JPH1143373A - Production of composite material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a composite material contrived in the improvement of mechanical and dynamic strengths, thermal characteristics, electric characteristics, chemical characteristics and optical characteristics by granulating a mixture comprising the first phase particles comprising a material for matrix, a sintering auxiliary and/or the second phase particles, calcining the obtained granules, and mixing the obtained porous calcined particles with the second phase particles. SOLUTION: This method for producing a composite material comprises granulating a mixture comprising the first phase particles comprising a matrix material such as silicon nitride, silicon nitride, titanium carbide, alumina, zirconia or mullite, a sintering auxiliary such as Y2 O3 , YN, Yb2 O3 , Eu2 O3 , La2 O3 , Nd2 O3 , CeO2 , Ey2 O3 , Sm2 O3 or Sc2 O3 , and the second phase particles such as silica, oxidized zirconia, molybdenum disilicide, titanium boride or diamond, calcining the obtained particles to obtain the porous calcination particles which have a particle diameter of 0.1-2,000 μm and in which a part of the first phase particles are sintered, and subsequently mixing the obtained porous particles with 3-70 vol.% preferably 3-70 vol.%, of the second particles having a particle diameter of 0.01-500 μm.

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 formed by combining a plurality of types of materials.

[0002]

2. Description of the Related Art By combining two or more different materials, properties that cannot be fully exhibited by a single material, such as abrasion resistance, oxidation resistance, corrosion resistance, heat resistance, superplastic deformation, electricity and heat A material having excellent properties such as conductivity and mechanical strength can be manufactured. In addition, properties that cannot be exhibited by a single material alone, such as magnetism, self-lubricating properties, optical properties, piezoelectricity, thermoelectric properties, insulating properties, thermal conductivity, heat insulating properties, dielectric properties, expandability, free-cutting properties, catalysts, Materials with new functions such as a filter function and electric conductivity can be manufactured. In order to realize desired characteristics, composite materials combining various materials are being studied.

[0003] In particular, in a composite material in which second-phase particles made of a different material are dispersed in a matrix serving as a base material in a three-dimensional network, the matrix side has mechanical strength, and the dispersed second-phase particles are of various types. Because it bears the characteristics, it is possible to design a wide range of materials with characteristics that cannot be obtained with a single material.

Heretofore, as such a composite material, there has been proposed a ceramic sintered body in which second phase particles made of a different material are dispersed in a continuous or discontinuous three-dimensional network form in a matrix material. (JP-A-63-968)
No. 83, JP-A-5-332241, JP-A-3-122
066, JP-A-4-37667, JP-B-4-618
No. 32). In the ceramic sintered body, the second phase particles are continuously distributed in the matrix. For this reason, the characteristics of the second phase particles can be more strongly developed as compared with the case where the second phase particles are uniformly dispersed in the matrix.

Examples of such a ceramic sintered body include, for example, JP-A-63-96883 and JP-A-5-3.
As a composite material disclosed in Japanese Patent Publication No. 32241 and Japanese Patent Publication No. 4-61832, there can be mentioned a sintered body for a ceramic heater which generates heat when energized. Here, the ceramic sintered body has been manufactured by mixing insulating ceramic raw material particles composed of coarse particles and conductive powder composed of fine particles, and molding and sintering the resulting mixture.

According to this manufacturing method, the conductive powder adheres so as to surround the surface of the insulating ceramic raw material particles having a larger particle diameter during the manufacturing process. Then, both are sintered while this state is maintained. Therefore, according to this manufacturing method, it is possible to obtain a ceramic sintered body in which the second phase particles are continuously dispersed in a three-dimensional network with respect to the matrix.

For example, MoSi _2, which is a conductive powder, has a low strength and is easily decomposed at a high temperature of 1000 ° C. or higher. Therefore, a ceramic sintered body composed of only this material has the same properties.
If a material that complements the low strength of MoSi ₂ and easily decomposes at medium to high temperatures is selected (for example, silicon nitride), and a sintered body made of a composite material is produced using both materials, Since the matrix compensates for the disadvantage of MoSi ₂ , a ceramic sintered body having high strength and stable at high temperatures can be obtained.

[0008]

However, the ceramic sintered body obtained by the above manufacturing method has the following problems. That is, as shown in FIG. 2, the ceramic sintered body 9 manufactured by the above-described manufacturing method has a continuous three-dimensional network 902 in which the second phase particles are formed in the matrix 90. The width of the network 902 is not uniform. Further, a cut portion 99 is partially formed. Note that reference numeral 901 in the figure denotes crystal grains forming a matrix.

In such a ceramic sintered body 9, there is a possibility that the characteristics of the second phase particles may not be sufficiently exhibited. This is because, when the continuous three-dimensional network 902 is cut, the characteristics that have been developed due to the continuous dispersion of the second phase particles are hardly developed, or the characteristics are unevenly generated. It is.

For example, in the above-described ceramic sintered body that can be used as a ceramic heater, a continuous three-dimensional network of conductive second-phase particles serves as a conductive path, and generates heat when a current flows therethrough. If the three-dimensional network is partially cut, abnormal heat generation occurs here because the cut portion has high resistance. As a result, softening and melting of the second phase particles occur,
There is a possibility that the cut portion of the continuous three-dimensional network is further enlarged, which causes a further increase in resistance. In such a ceramic sintered body, the electric resistance value may increase with time, and the heat generation temperature may increase with time.

As one method of solving this problem, the width of the continuous three-dimensional network can be made large and surely formed by increasing the amount of the second phase particles added and mixed when producing the ceramic sintered body. It would be possible to do so. However, in such a case, the sinterability is greatly reduced, and in some cases, sintering becomes impossible.

Further, since the width of the second phase particles dispersed in a continuous three-dimensional network state increases along the grain boundary phase of the matrix crystal, the strength, impact resistance, thermal shock resistance, Oxidation resistance and corrosion resistance may be significantly reduced. Further, closed pores serving as fracture starting points when a stress is applied are likely to be formed, and there is a possibility that mechanical strength is reduced. That is, the mechanical and mechanical strength, thermal properties, chemical properties, electrical properties, and optical properties of the ceramic sintered body may be reduced. Further, it may be difficult to obtain a predetermined characteristic value.

By the way, the surface of an inorganic insulating material such as SiO2, alumina, zirconia or the like is coated with conductive particles, or the surface of a conductive particle such as a soft magnetic material is coated with insulating particles. Composite powders such as insulating powders and catalyst materials in which the surface of an inorganic material is coated with an active metal;
Alternatively, a compact thereof has been proposed. When preparing such a composite powder, it is necessary to increase the particle size ratio between the powder to be coated and the second phase particles as much as possible, but it may be difficult to obtain the required particle size ratio. Further, a method of granulating particles to obtain a predetermined particle size ratio is known, but there is a problem that the powder granulated in the coating step is easily broken.

In view of the above problems, the present invention makes it possible to easily combine two or more kinds of materials having a required particle size ratio, and to uniformly coat with the second phase particles. A three-dimensional network with a uniform and continuous width consisting of particles can be reliably formed with a small amount of addition, and the characteristics and mechanical and mechanical strength of the second phase particles, thermal characteristics, electrical characteristics, It is an object of the present invention to provide a method for producing a composite in which physical properties, chemical properties, and optical properties are at the same time.

[0015]

According to the first aspect of the present invention, a first phase particle composed of a matrix material, or a sintering aid, or further a second phase particle is added and granulated to form a granular material.
The granular material is calcined to form porous calcined particles in which part of the first phase particles of the matrix are sintered together, and the second phase particles are added to the calcined particles and mixed. And a method for producing a composite.

The term "granulation" according to the present invention means that only the first phase particles, or a mixture of the first phase particles and a sintering aid, or a mixture of the first phase particles and the second phase particles is used. This shows an operation for obtaining a granular material by agglomerating to a size of.

As the above granulation, granulation by crushing, spray granulation, stirring granulation, tumbling granulation, extrusion granulation, crushing granulation and the like can be employed. Further, general spray granulation includes a high-pressure nozzle method, a rotating disk method and the like. In addition, as a binder used for granulation, carboxymethyl cellulose (CMC), methyl cellulose, polyvinyl alcohol, polyvinyl acetate, polyacrylamide copolymer, or the like can be used.

FIGS. 3A to 3C show the state of the granules obtained by the granulation, that is, the state of the granulated powder 151. FIG.
In FIG. 2A, the first phase particles 101 are formed by physically or chemically aggregating (suspending) the other first phase particles 101 with the binder 141 or van der Waals force and joining them. The granulated powder 151 is shown. (B) of FIG.
The granulated powder 151 formed by bonding the first phase particles 101 to each other while being coated with the other first phase particles 101 and the binder 141 is shown. FIG. 3C shows the granulated powder 151 in the same state as in FIG. 3A, but the sintering aid 13 and the first phase particles 101 are partially joined.

Next, various ceramic materials can be used as the first phase particles. Also, a metal material can be used. The second phase particles include electrical conductivity, thermal conductivity, insulation, heat insulation, dielectric properties, magnetism, abrasion resistance, oxidation resistance, creep resistance, corrosion resistance, heat resistance,
Various materials capable of exhibiting characteristics such as self-lubricating properties, superplastic deformation properties, optical properties, piezoelectric properties, thermoelectric properties, expandability, and free-cutting properties can be used.

The combination of the first phase particles and the second phase particles includes one or more of silicide, nitride, carbide, boride, sulfide and oxide selected from a metal element and a rare earth element. Can be cited. When a material containing a metal element is used as the first phase particles for the matrix, one or more pure metals and alloys selected from the first to sixth periods of the periodic table and one or more of the above ceramic materials are used. Combinations can be mentioned.

Preferred examples are as follows (first phase particles)
-(Second phase particles). That is, silicon nitride-silicon carbide, silicon nitride-silicon nitride, silicon nitride-silica, silicon nitride-zirconia, silicon nitride-boron nitride,
Silicon nitride-titanium nitride, silicon nitride-titanium boride, silicon nitride-zirconia, silicon nitride-molybdenum disilicide, silicon nitride-yttria, silicon nitride-yttrium oxide, silicon nitride-ferrite magnet, silicon nitride-carbonized Titanium, silicon nitride-vanadium nitride, silicon carbide-alumina,
Silicon carbide-aluminum nitride, titanium carbide-silicon carbide, alumina-zirconia, alumina-zircon, alumina-silicon nitride, alumina-diamond, alumina-aluminum nitride, mullite-alumina, zirconia-calcium oxide, zirconia-yttria, zirconia-oxidation Magnesium, mullite-zirconia, sialon-silicon carbide, zirconia-alumina, glass-silicon carbide, glass-alumina, glass-carbon, borosilicate glass-alumina, lead zirconate titanate-silicon carbide, lead zirconate titanate-titanium Barium oxide, lead titanate-strontium titanate, cordierite-mullite, cordierite-quartz, cordierite-ferrite magnet, aluminum-silicon carbide, zirconia-nickel-chromium alloy, and the like. That.

It is preferable to use particles having a smaller particle size as the first phase particles. Thereby, the sinterability of the first phase particles is increased, and the shape retention of the calcined particles can be enhanced. Therefore, a highly dense sintered body in which a continuous three-dimensional network is developed can be reliably obtained. In addition, since the first phase particles are granulated into granules,
Even if the particle size ratio with the phase particles is small, there is no problem that it is difficult to form a three-dimensional network. Further, since the cohesive force of the calcined particles is very high, the calcined particles are hard to be broken even by a mixing method in which a strong force is applied such as a ball mill or an attritor or a high shear pressure is applied.

The “calcination” according to the present invention refers to FIG.
As shown in (a), a solid phase reaction is caused around a contact point 110 between the first phase particle 11 and another first phase particle 11 in the granular material (granulated powder) produced by the above granulation. Thus, the two particles are bonded to each other to form the calcined particles 152 having high cohesiveness.

Alternatively, as shown in FIGS. 4B and 4C,
The first with a sintering aid which is a material with good wettability and low melting point
This shows that the phase particles 11 are bonded to the other first phase particles 11 to form the calcined particles 152 having high cohesiveness. Then, as shown in FIG.
The sintering agent 142 is distributed around the contact point 110 of the phase particle 11 where the two are adhered, and as shown in FIG. In some cases, the first phase particles 11 are bonded to each other. It should be noted that the calcined particles 152 shown in the figure are schematic, and some actual calcined particles 152 are formed by assembling a large number of first phase particles 11 as shown in FIG. .

The particle size of the calcined particles is 0.1 to 20.
00 μm, the particle size of the second phase particles is 0.01 to 500 μm
m, and the value of (particle size of second phase particles) / (calcined particles) is 1
/ 3 or less. As a result, a three-dimensional network composed of the second phase particles develops, and the characteristics of the second phase particles can be sufficiently exhibited. Further, the addition ratio of the second phase particles to the whole particles is 3 to 70% by volume.
It is preferable that It is particularly preferable that the content be 5 to 50%.

The second phase particles may be in the form of particles,
Those having a whisker-like, fiber-like, plate-like or other form can be used. Alternatively, the second phase particles produced by adding and mixing a sintering aid to the raw material of the second phase particles, followed by drying, pulverization, and the like may be used.

As the sintering aid, rare earth oxides such as Y ₂ O ₃ , YN, Yb ₂ O ₃ , Eu ₂ O ₃ ,
La ₂ O ₃ , CeO ₂ , Nd ₂ O ₃ , Er ₂ O ₃ , Sm
₂ O ₃ , Sc ₂ O _{3 and the} like can be used.

Further, aluminum oxide, aluminum nitride, magnesium oxide, spinel, lithium oxide, silicon dioxide, boron oxide, TiN, BN, Mg ₃ N ₂ , Be ₃
N ₂ , MgSiN ₂ , aluminum, aluminum carbide, aluminum boride, chromium boride, zirconium boride, Be ₂ SiO ₄ , B ₄ C, boron carbide, beryllium oxide, spinel, zirconia, hafnia, ZrB ₂ , Cr
B ₂ , TiB ₂ , nickel, and also Mg, Al, Y, S
Compounds composed of one or a combination of oxides or nitrides of i, La, Ce, Be, and Zr or the like can be used. In addition, as the sintering aid, the first
It is preferable to use those having a smaller particle size than the phase particles. Thereby, the sinterability can be further improved.

The composite powder obtained by the present invention can be molded or compacted and used as a compact or compact (compact). In this case, as a forming method,
For example, mold molding, extrusion molding, compression molding, transfer molding, doctor blade, screen printing, cast molding, injection molding, dry / semi-dry pressing, single film molding, CIP,
Various molding methods such as pressure molding such as HP and HIP can be used. In particular, in the case of injection molding, it is preferable to simultaneously add and mix a binder for injection molding when mixing the calcined particles and the second phase particles. Further, the composite powder obtained by the present invention can be sintered and used as a sintered body. Furthermore, after performing the above-mentioned molding, sintering can also be performed. In the present invention, the composite powder, the compact, the compact, the sintered compact, the sintered compact after molding, etc. are all expressed as a composite.

The operation of the present invention will be described below. In the production method according to the present invention, the first phase particles are granulated, calcined to obtain predetermined calcined particles, and then mixed with the second phase particles.
Since the first phase particles are calcined after granulation, they become granules (granulated powder) of a predetermined size, and have cohesive strength (shape retention).
Will be higher. For this reason, the calcined particles can be mixed with the second phase particles without breaking in the mixing step while substantially maintaining their shapes and the like, and the crystal grains (crystal clusters) constituting the matrix of the composite Becomes

However, by adjusting the calcining temperature, the composite can be crushed when the composite is formed to produce a molded body. In this case, it is possible to enhance the press moldability and to reduce the injection pressure when using a press, CIP or the like as the molding.

Here, as shown in FIGS. 5A and 5B, there is a large difference in the particle size between the calcined particles 152 composed of the first particles 11 and the second phase particles 12, so that the second phase particles 12 are easily dispersed and adhered to the surface of the calcined particles 152. Further, since the calcined particles 152 are porous, by mixing the calcined particles 152 and the second phase particles 12, the second phase particles 12 can be easily inserted into each pore on the surface of the calcined particles 152. In some cases, and may be retained on the surface of the calcined particles 152.

FIG. 4A corresponds to FIG. 4A, and a part of the first phase particle 11 is bonded or sintered around the contact point between the first phase particle 11 and the other first phase particle 11. These are calcined particles formed by bonding. Alternatively, corresponding to FIG. 4B, the sintering aid is distributed around the contact point between the first particle 11 and the other first phase particle 11, where a part of both is bonded or bonded. Calcined particles. FIG. 5B shows that the sintering aid 142 melts and coats or bonds between the first phase particles 11 while covering the entire surface of the first phase particles 11 as shown in FIG. The calcined particles 152 are formed.

By further firing this, a sintered body (composite) in which the first phase particles are densely sintered is obtained. FIG. 1 shows the structure of the cell 1 of the three-dimensional network formed in the sintered body. A three-dimensional network 102 of uniform width composed of the second phase particles 12 is formed between the crystal grains (or crystal clusters) 10 of the first phase particles (grain boundaries). Therefore, it is possible to obtain the composite 1 in which the characteristics of the second phase particles 12 are sufficiently exhibited.

In the cell 1 of FIG. 1, a continuous three-dimensional network 102 composed of second phase particles and having a uniform width is formed on a matrix 10 composed of crystal grains 101.

As shown in FIG. 6, the first phase particles 91,
When the second phase particles 92, the sintering aid 93, and the like are manufactured from a uniformly mixed state, a continuous three-dimensional network 902 including the second phase particles 92 is hardly formed as shown in FIG. It was difficult to develop the characteristics of the second phase particles 92.

According to the present invention, a continuous cell structure in which the second phase particles surround the plurality of first phase crystal grains with a uniform width without particularly increasing the mixing amount of the second phase particles. Alternatively, since a discontinuous three-dimensional network can be formed, a decrease in mechanical and mechanical strength of the composite due to the addition of the second phase particles hardly occurs.

Further, when the first phase particles are granulated,
By adding the phase particles, the composite effect can be further enhanced, and the thermal stress due to the difference in thermal expansion coefficient between the first phase particles and the second phase particles can be reduced. Thereby, a composite having excellent durability can be obtained.

In the present invention, the second phase particles are added before granulation, and the grains constituting the matrix in the granules (granulated powder) are grown by calcination to form the composite. It becomes easy to form a network structure of the second phase particles in the cells of the formed continuous three-dimensional network. Therefore, the characteristics of the second phase particles are more easily exhibited.

For example, as shown in Embodiment 4 which will be described later, α-Si ₃ N ₄ particles (first particles constituting a matrix)
Phase particles), Y ₂ O ₃ , Al ₂ O ₃ (sintering aid) and Mo
In a method for producing a composite using Si ₂ (second phase particles), a granular material (granulated powder) obtained by granulation is heated to 1600 ° C.
Α-Si ₃ N ₄ is converted to β-Si ₃
It changes to N ₄ and grows large grains. For this reason, MoSi
An effect that _two particles rearrange easily to form a network structure can be obtained.

Further, after adding an appropriate amount of the second-phase particles to the first-phase particles, the first-phase particles are granulated, so that the second-phase particles adhered and sintered to the first-phase particles in a subsequent step. The effect that particles are less likely to peel can be obtained.

As described above, according to the present invention, it is possible to easily combine two or more kinds of materials having a required particle size ratio, and to uniformly coat with the second phase particles. A three-dimensional network with a uniform and continuous width consisting of phase particles can be reliably formed with a small amount of addition, and the characteristics of the second phase particles and the mechanical and mechanical strength, thermal properties, It is possible to provide a method for manufacturing a composite in which electrical characteristics, chemical characteristics, and optical characteristics are at the same time.

In the method for producing such a composite, the second phase particles may be, for example, a conductive material selected from borides, nitrides, carbides, silicides, carbides, oxides and composite compounds thereof. When a material having high conductivity is used, a composite having electrical conductivity can be obtained. Using this composite powder, a composite that is a ceramic sintered body that can be further subjected to electrical discharge machining can be produced.

In addition, carbides, nitrides, silicides, borides,
When a metal-based material having high thermal conductivity is used as the second phase particles, a composite having high electrical conductivity and high thermal conductivity can be obtained. By using such a composite, a material having high applicability as a substrate material, a heater, a thermistor, a thermoelectric material, or the like can be obtained.

Also, a metal such as iron or stainless steel is used as the first phase particles, and ZrO ₂ , Al
_From a composite obtained by using a material such as ₂ O ₃ or SiO ₂ as the second phase particles, a metal sintered body for soft magnetism having low thermal conductivity and low iron loss can be obtained.

In particular, when a metal material is used as the first phase particles, the calcined particles are liable to be superplastically deformed during molding of the composite obtained therefrom. Molding can be performed, and a green compact having a high green compact density can be obtained.

The composite prepared in the present invention can form a three-dimensional network formed by coarser crystal grains and finer second phase particles. For this reason, the whole is formed by coarse particles and fine particles.

Here, it is generally known that when the constituent particles such as ceramics are coarse, they are excellent in fracture toughness, high-temperature strength, creep resistance and thermal conductivity.
It is known that when the constituent particles are fine, they have excellent room temperature strength, fatigue resistance and impact resistance. Therefore, according to the present invention, fracture toughness, high temperature strength, creep resistance, room temperature strength,
A composite having fatigue resistance and impact resistance can be obtained. Further, a molded body and a sintered body produced by molding, sintering, and the like of the composite can have the above-described properties.

The sintered body produced by sintering the composite manufactured according to the present invention includes a heating material, a gas sensor, a varistor, a capacitor, a humidity sensor, a solid electrolyte, a thermistor, a thermoelectric element, a piezoelectric material, and a pyroelectric material. , High thermal conductive material, heat insulating material, high resistance material, glow plug, memory element material, magnetic material,
Soft magnetic materials, high and low dielectric materials, electric discharge machining materials, low expansion materials, high expansion materials, high heat resistance materials, heat dissipation materials, high strength materials, high toughness materials, wear resistant materials, corrosion resistant materials, oxidation resistant materials, optics It can be used for materials, vibration damping materials, electrode materials and the like. Also, the compacts and compacts manufactured from the composites manufactured according to the present invention include catalyst materials, magnetic materials, filter materials, heat insulating materials, electrode materials,
It can also be used as a heat conductive material.

[0050]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1 A method for producing a composite (composite powder) according to an embodiment of the present invention and the performance of a composite (sintered body) produced from the composite powder will be described using a sample and a comparative sample. The outline of the manufacturing method according to this example will be described. As shown in FIG. 3, first phase particles 11 made of a matrix material are granulated together with a sintering aid 13 to form granules 151. Next, the granular material 151 is pre-fired, and as shown in FIG.
A part of the first phase particles 11 of the matrix forms porous sintered particles 152 sintered together. Thereafter, as shown in FIG. 5, the second phase particles are added to the calcined particles 152 and mixed.
Obtain a composite powder.

Hereinafter, Sample 1 made from this composite powder was used.
The method for producing the composite (sintered body) 1 will be described in detail. First, the first phase particles made of a ceramic material for a matrix have a particle size of 0.5 μm (specific surface area: 4 to 9).
m ² / g) of Si ₃ N ₄ was prepared. 91% by weight of Si ₃ N ₄ as the first phase particles and Y ₂ O _{3 as} a sintering aid
Was weighed at 6% by weight and Al ₂ O ₃ at 3% by weight, and these were wet-mixed with a ball mill. Thus, a first mixed powder was obtained. The first mixed powder was granulated into particles having a maximum particle size of 300 μm to obtain granules. Thereafter, the granular material was calcined at 1600 ° C. to obtain porous calcined particles.

Next, SiC was prepared as the second phase particles. The particle size is 0.2 μm (specific surface area: 9 to 13 m ²⁾
/ G) of 81% by weight of Si ₃ N ₄ and Y _{2 as} a sintering aid.
O ₃ and 6 wt% and Al ₂ O ₃ 3% by weight, and then weighed SiC is the second phase particles to 10 wt%, was wet-mixed together in a ball mill. Thus, a second mixed powder was obtained. Next, the calcined particles and the second mixed powder were mixed for 50 minutes.
The weight percentages were weighed, and they were mixed in a ball mill using a nylon ball in a wet condition under conditions in which the calcined particles were not broken.
Thus, a composite powder according to this example was obtained.

Then, the above-mentioned composite powder is filled in a mold, and
Press with the pressing force of MPa, diameter 60mmφ, height 10m
m of a disk-shaped compact. Further, the above-mentioned molded body is 185
Under a nitrogen gas atmosphere at 0 ° C for 60 minutes, pressure 20MPa
Hot pressed. Thus, a composite (sintered body) according to this example was obtained. This is designated as Sample 1-1.

Next, the composite serving as Sample 1-2 produced from the composite powder according to this example will be described in detail. First, the calcined particles and the second mixed powder used when preparing the sample 1-1 are prepared. Next, the calcined particles and the second mixed powder were weighed at 50% by weight and mixed in the same manner as in Sample 1-1 to obtain a composite powder according to the present example.

The composite powder was weighed to 87% by weight, and the binder for injection molding was weighed to 13% by weight (the breakdown was 60% by volume of petrolatum and 40% by volume of polyethylene), and these were mixed and kneaded with a kneader. Then, it was pelletized with a kneader. The above pellets are processed by an injection molding machine to a diameter of 60 mm.
A disk-shaped injection molded body having a diameter of φ and a height of 10 mm was produced.

After holding the above-mentioned injection molded body at 300 ° C. for 2 hours (under a nitrogen gas atmosphere), it was degreased under the conditions of 500 ° C. (in the air) × 2 hours, and then dried under nitrogen gas atmosphere at 1850 ° C. for 6 hours.
Hot pressing was performed at a pressure of 20 MPa for 0 minutes. Thus, the composite according to this example was obtained. This is designated as Sample 1-2.

Next, the samples 1-1 and 1-2 were cut, respectively.
The cut surface is referred to as ECR (Electron-Cycle).
(ron-resonance) plasma etching. The fine structure of the cut surface was observed by SEM (scanning electron microscope). As a result, in each of the cut surfaces, fine Si ₃ N ₄ crystal grains and SiC particles are mixed around the cluster of coarse Si ₃ N ₄ crystal grains gathered in an island shape, and the width is reduced. , And it was confirmed that a uniform continuous phase was dispersed in a three-dimensional network.

Here, the comparative sample C1 will be described.
61% by weight of Si ₃ N ₄ having a particle size of 1.0 μm, 6% by weight of Y ₂ O ₃ , ₃ % by weight of Al ₂ O ₃ and 30% by weight of SiC having a particle size of 0.6 μm were weighed. The mixture was wet-mixed in a ball mill. At this point, the first phase particles 91,
The second phase particles 92 and the sintering aid 93 form a uniform mixing state as shown in FIG. Fill the mold with this material,
Pressing with a pressing force of 0MPa, diameter 60mmφ, height 10
mm disk-shaped molded body. Further, the molded body was pressed at 1850 ° C. for 60 minutes under a nitrogen gas atmosphere at a pressure of 20 MPa
Hot-pressed in a. Thus, a sintered body according to Comparative Sample C1 was obtained.

The comparative sample C1 was cut, and the cut surface was subjected to ECR plasma etching. The microstructure of this cut surface was observed by SEM. As a result, it was confirmed that SiC crystal grains were dispersed in a discontinuous three-dimensional network at the crystal grain boundaries of the Si ₃ N ₄ crystal grains.

Next, the operation and effect of this embodiment will be described. In this example, at least a part of the first phase particles 11 is aggregated as shown in FIG. 3 and calcined as shown in FIG. 4 to form porous calcined particles 152, and then the second particles as shown in FIG. The powder was mixed with the phase particles 12 to form a composite powder, which was further fired to obtain a sintered body. FIG. 1 shows a structure of a cell 1 of a three-dimensional network formed in the sintered body. Since the first phase particles 11 are calcined after granulation, they are in a granular state of a required size, and therefore have high shape retention. Therefore, the calcined particles 152 become crystal grains constituting the matrix of the sintered body without being broken in the respective mixing and forming steps, and while substantially maintaining the shape and the like.

Since the calcined particles 152 are porous, by mixing the calcined particles 152 and the second phase particles 12, the second phase particles 12 are formed in the respective pores on the surface of the calcined particles 152. 5 and held on the surface of the calcined particles 152, as shown in FIG. 5, and as shown in FIG. A three-dimensional network 102 is formed. Therefore, it is possible to obtain a composite in which the characteristics of the second phase particles are sufficiently exhibited.

According to the manufacturing method according to the present embodiment,
As in the case of the composite material disclosed in Japanese Patent Application Laid-Open No. 63-96883 as disclosed in the prior art, that is, a powder having a large particle size ratio between the first phase particles and the second phase particles serving as a matrix material is assembled. Unlike the method of manufacturing together, there is no need to use coarse particles, and a sintering aid is added to the calcined particles, so that even if the size of the calcined particles becomes large, dense sintering is possible. Is easy to obtain.

From this, the composite of this example can be sintered at a low temperature when it is formed into a sintered body by sintering, and can be manufactured from low production methods such as normal pressure sintering and gas pressure sintering. Can be used. Therefore, the production cost can be significantly reduced. In addition, since the calcined particles have high shape retention in a state where the particle size is large, a continuous three-dimensional network is formed even when a mixing method in which a large force is applied, such as a wet or dry ball mill, is applied. be able to.

Further, in producing a sintered body from the composite powder, even if kneading with a binder to which a large shearing force is applied and injection molding, a continuous three-dimensional network in the composite powder can be maintained. Thus, the method of the present embodiment facilitates the production of a complex (sintered body) having a complicated shape, and can greatly increase the productivity.

According to the present invention, a uniform three-dimensional network having a desired width can be formed without particularly increasing the mixing amount of the second phase particles. -There is no decrease in mechanical strength.

On the other hand, from the comparative sample C1, even if the first phase particles are granulated, it must be calcined to increase the shape retention (cohesion) during the subsequent manufacturing process (particularly during injection molding). It was found that the coarse-granulated particles were re-pulverized into fine particles, which hindered the formation of a three-dimensional network.

The second phase particles according to the present embodiment are structural functional materials capable of exhibiting excellent properties of oxidation resistance, creep resistance, and electrical and thermal conductivity. Ceramics produced by sintering this material alone have problems of low strength and low toughness.

However, as shown in this example, high strength, high toughness, high oxidation resistance, and creep resistance can be exhibited by dispersing in a matrix composed of the first phase particles so as to form a continuous three-dimensional network. At the same time, it is possible to obtain a composite in which a small amount of conductive material is added and electric conductivity can be exhibited. Further, according to the production method of the present example, desired thermal conductivity and electric resistance can be easily obtained by adjusting the mixing amount of the second phase particles.

Embodiment 2 In this embodiment, samples 2-1 and 2 of a composite (sintered body) made from a composite powder using MoSi ₂ as the second phase particles will be described together with a comparative sample C2. The second phase particles are substances that exhibit high electrical conductivity. The sintered body according to the present example has low strength of MoSi ₂ and easily decomposes in a high temperature atmosphere (800 ° C. or lower). The high strength and the stability at high temperatures can be obtained.

The composite of Sample 2-1 will be described. First, as the first phase particles made of a ceramic material for a matrix, a particle size of 0.2 μm (specific surface area: 9 to 13 m ² /
g) Si ₃ N ₄ was prepared. The first phase particles S
i ₃ N ₄ to 91 wt%, a Y ₂ O ₃ is a sintering aid was weighed 6 wt% and Al ₂ O ₃ 3% by weight was wet-mixed together in a ball mill. Thus, a first mixed powder was obtained.

The above-mentioned first mixed powder has a maximum particle size of 50 to 80 μm.
The particles were granulated into particles having a particle size of m to obtain a granular material. Thereafter, the granules were calcined at 1600 ° C. for 4 hours (in a nitrogen gas atmosphere) at normal pressure to obtain porous calcined particles. Next, 10% by volume of MoSi ₂ having a particle size of 1.0 μm as the second phase particles and 90% by volume of the calcined particles were weighed and mixed by a wet ball mill using nylon balls to obtain a composite powder. Was.

Next, as in the first embodiment, the above-described composite powder is filled in a mold, pressed with a pressing force of 20 MPa, and
It was a disk-shaped compact having a diameter of 0 mm and a height of 10 mm. Further, the compact was hot-pressed at a pressure of 20 MPa in an argon gas atmosphere at 1800 ° C. for 60 minutes. Thus, the composite according to Sample 2-1 was obtained.

Next, the complex of Sample 2-2 will be described. First, as the first phase particles made of a ceramic material for a matrix, the particle size is 0.2 μm, and the specific surface area is 9 to 13 m.
² / g of Si ₃ N ₄ was prepared. 91% by weight of Si ₃ N ₄ as the first phase particles and 6% of Y ₂ O ₃ as a sintering aid
% By weight and Al ₂ O ₃ were weighed to 3% by weight, and these were wet-mixed with a ball mill under the condition that the calcined particles were not broken. Thus, a first mixed powder was obtained.

The first mixed powder was granulated into particles having a maximum particle size of 50 to 80 μm by using a spray drier to obtain granules. Thereafter, the granules were calcined at 1600 ° C. for 4 hours (in a nitrogen gas atmosphere) at normal pressure to obtain porous calcined particles. Next, Mo having a particle diameter of 1.0 μm, which is a second phase particle, is used.
10% by weight of Si ₂ , 87% by weight of the calcined particles, and 13% by weight of a binder for injection molding were weighed and kneaded with a kneader to obtain a composite powder.

Thereafter, the kneaded composite powder was injection-molded in the same manner as in Embodiment 1 to produce a disk-shaped compact having a diameter of 60 mm and a height of 10 m. The compact was hot-pressed at a pressure of 20 MPa in an argon gas atmosphere at 1800 ° C. for 60 minutes. Thus, a composite according to Sample 2-2 was obtained.

Next, the samples 2-1 and 2-2 were cut, respectively.
The cut surface obtained in the same manner as in the first embodiment was subjected to ECR plasma etching. The microstructure of the cut surface was observed by SEM. As a result, on any of the cut surfaces, MoSi ₂ is present in a continuous three-dimensional network with a uniform width around a cluster of a plurality of Si ₃ N ₄ grains aggregated in an island shape. Was confirmed.

Here, the comparative sample C2-1 will be described. 61% by weight of Si ₃ N ₄ having a particle size of 10 μm and Y ₂ O
₃ at 6% by weight, Al ₂ O ₃ at 3% by weight, particle size 1.0 μm
Of MoSi ₂ was weighed to 30% by weight. These were wet ball mill mixed using nylon balls. This material was filled in a mold in the same manner as in Example 1, and pressed with a pressing force of 20 MPa to obtain a disk-shaped molded body having a diameter of 60 mm and a height of 10 mm. The above molded body was placed in a nitrogen gas atmosphere for 18 minutes.
Hot pressing was performed at 00 ° C. for 60 minutes at a pressure of 20 MPa. Thus, a sintered body according to Comparative Sample C2-1 was obtained.

The sintered body of the comparative sample C2-1 was cut.
The cut surface obtained in the same manner as in the first embodiment was subjected to ECR plasma etching. The microstructure of the cut surface was observed by SEM. As a result, in the grain boundary phase of the Si ₃ N ₄ crystal grains, a three-dimensional network but a non-uniform width (there are local discontinuities) is present, and MoSi ₂ is continuously dispersed. It was confirmed that. Due to this, the sintered body of Comparative Sample C2-1 had a large initial resistance value variation and was inferior in continuous current durability (resistance stability at high temperature).

Next, the comparative sample C2-2 will be described. Si ₃ N having a particle size of 0.2 μm and a specific surface area of 9 m ² / g
₄ 91 wt%, Y ₂ O ₃ and 6 wt%, Al ₂ O ₃ of 3
Weighed to weight%. The mixture powder obtained by wet mixing these with a ball mill is subjected to a maximum particle size of 50 to 50 using a spray dryer.
The granules were 80 μm. Next, MoSi was added to the granules.
₂ and a binder for injection molding were added, and these were kneaded with a kneader.

The obtained material was injection-molded in the same manner as in Example 1 to produce a disk-shaped molded body having a diameter of 60 mmφ and a height of about 10 mm. After degreasing the molded body, it was hot-pressed at 1800 ° C. for 60 minutes under a pressure of 20 MPa in an argon gas atmosphere. Thus, a sintered body according to Comparative Sample C2-2 was obtained.

The sintered body of the comparative sample C2-2 was cut,
The cut surface was subjected to ECR plasma etching similarly to the first embodiment. The microstructure of the cut surface was observed by SEM. As a result, it was confirmed that MoSi ₂ was randomly dispersed in the grain boundaries of the Si ₃ N ₄ crystal grains. As a result, the comparative sample C2-2 had an extremely high specific resistance and was inferior as a heating element.

Embodiment 3 In this embodiment, iron powder which is a metal material is used as the first phase particles of the matrix material, and zirconia (Z
A metallic composite (sintered body) using (rO ₂ ) will be described. The second phase particles are a substance exhibiting low thermal conductivity and electrical insulation. By forming the sintered body according to the present example, the disadvantages of ZrO _{2 such} as low toughness, low strength and non-magnetism can be compensated. Metals can be given excellent properties such as high heat insulation and soft magnetism with low iron loss.

First, iron powder having a particle diameter of 0.6 μm was prepared as first phase particles made of a metal material. The first phase particles were formed into granules having a maximum particle size of 80 μm using a spray dryer. The granules were calcined at 750 ° C. for 1 hour (in vacuum) to obtain porous calcined particles.

Next, 80% by volume of the above calcined particles and 20% by volume of a ZrO ₂ powder having a particle size of 0.2 m as the second phase particles were weighed, and these were dry-ball-mixed using zirconia balls. Thus, a composite powder was obtained in which the porous calcined particles were uniformly coated with ZrO ₂ particles.

The above composite powder was filled in a mold, and 7 t / cm
^By pressing with a pressing force of ^2, a disk-shaped molded body having a diameter of 10 mmφ and a height of 3 mm was obtained. The above-mentioned molded body is 1200
Calcination was performed at 4 ° C. for 4 hours. Thus, a metallic composite was obtained.

The composite was cut, and the fine structure of the cut surface was observed with a metallographic microscope. As a result, it was confirmed that a three-dimensional network structure in which ZrO ₂ was continuously dispersed with a uniform width was formed around an iron crystal cluster having a size of about 60 μm which was gathered in an island shape. Furthermore, according to the production method of this example, even when a high pressure is applied when molding the composite powder with a mold, the particle structure is not destroyed, and a higher density (relative density; %) Was obtained.

Embodiment 4 In this embodiment, the electrical resistance characteristics of a composite (sintered body) produced by the manufacturing method according to the present invention will be described in comparison with a sintered body according to the prior art. First, the first phase particles, α-
Si ₃ N ₄ (made by Ube Industries) and sintering aid Y ₂ O ₃
(Manufactured by Shin-Etsu Chemical Co., Ltd.) and granulated in the same manner as in Embodiment 1.
Granules (granulated powder) were obtained. This granular material has a particle size of 50 μm. The particles were calcined at a temperature of 1600 ° C. to produce calcined particles. Using a nylon ball, the calcined particles were weighed at 90% by weight of the calcined particles and 10% by weight of SiC as the second phase particles, and were ball-milled for about 1 hour in a wet system. Thus, a composite powder according to this example was obtained.

The above composite powder is uniaxially formed, and the temperature is 1850 ° C.
(In a nitrogen gas atmosphere), hot-pressed for 1 hour at 20 MPa. From the sintered body thus obtained, 2 × 2
A test piece of × 20 mm was cut out and used for the test. When the electric resistance value of this test piece was measured, it was 1.7 × 10 ³ Ω.
cm.

Next, as comparative examples, Si ₃ N ₄ as the first phase particles, SiC as the second phase particles, and Y ₂ O ₃ as the sintering aid used for preparing the above-described test piece were used. The mixture was wet-mixed using a nylon ball as it was, and the mixed powder was molded and hot pressed to prepare a test piece. The measured electrical resistance of the test piece was 5 × 10 ⁸ Ωcm.

From the above test, it was found that the composite according to this example was S
It was found that a continuous and uniform conductive path of iC was formed, and the electric resistance value was five orders of magnitude lower than the comparative test piece. That is, it was found that the sintered body according to the present example had a feature capable of strongly expressing the characteristics of the second phase particles.

As described above, according to the present invention, it is possible to easily combine two or more kinds of materials having a required particle size ratio, and to uniformly coat with the second phase particles. A three-dimensional network consisting of two-phase particles with a uniform and continuous width can be reliably formed with a small amount of addition, and the characteristics of the second-phase particles, mechanical and mechanical strength, and thermal characteristics It is possible to provide a method for producing a composite in which electrical characteristics, chemical characteristics, and optical characteristics are made parallel.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a cell structure of a three-dimensional network including second phase particles inside a sintered body constituting a composite according to the present invention.

FIG. 2 is an explanatory view of a three-dimensional network inside a sintered body according to a conventional example.

FIG. 3 is an explanatory view of a granular material obtained by granulation according to the present invention.

FIG. 4 is an explanatory diagram of calcined particles obtained by calcining according to the present invention.

FIG. 5 is an explanatory view of second phase particles mixed with calcined particles according to the present invention.

FIG. 6 is an explanatory view showing a state in which first phase particles, second phase particles, and a sintering aid are uniformly dispersed according to a conventional example.

[Explanation of symbols]

 1. . . Cell in sintered body, 10, 90. . . Matrix, 11, 91. . . First phase particles, 12, 92. . . Second phase particles, 13, 142, 93. . . Sintering aid, 151. . . Granules, 152. . . Calcined particles,

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI C22C 1/05 C04B 35/64 L

Claims (1)

[Claims] A first phase particle comprising a material for a matrix, or together with a sintering aid, or a second phase particle is further added, and granulated to form a granular material. ,
A method for producing a composite, characterized in that a part of the first phase particles of a matrix is converted into sintered porous calcined particles, and the second phase particles are added to the calcined particles and mixed.