JP6852345B2

JP6852345B2 - Manufacturing method of nickel oxide fine powder

Info

Publication number: JP6852345B2
Application number: JP2016203312A
Authority: JP
Inventors: 法道米里; 渡辺　博文; 博文渡辺; 晶市黒川; 高橋　純一; 純一高橋; 雄太郎木道
Original assignee: Sumitomo Metal Mining Co Ltd
Current assignee: Sumitomo Metal Mining Co Ltd
Priority date: 2016-10-17
Filing date: 2016-10-17
Publication date: 2021-03-31
Anticipated expiration: 2036-10-17
Also published as: JP2018065700A

Description

本発明は、電子部品用材料や電池用材料として好適な酸化ニッケル微粉末の製造方法に関する。 The present invention relates to a method for producing fine nickel oxide powder, which is suitable as a material for electronic parts and a material for batteries.

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用材料等の多様な用途に用いられている。例えば、電子部品のフェライト部品に用いる場合は、酸化ニッケル微粉末を酸化鉄や酸化亜鉛等の他の金属酸化物と混合した後、焼結により複合金属酸化物の形態にすることが行われている。このフェライト部品のように、複数の材料の焼成反応で複合金属酸化物を製造する場合は、反応速度が固相の拡散に律速されるので、原料となる粉体の粒径を小さく微細にすることが生産効率の向上ための重要な要件となる。即ち、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より均一に進ませることが可能になる。 Nickel oxide fine powder is used in various applications such as materials for electronic parts and materials for electrodes of solid oxide fuel cells. For example, when used for ferrite parts of electronic parts, nickel oxide fine powder is mixed with other metal oxides such as iron oxide and zinc oxide, and then sintered to form a composite metal oxide. There is. When a composite metal oxide is produced by a firing reaction of a plurality of materials like this ferrite component, the reaction rate is regulated by the diffusion of the solid phase, so that the particle size of the raw material powder is made small and fine. This is an important requirement for improving production efficiency. That is, 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 more uniformly even at a low temperature and for a short time.

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固体酸化物形燃料電池が期待されており、その電極材料には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おり、燃料極には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。燃料極で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。そのため、上記のフェライト部品の場合と同様に、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件となる。 Further, a solid oxide fuel cell is expected as a new power generation system from both aspects of environment and energy, and nickel oxide fine powder is used as an electrode material thereof. Generally, the cell stack of a solid oxide fuel cell has a structure in which a plurality of single cells consisting of an air electrode, a solid electrolyte and a fuel electrode are laminated, and the fuel electrode is stabilized with nickel or nickel oxide. A mixture with a solid electrolyte made of zirconia is usually used. At the fuel electrode, it is reduced by a fuel gas such as hydrogen or hydrocarbon during power generation to form nickel metal, and the three-phase interface consisting of nickel, a solid electrolyte, and voids serves as a reaction field between the fuel gas and oxygen. Therefore, as in the case of the above-mentioned ferrite parts, it is an important requirement for improving the power generation efficiency to reduce the particle size of the powder as a raw material to make it finer.

ところで、粉体の細かさを測る指標として比表面積を用いることがあり、比表面積と粒径の間には、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の関係は粒子を真球と仮定して導き出したものであるため、計算式１から求めた粒径は実際の粒径とは異なりある程度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かる。 By the way, the specific surface area may be used as an index for measuring the fineness of the powder, and it is known that there is a relationship of the following formula 1 between the specific surface area and the particle size. Since the relationship of the following calculation formula 1 is derived by assuming that the particles are true spheres, the particle size obtained from the calculation formula 1 is different from the actual particle size and includes some error, but the specific surface area. It can be seen that the larger the value, 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性能化が求められており、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や電極材料等に広がっている。これに伴い、酸化ニッケル微粉末には上記のように微細であることに加えて不純物元素が低品位であることも求められている。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 are required to have higher performance, and the use of nickel oxide fine powder is expanding to electronic parts and electrode materials other than ferrite parts. Along with this, the nickel oxide fine powder is required to have a low quality of impurity elements in addition to being fine as described above. Among the impurity elements, chlorine and sulfur may react with silver used for the electrode 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である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, Patent Document 1 discloses a ferrite material in which the sulfur component content of the ferrite powder at the raw material stage is 300 to 900 ppm in terms of S and the content of chlorine component is 100 ppm in terms of Cl. 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.

上記した酸化ニッケル微粉末の製造方法としては、従来、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乾式法が採用されてきた。 Conventionally, as the above-mentioned method for producing fine nickel oxide powder, nickel salts such as nickel sulfate, nickel nitrate, nickel carbonate, nickel hydroxide or the like or nickel metal powder is continuously used in a rolling furnace such as a rotary kiln, a pusher furnace or the like. A dry method has been adopted in which firing is performed in an oxidizing atmosphere using a furnace or a batch furnace such as a burner furnace.

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焙焼温度９５０〜１０００℃未満で焙焼する第１段焙焼と、焙焼温度１０００〜１２００℃で焙焼する第２段焙焼とで処理して酸化ニッケル粉末を製造する方法が開示されている。この製造方法によれば、平均粒径が制御され、且つ硫黄含有量が５０質量ｐｐｍ以下の酸化ニッケル微粉末が得られると記載されている。 For example, Patent Document 2 describes first-stage roasting in which nickel sulfate as a raw material is roasted in an oxidizing atmosphere using a kiln or the like at a roasting temperature of less than 950 to 1000 ° C. A method for producing nickel oxide powder by processing with the second stage roasting for roasting is disclosed. According to this production method, it is described that a nickel oxide fine powder having a controlled average particle size and a sulfur content of 50 mass ppm or less can be obtained.

特許文献３には、４５０〜６００℃の仮焼による脱水工程と、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開示されている。この製造方法によれば、硫黄含有量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。さらに特許文献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９００〜１２５０℃で焙焼する方法が開示されている。この製造方法によっても、硫黄含有量が５００質量ｐｐｍ以下の不純物の少ない酸化ニッケル粉末が得られると記載されている。 Patent Document 3 discloses a method for producing nickel oxide powder in which a dehydration step by calcining at 450 to 600 ° C. and a decomposition step of nickel sulfate by roasting at 1000 to 1200 ° C. are clearly separated. According to this production method, it is described that nickel oxide powder having a low sulfur content and a small average particle size can be stably produced. Further, Patent Document 4 discloses a method of roasting at a maximum temperature of 900 to 1250 ° C. while forcibly introducing air using a horizontal rotary manufacturing furnace. It is described that this production method also provides nickel oxide powder having a sulfur content of 500 mass ppm or less and having a small amount of impurities.

また、酸化ニッケル微粉末を湿式法で合成する方法も提案されている。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し、得られた水酸化ニッケル粒子を５００〜８００℃の温度で熱処理し、これにより生成される酸化ニッケル粉末をスラリー化し、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、硫黄及び塩素の含有量が低く且つ微細な粒径の酸化ニッケル微粉末を得る方法が開示されている。 In addition, a method of synthesizing nickel oxide fine powder by a wet method has also been proposed. For example, in Patent Document 5, the nickel chloride aqueous solution is neutralized with alkali, the obtained nickel hydroxide particles are heat-treated at a temperature of 500 to 800 ° C., and the nickel oxide powder produced thereby is slurried and wet jet milled. Disclosed is a method for obtaining nickel oxide fine powder having a low content of sulfur and chlorine and a fine particle size by crushing and washing at the same time.

特開２００２−１９８２１３号公報JP-A-2002-198213 特開２００１−０３２００２号公報Japanese Unexamined Patent Publication No. 2001-032002 特開２００４−１２３４８８号公報Japanese Unexamined Patent Publication No. 2004-123488 特開２００４−１８９５３０号公報Japanese Unexamined Patent Publication No. 2004-189530 特開２０１１−０４２５４１号公報Japanese Unexamined Patent Publication No. 2011-042541

上記の特許文献１や２の方法によれば不純物含有量の低い酸化ニッケル微粉末が得られるものの、熱処理を２回行う必要があるため生産性が低く、生産コストが高くなるという問題を抱えている。また、上記特許文献２〜４のいずれの方法においても、硫黄含有量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、また粒子を微細にするために焙焼温度を下げると硫黄含有量が高くなるため、粒径と硫黄含有量を同時に最適値に制御するのは困難である。さらに、加熱する際に大量のＳＯｘを含むガスが発生し、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も抱えている。 According to the methods of Patent Documents 1 and 2 described above, nickel oxide fine powder having a low impurity content can be obtained, but there is a problem that productivity is low and production cost is high because heat treatment needs to be performed twice. There is. Further, in any of the methods of Patent Documents 2 to 4, when the roasting temperature is raised in order to reduce the sulfur content, the particle size becomes coarse, and when the roasting temperature is lowered in order to make the particles finer. Since the sulfur content is high, it is difficult to control the particle size and the sulfur content to the optimum values at the same time. Further, there is a problem that a gas containing a large amount of SOx is generated during heating, and expensive equipment is required for detoxifying the gas.

一方、上記特許文献５のように、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る場合は、得られた水酸化ニッケル粒子を焙焼することで酸化ニッケル微粉末を生成できるため、陰イオン成分由来のガスの発生を少なくでき、よって排ガス処理は不要となるか若しくは簡易な設備でよく、低コストでの製造が可能になると考えられる。さらに特許文献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が可能である。 On the other hand, as in Patent Document 5, a case where 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 is obtained. Since nickel oxide fine powder can be produced by roasting nickel hydroxide particles, the generation of gas derived from anionic components can be reduced, so exhaust gas treatment is not required or simple equipment is sufficient, and the cost is low. It is thought that manufacturing will be possible. Further, the method for producing fine nickel oxide powder in Patent Document 5 uses nickel chloride as a raw material, so that the sulfur grade can be reduced.

しかしながら、特許文献５の技術では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。すなわち、酸化ニッケル微粉末は、電子部品材料としての用途、特にフェライト部品の原料として用いる場合は、硫黄等の不純物の含有量を単に低減するだけでなく、硫黄の含有量を所定の範囲内に厳密に制御することを要求されることがある。このように、電子部品材料として用いられる酸化ニッケル微粉末の場合は、粒径の微細化と不純物の低減に加えて、硫黄の含有量の厳密な制御が必要になることがある。さらに、特許文献５の技術は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。 However, it has been difficult to control the sulfur grade within a predetermined range by the technique of Patent Document 5. That is, when nickel oxide fine powder is used as a material for electronic parts, especially as a raw material for ferrite parts, it not only reduces the content of impurities such as sulfur, but also keeps the sulfur content within a predetermined range. Strict control may be required. As described above, in the case of nickel oxide fine powder used as an electronic component material, it may be necessary to strictly control the sulfur content in addition to making the particle size finer and reducing impurities. Further, since the technique of Patent Document 5 requires wet crushing, particles may agglutinate during drying after the wet crushing, and the energy required for drying may be disadvantageous in terms of cost. ..

上記のように、従来の技術では微細な粒子径を有すると共に硫黄含有量が制御された酸化ニッケル微粉末を低コストで作製するのは困難であり、更なる改善が望まれていた。本発明は、上記した従来の技術が抱える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用材料として好適な微細な酸化ニッケル微粉末を低コストで作製することが可能な製造方法を提供することを目的とする。 As described above, it is difficult to produce nickel oxide fine powder having a fine particle size and a controlled sulfur content at low cost by the conventional technique, and further improvement has been desired. The present invention has been made in view of the problems of the above-mentioned conventional techniques, and has low grades of total alkali metals such as sodium and impurities such as sulfur, and is used as a material for electronic parts or an electrode of a solid oxide fuel cell. An object of the present invention is to provide a production method capable of producing fine nickel oxide fine powder suitable as a material for use at low cost.

本発明者らは、上記目的を達成するため、酸化ニッケル微粉末の製造プロセスについて鋭意研究を重ねた結果、湿式法で生成した水酸化ニッケル等のニッケル塩の中間体を、非還元性で且つ低酸素分圧雰囲気で焼成することにより、特に洗浄処理を施すことなく微細な酸化ニッケル粉末中の硫酸根や硫黄分を効率的に低減できる事を見出し、本発明を完成するに至った。 As a result of intensive research on the production process of nickel oxide fine powder in order to achieve the above object, the present inventors have made an intermediate of a nickel salt such as nickel hydroxide produced by a wet method non-reducing and non-reducing. We have found that the sulfate roots and sulfur content in fine nickel oxide powder can be efficiently reduced by firing in a low oxygen partial pressure atmosphere without performing a cleaning treatment, and have completed the present invention.

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塩基性水溶液で中和してニッケル塩の中間体粒子を晶析する工程と、得られた中間体粒子を水洗した後、焼成処理により酸化ニッケル粉末を生成する工程と、得られた酸化ニッケル粉末を解砕して（湿式解砕を除く）微粒子にする工程とを含み、前記焼成処理を温度５５０〜９５０℃の範囲内で且つ酸素分圧５ｋＰａ以下の非還元性雰囲気下で行うことを特徴としている。 That is, in the method for producing the nickel oxide fine powder of the present invention, a step of neutralizing the nickel sulfate aqueous solution with a basic aqueous solution to crystallize the intermediate particles of the nickel salt, and washing the obtained intermediate particles with water are followed. The firing treatment includes a step of producing nickel oxide powder by a firing treatment and a step of crushing the obtained nickel oxide powder into fine particles (excluding wet crushing) , and the firing treatment is performed within a temperature range of 550 to 950 ° C. Moreover, it is characterized in that it is carried out in a non-reducing atmosphere having an oxygen partial pressure of 5 kPa or less.

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電池用材料として好適な硫黄含有量が低く且つ微細な酸化ニッケル微粉末を低コストで作製することができる。 According to the present invention, it is possible to produce fine nickel oxide fine powder having a low sulfur content, which is suitable as a material for electronic parts such as ferrite parts and a material for batteries, at low cost.

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、硫酸ニッケル水溶液と塩基性水溶液との中和反応により水酸化ニッケル等のニッケル塩の中間体粒子を晶析する中和工程と、得られた中間体粒子を、温度５５０〜９５０℃の範囲内であって且つ酸素分圧５ｋＰａ以下の非還元性雰囲気で焼成処理して酸化ニッケル粉末を得る焼成工程と、得られた酸化ニッケル粉末を解砕する解砕工程とからなる。以下、これら一連の工程からなる酸化ニッケル微粉末の製造方法を工程ごとに詳細に説明する。 Hereinafter, a specific example of the method for producing the nickel oxide fine powder of the present invention will be described. A specific example of the method for producing nickel oxide fine powder of the present invention includes a neutralization step of crystallizing intermediate particles of a nickel salt such as nickel hydroxide by a neutralization reaction between a nickel sulfate aqueous solution and a basic aqueous solution. A firing step of obtaining nickel oxide powder by calcining the obtained intermediate particles in a non-reducing atmosphere having a temperature in the range of 550 to 950 ° C. and an oxygen partial pressure of 5 kPa or less, and the obtained nickel oxide powder. It consists of a crushing step of crushing. Hereinafter, a method for producing nickel oxide fine powder, which comprises a series of these steps, will be described in detail for each step.

（中和工程）
先ず中和工程では、原料としての硫酸ニッケルの水溶液に対して、中和剤としての塩基性水溶液を添加して中和反応を生じさせ、水酸化ニッケル等のニッケル塩の中間体粒子を晶析させる。原料として用いる硫酸ニッケルは、例えば硫酸ニッケル六水和物等を用いるのが好ましく、これを水で希釈して水溶液とする。なお、最終的に得られる酸化ニッケル微粉末は電子部品用材料や電池用材料として主に用いられるため、それらの腐食を防止するため、原料や中和剤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, a basic aqueous solution as a neutralizing agent is added to an aqueous solution of nickel sulfate as a raw material to cause a neutralization reaction, and intermediate particles of a nickel salt such as nickel hydroxide are crystallized. Let me. As the nickel sulfate used as a raw material, for example, nickel sulfate hexahydrate or the like is preferably used, and this is diluted with water to obtain an aqueous solution. Since the finally obtained nickel oxide fine powder is mainly used as a material for electronic parts and a material for batteries, impurities contained in the raw material and the neutralizing agent are less than 100 mass ppm in order to prevent their corrosion. Is desirable.

硫酸ニッケル水溶液中のニッケル濃度は特に限定はないが、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未満では生産性が悪くなる。一方、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 nickel concentration 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, the productivity will deteriorate. On the other hand, 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.

中和剤として用いる塩基性水溶液には、水酸化ナトリウムや水酸化カリウムのような水酸化塩、炭酸ナトリウムのような炭酸塩、硝酸ナトリウムや硝酸カリウムのような硝酸塩を用いることができる。これら中和剤を用いた中和反応により得られる中間体粒子は、水酸化塩の場合は水酸化ニッケル粒子、炭酸塩の場合は炭酸ニッケル粒子、硝酸塩の場合は硝酸ニッケルとなる。 As the basic aqueous solution used as the neutralizing agent, a hydroxide salt such as sodium hydroxide or potassium hydroxide, a carbonate such as sodium carbonate, or a nitrate such as sodium nitrate or potassium nitrate can be used. The intermediate particles obtained by the neutralization reaction using these neutralizing agents are nickel hydroxide particles in the case of hydroxide, nickel carbonate particles in the case of carbonate, and nickel nitrate in the case of nitrate.

上記の塩基性水溶液は、これらの２種以上の混合液でもよく、この場合に生成される中間体粒子は、水酸化ニッケル、炭酸ニッケル、及び硝酸ニッケルのうち２種以上が混合した粒子となる。中和反応時の液中に残留するニッケルの量を考慮すると、上記塩基性水溶液は水酸化塩とするのが好ましく、水酸化ナトリウム又は水酸化カリウムがより好ましく、コストを考慮すると水酸化ナトリウムが特に好ましい。この塩基性水溶液にはアルコール等の水溶性有機溶媒を混合させてもよい。 The above basic aqueous solution may be a mixed solution of two or more of these, and the intermediate particles produced in this case are particles in which two or more of nickel hydroxide, nickel carbonate, and nickel nitrate are mixed. .. Considering the amount of nickel remaining in the liquid during the neutralization reaction, the basic aqueous solution is preferably a hydroxide salt, more preferably sodium hydroxide or potassium hydroxide, and considering the cost, sodium hydroxide is used. Especially preferable. A water-soluble organic solvent such as alcohol may be mixed with this basic aqueous solution.

中和反応時の液温は一般的な反応条件であれば特に制約はなく、常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、液温を５０〜７０℃とすることが好ましい。このように中間体粒子を十分に成長させることで、中間体粒子中に硫黄が過度に含まれるのを防止することができる。上記中和反応により晶析した中間体粒子には硫黄が含まれており、例えば中間体粒子が水酸化ニッケル粒子の場合は１〜３質量％程度の硫黄を含有している。一方、原料に塩化ニッケルを用いないため塩素が混入する虞がほとんどなく、原料に不可避的に含まれる不純物以外は実質的に塩素を含有しない中間体粒子となる。 The liquid temperature at the time of the neutralization reaction is not particularly limited as long as it is a general reaction condition, and it can be carried out at room temperature, but the liquid temperature is set to 50 to 70 ° C. in order to sufficiently grow nickel hydroxide particles. It is preferable to do so. By sufficiently growing the intermediate particles in this way, it is possible to prevent excessive sulfur from being contained in the intermediate particles. The intermediate particles crystallized by the neutralization reaction contain sulfur. For example, when the intermediate particles are nickel hydroxide particles, they contain about 1 to 3% by mass of sulfur. On the other hand, since nickel chloride is not used as the raw material, there is almost no possibility that chlorine is mixed in, and the intermediate particles are substantially free of chlorine except for impurities inevitably contained in the raw material.

上記の中和反応の終了後は、晶析した中間体粒子を含むスラリーを濾過して中間体粒子を濾過ケーキの形態で回収する。この濾過ケーキは、次の焼成工程に移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、洗浄に用いる洗浄液としては水が好ましく、純水が特に好ましい。洗浄時の中間体粒子と水の混合割合は特に限定はなく、中間体粒子であるニッケル塩に含まれる陰イオン、特に硫酸イオン等の成分が、十分に除去できる混合割合とすればよい。洗浄後は必要に応じて脱水した後、乾燥するのが好ましい。 After completion of the above neutralization reaction, the slurry containing the crystallized intermediate particles is filtered to recover the intermediate particles in the form of a filtered cake. The filtered cake is preferably washed before moving on to the next baking step. The cleaning is preferably repulp cleaning, water is preferable as the cleaning liquid used for cleaning, and pure water is particularly preferable. The mixing ratio of the intermediate particles and water at the time of washing is not particularly limited, and the mixing ratio may be such that the components such as anions, particularly sulfate ions contained in the nickel salt which is the intermediate particles can be sufficiently removed. After washing, it is preferable to dehydrate if necessary and then dry.

（焼成工程）
次に焼成工程では、上記の中和工程で得た中間体粒子を熱処理して酸化ニッケル粉末の生成、即ち焼成が行われる。この熱処理は、温度が５５０〜９５０℃の範囲内で且つ酸素分圧が５ｋＰａ以下の非還元性雰囲気下で行われる。上記にて説明した通り、中間体粒子は硫黄を含有している。この硫黄は主に原料に由来する硫酸の形態を有しており、大部分は硫酸ニッケルのままで中間体粒子内若しくはその表面に存在している。この硫酸ニッケルは焼成により下記式１の通り分解、揮発して酸化ニッケルとなる。この式１に示す反応における分解反応を促進するため、焼成時の雰囲気を上記したように非還元性で且つ低酸素分圧にするのが良いと考えられる。 (Baking process)
Next, in the firing step, the intermediate particles obtained in the above neutralization step are heat-treated to produce nickel oxide powder, that is, firing is performed. This heat treatment is performed in a non-reducing atmosphere in which the temperature is in the range of 550 to 950 ° C. and the oxygen partial pressure is 5 kPa or less. As described above, the intermediate particles contain sulfur. This sulfur has the form of sulfuric acid mainly derived from the raw material, and most of it remains as nickel sulfate and exists in the intermediate particles or on the surface thereof. This nickel sulfate is decomposed and volatilized as shown in the following formula 1 by firing to become nickel oxide. In order to promote the decomposition reaction in the reaction represented by this formula 1, it is considered that the atmosphere at the time of firing should be non-reducing and have a low oxygen partial pressure as described above.

［式１］
２ＮｉＳＯ_４ → ２ＮｉＯ＋２ＳＯ_２＋Ｏ_２ [Equation 1]
2NiSO ₄ → 2NiO + 2SO ₂ + O ₂

焼成時の雰囲気の具体的な酸素分圧の値としては、５ｋＰａ以下にする。この酸素分圧は３ｋＰａ以下が好ましく、１ｋＰａ以下がより好ましい。この酸素分圧が５ｋＰａを超えると、上記式１における分解反応進みにくくなり、酸化ニッケル粉末の硫黄含有量が低下せず、解砕後の酸化ニッケル微粉末の硫黄含有量が２００質量ｐｐｍを超えることがある。酸素分圧の下限は特に限定はないが、１０Ｐａにすれば十分に酸化ニッケル粉末の硫黄含有量を低減することができる。もちろん酸素分圧が１０Ｐａよりもさらに低い場合を除外するものではない。 The specific oxygen partial pressure value of the atmosphere at the time of firing is set to 5 kPa or less. The oxygen partial pressure is preferably 3 kPa or less, and more preferably 1 kPa or less. When this oxygen partial pressure exceeds 5 kPa, the decomposition reaction in the above formula 1 becomes difficult to proceed, the sulfur content of the nickel oxide powder does not decrease, and the sulfur content of the nickel oxide fine powder after crushing exceeds 200 mass ppm. Sometimes. The lower limit of the oxygen partial pressure is not particularly limited, but if it is set to 10 Pa, the sulfur content of the nickel oxide powder can be sufficiently reduced. Of course, the case where the oxygen partial pressure is even lower than 10 Pa is not excluded.

さらに、水酸化ニッケル等の中間体粒子が還元されてニッケルになるのを防止するため、焼成時の雰囲気を非還元性にする。例えば、焼成時の雰囲気を構成するガスの主成分を、窒素、二酸化炭素、水蒸気、アルゴン、及びヘリウムからなる群から選ばれる１種にすればよい。具体的には、炉内にこれら窒素、二酸化炭素、水蒸気、アルゴン、及びヘリウムからなる群から選ばれる１種のガスを供給したり、これらガスのいずれかを主成分とする低酸素濃度のガスを供給したりしながら焼成すればよい。あるいは、炉内雰囲気の排気により酸素分圧５ｋＰａ以下にまで減圧した状態で焼成してもよい。 Further, in order to prevent intermediate particles such as nickel hydroxide from being reduced to nickel, the atmosphere at the time of firing is made non-reducing. For example, the main component of the gas constituting the atmosphere at the time of firing may be one selected from the group consisting of nitrogen, carbon dioxide, water vapor, argon, and helium. Specifically, one type of gas selected from the group consisting of nitrogen, carbon dioxide, water vapor, argon, and helium is supplied into the furnace, or a gas having a low oxygen concentration containing any of these gases as a main component. It may be fired while supplying. Alternatively, firing may be performed in a state where the oxygen partial pressure is reduced to 5 kPa or less by exhausting the atmosphere in the furnace.

焼成時の雰囲気温度を５５０〜９５０℃の範囲内にする理由は、この温度が５５０℃未満では、上記式１の分解反応が進行しにくくなり硫黄成分が残留するため、酸化ニッケル微粉末の硫黄含有量が２００質量ｐｐｍを超えることがあるからである。一方、この温度が９５０℃を超えると、中間体粒子の熱分解で生成した酸化ニッケル粉末同士の焼結が進行して、次工程で解砕を行っても焼結した粉末の分離が困難となり、電子部品用材料や電池用材料としては適さない程度に小さな比表面積を有するＤ５０の大きな粉末となってしまう。この焼成を行う装置は特に限定はなく、公知の装置を使用してもよいが、焼成時に発生する分解ガスを効率よく排出するため、炉内に強制的に雰囲気ガスを導入したり、炉内の雰囲気を強制的に排気する機構を有する装置を用いるのが好ましい。 The reason why the ambient temperature at the time of firing is kept in the range of 550 to 950 ° C. is that if this temperature is less than 550 ° C., the decomposition reaction of the above formula 1 will not proceed easily and the sulfur component will remain. This is because the content may exceed 200 mass ppm. On the other hand, when this temperature exceeds 950 ° C., sintering of nickel oxide powders generated by thermal decomposition of intermediate particles progresses, and it becomes difficult to separate the sintered powder even if crushing is performed in the next step. , It becomes a large powder of D50 having a small specific surface area that is not suitable as a material for electronic parts and a material for batteries. The apparatus for performing this firing is not particularly limited, and a known apparatus may be used. However, in order to efficiently discharge the decomposition gas generated during firing, an atmospheric gas may be forcibly introduced into the furnace or the inside of the furnace may be used. It is preferable to use a device having a mechanism for forcibly exhausting the atmosphere of.

（解砕工程）
次に解砕工程では、上記焼成により得た酸化ニッケル粉末の焼結体を物理的に分離、破壊して酸化ニッケル微粉末を形成する。上記焼成工程では中間体粒子が熱分解されて酸化ニッケル粉末が生成されるが、その際、粒径の微細化が起こると共に、高温の熱処理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。この焼結体を破壊するため、この工程では焼成後の酸化ニッケル粉末に対して解砕処理を行い、これにより酸化ニッケル微粉末を得るものである。解砕に用いられる装置は特に限定はなく、公知のものを用いることができる。例えば、ビーズミルやボールミル等の解砕メディアを用いた解砕装置や、ジェットミル等の解砕メディアを用いずに流体エネルギーを利用した解砕装置などを用いることができる。 (Crushing process)
Next, in the crushing step, the sintered body of the nickel oxide powder obtained by the above firing is physically separated and broken to form nickel oxide fine powder. In the above firing step, the intermediate particles are thermally decomposed to produce nickel oxide powder. At that time, the particle size is refined and the nickel oxide powders are sintered to some extent due to the influence of high temperature heat treatment. .. In order to destroy this sintered body, in this step, the nickel oxide powder after firing is crushed to obtain nickel oxide fine powder. The apparatus used for crushing is not particularly limited, and known ones can be used. For example, a crushing device using a crushing medium such as a bead mill or a ball mill, a crushing device using fluid energy without using a crushing medium such as a jet mill, or the like can be used.

（酸化ニッケル微粉末の物性）
上記した本発明の一具体例の製造方法により得られる酸化ニッケル微粉末は、ニッケル鍍金等に広く用いられる硫酸ニッケルを原料に用いても、レーザー散乱法で測定した中心粒径（粒度分布上で体積積算５０％となるＤ５０）が１μｍ以下でありながら低硫黄含有量を実現することができる。従って、この酸化ニッケル微粉末は、電子部品用材料や電池用材料として特に好適である。 (Physical characteristics of nickel oxide fine powder)
The nickel oxide fine powder obtained by the production method of one specific example of the present invention described above has a central particle size (on the particle size distribution) measured by a laser scattering method even when nickel sulfate widely used for nickel plating or the like is used as a raw material. A low sulfur content can be realized while D50) having a volume integration of 50% is 1 μm or less. Therefore, this nickel oxide fine powder is particularly suitable as a material for electronic parts and a material for batteries.

即ち、原料や中和剤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、塩素含有量が極めて低い。加えて、硫黄含有量が制御されていて微細である。具体的には、硫黄含有量が２００質量ｐｐｍ以下、より好ましくは１００質量ｐｐｍ以下であり、レーザー散乱法で測定したＤ５０が１μｍ以下、より好ましくは０.２〜０.８μｍ、さらに好ましくは０.３〜０.５μｍである。従って、電子部品材料、特にフェライト部品用の材料や、電池材料、特に固体酸化物形燃料電池の電極用材料として好適である。なお、固体酸化物形燃料電池の電極用材料としては、硫黄含有量が１００質量ｐｐｍ以下であることが好ましいとされている。 That is, the chlorine content is extremely low because it does not include a step of mixing chlorine other than mixing it as an unavoidable impurity from the raw material or the neutralizing agent. In addition, the sulfur content is controlled and fine. Specifically, the sulfur content is 200 mass ppm or less, more preferably 100 mass ppm or less, and the D50 measured by the laser scattering method is 1 μm or less, more preferably 0.2 to 0.8 μm, still more preferably 0. It is .3 to 0.5 μm. Therefore, it is suitable as a material for electronic parts, particularly a material for ferrite parts, and a material for batteries, particularly 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 content is preferably 100 mass ppm or less.

以下、本発明の実施例及び比較例によって本発明をさらに詳細に説明するが、本発明は、これらの実施例によってなんら限定されるものではない。なお、以下の実施例及び比較例で用いた酸化ニッケル微粉末の粒径及び比表面積、酸化ニッケル微粉末又はその中間体粒子の硫黄分析方法は、以下の通りである。 Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples of the present invention, but the present invention is not limited to these Examples. The particle size and specific surface area of the nickel oxide fine powder used in the following Examples and Comparative Examples, and the sulfur analysis method of the nickel oxide fine powder or its intermediate particles are as follows.

（１）酸化ニッケル微粉末の粒径の測定：粒子径測定装置（Ｍｉｃｒｏｔｒａｃ３２０−Ｘ１００、ＭｉｃｒｏｔｒａｃＩｎｃ製）を用いて、レーザー回折・散乱法で測定し、その粒度分布から体積積算５０％となる粒径Ｄ５０を求めた。
（２）酸化ニッケル微粉末の比表面積の測定：比表面積測定装置（ＮＯＶＡ１０００ｅ、ユアサアイオニクス社製）を用いて、ＢＥＴ法で行なった。
（３）酸化ニッケル微粉末又はその中間体粒子の硫黄分析：ＩＣＰ発光分光分析法で行なった。 (1) Measurement of particle size of nickel oxide fine powder: Measurement by laser diffraction / scattering method using a particle size measuring device (Microtrac 320-X100, manufactured by Microtrac Inc), and the volume integration is 50% from the particle size distribution. The particle size D50 was determined.
(2) Measurement of specific surface area of nickel oxide fine powder: The specific surface area was measured by the BET method using a specific surface area measuring device (NOVA 1000e, manufactured by Yuasa Ionics Co., Ltd.).
(3) Sulfur analysis of nickel oxide fine powder or its intermediate particles: ICP emission spectroscopy was performed.

（実施例１）
硫酸ニッケルの水溶液を撹拌しながら、水酸化ナトリウムによりｐＨ８.０、液温６０℃の条件下で中和し、得られた水酸化ニッケル沈殿物を水洗、脱水、乾燥して水酸化ニッケル粒子とした。得られた水酸化ニッケル粒子の硫黄含有量は、２.０質量％であった。この粒子１０ｇをアルミナの試料皿に充填し、長尺石英管にヒーターを付設した管状炉に装填した。 (Example 1)
While stirring the aqueous solution of nickel sulfate, neutralize with sodium hydroxide under the conditions of pH 8.0 and liquid temperature of 60 ° C., and the obtained nickel hydroxide precipitate is washed with water, dehydrated and dried to obtain nickel hydroxide particles. did. The sulfur content of the obtained nickel hydroxide particles was 2.0% by mass. 10 g of these particles were filled in an alumina sample dish and loaded into a tube furnace equipped with a heater in a long quartz tube.

この長尺石英管の端部から窒素濃度が９９.９９ｖｏｌ％で且つ酸素分圧が０.１ｋＰａ未満の非還元性ガスを毎分１Ｌで導入し、この気流雰囲気の下、上記の水酸化ニッケル粒子を８００℃で５時間の条件で焼成した。これにより得た酸化ニッケル粉末を乳鉢により解砕して微粉末状にした。得られた酸化ニッケル微粉末は、硫黄含有量が１２０質量ｐｐｍ、Ｄ５０が０.３１μｍ、比表面積が４.８ｍ^２／ｇであった。 A non-reducing gas having a nitrogen concentration of 99.99 vol% and an oxygen partial pressure of less than 0.1 kPa was introduced at 1 L / min from the end of this long quartz tube, and the above nickel hydroxide was introduced under this air flow atmosphere. The particles were calcined at 800 ° C. for 5 hours. The nickel oxide powder thus obtained was crushed in a mortar to make a fine powder. The obtained nickel oxide fine powder had a sulfur content of 120 mass ppm, a D50 of 0.31 μm, and a specific surface area of 4.8 m ² / g.

（実施例２）
焼成時の温度を８００℃に代えて８５０℃にした以外は上記実施例１と同様にして酸化ニッケル微粉末を作製した。得られた酸化ニッケル微粉末は、硫黄含有量が６０質量ｐｐｍ、Ｄ５０が０.３９μｍ、比表面積が４.３ｍ^２／ｇであった。 (Example 2)
Nickel oxide fine powder was prepared in the same manner as in Example 1 above except that the temperature at the time of firing was changed to 850 ° C instead of 800 ° C. The obtained nickel oxide fine powder had a sulfur content of 60 mass ppm, a D50 of 0.39 μm, and a specific surface area of 4.3 m ² / g.

（実施例３）
焼成時の温度を８００℃に代えて９００℃にした以外は上記実施例１と同様にして酸化ニッケル微粉末を作製した。得られた酸化ニッケル微粉末は、硫黄含有量が３０質量ｐｐｍ、Ｄ５０が０.４３μｍ、比表面積が３.８ｍ^２／ｇであった。 (Example 3)
Nickel oxide fine powder was prepared in the same manner as in Example 1 above except that the temperature at the time of firing was changed to 900 ° C instead of 800 ° C. The obtained nickel oxide fine powder had a sulfur content of 30 mass ppm, a D50 of 0.43 μm, and a specific surface area of 3.8 m ² / g.

（実施例４）
焼成時の温度を８００℃に代えて７００℃にした以外は上記実施例１と同様にして酸化ニッケル微粉末を作製した。得られた酸化ニッケル微粉末は、硫黄含有量が１５０質量ｐｐｍ、Ｄ５０が０.６１μｍ、比表面積が１５ｍ^２／ｇであった。 (Example 4)
Nickel oxide fine powder was prepared in the same manner as in Example 1 above except that the temperature at the time of firing was changed to 700 ° C instead of 800 ° C. The obtained nickel oxide fine powder had a sulfur content of 150 mass ppm, a D50 of 0.61 μm, and a specific surface area of 15 m ² / g.

（実施例５）
焼成時の温度を８００℃に代えて６００℃にした以外は上記実施例１と同様にして酸化ニッケル微粉末を作製した。得られた酸化ニッケル微粉末は、硫黄含有量が１７０質量ｐｐｍ、Ｄ５０が０.８７μｍ、比表面積が２８ｍ^２／ｇであった。 (Example 5)
Nickel oxide fine powder was prepared in the same manner as in Example 1 above except that the temperature at the time of firing was changed to 600 ° C instead of 800 ° C. The obtained nickel oxide fine powder had a sulfur content of 170 mass ppm, a D50 of 0.87 μm, and a specific surface area of 28 m ² / g.

（実施例６）
中和時のｐＨを８.０に代えて８.５にした以外は上記実施例１と同様にして水酸化ニッケル粒子を生成したところ、その硫黄含有量は１.８質量％になった。この粒子１００ｇを小型転動炉に充填し、窒素濃度９９.９９ｖｏｌ％で且つ酸素分圧０.１ｋＰａ未満の非還元性ガスを毎分１０Ｌで導入し、この気流雰囲気の下、上記の水酸化ニッケル粒子を８５０℃で２時間の条件で焼成した。これにより得た酸化ニッケル粉末を乳鉢により解砕して微粉末状にした。得られた酸化ニッケル微粉末は、硫黄含有量が１２０ｐｐｍ質量、Ｄ５０が０.３３μｍ、比表面積が４.６ｍ^２／ｇであった。 (Example 6)
When nickel hydroxide particles were produced in the same manner as in Example 1 above except that the pH at the time of neutralization was set to 8.5 instead of 8.0, the sulfur content was 1.8% by mass. 100 g of these particles are filled in a small rolling furnace, and a non-reducing gas having a nitrogen concentration of 99.99 vol% and an oxygen partial pressure of less than 0.1 kPa is introduced at 10 L / min. Nickel particles were calcined at 850 ° C. for 2 hours. The nickel oxide powder thus obtained was crushed in a mortar to make a fine powder. The obtained nickel oxide fine powder had a sulfur content of 120 ppm by mass, a D50 of 0.33 μm, and a specific surface area of 4.6 m ² / g.

（実施例７）
焼成時の温度を８５０℃に代えて９００℃にした以外は上記実施例６と同様にして酸化ニッケル微粉末を作製した。得られた酸化ニッケル微粉末は、硫黄含有量が８０質量ｐｐｍ、Ｄ５０が０.４０μｍ、比表面積が４.３ｍ^２／ｇであった。 (Example 7)
Nickel oxide fine powder was prepared in the same manner as in Example 6 above except that the temperature at the time of firing was changed to 900 ° C. instead of 850 ° C. The obtained nickel oxide fine powder had a sulfur content of 80 mass ppm, a D50 of 0.40 μm, and a specific surface area of 4.3 m ² / g.

（実施例８）
焼成時の温度を８５０℃に代えて６００℃にした以外は上記実施例６と同様にして酸化ニッケル微粉末を作製した。得られた酸化ニッケル微粉末は、硫黄含有量が１９０質量ｐｐｍ、Ｄ５０が０.８８μｍ、比表面積が３１ｍ^２／ｇであった。 (Example 8)
Nickel oxide fine powder was prepared in the same manner as in Example 6 above except that the temperature at the time of firing was changed to 600 ° C. instead of 850 ° C. The obtained nickel oxide fine powder had a sulfur content of 190 mass ppm, a D50 of 0.88 μm, and a specific surface area of 31 m ² / g.

（実施例９）
上記実施例６と同様にして水酸化ニッケル粒子を作製し、その粒子２０ｇをアルミナの匣鉢に充填してから小型減圧加熱炉内に載置し、排気量と吸気量とを調整して炉内の圧力が２０ｋＰａ以下、炉内の酸素分圧が４ｋＰａ以下の非還元性雰囲気において、８５０℃で２時間の条件で焼成した。これにより得た酸化ニッケル粉末を乳鉢により解砕して微粉末状にした。得られた酸化ニッケル微粉末は、硫黄含有量が１００質量ｐｐｍ、Ｄ５０が０.４０μｍ、比表面積が４.４ｍ^２／ｇであった。 (Example 9)
Nickel hydroxide particles are prepared in the same manner as in Example 6, 20 g of the particles are filled in an alumina bowl, and then placed in a small vacuum heating furnace, and the exhaust amount and the intake amount are adjusted to adjust the furnace. In a non-reducing atmosphere where the internal pressure was 20 kPa or less and the oxygen partial pressure in the furnace was 4 kPa or less, the fire was carried out at 850 ° C. for 2 hours. The nickel oxide powder thus obtained was crushed in a mortar to make a fine powder. The obtained nickel oxide fine powder had a sulfur content of 100 mass ppm, a D50 of 0.40 μm, and a specific surface area of 4.4 m ² / g.

（実施例１０）
上記実施例１と同様にして水酸化ニッケル粒子を管状炉に装填した後、長尺石英管の端部から酸素濃度５ｖｏｌ％の酸素と窒素の混合ガスを毎分１Ｌで導入し、酸素分圧が５ｋＰａの非還元性ガスの気流雰囲気の下、９００℃で５時間の条件で焼成した。これにより得た酸化ニッケル粉末を乳鉢により解砕して微粉末にした。得られた酸化ニッケル微粉末は、硫黄含有量が１９０質量ｐｐｍ、Ｄ５０が０.３８μｍ、比表面積が４.０ｍ^２／ｇであった。 (Example 10)
After loading the nickel hydroxide particles into the tube furnace in the same manner as in Example 1, a mixed gas of oxygen and nitrogen having an oxygen concentration of 5 vol% is introduced from the end of the long quartz tube at 1 L / min, and the oxygen partial pressure is divided. Was fired at 900 ° C. for 5 hours under an air flow atmosphere of a non-reducing gas at 5 kPa. The nickel oxide powder thus obtained was crushed in a mortar to make a fine powder. The obtained nickel oxide fine powder had a sulfur content of 190 mass ppm, a D50 of 0.38 μm, and a specific surface area of 4.0 m ² / g.

（実施例１１）
長尺石英管の端部から酸素濃度３ｖｏｌ％の酸素と窒素の混合ガスを毎分１Ｌで導入し、酸素分圧３ｋＰａの非還元性ガスの気流雰囲気の下で焼成した以外は上記実施例１０と同様にして酸化ニッケル微粉末を作製した。得られた酸化ニッケル微粉末は、硫黄含有量が１５０質量ｐｐｍ、Ｄ５０が０.３９μｍ、比表面積が４.０ｍ^２／ｇであった。 (Example 11)
Example 10 above except that a mixed gas of oxygen and nitrogen having an oxygen concentration of 3 vol% was introduced from the end of a long quartz tube at 1 L / min and calcined in an air flow atmosphere of a non-reducing gas having an oxygen partial pressure of 3 kPa. Nickel oxide fine powder was prepared in the same manner as in the above. The obtained nickel oxide fine powder had a sulfur content of 150 mass ppm, a D50 of 0.39 μm, and a specific surface area of 4.0 m ² / g.

（実施例１２）
長尺石英管の端部から酸素濃度１ｖｏｌ％の酸素と窒素の混合ガスを毎分１Ｌで導入し、酸素分圧１ｋＰａの非還元性ガスの気流雰囲気の下で焼成した以外は上記実施例１０と同様にして酸化ニッケル微粉末を作製した。得られた酸化ニッケル微粉末は、硫黄含有量が９０質量ｐｐｍ、Ｄ５０が０.４２μｍ、比表面積が３.９ｍ^２／ｇであった。 (Example 12)
Example 10 above except that a mixed gas of oxygen and nitrogen having an oxygen concentration of 1 vol% was introduced from the end of a long quartz tube at 1 L / min and calcined in an air flow atmosphere of a non-reducing gas having an oxygen partial pressure of 1 kPa. Nickel oxide fine powder was prepared in the same manner as in the above. The obtained nickel oxide fine powder had a sulfur content of 90 mass ppm, a D50 of 0.42 μm, and a specific surface area of 3.9 m ² / g.

（比較例１）
長尺石英管の端部から空気を毎分１Ｌで導入し、酸素分圧が２１ｋＰａの大気の気流雰囲気の下で焼成した以外は上記実施例１と同様にして酸化ニッケル微粉末を作製した。得られた酸化ニッケル微粉末は、硫黄含有量が３４０質量ｐｐｍ、Ｄ５０が０.３０μｍ、比表面積が５.３ｍ^２／ｇであった。 (Comparative Example 1)
Nickel oxide fine powder was prepared in the same manner as in Example 1 above, except that air was introduced from the end of the long quartz tube at 1 L / min and calcined in an air flow atmosphere with an oxygen partial pressure of 21 kPa. The obtained nickel oxide fine powder had a sulfur content of 340 mass ppm, a D50 of 0.30 μm, and a specific surface area of 5.3 m ² / g.

（比較例２）
長尺石英管の端部から空気を毎分１Ｌで導入し、酸素分圧２１ｋＰａの大気の気流雰囲気の下、８５０℃で５時間の条件で焼成した以外は上記実施例１と同様にして酸化ニッケル微粉末を作製した。得られた酸化ニッケル微粉末は、硫黄含有量が２３０質量ｐｐｍ、Ｄ５０が０.３５μｍ、比表面積が４.４ｍ^２／ｇであった。 (Comparative Example 2)
Air was introduced from the end of the long quartz tube at 1 L / min and calcined in the same manner as in Example 1 above except that it was calcined at 850 ° C. for 5 hours under an air flow atmosphere with an oxygen partial pressure of 21 kPa. Nickel fine powder was prepared. The obtained nickel oxide fine powder had a sulfur content of 230 mass ppm, a D50 of 0.35 μm, and a specific surface area of 4.4 m ² / g.

（比較例３）
上記実施例６と同様にして水酸化ニッケル粒子を作製し、これを上記実施例１と同様にして管状炉に装填した後、長尺石英管の端部から空気を毎分１Ｌで導入し、酸素分圧２１ｋＰａの大気の気流雰囲気の下、８５０℃で２時間の条件で焼成した。これにより得た酸化ニッケル粉末を乳鉢により解砕して微粉末にした。得られた酸化ニッケル粉末は、硫黄含有量が２７０質量ｐｐｍ、Ｄ５０が０.３１μｍ、比表面積が４.８ｍ^２／ｇであった。 (Comparative Example 3)
Nickel hydroxide particles were prepared in the same manner as in Example 6 above, loaded into a tube furnace in the same manner as in Example 1, and then air was introduced from the end of a long quartz tube at 1 L / min. It was calcined at 850 ° C. for 2 hours under an air flow atmosphere with an oxygen partial pressure of 21 kPa. The nickel oxide powder thus obtained was crushed in a mortar to make a fine powder. The obtained nickel oxide powder had a sulfur content of 270 mass ppm, a D50 of 0.31 μm, and a specific surface area of 4.8 m ² / g.

（比較例４）
長尺石英管の端部から空気を毎分１Ｌで導入し、酸素分圧２１ｋＰａの大気の気流雰囲気の下、６００℃で５時間の条件で焼成した以外は上記実施例１と同様にして酸化ニッケル微粉末を作製した。得られた酸化ニッケル微粉末は、硫黄含有量が４７０質量ｐｐｍ、Ｄ５０が０.９０μｍ、比表面積が２９ｍ^２／ｇであった。 (Comparative Example 4)
Air was introduced from the end of the long quartz tube at 1 L / min and calcined in the same manner as in Example 1 above except that it was calcined at 600 ° C. for 5 hours under an air flow atmosphere with an oxygen partial pressure of 21 kPa. Nickel fine powder was prepared. The obtained nickel oxide fine powder had a sulfur content of 470 mass ppm, a D50 of 0.90 μm, and a specific surface area of 29 m ² / g.

（比較例５）
焼成時の温度を８００℃に代えて１０００℃にした以外は上記実施例１と同様にして酸化ニッケル微粉末を作製した。得られた酸化ニッケル微粉末は、硫黄含有量が５０質量ｐｐｍ、Ｄ５０が１.６μｍ、比表面積が１.７ｍ^２／ｇであった。 (Comparative Example 5)
Nickel oxide fine powder was prepared in the same manner as in Example 1 above except that the temperature at the time of firing was changed to 1000 ° C instead of 800 ° C. The obtained nickel oxide fine powder had a sulfur content of 50 mass ppm, a D50 of 1.6 μm, and a specific surface area of 1.7 m ² / g.

（比較例６）
焼成時の温度を８００℃に代えて５００℃にした以外は上記実施例１と同様にして酸化ニッケル微粉末を作製した。得られた酸化ニッケル微粉末は、硫黄含有量が２７０質量ｐｐｍ、Ｄ５０が１.１μｍ、比表面積が６５ｍ^２／ｇであった。 (Comparative Example 6)
Nickel oxide fine powder was prepared in the same manner as in Example 1 above except that the temperature at the time of firing was changed to 500 ° C. instead of 800 ° C. The obtained nickel oxide fine powder had a sulfur content of 270 mass ppm, a D50 of 1.1 μm, and a specific surface area of 65 m ² / g.

（比較例７）
長尺石英管の端部から酸素濃度１０ｖｏｌ％の酸素と窒素の混合ガスを毎分１Ｌで導入し、酸素分圧１０ｋＰａの気流雰囲気の下、焼成した以外は上記実施例１０と同様にして酸化ニッケル微粉末を作製した。得られた酸化ニッケル微粉末は、硫黄含有量が２１０質量ｐｐｍ、Ｄ５０が０.３８μｍ、比表面積が４.１ｍ^２／ｇであった。上記した実施例及び比較例の結果を下記表１にまとめて示す。 (Comparative Example 7)
A mixed gas of oxygen and nitrogen having an oxygen concentration of 10 vol% was introduced from the end of a long quartz tube at 1 L / min, and the mixture was fired in an air flow atmosphere with an oxygen partial pressure of 10 kPa in the same manner as in Example 10 above. Nickel fine powder was prepared. The obtained nickel oxide fine powder had a sulfur content of 210 mass ppm, a D50 of 0.38 μm, and a specific surface area of 4.1 m ² / g. The results of the above-mentioned Examples and Comparative Examples are summarized in Table 1 below.

上記表１の結果から分かるように、全ての実施例において、電子部品用材料として好適な、酸化ニッケル微粉末の硫黄含有量が２００質量ｐｐｍ以下で且つＤ５０が１μｍ以下であり、硫黄含有量が低減された微細な酸化ニッケル粉末が得られた。特に実施例２、３、７、９、１２は硫黄含有量が１００質量ｐｐｍ以下であり、固体酸化物形燃料電池の電極材料としても好適である。これに対して、比較例１〜７は、酸化ニッケル微粉末の硫黄含有量及びＤ５０のうちの少なくとも一方において電子部品用材料として好適な範囲内のものが得られなかった。

As can be seen from the results in Table 1 above, in all the examples, the sulfur content of the nickel oxide fine powder suitable as a material for electronic parts is 200 mass ppm or less, D50 is 1 μm or less, and the sulfur content is 1 μm or less. A reduced fine nickel oxide powder was obtained. In particular, Examples 2, 3, 7, 9 and 12 have a sulfur content of 100 mass ppm or less and are suitable as an electrode material for a solid oxide fuel cell. On the other hand, in Comparative Examples 1 to 7, the sulfur content of the nickel oxide fine powder and at least one of D50 were not within the range suitable for the material for electronic parts.

Claims

A step of neutralizing the nickel sulfate aqueous solution with a basic aqueous solution to crystallize the intermediate particles of the nickel salt, and a step of washing the obtained intermediate particles with water and then firing to produce nickel oxide powder. The firing process includes a step of crushing the nickel oxide powder (excluding wet crushing) into fine powder, and the firing treatment is performed in a non-reducing atmosphere in a temperature range of 550 to 950 ° C. and an oxygen partial pressure of 5 kPa or less. A method for producing fine nickel oxide powder, which is characterized by the above-mentioned method.

The nickel oxide fine powder according to claim 1, wherein the non-reducing atmosphere is an atmosphere containing one kind selected from the group consisting of nitrogen, carbon dioxide, water vapor, argon, and helium as a main component. Manufacturing method.

The nickel oxide fine powder according to claim 1 or 2, wherein the intermediate particles are at least one kind of particles selected from the group consisting of nickel hydroxide, nickel carbonate, and nickel nitrate. Production method.

The method for producing a nickel oxide fine powder according to any one of claims 1 to 3, wherein the oxygen partial pressure is 3 kPa or less.

The method for producing a nickel oxide fine powder according to any one of claims 1 to 3, wherein the oxygen partial pressure is 1 kPa or less.

The fine nickel oxide according to any one of claims 1 to 5, wherein the sulfur content of the fine powder is 200 mass ppm or less, and D50 measured by a laser scattering method is 1 μm or less. How to make powder.

The method for producing a nickel oxide fine powder according to claim 6, wherein the sulfur content is 100 mass ppm or less.