JP5310462B2 - Nickel powder and method for producing the same - Google Patents
Nickel powder and method for producing the same Download PDFInfo
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- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 title claims description 185
- 238000004519 manufacturing process Methods 0.000 title claims description 36
- 239000000843 powder Substances 0.000 claims description 65
- BFDHFSHZJLFAMC-UHFFFAOYSA-L nickel(ii) hydroxide Chemical compound [OH-].[OH-].[Ni+2] BFDHFSHZJLFAMC-UHFFFAOYSA-L 0.000 claims description 43
- 229910000480 nickel oxide Inorganic materials 0.000 claims description 42
- GNRSAWUEBMWBQH-UHFFFAOYSA-N oxonickel Chemical compound [Ni]=O GNRSAWUEBMWBQH-UHFFFAOYSA-N 0.000 claims description 42
- 238000001035 drying Methods 0.000 claims description 38
- 230000009467 reduction Effects 0.000 claims description 31
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 31
- 125000002887 hydroxy group Chemical group [H]O* 0.000 claims description 28
- 238000005406 washing Methods 0.000 claims description 20
- 239000012298 atmosphere Substances 0.000 claims description 16
- 239000011777 magnesium Substances 0.000 claims description 16
- 229910052749 magnesium Inorganic materials 0.000 claims description 15
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 claims description 14
- 229910052759 nickel Inorganic materials 0.000 claims description 13
- 238000002835 absorbance Methods 0.000 claims description 10
- 230000001590 oxidative effect Effects 0.000 claims description 7
- 238000001028 reflection method Methods 0.000 claims description 5
- 239000002245 particle Substances 0.000 description 37
- 238000006722 reduction reaction Methods 0.000 description 31
- 238000000034 method Methods 0.000 description 23
- 230000003647 oxidation Effects 0.000 description 23
- 238000007254 oxidation reaction Methods 0.000 description 23
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 13
- 229940091250 magnesium supplement Drugs 0.000 description 13
- 239000002002 slurry Substances 0.000 description 12
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 11
- 229910001873 dinitrogen Inorganic materials 0.000 description 11
- 239000003985 ceramic capacitor Substances 0.000 description 10
- 238000011156 evaluation Methods 0.000 description 8
- 230000008569 process Effects 0.000 description 8
- 230000000052 comparative effect Effects 0.000 description 7
- 239000011230 binding agent Substances 0.000 description 6
- 239000001257 hydrogen Substances 0.000 description 6
- 229910052739 hydrogen Inorganic materials 0.000 description 6
- 239000000463 material Substances 0.000 description 6
- 238000005245 sintering Methods 0.000 description 6
- 239000002904 solvent Substances 0.000 description 6
- 238000004140 cleaning Methods 0.000 description 5
- 230000000694 effects Effects 0.000 description 5
- 239000010419 fine particle Substances 0.000 description 5
- 238000012423 maintenance Methods 0.000 description 5
- 239000000243 solution Substances 0.000 description 5
- 229910021586 Nickel(II) chloride Inorganic materials 0.000 description 4
- 238000006243 chemical reaction Methods 0.000 description 4
- 238000010304 firing Methods 0.000 description 4
- 238000010438 heat treatment Methods 0.000 description 4
- QMMRZOWCJAIUJA-UHFFFAOYSA-L nickel dichloride Chemical compound Cl[Ni]Cl QMMRZOWCJAIUJA-UHFFFAOYSA-L 0.000 description 4
- 239000000126 substance Substances 0.000 description 4
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 3
- 239000007864 aqueous solution Substances 0.000 description 3
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 3
- 239000003153 chemical reaction reagent Substances 0.000 description 3
- 239000011362 coarse particle Substances 0.000 description 3
- 239000007789 gas Substances 0.000 description 3
- 229930195733 hydrocarbon Natural products 0.000 description 3
- 150000002430 hydrocarbons Chemical class 0.000 description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 description 3
- 230000006872 improvement Effects 0.000 description 3
- 230000003993 interaction Effects 0.000 description 3
- 238000005259 measurement Methods 0.000 description 3
- 150000002815 nickel Chemical class 0.000 description 3
- 239000001301 oxygen Substances 0.000 description 3
- 229910052760 oxygen Inorganic materials 0.000 description 3
- 239000003208 petroleum Substances 0.000 description 3
- 239000001856 Ethyl cellulose Substances 0.000 description 2
- ZZSNKZQZMQGXPY-UHFFFAOYSA-N Ethyl cellulose Chemical compound CCOCC1OC(OC)C(OCC)C(OCC)C1OC1C(O)C(O)C(OC)C(CO)O1 ZZSNKZQZMQGXPY-UHFFFAOYSA-N 0.000 description 2
- OAKJQQAXSVQMHS-UHFFFAOYSA-N Hydrazine Chemical compound NN OAKJQQAXSVQMHS-UHFFFAOYSA-N 0.000 description 2
- 239000000654 additive Substances 0.000 description 2
- 230000002776 aggregation Effects 0.000 description 2
- 229910052784 alkaline earth metal Inorganic materials 0.000 description 2
- 150000001342 alkaline earth metals Chemical class 0.000 description 2
- 239000003990 capacitor Substances 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 239000003638 chemical reducing agent Substances 0.000 description 2
- 239000013078 crystal Substances 0.000 description 2
- 230000007423 decrease Effects 0.000 description 2
- 238000009826 distribution Methods 0.000 description 2
- 229920001249 ethyl cellulose Polymers 0.000 description 2
- 235000019325 ethyl cellulose Nutrition 0.000 description 2
- 239000012535 impurity Substances 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 239000012299 nitrogen atmosphere Substances 0.000 description 2
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 description 1
- 239000004372 Polyvinyl alcohol Substances 0.000 description 1
- 238000005054 agglomeration Methods 0.000 description 1
- 238000004220 aggregation Methods 0.000 description 1
- 239000012670 alkaline solution Substances 0.000 description 1
- WUOACPNHFRMFPN-UHFFFAOYSA-N alpha-terpineol Chemical compound CC1=CCC(C(C)(C)O)CC1 WUOACPNHFRMFPN-UHFFFAOYSA-N 0.000 description 1
- 229910002113 barium titanate Inorganic materials 0.000 description 1
- JRPBQTZRNDNNOP-UHFFFAOYSA-N barium titanate Chemical compound [Ba+2].[Ba+2].[O-][Ti]([O-])([O-])[O-] JRPBQTZRNDNNOP-UHFFFAOYSA-N 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- 229910010293 ceramic material Inorganic materials 0.000 description 1
- 238000002485 combustion reaction Methods 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 230000032798 delamination Effects 0.000 description 1
- SQIFACVGCPWBQZ-UHFFFAOYSA-N delta-terpineol Natural products CC(C)(O)C1CCC(=C)CC1 SQIFACVGCPWBQZ-UHFFFAOYSA-N 0.000 description 1
- 239000003989 dielectric material Substances 0.000 description 1
- 239000002003 electrode paste Substances 0.000 description 1
- 239000000945 filler Substances 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 238000004898 kneading Methods 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 150000002680 magnesium Chemical class 0.000 description 1
- 229940050906 magnesium chloride hexahydrate Drugs 0.000 description 1
- DHRRIBDTHFBPNG-UHFFFAOYSA-L magnesium dichloride hexahydrate Chemical compound O.O.O.O.O.O.[Mg+2].[Cl-].[Cl-] DHRRIBDTHFBPNG-UHFFFAOYSA-L 0.000 description 1
- 230000003472 neutralizing effect Effects 0.000 description 1
- LAIZPRYFQUWUBN-UHFFFAOYSA-L nickel chloride hexahydrate Chemical compound O.O.O.O.O.O.[Cl-].[Cl-].[Ni+2] LAIZPRYFQUWUBN-UHFFFAOYSA-L 0.000 description 1
- LGQLOGILCSXPEA-UHFFFAOYSA-L nickel sulfate Chemical compound [Ni+2].[O-]S([O-])(=O)=O LGQLOGILCSXPEA-UHFFFAOYSA-L 0.000 description 1
- 229910000363 nickel(II) sulfate Inorganic materials 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
- 229920002451 polyvinyl alcohol Polymers 0.000 description 1
- 230000001376 precipitating effect Effects 0.000 description 1
- 239000011164 primary particle Substances 0.000 description 1
- 238000010298 pulverizing process Methods 0.000 description 1
- 238000011946 reduction process Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 239000012266 salt solution Substances 0.000 description 1
- 150000003839 salts Chemical class 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 238000004904 shortening Methods 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 230000003746 surface roughness Effects 0.000 description 1
- 229940116411 terpineol Drugs 0.000 description 1
- 238000001291 vacuum drying Methods 0.000 description 1
- 239000012808 vapor phase Substances 0.000 description 1
Description
本発明は、ニッケル粉およびその製造方法に関する。より詳しくは、積層セラミックコンデンサの内部電極形成用導電ペーストのフィラー材料として好適に用いられるニッケル粉およびその製造方法に関するものである。 The present invention relates to nickel powder and a method for producing the same. More specifically, the present invention relates to nickel powder suitably used as a filler material for a conductive paste for forming an internal electrode of a multilayer ceramic capacitor and a method for producing the same.
積層セラミックコンデンサは、誘電体層と内部電極を交互に積層させた構造を有し、小型高容量のコンデンサーである。誘電体としては、チタン酸バリウムに代表されるセラミックス系材料が用いられ、内部電極にはニッケル系材料を用いることが主流となっている。 A multilayer ceramic capacitor has a structure in which dielectric layers and internal electrodes are alternately stacked, and is a small-sized high-capacitance capacitor. As the dielectric, a ceramic material typified by barium titanate is used, and a nickel material is mainly used for the internal electrode.
ニッケル粉を内部電極形成用材料として用いる積層セラミックコンデンサは次のように製造される。
誘電体のグリーンシートに、ニッケル粉、バインダーと有機溶剤を種々の添加剤とともに混練して製造した導電ペーストを印刷し、乾燥させる。次いで、これを所望数積層し、圧着した後にチップ形状に切断する。切断後、３００℃程度の温度で脱バインダーを行った後、内部電極と誘電体グリーンシートを千数百度の温度で焼結する。その後、ニッケルなどによる外部電極を形成する。
A multilayer ceramic capacitor using nickel powder as an internal electrode forming material is manufactured as follows.
A conductive paste produced by kneading nickel powder, a binder and an organic solvent together with various additives is printed on a dielectric green sheet and dried. Next, a desired number of layers are stacked, and after pressure bonding, cut into chips. After cutting, the binder is removed at a temperature of about 300 ° C., and then the internal electrode and the dielectric green sheet are sintered at a temperature of several thousand hundred degrees. Thereafter, an external electrode made of nickel or the like is formed.
脱バインダー工程は、酸化雰囲気中での熱処理によりバインダーを燃焼させる方法が行われている。誘電体グリーンシートのバインダーには、ポリビニルアルコール系の物質が用いられることが多く、内部電極形成用の導電ペーストのバインダーにはエチルセルロース系の物質が用いられることが多い。両者の燃焼タイミング、発生ガス量を制御する形で、脱バインダー工程での雰囲気、温度が調整されている。焼成工程は還元雰囲気中での熱処理により焼結させる方法が行われている。 In the binder removal step, a method of burning the binder by heat treatment in an oxidizing atmosphere is performed. A polyvinyl alcohol-based material is often used as the binder of the dielectric green sheet, and an ethyl cellulose-based material is often used as the binder of the conductive paste for forming the internal electrode. The atmosphere and temperature in the debinding process are adjusted so as to control the combustion timing and the amount of generated gas. In the firing step, a sintering method is performed by heat treatment in a reducing atmosphere.
このような製造方法により作られる積層セラミックコンデンサは、現在更なる小型化、高容量化を目指し、電極および誘電体厚みの薄層化、高積層化が進められてきている。 Multilayer ceramic capacitors manufactured by such a manufacturing method are currently being made thinner and higher in thickness of electrodes and dielectrics with the aim of further miniaturization and higher capacity.
ところで薄層化された電極には、膜表面粗さが小さく、膜密度の高い乾燥膜が得られる導電ペーストが求められている。
従来ニッケル粉は、ヒドラジンなどの還元剤で水溶性ニッケル溶液を還元して得る方法、ニッケルの水酸化物や炭酸塩を水素などの還元剤で乾式還元する方法など、種々の方法で製造されている。ニッケル粉においても、上記積層セラミックコンデンサ内部電極および誘電体厚みの薄層化、高積層化に伴い、さらに微細な平均粒径であり、粗大粒子、微細粒子が含まれないものが求められ、さまざまな平均粒径やその分布の提案およびその製造方法が提案されている。
By the way, a thinned electrode is required to have a conductive paste capable of obtaining a dry film having a small film surface roughness and a high film density.
Conventionally, nickel powder is manufactured by various methods such as a method of obtaining a water-soluble nickel solution by reducing with a reducing agent such as hydrazine, and a method of dry reduction of nickel hydroxide or carbonate with a reducing agent such as hydrogen. Yes. Nickel powders are also required to have finer average particle diameters that do not contain coarse particles and fine particles as the multilayer ceramic capacitor internal electrode and dielectric layers become thinner and higher in number. Proposal of an average particle size and distribution thereof and a production method thereof have been proposed.
例えば、特許文献１では、塩化ニッケル蒸気の気相水素還元法によって製造され、平均粒径が０．２〜０．６μｍで、平均粒径の２．５倍以上の素粒子の存在率が個数基準で０．１％以下であるニッケル粉が提案されている。 For example, in Patent Document 1, the abundance of elementary particles produced by a vapor phase hydrogen reduction method of nickel chloride vapor having an average particle size of 0.2 to 0.6 μm and 2.5 times or more of the average particle size is the number. Nickel powder having a standard of 0.1% or less has been proposed.
特許文献２では、ニッケル塩水溶液を湿式還元して得られた凝集体を含むニッケル粉を解粒処理して得られ、レーザー回折散乱式粒度分布測定による平均粒子径の１．５倍以上の粒子径を持つ粒子個数が全粒子個数の２０％以下であり、平均粒子径の０．５倍以下の粒子径を持つ粒子個数が全粒子個数の５％以下であり、ＳＥＭ観察による平均一次粒子径が０．１〜２μｍのニッケル粉が提案されており、製造技術の開示がある。 In Patent Document 2, particles obtained by pulverizing nickel powder containing aggregates obtained by wet reduction of an aqueous nickel salt solution are particles having an average particle diameter of 1.5 times or more by laser diffraction scattering type particle size distribution measurement. The number of particles having a diameter is 20% or less of the total number of particles, the number of particles having a particle size of 0.5 times or less of the average particle size is 5% or less of the total number of particles, and the average primary particle size by SEM observation Has proposed a nickel powder of 0.1 to 2 μm and discloses a manufacturing technique.
また、特許文献３には、４０〜８０℃の範囲で可能な限り一定温度に保持された反応槽内のスラリーに、含ニッケル溶液を連続的に添加しつつ、該スラリーが所定のｐＨ値を８．０〜９．５の範囲で可能な限り一定に保持するように、アルカリ溶液を添加して水酸化ニッケルを生成させ、該水酸化ニッケルを含むスラリーを連続的に槽外に払い出し、濾過し、水洗し、乾燥して水酸化ニッケルを得、これを水素を用いて４００〜５５０℃の温度で加熱還元するニッケル粉の製造方法が提案されている。 Patent Document 3 discloses that the slurry has a predetermined pH value while continuously adding the nickel-containing solution to the slurry in the reaction vessel maintained at a constant temperature as possible in the range of 40 to 80 ° C. An alkaline solution is added to produce nickel hydroxide so as to keep it as constant as possible in the range of 8.0 to 9.5, and the slurry containing the nickel hydroxide is continuously discharged out of the tank and filtered. Then, it is washed with water and dried to obtain nickel hydroxide, and a method for producing nickel powder is proposed in which this is heated and reduced at a temperature of 400 to 550 ° C. using hydrogen.
しかしながら、当然、このようなニッケル粉でも導電ペースト化時の分散性が悪ければ、また導電ペースト化後の粘度が安定していなければ導電ペーストとして意味を成さず、ペースト組成物である溶剤との親和性が高いことなどが重要となっている。
一般に、導電ペーストにおいては溶剤には石油系炭化水素が用いられることが多いことから、これにあわせたニッケル粉表面の調整や添加剤の選定がなされている。また、ニッケル粉には、脱バインダー工程や焼成工程などにて意図しないガス発生を生じさせたり、酸化、還元による顕著な体積変化が生じたりしないようにすることが求められ、ニッケル粉製造工程にて純度を厳密に制御したり、表面状態を調整したりすることが求められている。
However, as a matter of course, even if such nickel powder has poor dispersibility at the time of forming a conductive paste, and if the viscosity after forming the conductive paste is not stable, it does not make sense as a conductive paste. It is important to have a high affinity.
In general, since petroleum-based hydrocarbons are often used as the solvent in the conductive paste, the surface of the nickel powder and the selection of additives are made accordingly. In addition, nickel powder is required not to cause unintended gas generation in the debinding process or firing process, or to cause significant volume change due to oxidation or reduction. Therefore, it is required to strictly control the purity and adjust the surface state.
例えば、特許文献４では、ニッケル粉末を酸素含有量が１．５％以下となるように乾燥を実施して、弱還元性雰囲気下においてニッケル粉末を焼結する際の高温領域での収縮を抑制する方法が提案されている。これは、湿式還元によって得られるニッケル粉について、湿式還元後の乾燥工程において、５０〜１５０℃で、およそ１２時間に亘る乾燥条件で十分な乾燥を行うか、真空乾燥によってニッケル粉末の酸素含有量を１．５％以下となるよう低減することで、昇温・焼成過程においてニッケル粉間にネットワーク構造を形成させ、高温状態における体積の収縮を抑制するものである。
この提案よれば、焼成工程における焼結性改善の効果は報告されているものの、焼結性とともに重要な特性である導電ペーストにおける分散性や安定性については何ら報告されていない。また、対象としているニッケル粉は湿式還元法によるものであるが、湿式還元法は生産性が高くないため、コスト的に不利である。
For example, in Patent Document 4, the nickel powder is dried so that the oxygen content is 1.5% or less, and the shrinkage in the high temperature region is suppressed when the nickel powder is sintered in a weakly reducing atmosphere. A method has been proposed. This is because nickel powder obtained by wet reduction is sufficiently dried under a drying condition for about 12 hours at 50 to 150 ° C. in the drying step after wet reduction, or the oxygen content of the nickel powder by vacuum drying. Is reduced to 1.5% or less, a network structure is formed between the nickel powders in the temperature raising / firing process, and the shrinkage of the volume in a high temperature state is suppressed.
According to this proposal, although the effect of improving the sinterability in the firing process has been reported, there is no report on the dispersibility and stability in the conductive paste, which are important characteristics along with the sinterability. Moreover, although the target nickel powder is based on the wet reduction method, the wet reduction method is disadvantageous in terms of cost because the productivity is not high.
さらに、特許文献５では、ニッケル粉末を水素気流中で加熱し、ニッケル粒子表面の酸化物あるいは水酸化物を還元した後、ニッケル粉末を水中に浸漬し、空気をバブリングすることにより、ニッケル粉末の表面に、酸化ニッケルもしくは水酸化ニッケルを生成させるニッケル粉末の製造方法が提案されている。 Further, in Patent Document 5, the nickel powder is heated in a hydrogen stream to reduce the oxide or hydroxide on the surface of the nickel particles, and then the nickel powder is immersed in water and air is bubbled. There has been proposed a nickel powder manufacturing method for generating nickel oxide or nickel hydroxide on the surface.
この提案では、ニッケル粉末表面に酸化ニッケルもしくは水酸化ニッケルを生成させることで、インク成分、すなわち溶剤との親和性を高めてインク、すなわち導電ペースト中での分散性を向上させるものである。
しかしながら、この提案においても、導電ペースト中での分散性の向上は報告されているものの、導電ペーストにおける安定性は報告されていない。また、ニッケル粉末表面に生成させる水酸化ニッケルの量については言及されておらず、十分にその生成を制御しているとは言えるものではない。
In this proposal, nickel oxide or nickel hydroxide is generated on the surface of the nickel powder, thereby increasing the affinity with the ink component, that is, the solvent, and improving the dispersibility in the ink, that is, the conductive paste.
However, even in this proposal, although improvement in dispersibility in the conductive paste has been reported, stability in the conductive paste has not been reported. Further, the amount of nickel hydroxide generated on the nickel powder surface is not mentioned, and it cannot be said that the generation is sufficiently controlled.
以上のように、積層セラミックコンデンサ用ニッケル粉に対しては、微細な平均粒径であり、粗大粒子、微細粒子が含まれないものが求められるとともに、導電ペーストにおける分散性や安定性も求められており、ニッケル粉の表面状態の調整が重要な要求特性となっている。 As described above, nickel powder for multilayer ceramic capacitors is required to have a fine average particle diameter and not to include coarse particles and fine particles, and also to have dispersibility and stability in the conductive paste. Therefore, adjustment of the surface condition of nickel powder is an important required characteristic.
本発明は、上記の実情を鑑みてなされたもので、導電性ペースト中で経時的な粘度安定性が高いニッケル粉と大量に低コストで製造することが可能なその製造方法を提供することを目的とするものである。 The present invention has been made in view of the above circumstances, and provides a nickel powder having high viscosity stability over time in a conductive paste and a method for producing the same in large quantities at a low cost. It is the purpose.
本発明者らは、上記問題点を解決するため、大量、かつ低コストに製造できる水酸化ニッケル粉を加熱還元することで得られるニッケル粉について鋭意研究を行なったところ、ニッケル粉表面に存在する水酸化ニッケルを特定量に制御することで導電性ペースト中で経時的な粘度安定性が高いニッケル粉が得られること、および大量かつ低コストに製造可能な酸化ニッケルを、加熱還元することで得られるニッケル粉を特定条件で洗浄、乾燥させることにより、そのようなニッケル粉が得られることを見出し、本発明を完成した。 In order to solve the above problems, the present inventors conducted extensive research on nickel powder obtained by heating and reducing nickel hydroxide powder that can be produced in large quantities and at low cost. By controlling nickel hydroxide to a specific amount, nickel powder with high viscosity stability over time can be obtained in the conductive paste, and nickel oxide that can be produced in large quantities and at low cost can be obtained by heat reduction. It was found that such nickel powder can be obtained by washing and drying the nickel powder obtained under specific conditions, and the present invention has been completed.
すなわち、本発明に係るニッケル粉の製造方法は、水酸化ニッケル粉を酸化焙焼して酸化ニッケル粉とし、得られた酸化ニッケル粉を還元してニッケル粉を形成するニッケル粉の製造方法において、酸化ニッケル粉を還元して形成した還元ニッケル粉を、還元ニッケル粉１ｇに対して０．０３リットル以上の水量の水で洗浄した後、大気雰囲気中において１２０〜１８０℃の温度で乾燥するものである。 That is, the method for producing nickel powder according to the present invention is a method for producing nickel powder in which nickel hydroxide powder is oxidized and roasted to form nickel oxide powder, and the obtained nickel oxide powder is reduced to form nickel powder. was formed by reduction of nickel oxide powder reduced nickel powder, washed with water 0.03 liters or more of water relative to the reduced nickel powder 1g, in which drying at a temperature of 120 to 180 ° C. in an air atmosphere There is .
また、使用する水酸化ニッケル粉は、マグネシウムを０．００２〜１質量％含有する水酸化ニッケル粉である。 Moreover, the nickel hydroxide powder to be used is a nickel hydroxide powder containing 0.002 to 1% by mass of magnesium.
本発明に係るニッケル粉は、ニッケル粉表面に存在する水酸基の真空拡散反射法における吸光度が、その吸光度をニッケル粉の比表面積で規格化した値を用い、その値が０．０２０〜０．０２８であるニッケル粉である。 The nickel powder according to the present invention uses a value obtained by standardizing the absorbance of the hydroxyl group present on the surface of the nickel powder with the specific surface area of the nickel powder, and the value is 0.020 to 0.028. It is a nickel powder.
このニッケル粉は、水酸化ニッケル粉を酸化焙焼して酸化ニッケル粉とし、その酸化ニッケル粉を還元したものから得られるニッケル粉で、マグネシウムを０．００３〜１．６質量％を含有するニッケル粉である。 This nickel powder is nickel powder obtained by oxidizing and roasting nickel hydroxide powder to obtain nickel oxide powder, which is obtained by reducing the nickel oxide powder, and nickel containing 0.003-1.6% by mass of magnesium It is powder.
本発明により得られるニッケル粉は、導電性ペースト中で経時的な粘度安定性が高く、積層セラミックコンデンサの電極形成ペースト用材料として好適なものである。
また、本発明のニッケル粉の製造方法は、酸化ニッケルを加熱還元することで得られるニッケル粉を用いて容易に製造できるものであり、大量に低コストで製造するが可能であることから、工業的価値が極めて大きい。
The nickel powder obtained by the present invention has high viscosity stability over time in a conductive paste and is suitable as an electrode forming paste material for multilayer ceramic capacitors.
Further, the nickel powder production method of the present invention can be easily produced using nickel powder obtained by heating and reducing nickel oxide, and can be produced in large quantities at low cost. Value is extremely high.
本発明のニッケル粉の要件とその効果を説明し、次にそのニッケル粉の製造方法について説明する。 The requirements and effects of the nickel powder of the present invention will be described, and then the method for producing the nickel powder will be described.
［ニッケル粉］
本発明のニッケル粉は、ニッケル粉表面に存在する水酸基の真空拡散反射法における吸光度が、その吸光度をニッケル粉の比表面積で規格化した値を用い、その値が０．０２０〜０．０２８であるものである。
ここで、この吸光度を比表面積で規格化した値とは、比表面積に対する水酸基の真空拡散反射法における吸光度の比（吸光度／比表面積）を表わすもので、その意味するところは、ニッケル粉表面の単位面積あたりの水酸基量を示すものである。
[Nickel powder]
In the nickel powder of the present invention, the absorbance in the vacuum diffuse reflection method of the hydroxyl group present on the surface of the nickel powder is a value obtained by normalizing the absorbance with the specific surface area of the nickel powder, and the value is 0.020 to 0.028. There is something.
Here, the value obtained by normalizing the absorbance with the specific surface area represents the ratio of the absorbance of the hydroxyl group to the specific surface area in the vacuum diffuse reflection method (absorbance / specific surface area). It shows the amount of hydroxyl groups per unit area.
ニッケル粉表面に存在する水酸基の量をニッケル粉の比表面積で規格化した値（以下、単に水酸基量と称す）が高い場合、ニッケル粉の粒子は、導電ペーストの溶剤として用いられる石油系炭化水素との親和性が低くなる。 When the value obtained by standardizing the amount of hydroxyl groups present on the surface of the nickel powder with the specific surface area of the nickel powder (hereinafter simply referred to as the amount of hydroxyl groups) is high, the nickel powder particles are petroleum hydrocarbons used as a solvent for the conductive paste. Affinity with is low.
また、水酸基が多いと表面に不均一な酸化被膜が形成された状態となっているため、表面の石油系炭化水素との親和性も不均一な状態となり、粒子の親和性の低い部分同士が接触して凝集体を形成してしまう。したがって、水酸基量が０．０２８を超えると、ニッケル粉をペーストとした場合、分散性が悪化してニッケル粉が凝集する。一方、水酸基量が０．０２０未満または０．０２８を超えると、ニッケル粒子表面の水酸基と導電ペースト組成物、特に溶剤との相互作用が変化し、ペーストの粘度が経時的に変化するもの考えられ、この粘度が経時的に変化したニッケル粉を積層セラミックコンデンサの内部電極形成用に用いた場合、ニッケル粉の焼結特性が安定せず、結果としてクラックやデラミネーションといった問題が生じる。 In addition, since there is a non-uniform oxide film formed on the surface when there are many hydroxyl groups, the affinity with the petroleum-based hydrocarbons on the surface is also non-uniform, and the low affinity parts of the particles Contact will form aggregates. Therefore, when the amount of hydroxyl groups exceeds 0.028, when nickel powder is used as a paste, the dispersibility deteriorates and the nickel powder aggregates. On the other hand, when the amount of hydroxyl group is less than 0.020 or exceeds 0.028, the interaction between the hydroxyl group on the nickel particle surface and the conductive paste composition, particularly the solvent, changes, and the viscosity of the paste changes over time. When the nickel powder whose viscosity has changed over time is used for forming the internal electrode of the multilayer ceramic capacitor, the sintering characteristics of the nickel powder are not stable, resulting in problems such as cracks and delamination.
そこで、ニッケル粉表面の水酸基量を０．０２０〜０．０２８とすることで、導電性ペースト中でニッケル粒子の凝集を抑制して分散性を良好なものとするとともに、経時的な粘度安定性が高いニッケル粉とすることを可能とする。経時的な粘度安定性をより高めるためには、ニッケル粉表面の水酸基量を０．０２０〜０．０２６とすることがより好ましい。 Therefore, by setting the amount of hydroxyl group on the surface of nickel powder to 0.020 to 0.028, the aggregation of nickel particles in the conductive paste is suppressed to improve dispersibility, and the viscosity stability over time is improved. Makes it possible to obtain a high nickel powder. In order to further improve the viscosity stability over time, the amount of hydroxyl groups on the surface of the nickel powder is more preferably 0.020 to 0.026.
ここで、水酸基の量の規格化は、比表面積を基準にする必要がある。ニッケル粉の粒子の分散性あるいは粘度安定性は、ニッケル粉の粒子表面と溶剤との相互作用によるものであるため、表面あたりの水酸基の量に大きく影響される。したがって、例えば、質量比などのように比表面積を考慮していない値をもって制御しても、上記分散性あるいは粘度安定性を良好なものに維持することは困難である。
なお、水酸基の吸光度を測定する装置は、通常に用いられる分光器（例えば、日本分光社製ＦＴ／ＩＲ６８０Ｐｌｕｓ［Ｖ］など）でよく、真空拡散反射法による測定条件も通常の測定で推奨される条件でよい。
Here, the standardization of the amount of hydroxyl groups needs to be based on the specific surface area. Since the dispersibility or viscosity stability of the nickel powder particles is due to the interaction between the nickel powder particle surface and the solvent, it is greatly influenced by the amount of hydroxyl groups per surface. Therefore, for example, it is difficult to maintain the dispersibility or the viscosity stability at a good level even if the value is controlled with a value that does not consider the specific surface area such as a mass ratio.
The apparatus for measuring the absorbance of the hydroxyl group may be a commonly used spectrometer (for example, FT / IR680Plus [V] manufactured by JASCO Corporation), and the measurement conditions by the vacuum diffuse reflection method are also recommended for normal measurement. Conditions are acceptable.
本発明のニッケル粉は、表面の水酸基量が本発明の範囲内であれば特に限定されるものではないが、水酸化ニッケル粉を酸化焙焼して酸化ニッケル粉とし、その酸化ニッケル粉を還元したものから得られるニッケル粉であることが好ましい。この水酸化ニッケル粉を酸化焙焼して酸化ニッケル粉とし、得られた酸化ニッケル粉を還元してニッケル粉を形成する製造方法は、微細なニッケル粉を大量に低コストで得ることができる製造方法である。したがって、本発明のニッケル粉は、低コストで大量生産が可能である。また、比表面積も適度な大きさのものとなるため、好ましい。 The nickel powder of the present invention is not particularly limited as long as the amount of hydroxyl groups on the surface is within the range of the present invention, but the nickel hydroxide powder is oxidized and roasted into nickel oxide powder, and the nickel oxide powder is reduced. It is preferable that it is the nickel powder obtained from what was obtained. The nickel hydroxide powder is oxidized and roasted to obtain nickel oxide powder, and the manufacturing method in which the obtained nickel oxide powder is reduced to form nickel powder is a manufacturing method that can obtain a large amount of fine nickel powder at low cost. Is the method. Therefore, the nickel powder of the present invention can be mass-produced at a low cost. In addition, the specific surface area is preferable because it has an appropriate size.
また、本発明のニッケル粉は、マグネシウムを０．００３〜１．６質量％含有することが好ましい。マグネシウムを０．００３〜１．６質量％含有することで、粒径が微細で表面が平滑なニッケル粉となる。マグネシウムの含有量が０．００３質量％未満では、粒径が微細で表面が平滑なニッケル粉とならない。また、マグネシウムの含有量が１．６質量％を超えると、ニッケル粉のニッケル品位の低下により、積層セラミックコンデンサの内部電極として用いられた場合に、電極の電気抵抗値が大きくなり過ぎ、コンデンサーの損失係数の悪化を招いてしまう。 Moreover, it is preferable that the nickel powder of this invention contains 0.003-1.6 mass% of magnesium. By containing 0.003 to 1.6% by mass of magnesium, nickel powder having a fine particle size and a smooth surface is obtained. When the magnesium content is less than 0.003 mass%, nickel powder having a fine particle size and a smooth surface cannot be obtained. Also, if the magnesium content exceeds 1.6 mass%, the electrical resistance value of the electrode becomes too large when used as an internal electrode of a multilayer ceramic capacitor due to a decrease in the nickel quality of the nickel powder. The loss factor will be worsened.
本発明のニッケル粉において、その平均粒径は０．２〜１．０μｍであることが好ましく、０．２〜０．４μｍであることがより好ましい。すなわち、平均粒径が０．２μｍ未満であると、積層セラミックコンデンサの内部電極用ペーストとして用いたとき、ニッケル粉の焼結温度が低いため、誘電体セラミックスとの焼結挙動の差が大きく、電極の途切れや剥離が起こることがあり、他方、平均粒径が１．０μｍを超えると、薄層化された内部電極では、焼結後の電極に穴開きや途切れが発生することがあり好ましくない。 In the nickel powder of the present invention, the average particle diameter is preferably 0.2 to 1.0 μm, and more preferably 0.2 to 0.4 μm. That is, when the average particle size is less than 0.2 μm, when used as an internal electrode paste of a multilayer ceramic capacitor, the sintering temperature of nickel powder is low, so the difference in sintering behavior with dielectric ceramics is large, On the other hand, when the average particle diameter exceeds 1.0 μm, the thinned internal electrode may cause holes or breaks in the sintered electrode, which may occur. Absent.
さらに、その比表面積は、１〜５ｍ２／ｇであることが好ましい。比表面積が１ｍ２／ｇ未満になると、粒径が大きくなり過ぎ、焼結後の電極の穴開きや途切れが発生する。また、比表面積が５ｍ２／ｇを超えると、溶剤との相互作用が変化して、ニッケル粉の凝集やペースト粘度の経時的な変化が発生することがある。より好ましくは比表面積が２〜４ｍ２／ｇの範囲であれば、このような問題は発生せずに安定して用いることができる。 Furthermore, it is preferable that the specific surface area is 1-5 m < 2 > / g. When the specific surface area is less than 1 m 2 / g, the particle size becomes excessively large, and the electrodes are punctured or interrupted after sintering. On the other hand, if the specific surface area exceeds 5 m 2 / g, the interaction with the solvent may change, and agglomeration of nickel powder and changes in paste viscosity over time may occur. More preferably, when the specific surface area is in the range of 2 to 4 m 2 / g, such a problem does not occur and it can be used stably.
次に、本発明のニッケル粉の製造法について説明する。
［ニッケル粉の製造方法］
本発明のニッケル粉の製造方法（以下、本発明の製造方法と称す。）は、水酸化ニッケル粉を酸化焙焼して酸化ニッケル粉とし、得られた酸化ニッケル粉を還元してニッケル粉を形成するニッケル粉の製造方法において、酸化ニッケル粉を還元して得られた還元ニッケル粉を、還元ニッケル粉１ｇに対して０．０３リットル以上の水量で洗浄した後、１２０〜１８０℃の温度で乾燥することを特徴とするものである。
Next, the manufacturing method of the nickel powder of this invention is demonstrated.
[Production method of nickel powder]
The nickel powder production method of the present invention (hereinafter referred to as the production method of the present invention) comprises oxidizing and roasting nickel hydroxide powder to form nickel oxide powder, and reducing the obtained nickel oxide powder to obtain nickel powder. In the manufacturing method of the nickel powder to be formed, the reduced nickel powder obtained by reducing the nickel oxide powder is washed with a water amount of 0.03 liter or more with respect to 1 g of the reduced nickel powder, and then at a temperature of 120 to 180 ° C. It is characterized by drying.
すなわち、本発明の製造方法は、
（１）水酸化ニッケル粉を酸化焙焼して酸化ニッケル粉を得る酸化焙焼工程、
（２）酸化ニッケル粉を還元して還元ニッケル粉を得る還元工程、
（３）還元ニッケル粉を、還元ニッケル粉１ｇに対して０．０３リットル以上の水量で洗浄する洗浄工程、
（４）洗浄した還元ニッケル粉を、１２０〜１８０℃の温度で乾燥してニッケル粉を得る乾燥工程
を含むものである。
以下、工程毎に説明する。
That is, the production method of the present invention comprises:
(1) An oxidation roasting step in which nickel hydroxide powder is obtained by oxidation roasting of nickel hydroxide powder,
(2) A reduction step of reducing nickel oxide powder to obtain reduced nickel powder,
(3) A cleaning step of cleaning the reduced nickel powder with an amount of water of 0.03 liter or more with respect to 1 g of the reduced nickel powder.
(4) A drying step of drying the washed reduced nickel powder at a temperature of 120 to 180 ° C. to obtain nickel powder is included.
Hereinafter, it demonstrates for every process.
［酸化焙焼工程］
この酸化焙焼工程は、水酸化ニッケル粉を酸化焙焼して酸化ニッケル粉を得る工程であり、水酸化ニッケル１ｇに対して０．００２〜０．００５リットル／分の窒素ガスを流すとともに３５０〜７００℃の温度で酸化焙焼するものである。
[Oxidation roasting process]
This oxidation roasting step is a step in which nickel hydroxide powder is oxidized and roasted to obtain nickel oxide powder, and a nitrogen gas of 0.002 to 0.005 liter / min is supplied to 1 g of nickel hydroxide and 350 Oxidation roasting is performed at a temperature of ˜700 ° C.
この酸化焙焼時に流す窒素ガス量が、水酸化ニッケル１ｇに対して０．００２リットル／分未満であると、水酸化ニッケルの酸化ニッケルへの転換が徐々に進むために、得られる酸化ニッケルの結晶が成長する。また、７００℃を超える温度で焙焼すると、酸化焙焼中に焼結が進み粗大な酸化ニッケル粉となってしまう。
このように流す窒素ガス量が少ない場合、あるいは高い焙焼温度により得られた酸化ニッケルは、結晶が成長しているか粗大な粒径となっているため、還元するためには高温で、かつ長時間還元させる必要が生じてしまい、したがって高温かつ長時間の還元を行なった場合に、ニッケル粉の粒成長が進み、粗大で粒径が不均一なものとなってしまうことがあることから、次工程における還元ニッケル粉の還元を考慮すると、その焙焼温度は４６０℃以下が、より好ましい。
When the amount of nitrogen gas flowing during this oxidation roasting is less than 0.002 liter / min with respect to 1 g of nickel hydroxide, the conversion of nickel hydroxide to nickel oxide proceeds gradually. Crystal grows. Further, when roasting at a temperature exceeding 700 ° C., sintering progresses during oxidation roasting, resulting in coarse nickel oxide powder.
When the amount of nitrogen gas flowing in this way is small, or the nickel oxide obtained by a high roasting temperature, crystals are growing or have a coarse particle size. Therefore, when reduction is performed for a long time at a high temperature, the grain growth of the nickel powder proceeds and the grain size may become coarse and non-uniform. Considering the reduction of the reduced nickel powder in the process, the roasting temperature is more preferably 460 ° C. or less.
一方、酸化焙焼時に流す窒素ガス量が、上限を超えても均一微細なニッケル粉を得られるが、コスト増となる。また、多量の窒素ガスを流すと微細な酸化ニッケル粉が飛散して歩留まりも低下するため、好ましくない。 On the other hand, even if the amount of nitrogen gas flowing during oxidation roasting exceeds the upper limit, uniform fine nickel powder can be obtained, but the cost increases. In addition, flowing a large amount of nitrogen gas is not preferable because fine nickel oxide powder is scattered and the yield is lowered.
また、酸化焙焼する温度が２５０℃未満では、酸化焙焼に長時間要するのみならず水酸化ニッケルから酸化ニッケルへの転換が十分に進まず、還元時に還元が不均一に進むため、ニッケル粉の粒成長が起こることがある。 In addition, when the temperature for oxidation roasting is less than 250 ° C., not only does oxidation roasting take a long time, but also the conversion from nickel hydroxide to nickel oxide does not proceed sufficiently, and the reduction proceeds non-uniformly during reduction. Grain growth may occur.
本発明の製造方法において、酸化焙焼の雰囲気を窒素雰囲気とすることが好ましく、窒素雰囲気とすることによって、酸化ニッケルの形態が安定し、後工程での製造条件に幅を持たせることができる。 In the production method of the present invention, it is preferable that the oxidative roasting atmosphere is a nitrogen atmosphere. By making the nitrogen atmosphere, the form of nickel oxide is stabilized, and the production conditions in the subsequent steps can be widened. .
この酸化焙焼の時間は、特に限定されるものではなく、酸化焙焼時に流す窒素ガス量、焙焼温度、処理する水酸化ニッケル粉の量により、全ての水酸化ニッケルが酸化ニッケルに転換されるのに必要な時間とすればよいが、望ましくは、結晶性を低くするために、その焙焼時間は可能な限り短時間とする。 The time for this oxidation roasting is not particularly limited, and all the nickel hydroxide is converted to nickel oxide depending on the amount of nitrogen gas flowing during the oxidation roasting, the roasting temperature, and the amount of nickel hydroxide powder to be treated. However, it is desirable that the roasting time be as short as possible in order to lower the crystallinity.
本発明の製造方法において用いられる水酸化ニッケル粉は、公知の方法により得ることができる。
例えば、塩化ニッケルや硫酸ニッケルなどの水溶性ニッケル塩の水溶液を、ｐＨ制御して中和沈殿させることで得られる水酸化ニッケル粉を用いることができる。この水酸化ニッケル粉には、アルカリ土類金属、特にマグネシウムを０．００２〜１質量％含有する水酸化ニッケル粉を用いることが好ましい。この水酸化ニッケル粉に含有されるアルカリ土類金属は、水溶性塩などの水溶性物質としてニッケル塩水溶液に混合しておき、水酸化ニッケルの生成時に共沈させてやればよい。水酸化ニッケル粉を製造する反応設備に特に制限はなく、通常用いられる設備でよく、例えば攪拌機を有する貯槽でｐＨ管理が行なえるものであればよい。
The nickel hydroxide powder used in the production method of the present invention can be obtained by a known method.
For example, nickel hydroxide powder obtained by neutralizing and precipitating an aqueous solution of a water-soluble nickel salt such as nickel chloride or nickel sulfate by controlling pH can be used. As the nickel hydroxide powder, it is preferable to use nickel hydroxide powder containing 0.002 to 1% by mass of an alkaline earth metal, particularly magnesium. The alkaline earth metal contained in the nickel hydroxide powder may be mixed with a nickel salt aqueous solution as a water-soluble substance such as a water-soluble salt and coprecipitated when nickel hydroxide is produced. There are no particular limitations on the reaction equipment for producing the nickel hydroxide powder, and any equipment that is normally used may be used, for example, as long as the pH can be controlled in a storage tank having a stirrer.
この水酸化ニッケル粉に含有されるマグネシウム量を０．００２〜１質量％とすることで、最終的に得られるニッケル粉に含有されるマグネシウム量を０．００３〜１．６質量％とすることができ、粒径が微細で表面が平滑なニッケル粉が得られる。
このマグネシウムは、還元時におけるニッケル粒子生成時の粒子の微細化および球状化、粒子表面の平滑性改善、表面の酸化被膜形成に効果がある。水酸化ニッケル粉に含有されるマグネシウム量が０．００２質量％未満の場合には、微細化および平滑性改善の効果が得られないことがある。水酸化ニッケル粉に含有されるマグネシウムが１質量％を超えた場合には、得られるニッケル粉のマグネシウム含有される量が１．６質量％を超え、上記コンデンサーの損失係数の悪化を招くことがある。
By making the amount of magnesium contained in this nickel hydroxide powder 0.002 to 1% by mass, the amount of magnesium contained in the finally obtained nickel powder is 0.003 to 1.%. The amount can be 6 % by mass, and a nickel powder having a fine particle size and a smooth surface can be obtained.
This magnesium is effective in making the particles finer and spheroidized during nickel particle generation during reduction, improving the smoothness of the particle surface, and forming an oxide film on the surface. When the amount of magnesium contained in the nickel hydroxide powder is less than 0.002% by mass, the effect of refinement and smoothness improvement may not be obtained. When magnesium contained in the nickel hydroxide powder exceeds 1% by mass, the amount of magnesium contained in the obtained nickel powder is 1. If it exceeds 6 % by mass, the loss factor of the capacitor may be deteriorated.
［還元工程］
還元工程は、酸化焙焼工程で得られた酸化ニッケル粉を還元して還元ニッケル粉を得る工程である。
この還元工程では、酸化ニッケル粉１ｇに対して０．００３〜０．０２リットル／分の水素ガスを流すとともに、３００〜５５０℃の温度で還元することが好ましい。このとき、水素を含む雰囲気とすればよく、水素ガスのみを流してもよく、水素ガスと窒素ガスなどの不活性ガスとの混合ガスを流してもよい。
[Reduction process]
The reduction step is a step of obtaining reduced nickel powder by reducing the nickel oxide powder obtained in the oxidation roasting step.
In this reduction step, 0.003 to 0.02 liter / min of hydrogen gas is supplied to 1 g of nickel oxide powder, and reduction is preferably performed at a temperature of 300 to 550 ° C. At this time, an atmosphere containing hydrogen may be used, and only hydrogen gas may be supplied, or a mixed gas of hydrogen gas and an inert gas such as nitrogen gas may be supplied.
還元時に流す水素ガス量が酸化ニッケル１ｇに対して０．００３リットル／分未満の場合は、還元が徐々に進むためにニッケル粉の粒成長が起こり、所望の粒径で均一な還元ニッケル粉が得られない場合がある。対して水素ガス量が、酸化ニッケル１ｇに対して０．０２リットル／分を超えても還元反応を短時間化するなどの効果がなく、コスト増となるのみである。 When the amount of hydrogen gas flowing at the time of reduction is less than 0.003 liter / min with respect to 1 g of nickel oxide, the reduction gradually proceeds, so that nickel powder particles grow, and a uniform reduced nickel powder having a desired particle size is obtained. It may not be obtained. On the other hand, even if the amount of hydrogen gas exceeds 0.02 liter / min with respect to 1 g of nickel oxide, there is no effect of shortening the reduction reaction, and only the cost increases.
また、還元温度が５５０℃を超えると、還元された還元ニッケル粉が還元中に焼結し、結果として所望の粒径を精度良く得ることができない場合がある。対して３００℃未満の温度では、酸化ニッケル粉から還元ニッケル粉への還元が十分に進まないことがある。
還元時間は特に限定されるものではなく、還元時に流す水素量、還元温度、投入する酸化ニッケル粉の量により、全ての酸化ニッケル粉が還元ニッケル粉に還元されるのに必要な時間とすればよく、所望の粒径が得られるように時間を制御することが好ましい。
On the other hand, when the reduction temperature exceeds 550 ° C., the reduced nickel powder reduced may be sintered during the reduction, and as a result, a desired particle size may not be obtained with high accuracy. On the other hand, when the temperature is lower than 300 ° C., the reduction from nickel oxide powder to reduced nickel powder may not sufficiently proceed.
The reduction time is not particularly limited, and the time required for all the nickel oxide powder to be reduced to reduced nickel powder is determined depending on the amount of hydrogen flowing during reduction, the reduction temperature, and the amount of nickel oxide powder to be added. It is preferable to control the time so that the desired particle size is obtained.
焙焼および還元に用いる設備は、雰囲気を制御できれば特に制限はなく、例えば、バッチ式雰囲気炉、連続式ローラーハースキルン、連続式プッシャー炉などを用いることができる。 The equipment used for roasting and reduction is not particularly limited as long as the atmosphere can be controlled. For example, a batch-type atmosphere furnace, a continuous roller hearth kiln, a continuous pusher furnace, or the like can be used.
［洗浄工程］
洗浄工程は、還元工程で得られた還元ニッケル粉を還元ニッケル粉１ｇに対して０．０３リットル以上の水量で洗浄する工程である。洗浄時の水量が還元ニッケル粉１ｇに対して０．０３リットル未満の場合、還元ニッケル粉表面にある不純物イオンを十分に除去できず、また、還元ニッケル粉表面を充分に濡らすことができないために、水酸基量が０．０２０未満となってしまう。一方、洗浄時の水量の上限は、還元ニッケル粉１ｇに対して０．１リットル以下とすることが好ましい。洗浄時の水量が０．１リットルを超えても洗浄効果に改善は無く、コスト増となるのみである。
[Washing process]
The washing step is a step of washing the reduced nickel powder obtained in the reduction step with an amount of water of 0.03 liter or more with respect to 1 g of the reduced nickel powder. When the amount of water at the time of washing is less than 0.03 liters per 1 g of the reduced nickel powder, the impurity ions on the reduced nickel powder surface cannot be sufficiently removed, and the reduced nickel powder surface cannot be sufficiently wetted. The amount of hydroxyl group will be less than 0.020. On the other hand, the upper limit of the amount of water at the time of washing is preferably 0.1 liter or less with respect to 1 g of the reduced nickel powder. Even if the amount of water at the time of washing exceeds 0.1 liter, there is no improvement in the washing effect and only the cost is increased.
洗浄方法は、特に限定されるものではないが、例えば、規定量の水と還元ニッケル粉を混合してスラリー化し撹拌すればよい。ここで、洗浄に用いる水は、不純物混入の虞がないものがよく、純水が好ましい。また、洗浄に用いる設備は、ニッケル粉をスラリー化して攪拌できれば特に制限されるものではなく、攪拌機のついた槽や、それに類似した構造を持つ設備を用いることが出来る。水洗の条件も、粉体の水洗等で通常行なわれる条件に設定すればよい。還元ニッケル粉をスラリー化し撹拌した後は、ろ過などの通常の方法で、固液分離される。 The cleaning method is not particularly limited. For example, a predetermined amount of water and reduced nickel powder may be mixed to form a slurry and stirred. Here, the water used for washing should be free of impurities and is preferably pure water. The equipment used for washing is not particularly limited as long as nickel powder can be slurried and stirred, and a tank equipped with a stirrer or equipment having a similar structure can be used. The conditions for washing with water may be set to the conditions normally used for washing powder with water. After the reduced nickel powder is slurried and stirred, solid-liquid separation is performed by a normal method such as filtration.
［乾燥工程］
乾燥工程は、洗浄した還元ニッケル粉を１２０〜１８０℃の温度で乾燥してニッケル粉を得る工程である。本発明の製造方法においては、洗浄工程における水量とともに、この乾燥温度が水酸基量を制御するために重要である。
[Drying process]
The drying step is a step of obtaining nickel powder by drying the washed reduced nickel powder at a temperature of 120 to 180 ° C. In the production method of the present invention, this drying temperature is important for controlling the amount of hydroxyl groups together with the amount of water in the washing step.
すなわち、乾燥温度が１２０℃未満であると、乾燥が進まず、ニッケル粉表面の水酸基が増えて、水酸基量が０．０２８を超えてしまう。その乾燥温度が１８０℃以上では、ニッケル粉表面の水酸化物が分解するとともに酸素量が増加してニッケル粉表面の水酸基が減り、水酸基量が０．０２０未満となる。
この乾燥温度を１２０〜１８０℃とすることで、水酸基量を０．０２０〜０．０２８に制御することができ、ペーストに用いた場合の粘度の安定性が良好なニッケル粉が得られる。
That is, when the drying temperature is less than 120 ° C., the drying does not proceed, the number of hydroxyl groups on the nickel powder surface increases, and the amount of hydroxyl groups exceeds 0.028. When the drying temperature is 180 ° C. or higher, the hydroxide on the surface of the nickel powder is decomposed and the amount of oxygen increases, the number of hydroxyl groups on the surface of the nickel powder decreases, and the amount of hydroxyl groups becomes less than 0.020.
By setting the drying temperature to 120 to 180 ° C., the amount of hydroxyl group can be controlled to 0.020 to 0.028, and nickel powder having good viscosity stability when used in a paste can be obtained.
乾燥の雰囲気は、特に制限されるものではないが、表面の水酸基量の制御およびコスト面を考慮すると大気雰囲気とすることが好ましい。還元雰囲気で乾燥させると、表面の水酸基量が過度に減少することがあるため、好ましくない。 The drying atmosphere is not particularly limited, but is preferably an atmospheric atmosphere in consideration of the control of the amount of hydroxyl groups on the surface and the cost. Drying in a reducing atmosphere is not preferable because the amount of hydroxyl groups on the surface may be excessively reduced.
乾燥する時間は、特に制限されるものではなく、得られるニッケル粉の含有水分が十分に減少し、表面の水酸基量が所望の値となるように、乾燥温度、投入する酸化ニッケル粉の量により、調整すればよい。また、乾燥に用いる設備は、所望の温度で乾燥できれば特に制限は無く、静置式箱型乾燥器、流動層乾燥器、ミキサー型乾燥器、ロータリーキルン、ローラーハースキルン、プッシャー炉などを用いることが出来る。 The drying time is not particularly limited, and depends on the drying temperature and the amount of nickel oxide powder to be added so that the moisture content of the obtained nickel powder is sufficiently reduced and the surface hydroxyl group amount becomes a desired value. Adjust. The equipment used for drying is not particularly limited as long as it can be dried at a desired temperature, and a stationary box type dryer, fluidized bed dryer, mixer type dryer, rotary kiln, roller hearth kiln, pusher furnace, etc. can be used. .
各工程中に生成した凝集粉の解砕あるいは工程中に混入した異物を除去する目的から、各工程中で乾式または湿式による遠心力やフィルターを用いた解砕や分級を行なってもよい。用いられる装置は特に限定されるものではなく、通常のニッケル粉の製造に用いられるジェットミルやサイクロン形式の装置が使用される。 For the purpose of crushing the agglomerated powder produced during each step or removing foreign matter mixed during the step, crushing or classification using a dry or wet centrifugal force or a filter may be performed in each step. The apparatus to be used is not particularly limited, and a jet mill or a cyclone type apparatus that is used for producing ordinary nickel powder is used.
以下に、本発明の実施例を用いて詳細に説明するが、これらの実施例によって本発明は何ら限定されるものではない。 Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to these examples.
なお、ニッケル粉の評価は以下のようにして行なった。
（ａ）比表面積
比表面積計（ユアサアイオニクス社製マルチソーブ１６）によるＢＥＴ１点法で測定した。
The nickel powder was evaluated as follows.
(A) Specific surface area It measured by the BET 1-point method by the specific surface area meter (Multisorb 16 by Yuasa Ionics).
（ｂ）水酸基の吸光度
分光計（日本分光社製ＦＴ／ＩＲ６８０Ｐｌｕｓ(Ｖ)）による真空拡散反射法でピーク高さを測定した。
(B) Absorbance of hydroxyl group The peak height was measured by a vacuum diffuse reflection method using a spectrometer (FT / IR680Plus (V) manufactured by JASCO Corporation).
（ｃ）粘度比
ターピネオールに対し２０質量%のエチルセルロースをに投入し、撹拌しながら８０℃に加熱して溶解液を作製し、この溶液を、ニッケル粉に対し１８質量％、またターピネオール２９質量％を混合し、３本ロールミルにて混練することで、導電ペーストとした。これを粘度計（ＢＲＯＯＫＦＩＥＬＤ社製ＨＡＴ）で１ｒｐｍの時の粘度および１００ｒｐｍの時の粘度を測定し、その比を算出した。
粘度比維持率は、導電ペースト製造して密閉容器に室温保管した１日後の値で３０日後の値を除することにより算出した。
(C) Viscosity ratio 20% by mass of ethylcellulose with respect to terpineol was added to the mixture and heated to 80 ° C. with stirring to prepare a solution. Were mixed and kneaded with a three-roll mill to obtain a conductive paste. The viscosity at 1 rpm and the viscosity at 100 rpm were measured with a viscometer (HATOK manufactured by BROOKFIELD), and the ratio was calculated.
The viscosity ratio maintenance ratio was calculated by dividing the value after 30 days by the value after 1 day when the conductive paste was produced and stored in a sealed container at room temperature.
（ｄ）平均粒径
走査型電子顕微鏡（ＪＳＭ−５５１０、日本電子製）を用いて、１０，０００倍の写真を撮影し、写真一視野で確認できる全ての粒子の粒径を測定して、個数平均で求めた。
(D) Average particle diameter Using a scanning electron microscope (JSM-5510, manufactured by JEOL Ltd.), a 10,000-fold photograph was taken, and the particle diameters of all the particles that could be confirmed in one field of view were measured. The number average was obtained.
１００ｇの塩化ニッケル６水和物（試薬１級、和光純薬製）と塩化マグネシウム６水和物（試薬１級、和光純薬製）０．２ｇ（これは、水酸化ニッケル中Ｍｇ含有量０．０６質量％に相当する）を純水２５０ｍｌに溶解して塩化ニッケル水溶液を調製した。次いで、水酸化ナトリウム（試薬１級、和光純薬製）３５．５ｇを純水２５０ｍｌに溶解した溶液を前記塩化ニッケル水溶液に添加し、生成した水酸化物をろ過した。さらに、これを１リットルの純水で水洗し、再びろ過した（以下、本操作を「ろ過水洗」と呼ぶ）。同様にろ過水洗を４回繰り返した後に、箱型大気乾燥機（ＤＸ６０１、ヤマト科学製）で１５０℃、４８時間の乾燥を行い、水酸化ニッケル粉を得た。 100 g of nickel chloride hexahydrate (reagent grade 1, manufactured by Wako Pure Chemical Industries) and magnesium chloride hexahydrate (reagent grade 1, manufactured by Wako Pure Chemical Industries) 0.2 g (this is the content of Mg in nickel hydroxide is 0 (Corresponding to 0.06 mass%) was dissolved in 250 ml of pure water to prepare an aqueous nickel chloride solution. Next, a solution prepared by dissolving 35.5 g of sodium hydroxide (reagent grade 1, manufactured by Wako Pure Chemical Industries) in 250 ml of pure water was added to the nickel chloride aqueous solution, and the produced hydroxide was filtered. Further, this was washed with 1 liter of pure water and filtered again (hereinafter, this operation is referred to as “filtered water washing”). Similarly, after washing with filtered water four times, drying was performed at 150 ° C. for 48 hours with a box-type atmospheric dryer (DX601, manufactured by Yamato Kagaku) to obtain nickel hydroxide powder.
得られた水酸化ニッケル粉を解砕した後、バッチ式雰囲気炉（管状炉、入江製作所製）を用いて乾燥水酸化ニッケル粉１ｇあたり窒素ガス流量を０．００３リットル／分とし、４５０℃で１時間保持して酸化焙焼して酸化ニッケル粉を得た。
さらに、前記バッチ式雰囲気炉を用いて、酸化ニッケル粉を、酸化ニッケル粉１ｇあたり０．００３リットル／分の水素ガスと同量の窒素ガスを混合して流した雰囲気炉中に４５０℃で２時間保持して還元ニッケル粉を得た。
After crushing the obtained nickel hydroxide powder, using a batch-type atmosphere furnace (tubular furnace, manufactured by Irie Seisakusho), the nitrogen gas flow rate per 1 g of the dried nickel hydroxide powder is 0.003 liters / minute, at 450 ° C. The nickel oxide powder was obtained by holding for 1 hour and oxidizing and baking.
Furthermore, using the batch-type atmosphere furnace, nickel oxide powder was mixed at 450 ° C. in an atmosphere furnace in which the same amount of nitrogen gas as 0.003 liter / min of hydrogen gas was mixed and flowed per gram of nickel oxide powder. Holding for a time, reduced nickel powder was obtained.
得られた還元ニッケル粉を、還元ニッケル粉１ｇあたり０．０３リットルの純水と混合してスラリーとし、３０分間撹拌して洗浄後、ろ過した。洗浄後の還元ニッケル粉を箱型大気乾燥機（ＤＸ６０１、ヤマト科学製）を用いて乾燥温度１２０℃、４８時間の条件で乾燥した。乾燥後解砕して、１００メッシュの篩にかけてニッケル粉を得た。表１に酸化焙焼工程以後の製造条件を示し、表２に得られたニッケル粉の評価結果を示す。 The obtained reduced nickel powder was mixed with 0.03 liters of pure water per gram of reduced nickel powder to form a slurry, stirred for 30 minutes, washed, and then filtered. The reduced nickel powder after washing was dried using a box-type atmospheric dryer (DX601, manufactured by Yamato Kagaku) at a drying temperature of 120 ° C. for 48 hours. After drying, it was crushed and passed through a 100 mesh sieve to obtain nickel powder. Table 1 shows the manufacturing conditions after the oxidation roasting step, and Table 2 shows the evaluation results of the nickel powder obtained.
還元ニッケル粉１ｇあたり０．１リットルの純水と混合してスラリーとしたこと、乾燥温度を１８０℃としたこと以外は実施例１と同様にして、ニッケル粉を得た。表１に酸化焙焼工程以後の製造条件を示し、表２に得られたニッケル粉の評価結果を示す。 Nickel powder was obtained in the same manner as in Example 1 except that 0.1 g of pure water per 1 g of reduced nickel powder was mixed to form a slurry, and the drying temperature was 180 ° C. Table 1 shows the manufacturing conditions after the oxidation roasting step, and Table 2 shows the evaluation results of the nickel powder obtained.
還元ニッケル粉１ｇあたり０．０６リットルの純水と混合してスラリーとしたこと、乾燥温度を１５０℃としたこと以外は実施例１と同様にして、ニッケル粉を得た。表１に酸化焙焼工程以後の製造条件を示し、表２に得られたニッケル粉の評価結果を示す。 Nickel powder was obtained in the same manner as in Example 1 except that 0.06 liter of pure water was mixed with 1 g of reduced nickel powder to make a slurry, and the drying temperature was 150 ° C. Table 1 shows the manufacturing conditions after the oxidation roasting step, and Table 2 shows the evaluation results of the nickel powder obtained.
還元ニッケル粉１ｇあたり０．０５リットルの純水と混合してスラリーとしたこと、乾燥温度を１５０℃としたこと以外は実施例１と同様にして、ニッケル粉を得た。表１に酸化焙焼工程以後の製造条件を示し、表２に得られたニッケル粉の評価結果を示す。 Nickel powder was obtained in the same manner as in Example 1 except that 0.05 liter of pure water per 1 g of reduced nickel powder was mixed to form a slurry and the drying temperature was 150 ° C. Table 1 shows the manufacturing conditions after the oxidation roasting step, and Table 2 shows the evaluation results of the nickel powder obtained.
乾燥水酸化ニッケル粉１ｇあたり窒素ガス流量を０．００５リットル／分とし、４７０℃で酸化焙焼したこと、酸化ニッケル粉１ｇあたり０．０２リットル／分の水素ガスと同量の窒素ガスを混合して流し、４７０℃で保持したこと、還元ニッケル粉１ｇあたり０．１リットルの純水と混合してスラリーとしたこと以外は実施例１と同様にして、ニッケル粉を得た。表１に酸化焙焼工程以後の製造条件を示し、表２に得られたニッケル粉の評価結果を示す。 The flow rate of nitrogen gas per gram of dry nickel hydroxide powder was 0.005 liters / minute, oxidation roasting at 470 ° C, and the same amount of nitrogen gas as 0.02 liters / minute of hydrogen gas was mixed per gram of nickel oxide powder. The nickel powder was obtained in the same manner as in Example 1 except that the slurry was kept at 470 ° C. and mixed with 0.1 liter of pure water per gram of reduced nickel powder to form a slurry. Table 1 shows the manufacturing conditions after the oxidation roasting step, and Table 2 shows the evaluation results of the nickel powder obtained.
（比較例１）
洗浄工程において、還元ニッケル粉１ｇあたり０．０１リットルの純水と混合してスラリーとしたこと、および乾燥工程の乾燥温度を１５０℃としたこと以外は、実施例１と同様にしてニッケル粉を得た。表１に酸化焙焼工程以後の製造条件を示し、表２に得られたニッケル粉の評価結果を示す。
(Comparative Example 1)
In the washing step, the nickel powder was prepared in the same manner as in Example 1 except that it was mixed with 0.01 liter of pure water per gram of reduced nickel powder to make a slurry, and the drying temperature in the drying step was 150 ° C. Obtained. Table 1 shows the manufacturing conditions after the oxidation roasting step, and Table 2 shows the evaluation results of the nickel powder obtained.
（比較例２）
乾燥工程の乾燥温度を１００℃としたこと以外は、実施例１と同様にしてニッケル粉を得た。表１に酸化焙焼工程以後の製造条件を示し、表２に得られたニッケル粉の評価結果を示す。
(Comparative Example 2)
Nickel powder was obtained in the same manner as in Example 1 except that the drying temperature in the drying step was 100 ° C. Table 1 shows the manufacturing conditions after the oxidation roasting step, and Table 2 shows the evaluation results of the nickel powder obtained.
（比較例３）
洗浄工程において、還元ニッケル粉１ｇあたり０．２リットルの純水と混合してスラリーとしたこと、および乾燥工程の乾燥温度を２００℃としたこと以外は、実施例１と同様にしてニッケル粉を得た。表１に酸化焙焼工程以後の製造条件を示し、表２に得られたニッケル粉の評価結果を示す。
(Comparative Example 3)
In the washing step, nickel powder was prepared in the same manner as in Example 1 except that it was mixed with 0.2 liters of pure water per gram of reduced nickel powder to make a slurry, and the drying temperature in the drying step was 200 ° C. Obtained. Table 1 shows the manufacturing conditions after the oxidation roasting step, and Table 2 shows the evaluation results of the nickel powder obtained.
表１、表２の実施例から明らかなように、本発明のニッケル粉は、ペーストの粘度維持率が高く、したがって粘度安定性が高いことがわかる。また、実施例５は、酸化焙焼時の焙焼温度が４７０℃と高めであることから、次工程の還元温度も高くなるため、実施例１から４に比べて粘度維持率が少し低下しているが、本発明の洗浄条件および乾燥条件による洗浄、乾燥を施すことにより、比較例に比して良好な粘度維持率が得られることが伺える。 As is apparent from the examples in Tables 1 and 2, it can be seen that the nickel powder of the present invention has a high viscosity maintenance rate of the paste, and thus has high viscosity stability. In Example 5, the roasting temperature during oxidative roasting is as high as 470 ° C., so the reduction temperature in the next step is also high, so the viscosity maintenance rate is slightly lower than in Examples 1 to 4. However, it can be seen that by performing cleaning and drying under the cleaning conditions and drying conditions of the present invention, a better viscosity maintenance rate can be obtained as compared with the comparative example.
これに対して、還元ニッケル粉を洗浄する水量が少ない比較例１、乾燥温度が低い比較例２、乾燥温度が高い比較例３のニッケル粉では、ペーストの粘度維持率が低く、粘度安定性が劣っていることがわかる。 In contrast, the nickel powder of Comparative Example 1 with a small amount of water for washing the reduced nickel powder, Comparative Example 2 with a low drying temperature, and Comparative Example 3 with a high drying temperature has a low viscosity maintenance rate of the paste and is stable in viscosity. It turns out that it is inferior.
Claims (5)
前記酸化ニッケル粉の還元により形成される還元ニッケル粉を、還元ニッケル粉１ｇに対して０．０３リットル以上の水量の水で洗浄した後、大気雰囲気中において１２０〜１８０℃の温度で乾燥することを特徴とするニッケル粉の製造方法。 In the method for producing nickel powder, the nickel hydroxide powder is oxidized and roasted to form nickel oxide powder, and the obtained nickel oxide powder is reduced to form nickel powder.
The reduced nickel powder formed by reduction of the nickel oxide powder, washed with water 0.03 liters or more of water relative to the reduced nickel powder 1g, drying at a temperature of 120 to 180 ° C. in an air atmosphere A method for producing nickel powder characterized by the above.
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