JP2985512B2 - Particle-dispersed ZrO2-based ceramic material and method for producing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic material having a special structure and a method for producing the same. Specifically, thermal shock resistance,
The present invention relates to a high-toughness, high-strength ZrO ₂ -based ceramic material having excellent high-temperature characteristics and a method for producing the same.

[0002]

_2. Description of the Related Art ZrO ₂ (zirconium oxide) in which rare earth oxides represented by Y ₂ O ₃ (yttrium oxide) or the like are partially dissolved in a crystal lattice to form a solid solution has high toughness and high strength. Because it is a material, it is widely used as an industrial material.

[0003]

However, the partially stabilized ZrO ₂ obtained by the conventional technique exhibits excellent fracture strength and fracture toughness, but it does not contain Y ₂ O ₃ , CaO (calcium oxide) and MgO (magnesium oxide). )) And Zr
By forming a solid solution in the O ₂ crystal lattice, since the metastable phase of the tetragon is maintained, the mechanical and thermal properties are remarkably deteriorated at a high temperature higher than the transformation temperature. In addition, in a high temperature atmosphere during sintering or use, release (destabilization) of the stabilizer occurs. For this reason, when used repeatedly, the excellent initial thermal shock resistance and mechanical properties on the low temperature side are gradually lost, so that the ambient temperature for use is significantly limited to a relatively low temperature.

Therefore, in order to put the ZrO ₂ ceramic material into practical use in many industrial fields, it is necessary to improve these disadvantages at the same time.

An object of the present invention is to provide a high-toughness, high-strength particle-dispersed ZrO ₂ -based ceramic material having excellent thermal shock resistance and excellent high-temperature characteristics without impairing the properties of ZrO ₂ , and a method for producing the same. It is in.

[0006]

A particle-dispersed Z according to claim 1
The rO ₂ ceramic material contains nanometer-sized nanoparticles as a second phase in the ZrO ₂ crystal grains in an amount of 0.1 to 30 nm.
It is characterized by being dispersed by volume%.

[0007] particle-dispersed ZrO ₂ based ceramic material of claim 2, in ZrO ₂ based ceramic material of claim 1, a non-oxide nanoparticles is less than an average particle diameter of 400nm dispersed in ZrO ₂ crystal grains grains and And / or oxide particles.

[0008] The particle-dispersed ZrO ₂ -based ceramic material according to claim 3 is obtained by mixing a non-oxide powder and / or an oxide powder having an average particle diameter of 400 nm or less with ZrO ₂ powder and molding the resulting mixture. By sintering the compact at a sintering temperature of 1200 ° C. or more, the particle-dispersed ZrO ₂ ceramic material according to claim 1 or 2 is manufactured.

Hereinafter, the present invention will be described in detail.

The particle-dispersed ZrO ₂ -based ceramic material of the present invention is characterized in that ZrO ₂ is used as a matrix and non-oxide and / or oxide nanoparticles are used as a second phase of the dispersed particles. The average particle diameter of the nanoparticles is preferably 400 nm or less, and has a structure in which the nanoparticles are uniformly dispersed in a ZrO ₂ matrix.

In the method of the present invention, the reason why particles having an average particle diameter of 400 nm or less are used as a powder raw material is that ZrO
_{(2) It} is easy to be taken into crystal grains, and it is in a range where microcracks are not generated enough to cause material defects. In particular, the average particle diameter of the powder raw material is 50-30.
It is preferably set to 0 nm.

The reason why the addition amount of the nanoparticles as the dispersed particles is 0.1 to 30% by volume is that ZrO _{2 in} the sintered body is
Can maintain a tetragonal structure, can sufficiently develop stress-induced transformation of ZrO ₂ at the time of fracture, and can maintain a high fracture strength and fracture toughness even at a transformation temperature at or above the transformation temperature at which mechanical properties of conventional ZrO ₂ are greatly reduced. It depends.

In the present invention, non-oxide nanoparticles include carbides such as SiC (silicon carbide), TiC (titanium carbide) and WC (tungsten carbide), and TiN.
Preference is given to nitrides such as (titanium nitride) and borides such as TiB ₂ . The nanoparticles of oxide Al ₂ O ₃
(Aluminum oxide) and the like. These nanoparticles may be used alone or in combination of two or more.

[0014]

The present inventors have found that ZrO ₂ ceramics
The problems of the conventional ZrO ₂ ceramics have been overcome by giving the oxide and non-oxide nanoparticles dispersed in the O ₂ crystal grains roughly two roles as follows.

That is, in the particle-dispersed ZrO ₂ -based ceramic material of the present invention, the first role of the nanoparticles dispersed in the crystal grains of ZrO ₂ is the extremely local (in the diameter of the nanoparticles) inside or around the dispersed particles. approximately twice within) of, by using the thermal residual stresses generated during cooling from the production temperature mainly by the difference in thermal expansion coefficients between ZrO ₂ and a dispersed phase, oblique from tetragonal ZrO ₂ in the thermal residual stresses It is to control the transformation into crystals. Due to the magnitude of the coefficient of thermal expansion of the nanoparticles to be dispersed,
For example, SiC nanoparticles having a significantly lower coefficient of thermal expansion than ZrO ₂ greatly contribute to the stabilization of tetragonal crystals, and ZrO ₂
In the case of Al ₂ O ₃ having a slightly smaller coefficient of thermal expansion, the contribution to the stabilization of the tetragonal crystal is small. Therefore, by controlling the type and amount of nanoparticles to be dispersed, the transformation of ZrO ₂ can be easily controlled, and the toughness utilizing this transformation can be more efficiently exhibited. The conventional Zr
As described above, the crystal transformation of O ₂ -based ceramics has been controlled by a method completely different from that of the present invention, that is, by dissolving CaO, Y ₂ O ₃ , MgO, etc. in a crystal lattice.

[0016] In the particle-dispersed ZrO ₂ based ceramic material of the present invention, the second role of nanoparticles dispersed ZrO ₂ in the crystal grains, conventional ZrO ₂ based ceramic is remarkably fracture toughness, fracture above the transformation temperature It is to prevent the strength from decreasing and control the fracture by these nanoparticles even below the transformation temperature, to improve the fracture strength and fracture toughness more than the toughness due to transformation, and this role is classified as follows be able to.

Improvement of fracture strength by miniaturization of material structure, suppression of abnormal grain growth, and control of crystal grain shape. Crack deflection by fine particles dispersed in crystal grains,
Improvement of fracture toughness by generation of microcracks in crystal grains. Suppression of fracture source generation due to compressive stress generated in crystal grains and improvement of fracture strength. Suppression of fracture at high temperature, that is, improvement of high-temperature strength by inducing intragranular fracture by tensile stress generated around particles dispersed in the crystal grain. Improvement of high-temperature hardness, high-temperature strength, creep resistance, and brittle / ductile dislocation temperature (heat-resistant temperature) by pinning the movement of dislocation at high temperature of hard particles dispersed in crystal grains. In the present invention, by simultaneously giving the two different roles described above to the nanoparticles dispersed at a specific ratio in the ZrO ₂ crystal grains, the disadvantages of the conventional ZrO ₂ -based ceramic material can be all simultaneously achieved. Thus, it has become possible to realize a ZrO ₂ -based ceramic material that maintains high strength and high toughness up to a high temperature range, has excellent heat resistance, and has excellent thermal shock characteristics.

The particle-dispersed ZrO ₂ ceramic material of the present invention comprises nanoparticles dispersed in ZrO ₂ crystal grains and ZrO ₂
By utilizing the thermal residual stress generated during cooling from the sintering temperature due to the difference in the coefficient of thermal expansion of rO ₂ , ZrO 2
_It controls the phase transformation from tetragonal to monoclinic in No. ₂ and has a nanocomposite structure in which nanoparticles are dispersed in ZrO ₂ crystal grains. In the ZrO ₂ -based ceramic material according to the present invention, the nano-composite structure in which the nanoparticles are dispersed in the crystal grains of ZrO ₂ makes the starting raw material unstable ZrO 2.
No. ₂ retains a metastable phase (tetragonal) in the sintered body.

In the production method of the present invention, the unstable Zr
O ₂ and a non-oxide and / or oxide having an average particle diameter of 400 nm or less were mixed at a predetermined ratio, molded, and then sintered to obtain a dense structure having the above-described structure and to have the above characteristics. A nanoparticle-dispersed ZrO ₂ ceramic material is manufactured. That is, according to the method for producing a particle-dispersed ZrO ₂ -based ceramic material of the present invention, the matrix ZrO ₂
O ₂ is densely sintered during the sintering process, and a nanocomposite structure in which non-oxide or oxide nanoparticles as a dispersed phase are uniformly incorporated in the particles is formed.

In the method of the present invention, the ZrO ₂ powder is mixed with an oxide and / or non-oxide powder having an average particle diameter of 400 nm or less at a predetermined ratio, and the resulting mixture is molded.
Sinter. Here, as a sintering method, hot press sintering, normal pressure sintering, or normal pressure sintering / HIP (hot isostatic pressing) can be employed. In particular, normal pressure sintering / HIP is preferable because a complicated shaped product can be mass-produced. The gas pressure when HIP is used can be selected in a wide range, but in particular, 50
0 to 2000 kg / cm ² is preferred. The sintering temperature is 1200 ° C. or higher, preferably 1300 to 1500 ° C.

The particle-dispersed ZrO ₂ -based ceramic material of the present invention is particularly suitable as a heat-resistant material, such as a cutting tool, a construction tool material, a wear-resistant member, a sliding member, and a structural material requiring thermal shock resistance.

[0022]

The present invention will be described more specifically with reference to the following examples. In the following, Si is used as nanoparticles.
Examples in which C and TiC are added will be described. However, the present invention is not limited to the following examples as long as the gist of the present invention is not exceeded, and other configurations may be adopted for the types of nanoparticles and the like.

Examples 1 to 8 and Comparative Examples 1 to 3 (Carbide-based nanoparticles) As the ZrO ₂ powder, unstable ZrO ₂ manufactured by Daiichi Rare Element Co., Ltd.
(Average particle size: 0.3 μm). The following TiC and SiC were used as the nanoparticles. The TiC powder is TiC (average particle size 0.2 μm) manufactured by Hakusui Chemical Co., and the SiC powder is β-random (average particle size 0.2 μm) manufactured by Ibiden. This TiC or SiC was used in the proportions shown in Table 1 to form a balance of ZrO ₂ and mixed with ethanol as a dispersion medium in a wet ball mill for 24 hours. After this was sufficiently dried, the mixture was crushed and mixed by a dry ball mill for 12 hours to obtain a raw material powder.

Approximately 50 g of the raw material powder was filled in a graphite die and sintered with a hot press (manufactured by Fuji Denki Kogyo KK). The hot pressing conditions were as follows: after raising the temperature to a predetermined sintering temperature shown in Table 1, holding for 1 hour and pressing pressure of 30 MPa.

The various sintered bodies thus obtained are ground and subjected to J
The size of a 3 × 4 × 40 mm three-point bending test piece according to IS R1601 was measured, and the bending strength was measured at room temperature at a load speed of 0.5 mm / min and a span length of 30 mm by a three-point bending test method. In addition, load 5kg weight, holding time 1
At 0 seconds, the fracture toughness was measured by the IF method.

Table 1 shows that ZrO ₂ and TiC and / or SiC
Shows the flexural strength and fracture toughness for the composition of the composition. In addition,
Comparative Example 1 was an unstable ZrO ₂ without using TiC and SiC.
Was replaced with Y ₂ O ₃ stabilized ZrO ₂ , and ZrO ₂ (3
mol% Y ₂ O ₃ ).

As is clear from Table 1, the ZrO of the present invention
It can be seen that the fracture of the ₂ / TiC and ZrO ₂ / SiC ceramic composite materials is controlled by the nanoparticles, and the bending strength and fracture toughness are greatly improved.

Examples 9 to 12 and Comparative Example 4 (Nitride and boride-based nanoparticles) The following Examples and TiN and TiB ₂ were used as nanoparticles, and the sintering temperatures were as shown in Table 2. A sintered body was manufactured in the same manner as in the comparative example.

TiN: TiN manufactured by Hakusui Chemical Industry Co., Ltd. (average particle size: 0.2 μm).

TiB ₂ powder: A pulverized product of TiB ₂ manufactured by Idemitsu Chemical Co., Ltd. under pressure and agitated by a mill (average particle size: 0.3 μm).

The obtained sintered body flexural strength and fracture toughness Examples 13 and 14 shown in Table 2 and the following Al ₂ O ₃ used as comparative example 5 (oxide nanoparticles) nanoparticles, sintered Table 3
A sintered body was manufactured in the same manner as in the above Examples and Comparative Examples except that the conditions were as follows.

Al ₂ O ₃ powder: Al ₂ manufactured by Sumitomo Chemical Co., Ltd.
O ₃ (average particle size: 0.2 μm) The bending strength and fracture toughness of the obtained sintered body are shown in Table 3.

It is also apparent from Tables 2 and 3 that the composite material of the present invention has remarkably high flexural strength and fracture toughness.

[0034]

[Table 1]

[0035]

[Table 2]

[0036]

[Table 3]

From the X-ray diffraction, ZrO _{2 on} the polished surface of the composite sintered bodies obtained in Examples 1 to 14 was almost tetragonal, and stress induced from tetragonal to monoclinic at the time of fracture. It was confirmed that the rate of transformation was high.

Further, ZrO _2/10 obtained in Example 2
For the volume% TiC ceramic composite material and the ZrO ₂ (3 mol% Y ₂ O ₃ ) single phase obtained in Comparative Example 1, the bending strength at high temperature was measured in the same manner as above, and the change in high temperature strength is shown in Table 4. Was. From Table 4, in the ZrO ₂ single phase,
Although a remarkable decrease in strength occurs at high temperatures, it is clear that in the ceramic composite material of the present invention in which TiC nanoparticles are dispersed, a decrease in fracture strength is suppressed even at a transformation temperature or higher, and high strength is maintained even at high temperatures. .

[0039]

[Table 4]

[0040]

As described above, according to the particle-dispersed ZrO ₂ -based ceramic material of the present invention, by dispersing non-oxide and / or oxide nanoparticles in ZrO ₂ crystal grains, ZrO ₂ Can be easily controlled to achieve high toughness.

Further, not only does the conventional ZrO ₂ ceramic material prevent a remarkable decrease in fracture toughness and fracture strength above the transformation temperature, but it also controls the fracture with these nanoparticles even below the transformation temperature, thereby increasing the toughness due to transformation. It is possible to improve fracture toughness and fracture strength.

Therefore, according to the particle-dispersed ZrO ₂ ceramic material of the present invention, a high toughness and high strength ZrO ₂ ceramic material having excellent thermal shock resistance and high temperature characteristics is provided.

According to the production method of the present invention, the mechanical properties of thermal shock resistance, bending strength at room temperature and high temperature, and fracture toughness are greatly improved by controlling the phase transformation of ZrO ₂ by the dispersion of nanoparticles. Thus, a particle-dispersed ZrO ₂ -based ceramic material that can be applied to structural materials can be easily and efficiently produced.

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Koichi Niihara 9-7-1142, Karigaoka, Hirakata-shi, Osaka (56) References JP-A-5-246760 (JP, A) JP-A-2-255570 ( JP, A) JP-A-4-12058 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) C04B 35/48

Claims (3)

(57) [Claims] 1. A particle-dispersed ZrO ₂ -based ceramic material in which nanometer-sized nanoparticles are dispersed as 0.1% to 30% by volume as a second phase in ZrO ₂ crystal grains. 2. A ZrO ₂ grain non-oxide nanoparticles dispersed is less than the average particle size of 400nm in the particles and / or oxide particles distributed ZrO ₂ according to claim 1, wherein the particle is Series ceramic materials. 3. A non-oxide powder and / or an oxide powder having an average particle diameter of 400 nm or less are mixed with ZrO ₂ powder, and the resulting mixture is molded. Then, the molded body is heated at a sintering temperature of 1200 ° C. or more. A method for producing the particle-dispersed ZrO ₂ -based ceramic material according to claim 1 by sintering.