JP2727628B2 - Method for producing conductive zirconia sintered body - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for producing a conductive zirconia sintered body.

More specifically, the present invention relates to a method for producing a zirconia sintered body having not only excellent mechanical properties such as strength, toughness, and hardness but also having conductivity even in a low temperature range.

<Prior Art> Conventionally, the zirconia sintered body is considered toughness improved in order to apply to the material for cutting tools and engine Recently _{Y 2 O 3, MgO, CeO} 2
A partially stabilized zirconia sintered body was developed by
A zirconia sintered body can only be obtained in a simple shape due to the restriction of the sintered body manufacturing technology. Therefore, in order to make the final product shape, it is inevitable to rely on cutting work.However, since zirconia sintered body is an insulating material at low temperature, it is not possible to use electric discharge machining method with excellent machining efficiency. Had disadvantages.

As a method of imparting electrical conductivity to a zirconia sintered body and enabling electrical discharge machining, a method of mixing a conductive powder such as TiC or TiN with zirconia powder and sintering the mixture is known.

For example, Japanese Unexamined Patent Publication No. 62-202861 discloses an electric discharge machining ceramic in which a partially stabilized zirconia sintered body is mixed with an electric discharge machining property-imparting substance comprising titanium nitride and / or zirconium nitride. An electric discharge machining ceramic characterized in that a part thereof is constituted by titanium nitride and / or zirconium nitride obtained by using a hydride of Ti or Zr as a starting material is disclosed. However, in the method using these hydrides of Ti and Zr as starting materials, these hydrides are unstable in the air, are difficult to handle, and are expensive. There is no mention of the toughness of the sintered body.

On the other hand, conductivity-imparting substances such as TiC and TiN are generally difficult-to-sinter materials, so if they are simply mechanically mixed with zirconia, pressure sintering using a hot press or sintering at high temperatures is required. There is a disadvantage that the manufacturing cost is increased. In addition, it is difficult to obtain conductivity without reducing the strength, toughness, hardness, etc. of the sintered body, and there is no reduction in the physical properties inherent in these zirconia sintered bodies, and normal-pressure sintering or low-temperature sintering. It has been desired to develop a conductive zirconia sintered body that can be obtained by the method described above.

On the other hand, as a solid solution of zirconia and titanium oxide, a solid solution of mainly titania (TiO ₂ ) has been well known. Also S. R. Rayon (SRLy
on) et al. Journal of American Ceramic
Society 61 (9-10) 469-71 (1978) [J. Am. Cera
m. Soc., 61 (9-10) 469-71 (1978)], found that titanium monoxide (TiO) was dissolved in zirconia in a solid solution. The solid solution in zirconia is less than 1.5 wt% (0.78 mol%) at 1500 ° C, and is composed of cubic and monoclinic (eutectic structure with TiO above the solid solubility limit). " I have. However, since this sintered body is composed of a cubic crystal and a monoclinic crystal, it is difficult to say that the sintered body has excellent strength and toughness, and it is not disclosed as a zirconia sintered body having conductivity. Also, Neil. Nils Claussen et al. Reported that a cubic zirconia sintered body stabilized with nitrogen was obtained by hot pressing zirconium oxide powder and various nitride powders under a nitrogen atmosphere [Journal of American Ceramic Society 61,369-70 (197
8)] [J. Am. Ceram, Soc., 61, 369-70 (1978)].

In this case, zirconia reacts with ZrN, AlN, and Si ₃ N ₄ to produce cubic zirconia (zirconium oxynitride) and monoclinic zirconia.

However, when TiN is used as the nitride powder is described as produced no cubic zirconia, N ₂ and TiN as the reason for the order does not act as a supply medium of atomic nitrogen for stability is good Described. Furthermore, it has been reported that cubic zirconia stabilized by nitrogen is thermally unstable and separates to form a single crystal by heat treatment.

Therefore, these sintered bodies lack stability and are not practically usable.

<Problems to be solved by the invention> In view of such circumstances, the present inventors have obtained a sintered body having excellent strength, toughness, and hardness, and a conductive property capable of normal-pressure sintering and low-temperature sintering. As a result of intensive studies aimed at finding a method for producing a zirconia sintered body, the present invention has been completed.

<Means for Solving the Problems> That is, according to the present invention, a sintered body after sintering is composed of 60 to 90% by volume of a zirconium oxide solid solution and 10 to 40% by volume of titanium nitride, and the solid solution is composed of zirconium oxide and titanium. A conductive zirconia sintered body characterized in that zirconium oxide powder and titanium suboxide powder are mixed and formed so as to be made of a titanium oxide containing 0 <Ti ≦ 16% by weight, and then sintered under a nitrogen atmosphere. To provide a method for manufacturing the same.

 Hereinafter, the present invention will be described in more detail.

In the method for producing a sintered body according to the present invention, the sintered body after sintering is composed of 60 to 90% by volume of a zirconium oxide solid solution and 10 to 40% by volume of titanium nitride, and the solid solution is composed of zirconium oxide and titanium. Usually, zirconium oxide powder and titanium suboxide powder are mixed and formed so as to be made of a titanium oxide containing 0% by weight <Ti ≦ 16% by weight, and then sintered in a nitrogen atmosphere.

If the amount of titanium nitride in the sintered body is less than 10% by volume, it is difficult to develop a conductivity of 1 Ωcm or less in volume resistivity, while if it exceeds 40% by volume, the strength of the sintered body decreases. .

When the amount of titanium oxide forming a solid solution with zirconium oxide is more than 16% by weight of zirconium oxide as titanium, the strength of the sintered body decreases, and when the titanium oxide does not form a solid solution. No improvement in the physical properties of the sintered body can be expected.

The sintered body obtained by the method of the present invention has a structure in which zirconium oxide and titanium oxide form a solid solution, and titanium nitride is dispersed in the sintered body.

Instead of the titanium suboxide powder or in combination therewith, a nitrogen-containing titanium suboxide powder can be used.

The powder to be subjected to the reaction is preferably a fine powder having a sharp particle size distribution from the ease of the reaction, and in this regard, there is no particular limitation as long as the raw material powder used in the art is used, but it is usually used. Those having an average particle size of about 5 μm or less, preferably about 2 μm or less are used.

When TiO ₂ powder is used alone instead of titanium suboxide powder, only a solid solution reaction with zirconia occurs in the sintering temperature range used in the present invention, and a sintered body having a desired composition cannot be obtained. .

The titanium suboxide powder meant titanium oxide powder other than TiO _2, specifically a _{TiO, Ti 2 O 3, Ti} 3 O 5 , etc.,
Of these, titanium black is preferred.

Although the reason for these titanium suboxide powders is not clear,
In a sintering process with zirconium oxide powder in a nitrogen atmosphere, a part is nitrided to form titanium nitride, and a part is solid-dissolved in zirconium oxide to form a solid solution.

Zirconium oxide applied to the present invention is Y ₂ O ₃ , MgO, Ce
A partially stabilized zirconia powder obtained by adding a commonly known stabilizer such as O ₂ may be used, or an unstabilized zirconia powder containing no such auxiliary agent may be used.

The addition amount of the sintering aid is usually well be applied in the range of obtaining a known PSZ (partially stabilized zirconia) or TZP (tetragonal zirconia polycrystal), for example in the case of Y ₂ O ₃ in the zirconium oxide powder About 2 mol% to 5 mol%, about 8 mol% to 10 mol% for MgO, and about 6 mol% to 12 mol% for CeO ₂ may be used as targets. Of course, these sintering aids can be used in combination.

In the reaction, a zirconium oxide powder and a titanium suboxide powder may be used in combination with a nitrogen-containing titanium suboxide powder or a mixed powder of titanium oxide and a reducing agent such as carbon. When these are used together, it is easy to generate TiN by a nitriding reaction in the sintering process, and ZrTiO4
And the like.

It is also possible to add a part of TiN to the raw material beforehand.

In the case of using other materials such as titanium oxide and carbon, TiN together with these zirconium oxide or titanium suboxide, it is necessary to determine the raw material composition to be a zirconia sintered body having a desired composition by calculation and simple preliminary experiments. Preferably, 2% by weight or more of titanium suboxide (including nitrogen-containing titanium suboxide) is used with respect to zirconium oxide.

Then, after mixing the raw material powder and molding if necessary,
Sinter.

Mixing and molding may be performed by a method known in the art. For example, after mixing by a wet and / or cyclic method using a ball mill or the like, molding may be performed by a mold press or an isostatic rubber press.

The sintering conditions are not unique depending on the raw material composition to be applied, but usually about 1350 ° C to about 1600 ° C for 1 hour or more in a nitrogen atmosphere.
Preferably, firing may be performed at about 1400 ° C. to about 1550 ° C. for 1 to 5 hours.

The sintered body at this point usually consists mainly of tetragonal and cubic, and further contains about 15% by weight or less of monoclinic.
(However, if the sintered body does not contain a stabilizer such as Y ₂ O _3, it is composed of about 20% or more monoclinic after sintering.) Then, the sintered body should be heat-treated as necessary. Can be done.

The heat treatment conditions are not unique depending on the composition of the sintered body before the heat treatment, that is, the object to be treated.
° C to about 1300 ° C, more than 1 hour, preferably about 1100 ° C to about 1250
C. for 1 hour to 100 hours.

When such a heat treatment is performed, the ratio of the tetragonal and / or cubic crystals is reduced and the amount of the monoclinic is increased by at least about 5% by weight as compared with the sintered body without the heat treatment. Normally, about 5% by weight of monoclinic in the crystal phase
It has a composition of about 50% by weight, and although the reason is not clear, the mechanical strength and the fracture toughness are remarkably improved without lowering the conductivity as compared with those of the present invention without heat treatment. (However, since the sintered body containing no Y ₂ O ₃ is composed of about 20% or more of monoclinic after sintering, heat treatment after sintering is not necessarily required.) It is of course possible to mix substances other than zirconium oxide, titanium oxynitride and titanium oxide as long as the effect of the above is not impaired. For example, Al ₂ O
₃ , inorganic materials such as SiO ₂ , SiC, TiC, and TiB ₂ . The amount of these additions depends on the purpose of addition, but is usually used within a range of about 20% by volume based on zirconium oxide.

<Effect of the Invention> Since the zirconia sintered body obtained by the method of the present invention described above has excellent strength, toughness, hardness, and also has electrical conductivity, it can be used for a material itself such as a shaft for a micromotor or an industrial cutter. It can improve the compatibility with applications that require conductivity and the fields that require workability such as cutting tools and internal combustion engine parts, and can also be used under pressure, high temperature, like the conventional method using TiN or TiC as a raw material. Since it can be obtained without sintering, it is very economical and its industrial value is very large.

<Examples> Hereinafter, the present invention will be described specifically with reference to examples.

In the present invention, various physical properties of the sintered body were measured by the following methods.

Conductivity (volume resistivity): A test piece obtained by cutting out a sintered body was read at room temperature with a four-terminal microresistance meter, and calculated from the test piece dimensions.

Flexural strength (3-point flexural strength): Measured according to JIS-R1601.

Hardness: Vickers hardness (load: 20 kg) Fracture toughness: IF method (load: 20 kg) Calculated from Niihara's formula.

Crystal phase: This was performed by the X-ray diffraction method. A test piece mirror-polished with a 1 μm diamond paste was subjected to X-ray diffraction, and the ratio of each crystal phase was calculated from the following equation.

m / (t + c) = [Im (111) + Im (111) / [It (111) + Ic (111)] c / t = Ic (200) / [It (200) + It (002)] where m is Monoclinic, t is tetragonal, c is cubic, Im is the monoclinic plane integrated intensity, It is the tetragonal integrated intensity, and Ic is the cubic integrated intensity.

TiN generation amount: The mirror-polished sample surface was observed with an optical microscope, and the volume% of TiN was read.

Density of sintered body: Measured by the Archimedes-in-water method.

Solid solution nitrogen amount: Measured by EPMA analysis. (JEOL JXA-860
0S) Example 1 Commercially available 65% by weight of zirconia powder having an average particle diameter of 0.5 μm (0.1 mol% or less of impurities other than 3 mol% Y ₂ O ₃ and Y ₂ O ₃ , manufactured by Sumitomo Chemical Co., Ltd.) and an average particle diameter of 0.1 μm 35% by weight of titanium black powder (Mitsubishi Metals Titanium Black 13M) is mixed and pulverized in a wet ball mill (using ethanol).
A dried and crushed raw material for sintering was obtained. After the sintering raw material thus obtained was preformed by a die press forming machine,
Perform rubber press molding at a pressure of 0 kg / cm ² , sinter the resulting molded body in an electric furnace at a temperature of 1550 ° C in a nitrogen atmosphere for 2 hours, and then perform heat treatment at 1200 ° C for 10 hours. Was.

When the physical properties of the obtained sintered body were measured, the density was 5.43 g / cm ³ ,
Volume resistivity 1 × 10 ^-2 Ω · cm, bending strength 68 kg / mm ² , hardness
1250, a toughness 9.1 MPa · m ^0.5, also was analyzed sintered body, TiN is 16 volume%, the Ti in the zirconia solid solution 1
2.0% by weight, the amount of dissolved nitrogen was 0.26% by weight, and the monocrystalline phase of zirconia was 40% monoclinic, and the rest was cubic and tetragonal.

Example 2 55% by weight of commercially available zirconia powder having an average particle diameter of 0.5 μm (3% by mole or less of impurities other than Y ₂ O ₃ and Y ₂ O ₃ , 0.1% by weight or less, manufactured by Sumitomo Chemical Co., Ltd.) and titanium having an average particle diameter of 0.1 μm After mixing and pulverizing black powder (Mitsubishi Metals Titanium Black 13M) 45% by weight with a wet ball mill (using ethanol),
Drying and crushing yielded a raw material for sintering. After preforming the sintering raw material obtained in this way with a die press molding machine,
Rubber press molding was performed at a pressure of g / cm ² , and the obtained compact was sintered in an electric furnace at a temperature of 1400 ° C. for 4 hours in a nitrogen atmosphere, and then heat-treated at 1100 ° C. for 40 hours. .

When the physical properties of the obtained sintered body were measured, the density was 5.30 g / c.
m ³ , volume resistivity 3 × 10 ^-3 Ω · cm, bending strength 73 kg / mm ² ,
The hardness was 1290 and the toughness was 6.0 MPa · m ^{0.5. When the} sintered body was analyzed, the TiN content was 22% by volume and the T in the zirconia solid solution.
i was 15.2% by weight, the amount of solute nitrogen was 0.33% by weight, the crystal phase of zirconia was 20% monoclinic, and the rest was cubic and tetragonal.

Comparative Example 1 81% by weight of commercially available zirconia powder having an average particle diameter of 0.5 μm (3 mol% or less other than 0.1% by weight of impurities other than Y ₂ O ₃ and Y ₂ O ₃ , manufactured by Sumitomo Chemical) and titanium having an average particle diameter of 0.1 μm After mixing and pulverizing a black powder (Mitsubishi Metals Titanium Black 13M) 19% by weight with a wet ball mill (using ethanol),
Drying and crushing yielded a raw material for sintering. After preforming the sintering raw material obtained in this way with a die press molding machine,
Rubber press molding was performed at a pressure of g / cm ² , and the obtained molded body was sintered in an electric furnace at a temperature of 1550 ° C. for 2 hours in a nitrogen atmosphere.

When the physical properties of the obtained sintered body were measured, the density was 5.82 g / c.
m ³ , volume resistivity> 1Ω · cm, bending strength 30kg / mm ² , hardness
1000, a toughness 3.0 MPa · m ^0., also was analyzed sintered body, TiN 8 volume%, the Ti in the zirconia solid solution 6.4
% By weight, the amount of solute nitrogen was 0.15% by weight, and the crystal phase of zirconia was cubic and tetragonal without any monoclinic crystal being detected.

Comparative Example 2 45% by weight of commercially available zirconia powder having an average particle diameter of 0.5 μm (3 mol% or less than 0.1% by weight of impurities other than Y ₂ O ₃ and Y ₂ O ₃ , manufactured by Sumitomo Chemical Co., Ltd.) and titanium having an average particle diameter of 0.1 μm 55% by weight of black powder (Mitsubishi Metals Titanium Black 13M) is mixed and pulverized with a wet ball mill (using ethanol).
Drying and crushing yielded a raw material for sintering. After preforming the sintering raw material obtained in this way with a die press molding machine,
Rubber press molding was performed at a pressure of g / cm ² , and the obtained molded body was held in an electric furnace at 1550 ° C. for 2 hours in a nitrogen atmosphere at a temperature of 1550 ° C., followed by heat treatment at 1100 ° C. for 40 hours. .

When the physical properties of the obtained sintered body were measured, the density was 5.10 g / c.
m ³ , volume resistivity 4 × 10 ^-3 Ω · cm, bending strength 48 kg / mm ² ,
The hardness was 1249 and the toughness was 4.6 MPa · m ^{0.5. When the} sintered body was analyzed, the TiN was 26% by volume, and the T
i was 18.6% by weight to form ZrTiO ₄ , and the crystal phase of zirconia was 12% monoclinic and the rest was cubic and tetragonal.

Example 3 Commercially available 55% by weight of zirconia powder having an average particle diameter of 1.0 μm (not including Y ₂ O _{3 as} a stabilizer, impurities of 0.1% by weight or less, manufactured by Sumitomo Chemical Co., Ltd.) and titanium black powder having an average particle diameter of 0.1 μm (Mitsubishi Metals Titanium Black 13M) 45% by weight was mixed with a wet ball mill (using ethanol), pulverized, dried and disintegrated to obtain a raw material for sintering. After the sintering raw material thus obtained was preformed by a die press forming machine,
Rubber press molding was performed at a pressure of 500 kg / cm ² , and the obtained compact was sintered in an electric furnace at a temperature of 1400 ° C. for 4 hours in a nitrogen atmosphere.

When the physical properties of the obtained sintered body were measured, the density was 5.28 g / c.
m ³ , volume resistivity 3 × 10 ⁻³ Ω · cm, bending strength 60 kg / mm ² ,
The hardness was 950 and the toughness was 5.3 MPa · m ^{0.5. When the} sintered body was analyzed, the TiN was 22% by volume, and the Ti in the zirconia solid solution was
Was 15.2% by weight, the amount of dissolved nitrogen was 0.33% by weight, and the crystal phase of zirconia was 50% monoclinic and the rest was cubic and tetragonal.

Example 4 Commercially available zirconia powder having an average particle diameter of 1.0 μm (not including Y ₂ O _{3 as} a stabilizer, impurities of 0.1% by weight or less, manufactured by Sumitomo Chemical Co., Ltd.) 65% by weight and titanium black powder having an average particle diameter of 0.1 μm (Mitsubishi Metals Titanium Black 13M) 35% by weight and 28.5% by weight of titanium nitride (made by Nippon Shinmetal) with an average particle size of 13μm
(For zirconia powder and titanium black powder) mixed and pulverized by wet ball mill (using ethanol)
Drying and crushing yielded a raw material for sintering. After preforming the sintering raw material obtained in this way with a die press molding machine,
Rubber press molding was performed at a pressure of g / cm ² , and the obtained molded body was sintered in an electric furnace at a temperature of 1550 ° C. for 2 hours in a nitrogen atmosphere.

When the physical properties of the obtained sintered body were measured, the density was 5.37 g / c.
m ³ , volume resistivity 5 × 10 ^-4 Ωcm, bending strength 51 kg / mm ² ,
The hardness was 1097 and the toughness was 5.2 MPa · m ^{0.5. When the} sintered body was analyzed, the TiN was 40% by volume and the T in the zirconia solid solution was 40%.
i was 12.2% by weight, the amount of dissolved nitrogen was 0.26% by weight, the crystal phase of zirconia was 35% monoclinic, and the rest was cubic and tetragonal.

Examples 5 to 22, Comparative Example 7 A zirconia powder containing the same stabilizer as that used in Example 1 was used, and titanium nitride similar to that used in Example 4 was added in the amount shown in Table 1. A sintered body was obtained in the same manner as in Example 1 except that it was added in a ratio, and the physical properties of the sintered body were measured. Table 1 shows the results.

Comparative Example 3 Commercially available average particle diameter 0.5μm zirconia powder (3 _{mol% Y 2 O 3, Y 2} O 3 0.1 wt% impurities other than the following, manufactured by Sumitomo Chemical Co., Ltd.) Other performs only material preparation in Example 1 A sintered body was obtained in the same manner as described above, and the physical properties of the sintered body were measured. Table 1 shows the results.

Comparative Example 4 A sintered body was obtained in the same manner as in Example 1 except that in addition to zirconia powder in Comparative Example 3, titanium nitride similar to that used in Example 4 was added at the ratio shown in Table 1. The physical properties of the sintered body were measured. Table 1 shows the results.

Comparative Example 5 The raw material powder used in Comparative Example 4 was hot-pressed to 1550.
The temperature was maintained at ℃ for 0.5 hour to obtain a sintered body.

The physical properties of this sintered body were measured. Table 1 shows the results.

Comparative Example 6 In Example 2, the titanium black was changed to an average particle diameter of 0.3 μm.
A sintered body was obtained in the same manner as in Example 2 except that the titanium oxide was replaced with Titanium Oxide (manufactured by Ishihara Sangyo Co., Ltd., Taipaek A-100), and the heat treatment was not performed. Table 1 shows the results.

Claims (1)

(57) [Claims] The sintered body after sintering is composed of 60 to 90% by volume of a zirconium oxide solid solution and 10 to 40% by volume of titanium nitride, and the solid solution is composed of zirconium oxide and titanium as 0%.
<Production of a conductive zirconia sintered body characterized in that zirconium oxide powder and titanium suboxide powder are mixed and formed so as to be made of a titanium oxide containing Ti ≦ 16% by weight, and then sintered under a nitrogen atmosphere. Method.