JPH10160693A - Three-dimensional form measurement method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure the form of a specific phase in a polyphase material three-dimensionally by machining and eliminating the polyphase material to a specific depth and exposing one section as a flat surface, then successively repeating a machining/observation cycle for forming a two-dimensional observation image in depth direction, and synthesizing a two-dimensional observation image obtained for a plurality of sections as a three-dimensional image. SOLUTION: An observation surface is exposed (machined) and a two-dimensional observation image is formed for a plurality of two-dimensional observation surfaces F1 , F2 ,..., F3 in a sintered body that is a polyphase material by a consecutive machining observation. The obtained two-dimensional observation image is recognized by a computer with the contour of particle section as electronic information by a two-dimensional image processing. Then, the two-dimensional image is constructed three-dimensionally in the computer to obtain a three-dimensional image. By using the three-dimensional image, parameters (for example, a long diameter, a short diameter, and a distribution) are measured for the three-dimensional form of a second-phase particle. To obtain accurate information, a lager number of observation surfaces are used. Consecutive machining observation is repeated in sub μm pitch.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for three-dimensionally measuring a morphology of a specific phase in a multiphase material composed of a plurality of phases.

[0002]

2. Description of the Related Art As one typical example of a multi-phase material, for example, in a ceramic sintered body, various properties such as mechanical properties such as strength and toughness are determined by the structure constituting the sintered body, for example, It is known that there is a correlation with the form (shape, size, distribution, volume ratio, etc.) of the second phase existing in the one-phase matrix.

A ceramic sintered body as a multi-phase material is a mixture of a plurality of types of ceramics. Typically, the type of ceramic having the largest volume ratio constitutes the first phase matrix, and has a considerably larger volume. One or more kinds of ceramics having a small ratio are dispersed in the first phase matrix as the second phase. The morphology of the particles as the second phase is basically an important factor for such properties of the ceramic sintered body. Furthermore, voids and microcracks existing in the sintered body are also one of the structural factors that cannot be ignored, and may need to be considered as a third phase in some cases. It is also important to know the relationship between cracks and each tissue factor, especially in evaluating the effect of the tissue factors on toughness, and the cracks present during observation are one of the third phases present in the first phase matrix. It needs to be a target of morphometry as a part.

In some ceramic sintered bodies, the first phase is in the form of particles, such as silicon nitride, and the state of the particles greatly affects the characteristics of the sintered body. It is important to measure the one-phase particle morphology. 2. Description of the Related Art Conventionally, as a means for knowing the structure of a ceramic sintered body, a two-dimensional plane microscopic observation image or the like has been used. When a cross section of the sintered body is observed with a microscope, for example, a two-dimensional image as shown in FIG. 1 is obtained. In the same figure, the dispersed second phase particles are observed as indicated by hatching on a plane in the observation visual field represented by a white frame.

However, in observation on such a two-dimensional plane, for example, when the shape of the second phase particles is anisotropic,
There is a limit to the analysis of the causal relationship between material properties and second phase particles. For example, as shown in FIG. 2, it is known that the toughness of a composite material, which is one of the multiphase materials, is significantly affected by the anisotropy of particles (eg, Shigeo Inoue, Tetsuo Uchiyama, Koichi Niihara Co-author, "Ceramics", "Toughening of Ceramics by Whisker", P.621-629, Vol.21, No.7, 19
See 86. That is, the rod-shaped, disk-shaped, and spherical second-phase particles have the largest relative fracture toughness in the case of rod-shaped particles when compared at the same volume fraction. That is, it is more effective to use a disk-shaped or rod-shaped particle than a sphere to improve the toughness value. Therefore, in developing a material having a high toughness value, it is very important to obtain information on the three-dimensional shape of the second phase particles and to control manufacturing conditions based on the information.

In producing a ceramic material, second-phase particles (for example, fibers, whiskers, etc.) whose form can be measured are added at a predetermined volume fraction, and sintered without changing the form of the second phase. If possible, it is not necessary to measure the particle morphology after manufacture. However, for example, Si ₃ N
Actually, there are many materials such as ₄ sintered bodies whose particle morphology changes from almost spherical to rod-like during sintering.

In the case of measuring the particle morphology closely related to the material characteristics after sintering, as shown in FIG. 3, in the conventional observation on a two-dimensional plane, the short diameter of the rod-shaped particles can be measured but the long diameter can be measured. Cannot be measured. As described above, as long as observation is performed on a two-dimensional plane as in the related art, the longitudinal direction of the second phase (particles), the third phase (voids, cracks), and the like, which have a great influence on the properties of the material, are considered. Since information about a three-dimensional form including a change cannot be obtained, there is a problem that a causal relationship in a correlation with a characteristic cannot be sufficiently analyzed.

[0008]

SUMMARY OF THE INVENTION Accordingly, the present invention provides a method for three-dimensionally measuring the morphology of a specific phase (particles, voids, cracks, etc.) in a multi-phase material represented by a ceramic sintered body. The purpose is to:

[0009]

According to the present invention, there is provided a method for three-dimensionally measuring a form of a specific phase in a multi-phase material comprising a plurality of phases, the method comprising: After processing to the depth and exposing one cross section as a plane, the processing and observation cycle of forming a two-dimensional observation image of this plane is sequentially repeated in the depth direction, and two-dimensional observation obtained for multiple cross sections This is achieved by a three-dimensional morphological measurement method characterized in that images are combined in the repetition order to form a three-dimensional image.

According to the method of the present invention, a two-dimensional observation image of a specific phase such as particles, voids and cracks in a multi-phase material such as a ceramic sintered body is synthesized to form a three-dimensional image. Since the morphology of the phase can be known three-dimensionally and accurately, the causal relationship between the various properties of the material and the tissue factor can be more fully analyzed. Since the ion beam can be finely processed and has a large processing capability due to the large mass of the ions as compared with the electron beam, it is preferable that the above-mentioned processing and removal be performed by ion beam irradiation.

Since the processing rate by the ion beam differs depending on the material to be processed, when the ion beam is irradiated in a direction perpendicular to the plane to be exposed (the cross section to be observed), irregularities are formed on the processing surface and an accurate flat surface is formed. The above two-dimensional observation image may not be obtained. In this case, the irradiation direction of the ion beam is made substantially parallel to the plane to be exposed, so that unevenness is not formed due to a difference in processing rate, so that a two-dimensional observation image on an accurate plane can be obtained. Can be.

When processing is performed with an ion beam parallel to the plane to be exposed as described above, the material is removed, and the ion beam slightly escapes to the side where the free surface appears. When a tilted surface is revealed and two-dimensional observation is performed on a cross-section that is tilted with respect to the planned cross-section, the synthesized three-dimensional image becomes distorted with respect to the true internal state of the material There is. In such a case, by inclining the irradiation direction of the ion beam by a predetermined correction angle with respect to the plane to be exposed, an expected cross section can be exposed, and the true internal state of the material can be obtained. A three-dimensional image without reflected distortion can be obtained. This correction angle depends on the type of the target multiphase material, the characteristics of the ion beam used, or the processing speed (feed), etc.
It can be appropriately determined by preliminary experiments. In the results of the ceramic sintered body performed so far by the present inventor, the correction angle was within 1 °, but it is considered that the correction angle varies depending on the above conditions.

It is desirable that a two-dimensional observation image be recorded as electronic information and synthesized by a computer to form a three-dimensional image.

[0014]

FIG. 4 shows a typical example of a procedure for performing the three-dimensional shape measurement method of the present invention. First, in the sequential processing observation shown at the left end of the figure, the observation surface is expressed (processed) for a plurality of two-dimensional observation surfaces (F ₁ , F ₂ ,... F _n ) in the sintered body which is a multi-phase material. ) And processing removal to form a two-dimensional observation image
This is a step of sequentially performing an observation cycle. The obtained two-dimensional observation image of each observation surface is subjected to two-dimensional image processing shown in the center of FIG. Next, as shown at the right end of the figure, a two-dimensional image is three-dimensionally constructed in a computer to obtain a three-dimensional image.
Using the three-dimensional image, each parameter (major axis, minor axis, distribution, etc.) of the three-dimensional morphology of the second phase particles can be measured.

In order to obtain a three-dimensional form of a plurality of two-dimensional observation planes in the sintered body and obtain accurate information on the three-dimensional form, it is necessary to use as many observation planes as possible. Since the particles constituting a normal ceramic have a size of several μm, it is necessary to repeat the sequential processing observation at a pitch of at least sub-μm. When measuring particles of several μm, if the processing pitch is set to several μm, the entire target particle to be measured will be processed (removed) at the time of processing, and a two-dimensional observation image will be obtained for the removed particles. I can't get it.

As a result of studying various processing means capable of two-dimensional observation without leaking as fine particles as possible, a focused ion beam having a fine beam and larger energy than an electron beam was most suitable. FIG. 5 shows an example of a focused ion beam generator (irradiation / observation device). The ion source is composed of an emitter and an extraction electrode, and the tip of the tungsten emitter is wet with gallium metal that is molten at room temperature. By applying an acceleration voltage of several kV to the extraction electrode, molten gallium metal atoms are released as ions. The ions are narrowed down by an electric condenser lens and an objective lens, and irradiated on a sample by scanning with a polarizer. Since ions have a larger mass than electrons, they have an effect (sputtering effect) of repelling sample atoms when irradiated on a solid sample, and this effect was used for sequential processing. When the sample is irradiated with ions in the same manner as when the electron is irradiated, secondary electrons containing surface information of the sample are emitted. By supplementing the secondary electrons with a secondary electron detector, an image similar to that of a scanning electron microscope could be obtained, and this was used as a two-dimensional observation image.
Since processing and observation can be performed in the same device, there is no need for complicated operations such as transporting the sample between the devices,
Processing in sub-μm units and observation of the exposed surface can be easily performed.

When a ceramic sintered body containing a plurality of types of particles is processed by an ion beam as the second phase, if the ion beam is irradiated perpendicularly to the observation surface, the processing rate for each particle is different. It is selectively processed and cannot provide a smooth observation surface. Similarly, in the processing of a sample including pores, when an ion beam is irradiated perpendicularly to the observation surface, the material around the pores is selectively processed, and a smooth observation surface cannot be obtained.

Therefore, as shown in FIGS. 6 and 7, the processing direction (irradiation direction) of the ion beam is substantially parallel to the observation surface, that is, the processing direction is substantially perpendicular to the observation direction, so that a smooth observation surface is obtained. Obtainable. As described above, the operation of switching the direction of ion beam irradiation on the sample between processing and observation by approximately 90 ° can be easily performed by actually rotating the sample, not the ion beam, by approximately 90 °.

Hereinafter, the present invention will be described in more detail by way of examples.

[0020]

【Example】

[Example 1] As a sample, a ceramic sintered body in which a ceria-stabilized zirconia polycrystal was used as a first phase matrix and in which lanthanum-β-alumina crystal particles on a disk were dispersed as a second phase. Using.

The processing range by the focused ion beam is set to X × Y = 15 μm or more × 15 μm or more on the XY plane shown in the schematic diagram of FIG. 6, and the sequential processing pitch in the Z direction is set to 0.1.
100 μm was sequentially observed for processing. The acceleration voltage of the ion beam extraction electrode was set to 15 kV, the beam current during processing was set to 20 to 4500 pA, and the beam current during observation was set to 1 to 4 pA.

As shown in FIGS. 6 and 7, the sample is rotated by approximately 90 ° between the processing and the observation, and the processing direction (= irradiation direction) by the ion beam is substantially parallel to the observation surface, that is, the processing direction. The observation direction was rotated by about 90 °, and processing observation was sequentially performed. In performing the sequential processing, as shown in FIG. 8, the sample surface is inclined by a correction angle θ = 0.4 ° with respect to the ion beam irradiation direction, so that the sample surface and the processing before the ion beam irradiation are The exposed surface was made parallel. This correction angle is a value obtained in advance by a preliminary experiment. Although the reason is not clear, if processing is performed without this correction angle, the exposed surface by processing will not be parallel to the sample surface before processing.

FIG. 9 shows the first six images out of 100 two-dimensional observation images obtained by performing sequential processing observations under the above conditions. In the figure, each frame is an observation image of each time, and the number attached to the left of each frame indicates the number of times of observation of that frame. In this figure, the portion observed with the darkest contrast is the lanthanum-β-alumina crystal particles on the disk as the second phase. As long as one observes a two-dimensional image, this second
Although the phase particles appear to be simply rod-shaped, the two-dimensional observation images of 100 times obtained by the above sequential processing observation can be three-dimensionally synthesized on a computer to measure the shape as crystal particles on a disk. did it. FIG. 13 shows an example of the obtained three-dimensional image. This is because lantern-
This is a three-dimensional synthesis of 100 two-dimensional observation images obtained by selecting 12 β-alumina crystal particles. I have. Example 2 A silicon nitride sintered body of columnar particles was used as a sample. The conditions and procedure for sequential processing observation were the same as in Example 1. However, the correction angle θ during processing was set to 0.2 °. This correction angle is also a value obtained in advance by a preliminary experiment.

FIG. 10 shows the first six images out of 100 two-dimensional observation images obtained by performing sequential processing observations under the above conditions. In the figure, each frame is an observation image of each time, and the number attached to the left of each frame indicates the number of times of observation of that frame. In the figure, the portion observed with the darkest contrast is the columnar particles of silicon nitride, and the portion observed with the white contrast is the grain boundary. In this case, it can be handled as a multi-phase material having silicon nitride as the first phase and grain boundaries as the second phase. By three-dimensionally combining on a computer the two-dimensional observation images for 100 times obtained by the sequential processing observation,
The morphology could be measured using silicon nitride crystals as columnar particles. For example, it was possible to measure the length of columnar particles that could not be measured from one two-dimensional observation image. FIG. 14 shows an example of the obtained three-dimensional image. This is obtained by selecting eight silicon nitride crystals from the field of view in FIG. 10 and synthesizing two-dimensional observation images for 100 times three-dimensionally, and clearly shows the form of each individual silicon nitride crystal as hexagonal columnar particles. .

In the above example, an example was shown in which the three-dimensional morphology of the ceramic particles themselves was measured. However, according to the method of the present invention, not only the three-dimensional analysis of the particle morphology but also the 3D analysis is also possible. In order to develop a material that is difficult to break, it is necessary to clarify the relationship between particles and a fracture path (crack propagation path) guided by the particles. Conventionally, as shown in FIG. 11, the crack propagation path is observed with a two-dimensional image, but actually, the fracture occurs three-dimensionally. According to the method of the present invention, FIG.
As shown in the above, it is possible to more clearly observe the state in which the cracks propagate between the dispersed particles in the multi-phase material or are stopped by the dispersed particles. The measurement results of the three-dimensional form (shape, size, distribution, volume ratio, etc.) of the specific phase obtained in this way are extremely useful as information necessary for developing a material having excellent fracture toughness.

[0026]

As described above, according to the present invention,
A method is provided for three-dimensionally measuring the form of a specific phase (particles, voids, cracks, etc.) in a multiphase material represented by a ceramic sintered body. This makes it possible to obtain information that is extremely useful for developing a multiphase material having excellent characteristics.

[Brief description of the drawings]

FIG. 1 is a second view obtained by observation on a conventional two-dimensional plane.
It is a schematic diagram which shows a phase particle form.

FIG. 2 is a graph schematically showing a relationship between a particle volume fraction and a relative fracture toughness value when second phase particles having three-dimensionally different shapes are dispersed.

FIG. 3 is a schematic diagram illustrating a relationship between columnar particles having a major axis and a minor axis and a two-dimensional observation image thereof.

FIG. 4 is a flowchart showing a typical example of a procedure for performing the three-dimensional shape measurement method according to the present invention.

5 (A) and 5 (B) are (A) perspective view and (B) part of a focused ion beam generator (processing / observing apparatus) suitable for use in three-dimensional shape measurement of the present invention. It is an expanded sectional view.

FIG. 6 is a schematic diagram showing a relationship between a sample and an ion beam irradiation direction (processing / observation direction) when performing sequential processing observation according to the present invention.

FIG. 7 is a cross-sectional view taken along a plane A in FIG. 6;

FIG. 8 is a cross-sectional view schematically showing a state in which a processing surface of a sample is inclined by a predetermined correction angle θ with respect to an ion beam irradiation direction during processing according to the present invention.

FIG. 9 shows ceria-stabilized zirconia (ZrO ₂ )
Lanthanum-β in a first phase matrix consisting of
-It is a microscope picture which shows the first six times of the ceramics sintered compact in which the alumina particles (LBA) were dispersed as the second phase were sequentially processed and observed 100 times by the present invention.

FIG. 10 is a view showing columnar particles of silicon nitride (Si ₃ N);
₄ ) Photomicrographs showing the first six times of 100 successive processing observations on the sintered body.

FIG. 11 is a schematic diagram showing dispersed particles and cracks by conventional two-dimensional observation.

FIG. 12 is a schematic diagram showing a three-dimensional image of dispersed particles and cracks synthesized from a number of two-dimensional observation images according to the present invention.

FIG. 13 is a micrograph showing an example of a three-dimensional image synthesized from 100 two-dimensional images of the example shown in FIG. 9; In the figure, one side is 10 μm as a three-dimensional scale.
Filled the cube.

FIG. 14 is a photomicrograph showing an example of a three-dimensional image synthesized from 100 two-dimensional images of the example shown in FIG. 10; In the figure, one side is 10μ as a three-dimensional scale.
m is filled in.

Claims (5)

[Claims] 1. A method for three-dimensionally measuring a form of a specific phase in a multi-phase material comprising a plurality of phases, wherein the multi-phase material is processed and removed to a predetermined depth, and one section is exposed as a plane. Thereafter, a processing / observation cycle for forming a two-dimensional observation image of this plane is sequentially repeated in the depth direction, and a two-dimensional observation image obtained for a plurality of cross sections is combined in the above-described repetition order to form a three-dimensional image. A three-dimensional morphological measurement method characterized by the following. 2. The method according to claim 1, wherein the processing and removing are performed by irradiation with an ion beam. 3. The method according to claim 2, wherein the irradiation direction of the ion beam is substantially parallel to the plane to be exposed. 4. The method according to claim 2, wherein the irradiation direction of the ion beam is inclined by a predetermined correction angle with respect to the plane to be exposed. 5. The method according to claim 1, wherein the two-dimensional observation image is recorded as electronic information, and the combination is performed by a computer to form the three-dimensional image. .