JP2016108188A - Production method of molybdenum trioxide pellet - Google Patents
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- 239000008188 pellet Substances 0.000 title claims abstract description 71
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 35
- JKQOBWVOAYFWKG-UHFFFAOYSA-N molybdenum trioxide Chemical compound O=[Mo](=O)=O JKQOBWVOAYFWKG-UHFFFAOYSA-N 0.000 title claims abstract description 20
- 238000005245 sintering Methods 0.000 claims abstract description 51
- 239000002775 capsule Substances 0.000 claims abstract description 23
- 239000002994 raw material Substances 0.000 claims abstract description 6
- 238000001513 hot isostatic pressing Methods 0.000 claims description 6
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- 230000009257 reactivity Effects 0.000 claims description 3
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- 238000007906 compression Methods 0.000 claims 1
- 239000011888 foil Substances 0.000 claims 1
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- 239000000843 powder Substances 0.000 abstract description 11
- 239000002901 radioactive waste Substances 0.000 abstract description 5
- 238000000748 compression moulding Methods 0.000 abstract 1
- 238000000034 method Methods 0.000 description 55
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 17
- 239000000463 material Substances 0.000 description 9
- 230000008569 process Effects 0.000 description 7
- 238000002490 spark plasma sintering Methods 0.000 description 7
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 6
- 239000007789 gas Substances 0.000 description 6
- 238000005538 encapsulation Methods 0.000 description 5
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- 238000002059 diagnostic imaging Methods 0.000 description 4
- 239000012535 impurity Substances 0.000 description 4
- ZOKXTWBITQBERF-AKLPVKDBSA-N Molybdenum Mo-99 Chemical compound [99Mo] ZOKXTWBITQBERF-AKLPVKDBSA-N 0.000 description 3
- 238000002441 X-ray diffraction Methods 0.000 description 3
- 229910052786 argon Inorganic materials 0.000 description 3
- 238000005304 joining Methods 0.000 description 3
- 239000000523 sample Substances 0.000 description 3
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 2
- 238000004458 analytical method Methods 0.000 description 2
- 239000011230 binding agent Substances 0.000 description 2
- 229910052799 carbon Inorganic materials 0.000 description 2
- 239000000919 ceramic Substances 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
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- 239000002699 waste material Substances 0.000 description 2
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- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 1
- 206010028980 Neoplasm Diseases 0.000 description 1
- 208000006011 Stroke Diseases 0.000 description 1
- GKLVYJBZJHMRIY-OUBTZVSYSA-N Technetium-99 Chemical compound [99Tc] GKLVYJBZJHMRIY-OUBTZVSYSA-N 0.000 description 1
- 229910052770 Uranium Inorganic materials 0.000 description 1
- 230000004913 activation Effects 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 201000011510 cancer Diseases 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
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- 238000007922 dissolution test Methods 0.000 description 1
- 230000004992 fission Effects 0.000 description 1
- QOSATHPSBFQAML-UHFFFAOYSA-N hydrogen peroxide;hydrate Chemical compound O.OO QOSATHPSBFQAML-UHFFFAOYSA-N 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 229910052750 molybdenum Inorganic materials 0.000 description 1
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- 230000003647 oxidation Effects 0.000 description 1
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- JFALSRSLKYAFGM-UHFFFAOYSA-N uranium(0) Chemical compound [U] JFALSRSLKYAFGM-UHFFFAOYSA-N 0.000 description 1
- JFALSRSLKYAFGM-OIOBTWANSA-N uranium-235 Chemical compound [235U] JFALSRSLKYAFGM-OIOBTWANSA-N 0.000 description 1
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Abstract
Description
本発明は、がん、心筋梗塞、脳卒中をはじめとする疾病の画像診断において欠かせない放射性同位元素であるテクネチウム‐99m（99mTc）を製造する工程の前段階として、その親核種である放射性モリブデン（99Mo）を放射化法で製造するために必要な三酸化モリブデン(MoO3)のペレットを製造する方法に関するものである。 The present invention is a radionuclide that is a parent nuclide as a pre-stage of the process of producing technetium- 99m ( 99m Tc), which is a radioisotope indispensable in diagnostic imaging of diseases such as cancer, myocardial infarction, and stroke. The present invention relates to a method for producing molybdenum trioxide (MoO 3 ) pellets necessary for producing molybdenum ( 99 Mo) by an activation method.
画像診断に使用される99mTcの親核種である99Mo（半減期67時間）の製造方法として、ウラン-235の核分裂を利用する方法がある((n, f）法)。しかし、この方法では、濃縮ウランを原料とし、容器ごと試験研究炉で照射を行うため、同時に他の放射性同位体も大量に発生することとなり、煩雑な分離工程が必要となるだけでなく、放射性廃棄物の処理が加わることから製造コストが高価である。そこで、99Moの別の製造方法として、天然に存在する98Moを原料として、中性子照射により99Moを生成する方法が考えられている((ｎ，γ）法)。しかし、この方法では、99Moの生成量を増大させると共に、得られる99mTcの放射能濃度を高くすることが求められる。このため、高密度のMoO3ペレットを照射ターゲットとして使用する必要がある。 As a method for producing 99 Mo (the half-life of 67 hours), which is a parent nuclide of 99m Tc used for diagnostic imaging, there is a method using the nuclear fission of uranium-235 ((n, f) method). However, this method uses concentrated uranium as a raw material and irradiates the entire vessel in a test and research reactor. At the same time, a large amount of other radioisotopes are generated, which not only requires a complicated separation process but also radioactive. Manufacturing costs are high due to the added waste disposal. Therefore, as another production method of 99 Mo, a 98 Mo naturally occurring as a raw material, it has been considered a method of generating a 99 Mo by neutron irradiation ((n, gamma) method). However, this method requires increasing the amount of 99 Mo produced and increasing the radioactivity concentration of 99m Tc obtained. For this reason, it is necessary to use a high-density MoO 3 pellet as an irradiation target.
本発明は、この高密度のMoO3ペレットの製造方法に係るものであるが、最終的に画像診断に使用される99mTcは、高密度MoO3ペレットを製造した後、中性子を照射し、その後、MoO3ペレットを水酸化ナトリウム(NaOH)で溶解させ、その溶液から99mTc を抽出することによって得られる。本発明が関係している高密度のMoO3ペレットの製造方法としては、現在、放電プラズマ焼結法(SPS法)を用いたものが唯一の製造方法として着目されている(特許文献１等を参照)。
The present invention relates to a method for producing this high-density MoO 3 pellet, but finally 99m Tc used for diagnostic imaging is irradiated with neutrons after producing a high-density MoO 3 pellet. It is obtained by dissolving MoO 3 pellets with sodium hydroxide (NaOH) and extracting 99m Tc from the solution. As a manufacturing method of high-density MoO 3 pellets to which the present invention relates, a method using a discharge plasma sintering method (SPS method) is currently attracting attention as the only manufacturing method (
上述したように、放電プラズマ焼結法(SPS法)で製造したMoO3ペレットは約95%と高い焼結密度を有するものの、この方法は、以下のような問題点を有しており、さらなる改良が必要である。
（１）1つ 1つダイスに粉末を充填し焼結を行うことから、大量生産に不向きである。
（２）MoO3粉末の特性により製造条件が大きく変わり、条件設定が困難である。
（３）水酸化ナトリウム(NaOH)で溶解した際、溶液中に不溶解性残渣が多い。
（４）放射性廃棄物を低減することが困難である。
As described above, although the MoO 3 pellets produced by the spark plasma sintering method (SPS method) have a sintered density as high as about 95%, this method has the following problems, and further Improvement is needed.
(1) Since one die is filled with powder and sintered, it is not suitable for mass production.
(2) The manufacturing conditions vary greatly depending on the characteristics of the MoO 3 powder, making it difficult to set the conditions.
(3) When dissolved with sodium hydroxide (NaOH), there are many insoluble residues in the solution.
(4) It is difficult to reduce radioactive waste.
本発明の目的は、(ｎ，γ)法による99Mo製造の実用化を図るため、極めて簡単な方法で上述の４つの課題を克服できる、新たなMoO3ペレットの製造方法を提供することにある。 An object of the present invention is to provide a new method for producing MoO 3 pellets that can overcome the above four problems by a very simple method in order to put 99 Mo production into practice by the (n, γ) method. is there.
本発明者等は、高密度を有するMoO3ペレットの新たな製造方法として、従来から金属の接合や紛体の焼結などに使用されている熱間等方圧加圧法(HIP法)に着目し、大量製造性を確立するとともに、製造条件を粉末の特性による焼結条件の大きな変更のない製造方法を確立するに至った。 The inventors of the present invention have focused on the hot isostatic pressing method (HIP method) that has been conventionally used for metal joining and powder sintering as a new method for producing MoO 3 pellets having high density. In addition to establishing mass productivity, the manufacturing method has been established without greatly changing the sintering conditions depending on the characteristics of the powder.
具体的には、本発明に係るMoO3ペレットの製造方法は、原料であるMoO3粉末を圧縮成形してペレット化し、複数個の前記ペレットを、同一のカプセルに封入した後、熱間等方圧加圧装置を用いて焼結し、焼結された前記ペレットを前記カプセルから取り出す工程から成る。カプセリングによって複数個の圧縮成形したペレットを同時に熱間等方圧加圧することができるので、大量のMoO3ペレットを製造することができる。 Specifically, the method for producing MoO 3 pellets according to the present invention comprises compressing and molding the raw material MoO 3 powder into pellets, enclosing a plurality of the pellets in the same capsule, and then isothermally isothermally. It comprises a step of sintering using a pressure and pressure device and taking out the sintered pellets from the capsule. Since a plurality of compression-molded pellets can be simultaneously hot isostatically pressed by capsuleling, a large amount of MoO 3 pellets can be produced.
さらに詳細には、上述の製造方法において、前記熱間等方圧加圧装置におけるペレット焼結圧力が50MPa~190MPaの範囲にあって、ペレット焼結温度が300℃~600℃の範囲にある。後述するように、例えば、ペレット焼結圧力が190MPaで、ペレット焼結温度が300℃~600℃の範囲にある場合、常に95％T.D.以上の高い焼結密度が得られる。 More specifically, in the manufacturing method described above, the pellet sintering pressure in the hot isostatic pressing apparatus is in the range of 50 MPa to 190 MPa, and the pellet sintering temperature is in the range of 300 ° C. to 600 ° C. As will be described later, for example, when the pellet sintering pressure is 190 MPa and the pellet sintering temperature is in the range of 300 ° C. to 600 ° C., a high sintering density of 95% T.D. or higher is always obtained.
本発明に係るMoO3ペレットの製造方法によれば、短時間で大量の高密度MoO3ペレットを製造（具体的には、１回の焼結作業で例えば数十~数百個の高密度MoO3ペレットを製造）することが可能であり、結果的にさまざまな疾病の画像診断において欠かせない放射性同位元素である99mTc溶液を大量に製造することができるようになる。 According to the method for producing MoO 3 pellets according to the present invention, a large amount of high-density MoO 3 pellets can be produced in a short time (specifically, several tens to several hundreds of high-density MoO, for example, in one sintering operation). 3 pellets can be manufactured), and as a result, a large amount of 99m Tc solution, which is a radioisotope indispensable for diagnostic imaging of various diseases, can be produced.
また、本発明では、 (ｎ，γ）法の採用に加え、HIP法を用いているので、99mTc製造工程の最終段階でMoO3ペレットをNaOHで溶解した際、溶液中に不溶解性残渣がほとんど残らない上に、治具等の放射性廃棄物を最小限に留めることができる。 In the present invention, since the HIP method is used in addition to the (n, γ) method, when the MoO 3 pellet is dissolved in NaOH at the final stage of the 99m Tc manufacturing process, an insoluble residue is present in the solution. In addition, it is possible to minimize radioactive waste such as jigs.
本願発明の理解を助けるため、初めにMoO3ペレットの製造に使用する熱間等方圧加圧法(HIP法)について説明する。HIP法とは、アルゴンガスなどのガスを圧力媒体とし、高い圧力と温度の相乗効果を利用して、金属の接合及び紛体の焼結を行う方法である。この方法を実施するためのHIP装置の概略を図１に示す。この装置は、処理品を試料台に載せ、圧力容器内にアルゴンガスを充填した後、処理品の周囲に設置されたヒーターで加熱することにより、高温高圧環境を作り出し、金属の接合、金属やセラミックスの空孔の除去、粉体の焼結を行うように構成されている。 In order to help understanding of the present invention, the hot isostatic pressing method (HIP method) used for the production of MoO 3 pellets will be described first. The HIP method is a method of joining metals and sintering powder using a synergistic effect of high pressure and temperature using a gas such as argon gas as a pressure medium. An outline of the HIP apparatus for carrying out this method is shown in FIG. This device places a processed product on a sample stage, fills the pressure vessel with argon gas, and then heats it with a heater installed around the processed product, creating a high-temperature and high-pressure environment, joining metal, The ceramic pores are removed and the powder is sintered.
次に、図２を参照して、本発明に係る高密度MoO3ペレットの製造方法について説明する。図2は、本発明に係る高密度MoO3ペレットの製造方法のプロセスの概要を示す模式図である。最初に、原料であるMoO3粉末をプレス機により圧縮成形して成形品とする。その後でカプセルを用いてカプセリング(封止)を行い、先に示した手順に従ってHIP装置によって焼結させる。焼結後、カプセルを取り除く脱カプセルを行い、成形した高密度MoO3ペレットを得る。 Next, with reference to FIG. 2, a method for manufacturing the high-density MoO 3 pellets according to the present invention. FIG. 2 is a schematic diagram showing an outline of the process of the method for producing a high-density MoO 3 pellet according to the present invention. First, MoO 3 powder as a raw material is compression-molded by a press to obtain a molded product. Thereafter, the capsule is used for encapsulation (sealing), and the capsule is sintered by the HIP apparatus according to the procedure described above. After sintering, decapsulation is performed to remove the capsules, and molded high-density MoO 3 pellets are obtained.
図３に、HIP処理の前処理であるカプセリング方法の一例を示した。本発明に係る製造方法は、HIP処理の前処理であるカプセリング方法に一つの特徴を有する。本発明の製造方法では、カプセル材を溶接により円筒型に製作する。円筒型カプセル内へペレットを詰め、両端を溶接により封止することでカプセリングする。カプセルは、容器として封止することができれば使用可能なため、薄い材料でも良く、色々な形状とすることが可能である。またカプセルの材料として、高融点材料などMoO3と反応性の低い材料、例えばSUS304を用いることで、焼結体との反応も抑えることが可能となる。 FIG. 3 shows an example of a capsule method that is a pre-process of the HIP process. The manufacturing method according to the present invention has one feature in the encapsulation method that is a pretreatment of the HIP treatment. In the manufacturing method of the present invention, the capsule material is manufactured into a cylindrical shape by welding. It is encapsulated by filling pellets into a cylindrical capsule and sealing both ends by welding. Since the capsule can be used as long as it can be sealed as a container, it may be made of a thin material and can have various shapes. Further, by using a material having low reactivity with MoO 3 such as a high melting point material such as SUS304 as the capsule material, the reaction with the sintered body can be suppressed.
本発明で採用するカプセリング方法の特色は、数十個のペレットを一度にカプセリングすることにより、大量製造することが可能になることである。従来の工法である SPS法は、1時間程度の処理で 1個の高密度MoO3ペレットしか得られないが、HIP法と本発明で採用するカプセリング法を適用することで、数時間の処理で数百個の高密度MoO3ペレットを得ることが可能となる。 A feature of the encapsulation method employed in the present invention is that mass production is possible by encapsulating several tens of pellets at a time. The SPS method, which is a conventional method, can produce only one high-density MoO 3 pellet in a process of about 1 hour, but by applying the HIP method and the encapsulation method employed in the present invention, it can be processed in a few hours. Several hundred high-density MoO 3 pellets can be obtained.
また SPS法では、焼結後高密度MoO3ペレットに治具(ダイス等)であるカーボンの張切付きが起こるため、治具の交換を焼結体約1０個ごとに行なう必要があり、放射性廃棄物が増える。一方、HIP法は、カプセルを廃棄する必要があるものの、カプセルは0.05mm〜3mm程度と薄く、少量である。また廃棄されるカプセルは、ペレット数十個の製作に対して1つであるため、このようなカプセリング方法を適用することで、SPS法と比較して放射性廃棄物の低減が可能となる。 In addition, in the SPS method, carbon, which is a jig (die, etc.), is stuck to the high-density MoO 3 pellets after sintering. Therefore, it is necessary to replace the jig every 10 sintered bodies. Waste increases. On the other hand, in the HIP method, although it is necessary to discard the capsule, the capsule is as thin as about 0.05 mm to 3 mm, and the amount is small. Moreover, since one capsule is discarded for the production of several tens of pellets, application of such a capsule method makes it possible to reduce radioactive waste compared to the SPS method.
さらにまた、HIP法では、バインダーなどを使用せず焼結することが可能であるとともに、カプセル材に反応性の低い材料を選定することで、不純物の少ない高密度MoO3ペレットの製作が可能である. Furthermore, in the HIP method, sintering is possible without using a binder, and by selecting a low-reactivity material for the capsule material, it is possible to produce high-density MoO 3 pellets with less impurities. is there.
以下、図４乃至図６を参照して、本発明の一実施例について説明する。 Hereinafter, an embodiment of the present invention will be described with reference to FIGS.
本実施例では、HIP法において、アルゴンガスを圧力媒体とし、予め固形化したMoO3圧粉体を高温高圧環境で焼結し、所定の高密度のMoO3ペレットを得た。図４に、φ20×10mm MoO3 HIP焼結条件の一例を示す。HIP法では、ガスを圧力媒体として圧力をかけるため、ガスの出入りのないカプセルで処理品を覆う。カプセルでMoO3圧粉体を覆い真空封止した後、HIP装置で高温・高圧下にて焼結する。 In this example, in the HIP method, a pre-solidified MoO 3 compact was sintered in a high temperature and high pressure environment using argon gas as a pressure medium, and predetermined high density MoO 3 pellets were obtained. FIG. 4 shows an example of φ20 × 10 mm MoO 3 HIP sintering conditions. In the HIP method, gas is used as a pressure medium and pressure is applied, so that the treated product is covered with a capsule that does not allow gas to enter and exit. Cover the MoO 3 compact with a capsule, seal it in a vacuum, and then sinter it at high temperature and pressure in a HIP device.
このようにして焼結作製したMoO3ペレットの焼結特性を図５Ａと図５Ｂに示す。
図５Ａのグラフは、焼結圧力を190MPaで一定としたときの、焼結温度（℃）と焼結密度（%T.D.）の関係を示し、図５Ｂのグラフは、焼結温度を500℃で一定としたときの、焼結圧力（MPa）と焼結密度（%T.D.）の関係を示す。図５Ａは、250℃、300℃、400℃、500℃、550℃、600℃の各温度での焼結密度を示している。
The sintering characteristics of the MoO 3 pellets thus sintered are shown in FIGS. 5A and 5B.
The graph of FIG. 5A shows the relationship between the sintering temperature (° C.) and the sintering density (% TD) when the sintering pressure is constant at 190 MPa, and the graph of FIG. 5B shows the sintering temperature at 500 ° C. The relationship between sintering pressure (MPa) and sintering density (% TD) when constant is shown. FIG. 5A shows the sintered density at each temperature of 250 ° C., 300 ° C., 400 ° C., 500 ° C., 550 ° C., and 600 ° C.
HIP圧力190MPaにおいて、250℃で焼結密度が83.6%T.D.、300℃で焼結密度が96.4%T.D.、400℃で焼結密度が98.0%T.D.、500℃で焼結密度が98.5%T.D.、550℃で焼結密度が98.8%T.D.、600℃で焼結密度が98.3%T.D.を示し、550℃で最大の焼結密度となった。図５Ａのグラフから、焼結温度300℃以上において、高密度（焼結密度95%T.D.以上）のMoO3ペレットが得られることがわかった。なお、後述する、各焼結温度におけるMoO3ペレット破面部の走査型電子顕微鏡（SEM）観察結果から焼結温度600℃が上限温度であることから、焼結温度は300℃〜600℃の範囲が効果的であることがわかった。
At HIP pressure 190MPa, sintering density is 83.6% TD at 250 ℃, sintering density is 96.4% TD at 300 ℃, sintering density is 98.0% TD at 400 ℃, sintering density is 98.5% TD at 550 ℃, 550 The sintered density was 98.8% TD at ℃, the sintered density was 98.3% TD at 600 ℃, and the maximum sintered density at 550 ℃. From the graph of FIG. 5A, it was found that MoO 3 pellets having a high density (sintering density of 95% TD or more) were obtained at a sintering temperature of 300 ° C. or higher. Will be described later, the range from that
また、図５Ｂのグラフは、焼結温度500℃のときの焼結圧力（MPa）と焼結密度（%T.D.）の関係を示している。このグラフは一例であって、図５Ａのグラフとの関係で焼結温度が300℃以上ではほぼ同様の傾向が見られることがわかる。図５Ａ及び図５Ｂのグラフから、焼結圧力による依存性は少なく、焼結温度が300℃以上の場合には95%T.D.よりも大きな焼結密度が得られることがわかる。よって、HIP装置においては、ペレット焼結温度が300℃〜600℃の範囲にあれば、高密度MoO3ペレットを得られることがわかった。 The graph of FIG. 5B shows the relationship between the sintering pressure (MPa) and the sintering density (% TD) when the sintering temperature is 500 ° C. This graph is an example, and it can be seen that a similar tendency is seen when the sintering temperature is 300 ° C. or higher in relation to the graph of FIG. 5A. From the graphs of FIGS. 5A and 5B, it can be seen that there is little dependence on the sintering pressure, and a sintering density greater than 95% TD can be obtained when the sintering temperature is 300 ° C. or higher. Therefore, in the HIP apparatus, it was found that high density MoO 3 pellets can be obtained if the pellet sintering temperature is in the range of 300 ° C to 600 ° C.
次に、試作したMoO3ペレットについて、走査型電子顕微鏡(SEM)及びX線回折装置を用いて、MoO3ペレットの結晶粒径の観察及び結晶構造を調べた結果について説明する。結晶粒径は、MoO3ペレットを適当なサイズに破砕後、平らな欠片を選出し、真空蒸着器により炭素蒸着を行い、観察した。結晶構造は、平らなMoO3ペレット面をX線回折用試料ホルダーに取り付けて、測定した。 Next, the results of observation of the crystal grain size and crystal structure of the MoO 3 pellets using a scanning electron microscope (SEM) and an X-ray diffractometer will be described for the prototype MoO 3 pellets. The crystal grain size was observed by crushing the MoO 3 pellets to an appropriate size, selecting flat pieces, and depositing carbon using a vacuum evaporator. The crystal structure was measured by attaching a flat MoO 3 pellet surface to a sample holder for X-ray diffraction.
MoO3ペレットの SEM観察結果を図６に示す。この結果、焼結温度が 500℃では、粒成長は小さく、焼結温度が高温になるとともにMoO3ペレットの粒子径が成長していることが観察された。また、600℃の焼結温度では針状組織が一部生成されていた。したがって、焼結温度が600℃を超えると好ましくなく、600℃以内が望ましい。また、走査型電子顕微鏡(SEM)に付随している電子プローブマイクロアナライザ（EPMA）を用いてMoO3ペレットの定性分析を行い、観測された元素は主に酸素(O)とMoであった。 The SEM observation result of the MoO 3 pellet is shown in FIG. As a result, it was observed that when the sintering temperature was 500 ° C., the grain growth was small, the sintering temperature increased, and the particle diameter of the MoO 3 pellets grew. In addition, at the sintering temperature of 600 ° C., a part of the needle-like structure was generated. Accordingly, it is not preferable that the sintering temperature exceeds 600 ° C, and it is desirable that the sintering temperature is within 600 ° C. In addition, MoO 3 pellets were qualitatively analyzed using an electron probe microanalyzer (EPMA) attached to a scanning electron microscope (SEM), and the observed elements were mainly oxygen (O) and Mo.
始発粉末及び試作したMoO3ペレットのX線回折結果を図７に示す。この結果、全ての焼結条件でMoO3に関連するピークであり、始発粉末とのピーク位置との相違も観察されなかった。 FIG. 7 shows the X-ray diffraction results of the starting powder and the prototype MoO 3 pellet. As a result, it was a peak related to MoO 3 under all sintering conditions, and no difference from the peak position with the starting powder was observed.
また、試作したMoO3ペレットの6M-NaOHへの溶解試験を行ったところ、SPS法で製作したMoO3ペレットと同様な溶解特性が得られた。なお、Mo溶液は一部黒色になったため、これを改善する方法として、製作したMoO3ペレットの酸化処理工程や溶解時に過酸化水素水を添加したところ、無色透明なMo溶解液を得ることができた。 In addition, a dissolution test of the prototype MoO 3 pellet in 6M-NaOH was performed, and the dissolution characteristics similar to those of the MoO 3 pellet manufactured by the SPS method were obtained. In addition, since the Mo solution became partially black, as a method of improving this, a colorless and transparent Mo solution can be obtained by adding hydrogen peroxide water during the oxidation process or dissolution of the manufactured MoO 3 pellets. did it.
また、本発明ではMoO3ペレットを熱間等方圧加圧法(HIP法)によって焼結しているが、HIP法ではバインダーなどを使用せず焼結することができ、さらにカプセル材として三酸化モリブデンとの反応性が低い材料を選択採用することによって、不純物の少ない高密度MoO3ペレットを製作することができる。図８に試作したMoO3ペレットの不純物分析結果を示す。 Further, in the present invention, MoO 3 pellets are sintered by hot isostatic pressing (HIP method), but in HIP method, sintering can be performed without using a binder, and trioxide as a capsule material. By selectively adopting a material having low reactivity with molybdenum, a high-density MoO 3 pellet with few impurities can be produced. FIG. 8 shows the result of impurity analysis of the prototype MoO 3 pellet.
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