EP0034512A2 - Heating element for indirectly heated cathodes, process for manufacturing such an element and indirectly heated cathode comprising the same - Google Patents
Heating element for indirectly heated cathodes, process for manufacturing such an element and indirectly heated cathode comprising the same Download PDFInfo
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- EP0034512A2 EP0034512A2 EP81400096A EP81400096A EP0034512A2 EP 0034512 A2 EP0034512 A2 EP 0034512A2 EP 81400096 A EP81400096 A EP 81400096A EP 81400096 A EP81400096 A EP 81400096A EP 0034512 A2 EP0034512 A2 EP 0034512A2
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- alumina
- mixture
- heating element
- cylinder
- oxide
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- 238000010438 heat treatment Methods 0.000 title claims abstract description 26
- 238000004519 manufacturing process Methods 0.000 title claims description 6
- 238000000034 method Methods 0.000 title claims description 3
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims abstract description 52
- 239000000203 mixture Substances 0.000 claims abstract description 48
- SIWVEOZUMHYXCS-UHFFFAOYSA-N oxo(oxoyttriooxy)yttrium Chemical compound O=[Y]O[Y]=O SIWVEOZUMHYXCS-UHFFFAOYSA-N 0.000 claims abstract description 15
- 239000000843 powder Substances 0.000 claims description 13
- 239000011230 binding agent Substances 0.000 claims description 10
- 239000000126 substance Substances 0.000 claims description 8
- 229910018072 Al 2 O 3 Inorganic materials 0.000 claims description 7
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 claims description 7
- 229910052721 tungsten Inorganic materials 0.000 claims description 7
- 239000010937 tungsten Substances 0.000 claims description 7
- 230000000737 periodic effect Effects 0.000 claims description 6
- MRELNEQAGSRDBK-UHFFFAOYSA-N lanthanum(3+);oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[La+3].[La+3] MRELNEQAGSRDBK-UHFFFAOYSA-N 0.000 claims description 4
- 239000000463 material Substances 0.000 claims description 4
- 239000002245 particle Substances 0.000 claims description 4
- 238000001962 electrophoresis Methods 0.000 claims description 3
- 238000001704 evaporation Methods 0.000 claims description 3
- HYXGAEYDKFCVMU-UHFFFAOYSA-N scandium oxide Chemical compound O=[Sc]O[Sc]=O HYXGAEYDKFCVMU-UHFFFAOYSA-N 0.000 claims description 3
- OYPRJOBELJOOCE-UHFFFAOYSA-N Calcium Chemical compound [Ca] OYPRJOBELJOOCE-UHFFFAOYSA-N 0.000 claims description 2
- 229910021193 La 2 O 3 Inorganic materials 0.000 claims description 2
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 claims description 2
- QKYBEKAEVQPNIN-UHFFFAOYSA-N barium(2+);oxido(oxo)alumane Chemical compound [Ba+2].[O-][Al]=O.[O-][Al]=O QKYBEKAEVQPNIN-UHFFFAOYSA-N 0.000 claims description 2
- 229910052791 calcium Inorganic materials 0.000 claims description 2
- 239000011575 calcium Substances 0.000 claims description 2
- 229910052739 hydrogen Inorganic materials 0.000 claims description 2
- 239000001257 hydrogen Substances 0.000 claims description 2
- 238000002156 mixing Methods 0.000 claims description 2
- 229910052750 molybdenum Inorganic materials 0.000 claims description 2
- 239000011733 molybdenum Substances 0.000 claims description 2
- DECCZIUVGMLHKQ-UHFFFAOYSA-N rhenium tungsten Chemical compound [W].[Re] DECCZIUVGMLHKQ-UHFFFAOYSA-N 0.000 claims description 2
- 238000003756 stirring Methods 0.000 claims description 2
- 150000001768 cations Chemical class 0.000 claims 1
- 125000004435 hydrogen atom Chemical class [H]* 0.000 claims 1
- 238000004382 potting Methods 0.000 description 21
- 229910052727 yttrium Inorganic materials 0.000 description 8
- VWQVUPCCIRVNHF-UHFFFAOYSA-N yttrium atom Chemical compound [Y] VWQVUPCCIRVNHF-UHFFFAOYSA-N 0.000 description 8
- HIGRAKVNKLCVCA-UHFFFAOYSA-N alumine Chemical compound C1=CC=[Al]C=C1 HIGRAKVNKLCVCA-UHFFFAOYSA-N 0.000 description 7
- 230000008018 melting Effects 0.000 description 6
- 238000002844 melting Methods 0.000 description 6
- 238000005245 sintering Methods 0.000 description 6
- ODINCKMPIJJUCX-UHFFFAOYSA-N Calcium oxide Chemical compound [Ca]=O ODINCKMPIJJUCX-UHFFFAOYSA-N 0.000 description 4
- 230000008901 benefit Effects 0.000 description 4
- 238000010587 phase diagram Methods 0.000 description 4
- 230000004927 fusion Effects 0.000 description 3
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 description 2
- 229910052767 actinium Inorganic materials 0.000 description 2
- QQINRWTZWGJFDB-UHFFFAOYSA-N actinium atom Chemical compound [Ac] QQINRWTZWGJFDB-UHFFFAOYSA-N 0.000 description 2
- 238000005219 brazing Methods 0.000 description 2
- BRPQOXSCLDDYGP-UHFFFAOYSA-N calcium oxide Chemical compound [O-2].[Ca+2] BRPQOXSCLDDYGP-UHFFFAOYSA-N 0.000 description 2
- 239000000292 calcium oxide Substances 0.000 description 2
- 210000004027 cell Anatomy 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 230000005496 eutectics Effects 0.000 description 2
- 238000005470 impregnation Methods 0.000 description 2
- 238000009413 insulation Methods 0.000 description 2
- 229910052746 lanthanum Inorganic materials 0.000 description 2
- FZLIPJUXYLNCLC-UHFFFAOYSA-N lanthanum atom Chemical compound [La] FZLIPJUXYLNCLC-UHFFFAOYSA-N 0.000 description 2
- 238000002360 preparation method Methods 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- -1 - plus Inorganic materials 0.000 description 1
- 208000031968 Cadaver Diseases 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000010292 electrical insulation Methods 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 238000011049 filling Methods 0.000 description 1
- 238000002955 isolation Methods 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 230000005855 radiation Effects 0.000 description 1
- 229910052702 rhenium Inorganic materials 0.000 description 1
- WUAPFZMCVAUBPE-UHFFFAOYSA-N rhenium atom Chemical compound [Re] WUAPFZMCVAUBPE-UHFFFAOYSA-N 0.000 description 1
- 229910052706 scandium Inorganic materials 0.000 description 1
- SIXSYDAISGFNSX-UHFFFAOYSA-N scandium atom Chemical compound [Sc] SIXSYDAISGFNSX-UHFFFAOYSA-N 0.000 description 1
- 230000035939 shock Effects 0.000 description 1
- 239000012265 solid product Substances 0.000 description 1
- 239000013589 supplement Substances 0.000 description 1
- 239000002470 thermal conductor Substances 0.000 description 1
- RUDFQVOCFDJEEF-UHFFFAOYSA-N yttrium(III) oxide Inorganic materials [O-2].[O-2].[O-2].[Y+3].[Y+3] RUDFQVOCFDJEEF-UHFFFAOYSA-N 0.000 description 1
Images
Classifications
-
- 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
- H01J1/24—Insulating layer or body located between heater and emissive material
Definitions
- the present invention relates to a heating element for an indirectly heated cathode. It also relates to a method of manufacturing such an element and to indirectly heated cathodes comprising such an element.
- Indirectly heated cathodes which are used in electronic tubes are well known in the prior art. They generally consist of an emissive disc brazed at one of the ends of a cylinder of non-emissive material which serves as a housing. Inside the cylinder is placed a filament which ensures the so-called indirect heating of the cathode.
- the filament In cathodes with indirect heating by "potted” filament, the filament is less vulnerable to shocks and mechanical vibrations than in cathodes with indirect heating by free filament.
- the present invention relates to cathodes with indirect heating by "potted" filament.
- the "potting" consists of a mixture of alumina and of less than 10% by weight of an oxide of one of the elements of column III A of the periodic table of the elements, this mixture being sintered between 1700 and 1800 ° C.
- the mixture consists of yttrium oxide and alumina of chemical composition 3 Y 2 O 3 . 5 Al 2 O 3 , plus alumina in the ⁇ phase
- FIG. 1 represents a perspective view of an indirect heating cathode with potted filament.
- This cathode consists of an emissive disc 1 which occupies one of the ends of a cylinder 2 made of non-emissive material.
- the cylinder 2 is generally made of molybdenum. It serves as a housing for the cathode and is also called the "skirt" of the cathode.
- a porous entungsten disc 1 is brazed. Brazing takes place around 1900 ° C.
- a filament 3 made of tungsten or tungsten is introduced into the cylinder.
- potting 4 which blocks the filament 3 in the cylinder.
- the "potting" consists of a mixture of alumina and of less than 10% by weight of an oxide of one of the elements of column III A of the periodic table of the elements, this mixture being sintered between 1700 and 1800 ° C.
- FIG. 2 shows a detail of the phase diagram of the alumina-yttrium oxide mixture, which is taken from the work: "Phase diagrams for Ceramists - 1969 - supplement”.
- the thick line curve indicates the melting tempera- ture of the mixture of alumina Al 2 O 3, yttrium oxide Y 2 0 3 based on the percentages by weight of alumina and yttria.
- This curve is discontinuous. For certain percentages of alumina and yttrium oxide, melting occurs at a lower temperature than for the other percentages, they are eutectic compositions.
- the alumina-yttrium oxide mixture is a eutectic is interesting because it makes it possible to reduce the temperature of the sintering compared to pure alumina.
- the chemical composition of the solid product obtained is the same over a wide range of the respective percentages of alumina and yttrium oxide. Indeed, it is difficult when making a mixture of powders - here alumina powder and yttrium oxide powder - to ensure that the mixture is perfectly well produced and that the percentage of bodies present is constant. Consequently, it is advantageous to obtain the same chemical compound even if the mixture is not perfectly homogeneous.
- the alumina which enters into the composition of the "potting" can consist of several varieties of alumina of different particle size.
- grains less than 10 ⁇ m in diameter and gains of 10 to 50 ⁇ m in diameter are used.
- the "potting" can be carried out by sintering between 1700 and 1800 ° C. a mixture of alumina and less than 10% of a scandium oxide, lanthanum or actinium.
- the chemical composition of the bodies obtained will be, in the case of lanthanum oxide, La 2 O 3 . 11 Al 2 O 3 plus alumina in the ⁇ phase and in the case of scandium oxide, Sc 2 O 3 . Al 2 03, plus alumina in the ⁇ phase.
- the insulation layer deposited by cataphoresis on the filament 3 may be an alumina layer as has been indicated in the description of FIG. 1, but this insulation layer may also have the same composition as the mixture which is used for potting, for example alumina and yttrium oxide.
- alumina powder firstly intimately mixing, with stirring for at least 24 hours, powder of an oxide of one of the elements of column III A of the periodic table of the elements and one or more alumina powders different particle size.
- the alumina powder should not exceed 10% by weight of the mixture.
- a binder is then added to the mixture so as to obtain a paste.
- the face of the emissive disc 1 which is situated towards the inside of the cylinder 2 is coated with this paste 5. This step is shown in FIG. 3a.
- the binder is slowly evaporated using an electric lamp, for example 100 W, or leaving to dry naturally.
- the filament 3 is introduced into the cylinder 2. This step is shown in FIG. 3b.
- the cylinder is then filled several times with the paste, the consistency of which can be modified by adding the binder.
- the binder which may be acetone, is evaporated using the electric lamp.
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- Solid Thermionic Cathode (AREA)
- Powder Metallurgy (AREA)
Abstract
Cet élément chauffant est constitué d'un filament (3) et d'un mélange (4), fritté entre 1700 et 1800°C, d'alumine et de moins de 10 % en poids d'oxyde d'yttrium. Ce mélange remplit l'espace laissé libre par le filament à l'intérieur du cylindre (2) obturé par un disque émissif (1) qui constitue la cathode.This heating element consists of a filament (3) and a mixture (4), sintered between 1700 and 1800 ° C, alumina and less than 10% by weight of yttrium oxide. This mixture fills the space left free by the filament inside the cylinder (2) closed by an emissive disc (1) which constitutes the cathode.
Description
La présente invention concerne un élément chauffant pour cathode à chauffage indirect. Elle concerne également un procédé de fabrication d'un tel élément et les cathodes à chauffage indirect comportant un tel élément.The present invention relates to a heating element for an indirectly heated cathode. It also relates to a method of manufacturing such an element and to indirectly heated cathodes comprising such an element.
Les cathodes à chauffage indirect qui sont utilisées dans les tubes électroniques sont bien connues de l'art antérieur. Elles sont généralement constituées par un disque émissif brasé à l'une des extrê- mités d'un cylindre en matériau non émissif qui sert de boîtier. A l'intérieur du cylindre est placé un filament qui assure le chauffage dit indirect de la cathode.Indirectly heated cathodes which are used in electronic tubes are well known in the prior art. They generally consist of an emissive disc brazed at one of the ends of a cylinder of non-emissive material which serves as a housing. Inside the cylinder is placed a filament which ensures the so-called indirect heating of the cathode.
On distingue deux types de cathodes à chauffage indirect :
- - celles à chauffage par filament libre dans lesquelles le filament chauffe la cathode par rayonnement ;
- - celles à chauffage par filament dit potté, dans lesquelles l'espace laissé libre par le filament à l'intérieur du cylindre est rempli par un corps bon conducteur thermique, électriquement isolant à la température de fonctionnement, dont le point de fusion est élevé et qui enfin ne réagit pas à la température de fonctionnement avec le filament et le cylindre.
- - those with free filament heating in which the filament heats the cathode by radiation;
- - those with so-called potted filament heating, in which the space left free by the filament inside the cylinder is filled by a body which is a good thermal conductor, electrically insulating at operating temperature, the melting point of which is high and which finally does not react to the operating temperature with the filament and the cylinder.
Dans les cathodes à chauffage indirect par filament "potté", le filament est moins vulnérable aux chocs et aux vibrations mécaniques que dans les cathodes à chauffage indirect par filament libre.In cathodes with indirect heating by "potted" filament, the filament is less vulnerable to shocks and mechanical vibrations than in cathodes with indirect heating by free filament.
La présente invention concerne les cathode à chauffage indirect par filament "potté".The present invention relates to cathodes with indirect heating by "potted" filament.
Dans l'art antérieur, le "potting", c'est-à-dire le corps qui bloque le filament dans le cylindre, est constitué :
- - par de la poudre d'alumine frittée vers 2000°C ;
- - ou, par un mélange de poudre d'alumine et de poudre d'oxyde de calcium fritté entre 1750°C et 1800°C.
- - with alumina powder sintered at around 2000 ° C;
- - Or, by a mixture of alumina powder and sintered calcium oxide powder between 1750 ° C and 1800 ° C.
Selon la présente invention, le "potting" est constitué par un mélange d'alumine et de moins de 10 % en poids d'un oxyde d'un des éléments de la colonne III A de la table périodique des éléments, ce mélange étant fritté entre 1700 et 1800°C.According to the present invention, the "potting" consists of a mixture of alumina and of less than 10% by weight of an oxide of one of the elements of column III A of the periodic table of the elements, this mixture being sintered between 1700 and 1800 ° C.
Selon un mode préféré de réalisation de l'invention, le mélange est constitué d'oxyde d'yttrium et d'alumine de composition chimique 3 Y2 O3. 5 Al2 O3, plus de l'alumine en phase αAccording to a preferred embodiment of the invention, the mixture consists of yttrium oxide and alumina of
Le "potting" selon la présente invention présente les avantages suivants :
- - le frittage est réalisé entre 1700 et 1800°C et cette température ne peut pas fragiliser le filament en tungstène ou en tungstène rhénium, comme c'est le cas lorsqu'on doit monter à 2000°C pour fritter de la poudre d'alumine pure ;
- - le potting réalisé est solide et compact, il assure un bon contact thermique de longue durée entre le filament et le cylindre.Il assure un isolement électrique égal à celui obtenu avec un "potting " à base d'alumine uniquement.
- - l'oxyde d'yttrium'qui peut être utilisé est stable et très pur. Son coefficient de dilatation linéaire α égal à 8, 18. 10-6 est très proche de celui des filaments couramment utilisés et identique à celui de l'alumine, ce qui permet d'obtenir un "potting" dont le coefficient de dilatation ne dépend pas des proportions d'alumine et d'oxyde.De plus, la conductibilité thermique de l'oxyde d'yttrium est identique à celle de l'alumine (λ = 0,017 cal. S-1. cm-1.e-1 à 1800°C et 0,013 à 1000°C). Enfin, la température de fusion de l'oxyde d'yttrium (2410°C) est inférieure à celle de l'oxyde de calcium par exemple (2572°C).
- - the sintering is carried out between 1700 and 1800 ° C and this temperature cannot weaken the tungsten or rhenium tungsten filament, as is the case when it is necessary to go up to 2000 ° C to sinter alumina powder pure;
- - the potting produced is solid and compact, it ensures good long-term thermal contact between the filament and the cylinder. It provides electrical insulation equal to that obtained with a "potting" based on alumina only.
- - the yttrium'oxide which can be used is stable and very pure. Its coefficient of linear expansion α equal to 8.18. 10 -6 is very close to that of commonly used filaments and identical to that of alumina, which makes it possible to obtain a "potting" whose coefficient of expansion does not depend on the proportions of alumina and oxide. In addition, the thermal conductivity of yttrium oxide is identical to that of alumina (λ = 0.017 cal. S - 1. Cm -1 .e -1 at 1800 ° C and 0.013 at 1000 ° C). Finally, the melting temperature of yttrium oxide (2410 ° C) is lower than that of calcium oxide for example (2572 ° C).
D'autres objets, caractéristiques et résultats de l'invention ressortiront de la description suivante, donnée à titre d'exemple non limitatif et illustrée par les figures annexées qui représentent :
- - La figure 1, une vue en perpective d'une cathode à chauffage indirect à filament "potté" ;
- - La figure 2, un détail du diagramme de phase du mélange alumine-oxyde d'yttrium ;
- - Les figures 3a, b et c, des schémas illustrant le procédé de fabrication selon l'invention.
- - Figure 1, a perspective view of an indirect heating cathode filament "potté";
- - Figure 2, a detail of the phase diagram of the alumina-yttrium oxide mixture;
- - Figures 3a, b and c, diagrams illustrating the manufacturing process according to the invention.
Sur les différentes figures, les mêmes repères désignent les mêmes éléments, mais, pour des raisons de clarté, les cotes et proportions des divers éléments ne sont pas respectées.In the different figures, the same references designate the same elements, but, for reasons of clarity, the dimensions and proportions of the various elements are not observed.
La figure 1 représente une vue en perspective d'une cathode à chauffage indirect à filament potté.FIG. 1 represents a perspective view of an indirect heating cathode with potted filament.
Cette cathode est constituée d'un disque émissif 1 qui occupe l'une des extrémités d'un cylindre 2 en matériau non-émissif.This cathode consists of an
Le cylindre 2 est généralement en molybdène. Il sert de boîtier à la cathode et on l'appelle aussi "jupe" de la cathode.The
A l'une des extrémités du cylindre , on brase un disque 1 entungstène poreux. Le brasage s'effectue aux environs de 1900°C.At one end of the cylinder, a porous entungsten
Ce brasage effectué, on introduit dans le cylindre un filament 3 en tungstène ou en tungstène rhénium recouvert par cataphorèse d'une couche d'isolement en alumine. On réalise le "potting" 4 qui bloque le filament 3 dans le cylindre.Once this brazing is completed, a
On réalise ensuite à chaud, aux environs de 1750°C, l'imprégnation par de l'aluminate de baryum et de calcium du disque en tungstène poreux 1, ce qui rend ce disque émissif.Then carried out hot, around 1750 ° C., the impregnation with barium aluminate and calcium of the
L'imprégnation du tungstène poreux se faisant vers 1750°C alors que le filament 3 se trouve dans le cylindre 2, il n'y a pas d'inconvénient à ce que pour l'élaboration du "potting", la température atteigne 1700 ou 1800°C comme c'est le cas pour l'élaboration du "potting" selon l'invention.The impregnation of the porous tungsten being done at around 1750 ° C. while the
Selon l'invention, le "potting" est constitué par un mélange d'alumine et de moins de 10 % en poids d'un oxyde d'un des éléments de la colonne III A de la table périodique des éléments, ce mélange étant fritté entre 1700 et 1800°C.According to the invention, the "potting" consists of a mixture of alumina and of less than 10% by weight of an oxide of one of the elements of column III A of the periodic table of the elements, this mixture being sintered between 1700 and 1800 ° C.
La colonne III A de la table périodique des éléments comporte quatre éléments : le. scandium, Sc, l'yttrium, Y, le lanthane, La,et enfin l'actinium, Ac.Column III A of the Periodic Table of the Elements has four elements: the. scandium, Sc, yttrium, Y, lanthanum, La, and finally actinium, Ac.
Nous allons prendre d'abord à titre d'exemple l'yttrium.We will first take yttrium as an example.
Sur la figure 2, on a représenté un détail du diagramme de phase du mélange alumine-oxyde d'yttrium, qui est extrait de l'ouvrage : "Phase diagrams for Ceramists - 1969 - supplement".FIG. 2 shows a detail of the phase diagram of the alumina-yttrium oxide mixture, which is taken from the work: "Phase diagrams for Ceramists - 1969 - supplement".
La courbe en trait épais indique la tempéra- ture de fusion du mélange alumine Al2 O3, oxyde d'yttrium Y2 03 en fonction des pourcentages en poids d'alumine et d'oxyde d'yttrium.The thick line curve indicates the melting tempera- ture of the mixture of alumina Al 2 O 3, yttrium oxide Y 2 0 3 based on the percentages by weight of alumina and yttria.
Cette courbe est discontinue. Pour certains pourcentages d'alumine et d'oxyde d'yttrium, la fusion se produit à une température plus faible que pour les autres pourcentages, ce sont des compositions eutectiques.This curve is discontinuous. For certain percentages of alumina and yttrium oxide, melting occurs at a lower temperature than for the other percentages, they are eutectic compositions.
Sur la figure 2, on constate que pour le point A qui correspond sensiblement à 60 % d'alumine et 40 % d'oxyde d'yttrium, la température de fusion est de 1760°C. Autour du point A, on constate que la température de fusion est supérieure à 1760°C. De même, il est remarquable en observant la figure 2 qu'à partir d'un pourcentage supérieur à 43 % d'alu- nine environ, le mélange obtenu à l'état solide a la même constitution chimique qui est 3 Y2 O3 . 5 Al2 O3, plus de l'alumine en phase α.In FIG. 2, it can be seen that for point A, which corresponds substantially to 60% of alumina and 40% of yttrium oxide, the melting temperature is 1760 ° C. Around point A, it can be seen that the melting temperature is higher than 1760 ° C. Similarly, it is remarkable when observing FIG. 2 that from a percentage greater than about 43% of aluminum, the mixture obtained in the solid state has the same chemical constitution which is 3 Y 2 O 3 . 5 Al 2 O 3 , plus alumina in the α phase.
Le fait que le mélange alumine-oxyde d'yttrium soit un eutectique est intéressant car il permet de diminuer la température du frittage par rapport à l'alumine pure. De même, il est intéressant que la composition chimique du produit solide obtenu soit la même dans un large domaine des pourcentages respectifs d'alumine et d'oxyde d'yttrium. En effet, il est difficile lorsqu'on effectue un mélange de poudres -ici la poudre d'alumine et la poudre d'oxyde d'yttrium- de s'assurer que le mélange est parfaitement bien réalisé et que le pourcentage des corps en présence est constant. Par conséquent il est intéressant d'obtenir un même composé chimique même si le mélange n'est pas parfaitement homogène.The fact that the alumina-yttrium oxide mixture is a eutectic is interesting because it makes it possible to reduce the temperature of the sintering compared to pure alumina. Likewise, it is advantageous that the chemical composition of the solid product obtained is the same over a wide range of the respective percentages of alumina and yttrium oxide. Indeed, it is difficult when making a mixture of powders - here alumina powder and yttrium oxide powder - to ensure that the mixture is perfectly well produced and that the percentage of bodies present is constant. Consequently, it is advantageous to obtain the same chemical compound even if the mixture is not perfectly homogeneous.
On désire donc bénéficier des avantages du mélange alumine-oxyde d'yttrium par rapport à l'alumine pure,tout en cherchant à avoir un mélange comportant le maximum d'alumine.We therefore wish to benefit from the advantages of the alumina-yttrium oxide mixture compared to pure alumina, while seeking to have a mixture comprising the maximum of alumina.
En effet, si le mélange comporte trop d'oxyde d'yttrium, on risque le décollement du "potting" du cylindre qui sert de boîtier et le décollement du filament de son "potting".Indeed, if the mixture contains too much yttrium oxide, there is a risk of detachment of the "potting" from the cylinder which serves as a housing and detachment of the filament from its "potting".
Expérimentalement, on a déterminé qu'on obtenait le potting réunissant le maximum d'avantages souhaité en frittant entre 1700 et 1800°C et en limitant à 10 % en poids environ le pourcentage d'oxyde d'yttrium.Experimentally, we have determined that we get potting was born bringing together the maximum of desired advantages by sintering between 1700 and 1800 ° C. and limiting the percentage of yttrium oxide to around 10% by weight.
Il est cependant bien entendu qu'on obtient un "potting" de bonne qualité en frittant entre 1700 et 1800°C un mélange comportant environ 50 à 99 % d'alumine et donc environ 1 à 50 % d'oxyde d'yttrium.It is however understood that a good quality "potting" is obtained by sintering between 1700 and 1800 ° C. a mixture comprising approximately 50 to 99% of alumina and therefore approximately 1 to 50% of yttrium oxide.
Dans tous les cas, on obtient un mélange d'oxyde d'yttrium et d'alumine de composition chimique 3 Y2 O3 . 5 Al2 O3, - plus , de l'alumine en phase α.In all cases, a mixture of yttrium oxide and alumina with
Sur la figure 2, on n'a représenté que la partie intéressante du diagrammè de phase alumine-oxyde d'yttrium. En effet, sur le restant du diagramme, le pourcentage d'alumine est , faible (inférieur à 40 %) et la température dé'fusion et donc la température de frittage sont trop élevées.In Figure 2, only the interesting part of the alumina-yttrium oxide phase diagram has been shown. Indeed, on the rest of the diagram, the percentage of alumina is low (less than 40%) and the temperature of fusion and therefore the sintering temperature are too high.
L'alumine qui entre dans la composition du "potting" peut être constituée de plusieurs variétés d'alumine de granulométrie différente.The alumina which enters into the composition of the "potting" can consist of several varieties of alumina of different particle size.
On utilise ainsi, par exemple,des grains de moins de 10 µm de diamètre et des gains de 10 à 50 pm de diamètre.Thus, for example, grains less than 10 μm in diameter and gains of 10 to 50 μm in diameter are used.
Le mélange de plusieurs variétés d'alumine permet, -de trouver un compromis entre les défauts et les qualités inhérents à chaque variété. En effet, l'alumine à grains fins se prend en masse facilement mais présente un retreintimportant. Alors que l'alumine à grains de grand diamètre se prend en masse plus difficilement mais constitue une masse poreuse sans retreint.The mixture of several varieties of alumina makes it possible to find a compromise between the defects and the qualities inherent in each variety. Indeed, fine-grained alumina takes on mass easily but has a significant shrinkage. While alumina with large diameter grains is more difficult to take in mass but constitutes a porous mass without shrinking.
De même que cela vient d'être décrit en détail pour l'yttrium, le "potting" peut être réalisé en frittant entre 1700 et 1800°C un mélange d'alumine et de moins de 10 % d'un oxyde de scandium, de lanthane ou d'actinium. La composition chimique des corps obtenus sera dans le cas de l'oxyde de lanthane, La2 O3 . 11 Al2 O3 plus de l'alumine en phase α et dans le cas de l'oxyde de scandium, Sc2 O3 . Al2 03, plus de l'alumine en phase α.As has just been described in detail for yttrium, the "potting" can be carried out by sintering between 1700 and 1800 ° C. a mixture of alumina and less than 10% of a scandium oxide, lanthanum or actinium. The chemical composition of the bodies obtained will be, in the case of lanthanum oxide, La 2 O 3 . 11 Al 2 O 3 plus alumina in the α phase and in the case of scandium oxide, Sc 2 O 3 .
On peut signaler que la couche d'isolement déposée par cataphorèse sur le filament 3 peut être une couche d'alumine comme cela a été signalé dans la description de la figure 1, mais cette couche d'isolement peut avoir aussi la même composition que le mélange qui sert à réaliser le potting, par exemple de l'alumine et de l'oxyde d'yttrium.It may be pointed out that the insulation layer deposited by cataphoresis on the
Sur les figures 3a, b et c, on a représenté. un procédé de fabrication d'un élément chauffant selon l'invention.In Figures 3a, b and c, there is shown. a method of manufacturing a heating element according to the invention.
Selon ce procédé, on mélange d'abord intimement en agitant pendant 24 heures au moins, de la poudre d'un oxyde d'un des éléments de la colonne III A de la table périodique des éléments et une ou plusieurs poudres d'alumine de granulométrie différente. La poudre d'alumine ne doit pas dépasser 10 % en poids du mélange.According to this method, firstly intimately mixing, with stirring for at least 24 hours, powder of an oxide of one of the elements of column III A of the periodic table of the elements and one or more alumina powders different particle size. The alumina powder should not exceed 10% by weight of the mixture.
On ajoute ensuite au mélange un liant de façon à obtenir une pâte.A binder is then added to the mixture so as to obtain a paste.
On tapisse avec cette pâte 5 la face du disque émissif 1 qui est située vers l'intérieur du cylindre 2. Cette étape est représentée sur la figure 3a. Ensuite, on fait s'évaporer lentement le liant en utilisant une lampe électrique, de 100 W par exemple, ou en laissant sécher naturellement.The face of the
On introduit le filament 3 dans le cylindre 2. Cette étape est représentée sur la figure 3b.The
On remplit ensuite en plusieurs fois le cylindre avec la pâte dont la consistance peut être modifiée par addition du liant. A chaque fois qu"on a ajouté de la pâte dans le cylindre, on fait s'évaporer le liant, qui peut être de l'acétone, en utilisant la lampe électrique.The cylinder is then filled several times with the paste, the consistency of which can be modified by adding the binder. Whenever we have added paste to the cylinder, the binder, which may be acetone, is evaporated using the electric lamp.
Enfin, on fritte sous hydrogène entre 1700 et 1800°C pendant une demi-heure environ de façon à obtenir le "potting" 4.Finally, sintered under hydrogen between 1700 and 1800 ° C for about half an hour so as to obtain the "potting" 4.
En faisant s'évaporer le liant lentement et au fur et à mesure qu'on ajoute une couche de pâte dans le cylindre, on évite la formation de bulles dues à une évaporation rapide du liant de la totalité de la pâte remplissant le cylindre.By evaporating the binder slowly and as a layer of paste is added to the cylinder, the formation of bubbles is prevented due to rapid evaporation of the binder from all of the paste filling the cylinder.
Claims (9)
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
FR8003410A FR2476386A1 (en) | 1980-02-15 | 1980-02-15 | INDIRECT HEATING CATHODE HEATING ELEMENT, METHOD OF MANUFACTURING THE SAME, AND INDIRECT HEATING CATHODE COMPRISING SUCH A MEMBER |
FR8003410 | 1980-02-15 |
Publications (2)
Publication Number | Publication Date |
---|---|
EP0034512A2 true EP0034512A2 (en) | 1981-08-26 |
EP0034512A3 EP0034512A3 (en) | 1982-05-26 |
Family
ID=9238641
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP81400096A Withdrawn EP0034512A3 (en) | 1980-02-15 | 1981-01-23 | Heating element for indirectly heated cathodes, process for manufacturing such an element and indirectly heated cathode comprising the same |
Country Status (3)
Country | Link |
---|---|
US (1) | US4427916A (en) |
EP (1) | EP0034512A3 (en) |
FR (1) | FR2476386A1 (en) |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR2664427A1 (en) * | 1990-07-03 | 1992-01-10 | Thomson Tubes Electroniques | Indirect-heating cathode with integrated filament for linear beam tube |
WO2001015206A1 (en) * | 1999-08-22 | 2001-03-01 | Ip2H Ag | Light source |
Families Citing this family (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS60189447U (en) * | 1984-05-28 | 1985-12-16 | アップリカ葛西株式会社 | Child safety seat for automobiles |
JPH0624093B2 (en) * | 1984-12-26 | 1994-03-30 | 株式会社日立製作所 | Heater for indirectly heated cathode |
US5065070A (en) * | 1990-12-21 | 1991-11-12 | Hughes Aircraft Company | Sputtered scandate coatings for dispenser cathodes |
US5208508A (en) * | 1991-09-16 | 1993-05-04 | Raytheon Company | Cathode heater potting assembly |
FR2681726A1 (en) * | 1991-09-20 | 1993-03-26 | Thomson Tubes Electroniques | Insulating potting for indirect heating cathodes |
CN112490098B (en) * | 2020-12-09 | 2023-03-14 | 成都国光电气股份有限公司 | Mixed filling powder for hot wire component and preparation method thereof |
Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR1315581A (en) * | 1961-02-24 | 1963-01-18 | Siemens Ag | Process for manufacturing vacuum-holding insulating sintered bodies |
US3400294A (en) * | 1964-12-07 | 1968-09-03 | Gen Electric | Heated cathode and method of manufacture |
DE1805821A1 (en) * | 1968-10-29 | 1970-06-04 | Telefunken Patent | Indirectly heated emission electrode |
US3803441A (en) * | 1972-04-28 | 1974-04-09 | Tokyo Shibaura Electric Co | Indirectly heated type cathode devices using foil heater embedded in mixture of heat resistant dielectric and a metal |
-
1980
- 1980-02-15 FR FR8003410A patent/FR2476386A1/en active Granted
-
1981
- 1981-01-23 EP EP81400096A patent/EP0034512A3/en not_active Withdrawn
- 1981-02-09 US US06/232,571 patent/US4427916A/en not_active Expired - Lifetime
Patent Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR1315581A (en) * | 1961-02-24 | 1963-01-18 | Siemens Ag | Process for manufacturing vacuum-holding insulating sintered bodies |
US3400294A (en) * | 1964-12-07 | 1968-09-03 | Gen Electric | Heated cathode and method of manufacture |
DE1805821A1 (en) * | 1968-10-29 | 1970-06-04 | Telefunken Patent | Indirectly heated emission electrode |
US3803441A (en) * | 1972-04-28 | 1974-04-09 | Tokyo Shibaura Electric Co | Indirectly heated type cathode devices using foil heater embedded in mixture of heat resistant dielectric and a metal |
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
FR2664427A1 (en) * | 1990-07-03 | 1992-01-10 | Thomson Tubes Electroniques | Indirect-heating cathode with integrated filament for linear beam tube |
WO2001015206A1 (en) * | 1999-08-22 | 2001-03-01 | Ip2H Ag | Light source |
US6777859B1 (en) | 1999-08-22 | 2004-08-17 | Ip2H Ag | Light source |
Also Published As
Publication number | Publication date |
---|---|
EP0034512A3 (en) | 1982-05-26 |
FR2476386B1 (en) | 1982-08-20 |
US4427916A (en) | 1984-01-24 |
FR2476386A1 (en) | 1981-08-21 |
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