JP4239145B2 - Method for producing spherical powder - Google Patents
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【０００１】
【発明の属する技術分野】
本発明は、一定寸法の球状粉末を製造するためのプラズマを用いた球状粉末の製造方法に関するものである。
【０００２】
【従来の技術】
近年、電子機器に使用される接続部材としては、パッケージの端子としてのハンダ、ロウ材、金、銀、銅等の様々な一定寸法の球状粉末が使用されている。
また、ガラス等のセラミックスにおいてもレンズやフィルター等、一定寸法の球状粉末が使用される。
球状粉末を製造する方法としては、溶融液滴が飛行中に固化するガスアトマイズ法が広く用いられてきた。しかし、ガスアトマイズ法は、形状こそ球形になるものの、液体の噴霧による製造であるため、シャープな粒径を効率よく得ることは困難である。
また、他の方法として、あらかじめ粉末原料を準備し、これをプラズマ炎中に投入して球状化させる方法が提案されている（特許文献１参照。）。
【０００３】
【特許文献１】
特開平６−２８７０１２号公報（第３頁）
【０００４】
【発明が解決しようとする課題】
上述したプラズマ炎中で球状化させる技術としては、溶融球状化のためのプラズマ炎中の滞留時間制御といったところに着目され、一定寸法の球状粉末を効率良く得る手法は提案されていないのが現状である。
本発明の目的は、効率良く且つ極めてシャープな粒度分布をもつ球状粉末を形成することができる球状粉末の製造方法を提供することである。
【０００５】
【課題を解決するための手段】
本発明者は、プラズマ炎を利用した球状化技術において、線材を一定の間隔で切断した原料片の適用と、プラズマ炎の伸長を抑制することにより、一定寸法の球状粉末を凝集することなく効率的に生産できることを見いだし、本発明に到達した。
【０００６】
すなわち本発明は、線材とした原料を、一定の間隔で切断して原料片とし、ついで、該原料片の集合物を、尾部の伸長を抑制したプラズマ炎中に導入し、溶融、球状化させる球状粉末の製造方法である。
【０００７】
本発明において、プラズマ炎の尾部の外周に位置するプラズマトーチまたはチャンバの内径は、プラズマ発生部のプラズマトーチ内径の４倍以上とする。また、好ましくはプラズマの雰囲気圧力は、０．０４ＭＰａ〜大気圧とする。
本発明において使用する、原料片の体積は、球相当径として、２０〜１０００μｍであることが好ましく、また、原料粉末の融点は、１６００℃以下であることが好ましい。
【０００８】
【発明の実施の形態】
上述したように、本発明の重要な特徴の一つは、線材とした原料を、一定の間隔で切断してなる原料片の集合体を、プラズマ炎中に導入する構成を採用したことにある。
線材を一定に切断することで、原料の個々の体積が決定され、理想的には球状化すれば、直径が一定した球状粉末ができる。実際の生産では、原料片を一個ずつプラズマ炎に投入していたのでは、極めて非効率である。そこで、本発明ではまず、集合体でかつ連続的に導入することを要件とする。
【０００９】
この際問題となるのは、集合体として導入した時の粉末の接触・凝集およびプラズマという極めて高い温度域における蒸発による寸法の変化である。
本発明は、もう一つの特徴である炎の尾部の伸長を抑制したプラズマ炎を用いることで上記課題を解決した。プラズマ炎の尾部とは、高周波によって発生したプラズマが動作ガスの流れにより伸長されたプラズマ部分で、高周波コイルよりプラズマ下流部分を示す。
【００１０】
本発明者の検討によれば、プラズマの温度自体は、5000K以上であるため、原料表面は、集合体で連続的に導入しても、極めて短時間に溶融温度に達する。さらに、プラズマ炎から外れても、しばらくは、原料の融点を遙かに越える雰囲気にさらされる。そのため、高温域であるプラズマ炎に長くさらされると、溶融状態での粉末同士の接触機会も多くなり、球状化は達成されるものの、溶融した粉末同士の衝突による寸法の増大、減少、蒸発による体積減少等により、粒度分布が広がり、切断寸法通りの球状化という理想状態とはならないことが確認された。
【００１１】
これに対する本発明者の検討の結果、プラズマ炎による急速加熱後は、速やかにプラズマ炎から離脱し、プラズマ炎ほど高温ではないガス中で球状化させることが粒度分布を広げないために有効であり、その手段としてプラズマ炎の尾部の伸長を抑制することが必要であることを知見した。
【００１２】
プラズマ炎の尾部の伸長を抑制するための具体的な手法としては、たとえば、プラズマ発生部のガス流速に対して、プラズマ炎の尾部でのガス流速を下げることで達成できる。もっとも単純には、図２（ａ）に一例を示すようにプラズマの発生方向に対して、プラズマ炎の尾部の外周に位置するプラズマトーチまたはチャンパの内径を、プラズマ発生部１１のプラズマトーチ内径より大きくすることが挙げられる。これによりそうでない場合（図２（ｂ））と比べてプラズマ炎の尾部でのガス流速を下げ、尾部の伸長を抑制することができる。このプラズマトーチ又はチャンバの内径による尾部の伸長の抑制は、内径の比率を４倍以上とした場合にその効果が明確となり好ましい。
【００１３】
また、プラズマ炎の尾部の伸長を抑制するためには、プラズマの雰囲気圧力を比較的高い圧力である、０．０４Mpa〜大気圧で動作させるのが好ましい。ここで、０．０４ＭＰａ未満の圧力では、プラズマは長く尾を引いてしまうため、本発明の効果を達成しにくく、大気圧を超える加圧状態のプラズマは制御しにくいという問題があるため、０．０４Mpa〜大気圧で動作させるのが好ましいのである。
【００１４】
これらの他に、プラズマ炎の尾部のみにH2やN2などの電離エネルギーの高いガスを混合する方法や、不活性ガス等を用い、これを冷却ガスとして尾部に対して外周から吹き付けることによってもプラズマ炎の伸びを抑制することができる。
【００１５】
より好ましくは、上述の条件を組み合わせて適用する。例えば、プラズマトーチ又はチャンバの内径の比率を４倍以上、プラズマの雰囲気圧力を０．０４Mpa〜大気圧とし、プラズマ炎の尾部のみにH2やN2などの電離エネルギーの高いガスを混合することでプラズマ炎の尾部の伸びを抑制することがより好ましい。
【００１６】
また、本発明に適用する原料片としては、大きすぎると、球状化しにくくなり、小さ過ぎると表面積の増大から蒸発による体積変化が大きくなってしまうため、原料片の体積は、球相当径として、２０〜１０００μｍのものに適用することが好ましい。
また、本発明は、プラズマ炎での蒸発等が起こりやすい材料の球状化に適応することが好ましく、原料粉末の融点としては、１６００℃以下のもの、たとえばハンダ、ロウ材、金、銀、銅、ガラスなどに適用することが有効である。
【００１７】
本発明は例えば図１（ａ）（ｂ）に示す装置により実施することが出来る。図１（ａ）は装置全体の模式図、図１（ｂ）はプラズマトーチを拡大した模式図である。
図１において、水冷管１０により冷却されているプラズマトーチ８は、プラズマ動作ガス供給装置１１によりプラズマ動作ガス供給位置６から供給されるプラズマ動作ガスと、コイル７から発生する高周波エネルギによりプラズマ炎３を発生する。
【００１８】
原料供給装置１（例えば電磁振動原料供給装置）に投入された線材が一定の間隔で切断されてなる原料片は、キャリアガスと共に原料供給位置２よりプラズマ炎３内部の高温部（５０００〜１００００K）に投入される。プラズマ炎中に投入された原料片は瞬時に溶融し、表面張力により球状となる。
プラズマ炎内で処理された粉末はチャンバ４中を落下しながら不活性ガス雰囲気中で凝固し、球状粉末９として下部の球状粉末回収部５に集められ、回収される。
以上のようにして、球状粉末を効率的に製造することができる。
【００１９】
【実施例】
図１に記載のRFプラズマ装置を用いて、Ag-Cu合金（不可避的不純物を含む）の金属片を用い、目標直径が80.0μmの球状粉末を以下に示す製造条件で作製した。プラズマ炎に導入するAg-Cu合金（原料片）は直径20μmのワイヤを回転刃により、一定寸法（長さ853μm）に切断して作製した。
【００２０】
−製造条件（本発明例）−
原料片寸法：φ20μm×L853μm
プラズマ動作ガス：Ar 30L/min、H2 1L/min混合ガス（プラズマトーチ内の流速 0.26m/sec）
プラズマトーチ：水冷式石英管φ50mm、高周波誘導コイルφ70mm、図２（ａ）のプラズマトーチ
チャンバ：内径φ800mm、最大内高1500
チャンバ内雰囲気：Arガス雰囲気、大気圧
原料供給装置：電磁フィーダー
高周波誘導コイル入力条件：4MHz、8kW
【００２１】
比較の為、図２（ｂ）に記載のプラズマトーチを用い、下記のチャンバ内雰囲気条件を適用する以外は、上記の本発明例と同条件にて球状粉末を製造した。
−製造条件（比較例）−
チャンバ内雰囲気：Arガス雰囲気、0.03MPa
プラズマトーチ：水冷式石英管φ50mm、高周波誘導コイルφ70mm、図２（ｂ）のプラズマトーチ
【００２２】
プラズマ炎に導入後、球状粉末回収部に回収された球状粉末を、孔直径が75μmの丸孔篩と85μmの丸孔篩を用いて異形粉末の除去を行った。この結果、プラズマ導入前の原料片の重量と比較して、本発明例の製造方法では異形粉末の除去後には約83％の金属粉末を回収することが出来た。これに対し、比較例の製造方法では回収率は約3％であった。
丸孔篩により除去された異形粉末を確認したところ、目標とする80μｍの球体とは体積や形状が著しく異なるものであった。これらは、プラズマ炎中で溶融した原料片同士が接触して体積、形状が変動したものと考えられる。
【００２３】
次に、異形粉末を除去した後、無作為に100球を抽出し、平均直径、平均真球度を測定した。これらの測定は、平行透過光式で映し出した投影像をＣＣＤカメラによる画像認識しておこなった。この際、直径は投影像を真円と仮定した場合の円相当径で、真球度は円相当径を最大径で除した値として評価した。結果を表１に示す。
【００２４】
【表１】
表１に示すように、本発明例では異形粉末除去後の球状粉末の最大値、最小値は、除去に用いた丸孔篩の直径、言いかえると除去後の粉末直径の上、下限値である75、85μｍの幅より小さく、シャープな直径分布を達成している。目標直径である80μｍに近い値となっており、本発明の製造方法では、異形粉末となった球状粉末以外では、プラズマ炎導入前後での体積変化が小さいことが分かる。また、異形粉末除去後の球状粉末は、真球度において0.996を達成しており、球状化を達成している。これに対し、比較例では、最大径、最小径がほぼ丸孔篩の直径と同程度であり、ばらつきが大きい。加えて真球度も本発明例と比べて低く、十分な球状化を達成できていない。
したがって、本発明の球状粉末の製造方法によれば粒度分布が狭く、形状の揃った球状粉末を生産することが出来ることが判る。
【００２６】
【発明の効果】
本発明によれば、効率良く且つ極めてシャープな粒度分布をもつ球状粉末を形成することができる球状粉末の製造が可能となり、電子機器に使用される各種ろう材などの接続部材や、ガラス等からなるレンズやフィルター等、一定寸法の球状粉末を用いる分野において欠くことが出来ない技術となる。
【図面の簡単な説明】
【図１】 本発明の製造方法を実施する製造装置の一例を示す模式図である。
【図２】 プラズマ炎の尾部を示す模式図である。
【符号の説明】
１．原料供給装置、２．原料供給位置、３．プラズマ炎、４．チャンバ、５．球状粉末回収部、６．プラズマ動作ガス供給位置、７．コイル、８．プラズマトーチ、９．球状粉末、１０．水冷管、１１．プラズマ動作ガス供給装置、１２．プラズマ発生部[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for producing a spherical powder using plasma for producing a spherical powder of a certain size.
[0002]
[Prior art]
In recent years, spherical powders of various fixed dimensions such as solder, brazing material, gold, silver, and copper as package terminals have been used as connection members used in electronic devices.
Further, in ceramics such as glass, spherical powder having a certain size such as a lens or a filter is used.
As a method for producing a spherical powder, a gas atomization method in which molten droplets solidify during flight has been widely used. However, although the gas atomization method has a spherical shape, it is difficult to efficiently obtain a sharp particle size because it is manufactured by spraying a liquid.
As another method, a method has been proposed in which a powder raw material is prepared in advance, and this is put into a plasma flame to be spheroidized (see Patent Document 1).
[0003]
[Patent Document 1]
Japanese Patent Laid-Open No. 6-287012 (page 3)
[0004]
[Problems to be solved by the invention]
As a technique for spheroidizing in the above-mentioned plasma flame, attention has been focused on the residence time control in the plasma flame for melting spheroidization, and no method has been proposed for efficiently obtaining a spherical powder of a certain size. It is.
An object of the present invention is to provide a method for producing a spherical powder capable of forming a spherical powder having an efficient and extremely sharp particle size distribution.
[0005]
[Means for Solving the Problems]
In the spheroidization technology using a plasma flame, the present inventor is efficient without agglomerating spherical powder of a certain size by applying a raw material piece obtained by cutting a wire at regular intervals and suppressing the elongation of the plasma flame. The present invention has been found.
[0006]
That is, the present invention cuts the raw material used as a wire into a piece of raw material by cutting it at regular intervals, and then introduces the aggregate of the raw material piece into a plasma flame that suppresses the extension of the tail, and melts and spheroidizes it. It is a manufacturing method of spherical powder.
[0007]
Te present invention smell, a plasma torch or chamber inner diameter is located on the outer periphery of the tail portion of the plasma flame is four times or more plasma torches inside diameter of the plasma generator. Also, preferably atmospheric pressure plasma, and 0.04 M P a to atmospheric pressure.
The volume of the raw material piece used in the present invention is preferably 20 to 1000 μm as a sphere equivalent diameter, and the melting point of the raw material powder is preferably 1600 ° C. or less.
[0008]
DETAILED DESCRIPTION OF THE INVENTION
As described above, one of the important features of the present invention is that a configuration is adopted in which an assembly of raw material pieces obtained by cutting a raw material used as a wire at regular intervals is introduced into a plasma flame. .
By cutting the wire to a constant value, the individual volume of the raw material is determined. Ideally, if the material is spheroidized, a spherical powder with a constant diameter can be obtained. In actual production, it is extremely inefficient to put raw material pieces one by one into the plasma flame. Therefore, in the present invention, first, it is a requirement to introduce them in an aggregate and continuously.
[0009]
At this time, the problem is a change in dimensions due to evaporation in an extremely high temperature range of contact and aggregation of powder and plasma when introduced as an aggregate.
This invention solved the said subject by using the plasma flame which suppressed expansion | extension of the flame tail part which is another characteristic. The tail portion of the plasma flame is a plasma portion where the plasma generated by the high frequency is expanded by the flow of the working gas, and indicates the downstream portion of the plasma from the high frequency coil.
[0010]
According to the study of the present inventor, since the plasma temperature itself is 5000 K or higher, the raw material surface reaches the melting temperature in a very short time even if it is continuously introduced as an aggregate. Furthermore, even if it is removed from the plasma flame, it is exposed to an atmosphere that far exceeds the melting point of the raw material for a while. Therefore, when exposed to a plasma flame in a high temperature range for a long time, there are many opportunities for contact between powders in the molten state, and spheroidization is achieved. It was confirmed that the particle size distribution spreads due to volume reduction and the like, and the ideal state of spheroidizing according to the cut dimensions is not achieved.
[0011]
As a result of the inventor's investigation on this, it is effective in order not to spread the particle size distribution to quickly leave the plasma flame after being rapidly heated by the plasma flame and to spheroidize in a gas that is not as hot as the plasma flame. As a means, it has been found that it is necessary to suppress the extension of the tail of the plasma flame.
[0012]
As a specific method for suppressing the extension of the tail portion of the plasma flame, for example, it can be achieved by lowering the gas flow velocity at the tail portion of the plasma flame with respect to the gas flow velocity of the plasma generating portion. Most simply, as shown in FIG. 2A, the inner diameter of the plasma torch or the champ located at the outer periphery of the tail of the plasma flame is set to be larger than the inner diameter of the plasma torch of the plasma generator 11 with respect to the plasma generation direction. It can be enlarging. Thereby, compared with the case where it is not so (FIG.2 (b)), the gas flow rate in the tail part of a plasma flame can be lowered | hung and extension of a tail part can be suppressed. Suppression of tail extension due to the inner diameter of the plasma torch or chamber is preferable because the effect becomes clear when the ratio of the inner diameter is four times or more.
[0013]
In order to suppress the extension of the tail of the plasma flame, it is preferable to operate the atmospheric pressure of the plasma from 0.04 Mpa to atmospheric pressure, which is a relatively high pressure. Here, when the pressure is less than 0.04 MPa, the plasma has a long tail, so that it is difficult to achieve the effect of the present invention, and there is a problem that it is difficult to control the plasma in a pressurized state exceeding the atmospheric pressure. It is preferred to operate at .04 Mpa to atmospheric pressure.
[0014]
In addition to these, a method of mixing a gas with high ionization energy such as H 2 and N 2 only to the tail of the plasma flame, or using an inert gas etc., and blowing this from the outer periphery to the tail as a cooling gas Can also suppress the growth of the plasma flame.
[0015]
More preferably, the above conditions are applied in combination. For example, the ratio of the inner diameter of the plasma torch or chamber is 4 times or more, the atmospheric pressure of the plasma is 0.04 Mpa to atmospheric pressure, and a gas with high ionization energy such as H 2 or N 2 is mixed only in the tail part of the plasma flame. It is more preferable to suppress the extension of the tail of the plasma flame.
[0016]
In addition, as the raw material piece to be applied to the present invention, if it is too large, it is difficult to spheroidize, and if it is too small, the volume change due to evaporation increases from the increase in surface area. It is preferable to apply to a thing of 20-1000 micrometers.
In addition, the present invention is preferably adapted to spheroidization of a material that is likely to evaporate in a plasma flame, and the melting point of the raw material powder is 1600 ° C. or less, such as solder, brazing material, gold, silver, copper It is effective to apply to glass.
[0017]
The present invention can be implemented by the apparatus shown in FIGS. 1 (a) and 1 (b), for example. FIG. 1A is a schematic view of the entire apparatus, and FIG. 1B is an enlarged schematic view of a plasma torch.
In FIG. 1, a plasma torch 8 cooled by a water-cooled tube 10 has a
[0018]
The raw material piece formed by cutting the wire charged in the raw material supply device 1 (for example, the electromagnetic vibration raw material supply device) at regular intervals is a high temperature portion (5000 to 10000 K) inside the
The powder treated in the plasma flame is solidified in an inert gas atmosphere while falling in the chamber 4, and is collected and collected as a spherical powder 9 in the lower spherical powder collecting unit 5.
As described above, the spherical powder can be efficiently produced.
[0019]
【Example】
Using the RF plasma apparatus shown in FIG. 1, a spherical powder having a target diameter of 80.0 μm was produced under the production conditions shown below using a metal piece of an Ag—Cu alloy (including inevitable impurities). The Ag-Cu alloy (raw material piece) to be introduced into the plasma flame was prepared by cutting a wire with a diameter of 20 μm into a fixed dimension (length 853 μm) with a rotary blade.
[0020]
-Manufacturing conditions (examples of the present invention)-
Raw material piece size: φ20μm × L853μm
Plasma operating gas: Ar 30L / min, H 2 1L / min mixed gas (flow velocity in plasma torch 0.26m / sec)
Plasma torch: water-cooled quartz tube φ50mm, high frequency induction coil φ70mm, plasma torch chamber of Fig. 2 (a): inner diameter φ800mm, maximum inner height 1500
Chamber atmosphere: Ar gas atmosphere, atmospheric pressure material supply device: Electromagnetic feeder high frequency induction coil Input conditions: 4MHz, 8kW
[0021]
For comparison, a spherical powder was produced under the same conditions as in the above-described example of the present invention, except that the plasma torch shown in FIG.
-Manufacturing conditions (comparative example)-
Chamber atmosphere: Ar gas atmosphere, 0.03MPa
Plasma torch: water-cooled quartz tube φ50mm, high-frequency induction coil φ70mm, plasma torch in FIG. 2 (b)
After the introduction into the plasma flame, the irregular powder was removed from the spherical powder collected in the spherical powder collecting section using a round hole sieve having a pore diameter of 75 μm and a round hole sieve having a diameter of 85 μm. As a result, compared with the weight of the raw material pieces before introducing the plasma, the production method of the present invention example was able to recover about 83% of the metal powder after removing the irregular shaped powder. On the other hand, the recovery rate was about 3% in the manufacturing method of the comparative example.
When the irregular shaped powder removed by the round-hole sieve was confirmed, the volume and shape were significantly different from the target 80 μm sphere. These are considered to be a change in volume and shape due to contact between the raw material pieces melted in the plasma flame.
[0023]
Next, after removing the irregular powder, 100 balls were randomly extracted, and the average diameter and average sphericity were measured. These measurements were performed by recognizing the projected image projected by the parallel transmitted light system with a CCD camera. At this time, the diameter is an equivalent circle diameter when the projected image is assumed to be a perfect circle, and the sphericity is evaluated as a value obtained by dividing the equivalent circle diameter by the maximum diameter. The results are shown in Table 1.
[0024]
[Table 1]
As shown in Table 1, in the present invention example, the maximum value and the minimum value of the spherical powder after removing the irregular shaped powder are the diameter of the round-hole sieve used for the removal, in other words, the upper and lower limits of the powder diameter after the removal. It is smaller than a certain width of 75 and 85 μm and achieves a sharp diameter distribution. The value is close to the target diameter of 80 μm, and it can be seen that in the production method of the present invention, the volume change before and after the introduction of the plasma flame is small except for the spherical powder that has become a deformed powder. In addition, the spherical powder after removing the irregular shaped powder has achieved a sphericity of 0.996 and has achieved spheroidization. On the other hand, in the comparative example, the maximum diameter and the minimum diameter are almost the same as the diameter of the round hole sieve, and the variation is large. In addition, the sphericity is lower than that of the examples of the present invention, and sufficient spheroidization cannot be achieved.
Therefore, it can be seen that the spherical powder manufacturing method of the present invention can produce a spherical powder having a narrow particle size distribution and a uniform shape.
[0026]
【The invention's effect】
According to the present invention, it is possible to produce a spherical powder capable of forming a spherical powder having an efficient and extremely sharp particle size distribution, and from connection members such as various brazing materials used in electronic equipment, glass and the like. This technology is indispensable in the field of using spherical powder of a certain size, such as lenses and filters.
[Brief description of the drawings]
FIG. 1 is a schematic view showing an example of a production apparatus for carrying out a production method of the present invention.
FIG. 2 is a schematic view showing a tail portion of a plasma flame.
[Explanation of symbols]
1. 1. Raw material supply device, 2. Raw material supply position; 3. Plasma flame, Chamber, 5. 5. Spherical powder recovery unit, 6. Plasma operating gas supply position; Coil, 8. 8. Plasma torch, Spherical powder, 10. Water-cooled tubes, 11. Plasma operating gas supply device, 12. Plasma generator
Claims (4)
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| JP2002293786A JP4239145B2 (en) | 2002-10-07 | 2002-10-07 | Method for producing spherical powder |
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| JP2002293786A JP4239145B2 (en) | 2002-10-07 | 2002-10-07 | Method for producing spherical powder |
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| JP2004124231A JP2004124231A (en) | 2004-04-22 |
| JP2004124231A5 JP2004124231A5 (en) | 2005-11-10 |
| JP4239145B2 true JP4239145B2 (en) | 2009-03-18 |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US9908804B2 (en) | 2014-03-31 | 2018-03-06 | Corning Incorporated | Methods and apparatus for material processing using atmospheric thermal plasma reactor |
| US10059614B2 (en) | 2013-10-04 | 2018-08-28 | Corning Incorporated | Melting glass materials using RF plasma |
| US10167220B2 (en) | 2015-01-08 | 2019-01-01 | Corning Incorporated | Method and apparatus for adding thermal energy to a glass melt |
Families Citing this family (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| KR100840229B1 (en) | 2006-09-08 | 2008-06-23 | 재단법인 포항산업과학연구원 | Ultra fine solder, method for manufacturing ultra fine solder and manufacturing apparatus using the same |
| CN102672189A (en) * | 2012-05-17 | 2012-09-19 | 赣州海盛钨钼集团有限公司 | Preparation method of spherical tungsten powder |
| US9550694B2 (en) | 2014-03-31 | 2017-01-24 | Corning Incorporated | Methods and apparatus for material processing using plasma thermal source |
| CN106001594B (en) * | 2016-07-15 | 2017-12-22 | 北京科技大学 | A kind of preparation method of super thick globular tungsten powder |
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2002
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US10059614B2 (en) | 2013-10-04 | 2018-08-28 | Corning Incorporated | Melting glass materials using RF plasma |
| US9908804B2 (en) | 2014-03-31 | 2018-03-06 | Corning Incorporated | Methods and apparatus for material processing using atmospheric thermal plasma reactor |
| US10167220B2 (en) | 2015-01-08 | 2019-01-01 | Corning Incorporated | Method and apparatus for adding thermal energy to a glass melt |
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