JP5678421B2 - Powder for translucent alumina, method for producing the same, and method for producing translucent alumina sintered body using the same - Google Patents
Powder for translucent alumina, method for producing the same, and method for producing translucent alumina sintered body using the same Download PDFInfo
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本発明は透光性アルミナ焼結体用粉末およびその製造方法、並びにそれを用いた透光性アルミナ焼結体の製造方法に関する。 The present invention relates to a powder for a translucent alumina sintered body, a method for producing the same, and a method for producing a translucent alumina sintered body using the same.
透光性アルミナ焼結体は、透明性、耐熱性、機械的強度などが優れており、歯科矯正ブラケット、耐熱ランプ管、半導体用治工具等の幅広い用途で使用されている。 The translucent alumina sintered body is excellent in transparency, heat resistance, mechanical strength, etc., and is used in a wide range of applications such as orthodontic brackets, heat-resistant lamp tubes, and semiconductor jigs.
従来、透光性アルミナ焼結体の原料には高純度アルミナ粉末が使用され、例えば特許文献1に開示されているようなアンモニウムドーソナイト(NH4AlCO3(OH)2)を熱分解する方法(以下、「ドーソナイト法」と称す)で得られた高純度アルミナ粉末を原料として用いた透光性アルミナ焼結体の製造法が知られている(特許文献2〜6)。 Conventionally, a high-purity alumina powder has been used as a raw material for a translucent alumina sintered body, and, for example, ammonium dosonite (NH 4 AlCO 3 (OH) 2 ) as disclosed in Patent Document 1 is thermally decomposed. A method for producing a translucent alumina sintered body using a high-purity alumina powder obtained by a method (hereinafter referred to as “dawsonite method”) as a raw material is known (Patent Documents 2 to 6).
しかし、ドーソナイト法で得られる高純度アルミナ粉末は焼結性には優れるが、その製造工程が長く、コスト高になるという問題があった。 However, the high-purity alumina powder obtained by the dawsonite method is excellent in sinterability, but has a problem that the manufacturing process is long and the cost is high.
一方、ドーソナイト法以外で工業的に利用できる高純度アルミナ粉末として、アルミニウムアルコキシドの加水分解法(以下、「アルコキシド法」と称す)、アンモニウム明礬(NH4Al(SO4)2・12H2O)の熱分解法等が知られている。しかしながら、これらの粉体では焼結性が十分でなく、透明性の高いアルミナ焼結体を得るためには焼結条件の精密な制御が必要であった。 On the other hand, as a high-purity alumina powder that can be used industrially other than the dawsonite method, a hydrolysis method of aluminum alkoxide (hereinafter referred to as “alkoxide method”), ammonium alum (NH 4 Al (SO 4 ) 2 · 12H 2 O) The thermal decomposition method is known. However, these powders do not have sufficient sinterability, and precise control of the sintering conditions is necessary to obtain a highly transparent alumina sintered body.
他にも粉砕によって焼結性を高めた高純度アルミナ粉末が提案されている(特許文献7〜9)。しかし、その様なアルミナ粉末では焼結性が十分でなく、得られる焼結体の透光性が十分でなかった。さらに焼結性を向上させるために粉末の比表面積を増大させた場合、焼結体中に気孔が残存することにより透光性は逆に低下する結果となっていた。 In addition, high-purity alumina powder having improved sinterability by pulverization has been proposed (Patent Documents 7 to 9). However, such alumina powder has insufficient sinterability, and the resulting sintered body has insufficient translucency. Further, when the specific surface area of the powder was increased in order to improve the sinterability, the translucency was decreased due to the remaining pores in the sintered body.
本発明では、高透光性アルミナ焼結体の原料として有用な高純度アルミナ粉末およびその製造方法、並びにそれを用いた高透光性アルミナ焼結体の製法を提供する。 The present invention provides a high-purity alumina powder useful as a raw material for a highly light-transmitting alumina sintered body, a method for producing the same, and a method for producing a light-transmitting alumina sintered body using the same.
本発明者等は、透光性アルミナ焼結体の製造について鋭意検討を重ねた結果、高純度でなおかつ特定の比表面積と粒子径を有する粉末を常圧焼結とHIP処理をすることにより、極めて透光性の高いアルミナ焼結体が得られることを見出し、本発明を完成するに到ったものである。 As a result of intensive studies on the production of a translucent alumina sintered body, the present inventors have conducted high-purity powder having a specific surface area and particle size by atmospheric pressure sintering and HIP treatment. The inventors have found that an alumina sintered body with extremely high translucency can be obtained, and have completed the present invention.
以下に本発明のアルミナ焼結体の製造法を説明する。 The method for producing the alumina sintered body of the present invention will be described below.
本発明のアルミナ焼結体の製造方法は、純度99.9%以上、比表面積が16〜25m2/g、粒子径0.1μm以下の一次粒子が40〜80%(個数基準)含有するアルミナ粉末を成形、一次焼結した後、HIP処理をする製造方法である。 The method for producing an alumina sintered body according to the present invention is an alumina containing a purity of 99.9% or more, a specific surface area of 16 to 25 m 2 / g, and primary particles of 40 to 80% (number basis) having a particle diameter of 0.1 μm or less. In this manufacturing method, the powder is molded and subjected to primary sintering, and then subjected to HIP treatment.
従来、比表面積が大きいアルミナ粉末を焼結した場合、焼結体の透光性は低下することが知られており、比表面積が16m2/gを超える高表面積のアルミナ粉末を一次焼結とHIP処理することによって高透明なアルミナ焼結体は得られていなかった。 Conventionally, it is known that when alumina powder having a large specific surface area is sintered, the translucency of the sintered body is lowered, and alumina powder having a high surface area exceeding 16 m 2 / g is primarily sintered. A highly transparent alumina sintered body was not obtained by the HIP treatment.
本発明の方法では、得られるアルミナ焼結体の透光性は、焼結体厚み1mmにおける波長600nmでの全光線透過率が60%以上、特に65%以上、さらには70%以上であることが好ましい。 In the method of the present invention, the translucency of the obtained alumina sintered body is such that the total light transmittance at a wavelength of 600 nm at a sintered body thickness of 1 mm is 60% or more, particularly 65% or more, and further 70% or more. Is preferred.
本発明の方法で用いるアルミナ粉末は高純度であることが好ましく、99.9%以上、特に99.95%以上であることが好ましい。 The alumina powder used in the method of the present invention preferably has a high purity, preferably 99.9% or more, particularly 99.95% or more.
本発明の方法で用いるアルミナ粉末は、高純度であり、特にアルミナの焼結性を低下させる特定の不純物の総量が150ppm以下であることが好ましく、100ppm以下であることが特に好ましい。アルミナの焼結性を低下させる特定の不純物としては、例えば、Zr、Ti、3A族金属の酸化物、及びSiO2等を挙げることができる。 The alumina powder used in the method of the present invention has a high purity. In particular, the total amount of specific impurities that lower the sinterability of alumina is preferably 150 ppm or less, and particularly preferably 100 ppm or less. Specific examples of the impurities that lower the sinterability of alumina include Zr, Ti, Group 3A metal oxides, and SiO 2 .
本発明の方法で用いるアルミナ粉末の比表面積は16〜25m2/gであり、特に18〜25m2/gのものを用いることが好ましい。比表面積16m2/g未満では焼結性が十分でなく得られる焼結体の透光性が不十分となり、比表面積25m2/gを超えると、粉体が凝集しやすくなり、焼結体中に気孔が残存し、やはり透光性が低下する。 The specific surface area of the alumina powder used in the method of the present invention is 16 to 25 m 2 / g, and it is particularly preferable to use 18 to 25 m 2 / g. If the specific surface area is less than 16 m 2 / g, the sinterability is not sufficient, and the resulting sintered body has insufficient translucency. If the specific surface area exceeds 25 m 2 / g, the powder tends to aggregate, and the sintered body The pores remain inside, and the translucency is also lowered.
本発明の方法で用いるアルミナ粉末は個数基準で粒子径0.1μm以下の一次粒子を40〜80%含むものであり、特に50〜80%含有するものが好ましい。粒子径0.1μm以下の一次粒子が80%を超える、または、40%未満の粉末では粉末充填性が低下するため、得られる焼結体の透光性が低下する。前記の粒度構成とすることで、本発明のアルミナ粉末を成形した際に粒子径0.1μm以下の一次粒子が0.1μmを超える一次粒子の間隙に効率よく充填されることにより焼結体中に気孔が残存することが抑制される。 The alumina powder used in the method of the present invention contains 40 to 80% of primary particles having a particle diameter of 0.1 μm or less on the basis of the number, and particularly preferably contains 50 to 80%. When the primary particle having a particle diameter of 0.1 μm or less exceeds 80% or less than 40%, the powder filling property is lowered, and thus the translucency of the obtained sintered body is lowered. When the alumina powder of the present invention is molded, the primary particles having a particle size of 0.1 μm or less are efficiently filled in the gaps of primary particles exceeding 0.1 μm when the alumina powder of the present invention is formed. It is suppressed that pores remain.
本発明の方法で用いるアルミナ粉末の結晶型は99%以上がα−アルミナ粒子からなることが好ましく、特に99.5%以上、さらに全て(100%)がα−アルミナ粒子からなることが好ましい。α−アルミナ以外のアルミナを含む場合には得られる焼結体の透光性が低くなりやすい。 The crystal form of the alumina powder used in the method of the present invention is preferably 99% or more composed of α-alumina particles, more preferably 99.5% or more, and all (100%) are preferably composed of α-alumina particles. When alumina other than α-alumina is included, the translucent property of the obtained sintered body tends to be low.
本発明の方法で用いるアルミナ粉末は、上記の特性を満足することにより、大気圧下、大気中、温度1300℃以下の焼結で相対密度が98%以上となるものが好ましい。さらには、当該条件で2時間以下の焼結で相対密度が98%以上となるものが特に好ましい。この条件で焼結した際に相対密度が98%未満であると、高い透光性を有するアルミナ焼結体が得られにくい。 The alumina powder used in the method of the present invention preferably has a relative density of 98% or more by sintering at a temperature of 1300 ° C. or lower under atmospheric pressure and in the atmosphere by satisfying the above-mentioned characteristics. Furthermore, it is particularly preferable that the relative density becomes 98% or more by sintering under the above conditions for 2 hours or less. If the relative density is less than 98% when sintered under these conditions, it is difficult to obtain an alumina sintered body having high translucency.
本発明の方法では、焼結助剤等を用いずに高純度な焼結体が得るため、高透光性というだけでなく、高強度の焼結体が得られる。 In the method of the present invention, since a high-purity sintered body is obtained without using a sintering aid or the like, not only high translucency but also a high-strength sintered body is obtained.
本発明の方法におけるアルミナ粉末の成型方法は、一次焼結に供するために適切な形状の成型体が得られる方法であれば制限はなく、一般的にセラミックスの成型に用いられているプレス成型、冷間静水圧プレス成型、鋳込み成型、押し出し成型、射出成型等の成型方法を用いることができる。 The molding method of the alumina powder in the method of the present invention is not limited as long as it is a method capable of obtaining a molded body having an appropriate shape for use in primary sintering, and press molding generally used for molding ceramics. A molding method such as cold isostatic pressing, casting molding, extrusion molding or injection molding can be used.
本発明の方法で用いるアルミナ粉末の成形体密度は55%以上であることが好ましく、特に57%以上であることが好ましい。成形体密度は高いほど好ましいが、現実的には65%を超えるものを得ることは困難である。 The density of the compact of the alumina powder used in the method of the present invention is preferably 55% or more, particularly preferably 57% or more. The higher the density of the molded body, the better, but in reality it is difficult to obtain a density exceeding 65%.
本発明の方法における一次焼結の焼結温度は1250℃〜1350℃であり、1250〜1300℃であることが好ましい。焼結温度が1350℃を超えると一次焼結体の結晶粒子が大きくなりやすく、HIP処理後のアルミナ焼結体の透光性は低くなる。また、1250℃未満では得られる一次焼結体の相対密度が低くなり、同様にHIP処理後の透光性は低いものとなる。本発明の方法では、一次焼結の段階で95〜99%の相対密度を有する一次焼結体とすることが好ましい。 The sintering temperature of primary sintering in the method of the present invention is 1250 ° C to 1350 ° C, preferably 1250 to 1300 ° C. When the sintering temperature exceeds 1350 ° C., the crystal particles of the primary sintered body tend to be large, and the translucency of the alumina sintered body after the HIP treatment is lowered. Moreover, if it is less than 1250 degreeC, the relative density of the primary sintered compact obtained will become low, and the translucency after HIP processing will become low similarly. In the method of the present invention, it is preferable to obtain a primary sintered body having a relative density of 95 to 99% at the stage of primary sintering.
本発明の方法におけるHIP処理は温度1250℃以上で行うことが好ましく、特に1300〜1500℃が好ましい。HIP処理温度は高いほど得られるアルミナ焼結体の結晶粒子径が大きくなり、例えば本発明の方法では1300℃では1μm、1400℃では2μm、1500℃では3〜5μmの結晶粒径が得られる。HIP処理の圧力、圧力媒体は特に限定されないが、一般的に用いられる100〜200MPaの範囲が適用でき、圧力媒体として通常のアルゴンガスを用いることができる。 The HIP treatment in the method of the present invention is preferably performed at a temperature of 1250 ° C. or higher, particularly preferably 1300 to 1500 ° C. The higher the HIP treatment temperature, the larger the crystal grain size of the resulting alumina sintered body. For example, in the method of the present invention, a crystal grain size of 1 μm at 1300 ° C., 2 μm at 1400 ° C., and 3-5 μm at 1500 ° C. is obtained. Although the pressure and pressure medium of HIP processing are not particularly limited, a generally used range of 100 to 200 MPa can be applied, and ordinary argon gas can be used as the pressure medium.
本発明の方法により得られたアルミナ焼結体は、試料厚さ1mm、測定波長600nmにおける全光線透過率が60%以上、好ましくは65%以上の高い透光性を有する。 The alumina sintered body obtained by the method of the present invention has a high translucency with a total light transmittance of 60% or more, preferably 65% or more at a sample thickness of 1 mm and a measurement wavelength of 600 nm.
本発明の方法により得られるアルミナ焼結体の平均結晶粒径は1〜5μmとすることができ、粗大な結晶粒径を有さないため高強度、かつ、高い透光性を備えたアルミナ焼結体を得ることができる。 The average crystal grain size of the alumina sintered body obtained by the method of the present invention can be 1 to 5 μm, and since it does not have a coarse crystal grain size, it has high strength and high translucency. A ligation can be obtained.
本発明の方法で用いるアルミナ粉末は、アルミナ粉末の粉砕によって表面積、粒度を調整したものが好ましく、例えば、比表面積15m2/g以下のアルミナ粉末を粉砕し、比表面積を16〜25m2/gとすることによって粒子径0.1μm以下の一次粒子が40〜80%(個数基準)としたものが好ましい。 The alumina powder used in the method of the present invention preferably has a surface area and a particle size adjusted by pulverization of the alumina powder. For example, an alumina powder having a specific surface area of 15 m 2 / g or less is pulverized and the specific surface area is 16 to 25 m 2 / g. Therefore, it is preferable that the primary particles have a particle size of 40 to 80% (number basis) of 0.1 μm or less.
粉砕に供する原料アルミナ粉末は、高純度のアルミナ粉末であれば特に制限はなく、アルコキシド法や、アンモニウム明礬の熱分解法などの方法で製造された粉末や、ドーソナイト法により製造された粉末なども使用することができる。これらの一般的な製法で製造された原料アルミナ粉末は、合成中のα型アルミナへの結晶変化に伴って比表面積が顕著に減少する傾向があるため、直接合成にてα型アルミナの比率が高くなおかつ比表面積15m2/gを超えるアルミナ粉末は得られにくい。 The raw material alumina powder to be pulverized is not particularly limited as long as it is a high-purity alumina powder, and powders produced by a method such as an alkoxide method or a pyrolysis method of ammonium alum, a powder produced by a dawsonite method, etc. Can be used. Since the specific surface area of the raw material alumina powder produced by these general production methods tends to decrease remarkably with the crystal change to α-type alumina during synthesis, the ratio of α-type alumina in direct synthesis is low. Alumina powder that is high and has a specific surface area of more than 15 m 2 / g is difficult to obtain.
未粉砕の段階で既に比表面積が15m2/gを超える原料アルミナ粉末では、α−アルミナ以外の結晶相を多く含みやすく、そのような粉末を原料粉末に用いた場合、得られるアルミナ焼結体の透光性が低下しやすい。 In the raw material alumina powder whose specific surface area already exceeds 15 m 2 / g in the unmilled stage, it tends to contain many crystal phases other than α-alumina, and when such powder is used as the raw material powder, an alumina sintered body obtained The translucency of the glass tends to decrease.
原料アルミナ粉末の粉砕には、ジェットミル、攪拌ミルなどの粉砕方法が適用できるが、粉砕後の収率および不純物混入の観点からは攪拌ミルで粉砕することが好ましい。粉砕は不純物が混入しない状態で行うことが好ましく、攪拌ミルはアルミナ製撹拌ミルであることが好ましい。 For pulverization of the raw material alumina powder, a pulverization method such as a jet mill or a stirring mill can be applied. However, from the viewpoint of yield after pulverization and contamination with impurities, it is preferable to pulverize with a stirring mill. The pulverization is preferably performed in a state where impurities are not mixed, and the stirring mill is preferably an alumina stirring mill.
アルミナ製攪拌ミルとは、粉砕用ビーズ、及び攪拌棒、攪拌翼、攪拌室壁、セパレーター部品のすべてがアルミナから構成されているものであり、これにより、構成部品の磨耗による、アルミナ粉末への不純物混入量を最小限に抑えることができる。 Alumina stirring mill is a grinding bead, stirring rod, stirring blade, stirring chamber wall, and separator parts are all made of alumina. The amount of impurities mixed can be minimized.
攪拌ミルに使用する粉砕用ビーズは特に磨耗しやすいため、アルミナからなることが好ましく99.99%以上の高純度アルミナからなることが特に好ましい。 Since the grinding beads used in the stirring mill are particularly easily worn, the beads are preferably made of alumina and particularly preferably 99.99% or more of high-purity alumina.
粉砕用ビーズのサイズは直径1mm以下が好ましく、0.5mm以下であればさらに好ましい。粉砕用ビーズは微小なほど得られるアルミナ粉末が微粒化する。しかしながら、粉砕用ビーズが小さすぎるとアルミナ粉末中の微粒子が増加し、本発明の粒度構成を有するアルミナ粉末が得られにくくなる。本発明のアルミナ粉末を得るためには、粉砕用ビーズは0.1mm以上であればよい。 The size of the grinding beads is preferably 1 mm or less in diameter, and more preferably 0.5 mm or less. The finer the pulverized beads, the finer the alumina powder obtained. However, if the pulverizing beads are too small, the fine particles in the alumina powder increase, making it difficult to obtain the alumina powder having the particle size constitution of the present invention. In order to obtain the alumina powder of the present invention, the pulverizing beads may be 0.1 mm or more.
攪拌ミルによる粉砕は、図1に示したような装置を用い、アルミナ粉末と水溶媒からなるスラリーを攪拌室に送り、粉末粒子を攪拌されているビーズとの衝突で砕く操作で行うことができる。 The pulverization by the agitation mill can be performed by using an apparatus as shown in FIG. 1 and sending the slurry composed of the alumina powder and the aqueous solvent to the agitation chamber and crushing the powder particles by collision with the agitated beads. .
粉砕時間は、粉砕量やスラリー濃度により変わるため適宜調整されるものであるが、1時間以上8時間以下、好ましくは2時間以上6時間以下を例示できる。粉砕時間が1時間より短いと得られる粉末の粒度構成が本発明の範囲外になりやすく、一方、8時間を越えると粉末が過度に微細になり易く、また、工業的ではない。 The pulverization time is appropriately adjusted because it varies depending on the pulverization amount and slurry concentration, and examples thereof include 1 hour to 8 hours, preferably 2 hours to 6 hours. If the pulverization time is shorter than 1 hour, the particle size constitution of the obtained powder tends to be out of the range of the present invention. On the other hand, if it exceeds 8 hours, the powder tends to become excessively fine and is not industrial.
本発明の方法では、高い透光性を有するアルミナ焼結体を得ることができる。 In the method of the present invention, an alumina sintered body having high translucency can be obtained.
以下、実施例を挙げて本発明を具体的に説明するが、本発明はこれらの実施例に限定されるものではない。 EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated concretely, this invention is not limited to these Examples.
本発明の焼結体及び粉末の特性測定方法を以下に説明する。 A method for measuring the characteristics of the sintered body and powder of the present invention will be described below.
(比表面積)
比表面積測定装置を用い、窒素ガス吸着によるBET法により測定した。
(Specific surface area)
The specific surface area was measured by a BET method using nitrogen gas adsorption.
(粒度分布)
粉末の透過電子顕微鏡(TEM)写真から個々の一次粒子の大きさを計測し求めた。計測数は500個以上とした。0.1μm以下の一次粒子の個数の合計を粒子の全個数で除して個数基準割合とした。
(Particle size distribution)
The size of each primary particle was measured and determined from a transmission electron microscope (TEM) photograph of the powder. The number of measurements was 500 or more. The total number of primary particles of 0.1 μm or less was divided by the total number of particles to obtain a number-based ratio.
(成形体密度)
アルミナ粉末を金型に充填し、一軸プレスで500kgf/cm2の圧力を加え、円柱形状(φ20mm、厚さ5mm)とし、さらにそれを冷間等方加圧装置(CIP)で2t/cm2の圧力で等方加圧して成型体を作製し、寸法と重量から密度を計算した。
(Molded body density)
The alumina powder was filled in a mold, applying a pressure of 500 kgf / cm 2 in a uniaxial press, a cylindrical shape (20 mm in diameter, thickness 5mm) and, further cold isostatic pressing apparatus it (CIP) at 2t / cm 2 A molded body was produced by isotropic pressurization at a pressure of, and the density was calculated from the dimensions and weight.
(全光線透過率)
HIP処理後のアルミナ焼結体の全光線透過率はJISK7105「プラスティックスの光学特性試験方法」およびJISK7361−1「プラスティック・透明材料の全光線透過率の試験方法に基づいて測定した。測定試料は焼結体厚みを1mmに加工し表面粗さRa=0.02μm以下に両面鏡面研磨したものを用いた。測定にはダブルビーム方式の分光光度計(日本分光株式会社製、V−650型)を用い、光源(重水素ランプおよびハロゲンランプ)より発生した光を試料に透過および散乱させ積分球を用いて全光線透過量を測定した。測定波長領域は200〜800nmの領域とし、全光線透過率は可視光線領域の600nmの波長での全光線透過率とした。
(Total light transmittance)
The total light transmittance of the alumina sintered body after the HIP treatment was measured based on JISK7105 “Testing method of optical properties of plastics” and JISK7361-1 “Testing method of total light transmittance of plastic / transparent material. A double-beam spectrophotometer (manufactured by JASCO Corp., Model V-650) was used for processing the sintered body to a thickness of 1 mm and mirror polishing on both sides to a surface roughness Ra = 0.02 μm or less. The light generated from the light source (deuterium lamp and halogen lamp) was transmitted and scattered through the sample, and the total light transmission amount was measured using an integrating sphere.The measurement wavelength range was 200 to 800 nm, and the total light transmission was performed. The rate was the total light transmittance at a wavelength of 600 nm in the visible light region.
なお、全光線透過率は、以下の関係式を有するパラメーターである。 The total light transmittance is a parameter having the following relational expression.
Ti=Tt−Td ・・・(1)
Tt:全光線透過率(%)
Td:拡散透過率(%)
Ti:直線透過率(%)
Ti = Tt−Td (1)
Tt: Total light transmittance (%)
Td: diffuse transmittance (%)
Ti: Linear transmittance (%)
実施例1
原料粉末としてアルコキシド法で製造された市販高純度アルミナ粉末(製品名:AKP−53、比表面積13.4m2/g)を使用して、アルミナ製攪拌ミルで粉砕した。アルミナ製攪拌ミルの模式図を図1に示した。
Example 1
A commercially available high-purity alumina powder (product name: AKP-53, specific surface area of 13.4 m 2 / g) produced by the alkoxide method was used as a raw material powder, and was pulverized with an alumina stirring mill. A schematic diagram of an alumina stirring mill is shown in FIG.
粉砕は原料粉末450gに純水1500mlを加えてスラリーを調製し、粉砕用ビーズには直径0.3mmの高純度アルミナ(純度99.99%)製のビーズを使用し、スラリーを容積1リットルの攪拌室に7.5リットル/hrで循環させながら、2時間粉砕処理し、実施例1のアルミナ粉末(粉末A)を得た。 For pulverization, 1500 ml of pure water was added to 450 g of raw material powder to prepare a slurry, and beads made of high-purity alumina (purity 99.99%) having a diameter of 0.3 mm were used as pulverization beads. While being circulated through the stirring chamber at 7.5 liters / hr, the mixture was pulverized for 2 hours to obtain the alumina powder (powder A) of Example 1.
粉末Aの比表面積、0.1μm以下の一次粒子比率、不純物量、αアルミナの比率を表1に示した。また、粒度分布を図2に、TEM観察の結果を図3に示した。 Table 1 shows the specific surface area of powder A, the ratio of primary particles of 0.1 μm or less, the amount of impurities, and the ratio of α-alumina. The particle size distribution is shown in FIG. 2, and the result of TEM observation is shown in FIG.
次に、得られた粉末をメカニカルプレス(500kgf/cm2)、CIP(2t/cm2)により加圧成形して成形体を得、これを電気炉に入れ、昇温速度100℃/hrで加熱し、1250〜1400℃の所定温度で2時間保持して一次焼結体を得た。 Next, the obtained powder is pressure-molded by a mechanical press (500 kgf / cm 2 ) and CIP (2 t / cm 2 ) to obtain a molded body, which is put in an electric furnace, and heated at a rate of 100 ° C./hr. It heated and hold | maintained for 2 hours at the predetermined temperature of 1250-1400 degreeC, and the primary sintered compact was obtained.
成形体並びに一次焼結体の密度を測定した結果を表2に示した。一次焼結体の相対密度は1300℃で98%以上となった。 The results of measuring the density of the molded body and the primary sintered body are shown in Table 2. The relative density of the primary sintered body was 98% or more at 1300 ° C.
次に、1300℃で焼結した一次焼結体をHIP装置に入れ、温度1400℃、アルゴンガス圧150MPaとし、1時間処理してアルミナ焼結体を得た。得られたアルミナ焼結体の全光線透過率を表2に示した。 Next, the primary sintered body sintered at 1300 ° C. was put into an HIP apparatus, and the temperature was set to 1400 ° C. and the argon gas pressure was set to 150 MPa. Table 2 shows the total light transmittance of the obtained alumina sintered body.
実施例2
粉砕時間を4時間とした以外は実施例1と同様にしてアルミナ粉末(粉末B)を得た。得られた粉末の測定結果を表1に示した。
Example 2
An alumina powder (powder B) was obtained in the same manner as in Example 1 except that the pulverization time was 4 hours. The measurement results of the obtained powder are shown in Table 1.
粉末Bを実施例1と同様に処理して成形体、一次焼結体およびアルミナ焼結体を得た。結果を表2に示した。 Powder B was processed in the same manner as in Example 1 to obtain a molded body, a primary sintered body, and an alumina sintered body. The results are shown in Table 2.
実施例3
HIP処理温度を1350、1450℃、1500,1550℃の各温度とした以外は実施例1と同様に処理をしてアルミナ焼結体を得た。
Example 3
An alumina sintered body was obtained by the same treatment as in Example 1 except that the HIP treatment temperature was 1350, 1450 ° C, 1500, 1550 ° C.
得られた透光性アルミナの全光線透過率を測定した結果を図5に示した。600nmにおける全光線透過率はそれぞれ61.7%、74.3%、73.2%及び73.4%であった。 The result of measuring the total light transmittance of the obtained translucent alumina is shown in FIG. The total light transmittance at 600 nm was 61.7%, 74.3%, 73.2% and 73.4%, respectively.
比較例1
実施例1の原料粉末そのまま(未粉砕)を比較例1のアルミナ粉末(粉末C)とした。得られた粉末の測定結果を表1に、TEM観察の結果を図4に示した。
Comparative Example 1
The raw material powder of Example 1 as it was (unground) was used as the alumina powder of Comparative Example 1 (powder C). The measurement results of the obtained powder are shown in Table 1, and the results of TEM observation are shown in FIG.
比較例1は実施例1、2と比べて0.1μm以下の一次粒子比率が低かったが、不純物含有量は実施例と同程度であった。 Comparative Example 1 had a lower primary particle ratio of 0.1 μm or less than Examples 1 and 2, but the impurity content was almost the same as that of Examples.
次に、得られたアルミナ粉末を実施例1と同様に処理して成形体、一次焼結体およびアルミナ焼結体を得た。結果を表2に示した。 Next, the obtained alumina powder was processed in the same manner as in Example 1 to obtain a molded body, a primary sintered body, and an alumina sintered body. The results are shown in Table 2.
比較例2
ジルコニア製攪拌ミルおよびイットリア部分安定化ジルコニアビーズによって粉砕した以外は実施例1と同様に処理してアルミナ粉末(粉末D)を得た。
Comparative Example 2
Alumina powder (powder D) was obtained in the same manner as in Example 1 except that it was pulverized with a zirconia stirring mill and yttria partially stabilized zirconia beads.
得られた粉末の化学分析の結果、不純物としてZrO2として280ppm検出された。 As a result of chemical analysis of the obtained powder, 280 ppm as ZrO 2 was detected as an impurity.
得られた粉末を1300℃〜1400℃の所定の焼結温度で実施例1と同様に焼結し、一次焼結体を得た。 The obtained powder was sintered at a predetermined sintering temperature of 1300 ° C. to 1400 ° C. in the same manner as in Example 1 to obtain a primary sintered body.
得られた一次焼結体の相対密度は、焼結温度が1300℃のときに92.0%、1350℃のときに97.3%、1400℃のときに98.8%であり、1350℃の焼結によって相対密度98%以上は得られなかった。当該比較例の粉末は不純物が多く、緻密化しにくいものであった。 The relative density of the obtained primary sintered body is 92.0% when the sintering temperature is 1300 ° C, 97.3% when it is 1350 ° C, and 98.8% when it is 1400 ° C. A relative density of 98% or more was not obtained by sintering. The powder of the comparative example had many impurities and was difficult to be densified.
次に、1350℃で焼結した一次焼結体を実施例1と同様にHIP処理した。得られたアルミナ焼結体の全光線透過率は22%であり、透光性が低いものであった。 Next, the primary sintered body sintered at 1350 ° C. was subjected to HIP treatment in the same manner as in Example 1. The obtained alumina sintered body had a total light transmittance of 22% and low translucency.
相対密度の焼結温度依存性を実施例/比較例と比較して図6に示した。 The dependence of the relative density on the sintering temperature is shown in FIG. 6 in comparison with the example / comparative example.
本発明の方法では、耐熱ランプ管、歯科矯正ブラケット、半導体用治工具等の用途で用いられる透光性アルミナ焼結体を製造することができる。 According to the method of the present invention, a translucent alumina sintered body used for applications such as a heat-resistant lamp tube, an orthodontic bracket, and a jig for semiconductors can be produced.
Claims (6)
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