RU2131323C1 - Method of producing highly porous nonevaporable getter materials and materials produced by this method - Google Patents

Abstract

FIELD: methods of production nonevaporable getter materials featuring high mechanical strength, porosity and improved rate of gas absorption. SUBSTANCE: method includes mixing of metallic getter element, one or several getter alloys and solid organic substance with all components being in the form of powders with definite sizes of particles. Produced mixture is subjected to pressing at pressure below 1000 kg/sq.m and sintering at temperature from 900 to 1200 C for time from 5 min to 1 h. Produced getter material is used for production of gas-absorbing bodies in the form of granules, sheets or discs. EFFECT: improved mechanical strength, porosity and rate of gas absorption. 16 cl, 19 dwg, 1 tbl

Description

 The invention relates to a method for producing a non-volatile getter material having a very high porosity, and to getter materials obtained by this method.

 The present invention, in particular, relates to a method for producing non-volatile getter material, which has very high values of porosity and absorption rate of gas, and to non-volatile getter materials obtained by this method.

Non-volatile getter materials (known as NEG materials in this field) are widely used in the field of vacuum preservation, for example for thermal insulation, either inside lamps or in the purification of inert gases. The most common NEG materials are metals, for example Zr, Ti, Nb, Ta, V, or their alloys with the optional addition of one or more other elements; examples are an alloy having a composition in wt.%: Zr - 84, Al - 16, obtained and sold by SAES GETTERS, MILAN (Saes Getters, Milan) under the name St 101 ^® , or an alloy having a composition in wt.%: Zr - 70, V - 24.6, Fe - 5.4, obtained and sold by Saes Getters under the name St 707.

These materials act by surface chemisorption of reactive gases, for example CO, CO ₂ , H ₂ O, O ₂ , H ₂ . Apart from hydrogen, which dissociates into H atoms and diffuses into the material even at low temperatures, for other gases chemisorption is essentially a surface phenomenon up to temperatures which, depending on the NEG material, can vary in the range from about 200 ^° C to 500 ^° C Diffusion of chemisorbed species into the material occurs at higher temperatures.

 In the phenomenon of absorption of chemically active gases, the surface of the NEG material plays an essential role for any gas. Therefore, the large specific surface (surface per unit mass) of the material and the easy access of gases to the grain surface of the NEG material are parameters of significant importance. These characteristics can be achieved by using NEG materials in the form of powders, but in practice such a solution to the problem is not used.

 NEG materials are used in practice in the form of devices: getter devices are obtained from powders that can be pressed to obtain granules, which are then sintered to give them the necessary mechanical strength; powders can be loaded and pressed in open tanks; ultimately, the powders can be cold rolled on a substrate. Regardless of the method used to obtain the device, pressing and / or sintering operations lead to a decrease in the specific surface relative to the specific surface of the starting powder; moreover, there is an obstruction of the access of gases to the innermost particles of the getter, which subsequently leads to a decrease in the absorption capacity and, in particular, the gas absorption rate.

 In order to overcome these disadvantages, DE-A-2204714 discloses a method for producing devices from non-volatile getter materials based on zirconium metal. In accordance with this method, graphite powder and an organic component, for example, such as ammonium carbamate, are added to zirconium powder; the weight of the organic component can reach the sum of the weights of zirconium and graphite. During the heat treatment by sintering, the organic component evaporates and thus leaves the porous structure enclosed in zirconium and graphite, in which graphite acts as a substance that prevents the sintering of zirconium, which prevents an excessive decrease in the specific surface.

 The aforementioned patent application refers to the use of only elemental components, not alloys, and it does not mention the particle size of the components, not counting the organic component, which is added in the form of powder grains having a size in the millimeter range.

 Due to the size of the organic component, the final getter material has a structure with a high ratio between the pore volume and the geometric volume of the device; however, the porosity distribution obtained by the method presented in the aforementioned patent application is not such that it is possible to optimize the availability of gases to the surface of the innermost grains of the NEG material. Moreover, materials obtained in accordance with the method of the named patent application do not have good mechanical properties.

 GB-A-2077487 discloses a porous NEG material obtained from a powder mixture of a metal getter material, for example titanium or zirconium, and the St 707 alloy mentioned previously as an anti-sintering agent. According to the aforementioned patent, the particles of the metal component have a size less than about 125 microns, while the particles of the St 707 alloy have a size less than about 400 microns, but larger than the size of the metal component. The description of the patent indicates that this ratio between the size of the two materials is chosen in such a way as to prevent excessive sintering of the metal during heat treatment, which leads to a decrease in the specific surface and, therefore, to a reduced efficiency of the product as a getter. This patent does not indicate the use of an organic component.

 Ultimately, U.S. Pat. No. 4,428,856 discloses a porous non-volatile getter material containing by weight 50 to 98% titanium, 1.5 to 30% high melting metal selected from niobium, tantalum, molybdenum and tungsten, and 0, 5 to 20% titanium hydride; this patent states that zirconium powders are flammable and may cause an explosion, whereby one of the objectives of the patent is to provide a getter composition in which the use of zirconium is avoided.

 Although the porosity and specific surface characteristics of porous NEG materials in the prior art are improved relative to those of conventional NEG materials, they are still insufficient for specific applications, such as small volume getter pumps, which require high performance for getter materials.

 The aim of the present invention is to provide a method for producing a non-vaporizing getter material having improved characteristics of porosity and absorption rate of gas with respect to materials of the previous field, as well as good mechanical strength.

In accordance with the present invention, this and other objectives are achieved by a method for producing non-evaporative getter materials having improved characteristics of porosity and gas absorption rate, comprising the following stages:
A). Obtaining a mixture of:
i) powders of a metal getter element with a grain size lower than about 70 microns;
ii) powders of one or more getter alloys with grain sizes lower than about 40 microns;
iii) powders of an organic component, solid at room temperature, which has the property of being sublimated or decomposed into gaseous products without leaving residues, when exposed to air or during subsequent heat treatments consisting of two sieve fractions, while the grains of the first fraction have a size lower than about 50 microns, the grains of the second fraction have a size between 50 and 150 microns and the weight ratio between the two fractions can vary between 4: 1 and 1: 4.

IN). Exposure of the powder mixture from point A to compression at a pressure lower than 1000 kg / cm ² .

WITH). Sintering of the pressed powder mixture by vacuum treatment or treatment with an inert gas at a temperature between 900 ^o and 1200 ^o C for a time between 5 minutes and 1 hour.

 The metal getter element may be any of the metals in elemental form used in the art, for example zirconium, titanium, niobium, vanadium and tantalum; among these metals, titanium and zirconium are particularly preferred.

 The metal getter element is used in the form of a fine powder with a particle size lower than about 70 microns. The particle size of this component is preferably between about 40 and 60 microns.

The getter alloy component of the above mixture of powders may consist of powders of one or more getter alloys depending on the presence or absence of hydrogen in the gas mixture absorbed by the getter. In fact, in contrast to gases such as O ₂ , N ₂ , H ₂ O, CO, CO ₂ , etc., absorption by hydrogen getters is a reversible phenomenon that leads to equilibrium; according to the temperature and type of getter material, hydrogen is partly separated in the getter and partly in the surrounding atmosphere, so that a residual hydrogen pressure is always present inside the vessel to be evacuated. The amount of free hydrogen and, therefore, the pressure of hydrogen over the getter increases with temperature for all getter materials. At the same temperature, various getter materials have an equilibrium pressure of free hydrogen, which can vary by several orders of magnitude; materials that absorb more hydrogen at the same temperature leave a lower partial pressure of hydrogen in the environment and will be defined in the rest of the description and claims as getter materials for low hydrogen pressure.

 Given the difference in the behavior of getters with respect to hydrogen and other gases, it is preferable that when the intentional use of getter materials is carried out in an environment containing significant amounts of hydrogen, getter material for low hydrogen pressure is added to the mixture of powders constituting the getter material of the invention.

 Getter alloys are usually selected from titanium-based getter alloys with one or more transition valence elements, or from zirconium getter alloys with one or more transition valence elements, for example Zr-Al, Zr-V, Zr-Fe, and Zr- double alloys Ni or ternary alloys Zr-Mn-Fe or Zr-V-Fe. If hydrogen is not present in the mixture of gases to be absorbed, the getter alloy component preferably consists of a single getter alloy.

Preferred is the use of Zr-V-Fe ternary alloys, and in particular the above-mentioned St 707 alloy, having a composition in% by weight: Zr 70, V 24.6, Fe 5.4. In the case of significant quantities of absorbed hydrogen, it is preferred that the getter alloy component consists of more than one, preferably two different getter alloys comprising at least one getter material for low hydrogen pressure. A preferred combination of getter alloys in this case consists of a mixture of the aforementioned St 707 alloy and an alloy having a composition in wt.%: Zr 84, Al 16, obtained and sold by Caes Getters, Milan, under the name St 101 ^® .
Getter alloys are used in the form of a very fine powder with a maximum particle size lower than 40 microns and preferably lower than 30 microns.

 The weight ratio between the metal getter element and getter alloys can vary in a very wide range, but usually it is between 1: 10 and 10: 1 and preferably between 3: 1 and 1: 3. When two getter alloys are used, the weight ratio between the alloys, depending on the intended use, can vary over a wide range and is usually between 1:20 and 20: 1.

 Amounts of a metal element greater than those indicated above lead to a decrease in the efficiency of sample gettering, since the use of excessive amounts of getter alloys usually causes difficulties in sintering the getter bodies obtained by pressing the powder, which subsequently leads to poor mechanical strength of the getter getter bodies.

The organic compound of the invention is a solid material at room temperature which must have the property of evaporation without residue during heat treatment to sinter the getter material. The organic compound should preferably completely evaporate at a temperature lower than about 300 ^° C. so that at temperatures at which the getter material becomes active, chemically active vapors are not generated. Some of the examples of organic materials satisfying the above requirements are ammonium oxalate, ammonium benzoate, and ammonium carbamate is particularly preferred.

 The organic compound is used in powder form. This powder is used in the form of two fractions, the first of which has a particle size below 50 microns and the second fraction has a particle size between 50 and 150 microns. As for the method of the invention, it is necessary that both fractions be present in the powder mixture in an amount not lower than the minimum amount, while the weight ratio between the two fractions can vary between 4: 1 and 1: 4.

 The weight of the organic compound can reach up to 40% of the total weight of the powder mixture of point A, and is preferably from 10 to 35% of the total weight of the mixture before sintering. If the organic compound is used in too small amounts, the getter body obtained by sintering is unlikely to be porous, since it is impossible to obtain mechanically stable getter bodies with amounts of the organic compound higher than 40% by weight.

The powder mixture thus obtained is subjected to easy pressing at pressures lower than 1000 kg / cm ² , preferably between 50 and 800 kg / cm ² . Lower values of the applied pressure give the final sintered body having poor mechanical strength, while higher values of the pressure cause excessive powder compactness, which subsequently leads to a decrease in the specific surface and most of the porosity.

After pressing, the powder mixture is subjected to heat treatment in an inert gas atmosphere or preferably under vacuum, at a temperature between about 900 and 1200 ^o C, preferably between 1000 and 1100 ^o C, for a time in the range from 5 minutes to 1 hour.

 According to its second aspect, the invention relates to highly porous getter materials obtained by the above method.

In the description of getter materials of the invention, reference is made to the drawings, in which:
FIG. 1a shows a microphotographic image obtained using a scanning electron microscope (SEM), magnifying 700 times, getter material of the invention, the receipt of which is described in example 1;
FIG. 1b shows a pattern reproducing a microphotographic image of FIG. 1a;
figa shows a micrographic photograph obtained using SEM, magnifying 700 times, getter material, the receipt of which is described in example 2 of the method of the above patent application DE-A-2204714;
FIG. 2b shows a drawing reproducing a microphotographic image of FIG. 2a;
FIG. 3a shows a microphotographic image obtained using SEM, magnifying 700 times, getter material, which is described in example 3 of the above patent GB-2077487;
FIG. 3b shows a pattern reproducing a photomicrograph of FIG. 3a;
figa shows a micrographic photograph obtained using SEM, magnifying 700 times, comparative getter material obtained in accordance with the method described in example 4;
FIG. 4b shows a photograph reproducing a photograph of FIG. 4a;
figa shows a photomicrograph obtained using SEM, magnifying 700 times, comparative getter material obtained in accordance with the method described in example 5;
FIG. 5b shows a drawing reproducing a photograph of FIG. 5a;
figa shows a photomicrograph obtained using SEM, magnifying 700 times, comparative getter material obtained in accordance with the method described in example 6;
FIG. 6b shows a photograph reproducing a photograph of FIG. 6a;
7 illustrates a graph showing the getter properties of five getter material samples of FIGS. 1-5 when using CO as a test gas; the absorption rate (S), measured as the absorbed per second amount of cm ³ CO per 1 g of getter material, is presented as a function of the amount (Q) of absorbed CO, measured as cm ³ • Pa per 1 g of getter material;
FIG. 8 shows a graph similar to that of FIG. 7 obtained when using nitrogen as a test gas;
FIG. 9 shows a graph similar to that of FIGS. 7 and 8, showing the absorption properties of the getter material of the invention with respect to hydrogen and a comparative getter material; and
FIG. 10a-10d illustrate possible forms of getter bodies that can be obtained using the method of the present invention.

 The getter materials of the invention, due to the features of the production method, have a new combination of structural and functional properties with respect to the getter materials of the previous field. In particular, referring to fig.1b, it should be noted that the getter materials of the invention have a porous structure consisting of a first spatial grid of pores 1 of larger diameter, providing easy access of gases to even the innermost parts of the getter body. A second pore network 2 of smaller diameter, giving access to the surface of single grains of two getter materials, is superimposed on said first pore network.

 Due to the mentioned structural features, high values of porosity and surface area are obtained along with good mechanical strength.

 The getter bodies obtained in accordance with the method of the invention can be used in all applications requiring the presence of getter material, for example, while maintaining a vacuum inside the lamps or thermally insulating spaces (for example, in thermostatic vessels). A possible form of a getter body suitable for use in thermostatic vessels is, for example, a granule, which is shown in FIG. 10a. However, due to the special functional properties of the getter materials of the invention, the advantages that are obtained when using getter devices containing these materials are particularly evident in applications requiring high getter characteristics in devices with a small volume; for example, in the case of getter pumps, in which the volume available for getter material is small. Getter pumps of this type are presented, for example, in US patents NN 5320496 and 5324172 in the name of the applicant. In the first of these patents, a pump is presented in which the getter bodies are made in the form of stacked disks arranged coaxially with the pump body.

 Possible alternative forms of disks used in the pump, such as those of US Pat. No. 5,320,496, in addition to those described in the cited patent, are shown in FIGS. 10c and 10d. In the second patent, a getter pump is provided, made with getter bodies, similar to plates, radially arranged around the axis of the pump; a possible getter body similar to the plate used in this pump is shown in FIG. 10b.

 The objectives and advantages of the present invention will be apparent to those skilled in the art upon reading the following examples. These examples are given solely for the purpose of illustration and in no way limit the scope of the invention.

 Example 1

This example relates to the production of getter material of the invention. A mixture of 2.4 g of zirconium metal having a particle size between 40 and 50 μm, 3.6 g of St 707 alloy having a particle size lower than 30 μm, and 4.0 g of two-portion ammonium carbamate were prepared, each 2 g, respectively having a particle size between 0 and 50 microns, and between 50 and 150 microns. The mixture was homogenized in a V-shaped mixer for 4 hours and pressed by subjecting it to a pressure of up to 150 kg / cm ² . Then the pressed mixture was sintered by heat treatment in a vacuum oven while heating it to 1050 ^o C for a time of about 2 hours and maintaining it at the indicated temperature for 30 minutes. The getter body thus obtained is sample 1.

 Example 2 (comparative).

This example describes the preparation of getter material in accordance with the method described in patent application DE-A-2204714. A mixture of 5.8 g of zirconium metal having a particle size between 0 and 44 μm, 2.2 g of graphite powder having a particle size of between 75 and 128 μm, and 3 g of ammonium carbamate powder having a grain size of about 1 μm were obtained. The mixture was homogenized as in Example 1 and sintered by heating it to 1050 ^° C. for 55 minutes and maintaining it at the indicated temperature for 5 minutes. The sintered getter body taken out of the furnace is sample 2.

 Example 3 (comparative).

 This example describes the preparation of a porous getter material in accordance with GB-2077487.

 A mixture of 4 g of a metal zirconium powder having a particle size between 0 and 44 μm and 6 g of an alloy of St 707 having a particle size between 53 and 128 μm was obtained. The mixture was homogenized as in the previous examples and sintered using the heat treatment described in Example 2. The getter body thus obtained is sample 3.

 Example 4 (comparative).

 The production of getter material was repeated in accordance with the procedure of Example 2, but using a fine ammonium carbamate powder with a grain size lower than 44 μm. The getter body thus obtained is sample 4.

 Example 5 (comparative).

The production of getter material was repeated in accordance with the procedure of Example 3, but when pressing the powder mixture before sintering at a pressure value of 70 kg / cm ² . The getter body thus obtained is sample 5.

 Example 6

This example relates to the production of getter material of the invention. A mixture of 35 g of zirconium metal having a particle size of between 40 and 50 μm, 15 g of an alloy of St 707 having a particle size of lower than 30 μm, 50 g of an alloy of St 101 ^® having a particle size of lower than 30 μm, 13 g of ammonium carbamate was obtained having a particle size between 0 and 50 microns, and 20 g of ammonium carbamate having a particle size between 50 and 150 microns. The mixture was homogenized in a V-shaped mixer for 4 hours; 1.3 g of the homogenized mixture was pressed by subjecting them to a pressure of 600 kg / cm ² . Then the pressed mixture was sintered by heat treatment in a vacuum oven by heating it to 1050 ^o C for a time of about 2 hours and maintaining at this temperature for 30 minutes. The getter body thus obtained is sample 6.

 Example 7

The gas absorption rate and absorption capacity were measured on samples 1, 2, 3, 4, and 5 at room temperature after activation at 600 ^° C. for 10 minutes. The test was carried out by measuring the speed at which each sample absorbs the measured amount of gas during a series of consecutive gas flows into the test chamber in accordance with ASTM F 798-82 (American Standard Test Method). The gas used for the test was CO. The test results are shown in the graph of Fig. 7, respectively, in the form of curves 1-5 for five samples.

 Example 8

 Measurement of the absorption properties of samples 1-5 was carried out under the same conditions that are indicated in example 7, with the only difference that in this case, the test gas was nitrogen. The results are shown in FIG.

 Example 9

Measurements of the rate of hydrogen absorption and absorption capacity were carried out on sample 6 (invention) and 2 (comparative) at room temperature after their activation at 600 ^o C for 30 minutes. The test was carried out in accordance with ASTM method F 798-82. The test results are shown in the graph of FIG. 9 and respectively are presented in the form of curves 6 and 7 for two samples 6 and 2.

 Example 10

 Surface area measurements were carried out on samples 1-6 in accordance with the method of B.E.T. (BET) (Brunauer, Emmett and Teller) using Quantasorb QS-12 equipment. The results of this test are summarized in table.

 Example 11

The apparent density and percent porosity of samples 1-6 were measured. The apparent density was calculated as the ratio between the weight of the sample and its geometric volume. The term "porosity" indicates a percentage value calculated using the following formula:
porosity% = (1 - d _app / d _t ) • 100.

where d _app is the specified apparent density of the sample;
d _t is its theoretical density;
from the known absolute densities and weights of the fractions of the materials that make up the sample, we calculated, in turn, using the following two formulas, the value of d _t , respectively, using formula I, the value of d _t for samples consisting of two-component materials (samples 1-5), and using formula II - for samples consisting of three-component materials (sample 6)
d _t = (d _A d _B ) / (d _A X _B + d _B X _A ) (I)
and
d _t = (d _A d _B d _C ) / (d _A d _B X _C + d _A d _C X _B + d _B d _C X _A ) (II)
where d _A is the density of the first material constituting the sample;
d _B is the density of the second material making up the sample;
d _C is the density of the third material making up the sample;
X _A is the weight of the fraction of the first material constituting the sample;
X _B is the weight of the fraction of the second material making up the sample;
X _C is the weight of the fraction of the third material making up the sample.

 The results are tabulated.

 The method of obtaining comparative sample 4 does not correspond to the already known method, but is a variant of the method of example 2, in which the use of ammonium carbamate having a particle size lower than the particle size of ammonium carbamate of example 2, and comparable with the particle size of ammonium carbamate used in the method of the invention . Similarly, the method for producing comparative sample 5 does not correspond to any method of the previous field, but is a variant of the method of example 3, in which the use of light pressing of the powder mixture is carried out as in the method of the invention.

The surface area of sample 5 is lower than the reading limit of the used device, and, nevertheless, undoubtedly lower than 0.08 m ² / g, i.e. values obtained for sample 3.

As can be seen when viewing microphotographic images of FIG. 1-6, samples 1 and 6, corresponding to the getter materials of the invention, have a porous structure that differs from both comparative samples 2 and 3 of the previous region and comparative samples 4 and 5. In particular, the getter bodies of the invention have a porous structure that makes they are easily recognizable among other samples, since it consists of macroporosities 1 distributed in the body of the sample and microporosities 2 among zirconium and alloy grains; on the contrary, all samples 2-5 look more compact. The data in the table show that comparative samples 2 and 4 have specific surface and porosity values comparable with the specific surface and porosity of samples 1 and 6, while samples 3 and 5 have a specific surface and porosity much lower than for samples 1 and 6. On the other hand, samples 2 and 4 have poor mechanical strength, are brittle and easily lose particles, which makes them unsuitable in technological applications. In addition to this improved combination of structural and mechanical properties, sample 1 of the invention also has the best getter properties, which can be noted when considering the graphs of FIG. 7 and 8, in which the absorption curves at room temperature for samples 1-5 are presented for CO and N _2, respectively. In fact, sample 1 shows much higher absorption properties for both gases than samples 3 and 5, which are provided with a less porous structure. However, the sample of the invention also shows better absorption capacity for both gases than samples 2 and 4, the porosity characteristics of which are comparable with the porosity characteristics of sample 1. Sample 6 of the invention shows the same good combination of properties, i.e. high specific surface, high porosity and mechanical strength as in sample 1. Sample 6 also shows very good absorption properties of getter materials of the invention with respect to hydrogen when they are prepared using a mixture of getter alloys comprising a getter material with a low hydrogen pressure as a getter alloy . When considering the graph in FIG. 9, it can be noted that sample 6 shows higher absorption properties with respect to hydrogen than sample 2, provided with a structure with comparable porosity.

 Ultimately, a comparison of the absorption properties of samples 2 and 4 and samples 3 and 5 shows that only when working in accordance with the method of the invention can the excellent results described above be achieved. In fact, when considering these figures, it was found that when changing the preparation of sample 2 (the method presented in patent application DE-A-2204714) in order to make it more similar to the method of the invention, i.e. with ammonium carbamate having a finer particle size (sample 4), the absorption of gas deteriorates. Similarly, a change in the method for producing sample 3 (method of patent GB 2077487) by applying light compression of the powder mixture in order to make it more similar to the method of the invention (thus obtaining sample 5) leads to a deterioration in absorption properties. In conclusion, the tests showed that the samples of the invention show the best gas absorption properties with good mechanical strength, which makes them suitable for technological applications; comparing the properties of the samples of the invention and comparative samples also shows that this combination of properties depends on the features of the method, characterized by a combination of its parameters, which cannot be obtained with a simple attempt to change the parameters of known methods.

Claims (16)

1. A method of producing non-evaporative getter materials having improved characteristics of porosity, gas absorption rate and absorption capacity, comprising obtaining a mixture of powders of a metal getter element and powders of an organic component and subsequent sintering of a powder mixture, characterized in that the powder mixture further comprises one or more powders getter alloys, while the powders of the metal getter element have a grain size lower than 7 microns, powders of one or several of getter alloys have a grain size lower than 40 microns, powders of the organic component are powders of the organic component, solid at room temperature, which tends to sublimate or decompose into gaseous products, leaving no residue, when exposed to air or during subsequent heat treatments, consisting of two sieve fractions, moreover, the grains of the first fraction have a size lower than 50 microns, the grains of the second fraction have a size of 50 - 150 microns, and the weight ratio between the two fractions can change between 4: 1 and 1: 4, the powder mixture is pressed at a pressure lower than 1000 kg / cm ² , and the pressed powder mixture is sintered by vacuum treatment or inert gas treatment at 900 - 1200 ^o C for 5 min - 1 h  2. The method according to claim 1, characterized in that the weight ratio between the metal getter element and getter alloys is 1: 10 to 10: 1.  3. The method according to claim 2, characterized in that the weight ratio between the metal getter element and getter alloys 1: 3 to 3: 1.  4. The method according to claim 1, characterized in that the weight of the organic compound is up to 40% of the total weight of said powder mixture.  5. The method according to claim 4, characterized in that the weight of the organic compound is 10 - 35% of the total weight of said powder mixture.  6. The method according to claim 1, characterized in that the metal getter element is zirconium.  7. The method according to claim 1, characterized in that only one getter alloy is used.  8. The method according to claim 7, characterized in that the getter alloy is a Zr - V - Fe ternary alloy having a composition, wt.%: ZR 70, V 24.6, Fe 5.4.  9. The method according to claim 1, characterized in that two getter alloys are used.  10. The method according to claim 9, characterized in that the weight ratio between the two getter alloys is 1: 20 to 20: 1.  11. The method according to claim 9, characterized in that the first getter alloy is a Zr - V - Fe alloy having a composition, wt.%: Zr 70, V 24.6, Fe 5.4, and the second alloy is Zr-Al an alloy having a composition, wt.%: Zr 84, Al 16.  12. The method according to claim 1, characterized in that the organic compound is ammonium carbamate. 13. The method according to claim 1, characterized in that the powder mixture is pressed under a pressure of 50 - 800 kg / cm ² .  14. The method according to claim 1, characterized in that a highly porous getter material is obtained.  15. The method according to claim 1, characterized in that highly porous getter bodies are obtained.  16. The method according to claim 1, characterized in that the highly porous getter bodies are molded in the form of granules, sheets or disks.

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