JPS6115545B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a mercury release structure in which a cage holds an alloy mainly composed of a novel intermetallic compound.

Conventionally, when filling a tube, such as a Nixie tube or a low-pressure mercury vapor discharge tube, with mercury, a fixed amount of mercury was supplied into the tube from a so-called mercury doser through a supply pipe and an exhaust pipe. However, with this method, it is extremely difficult to accurately weigh out the several milligrams to tens of milligrams of mercury needed for the tube and seal it inside the tube, as mercury has a very high surface tension. It was hot. Furthermore, when mercury is sealed into the bulb through the supply pipe, a considerable amount of mercury adheres to the filling path such as the supply pipe and the exhaust pipe, making it impossible to fill the tube. The amount of mercury that has adhered to this filling path is a few tenths of the amount of mercury that was weighed out, as the amount of mercury that has adhered to this filling path is packed into the tube as it is filled several times. It varies between several times. Therefore, to ensure that the required amount is filled, several times the amount of mercury is weighed out and filled. Therefore, mercury is wasted, and a large amount of money is required to collect and remove the mercury attached to the sealing residue of the exhaust pipe to prevent pollution.Furthermore, the tubes that are discarded after use are subject to the above-mentioned For some reason, a large amount of mercury is encapsulated, and if the treatment is incomplete, there is a risk of environmental problems.

Additionally, since mercury is a liquid, it is easily spilled on the floor during handling, and the temperature at tube manufacturing sites is higher than normal working environments, so if mercury spills, there is a risk that mercury vapor will contaminate the working environment. There is also.

Encapsulating mercury as a solid is a highly preferred method since it can solve the above-mentioned drawbacks. As an example of this, the following method has been proposed.

A first example is a method of filling mercury in an amalgam with isodium, cadmium, or other metals. The original purpose of this method is to regulate the mercury vapor pressure inside the bulb by amalgamating it, and it is suitable for low-pressure mercury vapor discharge tubes used mainly in high-temperature environments, but The low-pressure mercury vapor discharge tube used below has the disadvantage that the mercury vapor pressure inside the tube is too low to be used.

A second example is to seal a certain amount of mercury in the form of an inorganic compound inside a tube, and after sealing the exhaust, separate the inorganic compound by heating from outside the tube, such as high-frequency heating. This is a method in which a certain amount of mercury is liberated within the tube, and at the same time, unnecessary harmful gases such as oxygen and sulfur compounds released are combined with appropriate metals such as titanium, zirconium, iron, etc. US Pat. No. 1,855,901 uses mercury sulfide and iron. Also US Patent Nos. 3230027 and 3385644
This method uses mercury oxide and a reducing metal. Further, US Pat. No. 3,401,296 discloses a method using mercury pyrophosphate and a reducing metal.

All of the examples in the above US patents cannot be put to practical use because they pose a risk of emitting harmful gases during heating. In particular, fluorescent lamps use more mercury than Nixie tubes, so they emit a large amount of harmful gas when heated, making them difficult to put into practical use.

The third example is that Mr. Bowl Pietrokowski
A compound of titanium, zirconium, and mercury described in a paper published in the Journal of Metals in February 1954, including TiEg, ZrHg, γ-Ti ₃ Hg, δ-
This is a mercury-releasing getter in which a cage holds a stable intermetallic compound such as Ti ₃ Hg. These are U.S. Patent No. 3733194: U.S. Patent No. 3722976: U.S. Patent No.
3657589: Described in Japanese Patent, Special Publication No. 49-5659.

The mercury-releasing getter described in these patents has recently been developed by SAES, Italy, under the trade name GEMEDIS, by crimping γ-Ti ₃ Hg powder onto one side of a nickel-plated iron ribbon, and applying Zr-A to the other side.
It was released by crimping a getter type alloy.

However, this method has the drawback that the mercury release rate is slow at low temperatures, and the metal constituting the cage evaporates at high temperatures. In other words, the technical report TR-22 provided by the Italian company SAES
According to the description in Figure 2 on page 5, it is stated that it takes 10 minutes to release 90% of the mercury by heating it at 900°C in a vacuum of 10 ^-4 mmHg.
However, this cannot be applied to the current tube manufacturing process, which operates at high speeds such as one tube per few seconds. Also, according to the same page of the same report, heating at 900°C ± 100°C for 15 to 30 seconds releases 70 to 80% of mercury. However, when this GEMEDIS (trade name) is heated too much, the cage material, such as nickel, evaporates and adheres to the tube wall and cathode material, deteriorating the tube characteristics.

Furthermore, in terms of manufacturing operations, it is difficult to strictly control the mounting position of the retainer on the mount. Therefore, it is difficult to keep the temperature of the cage constant during high-frequency heating, and it varies depending on variations in the assembly position.

Therefore, unless the temperature of the cage is set lower than 900°C, the cage will be overheated and the material forming the cage will likely evaporate.

Furthermore, in a low-pressure mercury vapor discharge tube, an inert gas such as argon gas is sealed in the tube at 2 to 3 mmHg. Under such conditions, the above-mentioned mercury release rate slows down, and in reality, it is difficult to release 75% or more of mercury even under good conditions. Therefore, the amount of encapsulated mercury decreases only slightly.

A fourth example is the use of an alloy of magnesium, nickel, and mercury, as described in US Pat. No. 3,318,649.

According to this patent, the proportion of mercury is 15% by weight.
However, if the above-mentioned alloy is used, mercury is liberated during the heating and exhausting process during the bulb manufacturing process and is released into the atmosphere, polluting the environment, making it unusable.

The present invention was made based on the above circumstances, and aims to provide a mercury release structure that can rapidly release most of the mercury at a relatively low temperature. The present invention consists in using the novel intermetallic compounds shown. In the above general formula, R has at least one of gadolinium, lanthanum, cerium, and samarium as a main constituent element.

When such an intermetallic compound is held in a cage together with an evacuation getter, installed in a tube, and subjected to high-frequency heating to release mercury, RxNig after releasing mercury is selective to oxygen and hydrogen. Since it exhibits a getter action, it has the advantage of preventing the evacuating getter from being oxidized and reducing its ability to adsorb relatively inert gases such as nitrogen.

The mercury release structure of the present invention includes an alloy whose main component is an intermetallic compound and a cage that holds the alloy. The alloy whose main component is an intermetallic compound, which is the main part of the present invention, will be explained below.

That is, the present inventors have discovered that a novel intermetallic compound can be obtained by reacting an intermetallic compound of a rare earth element and nickel with mercury. Furthermore, it has been discovered that this new intermetallic compound has very good mercury release properties, which are necessary when applied, for example, to tubes. Since no applications have been developed for intermetallic compounds of rare earth elements and _nickel , there is a _lack of reliable data.
Gd ₂ Ni ₇ and other mole ratios of gadolinium and nickel of 1:21, 1:25, 1:4, 1:
45, we prepared a 1:5 alloy and attempted to react with mercury.

We also prepared alloys of lanthanum, cerium, and samarium at each of the above molar ratios, and attempted to react with mercury.

When an alloy of gadolinium and nickel was reacted with mercury, a product other than the reaction product of GdNi ₂ and mercury was obtained that was sufficiently stable for practical use.

The same was found to be true for lanthanum, cerium and samarium.

Next, regarding embodiments of the present invention, FIGS. 1, 2,
This will be explained with reference to FIGS. 5 to 11.

Example 1 157.3 grams of gadolinium and 122.7 grams of nickel are placed in an aluminum crucible and heated to approximately 1500°C in a high frequency vacuum melting furnace to melt them. 500 for dissolving
A vacuum is maintained until the temperature reaches 500°C, and when the temperature exceeds 500°C, argon gas is introduced to create a pressure of 1 atmosphere inside the furnace, and the temperature is raised to 1500°C while preventing evaporation. Once dissolution is complete, cool at a rate of approximately 100°C/hour. Since the surface of the isogot thus obtained is slightly oxidized, this is removed by polishing.

Once the polishing is complete, put it into an iron pot and crush it.
Pass through a 200 mesh sieve. The thus obtained intermetallic compound powder of gadolinium and nickel
Put 100g and 40g of mercury into a quartz tube, evacuate it and seal it under vacuum.

The vacuum-sealed quartz tube is placed in an electric furnace, reacted at 720°C for 6 hours, and then cooled.

Since the reactant contains unreacted mercury, it is removed from the reaction tube and distilled at 400°C to recover the mercury. As a result of X-ray diffraction, the reaction product obtained in this way is
It has been revealed that this is a new intermetallic compound with a diffraction pattern completely different from that of the raw material.

The conditions for the formation of this intermetallic compound are as described above.
When a powder that has passed through 200 meshes is used as a raw material, a peak of unreacted substances can be seen in the diffraction diagram after 3 hours of reaction at 600℃ with the above charge composition.
A complete reaction product cannot be obtained unless the reaction is allowed to proceed for a longer period of time. However, from a practical point of view, it is not necessary to be a complete reactant, and it is sufficient if it is an alloy containing the above-mentioned intermetallic compound.

A mercury release structure in which alloy 2 containing the above intermetallic compound as a main component is held in cage 1 is placed in a vacuum (10 ^-4 mm
The mercury release characteristics when heated with Hg) are as shown in curve 1 in Figure 5, with temperature on the horizontal axis and mercury release rate on the vertical axis. Compared to Curve 2 showing the mercury release characteristics in Figure 5 of the intermetallic compound of mercury and titanium used in It is clear that mercury can be used effectively because the mercury release rate is high at the same temperature.

To explain the results of this example in more detail, conventionally, when synthesizing the intermetallic compound known in the above-mentioned literature, titanium powder and mercury are reacted, so dissolved gases re-released by heating are There are so many drawbacks.

On the other hand, the intermetallic compound obtained by the reaction of the intermetallic compound of gadolinium and nickel with mercury has a characteristic that the amount of dissolved gas is very small.

The reason for this is that when titanium powder is obtained, it is difficult to powder titanium alone, so it is pulverized into a hydride and dehydrogenated. The obtained powder will contain hydrogen gas if it is not completely dehydrogenated, and even if the dehydrogenation is complete, the titanium powder obtained by this method has a very large surface area and is active and can absorb a lot of gas. Therefore, there will inevitably be a large amount of re-emitted gas.

On the other hand, in the case of this example, the intermetallic compound of gadolinium and nickel, which are the raw materials, is very brittle, so powder with the desired particle size can be obtained without hydrogenation or dehydrogenation as in the case of titanium. It has easy characteristics.

Therefore, the raw material used in this example is in a very preferable form, and the amount of the gas is inevitably reduced.

If there is a large amount of re-emitted gas, high-frequency heating is performed when applying it to the tube, and as is well known, the discharge starting voltage increases due to the impure gas released.
In severe cases, it becomes impossible to turn on the light.

Of course, if such an intermetallic compound containing mercury is sealed in a tube and then the mercury is liberated by high-frequency heating, no gas will be emitted, so a getter that sorbs the emitted gas must be present. As is clear from the above explanation, the necessity of this cannot be avoided.

However, the small amount of gas released has the advantage of reducing the amount of getter used, which is advantageous in terms of price. Also, technically speaking, the use of a small amount of getter has the advantage that it is less likely to be subject to restrictions since there is no need to increase the area of the cage.

For example, when using an intermetallic compound of mercury and titanium together with Getter metal, conventionally the amount of the former was 25
If the weight percentage was not lowered, low-pressure mercury vapor discharge lamps tended to have high lighting voltages and would not turn on. On the other hand, with the intermetallic compound of the present invention, the amount can be increased to 50% by weight, which is very advantageous. This means that the intermetallic compound of the present invention releases less gas.

Example 2 An intermetallic compound was prepared from 138.9 g of lanthanum and 122.7 g of nickel in the same manner as described in Example 1, and then reacted with mercury in the same manner as in Example 1 to mainly form an intermetallic compound containing mercury. Figure 6 shows the release characteristics of mercury when Alloy 2 is held in cage 1 and heated in a vacuum atmosphere (10 ^-4 mmHg) (the horizontal axis is the heating temperature and the vertical axis is the mercury release rate). It is shown by curve 3.

When compared with the conventional mercury release characteristic curve 4 shown in the figure, it is clear that the same effect as described in Example 1 is exhibited.

Example 3 The example shown here is an example in which a metal consisting of multiple types of elements including gadolinium as a main component is used. Its composition, expressed in weight percent, is gadolinium
50 at%, cerium 30 at%, lanthanum 20 at%
It is.

The reaction was carried out in the same manner as in Example 1, and an alloy powder thought to be composed of multiple types of intermetallic compounds was obtained from 148.5 grams of the alloy having the above composition and 122.7 grams of nickel. Thereafter, operations such as reaction and distillation were carried out in the same manner as in Example 1 to obtain mercury alloy powder, which is considered to be a plurality of types of intermetallic compounds.

This mercury alloy powder was mixed in a vacuum atmosphere (10 ^-4 mm
The mercury release characteristic curve when heated with
As shown in curve 5 in the figure (horizontal axis is heating temperature, vertical axis is mercury release rate), when compared with curve 6 of the conventional example in the same figure, it shows the same effect as described in Example 1. That is clear.

Example 4 The molar ratio of gadolinium and nickel is 1:25,
The intermetallic compounds were prepared in the same manner as in the previous example for alloys of 1:3, 1:3.5, 1:4, 1:4.5, and 1:5, and the results of examining the release properties of mercury are shown in Section 8.
The figure shows the heating temperature on the horizontal axis and the mercury release rate on the vertical axis. In the figure, a diagonally shaded range C surrounded by curves 7 and 8 shows the mercury release characteristics when the alloy containing the intermetallic compound as a main component used in the present invention is heated in the same manner as in the above example. Range C indicated by this diagonal line
is located higher than Conventional Example 9, and has the same effect as the embodiment described above.

Example 5 The molar ratio of samarium and nickel is 1:2.1,
1:2.5, 1:3, 1:3.5, 1:4, 1:4.5,
An intermetallic compound was prepared using the same method as in the above example for a 1:5 alloy, and the mercury release properties were examined. The results are shown in Figure 9 (horizontal axis: heating temperature, vertical axis: mercury release rate). . In the figure, the diagonally shaded range D surrounded by curves 10 and 11 shows the mercury release characteristics when the alloy containing the above-mentioned intermetallic compound as a main component used in the present invention is heated in the same manner as in the above example.

The shaded range D is located above the conventional example 12 and has the same effect as the above-described embodiment.

Example 6 Regarding a nickel alloy of lanthanum and cerium, an alloy with the same molar ratio as in Example 5 was prepared, an intermetallic compound was prepared in the same manner as in the previous example, and the mercury release properties were examined. The figure shows the heating temperature on the horizontal axis and the mercury release rate on the vertical axis. Curve 1 in the figure
3 and the diagonally shaded range E surrounded by curve 14 shows the mercury release characteristics when the alloy containing the intermetallic compound as a main component used in the present invention is heated in the same manner as in the above example.

The shaded range E is located above the conventional example 15, and has the same effect as the embodiment described above.

Example 7 This example shows an example of an intermetallic compound containing samarium, lanthanum, and cerium as main components.

samarium, lanthanum and cerium respectively
An alloy was prepared with a ratio of 70 atomic percent to gadolinium and 30 atomic percent, and the molar ratio to nickel was the same as in Example 5 above. An intermetallic compound was prepared in the same manner as in the above example, and the mercury release properties were examined. The results are shown in FIG. 11 (horizontal axis: heating temperature; vertical axis: mercury release rate). Curve 1 in the figure
6 and the shaded area F surrounded by curve 17 shows the mercury release characteristics when the alloy containing the above-mentioned intermetallic compound as a main component used in the present invention is heated in the same manner as in the above example.

The shaded range F is located above the conventional example 18 and has the same effect as the embodiment described above.

The mercury release structure of the present invention has the general formula as described above.
RxNiyHgz (R=at least one of Gd, La, Ce, and Sm is the main component, and the molar ratio of y and x is 2<
The range is y/x≦5. ) is held in a cage, and is not practical in the range of y/x≦2, and 2<y/x≦
In addition to the above-mentioned advantages, the range of 5 has the advantage of increasing the reaction rate with mercury. Note that when y/x exceeds 5, it is difficult to react with Hg, which is the reason for this limitation. The shape and size of the cage used to hold the intermetallic compound can be modified in various ways depending on the purpose to which it is applied.

For example, in a ring-shaped mercury release structure as shown in FIGS. 1 and 2, the alloy 2
In addition to being filled with
This is a mercury release structure filled with the above-mentioned alloy.

It should be noted that the present invention includes not only plates, ribbons, coils, and other cages made of metal that have been conventionally used, but also cages that can be considered depending on the purpose.

The mercury release structure of the present invention may be prepared by mixing a metal having a getter function, such as zirconium, titanium, an alloy of zirconium and aluminum, or other metal powder, and an alloy mainly composed of an intermetallic compound that releases mercury. It may be held in a cage, or it may be held in two layers.
Alternatively, the metal powder having gettering ability and the above-mentioned alloy that releases mercury may be held in separate holders and made to coexist in the bulb.

The metal having gettering ability does not need to be in powder form, and may be in any shape such as a line, plate, ribbon, or pellet.

Application examples of the present invention include Nixie tubes, low-pressure mercury vapor discharge tubes such as germicidal lamps, fluorescent lamps, and other mercury-filled tubes, which can be used in various configurations depending on the purpose as described above. Furthermore, even if unstable substances such as YNi ₂ may be slightly mixed into the compounds of the examples, the effects of the examples will not be reduced, and even if a small amount of Ti, Zr, etc. is mixed, the compounds of the examples will not be affected. intermetallic compounds act effectively.

In addition to nickel shown in the above general formula, the metal is not limited to nickel as long as it is a metal that is reactive with both R in the general formula and mercury.

As mentioned above, the general formula RxNiyHgz (R=Gd,
The main component is at least one of La, Ce, and Sm, and the molar ratio of y and x is in the range of 2<y/x≦5. ) The mercury release structure in which an alloy containing an intermetallic compound as the main component is held in a cage has a higher mercury release rate than conventional ones, so it can be easily applied to high-speed tube manufacturing equipment, and Since the mercury release rate at the same temperature is high, it has the advantage that mercury can be used effectively.

This also allows the total amount of mercury sealed in the bulb to be reduced, which has a great effect on reducing environmental pollution.

[Brief explanation of the drawing]

FIG. 1 is a plan view showing an embodiment of the mercury discharge structure of the present invention, FIG. 2 is a sectional view taken along the line A--A in the same figure, and FIG. 3 is a plan view showing an embodiment of the mercury discharge structure of the present invention. A plan view showing another embodiment, FIG. 4 is the same figure B-
Cross-sectional views taken along line B, Figures 5 and 6
Figures 7, 8, 9, 10, and 11 show alloys containing various intermetallic compounds as main components used in the mercury release structure of the present invention and conventional alloys at various temperatures. FIG. 2 is a characteristic diagram showing a comparison of mercury release rates at 1, 3: Cage, 2, 4: Alloy.

Claims (1)

[Claims] 1 Intermetallic compound represented by the general formula RxNiyHgz (R = at least one of Gd, La, Ce, and Sm as a main component, and the molar ratio of y and x is in the range of 2<y/x≦5) A mercury release structure characterized by a cage holding an alloy containing as a main component.