GB2056490A

GB2056490A - Mercury releasing composition of matter, mercury releasing device and electron tubes made therewith

Info

Publication number: GB2056490A
Application number: GB8023400A
Authority: GB
Original assignee: SAES Getters SpA
Current assignee: SAES Getters SpA
Priority date: 1979-07-19
Filing date: 1980-07-17
Publication date: 1981-03-18
Also published as: IT1193796B; DE3027287A1; FR2462019A1; NL8004167A; GB2056490B; IT7924485A0; FR2462019B1; JPS5616649A

Abstract

A mercury releasing composition of matter comprising an alloy of titanium, copper and mercury has a high mercury content, is stable in air, and releases substantially all its mercury in a very short time on heating above 500 DEG C. An alloy is described whose composition in atom percent, when plotted on a ternary composition diagram in atom percent Ti, atom percent Cu and atom percent Hg lies within a polygon having as its corners the points defined by: (1) 70% Ti - 15% Cu - 15% Hg (2) 70% Ti - 22.1% Cu - 7.9% Hg (3) 31.2% Ti - 60% Cu - 8.8% Hg (4) 25% Ti - 60% Cu - 15% Hg (5) 25% Ti - 50% Cu - 25% Hg (6) 60% Ti - 15% Cu - 25% Hg. The alloy may be used to charge an electron tube with mercury.

Description

SPECIFICATION Mercury releasing composition of matter, mercury releasing device and electron tubes made therewith A large number of electron tubes require the presence of mercury vapour in order that they may function. Typical examples of such electron tubes include, among other, thyratrons, discharge display devices, numerical indicators, Nixi-tubes, fluorescent lamps etc. During some stage of their manufacture, it is therefore necessary to introduce mercury within the tube. Many methods have been proposed to accomplish this introduction of mercury.

for instance fluorescent lamps have been produced in which liquid mercury is allowed to drop into the almost finished lamp, which is subsequently sealed. Small glass or metal vials containing liquid mercury have also been used in the production of both fluorescent lamps and numerical indicators. The glass or metal vial is broken to release its mercury after the electron tube has been sealed. See U.S.

Patent No. 4,105,889. However, the use of liquid mercury dosing devices are apt to be "temperamental" and required frequent cleaning. The filling of vials with small (milligram) quantities of liquid mercury is troublesome and after breakage of the glass there my result in small pieces of loose glass within the electron tube which are deleterious to its functioning.

In order to avoid the use of liquid mercury, attempts have been made to seal mercury in the form of solids into the electron tube. Mercury amalgams have been used, for instance with indium, cadmium and other metals but this serves mainly to regulate the mercury vapour pressure when the tube is subject to working in a widely varying temperature ambient. Another method is to seal a predetermined amount of an inorganic compound of mercury in the tube. After evacuation and sealing of the tube, the inorganic compound is then caused to decompose. Such methods as described in U.S. Patent No.

1,855,901 , U.S. Patent No. 3,230,027, U.S. Patent No. 3,385,644 and U.S. Patent No. 3,401,296 are typical, but we have the disadvantage of producing undesirable quantities of noxious gases during mercury release.

More recently, the use of intermetallic compounds of mercury with such elements as Ti and Zr has been proposed. See for instance U.S. Patent No. 3,733,194, U.S. Patent No. 3,772,976 and U.S. Patent No. 3,657,589.

Mercury releasing devices employing such intermetallic compounds are obtainable commercially from SAES GETTERS S.p.A., Milan, Italy under the tradenames "GEMEDIS" and "STAHGSORB". They have the disadvantage of requiring an excessively long heating time (5 to 10 mins) in order to release 90% of their mercury content at 9000 C.

This time can be too long especially when tubes using the mercury releasing devices are being mass-produced very quickiy. Additional processing time can add substantially to the cost of the finished tube. Furthermore, additional energy is required for the heating process. As only a part of the mercury is released, there can be a fluctuation in the exact quantity released due to normal fabrication tolerances in, say, the temperature reached during heating.

In an attempt to overcome some of the deficiencies of these inter-metallic compounds, Japanese patent application publications Nos. 50-55181 to 50--55185, 50--56144, 50--56145 and 50-571 66 to 50-571 70 inclusive describe the alloying of zirconium or titanium with an additional metal (Me) before causing it to react with mercury. The additional metals (Me) described are Ni, Al, Mn, Si, Ge, V, Cr, and Fe.The amount of additional metal alloyed with the zirconium or titanium must be kept low enough so that after its reaction to form an intermetallic compound having the formula (Ti-Me, or Zr-Me) there remains enough free zirconium or titanium to laterform an intermetallic compound with mercury as the Ti-Me or Zr-Me does not react with mercury. Apparently, the Ti-Me (or Zr-Me) protects the alloy from oxidation during tube processing and stabilizes the alloy.

Unfortunately, since there is less free titanium available, the mercury content of the final Ti-Me-Hg or Zr-Me-Hg is considerably reduced.

Yet another ternary mercury alloy has been proposed in U.S. Patent No. 4,1 07,565. This alloy consists mainly of yttrium, nickel and mercury. It is claimed to be particularly useful when quick release of mercury is desirable. Its mercury content is, however, below a maximum of about 0.28 grams of mercury per gram of alloy.

A ternary intermetallic alloy of Ti, Cu, and Hg has been described in Japanese unexamined patent application publication No. 51-113452, which gives a publication date of October 6, 1976. This ternary alloy is said to be an intermetallic compound having a composition TiCuHg2. This structure has been described by M. Puselj and Z. Ban in the Journal of Less Common Metals Vol. 38 (1974), p.

15-18 and in Croatica Chemical Acta 41(1969), 79-83.

However, it has been found that this composition is not stable when left for long periods in air.

Furthermore, above 2000C the structure decomposes into TiHg and CuHg and above 3000C mercury starts to evaporate.

It is, therefore, an object of the present invention to provide a mercury releasing composition of matter which is stable on exposure to air.

It is another object of the present invention to provide a mercury releasing composition of matter which is able to release almost 1 00% of its mercury content.

It is yet another aobject of the present invention to provide a mercury releasing composition of matter which is capable of releasing its mercury content in a very short time.

It is another object of the present invention to provide a mercury releasing composition of matter which is stable up to 5000 C, and contains more than 25 wt% Hg.

It is another object of the present invention to provide a mercury releasing device employing compositions of the present invention.

It is yet another object of the present invention to provide a process for filling electron tubes with mercury using mercury releasing devices and compositions of the present invention.

Summary of the Invention It has been found that a certain class of Ti-cu-Hg alloys show superior properties when used as mercury releasing compositions. Such alloys have a composition which, when plotted on a ternary composition diagram in atom percent, lie within a polygon having as its corners the points defined by: (1)70%Ti-15%Cu-15%Hg (2) 70% Ti22.1 % Cu -7.9% Hg (3)31.2% Ti - 60% Cu - 8.8% Hg (4) Z5% Ti60% Cu- 15% Hg (5) 25% Ti50% Cu25% Hg (6) 60%Ti- 15% Cu 25% Hg.

These alloys are stable in air, do not release mercury below 5000 C, contain more than 25 wt% mercury and are able to release mercury over the temperature range 700-9000C within 30 seconds.

Furthermore, they release all their mercury in this short time which can be up to 0.5 g or more of mercury per gram of alloy.

Figure 1 is a ternary composition diagram showing, in atomic perce'nt, the range of compositions useful in the present invention.

Figure 2 is a perspective view showing one example of a mercury releasing device employing a composition of the present invention.

Figure 3a is a perspective view showing another example of a mercury releasing device employing a composition of the present invention.

Figure 3b is a plan view of yet another example of a mercury releasing device employing a composition of the present invention wherein the holder is a metal strip onto which the composition has been compression bonded.

Figure 4 is a graph showing the mercury emitting characteristics of the mercury releasing device shown in Figure 3 when heated for 30 seconds in a vacuum.

Figure 5 is a graph showing the mercury emitting characteristics of the mercury releasing device shown in Figure 3 when using another composition of the present invention.

Figure 6 is a graph showing the mercury emitting characteristics of the mercury releasing device shown in Figure 3 when using another composition of the present invention.

Figure 7 is a graph showing the mercury emitting characteristics of the mercury releasing device shown in Figure 3 when using another composition of the present invention.

Figure 8 is a graph showing the mercury emitting characteristics of the mercury releasing device shown in Figure 3 when using another composition of the present invention.

Figure 9 is a graph showing the mercury emitting characteristics of the composition used in obtaining Figure 5 except that a heating time of 5 minutes was used.

Figure 10 is a graph showing the mercury emitting characteristics of the composition used in obtaining Figure 7 except that a heating time of 5 minutes was used.

The mercury releasing composition of matter of the present invention comprises a ternary alloy of titanium, copper and mercury. If the composition of the alloy is within certain limits it has been found that the alloy ie extremely stable up to 5000 C, i.e., it does not release a detectable amount of mercury below that temperature. Furthermore, the compositions release 100% of their mercury content when heated to 9000C for the very short time of 30 seconds.

The preferred alloys have a composition which, when plotted on a ternary composition diagram in atom percent, lie within a polygon having as its corners the points defined by: (1)70%Ti-15%Cu-15%Hg (2) 70% Ti22.1 % Cu7.9% Hg (3) 31.2% Ti - 60% Cu - 8.8% Hg (4) 25% Ti - 60% Cu- 15% Hg (5) 25% Ti - 50% Cu - 25% Hg (6) 60%Ti- 15% Cu - 25% Hg The most preferred alloys have a composition which, when plotted on a ternary composition diagram in atom percent, lie within a polygon having as its corners the points defined by:: (1) 45% Ti - 35% Cu - 20% Hg (2) 56.8% Ti - 35% Cu - 8.2% Hg (3) 36.3% Ti - 55% Cu - 8.7% Hg (4) 30% Ti - 55% Cu - 15% Hg (5) 30% Ti - 50% Cu - 20% Hg.

The alloy compositions are preferably used in powder form and should pass through a screen of 35 mesh (500 Stt) and more preferably through a screen of 70 mesh (210,u). The powder may be compressed into pellet form or placed in a u-channel ring shaped container. Alternatively, it may be compression bonded onto a metal support as described in U.S. Patent No. 3,652,317.

Certain alloys of the present invention can conveniently be prepared starting from the intermetallic compounds Ti2Cu or TiCu.

One especially preferred composition of the present invention is an alloy of titanium, copper, and mercury wherein the atomic ratio of Ti:Cu is 2:1 and the atom percentage of Hg is from 8.1 to 25% based ona the combined weight of Ti, Cu and Hg. Another especially preferred composition of the present invention is an alloy wherein the atomic ratio of Ti:Cu is 1:1 and wherein the atom percentage of Hg is from 8.4 to 25% on the same basis.

The following examples will iilustrate the preparation and use of compositions of the present invention and their comparison with known mercury releasing compositions. Table I summarizes the prior art alloys prepared for comparative purposes and tested for mercury releasing properties. Table II summarizes the alloys of the present invention prepared and tested for mercury releasing properties.

TABLE I COMPARATIVE ALLOYS

1 2 Wt % composition Wt % composition of of reproduced alloy US No. 4,107,565 alloy Alloy Identification Y Ni Hg Y Ni Hg Notes A 21.9 50.6 27.5 23 53.3 23.7 As per Example 3 of USP 4,107,565 B 24.3 48.1 27;;6 24.4 48.5 27.1 As per Example 2 of USP 4,107,565 C 20.7 54.7 24.6 19.8 52.2 28 As per Example 1 of USP 4,107,565 TABLE II Composition wt. % Composition Atomic % Alloy Identification Ti Cu Hg Ti Cu Hg Notes 1 39.5 17,5 43,0 62.7 21.0 16.3 Mercury release curves reported in Figs 5 & 9 2 29.5 19.5 51 52.3 26.1 21.6 Mercury release curve reported in Fig. 4 3 32.2 21.4 46.4 54.2 27.2 18.6 4 28.4 37.7 33.9 43.7 - 43.8 12.5 5 40.2 15.1. 44.7 64.6 18.3 17.1 6 24.6 32.5 42.9 41.4 41.3 17.3 Mercury release curve reported in Fig. 6 7 31.4 41.6 27.0 45.4 45.3 9.3 Mercury release curve reported in Fig. 8 8 . 33.2 29.4 37.4 51.6 34.5 13.9 9 28.8 38.0 33.2 44.1 43.8 12.1 10 28.9 38.1 33.0 44.1 43.9 12.0 11 21.3 42.4 36.3 34.4 51.6 14.0 Mercury release curve reported in Figs 7 & 10 EXAMPLE 1 This comparative example describes an attempt to produce a mercury dispensing composition as described in Japanese Patent Application Publication No. 51-113452. Following the procedure described in this.Japanese publication 5 g of intermetallic compound TiCu with a powder size less than 200 mesh (74,u) were placed in a quartz tube together with 20 g mercury. The sealed quartz tube was heated for 6 hours at 7800C and then opened after cooling. An amount of unreacted mercury was put aside and part of the remaining powder was subjected to a vacuum distillation.

The powder was slowly heated up to 3500C with the following temperature cycle: a) room termperature to 2000C for 10 minutes b) 2000C to 2500C for 5 minutes c) 2500C to 3800C for 2 minutes d) 3800C to 3500C for 13 minutes.

At each stage continuous evolution of mercury was observed even after the cooling step from 3800C to 3500C. On removal of the powder it was found to have lost 40% in weight showing that it was unstable even at low temperatures. See also the paper by Puselj and Ban in Croata Chemica Acta cited above.

A comparison of the alloys of the present invention is, therefore, not possible with the TiCuHg2 alloy as described in Japanese Patent Application No. 51-113452. Alloys of yttrium, nickel and mercury were prepared for comparison purposes according to U.S. Patent No. 4,107,565.

EXAMPLE 2 A prior art yttrium, nickel and mercury ternary alloy 'A' was prepared, for comparative purposes, substantially as described in Example 3 of U.S. Patent No. 4,1 07,565. The absolute quantities of the metals used were smaller but the ratios were maintained.

The composition of alloy 'A' is given in Table I, Column 1, whereas the composition originally obtained in Example 3 of the above U.S. Patent is given in Column 2.

EXAMPLE 3 A prior art yttrium, nickel, and mercury ternary alloy 'B' was prepared, for comparative purposes, substantially as described in Example 2 of U.S. Patent No. 4,107,565. The absolute quantities of the metals used were smaller but the ratios were maintained.

The composition of alloy 'B' is given in Table I, Column 1, whereas the composition originally obtained in Example 2 of the above U.S. Patent is given in Column 2.

EXAMPLE 4 A prior art yttrium, nickel and mercury ternary alloy 'C' was prepared, for comparative purposes, substantially as described in Example 1 of U.S. Patent No.4,107,565. The absolute quantities of the metals used were smaller but the ratios were maintained.

The composition of alloy 'C' is given in Table I, Column 1, whereas the composition originally obtained in Example 1 of the above U.S. Patent is given in Column 2.

EXAMPLE 5 This example describes the preparation of a ternary alloy of the present invention.

2.12 g of Ti powder of particle size less than 37 y mixed with 0.94 g of powdered copper having a purity of greater than 99.5% and 2.95% g of mercury were placed in an iron crucible which was then sealed under argon. The iron crucible was placed in a vacuum furnace and heated slowly to 9000 C. On reaching 9000 C, the crucible was agitated vigorously for a short time and then maintained at 9000C for 5 hours. The crucible was then allowed to cool slowly to room temperature, opened, and degassed at 1 400C for 90 minutes to remove any unreacted mercury.The alloy was then ground to a particle size of less than 210 y. The composition was chemically analyzed for mercury content, the Ti and Cu contents were calculated from the proportions of these components in the original mixture. The results of the analysis are reported in Table II as alloy No. 1.

EXAMPLE 6 This example describes the preparation of a ternary alloy of the present invention.

5.32 g of Ti powder of particle size less than 44 y mixed with 3.53 g of powdered copper having a purity of greater than 99.5% and 11.15 g of mercury were placed in a quartz phial and sealed under vacuum. The phial was placed in a vacuum furnace and heated to 400"C for 1 6 hours. The temperature was increased to 7000C for 7 hours and then cooled to 4000C for 20 hours. The phial was then allowed to cool to room temperature and the alloy removed and ground to a particle size of less than 210 y and the Hg content analyzed. After a degassing to remove free Hg from a preweighted small sample in vacuum at 4000C for 10 minutes, the mercury loss was determined by reweighing the sample and the Ti and Cu contents were calculated. The composition is reported in Table II as alloy No. 2.

EXAMPLE 7 9 g of the intermetallic compound Ti2Cu having a particle size less than 37 w was placed in a quartz aphial with 9 g of mercury and sealed under an atmosphere of 300 torr (4 x 104 Pa) of argon.

The phial was placed in a vacuum furnace and over a period of several hours was brought upto a temperature of 7000C which was then maintained for 2 1/2 hours, after which the phial was allowed to cool slowly to room temperature. After grinding to a particle size of less than 210 y and degassing in vacuum at 4000C for 10 minutes, the alloy had a composition as reported in Table II as alloy No. 3.

EXAMPLE 8 Example 7 was repeated except that the Ti2Cu was replaced by the intermetallic compound TiCu (9 g) and the temperature of 7000C was maintained for 31 hours. After degassing, the alloy had a composition as reported in Table II as alloy No. 4.

EXAMPLE 9 Example 8 was repeated except that the TiCu intermetallic compound was replaced by 7.2 g of Ti having a particle size less than 44 y in mixture with 2.7 g copper powder and the weight of mercury was 8.1 g. After degassing, the alloy had a composition as reported in Table II as alloy No. 5.

EXAMPLE 10 Example 9 was repeated using 3.87 g Ti, 5.13 g Cu and 9.01 g Hg. However, in this case, a final temperature of 7500C was maintained for 3 2 hours. After degassing, the alloy had a composition as reported in Table II as alloy No. 6.

EXAMPLE 11 Example 10 was repeated using 14.92 g Ti, 19.83 g Cu and 25.20 g Hg. Instead of a quartz phial, the component metals were placed in a stainless steel crucible within a hermetically sealed stainless steel cylinder. After degassing, the alloy had a composition as reported in Table II as alloy No. 7.

EXAMPLE 12 Example 10 was repeated using 3.37 g Ti, 6.71 g Cu and 7.92 g Hg. The final temperature of 7500C was, however, maintained for 4- hours. After degassing, the alloy had a composition as reported n Table II as alloy No. 8.

SAMPLE 13 187.5 g of Ti powder having a particle size of less than 44 y was intimately mixed with 247.5 g of u powder. The mixture was placed in a stainless steel crucible with 31 5 g of Hg. The crucible was pealed within an iron cylinder under an inert atmosphere. The cylinder was placed in a vacuum furnace and its temperature raised slowly to 7500C over a period of 5 hours. After 3 hours at 7500 C, the :ylinder was allowed to cool to room temperature and the cylinder was opened. The resulting alloy was :hen heated under vacuum to 3200C to remove any unreacted mercury.After grinding to a particle size ess than 210 y and after further degassing at 4000C for 10 minutes, the alloy had a composition as reported in Table II as alloy No. 9.

EXAMPLE 14 20 g of Ti powder having a particle size of less than 44 ju were mixed with 26.4 g of Cu powder rnd were placed together with 33.6 g of mercury in an iron crucible which was then placed in an iron :ylinder which was hermetically sealed under an argon atmosphere of less than 500 torr (6.7 x 104 Pa).

The cylinder was placed in a vacuum furnace whose temperature was increased slowly over a period of 5 hours to reach 7800C which temperature was maintained for 8 hours. The resulting alloy was then heated under vacuum to remove any unreacted mercury and after grinding to a particle size ess than 2-10 was subjected to 4000C for 10 minutes. The alloy had a composition as reported in rable II as alloy No. 10.

EXAMPLE 1 5 3.37 g of Ti powder having a particle size of less than 44 fz were mixed with 6.71 g of Cu powder and were placed together with 7.92 g of mercury in a quartz phial and sealed under an atmosphere of 300 torr (4 x 104 Pa) of argon. The phial was placed in a vacuum furnace whose temperature was aised to 7000C over a period of 3 2 hours. This temperature was maintained for 46 hours after which :he phial was allowed to cool to room temperature.

The still sealed phial was then placed in a stainless steel cylinder which was hermetically sealed.

Phe steel cylinder was placed in a vacuum furnace whose temperature was raised to 7800C over a period of 5+ hours. This temperature was maintained for 4+ hours after which the cylinder was allowed to :ool to room temperature. The alloy obtained was subjected to a first degassing at 3800C for 30 ninutes and then after grinding to a particle size of less than 210 zz to a second degassing of 4000C for 10 minutes. The alloy had a composition as reported in Table II as alloy No. 11.

Referring now to the figures and in particular to Figure 1, there is shown a ternary composition diagram in atom percent showing the positions on the diagram of the alloys 1 to 11 of Ti-Cu-Hg of :he present invention reported in Table II and whose preparations were described in Examples 5 to 1 5.

The heavy lines indicate the boundaries of the preferred and most preferred composition ranges of the alloys of the present invention.

Figure 2 shows a pill 20 formed by pressing the powdered alloys of the present invention in a nould.

Figure 3a shows a mercury releasing device 30 comprising a U-shaped cross-section channel ring older 32 into which is compressed a mercury releasing alloy 34 of the present invention.

Figure 3b shows a mercury releasing device 36 comprising a metal support strip 37 onto which iave been compression bonded particles 38 of the mercury releasing alloy of the present invention.

Figures 4-10 show the mercury releasing characteristics of various alloys of the present nvention when tested according to the following method, compared with the characteristics of prior art alloys tested using the same method.

A U-shaped cross-section channel ring holder of approximately 12 mm external diameter and containing a known weight of about 1 00--1 500 mg of the mercury dispensing alloy, which has been Jegassed at 4000C for 10 minutes to remove any free mercury, is supported by means of a hermocouple within a continuously pumped vacuum system (about 10-4 torr = 1.33 x 10-2 Pa). The ing is then quickly heated to the desired test temperature and heating is continued for a total time of ither 30 seconds or 5 minutes. When the ring has cooled down the weight loss, i.e., the quantity of Hg 'eleased, is determined.The test is repeated a further two times and the average value of the 3 test results, expressed as a percentage of the alloy mercury content, is plotted on a graph of "%Hg loss" vs.

'temperature".

Figure 4 shows the mercury releasing characteristics of alloy 2 as line 40 when the ring is heated or a total time of 30 seconds.

Figure 5 shows the mercury releasing characteristics of alloy 1 as line 50 when the ring is heated or a total time of 30 seconds.

Figure 6 shows the mercury releasing characteristics of alloy 6 as line 60 when the ring is heated or a total time of 30 seconds.

Figure 7 shows the mercury releasing characteristics of alloy 11 as line 70 when the ring is heated or a total time of 30 seconds.

Figure 8 shows the mercury releasing characteristics of alloy 7 as line 80 when the ring is heated for a total time of 30 seconds.

Figure 9 shows the mercury releasing characteristics of alloy 1 as line 90 when the ring is heated for a total time of 5 minutes.

Figure 10 shows the mercury releasing characteristics of alloy 11 when the ring is heated for a total time of 5 minutes.

Figures 4-8 also show the mercury releasing characteristics of three prior art alloys A, B and C (see Table I) when the ring is heated for a total time of 30 seconds.

Figures 9 and 10 also show the mercury releasing characteristics of three prior art alloys A, B and C (see Table I) when the ring is heated for a total time of 5 minutes.

As can be seen from Figures 4 to 1 0, the alloys of the present invention are more stable than the prior art alloys at the lower temperature when heated for equal times. At higher temperatures, when the release of mercury becomes significant, the alloys of the present invention release a larger percentage of their mercury content and even in the very short time of 30 seconds at 9000C they release 100% of their mercury content, furthermore their mercury content is higher than that of the prior art alloys.

For instance, alloy 6 of Table II contains 42.9 by weight of mercury. As shown by line 60 in Figure 6 at 9000C, in 30 seconds all its mercury had been released. Thus, if a dispenser ring containing 100 mg of alloy 6 is used to release mercury a weight of 42.9 mg would be released. With a ring using prior art alloy B, under the same conditions, 1 00 mg of the alloy would release only 60% of its mercury content which from Table I is seen to be 27.6% of the alloy weight, i.e., only 16.6 mg Hg would be released.

Even when longer heating times are used, such as 5 minutes (Figures 9 and 10), the alloys of the present invention release at least the same percentage of their Hg content at intermediate temperatures (Figure 9 from 60000 - about 8500C) and, therefore, have the advantage of releasing a greater quantity of mercury. At 9000C, the alloys release 100% of their mercury content compared to about 83% for the prior art alloys.

When manufacturing an electron tube, which requires mercury in its atmosphere, a desired quantity of an alloy of the present invention, based on the amount of mercury required, is introduced within the tube. This can be done at any suitable production step, but usually before the final baking step. This baking step usually occurs at temperatures up to about 5000C and is used to degas the tube components. The alloy is introduced in any suitable form such as compressed powder pellet, held within a ring or compression bonded onto a metallic strip. After the baking stage, which usually takes place under vacuum, the tube is sealed. Just before sealing other gases can be introduced into the tube if required.In order to release mercury, the alloy is then heated by any suitable means to over 5000C and usually up to about 900--9500C. Higher temperatures are usually avoided as damage may otherwise occur to other components within the tube. Heating can be accomplished by directing laser radiation onto the alloy or its holder. Infra-red radiation could be used or an electric current could be passed through the holder. High frequency induction heating is a commonly used method for heating. After Hg release, the tube is generally tested to ensure that it functions correctrly whereupon it is ready for use.

Although the invention has been described in considerable detail with reference to certain preferred embodiments thereof, it will be understood that variations and modifications can be effected within the spirit and scope of the invention as described above and defined in the appended claims.

Claims

1. A mercury releasing composition of matter comprising an alloy of titanium, copper and mercury whose composition in atom percent, when plotted on a ternary composition diagram in atom percent Ti, atom percent Cu and atom percent Hg lies within a polygon having as its corners the points defined by: (1) 70%Ti- 15% Cu- 15% Hg (2) 70% Ti - 22.1% Cu - 7.9% Hg (3) 31.2% Tia60% Cu8.8% Hg (4) 25% Ti60% Cu15% Hg (5) 25% Ti50% Cu25% Hg (6) 60%Ti- 15% Cu25% Hg.

2. A mercury releasing composition of matter comprising an alloy of titanium, copper and mercury whose composition in atom percent, when plotted on a ternary composition diagram in atom percent Ti, atom percent Cu and atom percent Hg lies within a polygon having as its corners the points defined by: (1) 45% Ti35% Cu20% Hg (2) 56.8% Ti - 35% Cu - 8.2% Hg (3) 36.3% Ti -- 55% Cu -8.7% Hg (4) 30% Ti55% Cu- 15% Hg (5) 30% Ti -- 50% Cu - 20% Hg.

3. A mercury releasing composition of matter comprising an alloy of titanium, copper and mercury wherein the atomic ratio of Ti:Cu is 2:1 and the atomic % of Hg is from 8.1 to 25% based on the combined weight of Ti, Cu and Hg.

4. A mercury releasing composition of matter comprising an alloy of titanium, copper and mercury wherein the atomic ratio of Ti:Cu is 1:1 and the atomic % of Hg is from 8.4% to 25%, based on the combined weight of Ti, Cu and Hg.

5. A mercury releasing device comprising a holder and a mercury-releasing composition carried by the holder wherein the composition comprises an alloy of titanium, copper and mercury whose composition in atom percent, when plotted on a ternary composition diagram in atom percent Ti, atom percent Cu and atom percent Hg lies within a polygon having as its corners the points defined by: (1) 7O%Ti-15%Cu-15%Hg (2) 70% Ti--22.1 % Cu--7.9% Hg (3) 31.2% Ti -- 60% Cu -8.8% Hg (4) 25% Ti60% Cu15% Hg (5) 25% Ti50% Cu25% Hg (6) 60% Ti -- 15% Cu25% Hg

6.A mercury releasing device comprising a hqlder and a mercury releasing composition carried by the holder wherein the composition comprises an alloy of titanium, copper and mercury whose composition in atom percent, when plotted on a ternary composition diagram in atom percent Ti, atom percent Cu and atom percent Hg lies within a polygon having as its corners the points defined by: (1) 45% Ti35% Cu20% Hg (2) 56.8% Ti - 35% Cu - 8.2% Hg (3) 36.3% Ti -55% - 8.7% Hg (4) 30% Ti -- 55% Cu - 15% Hg (5) 30% Ti50% Cu20% Hg

7. A method for charging an electron tube with mercury comprising the steps of: I Inserting into the tube a mercury releasing composition of Claim 1 and then, II heating the composition to release mercury.

8. A method for charging an electron tube with mercury comprising the steps of: I In serting into the tube a mercury releasing composition comprising an alloy of Ti, Cu and Hg wherein the atomic ratio of Ti:Cu is 2:1 and the atomic % of Hg is from 8.1% to 25% and then, II evacuating the tube and then, Ill sealing the tube and then, IV heating the composition to a temperature of greater than 500 C for a time of less than 5 minutes to release mercury.

9. A method for charging an electron tube with mercury comprising the steps of: I Inserting into the tube a mercury releasing composition comprising an alloy of Ti, Cu and Hg wherein the atomic ratio of Ti:Cu is 1:1 and the atomic % of Hg is from 8.4% to 25% and then, II evacuating the tube and then, Ill sealing the tube and then, IV heating the composition to a temperature of greater than 500 C for a time of less than 5 minutes to release mercury.

10. An electron tube containing mercury and the residue of an alloy of Claim 1 from which the mercury came.

11. An alloy having a composition as specified in any one of claims 1 to 4.

12. An alloy having a composition as specified in claim 1 and specifically described herein.

13. An alloy having a composition as specified in Table II herein.

14. An alloy as claimed in any one of claims 11 to 13 which is capable of passing through a screen of 35 mesh.

1 5. A device comprising a holder and an alloy as claimed in any one of claims 11 to 14 carried by the holder.

16. A method for charging an electron tube with mercury which comprises introducing into the tube an alloy as claimed in any one of claims 11 to 14 and heating the alloy to release the mercury.

1 7. A method for charging an electron tube with mercury which comprises introducing into the tube an alloy as claimed in any one of claims 11 to 14, evacuating the tube, sealing the tube, and heating the alloy to a temperature of greater than 5000C for a time of less than 5 minutes to release mercury.

1 8. An electron tube containing mercury and the residue of an alloy as claimed in any one of claims 11 to 14 from which the mercury came.

19. A method for preparing an alloy as claimed in claim 11 carried out substantially as described herein.

20. Each and every new and novel feature disclosed herein.