JP2002284575A - Zirconia composite sintered compact, its manufacturing method and precise machinary part using it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ceramic having low specific gravity, low thermal expansion coefficient, and high Young's modulus with excellent productivity. SOLUTION: One or more kinds among silicon nitride, boron carbide, and silicon carbide are contained in potassium zirconium phosphate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zirconia composite sintered body, a method for producing the same, and a component for precision equipment using the same.

[0002]

2. Description of the Related Art Conventionally, parts for precision equipment are lightweight, and have small dimensional and shape changes due to temperature changes.
Ceramics such as alumina and silicon nitride have been frequently used.

[0003] These ceramics such as alumina and silicon nitride have small specific gravities of 3.0 to 3.8 as compared with metals, are lightweight, and have a coefficient of thermal expansion from room temperature to 80 ° C of 5.2 × 10 ^-6 / cm. ° C and 1.5 × 10 ^-6 / ° C.

[0004] However, with further miniaturization of equipment and higher precision of precision equipment, there is a demand for lighter materials having low thermal expansion properties.

Therefore, it has been proposed to use cordierite ceramics having low thermal expansion characteristics.

[0006] Such cordierite ceramics are:
After mixing and synthesizing magnesia, alumina, and silica powder to form cordierite powder or cordierite, adding calcia, silica, magnesia, etc. as a sintering aid and molding into a predetermined shape, at a temperature of 1000 to 1400 ° C. The cordierite ceramic obtained by calcination has a specific gravity of 2.6 to 2.7, a coefficient of thermal expansion of 0.2 × 10 ⁻⁶ / ° C., and a Young's modulus of 70 to 90 GPa.
(Japanese Patent Publication No. 57-3629;
29760).

Further, after adding a rare earth oxide as a sintering aid and forming it into a predetermined shape,
Has a specific gravity of 2.7 and a thermal expansion coefficient of 0.5.
It has a density of × 10 ⁻⁶ / ° C. and a Young's modulus of 130 GPa, and is expected to prevent deformation of precision equipment and improve the natural frequency (see JP-A-11-255557).

[0008]

In recent years, miniaturization and precision of precision equipment and the like have progressed, and cordierite ceramics having low thermal expansion characteristics have been studied in order to satisfy particularly high positioning accuracy. .

However, since the conventional cordierite ceramics have a low Young's modulus of 70 to 90 GPa, when they are used as parts for precision equipment, the influence of errors due to deformation due to deflection and occurrence of resonance due to lowering of the natural frequency of the member is low. It had the disadvantage of increasing.

Further, cordierite ceramics using a rare earth element oxide as a sintering aid have a small specific gravity, a small coefficient of thermal expansion and an excellent Young's modulus, but the cordierite ceramics have a low sintering temperature. Since the width is as narrow as about 50 ° C., the productivity was not stable and the cost was high.

The present invention has been made in view of the above-mentioned drawbacks, and has as its object to provide a ceramic which has a low specific gravity, a low coefficient of thermal expansion, a high Young's modulus and a stable productivity.

[0012]

SUMMARY OF THE INVENTION The present invention is characterized in that potassium zirconium phosphate contains at least one of silicon nitride, boron carbide and silicon carbide.

Further, the present invention is characterized in that at least one of silicon nitride, boron carbide and silicon carbide is contained in an amount of 20 to 70 parts by weight based on 100 parts by weight of the potassium zirconium phosphate. It is.

Further, the zirconia composite sintered body of the present invention is obtained by adding and mixing at least one powder of silicon nitride, boron carbide and silicon carbide to potassium zirconium phosphate powder having a particle size of 1 μm or less. The obtained powder is subjected to pressure molding, and in an atmosphere having an oxygen partial pressure of 0.01 MPa or less, 140
And baking at a temperature of 0 to 1600 ° C.

Still further, the present invention is characterized in that a component for precision equipment is formed using the zirconia composite.

According to the zirconia composite sintered body of the present invention, since specific potassium zirconium phosphate contains at least one of silicon nitride, boron carbide and silicon carbide, the specific gravity and the coefficient of thermal expansion are small and high. It can be a Young's modulus.

The above-mentioned potassium zirconium phosphate 1
Since at least one of silicon nitride, boron carbide and silicon carbide is contained in an amount of 20 to 70 parts by weight with respect to 00 parts by weight, thermal stability is provided and the Young's modulus can be further improved.

Further, the zirconia composite sintered body of the present invention is obtained by adding and mixing at least one powder of silicon nitride, boron carbide and silicon carbide to potassium zirconium phosphate powder having a particle size of 1 μm or less. The obtained powder is subjected to pressure molding, and in an atmosphere having an oxygen partial pressure of 0.01 MPa or less, 140
Since it comprises the step of firing at a temperature of 0 to 1600 ° C., it has high thermal stability and high Young's modulus, suppresses the occurrence of cracks, and has a low porosity and a high strength zirconia composite sintered body. Obtainable.

Furthermore, the zirconia composite sintered body of the present invention is excellent in dimensional stability against temperature changes, has very little influence of deformation and vibration, and is suitably used as a high-precision component for precision equipment. be able to.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention has a low specific gravity, a low coefficient of thermal expansion and a high Young's modulus by adding at least one of silicon nitride, boron carbide and silicon carbide to potassium zirconium phosphate. This is to obtain a zirconia composite sintered body.

The potassium zirconium phosphate is obtained by mixing potassium oxide (K ₂ O), zirconia (ZrO ₂ ) and phosphorus oxide (P ₂ O ₅ ) in a weight ratio of K ₂ O: ZrO ₂ : P ₂ O ₅ =
1: 4: 3, and the chemical formula
It is represented by Zr ₂ (PO ₄ ) ₃ . This potassium zirconium phosphate has a specific gravity of 3.2 and a thermal expansion coefficient of -2.7 to -2.5.
× 10 ⁻⁶ / ° C., having a material property of Young's modulus of 120 to 130 GPa.
By containing at least one of boron carbide and silicon carbide, a zirconia composite having a small specific gravity and a small coefficient of thermal expansion and having a high Young's modulus can be obtained.

This is because, in the composite of ceramics, the material properties show values in accordance with the compounding ratio. The potassium zirconium phosphate is added to silicon nitride (specific gravity 3.0, thermal expansion coefficient 1.5 to 2. 0 × 10 ^-6 / ° C, Young's modulus 300G
Pa), boron carbide (specific gravity 3.5, coefficient of thermal expansion 2.0 to
3.0 × 10 ⁻⁶ / ° C., Young's modulus 450 GPa), silicon carbide (specific gravity 3.1, coefficient of thermal expansion 2.0 to 3.0 × 10 ⁻⁶ /)
° C, Young's modulus 400 GPa), the specific gravity is 2.8 to 3.2, and the thermal expansion coefficient is -1.5 × 1.
0 ^{-6 to} 1.5 × 10 ^-6 / ° C, Young's modulus is 145 to 230
GPa.

The content of at least one selected from the group consisting of silicon nitride, boron carbide and silicon carbide is preferably 20 to 70 parts by weight based on 100 parts by weight of zirconium phosphate. If the content is less than 20 parts by weight, the Young's modulus of the obtained zirconia composite may decrease, while if it exceeds 70 parts by weight, it becomes difficult to densify the zirconia composite sintered body. Therefore,
The content of at least one selected from silicon nitride, boron carbide and silicon carbide is preferably 20 to 70 parts by weight, more preferably 25 to 60 parts by weight.

The contents of silicon nitride, boron carbide and silicon carbide in the zirconia composite sintered body can be measured by X-ray fluorescence analysis.

Based on the above structure, the specific gravity of the zirconia composite sintered body is 2.8 to 3.2, and the coefficient of thermal expansion from room temperature to 80 ° C. is −1.3 × 10 ^{−6 to} 1.3 ×. 10 ^-6 /
C. and a Young's modulus of 150 GPa or more, and a dense, high-strength zirconia composite sintered body having a lower specific gravity, a lower coefficient of thermal expansion, a higher Young's modulus, and the like can be obtained.

Next, a method for producing the zirconia composite sintered body of the present invention will be described.

First, zirconia powder having a specific surface area of 10 to 11 m ² / g and a particle size of 0.9 to 1.1 μm,
m ² / g, ammonium dihydrogen phosphate powder having a particle size of 2 to 3 μm, and potassium carbonate powder having a specific surface area of 1 to ² m ² / g, and a particle size of 2 to 4 μm, the composition ratio of which is K ₂ O.4ZrO ₂ .3P ₂
A predetermined amount is blended so as to be O ₅ .

Next, the above blended powder is mixed in a ball mill and heated stepwise at 200 ° C. and 900 ° C.
Finally, it is fired at 1400 ° C. for 4 hours to obtain a potassium zirconium phosphate raw material powder.

The obtained potassium zirconium phosphate raw material powder is pulverized by a ball mill into fine powder having a particle size of 1 μm or less, and sintering of magnesium oxide, zinc oxide or the like is performed with respect to 100 parts by weight of the obtained fine powder of potassium zirconium phosphate. 2 to 5 parts by weight of an auxiliary agent and at least one of silicon nitride, boron carbide and silicon carbide are added and mixed in a predetermined ratio.

In order to prevent the occurrence of microcracks in the obtained sintered body, it is preferable to mix the raw materials with a pulverizer to reduce the particle diameter of the mixed powder to 1 μm or less.

Thereafter, the mixed powder is formed into a desired shape by, for example, die pressing, casting, cold isostatic pressing, extrusion, or the like.
In a low oxygen atmosphere with an oxygen partial pressure of 0.01 MPa or less, 140
Baking at a temperature of 0 to 1600 ° C.

The firing temperature is 1400-160.
By setting the temperature in the range of 0 ° C., the pore occupancy can be reduced, and a dense and high-strength sintered body can be obtained. When the firing temperature is lower than 1400 ° C., the pore occupancy of the sintered body exceeds 0.2%. On the other hand, when the firing temperature exceeds 1600 ° C., zircon is generated by the reaction between zirconium phosphate and zirconia, and the zirconia phase is formed. This is because there is a possibility that the strength may be reduced by the stress relaxation effect due to the transformation. Therefore, the firing temperature is 1400-1600 ° C.,
The temperature is preferably in the range of 50 to 1580 ° C.

The atmosphere during the firing is an oxygen partial pressure of 0.0
The atmosphere is preferably a low oxygen atmosphere of 1 MPa or less, for example, a nitrogen atmosphere, a nitrogen / oxygen mixed atmosphere, an inert gas atmosphere such as argon, a vacuum atmosphere, or a method in which the entire molded body is buried in carbon or non-oxide powder and fired. A dense sintered body can be obtained by burying or the like. If the oxygen partial pressure exceeds 0.01 MPa, the occupancy of pores in the sintered body increases significantly. Therefore, the oxygen partial pressure is preferably 0.01 MPa or less, more preferably 0.005 MPa or less, and 0.001 MPa or less.

By firing at a low temperature in such a low oxygen concentration atmosphere, the porosity of the zirconia composite sintered body is reduced to 0.1%.
It is possible to obtain a zirconia composite having a density of 2% or less, a bending strength of 150 MPa or more, and a fracture toughness of 2.0 MPa · √m or more and a small number of defects and melting. The surface smoothness is improved, and a mirror surface state is easily obtained.

The zirconia composite sintered body obtained as described above has a specific gravity of 2.8 to 3.2 and a thermal expansion coefficient of -1.5.
~ 1.5 × 10 ^-6 / ° C, Young's modulus is 145 GPa
Since it has the above high value, weight reduction becomes possible,
Extremely small thermal deformation, excellent dimensional stability against temperature changes, and extremely little influence of deformation and vibration, for precision equipment such as spacers, columns and columns of three-dimensional measuring instruments that require precise positioning accuracy It can be suitably used as a part.

In addition, since it has a dense and smooth sintered body surface and high fracture toughness and bending strength, the range of application as a structural material having a complicated shape such as a lattice-like structure is widened, and The degree of freedom of design is increased, and labor and space savings such as weight reduction and hollowing are possible.

The zirconia composite sintered body of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the gist of the present invention.

[0038]

EXAMPLE First, the specific surface area was 10 m ² / g, and the particle size was 0.9 μm.
m zirconia powder, specific surface area 1.5 m ² / g, particle size 3
A predetermined amount of μm ammonium dihydrogen phosphate powder and potassium carbonate powder having a specific surface area of 1.2 m ² / g and a particle size of 4 μm are blended so that the composition ratio becomes K ₂ O.4ZrO ₂ .3P ₂ O ₅ , After mixing in a ball mill, the mixture is heated stepwise to 200 ° C. and 900 ° C., and finally fired at 1400 ° C. for 4 hours to obtain a potassium zirconium phosphate raw material powder.

Next, the obtained potassium zirconium phosphate raw material powder was pulverized by a ball mill into fine powder having a particle size of 0.3 to 1 μm, and this fine powder was mixed with silicon nitride (S) at a ratio shown in Table 1.
i ₃ N ₄ ), boron carbide (B ₄ C), silicon carbide (SiC)
And at least one selected from the group consisting of zinc oxide (Zn
A sintering aid of O) or magnesium oxide (MgO) was blended and mixed for 72 hours by a vibration mill to obtain a zirconia composite powder. After the granulation, a compact in the shape of a bending test specimen was obtained by dry press molding.

As a comparative example, a compact was prepared by mixing only the sintering aid with the above-mentioned potassium zirconium phosphate raw material powder.

Thereafter, each compact was fired under the firing conditions shown in Table 1, and the characteristics of the sintered body were evaluated.

The specific gravity was measured by Archimedes' method, and the coefficient of thermal expansion was measured according to JIS R 1618 (1994).
The Young's modulus was measured according to JIS R 1602 (1995). Further, the pore occupancy ratio is obtained by processing any one surface of the sintered body into a mirror surface, observing the mirror surface at a magnification of 200 times, and expressing the ratio of the pore area to the observation area, and assuming that the pore area is a circle. The bending strength is calculated according to JIS R 160
1 (1995), the four-point bending test method, and the fracture toughness
It was evaluated by the IF method according to IS R 1607 (1995).

Table 1 shows the results.

[0044]

[Table 1]

As can be seen from Table 1, the sample of the present invention in which potassium zirconium phosphate contains at least one selected from silicon nitride, boron carbide and silicon carbide (N
o. 1 to 35) have a specific gravity of 3.2 or less and a thermal expansion coefficient of -1.
5 × 10 ^{-6 to} 1.5 × 10 ^-6 / ° C, Young's modulus 145GP
a, a pore occupancy of 0.1% or less, a four-point bending strength of 150 MPa or more, and a fracture toughness of 2.0 MPa · √.
m and a low specific gravity, a coefficient of thermal expansion, a high Young's modulus, and a dense and high-strength sintered body could be obtained.

Particularly, a sample (No. 2) in which the total content of silicon nitride, boron carbide and silicon carbide is 20 to 70% by weight based on 100% by weight of potassium zirconium phosphate.
, 14, 17 to 22, 25 to 32, 34, and 35) have a thermal expansion coefficient of −1.3 × 10 ^{−6 to} 1.3 × 10 ⁻⁶ / ° C. and a Young's modulus of 150 GPa or more. Coefficient is low,
It was found to have a high Young's modulus.

On the other hand, the sample containing no silicon nitride, boron carbide or silicon carbide (No. 36) has a coefficient of thermal expansion of -2.6 × 10 ⁻⁶ / ° C. and a Young's modulus of 127 GP.
a was found to be extremely low.

[0048]

According to the zirconia composite sintered body of the present invention, the specific gravity and the coefficient of thermal expansion are increased because potassium zirconium phosphate contains at least one of silicon nitride, boron carbide and silicon carbide. A sintered body having a low and high Young's modulus can be obtained.

According to the zirconia composite sintered body of the present invention, at least one of silicon nitride, boron carbide, and silicon carbide is added in an amount of 20 to 70 parts by weight based on 100 parts by weight of the potassium zirconium phosphate. Due to the inclusion, the thermal expansion coefficient can be further reduced and a high Young's modulus can be obtained.

Further, the zirconia composite sintered body of the present invention is obtained by adding and mixing at least one powder of silicon nitride, boron carbide and silicon carbide to potassium zirconium phosphate powder having a particle size of 1 μm or less. The powder thus obtained was pressed and formed under an atmosphere having an oxygen partial pressure of 0.01 MPa or less.
Since it comprises the step of firing at a temperature of 0 to 1600 ° C., a dense sintered body having high strength and fracture toughness can be obtained.

Further, since the zirconia composite sintered body is used as a component for precision equipment, it is possible to reduce the weight, to have excellent dimensional stability against temperature changes, and to minimize the influence of deformation and vibration. Positioning accuracy can be achieved.

Claims (4)

[Claims] 1. A zirconia composite sintered body in which potassium zirconium phosphate contains at least one of silicon nitride, boron carbide and silicon carbide. 2. The method according to claim 1, wherein at least one of silicon nitride, boron carbide and silicon carbide is contained in an amount of 20 to 70 parts by weight based on 100 parts by weight of the potassium zirconium phosphate. The zirconia composite sintered body according to the above. 3. Addition and mixing of at least one powder of silicon nitride, boron carbide, and silicon carbide to potassium zirconium phosphate powder having a particle size of 1 μm or less, followed by compression molding of the resulting powder, The method for producing a zirconia composite sintered body according to claim 1 or 2, comprising a step of firing at a temperature of 1400 to 1600 ° C in an atmosphere having a pressure of 0.01 MPa or less. 4. A component for precision equipment using the zirconia composite sintered body according to claim 1.