JP3837555B2 - Method for producing foam sintered body containing metal or ceramics - Google Patents

Method for producing foam sintered body containing metal or ceramics Download PDF

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JP3837555B2
JP3837555B2 JP2003272559A JP2003272559A JP3837555B2 JP 3837555 B2 JP3837555 B2 JP 3837555B2 JP 2003272559 A JP2003272559 A JP 2003272559A JP 2003272559 A JP2003272559 A JP 2003272559A JP 3837555 B2 JP3837555 B2 JP 3837555B2
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foam
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foaming
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透 清水
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National Institute of Advanced Industrial Science and Technology AIST
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本発明は、金属又はセラミックス含有発泡焼結体の製造方法に関する。   The present invention relates to a method for producing a metal or ceramic-containing foam sintered body.

従来、金属発泡焼結成形体の製造法としては、溶融した金属中にガスを吹き込む方法、中空のバルーンを混入する方法、TiHなどの発泡剤を投入して発泡させて凝固させる方法などが知られている。
しかし、これらの方法は金属種として、融点が比較的低く溶湯の取り扱いが容易である金属材料或いは発泡剤のガス放出温度域と溶湯の温度域とが一致する金属材料等に限られ、広範な金属種を対象とすることができず、また溶湯内の気泡が抜けていかないように粘度の調整を行う必要があり、実使用上はアルミニウム等の金属の発泡焼結成形体を得る方法に適用されているに過ぎなかった。
Conventionally, methods for producing a metal foam sintered compact include a method of blowing gas into a molten metal, a method of mixing a hollow balloon, a method of injecting a foaming agent such as TiH 2 and foaming and solidifying. It has been.
However, these methods are limited to a metal material having a relatively low melting point and easy handling of the molten metal, or a metal material in which the gas releasing temperature range of the blowing agent and the molten metal temperature range coincide with each other. It is not possible to target metal species, and it is necessary to adjust the viscosity so that bubbles in the molten metal do not escape. In actual use, it is applied to a method for obtaining foamed sintered compacts of metals such as aluminum. It was only there.

また、これらの改良として、金属粉末に発泡材を混合したコンパウンドを、粉末鍛造法や押し出し法等の処理により個体化し、その後、発泡剤のガス発生温度付近で焼結することにより発泡させる方法が提案されている。
しかし、この方法も適用される金属種は発泡材の発泡温度と材料の溶融温度が対応する材料、例えばアルミニウムなどの金属材料に限られ、広範な金属種を対象とすることができないという欠点があった。
In addition, as an improvement to these, there is a method in which a compound obtained by mixing a metal powder with a foaming material is solidified by processing such as a powder forging method or an extrusion method, and then foamed by sintering near the gas generation temperature of the foaming agent. Proposed.
However, the metal species to which this method is also applied is limited to a material corresponding to the foaming temperature of the foaming material and the melting temperature of the material, for example, a metal material such as aluminum. there were.

また、金属粉体等を、バインダーと混ぜてコンパウンドあるいはスラリーとし、それに焼失部材を混入して焼結時に焼きとばす方法、コンパウンド・スラリーを直接発泡させる方法なども開発されているがそれぞれ問題を抱えている。
すなわち、焼失部材を混入する方法では気孔率に限界があり(80%) をこえる気孔率の発泡体を作製することは難しい。
In addition, methods such as mixing metal powders with binders into compounds or slurries, mixing burned-out members into them and burning them out during sintering, and directly foaming compound slurries have been developed. ing.
That is, the method of mixing the burned-out member has a limited porosity, and it is difficult to produce a foam having a porosity exceeding 80%.

一方、スラリーやコンパウンドを発泡させる方法では(95 %)を超える気孔率の発泡体を作製することが可能であり、その一つの方法として発泡ポリウレタン作製の前駆体に粉体を混入し、発泡ポリウレタン作製と同様の手順で発泡前駆体を作製する方法が知られている。この手法では高い気孔率を持つ微細な発泡前駆体が得られるものの、ポリウレタンに含まれ燒結後に金属中に残留するシリカやリンの成分などが問題となる。   On the other hand, a foam having a porosity exceeding (95%) can be produced by the method of foaming slurry or compound, and as one method, powder is mixed into the precursor for producing polyurethane foam, A method for producing a foam precursor in the same procedure as the production is known. Although this method can obtain a fine foam precursor having a high porosity, there is a problem with components of silica and phosphorus that are contained in polyurethane and remain in the metal after sintering.

また、スラリーに発泡剤を混入し、ドクターブレード法によりシート状にしながら同時に加熱して発泡,乾燥させて発泡前駆体を作製する方法も提案されている(特許文献1)。
この方法も97%を越える高気孔率の発泡材料の作製が可能であるが、スラリーを加熱によりそのまま発泡させているため、ある程度以上の厚さに成形すると乾燥以前に発泡した泡の結合・崩壊が進む。そのため成形可能な厚さに限界があり、厚さ1cmを超える発泡前駆体の製造は困難であった。
以上のように、金属粉体等の焼結により95%を超える気孔率のオープンセル型発泡材料のバルク素材を工業的に有利に作製する技術は未だ確立していないのが現状である。
特開平9−87704号公報
There has also been proposed a method in which a foaming agent is mixed in a slurry, and simultaneously foamed and dried while being formed into a sheet by a doctor blade method to produce a foam precursor (Patent Document 1).
This method can also produce a foam material with a high porosity exceeding 97%, but since the slurry is foamed as it is by heating, if foamed to a certain thickness or more, the foam that has been foamed before drying is bound and collapsed. Advances. Therefore, there is a limit to the thickness that can be molded, and it has been difficult to produce a foam precursor having a thickness exceeding 1 cm.
As described above, at present, a technology for industrially advantageously producing a bulk material of an open cell type foam material having a porosity exceeding 95% by sintering metal powder or the like has not been established yet.
JP-A-9-87704

本発明は、広範囲な金属は勿論のことセラミックスなどの難加工性材料を素材としても、高発泡、高気孔率のオープンセル型の金属又はセラミックス含有発泡焼結成形体の作製を可能にする、工業的に極めて有利な該発泡焼結成形体の製造方法を提供することを目的とする。   INDUSTRIAL APPLICABILITY The present invention enables the production of high-foamed, high-porosity open-cell metal or ceramic-containing foamed sintered compacts, not only from a wide range of metals but also from difficult-to-work materials such as ceramics. It is an object of the present invention to provide a method for producing such a foam sintered compact which is extremely advantageous.

本発明者は鋭意検討した結果、バインダーとして、高粘性の高分子水溶液を用いると共に該高分子と金属又はセラミックス粉末と発泡剤を含むスラリー混合物を減圧発泡させた後、直ちに凍結し、しかる後、凍結乾燥し、ついで焼結すると、高発泡、高気孔率のオープン型の金属又はセラミックス含有発泡焼結成形体が得られることを見いだし本発明を完成するに至った。
すなわち、本発明によれば、以下の発明が提供される。
(1)金属又はセラミックス粉末と高粘性の水溶性高分子と発泡剤を含む混合物を減圧発泡させ、得られる発泡体を凍結し、ついで凍結乾燥させた後、焼結することを特徴とする金属又はセラミックス含有発泡焼結体の製造方法。
(2)上記混合物が界面活性剤を含むものであることを特徴とする上記(1)に記載の金属又はセラミックス含有発泡焼結体の製造方法。
(3)粘度の高い水溶液がポリビニルアルコール水溶液であることを特徴とする上記(1)又は(2)に記載の金属又はセラミックス含有発泡焼結体の製造方法。
As a result of intensive studies, the present inventor used a high-viscosity polymer aqueous solution as a binder and foamed the slurry mixture containing the polymer and metal or ceramic powder and a foaming agent under reduced pressure, and then immediately frozen, and then, It was found that, when freeze-dried and then sintered, an open-type metal or ceramic-containing foam sintered compact with high foaming and high porosity can be obtained, and the present invention has been completed.
That is, according to the present invention, the following inventions are provided.
(1) A metal characterized in that a mixture containing a metal or ceramic powder, a highly viscous water-soluble polymer and a foaming agent is foamed under reduced pressure, the resulting foam is frozen, then freeze-dried and then sintered. Or the manufacturing method of a ceramic containing foam sintered body.
(2) The method for producing a metal- or ceramics-containing foamed sintered body as described in (1) above, wherein the mixture contains a surfactant.
(3) The method for producing a metal or ceramics-containing foam sintered body as described in (1) or (2) above, wherein the aqueous solution having a high viscosity is an aqueous polyvinyl alcohol solution.

本発明方法によれば、金属種として、融点が比較的低く溶湯の取り扱いが容易である金属材料或いは発泡剤のガス放出温度域と溶湯の温度域とが一致する金属材料等に限定されることなく、簡単な成形法で、広範囲な金属種あるいはセラミックスなどの難加工性材料を素材とした場合においても広範囲な金属は勿論のことセラミックスなどの難加工性材料を素材としても、高発泡、高気孔率のバルク状オープン型の金属又はセラミックス含有発泡焼結成形体を有利に製造することが可能となる。また得られた発泡焼結成形体は、・航空宇宙材料、スポーツ用品素材、等の軽量かつ高比強度が要求される分野、断熱特性、耐熱性、吸振性の要求される分野、緩衝材料、梱包材料などの衝撃エネルギーの吸収が要求される分野、軽量化の要求される分野、フィルター材料、触媒担体材料、電極材料など広い表面積が要求される分野、あるいは生体適合性の要求される分野における素材として応用する可能である。   According to the method of the present invention, the metal species is limited to a metal material having a relatively low melting point and easy handling of the molten metal, or a metal material in which the gas releasing temperature range of the blowing agent coincides with the molten metal temperature range. In addition, even when a wide range of metal species or difficult-to-work materials such as ceramics are used as a raw material by a simple molding method, not only a wide range of metals but also difficult-to-work materials such as ceramics are used as a material. It becomes possible to advantageously produce a porous open metal or ceramic-containing foam sintered compact having a porosity. In addition, the obtained foamed sintered compacts are used in fields that require lightweight and high specific strength, such as aerospace materials and sports equipment materials, fields that require heat insulation properties, heat resistance, and vibration absorption, buffer materials, and packaging. Materials in fields that require absorption of impact energy, such as materials, fields that require weight reduction, fields that require a large surface area, such as filter materials, catalyst carrier materials, electrode materials, or fields that require biocompatibility It is possible to apply as

以下、本発明を更に詳細に説明する。   Hereinafter, the present invention will be described in more detail.

本発明方法においては、バインダーとして粘度の高い水溶液を用い、これに金属又はセラミックス粉末を混合し、スラリー化した後、発泡剤を添加し、このスラリー組成物を、減圧発泡させ、ただちに凍結する。ついで該凍結発泡体を凍結乾燥した後、焼結させる。この手法によれば、発泡操作を減圧により行ない、また発泡形状の固定を凍結により行っており、それぞれ独立した操作として行っている。そのためスラリーを十分な厚みを持って起泡させることができ、同時に消泡過程に至る以前に発泡形状を固定化することが可能 となるので、従来、製造できなかった素材での高気孔率オープンセル型発泡材料のバルク素材の製造が可能となる。なお、本発明でいうオープンセルとは、発泡した状態において泡のセル壁(セルフェイス)がふさがれておらず、泡の支柱(セルエッジ)が主要な構成要素となる状態と定義される。すなわち、スポンジ等に特徴的に見られる発泡形態であり、高い通気性を持つ発泡状態にあるセルを意味する。   In the method of the present invention, a high-viscosity aqueous solution is used as a binder, and a metal or ceramic powder is mixed and slurried. Then, a foaming agent is added, the slurry composition is foamed under reduced pressure, and immediately frozen. The frozen foam is then lyophilized and then sintered. According to this method, the foaming operation is performed by decompression, and the foamed shape is fixed by freezing, which are performed as independent operations. Therefore, it is possible to foam the slurry with sufficient thickness, and at the same time, it is possible to fix the foam shape before reaching the defoaming process. It is possible to manufacture a bulk material of cellular foam material. The open cell as used in the present invention is defined as a state in which a foam cell wall (cell face) is not blocked in a foamed state, and a foam column (cell edge) is a main component. That is, it is a foamed form characteristic of sponges and the like, and means a cell in a foamed state having high air permeability.

本発明で用いる、金属粉末としては、金、白金、パラジウム、銀等の貴金属粉末やそれらの合金粉末、ニッケル系合金、ステンレス鋼粉末、超硬合金粉末、工具鋼、高速度鋼、チタン合金の他、水と接触させても急激に酸化しない金属粉末、などが挙げられる。
また、セラミックス粉末として、アルミナ、ジルコニア、PZT、その他のセラミックス粉末が挙げられる。
金属粉末およびセラミックス粉末の粒径に特別な制限はなく、平均粒径が100μmからサブミクロンの粉末が好ましく使用される。
The metal powder used in the present invention includes noble metal powders such as gold, platinum, palladium, silver and alloy powders thereof, nickel-based alloys, stainless steel powders, cemented carbide powders, tool steels, high-speed steels, and titanium alloys. Other examples include metal powder that does not oxidize rapidly even when contacted with water.
Examples of the ceramic powder include alumina, zirconia, PZT, and other ceramic powders.
There is no particular limitation on the particle diameter of the metal powder and the ceramic powder, and a powder having an average particle diameter of 100 μm to submicron is preferably used.

本発明で用いる、高粘性の高分子水溶液中としては、ポリビニールアルコール、アルギン酸ナトリウム、寒天、マンノース、クアーガム、ペクチン,キサンタンガム、メチルセルロース、エチルセルロース、などを選択する。本発明で好ましく使用される水溶性高分子はポリビニルアルコールである。   Polyvinyl alcohol, sodium alginate, agar, mannose, guar gum, pectin, xanthan gum, methylcellulose, ethylcellulose, and the like are selected as the highly viscous polymer aqueous solution used in the present invention. The water-soluble polymer preferably used in the present invention is polyvinyl alcohol.

金属又はセラミックス粉末と水溶液の混合割合は体積比で2:1から1:20まで広く選択することが可能であるが1:1から1:9程度の割合が推奨され、1:2から1:5程度が発泡操作が容易となる。   The mixing ratio of the metal or ceramic powder and the aqueous solution can be widely selected from a volume ratio of 2: 1 to 1:20, but a ratio of about 1: 1 to 1: 9 is recommended. About 5 makes the foaming operation easy.

本発明で用いる、発泡剤としては、ガスを発生して気泡を形成するものであれば、従来公知の発泡剤の何れもが使用できる。このような発泡剤としては、炭素数5〜8の炭化水素系有機溶剤のような有機発泡剤や炭酸水素ナトリウム等の無機発泡剤を挙げることができる。この場合、発泡剤としての有機溶剤は水より沸点が低いものの中から発泡特性を考慮しながら適宜選択するのが好ましく、このような有機溶剤としては、ペンタン類、ヘキサン類、ヘプタン類、ベンゼン類、トルエン類などが挙げられる。発泡剤の配合量は、スラリー全体の体積に対して0〜50%程度であり、希望する発泡率に対して適宜に調節する。   As the foaming agent used in the present invention, any conventionally known foaming agent can be used as long as it generates gas and forms bubbles. Examples of such foaming agents include organic foaming agents such as hydrocarbon organic solvents having 5 to 8 carbon atoms and inorganic foaming agents such as sodium hydrogen carbonate. In this case, the organic solvent as the blowing agent is preferably selected from those having a boiling point lower than that of water in consideration of the foaming characteristics. Examples of such organic solvents include pentanes, hexanes, heptanes, and benzenes. And toluene. The blending amount of the foaming agent is about 0 to 50% with respect to the volume of the entire slurry, and is adjusted as appropriate for the desired foaming rate.

本発明で用いる発泡前駆体混合物は、前記、金属又はセラミックス粉末と粘度の高い高分子水溶液を必須成分とするが、発泡剤を均質に分散し、また発泡状態を安定化させるために界面活性剤を使用することが望ましい。このような界面活性剤としては、従来公知の何れもが使用でき、例えばアルキルベンゼンスルホン酸塩、α−オレフィンスルホン酸塩、アルキル硫酸エステル塩、アルキルエーテル硫酸エステル塩、アルカンスルホン酸塩等のアニオン系界面活性剤、ポリエチレングリコール誘導体、多価アルコール誘導体等の非イオン系界面活性剤等が挙げられる。界面活性剤の使用量は、発泡剤の使用量に応じて適宜定められるが、通常、 発泡剤の体積を100%とすれば1〜200%、好ましくは5〜100%程度である。この体積割合は使用する界面活性剤の種類、発泡剤の分散状態により大幅に変動する。
更に、本発明においては、界面活性剤と共に、気孔率調整、分散効果の向上の目的で適宜、グリセリン、エチレングリコール その他の可塑剤を添加することもできる。
The foam precursor mixture used in the present invention contains the above-mentioned metal or ceramic powder and a high-viscosity polymer aqueous solution as essential components, but the surfactant is dispersed in order to uniformly disperse the foaming agent and stabilize the foamed state. It is desirable to use As such a surfactant, any conventionally known surfactant can be used, for example, anionic series such as alkylbenzene sulfonate, α-olefin sulfonate, alkyl sulfate ester salt, alkyl ether sulfate ester, alkane sulfonate, etc. Nonionic surfactants such as surfactants, polyethylene glycol derivatives, polyhydric alcohol derivatives and the like can be mentioned. The amount of the surfactant used is appropriately determined according to the amount of the foaming agent used, but is usually about 1 to 200%, preferably about 5 to 100% when the volume of the foaming agent is 100%. This volume ratio varies greatly depending on the type of surfactant used and the state of dispersion of the foaming agent.
Furthermore, in the present invention, glycerin, ethylene glycol and other plasticizers may be added as appropriate together with the surfactant for the purpose of adjusting the porosity and improving the dispersion effect.

本発明においては、前記した、金属又はセラミックス粉末、水溶性高分子を溶解した粘度の高い水溶液、発泡剤及び必要に応じて添加される界面活性剤、他の添加剤からなるスラリー混合物を減圧発泡させた後、凍結し、ついで凍結乾燥することが必要である。このような態様をとらず、スラリーを加熱発泡させ、焼結する方法では、発泡操作とその形状固定の操作を加熱により同時に行うため、十分な厚みを持って起泡させることは困難であり、また一時的に起泡できても乾燥までに自重によりつぶれたり、泡の結合による消泡を開始するため、バルク状の発泡焼結体を得ることが困難となる。
前記混合物を減圧発泡する場合、その圧力は、発泡状況を観察しながら適宜に調節すればよいが、好ましくは水の沸点以上の気圧で発泡させることが好ましい。
また、凍結温度は用いる水溶性高分子や発泡剤の種類によって異なるが、スラリーを発泡後直ちに凍結できることが好ましく、通常、−5℃以下、好ましくは−20℃以下である。
また、凍結乾燥の手段は特に制限されず、減圧容器を冷却してもよく、発泡容器そのものを冷却してもよい。凍結乾燥条件は凍結した発泡体を解凍することなく乾燥できればよく、好ましくは、凍結乾燥装置のトラッパーを−20℃以下に冷却して乾燥できれば効率的である。
In the present invention, the above-mentioned slurry mixture comprising a metal or ceramic powder, a high-viscosity aqueous solution in which a water-soluble polymer is dissolved, a foaming agent, a surfactant added as necessary, and other additives is foamed under reduced pressure. After being allowed to freeze, it is necessary to freeze and then freeze-dry. In the method of heating and foaming and sintering the slurry without taking such an embodiment, the foaming operation and the shape fixing operation are simultaneously performed by heating, so it is difficult to foam with sufficient thickness, In addition, even if foaming can be temporarily generated, it is crushed by its own weight before drying, or defoaming due to the bonding of bubbles is started, so that it is difficult to obtain a bulk foamed sintered body.
When the mixture is foamed under reduced pressure, the pressure may be appropriately adjusted while observing the foaming state, but it is preferably foamed at a pressure higher than the boiling point of water.
The freezing temperature varies depending on the type of water-soluble polymer and foaming agent used, but it is preferable that the slurry can be frozen immediately after foaming, and is usually −5 ° C. or lower, preferably −20 ° C. or lower.
The means for freeze-drying is not particularly limited, and the vacuum container may be cooled, or the foamed container itself may be cooled. The freeze-drying condition is not limited as long as the frozen foam can be dried without thawing. Preferably, it is efficient if the trapper of the freeze-drying apparatus can be cooled to −20 ° C. or lower and dried.

本発明方法において、ついで凍結乾燥発泡体をついで焼結させる。焼結温度、焼結雰囲気、焼結時間は、原料である金属やセラミックスの種類、粉末粒径によって適宜選択する必要がある。たとえば平均粒径20μmのステンレス鋼の場合900〜1200℃の真空、不活性ガス、水素ガス雰囲気、平均粒径0.2μmのアルミナ粉の場合1500〜1700℃の大気雰囲気が好ましい。
このような処理により、本発明方法においては、水と直接反応することなく焼結が可能な金属・セラミックス素材への適用が可能となるため、従来、製造できなかった素材での高気孔率オープンドセル型形発泡焼結材料のバルク素材の製造が可能となる。
In the process according to the invention, the freeze-dried foam is then sintered. The sintering temperature, the sintering atmosphere, and the sintering time must be appropriately selected depending on the type of metal or ceramic as a raw material and the powder particle size. For example, in the case of stainless steel having an average particle diameter of 20 μm, a vacuum of 900 to 1200 ° C., an inert gas or hydrogen gas atmosphere, and in the case of alumina powder having an average particle diameter of 0.2 μm, an air atmosphere of 1500 to 1700 ° C. is preferable.
By such treatment, the method of the present invention can be applied to metal / ceramic materials that can be sintered without directly reacting with water. It is possible to manufacture a bulk material of a docel type foam sintered material.

すなわち、本発明方法によれば、金属種として、融点が比較的低く溶湯の取り扱いが容易である金属材料或いは発泡剤のガス放出温度域と溶湯の温度域とが一致する金属材料等に限定されることなく、簡単な成形法で、広範囲な金属種あるいはセラミックスなどの難加工性材料を素材とした場合においても広範囲な金属は勿論のことセラミックスなどの難加工性材料を素材としても、高発泡、高気孔率のバルク状オープンセル型の金属又はセラミックス含有発泡焼結成形体を有利に製造することが可能となる。また得られた発泡焼結成形体は、・航空宇宙材料、スポーツ用品素材、等の軽量かつ高比強度が要求される分野、断熱特性、耐熱性、吸振性の要求される分野、緩衝材料、梱包材料などの衝撃エネルギーの吸収が要求される分野、軽量化の要求される分野、フィルター材料、触媒担体材料、電極材料など広い表面積が要求される分野、あるいは生体適合性の要求される分野における素材として応用する可能である。   That is, according to the method of the present invention, the metal species is limited to a metal material having a relatively low melting point and easy to handle the molten metal, or a metal material in which the gas releasing temperature range of the blowing agent and the molten metal temperature range coincide. Even when a wide range of metal species or difficult-to-work materials such as ceramics are used as a raw material, a simple foaming method can be used. It is possible to advantageously produce a high porosity bulk open cell type metal or ceramic-containing foam sintered compact. In addition, the obtained foamed sintered compacts are used in fields that require lightweight and high specific strength, such as aerospace materials and sports equipment materials, fields that require heat insulation properties, heat resistance, and vibration absorption, buffer materials, and packaging. Materials in fields that require absorption of impact energy, such as materials, fields that require weight reduction, fields that require a large surface area, such as filter materials, catalyst carrier materials, electrode materials, or fields that require biocompatibility It is possible to apply as

以下、本発明を実施例により更に詳細に説明する。
実施例1
Hereinafter, the present invention will be described in more detail with reference to examples.
Example 1

金属粉として、平均粒径3μmのSUS316Lステンレス粉((株)アトミックス)を用いた。高分子水溶液にはポリビニールアルコール水溶液を用いた。ポリビニールアルコールには平均分子量115000、鹸化度99%以上のものを用い、8wt%水溶液とした。さらに水溶液80vol %に対して10vol %のノルマルヘキサン、10vol%の中性洗剤(主成分:アルキルエーテル硫酸エステルナトリウム15vol%)を混合した。この水溶液と金属分を体積比で5:2で混合してスラリーとした。スラリーは0.2気圧程度まで減圧してスラリー体積の10倍程度まで発泡させ、その後直ちに凍結装置で凍結する。凍結した発泡体はそのままフリーズドライ装置により乾燥した。(この様に作製した発泡前駆体を真空炉により1100 ℃で焼結する。これらの操作により、厚み50mm以上、密度0.5以下 、気孔率93%以上の発泡材料が得られた。得られた発泡材料は目視によりオープンセル型であることが確認された。なお、この実施例での平均気孔径は5mm 程度であった。
実施例2
As the metal powder, SUS316L stainless steel powder (Atomic Co., Ltd.) having an average particle diameter of 3 μm was used. A polyvinyl alcohol aqueous solution was used as the polymer aqueous solution. Polyvinyl alcohol having an average molecular weight of 115,000 and a saponification degree of 99% or more was used as an 8 wt% aqueous solution. Further, 10 vol% normal hexane and 10 vol% neutral detergent (main component: sodium alkyl ether sulfate 15 vol%) were mixed with 80 vol% aqueous solution. This aqueous solution and the metal component were mixed at a volume ratio of 5: 2 to obtain a slurry. The slurry is decompressed to about 0.2 atm and foamed to about 10 times the volume of the slurry, and then immediately frozen in a freezing apparatus. The frozen foam was dried as it was with a freeze drying apparatus. (The foamed precursor thus produced was sintered at 1100 ° C. in a vacuum furnace. By these operations, a foamed material having a thickness of 50 mm or more, a density of 0.5 or less, and a porosity of 93% or more was obtained. The foamed material was confirmed to be an open cell type visually, and the average pore diameter in this example was about 5 mm.
Example 2

セラミックス粉として、平均粒径0.2μmのアルミナ粉(大明化学工業株式会社)を用いた。高分子水溶液にはポリビニールアルコール水溶液を用いた。ポリビニールアルコールには平均分子量115000、鹸化度99%以上のものを用い、8%水溶液とした。さらに水溶液80%に対して10%のノルマルヘキサン、10%の中性洗剤(主成分:アルキルエーテル硫酸エステルナトリウム)を混合した。この水溶液とセラミックス粉を体積比で10:3で混合してスラリーとした。スラリーは0.2気圧程度まで減圧してスラリー体積の6倍程度まで発泡させ、その後直ちに凍結装置で凍結する。凍結した発泡体はそのままフリーズドライ装置により乾燥する。この様に作製した発泡前駆体を大気炉により1550℃で焼結する。これらの操作により密度0.4、気孔率 90%程度の発泡材料が得られた。得られた発泡材料は実施例1と同様にオープンセル型であり、その平均気孔径は 2mm程度であった。   As ceramic powder, alumina powder having an average particle size of 0.2 μm (Daimei Chemical Co., Ltd.) was used. A polyvinyl alcohol aqueous solution was used as the polymer aqueous solution. Polyvinyl alcohol having an average molecular weight of 115,000 and a saponification degree of 99% or more was used as an 8% aqueous solution. Further, 10% normal hexane and 10% neutral detergent (main component: sodium alkyl ether sulfate) were mixed with 80% aqueous solution. This aqueous solution and ceramic powder were mixed at a volume ratio of 10: 3 to form a slurry. The slurry is decompressed to about 0.2 atm and foamed to about 6 times the volume of the slurry, and then immediately frozen in a freezer. The frozen foam is dried as it is with a freeze drying apparatus. The foam precursor thus produced is sintered at 1550 ° C. in an atmospheric furnace. By these operations, a foam material having a density of 0.4 and a porosity of about 90% was obtained. The obtained foamed material was an open cell type as in Example 1, and the average pore diameter was about 2 mm.

Claims (3)

金属又はセラミックス粉末と高粘性の高分子水溶液と発泡剤を含む混合物を減圧発泡させ、得られる発泡体を凍結し、ついで凍結乾燥させた後、焼結することを特徴とする金属又はセラミックス含有発泡焼結体の製造方法。 Metal or ceramics-containing foam characterized in that a mixture containing a metal or ceramic powder, a highly viscous aqueous polymer solution and a foaming agent is foamed under reduced pressure, the resulting foam is frozen, then freeze-dried and then sintered. A method for producing a sintered body. 上記混合物が界面活性剤を含むものであることを特徴とする請求項1に記載の金属又はセラミックス含有発泡焼結体の製造方法。 2. The method for producing a metal- or ceramic-containing foam sintered body according to claim 1, wherein the mixture contains a surfactant. 高粘性の水溶性高分子がポリビニルアルコールであることを特徴とする請求項1又は2に記載の金属又はセラミックス含有発泡焼結体の製造方法。 The method for producing a metal- or ceramic-containing foam sintered body according to claim 1 or 2, wherein the highly viscous water-soluble polymer is polyvinyl alcohol.
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