JPH02179837A - Manufacture of hydrogen storage alloy and electrode - Google Patents

Abstract

PURPOSE:To manufacture the alloy which is homogeneous and has good characteristics such as the amt. of hydrogen to be stored with good reproducibility by utilizing at least zircalloy as a starting material. CONSTITUTION:At least zircalloy (Zn-Sn alloy) is used as a starting material, which is melted by a high frequency furnace, an arc furnace or the like to manufacture the hydrogen storage alloy. Preferably, the alloy expressed by general formula ABalpha or its hydride is manufactured. In the formula, A denotes Zr, Ti, Hf, Ta, Y, etc., B denotes Sn or a mixture of Sn and Fe, V, Ni, Cr, Mn or the like, alpha=1.5 to 2.5 and A and B are regulated as different kinds of elements. The alloy phase substantially belongs to a Laves phase of intermetallic compounds and its crystal structure is regulated as the C14 type of hexagonal symmetry or the C15 type of cubic symmetry. The alloy is used to the storage, holding and transportation of hydrogen, a heat pump, material for the negative electrode of an alkali storage battery, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for producing a hydrogen storage alloy that reversibly absorbs and releases hydrogen, and in particular for hydrogen storage, retention, and transportation, heat pumps, and negative electrodes of alkaline storage batteries. This research focuses on the manufacturing method of hydrogen storage alloys used in industrial materials, etc.

Conventional technology Hydrogen storage alloys used for storing, retaining, and transporting hydrogen, and as negative electrode materials for heat pumps and alkaline storage batteries, include rare earth alloys, Zr(T:) series, and M9.
There are systems etc. Among these, z, ("r: )-Ni series, Zr(Ti)-V series,
Zr(Ti)-Mn-based alloys or alloys based on these alloys and substituted with or added with other elements are attracting attention.

Among them, a larvous phase alloy containing Zr as an essential component can safely store a large amount of hydrogen and is suitable as a practical hydrogen storage alloy.

Conventionally, the manufacturing method for this alloy has generally used simple Zr as a starting material for Zr. That is, for example, a porous alumina crucible or the like is prepared by mixing each of the component raw materials at a predetermined atomic ratio, and then melted directly in the crucible using a high-frequency induction heating furnace, high-temperature resistance heating furnace, arc furnace, etc. and synthesize it.

Problems to be Solved by the Invention However, when using Zr as a single metal as one of the raw materials and melting it, it tends to react with the crucible in a solution state, and at high temperatures, tends to cause compositional deviations due to differences in vapor pressure with other elements. , it is difficult to obtain a homogeneous alloy with the desired composition. In addition, since Zr single metal requires a complicated purification process in its manufacture, Zr.

Metal material prices are relatively high. Therefore, from the viewpoints of practicality, economy, and safety, a method that does not use Zr alone is desired for manufacturing Zr-containing alloys.

The present invention has been made in view of the above-mentioned problems in manufacturing Zr-containing hydrogen storage alloys, and provides a method for manufacturing hydrogen storage alloys that is low in raw material cost and manufacturing cost, and has high reliability and reproducibility, and a method using the same. The purpose is to provide an electrode.

Means for Solving the Problems The manufacturing method of the present invention replaces elemental Zr, which is a component raw material, with commercially available Zircaloy (Zr-Sn alloy), thereby achieving low raw material and manufacturing costs, high reliability, and uniform production. Therefore, it is possible to obtain a hydrogen storage alloy with good properties such as hydrogen storage capacity. Note that when Zircaloy is used, if it is insufficient to obtain an alloy with a desired composition, the same effect can be obtained depending on the amount added by supplementing with a single metal.

Function: The alloy produced using this method has good homogeneity due to little variation between lots,9 and its quality is stable and reliable.
Moreover, it is inexpensive and has excellent oxidation resistance.

As a result, the present invention provides a hydrogen storage alloy containing at least Zr and 80, particularly a hydrogen storage alloy of the general formula ABα (where A is Z
r, Ti, H+, T,, Y, C,
, Mg, L,.

C,,P,, Mm, Nb, Nd, Mo,
One or more elements selected from AI, S; B is Sn alone or S, and V, Ni, C,
,Mm,C,,C,,Zr.

AI, S:, Nb, Mo, W, M
m, ca, y, T,.

P dHAI1 Aup' Cd, Inp B
+J La) Ce, Pr.

One or more elements selected from Nd, Th, S, Mm (Mm indicates a mixture of rare earth elements),
α = 1.5 to 2.5, and A and B are different elements), and the alloy phase substantially belongs to the ravas phase of the intermetallic compound,
C14 type whose crystal structure is hexagonal symmetry or C whose crystal structure is cubic symmetry
15 type, especially for the C14 type with hexagonal symmetry, the crystal lattice constants a and C are respectively a = 4.8 to 5.2 A (Angstrom) and C = 7.9 to 8.3 A (Angstrom), and cubic symmetry. The C15 type is effective when applied to an alloy phase having a crystal lattice constant a of 6.92 to 7.70A (angstroms).

Further, when the alloy prepared by the above method is used as a hydrogen storage electrode, the effect is particularly remarkable.

Example The present invention will be explained in detail below.

Example 1 Table 1 compares an example of the composition and price ratio of zirconium (Zr) single metal and Zircaloy alloy as raw materials used to carry out the present invention.

As shown in Table 1, the price of elemental zirconium metal per unit weight is about 3 to 8 times higher than that of zircaloy.

For example, Zircaloy I in the product category has a high Zr ratio of 98%, but the price is about 1/7 of the conventional product. Furthermore, when the homogeneity of Zircaloy I and Zircaloy 2 was examined, both were found to be extremely good. Also, the vapor pressure when these are dissolved is Z.

It was found that it was lower than that of metals, and that there was less compositional deviation.

Conventional alloys containing Zr and Sn (especially Laves phase A
In the manufacturing method of Ba-based alloys, alloys are manufactured by adding electrolytic iron, monochrome nickel, elemental tin metal, etc. to this expensive zirconium at a desired mixing ratio. Therefore, in addition to the cost disadvantage of raw materials, the manufacturing process became complicated, and problems such as the ease of oxidation of elemental zirconium and non-uniformity of the alloy occurred, but the examples shown in Table 1 These drawbacks can be eliminated by using Zircaloys such as.

The manufacturing procedure of the present invention using Zircaloy as a raw material may be similar to a conventional melting method using a high frequency furnace or an arc furnace. Zr(T
i) -M-based alloy (here M is Sn and Fe, V,
Ma, Ca, Y, Hf, Nb.

Ta, Cr, Mo, W, Mo, C0,
Pd, Cu, Ag, Au+ Zn, Cd,
A++ Si+ Inn B:, La+
calM-, Pr, N, i, Th, S-
one or more elements selected from ) in a desired composition ratio,
When melted, the alloy after melting had better homogeneity than the conventional one, had almost no compositional deviation in Table 2, and had little variation between lots. Next, we investigated its properties as a hydrogen storage alloy (hydrogen storage capacity, reaction rate, ignitability in air, etc.) and found that
As shown in the table, the hydrogen storage capacity was large, and other properties such as reaction rate were also very good.

Example 2 Commercially available Zircaloy and Z
-, N, Ti, Hf, Ta, Y, C
-, N9゜L a) C+ly Mal Nbl
NdI S#+ Mo, A++ si.

V, C,, Mn, F-, C-, C,, Zn,
S:, Nb.

Mm, W, Ca, etc. are used as raw materials. Among the ABa alloys, the general formulas ZrαN, γMδ (Tadashi α.

γ and δ are the atomic ratios of Z7, N5, and M elements, respectively, and α
= 0.5~1.5, γ=0.4~2,5, δ=0.0
1 to 1.8, and γ+δ=1.2 to 3.7, M:S,
l alone or S, and Fe, V, N9. C
a.

Y, Hf, Nb, T,, C,, Mm,
W, Mn, Co, P 61 Cgp
Agp Au, Zn) CdHA++ S;
, [n.

B+, L-, C-, M-, P-, Na, T? ,
, S,) were selected, and alloys having compositions N016 to 11 in Table 2 were synthesized from among them.

Specifically, raw materials such as Zircaloy were first weighed to have the composition shown in the table, and directly melted in an argon arc melting furnace (or a high frequency induction heating furnace in argon inert gas). A part of the melted alloy sample is used for alloy analysis such as atomic composition, crystal structure, crystal lattice constant, homogeneity, etc., and the rest is used for measuring hydrogen absorption and release in hydrogen gas (mainly P (pressure)). -C (composition) -T (temperature) measurement) and electrochemical performance evaluation.

From the analysis results, alloys Nos. 6 to 11 in Table 2 are homogeneous, and the main alloy phase is the 014 type or C15 type Laves phase, and the crystal lattice constant is a and C are respectively a=4.8~5.2A (angstrom) and c=7.9~8.3A (angstrom).In addition, in the case of cubic symmetric C15 type, the crystal lattice constant a is 6.92~ I confirmed that it was 7.70A (angstrom). Furthermore, there was almost no compositional deviation. Table 2 shows the hydrogen storage capacity of these alloys obtained from ordinary P-C-T characteristic results with hydrogen gas. These values were larger than conventional values, and characteristics such as reaction rate were also good.

On the other hand, Alloy Nos. 12 to 15 in Table 2 are representative examples of alloys made by conventional manufacturing methods, shown for comparison. In these cases, homogeneity and compositional deviation occurred, and the amount of hydrogen storage was quite small, even though the systems were similar as shown in the table.

In addition, there are many alloy compositions other than those shown in Table 2 to which the manufacturing method of the present invention can be applied. Among these, the alloy phase substantially belongs to the Laves phase of an intermetallic compound, and its crystal structure is the 014 type with 60,000 symmetry or (and) the C15 type with cubic symmetry, and its crystal lattice constant is 6-way symmetric. C1 of
For type 4, a and C are each a=4.8 to 5.2
A (angstrom), c = 7.9~8.3A
(Angstrom) In addition, particularly for the cubic symmetric C15 type, alloys with a crystal lattice constant a of 6.92 to 7.70A (Angstrom) were particularly effective.

In this way, it is used as a starting material for hydrogen storage alloys.

According to the manufacturing method of synthesizing a hydrogen storage alloy using Zircaloy consisting of Zr and 80, the alloy has extremely good homogeneity.
JZr and S also have excellent performance as hydrogen storage, retention, and transport alloys.
It was superior to those using n-metal alone as a raw material, and the process was simpler.

Here, the alloys obtained by the present manufacturing method are strictly compared and evaluated in terms of the amount of hydrogen absorption and release, and the effects of the present invention due to each element are investigated to obtain an optimal composition example in which the present invention exhibits the most effect.

General formula ZrαN, γMδ (where α, γ, and δ are the atomic ratios of Zl, N1, and M elements, respectively, and α=0.5 to 1.
5, γ = 0.4 to 2.5, δ = 0.01 to 1.8, and γ + δ = 1.2 to 3.7, M: S, alone or S,
and F-, V, Ma, Ca, Y, Hr
.

Nb, Ta, C-, Mm, W, Mll,
C0, Pd, Cu.

A gp Aug Znp Cd) A+5
si, Inp B+$ L8? C,,M-,
An alloy system represented by one or more elements selected from P, Na, Th, S, and the atomic ratio δ is o.

Alloys smaller than 1 or larger than 1.8 also had slightly smaller amounts of hydrogen release. Further, alloys with an atomic ratio α smaller than 0.5 have a somewhat insufficient hydrogen storage capacity, and alloys with an atomic ratio α larger than 1.5 have a relatively small hydrogen release capacity. Furthermore, the atomic ratio γ
Alloys with a value smaller than 0.4 had insufficient hydrogen storage/release cycle durability, and alloys with a value larger than 2 or 5 had a slightly small amount of hydrogen storage. Alloys with a value of (γ+δ) smaller than 1.2 had a relatively small hydrogen release amount, and alloys with a value larger than 3 or 7 had a relatively small hydrogen storage amount. The reason for these is that the Zr content α is particularly related to the hydrogen storage capacity, and the Zr content α
The larger the number of l, the larger the amount of hydrogen storage, but since a stable hydride is formed, the hydrogen release rate is lower, and as a result, the amount of hydrogen released is smaller. Further, the amount of N1 is particularly related to storage/desorption cycle characteristics (durability), and the larger the amount of N1, the longer the life span, but there is a tendency for the amount of hydrogen storage to decrease. In particular, the M element content δ is particularly involved in the storage/desorption cycle characteristics and the desorption pressure, and as the amount of M increases, these characteristics improve, but the hydrogen absorption capacity decreases. In addition, the effect of making Sn an essential element is 9
Because the alloy has excellent solubility and homogeneity, and is inexpensive,
It has great advantages industrially and economically.

Further, as shown in Table 3, the hydrogen storage alloy negative electrodes for alkaline storage batteries formed using the alloys represented by the general formulas ZrαN and γMδ had large and good electric capacities.

Table 3 Effects of the Invention The alloys and electrodes manufactured by the manufacturing method of the present invention have good homogeneity, reproducibility, and little variation between lots, resulting in stable quality and high reliability.Moreover, the cost of raw materials is low, and the manufacturing method is Since the process is simple, the price of the two alloys is low, and as a result, it is possible to supply an alloy with excellent properties such as hydrogen absorption/release amount and cycle life, and is also preferable in terms of oxidation resistance.

Claims (5)

[Claims] (1) At least Zircaloy (Zr
-Sn alloy) A method for producing a hydrogen storage alloy. (2) At least Zircaloy (Zr
-Sn alloy) using the general formula ABα (where A is Z
r, Ti, Hr, Ta, Y, Ca, Mg, La, Ce,
One or more elements selected from Pr, Mm, Nb, Nd, Mo, Al, Si, B is Sn alone or Sn and Fe, V, Ni, Cr, Mn, Co, Cu, Zn,
Al, Si, Nb, Mo, W, Mg, Ca, Y, Ta,
Pd, Ag, Au, Cd, In, Bi, La, Ce, P
One or more elements selected from r, Nd, Th, Sm, Mm (here Mm indicates a mixture of rare earth elements), α = 1.5 to 2.5, and A and B are different elements ), the alloy phase substantially belongs to the Laves phase of an intermetallic compound, and its crystal structure is the C14 type with hexagonal symmetry or the C15 type with cubic symmetry, and especially the crystal lattice constant of the C14 type with hexagonal symmetry. a and c are respectively a=4.8-5.2A (angstrom) and c=7.9-8.3A (angstrom). Also, for the cubic symmetric C15 type, the crystal lattice constant a is 6.92-7. A method for producing a hydrogen storage alloy, the method comprising producing an alloy having a diameter of 70A (angstroms) or a hydride thereof. (3) The method for producing a hydrogen storage alloy according to claim 2, wherein the alloy or its hydride contains Zr as A in an amount of at least 30 atom %. (4) The alloy or its hydride substantially has the general formula Z
rαNiγMδ (however, α, γ, δ are each Zr
, Ni, M element atomic ratio, α=0.5 to 1.5, γ=
0.4-2,5, δ=0.01-1.8, and γ+δ
=1.2-3.7, M: Sn alone or Sn and Fe
, V, Mg, Ca, Y, Hf, Nb, Ta, Cr, Mo
, W, Mn, Co, Pd, Cu, Ag, Au, Zn, C
d, Al, Si, In, Bi, La, Ce, Mm, Pr
, Nd, Th, and Sm). (5) At least Zircaloy (Zr
-Sn alloy).