EP0441698A1 - Impregnated cathode manufacturing procedure and cathode obtained therewith - Google Patents
Impregnated cathode manufacturing procedure and cathode obtained therewith Download PDFInfo
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- EP0441698A1 EP0441698A1 EP91400272A EP91400272A EP0441698A1 EP 0441698 A1 EP0441698 A1 EP 0441698A1 EP 91400272 A EP91400272 A EP 91400272A EP 91400272 A EP91400272 A EP 91400272A EP 0441698 A1 EP0441698 A1 EP 0441698A1
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- powder
- cathode
- impregnated
- barium
- impregnated cathode
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J1/00—Details of electrodes, of magnetic control means, of screens, or of the mounting or spacing thereof, common to two or more basic types of discharge tubes or lamps
- H01J1/02—Main electrodes
- H01J1/13—Solid thermionic cathodes
- H01J1/20—Cathodes heated indirectly by an electric current; Cathodes heated by electron or ion bombardment
- H01J1/28—Dispenser-type cathodes, e.g. L-cathode
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
- H01J9/00—Apparatus or processes specially adapted for the manufacture, installation, removal, maintenance of electric discharge tubes, discharge lamps, or parts thereof; Recovery of material from discharge tubes or lamps
- H01J9/02—Manufacture of electrodes or electrode systems
- H01J9/04—Manufacture of electrodes or electrode systems of thermionic cathodes
Definitions
- the present invention relates to a method of manufacturing an impregnated cathode and a cathode obtained by this method. It finds an application in the production of cathodes for electronic tubes and more particularly but not exclusively for cathode ray display tubes.
- Impregnated cathodes are commonly used to provide electronic current densities of up to 1 to 2 A / cm2 continuously and more in pulses.
- the impregnated cathodes known from the prior art consist of a porous body of refractory metal, such as pure tungsten, or else of a mixture of tungsten, either with a metal originating from the platinum mine (mixed matrix), such as known from document FR A 2 356 263, either with scandium oxide or other rare earths in low concentration (3 to 5% by weight).
- This porous body is generally obtained by compressing a finely divided powder of the metal (or mixture of metals) using an isostatic press or a uniaxial press.
- the compacts thus obtained are then heated under hydrogen at high temperature, in order to sinter the particles together and to increase the density of the porous body.
- the porous body To facilitate machining of the porous body, it is infiltrated with copper or plastic, then machined to the desired shape. Subsequently, the copper or plastic is removed by dissolving in an acid or by heating.
- the porous body of the desired shape is then brazed on a molybdenum skirt which serves to hold, on one side, the emissive patch and, on the other, a filament potted in alumina which allows the heating of the cathode .
- a molybdenum skirt which serves to hold, on one side, the emissive patch and, on the other, a filament potted in alumina which allows the heating of the cathode .
- the pores of the porous body can be filled with barium and calcium aluminates.
- the body is impregnated with these aluminates, which constitute the emissive material of the finished cathode.
- the porous body is kept in close contact with an aluminate composition brought, under a reducing atmosphere, to a temperature above its melting point. Contact is ensured, either by immersing the porous body in the aluminate, or by placing the aluminate on the porous body. At the time of fusion, the aluminate diffuses by capillarity or by flow inside the open pores and fills them. The cathode is then cleaned mechanically and chemically, in order to remove the aluminate residues which have remained stuck on the surfaces.
- the cathode is activated, under vacuum, at a temperature at which tungsten reduces barium and calcium aluminate to release barium oxide.
- Metallic barium is produced in areas where the aluminate is in contact with the refractory metal (pores). The metallic barium reaches the end of the pores and diffuses over the entire emissive surface where it forms with oxygen a surface monolayer which promotes electronic emissivity by lowering the work of electron output.
- the deposition, on the emissive surface of these impregnated cathodes, of a film of osmium, iridium, ruthenium, or an alloy of these bodies, this film having a thickness of a few thousand Angstroms can improve emissivity by a factor of around 3.
- the mixed matrix cathode, covered with a refractory metal film, is known from document FR 4 2 469 792 in the name of the applicant.
- the method according to the present invention aims precisely to remedy these drawbacks.
- the invention recommends an original method which provides the advantages of impregnated cathodes, but with a procedure which is substantially simplified compared to those known from the prior art.
- the powder of tungsten or of a mixture of tungsten and of a metal of the platinum mine or of a scandium oxide or of the three materials is mixed with a powder of aluminate, barium and calcium in the desired stoichiometric proportions, then this mixture is pressed in the form of pellets and sintered, under a hydrogen atmosphere, at a temperature higher than the melting temperature of the aluminates.
- the mixture comprises tungsten or tungsten powder and other materials as above, with barium and calcium carbonates and of alumina in the desired stoichiometric proportions.
- This mixture is then compressed and sintered at the same temperature as above. In this way, the aluminate is formed during "in situ" sintering.
- the emissive surface of the pellet obtained according to the method of the invention is covered with a film of osmium, iridium or rhenium to increase its emissive properties.
- the filament is brought and potted in a conventional manner, and the cathode is activated in the same manner as above.
- the method according to the invention makes it possible to obtain all the advantages known from the prior art of impregnated cathodes, whether they are of simple matrix (pure tungsten) or mixed, covered or not, but with simplified procedures, shorter and less expensive, with a significantly reduced number of steps compared to the prior art, which makes it possible to obtain an equal quality of finished product with less critical handling and therefore with fewer controls.
- the method according to the invention is therefore particularly suitable for industrial production at high speed and at low cost of cathodes with high current density and with a relatively long service life, which makes it possible to envisage their use in equipment intended for wide distribution.
- the invention therefore relates to a method of manufacturing an impregnated cathode, characterized in that an emissive pellet is produced by co-pressing and sintering a mixture of at least one powder of refractory metal with a powder of barium and calcium aluminates, or with barium and calcium carbonates added with alumina.
- the subject of the invention is also an impregnated cathode as obtained by implementing the method which has just been defined.
- the invention also relates to variants of impregnated cathodes which can be produced using the process which has just been defined; for example cathodes produced according to the method of the invention and then covered with a metal film of platinum mine or the like in order to increase the electronic emissivity or to lower the operating temperature while keeping the emissivity constant.
- the subject of the invention is also variants of impregnated cathodes which can be produced on the basis of the same principle.
- FIG. 1 we see an example of an impregnated cathode manufactured according to the method of the invention, illustrated in these main steps in this FIG. 1.
- the emissive disc (1) is formed by pressing (c) and sintering (d), in a conventional manner, of a mixture (b), of a powder (w) of at least one refractory metal with a powder (y) barium and calcium aluminate or barium and calcium carbonates with alumina.
- At least one of the starting powders (w) is a powder of known elements such as tungsten, molybdenum, tantalum, rhenium or the alloys containing them, or a powder of an element capable of improving the electronic emission, such as osmium, ruthenium, iridium or alloys containing at least one of these elements or, finally, a powder of scandium oxide or particles of oxides containing scandium.
- the skirt (4) can be made integral with the assembly by a crimping (f) on the cup (3).
- the heating filament (5) previously covered with an alumina film (not shown), can be mounted in the skirt and held in place by an alumina body (6) commonly known by the English word “potting ".
- This "potting" operation can be done, for example, by sintering at 1800 ° C. under hydrogen from an alumina powder deposited using a suspension around the filament inside the skirt.
- the emissive pad could be covered with a thin metallic film with a thickness of between 10 and 30,000 Angstroms, for example, the metallic material being able to be selected from the group comprising osmium, ruthenium, iridium, and the alloys containing any of these.
- This film can be deposited by conventional means of sputtering, vacuum deposition, or any other suitable means.
- the method according to the invention has the advantage, compared to the prior art, of being achievable with a significantly reduced number of steps, and with less critical manipulations for the quality of the product. This results in the possibility of a better production yield, simultaneously with an accelerated rate and at lower cost per part.
Abstract
Description
La présente invention a pour objet un procédé de fabrication d'une cathode imprégnée et une cathode obtenue par ce procédé. Elle trouve une application dans la réalisation de cathodes pour tubes électroniques et plus particulièrement mais non exclusivement pour des tubes cathodiques de visualisation.The present invention relates to a method of manufacturing an impregnated cathode and a cathode obtained by this method. It finds an application in the production of cathodes for electronic tubes and more particularly but not exclusively for cathode ray display tubes.
Les cathodes imprégnées sont couramment utilisées pour fournir des densités de courant électronique allant jusqu'à 1 à 2 A/cm² en continu et plus en impulsions.Impregnated cathodes are commonly used to provide electronic current densities of up to 1 to 2 A / cm² continuously and more in pulses.
Les cathodes imprégnées connues de l'art antérieur sont constituées d'un corps poreux en métal réfractaire, comme le tungstène pur, ou encore d'un mélange de tungstène, soit avec un métal provenant de la mine du platine (matrice mixte), tel que connu par le document FR A 2 356 263, soit avec l'oxyde de scandium ou d'autre terres rares en faible concentration (3 à 5% en poids ).The impregnated cathodes known from the prior art consist of a porous body of refractory metal, such as pure tungsten, or else of a mixture of tungsten, either with a metal originating from the platinum mine (mixed matrix), such as known from document FR A 2 356 263, either with scandium oxide or other rare earths in low concentration (3 to 5% by weight).
Ce corps poreux est obtenu en général en comprimant une poudre finement divisée du métal (ou du mélange de métaux) à l'aide d'une presse isostatique ou d'une presse uniaxe.This porous body is generally obtained by compressing a finely divided powder of the metal (or mixture of metals) using an isostatic press or a uniaxial press.
Les corps compacts ainsi obtenus sont ensuite chauffés sous hydrogène à température élevée, afin de fritter les particules les unes aux autres et d'augmenter la densité du corps poreux.The compacts thus obtained are then heated under hydrogen at high temperature, in order to sinter the particles together and to increase the density of the porous body.
Pour faciliter l'usinage du corps poreux, celui-ci est infiltré avec du cuivre ou du plastique, puis usiné à la forme désirée. Par la suite, le cuivre ou le plastique sont retirés par dissolution dans un acide ou par chauffage.To facilitate machining of the porous body, it is infiltrated with copper or plastic, then machined to the desired shape. Subsequently, the copper or plastic is removed by dissolving in an acid or by heating.
Le corps poreux de la forme désirée est ensuite brasé sur une jupe en molybdène qui sert à maintenir, d'un côté, la pastille émissive et, de l'autre, un filament potté dans de l'alumine qui permet le chauffage de la cathode. Une fois le filament en place les pores du corps poreux peuvent être remplis avec des aluminates de baryum et de calcium. Autrement dit, le corps est imprégné avec ces aluminates, qui constituent la matière émissive de la cathode finie.The porous body of the desired shape is then brazed on a molybdenum skirt which serves to hold, on one side, the emissive patch and, on the other, a filament potted in alumina which allows the heating of the cathode . Once the filament is in place, the pores of the porous body can be filled with barium and calcium aluminates. In other words, the body is impregnated with these aluminates, which constitute the emissive material of the finished cathode.
Pour cette opération le corps poreux est maintenu en contact étroit avec une composition d'aluminate portée, sous atmosphère réductrice, à une température supérieure à son point de fusion. Le contact est assuré, soit en immergeant le corps poreux dans l'aluminate, soit en plaçant l'aluminate sur le corps poreux. Au moment de la fusion, l'aluminate diffuse par capillarité ou par écoulement à l'intérieur des pores ouverts et les remplit. La cathode est ensuite nettoyée mécaniquement et chimiquement, afin d'éliminer les résidus d'aluminates qui sont restés collés sur les surfaces.For this operation, the porous body is kept in close contact with an aluminate composition brought, under a reducing atmosphere, to a temperature above its melting point. Contact is ensured, either by immersing the porous body in the aluminate, or by placing the aluminate on the porous body. At the time of fusion, the aluminate diffuses by capillarity or by flow inside the open pores and fills them. The cathode is then cleaned mechanically and chemically, in order to remove the aluminate residues which have remained stuck on the surfaces.
Finalement, la cathode est activée, sous vide, à une température à laquelle la tungstène réduit l'aluminate de baryum et de calcium pour libérer l'oxyde de baryum. Du baryum métallique est produit dans les zones où l'aluminate est en contact avec le métal réfractaire (pores). Le baryum métallique atteint l'extrémité des pores et diffuse sur toute la surface émissive où il forme avec l'oxygène une monocouche superficielle qui favorise l'émissivité électronique en abaissant le travail de sortie d'électrons.Finally, the cathode is activated, under vacuum, at a temperature at which tungsten reduces barium and calcium aluminate to release barium oxide. Metallic barium is produced in areas where the aluminate is in contact with the refractory metal (pores). The metallic barium reaches the end of the pores and diffuses over the entire emissive surface where it forms with oxygen a surface monolayer which promotes electronic emissivity by lowering the work of electron output.
Par ailleurs, le dépôt, sur la surface émissive de ces cathodes imprégnées, d'un film d'osmium, d'iridium, de ruthénium, ou d'un alliage de ces corps, ce film ayant une épaisseur de quelques milliers d'Angströms, peut améliorer l'émissivité d'un facteur 3 environ.Furthermore, the deposition, on the emissive surface of these impregnated cathodes, of a film of osmium, iridium, ruthenium, or an alloy of these bodies, this film having a thickness of a few thousand Angstroms , can improve emissivity by a factor of around 3.
La cathode à matrice mixte, recouverte d'un film de métal réfractaire est connue par le document FR 4 2 469 792 au nom de la demanderesse.The mixed matrix cathode, covered with a refractory metal film, is known from document FR 4 2 469 792 in the name of the applicant.
Les performances obtenues des cathodes élaborées par les procédés connus de l'art antérieur sont satisfaisantes pour la plupart des applications professionnelles, car des fortes densités de courant peuvent être obtenues pendant une durée de vie qui ne limite pas la durée de vie de l'équipement dans lequel la cathode, ou le tube électronique comportant la cathode, sera installé.The performances obtained from the cathodes produced by the methods known from the prior art are satisfactory for most professional applications, because high current densities can be obtained during a lifetime which does not limit the lifetime of the equipment. in which the cathode, or the electronic tube comprising the cathode, will be installed.
Toutefois, les procédés connus de l'art antérieur et résumés brièvement ci-dessus sont longs, compliqués, et coûteux car ils comprennent de nombreux étapes, de natures différentes et d'exécution critique pour la qualité du produit fini. Ces inconvénients rendent leur coût prohibitif pour des applications grand public où le prix se doit de baisser avec l'augmentation du nombre de cathodes produites.However, the methods known from the prior art and briefly summarized above are long, complicated, and expensive because they include many steps, of different types and of execution critical for the quality of the finished product. These drawbacks make their cost prohibitive for consumer applications where the price must fall with the increase in the number of cathodes produced.
Le procédé selon la présente invention a justement pour but de remédier à ces inconvénients. A cette fin, l'invention préconise un procédé original qui procure les avantages des cathodes imprégnées, mais avec une procédure sensiblement simplifiée par rapport à celles connues de l'art antérieur.The method according to the present invention aims precisely to remedy these drawbacks. To this end, the invention recommends an original method which provides the advantages of impregnated cathodes, but with a procedure which is substantially simplified compared to those known from the prior art.
Selon l'invention, la poudre de tungstène ou d'un mélange de tungstène et d'un métal de la mine du platine ou d'un oxyde de scandium ou des trois matériaux est mélangée avec une poudre d'aluminate, de baryum et de calcium dans les proportions stoechimétriques désirées, puis ensuite ce mélange est pressé sous forme de pastilles et fritté, sous atmosphère d'hydrogène, à une température supérieure à la température de fusion des aluminates. On obtient alors une gangue de consistance égale au corps poreux, manipulable, qui est placée dans un support en molybdène ou tantale par pressage léger.According to the invention, the powder of tungsten or of a mixture of tungsten and of a metal of the platinum mine or of a scandium oxide or of the three materials is mixed with a powder of aluminate, barium and calcium in the desired stoichiometric proportions, then this mixture is pressed in the form of pellets and sintered, under a hydrogen atmosphere, at a temperature higher than the melting temperature of the aluminates. This gives a gangue of consistency equal to the porous body, which can be handled, which is placed in a molybdenum or tantalum support by light pressing.
Selon une caractéristique de l'invention, le mélange comprend la poudre de tungstène ou de tungstène et d'autre matériaux comme ci-dessus, avec des carbonates de baryum et de calcium et d'alumine dans les proportions stoechiométriques désirés. Ce mélange est ensuite compressé et fritté à la même température que précédemment. De cette manière, l'aluminate se forme lors du frittage "in situ".According to a characteristic of the invention, the mixture comprises tungsten or tungsten powder and other materials as above, with barium and calcium carbonates and of alumina in the desired stoichiometric proportions. This mixture is then compressed and sintered at the same temperature as above. In this way, the aluminate is formed during "in situ" sintering.
Selon une autre caractéristique de l'invention, la surface émissive de la pastille obtenue selon le procédé de l'invention est recouverte d'un film d'osmium, d'iridium ou de rhénium pour en augmenter les propriétés émissives.According to another characteristic of the invention, the emissive surface of the pellet obtained according to the method of the invention is covered with a film of osmium, iridium or rhenium to increase its emissive properties.
Ensuite, le filament est apporté et potté de façon classique, et la cathode est activée de la même manière que précédemment.Then, the filament is brought and potted in a conventional manner, and the cathode is activated in the same manner as above.
Ainsi, le procédé selon l'invention permet d'obtenir tous les avantages connus de l'art antérieur des cathodes imprégnées, soient-elles de matrice simple (tungstène pur) ou mixte, recouvertes ou non, mais avec des procédures simplifiées, moins longues et moins coûteuses, avec un nombre d'étapes réduit de façon significative par rapport à l'art antérieur, ce qui permet d'obtenir une qualité égale de produit fini avec moins de manipulation critique et donc avec moins de contrôles.Thus, the method according to the invention makes it possible to obtain all the advantages known from the prior art of impregnated cathodes, whether they are of simple matrix (pure tungsten) or mixed, covered or not, but with simplified procedures, shorter and less expensive, with a significantly reduced number of steps compared to the prior art, which makes it possible to obtain an equal quality of finished product with less critical handling and therefore with fewer controls.
Le procédé selon l'invention est donc particulièrement adapté à une production industrielle à haute cadence et à moindre coûts des cathodes à forte densité de courant et avec une durée de vie relativement longue, ce qui permet d'envisager leur utilisation dans des équipements destinés à une grande diffusion.The method according to the invention is therefore particularly suitable for industrial production at high speed and at low cost of cathodes with high current density and with a relatively long service life, which makes it possible to envisage their use in equipment intended for wide distribution.
De façon précise, l'invention a donc pour objet un procédé de fabrication d'une cathode imprégnée, caractérisé en ce que l'on réalise une pastille émissive par copressage et frittage d'un mélange d'au moins une poudre de métal réfractaire avec une poudre d'aluminates de baryum et de calcium, ou avec de carbonates de baryum et de calcium additionnés d'alumine.Specifically, the invention therefore relates to a method of manufacturing an impregnated cathode, characterized in that an emissive pellet is produced by co-pressing and sintering a mixture of at least one powder of refractory metal with a powder of barium and calcium aluminates, or with barium and calcium carbonates added with alumina.
L'invention a également pour objet une cathode imprégnée telle que l'on obtient en mettant en oeuvre le procédé qui vient d'être défini.The subject of the invention is also an impregnated cathode as obtained by implementing the method which has just been defined.
De façon ancillaire, l'invention a également pour objet des variantes de cathodes imprégnées qui peuvent être réalisées à partir du procédé qui vient d'être défini ; par exemple des cathodes réalisées selon le procédé de l'invention et ensuite recouvertes d'un film de métal de la mine de platine ou autre afin d'en augmenter l'émissivité électronique ou d'abaisser la température de fonctionnement en gardant l'émissivité constante. L'invention a aussi pour objet des variantes de cathodes imprégnées qui peuvent être réalisées à partir du principe même du procédé de l'invention, par exemple de cathodes réalisées selon le procédé de l'invention, mais avec en complément au mélange de la poudre d'un métal réfractaire et les aluminates ou les carbonates de baryum et calcium, adjonction de l'oxyde de scandium ou de terres rares, D'autres variantes du procédé selon l'invention pourraient facilement être imaginées et mises en oeuvre par l'homme de l'art, afin de récolter les avantages obtenus par l'invention avec des avantages particuliers connus par ailleurs, pour des applications spécifiques.Ancillarily, the invention also relates to variants of impregnated cathodes which can be produced using the process which has just been defined; for example cathodes produced according to the method of the invention and then covered with a metal film of platinum mine or the like in order to increase the electronic emissivity or to lower the operating temperature while keeping the emissivity constant. The subject of the invention is also variants of impregnated cathodes which can be produced on the basis of the same principle. of the process of the invention, for example of cathodes produced according to the process of the invention, but with, in addition to the mixture of the powder of a refractory metal and the aluminates or carbonates of barium and calcium, addition of the oxide of scandium or rare earths, Other variants of the process according to the invention could easily be imagined and implemented by a person skilled in the art, in order to reap the advantages obtained by the invention with particular advantages known by elsewhere, for specific applications.
De toute façon, les caractéristiques et avantages de l'invention apparaîtront mieux après la description qui va suivre avec ses exemples donnés à titre illustratif et nullement limitatif, et ses dessins annexés sur lesquels :
- la figure 1 représente, de façon schématique, les étapes principales d'un procédé simplifié selon l'invention de fabrication d'une cathode imprégnée ;
- la figure 2 représente une application possible de ces cathodes en tant qu'émetteur pour tube à rayon cathodique.
- Figure 1 shows, schematically, the main steps of a simplified method according to the invention for manufacturing an impregnated cathode;
- FIG. 2 represents a possible application of these cathodes as a transmitter for cathode ray tube.
Sur la figure 1, on voit un exemple d'une cathode imprégnée fabriquée selon le procédé de l'invention, illustré dans ces étapes principales dans cette figure 1.In FIG. 1, we see an example of an impregnated cathode manufactured according to the method of the invention, illustrated in these main steps in this FIG. 1.
La pastille émissive (1) est formée par pressage (c) et frittage (d), d'une manière classique, d'un mélange (b), d'une poudre (w) d'au moins un métal réfractaire avec une poudre (y) d'aluminate de baryum et calcium ou des carbonates de baryum et calcium avec de l'alumine.The emissive disc (1) is formed by pressing (c) and sintering (d), in a conventional manner, of a mixture (b), of a powder (w) of at least one refractory metal with a powder (y) barium and calcium aluminate or barium and calcium carbonates with alumina.
Au moins l'une des poudres de départ (w) est une poudre d'éléments connus tels que le tungstène, le molybdène, le tantale, le rhénium ou les alliages les contenant, ou une poudre d'un élément capable d'améliorer l'émission électronique, tels que l'osmium, le ruthénium, l'iridium ou les alliages contenant au moins l'un de ces éléments ou, enfin, une poudre d'oxyde de scandium ou des particules d'oxydes contenant du scandium.At least one of the starting powders (w) is a powder of known elements such as tungsten, molybdenum, tantalum, rhenium or the alloys containing them, or a powder of an element capable of improving the electronic emission, such as osmium, ruthenium, iridium or alloys containing at least one of these elements or, finally, a powder of scandium oxide or particles of oxides containing scandium.
Sur la figure 1 (e) l'on voit la pastille émissive encapsulée dans une coupelle, qui sera ensuite sertie (f) dans une jupe (4) en molybdene ou le tantale. Il ne reste plus que d'ajouter un filament (5) en tungstène-rhénium recouvert d'un film isolant (non montré) et à le maintenir dans la jupe (4) par un corps "potting" d'alumine (6), tel que l'on voit sur la figure 1 (g).In Figure 1 (e) we see the emissive disc encapsulated in a cup, which will then be crimped (f) in a skirt (4) made of molybdenum or tantalum. All that remains is to add a tungsten-rhenium filament (5) covered with an insulating film (not shown) and to hold it in the skirt (4) by an "alumina potting" body (6), as seen in Figure 1 (g).
A titre explicatif, on peut s'y prendre avec les paramètres suivants :
- les poudres à mélanger seront tamisées et de granulométrie de l'ordre de 5 à 10 microns. Elles seront ensuite mélangées dans des proportions stoechiométriques désirées pour obtenir les qualités requises de la cathode. Ces proportions appropriées seront déterminées par expérimentation pour une application donnée, mais pourrait être, par exemple : W = 80 %, Sc₂O₃ = 2 %, BaO = 12 %, CaO = 3 %, Al₂O₃ = 3 % ; ou bien la poudre de tungstène pourrait être remplacé par un mélange de poudres de tungstène et un autre métal, par exemple : W = 45 %, Os = 35 %.
- Les poudres mélangées sont pressées ensemble (c) dans une presse isostatique ou uniaxiale sous pression de l'ordre de 10 tonnes au cm², par exemple, pour former une pastille.
- la pastille est frittée (d) à haute température (de l'ordre de 2 000° C, par exemple) sous atmosphère d'hydrogène. La température choisie sera suffisante pour atteindre la température de fusion des aluminates contenus dans la pastille.
- la pastille émissive ainsi obtenue est ensuite montée mécaniquement sur une jupe (4) en Mo ou Ta, éventuellement à l'aide d'une coupelle (3) dans laquelle la pastille sera insérée par un léger pressage.
- the powders to be mixed will be sieved and with a particle size of the order of 5 to 10 microns. They will then be mixed in desired stoichiometric proportions to obtain the required qualities of the cathode. These appropriate proportions will be determined by experimentation for a given application, but could be, for example: W = 80%, Sc₂O₃ = 2%, BaO = 12%, CaO = 3%, Al₂O₃ = 3%; or the tungsten powder could be replaced by a mixture of tungsten powders and another metal, for example: W = 45%, Os = 35%.
- The mixed powders are pressed together (c) in an isostatic or uniaxial press under pressure of the order of 10 tonnes per cm², for example, to form a pellet.
- the pellet is sintered (d) at high temperature (of the order of 2000 ° C., for example) under a hydrogen atmosphere. The temperature chosen will be sufficient to reach the melting temperature of the aluminates contained in the tablet.
- the emissive patch thus obtained is then mechanically mounted on a skirt (4) in Mo or Ta, possibly using a cup (3) into which the patch will be inserted by light pressing.
La jupe (4) peut être rendue solidaire de l'ensemble par un sertissage (f) sur la coupelle (3).The skirt (4) can be made integral with the assembly by a crimping (f) on the cup (3).
Ensuite le filament (5) de chauffage, préalablement recouvert d'un film d'alumine (non montré), peut être monté dans la jupe et tenu en place par un corps d'alumine (6) connu couramment par le mot anglais "potting". Cette opération de "potting" peut se faire, par exemple, par frittage à 1800° C sous hydrogène d'une poudre d'alumine déposée à l'aide d'une suspension autour du filament à l'intérieur de la jupe.Then the heating filament (5), previously covered with an alumina film (not shown), can be mounted in the skirt and held in place by an alumina body (6) commonly known by the English word "potting ". This "potting" operation can be done, for example, by sintering at 1800 ° C. under hydrogen from an alumina powder deposited using a suspension around the filament inside the skirt.
Eventuellement, la pastille émissive pourrait être recouverte d'un film mince métallique d'épaisseur comprise entre 10 et 30000 Angströms, par exemple, la matière métallique pouvant être sélectionnée dans le groupe comprenant d'osmium, le ruthénium, l'iridium, et les alliages contenant l'un de ces éléments. Ce film peut être déposé par des moyens classiques de sputtering, dépôt sous vide, ou tout autre moyen approprié.Optionally, the emissive pad could be covered with a thin metallic film with a thickness of between 10 and 30,000 Angstroms, for example, the metallic material being able to be selected from the group comprising osmium, ruthenium, iridium, and the alloys containing any of these. This film can be deposited by conventional means of sputtering, vacuum deposition, or any other suitable means.
Sur la figure 2, on voit schématiquement et en coupe un montage possible d'une cathode fabriquée selon le procédé de l'invention, pour une application comme émetteur d'électrons pour tube à rayon cathodique.In Figure 2, we can see schematically and in section a possible mounting of a cathode manufactured according to the method of the invention, for application as an electron emitter for cathode ray tube.
A l'ensemble de la cathode imprégnée de la figure 1 (g), pour cette application, il est nécessaire seulement d'ajouter un support (7) pour tenir l'ensemble à l'endroit voulu dans l'équipement. La cathode fonctionnant généralement à haute tension dans un canon à électrons ce support (7) sera probablement électriquement isolant, en alumine ou céramique, par exemple.To the assembly of the cathode impregnated in FIG. 1 (g), for this application, it is only necessary to add a support (7) to hold the assembly at the desired location in the equipment. Since the cathode generally operates at high voltage in an electron gun, this support (7) will probably be electrically insulating, in alumina or ceramic, for example.
Le procédé selon l'invention à l'avantage, par rapport à l'art antérieur, d'être réalisable avec un nombre d'étapes sensiblement réduit, et avec des manipulations moins critiques pour la qualité du produit. Il en résulte la possibilité d'un meilleur rendement de production, simultanément avec une cadence accélérée et à moindre coût par pièce.The method according to the invention has the advantage, compared to the prior art, of being achievable with a significantly reduced number of steps, and with less critical manipulations for the quality of the product. This results in the possibility of a better production yield, simultaneously with an accelerated rate and at lower cost per part.
Ces avantages cumulés permettent d'envisager l'usage de ces cathodes, de performances comparables à celles auparavant destinées uniquement à des applications professionnelles à cause de leur prix élevé, pour des applications à diffusion plus large et éventuellement pour des applications grand public.These cumulative advantages make it possible to envisage the use of these cathodes, performances comparable to those previously intended only for professional applications because of their high price, for applications with wider diffusion and possibly for applications for the general public.
Claims (5)
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FR9001518 | 1990-02-09 | ||
| FR9001518A FR2658360B1 (en) | 1990-02-09 | 1990-02-09 | PROCESS FOR MANUFACTURING AN IMPREGNATED CATHODE AND CATHODE OBTAINED BY THIS PROCESS. |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| EP0441698A1 true EP0441698A1 (en) | 1991-08-14 |
| EP0441698B1 EP0441698B1 (en) | 1995-09-27 |
Family
ID=9393533
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| EP91400272A Expired - Lifetime EP0441698B1 (en) | 1990-02-09 | 1991-02-05 | Impregnated cathode manufacturing procedure and cathode obtained therewith |
Country Status (7)
| Country | Link |
|---|---|
| US (1) | US5334085A (en) |
| EP (1) | EP0441698B1 (en) |
| JP (1) | JP2710700B2 (en) |
| CA (1) | CA2035170C (en) |
| DE (1) | DE69113290T2 (en) |
| FR (1) | FR2658360B1 (en) |
| HK (1) | HK34097A (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE4234843A1 (en) * | 1992-10-15 | 1994-04-21 | Patent Treuhand Ges Fuer Elektrische Gluehlampen Mbh | Low pressure discharge lamp and manufacturing method for a low pressure discharge lamp |
| JPH0850849A (en) * | 1994-05-31 | 1996-02-20 | Nec Kansai Ltd | Cathode member and electronic tube using it |
| KR20020068644A (en) * | 2001-02-21 | 2002-08-28 | 삼성에스디아이 주식회사 | Metal cathode and indirectly heated cathode assembly having the same |
| US6771014B2 (en) * | 2001-09-07 | 2004-08-03 | The Boeing Company | Cathode design |
| CN101992374A (en) * | 2010-10-08 | 2011-03-30 | 杭州兴达机械有限公司 | Micropore repairing device and method for reduction gearbox body |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0028954A1 (en) * | 1979-11-09 | 1981-05-20 | Thomson-Csf | Thermionic cathode, process for manufacturing it and electron tube incorporating such a cathode |
| EP0091161A1 (en) * | 1982-04-01 | 1983-10-12 | Koninklijke Philips Electronics N.V. | Methods of manufacturing a dispenser cathode and dispenser cathode manufactured according to the method |
| WO1989009480A1 (en) * | 1988-03-28 | 1989-10-05 | Hughes Aircraft Company | Expandable dispenser cathode |
| EP0409275A2 (en) * | 1989-07-21 | 1991-01-23 | Nec Corporation | Method for fabricating an impregnated type cathode |
Family Cites Families (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| NL89470C (en) * | 1953-03-04 | |||
| BE564257A (en) * | 1957-01-26 | |||
| SU528632A1 (en) * | 1975-03-24 | 1976-09-15 | Предприятие П/Я А-1067 | A method of manufacturing a metalpressed molded cathode |
| JPS58154131A (en) * | 1982-03-10 | 1983-09-13 | Hitachi Ltd | Impregnation type cathode |
| JPS61128441A (en) * | 1984-11-28 | 1986-06-16 | Toshiba Corp | Manufacturing method of impregnating type cathode |
| FR2596198A1 (en) * | 1986-03-19 | 1987-09-25 | Thomson Csf | Cathodes for multibeam klystron, klystron containing such cathodes and method of manufacturing such cathodes |
| JPS63175313A (en) * | 1987-01-14 | 1988-07-19 | Nec Corp | Impregnated cathode and its manufacture |
| JPS63254636A (en) * | 1987-04-10 | 1988-10-21 | Hitachi Ltd | Impregnated cathode |
| JPS63311082A (en) * | 1987-06-12 | 1988-12-19 | 日本鋼管株式会社 | Production unit for high-density sintered body |
| NL8701584A (en) * | 1987-07-06 | 1989-02-01 | Philips Nv | METHOD FOR MANUFACTURING A SUPPLY CATHOD DELIVERY CATHOD MANUFACTURED ACCORDING TO THE METHOD; RUNNING WAVE TUBE, KLYSTRON AND TRANSMITTER CONTAINING A CATHOD MANUFACTURED BY THE METHOD. |
| NL8902793A (en) * | 1989-11-13 | 1991-06-03 | Philips Nv | SCANDAT CATHOD. |
-
1990
- 1990-02-09 FR FR9001518A patent/FR2658360B1/en not_active Expired - Fee Related
-
1991
- 1991-01-29 CA CA002035170A patent/CA2035170C/en not_active Expired - Fee Related
- 1991-02-05 DE DE69113290T patent/DE69113290T2/en not_active Expired - Fee Related
- 1991-02-05 EP EP91400272A patent/EP0441698B1/en not_active Expired - Lifetime
- 1991-02-08 JP JP3948191A patent/JP2710700B2/en not_active Expired - Fee Related
-
1992
- 1992-05-26 US US07/887,663 patent/US5334085A/en not_active Expired - Lifetime
-
1997
- 1997-03-20 HK HK34097A patent/HK34097A/en not_active IP Right Cessation
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0028954A1 (en) * | 1979-11-09 | 1981-05-20 | Thomson-Csf | Thermionic cathode, process for manufacturing it and electron tube incorporating such a cathode |
| EP0091161A1 (en) * | 1982-04-01 | 1983-10-12 | Koninklijke Philips Electronics N.V. | Methods of manufacturing a dispenser cathode and dispenser cathode manufactured according to the method |
| WO1989009480A1 (en) * | 1988-03-28 | 1989-10-05 | Hughes Aircraft Company | Expandable dispenser cathode |
| EP0409275A2 (en) * | 1989-07-21 | 1991-01-23 | Nec Corporation | Method for fabricating an impregnated type cathode |
Also Published As
| Publication number | Publication date |
|---|---|
| FR2658360B1 (en) | 1996-08-14 |
| US5334085A (en) | 1994-08-02 |
| DE69113290D1 (en) | 1995-11-02 |
| JP2710700B2 (en) | 1998-02-10 |
| JPH0785782A (en) | 1995-03-31 |
| CA2035170C (en) | 2001-05-29 |
| HK34097A (en) | 1997-03-27 |
| DE69113290T2 (en) | 1996-03-07 |
| EP0441698B1 (en) | 1995-09-27 |
| CA2035170A1 (en) | 1991-08-10 |
| FR2658360A1 (en) | 1991-08-16 |
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