US2855368A

US2855368A - Method of producing a non-vaporizing getter

Info

Publication number: US2855368A
Application number: US455752A
Authority: US
Inventors: Jr Hendrik Johannes Re Perdijk; Fast Johann Diedrich; Fransen Jan Josephus Bernardus
Original assignee: US Philips Corp
Current assignee: US Philips Corp; North American Philips Co Inc
Priority date: 1953-09-30
Filing date: 1954-09-13
Publication date: 1958-10-07
Anticipated expiration: 1975-10-07
Also published as: BE532147A

Description

Unite Y fates METHOD OF PRODUCING A NON-VAPORIZING GETTER Hendrik Johannes Reinierus Perdijk, Jr., 'Johann Diedricli Fast, and Jan Josephus Bernardus Fransen, Eindhoven, Netherlands, assignors, by mesne assignments, to North American Philips Company, Inc., New York, N. Y., a corporation of Delaware No Drawing. Application September 13, 1954 Serial No. 455,752

Claims priority, application Netherlands September 30, 1953 12 Claims. (Cl. 252--181.6)

consists of one or more refractory metals capable of forming non-gaseous hydrides, such as zirconium, thorium, titanium, tantalum, niobium and vanadium. Furthermore the invention relates to a getter produced by carrying out this method.

It is well known that the satisfactory gas-absorption effect of zirconium is adversely aifected by surface layers, for example consisting of oxide, and that the gas-absorption effect may be restored by heating in vacuo or in a non-corrodiug atmosphere to a temperature such that the oxide diffuses inwards.

It is also known to sinter a metal, such as titanium, zirconium, tantalum or thorium, with an alloy of cerium and aluminum, lanthanum and aluminum or cerium mixed metal (misc-h metal) and aluminum and to work the sintered material'into a fine powder. The powder obtained is already capable of absorbing gases and is usually secured in place on an electrode surface by means ofa binding liquid. The electrode having the powder applied to it is heated to a temperature such that the powder is secured to it by sintering, while the activity which has been reduced by gas-absorption is also partly restored. This heating process is affected before mounting in the tube or after mounting in and evacuation of the tube. In the first case the getter must again be activated by heating in the tube. The temperature required vstrong gas-absorption effect even at a low temperature,

preferably at room temperature.

According to the invention, in a method of producing a non-vaporizing getter for use in electric discharge tubes or other vacuum vessels the gas-absorbing constituent of which entirely or substantially consists of one or more refractory metals capable offorming non-gaseous-hydrides, such as zirconium, thorium, titanium, tantalum, niobium and vanadium, the powdered gas-absorbing metal is mixed and compressed with one or more of the following non-vaporizing likewise powdered elements, which may or may not be alloyed with one another, aluminum, silicon, beryllium, cerium, lanthanum and cerium mixed metal, after which the compressed mass is arranged in a discharge tube or vacuum vessel and activated by heating.

, 2,855,368 l atented Oct. 7, 1958 Due to the heating process the surface layers on the gas-binding metal are reduced entirely or in part, or the additional element exhibits a chemical or physical interaction with the closing layers such as to enable the subjacent refractory metal to exercise its gas-absorption efiect. The heating temperature required is not as high as if the oxide should be caused to diffuse inwards, in which case the refractory metal also sinters to compactn'ess with the result that the free surface is reduced and the gas-absorption effect is again adversely 'afiecte'd. If use is preferably made of a degassed refractory metal powder as starting material and this metal powder cannot be degassed without sintering to compactness, as is the case with powdered zirconium, it is possible to mix this metal powder with some other refractory metal powder which may not absorb gas, such as powdered tungsten, in which case sintering to compactness does not occur to the same extent and the "degassed product can readily be worked into powder.

In order to enable a large amount of the element upsetting the surface layers to be added, provision may also be made of a further metal which at a high temperature binds the added element, for example nickel, iron or titanium. Thus, the accessibility of the fine grains of the gas-absorbing metal can be improved while due to the liberated reaction heat the activation is accelerated. In order to obtain the refractory gas-absorbing metal powder it is also possible to start with the hydride which due to the heating process is already decomposed before the activation temperature is reached. If the refractory metal and the additional metal are capable of forming an alloy, this may contribute in some cases to the gas-absorption efiect. It will be appreciated that, if titanium is used as gas-absorbing metal, the additional metal should not be titanium also.

.The method according to the invention has the advantage that the getter is only produced in the discharge tube and then is immediately active. In the known methods the getter is kept in air and heated with a binding agent whileit is active, with the resultant formation of, for example, carbides and/or oxides. The gasabso'rption effect at room temperature of the getters according to the invention has a particular advantage in that there is a greater freedom in the choice of the point at which the getter should be arranged and that the gettter is active even in tubes in which no hot electrodes are available. The gas-binder is active even in a non-operative tube, as is also the case with, for example, barium.

If a further metal is added which is capable. of reacting with the added element with the production of heat, heating must only be effected to such a degree that this reaction sets in, whereupon the liberated heat causes the temperature to rise automatically. Under these conditions the activation of the getter is effected very rapidly and satisfactorily. In this event it is not necessary for the getter to be heated for a long period of time from without with the aid of high frequency fields with resultant reduction of the risk of damaging adjacent parts or tube wall.

The invention will now be explained with reference to the following examples. i

Example I Powdered zirconium and powdered aluminum in amounts of 98% and 2% respectively by weight of the mixture are mixed and compressed to form a pastille which is mounted on a metal band in a discharge tube. After evacuation the pastille is activated by heating it in vacuo for a few minutes at a temperature of approximately 800 C. Thereupon the tube is sealed. The gasabsorption effect at room temperature is very satisfactoryr After much gas has been absorbed the pastille pulverizes; In order to prevent the attendant disadvantages a fine gauze may be weldedover thepastille. Even if the relative amount of the aluminum is increased to 30%, the gas absorption effect remains satisfactory and the activity even increases with increase in the percentage of aluminum.

Example II Thorium and cerium silicon (Th and ICeSi) are mixed at a weight ratio of 3:1 and in the manner described hereinbefore worked into a pastille. In this case also, the

- gas absorption effect at room temperature is satisfactory after activation by heating at 800 (3., As an alternativ to CeSi use may be also made of CeAl Example III Zirconium or zirconium hydride are mixed with titanium aluminum (TiAl at. a weight ratio of 5:1.

pulverulent metal selected from the group consisting of nickel, iron and titanium to form a coherent mass, mounting said mass within a vessel, and then activating said mass for the first, time While within saidvessel by subjecting it to heat without sintering or vaporizing it.

In this case also a satisfactory getter at room temperature is obtained by activation,

Example I V Non-degassed powdered'zirconium is mixed'with pow dered aluminum and powdered nickel at a weight ratio of 3 :1 :2 and the mixture is compressed into apastille, which is mounted as getter in a discharge tube. After heating to 700 C. the aluminum activates the zirconium but also reacts with the nickel 'so that a spongy skeleton of an aluminum-nickel alloy is produced containing activated zirconium grains which are held by the skeleton,

with the result that on gas absorption no pulverization occurs. If the use of powdered nickeL'which is magnetic, presents difiiculty, the nickel may also be added in the form of nickel titanium-Ni Ti, which is not magnetic.

Example V If in the preceding example degassed powdered zirconium and tungsten are used instead of the non-degassed zirconium, the quantity by weight of the tungsten being one and a half times that of the zirconium, a satisfactory getter is also obtained. The mixing ratio ZrW- A1Ni is 3:4:5:1:2. This is also the case if tantalum is used as an alternative to tungsten.

Example VI coherent mass, mounting said mass within a vessel, andthen activating said mass for the first time while within said vessel by subjecting it to heat without sintering or vaporizing it. v

2. A method as set forth in claim 1 wherein a third 4. A method as set forth in claim 3 wherein the co- 'lierent mass also includes an element selected from the group consisting of cerium and lanthanum;

5. A method of producing a non-vaporizing getter comprising mixing and compressing without sintering pulverulent gas-absorbing zirconium and 2' to 30 weight percent of pulverulent aluminum to form a coherent body, mounting said body within a discharge tube, and acti vating said body'by subjecting the same to an elevated temperature without sintering or vaporizing it.

6. A method of producing a non-vaporizing getter comprising mixing and compressing without sintering,

pulverulent gas-absorbing thorium and pulverulent cerium-silicon in a weightratio of about 3:1 to form a coherent body, mounting saidbody within a discharge tube, and activating said body by subjecting the same to an elevated temperature without sintering or vaporizing it.

7. Amethod of producing anon-vaporizing getter comprising mixing and compressing without sintering pulverulent gas-absorbing Zirconium and pulverulent titanium-aluminum to form a, coherent body, mounting said body within a discharge tube, and activating said body by subjecting the same to an elevated temperature without'sinteringor vaporizing it. I I

8. A method as set forth in claim 7 wherein thezirconium and titanium-aluminum are in a weight ratio of about 5:1.

9. A method of producing a non-vaporizing getter comprising mixing and compressing without sintering pulverulent gas-absorbing zirconium, pulverulent aluminum and pulverulent nickel to form a coherent body, mounting said body within a discharge tube, and activating said body by subjecting thesame to an elevated temperature without sintering or vaporizing it.

10. A method as set forth in claim 9 wherein the body also contains an element selected from the group consisting of tungsten and tantalum. j

11. A method as set forth in claim 9 wherein the nickel is replaced by nickel-titanium.

12. A method as set forth in claim 10 wherein the zirconium, tungsten and tantalum, aluminum and nickel are in a weight ratio of about 3:4.5:1:2.

References Cited in the file of this patent UNITED STATES PATENTS 1,663,561 ONeill Mar. 27, 1928 1,958,967 Kniepen May 15, 1934 2,018,965 McQuade Oct. 29, 1935 2,362,468 Clark Nov. 14, 1944 2,368,060 Wooten Jan. 23, 1945 2,444,158 Driggs June 29, 1948 2,449,786 Lockwood Sept. 21, 1948

Claims

1. A METHOD OF PRODUCING A NON-VAPORIZING GETTER COMPRISING MIXING AND COMPRESSING WITHOUT SINTERING A FIRST PULVERULENT GAS-ABSORBING METAL SELECTED FROM THE GROUP CONSISTING OF ZIRCONIUM, THORIUM, TITANINUM, TANTALUM, NIOBIUM AND VANADIUM AND SELECTED FROM THE GROUP MATERIAL CONTAINING AN ELEMENT SELECTED FROM THE GROUP CONSISTING OF ALUMINUM, SILICON, AND BERYLLIUM TO FORM A COHERENT MASS, MOUNTING SAID MASS WITHIN A VESSEL, AND THEN ACTIVATING SAID MASS FOR THE FIRST TIME WHILE WITHIN SAID VESSEL BY SUBJECTING IT TO HEAT WITHOUT SINTERING OR VAPORIZING IT.

3. A METHOD OF PRODUCING A NON-VAPORIZING GETTER COMPRISING MIXING AND COMPRESSING WITHOUT SINTERING A FIRST PULVERULENT GAS-ABSORBENT METAL SELECTED FROM THE GROUP CONSISTING OF ZIRCONIUM, THORIUM, TITANIUM, TANTALUM, NIOBIUM AND VANADIUM, A SECOND PULVERULENT MATERIAL CONSISTING AN ELEMENT SELECTED FROM THE GROUP CONSISTING OF ALUMINUM, SILICON, AND BERYLLIUM AND A THIRD PULVERULENT METAL SELECTED FROM THE GROUP CONSISTING OF NICKEL, IRON AND TITANIUM TO FORM A COHERENT MASS, MOUNTING SAID MASS WITHIN A VESSEL, AND THEN ACTIVATING SAID MASS FOR THE FIRST TIME WHILE SAID VESSEL BY SUBJECTING IT TO HEAT WITHOUT SINTERING OR VAPORIZING IT.