JP2018154510A - Method of manufacturing nickel oxide fine powder - Google Patents
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本発明は、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 nickel oxide fine powder suitable as a material used for an electrode of an electronic component or a solid oxide fuel cell.
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、電子部品用材料としての用途では、酸化ニッケル微粉末を酸化鉄、酸化亜鉛等の他の原料と混合した後、焼結することによりフェライト部品等を作製することが行われている。このフェライト部品のように、複数の原料を混合して焼成することにより複合金属酸化物を製造する場合は、その生成反応は固相の拡散反応で律速されるので、当該原料はより微細であることが一般的に好ましい。その理由は、微細であれば他の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、低温で且つ短時間の処理であっても反応が均一に進むからである。従って、上記のような複合金属酸化物の製造では、原料となる粉末の粒径を小さくして微細にすることが効率向上の重要な要件となる。 Nickel oxide fine powders are used in various applications such as materials for electronic parts and materials for electrodes of solid oxide fuel cells. For example, in applications as materials for electronic parts, a nickel part fine powder is mixed with other raw materials such as iron oxide and zinc oxide and then sintered to produce a ferrite part or the like. When producing a composite metal oxide by mixing and firing a plurality of raw materials like this ferrite component, the raw material is finer because the formation reaction is limited by a solid phase diffusion reaction. It is generally preferred. The reason is that, if fine, the probability of contact with other materials increases and the activity of the particles increases, so that the reaction proceeds uniformly even at low temperature and for a short time. Therefore, in the production of the composite metal oxide as described above, it is an important requirement for improving efficiency to reduce the particle size of the raw material powder to be fine.
酸化ニッケル粉末は、上記のフェライト部品等の電子部品以外にも用途が広がっており、例えば、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、その電極材料に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順次積層された構造を有している。この燃料極には、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ため、上記の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。 Nickel oxide powder has a wide range of uses in addition to the above-mentioned electronic parts such as ferrite parts. For example, in a solid oxide fuel cell that is expected as a new power generation system from both environmental and energy perspectives, it can be used as an electrode material. Nickel oxide fine powder is used. In general, a cell stack of a solid oxide fuel cell has a structure in which single cells including an air electrode, a solid electrolyte, and a fuel electrode are sequentially stacked. As the fuel electrode, for example, a mixture of nickel or nickel oxide and a solid electrolyte made of stabilized zirconia is used. At the fuel electrode, it is reduced by fuel gas such as hydrogen or hydrocarbon during power generation to become nickel metal, and the three-phase interface consisting of nickel, solid electrolyte, and voids becomes the reaction field of fuel gas and oxygen. As in the case, reducing the particle size of the raw material powder to make it fine is an important factor for improving the power generation efficiency.
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、加えて上記の通り酸化ニッケル微粉末の用途はフェライト部品等の電子部品以外にも広がっている。そのため、酸化ニッケル微粉末に含まれる不純物元素のより一層の低減が求められている。不純物元素の中でも特に塩素（Ｃｌ）や硫黄（Ｓ）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。そこで、例えば特許文献１には、フェライト材料の原料段階におけるフェライト粉において、その硫黄成分の含有量をＳ換算で３００〜９００ｐｐｍにし、塩素成分の含有量をＣｌ換算で１００ｐｐｍにする技術が提案されている。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、これにより形成される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たものにすることができると記載されている。 In recent years, ferrite parts have a tendency to become more sophisticated, and in addition, as described above, the use of nickel oxide fine powder has spread to electronic parts other than ferrite parts. Therefore, further reduction of the impurity element contained in the nickel oxide fine powder is required. Chlorine (Cl) and sulfur (S), among other impurity elements, should be reduced as much as possible because they may react with the silver used for the electrodes, causing electrode deterioration and corroding the firing furnace. Is desirable. Therefore, for example, Patent Document 1 proposes a technique for setting the content of the sulfur component to 300 to 900 ppm in terms of S and the content of the chlorine component to 100 ppm in terms of Cl in the ferrite powder at the raw material stage of the ferrite material. ing. This ferrite material can be densified without using additives even in low-temperature firing, and the ferrite core and multilayer chip component formed thereby should have excellent moisture resistance and temperature characteristics. It is stated that it can be done.
従来、不純物含有量の低い酸化ニッケル微粉末の製造方法として、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方法が一般的に採用されてきた。例えば、特許文献２には、原料としての硫酸ニッケルに対して、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、制御された平均粒径を有し、且つ硫黄含有量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。 Conventionally, as a method for producing a fine nickel oxide powder having a low impurity content, nickel salts such as nickel sulfate, nickel nitrate, nickel carbonate, nickel hydroxide, or nickel metal powder is used in a rotary kiln or other rolling furnace, pusher furnace, or the like. A method of firing in an oxidizing atmosphere using a continuous furnace or a batch furnace such as a burner furnace has been generally employed. For example, in Patent Document 2, the first stage roasting is performed at a roasting temperature of less than 950 to 1000 ° C. in an oxidizing atmosphere using a kiln or the like with respect to nickel sulfate as a raw material; A method for producing nickel oxide powder by performing second-stage roasting at 1200 ° C. has been proposed. According to this manufacturing method, it is described that a nickel oxide fine powder having a controlled average particle diameter and having a sulfur content 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、硫黄の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。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、硫黄の含有量が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。 Patent Document 3 proposes 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 diameter can be produced stably. Furthermore, Patent Document 4 proposes a method of roasting at a maximum temperature of 900 to 1250 ° C. while forcibly introducing air using a horizontal rotary manufacturing furnace. This manufacturing method also describes that nickel oxide powder with less impurities and a sulfur content of 500 mass ppm or less can be obtained.
上記の乾式法に対して一部湿式法で酸化ニッケル微粉末を製造する方法として、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。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て水酸化ニッケルを生成し、得られた水酸化ニッケルを５００〜８００℃の温度で熱処理して酸化ニッケルを生成し、得られた酸化ニッケルに水を加えてスラリーにした後、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作製する方法が提案されている。この方法は水酸化ニッケル粒子を焙焼する際に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、よって低コストでの製造が可能になると記載されている。 As a method for producing nickel oxide fine powder by a partial wet method with respect to the dry method described above, an aqueous solution containing a nickel salt such as nickel sulfate or nickel chloride is neutralized with an alkali such as an aqueous sodium hydroxide solution and then hydroxylated. A method for crystallizing nickel particles and baking the nickel particles has also been proposed. For example, in Patent Document 5, a nickel chloride aqueous solution is neutralized with an alkali to produce nickel hydroxide, and the obtained nickel hydroxide is heat-treated at a temperature of 500 to 800 ° C. to produce nickel oxide. A method of producing nickel oxide fine powder having a low sulfur and chlorine content and a fine particle size by adding water to a slurry of nickel oxide to form a slurry, followed by crushing using a wet jet mill and washing at the same time Has been proposed. This method describes that when nickel hydroxide particles are roasted, there is little generation of anion component-derived gas, so that exhaust gas treatment is unnecessary or simple equipment can be used, and therefore it can be manufactured at low cost. Has been.
上記の特許文献２または３の製造方法により不純物含有量の低い酸化ニッケル微粉末を得ることができるものの、これら製造方法では熱処理を２回行うため生産性が低下し、コストが高くなるという問題を抱えている。また、特許文献２〜４のいずれの製造方法も、硫黄の含有量を低減するために焙焼温度を高くすると粒子が粗大になり、粒子の粗大化を抑えるために焙焼温度を下げると硫黄の含有量が高くなるという欠点があり、粒径と硫黄の含有量を同時に最適値に制御することは困難であった。また、熱処理の際に大量の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。 Although the nickel oxide fine powder having a low impurity content can be obtained by the production method described in Patent Document 2 or 3, the production method has a problem that productivity is lowered and costs are increased because heat treatment is performed twice. I have it. Also, in any of the production methods of Patent Documents 2 to 4, when the roasting temperature is increased to reduce the sulfur content, the particles become coarse, and when the roasting temperature is lowered to suppress the coarsening of the particles, sulfur Therefore, it has been difficult to control the particle size and the sulfur content to the optimum values at the same time. In addition, there is a problem that a gas containing a large amount of SOx is generated during the heat treatment, and expensive equipment is required to remove the gas.
更に、酸化ニッケル微粉末を電子部品用として、特にフェライト部品用の原料として用いる場合は、硫黄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。すなわち、酸化ニッケル微粉末を電子部品用材料として用いる場合は、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。しかしながら、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ことから硫黄の低減は可能であるが、硫黄の含有量を所定の範囲内に制御することは困難であった。また、湿式解砕を採用しているため、その後工程にコストがかかる乾燥処理が必要になる上、この乾燥処理時に凝集するおそれがあった。 Furthermore, when using nickel oxide fine powder for electronic parts, especially as a raw material for ferrite parts, not only reducing the sulfur content but also strictly controlling the sulfur content within a predetermined range. May be required. That is, when nickel oxide fine powder is used as an electronic component material, in addition to refinement of the particle size and reduction of impurities, it is sometimes necessary to strictly control the sulfur content. However, since the nickel oxide fine powder manufacturing method of Patent Document 5 uses nickel chloride as a raw material, sulfur can be reduced, but it is difficult to control the sulfur content within a predetermined range. there were. In addition, since wet crushing is employed, a costly drying process is required for the subsequent process, and there is a risk of aggregation during the drying process.
このように、従来の酸化ニッケル粉末の製造方法では、微細な粒子径を有すると共に、硫黄の含有量が制御された酸化ニッケル微粉末を得るのは困難であり、更なる改善が望まれていた。本発明は、上記した問題点に鑑みてなされたものであり、工業上広く用いられる硫酸ニッケルを原料として酸化ニッケル微粉末を製造する際に、微粒化と硫黄分の低減とを効率的に両立させることが可能な製造方法を提供することを目的としている。 Thus, in the conventional method for producing nickel oxide powder, it is difficult to obtain nickel oxide fine powder having a fine particle diameter and a controlled sulfur content, and further improvement has been desired. . The present invention has been made in view of the above-described problems, and when producing nickel oxide fine powder using nickel sulfate widely used in industry as a raw material, both atomization and reduction of sulfur content are efficiently achieved. An object of the present invention is to provide a manufacturing method that can be used.
硫酸ニッケル水溶液を水酸化ナトリウム、炭酸ナトリウム等のナトリウムを含む塩基性溶液で中和することで得られる水酸化ニッケル、炭酸ニッケル等の中間体粒子には、硫酸ニッケルの形態で硫黄分が存在しているため、この硫酸ニッケルの分解温度以上で該中間体粒子を焼成することにより、硫黄の含有量が低減した酸化ニッケル粒子を効率的に生成することができる。しかし、この焼成の過程では酸化ニッケルの粒子が成長するため、硫黄の含有量を所定の低濃度の範囲内に制御しつつ粒径を微細にするのは困難であった。 Intermediate particles such as nickel hydroxide and nickel carbonate obtained by neutralizing an aqueous solution of nickel sulfate with a basic solution containing sodium such as sodium hydroxide and sodium carbonate have a sulfur content in the form of nickel sulfate. Therefore, by firing the intermediate particles at a temperature equal to or higher than the decomposition temperature of nickel sulfate, nickel oxide particles having a reduced sulfur content can be efficiently generated. However, since nickel oxide particles grow during the firing process, it is difficult to make the particle size fine while controlling the sulfur content within a predetermined low concentration range.
本発明者らは、上記の硫黄品位の制御と微細な粒径を両立させるため、酸化ニッケル粉末の製造プロセスについて鋭意研究を重ねた結果、硫酸ニッケル水溶液を上記したナトリウムを含む塩基性溶液で中和して晶析することで得られる中間体粒子は微量のナトリウムを含んでおり、焼成の過程で難分解性の硫酸ナトリウムが生成され、また、この中間体粒子に含まれるナトリウムの含有量に応じた量の硫黄分が残存することが分かった。更に中間体粒子において微細な粒径を有する粒子の占める割合が高くなると晶析後に行う洗浄の際にナトリウムの含有量を低減しにくくなるので、中間体粒子において微粒子の比率を所定の値以下とすることで、ナトリウムだけでなく硫黄の含有量も低い微細な酸化ニッケル微粉末を得ることが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 both the above-described control of sulfur quality and fine particle size, the present inventors have conducted extensive research on the production process of nickel oxide powder, and as a result, the aqueous solution of nickel sulfate is a basic solution containing sodium as described above. The intermediate particles obtained by summing and crystallizing contain a trace amount of sodium, and hardly decomposable sodium sulfate is produced during the firing process. Also, the content of sodium contained in the intermediate particles It was found that a corresponding amount of sulfur remained. Furthermore, if the proportion of particles having a fine particle size in the intermediate particles becomes high, it becomes difficult to reduce the sodium content during washing after crystallization, so the proportion of fine particles in the intermediate particles is set to a predetermined value or less. As a result, it was found that fine nickel oxide fine powder having a low sulfur content as well as sodium can be obtained, 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とナトリウムを含む塩基性溶液との中和反応により中間体粒子を晶析させる中和工程と、前記中間体粒子を洗浄する洗浄工程と、前記洗浄された中間体粒子を熱処理して酸化ニッケル粉末を生成する焼成工程と、前記焼成工程の際に形成され得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に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、前記中和反応の条件を調整することによって前記洗浄工程後の中間体粒子の粒度分布を粒径１０μｍ未満の粒子が体積積算で全体の５％以下となるようにすることを特徴としている。 That is, the method for producing the nickel oxide fine powder of the present invention comprises a neutralization step of crystallizing intermediate particles by a neutralization reaction between a nickel sulfate aqueous solution and a basic solution containing sodium, and a washing for washing the intermediate particles. A step of heat-treating the washed intermediate particles to produce nickel oxide powder, and a nickel oxide powder sintered body that can be formed during the firing step to be crushed into nickel oxide fine powder A finely divided nickel oxide powder comprising a crushing step, wherein the particle size distribution of the intermediate particles after the washing step is integrated by volume by adjusting the conditions for the neutralization reaction. It is characterized by being made 5% or less of the whole.
本発明によれば、フェライト部品などの電子部品材料や電池材料として好適な、硫黄の含有量が低く且つ微細な酸化ニッケル微粉末を容易に作製することができる。 According to the present invention, a fine nickel oxide fine powder having a low sulfur content and suitable as an electronic component material such as a ferrite component or a battery material can be easily produced.
以下、本発明の実施形態に係る酸化ニッケル微粉末の製造方法について説明する。この製造方法は、硫酸ニッケル水溶液とナトリウムを含む塩基性溶液とを混ぜ合わせ、それらの中和反応により中間体粒子を晶析させる中和工程と、この中間体粒子を洗浄する洗浄工程と、洗浄後の中間体粒子を焼成して酸化ニッケル粉末を生成する焼成工程と、該焼成工程の際に形成され得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おり、上記の中和工程において、中和反応の諸条件を適切に設定することで上記洗浄工程後の中間体粒子において粒径１０μｍ未満の粒子が体積積算で全体の５％以下となる粒度分布を有するようにしている。 Hereinafter, the manufacturing method of the nickel oxide fine powder which concerns on embodiment of this invention is demonstrated. This production method comprises mixing a nickel sulfate aqueous solution and a basic solution containing sodium, and crystallization of intermediate particles by a neutralization reaction thereof, a cleaning step of cleaning the intermediate particles, a cleaning step A firing step in which the intermediate particles are fired to produce a nickel oxide powder, and a pulverization step in which a nickel oxide powder sintered body that can be formed during the firing step is crushed to obtain a nickel oxide fine powder. In the neutralization step, by appropriately setting various conditions for the neutralization reaction, the particles having a particle size of less than 10 μm in the intermediate particles after the washing step are 5% or less of the total by volume integration The particle size distribution is as follows.
上記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低硫黄含有量にすることができ、レーザー散乱法で測定した中心粒径Ｄ５０（粒度分布上における粒子量の体積積算５０％での粒径）が０.５μｍ以下の酸化ニッケル微粉末である。よって、電子部品材料や固体酸化物形燃料電池の電極用材料等に好適に用いることができる。以下、上記の酸化ニッケル微粉末の製造方法を構成する一連の工程の各々について詳細に説明する。 The nickel oxide fine powder obtained by the above production method can have a low sulfur content even when nickel sulfate widely used for nickel plating or the like is used as a raw material, and has a central particle size D50 (particle size measured by a laser scattering method). Nickel oxide fine powder having a particle size of 50% by volume of the particle amount on the distribution) of 0.5 μm or less. Therefore, it can be used suitably for electronic component materials, electrode materials for solid oxide fuel cells, and the like. Hereafter, each of a series of processes which comprise the manufacturing method of said nickel oxide fine powder is demonstrated in detail.
（中和工程）
中和工程では、硫酸ニッケル水溶液に水酸化ナトリウム、炭酸ナトリウム等のナトリウムを含む塩基性溶液を混合して中和することにより、水酸化ニッケル、炭酸ニッケル等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には、例えば硫酸ニッケル六水和物等を用いることができ、これと水とを混合することで水溶液にする。尚、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用いられることから、その腐食防止のため、原料中に含まれる不純物は１００質量ｐｐｍ未満であることが望ましい。
(Neutralization process)
In the neutralization step, intermediate particles such as nickel hydroxide and nickel carbonate are crystallized by mixing and neutralizing a nickel sulfate aqueous solution with a basic solution containing sodium such as sodium hydroxide and sodium carbonate. For example, nickel sulfate hexahydrate can be used as the nickel sulfate used as a raw material, and an aqueous solution is obtained by mixing this with water. In addition, since the nickel oxide fine powder finally obtained is used as an electronic component material or a battery material, the impurities contained in the raw material are preferably less than 100 ppm by mass in order to prevent corrosion.
硫酸ニッケル水溶液中のニッケルの濃度は、特に限定されるものではないが、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未満では生産性が悪くなり、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、晶析により生成される水酸化ニッケル等の中間体粒子中の硫黄含有量が高くなるため、最終的に得られる酸化ニッケル微粉末中の不純物含有量が十分に低くならない場合がある。 The concentration of nickel in the aqueous nickel sulfate solution is not particularly limited, but considering productivity, the nickel concentration is preferably 50 to 150 g / L. If this concentration is less than 50 g / L, the productivity is deteriorated. Conversely, if it exceeds 150 g / L, the anion concentration in the aqueous solution becomes too high, and sulfur in the intermediate particles such as nickel hydroxide produced by crystallization. Since the content becomes high, the impurity content in the finally obtained nickel oxide fine powder may not be sufficiently low.
中和に用いるナトリウムを含む塩基性溶液としては、水酸化ナトリウム、炭酸ナトリウム、又は硝酸ナトリウムの溶液を用いることができ、これらの中では入手しやすさや反応速度の点で水酸化ナトリウム及び炭酸ナトリウムのうちの１種以上を含む溶液が好ましい。中和反応により得られる中間体粒子は、水酸化ナトリウムを用いた場合は水酸化ニッケル粒子、炭酸ナトリウムを用いた場合は炭酸ニッケル粒子、硝酸ナトリウムを用いた場合は硝酸ニッケルとなる。塩基性溶液が上記のうちの２種類以上の混合液の場合、得られる中間体粒子は水酸化ニッケル、炭酸ニッケル、および硝酸ニッケルのうちの２種類以上の混合粒子となる。塩基性溶液の溶媒には特に限定はなく、水でもよいし、水にアルコール等の水溶性有機溶媒を混合させたものでもよい。 As a basic solution containing sodium used for neutralization, a solution of sodium hydroxide, sodium carbonate, or sodium nitrate can be used. Among these, sodium hydroxide and sodium carbonate are easy to obtain and have a reaction rate. A solution containing one or more of them is preferred. The intermediate particles obtained by the neutralization reaction are nickel hydroxide particles when sodium hydroxide is used, nickel carbonate particles when sodium carbonate is used, and nickel nitrate when sodium nitrate is used. When the basic solution is a mixture of two or more of the above, the resulting intermediate particles are two or more of the mixed particles of nickel hydroxide, nickel carbonate, and nickel nitrate. The solvent for the basic solution is not particularly limited, and may be water, or a water-soluble organic solvent such as alcohol mixed with water.
中和反応では、反応液のｐＨ、温度、撹拌状態（撹拌機の回転数）、反応時間等の諸条件を調整することにより粒径や比表面積の異なる種々の中間体粒子を得ることができる。例えば、中間体粒子のＤ５０は、上記中和反応の諸条件を適宜設定することにより、１０〜５０μｍの範囲内にすることができる。本発明の実施形態に係る酸化ニッケル微粉末の製造方法では、中和反応の上記諸条件を適切に調整することで、後工程の洗浄工程後の中間体粒子に対してレーザー散乱法による測定で得た粒度分布において、粒径１０μｍ未満の粒子の比率が体積積算で全体の５％以下となるようにしている。 In the neutralization reaction, various intermediate particles having different particle diameters and specific surface areas can be obtained by adjusting various conditions such as pH, temperature, stirring state (rotation speed of the stirrer) and reaction time of the reaction solution. . For example, the D50 of the intermediate particles can be set within a range of 10 to 50 μm by appropriately setting the various conditions for the neutralization reaction. In the manufacturing method of the nickel oxide fine powder according to the embodiment of the present invention, by appropriately adjusting the above-described various conditions of the neutralization reaction, the intermediate particles after the subsequent cleaning step can be measured by the laser scattering method. In the obtained particle size distribution, the ratio of particles having a particle size of less than 10 μm is set to 5% or less of the total volume.
上記の中間体粒子は、通常は１〜３質量％程度の硫黄と１００〜１０００質量ｐｐｍ程度のナトリウムを含有しているが、上記のように粒径１０μｍ未満の粒子の比率を体積積算で全体の５％以下とすることで、後工程の洗浄工程後の中間体粒子のナトリウム含有量を乾燥基準で好適には５０質量ｐｐｍ以下に、より好適には３０質量ｐｐｍ以下にすることができる。これに対して、上記の粒度分布において粒径１０μｍ未満の粒子の分布量が多くなると、中間体粒子を構成する微細な粒子の割合が高くなるので所望の洗浄効果が得られにくくなり、特に粒径１０μｍ未満の粒子比率が体積換算で全体の５％を超えると、洗浄後の中間体粒子のナトリウム含有量が乾燥基準で５０質量ｐｐｍを超えることがある。また、焼成工程において、後述するように、中間体粒子に含まれるナトリウムは焼成の過程で融点が８８４℃と高い難分解性の硫酸ナトリウムを形成するため、硫黄含有量の低減も困難となる。すなわち、ナトリウム含有量の多い中間体粒子から生成した酸化ニッケルは、ナトリウムだけでなく硫黄の含有量も多くなりやすい。 The intermediate particles usually contain about 1 to 3% by mass of sulfur and about 100 to 1000 ppm by mass of sodium, but as described above, the ratio of particles having a particle size of less than 10 μm is integrated by volume. By setting the content to 5% or less, the sodium content of the intermediate particles after the subsequent washing step can be preferably 50 ppm by mass or less, more preferably 30 ppm by mass or less on a dry basis. On the other hand, if the amount of particles having a particle size of less than 10 μm increases in the above particle size distribution, the ratio of fine particles constituting the intermediate particles increases, and thus it becomes difficult to obtain a desired cleaning effect. When the ratio of particles having a diameter of less than 10 μm exceeds 5% in terms of volume, the sodium content of the intermediate particles after washing may exceed 50 ppm by mass on a dry basis. Further, in the firing step, as will be described later, sodium contained in the intermediate particles forms hardly decomposable sodium sulfate having a melting point of 884 ° C. in the course of firing, so that it is difficult to reduce the sulfur content. That is, nickel oxide produced from intermediate particles having a high sodium content tends to increase not only sodium but also sulfur content.
従って中間体粒子の粒度分布において、上記の粒径１０μｍ未満の微粒が占める割合を低減するためには、中和反応における反応液のｐＨ、温度、撹拌状態（攪拌機の回転数）、及び反応時間の各パラメータのいずれかを所定の条件となるように調整することが重要になる。その際、中間体粒子の物性に応じて、上記パラメータのうちの２つ以上の調整を行うことが好ましい場合がある。いずれのパラメータを調整する場合においても、できるだけ精密な調整ができるように中和反応が行われる装置が構成されていることが好ましく、また、ｐＨセンサーや温度計等の校正、維持が適切に行われていることが好ましい。特に上記のパラメータの中では、反応時間を主たる調整パラメータとし、補助的にその他のパラメータを調整するのが好ましい。以下、各パラメータについて詳細に説明する。 Therefore, in order to reduce the proportion of fine particles having a particle size of less than 10 μm in the particle size distribution of the intermediate particles, the pH, temperature, stirring state (rotation speed of the stirrer), and reaction time in the neutralization reaction It is important to adjust any one of the parameters so as to satisfy a predetermined condition. At that time, it may be preferable to adjust two or more of the above parameters according to the physical properties of the intermediate particles. When adjusting any of the parameters, it is preferable to configure a device that performs the neutralization reaction so that it can be adjusted as precisely as possible, and calibration and maintenance of pH sensors, thermometers, etc. are performed appropriately. It is preferable that Among the above parameters, it is preferable that the reaction time is the main adjustment parameter, and other parameters are adjusted in an auxiliary manner. Hereinafter, each parameter will be described in detail.
上記中和反応時は反応液のｐＨを８.３〜９.０の範囲内に調整することが好ましく、ｐＨ８.３〜８.７の範囲に調整することがより好ましい。このｐＨが８.３未満であったり９.０を超えたりすると、得られる中間体粒子の粒径分布は粒径が小さい側にシフトし、粒径１０μｍ未満の粒子の比率が体積積算で全体の５％を超えるおそれがある。またｐＨが８.３未満では、中間体粒子に取り込まれる陰イオン成分が増加し、硫黄含有量が高くなるおそれがある。 During the neutralization reaction, the pH of the reaction solution is preferably adjusted within the range of 8.3 to 9.0, more preferably within the range of pH 8.3 to 8.7. When this pH is less than 8.3 or more than 9.0, the particle size distribution of the obtained intermediate particles shifts to the smaller particle size side, and the ratio of particles having a particle size of less than 10 μm is increased by volume integration. May exceed 5%. Moreover, if pH is less than 8.3, there exists a possibility that the anion component taken in by an intermediate particle may increase and sulfur content may become high.
尚、中和反応時の反応液のｐＨを９.０以下にすると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、上記中和工程での中和反応による晶析の後、該水溶液のｐＨを１０程度まで上げてから固液分離することによって、該固液分離後の濾液中のニッケル成分を低減することができる。中和反応時のｐＨはほぼ一定に保つのが好ましく、具体的には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、最終的に得られる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。 If the pH of the reaction solution during the neutralization reaction is set to 9.0 or less, a slight amount of nickel component may remain in the aqueous solution after the reaction. In this case, the neutralization reaction in the neutralization step described above may occur. After the crystallization, the nickel component in the filtrate after the solid-liquid separation can be reduced by raising the pH of the aqueous solution to about 10 and then performing solid-liquid separation. It is preferable to keep the pH during the neutralization reaction substantially constant, and specifically, it is preferable to control the fluctuation range to be within an absolute value of 0.2 around the set value. If the fluctuation range of the pH is larger than this, impurities may increase or the specific surface area of the finally obtained nickel oxide fine powder may decrease.
上記中和反応時は反応液の液温を５０〜７０℃に調整するのが好ましく、５５〜６５℃に調整するのがより好ましい。一般的には上記反応液の液温を高くするとこれに伴って中間体粒子の粒径分布におけるＤ５０が大きくなるが、液温が高くなると中和反応の反応速度が速くなって、中間体粒子の粒径分布も広くなる。従って、液温を５０〜７０℃の範囲にすれば、結果的に粒径１０μｍ未満の粒子の比率を低くすることができる。この液温が７０℃を超えると水の蒸発が顕著になり、水溶液中の硫黄等の不純物濃度が高くなるため、生成した中間体粒子中の硫黄等の不純物品位が高くなるおそれがある。逆にこの液温が５０℃未満では反応速度が遅くなるので生産効率が低下するおそれがある。 During the neutralization reaction, the temperature of the reaction solution is preferably adjusted to 50 to 70 ° C, and more preferably adjusted to 55 to 65 ° C. In general, when the liquid temperature of the reaction liquid is increased, D50 in the particle size distribution of the intermediate particles is increased accordingly. However, when the liquid temperature is increased, the reaction rate of the neutralization reaction is increased. The particle size distribution of the is also widened. Therefore, if the liquid temperature is in the range of 50 to 70 ° C., the ratio of particles having a particle diameter of less than 10 μm can be lowered as a result. When the liquid temperature exceeds 70 ° C., water evaporation becomes remarkable, and the concentration of impurities such as sulfur in the aqueous solution increases, so that the quality of impurities such as sulfur in the produced intermediate particles may be increased. On the contrary, when the liquid temperature is less than 50 ° C., the reaction rate becomes slow, so that the production efficiency may be lowered.
上記中和反応では均一な特性の中間体粒子を効率よく生産するため、反応槽内において反応液が十分に撹拌されて乱流状態となっているのが好ましい。すなわち、撹拌機の回転数が少なくなって反応槽内の反応液の流動速度が遅くなると中間体粒子の粒径分布が広がり、逆に撹拌機の回転数が多くなって反応液の流動速度が速くなると中間体粒子の粒径分布が小さい側にシフトする傾向がある。よって、攪拌機の回転数を変えることによって粒径１０μｍ未満の粒子の比率を調整することができる。尚、反応槽内の撹拌状態は上記の攪拌機の回転数のほか、撹拌羽根の数や形状、反応槽の大きさや形状等の影響を受けるため、攪拌機の回転数の好適な範囲はこれらの条件をも考慮して適宜設定するのが好ましい。 In the neutralization reaction, in order to efficiently produce intermediate particles having uniform characteristics, it is preferable that the reaction liquid is sufficiently stirred in a turbulent state in the reaction tank. That is, when the rotation speed of the stirrer decreases and the flow rate of the reaction liquid in the reaction vessel decreases, the particle size distribution of the intermediate particles spreads. Conversely, the rotation speed of the stirrer increases and the flow rate of the reaction liquid increases. As the speed increases, the particle size distribution of the intermediate particles tends to shift to a smaller side. Therefore, the ratio of particles having a particle size of less than 10 μm can be adjusted by changing the rotation speed of the stirrer. The stirring state in the reaction vessel is affected by the number and shape of the stirring blades, the size and shape of the reaction vessel, etc. in addition to the number of rotations of the agitator described above. It is preferable to set appropriately considering the above.
この中和工程においては、反応槽内に予め貯めておいた塩基性溶液に、硫酸ニッケル水溶液を添加することで中和しつつｐＨ調製用の塩基性溶液を適宜添加するバッチ晶析法でもよいし、反応槽内において十分に撹拌されている液（塩基性溶液等）に対して、予め調製しておいた硫酸ニッケル水溶液と塩基性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でもよい。これらいずれの晶析法においても、中和に要する時間、つまり反応時間は０.５〜２.５時間とするのが好ましく、１.０〜２.０時間とするのがより好ましい。 In this neutralization step, a batch crystallization method may be used in which a basic solution for pH adjustment is appropriately added to a basic solution previously stored in a reaction tank while neutralizing by adding an aqueous nickel sulfate solution. In a continuous crystallization method in which a nickel sulfate aqueous solution and a basic solution prepared in advance are added to a liquid (basic solution, etc.) sufficiently stirred in the reaction vessel by a so-called double jet method. Good. In any of these crystallization methods, the time required for neutralization, that is, the reaction time is preferably 0.5 to 2.5 hours, and more preferably 1.0 to 2.0 hours.
ここで反応時間とは、バッチ晶析法では、反応槽内に予め貯めておいた塩基性溶液に対して硫酸ニッケル水溶液を添加してから中和反応が終了するまでの時間を指す。この場合、中和反応の終了は所定量の硫酸ニッケル水溶液を添加した後、反応液が上記ｐＨの範囲内となり変動も十分に小さくなることで判断することができる。一方、連続晶析法では、反応槽の有効容量（貯留できる最大容量）を、硫酸ニッケル水溶液と塩基性溶液の合計添加速度で除して得られる時間を指す。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塩基性溶液とを合計２０Ｌ／ｈの添加速度で供給する場合、反応時間は１０／２０＝０.５時間になる。 Here, in the batch crystallization method, the reaction time refers to the time from the addition of the aqueous nickel sulfate solution to the basic solution stored in advance in the reaction tank until the completion of the neutralization reaction. In this case, the end of the neutralization reaction can be determined by adding a predetermined amount of the nickel sulfate aqueous solution, and then the reaction solution is within the above pH range and the fluctuation is sufficiently small. On the other hand, in the continuous crystallization method, it refers to the time obtained by dividing the effective capacity of the reaction tank (the maximum capacity that can be stored) by the total addition rate of the nickel sulfate aqueous solution and the basic solution. For example, when a nickel sulfate aqueous solution and a basic solution are supplied to a reaction vessel whose effective volume is maintained at 10 L by providing an overflow port at a total addition rate of 20 L / h, the reaction time is 10/20 = 0. 5 hours.
上記の反応時間が０.５時間未満では、中和反応時に中間体粒子の成長が不十分となってＤ５０が大きくならず、その結果、微粒が多く残るので粒径１０μｍ未満の粒子の比率が高くなる。逆に反応時間が２.５時間を超えると、中間体粒子が成長して粒径は大きくなるが、一部の粒子が撹拌により粉砕され、かえって粒径１０μｍ未満の粒子の比率が高くなるおそれがある。 When the reaction time is less than 0.5 hours, the intermediate particles do not grow sufficiently during the neutralization reaction, and D50 does not increase. As a result, a large number of fine particles remain, so that the ratio of particles having a particle size of less than 10 μm is present. Get higher. Conversely, if the reaction time exceeds 2.5 hours, the intermediate particles grow and the particle size increases, but some particles may be pulverized by stirring, and the ratio of particles having a particle size of less than 10 μm may be increased. There is.
（洗浄工程）
洗浄工程では、上記の中和工程の晶析により得た中間体粒子を含む沈殿物もしくはスラリーに対して濾過等の固液分離処理を行って固形分として湿潤状態の中間体粒子群の塊（ケーキ）を回収し、このケーキを水等の洗浄液を用いて洗浄した後、乾燥させる。この洗浄工程により、中間体粒子に混在している硫酸イオン等の陰イオンやナトリウム成分を除去することができる。
(Washing process)
In the washing step, the precipitate or slurry containing the intermediate particles obtained by the crystallization in the neutralization step is subjected to a solid-liquid separation process such as filtration, and a mass of intermediate particles in a wet state as a solid content ( Cake) is recovered, and the cake is washed with a washing liquid such as water and then dried. By this washing step, anions such as sulfate ions and sodium components mixed in the intermediate particles can be removed.
中間体粒子から陰イオンやナトリウムを効率よく除去するには、上記洗浄液には水を用いるのが好ましく、純水がより好ましい。洗浄方法は種々の一般的な方法を用いることができる。例えば上記固液分離により得たケーキを、攪拌機を備えた洗浄槽内に投入して洗浄液を加え、これらを撹拌することで洗浄することができる。あるいは中和工程で得た中間体粒子を含むスラリーをそのままフィルタープレス等の固液分離装置に導入し、初期の固液分離操作の後に固形分側に水を導入して洗浄を行ってもよい。 In order to efficiently remove anions and sodium from the intermediate particles, it is preferable to use water as the cleaning liquid, and more preferably pure water. Various general methods can be used as the cleaning method. For example, the cake obtained by the above-mentioned solid-liquid separation can be washed by adding it to a washing tank equipped with a stirrer, adding a washing solution, and stirring them. Alternatively, the slurry containing the intermediate particles obtained in the neutralization step may be introduced as it is into a solid-liquid separation device such as a filter press, and after the initial solid-liquid separation operation, water may be introduced into the solid content side for washing. .
洗浄液の量は、撹拌等の操作が損なわれないのであれば特に限定はないが、洗浄の効果を高めるにはできるだけ多い方が好ましい。洗浄時の液温も特に限定はないが、２０〜６０℃の温度範囲内とするのが好ましい。この場合、加温によりナトリウム量の一層の低減が期待できる。また、上記の洗浄操作を繰り返し行うことで洗浄の効果をより一層高めることができる。例えば、洗浄液に純水を用いる場合、洗浄後の洗浄液の導電率を測定して、所定の導電率以下となるまで洗浄を繰り返すことで、陰イオンやナトリウムを所望のレベルまで確実に除去することができる。 The amount of the cleaning liquid is not particularly limited as long as the operation such as stirring is not impaired, but it is preferably as large as possible to enhance the cleaning effect. The temperature of the liquid at the time of washing is not particularly limited, but is preferably within a temperature range of 20 to 60 ° C. In this case, further reduction in the amount of sodium can be expected by heating. In addition, the cleaning effect can be further enhanced by repeating the above-described cleaning operation. For example, when pure water is used as the cleaning liquid, the conductivity of the cleaning liquid after cleaning is measured, and the anion and sodium are surely removed to a desired level by repeating the cleaning until a predetermined conductivity or less. Can do.
（焼成工程）
焼成工程は、上記の洗浄工程で洗浄された中間体粒子を熱処理して酸化ニッケル粉末を得る工程である。この熱処理は、大気雰囲気下で行うか、又は非還元性で且つ酸素分圧が５ｋＰａ以下の低酸素雰囲気下で行うのが好ましい。前述した通り、中間体粒子は硫黄分を含有している。この硫黄分は主として原料に起因する硫酸の形態を有しており、大部分は硫酸ニッケルの形態で中間体粒子内も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熱分解するので、焼成処理後に得られる酸化ニッケル粉末は硫黄品位が低減している。
(Baking process)
The firing step is a step of obtaining a nickel oxide powder by heat-treating the intermediate particles washed in the washing step. This heat treatment is preferably performed in an air atmosphere or in a low oxygen atmosphere that is non-reducing and has an oxygen partial pressure of 5 kPa or less. As described above, the intermediate particles contain a sulfur content. This sulfur content mainly has the form of sulfuric acid derived from the raw material, and most of it is in the form of nickel sulfate and exists in the intermediate particles or on the surface thereof. Since this nickel sulfate is thermally decomposed by firing, the nickel oxide powder obtained after the firing treatment has a reduced sulfur quality.
大気雰囲気下での焼成の場合、その熱処理温度を８５０〜９５０℃の範囲とするのが好ましい。この熱処理温度が８５０℃未満では、硫酸ニッケルの分解温度が大気の１気圧中では８４０℃なので、硫酸ニッケルの熱分解が進行しにくくなって硫黄成分が残留し、硫黄含有量５０質量ｐｐｍ以下の酸化ニッケル微粉末が得られないことがある。逆に熱処理温度が９５０℃を超えると、中間体粒子の熱分解により得られる酸化ニッケル粉末の焼結が進行し、この焼結した粉末の分離が次工程の解砕において困難となり、電子部品材料や電池材料の用途には適さない程度に小さな比表面積と大きなＤ５０を有する粉末となるおそれがある。 In the case of firing in an air atmosphere, the heat treatment temperature is preferably in the range of 850 to 950 ° C. When the heat treatment temperature is less than 850 ° C., the decomposition temperature of nickel sulfate is 840 ° C. in 1 atmosphere of air, so that the thermal decomposition of nickel sulfate is difficult to proceed and the sulfur component remains, and the sulfur content is 50 mass ppm or less. Nickel oxide fine powder may not be obtained. Conversely, when the heat treatment temperature exceeds 950 ° C., the sintering of the nickel oxide powder obtained by thermal decomposition of the intermediate particles proceeds, and separation of the sintered powder becomes difficult in the crushing of the next process, and the electronic component material Or a powder having a small specific surface area and a large D50 that is unsuitable for battery materials.
なお、粉末の粒径と比表面積には下記式１の関係があるので、粉末の比表面積を指標にして粉末がどの程度微細であるか判断することができる。但し、下記式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、下記式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。
［式１］
粒径＝６／（密度×比表面積）
In addition, since there is a relationship of the following formula 1 between the particle size of the powder and the specific surface area, it is possible to determine how fine the powder is by using the specific surface area of the powder as an index. However, since the relationship of the following formula 1 is derived on the assumption that the particles are spherical, there is some error between the particle size obtained from the following formula 1 and the actual particle size. However, it can be seen that the larger the specific surface area, the smaller the particle size.
[Formula 1]
Particle size = 6 / (density × specific surface area)
上記の中間体粒子に含まれる硫黄分のほとんどは、前述したように硫酸ニッケルの形態であるが、この硫酸ニッケルの熱分解では、下記式２の反応により酸化ニッケルに分解される。
［式２］
２ＮｉＳＯ４→２ＮｉＯ＋２ＳＯ２＋Ｏ２
Most of the sulfur content contained in the intermediate particles is in the form of nickel sulfate as described above. However, in the thermal decomposition of nickel sulfate, it is decomposed into nickel oxide by the reaction of the following formula 2.
[Formula 2]
2NiSO 4 → 2NiO + 2SO 2 + O 2
この反応式からも分かる通り、酸素分圧が低くなると反応は右側に進行するので熱処理温度を下げることができる。よって非還元性で酸素分圧が５ｋＰａ以下の低酸素雰囲気での焼成の場合、熱処理温度を８００〜９５０℃の範囲内とするのが好ましい。この熱処理温度が８００℃未満では、硫酸ニッケルの熱分解が進行しにくくなり、硫黄成分が残留したり未反応の中間体粒子が残留したりすることがある。逆に熱処理温度が９５０℃を超えると、中間体粒子の熱分解により得られる酸化ニッケル粉末の焼結が進行して、この焼結した粉末の分離が次工程の解砕において困難となり、電子部品材料や電池材料の用途には適さない程度に小さな比表面積と大きなＤ５０を有する粉末となるおそれがある。 As can be seen from this reaction formula, when the oxygen partial pressure is lowered, the reaction proceeds to the right, so that the heat treatment temperature can be lowered. Therefore, in the case of firing in a low-oxygen atmosphere that is non-reducing and has an oxygen partial pressure of 5 kPa or less, the heat treatment temperature is preferably in the range of 800 to 950 ° C. When the heat treatment temperature is less than 800 ° C., the thermal decomposition of nickel sulfate is difficult to proceed, and sulfur components may remain or unreacted intermediate particles may remain. Conversely, when the heat treatment temperature exceeds 950 ° C., the sintering of the nickel oxide powder obtained by thermal decomposition of the intermediate particles proceeds, and separation of the sintered powder becomes difficult in the crushing of the next process, and the electronic component There is a possibility that the powder has a small specific surface area and a large D50 to an extent that it is not suitable for use as a material or battery material.
低酸素雰囲気下で焼成する場合、非還元性で且つ酸素分圧が５ｋＰａ以下とするのが好ましく、３ｋＰａ以下とするのがより好ましく、１ｋＰａ以下とするのがさらに好ましい。この酸素分圧が５ｋＰａを超えると、上記式２の分解反応が進みにくくなり、酸化ニッケル粉末の硫黄含有量が低下しないことがある。酸素分圧の下限値には特に限定はないが、１０Ｐａと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さらに低い場合を除外するものではない。 When firing in a low oxygen atmosphere, it is non-reducing and preferably has an oxygen partial pressure of 5 kPa or less, more preferably 3 kPa or less, and even more preferably 1 kPa or less. When this oxygen partial pressure exceeds 5 kPa, the decomposition reaction of the above formula 2 becomes difficult to proceed, and the sulfur content of the nickel oxide powder may not decrease. The lower limit value of the oxygen partial pressure is not particularly limited, but if it is 10 Pa, the sulfur content of the nickel oxide powder can be sufficiently reduced. Of course, this does not exclude the case where the oxygen partial pressure is even lower.
中間体粒子の焼成時は、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、その雰囲気を非還元性にするのが好ましい。具体的には、焼成時の雰囲気ガスの主成分を、窒素、二酸化炭素、水蒸気、アルゴン、及びヘリウムから選ばれる１種とするのが好ましい。具体的には、窒素、二酸化炭素、水蒸気、アルゴン、及びヘリウムから選ばれる１種のガスか、又はこれらの少なくともいずれかを主成分として更に酸素を低酸素分圧で含有させるかまたは含有しないガスを供給しながら焼成するのが好ましい。あるいは、炉内の酸素分圧が５ｋＰａ以下となるまで減圧した状態となるように炉内の雰囲気ガスを排気しながら焼成してもよい。 When firing the intermediate particles, the atmosphere is preferably made non-reducing in order to prevent the intermediate particles from being reduced to nickel. Specifically, the main component of the atmospheric gas during firing is preferably one selected from nitrogen, carbon dioxide, water vapor, argon, and helium. Specifically, one kind of gas selected from nitrogen, carbon dioxide, water vapor, argon, and helium, or a gas containing at least one of these as a main component and further containing oxygen at a low oxygen partial pressure or not containing it. Firing is preferably performed while supplying. Or you may bake, exhausting the atmospheric gas in a furnace so that it may be in the state reduced pressure until the oxygen partial pressure in a furnace becomes 5 kPa or less.
尚、中間体粒子中にナトリウムが残留していると、前述したように硫酸ニッケルから熱分解した硫酸根がこのナトリウムと化合して硫酸ナトリウムとなることがある。この硫酸ナトリウムは熱分解しにくく、融点も８８４℃と高いため、中間体粒子のナトリウム含有量が多くなると、最終的な酸化ニッケル粉末の硫黄含有量を所望の値まで低減できなくなるおそれがある。この場合、焼成温度を硫酸ナトリウムの融点より高くすれば酸化ニッケル粉末の硫黄およびナトリウム含有量を下げることができるが、酸化ニッケル粉末の焼結が進行してＤ５０が大きくなるので、微細な酸化ニッケル粉末が得られなくなる。 If sodium remains in the intermediate particles, the sulfate radical thermally decomposed from nickel sulfate may combine with sodium to form sodium sulfate as described above. Since this sodium sulfate is difficult to thermally decompose and the melting point is as high as 884 ° C., if the sodium content of the intermediate particles increases, the sulfur content of the final nickel oxide powder may not be reduced to a desired value. In this case, if the firing temperature is higher than the melting point of sodium sulfate, the sulfur and sodium contents of the nickel oxide powder can be lowered. However, since the sintering of the nickel oxide powder proceeds and D50 increases, the fine nickel oxide No powder can be obtained.
従って、酸化ニッケル微粉末において微粒化と低硫黄含有量とを両立させるため、上記したとおり、中間体粒子のナトリウム含有量を低減するのが好ましく、そのために中間体粒子において粒径１０μｍ未満の粒子の比率を体積積算で５％以下にしている。特にＤ５０が０.４μｍ以下の微細な酸化ニッケル微粒子を得るには、焼成時の焼結を抑えるため、硫酸ナトリウムの融点を考慮して熱処理温度を９００℃以下にするのが好ましく、８８０℃以下がより好ましい。 Therefore, in order to achieve both atomization and low sulfur content in the nickel oxide fine powder, it is preferable to reduce the sodium content of the intermediate particles as described above, and for this reason, particles having a particle size of less than 10 μm in the intermediate particles. The ratio is set to 5% or less by volume integration. In particular, in order to obtain fine nickel oxide fine particles having a D50 of 0.4 μm or less, it is preferable to set the heat treatment temperature to 900 ° C. or less in consideration of the melting point of sodium sulfate in order to suppress sintering during firing, and 880 ° C. or less. Is more preferable.
（解砕工程）
解砕工程は、上記の焼成工程の際に形成され得る酸化ニッケル粉末の焼結体を分離、破壊して酸化ニッケル微粉末を得る工程である。上記の焼成工程では中間体粒子が熱分解されて酸化ニッケル粒子が形成されるが、その際、粒径の微細化が起こると共に、高温の影響で酸化ニッケル粒子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、解砕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、粒子同士を衝突させたり、圧縮力やせん断力を加えたりすることにより所望の粒度を有する酸化ニッケル微粉末を得ている。
(Crushing process)
The crushing step is a step of obtaining a nickel oxide fine powder by separating and destroying a sintered body of the nickel oxide powder that can be formed during the firing step. In the firing step, the intermediate particles are thermally decomposed to form nickel oxide particles. At that time, the particle size is reduced and sintering of the nickel oxide particles proceeds to some extent due to the influence of high temperature. In order to destroy this sintered body, in the crushing step, the nickel oxide powder after firing is crushed, and the particles are collided with each other, and a desired particle size is obtained by applying compressive force or shearing force. Nickel oxide fine powder is obtained.
この解砕に用いる装置には特に限定はなく、一般的な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て解砕する装置でもよいし、ジェットミル等の解砕メディアを用いないで自身の流体エネルギーを利用して解砕する装置でもよい。 There is no limitation in particular in the apparatus used for this crushing, A general thing can be used. For example, a device for crushing using a crushing medium such as a bead mill or a ball mill may be used, or a device for crushing using its own fluid energy without using a crushing media such as a jet mill.
（酸化ニッケル微粉末の物性）
以上説明した一連の工程からなる製造方法により作製される酸化ニッケル微粉末は、制御された硫黄含有量を有するとともに、粒径が小さく微細である。具体的には、硫黄含有量が５０質量ｐｐｍ以下、より好ましくは３０質量ｐｐｍ以下であり、レーザー散乱法で測定したＤ５０が０.５μｍ以下、より好ましくは０.３〜０.５μｍである。また比表面積は２ｍ２／ｇ以上、より好ましくは３ｍ２／ｇ以上である。比表面積の上限は特に限定されないが、上記で説明した製造方法にて得られる酸化ニッケル微粉末は６ｍ２／ｇが上限となる。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。尚、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。
(Physical properties of fine nickel oxide powder)
The nickel oxide fine powder produced by the production method comprising the series of steps described above has a controlled sulfur content and a small particle size and is fine. Specifically, the sulfur content is 50 ppm by mass or less, more preferably 30 ppm by mass or less, and D50 measured by the laser scattering method is 0.5 μm or less, more preferably 0.3 to 0.5 μm. The specific surface area is 2 m 2 / g or more, more preferably 3 m 2 / g or more. The upper limit of the specific surface area is not particularly limited, but the upper limit of the nickel oxide fine powder obtained by the production method described above is 6 m 2 / g. Therefore, it is suitable as a material for an electronic component, particularly a ferrite component, a battery material, particularly an electrode material for a solid oxide fuel cell. In addition, as a material for electrodes of a solid oxide fuel cell, the sulfur content is preferably 100 mass ppm or less.
以下、実施例及び比較例により本発明を更に詳細に説明するが、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。なお、実施例及び比較例で用いた酸化ニッケル微粉末又はその中間体である水酸化ニッケル粒子の評価方法は、以下の通りである。
（１）粒径および粒度分布の測定：粒子径測定装置（Ｍｉｃｒｏｔｒａｃ ９３２０−Ｘ１００、Ｍｉｃｒｏｔｒａｃ Ｉｎｃ製）を用いて、レーザー回折・散乱法で行なった。
（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（ＮＯＶＡ １０００ｅ、ユアサアイオニクス社製）を用いて、ＢＥＴ法で行なった。
（３）硫黄含有量およびナトリウム含有量の分析：ＩＣＰ発光分光分析法で行なった。
EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further in detail, this invention is not limited at all by these Examples. In addition, the evaluation method of the nickel hydroxide fine powder which is the nickel oxide fine powder used in the Example and the comparative example or its intermediate is as follows.
(1) Measurement of particle size and particle size distribution: It was carried out by a laser diffraction / scattering method using a particle size measuring device (Microtrac 9320-X100, manufactured by Microtrac Inc).
(2) Measurement of specific surface area of nickel oxide fine powder: It was carried out by BET method using a specific surface area measuring device (NOVA 1000e, manufactured by Yuasa Ionics).
(3) Analysis of sulfur content and sodium content: The analysis was performed by ICP emission spectroscopy.
［実施例１］
撹拌機を備えた反応槽内で硫酸ニッケルの水溶液と水酸化ナトリウム水溶液とを混合して中和反応を行わせ、中間体粒子として水酸化ニッケルを晶析させた。中和反応の条件としては、反応時間１.０時間、攪拌機の回転数７００ｒｐｍに設定した。また、反応槽内では反応液の液温を６０℃にし、ｐＨは８.５を中心としてその変動幅が絶対値で０.２以内となるように制御しながら中和反応をおこなった（中和工程）。得られた中間体粒子を含むスラリーを、ヌッチェに載置した濾紙を用いて固液分離し、固形分側をレパルプ水洗してから、乾燥して水酸化ニッケルを得た（洗浄工程）。得られた水酸化ニッケル粒子は、硫黄含有量が２.２質量％、ナトリウム含有量が５０質量ｐｐｍであり、粒径１０μｍ未満の粒子の比率が体積積算で５％の粒度分布を有していた。
[Example 1]
A nickel sulfate aqueous solution and a sodium hydroxide aqueous solution were mixed in a reaction vessel equipped with a stirrer to cause a neutralization reaction, and nickel hydroxide was crystallized as intermediate particles. As conditions for the neutralization reaction, the reaction time was set to 1.0 hour and the rotation speed of the stirrer was set to 700 rpm. Further, in the reaction tank, the temperature of the reaction solution was set to 60 ° C., and the neutralization reaction was performed while controlling the pH to be within 0.2 in terms of the absolute value around 8.5 (middle). Japanese process). The obtained slurry containing the intermediate particles was subjected to solid-liquid separation using a filter paper placed on Nutsche, the solid content side was washed with repulp water, and dried to obtain nickel hydroxide (washing step). The obtained nickel hydroxide particles have a sulfur content of 2.2% by mass, a sodium content of 50 ppm by mass, and a ratio of particles having a particle size of less than 10 μm has a particle size distribution of 5% by volume. It was.
上記洗浄工程で得た水酸化ニッケル１０ｇをアルミナの試料皿に量り取り、管状炉を用いて毎分１Ｌの大気気流雰囲気において雰囲気温度９２０℃で５時間かけて焼成することで酸化ニッケル粉末を得た（焼成工程）。得られた酸化ニッケル粉末を乳鉢により粉砕して酸化ニッケル微粉末とした（解砕工程）。得られた酸化ニッケル微粉末は、硫黄含有量が４０質量ｐｐｍ、Ｄ５０が０.４８μｍ、比表面積が３.０ｍ２／ｇであった。 10 g of nickel hydroxide obtained in the above washing step is weighed in an alumina sample pan and calcined at a temperature of 920 ° C. for 5 hours in an air flow atmosphere of 1 L / min using a tubular furnace to obtain nickel oxide powder. (Firing process). The obtained nickel oxide powder was pulverized with a mortar to obtain fine nickel oxide powder (pulverization step). The obtained nickel oxide fine powder had a sulfur content of 40 mass ppm, a D50 of 0.48 μm, and a specific surface area of 3.0 m 2 / g.
［実施例２］
中和工程の反応時間を１.０時間に代えて１.５時間と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作製した。この水酸化ニッケル粒子は硫黄含有量が２.０質量％、ナトリウム含有量が３０質量ｐｐｍであり、粒径１０μｍ未満の粒子の比率が体積積算で３％の粒度分布を有していた。この水酸化ニッケル粒子に対して上記実施例１と同様に処理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２０ｐｐｍ、Ｄ５０が０.４８μｍ、比表面積が３.２ｍ２／ｇであった。
[Example 2]
Nickel hydroxide particles were produced in the same manner as in Example 1 except that the reaction time in the neutralization step was changed to 1.0 hour instead of 1.0 hour. The nickel hydroxide particles had a sulfur content of 2.0 mass%, a sodium content of 30 mass ppm, and had a particle size distribution in which the ratio of particles having a particle size of less than 10 μm was 3% by volume. The nickel hydroxide particles were treated in the same manner as in Example 1 to prepare nickel oxide fine powder. The obtained nickel oxide fine powder had a sulfur content of 20 ppm, a D50 of 0.48 μm, and a specific surface area of 3.2 m 2 / g.
［実施例３］
中和工程の液温を６０℃に代えて５５℃とし、洗浄工程ではレパルプ水洗に代えて濾紙上の固形分に水を供給する注水洗浄を行った以外は上記実施例２と同様にして水酸化ニッケル粒子を作製した。この水酸化ニッケル粒子は硫黄含有量が１.８質量％、ナトリウム含有量が２０質量ｐｐｍであり、粒径が１０μｍ未満の粒子の比率が体積積算で４％の粒度分布を有していた。この水酸化ニッケル粒子に対して上記実施例１と同様に処理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１０質量ｐｐｍ、Ｄ５０が０.４６μｍ、比表面積が３.４ｍ２／ｇであった。
[Example 3]
The liquid temperature in the neutralization step was changed to 60 ° C. to 55 ° C., and in the washing step, water was washed in the same manner as in Example 2 except that water washing was performed to supply water to the solid content on the filter paper instead of repulp water washing. Nickel oxide particles were prepared. The nickel hydroxide particles had a sulfur content of 1.8 mass%, a sodium content of 20 mass ppm, and a particle size distribution in which the ratio of particles having a particle size of less than 10 μm was 4% by volume. The nickel hydroxide particles were treated in the same manner as in Example 1 to prepare nickel oxide fine powder. The obtained nickel oxide fine powder had a sulfur content of 10 mass ppm, a D50 of 0.46 μm, and a specific surface area of 3.4 m 2 / g.
［実施例４］
中和工程の反応時間を１.０時間に代えて２.０時間とし、洗浄工程ではレパルプ水洗に代えて濾紙上の固形分に水を供給する注水洗浄を行っ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作製した。この水酸化ニッケル粒子は硫黄含有量が１.７質量％、ナトリウム含有量が１０質量ｐｐｍ、粒径１０μｍ未満の粒子の比率が体積積算で２％の粒度分布を有していた。この水酸化ニッケル粒子１００ｇを焼成工程において小型転動炉を用いて毎分１０Ｌの大気気流雰囲気で熱処理した以外は実施例１と同様にして酸化ニッケル微粉末を得た。得られた酸化ニッケル微粉末は硫黄含有量が１０質量ｐｐｍ、Ｄ５０が０.４５μｍ、比表面積が３.５ｍ２／ｇであった。
[Example 4]
The reaction time in the neutralization step was set to 2.0 hours instead of 1.0 hour, and in the washing step, the same procedure as in Example 1 was performed except that water washing was performed to supply water to the solid content on the filter paper instead of repulp water washing. Similarly, nickel hydroxide particles were prepared. The nickel hydroxide particles had a particle size distribution in which the sulfur content was 1.7 mass%, the sodium content was 10 mass ppm, and the proportion of particles having a particle size of less than 10 μm was 2% by volume. Fine nickel oxide powder was obtained in the same manner as in Example 1 except that 100 g of the nickel hydroxide particles were heat-treated in an airflow atmosphere of 10 L / min using a small rotatory furnace in the firing step. The obtained nickel oxide fine powder had a sulfur content of 10 mass ppm, a D50 of 0.45 μm, and a specific surface area of 3.5 m 2 / g.
［比較例１］
中和工程の反応時間を１.０時間に代えて６.０時間と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作製した。この水酸化ニッケル粒子は硫黄含有量が２.０質量％、ナトリウム含有量が１５０質量ｐｐｍ、粒径１０μｍ未満の粒子の比率が体積積算で１０％の粒度分布を有していた。この水酸化ニッケル粒子に対して上記実施例１と同様に処理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１２０質量ｐｐｍ、Ｄ５０が０.５１μｍ、比表面積が２.８ｍ２／ｇであった。
［比較例２］
中和工程の反応時間を１.０時間に代えて４.０時間とし、洗浄工程ではレパルプ水洗に代えて濾紙上の固形分に水を供給する注水洗浄を行っ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作製した。この水酸化ニッケル粒子は硫黄含有量が２.０％、ナトリウム含有量が９０質量ｐｐｍ、粒径１０μｍ未満の粒子の比率が体積積算で８％の粒度分布を有していた。この水酸化ニッケル粒子に対して上記実施例１と同様に処理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７０質量ｐｐｍ、Ｄ５０が０.４８μｍ、比表面積が２.９ｍ２／ｇであった。これら実施例１〜４および比較例１〜２の測定結果を下記表１にまとめて示す。
[Comparative Example 1]
Nickel hydroxide particles were produced in the same manner as in Example 1 except that the reaction time in the neutralization step was changed to 6.0 hours instead of 1.0 hour. The nickel hydroxide particles had a particle size distribution in which the sulfur content was 2.0% by mass, the sodium content was 150 ppm by mass, and the ratio of particles having a particle size of less than 10 μm was 10% by volume. The nickel hydroxide particles were treated in the same manner as in Example 1 to prepare nickel oxide fine powder. The obtained nickel oxide fine powder had a sulfur content of 120 mass ppm, a D50 of 0.51 μm, and a specific surface area of 2.8 m 2 / g.
[Comparative Example 2]
The reaction time in the neutralization step was set to 4.0 hours instead of 1.0 hour, and in the washing step, the same procedure as in Example 1 was performed except that water washing was performed to supply water to the solid content on the filter paper instead of repulp water washing. Similarly, nickel hydroxide particles were produced. The nickel hydroxide particles had a sulfur content of 2.0%, a sodium content of 90 ppm by mass, and a ratio of particles having a particle size of less than 10 μm had a particle size distribution of 8% in volume integration. The nickel hydroxide particles were treated in the same manner as in Example 1 to prepare nickel oxide fine powder. The obtained nickel oxide fine powder had a sulfur content of 70 mass ppm, a D50 of 0.48 μm, and a specific surface area of 2.9 m 2 / g. The measurement results of Examples 1 to 4 and Comparative Examples 1 and 2 are summarized in Table 1 below.
［実施例５］
焼成工程の雰囲気温度を９２０℃に代えて８６５℃とした以外は上記実施例２と同様にして酸化ニッケル微粉末作製した。この酸化ニッケル微粉末は硫黄含有量が３０ｐｐｍ、Ｄ５０が０.４０μｍ、比表面積が４.５ｍ２／ｇであった。
[Example 5]
A nickel oxide fine powder was produced in the same manner as in Example 2 except that the atmospheric temperature in the firing step was changed to 865 ° C. instead of 920 ° C. This nickel oxide fine powder had a sulfur content of 30 ppm, a D50 of 0.40 μm, and a specific surface area of 4.5 m 2 / g.
［実施例６］
焼成工程の炉に長尺石英管にヒーターを付設した管状炉を使用し、石英管端部から９９.９９ｖｏｌ％窒素を毎分１Ｌで導入して酸素分圧０．１ｋＰａ未満の気流雰囲気において雰囲気温度９２０℃で５時間焼成した以外は上記実施例２と同様にして酸化ニッケル微粉末作製した。この酸化ニッケル微粉末は硫黄含有量が２０質量ｐｐｍ、Ｄ５０が０.４７μｍ、比表面積が３.２ｍ２／ｇであった。
[Example 6]
A tubular furnace with a heater attached to a long quartz tube was used as the furnace for the firing process, and 99.99 vol% nitrogen was introduced at 1 L / min from the end of the quartz tube in an air flow atmosphere with an oxygen partial pressure of less than 0.1 kPa. A nickel oxide fine powder was prepared in the same manner as in Example 2 except that the baking was performed at a temperature of 920 ° C. for 5 hours. This nickel oxide fine powder had a sulfur content of 20 mass ppm, a D50 of 0.47 μm, and a specific surface area of 3.2 m 2 / g.
［実施例７］
雰囲気温度を９２０℃に代えて８００で焼成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。この酸化ニッケル微粉末は硫黄含有量が５０質量ｐｐｍ、Ｄ５０が０.３６μｍ、比表面積が５.１ｍ２／ｇであった。
[Example 7]
Nickel oxide fine powder was prepared in the same manner as in Example 6 except that the firing was carried out at 800 instead of 920 ° C. This nickel oxide fine powder had a sulfur content of 50 mass ppm, a D50 of 0.36 μm, and a specific surface area of 5.1 m 2 / g.
［実施例８］
実施例２と同様にして作製した中間体粒子としての水酸化ニッケル粒子２０ｇをアルミナの匣鉢に量り取り、小型減圧加熱炉内に載置した。排気量と吸気量を調整して炉内の圧力が２０ｋＰａ以下、炉内の酸素分圧が４ｋＰａ以下の雰囲気になるようにして８５０℃で２時間焼成することにより酸化ニッケル粉末を得た。得られた酸化ニッケル粉末を乳鉢により解砕して酸化ニッケル微粉末を作製した。この酸化ニッケル微粉末は硫黄含有量が３０質量ｐｐｍ、Ｄ５０が０.３９μｍ、比表面積が４.４ｍ２／ｇであった。これら実施例５〜８の測定結果を実施例２の測定結果と合わせて下記表２にまとめて示す。
[Example 8]
20 g of nickel hydroxide particles as intermediate particles produced in the same manner as in Example 2 were weighed in an alumina sagger and placed in a small vacuum heating furnace. The nickel oxide powder was obtained by calcining at 850 ° C. for 2 hours in an atmosphere in which the pressure in the furnace was 20 kPa or less and the oxygen partial pressure in the furnace was 4 kPa or less by adjusting the exhaust amount and the intake amount. The obtained nickel oxide powder was pulverized with a mortar to produce fine nickel oxide powder. This nickel oxide fine powder had a sulfur content of 30 mass ppm, a D50 of 0.39 μm, and a specific surface area of 4.4 m 2 / g. The measurement results of Examples 5 to 8 are shown together with the measurement results of Example 2 in Table 2 below.
上記表１の実施例１〜４の結果から分かるように、水酸化ニッケル粒子の粒度分布において粒径１０μｍ未満の粒子の比率が体積積算で５％以下であるため、水酸化ニッケル粒子のナトリウム含有量が５０質量ｐｐｍ以下であり、酸化ニッケル微粉末の硫黄含有量も４０質量ｐｐｍ以下であることが分かる。また実施例１〜８の酸化ニッケル微粉末はＤ５０が０.５０μｍ以下、比表面積が３.０ｍ２／ｇ以上と微粒化されており、酸化ニッケル微粉末の微粒化と硫黄含有量の低減とが両立できていることも分かる。 As can be seen from the results of Examples 1 to 4 in Table 1 above, since the ratio of particles having a particle size of less than 10 μm in the particle size distribution of nickel hydroxide particles is 5% or less by volume integration, the nickel hydroxide particles contain sodium. It can be seen that the amount is 50 ppm by mass or less, and the sulfur content of the nickel oxide fine powder is also 40 ppm by mass or less. In addition, the nickel oxide fine powders of Examples 1 to 8 were atomized with a D50 of 0.50 μm or less and a specific surface area of 3.0 m 2 / g or more, and the nickel oxide fine powder was atomized and the sulfur content was reduced. It can also be seen that both are compatible.
これに対して比較例１及び比較例２では、水酸化ニッケル粒子の粒度分布において粒径１０μｍ未満の粒子の比率が体積積算で５％を超えているため、水酸化ニッケル粒子のナトリウム含有量が５０質量ｐｐｍを超えているうえ、酸化ニッケル微粉末の硫黄含有量も５０質量ｐｐｍ以上であり、酸化ニッケル微粉末の硫黄含有量が低減できていないことが分かる。 On the other hand, in Comparative Example 1 and Comparative Example 2, the ratio of particles having a particle size of less than 10 μm in the particle size distribution of nickel hydroxide particles exceeds 5% by volume. In addition to exceeding 50 ppm by mass, the sulfur content of the nickel oxide fine powder is also 50 ppm by mass or more, indicating that the sulfur content of the nickel oxide fine powder has not been reduced.
Claims (10)
前記中和反応の条件を調整することによって前記洗浄工程後の中間体粒子の粒度分布を粒径１０μｍ未満の粒子が体積積算で全体の５％以下となるように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 crystallizing intermediate particles by a neutralization reaction between a nickel sulfate aqueous solution and a basic solution containing sodium, a washing step of washing the intermediate particles, and heat-treating the washed intermediate particles A method for producing fine nickel oxide powder, comprising: a firing step for producing nickel oxide powder; and a crushing step for crushing a sintered body of nickel oxide powder that can be formed during the firing step into nickel oxide fine powder Because
The nickel oxide characterized by adjusting the neutralization reaction conditions so that the particle size distribution of the intermediate particles after the washing step is 5% or less of the total particles having a particle size of less than 10 μm in volume integration. Production method of fine powder.
The sodium content of the intermediate particles obtained in the washing step is 30 ppm by mass or less on a dry basis, and the sulfur content of the nickel oxide fine powder is 30 ppm by mass or less. The manufacturing method of the nickel oxide fine powder of description.
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