JP2024035724A - Method for producing low melting point metal powder - Google Patents
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Abstract
【課題】低融点金属粉末の簡便な製造方法を提供する。【解決手段】粘度が１０００ｍＰａ・ｓ以上であって、低融点金属と化学反応の生じない高粘性分散媒と、融点が前記高粘性分散媒の熱分解温度よりも低い低融点金属の原料とを用意すること、前記高粘性分散媒と前記低融点金属の原料との配合物を、前記低融点金属の融点よりも高い温度であって、前記高粘性分散媒の熱分解温度よりも低い温度域に加熱するか、または、前記低融点金属の原料と、前記温度域に加熱した前記高粘性分散媒とを配合することによって、前記高粘性分散媒中の低融点金属の原料を溶融させること、前記温度域に加熱しながら、周速１ｍ／ｓ以上で高速撹拌を行い、溶融した低融点金属の分散した低融点金属分散液を得ること、および前記低融点金属分散液を、低融点金属の融点よりも低い温度域まで急冷して、低融点金属粉末を得る低融点金属粉末の製造方法。【選択図】図１The present invention provides a simple method for producing low melting point metal powder. [Solution] A high viscosity dispersion medium having a viscosity of 1000 mPa·s or more and which does not cause a chemical reaction with a low melting point metal, and a low melting point metal raw material having a melting point lower than the thermal decomposition temperature of the high viscosity dispersion medium. preparing a mixture of the high viscosity dispersion medium and the raw material of the low melting point metal in a temperature range higher than the melting point of the low melting point metal and lower than the thermal decomposition temperature of the high viscosity dispersion medium; or by blending the low melting point metal raw material and the high viscosity dispersion medium heated to the temperature range, melting the low melting point metal raw material in the high viscosity dispersion medium; While heating to the temperature range, high-speed stirring is performed at a circumferential speed of 1 m/s or more to obtain a low melting point metal dispersion in which the molten low melting point metal is dispersed; A method for producing low melting point metal powder, which involves rapidly cooling to a temperature range lower than the melting point to obtain low melting point metal powder. [Selection diagram] Figure 1
Description
本開示は、低融点金属粉末の製造方法に関する。 The present disclosure relates to a method of manufacturing a low melting point metal powder.
金属（本明細書では、純金属と合金を総称して「金属」という）粉末は、電池、電極などの電気部品、導電性樹脂などのコンポジット材料の製造に用いられ、例えばはんだ等に用いられる金属粉末として、低融点の金属粉末が挙げられる。金属粉末の代表的な製造方法として、金属材料を物理的に粉砕して粉末を得る機械的粉砕法が挙げられる。しかし上記低融点の金属粉末を機械的粉砕法で製造すると、粉砕時に生じる熱エネルギーにより低融点金属の融着・凝集が生じ、粉末が得られ難いといった問題がある。 Metal (herein, pure metals and alloys are collectively referred to as "metal") powder is used in the manufacture of electrical parts such as batteries and electrodes, and composite materials such as conductive resin, and is used, for example, in solders. Examples of the metal powder include metal powders with a low melting point. A typical method for producing metal powder includes a mechanical pulverization method in which a metal material is physically pulverized to obtain powder. However, when the above-mentioned low melting point metal powder is produced by a mechanical pulverization method, there is a problem that the thermal energy generated during pulverization causes fusion and aggregation of the low melting point metal, making it difficult to obtain powder.
金属粉末の別の代表的な製造方法として、金属溶湯に高圧の水やガスを吹き付けるアトマイズ法が知られている。例えば特許文献１には、アトマイズ法である熱プラズマガスを利用した技術であって、金属からなるコア部と、該コア部の表面に位置し、且つ該金属の化合物からなるシェル部とを有する粒子を製造することが示されている。 Another typical method for producing metal powder is the atomization method, in which high-pressure water or gas is sprayed onto molten metal. For example, Patent Document 1 describes a technology using thermal plasma gas, which is an atomization method, and includes a core portion made of metal and a shell portion located on the surface of the core portion and made of a compound of the metal. It has been shown to produce particles.
上記アトマイズ法は、装置が大掛かりであることに加え、安定的な製法を確立するためノウハウの積み重ねが必要である。本開示は、上記事情に鑑みてなされたものであって、その目的は、低融点金属粉末の簡便な製造方法を提供することにある。 In addition to requiring large-scale equipment, the atomization method described above requires extensive know-how in order to establish a stable manufacturing method. The present disclosure has been made in view of the above circumstances, and its purpose is to provide a simple method for producing low-melting metal powder.
本発明の態様１は、
低融点金属粉末を製造する方法であって、
粘度が１０００ｍＰａ・ｓ以上であって、低融点金属と化学反応の生じない高粘性分散媒と、融点が前記高粘性分散媒の熱分解温度よりも低い低融点金属の原料とを用意すること、
前記高粘性分散媒と前記低融点金属の原料との配合物を、前記低融点金属の融点よりも高い温度であって、前記高粘性分散媒の熱分解温度よりも低い温度域に加熱するか、または、前記低融点金属の原料と、前記温度域に加熱した前記高粘性分散媒とを配合することによって、前記高粘性分散媒中の低融点金属の原料を溶融させること、
前記温度域に加熱しながら、周速１ｍ／ｓ以上で高速撹拌を行い、溶融した低融点金属の分散した低融点金属分散液を得ること、および
前記低融点金属分散液を、低融点金属の融点よりも低い温度域まで急冷して、低融点金属粉末を得ること
を含む、低融点金属粉末の製造方法である。
Aspect 1 of the present invention is
A method of producing a low melting point metal powder, the method comprising:
Preparing a high viscosity dispersion medium having a viscosity of 1000 mPa·s or more and not causing any chemical reaction with the low melting point metal, and a raw material of the low melting point metal having a melting point lower than the thermal decomposition temperature of the high viscosity dispersion medium;
heating the mixture of the high viscosity dispersion medium and the raw material of the low melting point metal to a temperature range higher than the melting point of the low melting point metal and lower than the thermal decomposition temperature of the high viscosity dispersion medium; or, melting the low melting point metal raw material in the high viscosity dispersion medium by blending the low melting point metal raw material and the high viscosity dispersion medium heated to the temperature range;
obtaining a low melting point metal dispersion in which the molten low melting point metal is dispersed by performing high speed stirring at a circumferential speed of 1 m/s or more while heating to the temperature range; This is a method for producing a low melting point metal powder, which includes obtaining a low melting point metal powder by rapidly cooling to a temperature range lower than the melting point.
本発明の態様２は、
前記高速撹拌は、酸素含有雰囲気中で行う、態様１に記載の低融点金属粉末の製造方法である。
Aspect 2 of the present invention is
In the method for producing a low melting point metal powder according to aspect 1, the high-speed stirring is performed in an oxygen-containing atmosphere.
本発明の態様３は、
前記高速撹拌は、ディスパー羽根を用いて行う、態様１または２に記載の低融点金属粉末の製造方法である。
Aspect 3 of the present invention is
In the method for producing a low melting point metal powder according to aspect 1 or 2, the high-speed stirring is performed using a disper blade.
本発明の態様４は、
前記低融点金属は、ビスマス、鉛、スズ、インジウム、カドミウム、タリウム、ガリウム、およびアンチモンよりなる群から選択される１種以上の元素からなる純金属または合金である、態様１～３のいずれかに記載の低融点金属粉末の製造方法である。
Aspect 4 of the present invention is
Any one of aspects 1 to 3, wherein the low melting point metal is a pure metal or an alloy consisting of one or more elements selected from the group consisting of bismuth, lead, tin, indium, cadmium, thallium, gallium, and antimony. This is a method for producing a low melting point metal powder as described in .
本発明の態様５は、
前記高粘性分散媒は、シリコーンオイル、ポリエチレングリコール、ポリプロピレングリコールのうちの１以上である、態様１～４のいずれかに記載の低融点金属粉末の製造方法である。
Aspect 5 of the present invention is
In the method for producing a low melting point metal powder according to any one of aspects 1 to 4, the high viscosity dispersion medium is one or more of silicone oil, polyethylene glycol, and polypropylene glycol.
本発明の態様６は、
前記低融点金属粉末は、平均粒子径が５００μｍ以下である、態様１～５のいずれかに記載の低融点金属粉末の製造方法である。
Aspect 6 of the present invention is
The method for producing a low melting point metal powder according to any one of aspects 1 to 5, wherein the low melting point metal powder has an average particle size of 500 μm or less.
本発明の態様７は、
前記低融点金属粉末は、低融点金属をコアとし、該コアの表面に低融点金属の酸化被膜を有する、コアシェル粉末である、態様１～６のいずれかに記載の低融点金属粉末の製造方法である。
Aspect 7 of the present invention is
The method for producing a low melting point metal powder according to any one of aspects 1 to 6, wherein the low melting point metal powder is a core-shell powder having a core made of a low melting point metal and having an oxide film of the low melting point metal on the surface of the core. It is.
本発明の実施形態によれば、低融点金属粉末の簡便な製造方法を提供できる。 According to the embodiments of the present invention, it is possible to provide a simple method for producing low-melting point metal powder.
本発明者らは、低融点金属粉末を簡便に製造する方法、特には低融点金属粉末として微粒子粉末を簡便に得る方法について鋭意検討を行った。その結果、低融点金属の原料を、所定の高粘性分散媒と共に加熱し、かつ所定の条件で高速撹拌した後、低融点金属の融点よりも低い温度域まで急冷すればよいことを見出した。すなわち本実施形態に係る低融点金属粉末の製造方法は、
粘度が１０００ｍＰａ・ｓ以上であって、低融点金属と化学反応の生じない高粘性分散媒と、融点が前記高粘性分散媒の熱分解温度よりも低い低融点金属の原料とを用意すること、
前記高粘性分散媒と前記低融点金属の原料との配合物を、前記低融点金属の融点よりも高い温度であって、前記高粘性分散媒の熱分解温度よりも低い温度域に加熱するか、または、前記低融点金属の原料と、前記温度域に加熱した前記高粘性分散媒とを配合することによって、前記高粘性分散媒中の低融点金属の原料を溶融させること、
前記温度域に加熱しながら、周速１ｍ／ｓ以上で高速撹拌を行い、溶融した低融点金属の分散した低融点金属分散液を得ること、および
前記低融点金属分散液を、低融点金属の融点よりも低い温度域まで急冷して、低融点金属粉末を得ること
を含むようにすればよいことを見出した。以下、各条件について説明する。
The present inventors have conducted intensive studies on a method for easily producing a low-melting point metal powder, particularly a method for easily obtaining a fine particle powder as a low-melting point metal powder. As a result, they found that it is sufficient to heat the raw material of the low melting point metal together with a predetermined high viscosity dispersion medium, stir it at high speed under predetermined conditions, and then rapidly cool it to a temperature range lower than the melting point of the low melting point metal. That is, the method for producing low melting point metal powder according to the present embodiment is as follows:
Preparing a high viscosity dispersion medium having a viscosity of 1000 mPa·s or more and not causing any chemical reaction with the low melting point metal, and a raw material of the low melting point metal having a melting point lower than the thermal decomposition temperature of the high viscosity dispersion medium;
heating the mixture of the high viscosity dispersion medium and the raw material of the low melting point metal to a temperature range higher than the melting point of the low melting point metal and lower than the thermal decomposition temperature of the high viscosity dispersion medium; or, melting the low melting point metal raw material in the high viscosity dispersion medium by blending the low melting point metal raw material and the high viscosity dispersion medium heated to the temperature range;
obtaining a low melting point metal dispersion in which the molten low melting point metal is dispersed by performing high speed stirring at a circumferential speed of 1 m/s or more while heating to the temperature range; It has been found that it is sufficient to obtain a low melting point metal powder by rapidly cooling to a temperature range lower than the melting point. Each condition will be explained below.
［低融点金属の原料］
まず、低融点金属の原料と高粘性分散媒とを用意する。前記低融点金属は、融点が前記高粘性分散媒の熱分解温度よりも低い金属である。低融点金属として、融点が例えば３００℃以下である金属が挙げられる。なお低融点金属粉末の製造方法では、後述する通り、低融点金属を加熱して溶融後に冷却して固化することが挙げられ、低融点金属は、室温で固体、すなわち融点が室温よりも高い金属であることが挙げられる。低融点金属は、融点が例えば３０℃以上であることが挙げられる。しかし、低融点金属はこれに限定されず、融点が常温付近以下であって、常温で液状の低融点金属であってもよい。常温で液状の低融点金属であっても、後述の通り、酸素含有雰囲気中で高速撹拌することによって、溶融低融点金属の冷却時に、該低融点金属よりも融点の高い該低融点金属の酸化被膜がシェルとして形成され、例えば液状の低融点金属が密封されたコアシェル型の低融点金属粉末を得ることができる。
[Raw material of low melting point metal]
First, a raw material of a low melting point metal and a high viscosity dispersion medium are prepared. The low melting point metal is a metal whose melting point is lower than the thermal decomposition temperature of the high viscosity dispersion medium. Examples of the low melting point metal include metals having a melting point of, for example, 300° C. or lower. As described below, the method for producing low melting point metal powder includes heating a low melting point metal, melting it, and then cooling it to solidify it.Low melting point metal is a metal that is solid at room temperature, that is, a metal whose melting point is higher than room temperature. One example is that. The low melting point metal may have a melting point of, for example, 30° C. or higher. However, the low melting point metal is not limited thereto, and may be a low melting point metal that has a melting point around room temperature or lower and is liquid at room temperature. Even if the low melting point metal is liquid at room temperature, as described below, by stirring at high speed in an oxygen-containing atmosphere, the low melting point metal, which has a higher melting point than the low melting point metal, can be oxidized when the molten low melting point metal is cooled. It is possible to obtain a core-shell type low melting point metal powder in which a coating is formed as a shell and, for example, a liquid low melting point metal is sealed.
低融点金属としては、ビスマス、鉛、スズ、インジウム、カドミウム、タリウム、ガリウム、およびアンチモンよりなる群から選択される１種以上の元素からなる純金属または合金が挙げられる。例えば、Ｕアロイ７８（６０質量％Ｂｉ－２０質量％Ｓｎ－２０質量％Ｉｎ、融点７８．８℃）、フィールドメタル（３２．５質量％Ｂｉ－１６．５質量％Ｓｎ－５１質量％Ｉｎ、融点６２℃）などのＢｉ－Ｓｎ－Ｉｎ合金、ローズ合金（５０質量％Ｂｉ－２８質量％Ｐｂ－２２質量％Ｓｎ、融点１００℃）、ニュートン合金（５０質量％Ｂｉ－３１．２５質量％Ｐｂ－１８．７５質量％Ｓｎ、融点９５℃）、ダルセ合金（５０質量％Ｂｉ－２５質量％Ｐｂ－２５質量％Ｓｎ、融点９３℃）などのＢｉ－Ｐｂ－Ｓｎ合金、ウッド合金（５０質量％Ｂｉ－２４質量％Ｐｂ－１４質量％Ｓｎ－１２質量％Ｃｄ、融点７１℃）、ソボウイツ合金（５０質量％Ｂｉ－２７質量％Ｐｂ－１３質量％Ｓｎ－１０質量％Ｃｄ、融点６０℃）などのＢｉ－Ｐｂ－Ｓｎ-Ｃｄ合金、ビスマス－鉛－スズ－カドミウム－インジウム－タリウム合金（４０．３質量％Ｂｉ－２２．２質量％Ｐｂ－１０．７質量％Ｓｎ－１７．７質量％Ｉｎ－８．１質量％Ｃｄ－１．１質量％Ｔｌ、融点４１．５℃）、ガリンスタン（１．５質量％以下のＢｉ－９．５～１０．５質量％Ｓｎ－２１～２２質量％Ｉｎ－６８～６９質量％Ｇａ－１．５質量％以下のＳｂ、融点－１９℃）などが挙げられる。これらの中でも、環境への配慮や人体への影響から鉛フリーかつカドミウムフリーのＢｉ－Ｓｎ－Ｉｎ合金が好ましい。 Examples of the low melting point metal include pure metals or alloys made of one or more elements selected from the group consisting of bismuth, lead, tin, indium, cadmium, thallium, gallium, and antimony. For example, U Alloy 78 (60 mass% Bi-20 mass% Sn-20 mass% In, melting point 78.8°C), Field Metal (32.5 mass% Bi-16.5 mass% Sn-51 mass% In, Bi-Sn-In alloy (melting point 62°C), Rose alloy (50% Bi-28% Pb-22% Sn, melting point 100°C), Newton alloy (50% Bi-31.25% Pb by mass) Bi-Pb-Sn alloys such as -18.75 mass% Sn, melting point 95°C), Dulce alloy (50 mass% Bi-25 mass% Pb-25 mass% Sn, melting point 93 °C), Wood alloy (50 mass% Bi-24% by weight Pb-14% by weight Sn-12% by weight Cd, melting point 71°C), Sobowitsu alloy (50% by weight Bi-27% by weight Pb-13% by weight Sn-10% by weight Cd, melting point 60°C), etc. Bi-Pb-Sn-Cd alloy, bismuth-lead-tin-cadmium-indium-thallium alloy (40.3 mass%Bi-22.2 mass%Pb-10.7 mass%Sn-17.7 mass%In -8.1% by mass Cd - 1.1% by mass Tl, melting point 41.5°C), galinstan (1.5% by mass or less Bi - 9.5 to 10.5% by mass Sn - 21 to 22% by mass In -68 to 69% by mass Ga - 1.5% by mass or less Sb, melting point -19°C). Among these, a lead-free and cadmium-free Bi-Sn-In alloy is preferred from the viewpoint of environmental considerations and effects on the human body.
低融点金属の原料は、塊状であってもよいし、粒状、粉状であってもよい。塊状の原料である場合、高粘性分散媒との配合前に破砕等して、粒状、粉状としてもよい。前述の通り、融点が常温付近以下の原料の場合は液状であってもよい。 The raw material of the low melting point metal may be in the form of lumps, particles, or powder. If the raw material is in the form of a lump, it may be crushed or the like before being blended with a highly viscous dispersion medium to form granules or powder. As mentioned above, if the raw material has a melting point around room temperature or lower, it may be in liquid form.
［高粘性分散媒］
高粘性分散媒は、粘度が１０００ｍＰａ・ｓ以上であって、低融点金属と化学反応の生じない分散媒である。粘度が一定以上の高粘性分散媒を用いることで、後述の撹拌においてせん断応力を高めることができる。その結果、高粘性分散媒中の溶融した低融点金属（以下「溶融低融点金属」という）の沈降を防ぎ、撹拌によって容易に、溶融低融点金属を均一かつ微細に分散させることができる。前記粘度は、好ましくは３０００ｍＰａ・ｓ以上である。一方、溶融低融点金属を容易に撹拌する観点から、高粘性分散媒の粘度は７００００ｍＰａ・ｓ以下であることが好ましく、より好ましくは５００００ｍＰａ・ｓ以下である。前記粘度は、２５℃で、ＪＩＳ Ｚ ８８０３：２０１１に準じて求められる。粘度の測定装置として回転式粘度計を用いればよい。
[High viscosity dispersion medium]
The high-viscosity dispersion medium is a dispersion medium that has a viscosity of 1000 mPa·s or more and does not cause a chemical reaction with a low-melting point metal. By using a highly viscous dispersion medium having a viscosity above a certain level, shear stress can be increased during stirring described below. As a result, the molten low melting point metal in the highly viscous dispersion medium (hereinafter referred to as "molten low melting point metal") is prevented from settling, and the molten low melting point metal can be easily and uniformly and finely dispersed by stirring. The viscosity is preferably 3000 mPa·s or more. On the other hand, from the viewpoint of easily stirring the molten low-melting metal, the viscosity of the highly viscous dispersion medium is preferably 70,000 mPa·s or less, more preferably 50,000 mPa·s or less. The viscosity is determined at 25° C. according to JIS Z 8803:2011. A rotational viscometer may be used as the viscosity measuring device.
高粘性分散媒は、低融点金属と化学反応の生じない分散媒である。本明細書において「化学反応」とは、高粘性分散媒が低融点金属と反応し、低融点金属がイオン化する等して溶解すること、化合物を形成すること、高粘性分散媒の化学的構造が変化し分解等の変質が生じること等をいう。 A high viscosity dispersion medium is a dispersion medium that does not cause a chemical reaction with a low melting point metal. In this specification, "chemical reaction" refers to the reaction of a high viscosity dispersion medium with a low melting point metal, the low melting point metal ionizing and dissolving, the formation of a compound, and the chemical structure of the high viscosity dispersion medium. This refers to a change in the quality of the material, resulting in decomposition or other alterations.
高粘性分散媒は、その熱分解温度が、低融点金属の融点よりも高く、低融点金属の溶融後も化学的構造が安定し、高粘性等の特性が維持されるものである。高粘性分散媒の「熱分解温度」とは、高粘性分散媒の温度を徐々に高めたときに、高粘性分散媒の重量減少が始まる温度のことをいい、例えばＴＧ－ＤＴＡ（熱重量示差熱量分析）で測定される。高粘性分散媒はまた、低融点金属の融点よりも高い沸点を有するものでもある。高粘性分散媒は、融点が低融点金属よりも低く、低融点金属の溶融前後で液体状態であるのがよい。 The high viscosity dispersion medium has a thermal decomposition temperature higher than the melting point of the low melting point metal, has a stable chemical structure even after the low melting point metal is melted, and maintains properties such as high viscosity. The "thermal decomposition temperature" of a high viscosity dispersion medium refers to the temperature at which the weight of the high viscosity dispersion medium begins to decrease when the temperature of the high viscosity dispersion medium is gradually increased. Calorimetry). A highly viscous dispersion medium is also one that has a boiling point higher than the melting point of the low melting point metal. The high viscosity dispersion medium preferably has a melting point lower than that of the low melting point metal and is in a liquid state before and after melting the low melting point metal.
前記高粘性分散媒として、例えばシリコーンオイル、ポリエチレングリコール、ポリプロピレングリコールが挙げられ、これらのうちの１以上を用いることが好ましい。より好ましくは耐熱性に優れたシリコーンオイルである。 Examples of the high viscosity dispersion medium include silicone oil, polyethylene glycol, and polypropylene glycol, and it is preferable to use one or more of these. More preferred is silicone oil with excellent heat resistance.
［高粘性分散媒と低融点金属の原料との配合および加熱］
前記高粘性分散媒と前記低融点金属の原料との配合物を、前記低融点金属の融点よりも高い温度であって、前記高粘性分散媒の熱分解温度よりも低い温度域に加熱するか、または、前記低融点金属の原料と前記温度域に加熱した前記高粘性分散媒とを配合することで、高粘性分散媒中で低融点金属を溶融させる。溶融の効率を高め、原料の再凝縮を防ぐために、低融点金属の融点＋２０℃以上程度に加熱することが好ましい。低融点金属粒子として、後述する酸化被膜を有するコアシェル粉末を得る場合には、低融点金属の原料の融点に関わらず、低融点金属の原料の酸化反応が生じやすくなる１００℃以上まで加熱することが望ましい。本実施形態の製造方法では、低融点金属の溶融を、高粘性分散媒の熱分解温度よりも低い温度で行うことで、高粘性分散媒の粘性変動など特性劣化を生じることなく、良好に高速撹拌を行うことができる。この観点から、好ましくは、高粘性分散媒の熱分解温度－５０℃以下に加熱することが好ましい。
[Blending and heating of high viscosity dispersion medium and low melting point metal raw material]
heating the mixture of the high viscosity dispersion medium and the raw material of the low melting point metal to a temperature range higher than the melting point of the low melting point metal and lower than the thermal decomposition temperature of the high viscosity dispersion medium; Alternatively, the low melting point metal is melted in the high viscosity dispersion medium by blending the raw material of the low melting point metal and the high viscosity dispersion medium heated to the above temperature range. In order to increase the efficiency of melting and prevent recondensation of the raw material, it is preferable to heat the material to about 20° C. or more above the melting point of the low melting point metal. When obtaining a core-shell powder having an oxide film, which will be described later, as low-melting point metal particles, the powder should be heated to 100° C. or higher, where an oxidation reaction of the low-melting point metal raw material is likely to occur, regardless of the melting point of the low-melting point metal raw material. is desirable. In the manufacturing method of this embodiment, by melting the low-melting point metal at a temperature lower than the thermal decomposition temperature of the high-viscosity dispersion medium, it is possible to melt the low-melting-point metal at a high speed without causing property deterioration such as viscosity fluctuation of the high-viscosity dispersion medium. Stirring can be performed. From this point of view, it is preferable to heat the highly viscous dispersion medium to a thermal decomposition temperature of −50° C. or lower.
低融点金属に対する高粘性分散媒の割合は特に限定されず、加熱撹拌後に低融点金属が分散できる程度であればよい。前記高粘性分散媒と低融点金属の原料の配合方法は限定されず、撹拌用容器中に低融点金属の原料を投入後、高粘性分散媒を注入、または、撹拌用容器中に高粘性分散媒を注入後、低融点金属の原料を投入することができる。また、加熱の方法は限定されず、例えばホットスターラー等で加熱することができる。本明細書において、加熱温度は液温をいう。加熱温度は、前記温度域の範囲内にあればよく、一定温度でもよいし前記温度域の範囲内で変動してもよい。 The ratio of the high viscosity dispersion medium to the low melting point metal is not particularly limited, as long as the low melting point metal can be dispersed after heating and stirring. The method of blending the high viscosity dispersion medium and the low melting point metal raw material is not limited, and the high viscosity dispersion medium may be poured into the stirring container after the low melting point metal raw material is put into the stirring container, or the high viscosity dispersion medium may be dispersed into the stirring container. After injecting the medium, the low melting point metal raw material can be added. Further, the heating method is not limited, and for example, heating can be performed using a hot stirrer or the like. In this specification, heating temperature refers to liquid temperature. The heating temperature may be within the above temperature range, and may be constant or may vary within the above temperature range.
［高速撹拌］
高粘性分散媒中の溶融低融点金属を高速撹拌して分散させる。低融点金属の原料の溶融と高速撹拌は、併せて行ってもよく、この場合、高粘性分散媒中の低融点金属の原料が一部溶融した状態で撹拌される。または、低融点金属の原料を完全に溶融してから高速撹拌してもよい。
[High speed stirring]
The molten low melting point metal in the highly viscous dispersion medium is dispersed by high speed stirring. Melting of the low melting point metal raw material and high-speed stirring may be performed together, and in this case, the low melting point metal raw material in the high viscosity dispersion medium is stirred in a partially melted state. Alternatively, the low melting point metal raw material may be completely melted and then stirred at high speed.
高速撹拌の段階では、前記温度域に加熱しながら周速１ｍ／ｓ以上で高速撹拌を行って、溶融低融点金属の分散した低融点金属分散液を得る。本明細書における「周速」は、撹拌子あるいはディスパー撹拌羽根の外周を基準とした値として取り扱う。低融点金属の粒子径はこの周速に依存し、周速が速いほど粒径のより小さな低融点金属粉末を得ることができる。即ち、周速を変えることで、所望の粒子径の低融点金属粉末が得られる。本実施形態に係る製造方法では周速を１ｍ／ｓ以上とする。一方、撹拌装置のモーター負荷を抑制する等の観点から、周速の上限は６０ｍ／ｓ程度である。 In the high-speed stirring stage, high-speed stirring is performed at a circumferential speed of 1 m/s or more while heating to the above temperature range to obtain a low-melting metal dispersion in which molten low-melting metal is dispersed. In this specification, "peripheral speed" is treated as a value based on the outer circumference of the stirrer or disper stirring blade. The particle size of the low melting point metal depends on this circumferential speed, and the higher the circumferential speed, the smaller the particle size of the low melting point metal powder can be obtained. That is, by changing the peripheral speed, a low melting point metal powder with a desired particle size can be obtained. In the manufacturing method according to this embodiment, the circumferential speed is 1 m/s or more. On the other hand, from the viewpoint of suppressing the motor load of the stirring device, the upper limit of the peripheral speed is about 60 m/s.
低融点金属の粒子径は、撹拌において、撹拌における周速、分散媒の粘度、分散媒の温度の制御によりせん断応力を高めることで小さくすることができる。低融点金属の粒子径の制御は、特に撹拌における周速の制御により可能であり、これは、下記のニュートンの粘性法則（式１）により説明できる。
τ＝μ×（ｄｕ／ｄｙ） （式１）
せん断応力：τ、粘度：μ、せん断速度：ｄｕ／ｄｙ
The particle size of the low melting point metal can be reduced by increasing the shear stress during stirring by controlling the peripheral speed of stirring, the viscosity of the dispersion medium, and the temperature of the dispersion medium. The particle size of the low melting point metal can be controlled by controlling the circumferential speed, especially during stirring, and this can be explained by Newton's law of viscosity (Equation 1) below.
τ=μ×(du/dy) (Formula 1)
Shear stress: τ, viscosity: μ, shear rate: du/dy
即ち、撹拌における周速を上げると流体速度ｄｕが増し、せん断応力τが大きくなる。このことから、撹拌における周速を高めて溶融金属に与えるせん断力を高めることで、粒子径を微細化することができる。また、上記（式１）によると、粘度によるせん断応力の制御も可能である。更に粘度は温度により変化することから、粘度の制御手段として温度を用いることもできる。よって低融点金属の粒子径の制御手段として、撹拌における周速、分散媒の粘度、分散媒の温度の３つのパラメータを用いることができる。 That is, when the circumferential speed during stirring is increased, the fluid velocity du increases, and the shear stress τ increases. From this, the particle size can be made finer by increasing the peripheral speed during stirring and increasing the shear force applied to the molten metal. Furthermore, according to the above (Equation 1), it is also possible to control the shear stress using viscosity. Furthermore, since viscosity changes with temperature, temperature can also be used as a means of controlling viscosity. Therefore, as means for controlling the particle size of the low melting point metal, three parameters can be used: the circumferential speed in stirring, the viscosity of the dispersion medium, and the temperature of the dispersion medium.
また流体中の粒子の沈降速度ｖは、下記（式２）のストークスの法則で示され、流体粘度ηを大きくすることで沈降速度ｖを遅くすることができ、分散媒中に分散している溶融金属の沈降を防止できる。よって本実施形態に係る製造方法では、上述の通り高粘性分散媒を用いる。
ｖ＝［Ｄ２（ρｐ－ρｆ）ｇ］／１８η （式２）
沈降速度：ｖ、Ｄ：粒子径、ρｐ：粒子密度、ρｆ：流体密度、ｇ：重力加速度、η：流体粘度
In addition, the sedimentation velocity v of particles in a fluid is expressed by Stokes' law as shown below (Equation 2), and by increasing the fluid viscosity η, the sedimentation velocity v can be slowed down, and particles dispersed in the dispersion medium can be Prevents settling of molten metal. Therefore, in the manufacturing method according to this embodiment, a highly viscous dispersion medium is used as described above.
v=[D 2 (ρp−ρf)g]/18η (Formula 2)
Sedimentation velocity: v, D: particle diameter, ρp: particle density, ρf: fluid density, g: gravitational acceleration, η: fluid viscosity
上記周速を実現でき、高いせん断応力を与えることのできる手段として、電磁撹拌、ディスパー羽根を用いた撹拌などが挙げられる。その中でも、せん断力の強いディスパー羽根を用いて撹拌することが好ましい。 Examples of means that can achieve the above circumferential speed and apply high shear stress include electromagnetic stirring and stirring using disper blades. Among these, it is preferable to use a disper blade with strong shearing force for stirring.
前記高速撹拌の雰囲気は酸素含有雰囲気または不活性ガス雰囲気とすればよい。例えば大気中などの酸素含有雰囲気中で高速撹拌すること、窒素ガス、アルゴンガスなどの不活性ガス雰囲気中で高速撹拌することが挙げられる。酸素含有雰囲気中で高速撹拌を行うことで、低融点金属粉末として、低融点金属をコアとし、該コアの表面に低融点金属の酸化被膜を有する、コアシェル粉末を得てもよい。 The atmosphere for the high-speed stirring may be an oxygen-containing atmosphere or an inert gas atmosphere. Examples include high-speed stirring in an oxygen-containing atmosphere such as the air, and high-speed stirring in an inert gas atmosphere such as nitrogen gas or argon gas. By performing high-speed stirring in an oxygen-containing atmosphere, a core-shell powder having a core of a low melting point metal and an oxide film of the low melting point metal on the surface of the core may be obtained as a low melting point metal powder.
特許文献１のアトマイズ法である熱プラズマガスを利用した技術では、例えばコアシェル粒子を製造する場合、膜厚の調整が困難であり、サイクル試験で評価される耐久性の優れたコアシェル粒子を実現することが難しい。また、低融点金属粉末を例えばコンポジット材料へ利用する場合、当該低融点金属の融点以上の環境での溶出防止のため、金属粉末を生成後、更にマイクロカプセル化する工程が別途必要であり煩雑であった。それに対し、本実施形態では、大気中で上記高速撹拌を行うことにより、後述する実施例に示す通り均一な厚みの酸化被膜をシェルとして形成でき、コアシェル粉末を簡便に製造できる。一方、アルゴンガス、窒素ガスなどの不活性ガス雰囲気中で高速撹拌を行うことで、表面に酸化被膜を有さない低融点金属粉末を得ることができる。 With the technology using thermal plasma gas, which is the atomization method of Patent Document 1, for example, when producing core-shell particles, it is difficult to adjust the film thickness, and it is difficult to realize core-shell particles with excellent durability evaluated in a cycle test. It's difficult. Furthermore, when using low-melting point metal powders, for example, in composite materials, a separate and complicated process of microencapsulation is required after the metal powder is generated to prevent elution in an environment above the melting point of the low-melting point metal. there were. On the other hand, in this embodiment, by performing the above-mentioned high-speed stirring in the atmosphere, an oxide film with a uniform thickness can be formed as a shell as shown in Examples described later, and a core-shell powder can be easily produced. On the other hand, by performing high-speed stirring in an inert gas atmosphere such as argon gas or nitrogen gas, a low melting point metal powder without an oxide film on the surface can be obtained.
［冷却工程］
前記低融点金属分散液を、低融点金属の融点よりも低い温度域まで急冷して、低融点金属粉末を得る。前記融点を下回った後、更なる冷却は急冷でなくてもよい。急冷の手段として、例えば氷水による冷却等が挙げられる。
[Cooling process]
The low melting point metal dispersion liquid is rapidly cooled to a temperature range lower than the melting point of the low melting point metal to obtain a low melting point metal powder. After falling below the melting point, further cooling need not be rapid cooling. Examples of means for rapid cooling include cooling with ice water.
本実施形態の製造方法によれば、特殊な装置を必要とせず、汎用の撹拌装置と加熱装置のみの単純な構成で、低融点金属微粒子粉末を実現できる。 According to the manufacturing method of this embodiment, a low melting point metal fine particle powder can be produced with a simple configuration of only a general-purpose stirring device and a heating device without requiring any special equipment.
［その他の工程］
上記以外の工程を更に含んでいてもよく、例えば、上記冷却により得られた低融点金属粉末を含む分散液に対し、例えば遠心分離等を行うことで低融点金属粉末を回収する工程、その後の精製工程、乾燥工程等が含まれていてもよい。精製工程では、ヘキサン、変性アルコール等を用いて、精製することが挙げられる。乾燥工程では、真空乾燥を行うこと等が挙げられる。
[Other processes]
It may further include a step other than the above, for example, a step of recovering the low melting point metal powder by performing centrifugation on the dispersion containing the low melting point metal powder obtained by the above cooling, and a subsequent step. A purification step, a drying step, etc. may be included. In the purification step, purification may be performed using hexane, denatured alcohol, or the like. The drying step includes performing vacuum drying.
［低融点金属粉末］
本実施形態に係る製造方法によれば、平均粒子径が５００μｍ以下である低融点金属粉末を得ることができる。前記平均粒子径は、更には２００μｍ以下、更には１０μｍ以下でありうる。前記平均粒子径は後述する実施例に記載の方法で求められる。
[Low melting point metal powder]
According to the manufacturing method according to the present embodiment, it is possible to obtain a low melting point metal powder having an average particle size of 500 μm or less. The average particle size may further be 200 μm or less, and even 10 μm or less. The average particle diameter is determined by the method described in Examples below.
また前述の通り、高速撹拌を酸素含有雰囲気中で行うことで、低融点金属粉末として、低融点金属をコアとし、該コアの表面に低融点金属の酸化被膜をシェルとして有する、コアシェル粉末が得られる。本実施形態に係る製造方法によれば、シェルとして均一かつ薄い低融点金属の酸化被膜を形成できる。その結果、上記コアシェル粉末は、後述する実施例に示す通り、サイクルテストにおいて優れたサイクル特性を示す。または、前述の通り、高速撹拌を不活性ガス雰囲気中で行うことで、酸化被膜のない低融点合金微粒子を容易に得ることができる。酸化被膜のない低融点合金微粒子は、低融点合金微粒子の酸化物シェル（表面酸化物）の存在が好ましくない、例えばソルダーペースト用はんだ粉末などに有用である。 Furthermore, as mentioned above, by performing high-speed stirring in an oxygen-containing atmosphere, a core-shell powder can be obtained as a low-melting point metal powder, which has a low-melting point metal as a core and a low-melting point metal oxide film as a shell on the surface of the core. It will be done. According to the manufacturing method according to the present embodiment, a uniform and thin oxide film of a low melting point metal can be formed as a shell. As a result, the core-shell powder exhibits excellent cycle characteristics in a cycle test, as shown in the Examples described below. Alternatively, as described above, by performing high-speed stirring in an inert gas atmosphere, low melting point alloy fine particles without an oxide film can be easily obtained. Low-melting point alloy fine particles without an oxide film are useful for, for example, solder powder for solder paste, where the presence of an oxide shell (surface oxide) of low-melting point alloy fine particles is undesirable.
以下、実施例を挙げて本発明をより具体的に説明する。本開示は以下の実施例によって制限を受けるものではなく、前述および後述する趣旨に合致し得る範囲で、適宜変更を加えて実施することも可能であり、それらはいずれも本発明の技術的範囲に包含される。 Hereinafter, the present invention will be explained in more detail with reference to Examples. The present disclosure is not limited by the following examples, and can be implemented with appropriate changes within the scope of the above and below-mentioned purposes, and all of these are within the technical scope of the present invention. included in.
２００ｍＬビーカーに、高粘性溶媒としてのシリコーンオイルＳＩＬＰＯＴ１８４（ＤＯＷ製、動粘度５，０００ｍｍ２／ｓ、密度１．１１ｇ／ｃｍ３、粘度５，５５０ｍＰａ・ｓ）１２０ｍＬと、低融点合金としてＵアロイ７８（アサヒメタル製、６０質量％Ｂｉ－２０質量％Ｓｎ－２０質量％Ｉｎ、融点７８．８℃）９．６ｇを入れ、２３０℃に予熱したホットスターラーの上に載せ、低融点金属の原料塊が全て溶融したのを確認後、大気中にて２時間の加熱撹拌を実施した。前記シリコーンオイルの使用温度範囲は－４５～２００℃であり、熱分解温度は２００℃超である。液温は１００～１２０℃であった。撹拌は、電磁スターラー若しくはディスパー撹拌羽根を用い、撹拌回転数を表１に示す通り１０００ｒｐｍ、１５００ｒｐｍ、２０００ｒｐｍ、７０００ｒｐｍの４水準とした。周速は撹拌子あるいはディスパー撹拌羽根の回転外周を基準として算出した。２時間撹拌した後、氷水により室温まで冷却した。次いで、遠心分離により低融点金属粒子の回収及び精製を行った。精製はヘキサン（関東化学製）にて３回、変性アルコール（日本アルコール販売株式会社製ソルミックスＡＰ－１）にて１回実施した。その後、真空乾燥を行い、低融点合金微粒子の粉末を得た。 In a 200 mL beaker, 120 mL of silicone oil SILPOT184 (manufactured by DOW, kinematic viscosity 5,000 mm 2 /s, density 1.11 g/cm 3 , viscosity 5,550 mPa・s) as a high viscosity solvent and U alloy 78 as a low melting point alloy. (manufactured by Asahi Metal, 60 mass% Bi-20 mass% Sn-20 mass% In, melting point 78.8°C) was placed on a hot stirrer preheated to 230°C, and the low melting point metal raw material block was placed on a hot stirrer preheated to 230°C. After confirming that the mixture was completely melted, the mixture was heated and stirred in the atmosphere for 2 hours. The operating temperature range of the silicone oil is -45 to 200°C, and the thermal decomposition temperature is over 200°C. The liquid temperature was 100-120°C. For stirring, an electromagnetic stirrer or a disper stirring blade was used, and the stirring rotation speed was set to four levels: 1000 rpm, 1500 rpm, 2000 rpm, and 7000 rpm, as shown in Table 1. The circumferential speed was calculated based on the rotational circumference of the stirrer or disper stirring blade. After stirring for 2 hours, the mixture was cooled to room temperature with ice water. Next, the low melting point metal particles were collected and purified by centrifugation. Purification was carried out three times using hexane (manufactured by Kanto Kagaku) and once using denatured alcohol (Solmix AP-1, manufactured by Nippon Alcohol Sales Co., Ltd.). Thereafter, vacuum drying was performed to obtain a powder of low melting point alloy fine particles.
得られた低融点合金微粒子の粒子径はＦＥ－ＳＥＭ（ＪＥＯＬ社製ＪＳＭ－６７０１Ｆ）による観察像から求めた。その結果を（平均粒子径±標準偏差（σ））として表１に併記する。また、周速と低融点合金微粒子の平均粒子径の関係を示したグラフを図１に示す。図１から、周速と低融点合金微粒子の平均粒子径の間には、相関関係が見られ、周速により粒子径が制御可能であることが示された。撹拌方法による差異については、電磁撹拌を用いた実施例１の粒子径が１７８．９±５８．７μｍであったのに対し、ディスパー羽根撹拌を用いた実施例２の粒子径は１５３．２±５０．７μｍであり、平均粒子径、標準偏差共に小さいことがわかる。このことから、ディスパー羽根は、せん断力が高く分散状態が得られやすいことが示唆され、撹拌手法として望ましいと思われる。 The particle diameter of the obtained low melting point alloy fine particles was determined from an image observed by FE-SEM (JSM-6701F manufactured by JEOL). The results are also listed in Table 1 as (average particle diameter±standard deviation (σ)). Further, FIG. 1 shows a graph showing the relationship between the circumferential speed and the average particle diameter of the low melting point alloy fine particles. From FIG. 1, a correlation was observed between the circumferential speed and the average particle size of the low melting point alloy fine particles, indicating that the particle size could be controlled by the circumferential speed. Regarding the difference due to the stirring method, the particle size of Example 1 using electromagnetic stirring was 178.9±58.7 μm, while the particle size of Example 2 using disper blade stirring was 153.2±. It is found that the average particle diameter and standard deviation are both small. This suggests that disper blades have a high shear force and can easily obtain a dispersed state, and are considered desirable as a stirring method.
〔低融点合金微粒子のＸＲＤ測定〕
実施例１の低融点合金微粒子を試料として用い、リガク社製ＭｉｎｉＦｌｅｘ２を用いてＸ線回折（ＸＲＤ）測定を行い、ＸＲＤパターンを取得した。測定は、ＣｕＫα線を用い、スキャン速度は２０°ｍｉｎ－１に設定した。その結果を図２に示す。図２では、原料インゴットであるＵアロイ７８インゴットのＸＲＤパターン、ＢｉＩｎ合金のＸＲＤパターン、ＢｉのＸＲＤパターン、ＳｎのＸＲＤパターンも併せて示す。図２から、得られた低融点合金微粒子の組成は、原料インゴットと同一であることがわかる。
[XRD measurement of low melting point alloy particles]
Using the low melting point alloy fine particles of Example 1 as a sample, X-ray diffraction (XRD) measurement was performed using MiniFlex2 manufactured by Rigaku Corporation to obtain an XRD pattern. For the measurement, CuKα radiation was used, and the scanning speed was set at 20° min −1 . The results are shown in FIG. FIG. 2 also shows an XRD pattern of a U alloy 78 ingot, which is a raw material ingot, an XRD pattern of a BiIn alloy, an XRD pattern of Bi, and an XRD pattern of Sn. From FIG. 2, it can be seen that the composition of the obtained low melting point alloy fine particles is the same as that of the raw material ingot.
〔低融点合金微粒子のＴＥＭ観察〕
実施例１の低融点合金微粒子をエタノールに分散させて得た分散液を、透過型電子顕微鏡（ＴＥＭ）用のグリッド上に滴下し、自然乾燥させた。このようにして得られたＴＥＭ用グリッドを用いて、ＴＥＭ観察を行った。ＴＥＭ観察は、ＪＥＯＬ社製ＪＥＭ２０００－ＥＳを用いて、加速電圧２００ｋＶの条件で行った。ＴＥＭ観察で得られたＴＥＭ写真を図３に示す。図３のＴＥＭ写真から、実施例１の低融点合金微粒子は、低融点合金コアの外周部に、厚さが約７０ｎｍであってほぼ均一な酸化被膜（シェル）を有しており、マイクロカプセル化されていることが確認された。
[TEM observation of low melting point alloy particles]
A dispersion obtained by dispersing the low melting point alloy fine particles of Example 1 in ethanol was dropped onto a transmission electron microscope (TEM) grid and air-dried. TEM observation was performed using the TEM grid thus obtained. TEM observation was performed using JEM2000-ES manufactured by JEOL under the condition of an accelerating voltage of 200 kV. A TEM photograph obtained by TEM observation is shown in FIG. From the TEM photograph in FIG. 3, it can be seen that the low melting point alloy fine particles of Example 1 have a substantially uniform oxide film (shell) with a thickness of about 70 nm on the outer periphery of the low melting point alloy core, and microcapsules. It was confirmed that the
〔サイクルテスト〕
得られた低融点合金微粒子のコンポジット材料への適用を想定し、上記酸化被膜（シェル）の耐久性を確認するため、実施例１の低融点合金微粒子を用い、示差走査熱量測定（ＤＳＣ）により、サイクルテストを実施し、サイクル特性を評価した。示差走査熱量測定は、リガク製Ｔｈｅｒｍｏ Ｐｌｕｓ ＥＶＯ ＤＳＣ８２７０を用い、評価条件は、試料量５ｍｇ、温度範囲２５℃～１５０℃、大気下、昇降温速度２℃／ｍｉｎ、試験サイクル１００回とした。その結果として図４に、１回目、５０回目、１００回目のＤＳＣ曲線を示す。図４から、Ｕアロイ７８の融点７８．８℃に対して、吸熱ピークは８０℃付近であり殆ど同じ位置に生じた。また示差走査熱量測定の結果から、エンタルピー（ΔＨ）と吸熱ピーク温度（Ｔｐ）のサイクル数に対する変化を図５に示す。図５から、サイクル数を増やしても、吸熱ピーク温度（Ｔｐ）は８０℃前後、エンタルピー（ΔＨ）は－３６Ｊ／ｇ前後で安定的に推移することが確認された。
[Cycle test]
Assuming the application of the obtained low melting point alloy fine particles to a composite material, and in order to confirm the durability of the above oxide film (shell), the low melting point alloy fine particles of Example 1 were used and measured by differential scanning calorimetry (DSC). , a cycle test was conducted and the cycle characteristics were evaluated. Differential scanning calorimetry was carried out using Rigaku's Thermo Plus EVO DSC8270, and the evaluation conditions were a sample amount of 5 mg, a temperature range of 25° C. to 150° C., in the atmosphere, a temperature increase/decrease rate of 2° C./min, and 100 test cycles. As a result, FIG. 4 shows the DSC curves of the 1st, 50th, and 100th times. From FIG. 4, the endothermic peak occurred at around 80°C and at almost the same position as the melting point of U Alloy 78, which was 78.8°C. Further, from the results of differential scanning calorimetry, changes in enthalpy (ΔH) and endothermic peak temperature (Tp) with respect to the number of cycles are shown in FIG. From FIG. 5, it was confirmed that even if the number of cycles was increased, the endothermic peak temperature (Tp) remained stable at around 80°C and the enthalpy (ΔH) remained stable at around -36 J/g.
〔サイクルテスト前後の低融点合金微粒子のＳＥＭ観察〕
実施例１の低融点合金微粒子のサイクルテスト前後のＳＥＭ写真を取得した。そのＳＥＭ写真を、サイクルテスト前については図６Ａ、１００回のサイクルテスト後については図６Ｂに示す。これらの写真から、本実施形態に係る低融点合金微粒子は、１００サイクルを経ても低融点合金微粒子の粒径や形状に差異は見られなかった。このことから、酸化被膜（シェル）が、低融点合金コアの溶融時にその流出を防止していることが示唆された。
[SEM observation of low melting point alloy fine particles before and after cycle test]
SEM photographs of the low melting point alloy fine particles of Example 1 were taken before and after the cycle test. The SEM photographs are shown in FIG. 6A before the cycle test and in FIG. 6B after the 100 cycle test. From these photographs, no difference was observed in the particle size or shape of the low melting point alloy fine particles according to the present embodiment even after 100 cycles. This suggests that the oxide film (shell) prevents the low melting point alloy core from flowing out when it melts.
以上の実験結果から、原料インゴットをその融点以上の溶媒中で溶融させ、撹拌により原料を均一分散させた後、冷却して固化させるとの非常に簡便な方法で、低融点合金微粒子が得られることが確認された。また、本実施形態の低融点合金微粒子の製造方法によれば、低融点合金をコアとし、該低融点合金の酸化被膜（シェル）を有する、コアシェル粉末を安定的に製造できた。このマイクロカプセル構造は前述の通り、特別な形成手段を用いずとも、撹拌雰囲気を大気下にするとの簡便な手法で得ることができ、後工程でマイクロカプセル化するよりも、工数削減に大きく寄与し量産に適している。更に、得られたコアシェル粒子は、酸化被膜（シェル）がサイクル試験１００回後も強固な耐久性を示し、金属コアが融点以上の環境で溶け出すことのないマイクロカプセル構造を有しており、コンポジット材料や潜熱蓄熱材料に適しているコアシェル粉末が得られた。 From the above experimental results, it is possible to obtain low melting point alloy fine particles by a very simple method of melting the raw material ingot in a solvent with a temperature higher than its melting point, uniformly dispersing the raw material by stirring, and then cooling and solidifying it. This was confirmed. Further, according to the method for producing low melting point alloy fine particles of the present embodiment, core shell powder having a core of a low melting point alloy and an oxide film (shell) of the low melting point alloy could be stably produced. As mentioned above, this microcapsule structure can be obtained by a simple method of changing the stirring atmosphere to atmospheric air without using any special forming means, and contributes to a greater reduction in man-hours than microcapsule formation in a later process. It is suitable for mass production. Furthermore, the obtained core-shell particles have a microcapsule structure in which the oxide film (shell) exhibits strong durability even after 100 cycle tests, and the metal core does not melt in environments above the melting point. A core-shell powder suitable for composite materials and latent heat storage materials was obtained.
本実施形態の低融点合金粉末は、電池、電極、導電性ペースト、金属粉末フィラー、導電性樹脂などのコンポジット材料に用いられる金属粉末、３Ｄプリンター等の成型用金属粉末として有用である。更に、本実施形態の低融点合金粉末は、保温剤、蓄熱コンポジット材料、冷媒への添加に用いられる潜熱蓄熱材料、ソルダーペーストのはんだ粉末としても有用である。 The low melting point alloy powder of this embodiment is useful as a metal powder used in composite materials such as batteries, electrodes, conductive pastes, metal powder fillers, and conductive resins, and as a metal powder for molding in 3D printers and the like. Furthermore, the low melting point alloy powder of this embodiment is useful as a heat insulating agent, a heat storage composite material, a latent heat storage material used for addition to a refrigerant, and a solder powder for a solder paste.
Claims (7)
粘度が１０００ｍＰａ・ｓ以上であって、低融点金属と化学反応の生じない高粘性分散媒と、融点が前記高粘性分散媒の熱分解温度よりも低い低融点金属の原料とを用意すること、
前記高粘性分散媒と前記低融点金属の原料との配合物を、前記低融点金属の融点よりも高い温度であって、前記高粘性分散媒の熱分解温度よりも低い温度域に加熱するか、または、前記低融点金属の原料と、前記温度域に加熱した前記高粘性分散媒とを配合することによって、前記高粘性分散媒中の低融点金属の原料を溶融させること、
前記温度域に加熱しながら、周速１ｍ／ｓ以上で高速撹拌を行い、溶融した低融点金属の分散した低融点金属分散液を得ること、および
前記低融点金属分散液を、低融点金属の融点よりも低い温度域まで急冷して、低融点金属粉末を得ること
を含む、低融点金属粉末の製造方法。 A method of producing a low melting point metal powder, the method comprising:
Preparing a high viscosity dispersion medium having a viscosity of 1000 mPa·s or more and not causing any chemical reaction with the low melting point metal, and a raw material of the low melting point metal having a melting point lower than the thermal decomposition temperature of the high viscosity dispersion medium;
heating the mixture of the high viscosity dispersion medium and the raw material of the low melting point metal to a temperature range higher than the melting point of the low melting point metal and lower than the thermal decomposition temperature of the high viscosity dispersion medium; or, melting the low melting point metal raw material in the high viscosity dispersion medium by blending the low melting point metal raw material and the high viscosity dispersion medium heated to the temperature range;
obtaining a low melting point metal dispersion in which the molten low melting point metal is dispersed by performing high speed stirring at a circumferential speed of 1 m/s or more while heating to the temperature range; A method for producing a low melting point metal powder, the method comprising obtaining a low melting point metal powder by rapidly cooling to a temperature range lower than the melting point.
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