JP4460918B2 - Alumina / zirconia ceramics and process for producing the same - Google Patents

Description

  The present invention relates to alumina / zirconia ceramics, and particularly to alumina / zirconia ceramics suitably used for various structural members, cutting tools, medical instruments, and biomaterials, and a method for producing the same.

  In recent years, alumina and zirconia-based oxide ceramics have been widely used as structural members that require high strength, wear resistance, and corrosion resistance. In particular, alumina / zirconia ceramics containing alumina and zirconia at a certain ratio are attracting attention because of the effect of refining crystal grains, higher strength than the individual ceramics can be obtained (see Non-Patent Document 1). .

  However, the above-mentioned alumina / zirconia ceramics have a drawback of low fracture toughness.

On the other hand, it is known that the strength and fracture toughness can be improved by giving anisotropy to the particle shape of the sintered body. For example, Mn is added to the (12Ce) ZrO ₂ -Al ₂ O ₃ composite material, It has been reported that fracture toughness is greatly improved by generating a compound MnCeAl ₁₁ O ₁₉ having a magnetoplumbite structure (Non-patent Document 2). It has also been reported that fracture toughness is greatly improved by the same mechanism by adding Mg instead of the above Mn (Non-patent Document 3).
Ryoichi Shikata et al., “Powder and Powder Metallurgy”, Powder Powder Metallurgy Association Jing-Fong Tsai, “J.Am.Ceram.Soc”, American Ceramic Society Masahiro Nawa et al., “Ceramics”, Ceramics Association

  However, even if a compound having a magnetoplumbite structure disclosed in Non-Patent Documents 2 and 3 is precipitated on alumina / zirconia ceramics, it is required in the fields of cutting tools, medical instruments, biomaterials, and the like. The high strength, high toughness, and wear resistance cannot be satisfied. For example, zirconia-rich alumina / zirconia ceramics can improve strength and fracture toughness by precipitating a compound of magnetoplumbite structure, but it has low hardness, especially wear resistance like artificial joints The use as a material that requires properties is limited. On the other hand, alumina-rich alumina and zirconia ceramics show improvement in hardness and strength, but the effect of improving fracture toughness is not sufficient, and further improvement in fracture toughness is required to apply to the above applications. .

  Therefore, the object of the present invention is to improve all the characteristics of strength, wear resistance (hardness) and toughness, and particularly suitable for various structural members, cutting tools, medical instruments and biomaterials. The object is to provide alumina / zirconia ceramics.

According to the present invention, in an alumina / zirconia ceramic containing Al ₂ O ₃ particles and ZrO ₂ particles,
The Al containing terms _{of Al} 2 _{O 3} at 65 wt% or more, comprising 4 to 34 wt% of Zr in terms of ZrO _2, comprising 0.1 to 4 wt% of Ce in terms of CeO _2, oxidizing at least one of Mn or Mg Composite oxidation containing 0.01 to 1.5% by mass in terms of product and 0.6 to 4.5% by mass of SiO _{2 and} having at least one of Mn or Mg and Ce and Al as constituent elements Alumina-zirconia ceramics characterized by containing acicular crystals of the object are provided.

In the alumina-zirconia ceramics of the present invention,
(1) The composite oxide is a composite oxide having a magnetoplumbite type structure represented by the formula: Mn (Mg) CeAl ₁₁ O ₁₉
(2) Further, 0.22 to 4.5% by mass of TiO ₂ is contained,
(3) The bending strength is 925 MPa or more, the fracture toughness is 5.2 MPa · m ^1/2 or more, and the Vickers hardness is 1720 or more,
Is preferred.

Moreover, according to the present invention,
Al is contained in an amount of 65% by mass or more in terms of Al ₂ O ₃ , Zr is contained in an amount of 4 to 34% by mass in terms of ZrO ₂ , Ce is contained in an amount of 0.1 to 4% by mass in terms of CeO ₂ , and at least one of Mn or Mg Is prepared as a raw material powder containing 0.01 to 1.5% by mass in terms of oxide and further containing 0.6 to 4.5% by mass in terms of oxide,
The raw material powder is molded into a predetermined shape,
The obtained molded body was fired at a temperature range of 1300 ° C to 1500 ° C,
Furthermore, hot isostatic pressing at a temperature lower by 30 ° C. or more than the firing temperature,
A method for producing an alumina / zirconia ceramics is provided.

In the above manufacturing method,
(1) The raw material powder further contains 0.22 to 4.5 mass% of Ti in terms of oxide,
Is desirable.

In the present invention, in an alumina-rich alumina / zirconia ceramic, a needle-like crystal of a composite oxide having at least one of Mn or Mg and Ce and Al as constituent elements, for example, represented by the formula: Mn (Mg) CeAl ₁₁ O ₁₉ The composite oxide needle-shaped crystal (shape anisotropic crystal) having a magnetoplumbite structure is precipitated, but the alumina is present in an amount of 65% by mass or more, thereby providing high strength. And high hardness, and the metastabilization of tetragonal ZrO ₂ by Ce and the generation of anisotropic crystals are promoted by a predetermined amount of SiO ₂ derived from the sintering aid. As a result, the fracture toughness is improved. Improvements are also achieved. For example, even if anisotropic crystals as described above are precipitated, in a system in which SiO ₂ does not exist, the metastabilization of tetragonal ZrO ₂ and the generation of anisotropic crystals become insufficient, resulting in high toughness. Cannot be achieved, and the increase in strength is insufficient.

In the present invention, as a sintering aid, by using the TiO ₂ in addition to SiO _2, it can densify the sintered body at a low temperature, fine, further high strength by dense tissue formation Achieved.

Therefore, the alumina / zirconia ceramic of the present invention has characteristics of high strength, high hardness, excellent wear resistance, and high toughness. For example, the alumina / zirconia ceramic of the present invention has a bending strength of 925 MPa or more, a fracture toughness of 5.2 MPa · m ^1/2 or more, and a Vickers hardness of 1720 or more, and is particularly high like an artificial bone head. It is suitably used for biomaterials that require strength, high toughness, and wear resistance.

(Alumina / zirconia ceramics)
The ceramic of the present invention contains Al ₂ O ₃ particles and ZrO ₂ particles as basic components, but has an alumina-rich composition, and Al is 65 in terms of oxide (Al ₂ O ₃ ). It is contained in an amount of not less than mass%, preferably 75 to 85 mass%, and Zr is contained in an amount of 4 to 34 mass%, preferably 15 to 25 mass% in terms of oxide (ZrO ₂ ). That is, by containing 65% by mass or more of Al ₂ O ₃ , it is possible to achieve an effect of high strength and high hardness. When the content of ZrO ₂ is less than 4% by mass, the strength is lowered, and low toughness is achieved. On the other hand, if it exceeds 34% by mass, the hardness decreases due to a decrease in Young's modulus.

In the ceramic of the present invention, Ce is contained in an amount of 0.1 to 4% by mass, preferably 0.5 to 3% by mass in terms of oxide (CeO ₂ ), and Mn or Mg is an oxide ( MnO or MgO) is contained in an amount of 0.01 to 1.5% by mass, preferably 0.1 to 1% by mass. That is, by the presence of Ce in such an amount, the solid solution of CeO ₂ to ZrO ₂ proceeds during firing, tetragonal ZrO ₂ is metastable, improvement and enhancement of fracture toughness of strength is achieved Yes. Further, since Ce and Mn or Mg coexist, a part of Ce ⁴⁺ is reduced to Ce ³⁺ during firing, which will be described later, and a magnetoplumbite type represented by the formula: Mn (Mg) CeAl ₁₁ O ₁₉ A complex oxide needle-like crystal having a structure is deposited. This acicular crystal is usually a shape anisotropic crystal having an aspect ratio of 4 or more, and the fracture toughness is significantly improved by the crack deflection effect of such a shape anisotropic crystal. For example, if the Ce content or the Mn or Mg content is smaller than the above range, the metastabilization of tetragonal ZrO ₂ and the precipitation of shape anisotropic crystals become insufficient, and properties such as fracture toughness and strength are improved. It will be insufficient. On the other hand, if the Ce content or the Mn or Mg content is larger than the above range, the amount of alumina or zirconia is reduced, resulting in insufficient strength and hardness.

Furthermore, ceramics of the present invention, the SiO ₂ 0.6 to 4.5 wt%, containing in particular 1 to 3 wt%. That is, this oxide component is derived from the sintering aid, and by containing such a component, an appropriate liquid phase is formed at the time of firing, and the growth of anisotropic crystal particles is promoted. For example, the above-mentioned magnetoplumbite type complex oxide needle-like crystals are formed in an amount of about 1 to 20% by volume, and the fracture toughness is remarkably improved. In the case of not containing SiO ₂ , the amount of anisotropic crystal particles deposited becomes insufficient, and the fracture toughness cannot be improved.

In the present invention, the TiO ₂ 0.22-4.5 wt%, it is preferable to contain in particular from 0.22 to 1% by weight. This oxide is also derived from the sintering aid, and such a component makes it possible to densify the sintered body under low temperature conditions, and brings about a significant improvement in strength and hardness, particularly strength. In particular a part of Ti, precipitated in the form of an oxide or a composite oxide in solid solution in Al ₂ O _3, or crystal grains of Al ₂ O _3, reinforcing thereby the solid solution, remarkable by the effect of fine particle dispersion strengthening An increase in strength is brought about.

The alumina / zirconia ceramic of the present invention having the composition as described above has a bending strength of 925 MPa or more, a fracture toughness of 5.2 MPa · m ^1/2 or more, and a Vickers hardness of 1720 or more, as will be apparent from Examples described later. In particular, those containing TiO ₂ have a remarkably high bending strength of 1060 MPa or more. Such an alumina / zirconia ceramic of the present invention is suitably used for various structural members, cutting tools, medical instruments and biomaterials, and is particularly suitable as a biomaterial such as an artificial bone head.

(Alumina / zirconia ceramics manufacturing method)
The above-described alumina / zirconia ceramic of the present invention is produced by preparing a raw material powder having a predetermined composition, forming it into a predetermined shape, firing and hot isostatic pressing.

The raw material powder used includes various metal components so that a sintered body having the above-described composition can be obtained. For example, Al component serving as an Al ₂ O ₃ source, Zr component serving as a ZrO ₂ source, and a composite oxide The Ce-like crystal particle source and the Mn or Mg content, and the Si content as a sintering aid, and further the Ti content. These metal components are generally used in the form of oxides, but are not limited to oxides as long as they form the above-mentioned various oxides by firing. Or in the form of a salt such as carbonate. Further, the Ce component can be used as a powder previously dissolved in ZrO ₂ , or can be used as a powder separate from ZrO ₂ (for example, CeO ₂ powder). In particular, it is preferable to use a solid solution of Ce in advance in ZrO ₂ in terms of increasing the bending strength and hardness. The raw material powder is prepared by mixing these metal powders, and the content ratio of various metals in the raw material powder is Al, Zr, Ce, Mn or Mg, Si, and further the amount of Ti is an oxide. In conversion, it is set so as to correspond to the composition of the sintered body described above. The average particle size of the raw material powder is generally preferably 1.0 μm or less.

  The molding using the raw material powder is carried out by preparing a slurry or paste of the raw material powder or a powder obtained by drying these using a solvent such as water or an organic solvent, an organic binder, etc. It is also possible to use a paste or powder. Further, as the forming means, means known per se such as press molding, casting, cold isostatic pressing, or cold isostatic treatment can be employed.

The molded body is fired at a temperature in the range of 1300 to 1500 ° C., particularly 1300 to 1490 ° C., thereby promoting the grain growth of the magnetoplumbite type complex oxide acicular crystals that are anisotropic crystal grains. It can be densified. For example, when the calcination at a temperature higher than 1500 ° C., by monoclinic ZrO ₂ amount by grain growth of ZrO ₂ is increased, decrease in strength and hardness is provided. Further, densification becomes difficult by firing at a temperature lower than 1300 ° C.

As already described, in the present invention, an appropriate amount of liquid phase is formed by using a predetermined amount of SiO ₂ as a sintering aid, and the magnetoplumbite type complex oxide that is an anisotropic crystal particle is formed. Grain growth of acicular crystals is promoted, and further, due to the effects of solid solution strengthening and fine particle dispersion strengthening by using TiO ₂ , firing in a relatively low temperature region is excellent in fracture toughness and high in density, A sintered body with high hardness can be obtained.

  The baking time in the above temperature range may be such that the relative density by the Archimedes method is 95% or more, and is usually about 1 to 5 hours.

  The hot isostatic pressure treatment performed following the firing is performed at a temperature that is 30 ° C. or more lower than the firing temperature, preferably 50 ° C. or more, and more preferably 100 ° C. or more, whereby alumina or zirconia. Can be used to produce dense alumina / zirconia ceramics that suppress the growth of anisotropic grains of alumina. As already mentioned, this sintered body has high toughness, high strength, and high hardness. It has characteristics.

  The hot isostatic pressure treatment atomizes alumina or zirconia in a short time, and therefore the lower limit temperature is usually 1200 ° C. or higher, particularly 1250 ° C. or higher. It may be performed for about 2 hours.

Al ₂ O ₃ powder with a purity of 99.95% by mass and an average particle size of 0.22 μm, ceria-stabilized zirconia powder with a purity of 99.95% by mass and an average particle size of 0.4 μm, an average particle size of 0.6 μm Mn _{(OH) 2} powder, Mg _{(OH) 2} powder having an average particle diameter of 0.6 .mu.m, SiO ₂ powder having an average particle diameter of 0.5 [mu] m, and TiO ₂ having an average particle size of 0.1μm compositions shown in Table 1 Weighed and mixed to obtain a mixed powder. And this mixed powder was die-molded at a pressure of 1 t / cm ² and further subjected to hydrostatic pressure treatment at a pressure of 3 t / cm ² to produce a molded body. Firing was performed for 2 hours and hot isostatic firing (HIP) for 1 hour.

For each sintered body obtained, bending strength (JIS R 1601), fracture toughness (JIS R
1607), and Vickers hardness (JIS 2244) was measured. The fracture toughness value was measured by the IF method. The results are shown in Table 2.

Compared with the Al ₂ O ₃ — (10Ce) ZrO ₂ composite material (sample 10) and the material obtained by adding Mn or Mg to the material of sample 10 (samples 8, 9, 11, and 12), SiO ₂ as a sintering aid. In the material (samples 1 to 4) to which is added, high fracture toughness is obtained, and the strength and hardness are equal or higher.

Further, in Samples 5 to 7 in which either one or both of SiO ₂ and MnO or MgO are added to the Al ₂ O ₃ — (10Ce) ZrO ₂ composite material, and TiO ₂ is further added, the strength is greatly improved. ing.

Claims (6)

In the alumina / zirconia ceramics containing Al ₂ O ₃ particles and ZrO ₂ particles,
The Al containing terms _{of Al} 2 _{O 3} at 65 wt% or more, comprising 4 to 34 wt% of Zr in terms of ZrO _2, comprising 0.1 to 4 wt% of Ce in terms of CeO _2, oxidizing at least one of Mn or Mg Composite oxidation containing 0.01 to 1.5% by mass in terms of product and 0.6 to 4.5% by mass of SiO _{2 and} having at least one of Mn or Mg and Ce and Al as constituent elements Alumina-zirconia-based ceramics characterized by containing needle-like crystals. The composite oxide has the formula: Mn (Mg) CeAl ₁₁ alumina zirconia ceramics according to claim 1, which is a complex oxide having a magnetoplumbite-type structure represented by O _19. Further alumina zirconia ceramics according to claim 1 or 2 containing a TiO ₂ 0.22-4.5 mass%. The alumina / zirconia ceramic according to any one of claims 1 to 3, having a bending strength of 925 MPa or more, a fracture toughness of 5.2 MPa · m ^1/2 or more, and a Vickers hardness of 1720 or more. Al is contained in an amount of 65% by mass or more in terms of Al ₂ O ₃ , Zr is contained in an amount of 4 to 34% by mass in terms of ZrO ₂ , Ce is contained in an amount of 0.1 to 4% by mass in terms of CeO ₂ , and at least one of Mn or Mg Is prepared as a raw material powder containing 0.01 to 1.5% by mass in terms of oxide and further containing 0.6 to 4.5% by mass in terms of oxide,
The raw material powder is molded into a predetermined shape,
The obtained molded body was fired at a temperature range of 1300 ° C to 1500 ° C,
Furthermore, hot isostatic pressing at a temperature lower by 30 ° C. or more than the firing temperature,
A process for producing alumina-zirconia ceramics.   The said raw material powder is a manufacturing method of Claim 5 which contains further 0.22-4.5 mass% of Ti in conversion of an oxide.