JPS5934224B2 - Reversible hydrogen absorption/release material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a reversible hydrogen absorption/release material, and in particular to a material that can be used for hydrogen pressure control in thermionic tubes, television picture tubes, vacuum tube solar collectors, etc. It is related to.

Conventionally, various materials have been used for selective gas absorption.

For example, examples of nonmetallic gas adsorbents include activated carbon and zeolite.

Metal type gas absorbents such as barium are also widely used.

Generally, an evaporative material such as barium is released by heating its alloy, and during evaporation, it condenses and adheres to the inner wall surface of the equipment being used, thereby exhibiting its effect.

However, this type of evaporative gas absorbent inevitably stains the inner wall surface and is therefore often undesirable in certain situations.

Therefore, recently, non-evaporable gas absorbents such as Zr
A1 alloy, ZrTi alloy, etc. have been proposed.

However, since these alloys are usually covered with an inert coating layer such as an oxide or nitride, they must be heat treated at a high temperature of about 450°C or higher or activated before gas absorption. It must be treated as a chemical.

Furthermore, in applications such as thermionic tubes and vacuum tube solar thermal systems, ultra-high vacuum created solely by the hydrogen absorption effect of the hydrogen adsorbent is not necessarily effective; It has been found that vacuum equipment has a longer lifespan when the temperature is −3 mmHg.

In view of these problems, it is an object of the present invention to
In a relatively low temperature region below 0℃, without any activation treatment, and under a relatively low hydrogen pressure of several hundred mmHg or less, a large amount of hydrogen gas can be quickly and easily absorbed to generate a high To provide a hydrogen absorbing/releasing material capable of reversibly releasing any desired amount of hydrogen without creating a vacuum and by increasing the ambient temperature or lowering the ambient hydrogen pressure. That's true.

In other words, the object of the present invention is to provide a reversible hydrogen absorbing/releasing material that can arbitrarily control and maintain the hydrogen pressure inside a vacuum system device depending on the ambient temperature and residual hydrogen content.

The hydrogen absorbing/releasing material of the present invention is represented by the general formula ZrVx, and the atomic ratio X of V to Zr is x=0.01 to 0,
28, which is a binary alloy.

This alloy is somewhat viscous and will not ignite in air even after repeated hydrogen absorption and hydrogen release.

Moreover, unlike conventional Zr-based alloy getter materials, powder treatment is not required during use, and even in the form of lumps, it fully exhibits the expected performance.

Zr-V alloys form a homogeneous solid solution when heated to a temperature of 1860°C or higher, and alloys with desired compositions can be easily manufactured by, for example, argon arc melting or plasma arc melting. can.

In the composition range of the present invention, ■ is about 16.5 atoms (Z
rV□, 2o) and below, is mostly occupied by the β-Zr phase.

On the other hand, in the range of ZrV□, 20-ZrV□, 28, although a eutectic structure is formed at 1230°C or lower, 90 molar proportion or more of the entire alloy phase is the β-Zr phase. .

That is, Zr-
The V alloy must have a β-Zr phase with a molar ratio of 90 or more, and this composition range is ZrV□.

1 to Zrvo, corresponding to 28. 1E21.9 atomic%
(ZrVo, 23) If V75E is contained above (ZrVo, 23), the amount of the intermetallic compound Z r V 2 phase will increase, and as a result, hydrogen will be absorbed even more at lower hydrogen pressures and lower temperatures. Since hydrogen is released in a high pressure range (several hundred mmHg or more at room temperature), it is difficult to control the pressure inside the tubes of low-pressure devices such as thermionic tubes and vacuum tube solar collectors.

On the contrary, ZrV□.

If the v content is less than 1, hydrogen will hardly be absorbed in the low temperature region below 400° C., and pretreatment such as heat treatment or activation at a high temperature is required.

The alloy of the present invention can absorb impurity gases other than hydrogen gas, such as oxygen, carbon dioxide, carbon monoxide, methane, nitrogen, and water vapor, with great ease (1), and even by heating or reducing the ambient pressure, these impurity gases can be removed. It has an impurity removal effect that prevents the release of impurities, and can also be used as a getter material.

The following table shows the maximum (saturated) hydrogen uptake of the alloys of the invention.

As shown in the table, the alloy of the present invention very easily absorbed about 200 ml of hydrogen per gram at relatively low temperatures.

The figure also shows Z r V o,1 which is an embodiment of the present invention.
The hydrogen pressure and temperature characteristics of pentahydride are shown.

In the figure, the ordinate is the equilibrium hydrogen pressure of the metal hydride that has absorbed hydrogen, that is, the hydrogen pressure in the pipe containing the hydrogen absorption/release material, and the abscissa is the temperature of the hydrogen absorption/release material at that time. It is.

In the figure, the solid line shows the characteristics when hydrogen is absorbed, and the broken line shows the characteristics when hydrogen is released.

In addition, the measurement was carried out by putting 1 g of the alloy into a predetermined container and storing it in a sealed tube.
The tube was degassed to 6 mmHg for about 1 hour, and then hydrogen gas was introduced into the tube to perform hydrogenation under a hydrogen pressure of 200 mtnHg, followed by cooling to various temperatures.

In addition, in the figure, 1 indicates ZrV.

, 15 has a hydrogen content in the 20th factor of the saturated hydrogen absorption amount, 2 has the same 10th factor, and 311 has the same 5th factor.

In each of the examples, hydrogen was rapidly absorbed under a hydrogen pressure of 200 iiHg without any pretreatment to form a hydride, and the hydrogen pressure inside the tube was significantly reduced as shown in the figure.

Then, by lowering the temperature of the alloy that has formed the hydride, the hydrogen pressure inside the tube is rapidly reduced, and conversely,
By increasing the temperature, the hydrogen pressure inside the tube could be increased, and by controlling the temperature, the desired hydrogen pressure could be obtained.

Furthermore, as shown in the figure, the equilibrium hydrogen pressure could be controlled by adjusting the hydrogen content, and as a result, any desired hydrogen pressure could be obtained even if the temperature was constant.

As described above, the alloy of the present invention is a hydrogen absorbing/releasing material that has excellent reversibility in a wide range of hydrogen pressure and temperature ranges.

[Brief explanation of the drawing]

The drawing is a characteristic diagram showing the pollution level-equilibrium hydrogen pressure when the amount of hydrogen contained in ZrVo, t5 hydride, which is an example of the present invention, is varied.

Claims (1)

[Claims] 1 Represented by the general formula ZrVx. The atomic ratio X of V to Zr is 0. A reversible hydrogen absorption/release material made of an alloy that is O2N2.28.