JP6282301B2 - Hydrogen remaining amount sensor - Google Patents

Description

  The present invention relates to a remaining hydrogen sensor that is disposed in a space where the remaining amount of hydrogen changes and detects the remaining amount of hydrogen in the space.

  A hydrogen storage alloy container, which is one of hydrogen storage containers, has begun to spread due to its excellent volume storage density, but has a problem that it is difficult to obtain a clue to know the remaining amount of hydrogen in the container. If it is a normal hydrogen gas tank, the remaining amount of hydrogen can be easily known by attaching a pressure gauge. On the other hand, in the case of a hydrogen storage alloy, there is a flat region called a plateau represented by a PCT curve, and in addition to a small pressure difference (minimum and maximum pressure difference), this plateau will change if the temperature of the alloy changes. Since the pressure of the gas also changes, it is difficult to accurately know the remaining amount of hydrogen in the container using only a pressure gauge.

Although it is an indirect measurement method in the hydrogen storage system of a large-sized hydrogen storage alloy container, the remaining amount of hydrogen can be known from the integrated value using a high-precision mass flow meter. However, since the mass flow meter is expensive and difficult to downsize, it can be said that it is not suitable for a relatively small hydrogen storage alloy container.
In view of this, a hydrogen remaining amount meter or sensor that is suitable for a hydrogen storage alloy container and can directly know the remaining amount of hydrogen has been proposed as follows.

(1) As a sensor for putting an electrode in a hydrogen storage alloy and measuring the amount of hydrogen in the container from the relationship between the electrical resistance value or the amount of hydrogen, for example, as disclosed in Patent Document 1, the electromotive force and hydrogen of the alloy A method of knowing the remaining amount of hydrogen from the concentration has been proposed.
Patent Documents 2 to 4 propose a method of knowing the remaining amount of hydrogen by measuring the electrical resistance value of the hydrogen storage alloy.

(2) As a sensor for measuring the amount of hydrogen in the container from its displacement using the volume expansion of the hydrogen storage alloy, as shown in Patent Document 5, a strain gauge is attached to the wall of the container, and the hydrogen storage is measured in advance. There has been proposed a method for measuring the remaining amount of hydrogen based on comparison data between hydrogen absorption and strain of an alloy.
Patent Document 6 proposes a method of measuring volume expansion using an optical fiber.

(3) As a sensor for measuring the temperature and pressure of the hydrogen storage alloy and measuring the amount of hydrogen from the PCT curve, as in Patent Document 7, the temperature and pressure of the container are measured, and the hydrogen from the PCT curve of the hydrogen storage alloy is measured. Methods for measuring quantities have been proposed.
Further, Patent Document 8 proposes a fuel gauge in which alloys having different plateau pressures are put in a container, and a step-like change in pressure is regarded as a trigger for a remaining amount change.

  Furthermore, in patent document 9, in order to solve the conventional subject, it has in part a easily-strained part in which a distortion | strain easily arises with hydrogen absorption / release of the hydrogen storage alloy for sensors, and measures the distortion of a easily-strained part. By providing a strain gauge, the size of the remaining hydrogen sensor can be reduced and the structure can be simplified.

JP 2007-47125 A Japanese Patent No. 3624816 JP 2000-206073 A JP 2000-97931 A Patent 3203062 JP-A-6-249777 JP-A-2-140641 JP 59-78902 A JP 2008-180682 A

However, the one proposed in Patent Document 1 has a problem that the sensor holder is attached to the hydrogen storage alloy container body, the structure is complicated, and it is difficult to apply to a small container.
Moreover, in what was proposed by patent documents 2-4, since the contact area or contact pressure between particle | grains changes by progress of pulverization accompanying hydrogenation of a hydrogen storage alloy, the measurement value of hydrogen residual amount is changed. There is a problem with reliability.

  In what is proposed in Patent Document 5, the progress of pulverization accompanying hydrogenation of the hydrogen storage alloy causes a difference in the alloy density depending on the location in the container, and as a result, the strain generated in the container wall also increases. Since variations occur, in order to accurately measure the amount of hydrogen, a plurality of strain gauges must be stretched and averaged. Affixing a plurality of strain gauges to the outer surface of the small container has a problem that the possibility of damaging the strain gauges and lead wires increases.

  In the thing proposed by patent document 6, there exists a subject that a price is high, a structure becomes complicated, and it is difficult to apply to a small container.

  In the method proposed in Patent Document 7, in the process in which the hydrogen storage alloy releases hydrogen, there are many differences in the alloy temperature depending on the location in the container. Moreover, a pressure gauge and a thermometer must be provided, and there exists a subject that it is difficult to apply to a small container.

  In the one proposed in Patent Document 8, a difference in the alloy temperature often occurs depending on the location in the container. Therefore, an error is likely to occur in the remaining amount of hydrogen only by measuring the pressure.

  In what was proposed by patent document 9, since the precision as a hydrogen remaining amount sensor improves when the distortion of an easy strain part is enlarged, an easy strain part is a material with low rigidity, and does not raise | generate a plastic deformation. It needs to be adjusted. In addition, since the sensor hydrogen storage alloy allows expansion and contraction in many directions, it is difficult to obtain linearity in the relationship between strain and the amount of hydrogen in the container.

  The present invention has been made against the background of the above circumstances, and an object of the present invention is to provide a hydrogen remaining amount sensor capable of accurately measuring the remaining amount of hydrogen with a simple structure.

That is, among the hydrogen remaining amount sensors of the present invention, the first present invention is a hydrogen remaining amount sensor arranged in a space where the remaining amount of hydrogen changes,
It has a measurement container that houses the hydrogen storage alloy for measurement,
The measurement container has an opening that is at least partially open and capable of deforming the hydrogen storage alloy for measurement accompanying hydrogen absorption / release,
Deformation that can be elastically deformed by transmitting the deformation of the hydrogen storage alloy for measurement through the opening to a part of the measurement container placed in the space in a fixed position. Members,
And a detector for detecting elastic deformation of the deformable member.

  In the hydrogen remaining amount sensor of the second aspect of the present invention, in the first aspect of the present invention, the measurement container has a cylindrical shape, and the opening is provided at one end of the cylindrical shape.

  A hydrogen remaining amount sensor according to a third aspect of the present invention has a lid that covers at least a part of the hydrogen storage alloy for measurement located in the opening in the first or second aspect of the present invention, and the lid It has the transmission part which transmits the movement deformation | transformation of this to the said deformation member, It is characterized by the above-mentioned.

  According to a fourth aspect of the present invention, in the third aspect of the present invention, the deformation member is a leaf spring, and the transmission member is in contact with a plate surface on the free end side of the leaf spring. And

  The hydrogen remaining amount sensor according to a fifth aspect of the present invention is characterized in that, in the third or fourth aspect of the present invention, the transmission member has a rod shape.

  A remaining hydrogen sensor according to a sixth aspect of the present invention is characterized in that, in any of the first to third aspects of the present invention, the deformable member is fixed to the measurement container.

  A hydrogen remaining amount sensor according to a seventh aspect of the present invention is the measurement device according to any one of the first to fourth aspects, wherein the deformation member is partially fixed at a fixed position in the measurement space. The container is installed at a fixed position in the space, and a part of the deformation member is in a fixed position with respect to the measurement container.

  A hydrogen remaining amount sensor according to an eighth aspect of the present invention includes the strain gauge in the detection unit according to any one of the first to seventh aspects of the invention, and the strain gauge is attached to the deformation surface of the deformation member. It is characterized by that.

  A remaining hydrogen sensor according to a ninth aspect of the present invention is characterized in that, in any one of the first to eighth aspects of the present invention, the space in which the remaining amount of hydrogen changes is a space in a container containing a hydrogen storage alloy. To do.

  According to the present invention, since the deformation of the hydrogen storage alloy for measurement can be taken out as a bending deformation of the elastic member, a highly responsive and accurate hydrogen remaining amount sensor can be obtained, and the structure can be simplified. Cost reduction and miniaturization are easy.

It is a figure which shows the hydrogen residual amount sensor of one Embodiment of this invention, FIG. 1a is a top view of a hydrogen residual amount sensor, FIG. 1b is a side view of a hydrogen residual amount sensor. Similarly, it is a figure which shows the circuit diagram of the indicator which provided the indicator. Similarly, it is a figure which shows the example of application of a hydrogen remaining amount sensor. It is a graph which shows the output change of the distortion with respect to the amount of hydrogen in the hydrogen storage alloy container in an example. It is a graph which shows the output change of the distortion with respect to the amount of hydrogen in the hydrogen storage alloy container in an example.

Hereinafter, a hydrogen remaining amount sensor 1 according to an embodiment of the present invention will be described with reference to the accompanying drawings.
The remaining hydrogen sensor 1 accommodates the hydrogen storage alloy 4 in a measurement container (hereinafter referred to as sensor body 2), and the remaining hydrogen amount in the space where the remaining hydrogen amount changes based on the strain generated in the leaf spring 3. Is detected. The hydrogen remaining amount sensor 1 uses the hydrogen remaining amount sensor to change the remaining amount of hydrogen based on comparison data between the hydrogen storage amount of the hydrogen storage alloy measured in advance and the strain generated in the leaf spring 3. The remaining amount of hydrogen in the space to be measured is measured.

  An example of the space in which the remaining amount of hydrogen changes is the inside of a hydrogen storage alloy container in which a hydrogen storage alloy is accommodated and hydrogen is absorbed and released. However, the present invention is not limited to the inside of the hydrogen storage alloy container, and can be widely applied as long as the remaining amount of hydrogen changes.

  The sensor main body 2 has a container shape that accommodates the hydrogen storage alloy 4 for measurement therein, and at least a part of the sensor main body 2 is opened, so that the measurement hydrogen storage alloy 4 can be deformed along with hydrogen absorption / release. In this form, it has a bottomed cylindrical shape, one end of which opens and has an opening 2A. In addition, the container of the present invention for storing the hydrogen storage alloy is not limited to a cylindrical shape, and may be a cylindrical shape of various shapes such as a square tube, and is not limited to this, and may have various shapes. Can do. Further, the number of openings is not limited to one, and a plurality of openings may be provided, and the location provided in the container is not limited.

  The material of the sensor body 2 is not particularly limited in the present invention, but for example, carbon steel or stainless steel represented by SUS304 is desirable. It is desirable that the sensor body 2 has a strength that does not easily deform due to expansion / contraction caused by hydrogen absorption / release of the stored hydrogen storage alloy. Carbon steel and stainless steel make this characteristic relatively inexpensive. Can be provided.

The type of the hydrogen storage alloy 4 for measurement is not particularly limited in the present invention. For example, an AB ₂ alloy or an AB ₅ alloy can be used. When the hydrogen remaining amount sensor 1 is arranged in a hydrogen storage alloy container, it is desirable that the alloy filled in the hydrogen storage alloy container and the hydrogen storage alloy for measurement are of the same type. Thereby, the hydrogen storage / release operation according to temperature and pressure can be made the same between the hydrogen storage alloy and the measurement hydrogen storage alloy 4.
The hydrogen storage alloy 4 for measurement is used by being filled in the sensor body 2. The degree of filling is such that the hydrogen is absorbed and released satisfactorily and the expansion and contraction associated with the storage and release of hydrogen are sufficiently reflected in the movement in the opening 2A. A ventilation material may be housed in the sensor body 2 so that hydrogen can be absorbed and released smoothly.

One end of the leaf spring 3 is fixed to the side wall of the sensor body 2, is bent at a position away from the opening 2 </ b> A in the axial direction of the sensor body 2, and extends along the radial direction of the sensor body 2. The side is a freely deformable free end. The material of the leaf spring 3 does not need to be the same material as the sensor body 2, and stainless steel typified by SUS304 is desirable in consideration of the spring property.
In this embodiment, since the method of taking out the expansion and contraction of the hydrogen storage alloy for measurement as a bending deformation of a thin leaf spring, a highly responsive and accurate hydrogen remaining amount sensor can be obtained.

  A cover plate 5 that covers the opening 2A is disposed in the opening 2A. The cover plate 5 does not need to cover the entire opening 2A, but it is desirable to cover the opening 2A with as wide an area as possible so as to follow the expansion and contraction of the measurement hydrogen storage alloy 4 as much as possible. However, it is desirable that the entire outer peripheral edge of the opening 2A and the outer peripheral edge of the cover plate 5 have an interval so as not to contact the sensor body 2 at the peripheral edge of the opening 2A during the movement. The lid plate 5 corresponds to the lid member of the present invention. The lid member does not necessarily have a plate shape, and may have a sufficient thickness. However, a plate shape that can be made as light as possible is desirable so that the hydrogen storage alloy 4 for measurement can easily follow expansion and contraction. The lid plate 5 may be bonded to the measurement hydrogen storage alloy 4 in the opening 2A so as to reliably follow the deformation of the measurement hydrogen storage alloy. As a material for bonding, a silicon-based adhesive having a large elongation can be used.

On the front surface side of the cover plate 5, a thin bar 7 is erected on the outer side in the axial direction of the sensor body 2. It is desirable that the thin rod 7 has a tip located on the inner side of the leaf spring 3 on the free end side of the leaf spring 3. The thin rod 7 has a rod shape and corresponds to the transmission member of the present invention. The thin rod 7 may be formed integrally with the lid plate 5 or may be connected to the lid plate 5 by welding or rivets.
The thin rod 7 may be in contact with the plate surface of the leaf spring 3 in a state where the hydrogen storage alloy 4 for measurement does not occlude hydrogen, and the leaf spring 3 is elastically deformed to some extent in this state. May be.

  Since the contact between the thin rod 7 and the leaf spring 3 determines the detection start time, the length of the thin rod 7 can be set so that the detection start time is set at an appropriate time, and the hydrogen storage alloy 4 absorbs hydrogen. The thin rod 7 may not be in contact with the plate surface of the leaf spring 3 in a state in which it is not occluded or occluded to some extent. The thin bar 7 may not be provided depending on the shape of the leaf spring 3 or the like.

Further, the thin bar 7 may be movable along the extending direction of the leaf spring 3 as shown in FIG. Thereby, the elastic amount of the leaf | plate spring 3 accompanying the movement of the thin rod 7 can be adjusted.
The remaining hydrogen sensor 1 changes the strain detected by the strain gauge 6 by changing the position of the thin rod 7 even when the filling rate of the hydrogen storage alloy 4 for measurement incorporated in the sensor body 2 is the same. Is possible. This is because changing the position of the thin rod 7 changes the distance between the strain gauge 6 and the thin rod 7 and changes the bending moment applied to the leaf spring 3.
When the distance between the strain gauge 6 and the thin bar 7 is narrowed, the bending moment increases and the generated stress increases, so that the detected strain also increases. That is, when it is desired to increase the strain and increase the sensitivity of the sensor, the sensor sensitivity can be increased by shifting the position of the thin rod 7 to the side of the leaf spring 3 fixed to the sensor body 2. However, the strain must be kept within an elastic range where the leaf spring 3 does not yield.

  The remaining hydrogen sensor 1 of the present embodiment has a simple structure and can be reduced in cost, and the sensor size can be as small as about 20 mm square, so that it can be used for a small hydrogen storage alloy container. is there.

  In this embodiment, the leaf spring 3 is fixed to the sensor main body 2. However, a part of the leaf spring 3 is fixed to a wall portion of a space where the remaining amount of hydrogen such as a hydrogen storage alloy container changes, and the sensor By fixing the main body 2 at a fixed position of the wall portion, the plate spring 3 can be installed in a state where a part of the leaf spring 3 is at a fixed position with respect to the measurement container disposed in the space.

A strain gauge 6 is attached to the leaf spring 3 on the base side surface of a piece extending in the radial direction of the sensor body 2. When the leaf spring 3 is deformed, deformation stress is concentrated on the base side of the leaf spring 3. The strain gauge 6 corresponds to the detection unit of the present invention.
The strain gauge 6 may be configured by one that can detect elastic deformation of the leaf spring 3, and may be one that optically detects elastic deformation of the leaf spring 3. In addition to continuously detecting the deformation of the leaf spring, it may be detected in stages.

Moreover, in the strain gauge 6, in order to exclude the temperature influence of the leaf | plate spring 3 and the strain gauge 6, it is desirable for the leaf | plate spring 3 and the strain gauge 6 to have the same linear expansion coefficient.
The strain gauge 6 is connected to an indicator 60 shown in FIG. For example, by adopting a lead wire 8 having a three-wire specification, it is possible to eliminate the temperature influence.

  As shown in FIG. 2, the indicator 60 prepares a bridge circuit 61 corresponding to the electrical resistance value of the strain gauge 6 and takes out a resistance change accompanying the strain as a voltage change. The voltage change can be converted into a digital signal through, for example, the A / D converter 62, and the remaining amount of hydrogen can be displayed in multiple stages with an indicator 63 such as an LED.

  The leaf spring 3 corresponds to the deformable member of the present invention, and the strain gauge 6 corresponds to the detection unit of the present invention. The deformable member is not limited to a leaf spring, and an appropriate configuration such as a coil spring or an elastic body can be used. In addition, the detection unit is not limited to the strain gauge, and an appropriate configuration can be adopted as long as it can detect the deformation amount of the deformation member. For example, a sensor that optically reads the deformation of the deformable member may be used.

  By preparing a bridge circuit according to the electrical resistance value of the strain gauge outside the sensor body, it is possible to extract the resistance change accompanying the strain as a voltage change and display the hydrogen amount as a digital value. A packaged hydrogen storage alloy container is also possible.

FIG. 3 shows an application example in which the hydrogen remaining amount sensor 1 of the present embodiment is arranged in the hydrogen storage alloy container 20. The remaining hydrogen sensor 1 is disposed so as to be embedded in the upper part of the hydrogen storage alloy 21 filled in the hydrogen storage alloy container 20. This is to make it difficult to make a difference between the temperature of the hydrogen storage alloy 21 in the hydrogen storage alloy container 20 and the temperature of the hydrogen storage alloy 4 for measurement of the remaining hydrogen sensor 1. A space above the hydrogen storage alloy 21 in the hydrogen storage alloy container 20 is filled with a ceramic fiber 23. A valve 22 for controlling the release of hydrogen is provided at the opening of the hydrogen storage alloy container 20 so that hydrogen can be moved through the valve 22.
The lead wire 8 of the remaining hydrogen sensor 1 is taken out of the hydrogen storage alloy container 20 and connected to the indicator 60 described above.

  In this embodiment, the detection result of the strain gauge 6 serving as the detection unit is digitally displayed. For example, the hydrogen absorption amount of the hydrogen storage alloy for measurement and the output of the detection unit are associated with each other to detect the detection result. The hydrogen absorption amount may be indicated directly or indirectly based on the measurement result of the part. Further, the detection result of the detection unit may be collected through a network or the like and analyzed for hydrogen absorption.

Next, the operation of the remaining hydrogen sensor 1 will be described.
When absorption and release of hydrogen occur in the hydrogen storage alloy 21 in the hydrogen storage alloy container 20, hydrogen absorption and release also occur in the hydrogen storage alloy 4 for measurement in the hydrogen remaining amount sensor 1. Expansion or contraction occurs. The expansion or contraction of the hydrogen storage alloy 4 for measurement appears in the form of an axial movement of the sensor body 2 of the cover plate 5 and the thin rod 7.
When the hydrogen storage alloy 4 for measurement absorbs hydrogen, the hydrogen storage alloy 4 for measurement expands, and the thin rod 7 pushes the leaf spring 3 to increase the bending deformation, and the detection result in the strain gauge 6 changes. Further, when the hydrogen storage alloy 4 for measurement releases hydrogen, the hydrogen storage alloy 4 for measurement contracts, and the thin rod 7 decreases the bending deformation amount of the leaf spring 3 that has been bent and deformed. A change occurs in the detection result.

In the illustrated example, since the strain gauge 6 is attached to the side of the leaf spring 3 that generates the compressive strain, the strain gauge 6 detects the compressive strain. When the hydrogen storage alloy 4 for measurement releases hydrogen and contracts, the deformation of the leaf spring 3 returns to its original state, so that the compressive strain of the strain gauge 6 also decreases and returns to the zero point.
For example, even if a tensile force is applied to a thin plate-like elastic member, the deformation is extremely small unless a large force is applied, but in the case of bending, a bending deformation can be easily obtained with a small force. The deformable member may use tensile strain.

  The strain generated by the strain gauge 6 is extracted as a voltage change by the bridge circuit 61 of the indicator 60, converted into a digital signal by the A / D converter 62, and displayed on the indicator 63 based on the detection result.

An embodiment of the present invention will be described below.
A small steel container is filled with a hydrogen storage alloy, and the hydrogen remaining amount sensor 1 of this embodiment is attached to the small steel container, and the relationship between the strain of the leaf spring 3 and the amount of hydrogen in the container when hydrogen is released is shown. .
The hydrogen storage alloy used was AB ₅ alloy, and 100 g was filled in a steel container. The alloy used for the remaining hydrogen sensor 1 was also an AB ₅ alloy. The remaining hydrogen sensor 1 was disposed so as to be buried in a hydrogen storage alloy as shown in FIG.

Hydrogen absorption into the hydrogen storage alloy was absorbed up to a pressure of 1.0 MPa while the container was immersed in a 20 ° C. water bath. FIG. 4 shows test data in which hydrogen was released while the water temperature was 20 ° C., and FIG. 5 was test data in which hydrogen was released after the water temperature was raised to 40 ° C.
The release of hydrogen was controlled to 0.5 NL / min using a mass flow controller attached to the test apparatus, and was released until the remaining amount of hydrogen became zero. The strain of the leaf spring 3 was measured with a strain gauge and a dynamic strain meter and recorded in a data logger.

4 and 5 show a regression line and an approximate expression by the least square method. R ² in the figure is called a decision constant, and is an index indicating whether or not the data fits a straight line. It can be said that the closer to 1.0, the better the linearity. Since the R ² values of these two test data are 0.9839 when the water temperature is 20 ° C. and 0.9918 when the water temperature is 40 ° C., it is understood that the test data of the remaining hydrogen sensor 1 has good linearity. It was.

  That is, it was shown that the remaining hydrogen sensor 1 has high measurement accuracy as a sensor. The maximum strain value (full of hydrogen) is different between 20 ° C and 40 ° C, but when the water temperature is raised from 20 ° C to 40 ° C, the pressure exceeds 1.0 MPa. This is because it is released and held at 1.0 MPa. Therefore, the hydrogen absorption amount of the hydrogen storage alloy used in the hydrogen remaining amount sensor 1 is less at 40 ° C. than 20 ° C., and as a result, the expansion amount of the hydrogen storage alloy is small and the strain is also small. Represents.

  The present invention has been described based on the above embodiment, but the present invention is not limited to the content of the embodiment, and appropriate modifications to the embodiment are possible without departing from the scope of the present invention. It is.

DESCRIPTION OF SYMBOLS 1 Hydrogen remaining amount sensor 2 Sensor main body 3 Leaf spring 4 Hydrogen storage alloy for measurement 5 Lid plate 6 Detection part 7 Thin rod 8 Lead wire 20 Hydrogen storage alloy container
21 Hydrogen storage alloy

Claims (9)

A hydrogen remaining amount sensor disposed in a space where the remaining amount of hydrogen changes,
It has a measurement container that houses the hydrogen storage alloy for measurement,
The measurement container has an opening that is at least partially open and capable of deforming the hydrogen storage alloy for measurement accompanying hydrogen absorption / release,
Deformation that can be elastically deformed by transmitting the deformation of the hydrogen storage alloy for measurement through the opening to a part of the measurement container placed in the space in a fixed position. Members,
A hydrogen remaining amount sensor comprising: a detection unit that detects elastic deformation of the deformable member.   The residual hydrogen sensor according to claim 1, wherein the measurement container has a cylindrical shape, and has the opening at one end of the cylindrical shape.   It has a cover part which covers at least one part of the said hydrogen storage alloy for a measurement located in the said opening part, It has a transmission part which transmits the movement deformation of the said cover part to the said deformation member. Item 3. A hydrogen remaining amount sensor according to Item 1 or 2.   4. The hydrogen remaining amount sensor according to claim 3, wherein the deformable member is a plate spring, and the transmission member is in contact with a plate surface on a free end side of the plate spring.   The residual hydrogen sensor according to claim 3 or 4, wherein the transmission member has a rod shape.   The hydrogen remaining amount sensor according to claim 1, wherein the deformable member is fixed to the measurement container.   A part of the deformable member is fixed at a fixed position in the measurement space, the measurement container is installed at a fixed position in the space, and a part of the deformable member is located with respect to the measurement container. The hydrogen remaining amount sensor according to claim 1, wherein the hydrogen remaining amount sensor is in a fixed position.   The residual hydrogen sensor according to claim 1, wherein the detection unit includes a strain gauge, and the strain gauge is attached to a deformation surface of the deformation member.   The hydrogen remaining amount sensor according to any one of claims 1 to 8, wherein the space in which the remaining amount of hydrogen changes is an in-container space containing a hydrogen storage alloy.

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