JPH05345656A - Production of ceramic composite material - Google Patents

Abstract

(57) [Abstract] [Purpose] For example, even in the case of functionally graded ceramic composite materials, it is possible to manufacture at low cost and with high reliability, and it is also possible to manufacture various forms of ceramic composite materials. To [Structure] A slip cast molding method or an injection molding method is applied to manufacture a ceramic composite material containing two or more ceramic compositions having different compositions. Two or more types of ceramic compositions are made into sludges X and Y or kneaded products using the same or different dispersion media or solvents. The wettability of the dispersion medium and the solvent used at this time with respect to each ceramic composition is controlled. Two or more kinds of sludge X and Y are sequentially inlaid on the slip casting mold 1.
Alternatively, two or more kinds of kneaded products are sequentially and simultaneously injection-filled in an injection mold.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a ceramic composite material.

[0002]

2. Description of the Related Art Fine ceramic materials are excellent in high-temperature strength, wear resistance, corrosion resistance, etc., and are light in weight. Therefore, they are used in various engineering fields such as mechanical seals, cutting tools, pump parts, automobile engine parts, etc. Its use as a material has been studied, and some of them are being put to practical use. However, there are many kinds of materials even if they are simply fine ceramics materials, and each has its own characteristics.

Typical engineering ceramics include, for example, silicon nitride-based sintered bodies, sialon-based sintered bodies, silicon carbide-based sintered bodies, zirconium oxide-based sintered bodies, and aluminum oxide-based sintered bodies. Be done. For example, a silicon nitride-based sintered body has a feature that it is excellent in heat resistance and thermal shock resistance, but has a drawback that it is inferior in oxidation resistance and the like. Further, the sialon-based sintered body has small strength deterioration at high temperature and is excellent in oxidation resistance, but the absolute value of mechanical strength itself is inferior to that of silicon nitride, and the silicon carbide-based sintered body has high hardness. Although it has excellent wear resistance, it has the drawback of a large decrease in strength at high temperatures. Furthermore, in oxide-based ceramic materials,
Zirconium oxide-based sintered bodies have excellent toughness, and aluminum oxide-based sintered bodies are inexpensive and have excellent oxidation resistance, but on the other hand, in terms of mechanical strength and heat resistance, they are non-oxide ceramic materials. It is inferior in comparison.

As described above, each of the engineering ceramic materials has advantages and disadvantages, and naturally there is a limit when used alone. Therefore, it has been attempted to use a ceramic material having a single function as a hybrid material by combining the ceramic materials so as to form a composite. this is,
It utilizes the advantages of each material to compensate for the lacking function. Further, in such a hybrid material, not only a ceramic material having a different composition is multilayered and sintered but also a so-called functionally graded material in which each material has a concentration gradient between the ceramic materials is present. Has been noted for use.

As a method of manufacturing the functionally graded material as described above, for example, as shown in FIG.
Prepare two kinds of ceramic materials, that is, a plurality of raw material powders with different mixing ratios of A material powder and B material powder, and press-mold these sequentially to produce a molded body whose mixing ratio changes in order. However, a method of firing this molded body is adopted.

[0006]

However, in the above-mentioned method for producing a functionally graded ceramic composite material, the mixing ratio of the two types of ceramic materials to be composited can be changed only stepwise. If there is a difference in the coefficient of thermal expansion between these layers, there is a problem that cracks may occur between the layers, or there is a risk of destruction. Although the difference in the coefficient of thermal expansion of the composite ceramic materials can be alleviated to some extent by increasing the types of raw material powders with different mixing ratios, this method increases the manufacturing cost and significantly reduces the practicality. I will end up.

Further, in the above-mentioned manufacturing method, even if the kinds of the mixed raw material powders are changed, it is not possible to have a continuous composition gradient, and it cannot be said that it is sufficient to deal with diversified engineering ceramic materials. ..

The present invention has been made in order to solve such a problem. For example, a functionally graded ceramic composite material can be manufactured at low cost and with high reliability. It is an object of the present invention to provide a method for producing a ceramics composite material that enables the production of various forms of ceramics composite material.

[0009]

The first method for producing a ceramic composite material according to the present invention comprises the steps of producing a ceramic composite material containing two or more ceramic compositions having different compositions. Applying the slip cast molding method and making the above two or more ceramic compositions sludge using the same or different dispersion mediums respectively, and at the same time injecting these two or more sludge into the slip casting mold. Is characterized by.

The second method for producing a ceramics composite material comprises applying an injection molding method to the production of the ceramics composite material in producing a ceramics composite material containing two or more ceramic compositions having different compositions. Further, it is characterized in that the two or more kinds of ceramic compositions are kneaded using the same or different solvents, and these two or more kinds of kneaded products are sequentially filled in an injection molding die.

Further, in the third method for producing a ceramic composite material, in producing a ceramic composite material containing two or more ceramic compositions having different compositions, an injection molding method is applied to the production of the ceramic composite material. In addition, the two or more ceramic compositions are kneaded using the same or different solvents, and the two or more kneaded products are simultaneously filled into the injection mold through different filling ports.

Furthermore, in the above-mentioned method for producing a ceramic composite material, the dispersion medium or the solvent is selected so that the wettability to the two or more ceramic compositions is similar to each other, and the infiltration layer or the filling layer is filled. It is characterized in that the two or more kinds of ceramic compositions are present between layers so as to have a concentration gradient. Alternatively, in the method for producing a ceramic composite material described above,
Characterized in that the dispersion medium or the solvent is selected so as to have different wettability with respect to two or more ceramic compositions, and the two or more ceramic compositions are substantially separated between the inking layer or the filling layer. There is.

[0013]

In the method for producing the ceramic composite material of the present invention, the slip cast molding method or the injection molding method using the ceramic slurry or the kneaded material is applied, and
Two or more types of ceramic compositions to be composited are individually made into sludge or kneaded matter, and the ceramic sludge is inked sequentially or simultaneously, or because the ceramic kneaded matter is injected and filled, the dispersion medium or solvent Depending on the type, for example, each ceramic composition powder diffuses between the inking layer and the injection filling layer. As a result, each powder exists so as to have a concentration gradient, and its mixing ratio can be continuously changed. Further, depending on the type of the dispersion medium or the solvent, it is also possible to substantially separate the inking layers or the injection filling layers.

[0014]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing a manufacturing process of a ceramic composite material to which a slip casting method, which is one manufacturing method of the present invention, is applied. In this example,
First, to a ceramic composition having different compositions to be composited, for example, two types of ceramic compositions, individually add a dispersion medium and, if necessary, a binder, a dispersant, etc., and mix them thoroughly to obtain a ceramic slurry. To make.

Here, the ceramic composition used is not limited at all, and various ceramic compositions (including those containing a sintering aid component) can be used as long as they have different compositions. .. For example, a combination of silicon nitride, which is a high-strength material, and silicon carbide, which has excellent wear resistance, or zirconium oxide, which is a high-toughness material, a combination of silicon carbide and aluminum oxide, etc., depending on required characteristics. Various combinations can be selected. In addition, the types of ceramics are not limited to different types,
It is also possible to apply ceramics of the same kind having different compositions, specifically, sialon having different compositions.
Furthermore, the number of ceramic compositions to be composited is not limited to two, and it may be set according to the characteristics required for the ceramic composite material.

The dispersion media used for producing the two types of ceramic sludge may be the same or different, but depending on the mixing form of the ceramic composite material to be obtained, they are used for producing the respective ceramic sludge. The wettability of the dispersion medium with respect to the other ceramic composition is controlled. Thereby, the mixed state of the two types of ceramic compositions can be variously changed. For example, in the case of producing a ceramic slurry X prepared by slurrying the ceramic composition A with the dispersion medium a and a ceramic slurry Y prepared by slurrying the ceramic composition B with the dispersion medium b, wetting of the ceramic composition A and the dispersion medium b is performed. And ceramic composition B
By controlling the wettability of the dispersion medium a, various mixed states can be obtained.

Specifically, the combinations shown in Table 1 below can be considered. It shows in Table 1 including the mixed state according to each combination.

[0019]

[Table 1] Each wettability as shown in Table 1 may be selected according to the characteristics required of the ceramic composite material. For example,
When a functionally graded material having a gentle composition gradient is prepared, as shown in Type 1 of Table 1, each dispersion medium is made to have similar wettability to two types of ceramic compositions A and B. Select a and b. When different dispersion media are used at this time, a combination is selected so that the dispersion media show compatibility with each other. On the contrary, by selecting dispersion media a and b having different wettability with respect to the two types of ceramic compositions A and B and different surface tensions (for example, type 3 in Table 1), substantially separated ceramic composites are obtained. The material is obtained.

In order to produce a ceramic composite material by the slip casting method using the above-mentioned two types of ceramic sludge X and Y, as shown in FIG. It is poured into the liquid slip casting mold 1. Then, it is left for a predetermined time, and when the predetermined thickness is reached, the ceramic slurry X is discharged. As a result, as shown in FIG. 1B, the first inking layer 2 made of the ceramic composition A is obtained.

Next, while the first inking layer 2 is not dried, the other ceramic slurry Y as shown in FIG.
Is injected into the mold 1 so as to be in contact with the first inking layer 2. The injected ceramic sludge Y is absorbed by the first inking layer 2 to be infiltrated, and at this time, the two ceramic compositions A and B are dispersed so that they have similar wettability. If the media a and b (Type 1 in Table 1) are used, each ceramic composition powder diffuses at the interface of each inking layer, resulting in a composition gradient as shown in FIG. 2, for example.

Then, when the predetermined thickness is reached, the ceramic slurry Y is discharged. As a result, FIG. 1 (d)
As shown in FIG. 2, a second inking layer 3 of the ceramic composition B is obtained, and the ceramic compositions A and B are formed between the first and second inking layers 2 and 3, respectively. Exists so as to have a concentration gradient. As shown in FIG. 2, this portion can be one in which the amounts of the respective ceramic compositions A and B are changed gradually and continuously. The gradient of these mixing ratios can be variously controlled by changing the wettability of the dispersion medium with respect to the ceramic composition, and for example, a steep gradient can be provided.

In addition, in the above-mentioned production example, if the dispersion media a and b (Type 3 in Table 1) having different wettability with respect to the two types of ceramic compositions A and B are used, each infiltration layer is substantially formed. It is possible to obtain a ceramic composite material that is mechanically separated. Further, even in such a case, since the molding is performed by a wet method, the layers are not completely separated from each other unlike dry molding (for example, powder press molding).
Therefore, it is possible to suppress the occurrence of interlayer cracks even after drying.

In the above embodiment, an example in which a general sludge casting molding method is applied has been described, but the present invention is not limited to this, and for example, a pressure casting molding method can be applied. Is. When this pressure casting method is applied, a ceramic composite material similar to that of the above-mentioned embodiment can be obtained by sequentially changing the mold or the casting port as in the injection molding method described later. Further, the state between the respective ceramic layers can also have various forms.

When the pressure casting method is applied, it is preferable to release the obtained ceramic molded body by a method as described below. First, the pressure casting molding method will be described. As a mold structure for performing the pressure casting molding, for example, as shown in FIG. 3, a mold 11 having a divisible liquid absorption property,
12, for example, a structure in which a plaster mold or a porous resin mold is held by splittable backup dies 13 and 14 made of steel, for example, is used. A gas introduction path 15 for introducing a pressurized gas at the time of mold release is provided from the backup molds 13, 14 toward the liquid-absorbent molds 11, 12, respectively. Reference numeral 16 in the drawing denotes a cavity formed by the liquid-absorbent molds 11 and 12, and a slurry introduction path 17 connected to this cavity 16 is provided through the inside of the backup mold 14. Inside the cavity 16, a sludge introduction path 17
A ceramic compact is manufactured by pressure-casting a ceramic slurry from.

When a ceramic mold is pressure-cast using a mold having the above-mentioned structure and the ceramic mold is released from the liquid-absorbent molds 11 and 12, a molecular weight of air is used as a releasing gas. It is preferable to use a gas having a small value such as helium or hydrogen. This is because the release gas is ejected toward the ceramic molded body through the pores of the liquid-absorbent molds 11 and 12, so that the gas having a smaller molecular weight increases the effective volume passing through the liquid-absorbent molds 11 and 12. Therefore, the releasability can be improved. Air is generally used.

Further, the ceramic slurry used in the pressure casting method is preferably prepared using a dispersion medium having low wettability with the liquid-absorbent molds 11 and 12. This makes it possible to release the mold more easily. Also,
If a dispersion medium that has lower wettability to the mold than water is used, water can be ejected together with the mold release gas to form a water film between the ceramic compact and the mold, which further improves mold release properties. Can be planned.

In the case of using the pressure casting method of casting by applying a high pressure, it is possible to stably obtain a sound ceramic molded body by enhancing the releasability by the above-mentioned method. .. When a slurry using general water or air as a releasing gas is used, there is a high possibility that cracks will occur in the ceramic molded body at the time of releasing, and the yield may be lowered.

Next, a specific example of the method for producing the above ceramic composite material will be described.

Example 1 A production example of a composite material using alumina and silicon carbide will be described. Both alumina and silicon carbide can be satisfactorily dispersed in pure water, so that they were dispersed in separate pure water to prepare alumina slurry and silicon carbide slurry. In addition, as the raw material powder, a prepared powder in which a sintering aid component was mixed as needed was used.

Next, as shown in FIG. 1, first, alumina slurry was poured into the mold 1, and when the predetermined thickness was reached, the alumina slurry was discharged. Then, silicon carbide slurry was injected onto the alumina layer 2 and when the predetermined thickness was reached, the silicon carbide slurry was discharged. The ceramic composite molded body thus obtained had a single layer of alumina on the outer side and a single layer of silicon carbide on the inner side, and both materials existed so as to have a concentration gradient between these layers.

After drying the ceramic composite compact, it was fired at 1900 ° C. in an Ar atmosphere to produce an alumina-silicon carbide composite sintered body. When the appearance and the inside of the alumina-silicon carbide composite sintered body thus obtained were inspected, it was confirmed that no cracks or cracks were generated and that the composite sintered body was sound.

Next, a method of manufacturing a ceramic composite material to which an injection molding method which is another manufacturing method of the present invention is applied will be described with reference to FIG.

Also in this example, first, for a ceramic composition having a different composition to be composited, for example, two kinds of ceramic compositions, a thermoplastic resin, a solvent, a plasticizer, a lubricant, if necessary, and Add agents,
Sufficiently kneaded to prepare ceramics kneaded products for injection molding.

The solvent used for preparing the two kinds of ceramics kneaded materials may be the same or different, but as with the slip casting method described above, the other solvent used for preparing the respective ceramics kneaded materials is the same. The respective solvents are selected in consideration of the wettability with respect to the ceramic composition. As a result, the mixed state of the two types of ceramic compositions can be variously changed, as in the above-mentioned embodiment.

As shown in FIG. 4 (a), a ceramic composite material is produced by an injection molding method using such two types of injection-molded ceramics kneaded materials x and y.
First, one of the ceramics kneaded materials x is molded using a separable injection molding mold 22 (combination of an upper mold 22a and a lower mold 22b) in which a cavity 21 is formed according to the shape of the first ceramics layer. 22 is injection filled. Next, as shown in FIG. 4B, only the upper mold 21a is removed. At this stage, the first injection filling layer 23 of the ceramic composition A is obtained.

Next, before the first injection filling layer 23 has dried, as shown in FIG. 4C, the second upper mold 2 having the cavity 24 corresponding to the shape of the second ceramics layer is formed.
2c is a lower mold 22b on which the first injection filling layer 23 is formed.
Combine with. Thereafter, as shown in FIG. 4D, the other ceramic kneaded material y is injection-filled to form a second injection-filled layer 25 of the ceramic composition B.

At this time, if a solvent having similar wettability to the two types of ceramic compositions A and B is used, each ceramic composition powder diffuses at the interface of each injection filling layer, and A portion where the compositions A and B exist so as to have a concentration gradient is formed. The gradient of these mixing ratios can be variously controlled by changing the wettability of the solvent with respect to the ceramic composition, and for example, a steep gradient can be provided. In addition, in the above-described production example, by using a solvent having different wettability with respect to the two types of ceramic compositions A and B, it is possible to obtain a ceramic composite material in which each injection filling layer is substantially separated.

The injection mold used is as follows:
For example, as shown in FIG. 5, it is possible to use injection molding dies 27 provided according to the number of ceramic compositions in which the injection filling port 26 is composited. Even when such a mold is used, various forms of ceramic composite materials can be produced as in the above-mentioned embodiment.

Next, a specific example of the method for producing the above ceramic composite material will be described.

Example 2 As in Example 1, prepared powders of alumina and silicon carbide were used, and a thermoplastic resin and a solvent (both of which were kerosene) were added to them, and they were sufficiently kneaded and then kneaded with alumina. A material and a silicon carbide kneaded material were produced. In addition,
The wettability of alumina and silicon carbide with respect to the solvent is almost the same.

Next, as shown in FIG. 4, the first upper mold 2
First, an alumina kneaded material was injection-filled in an injection molding die 22 in which 2a and a lower die 22b were combined. Then the first
After removing the upper mold 21a and attaching the second upper mold 22c, a silicon carbide kneaded material was injected and filled.

Using the ceramic composite molded body thus obtained, as shown in FIG. 6A, a first injection filling layer 23 made of alumina and a second injection filling layer 25 made of silicon carbide were formed. The composition analysis and the coefficient of thermal expansion in the vicinity of the interface were measured. The result is shown in FIG. As is clear from FIG. 6B, the silicon carbide is distributed from the second injection filling layer 25 toward the first injection filling layer 23 so that the ratio thereof gradually decreases. The coefficient of thermal expansion is rising. Thus, one of the ceramic composite molded bodies was a single layer of alumina and the other was a single layer of silicon carbide, and both materials existed with a concentration gradient between these layers.

After drying the ceramic composite compact, it was fired at 1900 ° C. in an Ar atmosphere to produce an alumina-silicon carbide composite sintered body. When the appearance and the inside of the alumina-silicon carbide composite sintered body thus obtained were inspected, no cracks or cracks were found and it was confirmed that the sintered body was sound.

Example 3 To a mixed powder of alumina and silicon carbide, kerosene was added to alumina, trichloroethane was added to silicon carbide as a solvent, respectively, and a thermoplastic resin was added, and each was sufficiently kneaded. Then, an alumina kneaded material and a silicon carbide kneaded material were produced. The wetting of the solvent and the surface tension are completely different.

Next, as shown in FIG. 5, the above-mentioned alumina kneaded product and silicon carbide kneaded product were simultaneously injection-filled from each injection filling port using an injection molding die having two injection filling ports. In the ceramic composite molded body thus obtained, the alumina layer and the silicon carbide layer were substantially separated.

After the above ceramic composite compact was dried, it was fired at 1900 ° C. in an Ar atmosphere to produce an alumina-silicon carbide composite sintered body. When the appearance and the inside of the alumina-silicon carbide composite sintered body thus obtained were inspected, no cracks or cracks were found and it was confirmed that the sintered body was sound.

[0048]

As described above, according to the method for producing a ceramic composite material of the present invention, slip casting or injection is performed by using a mixture or a kneaded product of the ceramic composition to be composited. Since the filling is performed, for example, each material powder can be diffused between each ceramic layer, and thus a functionally graded ceramic composite material can be manufactured at low cost and with high reliability. Further, depending on the type of dispersion medium or solvent used to prepare the slurry, the ceramic layers can be substantially separated, and a healthy ceramic composite material can be obtained at this time as well. It is possible to manufacture the material well.

[Brief description of drawings]

FIG. 1 is a sectional view schematically showing a manufacturing process of a ceramic composite material according to an embodiment of the present invention.

FIG. 2 is a diagram showing an example of a mixed state of ceramic composite materials obtained in the manufacturing process shown in FIG.

FIG. 3 is a cross-sectional view showing a modified example of a slip casting mold.

FIG. 4 is a sectional view schematically showing a manufacturing process of a ceramic composite material according to another embodiment of the present invention.

FIG. 5 is a view showing another example of the injection molding die used in the examples of the present invention.

6 is a diagram showing an example of a mixed state and a coefficient of thermal expansion of the ceramic composite material obtained in the manufacturing process shown in FIG.

FIG. 7 is a diagram for explaining a conventional method for manufacturing a ceramic composite material.

[Explanation of symbols]

 1 ………… Slip casting mold 2 ………… First inking layer 3 ………… Second inking layer 22 …… Injection molding die 22a ... First upper die 22b ... Lower die 22c ... Second Upper mold 23 ... first injection packing layer 25 ... second injection packing layer

Claims (6)

[Claims] 1. When manufacturing a ceramic composite material containing two or more ceramic compositions having different compositions, a slip cast molding method is applied to the manufacture of the ceramic composite material, and the two or more ceramic compositions are A method for producing a ceramic composite material, which comprises using the same or different dispersion media to form sludge, and at least two kinds of these sludge are sequentially inked in a slip casting mold. 2. The method for producing a ceramic composite material according to claim 1, wherein each of the dispersion media is selected so that the wettability with respect to the two or more types of ceramic compositions is similar to each other, and A method for producing a ceramics composite material, which comprises allowing one or more kinds of ceramics compositions to exist with a concentration gradient. 3. In producing a ceramic composite material containing two or more ceramic compositions having different compositions, an injection molding method is applied to the production of the ceramic composite material, and the two or more ceramic compositions are the same. Alternatively, a method for producing a ceramic composite material is characterized in that the two or more kinds of the kneaded materials are kneaded by using different solvents and are sequentially filled in an injection molding die. 4. In producing a ceramic composite material containing two or more ceramic compositions having different compositions, an injection molding method is applied to the production of the ceramic composite material, and the two or more ceramic compositions are the same. Alternatively, a method for producing a ceramic composite material is characterized by kneading using different solvents and simultaneously filling two or more kinds of the kneaded materials into different injection molding molds through different filling ports. 5. The method for manufacturing a ceramic composite material according to claim 3, wherein the solvents are selected so that the wettability with respect to the two or more ceramic compositions is similar, and the filling layers are filled with each other. A method for producing a ceramics composite material, which comprises allowing two or more ceramics compositions to exist with a concentration gradient. 6. The method for producing a ceramic composite material according to claim 3 or 4, wherein the solvents are selected so that the wettability with respect to the two or more ceramic compositions is different, and the solvent is selected between the filling layers. A method for producing a ceramic composite material, which comprises substantially separating two or more ceramic compositions.