JP2008150220A - Alumina-zirconia composite powder and method for manufacturing the same - Google Patents
Alumina-zirconia composite powder and method for manufacturing the same Download PDFInfo
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本発明はアルミナより高い抗折強度を持ち、かつ高い耐摩耗性、耐熱衝撃性をもつ、アルミナ−ジルコニア複合材料を、より低温の焼結温度で緻密な焼結体を得ることを目的とした、アルミナ−ジルコニア複合粉末とそれをより安価な手法で製造する方法に関するものである。 An object of the present invention is to obtain an alumina-zirconia composite material having a higher bending strength than alumina and having a high wear resistance and thermal shock resistance, and a dense sintered body at a lower sintering temperature. The present invention relates to an alumina-zirconia composite powder and a method for producing it with a cheaper technique.
アルミナ焼結体の強度を向上させるために、アルミナマトリックス中にジルコニア粒子を分散させたアルミナ−ジルコニア複合材料が注目され、研究されてきた。また、さまざまな用途開発が進み、その特性を生かした分野で、使用されている。 In order to improve the strength of the alumina sintered body, an alumina-zirconia composite material in which zirconia particles are dispersed in an alumina matrix has attracted attention and has been studied. In addition, various applications are being developed, and they are used in fields that take advantage of their characteristics.
特許文献１によればイットリアで安定化したジルコニアを１５〜３０モル％の比率でアルミナマトリックス中に含有させ、ジルコニアの正方晶を安定的に残留させ、これによって強靭な焼結体とした技術が提示されている。 According to Patent Literature 1, zirconia stabilized with yttria is contained in an alumina matrix at a ratio of 15 to 30 mol%, and the tetragonal crystals of zirconia are stably left, thereby forming a tough sintered body. Presented.
このようなアルミナジルコニア材料はアルミナより強度・靱性が高い上に、アルミナ並みの耐摩耗性をもつことから、切削工具や軸受け部材、摺動部材に用いられている。
ただし、これらの材料の焼結温度はアルミナの焼結温度に依存し、理論密度の９８％以上の緻密度を得るためには１６００℃程度の焼結温度が必要となる。
Such an alumina zirconia material has higher strength and toughness than alumina and has wear resistance comparable to that of alumina, and is therefore used for cutting tools, bearing members, and sliding members.
However, the sintering temperature of these materials depends on the sintering temperature of alumina, and a sintering temperature of about 1600 ° C. is required to obtain a density of 98% or more of the theoretical density.
これらの材料を低温焼結化する試みとしては、特許文献２のように、アルミナの焼結助剤となるＭｎやＦｅ，Ｃｏなどを微量添加した材料が挙げられる。
またさらに最近の試みとして、特許文献３のようにＨＩＰ焼結をすることで焼結温度を下げる試みや、特許文献４のように、原料にナノ粒子を混ぜることにより焼結性が向上すると言った報告もある。
Furthermore, as a more recent attempt, it is said that the sintering temperature is improved by performing HIP sintering as in Patent Document 3 and that the sinterability is improved by mixing nanoparticles with the raw material as in Patent Document 4. There are also reports.
特許文献１または２のような粉末は、アルミナ原料粉末とジルコニア原料粉末を同時にポットに所定量入れて混合する方法をとっている。この方法は比較的廉価な製法であるが、アルミナの粒径に焼結性が影響されてしまい、低温で緻密な焼結体を得ることが難しい。
また特許文献２のようなアルミナの焼結助剤を添加して低温で焼結する方法では緻密な焼結体が得られるが、焼結体のアルミナの結晶粒子径が大きくなることでアルミナージルコニア複合材料の特徴である優れた耐摩耗性かつ、高強度・高靱性の性能が得られなくなる。
特許文献３のようにＨＩＰ処理することで、原料に関係なく低温で高密度な焼結体が得られるが、ＨＩＰ処理にはかなりの費用がかかるため、廉価な製品に使用することができない。
特許文献４には原料にアルコキシド法により得られたナノ粒子を混ぜることで低温焼結が可能になる方法が記載されている。本方法は優れた方法であるが、ナノ粒子を事前に準備する複雑な工程が必要であり、コストアップになってしまう。
Patent Document 1 or 2 uses a method in which a predetermined amount of alumina raw material powder and zirconia raw material powder are simultaneously put in a pot and mixed. This method is a relatively inexpensive method, but the sinterability is affected by the particle size of alumina, and it is difficult to obtain a dense sintered body at a low temperature.
In addition, a dense sintered body can be obtained by the method of sintering at a low temperature by adding an alumina sintering aid as in Patent Document 2, but the alumina crystal grain size is increased by increasing the crystal grain size of the sintered body. Excellent wear resistance and high strength and toughness, which are the characteristics of zirconia composite materials, cannot be obtained.
By performing the HIP treatment as in Patent Document 3, a high-density sintered body can be obtained at a low temperature regardless of the raw material. However, since the HIP treatment requires considerable cost, it cannot be used for an inexpensive product.
Patent Document 4 describes a method that enables low-temperature sintering by mixing nanoparticles obtained by an alkoxide method with a raw material. Although this method is an excellent method, it requires a complicated process for preparing nanoparticles in advance, resulting in an increase in cost.
このような課題に対してアルミナ−ジルコニア複合粉末に限り、焼結助剤を添加せずにより低温の焼結温度で緻密な焼結体となることができる原料粉末を得ることで、低コスト、低環境負荷、省エネルギー等の社会的要請にも適合したアルミナージルコニア複合焼結体を供与することが本発明の目的である。 To obtain a raw material powder that can be a dense sintered body at a low sintering temperature without adding a sintering aid, only for the alumina-zirconia composite powder for such a problem, low cost, It is an object of the present invention to provide an alumina-zirconia composite sintered body that meets social demands such as low environmental load and energy saving.
上記の目的を達成するために、本発明によれば、イットリアを１．５〜４モル％含むジルコニア粉末と、α−アルミナ粉末からなり、ジルコニア粉末／アルミナ粉末の重量割合が１５／８５〜４０／６０でありかつ、ジルコニア粉末の単斜晶の割合が４５〜６０モル％であることを特徴とするアルミナ−ジルコニア複合粉末とすることで、同じ重量割合で混合したジルコニア−アルミナ複合粉末と比べて約５０℃程度焼結温度を低くすることができる。 In order to achieve the above object, according to the present invention, the zirconia powder containing 1.5 to 4 mol% of yttria and α-alumina powder, and the weight ratio of zirconia powder / alumina powder is 15/85 to 40. / 60 and the proportion of monoclinic crystals in the zirconia powder is 45 to 60 mol%, compared with the zirconia-alumina composite powder mixed at the same weight ratio by using an alumina-zirconia composite powder characterized in that Thus, the sintering temperature can be lowered by about 50 ° C.
また本発明の原料粉末を製造する方法としては、イットリアを１．５〜４モル％を固溶させた単斜晶の割合が１０モル％未満のジルコニア粉末を、湿式粉砕し、単斜晶率が３５〜４５モル％になるまで単独で粉砕した後、α−アルミナ粉末を加えさらに湿式粉砕・混合を1時間以上継続し、ジルコニア粉末の単斜晶の割合が４５〜６０モル％となった時点で粉砕を終了し、得られたスラリーを乾燥させることで本発明のアルミナ−ジルコニア複合粉末が得られる。 In addition, as a method for producing the raw material powder of the present invention, zirconia powder having a monoclinic crystal ratio of less than 10 mol% in which 1.5 to 4 mol% of yttria is solid-solved is wet-pulverized to obtain a monoclinic crystal ratio. After being pulverized alone until 35 to 45 mol%, α-alumina powder was added and further wet pulverization and mixing were continued for 1 hour or more, and the ratio of monoclinic crystals of zirconia powder became 45 to 60 mol%. The pulverization is finished at the time point, and the resulting slurry is dried to obtain the alumina-zirconia composite powder of the present invention.
本発明の粉末を用いることで、従来の粉末より焼結温度が約５０℃低い温度で緻密なアルミナ−ジルコニア複合材料が得られることより、エネルギーコストが低下できる。さらには、本複合粉末の製造方法についても、特殊な設備を使用することが無いため、低コストで製造可能である。
本発明の粉末で、より低温な焼結温度で得られた焼結体は、焼結体の結晶粒子径が小さく、より耐摩耗性に優れた性能を持つことが期待できる。
By using the powder of the present invention, a dense alumina-zirconia composite material can be obtained at a temperature lower by about 50 ° C. than the conventional powder, thereby reducing the energy cost. Furthermore, the present composite powder can be manufactured at low cost because no special equipment is used.
The sintered body obtained with the powder of the present invention at a lower sintering temperature can be expected to have a smaller crystal grain size and a more excellent wear resistance.
以下、本発明を実施するための最良の形態について具体的に説明する。
まず、本発明の粉末は、アルミナ−ジルコニア複合材料の材料であり、焼結体におけるジルコニアは主に正方晶に準安定化されることが必要である。ジルコニアが正方晶に準安定化されることで、脆性破壊時に応力誘起変態で単斜晶に変態することで、アルミナに比べ高強度・高靱性の材料となるからである。
The best mode for carrying out the present invention will be specifically described below.
First, the powder of the present invention is a material of an alumina-zirconia composite material, and zirconia in a sintered body needs to be metastabilized mainly to tetragonal crystals. This is because zirconia is metastabilized to tetragonal crystal and transformed into monoclinic crystal by stress-induced transformation at the time of brittle fracture, resulting in a material having higher strength and higher toughness than alumina.
本発明のジルコニア粉末とアルミナ粉末の割合については、上記のアルミナージルコニア複合素材の性能を発揮する上でジルコニア／アルミナの重量比で１５／８５〜４０／６０であることが好ましい。さらには２０／８０〜３５／６５の割合であることがより好ましい。ジルコニアが１５重量％を下回ると、本発明のジルコニア添加による低温焼結性の発現についての効果が見られなくなること。さらには４０重量％より多いと、アルミナの本来持つ高い硬度が得られなくなるため好ましくない。 The ratio of the zirconia powder to the alumina powder of the present invention is preferably 15/85 to 40/60 in terms of the weight ratio of zirconia / alumina in order to exhibit the performance of the above-mentioned alumina-zirconia composite material. Furthermore, the ratio is more preferably 20/80 to 35/65. When zirconia is less than 15% by weight, the effect of low temperature sinterability due to the addition of zirconia of the present invention is not observed. Furthermore, if it exceeds 40% by weight, the high hardness inherent in alumina cannot be obtained, which is not preferable.
本発明のアルミナ−ジルコニア複合粉末は、α−アルミナ粉末とジルコニア粉末をそれぞれ湿式混合にて混合する方法により得られるものであり、アルミナおよびジルコニアを塩やアルコキシドの溶液状態で混合した状態から製作されるものについてはコストと均一度が劣るため好ましくない。 The alumina-zirconia composite powder of the present invention is obtained by a method of mixing α-alumina powder and zirconia powder by wet mixing, respectively, and is manufactured from a state in which alumina and zirconia are mixed in a solution state of salt or alkoxide. About thing, since cost and uniformity are inferior, it is not preferable.
混合前のα−アルミナ粉末については、比表面積が５〜１０ｍ2／ｇのものが好ましい。比表面積が５ｍ2／ｇ未満であると、焼結性が著しく劣り、焼結密度が低下するため好ましくない。また比表面積が１０ｍ2／ｇを超えると焼結性は向上するが、粉体としての嵩密度が高くなりすぎてしまい、成形充填時のブリッジングや成形圧力伝達ムラによる焼結体の変形等が発生しやすくなり好ましくない。また、使用するα−アルミナ粉末の平均二次粒子径は１μm以下であることが好ましい。平均二次粒子径が１μmより大きいと、混合時の粉砕により複合粉末としての平均二次粒子径が０．５μm以下にならないため、焼結性が劣り焼結密度が低くなるため好ましくない。なお、平均二次粒子径の測定方法については後述する。 The α-alumina powder before mixing preferably has a specific surface area of 5 to 10 m 2 / g. When the specific surface area is less than 5 m 2 / g, the sinterability is remarkably inferior and the sintered density is lowered, which is not preferable. In addition, if the specific surface area exceeds 10 m 2 / g, the sinterability is improved, but the bulk density as a powder becomes too high, and bridging during molding filling and deformation of the sintered body due to molding pressure transmission unevenness, etc. Is likely to occur. Moreover, it is preferable that the average secondary particle diameter of the alpha alumina powder to be used is 1 micrometer or less. When the average secondary particle diameter is larger than 1 μm, the average secondary particle diameter as a composite powder does not become 0.5 μm or less due to the pulverization at the time of mixing. In addition, the measuring method of an average secondary particle diameter is mentioned later.
一方ジルコニアについては安定化剤がすでに固溶されている状態の粉末により構成されることが必要である。ジルコニアに固溶される安定化剤については、代表的なものとしてイットリア、セリア、マグネシア、カルシア等があげられる。ここで本発明に最適な安定化剤としては、もっとも少量で正方晶に安定化され、強度が高いイットリアである。また正方晶に安定化させるために最適なイットリアの量については、ジルコニアに対し１．５から４モル％であることが好ましく、さらには２〜３．５モル％であることがさらに好ましい。イットリアの量が１．５モル％未満であると、ジルコニア全てが正方晶に安定することができずに高強度のアルミナ−ジルコニア複合材料にならない。また４モル％を超えるとジルコニアの中に立方晶に変態する割合が多くなり、応力誘起変態が発現しにくくなることから強度の低下がみられる。 On the other hand, zirconia needs to be composed of powder in a state where the stabilizer is already in solid solution. Representative examples of the stabilizer dissolved in zirconia include yttria, ceria, magnesia, calcia and the like. Here, the most suitable stabilizer for the present invention is yttria, which is stabilized to tetragonal crystal in the smallest amount and has high strength. The optimum amount of yttria for stabilizing the tetragonal crystal is preferably 1.5 to 4 mol%, more preferably 2 to 3.5 mol%, based on zirconia. If the amount of yttria is less than 1.5 mol%, all of the zirconia cannot be stabilized to tetragonal crystals, and a high-strength alumina-zirconia composite material cannot be obtained. On the other hand, when the amount exceeds 4 mol%, the ratio of transformation into cubic crystals in zirconia increases, and stress-induced transformation is less likely to occur, and thus a decrease in strength is observed.
ここで使用されるジルコニア粉末は安定化剤がすでに固溶している必要があると前述したが、このようなジルコニア粉末は、共沈法や加水分解法、熱分解法など液相段階でジルコニアとイットリアを溶液段階で均一混合して焼成することにより得られる。均一性の指標としては焼成された粉末の単斜晶の割合が１０モル％未満であることが必要である。単斜晶の割合についての測定方法については後述する。 As described above, the zirconia powder used here needs to have the stabilizer already dissolved therein, but such zirconia powder is used in the liquid phase stage such as coprecipitation method, hydrolysis method, thermal decomposition method. And yttria are uniformly mixed at the solution stage and fired. As an index of uniformity, the ratio of monoclinic crystals in the fired powder needs to be less than 10 mol%. A measuring method for the monoclinic crystal ratio will be described later.
また、この焼成粉末の物性としては、比表面積が５〜１５m2/gであることが好ましい。比表面積が５m2/g未満であると、ジルコニア粉末の焼結性が悪化し、焼結密度が低くなりすぎてしまう。また比表面積が１５m2/gを超えると粉砕後の粉末の嵩密度が低くなり、充填性が悪くなることで焼結体に内部欠陥を発生させる原因となるため好ましくない。また、各種の合成法により得られたジルコニア焼成粉末の平均二次粒子の大きさは５μm以下であることが好ましく、さらには３μm以下であることが好ましい。平均二次粒子の大きさが５μmより大きいと、粉砕により平均二次粒径を０．５μm以下にすることが難しくなるためである。 Moreover, as a physical property of this baked powder, it is preferable that a specific surface area is 5-15 m < 2 > / g. When the specific surface area is less than 5 m 2 / g, the sinterability of the zirconia powder deteriorates and the sintered density becomes too low. On the other hand, if the specific surface area exceeds 15 m 2 / g, the bulk density of the powder after pulverization becomes low and the filling property is deteriorated, thereby causing internal defects in the sintered body. In addition, the average secondary particle size of the zirconia fired powder obtained by various synthesis methods is preferably 5 μm or less, and more preferably 3 μm or less. This is because if the average secondary particle size is larger than 5 μm, it becomes difficult to reduce the average secondary particle size to 0.5 μm or less by pulverization.
本発明のアルミナ−ジルコニア複合粉末の特徴として、含まれるジルコニア粉末の単斜晶の割合が４５〜６０モル％であることで、焼結性が飛躍的に向上する効果があることを発明者は見出した。具体的に言うと、アルミナとジルコニアの混合割合が同じ粉末で理論密度の９９％に達する焼成温度が３０〜５０℃低下することが判明した。その効果については不明な点が多いが、次のように推察している。まず、ジルコニアはアルミナの焼結時の焼結阻害剤として働き、アルミナのみの焼結時に比べ焼結温度を５０℃程度上昇させる効果がある。ここで湿式粉砕されたジルコニア微粒子は粉砕により、表面エネルギーの高い新生面が生成している。この新生面の結晶相はもともと単斜晶が１０モル％未満であったものが粉末粉砕エネルギーによる応力誘起変態により単斜晶がかなり多くなっており、この表面エネルギーの高い単斜晶面は焼結時にアルミナに対する焼結阻害効果が著しく低下しており、結果、本来アルミナとジルコニア界面の焼結が進まなかった部分でより低温で焼結できるためと考えられる。ただし、本発明でいう粉末の単斜晶の割合４５〜６０モル％というのは、あくまでバルクとしての粉体の単斜晶の割合であり、破砕時の新生面の単斜晶の割合を示したものではない。 As a feature of the alumina-zirconia composite powder of the present invention, the inventor has the effect that the sinterability is drastically improved when the proportion of monoclinic crystals in the contained zirconia powder is 45 to 60 mol%. I found it. Specifically, it has been found that the firing temperature at which 99% of the theoretical density is reached with a powder having the same mixing ratio of alumina and zirconia is reduced by 30 to 50 ° C. There are many unclear points about the effect, but I guess as follows. First, zirconia acts as a sintering inhibitor during the sintering of alumina, and has the effect of raising the sintering temperature by about 50 ° C. compared to the sintering of alumina alone. Here, the wet-ground zirconia fine particles generate a new surface having a high surface energy by pulverization. Although the crystal phase of this new surface was originally monoclinic less than 10 mol%, the monoclinic crystal was considerably increased due to the stress-induced transformation by the powder grinding energy. This monoclinic surface with high surface energy was sintered. It is thought that sometimes the sintering inhibition effect on alumina is remarkably lowered, and as a result, it is possible to sinter at a lower temperature in the portion where the sintering of the alumina and zirconia interface did not proceed. However, the proportion of monoclinic crystals in the present invention of 45 to 60 mol% is the proportion of monoclinic crystals of powder as a bulk, and indicates the proportion of monoclinic crystals on the new surface at the time of crushing. It is not a thing.
ここで単斜晶率が４５モル％より低い場合、ジルコニアの破断面の単斜晶の燒結性に寄与する効果が小さく、焼成温度の低下がそれほど大きくならない。また６０モル％より大きいと焼結時に正方晶に戻りきらなくなるものが出てくるため焼結体の単斜晶の割合が大きくなりすぎてしまい強度、靱性に低下が見られるため好ましくない。 Here, when the monoclinic crystal ratio is lower than 45 mol%, the effect of contributing to the monoclinic sintering property of the fracture surface of zirconia is small, and the reduction in the firing temperature is not so great. On the other hand, if it is larger than 60 mol%, some of the sintered body will not return to tetragonal crystals, so the proportion of monoclinic crystals in the sintered body becomes too large, and the strength and toughness are reduced.
アルミナ−ジルコニア混合粉末としての平均二次粒子径は０．１μm〜０．５μmであることが好ましい。混合粉末の平均二次粒子径が０．１μm以下であると、スラリーとして分散状態を維持することが難しく、乾燥時に強い凝集を発生することから、成形時に乾燥粉末がつぶれずに焼結体に欠陥ポアが多数できてしまう。また０．５μmを超えると焼結性が低下し、焼結密度が高くならない。混合粉末の比表面積としては７〜２０m2/gであることが好ましい。これは上述したα−アルミナ及び、ジルコニアそれぞれの粉末を湿式粉砕混合した後の比表面積である。比表面積が７m2/g未満であると、焼結性が悪く焼結密度が高くならない。２０m2/g超えると粉砕後の粉末の嵩密度が低くなり、充填性が悪くなることで焼結体に内部欠陥を発生させる原因となるため好ましくない。 The average secondary particle size of the alumina-zirconia mixed powder is preferably 0.1 μm to 0.5 μm. If the average secondary particle size of the mixed powder is 0.1 μm or less, it is difficult to maintain a dispersed state as a slurry, and strong agglomeration occurs during drying. Many defective pores are formed. On the other hand, if it exceeds 0.5 μm, the sinterability is lowered and the sintered density is not increased. The specific surface area of the mixed powder is preferably 7 to 20 m 2 / g. This is the specific surface area after the above-mentioned α-alumina and each powder of zirconia are wet pulverized and mixed. When the specific surface area is less than 7 m 2 / g, the sinterability is poor and the sintered density is not increased. If it exceeds 20 m 2 / g, the bulk density of the powder after pulverization is lowered, and the filling property is deteriorated, which causes internal defects in the sintered body, which is not preferable.
本発明のアルミナ−ジルコニア複合粉末の作成方法について述べる。
上述したジルコニア焼成粉末をまず所定量計量し、所定量の水を加え、アトライターやビーズミルナノどのメディア分散型湿式粉砕機で単独で粉砕する。粉砕の効率は内部のメディアの種類・大きさや攪拌速度により変わるが、使用するメディアはアルミナまたは高強度ジルコニアであることが好ましい。またメディアの大きさはボール形状で５ｍｍ以下であることが好ましい。
A method for producing the alumina-zirconia composite powder of the present invention will be described.
First, a predetermined amount of the above-mentioned zirconia calcined powder is weighed, a predetermined amount of water is added, and it is pulverized independently by a media dispersion type wet pulverizer such as an attritor or a bead mill nano. The efficiency of pulverization varies depending on the type and size of the internal media and the stirring speed, but the media used is preferably alumina or high-strength zirconia. The media size is preferably 5 mm or less in a ball shape.
所定時間粉砕後、ジルコニアの単斜晶の割合が３５〜４５モル％になったことを確認し、上述のα−アルミナを所定量計量し、所定量の水を加え、再び湿式粉砕・混合を継続する。この際、内部のメディア径や攪拌速度などの条件を変更してもかまわない。さらにジルコニアとアルミナの均一度を高くするためにこの湿式粉砕の時間は１時間以上必要である。最終的にジルコニアの単斜晶の割合が４５〜６０モル％となっていることを確認し、湿式粉砕・混合を終了する。この湿式粉砕時にセルナＤ−３０５（中京油脂製）等の無機物質の残渣を含まない分散剤を所定量添加し、より分散した状態で湿式粉砕を実施すると効果が高い。湿式混合後のスラリーをスプレードライヤー等の噴霧乾燥機にて乾燥することで複合粉末が得られる。噴霧乾燥する前のスラリーに成形性を向上させるためのＰＶＡやアクリル樹脂系の有機バインダーを添加してもよい。 After grinding for a predetermined time, confirm that the proportion of monoclinic zirconia is 35 to 45 mol%, weigh a predetermined amount of the above-mentioned α-alumina, add a predetermined amount of water, and wet-grind and mix again. continue. At this time, conditions such as the internal media diameter and stirring speed may be changed. Furthermore, in order to increase the uniformity of zirconia and alumina, the wet pulverization time needs to be 1 hour or more. Finally, it is confirmed that the ratio of monoclinic zirconia is 45 to 60 mol%, and the wet pulverization / mixing is finished. When wet pulverization is carried out in a more dispersed state by adding a predetermined amount of a dispersant containing no inorganic substance residue such as Selna D-305 (manufactured by Chukyo Yushi) during this wet pulverization, the effect is high. The composite powder is obtained by drying the slurry after the wet mixing with a spray dryer such as a spray dryer. PVA or an acrylic organic binder for improving moldability may be added to the slurry before spray drying.
以下本発明を実施例及び比較例で具体的に説明する。ただし本発明はこれらの実施例のみにより限定されるものではない。
まず実施例の物性測定、評価の実施方法についてまとめた。
・ 平均二次粒子径
測定物質が粉末の場合は、０．５ｇ程度を水５０cm3に入れ、超音波分散器を利用して充分分散させる。また測定物質がスラリーの場合スポイトで１〜２ｇ程度を水５０cm3に入れ超音波分散器を利用して充分分散した試料を作成する。この試料をレーザー回折型粒度分布測定装置（ＨＯＲＩＢＡ製ＬＡ−９２０）にて測定する。測定結果のメジアン径を平均二次粒子径とした。
・ ジルコニアの単斜晶の割合
粉末Ｘ線回折測定によりジルコニアの単斜晶相の１１１面および１１−１面、正方晶相の１１１面の反射ピーク強度Ｉｍ（１１１）、Ｉｍ（１１−１）、Ｉｔ（１１１）、より、次の（１）式により算出される。
単斜晶相の割合[モル％]＝［Ｉｍ（１１１）＋Ｉｍ（１１−１）］／［Ｉｍ（１１１）＋Ｉｍ（１１−１）＋Ｉｔ（１１１）］×１００ （１）
焼結体の場合はＸ線回折測定により単斜晶相の１１１面および１１−１面、正方晶相の１１１面および立方晶相の１１１面の反射ピーク強度Ｉｍ（１１１）、Ｉｍ（１１−１）、Ｉｔ（１１１）、Ｉｃ（１１１）より、次の（２）式により算出される。
単斜晶相率＝［Ｉｍ（１１１）＋Ｉｍ（１１−１）］／［Ｉｍ（１１１）＋Ｉｍ（１１−１）＋Ｉｔ（１１１）＋Ｉｃ（１１１）］ （２）
・ 比表面積測定
モノソーブＭＳ−１７（ユアサアイオニクス社製）にて標準ガス（He/N2）を使用したＢＥＴ１点法により測定した。
・ 成形・焼結方法
粉末を水中等圧成形法（ＣＩＰ成形）で圧力９８ＭＰａで成形した成形体を所定形状に加工し、成形体の密度を測定した。
Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples. However, the present invention is not limited only to these examples.
First, physical property measurement and evaluation methods of the examples were summarized.
-Average secondary particle diameter When the substance to be measured is powder, about 0.5 g is put in 50 cm 3 of water and sufficiently dispersed using an ultrasonic disperser. When the measurement substance is a slurry, about 1 to 2 g is put into 50 cm 3 of water with a dropper, and a sufficiently dispersed sample is prepared using an ultrasonic disperser. This sample is measured with a laser diffraction type particle size distribution analyzer (LA-920 manufactured by HORIBA). The median diameter of the measurement result was taken as the average secondary particle diameter.
-Ratio of monoclinic zirconia: Reflection peak intensities Im (111) and Im (11-1) of the 111 and 11-1 planes of the monoclinic phase of zirconia and the 111 plane of the tetragonal phase by powder X-ray diffraction , It (111), and the following equation (1) is calculated.
Proportion of monoclinic phase [mol%] = [Im (111) + Im (11-1)] / [Im (111) + Im (11-1) + It (111)] × 100 (1)
In the case of a sintered body, the reflection peak intensities Im (111) and Im (11−) of the monoclinic phase 111 plane and the 11-1 plane, the tetragonal phase 111 plane, and the cubic phase 111 plane are measured by X-ray diffraction measurement. 1) It is calculated from the following equation (2) from It (111) and Ic (111).
Monoclinic phase ratio = [Im (111) + Im (11-1)] / [Im (111) + Im (11-1) + It (111) + Ic (111)] (2)
It was measured by BET1 point method using a standard gas (the He / N 2) at - specific surface area measuring Monosorb MS-17 (manufactured by Yuasa Ionics Inc.).
-Molding / Sintering Method A molded body obtained by molding powder at a pressure of 98 MPa by an underwater isobaric molding method (CIP molding) was processed into a predetermined shape, and the density of the molded body was measured.
有機バインダーが入っている物については５００℃で１０時間脱脂を実施し、１００℃／ｈで最高温度まで昇温して、最高温度で２時間キープ、その後１００℃／ｈで１０００℃まで冷却後炉冷で室温まで冷却する。
・ 焼結体密度測定方法
焼結体を固体比重測定方法（ＪＩＳ Ｚ ８８０７−１９７６）の液中秤量法にて焼結体密度を測定した。また、アルミナと正方晶ジルコニアの混合比による理論密度を求めて、理論密度比（測定密度）／（理論密度）×１００[％]を算出した。
For those containing organic binders, degrease at 500 ° C for 10 hours, raise the temperature to 100 ° C / h to the maximum temperature, keep at the maximum temperature for 2 hours, and then cool to 1000 ° C at 100 ° C / h Cool to room temperature with furnace cooling.
-Sintered body density measuring method The sintered compact density was measured by the submerged weighing method of the sintered compact of the solid specific gravity measuring method (JIS Z 8807-1976). Moreover, the theoretical density by the mixing ratio of alumina and tetragonal zirconia was obtained, and the theoretical density ratio (measured density) / (theoretical density) × 100 [%] was calculated.
実施例１
オキシ塩化ジルコニウムと塩化イットリウムをイットリアが２．８モル％となるように混合した溶液からアルカリ添加共沈法で得られたジルコニア水和物を１０００℃で焼成することで比表面積；７m2/g、平均二次粒子径が２．５μm、単斜晶の割合が３モル％のジルコニア粉末を得た。本ジルコニア粉末を約濃度４０重量％になるように水を添加し粉砕メディア径が３ｍｍのアトリッジミルで２００ｒｐｍの速度で湿式粉砕した。単斜晶の割合が４０モル％であることを確認し、湿式粉砕を1度停止し、比表面積７m2/g、平均二次粒子径０．５μmのα−アルミナ粉末をジルコニア／アルミナの重量比が３０／７０となる割合で添加し、濃度が約３５重量％となるように水を添加してさらに湿式粉砕を継続した。２時間後粉砕を停止し、粉末の物性を測定したところ表1の実施例１のとおりとなった。
本スラリーに成形助剤としてＰＶＡ（ＧＬ−０５）を固形分に対して１重量％添加して、噴霧乾燥機により顆粒状に噴霧乾燥した。
本粉末を成形し、１５００℃、１５５０℃、１６００℃でそれぞれ焼結し、焼結体密度を測定して理論密度比を求め、ＪＩＳ Ｒ １６０１−１９９５の３点曲げ試験により平均強度をもとめた。また、ビッカース法（荷重３０ｋｇ）により硬度を測定し、Ｘ線回折法で焼結体の単斜晶率を測定した。それぞれの測定結果を表2の実施例１欄にまとめた。
Example 1
Zirconia hydrate obtained by alkali addition coprecipitation method from a solution in which zirconium oxychloride and yttrium chloride are mixed so that yttria is 2.8 mol% is calcined at 1000 ° C., specific surface area: 7 m 2 / g A zirconia powder having an average secondary particle diameter of 2.5 μm and a monoclinic crystal ratio of 3 mol% was obtained. Water was added to the zirconia powder to a concentration of about 40% by weight, and wet pulverization was performed at a speed of 200 rpm in an attrid mill having a pulverization media diameter of 3 mm. After confirming that the monoclinic crystal ratio was 40 mol%, the wet grinding was stopped once, and α-alumina powder having a specific surface area of 7 m 2 / g and an average secondary particle size of 0.5 μm was added to the weight of zirconia / alumina. The ratio was 30/70, and water was added so that the concentration was about 35% by weight. After 2 hours, pulverization was stopped and the physical properties of the powder were measured.
1% by weight of PVA (GL-05) was added to the slurry as a molding aid based on the solid content, and the slurry was spray-dried in a granular form by a spray dryer.
This powder was molded, sintered at 1500 ° C., 1550 ° C., and 1600 ° C., respectively, and the density of the sintered body was measured to determine the theoretical density ratio, and the average strength was determined by a three-point bending test of JIS R 1601-1995. . Further, the hardness was measured by the Vickers method (load 30 kg), and the monoclinic rate of the sintered body was measured by the X-ray diffraction method. The respective measurement results are summarized in the column of Example 1 in Table 2.
比較例１
実施例１と同様の方法で表面積；７m2/g、平均二次粒子径が２．５μm、単斜晶の割合が３モル％のジルコニア粉末を得た。比表面積７m2/g、平均二次粒子径０．５μmのα−アルミナ粉末を濃度が約４０重量％となるように水を添加して粉砕メディア径が３ｍｍのアトリッジミルで２００ｒｐｍの速度で湿式粉砕した。1時間粉砕後、上記ジルコニア粉末をジルコニア／アルミナの重量比が３０／７０となる割合で添加し、濃度が約３５重量％となるように水を添加してさらに湿式粉砕を継続した。１時間後粉砕を停止した。
本スラリーに成形助剤としてＰＶＡ（ＧＬ−０５）を固形分に対して１重量％添加して、噴霧乾燥機により顆粒状に噴霧乾燥した。
本粉末を成形し、実施例１と同じ条件で焼結し、それぞれ物性評価を実施した結果を表２の比較例１欄にまとめた。
Comparative Example 1
A zirconia powder having a surface area of 7 m 2 / g, an average secondary particle size of 2.5 μm, and a monoclinic crystal ratio of 3 mol% was obtained in the same manner as in Example 1. Addition of water to α-alumina powder with specific surface area of 7m 2 / g and average secondary particle size of 0.5μm so that the concentration is about 40% by weight, and wet milling at 200rpm in an attrid mill with a grinding media diameter of 3mm did. After pulverization for 1 hour, the zirconia powder was added at a ratio such that the weight ratio of zirconia / alumina was 30/70, water was added so that the concentration was about 35% by weight, and wet pulverization was further continued. The grinding was stopped after 1 hour.
1% by weight of PVA (GL-05) was added to the slurry as a molding aid based on the solid content, and the slurry was spray-dried in a granular form by a spray dryer.
This powder was molded, sintered under the same conditions as in Example 1, and the results of physical property evaluation were summarized in the Comparative Example 1 column of Table 2.
実施例１と比較例１を比較すると、同じジルコニア粉末およびアルミナ粉末を混合したのにも関わらず、実施例１は１５００℃の焼結温度で理論密度の９８．０％、と強度６００ＭＰａ、硬度１６００となり、比較例１は１５００℃では理論密度の９６．１％、強度４１０ＭＰａ、硬度１４７０と実施例１より明らかに物性が低下している。また実施例１は比較例１の１５５０℃焼結時と同等の物性となり、焼結温度が約５０℃低くなっていることが確認された。 Comparing Example 1 and Comparative Example 1, although the same zirconia powder and alumina powder were mixed, Example 1 had a theoretical density of 98.0% at a sintering temperature of 1500 ° C., strength of 600 MPa, and hardness. The physical properties of Comparative Example 1 are clearly lower than those of Example 1 at 1500 ° C. and 96.1% of the theoretical density, the strength of 410 MPa, and the hardness of 1470. In addition, Example 1 has the same physical properties as those of Comparative Example 1 during sintering at 1550 ° C., and it has been confirmed that the sintering temperature is about 50 ° C. lower.
実施例２
オキシ塩化ジルコニウムと塩化イットリウムをイットリアが３．０モル％となるように混合した溶液からアルカリ添加共沈法で得られたジルコニア水和物を９３０℃で焼成することで比表面積；１２m2/g、平均二次粒子径が２．１μm、単斜晶の割合が７モル％のジルコニア粉末を得た。本ジルコニア粉末を約濃度４０重量％になるように水を添加し粉砕メディア径が１ｍｍのビーズミルで回転翼の周速１５ｍ／secの速度で湿式粉砕した。単斜晶の割合が３７モル％であることを確認し、湿式粉砕を1度停止し、比表面積１０m2/g、平均二次粒子径０．２μmのα−アルミナ粉末をジルコニア／アルミナの重量比が２０／８０となる割合で添加し、濃度が約３５重量％となるように水を添加してさらに同条件で湿式粉砕を継続した。スラリーのミル本体内の滞留時間が１時間となる時間で粉砕を停止し、粉末の物性を測定したところ表1の実施例２のとおりとなった。
本スラリーに成形助剤としてＰＶＡ（ＧＬ−０５）を固形分に対して１重量％添加して、噴霧乾燥機により顆粒状に噴霧乾燥した。
Example 2
Zirconia hydrate obtained by alkali addition coprecipitation method from a solution in which zirconium oxychloride and yttrium chloride are mixed so that yttria is 3.0 mol% is calcined at 930 ° C., specific surface area: 12 m 2 / g A zirconia powder having an average secondary particle diameter of 2.1 μm and a monoclinic crystal ratio of 7 mol% was obtained. The zirconia powder was wet-pulverized with a bead mill having a grinding media diameter of 1 mm at a peripheral speed of 15 m / sec. After confirming that the ratio of monoclinic crystal was 37 mol%, the wet grinding was stopped once, and α-alumina powder having a specific surface area of 10 m 2 / g and an average secondary particle diameter of 0.2 μm was added to the weight of zirconia / alumina. The ratio was 20/80, water was added so that the concentration was about 35% by weight, and wet grinding was continued under the same conditions. Grinding was stopped at a time when the residence time of the slurry in the mill body was 1 hour, and the physical properties of the powder were measured. The result was as shown in Example 2 in Table 1.
1% by weight of PVA (GL-05) was added to the slurry as a molding aid based on the solid content, and the slurry was spray-dried in a granular form by a spray dryer.
本粉末を成形し、１４５０℃、１５００℃、１５５０℃でそれぞれ焼結し、焼結体密度を測定して理論密度比を求め、ＪＩＳ Ｒ １６０１−１９９５の３点曲げ試験により平均強度をもとめた。また、ビッカース法（荷重３０ｋｇ）により硬度を測定し、Ｘ線回折法で焼結体の単斜晶率を測定した。それぞれの測定結果を表2の実施例２欄にまとめた。 This powder was molded, sintered at 1450 ° C., 1500 ° C. and 1550 ° C., respectively, and the density of the sintered body was measured to determine the theoretical density ratio, and the average strength was determined by a three-point bending test of JIS R 1601-1995. . Further, the hardness was measured by the Vickers method (load 30 kg), and the monoclinic rate of the sintered body was measured by the X-ray diffraction method. The respective measurement results are summarized in Example 2 column of Table 2.
比較例２
実施例２と同様の方法で比表面積；１２m2/g、平均二次粒子径が２．１μm、単斜晶の割合が７モル％のジルコニア粉末を得た。このジルコニア粉末と比表面積１０m2/g、平均二次粒子径０．２μmのα−アルミナ粉末をジルコニア／アルミナの重量比が２０／８０となる割合で秤量した粉末を、濃度が約３５重量％となるように水を添加して粉砕メディア径が１ｍｍのビーズミルで回転翼の周速１５ｍ／secの速度で滞留時間が３０分となる時間、湿式粉砕した。粉末の物性を測定したところ表１の比較例２の通りとなった。本スラリーに成形助剤としてＰＶＡ（ＧＬ−０５）を固形分に対して１重量％添加して、噴霧乾燥機により顆粒状に噴霧乾燥した。
Comparative Example 2
A zirconia powder having a specific surface area of 12 m 2 / g, an average secondary particle diameter of 2.1 μm, and a monoclinic crystal ratio of 7 mol% was obtained in the same manner as in Example 2. This zirconia powder and an α-alumina powder having a specific surface area of 10 m 2 / g and an average secondary particle diameter of 0.2 μm were weighed at a ratio of zirconia / alumina of 20/80, and the concentration was about 35% by weight. Water was added so that the pulverization media diameter was 1 mm, and wet pulverization was performed at a peripheral speed of 15 m / sec of the rotary blade for a residence time of 30 minutes. When the physical properties of the powder were measured, it was as shown in Comparative Example 2 in Table 1. 1% by weight of PVA (GL-05) was added to the slurry as a molding aid based on the solid content, and the slurry was spray-dried in a granular form by a spray dryer.
本粉末を成形し、１４５０℃、１５００℃、１５５０℃でそれぞれ焼結し、焼結体密度を測定して理論密度比を求め、ＪＩＳ Ｒ １６０１−１９９５の３点曲げ試験により平均強度をもとめた。また、ビッカース法（荷重３０ｋｇ）により硬度を測定し、Ｘ線回折法で焼結体の単斜晶率を測定した。それぞれの測定結果を表2の比較例２欄にまとめた。 This powder was molded, sintered at 1450 ° C., 1500 ° C. and 1550 ° C., respectively, and the density of the sintered body was measured to determine the theoretical density ratio, and the average strength was determined by a three-point bending test of JIS R 1601-1995. . Further, the hardness was measured by the Vickers method (load 30 kg), and the monoclinic rate of the sintered body was measured by the X-ray diffraction method. The respective measurement results are summarized in the Comparative Example 2 column of Table 2.
実施例２と比較例２を比較すると、同じジルコニア粉末およびアルミナ粉末を混合したのにも関わらず、実施例２は１４５０℃の焼結温度で理論密度の９８．０％、と強度４２０ＭＰａ、硬度１６５０となり、比較例２は１４５０℃では理論密度の９５．０％、強度２９０ＭＰａ、硬度１４５０と実施例２より明らかに物性が低下している。また実施例２は比較例２の１５００℃焼結時と同等の物性となり、焼結温度が約５０℃低くなっていることが確認された。 Comparing Example 2 and Comparative Example 2, although the same zirconia powder and alumina powder were mixed, Example 2 had a theoretical density of 98.0% at a sintering temperature of 1450 ° C., strength of 420 MPa, and hardness. The physical properties of Comparative Example 2 are clearly lower than those of Example 2 at 1450 ° C., 95.0% of the theoretical density, strength 290 MPa, and hardness 1450. In addition, Example 2 had the same physical properties as those of Comparative Example 2 during 1500 ° C. sintering, and it was confirmed that the sintering temperature was about 50 ° C. lower.
比較例３
オキシ塩化ジルコニウムと塩化イットリウムをイットリアが１．０モル％となるように混合した溶液からアルカリ添加共沈法で得られたジルコニア水和物を９００℃で焼成することで比表面積；１８m2/g、平均二次粒子径が２．０μm、単斜晶の割合が１９モル％のジルコニア粉末を得た。本ジルコニア粉末を約濃度４０重量％になるように水を添加し粉砕メディア径が１ｍｍのビーズミルで回転翼の周速１５ｍ／secの速度で滞留時間が１時間となるよう湿式粉砕したところ単斜晶の割合が７３モル％となっていた。湿式粉砕を1度停止し、比表面積１７m2/g、平均二次粒子径０．２μmのα−アルミナ粉末をジルコニア／アルミナの重量比が３０／８０となる割合で添加し、濃度が約３５重量％となるように水を添加してさらに同条件で湿式粉砕を継続した。スラリーのミル本体内の滞留時間が１時間となる時間で粉砕を停止し、粉末の物性を測定したところ表1の実施例３のとおりとなった。
本スラリーに成形助剤としてＰＶＡ（ＧＬ−０５）を固形分に対して１重量％添加して、噴霧乾燥機により顆粒状に噴霧乾燥した。
Comparative Example 3
Zirconia hydrate obtained by alkali addition coprecipitation method from a solution in which zirconium oxychloride and yttrium chloride are mixed so that yttria is 1.0 mol% is calcined at 900 ° C., specific surface area; 18 m 2 / g A zirconia powder having an average secondary particle diameter of 2.0 μm and a monoclinic crystal ratio of 19 mol% was obtained. When this zirconia powder was wet-pulverized with a bead mill having a grinding media diameter of 1 mm and a residence time of 1 hour at a peripheral speed of 15 m / sec. The proportion of crystals was 73 mol%. Wet pulverization is stopped once, α-alumina powder having a specific surface area of 17 m 2 / g and an average secondary particle size of 0.2 μm is added at a ratio of zirconia / alumina weight ratio of 30/80, and the concentration is about 35 Water was added so that it might become weight%, and the wet grinding was further continued under the same conditions. Crushing was stopped when the slurry stayed in the mill body for 1 hour, and the physical properties of the powder were measured. The results were as shown in Example 3 in Table 1.
1% by weight of PVA (GL-05) was added to the slurry as a molding aid based on the solid content, and the slurry was spray-dried in a granular form by a spray dryer.
本粉末を成形し、１５００℃で焼結し、焼結体密度を測定して理論密度比を求め、ＪＩＳ Ｒ １６０１−１９９５の３点曲げ試験により平均強度をもとめた。また、ビッカース法（荷重３０ｋｇ）により硬度を測定し、Ｘ線回折法で焼結体の単斜晶率を測定した。測定結果は表2の比較例３のとおりとなった。 This powder was molded, sintered at 1500 ° C., the density of the sintered body was measured to determine the theoretical density ratio, and the average strength was determined by a three-point bending test of JIS R 1601-1995. Further, the hardness was measured by the Vickers method (load 30 kg), and the monoclinic rate of the sintered body was measured by the X-ray diffraction method. The measurement results were as shown in Comparative Example 3 in Table 2.
比較例４
オキシ塩化ジルコニウムと塩化イットリウムをイットリアが５．０モル％となるように混合した溶液からアルカリ添加共沈法で得られたジルコニア水和物を１１５０℃で焼成することで比表面積；２．５m2/g、平均二次粒子径が５．５μm、単斜晶の割合が０モル％のジルコニア粉末を得た。このジルコニア粉末と比表面積５m2/g、平均二次粒子径０．６μmのα−アルミナ粉末をジルコニア／アルミナの重量比が３０／７０となる割合で秤量した粉末を、濃度が約３５重量％となるように水を添加して粉砕メディア径が３ｍｍのアトリッジミルで２００ｒｐｍの速度で湿式粉砕した。２時間後粉砕を停止し、粉末の物性を測定したところ表1の比較例４のとおりとなった。
Comparative Example 4
Zirconia hydrate obtained by alkali addition coprecipitation method from a solution in which zirconium oxychloride and yttrium chloride are mixed so that yttria is 5.0 mol% is calcined at 1150 ° C. to give a specific surface area of 2.5 m 2 A zirconia powder having an average secondary particle size of 5.5 μm and a monoclinic crystal ratio of 0 mol% was obtained. This zirconia powder and an α-alumina powder having a specific surface area of 5 m 2 / g and an average secondary particle diameter of 0.6 μm were weighed at a ratio of zirconia / alumina of 30/70, and the concentration was about 35% by weight. Water was added so that the wet grinding was performed at 200 rpm with an attrid mill having a grinding media diameter of 3 mm. After 2 hours, the pulverization was stopped, and the physical properties of the powder were measured.
本スラリーに成形助剤としてＰＶＡ（ＧＬ−０５）を固形分に対して１重量％添加して、噴霧乾燥機により顆粒状に噴霧乾燥した。 1% by weight of PVA (GL-05) was added to the slurry as a molding aid based on the solid content, and the slurry was spray-dried in a granular form by a spray dryer.
本粉末を成形し、１６００℃で焼結し、焼結体密度を測定して理論密度比を求め、ＪＩＳ Ｒ １６０１−１９９５の３点曲げ試験により平均強度をもとめた。また、ビッカース法（荷重３０ｋｇ）により硬度を測定し、Ｘ線回折法で焼結体の単斜晶率を測定した。測定結果は表2の比較例４のとおりとなった。 This powder was molded, sintered at 1600 ° C., the density of the sintered body was measured to determine the theoretical density ratio, and the average strength was determined by a three-point bending test of JIS R 1601-1995. Further, the hardness was measured by the Vickers method (load 30 kg), and the monoclinic rate of the sintered body was measured by the X-ray diffraction method. The measurement results are as shown in Comparative Example 4 in Table 2.
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| WO2014098208A1 (en) * | 2012-12-21 | 2014-06-26 | 東ソー株式会社 | Zirconia-alumina composite sintered body, and production method therefor |
| US9758434B2 (en) | 2015-06-01 | 2017-09-12 | Saint-Gobain Ceramics & Plastics, Inc. | Refractory articles and methods for forming same |
| CN113800895A (en) * | 2021-08-24 | 2021-12-17 | 萍乡市金刚科技工业园有限公司 | Wear-resistant zirconium-aluminum composite ball and preparation method thereof |
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| WO2014098208A1 (en) * | 2012-12-21 | 2014-06-26 | 東ソー株式会社 | Zirconia-alumina composite sintered body, and production method therefor |
| US9758434B2 (en) | 2015-06-01 | 2017-09-12 | Saint-Gobain Ceramics & Plastics, Inc. | Refractory articles and methods for forming same |
| US10093580B2 (en) | 2015-06-01 | 2018-10-09 | Saint-Gobain Ceramics & Plastics, Inc. | Refractory articles and methods for forming same |
| CN113800895A (en) * | 2021-08-24 | 2021-12-17 | 萍乡市金刚科技工业园有限公司 | Wear-resistant zirconium-aluminum composite ball and preparation method thereof |
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