JP3031730B2 - Ceramics molded body and method of manufacturing ceramics molded body - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic molded product and a method for producing a ceramic molded product, and more particularly to a method for significantly improving toughness and strength at a low cost without drastically changing a conventional production process. The present invention relates to a ceramic molded body and a method for manufacturing the ceramic molded body, which enables the above.

[0002]

2. Description of the Related Art Generally, when a ceramic material is compared with a metal material, both the brittleness and the toughness of the ceramic material are low, and since the strength distribution in the ceramic molded body is unevenly distributed, local concentration of stress is facilitated. Shows the tendency to occur. For the above-mentioned reasons, it is extremely difficult to use a ceramic molded body as a member having a complicated shape with a high load, and it has not been put to practical use.

[0003] Therefore, in order to put the ceramic molded body into practical use in various shapes in a wide range of applications, the brittleness is reduced and the toughness is improved, and the strength distribution in the ceramic molded body is made uniform to reduce the stress. There is a continuing need to avoid local concentration.

[0004] In response to the above demand, in the production of a ceramic molded body, a production method for achieving a composite by using whiskers and a production method for achieving a composite by using a new matrix composite have been adopted.

[0005]

However, in the ceramic molded body manufactured by the whisker compounding method, strength and physical properties are anisotropic due to the orientation of the grown whiskers and the added fiber components. In this case, the grown whiskers and the added fiber components hinder densification. Therefore, it is necessary to provide a sintering driving force for overcoming the inhibition on the densification in order to achieve the densification of the ceramic molded body. Since the production means for applying the sintering driving force is limited to the HIP sintering method or the HotPress method, not only a desired shape cannot be obtained but also a disadvantage that causes a rise in manufacturing cost becomes apparent. ing.

In the composite method using the new matrix composite, although the strength is improved as compared with the conventional example, it is very difficult to adjust the raw materials used, and the raw materials used are extremely expensive. Therefore, there is an inconvenience that causes a rise in manufacturing cost.

Further, as shown in FIG. 4, the ceramic molded body obtained by the above two methods is dense because the whiskers and fiber components as the basic constituent particles 40 are adjacent and entangled. A gap 42 is defined by the basic constituent particles 40. Then, using the gap 42 as a starting point of destruction, a problem of so-called grain boundary destruction is revealed.

Further, in order to overcome the above disadvantage, a method of filling the gap 42 with a large amount of a sintering aid or an additive is conceivable. However, since the sintering aid and the additive are glassy, Even if it is crystallized, it does not reach the strength of the basic constituent particles, and because it tends to soften at high temperatures, it has not yet achieved the desired strength and toughness.

Accordingly, an object of the present invention is to improve the strength and toughness of a ceramic molded body by strengthening the grain boundaries defined by basic constituent particles composed of whiskers, fiber components, and the like. It is another object of the present invention to provide a ceramic molded body capable of obtaining a desired shape and a method of manufacturing a ceramic molded body, without being limited to a production means.

[0010]

Means for Solving the Problems To solve the above problems, the present invention provides a basic structure containing at least one kind selected from the group consisting of silicon nitride (Si ₃ N ₄ ) and silicon carbide (SiC). Particles, and a grain boundary formed by filling a sintering aid into a gap defined by the basic constituent particles, and particles within the grain boundary precipitated in the grain boundary, And

[0011] The present invention also provides a method for burning the basic constituent particles containing at least one kind selected from the group consisting of silicon nitride (Si ₃ N ₄ ) and silicon carbide (SiC) and the gap between the basic constituent particles. This is a method for producing a ceramic molded body having a grain boundary formed by filling a binder and particles precipitated in the grain boundary precipitated in the grain boundary, wherein needles are formed in the grain boundary by firing or heat treatment. Alternatively, the method is characterized in that precipitated particles in a grain boundary composed of a granular single crystal and a composite crystal are precipitated.

[0012]

DETAILED DESCRIPTION OF THE STRUCTURE According to the ceramic molded body and the method of manufacturing the ceramic molded body according to the present invention, basically, at least one of silicon nitride (Si ₃ N ₄ ) and silicon carbide (SiC) is used. By filling a sintering aid into a gap generated between the basic constituent particles containing the above as a main raw material, cerium oxide (CeO ₂ ), lanthanum oxide (La ₂ O ₃ ), aluminum oxide (Al ₂ O) _3), yttrium oxide (Y ₂ O _3),
Zirconium oxide (ZrO ₂ ), dysprosium oxide (Dy ₂ O
₃ ), samarium oxide (Sm ₂ O ₃ ), neodymium oxide (Nd
₂ O ₃ ), magnesium oxide (MgO), titanium oxide (TiO ₂ )
, Silicon oxide (SiO ₂ ) and chromium oxide (Cr ₂ O ₃ ) to form a solid solution of a small amount of carbon (C) and nitrogen (N) to form a grain boundary. Further, titanium carbide (TiC), silicon carbide (SiC), titanium nitride (Ti N), chromium carbide (Cr ₄ C _3), zirconium carbide (ZrC), zirconium nitride (ZrN), at least one or more selected from the group consisting of chromium nitride (CrN) Precipitation particles in a grain boundary made of a needle-like or granular single crystal or a composite crystal are precipitated to improve the strength and toughness, and to make the strength distribution uniform.

The basic constituent particles containing at least one of silicon nitride (Si ₃ N ₄ ) and silicon carbide (SiC) as a main raw material are extremely high in purity when crystals are grown by firing or heat treatment. It is composed of single crystal hexagonal column whiskers.

Next, a method of manufacturing the ceramic molded body is shown in a flowchart of FIG. In the manufacturing method, in order to grow a hexagonal columnar crystal whisker made of a single crystal as the basic constituent particles with high purity, in the firing step in which the basic constituent particles are grown, other components are solidified in the basic constituent particles. Severely inhibits melting. Because, when other components are dissolved in the basic constituent particles, the whisker grows irregularly or grows into a shape different from a hexagonal column, so that defects are generated in the basic constituent particles themselves, This is because the strength is deteriorated.

Further, sintering aid to form a grain boundary is filled in the gap, first, Oite densification is started over enough for molding,
Finally, densification is completed in the firing process. Therefore, in the firing process, it is necessary to strictly control the temperature rising rate, the holding temperature, the holding time, the sintering atmosphere, and the like.

The volume of the grain boundary changes depending on the amount of the sintering aid added. It is preferable that the volume is small in order to reduce the brittleness of the grain boundary, so that the amount of the sintering aid added is adjusted according to the type and the amount of the precipitated particles in the grain boundary. Precipitation of grain boundary in the precipitated particles are other densification components in the second half of the burn formation process is started from just before completion, proceed with the Atsushi Nobori of the holding temperature.
Then, in the heat treatment process, the precipitated particles in the grain boundaries are stabilized and homogenized.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings. In the present embodiment, first, the ceramic molded body will be described, and then, in Examples 1 to 5, the operation and effect of the method of manufacturing the ceramic molded body will be described.

In FIG. 1 and FIG. 2, reference numeral 10 indicates basic constituent particles 10 constituting a ceramic molded body. The basic constituent particles 10 are obtained by using at least one of silicon nitride (Si ₃ N ₄ ) and silicon carbide (SiC) as a main raw material and growing a crystal by sintering or heat treatment. It is composed of hexagonal columnar whiskers made of crystals.

The basic constituent particles 10 have three sizes, and the first basic constituent particles 12 having the largest diameter have a hexagonal surface diameter of about 2 μm to 3.5 μm and a length of 10 μm.
It shows a hexagonal columnar whisker shape of about μm to about 14 μm. The first basic constituent particles 12 form the basic skeleton of the ceramic molded body, and the large-diameter gap defined by the first basic constituent particles 12 is filled with medium-sized second basic constituent particles 14. The second basic constituent particles 14 have a hexagonal columnar whisker shape having a hexagonal surface diameter of about 0.5 μm to 1.0 μm and a length of about 5 μm to 6 μm. Further, the gaps of the medium diameter defined by the second basic constituent particles 14 or between the first basic constituent particles 12 and the second basic constituent particles 14 are filled with the third basic constituent particles 16 having the smallest diameter. The third basic constituent particles 16 have a hexagonal diameter of 0.1.
About 3 μm to 0.5 μm and length from 10 μm to 14
It shows a hexagonal columnar whisker shape of about μm.

As described above, in the filled ceramic molded body obtained by growing hexagonal columnar whiskers, the ratio of the space occupied by the gap can be greatly reduced as compared with the conventional filled state shown in FIG. Accordingly, the ratio of the sintering aid, which is significantly inferior in strength and toughness to the basic constituent particles 10 used for filling the gap in the ceramic molded body, can be reduced, so that the toughness and strength are improved. At the same time, the strength distribution can be made uniform, and local concentration of stress can be avoided.

As can be easily understood from FIG. 2 which is an enlarged view of a portion surrounded by a circle in FIG. 1, even after the compressive stress is applied, the two basic constituent particles 10 still remain between each other.
A grain boundary 18 exists, and a larger grain boundary 19 exists in a portion surrounded by the three basic constituent particles 10. The grain boundaries 18 and 19 increase the brittleness of the ceramic molded body, increase the strength distribution, and make it easier to receive local concentration of stress. Therefore, the grain boundaries 18 and 19 serve as starting points of fracture and cause grain boundary fracture.

In order to avoid the grain boundary destruction, the grain boundaries 18, 19
While the crystallization, the titanium carbide in the grain boundary 18, 19 (TiC), silicon carbide (SiC), titanium nitride (TiN), chromium carbide (Cr ₄ C _3), zirconium carbide (ZrC), nitride zirconium
At least one kind of needle-like or granular single crystal or composite crystal selected from the group consisting of silicon (ZrN) and chromium nitride (CrN).
By precipitating the precipitated particles 20 in the grain boundaries in the grain boundaries 18 and 19, the grain boundaries, that is, the ratio of the sintering aid occupied in the ceramics compact can be reduced, so that the brittleness can be reduced and Ru can to strengthen the field 18 and 19.

In the case of needle-shaped crystals, the size of the precipitated particles 20 in the grain boundary is preferably about 0.001 μm to 0.01 μm in diameter and about 0.01 μm to 0.03 μm in length. , At most 0.2 μm in diameter and 1.5 μm in length. In the case of granular crystals, the diameter is 0.1 mm.
A shape of about 001 μm to 0.03 μm is preferable,
The diameter must be at most 0.5 μm or less.

If the size of the intragranular precipitated particles 20 is smaller than the above range, the effect is reduced because the surface energy of fracture does not increase so much. Further, when the ratio is more than the above range, the volume of the grain boundaries 18 and 19 increases with the increase, so that the brittleness increases and the toughness decreases.

The ceramic molded body according to the present invention is basically constructed as described above. Next, a method of manufacturing the ceramic molded body will be described including its operation and effects. Experimental Example 1 Assuming that the total weight of the powder material is 100 parts by weight, 89.67 parts by weight of silicon nitride (Si ₃ N ₄ ) having an average particle diameter of 0.8 μm and aluminum oxide (Al ₂ ) having an average particle diameter of 0.4 μm O ₃ ) 3 parts by weight,
4 parts by weight of yttrium oxide (Y ₂ O ₃ ) having an average particle size of 0.9 μm, and magnesium oxide (MgO) having an average particle size of 1.2 μm.
3 parts by weight, 2 parts by weight of dysprosium oxide (Dy ₂ O ₃ ) having an average particle size of 1.0 μm, 0.5 parts by weight of ceric oxide (CeO ₂ ) having an average particle size of 1.2 μm, and 1.5 μm in average particle size Lanthanum oxide (La ₂ O ₃ ) 0.5 parts by weight, average particle size 50 angstrom (0.005 μm) carbon black (C)
0.03 parts by weight of each was weighed to obtain a powder raw material.

To 100 parts by weight of the powder raw material, 32 parts by weight of purified water and an appropriate amount of a liquid component comprising an ammonium alginate solution and an acrylic resin emulsion are added, and then dispersed and mixed using a ball mill for 120 hours. Raw material was obtained.

A preform having a shape of 20 × 20 × 100 mm was formed from the mixed material by slip casting using a gypsum mold.

After drying and degreasing the pre-formed body, the pre-formed body was fired in a nitrogen atmosphere according to the firing step shown in FIG. 3 to obtain a ceramic shaped body.

[0029] This ceramic molded body was subjected to JIS1601.
According to the above, test materials to be subjected to various tests described below were cut out.

Further, in order to provide for Comparative Example 1, a powder material of the same quality as the test material was used, and the total weight of the powder material was 10%.
90 parts by weight of silicon nitride (Si ₃ N ₄ ), ₄ parts by weight of aluminum oxide (Al ₂ O ₃ ), and yttrium oxide (Y ₂
O ₃ ) Using the raw material powder weighed to 6 parts by weight,
The same process as the test material of Experimental Example 1 was performed to obtain a comparative test material.

The bending strength, hardness, fracture toughness value by the chevron notch method in which a V notch was introduced, and density by the Archimedes method were measured for the test material and the comparative test material, respectively. Using the same test material and comparative test material, a grain boundary structure using TEM, an optical microscope, and SE
Observation of defects in the surface and cross-sectional direction after mirror polishing using M was performed.

When observing the fractured surface, etching was performed with a mixed solution of 10% hydrogen fluoride (HF) and 25% nitric acid (HNO ₃ ), and the etched portion and the unetched portion were compared and observed.

Table 1 shows the physical property values, Table 2 shows the results of defect observation by an optical microscope, and Table 3 shows the results of defect observation by SEM.

From Table 1, it can be seen that in Experimental Example 1, the strength and toughness were significantly improved as compared with Comparative Example 1.

From Tables 2 and 3, it is determined that the number of voids in Experimental Example 1 is smaller than that in Comparative Example 1, and that there are almost no defects.

Observation with a TEM confirmed that in Experimental Example 1, a crystal plane composed of hexagonal columnar whiskers of a single crystal having extremely high crystallinity was observed. This crystal plane is formed by three basic constituent particles 10 of approximately three sizes.
Form a regular crystal lattice. The basic constituent particles 10 form a skeleton of a ceramic molded body.
First basic constituent particles 12 having a shape of 1 μm to 13 μm,
4.5 μm to 6 μm shaped second basic constituent particles 1 filling the gap defined by the first basic constituent particles 12
4. Filling small gaps defined by the first basic constituent particles 12 and the second basic constituent particles 0.3
and third basic constituent particles 16 having a shape of μm to 3 μm.

After the first basic constituent particles 12, the second basic constituent particles 14, and the third basic constituent particles 16 are filled with the basic constituent particles of a suitable size corresponding to the respective sizes, they are still formed. The remaining gaps are further filled with the sintering aid to form grain boundaries 18 (see FIG. 2).

In Experimental Example 1, 10
Acicular and ultrafine granular silicon carbide (SiC) -precipitated particles 20 of Å (0.001 μm) to 70 Å (0.007 μm) were confirmed. Also, a grain boundary 1 defined by three basic constituent particles
9, the particles 20 within the grain boundaries precipitate on average in a size of 100 angstroms (0.01 μm) to 500 angstroms (0.05 μm).
The deposit is 00 Å (0.1 μm).

In Experimental Example 1, in the fracture surface, both the intergranular fracture and the intragranular fracture were observed, and traces of crack deflection, crack pinning effect, and pull-out effect were confirmed. Therefore, it is determined that the toughness and strength shown in Table 1 were significantly improved by these factors.

In Experimental Example 1, at the grain boundary 18, it was confirmed that the precipitated particles 20 in the grain boundary branched off the crack and that the crack had a pinning effect. Therefore, it is determined that the strength is improved by the increase in the fracture energy required for the grain boundary fracture. Further, it can be easily understood that the strength and the toughness are improved by the residual stress generated by the solidification of the grain boundaries 18 and the precipitation of the precipitated particles 20 in the grain boundaries.

In contrast to Experimental Example 1, in Comparative Example 1, it was confirmed that the basic constituent particles constituting the ceramic molded body had a needle shape or a column shape, but the crystallinity was poor and the grain boundaries were not good. It is composed of a thick glass layer composed of uniform aggregates. Therefore, it was confirmed that these grain boundaries caused coarse defects, and nearly 90% of the grain boundaries were the starting points of fracture. Experimental Example 2 After weighing the raw material having the same quality as that of Experimental Example 1 so as to have the compounding ratio shown in Table 4, the same firing temperature, firing atmosphere, and heat treatment temperature as those of Experimental Example 1 were used. To give a ceramic molded body. The heat treatment temperature was set even if not subjected to post-baked formation heat treatment to another temperature range 1450 ° C. from 950 ° C..

The above-mentioned ceramic molded body is 50 × 25 × 6
A test material was obtained by cutting into a shape of 0 mm.

The test material was^#300,^#800,^#30
Polished with a 00 diamond grindstone and the residual stress
After the measurement using the chevron notch method,
Sex K _{I c}Was measured.

As Comparative Example 2, powder materials having the same quality as in Experimental Example 2 were weighed so as to have the compounding ratio shown in Table 5, and then the sintering temperature and the heat treatment temperature shown in Table 5 were used. After giving the same process to obtain a ceramic molded body, it was processed into the same shape as the test material to obtain a comparative test material.

FIG. 5 shows the relationship between the fracture toughness and the residual stress in Experimental Example 2 and Comparative Example 2. In addition, ● shows the data of Comparative Example 2 and ○ shows the data of Experimental Example 2.

From FIG. 5, it can be seen that in both Experimental Example 2 and Comparative Example 2, the residual stress is on the compression side, and the fracture toughness value is increased with the increase in the residual stress.

In Comparative Example 2, the upper limit of the compressive stress that could be applied was around 100 MPa.
In Experimental Example 2, the upper limit could be improved to around 200 MPa. Experimental Example 3 The same ceramic molded body as the test material of Experimental Example 1 was processed into the shape shown in FIG. 6 to obtain a test material to be subjected to a fatigue test. In the test material 28, the length of the test portion 30 was 20 mm, and the surface was polished with a ^# 600 dhammond grindstone and then mirror-finished to a surface roughness of 0.8.

The fatigue test was performed with a sine wave of 20 Hz using a hydraulic servo type tester. In addition, in order to make the effects of the average stress ρ _m and the amplitude stress ρ _a remarkable,
Stress ratio (ratio of maximum stress to minimum stress) R = -1: complete swing, R = 0: complete swing, R = 1/5, R = 1/2,
R = 4/5: Five cases of partial swing were set. Note that a guarantee test using a preload before the fatigue test was not performed.

FIG. 7 shows the results of the fatigue test at R = −1, and FIG. 8 shows the results of the fatigue test at R = 0.

In the tensile-compression fatigue test of R = -1,
Fatigue strength at 10 ⁷ cycles, about the tensile strength 60
%. Also, R = 0, R = 1/5, R = 4 /
With the 5 and the stress ratio R is increased sequentially, also increases the fatigue strength at 10 ⁷ cycles, 4 kgf / mm with respect to the stress ratio R
An increasing tendency of about ² to 7 kgf / mm ² was confirmed.

[0051] When comparing the fatigue strength at ¹⁰⁸ cycles with R = -1 and R = 0, the presence of the intensity difference of about 10 kgf / mm ² was confirmed. It is understood that this is because the tensile stress was relatively lower than the tensile fatigue strength due to the residual stress.

[0052] Figure 7 and to organize fatigue strength at 10 ⁷ cycles in the fatigue test with different stress ratio R shown in FIG. 8 the mean stress [rho _m and the amplitude stress [rho _a as an index shown in FIG.

FIG. 9 shows that the amplitude stress ρ _a decreases as the average stress ρ _m increases, and the average stress ρ _m and the amplitude stress ρ _a
The sum of, and the maximum stress is seen to exhibit an increasing trend with increasing mean stress [rho _m. And finally the fatigue strength
Matches tensile strength.

Further, the relationship between the average stress ρ _m and the amplitude stress ρ _a is as follows: ρ _a : Amplitude stress ρ _e : Fatigue strength under double swing stress ρ _m : Average stress ρ _t : Tensile strength

In FIG. 9, the area below the broken line connecting the fatigue strength ρ _e under the double swing stress on the Y axis and the (static) tensile strength ρ _t on the X axis represented by the equation 1 is a repetition. This is a region that shows safety stress under stress. The region showing the safety stress of Experimental Example 3 is surrounded by a value significantly higher than the region showing the safety stress in any of the conventional ceramics molded article, metal material and the like.

From the above results, when the tensile-tensile fatigue strength exceeds the tensile-compression fatigue strength, the average stress ρ
It is confirmed that the fatigue strength using the maximum stress as an index shows an increasing tendency with an increase in _m . Further, the average stress ρ _m is little involved in the formation and growth of cracks, and the amplitude stress ρ _a
It can be seen that it is greatly affected by

From the above, it is easily understood that the fatigue fracture occurs by the following two mechanisms. In the first case, when a large defect serving as a starting point of destruction exists in advance, micro-cracks occur due to repeated application of stress. When the area of the microcrack and the area surrounding the large defect exceeds a certain threshold value, fatigue failure occurs. Also, the second
In this case, the stress is repeatedly applied to the stress concentration portion of the defect existing in advance. Then, new microcracks are generated at the grain boundaries due to the repeated stress. Further, this new micro crack and the defect are bonded to form a crack, and the crack gradually expands to cause fatigue fracture.

The phenomena to be described later can be understood from the results shown in FIGS. That is, when a tensile stress is applied,
Even when the crack is pinned by silicon nitride (Si ₃ N ₄ ) having the shape of a hexagonal columnar whisker or the like and the crack is prevented from spreading, the tip of the crack is given by applying compressive stress in the following process. The part is closed and the hexagonal columnar whiskers detach from the crack. As a result, when a tensile stress is applied in the next process, the pinning is not performed and the crack is enlarged. Then, the cracks are repeatedly expanded by the above-described mechanism, and when a crack having a size equal to or larger than a certain threshold is formed, fatigue fracture occurs.

Further, the precipitation of the intragranular precipitation particles 20 in the grain boundaries 18 and 19 where crack propagation due to the above-mentioned action mechanism is most likely to progress enhances the grain boundaries. This increases the energy required for destruction in order to produce a pinning effect. This is also confirmed from the fact that the strength indicated by the average stress ρ _m and the amplitude stress ρ _a in FIG. 9 has been significantly improved. Experimental Example 4 A test material 3 which was formed by processing the same ceramic molded body as the test material of Experimental Example 1 into the shape shown in FIG.
2 was obtained. As a comparative example, the test material 32 of the experimental example 4 was used.
Comparative Example 4a using a comparative test material that does not precipitate precipitated particles in the grain boundaries, and Comparative Example 4b using a comparative test material made of the same ceramic molded body material as in Comparative Example 1.

FIG. 11 shows the results of a rotating bending fatigue test at 2960 rpm. In addition, ● represents Experimental Example 4 and ○ represents Comparative Example 4.
a and x show the data of Comparative Example 4b, respectively.

From the results shown in FIG. 11, the fatigue strength at 10 ⁷ cycles of Comparative Example 4b was 26 kg / mm ² , while that of Experimental Example 4 was greater than 60 kg / mm ² .
Further, in Comparative Example 4b in which no precipitated particles were precipitated in the grain boundary, 43 k was used.
g / mm ² , and about 150% improvement in the fatigue strength was confirmed by precipitation of the precipitated particles in the grain boundaries 18 and 19.

Comparing the above results with the results of the simple bending test, the fatigue strength of Experimental Example 4 indicates a value of 37% to 42% of the fatigue strength in the simple bending test, and the fatigue strength of Comparative Example 4b is 30% to 35%. %showed that.

When the results of the rotary bending fatigue test are compared with the results of the tensile-tensile fatigue test, the fatigue strength of Experimental Example 4 is about 65% of the fatigue strength in the simple bending test.
And Comparative Example 4b showed a value of about 57%.

From the results of the above comparative study, it was found that the fatigue fracture strength of the rotary bending fatigue test was lower than that of the tensile-tensile fatigue test. It is easily understood that the speed is limited. Therefore, in the ceramic molded body having such a mechanism of the fatigue fracture, fine crystals such as precipitated particles in the grain boundaries are precipitated in the grain boundaries, thereby preventing crack growth due to grain boundary strengthening and pinning effect. Thereby, strength and toughness can be significantly improved. EXPERIMENTAL EXAMPLE 5 Using the same raw materials as in Experimental Example 1, the total weight of the granular material was reduced to 1
When the amount is 00 parts by weight, the respective raw materials are weighed so as to have the compositions of Examples 1 to 12 described in Table 6 to obtain powdery and granular raw materials.

Purified water as a dispersion medium is added to the raw material
Add a dispersant and a binder and use a ball mill to add 1
The mixture was dispersed and mixed for 20 hours to obtain a mixed raw material.

Next, a preform was formed from the mixed raw material using a gypsum mold having a shape of 25 × 10 × 80.

Next, the pre-formed body was dried and degreased, and then fired and heat-treated at the firing temperature and heat treatment conditions shown in Table 6 to obtain a ceramic formed body. The gas atmosphere at this time is an argon gas atmosphere until 1550 ° C. in the firing process, and then 9.5 kg with nitrogen gas.
/ Cm ² . When the gas in the furnace after firing was analyzed, the partial pressure of nitrogen was 70% to 98%, the partial pressure of argon gas was 1.5% to 29%, and the partial pressure of carbon monoxide was 0.1% to 1%.
% Was detected.

Then, from the ceramic molded body, 8
× 60 × 5mm, surface roughness 0.8
S and all corners formed test materials chamfered to 0.3C.

Using the test material, the distance between fulcrums was 40 mm
Was performed in the three-point bending test.

Further, the above-mentioned ceramic molded body can be used in accordance with JIS.
Form R1601 test material and use chevron notch method
Fracture toughness values were measured. In addition, it is usually
Ru Si _ThreeN_Four−Al_TwoO_Three−Y_TwoO_ThreeComparative example of ceramics compact
5 was used.

Table 6 shows the physical property values obtained from the above two tests.
Shown in

From Table 6, it was confirmed that the physical property values obtained in Examples 1 to 12 of Experimental Example 5 were high in strength and high in all cases when compared with Comparative Example 5.

When observing the crystal structure, an irregular grain structure with abnormal grain growth was observed in Comparative Example 5, whereas Examples 1 to 12 of Experimental Example 5 were in all cases. In this case, it was observed that the whiskers were formed of single crystal hexagonal columnar whiskers of extremely high crystallinity having three kinds of sizes similar to those of Experimental Example 1.

Further, in the fractured surface, not only the grain boundary fracture but also a trace of the progress of the microcrack and the intragranular fracture were observed, and it was confirmed that the grain boundary was strengthened.

[0075]

[Table 1]

[0076]

[Table 2]

[0077]

[Table 3]

[0078]

[Table 4]

[0079]

[Table 5]

[0080]

[Table 6]

[0081]

As described above, according to the ceramic molded body and the method of manufacturing the ceramic molded body according to the present invention, the ceramic molded body is made of a single crystal having extremely large crystallinity having three kinds of sizes. It is composed of hexagonal columnar whiskers, and needle-like crystals or extremely fine granular crystals are precipitated at the grain boundaries as precipitated particles in the grain boundaries. As a result, the grain boundaries are strengthened, and the expansion of cracks is prevented by the pinning effect of the precipitated particles in the grain boundaries. Therefore, there is an effect that a ceramic molded body having extremely high toughness and strength can be obtained without limiting the production means.

As a result, it is possible to easily set the life expectancy of the ceramic molded body and diagnose the design safety strength.

[Brief description of the drawings]

FIG. 1 is a partially omitted enlarged view of a ceramic molded body according to the present invention.

FIG. 2 is an enlarged view of a portion surrounded by a circle of a partially omitted enlarged view of FIG.

FIG. 3 is a process chart of a preferred embodiment of the method for producing a ceramic molded body according to the present invention.

FIG. 4 is a partially omitted enlarged view of a ceramic molded body according to a conventional technique.

FIG. 5 is a view showing the relationship between the fracture toughness and the residual stress of Experimental Example 2 and Comparative Example 2 in a preferred embodiment of the ceramic molded body and the method of manufacturing the ceramic molded body according to the present invention.

FIG. 6 is a view showing a shape of a test material used in Experimental Example 3 in a preferred embodiment of the ceramic molded body and the method of manufacturing the ceramic molded body according to the present invention.

FIG. 7 is a diagram showing the results of a fatigue strength test when R = −1 in Experimental Example 3 in a preferred embodiment of the ceramic molded body and the method for manufacturing the ceramic molded body according to the present invention.

FIG. 8 is a view showing the results of a fatigue strength test when R = 0 in Experimental Example 3 in a preferred embodiment of the ceramic molded body and the method for manufacturing the ceramic molded body according to the present invention.

FIG. 9 is a diagram showing the fatigue strength of Experimental Example 3 in terms of the average stress ρ _m and the amplitude stress ρ _a in a preferred embodiment of the ceramic molded body and the method for manufacturing the ceramic molded body according to the present invention.

FIG. 10 is a view showing a shape of a test material to be subjected to a rotary bending fatigue test of Experimental Example 4 in a preferred embodiment of the ceramic molded body and the method for manufacturing the ceramic molded body according to the present invention.

FIG. 11 is a view showing the results of a rotating bending fatigue test of Experimental Example 4 in a preferred embodiment of the ceramic molded body and the method for manufacturing the ceramic molded body according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Basic constituent particle which comprises a ceramic molded body 12 ... 1st basic constituent particle 14 ... 2nd basic constituent particle 16 ... 3rd basic constituent particle 18, 19 ... Grain boundary 20 ... Precipitated particle in a grain boundary

Claims (11)

(57) [Claims] 1. A basic constituent particle containing at least one kind selected from the group consisting of silicon nitride (Si ₃ N ₄ ) and silicon carbide (SiC), and a sintering aid in a gap between the basic constituent particles. A ceramic molded body, comprising: a grain boundary formed by filling; and intragranular precipitated particles precipitated in the grain boundary. 2. The ceramic molded body according to claim 1, wherein the precipitated particles in the grain boundary are titanium carbide (TiC), silicon carbide (SiC), titanium nitride (Ti N ), chromium carbide (Cr ₄ C ₃ ), A ceramic molded body comprising at least one or more needle-like or granular single crystal and composite crystal selected from the group consisting of zirconium carbide (ZrC), zirconium nitride (ZrN), and chromium nitride (CrN). 3. The ceramic molded body according to claim 1, wherein the precipitated particles in the grain boundary have a size in the range of 10 Å to 1000 Å. 4. The ceramic compact according to claim 1, wherein the grain boundary is cerium oxide (Ce).
O ₂ ), lanthanum oxide (La ₂ O ₃ ), aluminum oxide (Al ₂ O
₃ ), yttrium oxide (Y ₂ O ₃ ), zirconium oxide (Zr
O ₂ ), dysprosium oxide (Dy ₂ O ₃ ), samarium oxide (Sm ₂ O ₃ ), neodymium oxide (Nd ₂ O ₃ ), magnesium oxide (MgO), titanium oxide (TiO ₂ ), silicon oxide (SiO ₂ ) And a group consisting of chromium oxide (Cr ₂ O ₃ ), and carbon (C) and nitrogen (N) dissolved in trace amounts in the group. 5. The ceramic molded body according to claim 1, wherein the basic constituent particles are made of high-purity single-crystal hexagonal column whiskers having three different sizes, The basic constituent particles are the first basic constituent particles having the largest area of the hexagonal surface of the hexagonal columnar whisker and forming the skeleton of the ceramic molded body, and the first basic constituent particles having the hexagonal surface area of the hexagonal columnar whisker. And the second basic constituent particles disposed in a large-diameter gap defined by the first basic constituent particles, and the area of the hexagonal surface of the hexagonal columnar whisker is the smallest;
And a third basic constituent particle disposed in a small gap defined by the first basic constituent particle and the second basic constituent particle. 6. A basic constituent particle containing at least one kind selected from the group consisting of silicon nitride (Si ₃ N ₄ ) and silicon carbide (SiC), and a sintering aid in a gap between the basic constituent particles. A method for producing a ceramic molded body having a grain boundary formed by filling and particles precipitated in the grain boundary precipitated in the grain boundary, wherein a needle-like or granular single body is formed in the grain boundary by firing or heat treatment. A method for producing a ceramic molded body, comprising: depositing precipitated particles in a grain boundary comprising a crystal and a composite crystal. 7. A method of producing a ceramic molded body according to claim 6, baked growth or heat treatment, the nitrogen partial pressure of 98% 70% or less in total pressure value, partial pressure of argon or helium 1.5% A method for producing a ceramic molded body, characterized in that the remaining part of the partial pressure of the two components is carried out in an atmosphere consisting of a partial pressure of carbon monoxide at 28% or less. 8. A method for producing a ceramic molded body according to claim 6, wherein 0.001% by weight to 2.0% by weight of carbon is added to 100% by weight of the sintering aid. Alternatively, a method for producing a ceramic molded body, characterized in that needle-shaped or granular single-crystal and composite-crystal precipitated particles in a grain boundary are precipitated in the grain boundary by heat treatment. 9. The method for producing a ceramic molded body according to claim 6, wherein the precipitated particles in the grain boundary are:
Titanium carbide (TiC), silicon carbide (SiC), titanium nitride (Ti
N), chromium carbide (Cr ₄ C _3), zirconium carbide (ZrC),
A method for producing a ceramic molded body, comprising at least one kind of needle-shaped or granular single crystal and composite crystal selected from the group consisting of zirconium nitride (ZrN) and chromium nitride (CrN). 10. The method for producing a ceramic molded body according to claim 6, wherein the precipitated particles in the grain boundary have a size in the range of 10 Å to 1000 Å. A method for producing a molded article. 11. A method according to claim 6, wherein the grain boundaries are cerium oxide (CeO ₂ ), lanthanum oxide (La ₂ O ₃ ), aluminum oxide (Al ₂ O ₃ ). ₃ ), yttrium oxide (Y ₂ O ₃ ), zirconium oxide (ZrO ₂ ), dysprosium oxide (Dy ₂ O ₃ ), samarium oxide (Sm ₂ O ₃ ), neodymium oxide (Nd ₂ O ₃ ), magnesium oxide (MgO ), Titanium oxide (TiO ₂ ), silicon oxide (SiO ₂ ), and chromium oxide (Cr ₂ O ₃ ) in a sintering aid that coagulate and precipitate a small amount of carbon (C) and nitrogen (N) A method for producing a ceramic molded body, characterized by comprising: