defoaming can be employed.

Subsequently, as shown in FIG. 4, after performing a defoaming process, the direction of the cut piece 15 immersed in the liquid resin 13' is changed. Specifically, the cut piece 15, which is arranged with the cut surface facing upward, is placed in the liquid resin 13' so that the cut surface faces downward and the cross section 11 of the porous sample 10 is in contact with the bottom surface of the container 20. 15 and place it in a different direction.

Next, the liquid resin 13' is hardened to obtain the resin-embedded sample 1 as shown in FIG. 1. In the resin-embedded sample 1, the liquid resin 13' is allowed to penetrate into the voids 12 in the cross section 11 of the porous sample 10 and hardened, so that the voids 12 are filled with the resin 13.

The method for hardening the liquid resin 13' is not particularly limited as long as it does not alter the porous sample 10, and may be, for example, drying at room temperature.

In the case of the resin-embedded sample 1, the cross section 11 of the porous sample 10, which is the observation surface, may be covered with the resin 13 and not be smooth, or the covering resin 13 may be thick, which may hinder analysis. For this reason, if necessary, it is advisable to polish the side of the resin-embedded sample 1 on which the cross section 11 of the porous sample 10 is located. As a polishing method, for example, rough polishing, intermediate polishing, and mirror polishing may be performed using a buff polishing machine. In addition to buff polishing, for example, ion polishing such as using a cross-section polisher or focused ion beam processing may be performed.

The cut pieces 15 may be arranged in the container 20 with the cut surface facing upward, but it is preferable to arrange them with the cut surface facing downward. If the cut pieces 15 are arranged with the cut surface facing upward and liquid resin is added, a thick layer of resin 13 may be formed on the cross section 11 of the porous sample 10. In this case, in order to expose the cross section 11, it is necessary to polish the thick resin 13, which may impair the production efficiency. In this regard, by arranging the cut pieces 15 with the cut surface facing downward, as shown in Figure 1, the cross section 11 can be placed near the surface of the resin-embedded sample 1, and the thickness of the resin 13 to be polished can be made thinner, thereby improving the production efficiency.

The shape of the resin-embedded sample 1 is not particularly limited. It is preferable that the shape be such that it is easy to hold in the analysis device used in the acquisition process described below, and for example, a cylindrical shape as shown in Figure 1 is preferable.

If necessary, a conductive film may be provided on the observation surface of the resin-embedded sample 1 by vapor deposition of a conductive material such as carbon to suppress charging due to electron beam irradiation.

In addition, the liquid resin used in the second embedding step may be the same as or different from that used in the first embedding step. In addition, it is preferable that the viscosity of the liquid resin used is low from the viewpoint of embedding in the void 12.

(Acquisition process)
Subsequently, the resin-embedded sample 1 is introduced into the MLA, and as shown in FIG. A backscattered electron image (hereinafter also referred to as a BSE image) is acquired as an electron image of the observation surface.

In a BSE image, the composition distribution on the observation plane is displayed as a gray level (black and white shading) having a plurality of gradations. In a BSE image of the observation surface of a resin-embedded sample, for example, pixels corresponding to constituent components (metal elements, etc.) of the porous sample are displayed as bright areas (white) with relatively large gray levels. On the other hand, pixels corresponding to resin are displayed as dark areas (black) with relatively small gray levels. In the BSE image of this embodiment, the resin covering the surface of the porous sample and the resin embedded in the voids are displayed as black. Specifically, as shown in FIG. 5, the white portion 20 represents the porous sample 10. Further, of the black portion (hatched portion) 21, a portion 21a located within the porous sample 10 corresponds to the void 12, and a portion 21b surrounding the porous sample 10 corresponds to the resin 13.

Note that BSE images can also be obtained using a scanning electron microscope (SEM) or other devices other than MLA.

(Image processing process)
From the obtained BSE image, pixels displayed in black corresponding to voids can be extracted and the voids can be evaluated from their shapes, but from the viewpoint of more accurate evaluation, it is preferable to provide an image processing step before the analysis step. As the image processing step, it is preferable to perform binarization processing on the BSE image.

Specifically, first, in the BSE image shown in FIG. 5, the boundary between the porous sample 10 and the outer resin 13 covering it is identified, and the black portion 21b corresponding to the outer resin 13 is excluded from the image processing target. Next, in the white portion 20 corresponding to the porous sample 10, the black portion 21a corresponding to the resin filling the voids 12 is subjected to binarization processing. In binarization, the gradation of each pixel in the black portion 21a is compared with a threshold value, and if the gradation of the pixel is smaller than the threshold value, it is judged to correspond to the resin and converted to black (e.g., 0 gradation). On the other hand, if the gradation of the pixel is equal to or greater than the threshold value, it is judged to correspond to a component of the porous sample and converted to white (e.g., 255 gradation). In this way, a monochrome two-tone image is obtained. This image allows the shape of the voids 13 to be accurately grasped, making it possible to evaluate the voids 13 with greater precision.

The threshold value of the gradation that separates the constituent components of the porous sample from the resin is not particularly limited, and may be changed as appropriate depending on the constituent components and the resin used.

(Analysis process)
Next, the voids are analyzed based on the obtained monochrome two-tone image. The analysis items are not limited to the shape and size of the void, but may include, for example, the volume ratio of each void size.

The volume of the voids can be calculated, for example, as follows. First, the area of the location corresponding to each void is calculated for the binarized image using image analysis software (such as Image J). Next, the diameter of each void, when considered as a circle, is calculated from each area. Then, each void is considered as a sphere having the calculated diameter, and its volume is calculated.

The volume fraction of each size of pore can be obtained from the correlation between the pore diameter and volume fraction calculated above. This volume fraction allows the size distribution of pores in a porous sample to be understood.

This makes it possible to evaluate voids in porous samples.

Note that the electron image is not limited to the BSE image, and a secondary electron image can also be used. However, from the viewpoint of achieving a high contrast ratio between the part corresponding to the porous sample 10 and the part corresponding to the voids 12 in the electron image and analyzing the voids 12 with more precision, the electron image is a BSE image. It is preferable that there be.

<Other embodiments of the present invention>
Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and can be modified in various ways without departing from the gist of the present invention.

<Effects of this embodiment>
According to this embodiment, one or more of the following advantages are achieved.

When a porous sample 10 having voids 12 is embedded in resin 13 and processed into a resin-embedded sample 1, in this embodiment, the porous sample 10 is first embedded in resin 13 and hardened to form a solidified body 14, and then the solidified body 14 is cut to divide the porous sample 10, and the resulting cut pieces 15 are embedded in resin 13 again and hardened. In the first resin embedding, the resin 13 cannot be sufficiently embedded in the voids 12 present inside the porous sample 10, but by performing resin embedding again after cutting, the resin 13 can be embedded in the voids 12 that were not filled in the first time. As a result, the resin 13 can be covered over the entire surface of the cross section 11 of the porous sample 10, which is the observation surface, and the resin 13 can be embedded in the voids 12 present in the cross section 11. According to the resin-embedded sample 1 obtained by such a process, when a backscattered electron image is acquired, it is possible to clearly distinguish the components that constitute the porous sample 10 from the resin 13 that fills the voids 12, and the voids 12 can be analyzed with high accuracy. Furthermore, the analysis of the voids 12 allows for accurate analysis of the porous sample 10.

In the present embodiment, it is preferable that the cut pieces 15 obtained by cutting are immersed in a liquid resin, placed in the container 20 with the cross section 11 facing downward, and then the liquid resin is cured. By embedding with the resin 13 in this manner, the cross section 11 serving as the observation surface can be placed near the surface of the resin-embedded sample 1, and the thickness of the resin 13 deposited on the observation surface can be reduced. As a result, the thickness of the resin 13 to be polished can be reduced, so that work efficiency can be improved.

In addition, in this embodiment, it is preferable to binarize the BSE image and perform image processing on it, rather than evaluating the obtained BSE image as is, and to evaluate the voids based on the image. The binarized image makes it possible to more clearly distinguish between the components that make up the porous sample 10 and the resin 13 that fills the voids 12, so that the voids 12 can be evaluated more accurately.

Further, when acquiring a BSE image from the resin-embedded sample 1, it is preferable to use a fully automatic mineral analyzer (MLA). According to MLA, since the observation area is large, even if the porous sample 10 has a large block shape with a maximum cross-sectional area in the range of 2 mm ² to 700 mm ² , the entire cross section can be observed. can be done in one go, and evaluation efficiency can be maintained at a high level.

Reference Signs List 1: resin-embedded sample 10: porous sample 11: cross section 12: void 13: resin 14: solidified body 15: cut piece

Claims (8)

a preparation step of preparing a porous sample having voids;
a first embedding step of embedding the porous sample in a resin to form a solid body;
a cutting step of cutting the solid body so as to divide the porous sample to form a cut piece in which a cross section of the porous sample is exposed;
a second embedding step of embedding the cut piece in a resin and filling the voids existing in the cross section of the porous sample with the resin ;
In the second embedding step, the cut piece is immersed in an epoxy resin, which is a liquid resin, so that the cross section faces upward to perform a defoaming treatment, and then the cut piece is immersed in an epoxy resin, which is a liquid resin, so that the cross section is curing the liquid resin by changing the direction so that the liquid resin faces downward;
Method for preparing resin-embedded samples. The porous sample has a size such that the maximum cross-sectional area is ² mm2 or more and ⁷⁰⁰ mm2 or less.
A method for preparing a resin-embedded sample according to claim 1. a preparation step of preparing a porous sample having voids;
a first embedding step of embedding the porous sample in a resin to form a solid body;
a cutting step of cutting the solid body so as to divide the porous sample to form a cut piece in which a cross section of the porous sample is exposed;
a second embedding step of embedding the cut piece in a resin and filling the voids present in the cross section of the porous sample with the resin;
an acquisition step of irradiating an electron beam to a surface of the resin-embedded sample obtained in the second embedding step where the porous sample is exposed to obtain an electron image;
an analysis step of analyzing the porous sample based on the electron image ,
In the second embedding step, the cut piece is immersed in an epoxy resin, which is a liquid resin, so that the cross section faces upward to perform a defoaming treatment, and then the cut piece is immersed in an epoxy resin, which is a liquid resin, so that the cross section is curing the liquid resin by changing the direction so that the liquid resin faces downward;
Analysis method for porous samples. The method further comprises, after the acquiring step, an image processing step of binarizing the electronic image,
In the analyzing step, the void is analyzed based on the binarized image.
The method for analyzing a porous sample according to claim 3. In the image processing step, a gradation is set for the electron image to distinguish between pixels corresponding to the porous sample and pixels corresponding to the resin, and the set gradation is used as a threshold value for each pixel to perform binarization.
The method for analyzing a porous sample according to claim 4. The electron image is a reflected electron image.
The method for analyzing a porous sample according to any one of claims 3 to 5. In the acquisition step, a fully automatic mineral analyzer is used,
The method for analyzing a porous sample according to any one of claims 3 to 6. In the analysis step, the volume ratio of each size of the void is measured.
The method for analyzing a porous sample according to any one of claims 3 to 7.

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