JP3323046B2 - Manufacturing method of composite ceramic material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a composite material in which two or more crystal phases are formed from a ceramic solid solution, and more particularly to a high-strength, high-toughness ceramic in which precipitated crystal phases are finely and uniformly dispersed. The present invention relates to a method for producing a composite material.

[0002]

2. Description of the Related Art Ceramic materials have insulating properties, dielectric properties,
Has excellent properties such as heat resistance, strength, and toughness.
Widely used as functional and structural materials. Also,
In order to further improve the properties of the material, a composite of a plurality of ceramics, for example, a nanocomposite in which a dispersed phase of about several tens of nm is dispersed in a matrix has been studied.

[0003] One of the composite methods of such ceramics is as follows.
Finally, a so-called precipitation treatment method in which a ceramic solid solution is produced and two or more types of crystal phases are generated from this solid solution is known. Such a solid solution precipitation treatment method involves the refinement and uniform distribution of a dispersed phase. Has attracted attention as being particularly effective in the formation of tissue. For example, the precipitating different other crystal phases as a main crystal phase in a particular main crystalline phase by heat treating a ceramic solid solution under predetermined conditions, so-called solid solution precipitation treatment method, the MgAl ₂ O ₄ crystal Al ₂ O ₃ crystal phase precipitated and dispersed, NiFe ₂ O ₄
Crystal phase dispersed and dispersed, Al ₂ O ₃
iO ₂ crystal phase dispersed and dispersed, and SnO ₂ −
A TiO ₂ -based spinodal decomposition reaction and the like are known.

[0004]

However, when a composite ceramic material is produced by the solid solution precipitation method described above, especially when a ceramic composite having a diameter of 20 mm or less is produced. Although there is no problem, when producing a large-sized material having a size exceeding 20 mm, it is difficult to obtain a precipitated phase at the center of the material due to a difference in temperature distribution between the inside and outside of the material during the heat treatment. There is a problem that unevenness of the structure occurs, for example, the precipitation phase of the portion becomes coarse, and the expected material properties, for example, strength, fracture toughness or functional properties cannot be obtained.

[0005] In particular, in the precipitation process utilizing the fact that the amount of solid solution changes depending on the heating atmosphere, ion diffusion from the surface to the center or from the center to the surface of the sintered body accompanies. When the heat treatment becomes large, heat treatment for several tens of hours or more may be required to obtain a structure precipitated to the central part. However, there was a problem that the cost was high. By increasing the heat treatment temperature, precipitation can be promoted in some material systems, but the precipitation amount deviates from the precipitation conditions, or the precipitation phase grows coarsely and a fine precipitation structure cannot be obtained. There was a problem.

[0006]

Means for Solving the Problems The present inventor has conducted repeated studies based on the viewpoint that it is important to improve the uniformity of heating and the diffusion rate in order to efficiently obtain a uniform and fine precipitate structure. When the precipitation treatment is performed by a microwave heating method in which the material absorbs electromagnetic waves and generates heat, the uniform heating and the effect of promoting diffusion are exhibited. Even in a large sintered body of several tens mm or more, a uniform and fine precipitate phase is formed. I found what I could get.

That is, a method for producing a composite ceramic material according to the present invention is directed to a method for producing a composite ceramic material comprising a step of producing a ceramic solid solution and a step of depositing two or more crystal phases from the ceramic solid solution. Performing the precipitation step by heat treatment with microwaves, the average particle size is 1 μm or less,
In which the particle size ratio is characterized and this <br/> precipitating a crystal phase becomes 0.91 to 1.11.

Further, with respect to solid solution which changes the amount of solid solution by changing the heating atmosphere the precipitation treatment is performed by microwave heating deposition process in an atmosphere amount of solid solution decreases, immediately
In an atmosphere different from the process of preparing the ceramic solid solution
By performing the above-mentioned precipitation treatment, in addition to the above-mentioned structure uniformity and fineness effects, the treatment time can be significantly reduced, among which, as a ceramic solid solution, alumina as a main component and at least Ti, Mg, and at least one of Fe A solid solution containing one kind is used, and TiO ₂ , Al ₂ TiO ₅ , FeAl ₂ O ₄ , MgA
It is effective for precipitating at least one crystal phase of l ₂ O _{4. In} this case, the heat treatment temperature is preferably 1600 ° C. or less.

[0009]

The method for producing a composite ceramic material of the present invention comprises:
The use of microwave heat treatment to generate two or more crystal phases from a ceramic solid solution allows for uniform heating and enhanced ion diffusion compared to conventional treatment methods, so that even large-sized materials can be made finer and finer. A uniform precipitation structure can be formed.

[0010] In addition, among the solid solution precipitation treatment methods, when a compound having a different solid solution amount due to a different atmosphere is used, and the precipitation treatment is carried out by microwave heating in an atmosphere having a small solid solution amount, the fine particles as described above can be obtained. In addition to controlling the precipitation structure, the heat treatment time can be significantly reduced.

The method of the present invention, among other things as a main component alumina, Ti, Mg, by precipitation heat treatment to the ceramic solid solution containing at least one of Fe, alumina crystal phase or grain boundaries fine TiO _2, Al ₂ Ti
This is effective for a method of precipitating at least one crystal of O ₅ , FeAl ₂ O ₄ and MgAl ₂ O _{4. In} this case, it is necessary to perform a heat treatment for 30 hours or more in the conventional method, depending on the temperature. However, according to the microwave heating method, the heat deposition treatment can be performed in a short time of 10 hours or less.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention relates to a method for precipitating a ceramic solid solution. The `` ceramic solid solution '' here is a solid solution in which atoms or ions not included in the mother phase crystal have entered the crystal lattice of the mother phase composed of metal oxides, nitrides, carbides, and other inorganic compounds. Generally, it is composed of at least three or more elements. For example, a solid solution composed of three elements includes one metal element and one light element such as carbon, nitrogen, oxygen, and fluorine, and the other one may be a metal element or a light element. As a special case, a solid solution deviated from a stoichiometric composition by a metal compound composed of two elements and a metastable amorphous phase are also considered as a solid solution.

In the solid solution precipitation treatment method, any of a powder sintering method, a melting method, a vapor phase deposition method, a sputtering method and the like can be used to produce a ceramic solid solution. Also,
A solid solution treatment can also be performed by heating a ceramic material made of a metal compound. This heating solid solution treatment can be adopted by any known heating method, for example, a resistance heating method, a high frequency heating method, a microwave heating method and the like. The time can be greatly reduced, and it is particularly effective for solid solution treatment of a dense body. At the time of producing the solid solution, it is desirable to carry out the treatment under the condition that the amount of atoms or ions not included in the mother phase crystal in the mother phase is large.

In the present invention, as a method for forming at least two or more crystal phases from the above-mentioned ceramic solid solution, for example, a large amount of atoms or ions not contained in the parent phase crystal in the parent phase is large. The ceramic solid solution prepared by processing under the conditions described above is treated at a temperature or an atmospheric condition in which the amount of atoms or ions solid-dissolved in the mother phase in a chemical equilibrium state becomes small, whereby the solid-dissolved atoms or The ions can be activated and detached from the matrix crystal lattice. Such heat deposition requires segregation of atoms and ions by activation and diffusion of solid solution atoms or ions.

According to the present invention, the above-mentioned heat deposition treatment is performed by heating with microwaves. The microwave heating in the present invention is a method of self-heating by vibration of a crystal lattice or an element by the action of an electromagnetic wave of a microwave having a frequency of 1 GHz or more.

Normally, in the above-mentioned heat deposition treatment, when the size of the material becomes several tens of mm, a temperature distribution occurs in which the temperature decreases from the surface to the center of the material. A phenomenon in which the precipitated phase gradually increases over the surface portion may occur, and the uniformity and stability of the material properties may be impaired. In the present invention, when this heat deposition treatment is performed by microwave heating, the entire material uniformly absorbs electromagnetic waves and generates heat, so that the temperature difference between the surface portion and the center portion as described above is almost eliminated, and the uniformity is achieved. A high precipitation structure is obtained. Further, the vibration width of the crystal lattice becomes larger than that of other heating methods due to the action of the electromagnetic wave, so that the precipitation is promoted and the deposition time can be greatly reduced.

According to the present invention, a solid solution precipitation treatment method for producing two or more crystal phases from a ceramic solid solution utilizes a change in the amount of solid solution due to a difference in atmosphere, that is, a solid solution preparation process. In the case where the heat precipitation treatment is performed in an atmosphere in which the amount of solid solution is small after the heat precipitation treatment is performed in an atmosphere having a large amount, it is particularly effective to perform the heat precipitation treatment by the above-described microwave heating method.

The heat deposition treatment in the above-described method is premised on an oxidation or reduction reaction of a solid solution ion. Therefore,
In addition to short-range diffusion such as precipitation and segregation of solid solution ions, diffusion of oxygen ions from the surface to the center or from the center to the surface of the sintered body, and diffusion of cation vacancies accompanying the precipitation Occurs. For example, for the precipitation of Ti ions,
Oxygen ions diffuse from the center to the surface of the sintered body from the center to the center of the sintered body. In this case, in addition to the temperature distribution, the concentration difference between the oxygen ions and the cation vacancies is also a main cause of the non-uniform precipitated structure.

Therefore, in the above method, the size is 1
In order to obtain a precipitate structure up to the center of a sintered body of about 0 mm,
With a normal heating method, heat treatment for several tens of hours or more may be required. Moreover, coarse growth of the precipitated phase on the surface of the sintered body due to the long-term treatment is inevitable. On the other hand, when microwave heating is used for the precipitation treatment of the solid solution, as described above, in addition to the uniform heating of the sintered body, the vibration of the crystal lattice is promoted by the action of electromagnetic waves. Diffusion of dissolved ions, vacancies, and oxygen ions is remarkably accelerated, and a uniform precipitation process with no difference between inside and outside can be completed in a short time without causing a difference in structure between the central portion and the surface portion of the sintered body.

Further, according to the present invention, specifically, a ceramic solid solution containing alumina as a main component and containing at least one of Ti, Mg and Fe is heated in an atmosphere in which the amount of solid solution becomes small. The microwave heating treatment is performed at the time of deposition. The content of Ti, Mg, and Fe at this time may be appropriately adjusted in composition according to the purpose of use. However, in terms of the function as a composite material, these metal elements are 0.5 mol% or more in terms of oxide. It is desirable to be contained.

[0021] In this method, Ti to alumina, the case of manufacturing a ceramic solid solution containing at least one of Mg and Fe, in a hydrogen atmosphere at TiO ₂ addition system, MgO + TiO ₂ addition system or Fe ₂ O ₃ The additive system can be produced by heat treatment at 1200 to 1750 ° C. in the air. Thereafter, if the precipitating crystal phase from a solid solution thereof, in an air atmosphere in TiO ₂ addition system, MgO + TiO ₂ addition system or Fe
_{In the} 2O ₃ added system, heat treatment in hydrogen allows T
A crystal phase different from the alumina crystal phase due to the valence change of i, Mg, and Fe can be precipitated in the alumina crystal phase or at the grain boundary.

The crystal phase different from the alumina crystal phase in this case is TiO ₂ , Al ₂ TiO ₅ , FeAl ₂ O
_And at least one of MgAl ₂ O ₄ .

These precipitated crystal phases can be formed into fine precipitate phases of 1 μm or less by performing the heat precipitation treatment by the above-mentioned microwave heating treatment. Further, in the heat deposition treatment, it is desirable to set the heating temperature to 1600 ° C. or less.

This is because there are two processes in the heating precipitation process, namely, nucleation and growth of the precipitated phase. When the ceramic solid solution having the above composition is treated by microwave heating at a temperature higher than 1600 ° C., This is because grain growth becomes remarkably fast, and it is difficult to obtain a nano-sized fine precipitation structure. In order to obtain a sufficient precipitation rate and a fine precipitate structure, the precipitation temperature is particularly preferably in the range of 1000 ° C to 1500 ° C.

[0025]

EXAMPLE An alumina (Al ₂ O ₃ ) powder, a magnesium oxide (MgO) powder, a titanium oxide (TiO ₂ ) powder, and an iron oxide (Fe ₂ O ₃ ) powder were prepared so as to have the composition shown in Table 1. did. After press-molding the mixed powder at a pressure of 1 t / cm ² , a hydrostatic pressure treatment was applied at a pressure of 3 t / cm ² . The size of the compact is shown in Table 1. The compact was fired by resistance heating under the conditions shown in Table 1. X-ray diffraction measurement revealed that a single-phase solid solution shown in Table 1 was formed.

Next, the solid solution was subjected to heat precipitation under the conditions shown in Table 2. Table 2 shows the crystal phases other than the parent phase among the precipitated phases detected by the X-ray diffraction measurement. The average particle size of the precipitated phase measured by SEM photograph is shown in Table 2 in comparison with the central part and the surface part (at a depth of 1 mm from the surface) of the sample.

[0027]

[Table 1]

[0028]

[Table 2]

From the results shown in Tables 1 and 2, it was found that Sample N which had been subjected to heat deposition treatment by microwave heating according to the present invention was used.
o. In all of 2, 5, 6, 7, 9, and 10, the average particle size ratio of the precipitated phase between the sample center portion and the surface portion was 0.91 to 1.11.
It can be seen that the average particle size is 1 μm or less. However, the sample N obtained by the conventional heating method
o. 1, No. 3, No. In No. 4, the average particle size ratio of the inner and outer precipitation phases was 0.6 or less. In particular, the sample No. 3
No precipitate phase was detected at the center of the sample by X-ray diffraction measurement. In addition, even for the sample subjected to the microwave heat treatment, the sample No. whose processing temperature exceeds 1600 ° C. In No. 8, there was almost no difference between the inside and outside of the average particle size of the precipitated phase, but the precipitated phase tended to become coarse.

[0030]

As described in detail above, the method for producing a composite ceramic material according to the present invention comprises a conventional processing method in which two or more types of crystal phases are formed from a ceramic solid solution by microwave heating. Even if the material is larger in size, a composite material having a fine and uniform precipitate structure can be obtained, and in addition to controlling the precipitate structure, the processing time can be significantly reduced.

Claims (5)

(57) [Claims] 1. A method for producing a composite ceramic material, comprising: a step of producing a ceramic solid solution; and a step of depositing two or more crystal phases from the ceramic solid solution. The average particle size is 1 μm or less, and the inner flat
A method for producing a composite ceramic material, wherein a crystal phase having a uniform particle size ratio of 0.91 to 1.11 is precipitated . 2. The atmosphere in the precipitation step is an atmosphere in which the amount of solid solution is small , and the ceramic solid solution is
2. The method for manufacturing a composite ceramic material according to claim 1 , wherein the atmosphere is different from the atmosphere in the manufacturing step . Wherein the ceramic solid solution as a main component alumina, Ti, Mg, method of producing a composite ceramic material according to claim 1 or 2, wherein it contains at least one of Fe. 4. The composite ceramic material comprises an alumina crystal phase, TiO ₂ , Al ₂ TiO ₅ , FeAl ₂ O ₄ , Mg
_4. The method for producing a composite ceramic material according to claim 3, comprising at least one crystal phase of Al ₂ O ₄ . 5. The method for producing a composite ceramic material according to claim 3, wherein said depositing step is performed by a heat treatment at 1600 ° C. or lower.