JP6772646B2 - Nickel oxide fine powder and its manufacturing method - Google Patents
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本発明は、酸化ニッケル微粉末及びその製造方法に関し、特に、硫黄やナトリウム等の不純物品位が低く、電子部品や固体酸化物形燃料電池の電極に用いられる材料として好適な微細な酸化ニッケル微粉末及びその製造方法に関する。 The present invention relates to a fine nickel oxide powder and a method for producing the same, and in particular, a fine nickel oxide fine powder having a low impurity grade such as sulfur and sodium and suitable as a material used for an electrode of an electronic component or a solid oxide fuel cell. And its manufacturing method.
一般に、酸化ニッケル微粉末は、硫酸ニッケル、硝酸ニッケル、炭酸ニッケル、水酸化ニッケル等のニッケル塩類又はニッケルメタル粉を、ロータリーキルン等の転動炉、プッシャー炉等のような連続炉、あるいはバーナー炉のようなバッチ炉を用いて酸化性雰囲気下で焼成することによって製造される。これらの酸化ニッケル微粉末は、電子部品用材料や固体酸化物形燃料電池の電極材料等の多様な用途に用いられている。例えば、電子部品用材料としての用途では、酸化ニッケル微粉末を酸化鉄や酸化亜鉛等の他の材料と混合した後、焼結することにより作製されるフェライト部品等が広く用いられている。 Generally, the nickel oxide fine powder is a nickel salt such as nickel sulfate, nickel nitrate, nickel carbonate, nickel hydroxide, or nickel metal powder, which is used in a rolling furnace such as a rotary kiln, a continuous furnace such as a pusher furnace, or a burner furnace. It is produced by firing in an oxidizing atmosphere using such a batch furnace. These nickel oxide fine powders are used in various applications such as materials for electronic parts and electrode materials for solid oxide fuel cells. For example, in applications as materials for electronic parts, ferrite parts and the like produced by mixing fine nickel oxide powder with other materials such as iron oxide and zinc oxide and then sintering them are widely used.
上記フェライト部品のように、複数の材料を混合して焼成することにより、これらを反応させて複合金属酸化物を製造する場合は、生成反応は固相の拡散反応で律速されるので、使用する原料としては一般に微細なものが好適に用いられている。その理由は、微細な原料を用いることで他材料との接触確率が高くなると共に粒子の活性が高くなるため、低温度且つ短時間でも反応を均一に進ませることができるからである。このように複合金属酸化物を製造する方法においては、原料となる粉体の粒径を小さくすることが効率向上の重要な要素となる。 When a plurality of materials are mixed and fired to produce a composite metal oxide as in the case of the above ferrite parts, the production reaction is rate-determined by the diffusion reaction of the solid phase, so that it is used. Generally, fine raw materials are preferably used. The reason is that by using a fine raw material, the probability of contact with other materials is increased and the activity of the particles is increased, so that the reaction can proceed uniformly even at a low temperature and for a short time. In the method for producing the composite metal oxide as described above, reducing the particle size of the powder as a raw material is an important factor for improving efficiency.
また、環境及びエネルギーの両面から新しい発電システムとして期待されている固体酸化物形燃料電池では、その電極材料として酸化ニッケル微粉末が用いられている。一般に、固体酸化物形燃料電池のセルスタックは、空気極、固体電解質及び燃料極からなる単セルが複数セル積層された構造を有している。この燃料極としては、例えばニッケル又は酸化ニッケルと、安定化ジルコニアからなる固体電解質とを混合したものが通常用いられている。燃料極は、発電時に水素や炭化水素等の燃料ガスにより還元されてニッケルメタルとなり、ニッケルと固体電解質と空隙からなる三相界面が燃料ガスと酸素の反応場となるため、フェライト部品として用いる場合と同様に原料となる粉体の粒径を小さくして微細にすることが発電効率向上の重要な要素となる。 Further, in a solid oxide fuel cell which is expected as a new power generation system from both aspects of environment and energy, nickel oxide fine powder is used as an electrode material thereof. Generally, a cell stack of a solid oxide fuel cell has a structure in which a plurality of single cells including an air electrode, a solid electrolyte, and a fuel electrode are stacked. As the fuel electrode, for example, a mixture of nickel or nickel oxide and a solid electrolyte made of stabilized zirconia is usually used. The fuel electrode is reduced to nickel metal by fuel gas such as hydrogen or hydrocarbon during power generation, and the three-phase interface consisting of nickel, solid electrolyte, and voids serves as a reaction field for fuel gas and oxygen, so when used as a ferrite component. Similarly, reducing the particle size of the raw material powder to make it finer is an important factor for improving power generation efficiency.
ところで、粉体が微細であることを測る指標としては、比表面積を用いることがある。また、粒径と比表面積には、下記の計算式１の関係があることが知られている。下記計算式１の関係は粒子が真球状であると仮定して導き出されたものであるため、計算式１から得られる粒径と実際の粒径との間にはいくらかの誤差を含むことになるが、比表面積が大きいほど粒径が小さくなることが分る。 By the way, the specific surface area may be used as an index for measuring the fineness of the powder. Further, it is known that the particle size and the specific surface area have a relationship of the following formula 1. Since the relationship of the following formula 1 is derived on the assumption that the particles are spherical, some error is included between the particle size obtained from the formula 1 and the actual particle size. However, it can be seen that the larger the specific surface area, the smaller the particle size.
［計算式１］
粒径＝６／（密度×比表面積）
[Calculation formula 1]
Particle size = 6 / (density x specific surface area)
近年、フェライト部品はますます高機能化する傾向にあり、また酸化ニッケル微粉末の用途はフェライト部品以外の電子部品等に広がっている。これに伴い、酸化ニッケル微粉末に含有される不純物元素の品位を低減することが求められている。不純物元素の中でも特に塩素や硫黄は、電極に利用されている銀と反応して電極劣化を生じさせたり、焼成炉を腐食させたりすることがあるため、できるだけ低減することが望ましい。 In recent years, ferrite parts have become more and more sophisticated, and the use of nickel oxide fine powder has expanded to electronic parts other than ferrite parts. Along with this, it is required to reduce the grade of impurity elements contained in the nickel oxide fine powder. Among the impurity elements, chlorine and sulfur may react with silver used for the electrodes to cause electrode deterioration and corrode the firing furnace, so it is desirable to reduce them as much as possible.
例えば特許文献１には、原料段階におけるフェライト粉の硫黄成分の含有量がＳ換算で３００〜９００ｐｐｍ且つ塩素成分の含有量がＣｌ換算で１００ｐｐｍであり、焼成後のフェライト焼結体の硫黄成分の含有量がＳ換算で１００ｐｐｍ以下且つ塩素成分の含有量がＣｌ換算で２５ｐｐｍ以下のフェライト材料が開示されている。このフェライト材料は、低温焼成においても添加物を用いることなく高密度化を図ることができ、これにより作製されたフェライト磁心及び積層チップ部品は、耐湿性と温度特性に優れていると記載されている。 For example, in Patent Document 1, the sulfur component content of the ferrite powder at the raw material stage is 300 to 900 ppm in S conversion, and the chlorine component content is 100 ppm in Cl conversion, and the sulfur component of the ferrite sintered body after firing is A ferrite material having a content of 100 ppm or less in terms of S and a chlorine component content of 25 ppm or less in terms of Cl is disclosed. It is stated that this ferrite material can be densified without using additives even in low-temperature firing, and that the ferrite core and laminated chip parts produced by this are excellent in moisture resistance and temperature characteristics. There is.
また、原料に硫酸ニッケルを用い、これを焙焼することで酸化ニッケル微粉末を製造する方法も提案されている。例えば、特許文献２には、原料としての硫酸ニッケルを、キルンなどを用いて酸化雰囲気中で９５０〜１０００℃で焙焼する第１段焙焼と、１０００〜１２００℃で焙焼する第２段焙焼とを行って酸化ニッケル粉末を製造する方法が提案されている。この製造方法によれば、平均粒径が制御され、且つ硫黄品位が５０質量ｐｐｍ以下である酸化ニッケル微粉末が得られると記載されている。 In addition, a method of producing nickel oxide fine powder by using nickel sulfate as a raw material and roasting it has also been proposed. For example, Patent Document 2 describes a first-stage roasting in which nickel sulfate as a raw material is roasted at 950 to 1000 ° C. in an oxidizing atmosphere using a kiln or the like, and a second-stage roasting in which it is roasted at 1000 to 1200 ° C. A method of producing nickel oxide powder by roasting has been proposed. According to this production method, it is described that nickel oxide fine powder having an average particle size controlled and a sulfur grade of 50 mass ppm or less can be obtained.
また、特許文献３には、４５０〜６００℃の仮焼による原料の硫酸ニッケルの脱水工程と、１０００〜１２００℃の焙焼による硫酸ニッケルの分解工程とを明確に分離した酸化ニッケル粉末の製造方法が提案されている。この製造方法によれば、硫黄品位が低く且つ平均粒径が小さい酸化ニッケル粉末を安定して製造できると記載されている。更に、特許文献４には、横型回転式製造炉を用いて、強制的に空気を導入しながら、最高温度を９００〜１２５０℃として硫酸ニッケルを焙焼する方法が提案されている。この製造方法によっても、不純物が少なく、硫黄品位が５００質量ｐｐｍ以下の酸化ニッケル粉末が得られると記載されている。 Further, Patent Document 3 describes a method for producing nickel oxide powder in which a step of dehydrating nickel sulfate as a raw material by calcining at 450 to 600 ° C. and a step of decomposing nickel sulfate by roasting at 1000 to 1200 ° C. are clearly separated. Has been proposed. According to this production method, it is described that nickel oxide powder having a low sulfur grade and a small average particle size can be stably produced. Further, Patent Document 4 proposes a method of roasting nickel sulfate at a maximum temperature of 900 to 1250 ° C. while forcibly introducing air using a horizontal rotary manufacturing furnace. It is described that nickel oxide powder having a small amount of impurities and a sulfur grade of 500 mass ppm or less can be obtained by this production method as well.
上記の特許文献２や特許文献３の方法によれば不純物品位の低い酸化ニッケル微粉末が得られるが、熱処理を２回行うため生産コストが高くなってしまう。また、上記特許文献２〜４のいずれの方法においても、硫黄品位を低減するために焙焼温度を高くすると粒径が粗大になり、逆に粒子を微細にするために焙焼温度を下げると硫黄品位が高くなるため、粒径と硫黄品位を共に最適値に制御することは困難である。更に、加熱する際にＳＯｘを含むガスが大量に発生し、これを除害処理するために高価な設備が必要になるという問題を抱えている。 According to the methods of Patent Document 2 and Patent Document 3 described above, nickel oxide fine powder having a low impurity grade can be obtained, but the production cost is high because the heat treatment is performed twice. Further, in any of the methods of Patent Documents 2 to 4, when the roasting temperature is raised in order to reduce the sulfur grade, the particle size becomes coarse, and conversely, when the roasting temperature is lowered in order to make the particles finer. Since the sulfur grade is high, it is difficult to control both the particle size and the sulfur grade to the optimum values. Further, there is a problem that a large amount of gas containing SOx is generated during heating, and expensive equipment is required for detoxifying the gas.
酸化ニッケル微粉末を合成する方法として、硫酸ニッケルや塩化ニッケル等のニッケル塩を含む水溶液を、水酸化ナトリウム水溶液等のアルカリで中和して水酸化ニッケル粒子を晶析させ、これを焙焼する方法も提案されている。このように、水酸化ニッケル粒子を焙焼する場合は、陰イオン成分由来のガスの発生が少ないため、排ガス処理が不要となるか若しくは簡易な設備でよく、生産コストを抑えることが可能になると考えられる。 As a method for synthesizing nickel oxide fine powder, an aqueous solution containing a nickel salt such as nickel sulfate or nickel chloride is neutralized with an alkali such as an aqueous solution of sodium hydroxide to crystallize nickel hydroxide particles, which are then roasted. A method has also been proposed. In this way, when roasting nickel hydroxide particles, the generation of gas derived from anionic components is small, so exhaust gas treatment is not required or simple equipment is sufficient, and production costs can be suppressed. Conceivable.
例えば、特許文献５には、塩化ニッケル水溶液をアルカリで中和することで生成した水酸化ニッケル粒子を５００〜８００℃の温度で熱処理して酸化ニッケル粉末を生成し、得られた酸化ニッケル粉末に水を加えてスラリー化した後、湿式ジェットミルを用いて解砕すると同時に洗浄することにより、硫黄品位及び塩素品位が低く、且つ微細な酸化ニッケル微粉末を得る方法が提案されている。 For example, in Patent Document 5, nickel hydroxide particles produced by neutralizing an aqueous nickel chloride solution with alkali are heat-treated at a temperature of 500 to 800 ° C. to produce nickel oxide powder, and the obtained nickel oxide powder is used. A method has been proposed in which water is added to form a slurry, which is then crushed using a wet jet mill and simultaneously washed to obtain fine nickel oxide fine powder having low sulfur and chlorine grades.
上記の特許文献５の酸化ニッケル微粉末の製造方法は、原料に塩化ニッケルを用いているので硫黄品位の低減は可能であるが、硫黄品位を所定の範囲内に制御することは困難であった。また、湿式解砕を要件としているため、この湿式解砕後の乾燥時に粒子同士が凝集するおそれがある上、乾燥に要するエネルギーがコスト的に不利になることがあった。 In the method for producing nickel oxide fine powder of Patent Document 5 above, nickel chloride is used as a raw material, so that the sulfur grade can be reduced, but it is difficult to control the sulfur grade within a predetermined range. .. Further, since wet crushing is a requirement, particles may agglutinate during drying after the wet crushing, and the energy required for drying may be disadvantageous in terms of cost.
本発明は、上記した従来の問題点に鑑みてなされたものであり、ナトリウム等の総アルカリ金属及び硫黄等の不純物品位が低く、電子部品用材料や固体酸化物形燃料電池の電極材料として好適な微細な酸化ニッケル微粉末及びその製造方法を提供することを目的とする。 The present invention has been made in view of the above-mentioned conventional problems, and has a low grade of total alkali metals such as sodium and impurities such as sulfur, and is suitable as a material for electronic parts and an electrode material for solid oxide fuel cells. It is an object of the present invention to provide a fine nickel oxide fine powder and a method for producing the same.
上記目的を達成するため、本発明者らは、ニッケル塩水溶液を中和することで生成される水酸化ニッケルを焙焼して酸化ニッケル微粉末を製造する方法は、熱処理時に除害を要するガス殆ど発生しない点に着目して鋭意研究を重ねた結果、硫酸ニッケル水溶液をアルカリ、好ましくは水酸化ナトリウムと炭酸ナトリウムの混合水溶液で中和することで生成される水酸化ニッケル粒子を所定の条件で熱処理することで、ナトリウム等の総アルカリ金属及び硫黄等の不純物品位が低い微細な酸化ニッケル微粉末を生成できることを見出し、本発明を完成するに至った。 In order to achieve the above object, the present inventors use a method of roasting nickel hydroxide produced by neutralizing an aqueous nickel salt solution to produce nickel oxide fine powder, which is a gas that requires detoxification during heat treatment. As a result of diligent research focusing on the fact that it hardly occurs, nickel hydroxide particles produced by neutralizing the nickel sulfate aqueous solution with an alkali, preferably a mixed aqueous solution of sodium hydroxide and sodium carbonate, are produced under predetermined conditions. It has been found that fine nickel oxide fine powder having a low grade of total alkali metal such as sodium and impurities such as sulfur can be produced by heat treatment, and the present invention has been completed.
すなわち、本発明の酸化ニッケル微粉末の製造方法は、硫酸ニッケル水溶液をアルカリ金属の水酸化物と炭酸ナトリウムとを含有するアルカリ水溶液で中和して水酸化ニッケル粒子を生成する中和工程と、前記水酸化ニッケル粒子を非還元性雰囲気中において８５０℃を超え９５０℃未満の温度で熱処理して酸化ニッケル粉末を生成する熱処理工程と、前記酸化ニッケル粉末を解砕する解砕工程とを含む酸化ニッケル微粉末の製造方法であって、前記アルカリ水溶液は炭酸ナトリウム濃度が０.４〜０.８ｍｏｌ／Ｌであり、前記中和は連続晶析法を用い、前記酸化ニッケル微粉末に求められる総アルカリ金属品位又は比表面積に応じて反応時間を０.２〜５ｈの範囲内で調整することを特徴としている。 That is, the method for producing fine nickel oxide powder of the present invention includes a neutralization step of neutralizing an aqueous solution of nickel sulfate with an alkaline aqueous solution containing an alkali metal hydroxide and sodium carbonate to generate nickel hydroxide particles. Oxidation including a heat treatment step of heat-treating the nickel hydroxide particles at a temperature of more than 850 ° C. and less than 950 ° C. in a non-reducing atmosphere to produce nickel oxide powder, and a crushing step of crushing the nickel oxide powder. A method for producing nickel fine powder, the alkaline aqueous solution has a sodium carbonate concentration of 0.4 to 0.8 mol / L, and the neutralization is performed by using a continuous crystallization method, and the total amount required for the nickel oxide fine powder. It is characterized in that the reaction time is adjusted within the range of 0.2 to 5 hours according to the alkali metal grade or the specific surface area .
本発明によれば、フェライト部品などの電子部品用材料や固体酸化物形燃料電池の電極材料として好適な、不純物品位が低くて微細な酸化ニッケル微粉末を塩素やＳＯｘガスを大量に発生させることなく容易に作製することができる。 According to the present invention, a large amount of chlorine or SOx gas is generated from fine nickel oxide fine powder having a low impurity grade, which is suitable as a material for electronic parts such as ferrite parts and an electrode material for a solid oxide fuel cell. It can be easily produced without any.
以下、本発明の酸化ニッケル微粉末の製造方法の一具体例について説明する。この本発明の一具体例の酸化ニッケル微粉末の製造方法は、原料としての硫酸ニッケル水溶液を炭酸ナトリウムを含んだアルカリ水溶液で中和することで水酸化ニッケル粒子を生成する中和工程と、該中和工程で得た水酸化ニッケル粒子を非還元性雰囲気中において８５０℃を超え９５０℃未満の温度で熱処理して酸化ニッケル粉末を生成する熱処理工程と、該熱処理の際に形成される酸化ニッケル粉末の焼結体を解砕して酸化ニッケル微粉末を得る解砕工程とを有している。 Hereinafter, a specific example of the method for producing the nickel oxide fine powder of the present invention will be described. A method for producing fine nickel oxide powder as a specific example of the present invention includes a neutralization step of producing nickel hydroxide particles by neutralizing an aqueous solution of nickel sulfate as a raw material with an alkaline aqueous solution containing sodium carbonate. A heat treatment step of heat-treating the nickel hydroxide particles obtained in the neutralization step at a temperature of more than 850 ° C. and lower than 950 ° C. in a non-reducing atmosphere to produce nickel oxide powder, and nickel oxide formed during the heat treatment. It has a crushing step of crushing a powder sintered body to obtain nickel oxide fine powder.
このように、本発明の一具体例の製造方法においては、原料のニッケル塩水溶液に硫酸ニッケルを使用することが重要である。すなわち、本発明者らは、硫黄成分の働きにより水酸化ニッケル粒子の熱処理時に熱処理温度が粒径に及ぼす影響を抑え得るとの知見を得、これに基づき原料に硫酸ニッケルを使用したところ、これにより生成される水酸化ニッケル粒子は、従来のニッケル塩の中和により生成した水酸化ニッケル粒子に比べて、後段の熱処理工程の温度を高温に設定しても微細な酸化ニッケル粉末が得られることを見出した。 As described above, in the production method of one specific example of the present invention, it is important to use nickel sulfate as the raw material nickel salt aqueous solution. That is, the present inventors have obtained the finding that the influence of the heat treatment temperature on the particle size can be suppressed during the heat treatment of nickel hydroxide particles by the action of the sulfur component, and based on this, nickel sulfate was used as a raw material. Compared to the conventional nickel hydroxide particles produced by neutralizing nickel salts, the nickel hydroxide particles produced by the above can obtain fine nickel oxide powder even if the temperature of the subsequent heat treatment step is set to a high temperature. I found.
更に、熱処理温度を特定の範囲で制御したところ、微細な粒径を維持したまま酸化ニッケル微粉末の硫黄品位を制御でき、電子部品用材料としての用途、特にフェライト部品の原料として用いる場合に好適な微細でかつ硫黄品位が制御された酸化ニッケル微粉末が得られることを見出した。しかも、この方法は塩化ニッケルを用いないため塩素が混入するおそれがなく、よって、原料に不可避的に含まれる不純物由来のもの以外は実質的に塩素を含有しない酸化ニッケル微粉末を得ることができる。 Furthermore, when the heat treatment temperature is controlled within a specific range, the sulfur grade of nickel oxide fine powder can be controlled while maintaining a fine particle size, which is suitable for use as a material for electronic parts, especially as a raw material for ferrite parts. It has been found that a fine nickel oxide fine powder having a controlled sulfur grade can be obtained. Moreover, since this method does not use nickel chloride, there is no risk of chlorine being mixed in, so that nickel oxide fine powder that does not substantially contain chlorine other than those derived from impurities inevitably contained in the raw material can be obtained. ..
上記方法で微細な粒径の酸化ニッケル微粉末が得られる明確な理由は不明であるが、硫酸ニッケルの分解温度は８４８℃と高温であるため、中和により晶析した水酸化ニッケル粒子の表面や界面に硫酸塩として巻きこまれた硫黄成分が酸化ニッケル粉末の焼結を高温まで抑制していると考えられる。この場合、硫酸ニッケルの分解温度より高温で熱処理すれば硫黄成分は揮発されるため、熱処理後の酸化ニッケル粉末の硫黄品位を低減することができる。 The clear reason why fine nickel oxide powder having a fine particle size can be obtained by the above method is unknown, but since the decomposition temperature of nickel sulfate is as high as 848 ° C., the surface of nickel hydroxide particles crystallized by neutralization. It is considered that the sulfur component caught as sulfate at the interface suppresses the sintering of nickel oxide powder to a high temperature. In this case, if the heat treatment is performed at a temperature higher than the decomposition temperature of nickel sulfate, the sulfur component is volatilized, so that the sulfur grade of the nickel oxide powder after the heat treatment can be reduced.
このように、水酸化ニッケル粒子内の水酸基の脱離により酸化ニッケル粉末の生成が行われる熱処理工程では、熱処理温度を適切に設定することによって、粒径の微細化と硫黄品位の制御が可能になる。具体的には、水酸化ニッケルの熱処理温度を、８５０℃を超え９５０℃未満の温度範囲、好ましくは８６０以上９００℃以下の温度範囲にすることで、酸化ニッケル微粉末の硫黄品位を２０質量ｐｐｍ以下に制御すると共に、比表面積を２ｍ２／ｇ以上４ｍ２／ｇ未満にすることができる。 In this way, in the heat treatment process in which the nickel oxide powder is produced by the desorption of the hydroxyl groups in the nickel hydroxide particles, the particle size can be made finer and the sulfur grade can be controlled by appropriately setting the heat treatment temperature. Become. Specifically, by setting the heat treatment temperature of nickel hydroxide in the temperature range of more than 850 ° C. and lower than 950 ° C., preferably in the temperature range of 860 or more and 900 ° C. or less, the sulfur grade of the nickel oxide fine powder is 20 mass ppm. and controls below the specific surface area can be less than 2m 2 / g or more 4m 2 / g.
また、本発明の一具体例の製造方法においては、中和工程における中和反応の反応時間を０.２ｈ〜５ｈにすることで、総アルカリ金属の品位が低い水酸化物を得ることができ、かつ最終的に酸化ニッケル微粉末中に残存する硫黄品位を２０質量ｐｐｍ以下、総アルカリ金属の品位を２０質量ｐｐｍ以下、より好ましくは１０質量ｐｐｍ以下に抑えることができる。この反応時間が５ｈを超えると、水酸化ニッケル中の総アルカリ金属の品位が５質量ｐｐｍを超え、その結果、酸化ニッケル微粉末中に残存する硫黄品位が２０質量ｐｐｍを超えることがある。以下、かかる本発明の一具体例の酸化ニッケルの製造方法を工程毎に詳細に説明する。 Further, in the production method of one specific example of the present invention, by setting the reaction time of the neutralization reaction in the neutralization step to 0.2 h to 5 h, a hydroxide having a low grade of total alkali metal can be obtained. Finally, the grade of sulfur remaining in the nickel oxide fine powder can be suppressed to 20 mass ppm or less, and the grade of the total alkali metal can be suppressed to 20 mass ppm or less, more preferably 10 mass ppm or less. When this reaction time exceeds 5 hours, the grade of the total alkali metal in nickel hydroxide may exceed 5 mass ppm, and as a result, the grade of sulfur remaining in the nickel oxide fine powder may exceed 20 mass ppm. Hereinafter, a method for producing nickel oxide according to a specific example of the present invention will be described in detail for each step.
［中和工程］
先ず中和工程において、原料としての硫酸ニッケル水溶液を炭酸ナトリウムを含んだアルカリ水溶液で中和することで水酸化ニッケル粒子の析出を行う。原料として用いる硫酸ニッケルは、特に限定するものではないが、最終的に作製される酸化ニッケル微粉末が電子部品用材料や固体酸化物形燃料電池の電極材料として用いられることから、腐食を生じにくくするため、原料中に含まれる不純物が１００質量ｐｐｍ未満であることが望ましい。
[Neutralization process]
First, in the neutralization step, nickel hydroxide particles are precipitated by neutralizing an aqueous solution of nickel sulfate as a raw material with an alkaline aqueous solution containing sodium carbonate. The nickel sulfate used as a raw material is not particularly limited, but since the nickel oxide fine powder finally produced is used as a material for electronic parts and an electrode material for a solid oxide fuel cell, corrosion is unlikely to occur. Therefore, it is desirable that the impurities contained in the raw material are less than 100 mass ppm.
また、硫酸ニッケル水溶液中のニッケルの濃度は、特に限定するものではないが、生産性を考慮するとニッケル濃度で５０〜１５０ｇ／Ｌが好ましい。この濃度が５０ｇ／Ｌ未満では生産性が低下するおそれがある。逆に１５０ｇ／Ｌを超えると水溶液中の陰イオン濃度が高くなりすぎ、生成した水酸化ニッケル中の硫黄品位が高くなるため、最終的に得られる酸化ニッケル微粉末中の不純物品位が十分に低くならない場合がある。 The concentration of nickel in the nickel sulfate aqueous solution is not particularly limited, but the nickel concentration is preferably 50 to 150 g / L in consideration of productivity. If this concentration is less than 50 g / L, productivity may decrease. On the contrary, if it exceeds 150 g / L, the anion concentration in the aqueous solution becomes too high, and the sulfur grade in the produced nickel hydroxide becomes high, so that the impurity grade in the finally obtained nickel oxide fine powder is sufficiently low. It may not be.
中和に用いるアルカリ水溶液に含まれるアルカリ成分としては、反応液中に残留するニッケルの量を考慮してアルカリ金属の水酸化物を使用する。アルカリ金属の水酸化物には例えば水酸化ナトリウムや水酸化カリウムを挙げることができ、コストの面から水酸化ナトリウムが好ましい。中和に用いるアルカリ水溶液は、上記のアルカリ金属の水酸化物以外に更に炭酸ナトリウムを０.４〜０.８ｍｏｌ／Ｌの濃度で含んでいる。これにより、詳細は不明ではあるが、晶析した水酸化ニッケル粒子の界面や表面に巻き込まれるナトリウム等のアルカリ金属成分や硫黄成分の量を低減することができる。 As the alkaline component contained in the alkaline aqueous solution used for neutralization, an alkali metal hydroxide is used in consideration of the amount of nickel remaining in the reaction solution. Examples of the alkali metal hydroxide include sodium hydroxide and potassium hydroxide, and sodium hydroxide is preferable from the viewpoint of cost. The alkaline aqueous solution used for neutralization further contains sodium carbonate at a concentration of 0.4 to 0.8 mol / L in addition to the above-mentioned alkali metal hydroxide. As a result, although the details are unknown, it is possible to reduce the amount of alkali metal components such as sodium and sulfur components that are involved in the interface and surface of the crystallized nickel hydroxide particles.
上記アルカリ水溶液中の炭酸ナトリウム濃度を０.４〜０.８ｍｏｌ／Ｌとする理由は、アルカリ水溶液に含まれる炭酸ナトリウムの濃度を徐々に増やしていくと、水酸化ニッケル粒子中の硫黄品位は一旦増加するが、炭酸ナトリウムの濃度を更に増やすと硫黄品位は減少に転じ、０.４ｍｏｌ／Ｌ以上では炭酸ナトリウムを添加しない場合よりも硫黄品位が低くなるからである。また、水酸化ニッケル粒子中のナトリウム等のアルカリ金属の品位は、アルカリ水溶液中の炭酸ナトリウムの濃度を徐々に増やすことで低下させることができるが、アルカリ水溶液中の炭酸ナトリウムの濃度が０.８ｍｏｌ／Ｌより高くなると逆にナトリウム等のアルカリ金属の品位は高くなるからである。 The reason for setting the sodium carbonate concentration in the alkaline aqueous solution to 0.4 to 0.8 mol / L is that when the concentration of sodium carbonate contained in the alkaline aqueous solution is gradually increased, the sulfur grade in the nickel hydroxide particles is once improved. This is because the sulfur grade starts to decrease when the concentration of sodium carbonate is further increased, and the sulfur grade becomes lower at 0.4 mol / L or more than when sodium carbonate is not added. Further, the grade of alkali metal such as sodium in nickel hydroxide particles can be lowered by gradually increasing the concentration of sodium carbonate in the alkaline aqueous solution, but the concentration of sodium carbonate in the alkaline aqueous solution is 0.8 mol. This is because the quality of alkali metals such as sodium increases when the value is higher than / L.
このように、アルカリ水溶液中の炭酸ナトリウムの濃度が０.４ｍｏｌ／Ｌ未満では、中和により得られる水酸化ニッケル粒子の硫黄品位が炭酸ナトリウムを含有させない場合よりも高くなることがあり、０.８ｍｏｌ／Ｌを超えると、中和により得られる水酸化ニッケル粒子のナトリウム等のアルカリ金属の品位が炭酸ナトリウムを含有させない場合よりも高くなることがある。ナトリウム等のアルカリ金属は、後段の熱処理工程において高融点の硫酸塩を形成し、硫黄成分の分解や揮発を阻害する方向に働くので、水酸化ニッケル粒子のアルカリ金属の品位が高いと、酸化ニッケル微粉末の硫黄品位も高くなりやすい。 As described above, when the concentration of sodium carbonate in the alkaline aqueous solution is less than 0.4 mol / L, the sulfur grade of the nickel hydroxide particles obtained by neutralization may be higher than that in the case where sodium carbonate is not contained. If it exceeds 8 mol / L, the grade of the alkali metal such as sodium of the nickel hydroxide particles obtained by neutralization may be higher than that in the case where sodium carbonate is not contained. Alkali metals such as sodium form a high melting point sulfate in the subsequent heat treatment process and work in a direction to inhibit the decomposition and volatilization of sulfur components. Therefore, if the alkali metal grade of nickel hydroxide particles is high, nickel oxide The sulfur grade of fine powder tends to be high.
尚、上記中和反応の晶析により生成される水酸化ニッケル粒子は、硫黄品位が２質量％以下であるのが好ましい。下限については特に限定はないが、アルカリ水溶液中の炭酸ナトリウムの濃度が０.４〜０.８ｍｏｌ／Ｌの範囲では０.５質量％以上となる。アルカリ水溶液中の炭酸ナトリウム濃度を適宜調整することで、水酸化ニッケル粒子の硫黄品位をより好適な１.０〜２.０質量％に、最も好適な１.２〜１.８質量％にすることができる。 The nickel hydroxide particles produced by the crystallization of the neutralization reaction preferably have a sulfur grade of 2% by mass or less. The lower limit is not particularly limited, but the concentration of sodium carbonate in the alkaline aqueous solution is 0.5% by mass or more in the range of 0.4 to 0.8 mol / L. By appropriately adjusting the sodium carbonate concentration in the alkaline aqueous solution, the sulfur grade of the nickel hydroxide particles is adjusted to a more preferable 1.0 to 2.0% by mass and the most suitable 1.2 to 1.8% by mass. be able to.
上記中和工程では均質な水酸化ニッケル粒子を効率よく生産するため、反応槽内において十分に撹拌されている液に、予め調製しておいたニッケル塩水溶液である硫酸ニッケル水溶液とアルカリ水溶液とをいわゆるダブルジェット方式で添加する連続晶析法を採用している。即ち、反応槽内に予め準備したニッケル塩水溶液及びアルカリ水溶液のうちのいずれか一方に対して、もう一方を添加することで中和を行うのではなく、反応槽内において十分に攪拌されている乱流状態の液中に、好適には該攪拌を継続しながらニッケル塩水溶液とアルカリ水溶液とを同時並行的に且つ連続的に添加することで中和を行う。その際、反応槽内に予め入れておく液は、純水に上記アルカリ成分を添加して所定のｐＨに調整したものが好ましい。 In the above neutralization step, in order to efficiently produce homogeneous nickel hydroxide particles, a nickel sulfate aqueous solution and an alkaline aqueous solution, which are nickel salt aqueous solutions prepared in advance, are added to a solution that is sufficiently stirred in the reaction vessel. The continuous crystallization method of adding by the so-called double jet method is adopted. That is, one of the nickel salt aqueous solution and the alkaline aqueous solution prepared in advance in the reaction vessel is not neutralized by adding the other, but is sufficiently stirred in the reaction vessel. Neutralization is preferably carried out by adding a nickel salt aqueous solution and an alkaline aqueous solution to the turbulent liquid in parallel and continuously while continuing the stirring. At that time, it is preferable that the liquid to be put in the reaction vessel in advance is adjusted to a predetermined pH by adding the above alkaline component to pure water.
上記中和反応時は、反応槽内の反応液のｐＨを８.３〜９.０の範囲内に調整することが好ましい。このｐＨが８.３より低いと、水酸化ニッケル粒子中に残存する硫酸イオン等の陰イオン成分の濃度が増大し、これらが後段の熱処理工程の際に大量のＳＯｘ等となって炉体を傷めるおそれがある。逆にこのｐＨが９.０より高くなると、析出する水酸化ニッケル粒子が微細になりすぎ、この水酸化ニッケル粒子を含むスラリーを例えば濾過装置で固液分離する際に濾過性が低下することがある。更に、後段の熱処理工程で焼結が進みすぎて、微細な酸化ニッケル微粉末を得ることが困難になることがある。 At the time of the above neutralization reaction, it is preferable to adjust the pH of the reaction solution in the reaction vessel within the range of 8.3 to 9.0. When this pH is lower than 8.3, the concentration of anionic components such as sulfate ions remaining in the nickel hydroxide particles increases, and these become a large amount of SOx or the like during the subsequent heat treatment step to form the furnace body. It may be damaged. On the contrary, when the pH is higher than 9.0, the precipitated nickel hydroxide particles become too fine, and the filterability may be lowered when the slurry containing the nickel hydroxide particles is solid-liquid separated by, for example, a filtration device. is there. Further, sintering may proceed too much in the heat treatment step in the subsequent stage, making it difficult to obtain fine nickel oxide fine powder.
上記した好適な中和条件であるｐＨ９.０以下では反応後の水溶液中に僅かにニッケル成分が残存することがあるが、この場合は、上記の中和工程による晶析がほぼ完了した後にｐＨを１０程度まで上げることによって、上記の濾過により得られる濾液中のニッケル成分を低減させることができる。中和反応時は、ｐＨをほぼ一定に保つことが好ましく、特にその変動幅が設定値を中心として絶対値で０.２以内となるように一定に制御することが好ましい。ｐＨの変動幅がこれより大きくなると、不純物が増大したり酸化ニッケル微粉末の比表面積が低下したりするおそれがある。 At pH 9.0 or lower, which is the above-mentioned suitable neutralization condition, a small amount of nickel component may remain in the aqueous solution after the reaction. In this case, the pH is almost completed after the crystallization by the above-mentioned neutralization step is almost completed. The nickel component in the filtrate obtained by the above filtration can be reduced by increasing the pH to about 10. During the neutralization reaction, it is preferable to keep the pH substantially constant, and it is particularly preferable to control the fluctuation range to be within 0.2 in absolute value around the set value. If the fluctuation range of pH is larger than this, impurities may increase or the specific surface area of the nickel oxide fine powder may decrease.
上記の中和反応時の反応液の温度には特に制約がなく、室温で行うことも可能であるが、水酸化ニッケル粒子を十分に成長させるためには５０〜７０℃の範囲内が好ましい。水酸化ニッケル粒子を十分に成長させることで、水酸化ニッケル粒子中への硫黄の過度の含有を防止することができる。また、水酸化ニッケル粒子中へのナトリウムなどの不純物の巻き込みを抑制し、最終的に得られる酸化ニッケル微粉末の不純物を低減することができる。この液温が５０℃未満では水酸化ニッケル粒子の成長が不十分になって、水酸化ニッケル中への硫黄等の不純物の巻き込みが多くなるおそれがある。逆に液温が７０℃を超えると水の蒸発量が増加し、水溶液中の硫黄等の不純物濃度が高くなるため、生成した水酸化ニッケル粒子中の硫黄等の不純物品位が高くなるおそれがある。 The temperature of the reaction solution at the time of the above neutralization reaction is not particularly limited, and it can be carried out at room temperature, but it is preferably in the range of 50 to 70 ° C. in order to sufficiently grow the nickel hydroxide particles. By sufficiently growing the nickel hydroxide particles, it is possible to prevent excessive inclusion of sulfur in the nickel hydroxide particles. In addition, it is possible to suppress the entrainment of impurities such as sodium in the nickel hydroxide particles and reduce the impurities of the nickel oxide fine powder finally obtained. If the liquid temperature is less than 50 ° C., the growth of nickel hydroxide particles will be insufficient, and impurities such as sulfur may be more involved in nickel hydroxide. On the contrary, when the liquid temperature exceeds 70 ° C., the amount of water evaporation increases and the concentration of impurities such as sulfur in the aqueous solution increases, so that the grade of impurities such as sulfur in the generated nickel hydroxide particles may increase. ..
上記の中和工程では、中和の反応時間を０.２〜５時間にしている。ここで中和の反応時間とは、所定の中和反応条件が維持される時間であり、例えば連続式完全混合槽型の反応槽で中和反応を行う場合は、その有効容量を硫酸ニッケル水溶液とアルカリ水溶液との合計供給量で除して得られる時間であり、この場合は中和工程に要する平均時間に相当する。例えば、オーバーフロー口を設けることで有効容積が１０Ｌに維持されている反応槽に硫酸ニッケル水溶液とアルカリ水溶液とを合計２０Ｌ／ｈで供給する場合、反応時間は１０／２０＝０.５時間になる。 In the above neutralization step, the neutralization reaction time is set to 0.2 to 5 hours. Here, the neutralization reaction time is a time during which a predetermined neutralization reaction condition is maintained. For example, when a neutralization reaction is carried out in a continuous complete mixing tank type reaction tank, its effective capacity is set to an aqueous nickel sulfate solution. It is the time obtained by dividing by the total supply amount of the alkaline aqueous solution and the alkali aqueous solution, and in this case, it corresponds to the average time required for the neutralization step. For example, when a nickel sulfate aqueous solution and an alkaline aqueous solution are supplied at a total of 20 L / h to a reaction vessel whose effective volume is maintained at 10 L by providing an overflow port, the reaction time is 10/20 = 0.5 hours. ..
上記反応時間が０.２ｈ未満では、水酸化ニッケル粒子中に残存する硫黄量が増加して、最終的に得られる酸化ニッケル微粉末の硫黄品位が２０質量ｐｐｍを超えることがある。逆に反応時間が５ｈを超えると、水酸化ニッケル中に残存する総アルカリ金属の量が増加し、その結果、酸化ニッケル微粉末とした際の総アルカリ金属の品位が２０質量ｐｐｍを超えるだけでなく、硫黄品位も２０ｐｐｍを超えることがある。尚、酸化ニッケル微粉末の総アルカリ金属品位をより低くすることが求められる場合は、反応時間を０.２〜２.５時間とするのが好ましく、一方、比表面積が大きい酸化ニッケル微粉末が求められる場合は、反応時間を３.５〜５時間とするのが好ましい。 If the reaction time is less than 0.2 h, the amount of sulfur remaining in the nickel hydroxide particles may increase, and the sulfur grade of the finally obtained nickel oxide fine powder may exceed 20 mass ppm. On the contrary, when the reaction time exceeds 5 hours, the amount of total alkali metal remaining in nickel hydroxide increases, and as a result, the grade of total alkali metal in the form of nickel oxide fine powder exceeds only 20 mass ppm. The sulfur grade may also exceed 20 ppm. When it is required to lower the total alkali metal grade of the nickel oxide fine powder, the reaction time is preferably 0.2 to 2.5 hours, while the nickel oxide fine powder having a large specific surface area is used. When required, the reaction time is preferably 3.5 to 5 hours.
上記中和反応の終了後は、析出した水酸化ニッケル粒子を含むスラリーを濾過等の固液分離手段により固液分離して該水酸化ニッケル粒子を濾過ケーキ等の湿潤状態の固形分の形態で回収する。この湿潤状態の固形分は、次の熱処理工程で処理する前に洗浄することが好ましい。洗浄はレパルプ洗浄とすることが好ましく、その場合に用いる洗浄液としては水が好ましく、純水がより好ましい。 After the completion of the neutralization reaction, the slurry containing the precipitated nickel hydroxide particles is solid-liquid separated by a solid-liquid separation means such as filtration, and the nickel hydroxide particles are separated into wet solids such as a filtration cake. to recover. The wet solid content is preferably washed before being treated in the next heat treatment step. The cleaning is preferably repulp cleaning, and water is preferable and pure water is more preferable as the cleaning liquid used in that case.
洗浄時の水酸化ニッケルと水との混合割合は特に限定がないが、ニッケル塩に含まれるナトリウム等のアルカリ金属成分が十分に除去できる混合割合が好ましい。具体的には、残留するアルカリ金属等の不純物が十分に低減でき且つ水酸化ニッケル粒子を良好に分散させるため、５０〜１５０ｇの水酸化ニッケルに対して１Ｌの洗浄液を混合することが好ましく、１００ｇ程度の水酸化ニッケルに対して１Ｌの洗浄液を混合するのがより好ましい。 The mixing ratio of nickel hydroxide and water at the time of washing is not particularly limited, but a mixing ratio that can sufficiently remove alkali metal components such as sodium contained in the nickel salt is preferable. Specifically, in order to sufficiently reduce residual impurities such as alkali metals and to disperse nickel hydroxide particles satisfactorily, it is preferable to mix 1 L of the cleaning liquid with 50 to 150 g of nickel hydroxide, preferably 100 g. It is more preferable to mix 1 L of the cleaning solution with respect to the degree of nickel hydroxide.
尚、洗浄時間については、上記の洗浄液の量や温度などの洗浄条件に応じて適宜定めることができ、残留不純物が十分に低減可能な時間とすればよい。また、１回の洗浄でアルカリ金属等の不純物が十分に低減しない場合は、複数回繰り返して洗浄することが好ましい。特に、ナトリウム等のアルカリ金属は次工程の熱処理によっても除去できないため、この洗浄によって十分に除去することが好ましい。洗浄液に純水を用いる場合は、例えば洗浄後に測定した洗浄液の導電率が所定の値以下になるまで洗浄を繰り返すことで、不純物品位のばらつきを抑えることができる。 The cleaning time can be appropriately determined according to the cleaning conditions such as the amount and temperature of the cleaning liquid, and may be a time during which residual impurities can be sufficiently reduced. Further, when impurities such as alkali metals are not sufficiently reduced by one cleaning, it is preferable to repeat the cleaning a plurality of times. In particular, since alkali metals such as sodium cannot be removed by the heat treatment in the next step, it is preferable to sufficiently remove them by this cleaning. When pure water is used as the cleaning liquid, for example, by repeating the cleaning until the conductivity of the cleaning liquid measured after the cleaning becomes a predetermined value or less, the variation in the impurity grade can be suppressed.
［熱処理工程］
上記中和工程で生成された水酸化ニッケル粒子は、次に熱処理工程において非還元性雰囲気で熱処理が施されることで水酸基が脱離し、酸化ニッケル粉末となる。この熱処理は、８５０℃を超え９５０℃未満の温度範囲で行われる。この熱処理温度が９５０℃以上では、硫黄成分の分解が進行して上記焼結の抑制効果が不十分になる。その結果、熱処理によって生成される酸化ニッケル微粉末同士の焼結が顕著になり、その結合力も増大するので、後段の解砕工程での酸化ニッケル粉末の焼結体の解砕が困難になり、解砕できたとしても微細な酸化ニッケル微粉末を得るのは難しい。逆に、上記水酸化ニッケル粒子の熱処理温度が８５０℃以下の場合は、硫酸塩等の硫黄成分の分解による硫黄成分の揮発が不十分となり、水酸化ニッケル中に硫黄成分が残留するため、酸化ニッケル微粉末の硫黄品位が２０質量ｐｐｍを超えるおそれがある。
[Heat treatment process]
The nickel hydroxide particles produced in the neutralization step are then heat-treated in a non-reducing atmosphere in the heat treatment step to desorb hydroxyl groups to form nickel oxide powder. This heat treatment is carried out in a temperature range above 850 ° C and below 950 ° C. When the heat treatment temperature is 950 ° C. or higher, the decomposition of the sulfur component proceeds and the effect of suppressing the sintering becomes insufficient. As a result, the sintering of the nickel oxide fine powders produced by the heat treatment becomes remarkable, and the bonding force thereof also increases, so that it becomes difficult to crush the sintered body of the nickel oxide powder in the subsequent crushing step. Even if it can be crushed, it is difficult to obtain fine nickel oxide fine powder. On the contrary, when the heat treatment temperature of the nickel hydroxide particles is 850 ° C. or lower, the sulfur component volatilizes insufficiently due to the decomposition of the sulfur component such as sulfate, and the sulfur component remains in the nickel hydroxide, so that oxidation occurs. The sulfur grade of nickel fine powder may exceed 20% by mass ppm.
上記熱処理時の雰囲気は、非還元性雰囲気であれば特に限定はないが、経済性を考慮すると大気雰囲気とすることが好ましい。また、熱処理の際に水酸基の脱離により発生する水蒸気を効率よく排出するため、十分な流速を持った気流中で行うことが好ましい。尚、熱処理を行う装置には、一般的な焙焼炉を使用することができる。 The atmosphere at the time of the heat treatment is not particularly limited as long as it is a non-reducing atmosphere, but it is preferably an air atmosphere in consideration of economic efficiency. Further, in order to efficiently discharge the water vapor generated by the desorption of hydroxyl groups during the heat treatment, it is preferable to carry out the heat treatment in an air flow having a sufficient flow velocity. A general roasting furnace can be used as the device for performing the heat treatment.
熱処理時間は、熱処理温度や処理量等の熱処理条件に応じて適宜設定することができ、最終的に得られる酸化ニッケル微粉末の比表面積が２ｍ２／ｇ以上４ｍ２／ｇ未満になるように設定すればよい。前述したように、水酸化ニッケルに含まれる硫黄成分の働きにより、熱処理により生成される酸化ニッケルは微細となり、焼結体が含まれる場合であってもその結合力は比較的弱いので容易に解砕することができる。 The heat treatment time can be appropriately set according to the heat treatment conditions such as the heat treatment temperature and the treatment amount, so that the specific surface area of the finally obtained nickel oxide fine powder is 2 m 2 / g or more and less than 4 m 2 / g. You can set it. As described above, nickel oxide produced by heat treatment becomes fine due to the action of the sulfur component contained in nickel hydroxide, and even if a sintered body is contained, its bonding force is relatively weak and can be easily solved. Can be crushed.
この焼結体の粉砕では、解砕後に得られる酸化ニッケル微粉末の比表面積は、解砕前の酸化ニッケル粉末の比表面積に対して約１.５〜２.５ｍ２／ｇ程度増加するだけである。従って、熱処理後の酸化ニッケル粉末の比表面積に基づいて熱処理条件を設定することができる。すなわち、解砕前の酸化ニッケル粉末の比表面積が０.５〜１.５ｍ２／ｇとなるような条件で熱処理することが好ましい。熱処理温度を上記範囲で設定することにより、硫黄品位と比表面積を容易に制御できる。 In the crushing of this sintered body, the specific surface area of the nickel oxide fine powder obtained after crushing is only increased by about 1.5 to 2.5 m 2 / g with respect to the specific surface area of the nickel oxide powder before crushing. Is. Therefore, the heat treatment conditions can be set based on the specific surface area of the nickel oxide powder after the heat treatment. That is, it is preferable to heat-treat the nickel oxide powder under the condition that the specific surface area of the nickel oxide powder before crushing is 0.5 to 1.5 m 2 / g. By setting the heat treatment temperature in the above range, the sulfur grade and the specific surface area can be easily controlled.
［解砕工程］
上記熱処理工程で生成された酸化ニッケル微粉末は、解砕工程で処理される。この解砕工程により、熱処理の際に形成される酸化ニッケル微粉末の焼結体を解砕することができる。前述したように熱処理工程では水酸化ニッケル粒子中の水酸基が離脱して酸化ニッケル粉末が形成されるが、その際、粒径の微細化が起こると共に、硫黄成分により抑制されてはいるものの、高温の影響で酸化ニッケル粉末同士の焼結がある程度進行する。熱処理後の酸化ニッケル粉末に対して解砕処理を行うことで、この焼結体が破壊されるため、極めて微細な酸化ニッケル微粉末が得られる。
[Crushing process]
The nickel oxide fine powder produced in the heat treatment step is processed in the crushing step. By this crushing step, the sintered body of nickel oxide fine powder formed during the heat treatment can be crushed. As described above, in the heat treatment step, the hydroxyl groups in the nickel hydroxide particles are separated to form nickel oxide powder. At that time, the particle size is refined and the high temperature is suppressed by the sulfur component. Due to the influence of, the sintering of nickel oxide powders progresses to some extent. By crushing the nickel oxide powder after the heat treatment, the sintered body is destroyed, so that extremely fine nickel oxide fine powder can be obtained.
解砕方法としては、一般的にビーズミルやボールミル等の解砕メディアを用いる解砕法、又はジェットミル等の解砕メディアを用いない流体エネルギーによる解砕法があるが、上記の熱処理後の酸化ニッケル粉末の解砕処理においては、後者の解砕メディアを用いない解砕法を採用することが好ましい。なぜなら、解砕メディアを用いると解砕自体は容易になるものの、ジルコニア等の解砕メディアを構成している成分が不純物として混入するおそれがあるからである。特に、電子部品用材料として酸化ニッケル微粉末を用いる場合は、解砕メディアを用いない解砕方法を採用することが好ましい。 As a crushing method, there are generally a crushing method using a crushing medium such as a bead mill or a ball mill, or a crushing method using fluid energy without using a crushing medium such as a jet mill. Nickel oxide powder after the above heat treatment In the crushing treatment of the above, it is preferable to adopt the latter crushing method that does not use a crushing medium. This is because, although crushing itself is facilitated by using crushing media, components constituting the crushing media such as zirconia may be mixed as impurities. In particular, when nickel oxide fine powder is used as a material for electronic parts, it is preferable to adopt a crushing method that does not use a crushing medium.
低減すべき不純物がジルコニウムのみであるならば、解砕メディアにジルコニア等のジルコニウムを含有しないものを用いて解砕することが考えられるが、この場合であっても解砕メディアを構成する他の不純物が混入し得るので、結果的に低不純物品位の酸化ニッケル微粉末を得るのが困難になる。更に、解砕メディアがイットリア安定化ジルコニアに代表されるジルコニウムを含有しない場合は、強度や耐摩耗性が不十分になるため、この観点からも解砕メディアを用いない解砕法が望ましい。 If the only impurity to be reduced is zirconium, it is conceivable to use a crushing medium that does not contain zirconium, such as zirconia, for crushing, but even in this case, other crushing media constituting the crushing media may be used. Since impurities can be mixed in, it becomes difficult to obtain nickel oxide fine powder having a low impurity grade as a result. Further, when the crushing media does not contain zirconium typified by yttria-stabilized zirconia, the strength and wear resistance become insufficient, and from this viewpoint, a crushing method without using the crushing media is desirable.
解砕メディアを用いない解砕法としては、ガス（気体）や溶媒（液体）を用い、それら流体により粉体の粒子同士を衝突させる方法や、液体などの溶媒により粉体にせん断力をかける方法、溶媒のキャビテーションによる衝撃力を用いる方法等がある。粉体の粒子同士を衝突させる解砕法を適用した装置としては、例えば、乾式ジェットミルや湿式ジェットミルがあり、具体的には前者にはナノグラインディングミル（登録商標）や、クロスジェットミル（登録商標）、後者にはアルティマイザー（登録商標）、スターバースト（登録商標）等がある。また、溶媒によりせん断力を与える解砕法を適用した装置としては、例えば、ナノマイザー（登録商標）等があり、溶媒のキャビテーションによる衝撃力を用いた解砕法を適用した装置としては、例えば、ナノメーカー（登録商標）等がある。 As a crushing method that does not use a crushing medium, a method of using a gas (gas) or a solvent (liquid) and causing the powder particles to collide with each other by the fluid, or a method of applying a shearing force to the powder with a solvent such as a liquid. , There is a method using impact force due to cavitation of solvent. Devices to which the crushing method of colliding powder particles collide with each other include, for example, a dry jet mill and a wet jet mill. Specifically, the former includes a nano grinding mill (registered trademark) and a cross jet mill (registered trademark). (Registered trademark), the latter includes Ultimater (registered trademark), Starburst (registered trademark), etc. Further, as an apparatus to which a crushing method applying a shearing force by a solvent is applied, for example, there is a nanomizer (registered trademark), and as an apparatus to which an impact force by cavitation of a solvent is applied, for example, a nanomaker (Registered trademark), etc.
上記解砕法のうち、粉体の粒子同士を衝突させる方法が、不純物混入のおそれが少なく、比較的大きな解砕力が得られることから好ましく、乾式によるものが特に好ましい。乾式が好ましい理由は、湿式解砕では解砕後に行う乾燥処理の際に酸化ニッケル微粉末が再凝集するおそれがあるが、乾式解砕ではこのような再凝集の問題が生じにくいからである。尚、本発明の一具体例の製造方法では、硫酸ニッケルを原料とするため、塩素除去のために洗浄を行う必要が特にない。従って乾燥工程の不要な乾式解砕を採用することができるため、製造コストを抑えることができる。上記の解砕条件には特に限定がなく、通常の条件の範囲内での調整により目的とする粒度分布を有する酸化ニッケル微粉末を容易に得ることができる。これにより、フェライト部品などの電子部品材料として好適な分散性に優れた微細な酸化ニッケル微粉末を得ることができる。 Of the above crushing methods, the method of colliding powder particles with each other is preferable because there is little risk of impurities being mixed in and a relatively large crushing force can be obtained, and the dry method is particularly preferable. The reason why the dry method is preferable is that the nickel oxide fine powder may reaggregate during the drying treatment performed after the crushing in the wet crushing method, but the problem of such reaggregation does not easily occur in the dry crushing method. In addition, in the production method of one specific example of the present invention, since nickel sulfate is used as a raw material, it is not particularly necessary to perform cleaning for removing chlorine. Therefore, since dry crushing that does not require a drying step can be adopted, the manufacturing cost can be suppressed. The above-mentioned crushing conditions are not particularly limited, and nickel oxide fine powder having a desired particle size distribution can be easily obtained by adjusting within the range of normal conditions. As a result, it is possible to obtain fine nickel oxide fine powder having excellent dispersibility, which is suitable as a material for electronic parts such as ferrite parts.
［酸化ニッケル微粉末の物性］
以上説明した本発明の一具体例の酸化ニッケル微粉末の製造方法により製造される酸化ニッケル微粉末は、原料から不可避不純物として混入する以外に塩素が混入する工程を含まないので、塩素品位が極めて低い。加えて、硫黄品位が制御されると共に、ナトリウム等の総アルカリ金属の品位が低く、比表面積が大きい。具体的には、硫黄品位が２０質量ｐｐｍ以下、塩素品位が２０質量ｐｐｍ以下、総アルカリ金属の品位が２０質量ｐｐｍ以下、より好ましくは１０質量ｐｐｍ以下である。また、比表面積は２ｍ２／ｇ以上４ｍ２／ｇ未満である。従って、電子部品用、特にフェライト部品用の材料や固体酸化物形燃料電池の電極用材料として好適である。尚、固体酸化物形燃料電池の電極用材料としては、硫黄品位が１００質量ｐｐｍ以下であることが好ましいとされている。
[Physical properties of nickel oxide fine powder]
The nickel oxide fine powder produced by the method for producing the nickel oxide fine powder of one specific example of the present invention described above does not include a step of mixing chlorine other than being mixed as an unavoidable impurity from the raw material, so that the chlorine grade is extremely high. Low. In addition, the sulfur grade is controlled, the grade of the total alkali metal such as sodium is low, and the specific surface area is large. Specifically, the sulfur grade is 20 mass ppm or less, the chlorine grade is 20 mass ppm or less, and the total alkali metal grade is 20 mass ppm or less, more preferably 10 mass ppm or less. The specific surface area is 2 m 2 / g or more and less than 4 m 2 / g. Therefore, it is suitable as a material for electronic parts, particularly for ferrite parts, and as a material for electrodes of solid oxide fuel cells. As a material for electrodes of solid oxide fuel cells, it is said that the sulfur grade is preferably 100 mass ppm or less.
また、上記した本発明の一具体例の酸化ニッケル微粉末の製造方法においては、マグネシウム等の第２族元素を添加する工程を含まないので、これらの元素が不純物として含まれることは実質的にない。更に、解砕メディアを使用せずに解砕する場合はジルコニアも含まれなくなるので、ジルコニア品位及び第２族元素品位を３０質量ｐｐｍ以下にすることができる。 Further, since the method for producing the nickel oxide fine powder of one specific example of the present invention does not include the step of adding a Group 2 element such as magnesium, it is substantially possible that these elements are contained as impurities. Absent. Further, when crushing without using a crushing medium, zirconia is not contained, so that the zirconia grade and the Group 2 element grade can be reduced to 30 mass ppm or less.
上記した本発明の一具体例の酸化ニッケル微粉末の製造方法で作製した酸化ニッケル微粉末は、レーザー散乱法で測定したＤ９０（粒度分布曲線における粒子量の体積積算９０％での粒径）が１μｍ以下であることが好ましく、０.２〜０.９μｍがより好ましく、０.４〜０.８μｍが最も好ましい。尚、酸化ニッケル微粉末は電子部品等の製造工程において、他の材料と混合されるときに解砕されて小さくなることがあり、レーザー散乱法で測定したＤ９０も小さくなるが、この解砕によって比表面積が大きくなる可能性は低いため、酸化ニッケル微粉末の比表面積で評価を行う方がより確実である。更に、本発明の実施形態の酸化ニッケル微粉末の製造方法においては、湿式法により製造した水酸化ニッケルを熱処理するため、有害なＳＯｘが大量に発生することがない。従って、これを除害処理するための高価な設備が不要である。更に熱処理回数も１回で済むので、製造コストを低く抑えることができる。 The nickel oxide fine powder produced by the method for producing the nickel oxide fine powder of one specific example of the present invention has a D90 (particle size at a volume integration of 90% of the particle amount in the particle size distribution curve) measured by the laser scattering method. It is preferably 1 μm or less, more preferably 0.2 to 0.9 μm, and most preferably 0.4 to 0.8 μm. In addition, nickel oxide fine powder may be crushed and reduced when mixed with other materials in the manufacturing process of electronic parts, etc., and D90 measured by the laser scattering method is also reduced, but this crushing causes Since it is unlikely that the specific surface area will increase, it is more reliable to evaluate by the specific surface area of the nickel oxide fine powder. Further, in the method for producing fine nickel oxide powder according to the embodiment of the present invention, since the nickel hydroxide produced by the wet method is heat-treated, a large amount of harmful SOx is not generated. Therefore, expensive equipment for detoxifying this is not required. Further, since the number of heat treatments is only one, the manufacturing cost can be kept low.
次に、実施例及び比較例を挙げて本発明を説明するが、本発明はこれらの実施例等によってなんら限定されるものではない。尚、以下の実施例及び比較例の塩素品位の分析は、分析対象物を塩素の揮発を抑制できる密閉容器内にてマイクロ波照射下で硝酸に溶解し、硝酸銀を加えて塩化銀を沈殿させ、得られた沈殿物中の塩素を蛍光Ｘ線定量分析装置（ＰＡＮａｌｙｔｉｃａｌ社製 Ｍａｇｉｘ）を用いて検量線法で評価することによって行った。硫黄品位の分析は、分析対象物を硝酸に溶解した後、ＩＣＰ発光分光分析装置（セイコー社製 ＳＰＳ−３０００）によって行った。ナトリウム品位の分析は、分析対象物を硝酸に溶解した後、原子吸光装置（日立ハイテク社製 Ｚ−２３００）により評価することによって行った。酸化ニッケル微粉末の粒径は、レーザー散乱法により測定し、その粒度分布から体積積算９０％での粒径Ｄ９０を求めた。比表面積の分析は、窒素ガス吸着によるＢＥＴ法により求めた。 Next, the present invention will be described with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples and the like. In the chlorine grade analysis of the following examples and comparative examples, the object to be analyzed is dissolved in nitric acid under microwave irradiation in a closed container capable of suppressing the volatilization of chlorine, and silver nitrate is added to precipitate silver chloride. , Chlorine in the obtained precipitate was evaluated by a calibration beam method using a fluorescent X-ray quantitative analyzer (Magic manufactured by PANalytical Co., Ltd.). The sulfur grade was analyzed by dissolving the analysis object in nitric acid and then using an ICP emission spectroscopic analyzer (SPS-3000 manufactured by Seiko Corporation). The sodium grade analysis was performed by dissolving the analysis object in nitric acid and then evaluating it with an atomic absorption spectrophotometer (Z-2300 manufactured by Hitachi High-Tech). The particle size of the nickel oxide fine powder was measured by a laser scattering method, and the particle size D90 at a volume integration of 90% was determined from the particle size distribution. The analysis of the specific surface area was determined by the BET method by adsorbing nitrogen gas.
［実施例１］
邪魔板とオーバーフロー口を有する攪拌機構付きの有効容積４Ｌの反応槽に純水を入れてから炭酸ナトリウムと水酸化ナトリウムを添加して十分に攪拌し、炭酸ナトリウム濃度０.６ｍｏｌ／Ｌ、ｐＨ８.５の混合水溶液４Ｌを調製した。また、硫酸ニッケルを純水に溶解してニッケル濃度１２０ｇ／Ｌに調整したニッケル水溶液と、水酸化ナトリウム及び濃度０.６ｍｏｌ／Ｌに調整された炭酸ナトリウムを含む添加用混合水溶液とを用意した。これらニッケル水溶液と添加用混合水溶液とを、前述の炭酸ナトリウムと水酸化ナトリウムとを含む反応槽内の混合水溶液に同時並行的且つ連続的に添加して混合させ、中和反応を行った。この時、両供給ノズル出口部からそれぞれ供給を行ったニッケル水溶液及び添加用混合水溶液は、各々供給先の反応槽内において乱流状態で混合されていた。
[Example 1]
Pure water is put into a reaction vessel having an effective volume of 4 L with a stirrer plate and an overflow port, and then sodium carbonate and sodium hydroxide are added and sufficiently stirred. Sodium carbonate concentration 0.6 mol / L, pH 8. 4 L of the mixed aqueous solution of 5 was prepared. Further, a nickel aqueous solution prepared by dissolving nickel sulfate in pure water to adjust the nickel concentration to 120 g / L and an additive mixed aqueous solution containing sodium hydroxide and sodium carbonate adjusted to a concentration of 0.6 mol / L were prepared. These nickel aqueous solutions and the mixed aqueous solution for addition were added simultaneously and continuously to the above-mentioned mixed aqueous solution in the reaction vessel containing sodium carbonate and sodium hydroxide and mixed to carry out a neutralization reaction. At this time, the nickel aqueous solution and the mixed aqueous solution for addition, which were supplied from the outlets of both supply nozzles, were mixed in a turbulent state in the reaction tank of the supply destination, respectively.
この中和反応の際、反応槽内の反応液はｐＨ８.５を中心としてその変動幅が絶対値で０.２以内となるように調整した。また、ニッケル水溶液を７５ｍＬ／分の流量で添加することによって、添加用混合水溶液の流量と合わせて中和の反応時間を０.５時間に調整した。更に、反応槽内では反応液の温度を６０℃とし、攪拌翼を用いて７００ｒｐｍで撹拌した。 At the time of this neutralization reaction, the reaction solution in the reaction vessel was adjusted so that the fluctuation range centered on pH 8.5 was within 0.2 in absolute value. Further, by adding the nickel aqueous solution at a flow rate of 75 mL / min, the reaction time of neutralization was adjusted to 0.5 hours in combination with the flow rate of the mixed aqueous solution for addition. Further, in the reaction vessel, the temperature of the reaction solution was set to 60 ° C., and the mixture was stirred at 700 rpm using a stirring blade.
上記の連続晶析法により水酸化ニッケル粒子を連続的に晶析させた。この晶析により生成した水酸化ニッケル粒子の沈殿物を含むスラリーをオーバーフローにより連続的に回収し、ヌッチェによる濾過と保持時間３０分の純水レパルプを１０回繰り返して、水酸化ニッケル粒子の濾過ケーキを得た。この濾過ケーキを送風乾燥機を用いて１３０℃の大気中にて２４時間かけて乾燥し、水酸化ニッケル粒子を得た（中和工程）。 Nickel hydroxide particles were continuously crystallized by the above continuous crystallization method. The slurry containing the precipitate of nickel hydroxide particles produced by this crystallization is continuously recovered by overflow, and filtration by Nutche and pure water repulp with a holding time of 30 minutes are repeated 10 times to filter the nickel hydroxide particles. Got This filtered cake was dried in the air at 130 ° C. for 24 hours using a blower dryer to obtain nickel hydroxide particles (neutralization step).
得られた水酸化ニッケル粒子のうち５００ｇを大気焼成炉に供給し、９００℃の大気で５時間かけて熱処理して酸化ニッケル粉末を生成した（熱処理工程）。この酸化ニッケル粒子の硫黄品位は１０質量ｐｐｍであった。次に、得られた酸化ニッケル粉末から分取した３００ｇをナノグラインディングミル（登録商標、徳寿工作所製）にてプッシャーノズル圧力１.０ＭＰａ、グラインディング圧力０.９ＭＰａにて粉砕した（解砕工程）。このようにして作製した酸化ニッケル微粉末に対して硫黄（Ｓ）、塩素（Ｃｌ）、及びナトリウム（Ｎａ）の不純物品位を分析し、Ｄ９０及び比表面積を測定した。 500 g of the obtained nickel hydroxide particles were supplied to an air firing furnace and heat-treated in the air at 900 ° C. for 5 hours to produce nickel oxide powder (heat treatment step). The sulfur grade of the nickel oxide particles was 10 mass ppm. Next, 300 g of the obtained nickel oxide powder was pulverized with a nano grinding mill (registered trademark, manufactured by Tokuju Kosakusho) at a pusher nozzle pressure of 1.0 MPa and a grinding pressure of 0.9 MPa (crushing). Process). The impurity grades of sulfur (S), chlorine (Cl), and sodium (Na) were analyzed for the nickel oxide fine powder thus prepared, and D90 and the specific surface area were measured.
［実施例２〜７］
中和工程の反応時間を０.５時間に代えてそれぞれ０.２時間（実施例２）、１.０時間（実施例３）、１.５時間（実施例４）、２.５時間（実施例５）、３.５時間（実施例６）、５.０時間（実施例７）に調整した以外は実施例１と同様にして酸化ニッケル微粉末を作製し、不純物品位等の分析、測定を行った。
[Examples 2 to 7]
The reaction time of the neutralization step was changed from 0.5 hours to 0.2 hours (Example 2), 1.0 hours (Example 3), 1.5 hours (Example 4), and 2.5 hours (Example 4), respectively. Example 5), a nickel oxide fine powder was prepared in the same manner as in Example 1 except that the time was adjusted to 3.5 hours (Example 6) and 5.0 hours (Example 7), and analysis of impurity grade and the like was performed. Measurements were made.
［比較例１〜３］
中和工程の反応時間を０.５時間に代えてそれぞれ０.１時間（比較例１）、６.０時間（比較例２）、１０.０時間（比較例３）に調整した以外は実施例１と同様にして酸化ニッケル微粉末を作製し、不純物品位等の分析、測定を行った。
[Comparative Examples 1 to 3]
The reaction time of the neutralization step was changed to 0.1 hour (Comparative Example 1), 6.0 hours (Comparative Example 2) and 10.0 hours (Comparative Example 3), respectively, instead of 0.5 hours. Nickel oxide fine powder was prepared in the same manner as in Example 1, and the impurity grade and the like were analyzed and measured.
［実施例８〜１１］
中和工程の反応時間を０.５時間に代えてそれぞれ０.２時間（実施例８）、２.５時間（実施例９）、３.５時間（実施例１０）、５.０時間（実施例１１）に調整し、熱処理工程の熱処理温度を９００℃に代えて８６０℃とした以外は実施例１と同様にして酸化ニッケル微粉末を作製し、不純物品位等の分析、測定を行った。
[Examples 8 to 11]
The reaction time of the neutralization step was changed from 0.5 hours to 0.2 hours (Example 8), 2.5 hours (Example 9), 3.5 hours (Example 10), and 5.0 hours (Example 10), respectively. A nickel oxide fine powder was prepared in the same manner as in Example 1 except that the heat treatment temperature in the heat treatment step was set to 860 ° C instead of 900 ° C, and the impurity grade and the like were analyzed and measured. ..
［比較例４、５］
中和工程の反応時間を０.５時間に代えてそれぞれ０.１時間（比較例４）、６.０時間（比較例５）に調整し、熱処理工程の熱処理温度を９００℃に代えて８６０℃とした以外は実施例１と同様にして酸化ニッケル微粉末を作製し、不純物品位等の分析、測定を行った。
[Comparative Examples 4 and 5]
The reaction time of the neutralization step was adjusted to 0.1 hour (Comparative Example 4) and 6.0 hours (Comparative Example 5), respectively, instead of 0.5 hours, and the heat treatment temperature of the heat treatment step was changed to 860 ° C., respectively. Nickel oxide fine powder was prepared in the same manner as in Example 1 except that the temperature was set to ° C., and the impurity grade and the like were analyzed and measured.
［実施例１２〜１５］
中和工程の反応時間を０.５時間に代えてそれぞれ０.２時間（実施例１２）、２.５時間（実施例１３）、３.５時間（実施例１４）、５.０時間（実施例１５）に調整し、熱処理工程の熱処理温度を９００℃に代えて９４０℃とした以外は実施例１と同様にして酸化ニッケル微粉末を作製し、不純物品位等の分析、測定を行った。
[Examples 12 to 15]
The reaction time of the neutralization step was changed from 0.5 hours to 0.2 hours (Example 12), 2.5 hours (Example 13), 3.5 hours (Example 14), and 5.0 hours (Example 14), respectively. A nickel oxide fine powder was prepared in the same manner as in Example 1 except that the heat treatment temperature in the heat treatment step was set to 940 ° C instead of 900 ° C, and the impurity grade and the like were analyzed and measured. ..
［比較例６、７］
中和工程の反応時間を０.５時間に代えてそれぞれ０.１時間（比較例６）、６.０時間（比較例７）に調整し、熱処理工程の熱処理温度を９００℃に代えて９４０℃とした以外は実施例１と同様にして酸化ニッケル微粉末を作製し、不純物品位等の分析、測定を行った。
[Comparative Examples 6 and 7]
The reaction time of the neutralization step was adjusted to 0.1 hour (Comparative Example 6) and 6.0 hours (Comparative Example 7), respectively, instead of 0.5 hours, and the heat treatment temperature of the heat treatment step was changed to 900 ° C. and 940. Nickel oxide fine powder was prepared in the same manner as in Example 1 except that the temperature was set to ° C., and the impurity grade and the like were analyzed and measured.
［比較例８、９］
中和工程の反応時間を０.５時間に代えて２.５時間に調整し、熱処理工程の熱処理温度を９００℃に代えてそれぞれ８５０℃（比較例８）、９５０℃（比較例９）とした以外は実施例１と同様にして酸化ニッケル微粉末を作製し、不純物品位等の分析、測定を行った。上記の実施例１〜１５及び比較例１〜９の酸化ニッケル微粉末の分析、測定結果を反応時間及び熱処理温度と共に下記表１に示す。
[Comparative Examples 8 and 9]
The reaction time of the neutralization step was adjusted to 2.5 hours instead of 0.5 hours, and the heat treatment temperature of the heat treatment step was changed to 900 ° C. (Comparative Example 8) and 950 ° C. (Comparative Example 9), respectively. Nickel oxide fine powder was prepared in the same manner as in Example 1 except for the above, and the impurity grade and the like were analyzed and measured. The analysis and measurement results of the nickel oxide fine powders of Examples 1 to 15 and Comparative Examples 1 to 9 are shown in Table 1 below together with the reaction time and the heat treatment temperature.
上記表１の結果から分るように、実施例１〜１５の酸化ニッケル微粉末はいずれも硫黄品位が２０質量ｐｐｍ以下に制御されている上、塩素品位は２０質量ｐｐｍ未満、ナトリウム品位が１０質量ｐｐｍ未満と不純物品位が極めて低くなっている。また、比表面積はいずれも２.０ｍ２／ｇ以上４.０ｍ２／ｇ未満の範囲内に収まっている。すなわち、電子部品用材料や固体酸化物形燃料電池の電極材料として好適な不純物品位が低くて微細な酸化ニッケル微粉末が得られていることが分かる。これに対して比較例１〜９の酸化ニッケル微粉末は、不純物品位、比表面積値、及びＤ９０のうちの少なくともいずれかが上記の範囲から外れており、電子部品用材料や固体酸化物形燃料電池の電極材料として好適な酸化ニッケル微粉末が得られていないことが分かる。
As can be seen from the results in Table 1 above, the sulfur grades of the nickel oxide fine powders of Examples 1 to 15 are all controlled to 20 mass ppm or less, the chlorine grade is less than 20 mass ppm, and the sodium grade is 10. Impurity grade is extremely low with less than mass ppm. In addition, the specific surface areas are all within the range of 2.0 m 2 / g or more and less than 4.0 m 2 / g. That is, it can be seen that fine nickel oxide fine powder having a low impurity grade suitable as a material for electronic parts and an electrode material for a solid oxide fuel cell is obtained. On the other hand, in the nickel oxide fine powders of Comparative Examples 1 to 9, at least one of the impurity grade, the specific surface area value, and D90 is out of the above range, and the material for electronic parts and the solid oxide fuel cell are used. It can be seen that nickel oxide fine powder suitable as an electrode material for a battery has not been obtained.
Claims (11)
前記アルカリ水溶液は炭酸ナトリウム濃度が０.４〜０.８ｍｏｌ／Ｌであり、前記中和は連続晶析法を用い、前記酸化ニッケル微粉末に求められる総アルカリ金属品位又は比表面積に応じて反応時間を０.２〜５ｈの範囲内で調整することを特徴とする酸化ニッケル微粉末の製造方法。 A neutralization step of neutralizing a nickel sulfate aqueous solution with an alkaline aqueous solution containing an alkali metal hydroxide and sodium carbonate to generate nickel hydroxide particles, and a neutralization step in which the nickel hydroxide particles are subjected to a non-reducing atmosphere at 850 ° C. A method for producing fine nickel oxide powder, which comprises a heat treatment step of producing nickel oxide powder by heat treatment at a temperature of more than 950 ° C. and a crushing step of crushing the nickel oxide powder.
The alkaline aqueous solution has a sodium carbonate concentration of 0.4 to 0.8 mol / L, and the neutralization uses a continuous crystallization method and reacts according to the total alkali metal grade or specific surface area required for the nickel oxide fine powder. A method for producing fine powder of nickel oxide , which comprises adjusting the time within a range of 0.2 to 5 hours.
The nickel oxide fine powder according to claim 9 or 10, wherein the D90 measured by the laser scattering method is 1 μm or less.
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