KR960010597B1 - Method of manufacturing tough and porous getter by means of hydrogen pulverization and getters produced thereby - Google Patents

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Description

Strong porous getter manufacturing method by hydrogen fine powder

1 is a room temperature H ₂ absorbance curve obtained in the hydrogen fines of these ingots as a function of time for the four getter alloy ingots of the various compositions according to the invention, and the relevant alloy compositions are shown in the table of Example 1. Indicated.

FIG. 2 shows an alloy in which the 3 × 10 ⁻⁶ torr for four compositions according to the present invention, prepared in the form of the final porous getter, is indicated by room temperature getter curves for CO and H ₂ at pressure. Indicated.

3 shows 85 wt% Zr-10 wt%, V-25 wt% Fe-2.5 wt%, for Ni alloys, at 3 × 10 ⁻⁶ Torr pressure, after preparation with a porous getter using the method of the present invention. The room temperature getter curves for CO and H ₂ are given in Example 2.

FIG. 4 shows 3 × 10 for two getter shapes made from different particle sizes using 70 wt%, Zr-25.5 wt% V-3 wt% Fe-1.5 wt% Ni-alloy according to the method of the present invention. Room temperature getter curves for CO and H ₂ at a pressure of ⁻⁶ Torr, pertaining to Example 3.

FIG. 5 shows CO and CO at a pressure of 3 × 10 ⁻⁶ Torr for a porous particulate getter of 70 wt% Zr-25.5 wt%, V-3 wt% Fe—1.5 wt% Ni composition prepared by the inventive method. Room temperature getter curve for H ₂ , relating to Example 4.

The present invention relates to a method of making a strong porous metallic getter and a getter made therein.

In particular, the present invention relates to a process for producing a non-evaporable getter that contains higher zirconium together with vanadium and other elements without being pulverized by conventional mechanical methods.

Non-evaporable getters are porous metal structures that are widely used for vacuum maintenance and purification of inert gases. Getters are treated by strong surface chemisorption of reactive gases such as H ₂ , CO, CO ₂ , H ₂ O, O ₂ , N _2, etc. In the case of H ₂ , in addition to dissociative surface compound adsorption, H atoms are actually introduced into the metal crystal lattice to form interstitial solutions and sometimes hydride phases. For all other reactive gases, the getter reaction is much limited to the metal surface at least near ambient temperature.

Thus, from the viewpoint of reactivity and capacity, the getter structure has desirable properties with porosity and large surface area. This property means that getters are generally manufactured by powder metallurgy methods. Also, in general, the getter structure must be mechanically strong to prevent fragmentation and atomization during rough service. Ease of powder preparation generally requires brittleness of the alloy: Typically the getter structure requires alloy toughness. One of the objects of the present invention as follows is to solve this apparent metallurgical problem.

Zirconium and vanadium element-mechanical alloys and intermetallic compounds have been found to have desirable getter properties.

In 1996, Peebler and Gulbransen published in Electrochemical Technology, Vol. 4, No. 5-6, pp. 211-215 showed that the intermetallic compound ZrV ₂ has excellent room temperature solubility in hydrogen. After the Charlotte Thiel, Davy Dove and jyakop (Shaltiel, Davidov and jacob) Fe is substituted prosthesis, that is, the general formula Zr (V ₁ -xFex) metal of the _second intermetallic compound of a ZrV ₂ in U.S. Patent No. 4,163,666 No. 1979 The H ₂ getter potential was described. The intermetallic compounds are obviously brittle and can be easily pulverized into powders by mechanical methods, but as mentioned above the brittle material is not expected to produce a generally robust sintered structure. In addition, the vanadium content of these materials is high, from 26 to 53% by weight. For H ₂ getters, the increase in V in the Zr-V alloy undesirably decreases the saturation at a given temperature and pressure. In addition, the increase in V increases the raw material cost.

Therefore, it is desirable to minimize the V content and maximize the Zr content.

Methods for achieving this purpose are described in Mendelsohn and Gruen, 1982, US Pat. No. 4,360,445. The inventors produced oxygen stabilized compounds containing Zr, V, Fe and other elements. Specific example is Zr _1.4 V _0.5 Fe _0.5 O _0.25 . The compound contains only about 14% by weight of V and 69% by weight of Zr, while containing a higher amount of Fe (15% by weight), which allows the inventors to increase the brittleness for fracturing and powdering the alloy. I'm saying. Since iron has a low affinity for hydrogen, large amounts of iron would be undesirable to reduce the hydrogen getter ability. In fact, the hydrogen capacity for the oxygen stabilized compound is not particularly high at low pressures.

The most successful methods of the Zr-V type getters are reported in 1982 US Pat. No. 4,312,669 to Boffito, Verosi and Figini (Boffito, Barosi and Figini).

The inventors have patented a Zr-V-Fe ternary getter alloy combination. The best of these alloys is 70% by weight Zr, 24.6% by weight V and 5.4% by weight Fe, which is sold under the trademark St-707 of SAES Getters SPA, Milan, Italy. do. 1984 by Boffito, Doni and Rosai, see Journal of less-common metals, Vol. 104, pp 149-157, this alloy consists of phase Zr (V _0.83 Fe _0.17 ) ₂ and α-Zr. That is, the alloy combination results in much more Zr than intermetallic Zr (V, Fe) _{2 with} better H ₂ and H ₂ O getter properties.

In addition, the presence of the soft α-Zr phase helps to increase the mechanical strength.

However, the alloy causes the problem of generating too much plastic material when transformed into fine powder, and therefore US Patent No. 4,312,669 limits the Zr content to 75% by weight or less. In addition, in 1981 United States Patent No. 4,269,624 for a method for producing such a three-way getter alloy, Figini was mechanically applied in all examples and claims so that the Zr content was 75 wt% or less after a conventional melting process. It is described as grinding (ball milling). Therefore, all known prior art reports that it is practically impossible to prepare powders in the preparation of Zr-V type getter alloys, wherein the Zr content is 75% by weight or more by the prior art methods.

The pulverizable 70 Zr -24.6 V -5.4 Fe alloy, St-707, is characterized by preliminary elemental Zr powder and pre-sintering prior to final sintering as described in St 172 Advanced porous gett published May, 1987, by SAES Getters SPA. The ground alloy powder may be mixed to produce a stronger getter shape. This reinforcement is useful but has certain drawbacks.

First, as in the case of the present invention, the mechanical mixture of such powders does not produce a strongly sintered structure as in the case of metallurgical incorporation of increased Zr during primary alloy melting.

This may be the preferred product of a denser mixture of phases that can be produced during metal alloy to mechanical mixing.

Second, elemental Zr powder is much more expensive than agglomerate Zr sponges applied during primary alloy melting. Third, the Zr mixing process is an additional manufacturing step that must be performed carefully in an inert atmosphere because of latent powder flammability.

As described below, the present invention prepares fine powders from a high Zr getter alloy, especially a Zr-V type (where Zr is 75% by weight or more; that is, the alloy is not actually finely divided by conventional methods). It completely solves the problem.

The inventors have found that such alloys are typically simply finely divided, and that metal ingots or pieces of ingots are reacted directly with hydrogen gas to produce hydrogen absorption, alloy brittleness, hydride formation and crystal lattice expansion, all of which add together the powder and Or spontaneous generation into small particles. The hydrogen thus introduced is continuously removed in large quantities by a vacuum / temperature method, producing a lower hydrogen alloy powder that is used directly for the production of sintered porous getters or for getters.

It is known to use hydrogenation, milling and then dehydrogenation, in order to produce usually ductile pure elemental powders such as Ti and Zr. In the case of Zr, it must be mechanically milled before actually dehydrogenating the Zr hydride. In contrast, the getter alloy used in the present invention does not have to be pulverized much to raise the temperature or to produce the powder for hydrogenation. These alloys react directly with H ₂ at room temperature to spontaneously produce powder. Although hydrogenation / dehydrogenation methods are used to produce Sm-Co and Nd-Fe-B magnetic alloy powders, these methods are too tough to produce Zr getter powders from alloys that cannot be ground by conventional mechanical methods. It was not available for.

It is a primary object of the present invention to provide an improved method for preparing getters comprising grinding of alloys that cannot be ground by conventional methods.

It is another object of the present invention to provide ternary and quaternary alloy combinations that are suitable for the processes included herein and result in improved getter properties in the product form.

Another object of the present invention is to provide a method for producing getter alloy powder with improved and increased surface area.

Another object of the present invention is to provide a method for producing getter powder having higher cleanliness and purity than can be obtained by a conventional mechanical grinding method.

Another object of the present invention is to provide a method for preparing getter powder, which is safer than a conventional milling method.

Another object of the present invention is to provide a method of making a sintered porous getter having improved mechanical strength.

It is another object of the present invention to provide a method for preparing getters which optionally produces a containing hydrogen which can be preferably released during activation.

Other objects are shown in the following specification, drawings, examples and claims.

The invention is best described by a series of manufacturing steps, some of which are designated and some of which are optional:

Step 1: Select Composition

The alloy according to the present invention is constituted in the widest range of 65 to 90% by weight of Zr, 10 to 35% by weight of V, and one or more of the following elements E (Fe, Ni, Mn, Al) to 7% by weight or less. Preferred levels consist of at least about 75 weight percent Zr, less than about 20 weight percent V, and less than about 5 weight percent E. All compositions within a wide range are used as good getters when prepared by the described continuous method. Preferred alloys cannot be finely divided by mechanical methods, but generally provide better getter properties. However, the best composition depends on the desired getter use. The compositions of the present invention should actually be considered in a wide variety of combinations. As shown in the following examples, it is important to contain element E in order to promote the manufacturing steps of the present invention and the improvement of getter properties. In addition, for Fe and Al, a flow amount Vector is provided to add element V in the form of an inexpensive V-Fe iron alloy or V-Al masteralloy.

Step 2: melting the alloy

Alloys related to the present invention should be prepared in the form of ingots by conventional metallurgical melting methods such as consumable electrodes or non-consumable arc melting or induction melting under vacuum or inert gas. Water-cooled copper crucibles are preferred. Oxide crucibles should not be used because of melt reactivity. The raw materials are commercially available pure elements or iron alloys and master alloys as described above.

Step 3: Hydrogen Differential

Prepare the hydrogen finely divided ingot produced in step 2. If the ingot is clean and free of oxides, no further ingot needs to be produced. If there is a significant oxide film on the surface, it is useful to clean the ingot with a metal base by sandblasting or grinding in order to easily introduce hydrogen in the final getter product and minimize the presence of oxidizing impurities. The entire ingot or its desired portion is placed in a hermetically sealed container. The vessel must be of a suitable material so that the vessel is not hydrogen brittle. Austenitic stainless steel is preferred.

Since the getter alloy will expand significantly during continuous H ₂ absorption, it is important to provide a porosity of at least about 60% in addition to the ingot. The vessel is sealed and purged with an inert gas (such as argon or helium), or with a vacuum pump that can achieve a maximum vacuum of preferably less than 100 millitorr, carefully removing air from the voids in the vessel. The inert gas purge or pump is then stopped and commercially available hydrogen gas is introduced into the vessel. This H ₂ introduction is carried out at room temperature at a convenient pressure in the range of 0.1 to 10 absolute pressures. For safety reasons, for containers capable of leaking accidental air, it is desirable to maintain H ₂ pressure above 1.0 absolute pressure (760 absolute torr). After incubation for less than 1 minute to over 1 hour, hydrogen begins to be absorbed into the ingot depending on the alloy composition and H ₂ pressure.

H ₂ is absorbed and the solid ingot spontaneously pulverizes into powder and / or small particles, affecting the hydrogen embrittlement, hydride phase formation and crystal lattice expansion of the alloy. The sound of this differential process is usually reliably heard through the walls of the vessel in the form of popping and cracking. In addition, hydrogen absorption is an intense exothermic reaction and the vessel will begin to heat rapidly. Without cooling, the temperature of the vessel reaches several hundred degrees Celsius. In order to maximize the H ₂ uptake, it is preferable to remove this heat, for example, by pressurized air or water cooling the reaction vessel. As H ₂ is absorbed, more H ₂ must be fed into the reaction vessel from the gas cylinder through the desired pressure regulator at the desired reaction pressure. The amount of hydrogen absorbed can be removed by lowering the pressure in the feed cylinder. H ₂ introduced should be continued until the absorption of H ₂ / g of a 0.006 to 0.011 mol of an ingot in the time that the ingot is finely divided well.

The H ₂ differential method, which is the subject of the present invention, has several advantages over the mechanical methods of crushing and grinding, such as jaw crushing, roller crushing, ball milling and the like. Above all, the method of the present invention makes it possible to finely classify higher Zr alloys which cannot be easily crushed and crushed by mechanical methods due to their high ductility or high strength. Also in the present invention, even a Zr-V type alloy having a lower Zr content that can be crushed and pulverized by conventional methods can be used. This alloy ignites and burns easily when mechanically crushed or crushed in air.

Therefore, to be safe and to prevent product loss, all mechanical grinding is preferably carried out in an inert atmosphere such as argon. Air leaking during crushing or pulverization also produces oxides and nitrides of Zr that affect the reduction in cleanliness and amount of the getter powder product. In addition, conventional grinding methods, such as ball milling, erode grinding media (eg, metal ceramic particles form grinding balls) to create more undesirable contaminants.

In addition, mechanical grinding causes wear of the particle surface, which is undesirable for continuous process steps or for maximum getter properties. Hydrogen derivatives solve all of these potential problems. This method is performed under protective H ₂ conditions to produce a getter powder that is not mechanical, very clean, and virtually free of chemical or particulate contaminants. In addition, the H ₂ fine powder produces a thinner form than mechanical grinding. Hydrogen fines are preferred because the hydrogen fines in the getter form a larger surface area per unit mass of powder and thus result in improved getter properties in the sintered getter product. The particle size of the hydrogen atomized powder can be influenced by the amount of H ₂ filled with the ingot during crushing. The higher the amount of H ₂ filled, the finer the powder produced. If necessary, repeated hydrogenation / dehydrogenation cycles further reduce particle size. In general, however, it is more practical to carry out a limited amount of mechanical grinding to achieve the desired particle size range as described in step 5.

Step 4: air stabilization (optional process)

The hydrogenated powder produced by step 3 is potentially autoignitable or flammable, depending on the composition and particle size, so if this step is not absolutely necessary, the preferred size fractionation and further milling (step 5) should be carried out in an inert atmosphere. . This is particularly true of the Al or Mn-containing compositions of the invention that are more autoignitable. However, it is desirable to handle or store hydrogen containing powders or granules in air under certain conditions. In this case, the powder must be stabilized against autoignition, which can occur due to sudden exposure to air.

The air stabilization process begins by completing pump _{3 and} then simply pumping or purging the gas H ₂ remaining in the hydrogen reaction vessel. In addition, hydrogen is separated from the powdery substance, and a small amount of endothermic cooling is observed below room temperature.

The exhaust vessel is then slowly backfilled with air over about one minute. The oxygen fraction of air chemisorbs on the surface of the hydride powder, and the reaction takes place slowly at room temperature. At several seconds to minutes, the atmosphere actually depletes oxygen. That is, essentially all N ₂ and Ar. This residual gas must be pumped out and the vessel backfilled with air. This process is repeated several times until no further temperature rise occurs in the furthest part of the powder bed due to air inflow. Since the hydride powder is now passed through oxygen (air stabilized), the reaction vessel can be exposed to air, and the powder contained therein can be removed with caution. Since hydride powders are potentially flammable, operators should always be careful when handling and handling them in the air.

Step 5: Size Sorting and Crushing

The powders and granules produced by step 3 are sieved or gas sorted into the range of particle sizes desired for the particular getter product required. If step 3 produces a coarser particle component than desired, it may be easily mechanically shredded using a motor or manual mortar and pestle to further reduce the product particle size. At this stage, the granules are large in hydride form, so they are typically very brittle and sometimes cracking to be able to reduce the particle size much more simply by mulling or tumbling. will be.

It is recommended that both size classification and grinding (if necessary) be carried out under an almost inert gas atmosphere to obtain safety and minimal product loss. Inert gases are noble gases, ie He, Ne, Ar, Kr and Xe, with Ar being the most practical and economical. Since Zr alloy powder burns in N ₂ and CO ₂ gas, N ₂ and CO ₂ are not preferred inert gases.

Step 6: hydrogen bakeout (optional process)

After performing step 5, it is generally desirable to remove most of the hydrogen in the powder in order to minimize H ₂ generation during the last sintering step before secondary processing and fine sintering. In some cases, however, it is possible to proceed to the final sintering step with a powder completely filled with hydrogen, which is considered an optional step.

The hydrogenated powder is transferred from the step 5 to a vacuum hermetic vessel, using a dynamic vacuum with a mechanical vacuum pump, and heating the vessel and / or powder therein to remove hydrogen. Hydrogen is desorbed and pumped off with a vacuum pump. In the absence of a vacuum pump, a flowing inert gas is optionally used to convey the desorbed H ₂ . The powder should be heated to 700 to 850 ° C. Exhaust or continue purging with inert gas until the equilibrium partial pressure is reduced at the bakeout temperature, preferably below 1 Torr. Depending on the amount of degassed powder, powder particle size, pump size and pump impedance factors, this process may require up to several hours. After the bakeout is complete, the vessel must be separated from the vacuum pump and cooled.

Note that this step is not intended to remove all of the H ₂ introduced in step 3. For example, a representative powder baked at 800 ° C. at a pressure of about 1 Torr still retains 3 to 5% of the hydrogen introduced in Step 3, ie 5 × 10 ⁻⁴ mols / g or 8 Torr / l / g . As described below, this residual H ₂ can be preferably used during final sintering.

In consideration of safety, the abundant amount of H ₂ released during this idle stage is also carefully placed by burning or venting at the outlet of the vacuum pump. In actual production, this hydrogen can be obtained and reused using a hydrogen / metal hydride press manufactured by Wyckoff Ergenics, Inc.

Step 7: air stabilization

It should be taken into account that the degassing powder produced from step 6 is potentially auto ignitable when suddenly exposed to air. Therefore, the air stabilization described in step 4 must be performed in this respect.

Step 8: Mulling

The degassing powder produced in step 6 is slightly sintered into a soft mass. Typically the powder is preferably fluid so that it can be sieved to approximately the same powder size after step 5 after some watering or tumbling. It is also preferred to carry out under almost inert gas conditions.

The principle of the present invention is to produce a sintered getter, but it is also possible to use low hydrogen hydrogen getter powder or granules produced for getter purposes under unsintered conditions. In other words, you can skip the next step. This method should also be considered within the scope of the present invention.

Step 9: Forming and Sintering

The getter powder produced by this method is secondary processed to the final getter product. First, the powder is pressed into a die of a preferred shape or filled with a suitable internal mold to form the desired shape. The raw powder form should be solidified at a higher temperature than used in step 6 to achieve the desired mechanical strength, but not so high that melting occurs and the porosity inherent to the sintered powder product is lost. Depending on the alloy composition and powder particle size, useful sintering temperatures are about 900 to 1200 ° C. In order to prevent damage or crushing of the getter powder and to promote effective sinter bonding, the sintering is carried out under vacuum or inert gas so that the effective partial pressure of all non-inert gases (except H ₂ ) is preferably less than 10 ^-5 Torr. . After sintering, the getter is cooled to room temperature in a vacuum or inert gas and exposed to air to prepare for use as a getter.

After step 6, the small amount of hydrogen remaining in the getter powder is actually removed to zero during the final high temperature sintering step. Venting this H ₂ during final sintering is desirable to clean the getter face and to remove undesirable residual gases (H ₂ O vapor and vacuum pump oil) from the getter. In fact, the getter is wrapped with a loosely fixed Zr-flake seal during sintering to increase the residence time of the protective H ₂ .

In applications, when manufacturing the getter device to release preferably during the activation step, it is desirable for the getter user to leave a small amount of hydrogen (eg, 10 to 500 cc-tor H ₂ ) of the final treated getter. Activation generally heat activates the getter under vacuum in an in situ near the final processing unit. H ₂ is useful for removing undesirable absorbers from the surface of the device. For example, carbon or bihydrocarbons can be reacted with H ₂ and converted to light gas (pumpable) hydrocarbons such as CH ₄ . It is also believed that H ₂ release during activation is useful to clean the getter face itself and to make it the most active condition of the continuous getter. Excess unused H ₂ can be removed by pumping during activation or gettered again during subsequent activation cooling. Therefore, the present invention provides a method for producing a getter, which optionally contains a measured amount of hydrogen, which can be distributed to the final getter type. In fact, the amount of hydrogen retained in the final getter can be easily adjusted by adjusting the H ₂ partial pressure during the sintering and post sinter cooling steps. Since H ₂ exhaust is an undesirable application, all H ₂ can be removed by complete vacuum sintering.

Hydrogen bakeout and sintering may optionally be carried out in the same step. That is, the hydrogenated powder of step 5 can be separated and proceed directly to step 9. In this case, the H ₂ exhaust should be carefully limited to the rate of reaction during sintering such that it is not rapid enough to introduce powder from the mold or undesirably react with the sinter plant components (eg, hydrogen brittle heating components). The getter product produced by this shortening method has a higher porosity, but has a lower soot density than that produced by the whole process including hydrogen pre-removal in step 6. Good getter properties alter this basic method.

The present invention uses high-Zr alloys, and because of their inherent strength and ductility, cannot be easily pulverized into powder form by conventional mechanical methods, thereby producing a mechanically strong getter product. Although the present invention is directed to alloys consisting primarily of Zr and V with smaller additions of elements such as Fe, Ni, Mn and Al, the method described herein also applies to other higher-Zr getter alloys. useful. The invention is further clarified by the following examples which are attached to the specification and which are part of the drawings. As various changes can be made from this aspect without departing from the spirit of the invention, these examples and figures are intended to illustrate and not to limit the preferred embodiments of the invention.

Example 1

Four getter alloys are prepared in a 25 g button type by melting elements of normal purity in a non-consumable electrode arc furnace in an argon atmosphere with the following composition:

All buttons that are metallurgically strong and non-hammerable are, in fact, considered non-crushable. Each is placed in a small pressurized container interchanged with a total of about 1 liter glass volume and pressure measuring transducer. Using a vacuum pump to evacuate air to less than 25 milli-torr, remove the valve from the vacuum pump, record the pressure change as a function of the time of hydrogen addition at about 1300 torr absolute pressure, observe the H uptake and plot it on the graph do. The sample reactor is maintained in an external pan near room temperature. As shown in FIG. 1, each button reacts with H within 28 hours after various incubations to absorb less H at least 0.01 mols / g. At the end of each experiment, the H pressure is reduced to about 130 absolute torr. The time required for saturation varies with each composition. Four-membered addition of Ni or Mn to the Zr-V-Fe ternary preferably promotes slightly H absorption. The quaternary alloy Zr-V-Al-Ni reacts with H most rapidly. After the reaction shown in FIG. 1 is completed, an air stabilization reaction is carried out. When the reactor was opened, it was found that each alloy desorbs into powder and fine particles, which are direct products of the hydrogen grinding process. The particles are ground slightly in a ceramic mortar and pestle, and continue until all of the resulting powder passes through a 230 mesh (63 μm) sieve. The powders are then placed in different reactors, and exhausted with a vacuum pump and heated to about 800 ° C. while H-rich exhaust is assured by an increase in the vacuum pressure and the sound of the vacuum pump. The pump is continued for several hours at 800 ° C. until the equilibrium (closed) pressure is below tormi at room temperature. Each sample is then cooled, air stabilized and removed from the reactor. Each sample is surface sintered into a soft mass and crushed slightly until it passes through a 230 mesh sieve.

Then, a small AlO-coated Mo-heater superimposed 450-550 mg of each powder sample into graphite centered to produce a hollow cylinder of approximately 7.5 mm outer surface diameter x 3.5 mm inner diameter x 7 mm height Fill around the coil. The filled mold is then placed in a vacuum furnace in a loose-fixed Zr thin box, depending on the composition. Sintering is carried out for 15 minutes at a pressure less than Thor and at 1050-1150 캜. After the sintering treatment, the samples are cooled to room temperature, removed in a vacuum furnace and separated from each graphite mold. The product is a strongly porous finished getter. To calculate the amount of each getter so produced, each must be tested according to the standard test method for non-evaporable getters as described in ASTM designation F 798-82. 3 × 10 for Co and H when the sample was activated under vacuum at 750 ° C. for 10 minutes using an embedded Mo heater. Measure the ratio-content curve at the test pressure of the tor. Reactivation is performed between each gas. The data from this test is shown in Figure 2. All samples show excellent getter properties for Co and H. It will also be appreciated the benefits for the particular composition. For example, alloy C (Zr-V-Fe-Mn) has the highest capacity for Co getters, while alloys A (Zr-V-Fe) and D (Zr-V-Al-Ni) are both better. H Gettering speed. What is shown is therefore the possibility of this alloy combination represented by the present invention for certain gases expected for various getter applications.

Example 2

A 25-g button of 85% Zr-10% V-2.5% Fe-2.5% Ni (weight ratio) designated herein as alloy E is prepared by the method described in Example 1 and hydrogenated in the same manner. After 40 hours the sample absorbed 0.0105 molar H / g and found to be successfully desorbed into powder and small granules. An essentially continuous process is carried out in the manner described in Example 1 to produce Mo-heated hollow cylinder getters of the same dimension. Sintering temperature is 1050 degreeC. The getter test is performed at room temperature under the conditions as indicated in Example 1 with the results shown in FIG. These data clearly indicate the successful application of the present invention to the above Zr-levels, particularly high content-Zr compositions, which can be mechanically ground into powder. In particular, the improvement in H gettering rate and Co getter degree of the quaternary Zr-V-Fe-Ni quaternary system by the increase of the Zr content and the decrease of the V content of the alloy E is compared with that of the alloy B of FIG. Record it.

Example 3

51 kg of ingot of 70% Zr-25.5% V-3% Fe-1.5% Ni (parts by weight), denoted as alloy F herein, was secondaryly processed into an electrode mechanically squeezed commercially available purity components and used in a conventional consumable electrode arc furnace. It is prepared by melting. It has been found that the composition consists of a relatively low content of Zr and a relatively high content of V and can be crushed by abrasion much on a mechanical crusher. After the ingot is crushed into a primary sized material, 3 kg is placed in a reactor which is evacuated and pressurized to about 2.4 atmospheres of H and held by a pressure regulator attached to the H feed cylinder. Within one minute, hydrogen absorption starts and the reactor makes a sound and the temperature rises. Within 10 minutes, the temperature of the sample reaches 550 ° C, and heat is generated by the H absorption reaction. After 3 hours, the reaction appears to be complete by absorbing a total of 0.0105 mols / g. After air stabilization, the reactor is opened to expose the finely divided granule powder mixture. The material is ground and sifted into two size components. (A) 80 mesh (177 μm) to 230 mesh (63 μm) and (B) 230 mesh or less, then both size fractions are treated by the method described in steps 6 to 8 to obtain a dehydrogenated powder (some of size B Collected in the hydrogenation type of Example 4). Some of the about 300 mg of dehydrogenated powder is compressed in a carbide die to produce pills about 6 mm in diameter and 2.5 mm thick. Some of about 500 mg of dehydrogenated powder are molded into Mo-heated hollow cylinders of the same dimensions as used in Examples 1 and 2. The product is sintered at 1150 ° C. under all vacuum and activated to 700-800 ° C. according to ASTM designation F 7980-82 above, followed by 3 × 10 Getter activity is tested at Thor Co and H. The velocity-content curve thus made is shown in FIG.

This data shows excellent properties for each getter product. This curve also shows that the present invention can be used to produce different particle sizes desirable for other final getter products. It also demonstrates the usefulness of the present invention for producing getters in alloys containing relatively low Zr and relatively high V. However, by comparing FIGS. 2 and 3 with FIG. 4, the low content Zr alloy F by comparison of its type and granule size generally has a lower gettering rate for H than high content Zr alloys A to E. It can be seen. This comparison enhances the particular utility of the present invention for producing hard to ground high-Zr compositions.

Example 4

A portion of the size B (minus 230 mesh) powder in the fully hydrogen filled state (ie after step 5) prepared in Example 3 is poured into an Inconel tray about 4-6 cm deep. This tray is then placed in a horizontal tube furnace to initiate argon gas flow. The tray is then heated to room temperature to about 1100 to 1150 [deg.] C. over about 2 hours, held at this temperature for at least about 2 hours, then transferred to a cold to tube and cooled to room temperature. The Ar flow is maintained for the whole while heating, leaving and cooling. Samples are air stabilized and tested. Slow cooling in flowing Ar removes H from the sample, and the powder layer is gravity sintered into a lightweight, highly porous plate. In essence, the method of this embodiment should be regarded as a shorthand method of the present invention, whereby the method comprising steps 6 to 8 is omitted. Thereafter, the plate produced by this abbreviated method is mechanically broken into granules having a size of about 10 mesh (2 mm). 3 × 10 after activation at 750 ° C. according to the ASTM test method used in the above examples 500 mg of sample at the pressure of Thor is tested for Co and H gettering properties. The resulting data is shown in FIG. Obviously this shorthand method allows the production of products with good gettering properties. In fact, the data of FIG. 5 is clear compared to the data of the labeled cylinder in FIG. 4, which is good because both are 500 mg of a sample of minus 230 mesh powder. This comparison points out that both the overall method and the abbreviated method of the present invention can be used for secondary processing of superior getters. The abbreviated method produces a getter product with higher porosity and lower mass density than the overall method, and the use of one method over another depends on the conditions of the application.

Claims (1)

E (where E is composed of Fe, Ni, Mn and / or Al) is 7% by weight or less, V is 10-35% by weight and Zr is 100% by weight in the remaining amounts of Zr, V and E Or a mixture of both of them in a furnace of vacuum or an inert gas and the resulting melt is cooled to form a solid alloy; Introducing this alloy into the chamber, thereby substantially removing air by dynamic vacuum or flowing inert gas medium; This alloy is filled with hydrogen for hydride formation to spontaneously finely powder the alloy into hydride powders or granules; Hydride powder or granules are mechanically ground to a desired size and sieved; The powder or granules are pressed in a die or filled with a suitable internal mold to form a getter of the desired form; At a temperature below the melting temperature in the range from 900 to 1200 ° C., the getter is sintered under dynamic vacuum or flowing inert gas such that the effective partial pressure of all non-inert gases (except H ₂ ) is less than 10 ⁻⁵ Torr; A method of making a highly porous non-evaporable getter consisting of cooling the getter to room temperature in a vacuum or inert gas.

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