JPH04124058A - Al2o3-based ceramic - Google Patents

Abstract

PURPOSE:To obtain the subject high-strength Al2O3-based ceramics by mixing, in a grain of Al2O3, particles of a compound of a transition element and elements selected from C, N and B in a state where dislocation can be formed. CONSTITUTION:In an Al2O3 grain, a compound, e.g. TiC of a transition element selected from IVa, Va, and VIa groups and elements selected from C, N and B, having >=10mum particle diameter is mixed in an amount of 0.4-40wt.% and the resultant mixture is converted to a state where dislocation is formed in the Al2O3 grain, thus obtaining the objective high-strength Al2O3-based ceramics. A higher strength can be obtained by adding an SiC whisker and/or an Si3N4 whisker in an amount of 3-40wt.% to the Al2O3-based ceramics. In addition, 0.5-10wt.% oxide of Mg, Si, Ca, Ti, Zr, Cr, Ni, Y or a rare earth metal may be added as a sintering assistant, in case of sintering (preferably at >=1600 deg.C) the above-mentioned ceramics.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to Al2O3 ceramics, and more particularly to A120a ceramics with improved strength.

[Prior Art] Al2O ceramics have high strength, excellent corrosion resistance, oxidation resistance, and wear resistance, and are known as engineering ceramics suitable for machine parts, jigs, tools, etc.

In sintering the Al2O3-based ceramics, a temperature is used that does not allow coarse crystals to grow, and is generally sintered at a temperature of about 1500°C.

Furthermore, as a technique for improving the strength and toughness of the Al2O3 ceramics, there is a method of adding SiC whiskers as disclosed in U.S. Pat. requested. However, in this case as well, due to the crystal grain growth suppressing effect of the SiC whiskers, if the SiC whiskers are uniformly dispersed, no growth of coarse crystals will be observed.

[Problems to be Solved by the Invention] Even Al2O3 ceramics having excellent properties as described above are required to have even higher strength, and there is a demand for the development of new techniques for improving strength. The present invention has been made in view of the above-mentioned circumstances, and is based on Al2O having high strength. The aim is to provide ceramics based on

[Means for Solving the Problems] The AI, O, ceramic of the present invention that achieves the above object is composed of one or more transition elements selected from the group consisting of IVa and VIa groups, and C, N, and B. Al2 contains 0.5 to 40% by weight of at least one compound consisting of one or more elements selected from the group consisting of at least one compound selected from the group consisting of:
The gist is that O exists within the grains, and dislocations are further formed within the A1□03 grains. Moreover, even higher strength can be obtained by adding 3 to 40% by weight of SiC whiskers and/or Si3N whiskers to the above-mentioned AI, O, series ceramics.

[Function] As a result of extensive research by the present inventors on techniques for improving the strength of Al2O3 ceramics, we found that coarse crystals grow in A11as ceramics due to conventional high-temperature sintering;
Although it was thought that the strength would decrease, the present invention was based on the knowledge that, depending on the conditions, high-temperature sintering could actually cause dislocations to form within the Al2O3 grains, leading to a significant improvement in strength. The above conditions refer to a compound of one or more transition elements selected from the group consisting of rVa, Va, and Vla groups and one or more elements selected from the group consisting of C1N and B. It is to contain particles with a diameter of 1.0 nm or more (hereinafter sometimes referred to as additive particles), and if the above elements are combined, each has the same effect, so below we will take TiC as a representative example. This will be explained in detail.

First, using Al2O3 mixed with 5% TiC powder,
Sintering was performed by a hot press method at two different sintering temperatures, 00°C and 1850°C, and the mechanical properties thereof were investigated, and the results shown in Table 1 were obtained.

Table 1: Contrary to previous knowledge that high-temperature sintering causes the growth of coarse crystals and reduces strength, TiC-containing Al2O3 sintered at 1850°C has a room-temperature flexural strength of approximately 15 kg. /+u+' was also found to have high strength. Therefore, the inventors of the present application observed the fractured surfaces of both of the above-mentioned ceramics after the room temperature bending strength test using an electron microscope. However, the results are as shown in Figure 2.3. At 1500℃ [Figure 2], the Al2O3 crystal grains are fine, but at 1850℃ [Figure 3], the Al2O3 crystal grains grow and become coarse. , which is similar to conventional findings.

Therefore, TiC-containing AI, O was further sintered at 1850°C using a TEM11 microscope.

The microstructure was investigated. The results are as shown in the photograph substituted for the drawing shown in Figure 1, and A1. O, T existing within the grains
It was found that dislocations were formed starting from iC particles, and that these dislocations contributed to improving the strength of TiC-containing Al2O3 sintered at 1850°C.

In the AI, O, ceramics according to the present invention, Ti
The maximum particle size of the additive particles represented by C becomes a starting point for dislocations that are effective for improving strength, or the maximum particle size is 10 to cause dislocations.
It needs to be equal to or higher than nlD. The maximum particle size is 10
~1000 nl is preferred. As long as there are at least several large-diameter particles as described above, there is no restriction on the particle size of other TiC particles, but - for boat fishing, small particle sizes on the order of nanometers are recommended.

In addition, the content of the above-mentioned additive particles was limited to 0.5 to 40% (meaning by weight %, the same applies hereinafter) because if it is less than 0.5%, the effect of improving strength will hardly be exhibited, and if there is too much. The upper limit was set at 40% because the amount of Al2O3 is relatively reduced and the excellent properties of AlzOs are deteriorated.

The A1□03 series ceramics of the present invention has A1z after sintering.
It is sufficient that dislocations are formed in Os crystal grains, and there are no particular limitations on the sintering conditions or the grain size of Al2O3, but if the sintering temperature is low or the average grain size of Al2O3 used as a raw material is too large, Since dislocations may not be effectively formed, the sintering temperature is preferably as high as 1500°C or higher, and more preferably 1600°C or higher. Further, the average particle size of A1.0' used as a raw material is preferably 10 μm or less, more preferably 0.1 to 3 μm. Conventionally, it has been thought that the smaller the particle size of AI, O, the better for strength and toughness, but even if the particle size of Al2O is relatively large, by adding particles such as TfC, It has been found that Al2O-based ceramics with high strength can be obtained.

Furthermore, in the Al2O3 ceramic according to the present invention, the strength and toughness are significantly improved by adding 3 to 40% of SiC whiskers and/or Si, N4 whiskers. However, if it is less than 3%, sufficient effects cannot be expected.
On the other hand, if it exceeds 40%, the amount of Al2O and the particles to be added will be relatively reduced, which is undesirable.
, Ni, Y, and rare earth element oxides may be added in an amount of 0.5 to 10%.

[Example] A12o3 powder with an average particle size of 0.2 μm was added with an average particle size of 20 μm.
Additive particles such as Or+m TiC were added, and both were stirred and mixed using a wet mill for 20 hours to obtain a mixture. The mixture was dried and granulated using a spray dryer, or whiskers and/or sintering aids were added to the mixture as required, and the mixture was stirred and mixed using a wet mill for 20 hours, and then dried and granulated using a spray dryer. In addition, the above additive particles,
The types and contents of whiskers and sintering aids are shown in Table 2.

The obtained mixed powder was packed into a graphite mold and heated in an Ar air flow for 1
Uniaxial pressure sintering was carried out using a hot press at 850° C., 200 Kg/crm” for 45 minutes to obtain Al2O3 ceramics Examples 1 to 9 according to the present invention.

For the A12o3 ceramics obtained in this way, the bending strength at room temperature, the bending strength at high temperature (1400° C.), and the relative density were measured. The results are also listed in Table 2. As Comparative Example 1, A.
12O, based ceramics were obtained. In addition, Comparative Examples 2 to 4 are 1
Sintering was performed at 500°C, and other than that, an Al2O3-based ceramic was obtained in the same manner as in the above example.

The same measurements as in the example were also carried out on the Al2O ceramic obtained as a comparative example. The results are also listed in Table 2.

Example 1 of Al2O-based ceramics according to the present invention
It can be seen that Samples 9 to 9 all have high relative densities, and both room temperature and high temperature transverse strength are high. On the other hand, in Comparative Example 1, the relative density was low because the amount of SiC whiskers was too large.
Both room temperature bending strength and high temperature bending strength are low. 150 again
Comparative Examples 2 to 4, which were sintered at 0°C, also had A1zOs after sintering.
No dislocations were formed in the crystal grains, and the room temperature flexural strength and high temperature flexural strength were extremely low.

[Effects of the Invention] Since the present invention is configured as described above, the A
Now we can provide I, O, ceramics.

[Brief explanation of drawings]

FIG. 1 is a photograph substituted for a drawing showing the structure of a crystal in which dislocations are formed in the Al2O5-based ceramic according to the present invention;
Figure 2 is a photograph substituted for a drawing showing the crystal structure of AI, O, ceramics sintered at 1500℃, Figure 3 is 18
It is a photograph substituted for a drawing showing the crystal structure of Al2O3-based ceramics sintered at 50°C. Higanjin Kobe Steel Co., Ltd. Figure 1 Kawa C-no) Kou 114 0.5 μm Figure 2 Figure 3 Procedural amendment (method) % formula % Name of the invention Relationship to the Al2O3 ceramics amendment person case

Claims (3)

[Claims] (1) 1 selected from the group consisting of IVa, Va, and VIa groups
Contains 0.5 to 40% by weight of at least one compound consisting of one or more transition elements and one or more elements selected from the group consisting of C, N, and B, and the compound has at least a particle size of: Al has a particle size of 10 nm or more.
Al_2O, which is present in the Al_2O_3 grains and further has dislocations formed within the Al_2O_3 grains.
_3 series ceramics. (2) The Al_2O_3 ceramic according to claim (1), containing 3 to 40% by weight of SiC whiskers and/or Si_3N_4 whiskers. (3) Mg, Si, Ca, Ti, Zr as sintering aids
, Cr, Ni, Y, and oxides of rare earth elements in an amount of 0.5 to 10% by weight.
Al_2 according to claim (1) or (2) containing
O_3 series ceramics.