JPH04323335A - Method and device for producing hydrogen storage alloy - Google Patents

Abstract

PURPOSE:To economically produce a hydrogen storage alloy enhanced in alloying rate. CONSTITUTION:This hydrogen storage alloy is produced by the following steps. Namely, (1) the powders M of >=2 different kinds of metals, e.g. Mg and Ni giving a hydrogen storage alloy on alloying, a crushing ball B and 0.5-1.5wt.% of a higher fatty acid based on the metal powder are charged into the mill pot 21 of a high-speed ball mill. (2) The mill pot is filled in with a nonoxidizing atmosphere. The mill is operated under conditions where the resultant crushing acceleration ratio G expressed by the following equation is controlled to >=30 and the ratio R of the rotating to revolving angular velocity to <=1.9 to exert an effective mechanical alloying effect. The equation is expressed by G=amax/g=(omega1)<2>/2g(K+NX(1+R)<2>, where G is the resultant crushing acceleration ratio, amax is the resultant crushing acceleration, omega1 is the revolving angular velocity (1/S), K is the diameter (m) of revolution, N is the inner diameter (m) of the mill pot, omega2 is the relative angular velocity (1/S) of the rotation to revolution, and R=omega2/omega1.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing hydrogen storage alloys.

0002

[Prior Art] Technology has been developed to absorb hydrogen in certain metals or alloys, store or transport it in the form of metal hydrides, and use the hydrogen as a component in hydrogen purification, heat pumps, and heating and cooling systems. There is. In this case, when a metal hydride absorbs or releases hydrogen, it always generates heat or absorbs heat, so this property can be used for heat exchange devices and heat pumps. The alloy combinations that have been announced and partially put into practical use as hydrogen storage alloys to date include Mg-Ni, Mg-Cu, Ca-Ni, Fe-T.
Many alloys have been reported in which the main basic components are i, Ti-Mn, La-Ni, Mischmetal-Ni, etc., and some of these are replaced with other metals. For example, Mg2Ni
0.75Cr0.25, Ca0.7Mn0.3Ni
5, LaNi4.7Al0.3, TiFe0.8
Mn0.2 etc. are known. Generally speaking,
One or more metals selected from the group consisting of Mg, Ca, La, misch metal, Ti, etc. and Ni, Al, V
, Cr, Fe, Co, Zn, Cu, and Mn. To manufacture hydrogen storage alloys, raw materials of different metals are melted in a high-frequency induction furnace or arc-type high-temperature melting furnace. High-frequency induction furnaces are suitable for mass production, but many of the raw metals, especially Mg, Ca, and Al, have high vapor pressures and strong affinity for oxygen, so the inside of the furnace must be kept in an inert atmosphere with Ar gas, etc. must be adjusted to prevent metal oxidation. When the material metals are melted and mixed with each other, and the alloy reaction progresses sufficiently under high temperature conditions so that all the materials have the desired alloy composition, they are cast into a mold in a non-oxidizing atmosphere to form an ingot. The obtained ingot is heat treated,
After the alloy is completed, it is crushed in a crusher in a non-oxidizing atmosphere to obtain a hydrogen storage alloy powder with a desired particle size.

On the other hand, a technique for obtaining a desired alloy composition while remaining solid without melting has recently been in the spotlight. This is generally called the mechanical alloying method, and was first developed by Benjamin of INCO in the United States in the 1970s. It involves applying mechanical energy to metal powder using a high-energy ball mill (attritor), etc. to achieve cold compression and fracture. This is a method of repeating the steps to disperse ultrafine particles. The principle of mechanical alloying is that the powder is first forged by milling with a high impact force to flatten and flake, then the work-hardened particles are broken or exfoliated and cold forge welding is repeated (kneading), and then the alloy components are The theory is that a lamellar structure develops during this period, the crystal grains rapidly become finer, one grain becomes finely dispersed within the other, and finally the grain shape becomes equiaxed and becomes random. M Y
Song and Yi Ivanov published their experimental results in Hydrozen Energy magazine (H
Hydrogen Energy vol10 No. 3
P169-178, 1985). In this report, the acceleration of the planetary ball mill is 6.1G, and N
i compares and examines samples obtained by mixing for 30 minutes in an Ar gas atmosphere using a carbonyl type and subjected to various hydrogenation treatments by X-ray diffraction. As a result, among the samples that were hydrogenated from 1 to 58 times, those with the lowest hydrogenation number were Mg2Ni, with a trace amount of Mg.
It was detected that O, Mg, and Ni phases coexisted, but in cases where heat treatment (annealing) was applied and the number of hydrogenations was high, it was recognized that most of the Mg and Ni became Mg2Ni, especially when hydrogenated. The effect of heat treatment was recognized to be stronger than that of repetition, and this was the first report on a method for producing a hydrogen storage alloy without melting, although it was incomplete.

0004

Among the conventional techniques, manufacturing hydrogen storage alloys by melting requires considerably sophisticated technology and well-managed equipment. For example, Mg2Ni
When manufacturing Ni, the vapor pressure of Ni is 2057 mm at 10°C.
Hg, fluctuates at a high level of 2732 mmHg at 760°C, while Mg also varies from 743 mmHg to 11
It fluctuates at 0.07 mmHg. Ca also fluctuates from 983 mmHg to 1487 mmHg, and it is extremely difficult to raise the temperature inside the furnace while maintaining the balance of these vapor pressures. On the other hand, from the general principle of melting, the degree of solid solubility of both components influences the difficulty of forming an alloy, but the most problematic one is the difference in density and melting point of both components. That of Ni is 8.90g
/cm3, 1455°C, and Mg is 1.74g/cm
3,650°C, Ca is 1.55g/cm3,850°C. Therefore, it is clear from this fact alone how difficult it is to alloy Mg or Ca with Ni. On the other hand, La has a density of 6.15 g/cm3 and a melting point of 826°C, and although the difficulty is alleviated simply because the density is close to that of Ni, rare earth elements are generally valuable resources and expensive. . A major problem when alloying Mg and Ni is that the vapor pressure of Mg is approximately 2 near the melting point of Ni.
The vapor pressure reaches 5 atm, and because of this vapor pressure, it is difficult to avoid evaporation of Mg from the molten metal, so Ni becomes excessive and a part of the product becomes MgNi2, which does not form hydrides. In addition, if excessive Mg is blended from the beginning to prevent this, for example, although the chemical formula is expressed as Mg2.35Ni, in reality, it becomes a cause of containing free Mg alone, such as Mg2Ni+Mg0.35.

How this relates to the characteristics of the hydrogen storage alloy will be explained with reference to FIGS. 8 and 9. Figure 8 is a pressure-composition isotherm diagram (hereinafter referred to as "PCT diagram") of the hydrogen storage alloy Mg2.35Ni manufactured by the melting method, where the vertical axis represents hydrogen pressure P (unit: MPa) and the horizontal axis represents The atomic ratio H/M of hydrogen gas and metal is taken and the temperature is set at a constant temperature (350℃
) is a graphical representation of the behavior of the atomic ratio as hydrogen gas is absorbed and released. In the figure, the curve shows the hydrogen pressure at 0.
5, it is clearly divided into range A where both occlusion and desorption follow a gentle slope to the right, and range B where it moves almost horizontally to the right. The range B indicates the absorption and desorption of hydrogen by Mg2Ni. In other words, the fact that range A is observed indicates the presence of Mg that binds to hydrogen gas, and Mg has a far inferior affinity to hydrogen than Mg2Ni.
is contained in the alloy, reducing the functionality required as a hydrogen storage alloy.

FIG. 9 is a high-pressure differential thermal analysis diagram (hereinafter referred to as "DTA diagram") of the same sample, with temperature on the vertical axis and time on the horizontal axis, with hydrogen at a constant pressure (1.1 MPa) When the container is heated from the outside up to a maximum of 500°C or cooled from 500°C, the M sealed in the container is sealed.
Curve C shows the measured temperature of g2.35Ni, and Curve D shows the temperature difference between this sample and a standard sample (alumina) sealed in a container for comparison. Since a hydrogen storage alloy generates heat when storing hydrogen gas and absorbs heat when releasing hydrogen gas, curve D also shows a downward peak due to release during heating, and an upward peak due to occlusion during cooling. However, as clearly seen at points P, Q, and R, there is not only one point where the peak is sharp, but also a double peak or an abnormal refraction point close to the peak.In addition to the phase change between Mg2Ni and Mg2NiH4, This shows that there is also a phase change between Mg and MgH2. This occurs because Mg dissociates at a higher temperature than Mg2Ni under the same hydrogen pressure. In any case, hydrogen storage alloys manufactured by the melting method have the problem that, in addition to manufacturing difficulties, it is difficult to avoid the presence of components that cause functional deterioration.

On the other hand, it has been suggested that an attempt to obtain Mg2Ni by a so-called mechanical alloying method without dissolution is technically possible. However, by repeatedly hydrogenating and dehydrogenating the sample alloy at a hydrogen pressure of 0.7 MPa and at a temperature of 300°C, it was found that single-phase Mg and Ni The presence cannot be eliminated, so heat treatment is performed to maintain a temperature of 270 to 300 ° C for 2 months at a hydrogen pressure of 0.25 to 0.85 MPa,
Moreover, it was only after repeating the hydrogenation treatment 58 times that it was recognized that almost the entire amount had become Mg2Ni. I believe that the mechanical alloying method is now translated into Japanese as a mechanical alloying method, but at the current technological level, it is not recognized that complete alloying of single dissimilar metals has been achieved, and there are It is appropriate to evaluate that the same type of oxide is dispersed in ultrafine particles or that the intermetallic compound is used as a starting material and changes to a different phase (for example, an amorphous phase). In order to solve the above problems, the present invention aims to provide a method and an apparatus for producing a hydrogen storage alloy with a high alloying ratio without melting two or more selected metals.

[0008]

[Means for Solving the Problems] A method for producing a hydrogen storage alloy according to the present invention comprises powders of two or more dissimilar metals that can be alloyed to form a hydrogen storage alloy, and 0.5% of the metal powder as an auxiliary agent. ~1.5% by weight of higher fatty acids and grinding balls as grinding media are sealed in the mill pot of a high-speed ball mill, and after adjusting the inside of the mill pot to a non-oxidizing atmosphere, an acceleration of more than 30 times the gravitational acceleration is applied inside the mill pot. In addition to,
The above problem was solved by forming a hydrogen storage alloy with a high alloying rate through mixing, pulverization, and dispersion. Specifically, the non-oxidizing atmosphere includes Ar gas, He gas, N2
The mill pot was filled with one of the gases, and the two or more dissimilar metals were one or more metals selected from the group of Mg, Ca, La, misch metal, and Ti, and Ni.
, Al, V, Cr, Fe, Co, Zr, Cu, Mn, and among the higher fatty acids added as an auxiliary agent, stearic acid is the most desirable. Ta. Furthermore, the high-speed ball mill essential to carrying out the present invention has a means for adjusting a non-oxidizing atmosphere and a mill pot that is detachably connected.
It revolves around the rotation of the main axis, and also rotates around its own axis of rotation, and

It has been clarified that this is a batch planetary ball mill in which the synthetic crushing acceleration ratio G applied to the inside of the mill pot, expressed by Equation 2, is at least 30 or more, and the rotation-revolution angular velocity ratio R is 1.9 or less.

[0009]

[Function] The manufacturing method according to the present invention alloys two or more metals that can form a hydrogen storage alloy without melting them in a furnace, so it can be said to be a type of mechanical alloying method. By applying an extraordinary acceleration inside the mill pot compared to the well-known and conventional high-speed ball mill, we were able to obtain an alloy with a much higher alloying rate than the conventional method. Since this acceleration is required to be at least 30 times the gravitational acceleration, it goes without saying that an apparatus capable of obtaining this acceleration is the greatest prerequisite for implementing the manufacturing method. The mechanical alloying process is still under research and the exact details are not known, but it is believed that the important conditions are that sufficient interdiffusion of atoms occurs and that the enthalpy of mixing ΔHm is large and negative. It's dark. It is natural that the interdiffusion of atoms at low temperatures accelerates as the effective energy provided increases. In contrast to conventional mechanical alloying, which is refined and homogenized through the process of flattening, flaking, cold forging (kneading), lamellar structure, dispersion, and randomization of particles,
It is considered that in the case of the present invention, alloying should be considered to have been completed to the stage of stronger atomic bonds.

It can be easily inferred that the larger the synthetic grinding acceleration ratio G is, the shorter the time required to complete mechanical alloying is. It was confirmed that there was a significant difference in the time required to complete the process when an auxiliary agent was added. Select a type of fatty acid as an auxiliary agent, change the amount added, operate a high-speed ball mill under exactly the same conditions, and after stopping the operation in a relatively short time, examine the progress of alloying. It is recognized that there is a causal relationship between the presence or absence and the proportion of addition thereof and the actual product, and if preferable conditions are set using this relationship, the purpose of the invention can be achieved more easily and more reliably. The theoretical elucidation will be left to future research, but stearic acid is selected as an auxiliary agent and 0.5 to 1.5% by weight of the charged metal powder is used.
It was confirmed that alloying progressed most actively when

[0011]

[Embodiment] An embodiment of a batch-type planetary ball mill 1, which is the premise of the manufacturing method, is shown in FIGS. 1 and 2. To explain the general structure in the figure, a main shaft 22 driven by a motor 6
A plurality of mill pots 21 are arranged evenly around the main shaft 22 (symmetrically if there are two mill pots, radially equidistant from the main shaft 22 if there are three or more mill pots 21), which revolve in response to the rotation of the mill pots 21 themselves. also rotates around its own axis of rotation. Specifically, a planetary gear 8 is provided around the outer periphery of the mill pot 21 that rotates together with the main shaft 22, and the sun gear 7 that meshes with the planetary gear 8 is separately rotated or stopped (stopped in the figure).
, rotates the mill pot 21 while revolving around it. The sun gear 7 is externally fitted onto the main shaft 22. Grinding balls B, which are grinding media, and metal powder M are stored inside the mill pot 21, and the internal atmosphere is replaced with an inert gas such as Ar gas to prevent oxidation of the metal powder M during processing. There is. In order to replace the atmosphere with Ar gas as an example of the atmosphere adjustment means 2, as shown in FIG. It is connected to a vacuum pump 41, to a pressure gauge 61 via a valve 13 and a pipe 34, and to an Ar gas cylinder 51 via a pipe 35 and a valve 12. With the valve 12 fully closed and the valves 11 and 13 fully open, the vacuum pump 41 is used to evacuate the mill pot 2.
Eliminate the air inside 1. After confirming that the predetermined degree of vacuum has been reached using the pressure gauge 61, fully close the valve 11 and close the valve 12.
The mill pot 21 is filled with Ar gas from the Ar gas cylinder 51. After confirming with the pressure gauge 61 that the filled Ar gas pressure has reached a predetermined pressure equal to or higher than atmospheric pressure, the valve 12 is also fully closed, and the one-touch coupler 3 is closed.
Separate the pipe 31 and the pipe 33 in two parts. Ar gas in the mill pot 21 is held by one side of the one-touch coupler 32. This Ar gas filling operation is performed at least once. As described above, put the grinding balls B and metal powder M into the mill pot 21 and
After filling with gas, by operating the planetary ball mill, the centrifugal force and Coriolis force due to the revolution and rotation motion act synergistically on the grinding balls B and the metal powder M, and the metal powder M
is processed.

FIG. 2 is a schematic diagram of the motion of the mill pot of a planetary ball mill, where the revolution angular velocity ω1 and the revolution diameter K are 0.
．． 52m, Mill pot inner diameter N is 0.075m, R=
ω2/ω1, ω2 is the relative angular velocity of rotation with respect to revolution, and the composite crushing angular velocity ratio G is calculated using the formula listed above and is 9
Set ω1 to 43.4 (1/s) and ω2 to 59 so that it becomes 0.
．． It was set to 0 (1/s). Here ω2/ω1 (=
The reason why R) was set to 1.36 is as follows. Figure 3 (
A), (B), and (C) are ball B in the mill pot.
This figure shows the relationship between the state of motion of the mill and the relative ratio of the angular velocities of the mill's revolution and rotation. Assuming that the angular velocity of revolution is ω1, the relative angular velocity of rotation is ω2, and the ratio of the two is R=ω2/ω1, Figure (a) shows the state inside the mill pot where R is 0.5. Here, the balls collectively and collectively surge along the inner circumferential surface of the mill pot, applying effective compressive force and shearing force to the inner circumferential surface, the balls, and the metal charged between the balls. It has an effective effect on ing. Figure (b) is R=1.0, figure (c) is R=1.2
This figure shows the behavior of the ball in case 2. As the rotational angular velocity becomes relatively large, a part of the ball separates from the inner peripheral surface and begins to fly through the space inside the mill pot, and the energy is absorbed by collisions between the balls. The purpose of mechanical alloying begins to show signs of a regression as parts are wasted and the purpose of mechanical alloying is lost. This tendency increases as R increases, and when R exceeds 1.9, a hydrogen storage alloy with a high alloying ratio cannot be obtained no matter how high the synthetic crushing acceleration ratio G is 30 or more. This time, we took this point into consideration and selected R to be 1.36, but it is considered that R is desirably in the range of 1.5 to 0.5.

In this example, among the hydrogen storage alloys, Mg
2Ni was selected as the raw material, and Ni powder with an average particle size of 9μ and Mg powder with an average particle size of 85μ were weighed in the proportion of the alloy composition and charged into a mill pot, and a diameter of 3.9mm made of high carbon Cr bearing steel was prepared. The space volume of the mill pot is 3.
Only the amount corresponding to 0% was charged. As the auxiliary higher fatty acid, stearic acid [CH3(CH2)16COOH] was selected from a group of compositions such as mystilic acid, palmitic acid, lauric acid, oleic acid, and linolenic acid, and the amount added was 0 in weight ratio to the metal powder. ~ Changed to 2.0%, added amount 0
The grinding time was set to 240 minutes only in the case of 1, and the other conditions were kept constant at 30 minutes regardless of the amount of addition. For each sample, it was examined by DTA analysis whether all the metal powders were alloyed or whether unreacted Mg remained in the form of a single phase. Table 1 shows the sample number, the proportion of stearic acid added, and the proportion of free flour. Here, the term "free powder" refers to the proportion of the processed material that is immediately collected without adhering to the balls or the inner surface of the mill pot when the lid of the mill pot is opened and the processed material inside is taken out after the grinding process is completed. That is, the ratio is 10
0% indicates that the entire amount of processed material was recovered without any modification.

[0014]

[Table 1]

In the actual grinding work, in sample 1, all of the processed materials in the mill pot adhered to the grinding balls and the inner peripheral surface of the mill pot, and the processed materials that could be recovered without any modification were zero.
Met. In addition, in sample 2, there is no adhesion and recovery as free powder is almost 100%, but ignition occurs during the separation process between the grinding balls and the powder by sieving, making it unsuitable.

What is most clearly revealed in DTA analysis is the temperature dependence of the dissociation pressure of metal hydrides, which differs from component to component. In Figure 4, if we now find the temperature at which the dissociation pressure of hydrogen is 1 MPa, the temperature T1 at which Mg crosses 1 MPa is Mg
It is shown that 2Ni is always on the higher temperature side than the temperature T2 which crosses 1 MPa. Therefore, whether the metal forming the hydride is a single phase or a complex phase in which two or more types coexist can be determined by whether the temperature at which hydrogen dissociates or bonds is single or multiple. Can be done.

DTA analysis and P for samples 1 to 6
A CT diagram was created and alloying into Mg2Ni was examined based on the above principle. Among these, Sample 1 and Sample 4 are taken as representative examples and the results are illustrated. (1) Sample 1 Figure 5 shows the DTA analysis of this sample. In curve D representing differential heating, in addition to peak point E where Mg2NiH4 dissociates into Mg2Ni and H2, there is peak point F where MgH2 dissociates into Mg and H2, and in addition to peak point I where Mg2Ni combines with H2, MgH2 is generated. There is a peak point J, indicating that a considerable amount of single-phase Mg exists. (2) Sample 4 FIG. 6 is a PCT diagram of this sample, and a clear difference is recognized when compared with the conventional technique (dissolution method) shown in FIG. In other words, in Figure 8, when the hydrogen pressure reaches nearly 0.6 MPa, there is a range A where both occlusion and desorption follow a gentle slope, and it was explained that this indicates the existence of a single Mg phase, but sample 4 corresponds to range A. There is no such part and Mg is almost completely Mg
This indicates that it is 2Ni. Figure 7 is a DTA analysis of the same sample;

Only the phase change shown by Equation 3 is observed, and no double peak or inflection point indicating the presence of single-phase Mg is observed.

As mentioned above, when stearic acid is added as an auxiliary agent, adhesion of the powder to the grinding balls and the inner peripheral surface of the mill pot is suppressed, and the dispersion is improved and the alloying reaction is accelerated, and the process continues until the alloying is completed. The time required will be significantly reduced. In other words, in this example, when the addition ratio of stearic acid is 0, even if the grinding time is 240 minutes, some single-phase Mg still remains (sample 1), but if 0.25 or more stearic acid is added, the grinding time is 1 /6, it was possible to obtain an alloy in which single phase Mg disappeared. However, considering the proportion of free powder, the lower limit for stearic acid is preferably 0.5 or more, and if it is more than 2%, the activity will become too large and there is a risk of ignition when the grinding balls and powder are separated by a sieve, so it is 1.5. It is desirable to set the upper limit to 0.5% to 1.5%.
This was the basis for specifying the weight percentage.

[0019]

[Effects of the Invention] As described above, the present invention produces a hydrogen storage alloy without melting, and contains only an alloy that undergoes a phase change to a hydride more effectively and quickly than in the past, and does not contain other single-phase metals. It is possible to obtain an alloy body with an extremely high alloying rate. Therefore, the reaction rate with hydrogen is fast, and its absorption and desorption capabilities are enhanced to near the theoretical value. Therefore, when installed in various applications that have been applied in the past, it is expected that results far superior to those of the past will be produced. Moreover, among non-melting manufacturing methods, we focused on the speed of alloying and found one of the best conditions, and found one of the most efficient manufacturing methods, surpassing the conventional level in terms of mass production and economy. We were able to improve significantly. Furthermore, the manufacturing cost is much lower than the conventional melting method, and alloys that do not use expensive La can also be manufactured freely, so in this regard, it is possible to obtain large economic effects as well as quality improvement. Needless to say.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional front view of an apparatus used to implement the present invention.

FIG. 2 is a schematic diagram of the movement of the device.

[Fig. 3] (A), (B), and (C) show the relationship between the operating state of the ball and the relative ratio of angular velocities of rotation and revolution of the mill.

FIG. 4 is a diagram showing the relationship between hydrogen dissociation pressure and temperature for Mg, Mg2Ni, etc.

FIG. 5 is a DTA diagram of a comparative example of the present invention.

FIG. 6 is a PCT diagram of an example of the present invention.

FIG. 7 is a DTA diagram of an embodiment of the present invention.

FIG. 8 is a PCT diagram of the prior art.

FIG. 9 is a DTA diagram of the prior art.

[Explanation of symbols]

1 Planetary ball mill 2 Atmosphere adjustment means 7 Sun gear 8 Planetary gear 21 Mill pot 22 Main shaft 41 Vacuum pump 51 Ar gas filled cylinder

Claims (5)

[Claims] Claim 1: Powders of two or more different metals that can be alloyed to form a hydrogen storage alloy, and 0% of the metal powder as an auxiliary agent.
．． 5 to 1.5% by weight of higher fatty acids and grinding balls as grinding media are sealed in a mill pot of a high-speed ball mill,
After adjusting the inside of the mill pot to a non-oxidizing atmosphere, an acceleration of 30 times or more of the gravitational acceleration is applied to the inside of the mill pot, and a hydrogen storage alloy with a high alloying rate is formed through mixing, crushing, and dispersion. Method for manufacturing hydrogen storage alloy. 2. In claim 1, the non-oxidizing atmosphere is
A method for producing a hydrogen storage alloy, characterized in that a mill pot is filled with any one of Ar gas, He gas, and N2 gas. 3. In claim 1 or 2, the two or more dissimilar metals are one or more metals selected from the group of Mg, Ca, La, misch metal, Ti, and Ni, Al, V, Cr.
, Fe, Co, Zr, Cu, and Mn. [Claim 4] In any one of claims 1 to 3,
A method for producing a hydrogen storage alloy, characterized in that the higher fatty acid is stearic acid. 5. The high-speed ball mill according to claim 1,
It has a mill pot that is removably connected to a non-oxidizing atmosphere adjustment means, revolves around the rotation of the main shaft and rotates around its own rotation axis, and has a synthetic pulverization acceleration applied to the inside of the mill pot expressed by [Equation 1] An apparatus for producing a hydrogen storage alloy, characterized in that it is a batch planetary ball mill having a ratio G of at least 30 and a revolution-revolution angular velocity ratio R of 1.9 or less.