JP6636307B2 - Alumina sintered body with excellent high temperature properties and corrosion resistance - Google Patents
Alumina sintered body with excellent high temperature properties and corrosion resistance Download PDFInfo
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- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 title claims description 113
- 230000007797 corrosion Effects 0.000 title description 38
- 238000005260 corrosion Methods 0.000 title description 38
- CPLXHLVBOLITMK-UHFFFAOYSA-N Magnesium oxide Chemical compound [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 claims description 64
- 239000002245 particle Substances 0.000 claims description 59
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 claims description 50
- 239000013078 crystal Substances 0.000 claims description 48
- 229910052596 spinel Inorganic materials 0.000 claims description 42
- 239000011029 spinel Substances 0.000 claims description 42
- 229910020068 MgAl Inorganic materials 0.000 claims description 41
- 239000000395 magnesium oxide Substances 0.000 claims description 32
- 239000000377 silicon dioxide Substances 0.000 claims description 25
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 claims description 16
- ODINCKMPIJJUCX-UHFFFAOYSA-N Calcium oxide Chemical compound [Ca]=O ODINCKMPIJJUCX-UHFFFAOYSA-N 0.000 claims description 7
- 239000000292 calcium oxide Substances 0.000 claims description 7
- 235000012255 calcium oxide Nutrition 0.000 claims description 7
- 238000012360 testing method Methods 0.000 description 28
- 230000035939 shock Effects 0.000 description 22
- 238000010438 heat treatment Methods 0.000 description 18
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- 239000012535 impurity Substances 0.000 description 14
- 238000000465 moulding Methods 0.000 description 12
- 239000000843 powder Substances 0.000 description 12
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- 238000010298 pulverizing process Methods 0.000 description 8
- 230000007423 decrease Effects 0.000 description 7
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- 238000005245 sintering Methods 0.000 description 7
- 239000011521 glass Substances 0.000 description 6
- 230000002159 abnormal effect Effects 0.000 description 5
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- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 5
- 238000005266 casting Methods 0.000 description 4
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- VTHJTEIRLNZDEV-UHFFFAOYSA-L magnesium dihydroxide Chemical compound [OH-].[OH-].[Mg+2] VTHJTEIRLNZDEV-UHFFFAOYSA-L 0.000 description 4
- 239000000347 magnesium hydroxide Substances 0.000 description 4
- 229910001862 magnesium hydroxide Inorganic materials 0.000 description 4
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- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 2
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 2
- 238000002441 X-ray diffraction Methods 0.000 description 2
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- 229910052744 lithium Inorganic materials 0.000 description 2
- 238000002844 melting Methods 0.000 description 2
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- 239000002002 slurry Substances 0.000 description 2
- 239000007921 spray Substances 0.000 description 2
- 238000003786 synthesis reaction Methods 0.000 description 2
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 1
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- 229910045601 alloy Inorganic materials 0.000 description 1
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- 229920000609 methyl cellulose Polymers 0.000 description 1
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Description
本発明は高温特性及び耐食性に優れたアルミナ焼結体に関するものである。 The present invention relates to an alumina sintered body having excellent high-temperature characteristics and corrosion resistance.
アルミナ焼結体は、耐食性、耐熱性に優れ、他のセラミックスに比べて安価で取り扱いが容易であるため、古くから高温部材、熱処理用容器、セッター、炉芯管、測温用保護管等の分野で使用されている。
最近ではリチウム２次電池用正極材、電子材料や蛍光体材料等の熱処理用としても使用されているが、急速昇温、降温等の過酷な条件で使用されるケースが多い。また、熱処理の効率化のため、１度に多くの処理物が熱処理されており、従来品よりも大きな熱処理用部材が必要とされているが、このような大型熱処理用部材にかかる負荷は、小型熱処理用部材にかかる負荷よりも大きい。そこで、過酷な条件でも使用可能な、高温強度、クリープ特性、熱衝撃抵抗性等の高温特性に優れたアルミナ製熱処理用部材が要求されている。また、アルミナ製熱処理用部材の場合、繰り返し使用され高温環境に置かれる時間が長くなると、アルミナ粒子が粒成長し、特性の低下や特性のバラツキが大きくなる。そこで、長時間高温環境に置かれても粒成長しにくい、熱安定性に優れたアルミナ製熱処理用部材が要求されている。
しかし、従来のアルミナ焼結体は、該焼結体に含まれる不純物により結晶粒界に第２相やガラス相を有するため、温度の上昇に伴って高温強度、クリープ特性が低下するだけでなく、耐食性が低いという問題を有している。
Since alumina sintered body has excellent corrosion resistance and heat resistance, it is cheaper and easier to handle than other ceramics, it has been used since ancient times for high temperature members, heat treatment vessels, setters, furnace core tubes, temperature measurement protection tubes, etc. Used in the field.
Recently, it is also used for heat treatment of a positive electrode material for a lithium secondary battery, an electronic material, a phosphor material, and the like, but is often used under severe conditions such as rapid temperature rise and fall. In addition, in order to improve the efficiency of heat treatment, many processed materials are heat-treated at one time, and a heat treatment member larger than a conventional product is required. It is larger than the load applied to the small heat treatment member. Therefore, there is a demand for a heat treatment member made of alumina which has excellent high temperature characteristics such as high temperature strength, creep characteristics, and thermal shock resistance, which can be used under severe conditions. Further, in the case of the heat treatment member made of alumina, when the time of repeated use and being placed in a high-temperature environment becomes longer, the alumina particles grow and the characteristics are deteriorated and the characteristics vary greatly. Therefore, there is a demand for a heat treatment member made of alumina having excellent thermal stability, which is difficult to grow grains even in a high temperature environment for a long time.
However, the conventional alumina sintered body has a second phase or a glass phase at a crystal grain boundary due to impurities contained in the sintered body, so that not only the high-temperature strength and creep characteristics decrease with increasing temperature, but also And has a problem of low corrosion resistance.
従来技術として、特許文献１には、アルミナを主成分とし、ジルコニア、マグネシア、カルシアの含有量が０．０５〜１０重量％で、最大結晶粒径が３０μｍ以下のアルミナ焼結体が開示されている。しかし、アルミナ焼結体にジルコニアが含まれていると、高温での機械的特性や耐食性が低下するという問題があり、カルシアが含まれていると、異常粒成長により強度が低下するという問題がある。また、シリカは高温特性だけでなく耐食性にも大きく影響を与える不純物であって、特性を左右する重要な因子であるが、シリカ量を制御する必要性については全く記載されていない。 As a prior art, Patent Document 1 discloses an alumina sintered body having alumina as a main component, a zirconia, magnesia, and calcia content of 0.05 to 10% by weight and a maximum crystal grain size of 30 μm or less. I have. However, when zirconia is contained in the alumina sintered body, there is a problem that mechanical properties and corrosion resistance at high temperatures are reduced, and when calcia is contained, there is a problem that strength is reduced due to abnormal grain growth. is there. Further, silica is an impurity which greatly affects not only high-temperature properties but also corrosion resistance, and is an important factor that affects properties, but there is no mention of the necessity of controlling the amount of silica.
また、特許文献２には、アルミナ含有量が９９．８重量％以上、平均結晶粒径が２μｍ以上で、高温での耐クリープ性に優れたアルミナ焼結体が開示されている。しかし、このアルミナ焼結体は、アルミナが高純度で、かつ添加する焼結助剤量が０．２重量％以下と非常に少ないため、焼成時にアルミナ粒子が異常成長し易く、結晶粒径が不均一となり、高温特性や耐食性の低下及びバラツキが大きくなるといった問題がある。また、アルミナ焼結体を高温下で使用する場合には、熱衝撃抵抗性がアルミナ焼結体の寿命を左右するにも関わらず、熱衝撃抵抗性について全く記載されていない。 Patent Literature 2 discloses an alumina sintered body having an alumina content of 99.8% by weight or more, an average crystal grain size of 2 μm or more, and having excellent creep resistance at high temperatures. However, this alumina sintered body has a high purity of alumina and a very small amount of sintering aid to be added of 0.2% by weight or less. There is a problem that it becomes non-uniform, and the high-temperature characteristics and the corrosion resistance are reduced and the variation is increased. Further, when the alumina sintered body is used at a high temperature, the thermal shock resistance is not described at all even though the thermal shock resistance affects the life of the alumina sintered body.
また、特許文献３には、α−Ａｌ２Ｏ３及びその粒界に分散しているＭｇＡｌ２Ｏ４スピネルよりなる焼結体において、上記スピネルの粒径が０．１μｍ以下で、その含有量がマグネシア換算で１．５〜３．０重量％である耐熱セラミックスが開示されている。しかし、ＭｇＡｌ２Ｏ４スピネルはアルミナよりも耐食性は高いが熱衝撃抵抗性が低いため、ＭｇＡｌ２Ｏ４スピネル相を多く含有すると、熱衝撃抵抗性が低下し、様々な用途に適用可能な耐熱材料にはならない。また、同じ温度差でも、アルミナ焼結体のサイズが大きくなるに伴い、生じる熱衝撃は大きくなるため、上記のようなＭｇＡｌ２Ｏ４スピネルを多く含有する熱衝撃抵抗性が低いセラミックスは、大型化が難しいという問題がある。 Patent Document 3 discloses that in a sintered body composed of α-Al 2 O 3 and MgAl 2 O 4 spinel dispersed in its grain boundary, the particle diameter of the spinel is 0.1 μm or less, and the content thereof is Is 1.5 to 3.0% by weight in terms of magnesia. However, MgAl 2 O 4 spinel has higher corrosion resistance than alumina but lower thermal shock resistance. Therefore, when a large amount of MgAl 2 O 4 spinel phase is contained, the thermal shock resistance decreases, and heat resistance applicable to various applications is reduced. It does not become a material. Also, even at the same temperature difference, the thermal shock generated increases as the size of the alumina sintered body increases, so that ceramics having a low thermal shock resistance containing a large amount of MgAl 2 O 4 spinel as described above are large. There is a problem that it is difficult to make.
本発明は、高温特性及び耐食性に優れたアルミナ焼結体の提供を目的とする。 An object of the present invention is to provide an alumina sintered body having excellent high-temperature characteristics and corrosion resistance.
本発明者らは、前述したような現状に鑑み、アルミナ焼結体の化学組成、微構造に着目して鋭意研究を重ねた結果、焼結助剤としてマグネシアを用い、マグネシア添加量及び高温特性や耐食性を低下させる不純物量を一定の範囲とし、平均結晶粒径を特定の範囲内にすると共に、アルミナ粒子の粒界にＭｇＡｌ２Ｏ４スピネル粒子を特定の割合で生成させることにより、高温強度、耐クリープ性、熱衝撃抵抗性、熱安定性等の高温特性及び耐食性に優れたアルミナ焼結体が得られることを見出し、本発明を完成した。 In view of the current situation as described above, the present inventors have conducted intensive studies focusing on the chemical composition and microstructure of the alumina sintered body, and as a result, using magnesia as a sintering aid, the amount of magnesia added and the high temperature characteristics And the amount of impurities that reduce the corrosion resistance are set within a certain range, the average crystal grain size is set within a certain range, and MgAl 2 O 4 spinel particles are generated at a specific ratio at the grain boundaries of alumina particles, so that high-temperature strength is obtained. It has been found that an alumina sintered body excellent in high-temperature properties such as creep resistance, thermal shock resistance and thermal stability and corrosion resistance can be obtained, and the present invention has been completed.
即ち、上記課題は、次の１）〜３）の発明によって解決される。
１） 次の要件＜１＞〜＜７＞を満たすことを特徴とするアルミナ焼結体。
＜１＞アルミナ含有量が９８．３重量％以上
＜２＞マグネシア含有量が０．１〜１．０重量％
＜３＞シリカ含有量が０．１０重量％以下
＜４＞マグネシアとシリカの重量比（マグネシア／シリカ）が２．０以上
＜５＞かさ密度が３．８５ｇ／ｃｍ３以上
＜６＞平均結晶粒径が３〜２０μｍ
＜７＞ＭｇＡｌ２Ｏ４スピネルとアルミナの結晶相量の比（ＭｇＡｌ２Ｏ４スピネル／アルミナ）が０．０１〜０．０７
２） 次の要件＜８＞を満たすことを特徴とする１）記載のアルミナ焼結体。
＜８＞アルミナ結晶粒径の分布の変動係数が２０％以下
３） 次の要件＜９＞を満たすことを特徴とする１）又は２）記載のアルミナ焼結体。
＜９＞ジルコニア含有量が０．１０重量％以下、カルシア含有量が０．５重量％以下
That is, the above problem is solved by the following inventions 1) to 3).
1) An alumina sintered body satisfying the following requirements <1> to <7>.
<1> Alumina content is 98.3% by weight or more <2> Magnesia content is 0.1 to 1.0% by weight
<3> Silica content is 0.10% by weight or less <4> Weight ratio of magnesia to silica (magnesia / silica) is 2.0 or more <5> Bulk density is 3.85 g / cm 3 or more <6> Average crystal Particle size 3 ~ 20μm
<7> The ratio of the crystal phase amount of MgAl 2 O 4 spinel to alumina (MgAl 2 O 4 spinel / alumina) is 0.01 to 0.07.
2) The alumina sintered body according to 1), which satisfies the following requirement <8>.
<8> The alumina sintered body according to 1) or 2), wherein the variation coefficient of the distribution of the alumina crystal grain size is 20% or less. 3) The following requirement <9> is satisfied.
<9> Zirconia content is 0.10% by weight or less, calcia content is 0.5% by weight or less
本発明によれば、高温特性及び耐食性に優れたアルミナ焼結体を提供できる。
このアルミナ焼結体は、高温特性及び耐食性に優れるので、リチウム２次電池正極材料の合成、蛍光体材料の合成、圧電体、誘電体、磁性体、セラミックコンデンサー等の電子部品の焼成用部材として好適である。更に、金属及び合金の溶解用ルツボとしても好適である。更に、優れた熱衝撃抵抗性を有するので、各種電気炉用炉芯管、高温搬送用ローラー、サポートチューブ、ラジアンとチューブ、ガス吹込管、ガス採取管にも好適である。
ADVANTAGE OF THE INVENTION According to this invention, the alumina sintered compact excellent in high temperature property and corrosion resistance can be provided.
Since this alumina sintered body is excellent in high-temperature characteristics and corrosion resistance, it is used as a material for the synthesis of cathode materials for lithium secondary batteries, the synthesis of phosphor materials, and the firing of electronic components such as piezoelectric, dielectric, magnetic, and ceramic capacitors. It is suitable. Further, it is also suitable as a melting crucible for melting metals and alloys. Further, since it has excellent thermal shock resistance, it is suitable for furnace tubes for various electric furnaces, high-temperature transfer rollers, support tubes, radians and tubes, gas injection tubes, and gas sampling tubes.
以下、上記本発明について詳しく説明する。
・要件＜１＞について
本発明では、アルミナ含有量を９８．３重量％以上とする。好ましくは９９．１重量％以上である。アルミナ含有量が９８．３重量％未満の場合は、アルミナ粒子の粒界に第２相及びガラス相が多くなって耐食性が低下する上に、機械的特性、特に高温下での強度やクリープ特性が低下する。また、使用する原料に含まれる不純物量や原料処理中に混入する不純物量を考慮すると、上限は９９．８重量％程度である。
Hereinafter, the present invention will be described in detail.
-Regarding requirement <1> In the present invention, the alumina content is 98.3% by weight or more. Preferably, it is at least 99.1% by weight. When the alumina content is less than 98.3% by weight, the second phase and the glass phase increase in the grain boundaries of the alumina particles, thereby deteriorating the corrosion resistance. In addition, the mechanical properties, particularly the strength and creep properties at high temperatures. Decrease. Also, in consideration of the amount of impurities contained in the raw materials used and the amount of impurities mixed during the processing of the raw materials, the upper limit is about 99.8% by weight.
・要件＜２＞について
本発明では、焼結助剤としてマグネシアを０．１〜１．０重量％含有させる。好ましくは０．２〜０．７重量％である。マグネシア含有量が前記範囲であると、焼成時にマグネシアがアルミナ粒子の異常粒成長を抑制するため、結晶粒径が均一なアルミナ焼結体が得られる。更に、アルミナ粒子の粒界にＭｇＡｌ２Ｏ４スピネル粒子が生成して耐食性が向上し、粒界が強化されて、高温強度、耐クリープ性、熱衝撃抵抗性、熱安定性等の高温特性が向上する。マグネシア含有量が０．１重量％未満の場合は、生成するＭｇＡｌ２Ｏ４スピネル粒子の量が少なく、高温特性及び耐食性を向上させる効果が小さい上に、焼成時にマグネシアがアルミナ粒子の異常粒成長を抑制する効果が小さいため、結晶粒径が大きくなり、更には粒径分布のバラツキも大きくなり、機械的特性が低下する。また、マグネシア含有量が１．０重量％を超えると、アルミナ粒子粒界に第２相やガラス相が多く形成されて耐食性が低下するし、アルミナ焼結体に含まれる、熱衝撃抵抗性が低いＭｇＡｌ２Ｏ４スピネル粒子が多くなったり大きくなったりするため、母材であるアルミナ焼結体の熱衝撃抵抗性が低下する。
-Regarding requirement <2> In the present invention, magnesia is contained in an amount of 0.1 to 1.0% by weight as a sintering aid. Preferably it is 0.2 to 0.7% by weight. When the magnesia content is in the above range, magnesia suppresses abnormal grain growth of alumina particles during firing, so that an alumina sintered body having a uniform crystal grain size can be obtained. Furthermore, MgAl 2 O 4 spinel particles are formed at the grain boundaries of the alumina particles to improve the corrosion resistance, strengthen the grain boundaries, and provide high-temperature properties such as high-temperature strength, creep resistance, thermal shock resistance, and thermal stability. improves. When the magnesia content is less than 0.1% by weight, the amount of generated MgAl 2 O 4 spinel particles is small, the effect of improving high-temperature characteristics and corrosion resistance is small, and magnesia has abnormal grain growth of alumina particles during firing. Since the effect of suppressing the particle size is small, the crystal grain size increases, and the variation in the particle size distribution also increases, and the mechanical characteristics deteriorate. On the other hand, when the magnesia content exceeds 1.0% by weight, a large amount of the second phase and the glass phase are formed at the grain boundaries of the alumina particles, thereby deteriorating the corrosion resistance and reducing the thermal shock resistance contained in the alumina sintered body. Since the number of low MgAl 2 O 4 spinel particles increases or increases, the thermal shock resistance of the alumina sintered body as a base material decreases.
・要件＜３＞について
本発明では、不純物であるシリカを０．１０重量％以下とする。好ましくは０．０７重量％以下、更に好ましくは０．０５重量％以下である。シリカが０．１０重量％を超えると、結晶粒界にシリカ以外の不純物とのガラス相や第２相を形成しやすくなり、耐食性の低下及び、高温強度や耐クリープ性、熱安定性等の高温特性の低下が起こる。特にシリカは、圧電体等に使用される鉛との反応性が高いため、鉛を使用する分野では極力シリカ含有量を減らし、鉛に対する耐食性を向上させることが望ましい。
-Regarding requirement <3> In the present invention, silica as an impurity is set to 0.10% by weight or less. Preferably it is 0.07% by weight or less, more preferably 0.05% by weight or less. When the silica content exceeds 0.10% by weight, a glass phase or a second phase with impurities other than silica is easily formed at the crystal grain boundary, and the corrosion resistance is lowered, and the high temperature strength, creep resistance, heat stability, etc. Deterioration of high temperature properties occurs. In particular, since silica has high reactivity with lead used for a piezoelectric body or the like, in the field of using lead, it is desirable to reduce the silica content as much as possible and to improve the corrosion resistance to lead.
・要件＜４＞について
本発明ではマグネシアとシリカの重量比（マグネシア／シリカ）を２．０以上とする。マグネシア含有量０．１〜１．０重量％、かつシリカ含有量０．１０重量％以下という要件を満たしても、前記重量比が２．０未満の場合は、シリカとその他の成分でガラス相や第２相が多く形成され、ＭｇＡｌ２Ｏ４スピネル粒子による高温強度、耐クリープ性、熱安定性等の高温特性及び耐食性向上の効果よりも、ガラス相や第２相による耐食性及び高温特性の低下の影響が著しくなる。また、シリカは高温特性を低下させる不純物であるから含有量は極力少ない方が望ましい。したがって、マグネシア／シリカの重量比が無限大に近付く可能性があるが、どれだけ大きい値になっても、得られるアルミナ焼結体の特性に悪影響を及ぼすことはないから、前記重量比に上限はない。
-Regarding requirement <4> In the present invention, the weight ratio of magnesia to silica (magnesia / silica) is 2.0 or more. Even if the requirements of magnesia content of 0.1 to 1.0% by weight and silica content of 0.10% by weight or less are satisfied, if the weight ratio is less than 2.0, silica and other components may be used to form a glass phase. And a large number of second phases are formed, and the corrosion resistance and high temperature properties of the glass phase and the second phase are more improved than the effects of the high temperature properties such as high temperature strength, creep resistance, and thermal stability and the improvement of corrosion resistance by the MgAl 2 O 4 spinel particles. The effect of the drop is significant. In addition, since silica is an impurity that deteriorates high-temperature characteristics, the content is desirably as small as possible. Therefore, the weight ratio of magnesia / silica may approach infinity. However, no matter how large the value, there is no adverse effect on the characteristics of the obtained alumina sintered body. There is no.
・要件＜５＞について
本発明では、アルミナ焼結体のかさ密度を３．８５ｇ／ｃｍ３以上とする。好ましくは３．９０ｇ／ｃｍ３以上である。かさ密度が３．８５ｇ／ｃｍ３未満の場合は、焼結体内部に気孔が多く存在することになり、強度及び熱衝撃抵抗性の低下を引き起こす。また、気孔が起点となって腐食及び反応が進行し易くなるため耐食性の低下が起こる。アルミナ焼結体のかさ密度は理論上最大で３．９９ｇ／ｃｍ３であるが、実際の上限は３．９８ｇ／ｃｍ３程度である。かさ密度はＪＩＳ Ｒ １６３４に準拠して測定する。
-Regarding requirement <5> In the present invention, the bulk density of the alumina sintered body is set to 3.85 g / cm 3 or more. Preferably it is 3.90 g / cm 3 or more. If the bulk density is less than 3.85 g / cm 3 , many pores will be present inside the sintered body, causing a decrease in strength and thermal shock resistance. In addition, the pores serve as a starting point, so that the corrosion and the reaction easily proceed, so that the corrosion resistance is reduced. The bulk density of the alumina sintered body is theoretically 3.99 g / cm 3 at maximum, but the actual upper limit is about 3.98 g / cm 3 . The bulk density is measured according to JIS R 1634.
・要件＜６＞について
本発明では、アルミナ焼結体の平均結晶粒径を３〜２０μｍとする。好ましくは、５〜１５μｍである。平均結晶粒径が３μｍ未満の場合は、耐食性が低下し、特に高温下での耐クリープ性が低下する。一方、２０μｍを超えると、強度等の機械的特性が低下する。
なお、平均結晶粒径はアルミナ焼結体を鏡面研磨し、熱エッチングを施した後、走査型電子顕微鏡で、１視野にアルミナ粒子が１００個以上入るように設定した倍率で観察し、インターセプト法による１０点平均から下式により求めた。
Ｄ＝１．８×Ｌ／ｎ
［Ｄ：平均結晶粒径（μｍ）、Ｌ：測定長さ（μｍ）、ｎ：長さＬ当たりの結晶の数］
-Regarding requirement <6> In the present invention, the average crystal grain size of the alumina sintered body is 3 to 20 µm. Preferably, it is 5 to 15 μm. When the average crystal grain size is less than 3 μm, the corrosion resistance is reduced, and in particular, the creep resistance at high temperatures is reduced. On the other hand, when it exceeds 20 μm, mechanical properties such as strength are reduced.
The average crystal grain size was determined by subjecting the alumina sintered body to mirror polishing and thermal etching, then observing with a scanning electron microscope at a magnification set such that 100 or more alumina particles were included in one field of view, and using an intercept method. From the 10-point average according to the following formula.
D = 1.8 × L / n
[D: average crystal grain size (μm), L: measured length (μm), n: number of crystals per length L]
・要件＜７＞について
本発明では、アルミナ焼結体中にＭｇＡｌ２Ｏ４スピネル粒子を含有する必要がある。アルミナ粒子の粒界にＭｇＡｌ２Ｏ４スピネル粒子が存在することにより耐食性が向上し、粒界が強化されて高温強度、耐クリープ性、熱衝撃抵抗性、熱安定性等の高温特性が向上する。更に本発明では、アルミナ焼結体中に存在するＭｇＡｌ２Ｏ４スピネルとアルミナの結晶相量比（ＭｇＡｌ２Ｏ４スピネル／アルミナ）が０．０１〜０．０７である必要があり、好ましくは０．０２〜０．０５の範囲である。マグネシア含有量０．１〜１．０重量％という要件＜２＞を満たしていても、前記比が０．０１未満の場合は、アルミナ粒子の粒界に存在するＭｇＡｌ２Ｏ４スピネル粒子が少ないため、高温強度、耐クリープ性、熱衝撃抵抗性等の高温特性及び耐食性を向上させる効果が小さい上に熱安定性も著しく低下する。また、前記比が０．０７を超えると、アルミナ粒子の粒界に存在するＭｇＡｌ２Ｏ４スピネル粒子が多くなったり大きくなったりする。ＭｇＡｌ２Ｏ４スピネルはアルミナよりも熱衝撃抵抗性が低いため、ＭｇＡｌ２Ｏ４スピネル粒子を多く含有するアルミナ焼結体は熱衝撃抵抗性が低下する。また、ＭｇＡｌ２Ｏ４スピネル粒子のサイズは５μｍ以下が好ましく、５μｍを超えるＭｇＡｌ２Ｏ４スピネル粒子を含有するアルミナ焼結体は熱衝撃抵抗性が低下する。上記ＭｇＡｌ２Ｏ４スピネル粒子のサイズは、アルミナ焼結体を鏡面研磨し、熱エッチングを施した後、走査型電子顕微鏡で、１視野にアルミナ粒子が１００個以上入るように設定した倍率で観察及びＥＤＸ分析し、マグネシアとアルミナが共存している粒子をＭｇＡｌ２Ｏ４スピネル粒子と定義し、ＭｇＡｌ２Ｏ４スピネル粒子１０個の最大径の平均から求めた。
-Regarding requirement <7> In the present invention, it is necessary to contain MgAl 2 O 4 spinel particles in the alumina sintered body. The presence of MgAl 2 O 4 spinel particles at the grain boundaries of alumina particles improves corrosion resistance and strengthens the grain boundaries to improve high temperature properties such as high temperature strength, creep resistance, thermal shock resistance, and thermal stability. . Further, in the present invention, the crystal phase ratio of MgAl 2 O 4 spinel and alumina (MgAl 2 O 4 spinel / alumina) present in the alumina sintered body needs to be 0.01 to 0.07, and is preferably. It is in the range of 0.02 to 0.05. Even if the requirement <2> of a magnesia content of 0.1 to 1.0% by weight is satisfied, if the ratio is less than 0.01, the amount of MgAl 2 O 4 spinel particles present at the grain boundaries of the alumina particles is small. Therefore, the effect of improving high-temperature properties such as high-temperature strength, creep resistance, and thermal shock resistance and corrosion resistance is small, and the thermal stability is significantly reduced. If the ratio exceeds 0.07, the number of MgAl 2 O 4 spinel particles existing at the grain boundaries of the alumina particles increases or increases. Since MgAl 2 O 4 spinel has lower thermal shock resistance than alumina, an alumina sintered body containing a large amount of MgAl 2 O 4 spinel particles has low thermal shock resistance. The size of the MgAl 2 O 4 spinel particles is preferably 5 μm or less, and an alumina sintered body containing MgAl 2 O 4 spinel particles exceeding 5 μm has reduced thermal shock resistance. The size of the MgAl 2 O 4 spinel particles is determined by mirror-polishing the alumina sintered body, performing thermal etching, and then observing with a scanning electron microscope at a magnification set so that 100 or more alumina particles enter one visual field. and to EDX analysis, the particles magnesia and alumina coexist defined as MgAl 2 O 4 spinel particles were determined from the average of the maximum diameter of 10 MgAl 2 O 4 spinel particles.
なお、本発明でアルミナ焼結体中にＭｇＡｌ２Ｏ４スピネル粒子を含有するとは、アルミナ焼結体を研磨し、その鏡面を、Ｘ線源ＣｕＫα、管電圧４０ｋＶ、管電流４０ｍＡ、発散スリット０．３°、受光側スリットＯＰＥＮ、スキャンスピード３．０°／ｍｉｎ、走査軸２θ／θ、走査範囲１０°〜７０°の条件で、ＸＲＤ（Ｘ線回折）測定した際に、アルミナ以外にＭｇＡｌ２Ｏ４スピネルの回折ピークが観測されることを言う。
そして、アルミナ焼結体中に存在するＭｇＡｌ２Ｏ４スピネル結晶相量とアルミナの結晶相量の比は、上記測定で得られたＭｇＡｌ２Ｏ４スピネル結晶相の（３１１）面ピークとアルミナ結晶相の（１１３）面ピークの強度比（次式参照）より求めた。
結晶相量の比＝ＭｇＡｌ２Ｏ４スピネルの（３１１）面のピーク強度／
アルミナの（１１３）面のピーク強度
In the present invention, the expression that MgAl 2 O 4 spinel particles are contained in the alumina sintered body means that the alumina sintered body is polished and its mirror surface is formed with an X-ray source CuKα, a tube voltage of 40 kV, a tube current of 40 mA, and a divergence slit of 0. 0.3 °, light receiving side slit OPEN, scan speed 3.0 ° / min, scan axis 2θ / θ, scan range 10 ° to 70 °, when XRD (X-ray diffraction) measurement was performed, MgAl was used in addition to alumina. It means that a diffraction peak of 2 O 4 spinel is observed.
The ratio between the amount of MgAl 2 O 4 spinel crystal phase and the amount of alumina crystal phase present in the alumina sintered body is determined by the (311) plane peak of the MgAl 2 O 4 spinel crystal phase obtained by the above measurement and the alumina crystal. It was determined from the intensity ratio of the (113) plane peak of the phase (see the following equation).
Ratio of crystal phase amount = Peak intensity of (311) plane of MgAl 2 O 4 spinel /
Peak intensity of (113) plane of alumina
・要件＜８＞について
本発明では、アルミナ結晶粒径の分布の変動係数が２０％以下であることが好ましい。変動係数は、結晶粒径の標準偏差を平均結晶粒径で割った値（次式参照）である。
変動係数（％）＝（アルミナ結晶粒径の標準偏差／アルミナの平均結晶粒径）×１００
変動係数が２０％より大きいとは、結晶粒径の分布が広いことを意味し、結晶粒径が小さい部分と大きい部分が存在し、結晶粒径が小さい部分は耐食性の低下、特に耐クリープ性の低下を引き起こし、結晶粒径が大きい部分は曲げ強度や熱衝撃抵抗性の低下を引き起こすので好ましくない。
-Regarding requirement <8> In the present invention, it is preferable that the variation coefficient of the distribution of the alumina crystal grain size is 20% or less. The coefficient of variation is a value obtained by dividing the standard deviation of the crystal grain size by the average crystal grain size (see the following equation).
Coefficient of variation (%) = (standard deviation of alumina grain size / average alumina grain size) × 100
When the coefficient of variation is larger than 20%, it means that the distribution of crystal grain size is wide, and there are a portion having a small crystal grain size and a portion having a large crystal grain size, and a portion having a small crystal grain size has reduced corrosion resistance, particularly creep resistance. And a portion having a large crystal grain size is not preferable because it causes a decrease in bending strength and thermal shock resistance.
・要件＜９＞について
シリカ以外の不純物もアルミナ焼結体の高温特性及び耐食性を低下させるため、少ない方が好ましい。中でも、ジルコニアは０．１０重量％以下が好ましく、０．０５重量％以下がより好ましく、０．０１重量％以下が更に好ましい。０．１０重量％を超えると、高温での機械的特性の低下や耐食性の低下を引き起こす可能性があるので好ましくない。
更に、カルシアは０．５重量％以下が好ましく、０．３重量％以下がより好ましく、０．１重量％以下が更に好ましい。０．５重量％を超えると、アルミナ粒子の異常粒成長を助長し、結晶粒径が大きくなり、更には粒径分布のバラツキが大きくなり、機械的特性の低下を引き起こす可能性があるので好ましくない。
-Regarding requirement <9> Since impurities other than silica also lower the high-temperature characteristics and corrosion resistance of the alumina sintered body, it is preferable that the amount is small. Among them, zirconia is preferably 0.10% by weight or less, more preferably 0.05% by weight or less, and still more preferably 0.01% by weight or less. If it exceeds 0.10% by weight, the mechanical properties at high temperatures and the corrosion resistance may decrease, which is not preferable.
Further, the calcia is preferably 0.5% by weight or less, more preferably 0.3% by weight or less, and still more preferably 0.1% by weight or less. When the content exceeds 0.5% by weight, the abnormal grain growth of the alumina particles is promoted, the crystal grain size becomes large, and the variation of the grain size distribution becomes large. Absent.
本発明のアルミナ焼結体は次のようにして製造できる。
アルミナ原料には、純度９９．７重量％以上、好ましくは９９．８重量％以上、平均粒子径３μｍ以下、好ましくは２μｍ以下、比表面積３〜１０ｍ２／ｇ、好ましくは４〜８ｍ２／ｇのものを使用する。平均粒子径が３μｍより大きく、比表面積が３ｍ２／ｇより小さい粉体は成形性が低く、そのため焼結体内部に欠陥が生じやすく、強度及び耐食性が低下するので好ましくない。また、比表面積が１０ｍ２／ｇより大きい粉体は、焼成時に異常粒成長を起こし易いため、アルミナ焼結体の微構造が不均一になり、高温特性及び耐食性が低下するので好ましくない。
The alumina sintered body of the present invention can be manufactured as follows.
The alumina raw material has a purity of 99.7% by weight or more, preferably 99.8% by weight or more, an average particle diameter of 3 μm or less, preferably 2 μm or less, a specific surface area of 3 to 10 m 2 / g, and preferably 4 to 8 m 2 / g. Use those. Powders having an average particle diameter of more than 3 μm and a specific surface area of less than 3 m 2 / g are not preferred because they have low moldability and tend to cause defects inside the sintered body, resulting in reduced strength and corrosion resistance. Further, a powder having a specific surface area of more than 10 m 2 / g is not preferable because abnormal grain growth is apt to occur during firing, so that the microstructure of the alumina sintered body becomes non-uniform and high-temperature characteristics and corrosion resistance deteriorate.
焼結助剤としては、純度９８重量％以上、好ましくは９９重量％以上、平均粒子径５μｍ以下、比表面積５ｍ２／ｇ以上のマグネシア粉体が使用可能であるが、均一分散性等の点から、平均粒子径８μｍ以下、比表面積１０ｍ２／ｇ以上で、酸化物にした場合の純度が９８重量％以上の水酸化物、炭酸化物等の塩、又は、平均粒子径３μｍ以下、比表面積５ｍ２／ｇ以上のＭｇＡｌ２Ｏ４スピネル粉体が好ましい。
これらの粉体の平均粒子径や比表面積が上記範囲を外れると、粉砕・分散混合においてアルミナ粉体への混合分散性が低下し、焼結体に含まれるＭｇＡｌ２Ｏ４スピネル相量やＭｇＡｌ２Ｏ４スピネル粒子サイズが所定の範囲にならず、耐食性及び高温特性が低下したりバラツキが大きくなるため好ましくない。
Magnesia powder having a purity of 98% by weight or more, preferably 99% by weight or more, an average particle diameter of 5 μm or less, and a specific surface area of 5 m 2 / g or more can be used as the sintering aid. From hydroxides, carbonates and the like having an average particle diameter of 8 μm or less and a specific surface area of 10 m 2 / g or more and having a purity of 98% by weight or more as an oxide, or an average particle diameter of 3 μm or less and a specific surface area of MgAl 2 O 4 spinel powder of 5 m 2 / g or more is preferred.
If the average particle size or specific surface area of these powders is out of the above range, the mixing and dispersibility in the alumina powder during the pulverization / dispersion mixing is reduced, and the amount of MgAl 2 O 4 spinel phase and MgAl contained in the sintered body is reduced. The size of the 2 O 4 spinel particles does not fall within the predetermined range, and the corrosion resistance and high-temperature characteristics are undesirably reduced or the dispersion is increased.
アルミナ原料に対し、所定の量及び組成になるように焼結助剤を添加し、水を溶媒として湿式でポットミル、アトリッションミル等により高純度アルミナボールを用いて粉砕・分散混合する。粉砕・分散混合後の粉体の平均粒子径は０．４〜１．５μｍ、好ましくは０．５〜１．０μｍとする必要がある。平均粒子径が上記範囲を外れると、成形性の低下や焼結性の低下を来たし、焼結体内部にポア等の欠陥が多くなり、機械的特性及び耐食性が低下するので好ましくない。また、粉砕・分散混合により、ミル、ボール等からの不純物の混入があるため、不純物混入量が極力少なくなるように粉砕・分散混合条件を適宜設定し、得られる粉体の平均粒子径及び不純物量が特定の範囲内になるようにする。
成形方法としてプレス成形、ラバープレス成形等を採用する場合には、分散・混合スラリーに、必要に応じて公知の成形助剤（例えばワックスエマルジョン、ＰＶＡ、アクリル系樹脂等）を加え、スプレードライヤー等の公知の方法で乾燥させて成形粉体を作製し、これを用いて成形する。
A sintering aid is added to the alumina raw material so as to have a predetermined amount and composition, and the mixture is wet-pulverized with water as a solvent by a pot mill, an attrition mill or the like using high-purity alumina balls and dispersed and mixed. The average particle size of the powder after pulverization / dispersion and mixing needs to be 0.4 to 1.5 μm, preferably 0.5 to 1.0 μm. If the average particle size is out of the above range, the moldability and sinterability are reduced, defects such as pores are increased inside the sintered body, and mechanical properties and corrosion resistance are undesirably reduced. Also, due to the mixing of the impurities from the mill, balls and the like due to the pulverization / dispersion / mixing, the pulverization / dispersion / mixing conditions are appropriately set so that the amount of the impurities is minimized, and the average particle diameter and the impurities Make sure the amount is in the specified range.
In the case where press molding, rubber press molding, or the like is employed as a molding method, a known molding aid (eg, wax emulsion, PVA, acrylic resin, or the like) is added to the dispersion / mixed slurry as necessary, and a spray dryer or the like is used. To form a molding powder, and molding is performed using this.
また、鋳込成形法を採用する場合には、分散・混合スラリーに、必要に応じて公知の成形助剤（ワックスエマルジョン、アクリル系樹脂等）を加え、石膏型又は樹脂型を用いて排泥鋳込、充填鋳込、加圧鋳込法により成形する。
また、押出成形法を採用する場合には、分散・混合したスラリーを乾燥させ、整粒し、混合機を用いて水、バインダー（例えばメチルセルロース等）などを混合して坏土を作製し、押出成形する。
以上のようにして得られた成形体を１５００℃〜１７５０℃、好ましくは１５５０℃〜１７００℃で焼成することによって、本発明の高温特性及び耐食性に優れたアルミナ焼結体が得られる。焼成温度が上記範囲外の場合、得られるアルミナ焼結体は、本発明の要件を少なくとも１つ以上満たさなくなるため、本発明の高温特性及び耐食性に優れたアルミナ焼結体が得られない。
When the casting method is adopted, a known molding aid (a wax emulsion, an acrylic resin or the like) is added to the dispersion / mixed slurry as necessary, and the slurry is discharged using a gypsum mold or a resin mold. It is formed by casting, filling casting, and pressure casting.
When the extrusion molding method is adopted, the dispersed / mixed slurry is dried, sized, and mixed with water, a binder (eg, methylcellulose) using a mixer to produce a kneaded material, and the extruding is performed. Molding.
By firing the molded body obtained as described above at 1500 to 1750 ° C, preferably 1550 to 1700 ° C, an alumina sintered body having excellent high-temperature characteristics and corrosion resistance of the present invention can be obtained. When the sintering temperature is outside the above range, the obtained alumina sintered body does not satisfy at least one of the requirements of the present invention, so that the alumina sintered body excellent in high-temperature characteristics and corrosion resistance of the present invention cannot be obtained.
以下、実施例及び比較例を挙げて本発明を更に具体的に説明するが、本発明はこれらの実施例により何等限定されるものではない。 Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.
実施例１〜１４、比較例１〜１１
平均粒子径０．８μｍ、比表面積６ｍ２／ｇ、アルミナ純度９９．８重量％のアルミナ原料に、焼結助剤のマグネシア源である水酸化マグネシウム（比表面積３２ｍ２／ｇ）を、表１の実施例及び比較例の各欄に示すようなマグネシア含有量となるように添加配合し、９２重量％アルミナ製ポットミル及びボールを用いて粉砕・混合した。得られたスラリーにバインダーとしてアクリル樹脂を添加し、スプレードライヤー乾燥して成形用粉体を作製した。得られた成形用粉体を成形圧１００ＭＰａでＣＩＰ成形し、大気中、１４８０〜１７８０℃で２時間焼成した。得られたアルミナ焼結体を研削加工し、曲げ試験用テストピース（３ｍｍ×４ｍｍ×５０ｍｍ）、クリープ試験用テストピース（２ｍｍ×５ｍｍ×１４０ｍｍ）、熱衝撃試験用テストピース（５ｍｍ×６ｍｍ×５０ｍｍ）、熱安定性試験用テストピース（２０ｍｍ×２０ｍｍ×５ｍｍ）、耐ＰｂＯ性試験用テストピース（１５ｍｍ×１５ｍｍ×２ｍｍ）を作製した。テストピースの表面粗さは０．２０μｍＲａ以下とした。
なお、比較例５では、粉砕・分散混合に使用するボールとしてジルコニアボールを使用した。
また、比較例９では、平均粒子径３．５μｍのアルミナ原料を使用したため、粉砕・分散混合後の粉体平均粒子径が１．５９μｍと、所定の範囲を超えていた。
Examples 1 to 14, Comparative Examples 1 to 11
To an alumina raw material having an average particle diameter of 0.8 μm, a specific surface area of 6 m 2 / g and an alumina purity of 99.8% by weight, magnesium hydroxide (specific surface area of 32 m 2 / g), which is a magnesia source of a sintering aid, was added to Table 1. Were added and blended so as to have a magnesia content as shown in each column of Examples and Comparative Examples, and were pulverized and mixed using a 92% by weight alumina pot mill and balls. An acrylic resin was added as a binder to the obtained slurry, and dried by a spray drier to prepare a molding powder. The obtained molding powder was subjected to CIP molding at a molding pressure of 100 MPa, and calcined at 1480 to 1780 ° C. for 2 hours in the air. The obtained alumina sintered body was ground, and a test piece for bending test (3 mm × 4 mm × 50 mm), a test piece for creep test (2 mm × 5 mm × 140 mm), a test piece for thermal shock test (5 mm × 6 mm × 50 mm) ), A test piece (20 mm × 20 mm × 5 mm) for a thermal stability test and a test piece (15 mm × 15 mm × 2 mm) for a PbO resistance test were prepared. The surface roughness of the test piece was 0.20 μm Ra or less.
In Comparative Example 5, zirconia balls were used as balls used for pulverization / dispersion mixing.
In Comparative Example 9, since an alumina raw material having an average particle diameter of 3.5 μm was used, the average particle diameter of the powder after pulverization / dispersion and mixing was 1.59 μm, which exceeded a predetermined range.
実施例及び比較例の原料特性を表１に、焼結体特性を表２に示す。各特性の測定方法は以下のとおりである。
＜原料特性＞
アルミナ含有量、マグネシア含有量及び不純物含有量は、島津製作所社製ＩＣＰ発光分析装置ＩＣＰＳ−８１００を用いて測定した。粉砕・混合後の粉体の平均粒子径は、日機装社製マイクロトラック３３００ＥＸを用いて測定した。
＜焼結体特性＞
かさ密度は、ＪＩＳ Ｒ １６３４に準拠し、メトラー・トレド社製電子天秤ＸＰ２０５ＤＲを用いて測定した。
平均結晶粒径は、アルミナ焼結体を鏡面研磨し、熱エッチングを施した後、日立ハイテクノロジーズ社製の電界放出形走査電子顕微鏡ＳＵ８０２０を用いてインターセプト法により求めた。また、得られた平均結晶粒径及び標準偏差から、結晶粒径の分布の変動係数（結晶粒径変動係数）を求めた。
ＭｇＡｌ２Ｏ４スピネル／アルミナ結晶相量比は、ブルカー・エイエックスエス社製Ｘ線回折装置Ｄ８ＡＤＶＡＮＣＥを用いて測定した。
Table 1 shows the raw material characteristics of the examples and comparative examples, and Table 2 shows the sintered body characteristics. The measuring method of each characteristic is as follows.
<Raw material characteristics>
The alumina content, magnesia content, and impurity content were measured using an ICP emission spectrometer ICPS-8100 manufactured by Shimadzu Corporation. The average particle diameter of the pulverized and mixed powder was measured using a Nikkiso Co., Ltd. Microtrac 3300EX.
<Sintered body characteristics>
The bulk density was measured according to JIS R 1634 using an electronic balance XP205DR manufactured by METTLER TOLEDO.
The average crystal grain size was determined by an intercept method using a field emission scanning electron microscope SU8020 manufactured by Hitachi High-Technologies Corporation after mirror polishing the alumina sintered body and performing thermal etching. From the obtained average crystal grain size and standard deviation, the variation coefficient of the crystal grain size distribution (crystal grain size variation coefficient) was determined.
The MgAl 2 O 4 spinel / alumina crystal phase ratio was measured using an X-ray diffractometer D8ADVANCE manufactured by Bruker AXS.
上記実施例及び比較例の各試験用テストピースを用いて、下記のテストを行った。
結果を纏めて表２に示す。
＜曲げ強さ＞
室温ではＪＩＳ Ｒ １６０１に準拠し、１４００℃（高温）ではＪＩＳ Ｒ １６０４に準拠し曲げ試験を行い、曲げ強さ（ＭＰａ）を測定した。室温での曲げ強さの測定にはＩＮＳＴＲＯＮ社製の万能材料試験機５９６５型を用い、高温での曲げ強さの測定には島津製作所製の精密万能試験機ＡＧ−５００Ｃを用いた。
The following tests were performed using the test pieces for each test of the above Examples and Comparative Examples.
Table 2 summarizes the results.
<Bending strength>
A bending test was performed at room temperature in accordance with JIS R 1601 and at 1400 ° C. (high temperature) in accordance with JIS R 1604, and a bending strength (MPa) was measured. The universal strength tester 5965 manufactured by INSTRON was used to measure the bending strength at room temperature, and the precision universal testing machine AG-500C manufactured by Shimadzu Corporation was used to measure the bending strength at high temperature.
＜耐クリープ性＞
支点間距離１００ｍｍで固定したテストピースの中央に、負荷応力が２ＭＰａになるように長さ３１ｍｍのアルミナ焼結体からなるオモシを載せ、電気炉を用いて大気中、１４５０℃で２時間加熱し、加熱後のテストピースのたわみ量（ｍｍ）を測定した。測定にはＭＩＴＵＴＯＹＯ社製のＬＩＮＥＡＲ ＧＡＧＥ ＬＧ−１５０を用いた。
<Creep resistance>
At the center of the test piece fixed at a distance between the fulcrum points of 100 mm, an Omosh made of an alumina sintered body having a length of 31 mm was placed so that the applied stress was 2 MPa, and heated at 1450 ° C. for 2 hours in the air using an electric furnace. Then, the deflection (mm) of the test piece after heating was measured. For measurement, LINEAR GAGE LG-150 manufactured by MITUTOYO was used.
＜熱衝撃抵抗性＞
テストピースを大気中で１００〜２３０℃に保持した電気炉に挿入し、３０分保持した後、１０℃の水中へ投入し、３０分後に水中からテストピースを取り出して室温での曲げ試験を行い、曲げ強さが低下する温度差〔ΔＴ（℃）〕を測定した。なおΔＴ（℃）は次式により求めた。
ΔＴ（℃）＝電気炉での加熱温度（℃）−水温（℃）
<Heat shock resistance>
The test piece is inserted in an electric furnace maintained at 100 to 230 ° C. in the air, and is held for 30 minutes. Then, the test piece is poured into water at 10 ° C., and after 30 minutes, the test piece is taken out of the water and subjected to a bending test at room temperature. And the temperature difference [ΔT (° C.)] at which the flexural strength decreased was measured. ΔT (° C.) was determined by the following equation.
ΔT (° C) = heating temperature in electric furnace (° C)-water temperature (° C)
＜熱安定性＞
テストピースを、電気炉を用いて、大気中、１５００℃で１００時間加熱した。加熱前後のテストピースをそれぞれ鏡面研磨し、熱エッチングを施した後、走査型電子顕微鏡を用いてインターセプト法により、加熱前後のアルミナ粒子の平均結晶粒径を求め、次式により粒成長率（％）を算出した。微構造の観察には、日立ハイテクノロジーズ社製の電界放出形走査電子顕微鏡ＳＵ８０２０を用いた。
粒成長率（％）＝〔（加熱後平均結晶粒径−加熱前平均結晶粒径）／
加熱前平均結晶粒径〕×１００
<Thermal stability>
The test piece was heated at 1500 ° C. for 100 hours in the air using an electric furnace. After the test pieces before and after heating are each mirror-polished and subjected to thermal etching, the average crystal grain size of alumina particles before and after heating is determined by an intercept method using a scanning electron microscope, and the grain growth rate (% ) Was calculated. For observation of the microstructure, a field emission scanning electron microscope SU8020 manufactured by Hitachi High-Technologies Corporation was used.
Grain growth rate (%) = [(average crystal grain size after heating−average crystal grain size before heating) /
Average grain size before heating] x 100
＜耐ＰｂＯ性＞
テストピースにφ１２ｍｍ×１ｍｍのＰｂＯ成形体を載せ、その上に、荷重が０．５×１０２Ｐａになるように高純度ＺｒＯ２焼結体からなるオモシを載せ、アルミナ焼結体からなる容器で密閉し、電気炉を用いて、大気中、８７０℃で２０時間の加熱を３サイクル行い、加熱前後のテストピースの重量を測定して、次式により重量変化率を算出した。
測定にはｓａｒｔｏｒｉｕｓ社製の電子天秤ＬＣ１２０１Ｓを用いた。
重量変化率（％）＝
〔（加熱後テストピース重量−加熱前テストピース重量）／加熱前テストピース重量〕
×１００
<PbO resistance>
A PbO molded body having a diameter of 12 mm × 1 mm is placed on a test piece, and an Omoshi made of a high-purity ZrO 2 sintered body is placed thereon so that the load becomes 0.5 × 10 2 Pa, and a container made of an alumina sintered body is placed. , And heating was performed at 870 ° C. for 20 hours in the atmosphere using an electric furnace for 3 cycles. The weight of the test piece before and after heating was measured, and the weight change rate was calculated by the following equation.
An electronic balance LC1201S manufactured by Sartorius was used for the measurement.
Weight change rate (%) =
[(Test piece weight after heating-Test piece weight before heating) / Test piece weight before heating]
× 100
上記表１、表２から分かるように、本発明のアルミナ焼結体は、マグネシア源添加量の制御によりアルミナ粒子の粒界にＭｇＡｌ２Ｏ４スピネル粒子が生成し、それにより粒界が強化されて高温強度、耐クリープ性、熱衝撃抵抗性等の高温特性が向上し、更に粒界にＭｇＡｌ２Ｏ４スピネル粒子が存在し且つ粒界の不純物が少ないため、高い耐食性を有している。
したがって、耐熱及び耐食材料として有用であり、更に、高温下での結晶粒成長が非常に小さく熱安定性に優れるため、熱処理用部材として長寿命を有している。
これに対し、本発明の要件＜１＞〜＜７＞を一つ以上満たさないアルミナ焼結体は高温特性及び耐食性が劣る。
As can be seen from Tables 1 and 2, in the alumina sintered body of the present invention, MgAl 2 O 4 spinel particles are generated at the grain boundaries of alumina particles by controlling the amount of the magnesia source added, whereby the grain boundaries are strengthened. As a result, high-temperature properties such as high-temperature strength, creep resistance, and thermal shock resistance are improved, and MgAl 2 O 4 spinel particles are present at the grain boundaries and the impurities at the grain boundaries are few, so that they have high corrosion resistance.
Therefore, it is useful as a heat-resistant and corrosion-resistant material, and furthermore, has a long life as a heat-treating member because of extremely small crystal grain growth at high temperatures and excellent thermal stability.
On the other hand, an alumina sintered body that does not satisfy one or more of the requirements <1> to <7> of the present invention is inferior in high-temperature characteristics and corrosion resistance.
即ち、比較例１、２は、マグネシア含有量が要件＜２＞の範囲外の例である。
比較例３は、マグネシア含有量が要件＜２＞の下限値に近く且つ焼成温度が１５００℃より低かったため、ＭｇＡｌ２Ｏ４スピネル粒子の生成量が少なくなり、ＭｇＡｌ２Ｏ４スピネル／アルミナの結晶相量比が要件＜７＞の範囲より小さくなった例である。
比較例４は、マグネシア含有量が要件＜２＞の上限値に近く且つ焼成温度が１７５０℃より高かったため、ＭｇＡｌ２Ｏ４スピネル粒子の生成量が多くなり、ＭｇＡｌ２Ｏ４スピネル／アルミナの結晶相量比が要件＜７＞の範囲より大きくなった例である。
比較例５は、アルミナ原料及び水酸化マグネシウムを粉砕・分散混合する際に、アルミナボールではなくジルコニアボールを使用したため、ミル容器や粉砕ボールからシリカやジルコニアが混入して含有量が増加した例である。
比較例６は、アルミナ原料及び水酸化マグネシウムを粉砕・分散混合する際に、シリカ含有量が要件＜３＞の範囲より多くなるようにシリカを添加した例である。
比較例７は、アルミナ原料及び水酸化マグネシウムを粉砕・分散混合する際に、カルシア含有量が０．５重量％より多くなるようにカルシアを添加したため、アルミナ含有量が要件＜１＞の範囲よりも少なくなった例である。
比較例８は、マグネシア及びシリカ含有量は要件＜２＞＜３＞の範囲内であるが、マグネシア／シリカの重量比が要件＜４＞の範囲より小さい例である。
比較例９は、平均粒子径の大きいアルミナ原料を使用したため、粉砕・分散混合後の粉体平均粒子径が大きく、且つ、焼成温度が１５００℃より低かったため、かさ密度が要件＜５＞の範囲より小さくなった例である。
比較例１０は、焼成温度が１５００℃より低かったため、アルミナ結晶粒子の平均結晶粒径が要件＜６＞の範囲より小さくなった例である。
比較例１１は、焼成温度が１７５０℃より高かったため、アルミナ結晶粒子の平均結晶粒径が要件＜６＞の範囲より大きくなった例である。
That is, Comparative Examples 1 and 2 are examples in which the magnesia content is out of the range of the requirement <2>.
In Comparative Example 3, since the magnesia content was close to the lower limit of requirement <2> and the firing temperature was lower than 1500 ° C., the amount of generated MgAl 2 O 4 spinel particles was small, and the crystal of MgAl 2 O 4 spinel / alumina was used. This is an example in which the phase amount ratio is smaller than the range of requirement <7>.
In Comparative Example 4, since the magnesia content was close to the upper limit of requirement <2> and the firing temperature was higher than 1750 ° C., the amount of generated MgAl 2 O 4 spinel particles was large, and the crystal of MgAl 2 O 4 spinel / alumina was obtained. This is an example in which the phase ratio is larger than the range of requirement <7>.
Comparative Example 5 was an example in which zirconia balls were used instead of alumina balls when pulverizing, dispersing, and mixing the alumina raw material and magnesium hydroxide, so that silica and zirconia were mixed from the mill container or the pulverized balls to increase the content. is there.
Comparative Example 6 is an example in which silica was added so that the silica content was more than the range of requirement <3> when the alumina raw material and magnesium hydroxide were pulverized, dispersed and mixed.
In Comparative Example 7, when the alumina raw material and magnesium hydroxide were pulverized and dispersed and mixed, calcia was added so that the calcia content was more than 0.5% by weight, so that the alumina content was less than the range of requirement <1>. This is an example in which the number has also decreased.
Comparative Example 8 is an example in which the magnesia and silica contents are within the range of requirement <2><3>, but the weight ratio of magnesia / silica is smaller than the range of requirement <4>.
In Comparative Example 9, since the alumina raw material having a large average particle diameter was used, the powder average particle diameter after pulverization / dispersion and mixing was large, and the firing temperature was lower than 1500 ° C., so that the bulk density was within the range of requirement <5>. Here is an example that has become smaller.
Comparative Example 10 is an example in which the firing temperature was lower than 1500 ° C., so that the average crystal grain size of the alumina crystal particles was smaller than the range of requirement <6>.
Comparative Example 11 is an example in which the firing temperature was higher than 1750 ° C., so that the average crystal grain size of the alumina crystal particles was larger than the range of requirement <6>.
Claims (3)
＜１＞アルミナ含有量が９８．３重量％以上
＜２＞マグネシア含有量が０．１〜１．０重量％
＜３＞シリカ含有量が０．１０重量％以下
＜４＞マグネシアとシリカの重量比（マグネシア／シリカ）が２．０以上
＜５＞かさ密度が３．８５ｇ／ｃｍ３以上
＜６＞平均結晶粒径が３〜２０μｍ
＜７＞ＭｇＡｌ２Ｏ４スピネルとアルミナの結晶相量の比（ＭｇＡｌ２Ｏ４スピネル／アルミナ）が０．０１〜０．０７ An alumina sintered body characterized by satisfying the following requirements <1> to <7>.
<1> Alumina content is 98.3% by weight or more <2> Magnesia content is 0.1 to 1.0% by weight
<3> Silica content is 0.10% by weight or less <4> Weight ratio of magnesia to silica (magnesia / silica) is 2.0 or more <5> Bulk density is 3.85 g / cm 3 or more <6> Average crystal Particle size 3 ~ 20μm
<7> The ratio of the crystal phase amount of MgAl 2 O 4 spinel to alumina (MgAl 2 O 4 spinel / alumina) is 0.01 to 0.07.
＜８＞アルミナ結晶粒径の分布の変動係数が２０％以下 The alumina sintered body according to claim 1, wherein the following requirement <8> is satisfied.
<8> The coefficient of variation of the distribution of alumina crystal grain size is 20% or less
＜９＞ジルコニア含有量が０．１０重量％以下、カルシア含有量が０．５重量％以下 The alumina sintered body according to claim 1 or 2, wherein the following requirement <9> is satisfied.
<9> Zirconia content is 0.10% by weight or less, calcia content is 0.5% by weight or less
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| JP2021008367A (en) * | 2017-10-12 | 2021-01-28 | 住友電気工業株式会社 | Ceramic substrate, laminate, and saw device |
| CN115333501A (en) * | 2017-10-12 | 2022-11-11 | 住友电气工业株式会社 | Ceramic substrate, layered body, and SAW device |
| KR102497967B1 (en) * | 2018-03-28 | 2023-02-10 | 엔지케이 인슐레이터 엘티디 | Composite sintered body, semiconductor manufacturing equipment member, and manufacturing method of composite sintered body |
| KR102394008B1 (en) | 2018-12-26 | 2022-05-04 | 스미또모 가가꾸 가부시끼가이샤 | Alumina, alumina slurry, alumina film, multilayer separator and non-aqueous electrolyte secondary battery and manufacturing method thereof |
| JP7328360B2 (en) * | 2020-01-10 | 2023-08-16 | 京セラ株式会社 | Heat resistant material |
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| JPH0952758A (en) * | 1995-08-10 | 1997-02-25 | Nippon Steel Corp | Alumina ceramic and its production |
| JP3035582B2 (en) * | 1996-12-26 | 2000-04-24 | 日本特殊陶業株式会社 | Alumina sintered body |
| JP4927292B2 (en) * | 2002-04-25 | 2012-05-09 | 株式会社ニッカトー | Alumina ceramics with excellent wear and corrosion resistance |
| JP2004292230A (en) * | 2003-03-26 | 2004-10-21 | Kyocera Corp | Wear resistant alumina sintered compact and method of manufacturing the same |
| JP4959113B2 (en) * | 2004-02-25 | 2012-06-20 | 京セラ株式会社 | Alumina sintered body |
| JP5351405B2 (en) * | 2007-10-09 | 2013-11-27 | 株式会社ニッカトー | Alumina ceramics with excellent wear resistance |
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