SU63461A3 - Getter - Google Patents

Description

The present invention relates to a technique for introducing getters into vacuum devices (electronic and other lamps), i.e., chemically active, evaporating substances or agents used in the vacuum device after the evacuation of the vacuum device or after it to reduce the pressure of residual gases or increase electron emission from cathodes.

The beryllium oxide compound with alkaline earth metal, such as barium, was used as a getter and gave good results, as KaiK develops a small amount of free metallic barium and gaseous by-products when heated in vacuum. However, this combination, when working with it in production and staying in a more or less moist atmosphere, is not completely stable and gradually deteriorates, since, obviously, hydrolysis occurs in a humid atmosphere.

The subject of the invention is a stable oxide compound of beryllium and alkali metals, free from harmful amounts of gas, emitting insignificant amounts of active metals and sufficiently stable during prolonged exposure to a humid atmosphere.

The invention of using double barium and strontium beryllate is illustrated in the accompanying drawing, in which FIG. I represents an electron lamp with a getter according to the invention; FIG. 2 shows an enlarged view of the getter, FIG. 3 shows one of the means of heating the getter, and FIG. 4 - filament cathode with a new coating.

The flask I closes the electrode system 2 containing the oxide cathode and its surrounding grid and anode. The flask was metal, in its lower part there is a leg 3 with a tube 4 for pumping out. After absorption of gases, the getter material is heated to absorb. Getter material can be pressed into balls and placed on a getter tail in the usual way; However, for practical reasons (and especially in metal lamps), it is preferable to thread a thin layer of material placed on an electrically heated core.

In one preferred form of the getter 5; consists of a core (refractory material) with a groove - a strip 6. p-placed in any place of the flask. More clearly, this is shown in FIG. 2, where the getter material is denoted by 7. The getter can be conveniently heated electrically by attaching one of the ends of the strip b to the inlet 8, and the other to the body of the flask or another outlet.

In glass flasks, heating by an induction furnace can be applied by arranging a getter strip, as shown in FIG. 3, a conducting arc 9.

The open side of the strip 6 is made to face or to the side of the bulb, like 1 in FIG. 1, or down, as in FIG. 3, due to which getter deposits fall down the flasks. After the pressure in the flask reaches several microns, the strip 6 is heated enough times to remove the required amount of getter copiers and clean the flask from residual gases. After that, the flask can be dispensed and separated out in the usual way. If, after aging, the gas is again in a flask, then it will be possible to release some more of the getter oaipa, “heating again the strip.

During the preparation of the refractory metal strip 6, made in the form of a shallow groove, is filled with a thin paste with a mask consisting of the proposed goethe material and a binder. In factory production, the material is prepared in large quantities and inevitably lasts for a long time in the open air (before being placed in the lamp and taped off).

After experiments on various combinations of alkaline earth metals and their oxides, in order to obtain gas-free mixtures that liberate a large amount of metal and are stable under different atmospheric conditions, it was found that double beryllate was only 3%: milliards; allov like barium, strontium , calcium and magnesium (preferably, beryllium, barium and strhenium oxide mixtures) is an excellent material for this purpose. The double beryllate barium and strontium is a double barium-strontium salt in which for the latter beryllium oxide is an acid radical.

An indicator of the sustainability of a new material and the deterioration of simple barium beryllate under the conditions of factory production, associated with the material being in air, is the amount of gas that can be obtained by the material under conditions of vacuum in vacuum up to 700 ° C. Barium and strontium beryllates or mechanical mixtures per milligram of beryllate, at a pressure of one micron, after being in an atmosphere of relative humidity in and at a temperature of 30 ° C for several hours, give more than a thousand liters of gas, while the proposed oxide mpaund barium, strontium and beryllium giving per milligram oosle finding in a similar atmosphere for several days - only eight liters. Under those atmospheric conditions that are usual for summer months, the moist beryllate mixture swells several times when heated with a normal one.

Tests have shown that the material proposed is a valid mixture of barium, strontium, beryllium and oxygen. The index of light refraction, determined by immersion in oil and using a petrographic microscope, lies between the I1deks of barium and strontium beryllates, and the microscopic test showed a distinct hexagonal crystal structure different from the crystals and barium and strontium beryllates. The X-ray unit can also show that the material represents the determined compound of barium, strontium, beryllium and oxygen.

The proposed material is double berillat barium and strontium and, in the opinion of the inventor, can be correctly represented by the formula BaO. SrO. BEo or BaSrBesOs. While the total weight of two metals must be in a certain relation to the acid radical BeO, the proportionality of the two metals is barium and. strontium can vary widely. In order to increase the yield of barium and strontium, the getter material may be prepared with an excess (against the formula required by the BaSrEe-aOs) barium and strontium oxides.

Although the technology for the preparation of this new compound may be different, the inventor obtained the best results in the manufacture of large quantities by joint grinding and roasting of barium and strontium carbonates and beryllium oxide. A getter material with an excess of approximately 20% BaO and SrO was produced by grinding 1400 g of barium-strontium carbonate and 520 g of beryllium oxide with annealing for up to fifteen hours. The crushed mixture was leveled in a flat nickel bath in a layer with a thickness other than 1/4 inch and then annealed from thirty to sixty minutes in hydrogen at a temperature of 1065 ° ± 20 ° C. At this temperature, the barium-strontium-beryllium compound {Ba. Sr. ) is formed, probably, by the conversion of carbonates to hydroxides, due to the action of hydrogen and the reaction of hydroxide with beryllium oxide. The compound thus obtained is sintered and its density is increased by heating it in air in a Denver firestone clay crucible for four hours, from 1200 to 1250 ° C. After cooling, the resulting product is crushed dry or turned into the finest powder in another way.

The powdered compound is applied as a coating.

or sprayed solution in an organic binder. A pasty thin covering material suitable for filling the channels of the tape getter core (Fig. 2) can be made by mixing 400 g of barium-astronomic berylllate made according to the indicated method with 95 cm of binding liquid consisting of commercial butyl carbite oil, nitrocellulose and natural or synthetic camphor. For large-scale industries, the binder was prepared by mixing 1000 cm of butyl carbite oil with 39 g of nitrocellulose and 10 g of camphor. In some cases, camphor can be successfully replaced by commercial plastics.

Good results were achieved with a ba / rivium-strontium-beryllium compound, as a getter, by applying a coating of 2.5 mg in a groove on a tantalum strip of 0.001 inch thick, 0.04 inch wide and 0.65 inch long. A current of about 3.8-4 amps heats the band to a temperature of about 1300 ° C and releases more than 750/0 barium and strontium that are in the mix. After decomposition, an unintelligent gas is released, the residue is solid, fire-resistant and non-volatile.

The tantalum strip (core) is easily reducing for barium-strontium-beryllate and gives good results, but, if desired, a powdered metal can be taken as a reducing agent, which can be mixed with the compound. Good results were obtained by mixing 16.5 V / o by weight of titanium powder with 83, barium-strontium berylllate and applied to the molybdenum strip. Pyrcon, vanadium, hafnium, or Columbia, as well as titanium or tantalum, are refractory metals, possessing the necessary reducing properties, liberating the active metals, and therefore can also be used as a material for the core or powder mixed into the compound.