JP4063151B2 - Porous spherical nickel powder and method for producing the same - Google Patents
Porous spherical nickel powder and method for producing the same Download PDFInfo
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- JP4063151B2 JP4063151B2 JP2003166264A JP2003166264A JP4063151B2 JP 4063151 B2 JP4063151 B2 JP 4063151B2 JP 2003166264 A JP2003166264 A JP 2003166264A JP 2003166264 A JP2003166264 A JP 2003166264A JP 4063151 B2 JP4063151 B2 JP 4063151B2
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- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 title claims description 117
- 238000004519 manufacturing process Methods 0.000 title claims description 36
- 239000002245 particle Substances 0.000 claims description 76
- 239000000843 powder Substances 0.000 claims description 56
- 150000002816 nickel compounds Chemical class 0.000 claims description 42
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims description 35
- 239000001257 hydrogen Substances 0.000 claims description 31
- 229910052739 hydrogen Inorganic materials 0.000 claims description 31
- 229910052759 nickel Inorganic materials 0.000 claims description 21
- 229910000480 nickel oxide Inorganic materials 0.000 claims description 19
- GNRSAWUEBMWBQH-UHFFFAOYSA-N oxonickel Chemical compound [Ni]=O GNRSAWUEBMWBQH-UHFFFAOYSA-N 0.000 claims description 19
- 229910000008 nickel(II) carbonate Inorganic materials 0.000 claims description 15
- BFDHFSHZJLFAMC-UHFFFAOYSA-L nickel(ii) hydroxide Chemical compound [OH-].[OH-].[Ni+2] BFDHFSHZJLFAMC-UHFFFAOYSA-L 0.000 claims description 15
- 239000011164 primary particle Substances 0.000 claims description 15
- ZULUUIKRFGGGTL-UHFFFAOYSA-L nickel(ii) carbonate Chemical compound [Ni+2].[O-]C([O-])=O ZULUUIKRFGGGTL-UHFFFAOYSA-L 0.000 claims description 14
- 239000012798 spherical particle Substances 0.000 claims description 13
- 229910052751 metal Inorganic materials 0.000 claims description 9
- 239000002184 metal Substances 0.000 claims description 9
- 230000003472 neutralizing effect Effects 0.000 claims description 7
- 230000001590 oxidative effect Effects 0.000 claims description 7
- 230000003647 oxidation Effects 0.000 claims description 3
- 238000007254 oxidation reaction Methods 0.000 claims description 3
- 238000010438 heat treatment Methods 0.000 description 48
- 238000006722 reduction reaction Methods 0.000 description 42
- 238000000034 method Methods 0.000 description 23
- 238000004458 analytical method Methods 0.000 description 9
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 9
- 238000009826 distribution Methods 0.000 description 9
- 238000011156 evaluation Methods 0.000 description 9
- 239000001301 oxygen Substances 0.000 description 9
- 229910052760 oxygen Inorganic materials 0.000 description 9
- 239000007864 aqueous solution Substances 0.000 description 7
- 230000000052 comparative effect Effects 0.000 description 7
- 239000002994 raw material Substances 0.000 description 7
- 238000000635 electron micrograph Methods 0.000 description 6
- 238000011282 treatment Methods 0.000 description 6
- 229910021586 Nickel(II) chloride Inorganic materials 0.000 description 5
- QMMRZOWCJAIUJA-UHFFFAOYSA-L nickel dichloride Chemical compound Cl[Ni]Cl QMMRZOWCJAIUJA-UHFFFAOYSA-L 0.000 description 5
- 239000012808 vapor phase Substances 0.000 description 5
- 230000015572 biosynthetic process Effects 0.000 description 4
- 239000007788 liquid Substances 0.000 description 4
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 3
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 3
- 238000001816 cooling Methods 0.000 description 3
- 239000000446 fuel Substances 0.000 description 3
- 239000007789 gas Substances 0.000 description 3
- 238000005259 measurement Methods 0.000 description 3
- -1 rare earth halide Chemical class 0.000 description 3
- 230000000630 rising effect Effects 0.000 description 3
- 229910052717 sulfur Inorganic materials 0.000 description 3
- 239000011593 sulfur Substances 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- BVKZGUZCCUSVTD-UHFFFAOYSA-L Carbonate Chemical compound [O-]C([O-])=O BVKZGUZCCUSVTD-UHFFFAOYSA-L 0.000 description 2
- 150000001340 alkali metals Chemical class 0.000 description 2
- 150000001341 alkaline earth metal compounds Chemical class 0.000 description 2
- 239000011362 coarse particle Substances 0.000 description 2
- 229910001873 dinitrogen Inorganic materials 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 150000004820 halides Chemical class 0.000 description 2
- 150000002431 hydrogen Chemical class 0.000 description 2
- 238000002156 mixing Methods 0.000 description 2
- LGQLOGILCSXPEA-UHFFFAOYSA-L nickel sulfate Chemical compound [Ni+2].[O-]S([O-])(=O)=O LGQLOGILCSXPEA-UHFFFAOYSA-L 0.000 description 2
- 229910000363 nickel(II) sulfate Inorganic materials 0.000 description 2
- KBJMLQFLOWQJNF-UHFFFAOYSA-N nickel(ii) nitrate Chemical compound [Ni+2].[O-][N+]([O-])=O.[O-][N+]([O-])=O KBJMLQFLOWQJNF-UHFFFAOYSA-N 0.000 description 2
- 239000012071 phase Substances 0.000 description 2
- 239000007774 positive electrode material Substances 0.000 description 2
- 238000012545 processing Methods 0.000 description 2
- 238000010298 pulverizing process Methods 0.000 description 2
- 239000010453 quartz Substances 0.000 description 2
- 238000005096 rolling process Methods 0.000 description 2
- 150000003839 salts Chemical class 0.000 description 2
- 238000001878 scanning electron micrograph Methods 0.000 description 2
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N silicon dioxide Inorganic materials O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- 238000005245 sintering Methods 0.000 description 2
- QGZKDVFQNNGYKY-UHFFFAOYSA-O Ammonium Chemical compound [NH4+] QGZKDVFQNNGYKY-UHFFFAOYSA-O 0.000 description 1
- 238000004438 BET method Methods 0.000 description 1
- 230000004931 aggregating effect Effects 0.000 description 1
- 238000004220 aggregation Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- 229910052783 alkali metal Inorganic materials 0.000 description 1
- 229910000272 alkali metal oxide Inorganic materials 0.000 description 1
- 229910052784 alkaline earth metal Inorganic materials 0.000 description 1
- 229910000287 alkaline earth metal oxide Inorganic materials 0.000 description 1
- 150000001342 alkaline earth metals Chemical class 0.000 description 1
- 239000011324 bead Substances 0.000 description 1
- 239000011230 binding agent Substances 0.000 description 1
- 239000003518 caustics Substances 0.000 description 1
- 239000003985 ceramic capacitor Substances 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000004020 conductor Substances 0.000 description 1
- 238000006114 decarboxylation reaction Methods 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 230000018044 dehydration Effects 0.000 description 1
- 238000006297 dehydration reaction Methods 0.000 description 1
- 239000007772 electrode material Substances 0.000 description 1
- 238000005187 foaming Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-M hydroxide Chemical compound [OH-] XLYOFNOQVPJJNP-UHFFFAOYSA-M 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 239000000463 material Substances 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 229910052987 metal hydride Inorganic materials 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000000465 moulding Methods 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
- 229920003023 plastic Polymers 0.000 description 1
- 239000004033 plastic Substances 0.000 description 1
- 238000007747 plating Methods 0.000 description 1
- 229920005749 polyurethane resin Polymers 0.000 description 1
- 229910052761 rare earth metal Inorganic materials 0.000 description 1
- 229910001404 rare earth metal oxide Inorganic materials 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
- 239000000243 solution Substances 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
- 239000004094 surface-active agent Substances 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
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- Manufacture Of Metal Powder And Suspensions Thereof (AREA)
- Powder Metallurgy (AREA)
Description
【０００１】
【発明の属する技術分野】
本発明は、多孔質の球状ニッケル粉末とその製造方法に関し、さらに詳しくは、電極形成用の導電粉末として好適な、所望の平均粒径と比表面積を有する多孔質の微細構造の球状ニッケル粉末とその製造方法に関する。特に、溶融塩型燃料電池やアルカリ２次電池用の電極材料分野、及び積層セラミックスコンデンサ内部電極等の厚膜導電体用導電ペースト分野で利用される球状ニッケル粉末として好適である。
【０００２】
【従来の技術】
従来、各種フィルター、燃料電池やアルカリ２次電池の電極基板等には、スポンジ状多孔質ニッケル金属板が使用されている。前記多孔質ニッケル金属板の製造方法としては、カーボニル法ニッケル粉を焼結する方法、ポリウレタン樹脂板にニッケルメッキ法で発泡状態を形成させる方法、酸化ニッケル粉末、ニッケル粉末、水溶性樹脂バインダー、可塑材、界面活性剤、揮発性有機溶剤及び水からなるスラリーを成形し、発泡させる方法等があり、その用途に応じてこれらの中から選ばれて用いられている。
【０００３】
しかしながら、近年アルカリ２次電池や燃料電池の性能の向上に伴ない、導電性の向上に対する要求がある。このために、スポンジ状多孔質ニッケル金属板の製造方法に対する新たな提案等がなされているが、この代替技術として導電性を有し、かつバラバラに崩れないで形状を維持できる機械的強度を有する多孔質の球状ニッケル粉末を用いた圧粉体又は焼結体が注目されている。この用途として、上記のような電極形成用の導電粉末として好適な、例えば平均粒径が５０μｍ以下で、多孔質の微細構造を有する球状ニッケル粉末が求められている。
【０００４】
従来、微粒のニッケル粉末の製造方法として、気相還元法、湿式還元法等が提案されており、代表的なニッケル粉末とその製造方法としては、以下のようなものが挙げられる。
（１）平均粒径が０．１〜１．０μｍ、タップ密度が所定のニッケル粉末で、塩化ニッケル蒸気の気相還元法によって製造する（例えば、特許文献１参照）。
（２）平均粒径が０．１〜１．０μｍ、硫黄含有率が０．０２〜１．０％のニッケル球状粒子で、塩化ニッケル蒸気の気相水素還元法で製造する（例えば、特許文献２参照）。
【０００５】
（３）粒径が０．１〜１．０μｍ、硫黄含有率が０．０５〜０．２％、かつ硫黄が主として表面部分に存在する球状ニッケル粉末で、硫黄を含有する雰囲気にて、塩化ニッケルの蒸気に気相還元反応を行わせることにより製造する（例えば、特許文献３参照）。
（４）平均粒径が０．２〜０．６μｍ、かつ平均粒径の２．５倍以上の粗粒子の存在率が個数規準で０．１％以下であるニッケル超微粉で、塩化ニッケル蒸気の気相水素還元法で製造する（例えば、特許文献４参照）。
（５）ＳＥＭ観察により測定した平均粒子径が１μｍ以下、特定の粒子密度、結晶子径であるニッケル粉末で、塩化ニッケル蒸気の気相水素還元法で製造する（例えば、特許文献５参照）。
【０００６】
（６）平均粒径が０．１〜２μｍの球状ニッケル粉末で、ニッケル化合物粉末とアルカリ土類金属化合物粉末を含む混合物を水素還元し、得られた還元生成物を湿式処理してニッケル粉末を製造する方法であり、さらに、混合工程でニッケル水溶液とアルカリ土類金属化合物の水溶液か粉末を混ぜアルカリで沈殿させ、固液分離して用いることもできる（例えば、特許文献６参照）。
（７）金属塩粉末とアルカリ金属、アルカリ土類金属又は希土類のハロゲン化物のうち少なくとも１種とを混合し、水素還元した後、前記ハロゲン化物の融点以上まで昇温し、得られた反応物を湿式処理してハロゲン化物を除去して、金属粉を製造する方法であり、さらに、混合において、アルカリ金属、アルカリ土類又は希土類の酸化物、水酸化物、炭酸化物等を添加することができる（例えば、特許文献７参照）。
【０００７】
これらの提案により、それぞれの用途に応じた分散性の良い球状ニッケル粉末を得ることができるが、これらの提案を含む従来技術では、上記の圧粉体又は焼結体に好適な、導電性を有し、かつバラバラに崩れないで形状を維持できる機械的強度を有する多孔質の球状ニッケル粉末を得ることができない。
以上の状況から、焼結体や圧粉体を形成してなる電極用の導電粉末として好適な、所望の平均粒径と比表面積を有する多孔質の微細構造の球状ニッケル粉末とその製造方法が求められている。
【０００８】
【特許文献１】
特開平０８−２４６００１号公報（第１頁、第２頁）
【特許文献２】
特開平１１−８０８１７号公報（第１〜３頁）
【特許文献３】
特開平１１−８０８１６号公報（第１〜３頁）
【特許文献４】
特開平１１−１８９８０１号公報（第１頁、第２頁）
【特許文献５】
特開２００１−２２０６０８号公報（第１頁、第２頁）
【特許文献６】
特開平１１−１４０５１３号公報（第１頁、第２頁）
【特許文献７】
特開平１１−２１６０３号公報（第１頁、第２頁）
【０００９】
【発明が解決しようとする課題】
本発明の目的は、上記の従来技術の問題点に鑑み、電極形成用の導電粉末として好適な、所望の平均粒径と比表面積を有する多孔質の微細構造の球状ニッケル粉末が高収率で得られる製造方法を提供することにある。
【００１０】
【課題を解決するための手段】
本発明者らは、上記目的を達成するために、焼結体や圧粉体の原料として好適な球状ニッケル粉末の製造方法について、鋭意研究を重ねた結果、特定のニッケル化合物を特定の条件で加熱処理した後、水素還元したところ、所望の平均粒径と比表面積を有する多孔質の微細構造の球状ニッケル粉末が高収率で得られることを見出し、本発明を完成した。
【００１１】
すなわち、本発明の第１の発明によれば、一次粒子が凝集して球状粒子を形成しているニッケル化合物を還元して多孔質の球状ニッケル粉末を製造する方法であって、
（１）前記ニッケル化合物を、中性又は酸化性雰囲気下３００〜５００℃、次いで８００〜１３００℃の二段階で加熱処理して酸化ニッケル粉末を生成する第１の工程、及び
（２）前記酸化ニッケル粉末を水素還元して金属ニッケル粉末を生成する第２の工程、を含むことを特徴とする球状ニッケル粉末の製造方法が提供される。
【００１２】
また、本発明の第２の発明によれば、第１の発明において、前記ニッケル化合物が、水酸化ニッケル、炭酸ニッケル又は塩基性炭酸ニッケルから選ばれる少なくとも１種であることを特徴とする球状ニッケル粉末の製造方法が提供される。
【００１３】
また、本発明の第３の発明によれば、第１又は２の発明の製造方法により得られる、平均粒径が１〜５０μｍ及び比表面積が０．１〜５．０ｍ２／ｇの範囲の所定値に制御される多孔質の微細構造を有する球状ニッケル粉末が提供される。
【００１４】
【発明の実施の形態】
以下、本発明の多孔質の球状ニッケル粉末とその製造方法を詳細に説明する。本発明の多孔質の球状ニッケル粉末の製造方法は、一次粒子が凝集して球状粒子を形成しているニッケル化合物を、中性又は酸化性雰囲気下３００〜５００℃、次いで８００〜１３００℃の二段階で加熱処理して酸化ニッケル粉末を生成する第１の工程、及び前記酸化ニッケル粉末を水素還元して金属ニッケル粉末を生成する第２の工程を含む製造方法であり、これによって一次粒子からなる多孔質の微細構造が形成され、かつ所望の平均粒径及び比表面積に制御することができるので、例えば、平均粒径が１〜５０μｍ及び比表面積が０．１〜５．０ｍ２／ｇの範囲の所定値に制御された、多孔質の微細構造を有する球状ニッケル粉末が高収率で得られる。
【００１５】
１．ニッケル化合物
本発明では、ニッケル原料として、一次粒子が凝集して球状粒子を形成している形態のニッケル化合物を用いることに重要な意義がある。これによって、一次粒子からなる多孔質の微細構造と同時にニッケル粉末の焼結性に大きく影響する粉末の粒径と形状の制御が行える。すなわち、所定の平均粒径と粒度分布の上記形態のニッケル化合物を用いて、所定条件での処理方法を行うことによって、所望の平均粒径、粒度分布、比表面積等の特性を有する、焼結体や圧粉体を形成してなる電極用として好適な球状粒子を得ることができる。
これに対して、例えば、上記の形態を持たない通常のニッケル化合物を用いた場合、微細構造が得られる低温度での還元では、粒径が微細で焼結性に問題が生ずる。一方粒径の制御が行える高温度での還元では、良好な微細構造が実現できない。
【００１６】
上記形態のニッケル化合物としては、ニッケル水素電池正極材料用水酸化ニッケル等、市販の多孔質の球状ニッケル化合物を用いることができる。上記形態のニッケル化合物の製造方法としては、特に限定されるものではなく、形態として一次粒子が凝集した球状粒子を形成できるニッケル化合物の製造方法が用いられる。例えば、水酸化ニッケル、炭酸ニッケル又は塩基性炭酸ニッケルの場合には、硫酸ニッケル、塩化ニッケル、硝酸ニッケル等の各種ニッケルを含む水溶液と、カ性アルカリ水溶液、炭酸アルカリ水溶液、又はアンモニウム水溶液から選ばれる少なくとも１種とを、液の供給速度、液の供給場所、液温度、ｐＨ、撹拌等を適正化した条件で反応させることによって所定の平均粒径と粒度分布の球状粒子が調製できる。
【００１７】
上記ニッケル化合物としては、特に限定されるものではなく、本発明の第１の工程での加熱温度で分解し、その特性上許容できる範囲内での不純物を含有する酸化ニッケルが得られる水酸化ニッケル、炭酸ニッケル、塩基性炭酸ニッケル、硝酸ニッケル等のニッケル化合物が使用されるが、その中で、特に多孔質の微細構造が得られる水酸化ニッケル、炭酸ニッケル又は塩基性炭酸ニッケルから選ばれる少なくとも１種が好ましく、水酸化ニッケル及び／又は塩基性炭酸ニッケルが特に好ましい。すなわち、水酸化ニッケル及び／又は塩基性炭酸ニッケルを用いた場合には、加熱過程での脱水や脱炭酸による微細孔の形成効果がより顕著になるからである。
【００１８】
これらの中で、特に、球状の水酸化ニッケルあるいは塩基性炭酸ニッケルとしては、０．０５〜０．１μｍの一次粒子を凝集させて、１〜１００μｍの平均粒径に調製されることが好ましく、５〜５０μｍの平均粒径に調製されることがさらに好ましい。
【００１９】
２．製造方法
（１）第１の工程
本発明の製造方法の第１の工程は、上記ニッケル化合物を、中性又は酸化性雰囲気下３００〜５００℃、次いで８００〜１３００℃の二段階で加熱処理して酸化ニッケル粉末を生成する工程である。
【００２０】
第１の工程では、上記ニッケル化合物を用いて、これを中性又は酸化性雰囲気下所定の温度で二段階で加熱処理することが重要である。しかも、前段の加熱処理で上記ニッケル化合物の分解反応を十分に行い、後段の加熱処理で通常水素還元が行われる温度よりも高い加熱温度を用いることが重要な意義がある。これによって、ニッケル化合物が熱分解して酸化物を生成する際に、多孔質の微細構造を有し、強固な球状の外郭構造の酸化ニッケル粉末が高収率で得られる。このため、次工程の水素還元に際しても強固な球状の外郭構造が維持できる。
すなわち、加熱処理において一気に高温まで昇温する方法では、昇温途中でニッケル化合物が急激に熱分解して、球状の外郭構造及び内部の微細構造が壊れ、微粉化し飛散する等で収率が低下する。そこで、前段の加熱処理でニッケル化合物を十分に熱分解した後、後段の高温での加熱処理で強固な球状の外郭構造の酸化ニッケル粉末を形成するようにする。
【００２１】
これに対して、通常の水素還元方法においては、昇温過程で原料のニッケル化合物を分解して、あるいは酸化して生成される酸化ニッケルを経て、それから還元してニッケル粉末を得る。しかし、この方法では、一次粒子が凝集して球状粒子を形成しているニッケル化合物を原料として用いても、生成される酸化ニッケルの外郭が脆弱であるので、水素還元に際して割れたり、崩れたりして外郭構造が壊れ、原料の球状粒子構造を維持した金属ニッケル粉末を形成できない。
【００２２】
上記加熱処理の前段の温度は、３００〜５００℃である。すなわち、前段の温度が３００℃未満では、ニッケル化合物が分解して酸化ニッケルを生成する反応が不十分であり、一方５００℃を超えるとニッケル化合物が急激に熱分解して球状の外郭構造及び内部の微細構造が壊れる。
【００２３】
上記加熱処理の後段の温度は、８００〜１３００℃であり、好ましくは８００〜９００℃である。すなわち、後段の温度が８００℃未満では、強固な球状の外郭構造の形成ができない。一方、１３００℃を超えると、比表面積が低下するので、高比表面積で多孔質の酸化ニッケル粉末が得られない。
【００２４】
ここで、使用するニッケル化合物の種類及び加熱処理装置に応じて、上記加熱処理の前段及び後段の温度範囲の中で所定の温度及び処理時間を選ぶことによって、平均粒径、粒度分布、比表面積等の特性を制御できる。また、加熱処理の前段から後段への昇温パターンは、特に限定されるものではなく、連続して、又は一旦冷却してから行ってもよい。すなわち、第１の工程では上記の各段階の加熱処理で各々所定の温度範囲で所定の処理時間を保持することが不可欠である。
【００２５】
上記加熱処理の雰囲気としては、中性又は酸化性雰囲気で行う。すなわち、還元性雰囲気では、金属ニッケルが生成するからである。
上記加熱処理で使用する加熱装置としては、特に限定されるものではなく、中性又は酸化性雰囲気に調整されたマッフル炉、ポット炉、管状炉、転動炉などが用いられる。
以上、本発明の製造方法の第１の工程により、所望の平均粒径と粒度分布、比表面積等の特性を有する一次粒子からなる多孔質の微細構造の球状酸化ニッケル粉末が得られる。
【００２６】
本発明の製造方法では、特に限定されるものではないが、必要によっては第２の工程に先立って、第１の工程によって得られる球状酸化ニッケル粉末を微粉砕処理できる。これによって、球状酸化ニッケル粉末の粒径を調整することができるので、得られる球状ニッケル粉末の粒径を制御することができる。上記微粉砕処理においては、特に限定されるものではないが、ボールミル、ビーズミル、アトライターミル、ジェットミル、スタンプミルなど市販の各種粉砕装置が用いられる。
【００２７】
（２）第２の工程
本発明の製造方法の第２の工程は、上記工程で得られる球状酸化ニッケル粉末を、水素雰囲気で加熱して水素還元し、球状の金属ニッケル粉末を生成する工程である。
第２の工程において、水素還元の加熱温度は、特に限定されるものではなく、３５０〜７００℃が好ましく、４５０〜６５０℃がさらに好ましい。すなわち、温度が３５０℃未満では、未還元の酸化ニッケルが残留し金属ニッケル粒子の酸素濃度が上昇する。一方７００℃を超えると、生成された金属ニッケル粒子同士の凝集によって粗大粒子が形成される。
ここで、第１の工程で得られる球状酸化ニッケルの性状及び使用する還元装置に応じて、前記加熱温度の範囲内で所定の温度及び処理時間を選ぶことによって、平均粒径、粒度分布、比表面積等の特性を制御できる。
【００２８】
第２の工程において用いる還元装置としては、特に限定されるものではなく、所定の濃度の水素雰囲気に調整されたマッフル炉、ポット炉、管状炉、転動炉などが用いられる。
以上、本発明の製造方法により、平均粒径、粒度分布、比表面積等の特性が所望値になるように制御された一次粒子からなる多孔質の微細構造の球状ニッケル粉末が得られる。
【００２９】
３．球状ニッケル粉末
上記製造方法で得られるニッケル粉末は、一次粒子からなる多孔質の微細構造を有する球状ニッケル粉末であって、平均粒径、粒度分布、比表面積等の特性が所望値になるように制御されて生成できるので、焼結体や圧粉体を形成してなる電極用の導電粉末として好適なニッケル粉末である。
【００３０】
本発明の球状ニッケル粉末と従来技術によるニッケル粉末の微細構造の違いを明確にするため、本発明の代表的な球状ニッケル粉末の形状と微細構造の一例と従来技術によるニッケル粉末の微細構造を図を用いて説明する。図１は、本発明の製造方法で得られる球状ニッケル粉末の走査型電子顕微鏡写真の一例を示す。また、図２は、本発明の製造方法で得られる代表的な球状ニッケル粒子（直径約１０μｍ）断面の電子顕微鏡写真を示す。また、図３は、不規則形状の粉末状水酸化ニッケル（平均粒径０．５μｍ）を水素還元して得た不規則形状ニッケル粒子（直径０．２〜１μｍ）断面の電子顕微鏡写真を示す。また、図４は、気相水素還元法で得られた球状ニッケル粒子（直径約０．５μｍ）断面の電子顕微鏡写真を示す。
【００３１】
図１より、本発明では１〜５０μｍの球状粒子が非常に優れた分散状態で存在することが分る。なお、本発明の球状ニッケル粉末の平均粒径と粒度分布は、原料のニッケル化合物に大きく依存する。また、図２〜４より、本発明の球状粒子内部は微細な１次粒子からなる多孔質の微細構造が形成され、均一組織である従来のニッケル粉末と大きく異なることが分る。
【００３２】
例えば、多孔質の度合を断面画像を２階調化して画像解析装置で面積分析して得られた空隙率で表すと、従来のニッケル粉末が１０％以下であるのに対して、本発明の球状ニッケル粉末の空隙率は２０〜８０％、好ましくは３０〜７０％、さらに好ましくは４０〜６０％である。
【００３３】
上記ニッケル粉末の中で、特に、平均粒径が１〜５０μｍ及び比表面積が０．１〜５．０ｍ２／ｇの範囲の所定値に制御された、微細な１次粒子からなる多孔質の球状ニッケル粉末が、上記電極形成用として好ましく用いられる。
【００３４】
【実施例】
以下に、本発明の実施例及び比較例によって本発明をさらに詳細に説明するが、本発明は、これらの実施例によってなんら限定されるものではない。なお、実施例及び比較例で用いた酸素の分析方法と粉末収率、粒子形状、平均粒径、粉末の微細構造、及び比表面積の評価方法は、以下の通りである。
（１）酸素の分析：抵抗加熱伝導度分析法で行った。
（２）粉末収率の測定：使用原料のＮｉ量に対して回収されたＮｉ粉末量から算出した。
（３）粒子形状の評価：走査型電子顕微鏡観察で行った。
（４）平均粒径の測定：走査型電子顕微鏡観察で行った。
（５）粉末の微細構造の評価：断面の電子顕微鏡観察で行った。
（６）比表面積の測定：ＢＥＴ法で行った。
【００３５】
また、実施例及び比較例で用いたニッケル化合物は、以下の通りである。
［ニッケル化合物］
［Ａ］：球状水酸化ニッケル粉末（住友金属鉱山（株）製、ニッケル水素電池正極材料用水酸化ニッケル、平均粒径８μｍ）。
［Ｂ］：球状塩基性炭酸ニッケル粉末（住友金属鉱山（製）、Ｇ−炭酸ニッケル、平均粒径１０μｍ）
［Ｃ］：硫酸ニッケル水溶液と水酸化ナトリウム水溶液を反応させて得た水酸化ニッケルを粉砕して得た不規則形状の粉末状水酸化ニッケル（平均粒径０．５μｍ）。
【００３６】
（実施例１）
ニッケル化合物［Ａ］を用いて、まず、この９５０ｇを石英製ボートに入れて、割型管状炉にて空気気流中（流量：２．０Ｌ／ｍｉｎ）で昇温して下記の所定温度で各２時間加熱処理を行った。
次いで、前記の炉の温度を室温まで冷却した後、窒素ガスを２．０Ｌ／ｍｉｎの流量で装入しながら昇温して所定温度で水素ガスに切り替えて、下記の条件で水素還元を行った。還元終了後、装入ガスを再度窒素ガスに切り替えて冷却を行ない、石英製ボートを前記の炉から取り出しニッケル粉末を得た。その後、ニッケル粉末の酸素濃度の分析、粒子形状の評価並びに粉末収率、平均粒径、粉末の微細構造及び比表面積を測定した。結果を表１に示す。なお、断面画像から求めた空隙率は４９．６％であった。
【００３７】
［加熱処理の温度条件］
二段階加熱処理で前段は加熱温度５００℃、後段は加熱温度９００℃。
［水素還元条件］
（１）還元温度：６００℃、（２）還元時間：３時間、及び（３）水素ガス流量：３．６Ｌ／ｍｉｎ。
【００３８】
（実施例２）
ニッケル化合物の装入量を９８０ｇとし、下記の加熱処理の温度条件及び水素還元条件で行った以外は実施例１と同様に行い、ニッケル粉末を得た。その後、ニッケル粉末の酸素濃度の分析、粒子形状の評価並びに粉末収率、平均粒径、粉末の微細構造及び比表面積を測定した。結果を表１に示す。
【００３９】
［加熱処理の温度条件］
二段階加熱処理で前段は加熱温度３００℃、後段は加熱温度９００℃。
［水素還元条件］
（１）還元温度：６００℃、（２）還元時間：３時間、及び（３）水素ガス流量：３．９Ｌ／ｍｉｎ。
【００４０】
（実施例３）
ニッケル化合物［Ｂ］を用いて、下記の加熱処理の温度条件及び水素還元条件で行った以外は実施例１と同様に行い、ニッケル粉末を得た。その後、ニッケル粉末の酸素濃度の分析、粒子形状の評価並びに粉末収率、平均粒径、粉末の微細構造及び比表面積を測定した。結果を表１に示す。
【００４１】
［加熱処理の温度条件］
二段階加熱処理で前段は加熱温度３００℃、後段は加熱温度８００℃。
［水素還元条件］
（１）還元温度：６００℃、（２）還元時間：３時間、及び（３）水素ガス流量：３．０Ｌ／ｍｉｎ。
【００４２】
（比較例１）
ニッケル化合物の装入量を１１５ｇとし、下記の加熱処理の温度条件及び水素還元条件で行った以外は実施例１と同様に行い、ニッケル粉末を得た。その後、ニッケル粉末の酸素濃度の分析、粒子形状の評価並びに粉末収率、平均粒径、粉末の微細構造及び比表面積を測定した。結果を表１に示す。
【００４３】
［加熱処理の温度条件］
一段階の加熱処理で、加熱温度は９００℃。
［水素還元条件］
（１）還元温度：４５０℃、（２）還元時間：３時間、及び（３）水素ガス流量：０．８Ｌ／ｍｉｎ。
【００４４】
（比較例２）
ニッケル化合物の装入量を７２３ｇとし、下記の加熱処理の温度条件及び水素還元条件で行った以外は実施例１と同様に行い、ニッケル粉末を得た。その後、ニッケル粉末の酸素濃度の分析、粒子形状の評価並びに粉末収率、平均粒径、粉末の微細構造及び比表面積を測定した。結果を表１に示す。
【００４５】
［加熱処理の温度条件］
一段階の加熱処理で、加熱温度は９００℃。
［水素還元条件］
（１）還元温度：６００℃、（２）還元時間：２時間、及び（３）水素ガス流量：４．４Ｌ／ｍｉｎ。
【００４６】
（比較例３）
ニッケル化合物［Ｃ］を用いた以外は実施例１と同様に行い、ニッケル粉末を得た。その後、ニッケル粉末の酸素濃度の分析、粒子形状の評価並びに粉末収率、平均粒径、粉末の微細構造及び比表面積を測定した。結果を表１に示す。
【００４７】
【表１】
表１より、実施例１〜３では、ニッケル化合物として一次粒子が凝集して球状粒子を形成している球状ニッケル化合物粉末を用い、かつ第１の工程での特定の加熱温度による二段階の加熱処理及び第２の工程で本発明の方法に従って行われたので、平均粒径が１〜５０μｍ及び比表面積が０．１〜５．０ｍ２／ｇの範囲で特性が制御され、焼結体や圧粉体を形成してなる電極用の導電粉末として好適な多孔質の球状ニッケル粉末が高収率で得られることが分かる。
【００４９】
これに対して、比較例１〜３では、ニッケル化合物の粒子形態と加熱処理の温度条件のいずれかがこれらの条件に合わないので、粉末の収率、粒子形状、又は粉末の微細構造によって満足すべき結果が得られないことが分かる。
【００５０】
【発明の効果】
以上説明したように、本発明の多孔質の球状ニッケル粉末とその製造方法は、電極形成用の導電粉末として好適な、所望の平均粒径と比表面積を有する多孔質の微細構造の球状ニッケル粉末、及びそれが高収率で得られる製造方法であり、その工業的価値は極めて大きい。
【図面の簡単な説明】
【図１】本発明の製造方法で得られる球状ニッケル粉末の走査型電子顕微鏡写真の一例である。
【図２】本発明の製造方法で得られる代表的な球状ニッケル粒子（直径約１０μｍ）断面の電子顕微鏡写真である。
【図３】不規則形状の粉末状水酸化ニッケルを水素還元して得た不規則形状ニッケル粒子（直径０．２〜１μｍ）断面の電子顕微鏡写真である。
【図４】気相水素還元法で得られた球状ニッケル粒子（直径約０．５μｍ）断面の電子顕微鏡写真である。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a porous spherical nickel powder and a method for producing the same, and more particularly, a porous fine-structured spherical nickel powder having a desired average particle diameter and specific surface area, which is suitable as a conductive powder for electrode formation, and It relates to the manufacturing method. In particular, it is suitable as a spherical nickel powder used in the field of electrode materials for molten salt fuel cells and alkaline secondary batteries, and the field of conductive paste for thick film conductors such as multilayer ceramic capacitor internal electrodes.
[0002]
[Prior art]
Conventionally, sponge-like porous nickel metal plates have been used for various filters, electrode substrates for fuel cells and alkaline secondary batteries, and the like. The method for producing the porous nickel metal plate includes a method of sintering carbonyl nickel powder, a method of forming a foamed state by a nickel plating method on a polyurethane resin plate, nickel oxide powder, nickel powder, water-soluble resin binder, plastic There are methods such as molding and foaming a slurry composed of a material, a surfactant, a volatile organic solvent, and water, and these are selected and used depending on the application.
[0003]
However, in recent years, with improvements in the performance of alkaline secondary batteries and fuel cells, there is a demand for improved conductivity. For this reason, new proposals have been made for a method for producing a sponge-like porous nickel metal plate, but as an alternative technique, it has electrical conductivity and mechanical strength that can maintain its shape without breaking apart. A green compact or sintered body using a porous spherical nickel powder has attracted attention. For this purpose, there is a demand for spherical nickel powder having an average particle diameter of 50 μm or less and having a porous fine structure, which is suitable as the conductive powder for electrode formation as described above.
[0004]
Conventionally, a vapor phase reduction method, a wet reduction method, and the like have been proposed as a method for producing a fine nickel powder, and typical nickel powders and production methods thereof include the following.
(1) A nickel powder having an average particle diameter of 0.1 to 1.0 μm and a tap density of a predetermined value is manufactured by a vapor phase reduction method of nickel chloride vapor (see, for example, Patent Document 1).
(2) Nickel spherical particles having an average particle diameter of 0.1 to 1.0 μm and a sulfur content of 0.02 to 1.0%, which are produced by a vapor phase hydrogen reduction method of nickel chloride vapor (for example, patent document) 2).
[0005]
(3) A spherical nickel powder in which the particle size is 0.1 to 1.0 μm, the sulfur content is 0.05 to 0.2%, and sulfur is mainly present in the surface portion. It manufactures by making vapor phase reduction reaction to the vapor | steam of nickel (for example, refer patent document 3).
(4) Nickel chloride vapor, which is an ultrafine nickel powder having an average particle size of 0.2 to 0.6 μm and a presence ratio of coarse particles having an average particle size of 2.5 times or more of 0.1% or less on the number basis. (See, for example, Patent Document 4).
(5) A nickel powder having an average particle size of 1 μm or less, a specific particle density and a crystallite size measured by SEM observation is produced by a vapor phase hydrogen reduction method of nickel chloride vapor (see, for example, Patent Document 5).
[0006]
(6) A spherical nickel powder having an average particle diameter of 0.1 to 2 μm, a mixture containing the nickel compound powder and the alkaline earth metal compound powder is reduced by hydrogen, and the resulting reduction product is wet-treated to obtain a nickel powder. In addition, a nickel aqueous solution and an alkaline earth metal compound aqueous solution or powder are mixed in a mixing step, precipitated with an alkali, and solid-liquid separated (for example, see Patent Document 6).
(7) A metal salt powder and at least one of an alkali metal, alkaline earth metal or rare earth halide are mixed, reduced with hydrogen, and then heated to a temperature equal to or higher than the melting point of the halide. Is a method of producing a metal powder by removing a halide by wet treatment, and further, in mixing, an alkali metal, alkaline earth or rare earth oxide, hydroxide, carbonate, etc. may be added. (For example, refer to Patent Document 7).
[0007]
With these proposals, it is possible to obtain a spherical nickel powder with good dispersibility according to each application. However, in the prior art including these proposals, the conductivity suitable for the above-mentioned green compact or sintered body is obtained. It is not possible to obtain a porous spherical nickel powder having a mechanical strength that can be maintained without breaking apart.
From the above situation, a porous fine-structured spherical nickel powder having a desired average particle diameter and specific surface area, which is suitable as a conductive powder for an electrode formed of a sintered body or a green compact, and a method for producing the same It has been demanded.
[0008]
[Patent Document 1]
JP 08-246001 (first page, second page)
[Patent Document 2]
Japanese Patent Laid-Open No. 11-80817 (pages 1 to 3)
[Patent Document 3]
Japanese Patent Laid-Open No. 11-80816 (pages 1 to 3)
[Patent Document 4]
JP-A-11-189801 (first page, second page)
[Patent Document 5]
Japanese Patent Laid-Open No. 2001-220608 (first page, second page)
[Patent Document 6]
JP-A-11-140513 (first page, second page)
[Patent Document 7]
JP 11-21603 A (first page, second page)
[0009]
[Problems to be solved by the invention]
In view of the above-mentioned problems of the prior art, an object of the present invention is to obtain a porous microstructured spherical nickel powder having a desired average particle size and specific surface area, which is suitable as a conductive powder for electrode formation, in a high yield. It is in providing the manufacturing method obtained.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, the present inventors have conducted extensive research on a method for producing a spherical nickel powder suitable as a raw material for sintered bodies and green compacts. As a result, specific nickel compounds have been produced under specific conditions. As a result of hydrogen reduction after heat treatment, it was found that a porous fine-structured spherical nickel powder having a desired average particle diameter and specific surface area can be obtained in a high yield, and the present invention was completed.
[0011]
That is, according to the first aspect of the present invention, a method for producing a porous spherical nickel powder by reducing a nickel compound in which primary particles aggregate to form spherical particles,
(1) a first step of producing a nickel oxide powder by heat-treating the nickel compound in two stages of 300 to 500 ° C. and then 800 to 1300 ° C. in a neutral or oxidizing atmosphere; and (2) the oxidation There is provided a method for producing a spherical nickel powder, comprising a second step of producing a metallic nickel powder by hydrogen reduction of the nickel powder.
[0012]
According to a second aspect of the present invention, in the first aspect, the nickel compound is at least one selected from nickel hydroxide, nickel carbonate, or basic nickel carbonate, and the spherical nickel is characterized in that A method for producing a powder is provided.
[0013]
Moreover, according to the 3rd invention of this invention, the average particle diameter obtained by the manufacturing method of the 1st or 2nd invention is 1-50 micrometers, and a specific surface area is the range of 0.1-5.0 m < 2 > / g. A spherical nickel powder having a porous microstructure controlled to a predetermined value is provided.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the porous spherical nickel powder of the present invention and the production method thereof will be described in detail. The method for producing a porous spherical nickel powder of the present invention comprises a nickel compound in which primary particles are aggregated to form spherical particles at a temperature of 300 to 500 ° C. and then 800 to 1300 ° C. in a neutral or oxidizing atmosphere. It is a manufacturing method including a first step of producing nickel oxide powder by heat treatment in stages and a second step of producing a nickel metal powder by hydrogen reduction of the nickel oxide powder, thereby comprising primary particles Since a porous fine structure is formed and can be controlled to a desired average particle diameter and specific surface area, for example, the average particle diameter is 1 to 50 μm and the specific surface area is 0.1 to 5.0 m 2 / g. A spherical nickel powder having a porous microstructure controlled to a predetermined value within the range can be obtained in high yield.
[0015]
1. Nickel Compound In the present invention, it is important to use a nickel compound in a form in which primary particles are aggregated to form spherical particles as a nickel raw material. This makes it possible to control the particle size and shape of the powder, which has a large influence on the sinterability of the nickel powder as well as the porous fine structure composed of primary particles. That is, by using a nickel compound of the above-mentioned form having a predetermined average particle size and particle size distribution, a sintering method having characteristics such as a desired average particle size, particle size distribution, specific surface area, etc. by performing a treatment method under predetermined conditions Spherical particles suitable for an electrode formed with a body or a green compact can be obtained.
On the other hand, for example, when an ordinary nickel compound not having the above-described form is used, reduction at a low temperature at which a fine structure is obtained causes a problem in the sinterability because the particle size is fine. On the other hand, reduction at a high temperature where the particle size can be controlled cannot achieve a good microstructure.
[0016]
As a nickel compound of the said form, commercially available porous spherical nickel compounds, such as nickel hydroxide for nickel hydrogen battery positive electrode materials, can be used. The method for producing the nickel compound of the above form is not particularly limited, and a method for producing a nickel compound capable of forming spherical particles in which primary particles are aggregated is used. For example, in the case of nickel hydroxide, nickel carbonate, or basic nickel carbonate, it is selected from aqueous solutions containing various nickels such as nickel sulfate, nickel chloride, nickel nitrate, caustic alkaline aqueous solution, alkaline carbonate aqueous solution, or aqueous ammonium solution. Spherical particles having a predetermined average particle size and particle size distribution can be prepared by reacting at least one kind under conditions that optimize the liquid supply rate, the liquid supply location, the liquid temperature, pH, stirring, and the like.
[0017]
The nickel compound is not particularly limited, and nickel hydroxide that can be decomposed at the heating temperature in the first step of the present invention to obtain nickel oxide containing impurities within an acceptable range in its characteristics is obtained. Nickel compounds such as nickel carbonate, basic nickel carbonate, and nickel nitrate are used, and among them, at least one selected from nickel hydroxide, nickel carbonate, or basic nickel carbonate, in particular, a porous microstructure can be obtained. Species are preferred, with nickel hydroxide and / or basic nickel carbonate being particularly preferred. That is, when nickel hydroxide and / or basic nickel carbonate is used, the effect of forming micropores by dehydration or decarboxylation during the heating process becomes more prominent.
[0018]
Among these, in particular, spherical nickel hydroxide or basic nickel carbonate is preferably prepared by aggregating primary particles of 0.05 to 0.1 μm to an average particle diameter of 1 to 100 μm, More preferably, the average particle diameter is 5 to 50 μm.
[0019]
2. Production Method (1) First Step In the first step of the production method of the present invention, the nickel compound is heated in two steps of 300 to 500 ° C. and then 800 to 1300 ° C. in a neutral or oxidizing atmosphere. And producing nickel oxide powder.
[0020]
In the first step, it is important to heat-treat the nickel compound in two steps at a predetermined temperature in a neutral or oxidizing atmosphere. In addition, it is important to sufficiently perform the decomposition reaction of the nickel compound in the preceding heat treatment and to use a heating temperature higher than the temperature at which hydrogen reduction is normally performed in the subsequent heat treatment. Thereby, when the nickel compound is thermally decomposed to produce an oxide, a nickel oxide powder having a porous fine structure and a strong spherical outer structure can be obtained in a high yield. For this reason, a strong spherical outer structure can be maintained in the subsequent hydrogen reduction.
That is, in the method of heating to a high temperature at a stretch in the heat treatment, the nickel compound is rapidly pyrolyzed during the temperature rising, the spherical outer structure and the internal fine structure are broken, pulverized and scattered, and the yield is reduced. To do. Therefore, after the nickel compound is sufficiently thermally decomposed by the heat treatment at the former stage, the nickel oxide powder having a strong spherical outer structure is formed by the heat treatment at the subsequent stage at a high temperature.
[0021]
On the other hand, in a normal hydrogen reduction method, the nickel compound as a raw material is decomposed in the temperature rising process or passed through nickel oxide produced by oxidation, and then reduced to obtain nickel powder. However, in this method, even when a nickel compound in which primary particles are aggregated to form spherical particles is used as a raw material, the outer shape of the produced nickel oxide is fragile, so that it is cracked or collapsed during hydrogen reduction. As a result, the outer structure is broken, and metallic nickel powder that maintains the spherical particle structure of the raw material cannot be formed.
[0022]
The temperature before the heat treatment is 300 to 500 ° C. That is, when the temperature of the previous stage is less than 300 ° C., the reaction of the nickel compound being decomposed to produce nickel oxide is insufficient, while when it exceeds 500 ° C., the nickel compound is rapidly pyrolyzed to form a spherical outer structure and internal structure. Breaks the microstructure.
[0023]
The temperature after the heat treatment is 800 to 1300 ° C, preferably 800 to 900 ° C. That is, when the temperature at the latter stage is less than 800 ° C., a strong spherical outer structure cannot be formed. On the other hand, when the temperature exceeds 1300 ° C., the specific surface area decreases, so that a porous nickel oxide powder having a high specific surface area cannot be obtained.
[0024]
Here, depending on the type of nickel compound used and the heat treatment apparatus, the average particle size, particle size distribution, specific surface area can be selected by selecting a predetermined temperature and treatment time within the temperature range of the former stage and the latter stage of the heat treatment. Etc. can be controlled. Moreover, the temperature rising pattern from the front | former stage of a heat processing to a back | latter stage is not specifically limited, You may carry out after cooling continuously or once. That is, in the first process, it is indispensable to maintain a predetermined processing time in a predetermined temperature range in each of the above-described heat treatments.
[0025]
The atmosphere for the heat treatment is a neutral or oxidizing atmosphere. In other words, metallic nickel is generated in a reducing atmosphere.
The heating device used in the heat treatment is not particularly limited, and a muffle furnace, a pot furnace, a tubular furnace, a rolling furnace and the like adjusted to a neutral or oxidizing atmosphere are used.
As described above, the first step of the production method of the present invention provides a porous fine-structure spherical nickel oxide powder composed of primary particles having characteristics such as a desired average particle size, particle size distribution, and specific surface area.
[0026]
Although it does not specifically limit in the manufacturing method of this invention, The spherical nickel oxide powder obtained by a 1st process can be pulverized before the 2nd process as needed. Thereby, since the particle diameter of spherical nickel oxide powder can be adjusted, the particle diameter of the obtained spherical nickel powder can be controlled. The fine pulverization treatment is not particularly limited, and various commercially available pulverizers such as a ball mill, a bead mill, an attritor mill, a jet mill, and a stamp mill are used.
[0027]
(2) Second step The second step of the production method of the present invention is a step in which the spherical nickel oxide powder obtained in the above step is heated in a hydrogen atmosphere and hydrogen reduced to produce a spherical metallic nickel powder. is there.
In the second step, the heating temperature for hydrogen reduction is not particularly limited, and is preferably 350 to 700 ° C, more preferably 450 to 650 ° C. That is, when the temperature is lower than 350 ° C., unreduced nickel oxide remains and the oxygen concentration of the metallic nickel particles increases. On the other hand, when the temperature exceeds 700 ° C., coarse particles are formed by aggregation of the generated metallic nickel particles.
Here, depending on the properties of the spherical nickel oxide obtained in the first step and the reducing apparatus to be used, by selecting a predetermined temperature and treatment time within the range of the heating temperature, the average particle size, particle size distribution, ratio Properties such as surface area can be controlled.
[0028]
The reducing device used in the second step is not particularly limited, and a muffle furnace, a pot furnace, a tubular furnace, a rolling furnace and the like adjusted to a hydrogen atmosphere with a predetermined concentration are used.
As described above, by the production method of the present invention, a porous fine-structure spherical nickel powder composed of primary particles whose properties such as average particle size, particle size distribution, and specific surface area are controlled to have desired values can be obtained.
[0029]
3. Spherical nickel powder The nickel powder obtained by the above production method is a spherical nickel powder having a porous fine structure composed of primary particles, so that characteristics such as average particle size, particle size distribution, and specific surface area become desired values. Since it can be generated by being controlled, it is a nickel powder suitable as a conductive powder for electrodes formed by forming a sintered body or a green compact.
[0030]
In order to clarify the difference in the microstructure between the spherical nickel powder of the present invention and the nickel powder according to the prior art, an example of the shape and microstructure of a typical spherical nickel powder according to the present invention and the microstructure of the nickel powder according to the prior art are illustrated. Will be described. FIG. 1 shows an example of a scanning electron micrograph of spherical nickel powder obtained by the production method of the present invention. FIG. 2 shows an electron micrograph of a cross section of typical spherical nickel particles (diameter: about 10 μm) obtained by the production method of the present invention. FIG. 3 shows an electron micrograph of a cross section of irregularly shaped nickel particles (diameter 0.2 to 1 μm) obtained by hydrogen reduction of irregularly shaped powdered nickel hydroxide (average particle size 0.5 μm). . FIG. 4 shows an electron micrograph of a cross section of spherical nickel particles (diameter: about 0.5 μm) obtained by the gas phase hydrogen reduction method.
[0031]
From FIG. 1, it can be seen that spherical particles of 1 to 50 μm are present in a very excellent dispersed state in the present invention. The average particle size and particle size distribution of the spherical nickel powder of the present invention greatly depend on the raw material nickel compound. 2 to 4, it can be seen that the inside of the spherical particles of the present invention is formed with a porous fine structure composed of fine primary particles, which is greatly different from the conventional nickel powder having a uniform structure.
[0032]
For example, when the degree of porosity is represented by the porosity obtained by converting the cross-sectional image into two gradations and analyzing the area with an image analyzer, the conventional nickel powder is 10% or less, whereas The porosity of the spherical nickel powder is 20 to 80%, preferably 30 to 70%, more preferably 40 to 60%.
[0033]
Among the above nickel powders, in particular, porous particles composed of fine primary particles whose average particle diameter is controlled to a predetermined value in a range of 1 to 50 μm and a specific surface area of 0.1 to 5.0 m 2 / g. Spherical nickel powder is preferably used for forming the electrode.
[0034]
【Example】
Hereinafter, the present invention will be described in more detail by way of examples and comparative examples of the present invention, but the present invention is not limited to these examples. In addition, the analysis method of oxygen used by the Example and the comparative example, and the evaluation method of a powder yield, particle shape, an average particle diameter, the fine structure of a powder, and a specific surface area are as follows.
(1) Analysis of oxygen: The resistance heating conductivity analysis was performed.
(2) Measurement of powder yield: It was calculated from the amount of Ni powder recovered relative to the amount of Ni in the raw material used.
(3) Evaluation of particle shape: It was performed by scanning electron microscope observation.
(4) Measurement of average particle diameter: It was carried out by observation with a scanning electron microscope.
(5) Evaluation of fine structure of powder: The cross section was observed with an electron microscope.
(6) Measurement of specific surface area: The BET method was used.
[0035]
The nickel compounds used in the examples and comparative examples are as follows.
[Nickel compounds]
[A]: Spherical nickel hydroxide powder (manufactured by Sumitomo Metal Mining Co., Ltd., nickel hydroxide for nickel metal hydride battery positive electrode material, average particle size 8 μm).
[B]: Spherical basic nickel carbonate powder (Sumitomo Metal Mining Co., Ltd., G-nickel carbonate, average particle size 10 μm)
[C]: Irregularly shaped powdered nickel hydroxide (average particle size 0.5 μm) obtained by pulverizing nickel hydroxide obtained by reacting a nickel sulfate aqueous solution and a sodium hydroxide aqueous solution.
[0036]
Example 1
Using the nickel compound [A], first, 950 g of this was put into a quartz boat and heated in an air stream (flow rate: 2.0 L / min) in a split-type tubular furnace, and at each of the following predetermined temperatures. Heat treatment was performed for 2 hours.
Next, after cooling the temperature of the furnace to room temperature, the temperature was raised while charging nitrogen gas at a flow rate of 2.0 L / min and switched to hydrogen gas at a predetermined temperature to perform hydrogen reduction under the following conditions. It was. After the reduction, the charging gas was switched to nitrogen gas again for cooling, and the quartz boat was taken out of the furnace to obtain nickel powder. Thereafter, analysis of the oxygen concentration of the nickel powder, evaluation of the particle shape, powder yield, average particle diameter, powder microstructure and specific surface area were measured. The results are shown in Table 1. The porosity determined from the cross-sectional image was 49.6%.
[0037]
[Temperature conditions for heat treatment]
In the two-stage heat treatment, the first stage is a heating temperature of 500 ° C., and the second stage is a heating temperature of 900 ° C.
[Hydrogen reduction conditions]
(1) Reduction temperature: 600 ° C., (2) Reduction time: 3 hours, and (3) Hydrogen gas flow rate: 3.6 L / min.
[0038]
(Example 2)
A nickel powder was obtained in the same manner as in Example 1 except that the amount of the nickel compound charged was 980 g, and the heat treatment was performed under the following temperature conditions and hydrogen reduction conditions. Thereafter, analysis of the oxygen concentration of the nickel powder, evaluation of the particle shape, powder yield, average particle diameter, powder microstructure and specific surface area were measured. The results are shown in Table 1.
[0039]
[Temperature conditions for heat treatment]
In the two-stage heat treatment, the first stage is a heating temperature of 300 ° C., and the second stage is a heating temperature of 900 ° C.
[Hydrogen reduction conditions]
(1) Reduction temperature: 600 ° C., (2) Reduction time: 3 hours, and (3) Hydrogen gas flow rate: 3.9 L / min.
[0040]
(Example 3)
The nickel compound [B] was used in the same manner as in Example 1 except that the nickel powder [B] was used except that it was performed under the temperature condition and hydrogen reduction condition of the following heat treatment to obtain a nickel powder. Thereafter, analysis of the oxygen concentration of the nickel powder, evaluation of the particle shape, powder yield, average particle diameter, powder microstructure and specific surface area were measured. The results are shown in Table 1.
[0041]
[Temperature conditions for heat treatment]
In the two-stage heat treatment, the first stage is a heating temperature of 300 ° C., and the second stage is a heating temperature of 800 ° C.
[Hydrogen reduction conditions]
(1) Reduction temperature: 600 ° C., (2) Reduction time: 3 hours, and (3) Hydrogen gas flow rate: 3.0 L / min.
[0042]
(Comparative Example 1)
A nickel powder was obtained in the same manner as in Example 1 except that the amount of the nickel compound charged was 115 g, and the heat treatment was performed under the temperature conditions and hydrogen reduction conditions described below. Thereafter, analysis of the oxygen concentration of the nickel powder, evaluation of the particle shape, powder yield, average particle diameter, powder microstructure and specific surface area were measured. The results are shown in Table 1.
[0043]
[Temperature conditions for heat treatment]
The heating temperature is 900 ° C. in one stage heat treatment.
[Hydrogen reduction conditions]
(1) Reduction temperature: 450 ° C., (2) Reduction time: 3 hours, and (3) Hydrogen gas flow rate: 0.8 L / min.
[0044]
(Comparative Example 2)
A nickel powder was obtained in the same manner as in Example 1 except that the amount of the nickel compound charged was 723 g and the heat treatment was performed under the following temperature conditions and hydrogen reduction conditions. Thereafter, analysis of the oxygen concentration of the nickel powder, evaluation of the particle shape, powder yield, average particle diameter, powder microstructure and specific surface area were measured. The results are shown in Table 1.
[0045]
[Temperature conditions for heat treatment]
The heating temperature is 900 ° C. in one stage heat treatment.
[Hydrogen reduction conditions]
(1) Reduction temperature: 600 ° C., (2) Reduction time: 2 hours, and (3) Hydrogen gas flow rate: 4.4 L / min.
[0046]
(Comparative Example 3)
A nickel powder was obtained in the same manner as in Example 1 except that the nickel compound [C] was used. Thereafter, analysis of the oxygen concentration of the nickel powder, evaluation of the particle shape, powder yield, average particle diameter, powder microstructure and specific surface area were measured. The results are shown in Table 1.
[0047]
[Table 1]
As shown in Table 1, in Examples 1 to 3, a spherical nickel compound powder in which primary particles are aggregated to form spherical particles is used as the nickel compound, and two-stage heating is performed at a specific heating temperature in the first step. Since the treatment and the second step were carried out according to the method of the present invention, the characteristics were controlled in the range of an average particle size of 1 to 50 μm and a specific surface area of 0.1 to 5.0 m 2 / g. It can be seen that a porous spherical nickel powder suitable as a conductive powder for an electrode formed with a green compact can be obtained in a high yield.
[0049]
On the other hand, in Comparative Examples 1 to 3, since either the particle form of the nickel compound or the temperature condition of the heat treatment does not meet these conditions, it is satisfied by the powder yield, the particle shape, or the fine structure of the powder. It turns out that the result which should be cannot be obtained.
[0050]
【The invention's effect】
As described above, the porous spherical nickel powder of the present invention and the method for producing the same are suitable as a conductive powder for electrode formation, and have a porous microstructure nickel powder having a desired average particle diameter and specific surface area. , And a production method that can be obtained in a high yield, and its industrial value is extremely large.
[Brief description of the drawings]
FIG. 1 is an example of a scanning electron micrograph of spherical nickel powder obtained by the production method of the present invention.
FIG. 2 is an electron micrograph of a cross section of typical spherical nickel particles (diameter: about 10 μm) obtained by the production method of the present invention.
FIG. 3 is an electron micrograph of a cross section of irregularly shaped nickel particles (diameter 0.2 to 1 μm) obtained by hydrogen reduction of irregularly shaped powdered nickel hydroxide.
FIG. 4 is an electron micrograph of a cross section of spherical nickel particles (diameter: about 0.5 μm) obtained by a gas phase hydrogen reduction method.
Claims (3)
（１）前記ニッケル化合物を、中性又は酸化性雰囲気下３００〜５００℃、次いで８００〜１３００℃の二段階で加熱処理して酸化ニッケル粉末を生成する第１の工程、及び
（２）前記酸化ニッケル粉末を水素還元して金属ニッケル粉末を生成する第２の工程、を含むことを特徴とする球状ニッケル粉末の製造方法。A method for producing a porous spherical nickel powder by reducing a nickel compound in which primary particles are aggregated to form spherical particles,
(1) a first step of producing a nickel oxide powder by heat-treating the nickel compound in two stages of 300 to 500 ° C. and then 800 to 1300 ° C. in a neutral or oxidizing atmosphere; and (2) the oxidation A method for producing spherical nickel powder, comprising a second step of producing nickel metal powder by hydrogen reduction of nickel powder.
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| CN107150127A (en) * | 2016-03-04 | 2017-09-12 | 荆门市格林美新材料有限公司 | The preparation method of spherical cobalt powder |
| CN107150127B (en) * | 2016-03-04 | 2020-07-21 | 荆门市格林美新材料有限公司 | Preparation method of spherical cobalt powder |
| CN106670489A (en) * | 2016-11-28 | 2017-05-17 | 荆门市格林美新材料有限公司 | Preparing method for spherical high-purity nickel powder |
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