WO2010108591A1 - Production of fibers made of platinum or palladium or alloys based on platinum or palladium, and of non-woven mats or meshes thereof - Google Patents

Production of fibers made of platinum or palladium or alloys based on platinum or palladium, and of non-woven mats or meshes thereof Download PDF

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Publication number
WO2010108591A1
WO2010108591A1 PCT/EP2010/001416 EP2010001416W WO2010108591A1 WO 2010108591 A1 WO2010108591 A1 WO 2010108591A1 EP 2010001416 W EP2010001416 W EP 2010001416W WO 2010108591 A1 WO2010108591 A1 WO 2010108591A1
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Prior art keywords
palladium
platinum
fibers
boron
atomization
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PCT/EP2010/001416
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German (de)
French (fr)
Inventor
Harald Manhardt
Tanja Eckardt
Nicole GÜBLER
Annette Lukas
David Francis Lupton
Friedhold Schölz
Ulrich Koops
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W. C. Heraeus Gmbh
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Priority to DE112010001371T priority Critical patent/DE112010001371A5/en
Publication of WO2010108591A1 publication Critical patent/WO2010108591A1/en

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    • D—TEXTILES; PAPER
    • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
    • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
    • D01F1/00—General methods for the manufacture of artificial filaments or the like
    • D01F1/02—Addition of substances to the spinning solution or to the melt
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
    • B01J23/40—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals of the platinum group metals
    • B01J23/42—Platinum
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
    • B01J23/40—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals of the platinum group metals
    • B01J23/44—Palladium
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
    • B01J23/40—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals of the platinum group metals
    • B01J23/46—Ruthenium, rhodium, osmium or iridium
    • B01J23/464—Rhodium
    • B01J35/51—
    • B01J35/58—
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
    • B01J37/0081—Preparation by melting
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F1/00—Metallic powder; Treatment of metallic powder, e.g. to facilitate working or to improve properties
    • B22F1/06—Metallic powder characterised by the shape of the particles
    • B22F1/062—Fibrous particles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
    • B22F9/00—Making metallic powder or suspensions thereof
    • B22F9/02—Making metallic powder or suspensions thereof using physical processes
    • B22F9/06—Making metallic powder or suspensions thereof using physical processes starting from liquid material
    • B22F9/08—Making metallic powder or suspensions thereof using physical processes starting from liquid material by casting, e.g. through sieves or in water, by atomising or spraying
    • B22F9/082—Making metallic powder or suspensions thereof using physical processes starting from liquid material by casting, e.g. through sieves or in water, by atomising or spraying atomising using a fluid
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C5/00—Alloys based on noble metals
    • C22C5/04—Alloys based on a platinum group metal
    • D—TEXTILES; PAPER
    • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
    • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
    • D01F9/00—Artificial filaments or the like of other substances; Manufacture thereof; Apparatus specially adapted for the manufacture of carbon filaments
    • D01F9/08—Artificial filaments or the like of other substances; Manufacture thereof; Apparatus specially adapted for the manufacture of carbon filaments of inorganic material

Definitions

  • the invention relates to the production of fibers of platinum or palladium or alloys based on platinum or palladium, and nonwovens or nets thereof.
  • Serole has described a process for producing metal powder (EP 0 726 806 B1) in which the material is passed as a melt through nozzles and cooled rapidly.
  • the aim is, in particular, to modify noble metal alloys based on platinum or palladium in such a way that they solidify into fibers in the course of the gas atomization.
  • the invention accordingly relates to a process for the production of fibers from a Pt-based alloy by gas atomization by adjusting the viscosity of the Pt melt by adding boron so that no powder is formed during the atomization, but fibers.
  • platinum, palladium or Pt or Pd-based fibers can be produced, each containing about 2% of boron. This both reduces the melting point and improves the sinterability of the fibers.
  • Pt and Pd alloy fibers produced according to the invention are suitable for sintered nonwovens used in catalytic processes (eg nitric acid production).
  • FIG. 34 shows the essential features of a very simple atomizer for producing metal powder.
  • a gas is conveyed through the annular gap 34, which is designed as Venturi nozzle, at high speed.
  • the atomizing nozzle consists of an upper chamber, which is parabolic in the above figure, with a passage 31 to a conical expansion region 35.
  • the gas flow through the annular gap 34 generates a negative pressure in the region of the outlet opening 33.
  • the conicity angles of the annular gap and the expansion region are adjusted to maximize the negative pressure in the region of the outlet opening in order to generate another gas flow from the upper chamber of the atomizing nozzle through the passage 31 into the expansion region.
  • the geometric shape of the upper chamber, the passageway, and the expansion area is designed using finite element modeling and experimental design to make this gas flow largely laminar.
  • the melt is passed from a crucible via a capillary tube above the passage into the upper chamber. Adjusting the inside diameter of the capillary tube and the height of the tube above the passage will ensure that the melt enters the passage in the form of a thin continuous thread.
  • the melt jet is accelerated by the gas flow until the jet is torn apart. Due to the high surface tension and low viscosity of molten metal, the individual droplets contract into small spheres, which solidify rapidly. This creates a largely spherical powder.
  • the boron is preferably mixed with the metal under a protective gas atmosphere. Further, it is preferred that the fibers be sintered into a nonwoven or web.
  • Boron is thermally removed as an oxide from the fibers in another embodiment of the process.
  • a nozzle made of boron nitride is produced.
  • the annular gap nozzle is designed with a half opening angle of 20 °.
  • the nozzle is installed in an atomizing apparatus between an upper and a lower chamber.
  • In the upper chamber is an induction melting device with a zirconium oxide crucible.
  • a capillary tube of aluminum oxide with an inner diameter of 2.5 mm is cemented.
  • the upper end of the capillary tube can be closed with a stopper rod during the melting process.
  • the capillary tube is heated to prevent the freezing of the molten metal as it passes through the tube.
  • the annular die is fed with nitrogen at a pressure between 5 and 6 bar.
  • the lower chamber is connected via a cyclone separator to a water ring pump, which can generate a vacuum corresponding to about 800 mbar in the chamber and thus conveys the nitrogen introduced via the annular gap nozzle out of the chamber.
  • the negative pressure created by the Venturi effect in the vicinity of the annular gap nozzle opening leads to a gas flow from the upper to the lower chamber.
  • the upper chamber is fed with nitrogen so that the pressure is maintained between 1000 and 1100 mbar.
  • the crucible is charged with 600 g of an AgCu 7.5 alloy.
  • This alloy also called “sterling silver”
  • the alloy is heated to 850 0 C and shows a doughy consistency, since it is not completely melted.
  • the stopper rod is pulled out of the crucible.
  • the molten metal flows through the capillary tube and is accelerated by the gas flow in the nozzle into small particles that are mostly trapped in the cyclone separator. After the evaporation process, it can be seen that the particles are essentially spherical and have an average diameter of 27 ⁇ m.
  • an alloy of 98.4 wt.% Pt and 1.6 wt.% B is melted by melting in a vacuum arc furnace.
  • This alloy has a liquidus of about 1000 0 C and a solidus of about 825 0 C.
  • 6-alloy at 950 ° C in about the same viscosity as the alloy at 850 AgCu7,5 0 C and can also pass through the capillary tube.
  • the pouring stream breaks down into small particles, most of which are collected in the cyclone separator. After the atomization process, it should be noted that the particles are essentially fibrous.
  • the investigation in the scanning electron microscope shows a circular cross section with a mean diameter of about 35 microns and an average length of about 4.5 mm.
  • Example 2 The same alloy as in Example 2 is heated in the crucible of Verdüsungsap- paratur 1020 0 C and subjected in an analogous manner to the atomisation process. Also in this case, the pouring stream breaks up into small particles, which are mostly collected in the cyclone separator. After the atomization process, it should be noted that the particles are essentially spherical. The particles have an average particle size of 32 microns.
  • Embodiment 4 Atomization to fibers
  • an alloy is prepared from 98.4 wt .-% of a prefabricated PtRh ⁇ alloy and 1, 6 wt .-% B in a vacuum arc furnace and fed to the atomization process at 950 0 C. After the atomization process, it is found that the particles are essentially fibrous.
  • the investigation in a scanning electron microscope shows a circular cross section with an average diameter of about 40 microns and an average length of about 5.5 mm.

Abstract

The invention relates to a method for producing fibers made of platinum, palladium, or alloys based on Pt or Pd from a melt by gas atomizing, wherein the viscosity of the melt is adjusted by alloying boron so that fibers, not powder, are created by atomizing. The fibers thus created can be sintered into non-woven mats or meshes. The boron can be thermally removed as an oxide. The method is particularly suitable for fibers made of PtRh alloys.

Description

Herstellung von Fasern aus Platin oder Palladium oder Legierungen auf Platinoder Palladiumbasis und von Vliesen oder Netzen daraus Production of fibers of platinum or palladium or alloys based on platinum or palladium and nonwovens or nets thereof
Die Erfindung betrifft die Herstellung von Fasern aus Platin oder Palladium oder Legierungen auf Platin- oder Palladiumbasis, und von Vliesen oder Netzen daraus.The invention relates to the production of fibers of platinum or palladium or alloys based on platinum or palladium, and nonwovens or nets thereof.
B. Serole hat ein Verfahren zur Herstellung von Metallpulver beschrieben (EP 0 726 806 B1), bei dem das Material als Schmelze durch Düsen geleitet und schnell abgekühlt wird.B. Serole has described a process for producing metal powder (EP 0 726 806 B1) in which the material is passed as a melt through nozzles and cooled rapidly.
Demgegenüber haben sich die Erfinder die Aufgabe gestellt, zu Vliesen verarbeitbare Fasern zu erzeugen. Ziel ist es insbesondere, Edelmetalllegierungen auf der Basis von Platin oder Palladium so zu modifizieren, dass sie im Laufe der Gasverdüsung zu Fasern erstarren.By contrast, the inventors have set themselves the task of producing nonwoven fibers. The aim is, in particular, to modify noble metal alloys based on platinum or palladium in such a way that they solidify into fibers in the course of the gas atomization.
Die Erfindung betrifft demgemäß ein Verfahren zur Herstellung von Fasern aus einer Legierung auf Pt-Basis durch Gasverdüsung, indem durch Zulegieren von Bor die Viskosität der Pt- Schmelze so eingestellt wird, dass bei der Verdüsung kein Pulver entsteht, sondern Fasern. Erfindungsgemäß können Fasern aus Platin, Palladium oder Legierungen auf Pt- oder Pd-Basis hergestellt werden, die jeweils etwa 2 % Bor enthalten. Dadurch wird sowohl der Schmelzpunkt reduziert als auch die Sinterfähigkeit der Fasern verbessert.The invention accordingly relates to a process for the production of fibers from a Pt-based alloy by gas atomization by adjusting the viscosity of the Pt melt by adding boron so that no powder is formed during the atomization, but fibers. According to the invention, platinum, palladium or Pt or Pd-based fibers can be produced, each containing about 2% of boron. This both reduces the melting point and improves the sinterability of the fibers.
Erfindungsgemäß hergestellte Fasern aus Pt- und Pd-Legierungen eignen sich für gesinterte Vliese, die in katalytischen Prozessen (z. B. Salpetersäureherstellung) verwendet werden.Pt and Pd alloy fibers produced according to the invention are suitable for sintered nonwovens used in catalytic processes (eg nitric acid production).
Ein typisches Beispiel für ein einfaches Gasverdüsungsverfahren wird in der EP 0 726 806 B1 , Figur 7 (Patent ITO-Verfahren, B. Serole) angegeben:A typical example of a simple gas atomization process is given in EP 0 726 806 B1, FIG. 7 (Patent ITO process, B. Serole):
Obwohl diese Abbildung wegen der im o. a. Patent beschriebenen reaktiven Plasma-Verdüsung von Indium-Zinn-Legierung zu Indium-Zinn-Oxid relativ komplex ausgeführt ist, zeigt sie die wesentlichen Merkmale einer sehr einfachen Verdüsungseinrichtung zur Erzeugung von Metallpulver. Ein Gas wird durch den Ringspalt 34, der als Venturidüse ausgelegt ist, mit hoher Geschwindigkeit gefördert. Die Zerstäubungsdüse besteht aus einer oberen Kammer, die in der o. a. Figur parabolisch ausgebildet ist, mit einem Durchlass 31 zu einem konischen Expansionsbereich 35. Die Gasströmung durch den Ringspalt 34 erzeugt im Bereich der Auslassöffnung 33 einen Unterdruck. Experimentell werden die Konizitäts-Winkel des Ringspalts sowie des Expansionsbereichs so eingestellt, dass der Unterdruck im Bereich der Auslassöffnung maximiert wird, damit eine weitere Gasströmung von der oberen Kammer der Zerstäubungsdüse durch den Durchlass 31 in den Expansionsbereich erzeugt wird. Die geometrische Form der oberen Kammer, des Durchlasses sowie des Expansionsbereichs wird anhand von Finite-Elementen-Modellierung sowie experimentell so ausgelegt, dass diese Gasströmung weitestgehend laminar ist.Although this figure is relatively complex because of the reactive plasma atomization of indium tin alloy to indium tin oxide described in the above-mentioned patent, it shows the essential features of a very simple atomizer for producing metal powder. A gas is conveyed through the annular gap 34, which is designed as Venturi nozzle, at high speed. The atomizing nozzle consists of an upper chamber, which is parabolic in the above figure, with a passage 31 to a conical expansion region 35. The gas flow through the annular gap 34 generates a negative pressure in the region of the outlet opening 33. Experimentally, the conicity angles of the annular gap and the expansion region are adjusted to maximize the negative pressure in the region of the outlet opening in order to generate another gas flow from the upper chamber of the atomizing nozzle through the passage 31 into the expansion region. The geometric shape of the upper chamber, the passageway, and the expansion area is designed using finite element modeling and experimental design to make this gas flow largely laminar.
Die Schmelze wird aus einem Schmelztiegel über ein Kapillarröhrchen oberhalb des Durchlasses in die obere Kammer geleitet. Durch Einstellung des Innendurchmessers des Kapillarröhr- chens sowie der Höhe des Röhrchens oberhalb des Durchlasses wird sichergestellt, dass die Schmelze in der Form eines dünnen kontinuierlichen Fadens in den Durchlass eintritt. Hier wird der Schmelzstrahl von der Gasströmung beschleunigt, bis der Strahl auseinander gerissen wird. Bedingt durch die hohe Oberflächenspannung und geringe Viskosität von Metallschmelzen ziehen sich die einzelnen Tropfen zu kleinen Kugeln zusammen, die rasch erstarren. Dadurch entsteht ein weitgehend kugeliges Pulver.The melt is passed from a crucible via a capillary tube above the passage into the upper chamber. Adjusting the inside diameter of the capillary tube and the height of the tube above the passage will ensure that the melt enters the passage in the form of a thin continuous thread. Here the melt jet is accelerated by the gas flow until the jet is torn apart. Due to the high surface tension and low viscosity of molten metal, the individual droplets contract into small spheres, which solidify rapidly. This creates a largely spherical powder.
Überraschenderweise wurde festgestellt, dass durch das Zulegieren von Bor zu Pt und seinen Legierungen (z. B. PtRh-Legierungen) im untereutektischen Bereich (ca. 1 ,5 Gew.-% B im Vergleich zur Zusammensetzung des Eutektikums zwischen BPt3 und BPt2 bei 2,1 Gew.-% B) bei einer Temperatur etwas oberhalb der eutektischen Temperatur von 790 0C (s. Zustandsdiag- ramm, Anlage 1) eine extrem zähflüssige, teigige Schmelze erzielt werden konnte. Durch sorgfältige Einstellung der Viskosität entstand bei der oben beschriebenen Gasverdüsung kein kugeliges Pulver, sondern eine Vielzahl feiner Fasern. Zur Ermittlung der Viskosität reicht eine vergleichende Methode aus. Bei den vorliegenden Untersuchungen wurde das im Lehrbuch „Keramische Glasuren und ihre Farben für Studium - Handwerk - Industrie" von Werner Lehnhäuser, Verlag Ritterbach, 4. Auflage, Seiten 477-478, beschriebene Rinnenviskosimeter angewendet, wobei die Rinnenplatte speziell aus Aluminiumoxid angefertigt wurde, um einen Angriff der Rinnenoberfläche durch den Boranteil der Legierung zu vermeiden.It has surprisingly been found that by alloying boron to Pt and its alloys (eg PtRh alloys) in the hypoeutectic region (about 1.5% by weight B in comparison to the composition of the eutectic between BPt 3 and BPt 2 slightly above the eutectic temperature of 790 C wt .-% 0 B) at a temperature (at 2.1 s. Zustandsdiag- Ramm, Appendix 1) an extremely viscous, pasty melt could be obtained. By careful adjustment of the viscosity, no spherical powder was produced in the gas atomization described above, but a large number of fine fibers. To determine the viscosity, a comparative method is sufficient. In the present studies, the gutter viscometer described in the textbook "Ceramic glazes and their colors for study - craft industry" by Werner Lehnhäuser, Verlag Ritterbach, 4th edition, pages 477-478, was applied, the gutter plate was made specifically from alumina, to avoid an attack of the gutter surface by the boron content of the alloy.
Das Bor wird bevorzugt unter Schutzgasatmosphäre mit dem Metall gemischt. Weiter ist es bevorzugt, dass die Fasern zu einem Vlies oder Netz gesintert werden.The boron is preferably mixed with the metal under a protective gas atmosphere. Further, it is preferred that the fibers be sintered into a nonwoven or web.
Das Bor wird in einer weiteren Ausführungsform des Verfahrens thermisch als Oxid aus den Fasern entfernt.Boron is thermally removed as an oxide from the fibers in another embodiment of the process.
Vergleichsbeispiel 1 Verdüsung zu KugelnComparative Example 1 Atomization into spheres
In Anlehnung an Figur 7 der EP 0 726 806 B1 wird eine Düse aus Bornitrid angefertigt. Anhand von Vorversuchen wird die Ringspaltdüse mit einem halben Öffnungswinkel von 20° ausgelegt. Die Düse wird in eine Verdüsungsapparatur zwischen einer oberen und einer unteren Kammer installiert. In der oberen Kammer ist eine Induktionsschmelzvorrichtung mit einem Tiegel aus Zirkoniumoxid. In den Boden des Tiegels wird ein Kapillarröhrchen aus Aluminiumoxid mit Innendurchmesser 2,5 mm einzementiert. Das obere Ende des Kapillarröhrchens kann während des Aufschmelzvorgangs mit einer Stopfenstange verschlossen werden. Mittels einer Heizwendel wird das Kapillarröhrchen beheizt, um das Einfrieren der Metallschmelze beim Passieren des Röhrchens zu verhindern.On the basis of FIG. 7 of EP 0 726 806 B1, a nozzle made of boron nitride is produced. On the basis of preliminary tests, the annular gap nozzle is designed with a half opening angle of 20 °. The nozzle is installed in an atomizing apparatus between an upper and a lower chamber. In the upper chamber is an induction melting device with a zirconium oxide crucible. In the bottom of the crucible, a capillary tube of aluminum oxide with an inner diameter of 2.5 mm is cemented. The upper end of the capillary tube can be closed with a stopper rod during the melting process. By means of a heating coil, the capillary tube is heated to prevent the freezing of the molten metal as it passes through the tube.
Zum Betrieb der Verdüsungsapparatur wird die Ringspaltdüse mit Stickstoff bei einem Druck zwischen 5 und 6 bar gespeist. Die untere Kammer wird über einen Zyklonabscheider an eine Wasserringpumpe angeschlossen, die in der Kammer einen Unterdruck entsprechend etwa 800 mbar erzeugen kann und so den über die Ringspaltdüse eingeleiteten Stickstoff aus der Kammer befördert.To operate the atomizing apparatus, the annular die is fed with nitrogen at a pressure between 5 and 6 bar. The lower chamber is connected via a cyclone separator to a water ring pump, which can generate a vacuum corresponding to about 800 mbar in the chamber and thus conveys the nitrogen introduced via the annular gap nozzle out of the chamber.
Der durch den Venturi-Effekt erzeugte Unterdruck in der Nähe der Ringspaltdüsenöffnung führt zu einer Gasströmung von der oberen in die untere Kammer. Über eine geeignete Druckregelung wird die obere Kammer so mit Stickstoff gespeist, dass der Druck zwischen 1000 und 1100 mbar gehalten wird.The negative pressure created by the Venturi effect in the vicinity of the annular gap nozzle opening leads to a gas flow from the upper to the lower chamber. By means of a suitable pressure control, the upper chamber is fed with nitrogen so that the pressure is maintained between 1000 and 1100 mbar.
Zur Überprüfung der Verdüsungsapparatur wird der Schmelztiegel mit 600 g einer AgCu7,5- Legierung chargiert. Diese Legierung, auch „Sterling Silber" bezeichnet, hat einen Liquidus von ca. 880 0C und einen Solidus von ca. 770 0C. Die Legierung wird auf 850 0C erwärmt und zeigt eine teigige Konsistenz, da sie nicht vollständig aufgeschmolzen ist. Nach dem Einschalten der Wasserringpumpe sowie der Stickstoffversorgung zur Ringspaltdüse und der oberen Kammer wird die Stopfenstange aus dem Tiegel gezogen. Die Metallschmelze strömt durch das Kapillarröhrchen und wird durch die Gasströmung in der Düse beschleunigt. Der Gießstrahl zerteilt sich in kleine Partikel, die größtenteils im Zyklonabscheider aufgefangen werden. Nach dem Verdü- sungsvorgang ist festzustellen, dass die Partikel im Wesentlichen kugelförmig sind und einen mittleren Durchmesser von 27 μm aufweisen.To check the atomization apparatus, the crucible is charged with 600 g of an AgCu 7.5 alloy. This alloy, also called "sterling silver", has a liquidus of about 880 0 C and a solidus of about 770 0 C. The alloy is heated to 850 0 C and shows a doughy consistency, since it is not completely melted. After switching on the water ring pump and the nitrogen supply to the annular gap nozzle and the upper chamber, the stopper rod is pulled out of the crucible.The molten metal flows through the capillary tube and is accelerated by the gas flow in the nozzle into small particles that are mostly trapped in the cyclone separator. After the evaporation process, it can be seen that the particles are essentially spherical and have an average diameter of 27 μm.
Ausführungsbeispiel 2 Verdüsung zu FasernEmbodiment 2 Atomization to fibers
Zum Vergleich wird eine Legierung aus 98,4 Gew.-% Pt und 1 ,6 Gew.-% B durch Schmelzen in einem Vakuumlichtbogenofen geschmolzen. Diese Legierung hat einen Liquidus von ca. 1000 0C und einen Solidus von ca. 825 0C. Anhand von Messungen am Rinnenviskosimeter erreicht diese PtB1 ,6-Legierung bei 950 °C in etwa die gleiche Viskosität wie die Legierung AgCu7,5 bei 850 0C und kann ebenfalls das Kapillarröhrchen passieren. Nach dem Einschalten der Wasserringpumpe sowie der Stickstoffversorgung zur Ringspaltdüse und der oberen Kammer wird die Stopfenstange aus dem Tiegel gezogen. Die auf 950 0C erhitzte Metallschmelze strömt durch das Kapillarröhrchen und wird durch die Gasströmung in der Düse beschleunigt. Der Gießstrahl zerteilt sich in kleine Partikel, die größtenteils im Zyklonabscheider aufgefangen werden. Nach dem Verdüsungsvorgang ist festzustellen, dass die Partikel im Wesentlichen faserförmig sind. Die Untersuchung im Rasterelektronenmikroskop zeigt einen kreisrunden Querschnitt mit einem mittleren Durchmesser von etwa 35 μm und eine mittlere Länge von etwa 4,5 mm.For comparison, an alloy of 98.4 wt.% Pt and 1.6 wt.% B is melted by melting in a vacuum arc furnace. This alloy has a liquidus of about 1000 0 C and a solidus of about 825 0 C. On the basis of measurements on the Rinnenviskosimeter reaches this pTB1, 6-alloy at 950 ° C in about the same viscosity as the alloy at 850 AgCu7,5 0 C and can also pass through the capillary tube. After switching on the water ring pump and the nitrogen supply to the annular gap nozzle and the upper chamber, the stopper rod is pulled out of the crucible. The molten metal heated to 950 ° C. flows through the capillary tube and is accelerated by the gas flow in the nozzle. The pouring stream breaks down into small particles, most of which are collected in the cyclone separator. After the atomization process, it should be noted that the particles are essentially fibrous. The investigation in the scanning electron microscope shows a circular cross section with a mean diameter of about 35 microns and an average length of about 4.5 mm.
Vergleichsbeispiel 3 Verdüsung zu KugelnComparative Example 3 Atomization into spheres
Die gleiche Legierung wie im Ausführungsbeispiel 2 wird im Schmelztiegel der Verdüsungsap- paratur auf 1020 0C erhitzt und auf analoge Weise dem Verdüsungsprozess unterzogen. Auch in diesem Fall zerteilt sich der Gießstrahl in kleine Partikel, die größtenteils im Zyklonabscheider aufgefangen werden. Nach dem Verdüsungsvorgang ist festzustellen, dass die Partikel im Wesentlichen kugelförmig sind. Die Teilchen haben eine mittlere Teilchengröße von 32 μm.The same alloy as in Example 2 is heated in the crucible of Verdüsungsap- paratur 1020 0 C and subjected in an analogous manner to the atomisation process. Also in this case, the pouring stream breaks up into small particles, which are mostly collected in the cyclone separator. After the atomization process, it should be noted that the particles are essentially spherical. The particles have an average particle size of 32 microns.
Ausführungsbeispiel 4 Verdüsung zu FasernEmbodiment 4 Atomization to fibers
Analog dem Ausführungsbeispiel 2 wird aus 98,4 Gew.-% einer vorgefertigten PtRhδ-Legierung und 1 ,6 Gew.-% B im Vakuumlichtbogenofen eine Legierung hergestellt und bei 950 0C dem Verdüsungsprozess zugeführt. Nach dem Verdüsungsvorgang wird festgestellt, dass die Partikel im Wesentlichen faserförmig sind. Die Untersuchung im Rasterelektronenmikroskop ergibt einen kreisrunden Querschnitt mit einem mittleren Durchmesser von etwa 40 μm und eine mittlere Länge von etwa 5,5 mm. Analogous to Embodiment 2, an alloy is prepared from 98.4 wt .-% of a prefabricated PtRhδ alloy and 1, 6 wt .-% B in a vacuum arc furnace and fed to the atomization process at 950 0 C. After the atomization process, it is found that the particles are essentially fibrous. The investigation in a scanning electron microscope shows a circular cross section with an average diameter of about 40 microns and an average length of about 5.5 mm.

Claims

Patentansprüche claims
1. Verfahren zur Herstellung von Fasern aus Platin, Palladium oder Legierungen auf Pt- oder Pd-Basis aus einer Schmelze durch Gasverdüsung, indem durch Zulegieren von Bor die Viskosität der Schmelze so eingestellt wird, dass bei der Verdüsung kein Pulver entsteht, sondern Fasern.1. A process for the production of fibers from platinum, palladium or alloys based on Pt or Pd from a melt by gas atomization by the addition of boron, the viscosity of the melt is adjusted so that no powder is produced during the atomization, but fibers.
2. Verfahren nach Anspruch 1 , dadurch gekennzeichnet, dass das Bor unter Schutzgasatmosphäre mit dem Metall gemischt wird.2. The method according to claim 1, characterized in that the boron is mixed under a protective gas atmosphere with the metal.
3. Verfahren nach einem der Ansprüche 1 und 2, dadurch gekennzeichnet, dass die entstandenen Fasern zu einem Vlies oder Netz gesintert werden.3. The method according to any one of claims 1 and 2, characterized in that the resulting fibers are sintered to form a web or web.
4. Verfahren nach einem der Ansprüche 1 bis 3, dadurch gekennzeichnet, dass das Bor thermisch als Oxid entfernt wird.4. The method according to any one of claims 1 to 3, characterized in that the boron is removed thermally as oxide.
5. Verfahren nach einem der vorstehenden Ansprüche, dadurch gekennzeichnet, dass die Legierung auf Pt-Basis eine PtRh-Legierung ist. 5. The method according to any one of the preceding claims, characterized in that the Pt-based alloy is a PtRh alloy.
PCT/EP2010/001416 2009-03-27 2010-03-06 Production of fibers made of platinum or palladium or alloys based on platinum or palladium, and of non-woven mats or meshes thereof WO2010108591A1 (en)

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