JP4396123B2 - Partially stabilized ZrO2 sphere and method for producing the same - Google Patents

Description

【００１７】
本発明は、また、上述の球体を製造する方法として、３〜６重量％の範囲内の、Ｙ₂Ｏ₃、ＣｅＯ₂等の安定化剤と、０．３６〜０．４重量％の範囲内のＡｌ₂Ｏ₃とを含み、Ｆｅの含有量がＦｅ₂Ｏ₃換算で０．００３重量％以下であり、Ｔｉの含有量がＴｉＯ₂換算で０．００２重量％以下であり、Ｎａの含有量がＮａ₂Ｏ換算で０．００１〜０．０２重量％の範囲内にあり、硫酸化合物の含有量がＳＯ₄換算で０．００１〜０．０２重量％の範囲内にあり、比表面積が８〜１３ｍ²／ｇの範囲内にあり、平均二次粒子径が０．３〜０．６μｍの範囲内にあるＺｒＯ₂粉末を転動造粒して成形球体を得た後、成形球体を酸化性雰囲気中にて１，３００〜１，４５０℃の範囲内の温度で焼結することを特徴とする部分安定化ＺｒＯ₂球体の製造方法を提供する。また、３〜６重量％の範囲内の、Ｙ₂Ｏ₃、ＣｅＯ₂等の安定化剤と、０．１〜０．５重量％の範囲内のＡｌ₂Ｏ₃とを含み、Ｆｅの含有量がＦｅ₂Ｏ₃換算で０．００３重量％以下であり、Ｔｉの含有量がＴｉＯ₂換算で０．００２重量％以下であり、Ｎａの含有量がＮａ₂Ｏ換算で０．００１〜０．００５重量％の範囲内にあり、硫酸化合物の含有量がＳＯ₄換算で０．００５〜０．０３重量％の範囲内にあり、比表面積が８〜１３ｍ²／ｇの範囲内にあり、平均二次粒子径が０．３〜０．６μｍの範囲内にあるＺｒＯ₂粉末を噴霧造粒して成形球体を得た後、成形球体を酸化性雰囲気中にて１，３００〜１，４５０℃の範囲内の温度で焼結することを特徴とする部分安定化ＺｒＯ₂球体の製造方法を提供する。
【００１８】
上記において、Ｙ₂Ｏ₃、ＣｅＯ₂、Ａｌ₂Ｏ₃ 、Ｆｅ₂Ｏ₃、ＴｉＯ₂の含有量は、次のようにして求める。すなわち、約０．５ｇのＺｒＯ₂粉末を白金るつぼに入れ、硫酸水素カリウムで融解する。これを希硝酸で溶解して定溶し、ＩＣＰ発光分光分析法を用いてＹ、Ｃｅ、Ａｌ、Ｆｅ、Ｔｉを定量し、さらにそれらをＹ₂Ｏ₃、ＣｅＯ₂、Ａｌ₂Ｏ₃、Ｆｅ₂Ｏ₃、ＴｉＯ₂に換算する。
【００１９】
また、Ｎａ₂Ｏの含有量は、次のようにして求める。すなわち、約０．１ｇのＺｒＯ₂粉末を白金るつぼに入れ、硫酸水素カリウムで融解する。これを希硝酸で溶解して定溶し、原子吸光分析法を用いてＮａを定量し、さらにそれをＮａ₂Ｏに換算する。
【００２０】
さらに、ＳＯ₄の含有量は、次のようにして求める。すなわち、水を用いてＺｒＯ₂粉末から抽出した抽出液をイオンクロマトグラフ法を用いて硫酸化合物として定量し、得られた値をＳＯ₄に換算する。
【００２１】
また、比表面積は、ＪＩＳ Ｒ １６２６「ファインセラミックス粉体の気体吸着ＢＥＴ法による比表面積の測定方法」に規定される方法に準拠し、ＢＥＴ１点法で求める。
【００２２】
さらに、平均二次粒子径は、次のようにして求める。すなわち、３００ｍｌのビーカに電気伝導度が５μＳ／ｃｍの純水２１０ｇとＺｒＯ₂粉末９０ｇとを入れ、よく攪拌した後、超音波発生機に１０分間かけて３０重量％のスラリーを調製する。しかる後、粒度分布測定器を用いて平均二次粒子径を測定する。なお、平均二次粒子径は、累積分布が５０％に相当する、いわゆるメジアン径である。
【００２３】
【発明の実施の形態】
本発明の球体は、３〜６重量％の範囲内の安定化剤と、０．３６〜０．４重量％または０．１〜０．５重量％の範囲内（製造方法により異なる）のＡｌ₂Ｏ₃とを含み、かさ密度が理論密度の少なくとも９８％であり、平均結晶粒子径が０．１〜０．４μｍの範囲内にあり、かつ、表面から半径の１／３までの領域における平均結晶粒子径Ｃｓと球心から半径の２／３までの領域における平均結晶粒子径Ｃｉとの比Ｃｉ／Ｃｓが０．８〜１．２の範囲内にある。
【００２４】
球体は、３〜６重量％の範囲内の安定化剤を含んでいる。安定化剤を含むことにより、常温で単斜晶であるＺｒＯ₂の結晶構造は多くが正方晶となり、正方晶から単斜晶への応力誘起変態による強度の向上が期待できるようになる。安定化剤としては、通常、Ｙ₂Ｏ₃を用いる。Ｙ₂Ｏ₃はＺｒＯ₂の強度や靱性を向上させる。Ｙ₂Ｏ₃を用いる場合、その含有量は３〜６重量％の範囲内とする。含有量が３重量％未満では正方晶が安定化せず、常温で単斜晶の占める割合が多くなって高強度、高靱性にならない。６重量％を超えると、正方晶が完全に安定化されてしまい、常温で応力誘起変態が起こりにくくなって強度が低下する。Ｙ₂Ｏ₃の好ましい含有量の範囲は４〜６重量％である。また、安定化剤としてＣｅＯ₂を用いることができる。ＣｅＯ₂は、通常、Ｙ₂Ｏ₃と併用する。ＣｅＯ₂は、耐衝撃性を向上させるうえに、ごく少量であってもＺｒＯ₂の熱劣化を抑制し、耐摩耗性を向上させる。Ｙ₂Ｏ₃と併用する場合、両者の合計量が３〜６重量％の範囲内になるようにする。
【００２５】
球体は、また、０．３６〜０．４重量％または０．１〜０．５重量％の範囲内のＡｌ₂Ｏ₃を含んでいる。後述するが、Ａｌ₂Ｏ₃の含有量は、焼結に供するための成形球体の製造を転動造粒法によった場合には０．３６〜０．４重量％の範囲内となり、噴霧造粒法によった場合には０．１〜０．５重量％の範囲内となる。ＺｒＯ₂が高強度であることは、正方晶ＺｒＯ₂から単斜晶ＺｒＯ₂への応力誘起変態に起因するが、少量のＡｌ₂Ｏ₃が含まれていると、一層高強度となる。これは、焼結の際、Ａｌ₂Ｏ₃の収縮量がＺｒＯ₂のそれにくらべて小さいために、圧縮の内部応力がかかるようになるからである。また、Ａｌ₂Ｏ₃には粒界を強化する作用があるため、耐引張応力が向上する。しかしながら、Ａｌ₂Ｏ₃が多くなりすぎると、靭性が低くなり、耐摩耗性が低下するようになる。本発明においては、得られる球体においてＡｌ₂Ｏ₃が示す上述の作用と、後述する造粒時におけるＡｌ₂Ｏ₃の作用とのバランスを考慮し、その範囲を０．３６〜０．４重量％または０．１〜０．５重量％の範囲内としている。
【００２６】
球体のかさ密度は、理論密度の少なくとも９８％である。これにより、耐摩耗性が大きく向上する。すなわち、かさ密度が理論密度の９８％未満であるようなものは、内部空隙が多く、摩耗が多くなる。また、強度が不足するようになり、使用時の衝撃で割れたり欠けたりするようになる。かさ密度は、理論密度の９９％以上であるのが好ましい。
【００２７】
また、球体の耐摩耗性は、平均結晶粒子径にも依存する。すなわち、平均結晶粒子径が０．１μｍを下回るようなものは、粒界が多くて腐食が進みやすいために耐摩耗性、耐衝撃性が大きく低下する。また、０．４μｍを超えるようなものは、応力誘起変態が起こりにくいために、強度はもちろん、硬度、靱性にも劣り、やはり耐摩耗性、耐衝撃性が大きく低下するようになる。平均結晶粒子径の好ましい範囲は０．１５〜０．３５μｍであり、より好ましい範囲は０．２〜０．３５μｍである。
【００２８】
さらに、耐摩耗性を向上させるためには、平均結晶粒子径が上述の範囲内にあることに加え、表面から半径の１／３までの領域における平均結晶粒子径Ｃｓと球心から半径の２／３までの領域における平均結晶粒子径Ｃｉとの比Ｃｉ／Ｃｓが０．８〜１．２の範囲内にあることが必要である。たとえば、成形球体の製造を転動造粒法によった場合、得られる球体の平均結晶粒子径は、表面よりも内部のほうが大きくなる傾向にある。そのような球体を粉砕・分散媒体として用いると、初期の段階で摩耗が著しく進行し、不純物の混入量が激増する。また、成形球体の製造を噴霧造粒法によった場合、得られる球体の平均結晶粒子径は、表面付近のほうが内部よりも大きくなる傾向にある。すなわち、内部の平均結晶粒子径は小さく、内部空隙が多くなってその空隙が破壊の起点となるので強度が大きく低下する。そのような球体を粉砕・分散媒体として用いると、衝撃によって容易に割れてしまう。また、内部が表れ始めると摩耗が激しくなり、不純物の混入量が急激に多くなる。このように、平均結晶粒子径の均一性は摩耗の進行に大きく影響する。そして、球体の平均結晶粒子径が０．１〜０．４μｍの範囲内にあっても、平均結晶粒子径の比Ｃｉ／Ｃｓが０．８未満であると、内部の焼結が不十分で粉砕・分散媒体として用いたときに衝撃による割れが発生したり、表面付近が摩耗してきたときの内部の摩耗が激しくなり、また、比Ｃｉ／Ｃｓが１．２を超えると、初期段階における表面の摩耗が著しくなる。好ましい平均結晶粒子径の比Ｃｉ／Ｃｓの範囲は、０．９〜１．１である。
【００２９】
球体は、表面の算術平均高さＲａが０．０５μｍ以下であるのが好ましい。算術平均高さＲａが大きすぎると、初期摩耗が増大する。また、衝撃を受けたときに割れやすくなる。好ましい算術平均高さＲａは、０．０３μｍ以下である。
【００３０】
球体は、また、単斜晶ＺｒＯ₂の含有量が１０重量％以下であるのが好ましい。単斜晶ＺｒＯ₂の量が多くなりすぎると強度が低下してくるし、衝撃による割れや摩耗が起こりやすくなるからである。
【００３１】
上述した本発明の球体は、二つの方法によって製造することができる。焼結に供する成形球体の製造方法の相異による。一つは、成形球体の製造を転動造粒法によるものであり、他の一つは、噴霧造粒法によるものである。前者の転動造粒法を経由する方法は、球径が０．２〜１０ｍｍ程度の範囲内にある球体を製造するのに適している。また、後者の噴霧造粒法を経由する方法は、球径が０．２ｍｍ以下の球体を製造するときに適している。
【００３２】
転動造粒法を経由する方法は、３〜６重量％の範囲内の安定化剤と、０．３６〜０．４重量％の範囲内のＡｌ₂Ｏ₃とを含み、Ｆｅの含有量がＦｅ₂Ｏ₃換算で０．００３重量％以下であり、Ｔｉの含有量がＴｉＯ₂換算で０．００２重量％以下であり、Ｎａの含有量がＮａ₂Ｏ換算で０．００１〜０．０２重量％の範囲内にあり、硫酸化合物の含有量がＳＯ₄換算で０．００１〜０．０２重量％の範囲内にあり、比表面積が８〜１３ｍ²／ｇの範囲内にあり、平均二次粒子径が０．３〜０．６μｍの範囲内にあるＺｒＯ₂粉末を転動造粒して成形球体を得た後、成形球体を酸化性雰囲気中にて１，３００〜１，４５０℃の範囲内の温度で焼結する方法である。
【００３３】
転動造粒法は、よく知られているように、回転皿型造粒機や回転ドラム型造粒機等の造粒機を用い、水を造粒剤として粉末を転動させて微細な核を形成するとともに、水と粉末とを添加しながら核を成長させ、圧密化された成形球体を得る方法である。すなわち、この方法は、粉末の自重を利用して圧密化を図りながら成形球体を成長させるものである。
【００３４】
さて、この転動造粒法を経由する方法においては、３〜６重量％の範囲内の安定化剤を含む球体を得るために、同量の安定化剤を含むＺｒＯ₂粉末を用いる。このとき、安定化剤としてＹ₂Ｏ₃に加えてＣｅＯ₂を併用すると、焼結温度を低くすることができるようになる。
【００３５】
ＺｒＯ₂粉末は、また、０．３６〜０．４重量％の範囲内のＡｌ₂Ｏ₃を含むものを用いる。Ａｌ₂Ｏ₃は、造粒時における成形球体の圧密化に関与し、含有量が０．３６重量％未満であっても０．４重量％を超えても、核と、その周りに成長する、いわゆる肉部分との密着性が悪くなって圧密化が十分でない部分ができるようになる。
【００３６】
また、ＺｒＯ₂粉末は、Ｆｅの含有量がＦｅ₂Ｏ₃換算で０．００３重量％以下であり、Ｔｉの含有量がＴｉＯ₂換算で０．００２重量％以下であり、Ｎａの含有量がＮａ₂Ｏ換算で０．００１〜０．０２重量％の範囲内にあるものを選択、使用する。すなわち、ＺｒＯ₂粉末には、その原料に起因する金属元素が不純物として含まれている。Ｆｅは、ＺｒＯ₂に固溶するため、その量が多いとＺｒＯ₂が安定化の方向に向かい、強度が低下するようになる。また、少量でも色調が黄色を呈するようになって球体の商品価値を低下させるため、含有量がＦｅ₂Ｏ₃換算で０．００３重量％以下のものを選択、使用する。Ｔｉは、Ａｌ₂Ｏ₃と反応して化合物を形成し、Ａｌ₂Ｏ₃の上述した造粒作用を阻害するので、含有量がＴｉＯ₂換算で０．００２重量％以下のものを選択、使用する。Ｎａは、少なすぎると、水とのなじみが悪くなって造粒時における圧密化を十分に行えなくなる。また、多すぎると、ＺｒＯ₂粉末同士がくっつきすぎて形状のよい成形球体が得られなくなるし、後の焼結時に粒子が異常に成長することもある。それゆえ、Ｎａの含有量がＮａ₂Ｏ換算で０．００１〜０．０２重量％の範囲内にあるものを選択、使用する。
【００３７】
上述したように、Ｎａは造粒時における成形性を大きく左右するが、このとき、硫酸化合物、たとえば硫酸ナトリウムや硫酸アンモニウムが適量存在していると、Ｎａによる成形性の阻害を抑制することができるようになる。それゆえ、本発明においては、硫酸化合物の含有量がＳＯ₄換算で０．００１〜０．０２重量％の範囲内にあるＺｒＯ₂粉末を選択、使用する。０．００１重量％より少ないと上述した抑制作用が期待できず、０．０２重量％よりも多いと圧密化が阻害されるようになる。
【００３８】
また、ＺｒＯ₂粉末は、比表面積が８〜１３ｍ²／ｇの範囲内にあり、平均二次粒子径が０．３〜０．６μｍの範囲内にあるものを選択、使用する。すなわち、本発明の球体は、上述したようにかさ密度が理論密度の少なくとも９８％であり、平均結晶粒子径が０．１〜０．４μｍの範囲内にあるが、そのようにかさ密度が高く、平均結晶粒子径の小さな球体を得るためには、低温焼結性に優れたＺｒＯ₂粉末を用いることが必要になる。しかるに、比表面積が８ｍ²／ｇ未満のものは低温焼結性に劣り、必要なかさ密度とするためには焼結温度を高くしなければならなくなって平均結晶粒子径が上述した範囲を超えてしまう。１３ｍ²／ｇを超えるようなものは、焼結性がよいのでかさ密度や平均結晶粒子径の範囲は満足するものの、造粒時に多くの水が必要となり、粉末同士の付着が激しくなって圧密化が不均一となってしまう。一方、平均二次粒子径を０．３μｍ未満とするためには粉末の粉砕が必要となるが、粉砕すると単斜晶ＺｒＯ₂が増えてくるために強度が低くなる。０．６μｍを超えるようなものは、低温焼結性に劣り、必要なかさ密度とするためには焼結温度を高くしなければならなくなって平均結晶粒子径が上述した範囲を超えてしまう。
【００３９】
上述したようなＺｒＯ₂粉末自体は、一般に、ＺｒＯ₂等の原料として塩化物を用い、加水分解法、中和共沈法、熱分解法、水熱法等を用いて粉末を合成した後、９００〜１，０００℃で焼成し、ボールミル等で湿式粉砕し、さらに乾燥することによって得ることができる。このとき、Ａｌ₂Ｏ₃は合成時に塩化物で添加する方法と、粉砕時に酸化物で添加する方法とがある。また、中和共沈法による場合、Ｎａは、粉末の合成に際して中和剤として添加する方法があり、硫酸化合物は、安定化剤の分布の均一性を向上させるための添加剤として添加する方法がある。いずれも、粉末中に不純物として残存することになるが、その量は焼成後の水洗によって制御することができる。
【００４０】
さて、本発明においては、上述した粉末を転造動粒し、得られた成形球体を乾燥した後、酸化性雰囲気中にて１，３００〜１，４５０℃の範囲内の温度で焼結し、球体とする。低温焼結性に優れたＺｒＯ₂粉末を用いて成形球体としているために、１，３５０〜１，４５０℃の範囲内の温度で焼結することでかさ密度が理論密度の少なくとも９８％であり、平均結晶粒子径が０．１〜０．４μｍの範囲内にある球体とすることができる。なお、焼結条件、すなわち焼結温度や焼結時間は、成形球体の大きさによって適宜選定する。たとえば、球径が１ｍｍ以下の場合には１，３５０℃〜１，４００℃で２時間程度とし、球径がそれよりも大きなものに対しては１，４００〜１，４５０℃で２〜３時間程度とする。
【００４１】
焼結後は、表面を研磨してうねりや傷を取り除き、さらに鏡面に仕上げて算術平均高さＲａが０．０５μｍ以下になるようにする。研磨には、バレル研磨機を用いることができ、研磨材としてはＳｉＣ、Ａｌ₂ Ｏ₃ 等の微粒子を用いることができる。研磨の後は、篩い分けにより、所望の球径にそろえる。
【００４２】
一方、噴霧造粒法は、よく知られているように、水と粉末とを含むスラリーをディスク式噴霧乾燥機やノズル式噴霧乾燥機等の噴霧乾燥機内に噴霧し、すなわち、加熱空間に噴霧し、造粒する方法である。本発明においては、成形球体の製造にかかる噴霧造粒法を用いることができる。このとき用いるＺｒＯ₂粉末は、基本的には上述した転動造粒法による場合と同じものでよい。また、成形球体の焼結、得られる球体の研磨、分級等については転動造粒法による場合と全く同じである。以下においては、転動造粒法による場合と異なる部分についてのみ説明する。
【００４３】
ＺｒＯ₂粉末としては、Ａｌ₂Ｏ₃の含有量が０．１〜０．５重量％の範囲内にあるものを用いる。すなわち、噴霧造粒法による場合、Ａｌ₂Ｏ₃は成形に影響を及ぼさない。したがって、得られる球体の強度の向上に着目してその含有量を決定すればよい。Ａｌ₂Ｏ₃の含有量は、転動造粒法による場合よりも広くてよく、０．１〜０．５重量％の範囲内にあるものを用いることができる。含有量が０．１重量％未満と少ないものは、強度の向上作用が期待できず、得られる球体は耐摩耗性に劣るものとなる。また、０．５重量％を超えるものは、靱性が低くなるため、やはり耐摩耗性に劣るものとなる。
【００４４】
また、ＺｒＯ₂粉末としては、Ｎａの含有量がＮａ₂Ｏ換算で０．００１〜０．００５重量％の範囲内にあり、硫酸化合物の含有量がＳＯ₄換算で０．００５〜０．０３重量％の範囲内にあるものを用いる。噴霧造粒法による成形球体は、スラリーの性状によるところが大きいが、乾燥中に成形球体の内部に大きな空隙や粗な部分が発生しないようにすることが重要である。乾燥時、内部の水分が表面に移動し、表面から蒸発するが、水分の移動に伴って粒子が移動すると内部に空隙ができたり、内部が粗になるため、粒子が移動しないように粒子同士をある程度の凝集状態におく。この点、ＮａをＮａ₂Ｏ換算で０．００１〜０．００５重量％の範囲内で含み、硫酸化合物をＳＯ₄換算で０．００５〜０．０３重量％の範囲内で含み、平均二次粒子径が０．３〜０．６μｍの範囲内にあるＺｒＯ₂粉末を用い、これをＺｒＯ₂粉末の濃度が４０〜７０重量％程度の範囲内のスラリーにすると、適度な凝集状態が得られ、内部に空隙や粗な部分の非常に少ない成形球体を得ることができるようになる。ＮａがＮａ₂Ｏ換算で０．００１重量％未満であると、スラリーの粘度が低くなり、成形球体の内部に空隙や粗な部分が多く発生するようになる。また、０．００５重量％を超えると、粒子同士の凝集が強くなって安定した送液ができなくなり、成形球体は形状、球径、内部構造等において均一性の極めて低いものとなる。一方、硫酸化合物がＳＯ₄換算で０．００５重量％未満であると、凝集を抑制する作用が期待できず、また、０．０３重量％を超えると、成形球体の内部に大きな空隙や粗な部分が多く発生するようになる。
【００４５】
【実施例および比較例】
以下に示す実施例および比較例において、球体の平均球径と耐摩耗率は次のようにして求めた。
平均球径：
球体を実体顕微鏡で観察して画像を取り込み、画像処理して円相当径を求め、平均円相当径を求めて平均球径とした。ｎ数は１００とした。
耐摩耗率：
内容積が６６０ｍｌのボールミルに球体１．８ｋｇを入れ、２０〜３０℃に維持した水を循環させながらディスクの周速を１２ｍ／秒として４０時間とも擦りをさせ、試験前の重量Ｗｂと試験後の重量Ｗａとから次式によって求めた。
【００４６】
耐摩耗率（％）＝（（Ｗｂ−Ｗａ）／Ｗｂ）×１００
実施例１：
ＺｒＯＣｌ₂水溶液にＹＣｌ₃水溶液をＹ₂Ｏ₃濃度として４．７８重量％となるように加え、さらにＡｌＣｌ₃水溶液をＡｌ₂Ｏ₃濃度として０．３８重量％となるように加え、これに硫酸アンモニウム水溶液を添加した後アンモニア水を加えて水酸化物を共沈させ、共沈物を遠心分離機で水洗し、乾燥した後、９７０℃で２時間焼成して焼成体を得た。
【００４７】
次に、得られた焼成体を乾式粉砕し、ボールミルを用いて５時間、純水中にて湿式粉砕し、湿式分級装置で微細粒子と粗大粒子とを除去し、限外ろ過装置を用いて水洗し、噴霧乾燥し、さらに乾式分級装置を用いて粗大粒子を除去し、脱鉄装置で脱鉄して粉末を得た。なお、水洗に際しては、限外ろ過装置で分離される水溶液の電気伝導度が４０μｓ／ｃｍになった時点で水洗を終了した。得られた粉末の諸元は以下のとおりであった。
【００４８】
Ｙ₂Ｏ₃の含有量 ：４．７８重量％
Ａｌ₂Ｏ₃の含有量 ：０．３８重量％
Ｆｅ₂Ｏ₃の含有量 ：０．０００２重量％
ＴｉＯ₂の含有量 ：０．００１重量％
Ｎａ₂Ｏの含有量 ：０．００１１重量％
ＳＯ₄の含有量 ：０．００６重量％
比表面積 ：９．８ｍ²／ｇ
平均二次粒子径 ：０．４２μｍ
単斜晶ＺｒＯ₂の含有量：３０重量％
次に、上記粉末を用いて転動造粒し、成形球体を得た。得られた成形球体を篩い分けした後、大気中にて１，３８０℃で２時間焼結した。焼結の際、成形球体をＡｌ₂Ｏ₃製のセッタに載せ、そのセッタをＡｌ₂Ｏ₃製のこう鉢に入れて蓋をした。得られた焼結体を再度篩い分けし、バレル研磨した。研磨は、ＳｉＣ研磨材による粗研磨を４時間、Ａｌ₂Ｏ₃研磨材とＳｉＣ研磨材による本研磨を４時間、研磨材を用いないとも摺りによる研磨を４時間とした。かくして得られた球体の諸元を以下に示す。
【００４９】
平均球径 ：０．３ｍｍ
Ｙ₂Ｏ₃の含有量 ：４．７８重量％
Ａｌ₂Ｏ₃の含有量 ：０．３８重量％
かさ密度 ：理論密度の９９．３％
平均結晶粒子径 ：０．２８μｍ
平均結晶粒子径比（ｃｉ／Ｃｓ）：０．９６
算術平均高さＲａ ：０．０１６μｍ
単斜晶ＺｒＯ₂の含有量 ：６重量％
耐摩耗率 ：０．０５％
実施例２：
ＺｒＯＣｌ₂水溶液にＹＣｌ₃水溶液をＹ₂Ｏ₃濃度として４．７０重量％となるように加え、これに硫酸ナトリウム水溶液を添加した後水酸化ナトリウム水溶液を加えて水酸化物を共沈させ、共沈物を遠心分離機で水洗し、乾燥した後、９８０℃で２時間焼成して焼成体を得た。
【００５０】
次に、得られた焼成体を乾式粉砕し、Ａｌ₂Ｏ₃粉末を０．３７重量％になるように加え、ボールミルを用いて５時間、純水中にて湿式粉砕し、湿式分級装置で微細粒子と粗大粒子とを除去し、限外ろ過装置を用いて水洗し、噴霧乾燥し、さらに乾式分級装置を用いて粗大粒子を除去し、脱鉄装置で脱鉄して粉末を得た。なお、水洗に際しては、限外ろ過装置で分離される水溶液の電気伝導度が１８０μｓ／ｃｍになった時点で水洗を終了した。得られた粉末の諸元は以下のとおりであった。
【００５１】
Ｙ₂Ｏ₃の含有量 ：４．７０重量％
Ａｌ₂Ｏ₃の含有量 ：０．３７重量％
Ｆｅ₂Ｏ₃の含有量 ：０．０００３重量％
ＴｉＯ₂の含有量 ：０．００１重量％
Ｎａ₂Ｏの含有量 ：０．０１６重量％
ＳＯ₄の含有量 ：０．０１３重量％
比表面積 ：８．５ｍ²／ｇ
平均二次粒子径 ：０．４６μｍ
単斜晶ＺｒＯ₂の含有量：２３重量％
次に、上記粉末を用いて転動造粒し、成形球体を得た。得られた成形球体を篩い分けした後、実施例１と同様にして大気中にて１，４００℃で２時間焼結した。さらに、実施例１と同様に研磨して球体を得た。かくして得られた球体の諸元を以下に示す。
【００５２】
平均球径 ：３．０ｍｍ
Ｙ₂Ｏ₃の含有量 ：４．７０重量％
Ａｌ₂Ｏ₃の含有量 ：０．３７重量％
かさ密度 ：理論密度の９９．３％
平均結晶粒子径 ：０．３０μｍ
平均結晶粒子径比（ｃｉ／Ｃｓ）：０．９３
算術平均高さＲａ ：０．０２２μｍ
単斜晶ＺｒＯ₂の含有量 ：４．３重量％
耐摩耗率 ：０．０４％
実施例３：
ＺｒＯＣｌ₂水溶液にＹＣｌ₃水溶液をＹ₂Ｏ₃濃度として５．１６重量％となるように加え、これにＡｌＣｌ₃水溶液をＡｌ₂Ｏ₃濃度として０．３８重量％となるように加え、さらに硫酸アンモニウム水溶液を添加した後アンモニア水を加えて水酸化物を共沈させ、共沈物を遠心分離機で水洗し、乾燥した後、９５０℃で２時間焼成して焼成体を得た。
【００５３】
次に、得られた焼成体を乾式粉砕し、ボールミルを用いて５時間、純水中にて湿式粉砕し、湿式分級装置で微細粒子と粗大粒子とを除去し、限外ろ過装置を用いて水洗し、噴霧乾燥し、さらに乾式分級装置を用いて粗大粒子を除去し、脱鉄装置で脱鉄して粉末を得た。なお、水洗に際しては、限外ろ過装置で分離される水溶液の電気伝導度が３０μｓ／ｃｍになった時点で水洗を終了した。得られた粉末の諸元は以下のとおりであった。
【００５４】
Ｙ₂Ｏ₃の含有量 ：５．１６重量％
Ａｌ₂Ｏ₃の含有量 ：０．３８重量％
Ｆｅ₂Ｏ₃の含有量 ：０．０００２重量％
ＴｉＯ₂の含有量 ：０．００１重量％
Ｎａ₂Ｏの含有量 ：０．００１０重量％
ＳＯ₄の含有量 ：０．０２０重量％
比表面積 ：１３．０ｍ²／ｇ
平均二次粒子径 ：０．４２μｍ
単斜晶ＺｒＯ₂の含有量：２８重量％
次に、上記粉末を濃度が５０重量％のスラリーとして噴霧造粒し、成形球体を得た。得られた成形球体を篩い分けした後、実施例１と同様にして大気中にて１，３５０℃で２時間焼結した。さらに、実施例１と同様に研磨して球体を得た。かくして得られた球体の諸元を以下に示す。
【００５５】
平均球径 ：０．１ｍｍ
Ｙ₂Ｏ₃の含有量 ：４．７８重量％
Ａｌ₂Ｏ₃の含有量 ：０．３８重量％
かさ密度 ：理論密度の９９．４％
平均結晶粒子径 ：０．２７μｍ
平均結晶粒子径比（ｃｉ／Ｃｓ）：０．９８
算術平均高さＲａ ：０．００９μｍ
単斜晶ＺｒＯ₂の含有量 ：２．３重量％
耐摩耗率 ：０．０６％
実施例４：
ＺｒＯＣｌ₂水溶液にＹＣｌ₃水溶液をＹ₂Ｏ₃濃度として５．３９重量％となるように加え、これにＣｅＣｌ₄水溶液をＣｅＯ₂濃度として０．３５重量％となるように加え、ＡｌＣｌ₃水溶液をＡｌ₂Ｏ₃濃度として０．２６重量％となるように加え、さらに硫酸アンモニウム水溶液を添加した後アンモニア水を加えて水酸化物を共沈させ、共沈物を遠心分離機で水洗し、乾燥した後、９６０℃で２時間焼成して焼成体を得た。
【００５６】
次に、得られた焼成体を乾式粉砕し、ボールミルを用いて５時間、純水中にて湿式粉砕し、湿式分級装置で微細粒子と粗大粒子とを除去し、限外ろ過装置を用い水洗し、噴霧乾燥し、さらに乾式分級装置を用いて粗大粒子を除去し、脱鉄装置で脱鉄して粉末を得た。なお、水洗に際しては、限外ろ過装置で分離される水溶液の電気伝導度が５０μｓ／ｃｍになった時点で水洗を終了した。得られた粉末の諸元は以下のとおりであった。
【００５７】
Ｙ₂Ｏ₃の含有量 ：５．３９重量％
ＣｅＯ₂の含有量 ：０．３５重量％
Ａｌ₂Ｏ₃の含有量 ：０．２６重量％
Ｆｅ₂Ｏ₃の含有量 ：０．０００４重量％
ＴｉＯ₂の含有量 ：０．００１２重量％
Ｎａ₂Ｏの含有量 ：０．００１１重量％
ＳＯ₄の含有量 ：０．０２５重量％
比表面積 ：１１．８ｍ²／ｇ
平均二次粒子径 ：０．４５μｍ
単斜晶ＺｒＯ₂の含有量：２０重量％
次に、上記粉末を濃度が５２重量％のスラリーとして噴霧造粒し、成形球体を得た。得られた成形球体を篩い分けした後、実施例１と同様にして大気中にて１，３５０℃で２時間焼結した。さらに、実施例１と同様に研磨して球体を得た。かくして得られた球体の諸元を以下に示す。
【００５８】
平均球径 ：０．１ｍｍ
Ｙ₂Ｏ₃の含有量 ：４．７８重量％
Ａｌ₂Ｏ₃の含有量 ：０．３８重量％
かさ密度 ：理論密度の９９．０％
平均結晶粒子径 ：０．２４μｍ
平均結晶粒子径比（ｃｉ／Ｃｓ）：１．０４
算術平均高さＲａ ：０．０１５μｍ
単斜晶ＺｒＯ₂の含有量 ：５．７重量％
耐摩耗率 ：０．０８％
実施例５：
ＺｒＯＣｌ₂水溶液にＹＣｌ₃水溶液をＹ₂Ｏ₃濃度として４．７５重量％となるように加え、これにＡｌＣｌ₃水溶液をＡｌ₂Ｏ₃濃度として０．３９重量％となるように加え、さらに硫酸ナトリウム水溶液を添加した後水酸化ナトリウム水溶液を加えて水酸化物を共沈させ、共沈物を遠心分離機で水洗し、乾燥した後、９７０℃で２時間焼成して焼成体を得た。
【００５９】
次に、得られた焼成体を乾式粉砕し、ボールミルを用いて５時間、純水中にて湿式粉砕し、湿式分級装置で微細粒子と粗大粒子とを除去し、限外ろ過装置を用い水洗し、噴霧乾燥し、さらに乾式分級装置を用いて粗大粒子を除去し、脱鉄装置で脱鉄して粉末を得た。なお、水洗に際しては、限外ろ過装置で分離される水溶液の電気伝導度が１００μｓ／ｃｍになった時点で水洗を終了した。得られた粉末の諸元は以下のとおりであった。
【００６０】
Ｙ₂Ｏ₃の含有量 ：４．７５重量％
Ａｌ₂Ｏ₃の含有量 ：０．３９重量％
Ｆｅ₂Ｏ₃の含有量 ：０．０００３重量％
ＴｉＯ₂の含有量 ：０．００１１重量％
Ｎａ₂Ｏの含有量 ：０．００３５重量％
ＳＯ₄の含有量 ：０．０１１重量％
比表面積 ：１０．５ｍ²／ｇ
平均二次粒子径 ：０．３８μｍ
単斜晶ＺｒＯ₂の含有量：２２重量％
次に、上記粉末を濃度が５２重量％のスラリーとして噴霧造粒し、成形球体を得た。得られた成形球体を篩い分けした後、実施例１と同様にして大気中にて１，３７０℃で２時間焼結した。さらに、実施例１と同様に研磨して球体を得た。かくして得られた球体の諸元を以下に示す。
【００６１】
平均球径 ：０．２ｍｍ
Ｙ₂Ｏ₃の含有量 ：４．７８重量％
Ａｌ₂Ｏ₃の含有量 ：０．３８重量％
かさ密度 ：理論密度の９９．３％
平均結晶粒子径 ：０．２６μｍ
平均結晶粒子径比（ｃｉ／Ｃｓ）：０．９５
算術平均高さＲａ ：０．００８μｍ
単斜晶ＺｒＯ₂の含有量 ：６．０重量％
耐摩耗率 ：０．０６％
比較例１：
ＺｒＯＣｌ₂水溶液にＹＣｌ₃水溶液をＹ₂Ｏ₃濃度として５．４重量％となるように加え、これに硫酸ナトリウム水溶液を添加した後水酸化ナトリウム水溶液を加えて水酸化物を共沈させ、共沈物を遠心分離機で水洗し、乾燥した後、１，０５０℃で２時間焼成して焼成体を得た。なお、水洗に際しては、遠心分離機で分離される水溶液の電気伝導度が４００μｓ／ｃｍになった時点で水洗を終了した。
【００６２】
次に、得られた焼成体を乾式粉砕し、Ａｌ₂Ｏ₃粉末を０．３０重量％になるように加え、ボールミルを用いて３時間湿式粉砕し、噴霧乾燥し、さらに乾式分級装置を用いて粗大粒子を除去して粉末を得た。得られた粉末の諸元は以下のとおりであった。
【００６３】
Ｙ₂Ｏ₃の含有量 ：５．４重量％
Ａｌ₂Ｏ₃の含有量 ：０．３０重量％
Ｆｅ₂Ｏ₃の含有量 ：０．００８重量％
ＴｉＯ₂の含有量 ：０．０１重量％
Ｎａ₂Ｏの含有量 ：０．０３重量％
ＳＯ₄の含有量 ：０．０５重量％
比表面積 ：６．５ｍ²／ｇ
平均二次粒子径 ：１．２μｍ
単斜晶ＺｒＯ₂の含有量：１２重量％
次に、上記粉末を用いて転動造粒し、成形球体を得た。得られた成形球体を篩い分けした後、実施例１と同様にして大気中にて１，５００℃で２時間焼結した。さらに、実施例１と同様に研磨し、球体を得た。かくして得られた球体の諸元を以下に示す。
【００６４】
平均球径 ：０．３ｍｍ
Ｙ₂Ｏ₃の含有量 ：５．４重量％
Ａｌ₂Ｏ₃の含有量 ：０．３０重量％
かさ密度 ：理論密度の９８．３％
平均結晶粒子径 ：０．４６μｍ
平均結晶粒子径比（ｃｉ／Ｃｓ）：１．２３
算術平均高さＲａ ：０．０６μｍ
単斜晶ＺｒＯ₂の含有量 ：１２．３重量％
耐摩耗率 ：０．３２％
比較例２：
ＺｒＯＣｌ₂水溶液にＹＣｌ₃水溶液をＹ₂Ｏ₃濃度として５．０重量％となるように加え、これに水酸化ナトリウム水溶液を添加して水酸化物を共沈させ、共沈物を遠心分離機で水洗し、乾燥した後、９５０℃で２時間焼成して焼成体を得た。なお、水洗に際しては、遠心分離機で分離される水溶液の電気伝導度が４００μｓ／ｃｍになった時点で水洗を終了した。
【００６５】
次に、得られた焼成体を乾式粉砕し、ボールミルを用いて１０時間湿式粉砕し、噴霧乾燥して粉末を得た。得られた粉末の諸元は以下のとおりであった。
【００６６】
Ｙ₂Ｏ₃の含有量 ：５．０重量％
Ａｌ₂Ｏ₃の含有量 ：０重量％
Ｆｅ₂Ｏ₃の含有量 ：０．００５重量％
ＴｉＯ₂の含有量 ：０．０２重量％
Ｎａ₂Ｏの含有量 ：０．０４重量％
ＳＯ₄の含有量 ：０．００１重量％
比表面積 ：１６．０ｍ²／ｇ
平均二次粒子径 ：０．３０μｍ
単斜晶ＺｒＯ₂の含有量：４４重量％
次に、上記粉末を濃度が３３重量％のスラリーとして噴霧造粒し、成形球体を得た。得られた成形球体を篩い分けした後、実施例１と同様にして大気中にて１，３５０℃で２時間焼結した。さらに、実施例１と同様に研磨し、球体を得た。かくして得られた球体の諸元を以下に示す。
【００６７】
平均球径 ：０．１ｍｍ
Ｙ₂Ｏ₃の含有量 ：５．０重量％
Ａｌ₂Ｏ₃の含有量 ：０重量％
かさ密度 ：理論密度の９７．８％
平均結晶粒子径 ：０．２４μｍ
平均結晶粒子径比（ｃｉ／Ｃｓ）：０．７７
算術平均高さＲａ ：０．０８μｍ
単斜晶ＺｒＯ₂の含有量 ：８．９重量％
耐摩耗率 ：０．２４％
比較例３：
ＺｒＯＣｌ₂水溶液にＹＣｌ₃ 水溶液をＹ₂Ｏ₃濃度として５．７重量％となるように加え、これに硫酸アンモニウム水溶液を添加した後アンモニウム水溶液を加えて水酸化物を共沈させ、共沈物を遠心分離機で水洗し、乾燥した後、９２０℃で２時間焼成して焼成体を得た。
【００６８】
次に、得られた焼成体を乾式粉砕し、Ａｌ₂Ｏ₃粉末を０．３２重量％になるように加え、ボールミルを用いて１０時間湿式粉砕し、限外ろ過装置を用いて水洗し、噴霧乾燥し、さらに乾式分級装置を用いて粗大粒子を除去して粉末を得た。なお、水洗に際しては、限外ろ過装置で分離される水溶液の電気伝導度が５μｓ／ｃｍになった時点で水洗を終了した。得られた粉末の諸元は以下のとおりであった。
【００６９】
Ｙ₂Ｏ₃の含有量 ：５．７重量％
Ａｌ₂Ｏ₃の含有量 ：０．３２重量％
Ｆｅ₂Ｏ₃の含有量 ：０．００８重量％
ＴｉＯ₂の含有量 ：０．００２重量％
Ｎａ₂Ｏの含有量 ：０．０００４重量％
ＳＯ₄の含有量 ：０．００１重量％
比表面積 ：１８．０ｍ²／ｇ
平均二次粒子径 ：０．２８μｍ
単斜晶ＺｒＯ₂の含有量：４５重量％
次に、上記粉末を濃度が３５重量％のスラリーとして噴霧造粒し、成形球体を得た。得られた成形球体を篩い分けした後、実施例１と同様にして大気中にて１，３５０℃で２時間焼結した。さらに、実施例１と同様に研磨し、球体を得た。かくして得られた球体の諸元を以下に示す。
【００７０】
平均球径 ：０．２ｍｍ
Ｙ₂Ｏ₃の含有量 ：５．７重量％
Ａｌ₂Ｏ₃の含有量 ：０．３２重量％
かさ密度 ：理論密度の９７．３％
平均結晶粒子径 ：０．２３μｍ
平均結晶粒子径比（ｃｉ／Ｃｓ）：１．２３
算術平均高さＲａ ：０．１０μｍ
単斜晶ＺｒＯ₂の含有量 ：８．３重量％
耐摩耗率 ：０．２２％
【００７１】
【発明の効果】
本発明の球体は、３〜６重量％の範囲内の安定化剤と、０．３５〜０．４重量％の範囲内または０．１〜０．５重量％の範囲内のＡｌ₂Ｏ₃とを含み、かさ密度が理論密度の少なくとも９８％であり、平均結晶粒子径が０．１〜０．４μｍの範囲内にあり、かつ、表面から半径の１／３までの領域における平均結晶粒子径Ｃｓと球心から半径の２／３までの領域における平均結晶粒子径Ｃｉとの比Ｃｉ／Ｃｓが０．８〜１．２の範囲内にあるものであるから、実施例と比較例との対比からも明らかなように、耐摩耗性に優れ、耐久性に優れている。そのため、粉砕・分散媒体として好適である。しかも、そのような球体は転動造粒法または噴霧造粒法によって容易に得ることができる。[0001]
BACKGROUND OF THE INVENTION
The present invention is a partially stabilized ZrO suitable for use as a grinding / dispersing medium in a ball mill or the like. ₂ The present invention relates to a sphere and a manufacturing method thereof.
[0002]
[Prior art]
As is well known, ZrO is used as a grinding and dispersion medium in ball mills and the like. ₂ Sphere, Al ₂ O _Three Ceramic spheres such as spheres are often used. Such a pulverizing / dispersing medium is required to have high purity and low wear during use so that impurities are not mixed and affect the quality and performance of the final product. In recent years, in order to improve the efficiency of pulverization and dispersion, those having a smaller diameter have been demanded.
[0003]
Now, as such a grinding / dispersing medium, at least 50% by weight of Al ₂ O _Three And 15 to 40 wt%, 0.1 to 5 mol% Y ₂ O _Three And / or CeO ₂ Containing ZrO ₂ Are known (for example, see Patent Document 1). However, this conventional grinding media is Al ₂ O _Three As a main component, the toughness is low, it is easily cracked or chipped by impact during use, and the durability is poor.
[0004]
Moreover, 2-4 mol% Y ₂ O _Three And 0.05 to 1% by weight of Al ₂ O _Three And the mirror-finished surface contains monoclinic ZrO ₂ Is substantially free of monoclinic ZrO when heat-treated, annealed, and pulverized. ₂ Tetragonal ZrO transformed to ₂ 30% or more, and the balance is cubic ZrO ₂ The average crystal particle diameter is 0.5 μm or less, and the bulk density is 5.98 g / cm. ^Three It is the above and the thing whose wear amount by a ball mill is 0.01% or less is known (for example, refer patent document 2). However, this conventional grinding medium is a cubic ZrO. ₂ Therefore, there is a problem that the strength and the hardness are low, the crack is easily broken by an impact during use, and the wear resistance is inferior.
[0005]
Furthermore, mainly ZrO ₂ And Y ₂ O _Three Y in molar ratio ₂ O _Three / ZrO ₂ Is in the range of 1.5 / 98.5 to 2.6 / 97.4, and 0.005 to 4.5% by weight of Al. ₂ O _Three 1 wt% or less of CaO and / or MgO, and SiO ₂ , Na ₂ O and K ₂ The total amount of O is 0.3% by weight or less, and SiO ₂ Is 0.2 wt% or less, Na ₂ O is 0.05% by weight or less, K ₂ O is 0.05 wt% or less, and tetragonal ZrO ₂ 60% by volume or more, and bulk density is 5.85 g / cm ^Three As described above, the average crystal particle size is 0.3 to 0.7 μm, and the wear amount by a ball mill or the like measured under specific conditions is 40 ppm / hour or less (for example, patents) Reference 3). This conventional ceramic sphere contains CaO and MgO to suppress thermal degradation and to increase the crystal grain size in order to reduce grain boundaries. However, its strength and hardness are low. However, there is a problem that it is easily cracked or chipped by an impact during use, and is inferior in wear resistance.
[0006]
[Patent Document 1]
JP-A-10-85619
[0007]
[Patent Document 2]
Japanese Patent Publication No. 8-25798
[0008]
[Patent Document 3]
Japanese Patent No. 2860953
[0009]
[Problems to be solved by the invention]
The object of the present invention is to solve the above-mentioned problems of the prior art, and to provide a partially stabilized ZrO suitable as a grinding / dispersing medium having excellent wear resistance and durability. ₂ Spheres and such partially stabilized ZrO ₂ It is in providing the method of manufacturing a sphere easily.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides Y in the range of 3 to 6% by weight. ₂ O _Three , CeO ₂ And a stabilizer within the range of 0.36 to 0.4 wt% or 0.1 to 0.5 wt% ₂ O _Three The bulk density is at least 98% of the theoretical density, that is, the relative density is at least 98%, and the average crystal grain size is in the range of 0.1 to 0.4 μm. The ratio Ci / Cs of the average crystal particle diameter Cs in the region from the surface to 1/3 of the radius and the average crystal particle diameter Ci in the region from the spherical center to 2/3 of the radius is 0.8 to 1.2. Partially stabilized ZrO, characterized in that ₂ Provide a sphere. The arithmetic average height Ra of the surface is preferably 0.05 μm or less. Monoclinic ZrO ₂ The content of is preferably 10% by weight or less. In the following, for the sake of convenience, partially stabilized ZrO ₂ A sphere is simply called a sphere.
[0011]
In the above, the bulk density is determined by Archimedes method with about 20 g of spheres put in a container. The theoretical density is 6.08 g / cm. ^Three And
[0012]
In addition, Y as a stabilizer ₂ O _Three , CeO ₂ Content and Al ₂ O _Three The content of is determined as follows. That is, Y with HIP processing ₂ O _Three Partially stabilized ZrO ₂ The sphere is crushed using a universal testing machine having a crushed portion made of ceramics, and about 0.3 g of the crushed piece is placed in a platinum crucible and melted with potassium hydrogen sulfate. This is dissolved in dilute nitric acid and dissolved, and ICP emission spectroscopic analysis is used to quantify Y, Ce, and Al. ₂ O _Three , CeO ₂ , Al ₂ O _Three Convert to.
[0013]
Further, the average crystal particle diameters Cs and Ci and their ratio Ci / Cs are obtained as follows. That is, the sphere is embedded and held in a resin, the holding surface is polished until the sphere is substantially hemispherical, the polished surface is mirror finished, and further thermally etched at a temperature 50 ° C. lower than the sintering temperature for 3 hours. Thereafter, the etched surface is observed using a scanning electron microscope, and 30 points for any 3 points in the region from the surface to 1/3 of the radius and 3 points in the region from the spherical center to 2/3 of the radius. Take 1,000,000 photos. Next, an average crystal particle diameter Cs in a region from the surface to 1/3 of the radius from the surface and an average crystal particle diameter Ci in a region from the sphere center to 2/3 of the radius are obtained using an image processing apparatus, and the ratio thereof is further determined. Ci / Cs is obtained.
[0014]
Further, the arithmetic average height Ra of the surface is obtained as follows. That is, a secondary electron beam emitted by observing a sphere with a scanning electron microscope and irradiating an electron beam to any five points using the secondary electron mode surface morphology observation function of the electron beam three-dimensional measurement method. Then, the surface irregularities are measured and simply averaged to obtain the arithmetic average height Ra.
[0015]
In addition, monoclinic ZrO ₂ The content of is determined as follows. That is, the sphere is X-ray diffracted and calculated from the diffraction intensity (area of the diffraction peak) by the following equation. However, the value after correction by the Lorentz factor is used for the diffraction intensity. The X-ray is CuKα ray, the voltage is 40 kv, and the current is 20 mA.
[0016]
[Expression 1]

[0017]
The present invention also provides a method for producing the above-mentioned sphere, wherein Y is in the range of 3 to 6% by weight. ₂ O _Three , CeO ₂ And a stabilizer in the range of 0.36 to 0.4% by weight ₂ O _Three And the Fe content is Fe ₂ O _Three It is 0.003% by weight or less in terms of conversion, and the Ti content is TiO. ₂ It is 0.002% by weight or less in terms of conversion, and the Na content is Na ₂ It is within the range of 0.001 to 0.02% by weight in terms of O, and the content of the sulfate compound is SO. _Four It is within the range of 0.001 to 0.02% by weight in terms of conversion, and the specific surface area is 8 to 13m. ² / ZrO in the range of 0.3 to 0.6 μm in average secondary particle diameter ₂ Partially-stabilized ZrO, characterized in that, after rolling and granulating the powder to obtain a molded sphere, the molded sphere is sintered at a temperature in the range of 1,300 to 1,450 ° C. in an oxidizing atmosphere. ₂ A method of manufacturing a sphere is provided. Y in the range of 3 to 6% by weight ₂ O _Three , CeO ₂ And a stabilizer within the range of 0.1 to 0.5% by weight. ₂ O _Three And the Fe content is Fe ₂ O _Three It is 0.003% by weight or less in terms of conversion, and the Ti content is TiO. ₂ It is 0.002% by weight or less in terms of conversion, and the Na content is Na ₂ It is within the range of 0.001 to 0.005% by weight in terms of O, and the content of the sulfate compound is SO. _Four It is within the range of 0.005 to 0.03% by weight in terms of conversion, and the specific surface area is 8 to 13 m. ² / ZrO in the range of 0.3 to 0.6 μm in average secondary particle diameter ₂ Partially stabilized ZrO, characterized by spraying and granulating the powder to obtain a molded sphere, and then sintering the molded sphere in an oxidizing atmosphere at a temperature in the range of 1,300 to 1,450 ° C. ₂ A method of manufacturing a sphere is provided.
[0018]
In the above, Y ₂ O _Three , CeO ₂ , Al ₂ O _Three , Fe ₂ O _Three TiO ₂ The content of is determined as follows. That is, about 0.5 g of ZrO ₂ Place the powder in a platinum crucible and melt with potassium hydrogen sulfate. This is dissolved in dilute nitric acid and dissolved, ICP emission spectroscopic analysis is used to quantify Y, Ce, Al, Fe, and Ti. ₂ O _Three , CeO ₂ , Al ₂ O _Three , Fe ₂ O _Three TiO ₂ Convert to.
[0019]
Na ₂ The O content is determined as follows. That is, about 0.1 g of ZrO ₂ Place the powder in a platinum crucible and melt with potassium hydrogen sulfate. This was dissolved in dilute nitric acid and fixed, and Na was quantified using atomic absorption spectrometry. ₂ Convert to O.
[0020]
In addition, SO _Four The content of is determined as follows. That is, using water, ZrO ₂ The extract extracted from the powder was quantified as a sulfate compound using ion chromatography, and the obtained value was determined as SO. _Four Convert to.
[0021]
The specific surface area is determined by the BET 1-point method in accordance with the method defined in JIS R 1626 “Method for measuring specific surface area of fine ceramic powder by gas adsorption BET method”.
[0022]
Further, the average secondary particle size is determined as follows. That is, 210 g of pure water having an electric conductivity of 5 μS / cm and ZrO in a 300 ml beaker. ₂ After adding 90 g of powder and stirring well, a 30 wt% slurry is prepared in an ultrasonic generator over 10 minutes. Thereafter, the average secondary particle size is measured using a particle size distribution analyzer. The average secondary particle diameter is a so-called median diameter corresponding to a cumulative distribution of 50%.
[0023]
DETAILED DESCRIPTION OF THE INVENTION
The spheres of the present invention comprise a stabilizer in the range of 3 to 6% by weight and Al in the range of 0.36 to 0.4% by weight or 0.1 to 0.5% by weight (depending on the production method). ₂ O _Three The average crystal particle in the region from the surface to 1/3 of the radius, the bulk density is at least 98% of the theoretical density, the average crystal particle diameter is in the range of 0.1 to 0.4 μm The ratio Ci / Cs between the diameter Cs and the average crystal particle diameter Ci in the region from the spherical center to 2/3 of the radius is in the range of 0.8 to 1.2.
[0024]
The sphere contains a stabilizer in the range of 3-6% by weight. By containing a stabilizer, ZrO is monoclinic at room temperature. ₂ Most of the crystal structure is tetragonal, and it is expected that the strength is improved by stress-induced transformation from tetragonal to monoclinic. As a stabilizer, usually Y ₂ O _Three Is used. Y ₂ O _Three Is ZrO ₂ Improves strength and toughness. Y ₂ O _Three When is used, the content is within the range of 3 to 6% by weight. If the content is less than 3% by weight, the tetragonal crystals will not be stabilized, and the proportion of monoclinic crystals will increase at room temperature and will not have high strength and high toughness. If it exceeds 6% by weight, the tetragonal crystal is completely stabilized, and stress-induced transformation hardly occurs at room temperature, resulting in a decrease in strength. Y ₂ O _Three The preferred content range is 4 to 6% by weight. CeO as a stabilizer ₂ Can be used. CeO ₂ Is usually Y ₂ O _Three Used together. CeO ₂ In addition to improving impact resistance, ZrO even in very small amounts ₂ Suppresses thermal degradation of the material and improves wear resistance. Y ₂ O _Three When used together, the total amount of both is in the range of 3 to 6% by weight.
[0025]
The spheres are also Al within the range of 0.36 to 0.4 wt% or 0.1 to 0.5 wt%. ₂ O _Three Is included. As will be described later, Al ₂ O _Three The content of is in the range of 0.36 to 0.4% by weight when the rolling sphere method is used to produce molded spheres for sintering, and when the spray granulation method is used. Is in the range of 0.1 to 0.5% by weight. ZrO ₂ The high strength of tetragonal ZrO ₂ To monoclinic ZrO ₂ Due to the stress-induced transformation to ₂ O _Three If it is contained, the strength becomes even higher. This is because during sintering, Al ₂ O _Three Shrinkage amount of ZrO ₂ This is because the internal stress of compression is applied because it is smaller than the above. Al ₂ O _Three Has the effect of strengthening the grain boundary, so that the tensile stress resistance is improved. However, Al ₂ O _Three If the amount is too large, the toughness is lowered and the wear resistance is lowered. In the present invention, in the resulting sphere, Al ₂ O _Three The above-mentioned action shown by, and Al during granulation described later ₂ O _Three In consideration of the balance with the above action, the range is set within the range of 0.36 to 0.4% by weight or 0.1 to 0.5% by weight.
[0026]
The bulk density of the sphere is at least 98% of the theoretical density. Thereby, the wear resistance is greatly improved. That is, when the bulk density is less than 98% of the theoretical density, there are many internal voids and wear increases. In addition, the strength becomes insufficient, and it is cracked or chipped by an impact during use. The bulk density is preferably 99% or more of the theoretical density.
[0027]
The wear resistance of the sphere also depends on the average crystal particle size. That is, when the average crystal grain size is less than 0.1 μm, the wear resistance and impact resistance are greatly lowered because there are many grain boundaries and corrosion is likely to proceed. In addition, when the thickness exceeds 0.4 μm, stress-induced transformation is unlikely to occur, so that not only strength but also hardness and toughness are inferior, and wear resistance and impact resistance are also greatly reduced. A preferable range of the average crystal particle diameter is 0.15 to 0.35 μm, and a more preferable range is 0.2 to 0.35 μm.
[0028]
Further, in order to improve the wear resistance, in addition to the average crystal particle diameter being in the above-mentioned range, the average crystal particle diameter Cs in the region from the surface to 1/3 of the radius and 2 / The ratio Ci / Cs to the average crystal particle diameter Ci in the region up to 3 needs to be in the range of 0.8 to 1.2. For example, when the molded spheres are produced by the rolling granulation method, the average crystal particle diameter of the obtained spheres tends to be larger on the inside than on the surface. When such a sphere is used as a pulverizing / dispersing medium, wear progresses remarkably at the initial stage, and the amount of impurities mixed increases drastically. Further, when the molded spheres are produced by the spray granulation method, the average crystal particle diameter of the obtained spheres tends to be larger near the surface than inside. In other words, the average crystal particle diameter inside is small, the number of internal voids increases, and the voids become the starting point of fracture, so the strength is greatly reduced. When such a sphere is used as a pulverizing / dispersing medium, it is easily broken by impact. Moreover, when the inside begins to appear, wear becomes intense, and the amount of impurities mixed in increases rapidly. Thus, the uniformity of the average crystal particle size greatly affects the progress of wear. And even if the average crystal particle diameter of the sphere is in the range of 0.1 to 0.4 μm, if the ratio Ci / Cs of the average crystal particle diameter is less than 0.8, the internal sintering is insufficient. When used as a pulverization / dispersion medium, cracks due to impacts occur, internal wear becomes severe when the surface is worn, and if the ratio Ci / Cs exceeds 1.2, the surface in the initial stage Wear becomes remarkable. A preferred range of the average crystal particle diameter ratio Ci / Cs is 0.9 to 1.1.
[0029]
The sphere preferably has a surface arithmetic average height Ra of 0.05 μm or less. If the arithmetic average height Ra is too large, the initial wear increases. Moreover, it becomes easy to crack when it receives an impact. A preferable arithmetic average height Ra is 0.03 μm or less.
[0030]
The sphere is also monoclinic ZrO ₂ The content of is preferably 10% by weight or less. Monoclinic ZrO ₂ This is because if the amount is too large, the strength decreases, and cracks and wear due to impacts are likely to occur.
[0031]
The sphere of the present invention described above can be manufactured by two methods. This is due to the difference in the manufacturing method of the molded spheres used for sintering. One is the production of molded spheres by rolling granulation, and the other is by spray granulation. The former method using the rolling granulation method is suitable for producing a sphere having a sphere diameter in the range of about 0.2 to 10 mm. The latter method via the spray granulation method is suitable for producing a sphere having a sphere diameter of 0.2 mm or less.
[0032]
The method via the rolling granulation method consists of a stabilizer in the range of 3 to 6% by weight and Al in the range of 0.36 to 0.4% by weight. ₂ O _Three And the Fe content is Fe ₂ O _Three It is 0.003% by weight or less in terms of conversion, and the Ti content is TiO. ₂ It is 0.002% by weight or less in terms of conversion, and the Na content is Na ₂ It is within the range of 0.001 to 0.02% by weight in terms of O, and the content of the sulfate compound is SO. _Four It is within the range of 0.001 to 0.02% by weight in terms of conversion, and the specific surface area is 8 to 13m. ² / ZrO in the range of 0.3 to 0.6 μm in average secondary particle diameter ₂ In this method, the powder is rolled and granulated to obtain a molded sphere, and then the molded sphere is sintered in an oxidizing atmosphere at a temperature in the range of 1,300 to 1,450 ° C.
[0033]
As is well known, the rolling granulation method uses a granulator such as a rotary dish granulator or a rotary drum granulator, and rolls the powder using water as a granulating agent. This is a method of forming a nucleus and growing the nucleus while adding water and powder to obtain a compacted molded sphere. That is, in this method, a molded sphere is grown while compacting by utilizing the weight of the powder.
[0034]
Now, in the method via the rolling granulation method, ZrO containing the same amount of stabilizer is used in order to obtain a sphere containing the stabilizer in the range of 3 to 6% by weight. ₂ Use powder. At this time, Y as a stabilizer ₂ O _Three In addition to CeO ₂ When used together, the sintering temperature can be lowered.
[0035]
ZrO ₂ The powder is also Al within the range of 0.36 to 0.4% by weight. ₂ O _Three Use the one containing. Al ₂ O _Three Is involved in the compaction of the molded spheres during granulation, and the so-called meat portion grows around the core regardless of whether the content is less than 0.36% by weight or more than 0.4% by weight. As a result, the adhesiveness becomes poor and a part where the consolidation is not sufficient can be formed.
[0036]
ZrO ₂ The powder has an Fe content of Fe ₂ O _Three It is 0.003% by weight or less in terms of conversion, and the Ti content is TiO. ₂ It is 0.002% by weight or less in terms of conversion, and the Na content is Na ₂ A substance in the range of 0.001 to 0.02% by weight in terms of O is selected and used. That is, ZrO ₂ The powder contains metal elements derived from the raw materials as impurities. Fe is ZrO ₂ When the amount is large, ZrO ₂ Goes in the direction of stabilization, and the strength decreases. In addition, even in a small amount, the color tone becomes yellow and the commercial value of the sphere is reduced, so the content is Fe ₂ O _Three Select and use 0.003% by weight or less in terms of conversion. Ti is Al ₂ O _Three Reacts to form a compound, Al ₂ O _Three Since the above-mentioned granulation action is inhibited, the content is TiO. ₂ Select and use 0.002% by weight or less in terms of conversion. If the amount of Na is too small, the familiarity with water deteriorates and consolidation during granulation cannot be performed sufficiently. If too much, ZrO ₂ The powders stick together so that a molded sphere with a good shape cannot be obtained, and the particles may grow abnormally during subsequent sintering. Therefore, the Na content is Na ₂ A substance in the range of 0.001 to 0.02% by weight in terms of O is selected and used.
[0037]
As described above, Na greatly affects the moldability during granulation. At this time, if an appropriate amount of a sulfate compound such as sodium sulfate or ammonium sulfate is present, inhibition of moldability by Na can be suppressed. It becomes like this. Therefore, in the present invention, the content of the sulfate compound is SO. _Four ZrO in the range of 0.001 to 0.02% by weight in terms of conversion ₂ Select and use powder. When the amount is less than 0.001% by weight, the above-described suppressing action cannot be expected, and when the amount is more than 0.02% by weight, consolidation is inhibited.
[0038]
ZrO ₂ The powder has a specific surface area of 8-13m ² / G and an average secondary particle diameter in the range of 0.3 to 0.6 μm are selected and used. That is, as described above, the sphere of the present invention has a bulk density of at least 98% of the theoretical density and an average crystal particle diameter in the range of 0.1 to 0.4 μm. In order to obtain a sphere with a small average crystal particle diameter, ZrO excellent in low-temperature sinterability ₂ It is necessary to use powder. However, the specific surface area is 8m. ² If it is less than / g, the low-temperature sinterability is inferior, and in order to obtain the required bulk density, the sintering temperature must be increased, and the average crystal grain size exceeds the above range. 13m ² If it exceeds / g, the sinterability is good, so the bulk density and the average crystal particle size range are satisfied, but a lot of water is required during granulation, and the adhesion between the powders becomes intense and compaction occurs. It becomes non-uniform. On the other hand, in order to make the average secondary particle diameter less than 0.3 μm, it is necessary to pulverize the powder, but when pulverized, monoclinic ZrO ₂ The strength decreases because of the increase. Those exceeding 0.6 μm are inferior in low-temperature sinterability, and in order to obtain the required bulk density, the sintering temperature must be increased, and the average crystal particle diameter exceeds the above-mentioned range.
[0039]
ZrO as described above ₂ The powder itself is generally ZrO ₂ Using chloride as a raw material, etc., after synthesizing powder using hydrolysis method, neutralization coprecipitation method, thermal decomposition method, hydrothermal method, etc., it is fired at 900-1,000 ° C. and wet by ball mill etc. It can be obtained by grinding and further drying. At this time, Al ₂ O _Three There are a method of adding with chloride during synthesis and a method of adding with oxide during grinding. In the case of the neutralization coprecipitation method, there is a method in which Na is added as a neutralizing agent in the synthesis of the powder, and a sulfuric acid compound is added as an additive for improving the uniformity of the distribution of the stabilizer. There is. Any of these will remain as impurities in the powder, but the amount can be controlled by washing with water after firing.
[0040]
In the present invention, the above-mentioned powder is rolled and granulated, and the obtained molded sphere is dried and then sintered at a temperature in the range of 1,300 to 1,450 ° C. in an oxidizing atmosphere. A sphere. ZrO with excellent low-temperature sinterability ₂ Since the powder is formed into a molded sphere, the bulk density is at least 98% of the theoretical density by sintering at a temperature within the range of 1,350 to 1,450 ° C., and the average crystal particle diameter is 0.1 to The sphere can be in the range of 0.4 μm. The sintering conditions, that is, the sintering temperature and the sintering time are appropriately selected depending on the size of the molded sphere. For example, when the sphere diameter is 1 mm or less, it is about 2 hours at 1,350 ° C. to 1,400 ° C., and for those with a larger sphere diameter, it is 2 to 3 at 1,400 to 1,450 ° C. About time.
[0041]
After sintering, the surface is polished to remove undulations and scratches, and further finished to a mirror surface so that the arithmetic average height Ra is 0.05 μm or less. For polishing, a barrel polishing machine can be used. As the abrasive, SiC, Al ₂ O _Three Fine particles such as these can be used. After polishing, the desired sphere diameter is obtained by sieving.
[0042]
On the other hand, the spray granulation method, as is well known, sprays a slurry containing water and powder into a spray dryer such as a disk type spray dryer or a nozzle type spray dryer, that is, sprays into a heating space. And granulating. In the present invention, a spray granulation method for producing a molded sphere can be used. ZrO used at this time ₂ The powder may be basically the same as that obtained by the rolling granulation method described above. The sintering of the molded spheres, the polishing of the resulting spheres, the classification, etc. are exactly the same as in the rolling granulation method. Below, only a different part from the case by a rolling granulation method is demonstrated.
[0043]
ZrO ₂ As powder, Al ₂ O _Three Is used in a range of 0.1 to 0.5% by weight. That is, when spray granulation is used, Al ₂ O _Three Does not affect the molding. Therefore, what is necessary is just to determine the content paying attention to the improvement of the intensity | strength of the obtained sphere. Al ₂ O _Three The content of may be wider than that by the rolling granulation method, and those in the range of 0.1 to 0.5% by weight can be used. If the content is less than 0.1% by weight, an effect of improving the strength cannot be expected, and the resulting sphere is inferior in wear resistance. Moreover, since the toughness will become low if it exceeds 0.5% by weight, it will also be inferior in wear resistance.
[0044]
ZrO ₂ As the powder, the Na content is Na ₂ It is within the range of 0.001 to 0.005% by weight in terms of O, and the content of the sulfate compound is SO. _Four The thing in the range of 0.005-0.03 weight% in conversion is used. Molded spheres by spray granulation are largely dependent on the properties of the slurry, but it is important to prevent large voids and rough parts from being generated inside the molded spheres during drying. During drying, the internal moisture moves to the surface and evaporates from the surface, but if the particles move as the moisture moves, voids are created inside and the interior becomes rough, so the particles do not move. To a certain degree of aggregation. In this regard, Na is Na ₂ In the range of 0.001 to 0.005% by weight in terms of O, the sulfuric acid compound is SO _Four ZrO in the range of 0.005 to 0.03% by weight in terms of average secondary particle diameter in the range of 0.3 to 0.6 μm ₂ Use powder and replace this with ZrO ₂ When the slurry has a powder concentration in the range of about 40 to 70% by weight, an appropriate agglomerated state is obtained, and a molded sphere with very few voids and rough portions can be obtained. Na is Na ₂ If it is less than 0.001% by weight in terms of O, the viscosity of the slurry becomes low, and many voids and rough parts are generated inside the molded sphere. On the other hand, if it exceeds 0.005% by weight, aggregation of particles becomes strong and stable liquid feeding cannot be performed, and the molded sphere has extremely low uniformity in shape, sphere diameter, internal structure and the like. On the other hand, sulfate compounds are SO _Four If the amount is less than 0.005% by weight, the effect of suppressing aggregation cannot be expected, and if it exceeds 0.03% by weight, many large voids and rough parts are generated inside the molded sphere. Become.
[0045]
Examples and Comparative Examples
In the following examples and comparative examples, the average sphere diameter and wear resistance of the spheres were determined as follows.
Average sphere diameter:
The sphere was observed with a stereomicroscope, the image was captured, image processing was performed to determine the equivalent circle diameter, and the average equivalent circle diameter was determined as the average spherical diameter. The n number was 100.
Wear resistance:
Place 1.8 kg of spheres in a ball mill with an internal volume of 660 ml, rub the disc at a speed of 12 m / sec for 40 hours while circulating water maintained at 20 to 30 ° C., and weight Wb before test and after test From the weight Wa of this, it calculated | required by following Formula.
[0046]
Abrasion resistance (%) = ((Wb−Wa) / Wb) × 100
Example 1:
ZrOCl ₂ YCl in aqueous solution _Three Y ₂ O _Three The concentration is 4.78% by weight, and further AlCl is added. _Three Alkaline solution ₂ O _Three A concentration of 0.38 wt% was added, an aqueous ammonium sulfate solution was added thereto, ammonia water was added to coprecipitate the hydroxide, the coprecipitate was washed with a centrifuge and dried, then 970 A fired body was obtained by firing at 0 ° C. for 2 hours.
[0047]
Next, the obtained fired body is dry-pulverized, wet-pulverized in pure water for 5 hours using a ball mill, fine particles and coarse particles are removed using a wet classifier, and an ultrafiltration apparatus is used. After washing with water, spray drying, coarse particles were removed using a dry classifier, and iron was removed using a deironing device to obtain a powder. In the water washing, the water washing was terminated when the electric conductivity of the aqueous solution separated by the ultrafiltration device reached 40 μs / cm. The specifications of the obtained powder were as follows.
[0048]
Y ₂ O _Three Content: 4.78% by weight
Al ₂ O _Three Content: 0.38% by weight
Fe ₂ O _Three Content: 0.0002% by weight
TiO ₂ Content: 0.001% by weight
Na ₂ O content: 0.0011% by weight
SO _Four Content: 0.006% by weight
Specific surface area: 9.8 m ² / G
Average secondary particle size: 0.42 μm
Monoclinic ZrO ₂ Content: 30% by weight
Next, rolling granulation was performed using the above powder to obtain a molded sphere. The obtained molded spheres were sieved and then sintered in air at 1,380 ° C. for 2 hours. During sintering, the molded sphere is made of Al. ₂ O _Three Place the setter on the aluminum setter ₂ O _Three It was put in a metal pot and covered. The obtained sintered body was sieved again and barrel-polished. For polishing, rough polishing with a SiC abrasive for 4 hours, Al ₂ O _Three The main polishing with the abrasive and the SiC abrasive was 4 hours, and the polishing by rubbing was 4 hours without using the abrasive. The specifications of the sphere thus obtained are shown below.
[0049]
Average sphere diameter: 0.3 mm
Y ₂ O _Three Content: 4.78% by weight
Al ₂ O _Three Content: 0.38% by weight
Bulk density: 99.3% of theoretical density
Average crystal particle size: 0.28 μm
Average crystal particle size ratio (ci / Cs): 0.96
Arithmetic mean height Ra: 0.016 μm
Monoclinic ZrO ₂ Content: 6% by weight
Wear resistance: 0.05%
Example 2:
ZrOCl ₂ YCl in aqueous solution _Three Y ₂ O _Three It was added to a concentration of 4.70% by weight, an aqueous sodium sulfate solution was added thereto, an aqueous sodium hydroxide solution was added to coprecipitate the hydroxide, and the coprecipitate was washed with water in a centrifuge and dried. Then, it baked at 980 degreeC for 2 hours, and obtained the sintered body.
[0050]
Next, the fired body obtained was dry-ground and Al ₂ O _Three Add the powder to 0.37% by weight, wet pulverize in pure water for 5 hours using a ball mill, remove fine particles and coarse particles with a wet classifier, and use an ultrafiltration device. After washing with water, spray drying, coarse particles were removed using a dry classifier, and iron was removed using a deironing device to obtain a powder. In the water washing, the water washing was terminated when the electrical conductivity of the aqueous solution separated by the ultrafiltration device reached 180 μs / cm. The specifications of the obtained powder were as follows.
[0051]
Y ₂ O _Three Content: 4.70% by weight
Al ₂ O _Three Content: 0.37% by weight
Fe ₂ O _Three Content: 0.0003 wt%
TiO ₂ Content: 0.001% by weight
Na ₂ O content: 0.016% by weight
SO _Four Content: 0.013% by weight
Specific surface area: 8.5 m ² / G
Average secondary particle size: 0.46 μm
Monoclinic ZrO ₂ Content: 23% by weight
Next, rolling granulation was performed using the above powder to obtain a molded sphere. The obtained molded spheres were sieved and then sintered in the atmosphere at 1,400 ° C. for 2 hours in the same manner as in Example 1. Furthermore, it grind | polished like Example 1 and obtained the sphere. The specifications of the sphere thus obtained are shown below.
[0052]
Average sphere diameter: 3.0 mm
Y ₂ O _Three Content: 4.70% by weight
Al ₂ O _Three Content: 0.37% by weight
Bulk density: 99.3% of theoretical density
Average crystal particle size: 0.30 μm
Average crystal particle size ratio (ci / Cs): 0.93
Arithmetic mean height Ra: 0.022 μm
Monoclinic ZrO ₂ Content: 4.3% by weight
Abrasion resistance: 0.04%
Example 3:
ZrOCl ₂ YCl in aqueous solution _Three Y ₂ O _Three The concentration is 5.16% by weight, and AlCl _Three Alkaline solution ₂ O _Three After adding an aqueous ammonium sulfate solution to a concentration of 0.38% by weight, ammonia water was added to coprecipitate the hydroxide, and the coprecipitate was washed with a centrifuge and dried, and then 950 ° C. Was fired for 2 hours to obtain a fired body.
[0053]
Next, the obtained fired body is dry-pulverized, wet-pulverized in pure water for 5 hours using a ball mill, fine particles and coarse particles are removed using a wet classifier, and an ultrafiltration apparatus is used. After washing with water, spray drying, coarse particles were removed using a dry classifier, and iron was removed using a deironing device to obtain a powder. In the water washing, the water washing was terminated when the electrical conductivity of the aqueous solution separated by the ultrafiltration device reached 30 μs / cm. The specifications of the obtained powder were as follows.
[0054]
Y ₂ O _Three Content: 5.16% by weight
Al ₂ O _Three Content: 0.38% by weight
Fe ₂ O _Three Content: 0.0002% by weight
TiO ₂ Content: 0.001% by weight
Na ₂ O content: 0.0010% by weight
SO _Four Content: 0.020% by weight
Specific surface area: 13.0m ² / G
Average secondary particle size: 0.42 μm
Monoclinic ZrO ₂ Content: 28% by weight
Next, the powder was spray-granulated as a slurry having a concentration of 50% by weight to obtain molded spheres. The obtained molded spheres were sieved and then sintered in the atmosphere at 1,350 ° C. for 2 hours in the same manner as in Example 1. Furthermore, it grind | polished like Example 1 and obtained the sphere. The specifications of the sphere thus obtained are shown below.
[0055]
Average sphere diameter: 0.1 mm
Y ₂ O _Three Content: 4.78% by weight
Al ₂ O _Three Content: 0.38% by weight
Bulk density: 99.4% of theoretical density
Average crystal particle size: 0.27 μm
Average crystal particle size ratio (ci / Cs): 0.98
Arithmetic mean height Ra: 0.009 μm
Monoclinic ZrO ₂ Content: 2.3% by weight
Abrasion resistance: 0.06%
Example 4:
ZrOCl ₂ YCl in aqueous solution _Three Y ₂ O _Three The concentration is 5.39 wt%, and CeCl _Four Aqueous solution of CeO ₂ In addition to the concentration of 0.35% by weight, AlCl _Three Alkaline solution ₂ O _Three After adding an aqueous ammonium sulfate solution to a concentration of 0.26 wt%, ammonia water was added to coprecipitate the hydroxide, and the coprecipitate was washed with water by a centrifuge and dried, then 960 ° C. Was fired for 2 hours to obtain a fired body.
[0056]
Next, the fired body obtained is dry-pulverized, wet-pulverized in pure water for 5 hours using a ball mill, fine particles and coarse particles are removed with a wet classifier, and washed with water using an ultrafiltration device. Then, the particles were spray-dried, coarse particles were removed using a dry classifier, and iron was removed using a deironing device to obtain a powder. In the water washing, the water washing was terminated when the electrical conductivity of the aqueous solution separated by the ultrafiltration device reached 50 μs / cm. The specifications of the obtained powder were as follows.
[0057]
Y ₂ O _Three Content: 5.39% by weight
CeO ₂ Content: 0.35% by weight
Al ₂ O _Three Content: 0.26% by weight
Fe ₂ O _Three Content: 0.0004% by weight
TiO ₂ Content: 0.0012% by weight
Na ₂ O content: 0.0011% by weight
SO _Four Content: 0.025% by weight
Specific surface area: 11.8m ² / G
Average secondary particle size: 0.45 μm
Monoclinic ZrO ₂ Content: 20% by weight
Next, the powder was spray-granulated as a slurry having a concentration of 52% by weight to obtain molded spheres. The obtained molded spheres were sieved and then sintered in the atmosphere at 1,350 ° C. for 2 hours in the same manner as in Example 1. Furthermore, it grind | polished like Example 1 and obtained the sphere. The specifications of the sphere thus obtained are shown below.
[0058]
Average sphere diameter: 0.1 mm
Y ₂ O _Three Content: 4.78% by weight
Al ₂ O _Three Content: 0.38% by weight
Bulk density: 99.0% of theoretical density
Average crystal particle size: 0.24 μm
Average crystal particle size ratio (ci / Cs): 1.04
Arithmetic average height Ra: 0.015 μm
Monoclinic ZrO ₂ Content: 5.7% by weight
Abrasion resistance: 0.08%
Example 5:
ZrOCl ₂ YCl in aqueous solution _Three Y ₂ O _Three The concentration is 4.75% by weight, and AlCl is added thereto. _Three Alkaline solution ₂ O _Three After adding a sodium sulfate aqueous solution after adding 0.39% by weight as a concentration, sodium hydroxide aqueous solution was added to coprecipitate the hydroxide, and the coprecipitate was washed with a centrifuge and dried. Baked at 970 ° C. for 2 hours to obtain a fired body.
[0059]
Next, the fired body obtained is dry-pulverized, wet-pulverized in pure water for 5 hours using a ball mill, fine particles and coarse particles are removed with a wet classifier, and washed with water using an ultrafiltration device. Then, it was spray dried, coarse particles were removed using a dry classifier, and iron was removed using a deironing device to obtain a powder. In the water washing, the water washing was terminated when the electric conductivity of the aqueous solution separated by the ultrafiltration device reached 100 μs / cm. The specifications of the obtained powder were as follows.
[0060]
Y ₂ O _Three Content: 4.75% by weight
Al ₂ O _Three Content: 0.39% by weight
Fe ₂ O _Three Content: 0.0003 wt%
TiO ₂ Content: 0.0011% by weight
Na ₂ O content: 0.0035% by weight
SO _Four Content: 0.011% by weight
Specific surface area: 10.5m ² / G
Average secondary particle size: 0.38 μm
Monoclinic ZrO ₂ Content: 22% by weight
Next, the powder was spray-granulated as a slurry having a concentration of 52% by weight to obtain molded spheres. The obtained molded spheres were sieved and then sintered in the atmosphere at 1,370 ° C. for 2 hours in the same manner as in Example 1. Furthermore, it grind | polished like Example 1 and obtained the sphere. The specifications of the sphere thus obtained are shown below.
[0061]
Average sphere diameter: 0.2 mm
Y ₂ O _Three Content: 4.78% by weight
Al ₂ O _Three Content: 0.38% by weight
Bulk density: 99.3% of theoretical density
Average crystal particle size: 0.26 μm
Average crystal particle size ratio (ci / Cs): 0.95
Arithmetic mean height Ra: 0.008 μm
Monoclinic ZrO ₂ Content: 6.0% by weight
Abrasion resistance: 0.06%
Comparative Example 1:
ZrOCl ₂ YCl in aqueous solution _Three Y ₂ O _Three The concentration was 5.4% by weight, an aqueous sodium sulfate solution was added thereto, and then an aqueous sodium hydroxide solution was added to coprecipitate the hydroxide, and the coprecipitate was washed with water in a centrifuge and dried. Thereafter, it was fired at 1,050 ° C. for 2 hours to obtain a fired body. In the water washing, the water washing was terminated when the electrical conductivity of the aqueous solution separated by the centrifuge reached 400 μs / cm.
[0062]
Next, the fired body obtained was dry-ground and Al ₂ O _Three The powder was added to 0.30% by weight, wet pulverized for 3 hours using a ball mill, spray-dried, and coarse particles were removed using a dry classifier to obtain a powder. The specifications of the obtained powder were as follows.
[0063]
Y ₂ O _Three Content: 5.4% by weight
Al ₂ O _Three Content: 0.30% by weight
Fe ₂ O _Three Content: 0.008% by weight
TiO ₂ Content: 0.01% by weight
Na ₂ O content: 0.03% by weight
SO _Four Content: 0.05% by weight
Specific surface area: 6.5 m ² / G
Average secondary particle size: 1.2 μm
Monoclinic ZrO ₂ Content: 12% by weight
Next, rolling granulation was performed using the above powder to obtain a molded sphere. The obtained molded spheres were sieved and then sintered in the atmosphere at 1,500 ° C. for 2 hours in the same manner as in Example 1. Furthermore, it grind | polished like Example 1 and obtained the spherical body. The specifications of the sphere thus obtained are shown below.
[0064]
Average sphere diameter: 0.3 mm
Y ₂ O _Three Content: 5.4% by weight
Al ₂ O _Three Content: 0.30% by weight
Bulk density: 98.3% of theoretical density
Average crystal particle size: 0.46 μm
Average crystal particle size ratio (ci / Cs): 1.23
Arithmetic mean height Ra: 0.06 μm
Monoclinic ZrO ₂ Content: 12.3% by weight
Abrasion resistance: 0.32%
Comparative Example 2:
ZrOCl ₂ YCl in aqueous solution _Three Y ₂ O _Three A concentration of 5.0% by weight was added, and a sodium hydroxide aqueous solution was added thereto to coprecipitate the hydroxide. The coprecipitate was washed with a centrifuge and dried, and then at 950 ° C., 2%. A fired body was obtained by firing for a period of time. In the water washing, the water washing was terminated when the electrical conductivity of the aqueous solution separated by the centrifuge reached 400 μs / cm.
[0065]
Next, the obtained fired body was dry-ground, wet-ground for 10 hours using a ball mill, and spray-dried to obtain a powder. The specifications of the obtained powder were as follows.
[0066]
Y ₂ O _Three Content: 5.0% by weight
Al ₂ O _Three Content: 0% by weight
Fe ₂ O _Three Content: 0.005% by weight
TiO ₂ Content: 0.02% by weight
Na ₂ O content: 0.04% by weight
SO _Four Content: 0.001% by weight
Specific surface area: 16.0 m ² / G
Average secondary particle size: 0.30 μm
Monoclinic ZrO ₂ Content: 44% by weight
Next, the powder was spray-granulated as a slurry having a concentration of 33% by weight to obtain a molded sphere. The obtained molded spheres were sieved and then sintered in the atmosphere at 1,350 ° C. for 2 hours in the same manner as in Example 1. Furthermore, it grind | polished like Example 1 and obtained the spherical body. The specifications of the sphere thus obtained are shown below.
[0067]
Average sphere diameter: 0.1 mm
Y ₂ O _Three Content: 5.0% by weight
Al ₂ O _Three Content: 0% by weight
Bulk density: 97.8% of theoretical density
Average crystal particle size: 0.24 μm
Average crystal particle size ratio (ci / Cs): 0.77
Arithmetic mean height Ra: 0.08 μm
Monoclinic ZrO ₂ Content: 8.9% by weight
Wear resistance: 0.24%
Comparative Example 3:
ZrOCl ₂ YCl in aqueous solution _Three Y ₂ O _Three A concentration of 5.7% by weight was added, an aqueous ammonium sulfate solution was added thereto, an aqueous ammonium solution was added to coprecipitate the hydroxide, and the coprecipitate was washed with water in a centrifuge and dried, then 920 A fired body was obtained by firing at 0 ° C. for 2 hours.
[0068]
Next, the fired body obtained was dry-ground and Al ₂ O _Three Add the powder to 0.32% by weight, wet pulverize for 10 hours using a ball mill, wash with water using an ultrafiltration device, spray dry, and remove coarse particles using a dry classifier. A powder was obtained. In the water washing, the water washing was terminated when the electrical conductivity of the aqueous solution separated by the ultrafiltration device reached 5 μs / cm. The specifications of the obtained powder were as follows.
[0069]
Y ₂ O _Three Content: 5.7% by weight
Al ₂ O _Three Content: 0.32% by weight
Fe ₂ O _Three Content: 0.008% by weight
TiO ₂ Content: 0.002% by weight
Na ₂ O content: 0.0004% by weight
SO _Four Content: 0.001% by weight
Specific surface area: 18.0 m ² / G
Average secondary particle size: 0.28 μm
Monoclinic ZrO ₂ Content: 45% by weight
Next, the powder was spray-granulated as a slurry having a concentration of 35% by weight to obtain molded spheres. The obtained molded spheres were sieved and then sintered in the atmosphere at 1,350 ° C. for 2 hours in the same manner as in Example 1. Furthermore, it grind | polished like Example 1 and obtained the spherical body. The specifications of the sphere thus obtained are shown below.
[0070]
Average sphere diameter: 0.2 mm
Y ₂ O _Three Content: 5.7% by weight
Al ₂ O _Three Content: 0.32% by weight
Bulk density: 97.3% of theoretical density
Average crystal particle size: 0.23 μm
Average crystal particle size ratio (ci / Cs): 1.23
Arithmetic mean height Ra: 0.10 μm
Monoclinic ZrO ₂ Content: 8.3% by weight
Wear resistance: 0.22%
[0071]
【The invention's effect】
The spheres of the present invention comprise a stabilizer in the range of 3-6% by weight and Al in the range of 0.35-0.4% by weight or in the range of 0.1-0.5% by weight. ₂ O _Three The average crystal particle in the region from the surface to 1/3 of the radius, the bulk density is at least 98% of the theoretical density, the average crystal particle diameter is in the range of 0.1 to 0.4 μm Since the ratio Ci / Cs between the diameter Cs and the average crystal particle diameter Ci in the region from the sphere center to 2/3 of the radius is in the range of 0.8 to 1.2, the examples and comparative examples As is clear from the comparison, it has excellent wear resistance and durability. Therefore, it is suitable as a pulverizing / dispersing medium. Moreover, such spheres can be easily obtained by rolling granulation or spray granulation.

Claims (7)

A stabilizing agent in the range of 3-6 wt%, and a Al ₂ O ₃ in the range of 0.36 to 0.4 wt%, bulk density of at least 98% of the theoretical density, average crystal grain The average crystal particle diameter Cs in the region from 0.1 to 0.4 μm in diameter and from the surface to 1/3 of the radius and the average crystal particle size Ci in the region from the sphere center to 2/3 of the radius. A partially stabilized ZrO ₂ sphere, wherein the ratio Ci / Cs is in the range of 0.8 to 1.2. Average crystal grains comprising a stabilizer in the range of 3-6% by weight and Al ₂ O ₃ in the range of 0.1-0.5% by weight, the bulk density being at least 98% of the theoretical density The average crystal particle diameter Cs in the region from 0.1 to 0.4 μm in diameter and from the surface to 1/3 of the radius and the average crystal particle size Ci in the region from the sphere center to 2/3 of the radius. A partially stabilized ZrO ₂ sphere, wherein the ratio Ci / Cs is in the range of 0.8 to 1.2. The partially stabilized ZrO ₂ sphere according to claim 1 or 2, wherein the arithmetic average height Ra of the surface is 0.05 µm or less. The partially stabilized ZrO ₂ sphere according to any one of claims 1 to 3, wherein the content of monoclinic ZrO ₂ is 10% by weight or less. A pulverizing / dispersing medium comprising the partially stabilized ZrO ₂ sphere according to claim 1. It contains a stabilizer in the range of 3 to 6% by weight and Al ₂ O ₃ in the range of 0.36 to 0.4% by weight, and the Fe content is 0.003% in terms of Fe ₂ O ₃ % Or less, the Ti content is 0.002% by weight or less in terms of TiO ₂ , the Na content is in the range of 0.001 to 0.02% by weight in terms of Na ₂ O, and the sulfuric acid compound Is in the range of 0.001 to 0.02% by weight in terms of SO ₄ , the specific surface area is in the range of 8 to 13 m ² / g, and the average secondary particle size is 0.3 to 0.00. After rolling and granulating ZrO ₂ powder in the range of 6 μm to obtain molded spheres, the molded spheres are sintered in an oxidizing atmosphere at a temperature in the range of 1,300 to 1,450 ° C. A method for producing a partially stabilized ZrO ₂ sphere characterized by It contains a stabilizer in the range of 3 to 6% by weight and Al ₂ O ₃ in the range of 0.1 to 0.5% by weight, and the Fe content is 0.003% in terms of Fe ₂ O ₃ And the content of Ti is 0.002% by weight or less in terms of TiO ₂ , the content of Na is in the range of 0.001 to 0.005% by weight in terms of Na ₂ O, and the sulfuric acid compound Is in the range of 0.005 to 0.03% by weight in terms of SO ₄ , the specific surface area is in the range of 8 to 13 m ² / g, and the average secondary particle size is 0.3 to 0.00. After spray granulating ZrO ₂ powder in the range of 6 μm to obtain a molded sphere, sintering the molded sphere at a temperature in the range of 1,300 to 1,450 ° C. in an oxidizing atmosphere. A method for producing a partially stabilized ZrO ₂ sphere characterized.