JP5036110B2 - Lightweight ceramic sintered body - Google Patents
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- JP5036110B2 JP5036110B2 JP2001224178A JP2001224178A JP5036110B2 JP 5036110 B2 JP5036110 B2 JP 5036110B2 JP 2001224178 A JP2001224178 A JP 2001224178A JP 2001224178 A JP2001224178 A JP 2001224178A JP 5036110 B2 JP5036110 B2 JP 5036110B2
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- 239000000919 ceramic Substances 0.000 title claims description 16
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- KZHJGOXRZJKJNY-UHFFFAOYSA-N dioxosilane;oxo(oxoalumanyloxy)alumane Chemical compound O=[Si]=O.O=[Si]=O.O=[Al]O[Al]=O.O=[Al]O[Al]=O.O=[Al]O[Al]=O KZHJGOXRZJKJNY-UHFFFAOYSA-N 0.000 description 2
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- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 1
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Description
【０００１】
【発明の属する技術分野】
本発明は、耐熱性、耐クリープ性、耐食性などにすぐれた軽量セラミック焼結体に関する。なお、本発明でいう耐熱性とは耐熱衝撃抵抗性だけでなく、加熱・冷却の繰り返しに対する耐久性をも意味する。
【０００２】
【従来技術とその問題点】
従来の多孔質焼結体は、焼結体が有する気孔が必ずしも密閉でなく、貫通気孔を多く含み、機械的特性および耐食性が低く、耐火物としての用途しか使用できないものであった。また、緻密質からなる焼結体は機械的特性および耐食性は多孔質焼結体に比べて高いものの耐熱性に欠けるという問題を有している。
【０００３】
さらに、最近では、焼結体を作製する際に気孔形成剤を添加して、気孔を有効に利用して耐熱性の向上をねらったものもあるが、気孔径だけでなく、その気孔径分布ならびに気孔形状までは制御されていないため、十分な効果が得られていないのが実状である。
【０００４】
【発明が解決しようとする課題】
本発明の目的は、耐熱性、耐クリープ性および耐食性にすぐれた軽量セラミック焼結体を提供することにある。
【０００５】
【課題を解決するための手段】
本発明者らは、前記のような現状を鑑み鋭意研究を重ねた結果、相対密度、結晶粒径、密閉気孔径およびその形状を制御することによりすぐれた耐熱性、耐クリープ性および耐食性を有する軽量セラミック焼結体が得られることを見出した。
なお、一般的に十分に焼結させた場合は、結晶粒子同士がきっちりと隙間なくひっついた状態になるが、十分に焼結させない場合には結晶粒子と結晶粒子との間に隙間（気孔）ができる。このようにしてできた隙間を利用したのが、従来タイプの軽量セラミック焼結体であり、当然耐熱性をはじめとする機械的特性が低い。もう１つの従来タイプの軽量セラミック焼結体は耐火物であり、粒度の大きい原料を使用して高温で焼成したものであるため、結晶粒径がかなり大きく機械的特性が低く、耐食性が低いなどの欠点がある。これに対して、本発明のものは、結晶粒子同士をきっちり焼結させ、気孔径および気孔形状を制御しているため、耐熱性、耐クリープ性および強度が高く、耐食性にすぐれた軽量セラミック焼結体とすることができる。
【０００６】
本発明は、（ａ）相対密度が７０〜９５％である焼結体からなり、（ｂ）その平均結晶粒径が５〜５０μｍであり、（ｃ）存在する気孔は実質的に密閉したものであって、その平均密閉気孔径が２〜５０μｍであり、（ｄ）その密閉気孔断面の短径と長径の比の平均値が０．６０以上であり、（ｅ）平均密閉気孔径と密閉気孔径の標準偏差から求められる変動係数が４０％以下であり、（ｆ）密閉気孔断面の短径と長径の比の平均値と密閉気孔断面の短径と長径の比の標準偏差とから求められる変動係数が３０％以下であることを特徴とする軽量セラミック焼結体に関する。
【０００７】
本発明の軽量セラミック焼結体はアルミナ質、マグネシア質、ムライト質、スピネル質、ジルコニア質に適用することが可能である。
【０００８】
本発明における密閉気孔の形成には、粉砕・分散スラリーに所定の相対密度および気孔径になるように気孔形成剤としてのアクリル系樹脂球状粒子や多糖類球状粒子などの有機質球状粒子のような有機質で丸味を帯びた粒子を使用することが必要である。この気孔形成剤をセラミック粉体に添加、混合して成形し、これを焼成すると、有機質の気孔形成剤は消失し、跡形としての密閉気孔が残るので、密閉気孔の形状は本質的には気孔形成剤の形状に基因した形状となり、密閉気孔は丸味を帯びた形状となる。気孔形状が丸味を帯びていない場合には、焼結体に応力が負荷されると気孔に応力集中がおこりやすくなって、耐熱性、耐クリープ性および強度の低下が起るので好ましくない。また、気孔径および気孔径分布は気孔形成剤の粒子径に依存するため、使用する気孔形成剤は所定の気孔径および気孔径分布になるように整粒することが必要である。
【０００９】
本発明においては、（ａ）相対密度は７０〜９５％であり、より好ましくは７５〜９０％であることが必要である。本発明でいう相対密度とは（焼結体かさ密度／理論密度）×１００（％）で算出したものを表す。相対密度が７０％未満の場合は気孔量が多くなり、各々の気孔がつながって気孔径が大きくなり、強度低下、耐クリープ性の低下や耐食性の低下をきたすので好ましくない。また、相対密度が９５％を越える場合は耐熱性の低下をきたすので好ましくない。
【００１０】
本発明においては、（ｂ）平均結晶粒径は５〜５０μｍであることが必要であり、より好ましくは１０〜４０μｍである。平均結晶粒径が５μｍ未満の場合は、耐熱性が低下するだけでなく、耐食性が低下するので好ましくない。一方、５０μｍを越える場合には耐熱性が低下するので好ましくない。
【００１１】
平均結晶粒径は、焼結体を鏡面仕上げし、熱エッチングを施し、走査電子顕微鏡で観察し、インターセプト法により１０点平均から求める。算出式としては、
【数１】
Ｄ＝１．５×Ｌ／ｎ
〔Ｄ：平均結晶粒径（μｍ）、Ｌ：測定長さ（μｍ）、
ｎ：長さＬ当たりの結晶数〕
を用いる。
【００１２】
本発明においては、（ｃ）平均密閉気孔径は２〜５０μｍ、好ましくは５〜３０μｍ、より好ましくは５〜２５μｍである。平均密閉気孔径が２μｍ未満の場合は気孔形成による耐熱性の向上の効果が少なく、５０μｍを越える場合には密閉気孔が連続状態になったり、強度低下および耐クリープ性の低下をきたすため好ましくない。
【００１３】
平均密閉気孔径は焼結体断面を鏡面仕上げし、走査電子顕微鏡で観察し、気孔部分と気孔でない部分との二値化像から１００個の気孔断面積を測定し、その測定した断面積（Ｓ）から下式により等価円直径（Ｌ）に換算し、その等価円直径の平均値（Ｐ）を求め、平均密閉気孔径＝１．５×Ｐとして求める。
【数２】
Ｌ＝（Ｓ／π）０．５
【００１４】
本発明においては、（ｄ）その密閉気孔断面の短径と長径の比（短径／長径）の平均値が０．６０以上、より好ましくは０．６５以上であることが必要であり、可能な限り１に近い方が好ましい。これらの数値は、上記の平均密閉気孔径の測定方法と全く同様に焼結体断面を鏡面仕上げし、走査電子顕微鏡で観察し、二値化像から１００個の気孔の長径と短径を測定し、短径と長径の比を求め、その平均値を求める。短径と長径の比が０．６０未満の場合は、気孔形状が細長くなり、気孔の曲率半径が小さくなり、応力集中が起こりやすくなって、耐熱性、耐クリープ性および強度の低下をきたすので好ましくない。
【００１５】
短径と長径の比が本発明の範囲内のものである実施例３の焼結体断面を走査電子顕微鏡で観察し、その微構造観察写真を図１の（Ａ）に、気孔分布状態（二値化像）を図１の（Ｂ）に示し、本発明の範囲外のものである比較例７の焼結体断面を走査電子顕微鏡で観察し、その微構造観察写真を図２の（Ａ）に、気孔分布状態（二値化像）を図２の（Ｂ）に示す。
【００１６】
本発明においては、（ｅ）平均密閉気孔径と密閉気孔径の標準偏差から求められる変動係数を４０％以下とするが、０％に近いほど好ましい。変動係数とは下記により求められる係数であり、変動係数が大きいということは密閉気孔径分布が広いことを意味する。
〔数３〕
変動係数＝（密閉気孔径の標準偏差／平均密閉気孔径）×１００（％）
本発明の軽量セラミック焼結体は、密閉気孔径分布を狭くすることにより、加わる負荷応力を分散させる効果があるが、変動係数が４０％を越えると密閉気孔径の分布が広くなり、負荷応力に対し、気孔に応力集中が起きやすくなり、耐熱性、耐クリープ性および強度の低下が起こるので好ましくない。
【００１７】
本発明においては、（ｆ）密閉気孔断面の短径と長径の比の平均値と密閉気孔断面の短径と長径の比の標準偏差とから求められる変動係数が３０％以下、より好ましくは２５％以下であることが望ましく、０％に近いほど好ましい。密閉気孔の短径と長径の比の変動係数が３０％を越えると密閉気孔形状が扁平した形状の気孔が多く存在し、扁平形状を有する気孔に応力集中が起きやすくなって耐熱性、耐クリープ性および強度の低下が起こるので好ましくない。
【００１８】
本発明の軽量セラミック焼結体は種々の方法で作製できるが、その一例を以下に示す。
所望の組成になるようにアルミナ、マグネシア、ムライト、スピネルおよびジルコニアから選ばれた原料粉末を配合し、溶媒として水または有機溶媒を用いて、ポットミル、アトリッションミル等の粉砕機により粉砕・分散・混合する。なお、原料粉末は純度が９９％以上、平均粒子径が２μｍ以下であることが好ましく、より好ましくは１．５μｍ以下である。平均粒子径が２μｍを越える場合には、焼結体内部に欠陥が多く存在するため、耐熱性をはじめとする機械的特性の低下をきたすので好ましくない。得られた混合粉体の平均粒子径は１．５μｍ以下、より好ましくは１．０μｍ以下である。平均粒子径がこれらの範囲外の場合には成形性の低下や得られた焼結体に欠陥が多く存在するだけでなく、本発明の微構造を有した焼結体が得られず、耐熱性が低下するだけでなく、その他の機械的特性および耐食性の低下が起こるので好ましくない。
【００１９】
得られた混合粉体の成形方法としてプレス成形、ラバープレス成形等の方法を採用する場合には、混合粉体の分散スラリーに必要により公知の成形助剤（例えばワックスエマルジョン、ＰＶＡ、アクリル系樹脂等）を加え、さらに気孔形成剤としてアクリル系球状粒子または多糖類球状粒子を所定の相対密度になるように添加し、スプレードライヤー等の公知の方法で乾燥させて成形粉体を作製し、これを用いて成形する。また、鋳込成形法を採用する場合には、混合粉体の分散スラリーに必要により公知のバインダー（例えばワックスエマルジョン、アクリル系樹脂等）を加え、さらに気孔形成剤としてアクリル系球状粒子または多糖類球状粒子を所定の相対密度になるように添加し、石膏型あるいは樹脂型を用いて排泥鋳込、充填鋳込、加圧鋳込法により成形する。なお、添加する気孔形成剤は所定の気孔径および気孔分布になるように整粒することが必要である。さらに、押出成形法を採用する場合には、混合粉体の分散したスラリーに気孔形成剤としてアクリル系球状粒子または多糖類球状粒子を所定の相対密度になるように添加し、乾燥、整粒し、混合機を用いて水、バインダー（例えばメチルセルロース等）を混合して坏土を作製し、押出成形する。
【００２０】
以上のようにして得られた成形体を１５００〜１８００℃、より好ましくは１６００〜１７５０℃で焼成することによって焼結体を得る。
【００２１】
【実施例】
以下に実施例を示し、本発明を説明するが、本発明はこれにより何ら限定されるものでない。
【００２２】
実施例１〜８および比較例１〜８
純度９９．８％、平均粒子径２μｍからなるアルミナ粉末と溶媒に水を用いてポットミルで粉砕・分散・混合し、スラリーを作製した。気孔形成剤としてはアクリル系樹脂球状粒子、多糖類球状粒子またはセルロースパウダーを表１に示すような量で添加、混合した。得られたスラリーにＰＶＡ等のバインダーを添加し、スプレードライヤー乾燥を施して成形用粉体とした。得られた成形用粉体を金型を用いて１ｔｏｎｆ／ｃｍ２の圧力でプレス成形し、１４５０〜２２００℃で焼成して、１５０ｍｍ角で厚さ５ｍｍの板を作製した。得られた実施例１〜８、比較例１〜８の板状セッターの焼結体特性を表１〜２に示す。
【００２３】
実施例１〜８は本発明の範囲内の高機能多孔質焼結体であり、比較例１〜８は本発明の要件を少なくとも一つ以上満足させていない焼結体である。なお、比較例３および８は整粒しない気孔形成剤を使用し、比較例７は不定形からなるセルロースパウダーを使用した。また、比較例２および４は気孔形成剤を添加せずに作製した焼結体で、比較例２は平均粒子径１０μｍからなる粉末を使用した。これらのデーターから本発明の軽量セラミック焼結体はすぐれた耐熱性を有することが明らかである。
【００２４】
耐熱衝撃抵抗性は、耐火物の上に得られた板を載せて１０００℃に加熱保持している電気炉中に挿入し、３０分加熱保持後、耐火物に載せたまま即座に炉外に取り出し、室温下で急冷し、割れの有無により評価した。また、上記と同条件の繰り返しによるクラック発生の有無により耐久性を評価した。
また、耐クリープ性は焼結体を５×２×１５０ｍｍに加工し、上スパン：３１．３ｍｍ、下スパン：１００ｍｍの４点曲げで、２ＭＰａの応力で１４００℃、５時間保持後のサンプルの下スパン５０ｍｍの位置のたわみ量を測定した。
さらに、耐食性は市販のＰＺＴ粉末を直径２５ｍｍ、厚さ５ｍｍに成形した成形体を焼結体の上にのせ、さらに成形体に１ｋＰａの応力をかけた状態で１３００℃、５時間保持を２サイクル行い、テスト後の焼結体断面を鏡面仕上げし、ＥＤＸ分析により浸食深さを測定した。
【００２５】
【表１】
【発明の効果】
本発明の軽量セラミック焼結体は表１〜２に示すとおり耐熱性および耐食性にすぐれている。そのため圧電体、誘電体などの電子部品材料、リチウムイオン２次電池正極材料、蛍光体材料およびセラミック材料の熱処理用容器、単結晶育成用ルツボ、金属溶解用ルツボ、各種電気炉用炉心管、サポートチューブ、ラジアントチューブ、ガス吹込管、ガス採取管、測温用熱電対および各種機器用の保護管、サポート用治具材などの熱処理用部材だけでなく、気孔径だけでなく気孔形状をも制御した密閉気孔からなるため、緻密質の焼結体と同等の機械的特性および耐食性を有しながら、軽量であるため、熱処理用部材として省エネルギー効果があり、また耐熱性が要求される機械部品にも十分使用可能である。
【図面の簡単な説明】
【図１】図１の（Ａ）は、短径と長径の比が本発明の範囲内である実施例３の焼結体断面を走査電子顕微鏡で観察して得られた微構造観察写真であり、（Ｂ）は、その気孔分布状態（二値化像）を示す。
【図２】図２の（Ａ）は、短径と長径の比が本発明の範囲外である比較例７の焼結体断面を走査電子顕微鏡で観察して得られた微構造観察写真であり、（Ｂ）はその気孔分布状態（二値化像）を示す。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a lightweight ceramic sintered body excellent in heat resistance, creep resistance, corrosion resistance and the like. The heat resistance referred to in the present invention means not only thermal shock resistance but also durability against repeated heating and cooling.
[0002]
[Prior art and its problems]
The conventional porous sintered body is not necessarily hermetically sealed in pores, contains many through-holes, has low mechanical properties and corrosion resistance, and can only be used as a refractory. In addition, a sintered body made of a dense material has a problem that it lacks heat resistance although it has higher mechanical properties and corrosion resistance than a porous sintered body.
[0003]
In addition, recently, there are those that aim to improve the heat resistance by effectively using the pores by adding a pore forming agent when producing the sintered body, but not only the pore diameter but also the pore size distribution. In addition, since the pore shape is not controlled, a sufficient effect is not obtained.
[0004]
[Problems to be solved by the invention]
An object of the present invention is to provide a lightweight ceramic sintered body excellent in heat resistance, creep resistance and corrosion resistance.
[0005]
[Means for Solving the Problems]
As a result of intensive studies in view of the above situation, the present inventors have excellent heat resistance, creep resistance and corrosion resistance by controlling the relative density, crystal grain size, closed pore size and shape thereof. It has been found that a lightweight ceramic sintered body can be obtained.
In general, when fully sintered, the crystal particles are tightly attached with no gap, but when not fully sintered, there is a gap (pore) between the crystal particles. Can do. The gap formed in this way is a conventional lightweight ceramic sintered body, which naturally has low mechanical properties such as heat resistance. Another conventional type of lightweight ceramic sintered body is a refractory material, which is fired at a high temperature using a raw material with a large particle size, so the crystal grain size is quite large, the mechanical properties are low, the corrosion resistance is low, etc. There are disadvantages. In contrast, according to the present invention, since the crystal grains are precisely sintered and the pore diameter and pore shape are controlled, the heat resistance, creep resistance and strength are high, and the lightweight ceramic firing excellent in corrosion resistance is achieved. It can be a ligation.
[0006]
The present invention comprises (a) a sintered body having a relative density of 70 to 95%, (b) an average crystal grain size of 5 to 50 μm, and (c) existing pores being substantially sealed. And the average closed pore diameter is 2 to 50 μm, (d) the average ratio of the short diameter and long diameter of the closed pore cross section is 0.60 or more, and (e) the average closed pore diameter and the sealed The coefficient of variation obtained from the standard deviation of the pore diameter is 40% or less. (F) It is obtained from the average value of the ratio of the minor axis to the major axis of the closed pore section and the standard deviation of the ratio of the minor axis to the major axis of the sealed pore section. The present invention relates to a lightweight ceramic sintered body characterized by having a variation coefficient of 30% or less.
[0007]
The lightweight ceramic sintered body of the present invention can be applied to alumina, magnesia, mullite, spinel, and zirconia.
[0008]
In the formation of closed pores in the present invention, organic substances such as organic spherical particles such as acrylic resin spherical particles and polysaccharide spherical particles are used as pore forming agents so as to have a predetermined relative density and pore diameter in the pulverized / dispersed slurry. It is necessary to use rounded particles. When this pore-forming agent is added to ceramic powder, mixed and molded, and then fired, the organic pore-forming agent disappears and the closed pores remain as traces, so the shape of the closed pores is essentially a pore. The shape is based on the shape of the forming agent, and the closed pores are rounded. When the pore shape is not round, stress is easily concentrated on the pores when stress is applied to the sintered body, which is not preferable because heat resistance, creep resistance, and strength are reduced. Moreover, since the pore diameter and the pore diameter distribution depend on the particle diameter of the pore-forming agent, the pore-forming agent to be used needs to be sized so as to have a predetermined pore diameter and pore diameter distribution.
[0009]
In the present invention, (a) the relative density is 70 to 95%, more preferably 75 to 90%. The relative density referred to in the present invention represents a value calculated by (sintered body bulk density / theoretical density) × 100 (%). When the relative density is less than 70%, the amount of pores is increased, and the pores are connected to increase the pore diameter, resulting in a decrease in strength, a decrease in creep resistance, and a decrease in corrosion resistance. On the other hand, if the relative density exceeds 95%, the heat resistance is lowered, which is not preferable.
[0010]
In the present invention, (b) the average crystal grain size needs to be 5 to 50 μm, more preferably 10 to 40 μm. When the average crystal grain size is less than 5 μm, not only the heat resistance is lowered but also the corrosion resistance is lowered. On the other hand, if it exceeds 50 μm, the heat resistance is lowered, which is not preferable.
[0011]
The average crystal grain size is obtained from an average of 10 points by the intercept method after mirror-finishing the sintered body, applying thermal etching, and observing with a scanning electron microscope. As a formula,
[Expression 1]
D = 1.5 × L / n
[D: average crystal grain size (μm), L: measurement length (μm),
n: number of crystals per length L]
Is used.
[0012]
In the present invention, (c) the average closed pore diameter is 2 to 50 μm, preferably 5 to 30 μm, more preferably 5 to 25 μm. When the average closed pore diameter is less than 2 μm, the effect of improving the heat resistance by pore formation is small, and when it exceeds 50 μm, the closed pores become continuous or decrease in strength and creep resistance. .
[0013]
The average hermetic pore diameter is obtained by mirror-sintering the sintered body cross section, observing with a scanning electron microscope, measuring 100 pore cross sections from the binarized image of the pore portion and the non-pore portion, and measuring the measured cross sectional area ( The equivalent circle diameter (L) is converted from S) to the equivalent circle diameter (L), the average value (P) of the equivalent circle diameter is obtained, and the average closed pore diameter is obtained as 1.5 × P.
[Expression 2]
L = (S / π) 0.5
[0014]
In the present invention, (d) the average value of the ratio of the minor axis to the major axis (minor axis / major axis) of the hermetic pore cross section is required to be 0.60 or more, more preferably 0.65 or more. As close to 1 as possible. These numerical values are the same as the measurement method of the average closed pore diameter described above, and the cross section of the sintered body is mirror-finished and observed with a scanning electron microscope, and the major and minor diameters of 100 pores are measured from the binarized image. Then, the ratio of the minor axis to the major axis is obtained, and the average value is obtained. If the ratio of the minor axis to the major axis is less than 0.60, the pore shape becomes elongated, the radius of curvature of the pores becomes smaller, stress concentration tends to occur, and heat resistance, creep resistance and strength are reduced. It is not preferable.
[0015]
The cross section of the sintered body of Example 3 in which the ratio of the minor axis to the major axis is within the scope of the present invention is observed with a scanning electron microscope, and the microstructure observation photograph is shown in FIG. (Binarized image) is shown in FIG. 1 (B), the cross section of the sintered body of Comparative Example 7 which is outside the scope of the present invention is observed with a scanning electron microscope, and the microstructure observation photograph is shown in FIG. FIG. 2B shows a pore distribution state (binarized image) in FIG.
[0016]
In the present invention, (e) the coefficient of variation obtained from the average hermetic pore diameter and the standard deviation of hermetic pore diameter is 40 % or less , but it is preferably as close to 0% as possible. The coefficient of variation is a coefficient obtained by the following, and a large coefficient of variation means that the closed pore size distribution is wide.
[Equation 3]
Coefficient of variation = (standard deviation of sealed pore diameter / average sealed pore diameter) x 100 (%)
The lightweight ceramic sintered body of the present invention has the effect of dispersing the applied stress by narrowing the closed pore size distribution, but if the coefficient of variation exceeds 40 %, the distribution of the sealed pore size becomes wider and the load stress is increased. On the other hand, stress concentration tends to occur in the pores, and heat resistance, creep resistance, and strength are reduced, which is not preferable.
[0017]
In the present invention, the coefficient of variation obtained from (f) the average value of the ratio of the minor axis to the major axis of the closed pore section and the standard deviation of the ratio of the minor axis to the major axis of the sealed pore section is 30% or less, more preferably 25. % Or less is desirable, and the closer to 0%, the better. If the coefficient of variation of the ratio between the short diameter and long diameter of the closed pore exceeds 30%, there are many pores with a flat closed pore shape, and stress concentration tends to occur in the flat pores, resulting in heat resistance and creep resistance. It is not preferable because the property and strength are lowered.
[0018]
The lightweight ceramic sintered body of the present invention can be produced by various methods, an example of which is shown below.
A raw material powder selected from alumina, magnesia, mullite, spinel and zirconia is blended so as to have a desired composition, and water or an organic solvent is used as a solvent, and pulverized and dispersed by a pulverizer such as a pot mill or an attrition mill.・ Mix. The raw material powder preferably has a purity of 99% or more and an average particle size of 2 μm or less, more preferably 1.5 μm or less. When the average particle diameter exceeds 2 μm, many defects are present inside the sintered body, which is not preferable because the mechanical properties such as heat resistance are deteriorated. The average particle size of the obtained mixed powder is 1.5 μm or less, more preferably 1.0 μm or less. When the average particle size is outside these ranges, not only the moldability is deteriorated and the obtained sintered body has many defects, but the sintered body having the microstructure of the present invention cannot be obtained, This is not preferable because the mechanical properties and the corrosion resistance are lowered.
[0019]
When a method such as press molding or rubber press molding is employed as a molding method for the obtained mixed powder, a known molding aid (for example, wax emulsion, PVA, acrylic resin) is used for the dispersed slurry of the mixed powder as necessary. In addition, acrylic spherical particles or polysaccharide spherical particles are added as pore forming agents so as to have a predetermined relative density, and dried by a known method such as a spray dryer to produce a molded powder. To mold. In addition, when adopting the casting method, a known binder (for example, wax emulsion, acrylic resin, etc.) is added to the dispersed slurry of the mixed powder as required, and acrylic spherical particles or polysaccharides are further used as pore forming agents. Spherical particles are added so as to have a predetermined relative density, and molding is performed using a gypsum mold or a resin mold by waste mud casting, filling casting, or pressure casting. The pore forming agent to be added needs to be sized so as to have a predetermined pore diameter and pore distribution. Furthermore, when adopting the extrusion molding method, acrylic spherical particles or polysaccharide spherical particles are added as a pore-forming agent to the slurry in which the mixed powder is dispersed so as to have a predetermined relative density, dried and sized. Then, using a mixer, water and a binder (for example, methylcellulose) are mixed to prepare a clay, and extrusion molding is performed.
[0020]
The molded body obtained as described above is fired at 1500 to 1800 ° C., more preferably 1600 to 1750 ° C., to obtain a sintered body.
[0021]
【Example】
The present invention will be described below with reference to examples, but the present invention is not limited thereby.
[0022]
Examples 1-8 and Comparative Examples 1-8
A slurry was prepared by pulverizing, dispersing, and mixing with a pot mill using alumina powder having a purity of 99.8% and an average particle diameter of 2 μm and water as a solvent. As the pore forming agent, acrylic resin spherical particles, polysaccharide spherical particles or cellulose powder was added and mixed in an amount as shown in Table 1. A binder such as PVA was added to the obtained slurry, followed by spray dryer drying to obtain a molding powder. The obtained molding powder was press-molded with a mold at a pressure of 1 tonf / cm 2 and fired at 1450 to 2200 ° C. to produce a 150 mm square and 5 mm thick plate. The sintered compact characteristic of the plate-shaped setter of obtained Examples 1-8 and Comparative Examples 1-8 is shown to Tables 1-2.
[0023]
Examples 1 to 8 are highly functional porous sintered bodies within the scope of the present invention, and Comparative Examples 1 to 8 are sintered bodies that do not satisfy at least one of the requirements of the present invention. In Comparative Examples 3 and 8, a pore-forming agent that does not adjust the size was used, and in Comparative Example 7, cellulose powder having an irregular shape was used. Comparative Examples 2 and 4 were sintered bodies prepared without adding a pore-forming agent, and Comparative Example 2 used a powder having an average particle diameter of 10 μm. From these data, it is clear that the lightweight ceramic sintered body of the present invention has excellent heat resistance.
[0024]
The thermal shock resistance is determined by inserting the plate obtained on the refractory and inserting it into an electric furnace that is heated and held at 1000 ° C. After heating and holding for 30 minutes, it is immediately put out of the furnace while being placed on the refractory. The sample was taken out, rapidly cooled at room temperature, and evaluated by the presence or absence of cracks. Moreover, durability was evaluated by the presence or absence of the crack generation by repetition of the same conditions as the above.
In addition, the creep resistance is obtained by processing the sintered body to 5 × 2 × 150 mm, and bending the sample after holding it at 1400 ° C. for 5 hours with a stress of 2 MPa by four-point bending with an upper span of 31.3 mm and a lower span of 100 mm. The amount of deflection at the position of the lower span of 50 mm was measured.
Furthermore, the corrosion resistance is 2 cycles of holding 1300 ° C. for 5 hours under the condition that a molded body made of commercially available PZT powder with a diameter of 25 mm and a thickness of 5 mm is placed on the sintered body and a stress of 1 kPa is applied to the molded body. The cross section of the sintered body after the test was mirror finished, and the erosion depth was measured by EDX analysis.
[0025]
[Table 1]
【Effect of the invention】
The lightweight ceramic sintered body of the present invention is excellent in heat resistance and corrosion resistance as shown in Tables 1 and 2. Therefore, electronic component materials such as piezoelectrics and dielectrics, lithium ion secondary battery positive electrode materials, phosphor materials and ceramics heat treatment vessels, single crystal growth crucibles, metal melting crucibles, various electric furnace core tubes, support Controls not only the pore diameter but also the pore shape as well as heat treatment members such as tubes, radiant tubes, gas injection tubes, gas sampling tubes, thermocouples for temperature measurement and protection tubes for various devices, support jig materials, etc. Because it is made of sealed pores, it has the same mechanical properties and corrosion resistance as a dense sintered body, but it is lightweight, so it has an energy saving effect as a heat-treating member, and it is a mechanical part that requires heat resistance. Can also be used sufficiently.
[Brief description of the drawings]
FIG. 1 (A) is a microstructure observation photograph obtained by observing a cross section of a sintered body of Example 3 in which the ratio of the minor axis to the major axis is within the scope of the present invention, with a scanning electron microscope. Yes, (B) shows the pore distribution state (binarized image).
FIG. 2A is a microstructure observation photograph obtained by observing a cross section of a sintered body of Comparative Example 7 in which the ratio of the minor axis to the major axis is outside the scope of the present invention with a scanning electron microscope. Yes, (B) shows the pore distribution state (binarized image).
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| JP2016150989A (en) * | 2015-02-18 | 2016-08-22 | 日東電工株式会社 | Method for producing phosphor ceramic |
| JP6625841B2 (en) * | 2015-07-23 | 2019-12-25 | 株式会社メタルスファンドリィ | Manufacturing method of castable refractory with enhanced heat insulation |
| KR20210121024A (en) * | 2019-02-01 | 2021-10-07 | 가부시키가이샤 노리타케 캄파니 리미티드 | Metal bond grindstone for hard and brittle materials |
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| JP7387898B2 (en) * | 2020-06-08 | 2023-11-28 | 日本特殊陶業株式会社 | Fluorescent screen, wavelength conversion member, and light source device |
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| JP7615747B2 (en) * | 2021-02-19 | 2025-01-17 | セイコーエプソン株式会社 | Amorphous metal ribbon, manufacturing method thereof, and magnetic core |
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