JPH0437667A - Lightweight and high-rigidity ceramics and their uses - Google Patents

Abstract

PURPOSE:To provide the lightweight and high-rigidity (high specific elastic modulus) composite ceramic structural body which is not possible heretofore by forming three-dimensional open network structural bodies into a reaction sintered ceramic matrix having the porosity of a specific value or be low. CONSTITUTION:One or more kinds of the three-dimensional open network structural bodies, hollow particles and hollow fibers are formed in the reaction sintered ceramic matrix having <=40vol.% porosity (the mechanical strength degrades if the porosity exceeds 40%). For example, the carbonaceous three- dimensional open network structural bodies(a)formed by sintering are installed in a forming mold, and further, a slurry prepd. by mixing a deflocculating agent and distilled water with Si powder is poured into the mold to form a molding. This molding is stepwise subjected, after removal of moisture, to a heating treatment over a long period of time in gaseous nitrogen to obtain the ceramics of the structural body (a) sintered with Si3N4b. The structural body(a) is so oriented that the specific elastic modulus improves in one- dimensional direction, by which the rigidity to the driving direction of mechanism parts which repeat driving and stopping is improved.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a lightweight and highly rigid ceramic structure, and in particular, a three-dimensional continuous network structure, hollow particles, hollow This invention relates to lightweight, high-rigidity ceramics with a composite structure made of fibers and their uses.

[Conventional technology]

In general, nitrides and carbides have been developed as ceramics suitable for mechanical structural parts such as engines. Conventional ceramics are mainly composed of a single composition such as silicon nitride or silicon carbide, and have the disadvantage of low toughness. Recently, fiber-reinforced composite ceramics have been studied with the aim of improving toughness and strength. In addition, as a material with a high specific modulus,
Carbon composite materials have been developed in which carbon is treated with wax and reinforced with carbon fibers.

However, the above composite material is characterized in that its mechanical properties are improved by fiber orientation.

[Problem to be solved by the invention]

However, although the above-mentioned conventional technology improves the toughness of ceramics, no consideration is given to improving the specific modulus of elasticity.

An object of the present invention is to provide a composite ceramic structure that is unprecedented in weight and has high rigidity, that is, a high specific modulus of elasticity.

[Means to solve the problem]

As a result of intensive research aimed at improving the specific elastic modulus of ceramics, the present inventors have found that by configuring a three-dimensional continuous network structure, hollow particles, and hollow fibers in a reaction sintered ceramic matrix, the specific elastic modulus of ceramics can be improved. He invented something that could improve the rate.

The above object is achieved by forming at least one of a three-dimensional continuous network structure, hollow particles, and hollow fibers in a reactive sintered ceramic matrix having a porosity of 40 vol% or less.

An essential condition for the present invention is that the IJ sock be constructed using a reaction sintered ceramic bran. In the conventional pressureless sintering method and hot press method, which involve large shrinkage, the three-dimensional continuous network structure, hollow fibers, and hollow particles are destroyed during shrinkage, and tensile stress remains inside, resulting in good sintering. I can't get a body. In contrast, the ceramics of the present invention have a small dimensional change rate of about 1% during sintering, so a sintered body can be obtained without destroying the three-dimensional continuous network structure, hollow fibers, and hollow particles. As a result, almost no tensile stress remains inside the sintered body.
A structure with a high specific elastic modulus can be obtained.

According to the present invention, the specific elastic modulus is 90 GPa/(g/cm3)
Reaction sintered 5i3N4u high-rigidity ceramics, or specific elastic modulus of 130'GPa/(g/cm3) or more.
A second reaction-sintered SiC lightweight and highly rigid ceramic is obtained. This improves rigidity, which is a disadvantage of reaction sintered ceramics, and makes it possible to manufacture lightweight, highly rigid ceramics with complex shapes almost without machining due to high dimensional precision sintering, which is an advantage of reaction sintered ceramics. .

The three-dimensional continuous network structure, hollow fibers, and hollow particles of the present invention are preferably composed of at least one of metals, carbides, nitrides, oxides, oxynitrides, silicides, and borides. In particular, tungsten, molybdenum, silicon carbide, silicon nitride, aluminum nitride, carbon, silicon oxide, boron nitride,
Boron carbide is preferred.

The porosity (including hollow portions) in the ceramic matrix forming the hollow particles and hollow fibers is preferably 40 vol % or less. This is because if the amount exceeds 40 vol%, the mechanical strength will decrease and it will not contribute to improving the specific elastic modulus.

The three-dimensional continuous network structure may be a honeycomb structure, for example, one having a hexagonal, pentagonal, square, or round cross-sectional shape, and holes may be provided in the longitudinal cross-sectional direction. Furthermore, the weight can be further reduced by using a honeycomb with a hollow structure.

Furthermore, the specific elastic modulus can be similarly improved with a skeleton structure. The three-dimensional continuous network structure is not limited to the above shape, and may be any three-dimensional continuous network structure.

The three-dimensional continuous network structure can be manufactured by any method such as extrusion molding and then sintering, or coating the three-dimensional fiber surface with ceramics or metal particles and then sintering. A shaped structure can be manufactured by a known method.

The hollow particles have an outer diameter of about 1 μm to 1 mm and an inner diameter of 0.
A thickness of about 5 μm to 0.5 nun can be used, but it is not limited to this range. Further, if a hollow particle having a bell-like shape in which second particles are mixed is used, a damping effect can also be produced.

The hollow particles are preferably hollow particles with closed pores.

The hollow fiber has an outer diameter of about 1 μm to 1 nm+m and an inner diameter of 0.
From 5μm to about 0.5μm, aspect ratio: 10
to 100 can be used, but is not limited to this range. Compared to solid fibers, the weight can be reduced and the specific modulus can be improved.

In the present invention, by orienting the three-dimensional continuous network structure and the hollow fibers so that the specific elastic modulus is improved in one dimension, the rigidity is improved in the direction of the driving force of mechanical parts that are repeatedly driven and stopped. This enables precise control.

The elastic modulus of the three-dimensional continuous network structure, hollow particles, and hollow fibers is preferably larger than the elastic modulus of the reaction sintered ceramic matrix.

The reactive sintered ceramic matrix comprises a conductive material,
Ceramics having properties such as insulating materials, piezoelectric materials, dielectric materials, magnetic materials, thermal conductive materials, catalyst materials, electron emitting materials, and sensor materials can be used. In addition, a three-dimensional continuous network structure formed in a reactive sintered ceramic matrix,
As for the hollow fibers and hollow particles, those having characteristics such as conductive materials, insulating materials, piezoelectric materials, dielectric materials, magnetic materials, heat conductive materials, catalyst materials, electron emitting materials, sensor materials, etc. can be similarly used. This allows application to various functional materials.

The reactive sintered ceramic matrix may be composed of particles and/or whiskers of at least one selected from nitrides, oxides, oxynitrides, and carbides. In particular, it is preferable to use 31N, Si3N4, and 8IN as main components, which have low density and excellent heat resistance. Furthermore, toughness can also be improved by forming a composite material of whiskers and particles.

Structural diagrams of the bonding state of the reaction sintered matrix and the three-dimensional continuous network structure, hollow fibers, and hollow particles are shown in FIGS. 8 and 9.

The present invention is characterized in that particles B are produced by reaction sintering between the three-dimensional continuous network structure, hollow fibers, and hollow particles, which are part A;
Alternatively, particles B and whiskers C generated by reaction sintering
It is characterized by a structure that is connected by. The present invention provides the three-dimensional continuous network structure, hollow fibers,
To bond the hollow particles, a reactive sintered matrix and the three
Dimensional continuous network structures, hollow fibers, and hollow particles with different compositions can be easily manufactured.

The reactive sintered ceramic matrix has an average grain size of 100
At least one inorganic compound selected from carbides, oxides, nitrides, and oxynitrides of μm or less, Si3N4 with an average particle size smaller than the inorganic compound, and a pore volume of 40 vol%
Hereinafter, the specific modulus of elasticity can be improved by configuring the pores to have a maximum pore diameter of 30 μm or less.

In particular, at least one type of three-dimensional continuous network structure, hollow fibers, and hollow particles, at least one inorganic compound selected from carbides, oxides, nitrides, and oxynitrides with an average particle size of 100 μm or less, and metal S1 Sintering is achieved by sintering by composing ceramics in which one or more of three-dimensional continuous network structures, hollow fibers, and hollow particles are combined with Si3N or 8IN obtained by nitriding a molded body made of powder or metal layer powder. Since the dimensional change rate is small, precision sintering is possible, and since post-processing is hardly required, it can be manufactured at low cost.

Here, by performing reaction sintering using CO gas, a ceramic in which one or more of a honeycomb structure, hollow fibers, and hollow particles are bonded with carbide can be obtained.

In the present invention, plastic, glass, metal,
The surface of the ceramic is impregnated with at least seeds and covered with these.

Since the generation of cranks from the surface can be prevented, more reliable ceramics can be obtained.

The present invention is capable of bonding one or more types of three-dimensional continuous network structures, hollow fibers, and hollow particles, and reducing voids between particles using nitrides generated from metal powder in a compact during sintering. It is also possible to reduce the dimensional change rate during sintering and to arbitrarily control the electrical resistivity by controlling the type of nitride produced from the metal powder.

In the present invention, the metal powders include those belonging to groups 1 to 2 of the periodic table, especially Ti, Zr, V, and Nb.

Ta, Cr, Ce, Co, Mn, tlf,
W, Mo, FeAl, Si, Pr, N
t3. Sm, Eu, Gd, Tb.

Dy, Ha, Yb, Lu, Th, co, N
At least one selected from i can be used. For example, T1 nitride has an electrical resistivity of about 10-5Ω
It is small, on the order of cm, and on the other hand, Si nitride has a resistance of about 1015Ω.
It is large, on the order of cm. As described above, the resistivity of nitride differs depending on the type of metal powder, and by combining metal nitrides having different resistivities, it is possible to control the resistivity from conductivity to insulation.

Furthermore, by mixing an inorganic compound in addition to the metal powder, it is possible to control electrical properties, mechanical properties, etc., and it is also effective in improving the elastic modulus.

As the metal powder, commercially available ones can be used as they are, or rounded particles pulverized by a mill or the like may be used.

In the reaction sintering, it is preferable to heat the compact in a nitriding gas atmosphere containing nitrogen and/or ammonia with hydrogen, argon, helium, etc. added as necessary, or in a carbonizing gas atmosphere such as CO gas. Thereby, nitrides and carbides can be generated. Further, the reactive sintering in the present invention is characterized by the absence of a liquid layer portion that can cause shrinkage during sintering. In other words, it is characterized in that there is no glass layer or alloy layer, which serves as a liquid layer, between the metal powder, the three-dimensional continuous network structure, the hollow fibers, and the hollow particles.

The reaction sintered body of the present invention has an extremely small dimensional change rate during sintering, so even complex shapes such as carriages can be created without secondary processing, and the surface has the shape of the inner surface of the mold transferred. A sintered body having the following properties can be obtained.

In the present invention, the molding binder contains an appropriate amount of an organic polymer compound such as polyvinyl butyral or polyethylene, or an organic Si polymer compound such as a silicon imide compound or a polysilane compound, preferably 8 to 15 parts by weight. It is preferable that the particle volume filling rate is 65% or more. The molding method is selected depending on the shape and required characteristics, such as injection molding, press molding, rubber press molding, extrusion molding, casting molding, or mold powder molding.

In the present invention, it is also possible to impregnate resin, oil, lubricant, etc. into the pores of the composite ceramic sintered body, and it is also applicable to sliding members.

The lightweight, high-rigidity ceramics of the present invention can be applied to various mechanical parts that require precise position control, such as carriages and arms for disk drives, arms and arms for automatic mounting machines for inserting electronic components onto printed circuit boards. Suitable for stages, actuator parts, robot arms, etc.

Additionally, due to its low coefficient of thermal expansion and high rigidity, it is suitable for structural parts such as stages of machine tools.

[Effect]

The present invention relates to lightweight and highly rigid ceramics,
In particular, by configuring one or more of three-dimensional continuous network structures, hollow fibers, and hollow particles in a reactive sintered ceramic matrix, a ceramic having a high specific elastic modulus can be obtained.

In addition, it is possible to obtain a material that is effective as an anti-vibration effect.
It can be applied to various mechanical parts that require precise position control, and access time can be greatly reduced.

〔Example〕

Hereinafter, the present invention will be explained in more detail with reference to Examples.
The invention is not limited to these examples.

Example 1 A carbonaceous three-dimensional continuous network structure (a in Figure 1) with a relative density of 95% produced by extrusion molding and sintering was placed in a mold, and Si with an average particle size of 0.8 μm was placed in a mold. A slurry of powder mixed with a peptizer and distilled water was poured into a mold to produce a molded body. After removing moisture from the molded body, it was heat-treated stepwise to 1380°C over a long period of time in nitrogen gas, resulting in a carbonaceous three-dimensional continuous network structure bonded with Si3N4 (b in Figure 1). Ceramics (Fig. 1) were obtained. A cross section is shown in FIG. Further, a schematic diagram of the microstructure of the reaction sintered ceramic and the carbonaceous three-dimensional continuous network structure is shown in FIG. The carbonaceous three-dimensional continuous network structure consists of Si3N, which is a product of Sl, particles and Si3N4.
joined by whiskers. S l 3 IQ-particles and Si3N4 whiskers are generated in gas phase reaction, so
A composition that softens at high temperatures, such as a glass phase, is not present in this grain boundary.

At this time, the dimensional change rate from the molded body to the sintered body was as small as 0.1%, and a product with excellent dimensional accuracy was obtained. The porosity of the sintered body is 18%, the pore diameter is 20 μm or less, and the specific elastic modulus is 124.
It was GPa/(g/cm3).

The specific modulus of elasticity was determined by calculating the elastic modulus from the deflection using a three-point bending method, and dividing the value by the density of the sintered body.

For comparison, reactive sintered 5iaL ceramics containing no carbonaceous three-dimensional continuous network structure were similarly prepared and measured, and the specific elastic modulus was found to be 63 GPa/(g/c
m3). This shows that the product of the present invention has an extremely high modulus of elasticity.

The three-dimensional continuous network structure of this example is made of tungsten, Si3N, SiC, and AlN in addition to carbon.

Si02, A1. Mouth, TiN, Mullite, ZrO
Sintering is possible in the same manner using 2 or the like.

In addition, by treating the above-mentioned molded body in a CO gas atmosphere, the carbonaceous material 3 in which Sl is carbonized and bonded with SiC
A dimensional continuous network structure ceramic is obtained. At this time, the surface of carbon changes to SiC, making it possible to further improve the specific elastic modulus. As a result, the specific elastic modulus is 160
A structure of GPa/(g,'cm3) was obtained. Here, reaction sintered SiC containing no three-dimensional continuous network structure
The specific elastic modulus of ceramics is 125 GPa/(g/c
m3), indicating that the product of the present invention has an extremely high specific modulus.

Example 2 A SiC three-dimensional continuous network structure molded product produced by extrusion molding was placed in a mold for molding, and the average particle size was 0.8μ.
A slurry in which a peptizer and distilled water were mixed with m Ti powder was poured into a mold to produce a molded body. After moisture was removed from the molded bodies, they were simultaneously heat-treated to 1500° C. in nitrogen gas to obtain a composite ceramic structure in which a SiC three-dimensional continuous network structure was bonded with TiN. The porosity of the sintered body is 1
8%, and the specific elastic modulus was 98 GPa/(g/cm3). This structure has a conductivity of 4×10 −′Ωm.

Further, a slurry of 20 tons of SiC powder with an average particle size of 2 μm and 80 wt % of Ti powder with an average particle size of 0.8 μm was similarly poured into a mold, and molded and sintered. As a result, the specific elastic modulus could be improved to 1 13 GPa/(g/cm3).

Example 3 70 parts by weight of 81 powder with an average particle size of 0.8 μm and an average particle size of 1
13 parts by weight of a thermoplastic resin was added to 30 parts by weight of 8102 hollow particles of 0 μm (inner diameter 5 μm) and mixed, and a molded article was produced by injection molding. After removing the resin from the molded body,
Heat treatment was performed stepwise to 1380° C. over a long period of time in nitrogen gas to obtain Si02 hollow particle ceramics bonded with Si3N4 (Fig. 5). At this time, the dimensional change rate from the molded body to the sintered body was as small as 0.1%, and a product with excellent dimensional accuracy was obtained. The sintered body had a porosity of 25%, a pore diameter of 20 μn or less, and a specific modulus of elasticity of 9 8 GPa/(g/cm3).

In addition, by treating the above sintered body at 1500°C in nitrogen at 50 atm, the surface layer of the Si opening and the hollow particle was changed to Si.
Ceramic that changes to 3N4 and has a higher specific modulus [
1 1 4 GPa/(g/cm3) j was obtained.

Example 4 In the same manner as in Example 3, the outer diameter was 1 mm, the inner diameter was 0.5 mm,
30wt% of SiC hollow fibers and 70ivt% of Sl powder each having a length of 5 mm were molded and sintered. As a result, Si3N4
A SiC hollow fiber ceramic (FIG. 4) bonded with the above was obtained. As a result, the specific elastic modulus was 1 20 GPa/(g/
cm3) structure was obtained.

Example 5 In the same manner as in Example 2, sintered bodies with different porosities were produced by changing the sintering conditions, and the specific modulus of elasticity was determined. The result is the 6th
As shown in the figure. From this, it can be seen that when the porosity exceeds 40 vol%, the specific elastic modulus decreases, which is not preferable as a lightweight and high-rigidity material.

Example 6 Using the three-dimensional continuous network structure ceramic obtained in Example 1, a carriage and arm parts of a magnetic disk device as shown in FIG. 7 were constructed. The magnetic disk 2 is held by a spindle 19 and rotates at high speed. The thin film magnetic head assembly 13 is held by an arm assembly 14,
A thin film magnetic head is provided at the tip. This assembly 13 has the same number of magnetic disks 20, and the carriage 16
The bearing 5 is fixed integrally with the guide rail 6.
move at the same time. Movement is automatically carried out by the magnetic circuit 15. Compared to conventional aluminum products, the specific elastic modulus has been improved by more than twice, and the vibration (chatter) associated with driving and stopping has been reduced, greatly improving the reliability of magnetic disk drives.

〔Effect of the invention〕

According to the present invention, the specific elastic modulus of ceramics can be significantly improved. Therefore, the rigidity and reliability of mechanical parts that are repeatedly driven and stopped can be significantly improved, and it is possible to provide mechanical parts that can be controlled with high precision, which has not been seen before.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing a composite ceramic with a three-dimensional continuous network structure, Fig. 2 is a schematic cross-sectional view of Fig. 1, and Fig. 3 is a joint portion between the reaction sintered ceramic matrix and the three-dimensional continuous network structure. Fig. 4 is a perspective view showing hollow fiber composite ceramics, Fig. 5 is a perspective view showing hollow particle composite ceramics, and Fig. 6 shows the relationship between sintered body porosity and specific modulus. The graphs shown in Fig. 7 are cross-sectional views of the magnetic disk device, and Figs. 8 and 9 are graphs showing particles, whiskers, and 3
FIG. 2 is an enlarged structural diagram showing a bonding state of a dimensional continuous network structure, hollow particles, and hollow fibers. a: three-dimensional continuous network structure, b: ceramic matrix, C: hollow fiber, d: hollow particle, e
... Ceramic particle, f... Ceramic whisker, 5... Bearing, 6... Guide rail, 13
... Thin film magnetic head assembly, 14... Arm, 1
5... Magnetic circuit, 16... Carriage, 17...
Conductor, 18...Enclosure, 19...Spindle, 20...Magnetic disk, A...Three-dimensional continuous network structure, hollow fiber, hollow particle Patent applicant Hitachi, Ltd. Agent Nakamoto Orientation
Engraving of Akira Inoue's drawings (no changes to the content) 1st (B) Engraving of the drawings (no changes to the content) 3rd drawing I2 Hou'71! 1 Jao Peng

Claims (1)

[Scope of Claims] 1. A lightweight and highly rigid ceramic characterized in that a three-dimensional continuous network structure is formed in a reactive sintered ceramic matrix with a porosity of 40 vol% or less. 2. A lightweight, high-rigidity ceramic characterized in that hollow particles are formed in a reactive sintered ceramic matrix with a porosity of 40 vol% or less. 3. A lightweight, high-rigidity ceramic characterized in that hollow fibers are formed in a reactive sintered ceramic matrix with a porosity of 40 vol% or less. 4. In claim 1, 2 or 3, the reactive sintered ceramic matrix is Si_3N_4 or SiC.
Lightweight and highly rigid ceramics characterized by the use of ceramics made of. 5. In claim 4, the matrix is Si_
Ceramic made of 3N_4, specific elastic modulus 90GPa
/(g/cm^3) or more. 6. The matrix according to claim 4, wherein the matrix is SiC.
Ceramics consisting of 140GPa/(g
A lightweight, high-rigidity ceramic characterized by having properties of /cm^3) or more. 7. In claim 1, 2 or 3, the three-dimensional continuous network structure, hollow particles or hollow fibers are metals, carbides,
A lightweight, highly rigid ceramic comprising at least one selected from nitrides, oxides, oxynitrides, silicides, and borides. 8. In any one of claims 1 to 4, the pores of the reactive sintered ceramic matrix are made of plastic,
A lightweight, high-rigidity ceramic characterized by being filled with at least one type selected from glass and metal. 9. The lightweight material according to claim 1, 2 or 3, characterized in that the reactive sintered ceramic matrix is composed of at least one kind of particles and/or whiskers selected from nitrides, oxides, oxynitrides, and carbides. Highly rigid ceramics. 10. Claim 1, 2 or 3, wherein the reactive sintered ceramic matrix comprises at least one inorganic compound selected from carbides, oxides, nitrides, and oxynitrides with an average particle size of 100 μm or less; Si_3N_4 is smaller than the inorganic compound, and the pore volume is 4.
A lightweight, high-rigidity ceramic comprising pores of 0 vol% or less and a maximum pore diameter of 30 μm or less. 11. A reaction product obtained by reaction-sintering a molded body consisting of at least one of three-dimensional continuous network structures, hollow particles, and hollow fibers and metal powder, and three-dimensional continuous network structures, hollow At least one type of particles and hollow fibers are combined.
A lightweight, high-rigidity ceramic consisting of pores with a pore volume of 40 vol% or less and a maximum pore diameter of 30 μm or less. 12. A reaction product obtained by reaction-sintering a molded body consisting of at least one of a three-dimensional continuous network structure, hollow particles, and hollow fibers, a metal powder, and an inorganic compound, and a three-dimensional continuous network structure. A lightweight, high-rigidity ceramic consisting of pores with a pore volume of 40 vol% or less and a maximum pore diameter of 30 μm or less, which combines at least one of a solid body, hollow particles, and hollow fibers. 13. A molded body consisting of at least one of a three-dimensional continuous network structure, hollow particles, and hollow fibers and metal Si powder,
A lightweight, high-rigidity ceramic made of Si_3N_4 obtained by nitriding and having pores with a pore volume of 40 vol% or less and a maximum pore diameter of 30 μm or less, which is bonded with at least one of a three-dimensional continuous network structure, hollow particles, and hollow fibers. 14. A molded body consisting of at least one of a three-dimensional continuous network structure, hollow particles, and hollow fibers and metal Al powder,
A three-dimensional continuous network structure made of AlN obtained by nitriding,
A lightweight, high-rigidity ceramic comprising pores with a pore volume of 40 vol% or less and a maximum pore diameter of 30 μm or less, which is bonded with at least one of hollow particles and hollow fibers. 15. A drive mechanism component for reciprocating motion and/or rotational motion, characterized in that it is molded using the lightweight and highly rigid ceramic according to any one of claims 1 to 14. 16. A carriage and arm for a magnetic, optical, or magneto-optical disk device, characterized in that they are molded using the lightweight and highly rigid ceramic according to any one of claims 1 to 14.