CA2456823A1 - Ca-mm-ni based hydrogen storage alloys - Google Patents
Ca-mm-ni based hydrogen storage alloys Download PDFInfo
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- CA2456823A1 CA2456823A1 CA002456823A CA2456823A CA2456823A1 CA 2456823 A1 CA2456823 A1 CA 2456823A1 CA 002456823 A CA002456823 A CA 002456823A CA 2456823 A CA2456823 A CA 2456823A CA 2456823 A1 CA2456823 A1 CA 2456823A1
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
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- C22C1/00—Making non-ferrous alloys
- C22C1/04—Making non-ferrous alloys by powder metallurgy
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B3/00—Hydrogen; Gaseous mixtures containing hydrogen; Separation of hydrogen from mixtures containing it; Purification of hydrogen
- C01B3/0005—Reversible uptake of hydrogen by an appropriate medium, i.e. based on physical or chemical sorption phenomena or on reversible chemical reactions, e.g. for hydrogen storage purposes ; Reversible gettering of hydrogen; Reversible uptake of hydrogen by electrodes
- C01B3/001—Reversible uptake of hydrogen by an appropriate medium, i.e. based on physical or chemical sorption phenomena or on reversible chemical reactions, e.g. for hydrogen storage purposes ; Reversible gettering of hydrogen; Reversible uptake of hydrogen by electrodes characterised by the uptaking medium; Treatment thereof
- C01B3/0031—Intermetallic compounds; Metal alloys; Treatment thereof
- C01B3/0047—Intermetallic compounds; Metal alloys; Treatment thereof containing a rare earth metal; Treatment thereof
- C01B3/0057—Intermetallic compounds; Metal alloys; Treatment thereof containing a rare earth metal; Treatment thereof also containing nickel
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- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/38—Selection of substances as active materials, active masses, active liquids of elements or alloys
- H01M4/383—Hydrogen absorbing alloys
- H01M4/385—Hydrogen absorbing alloys of the type LaNi5
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M8/00—Fuel cells; Manufacture thereof
- H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
- H01M8/04082—Arrangements for control of reactant parameters, e.g. pressure or concentration
- H01M8/04201—Reactant storage and supply, e.g. means for feeding, pipes
- H01M8/04216—Reactant storage and supply, e.g. means for feeding, pipes characterised by the choice for a specific material, e.g. carbon, hydride, absorbent
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
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Abstract
New alloys of the AB5 type are disclosed which are of the formula:
(Ca x M1-x)t(N1-y T y)5 where M is one or several metals selected from the group consisting of misch metal (Mm) and other rare earth metals T is one or several semi-metals such as Si, Ge and Ga;
0<x <=1;
0<y <=0.5 and 0.8 <= t <= 1.2.
Also disclosed is a process for preparing these new alloys and their use for hydrogen storage.
(Ca x M1-x)t(N1-y T y)5 where M is one or several metals selected from the group consisting of misch metal (Mm) and other rare earth metals T is one or several semi-metals such as Si, Ge and Ga;
0<x <=1;
0<y <=0.5 and 0.8 <= t <= 1.2.
Also disclosed is a process for preparing these new alloys and their use for hydrogen storage.
Description
, 5 Ca-Mm-Ni BASED HYDROGEhI STORAGE ALLOYS
Field of the invention The present invention relates to new Ca-Mm-Ni based alloys of the ABS type.
The invention also relates to a process for preparing these new alloys and to the use of such new alloys for hydrogen storage.
Back~,round of the invention The use of hydrogen gas as a fuel for PEM fuel cells has received considerable attention in recent years in view of the fact that PEM fuel cells using pure hydrogen can provide high efficiency and ultra clean power. Unfortunately, the widespread use of hydrogen energy is limited by economic and technological barriers. One of the important barriers is the lack of cost effective, safe hydrogen storage method.
Hydrogen gas is very light. It can be compressed under high pressure and stored in pressurized vessels. It can also be liquefied and stored in liquid form.
Hydrogen also reacts with metal or non-metals to form hydrides. Some metal hydrides are reversible at ambient temperature and pressures. From a safety point of view, metal hydrides are intrinsically safe since the hydrogen must be released from the hydrides by an endothermic process before it can burn or be oxidized.
The volumetric density of hydrogen storage in metal hydrides is usually high.
The most serious shortcomings of the reversible low temperature metal hydrides are their low gravimetric storage density and their high cost. For stationary and some mobile applications, the weight of the hydrogen storage tank is not a problem. However, the high cost of conventional low temperature metal hydrides results in too expensive storage devices.
CaNiS intermetallic compound represents a category of low cost hydrogen storage materials with a maximum storage capacity up to l.9wt.% (see reference 1). However, little attention has been paid to this system, probably due to its well-known bad cycling stability (see reference 2). Improvement of
Field of the invention The present invention relates to new Ca-Mm-Ni based alloys of the ABS type.
The invention also relates to a process for preparing these new alloys and to the use of such new alloys for hydrogen storage.
Back~,round of the invention The use of hydrogen gas as a fuel for PEM fuel cells has received considerable attention in recent years in view of the fact that PEM fuel cells using pure hydrogen can provide high efficiency and ultra clean power. Unfortunately, the widespread use of hydrogen energy is limited by economic and technological barriers. One of the important barriers is the lack of cost effective, safe hydrogen storage method.
Hydrogen gas is very light. It can be compressed under high pressure and stored in pressurized vessels. It can also be liquefied and stored in liquid form.
Hydrogen also reacts with metal or non-metals to form hydrides. Some metal hydrides are reversible at ambient temperature and pressures. From a safety point of view, metal hydrides are intrinsically safe since the hydrogen must be released from the hydrides by an endothermic process before it can burn or be oxidized.
The volumetric density of hydrogen storage in metal hydrides is usually high.
The most serious shortcomings of the reversible low temperature metal hydrides are their low gravimetric storage density and their high cost. For stationary and some mobile applications, the weight of the hydrogen storage tank is not a problem. However, the high cost of conventional low temperature metal hydrides results in too expensive storage devices.
CaNiS intermetallic compound represents a category of low cost hydrogen storage materials with a maximum storage capacity up to l.9wt.% (see reference 1). However, little attention has been paid to this system, probably due to its well-known bad cycling stability (see reference 2). Improvement of
2 the hydrogen storage properties of CaNiS by substitution of Ca or Ni with other elements has been tried (see references 3 to 5). Ternary CaxMmt-XNis and quaternary CaXMm~_xNi;_yCuy alloys have been produced by melt casting and patented 20 years ago (see reference 6). Substitution of Mm (mishmetal) for Ca can raise the plateau pressure of CaNis. However, the plateau slope is big for the as-cast ternary alloys due to segregation. Annealing at elevated temperaWres (>1000C) can reduce the slope to some extent. The inventor's previous work show that CaNis and Mm andlor Zn-substituted CaNiS type alloys with flat plateau can be successfully produced (see reference 7).
Substitution of Ni by Mm and AI in the CaNiS type alloys can improve the cycling stability as disclosed in US 4,631,170 (see reference 8). However, the long term cycling stability of the alloys according to this patent is still not good enough. Typically more than 20% of the capacity is lost upon 200 times of hydrogen absorption/desorption cycling.
Further improvement has been achieved by concomitant substihition of Mm for Ca and Zn and A1 for Ni, as reported by the present inventors of record (see reference 9). The capacity loss after 500 cycles has proved to be less than 20% for Cao_BMmo.2Ni4,8Zno.~Alo,, and less than 10% for Cao~Mmo,3Ni4,8Alo.lZno,l, However, the maximum storage capacity is significantly reduced by substitution of Zn and Al for Ni.
Summary of the invention In accordance with the present invention, it- has now been found that substitution of Si, Ge and some other metalloid elements (also called "semi- _ metals") for Ni in a ternary Ca-Mm-Ni alloy of the ABS type can substantially improve the long term stability of such an alloy without causing much reduction of the storage capacity. Essentially, no capacity loss has been observed after 500 hydrogen absorption and desorption cycles.
Thus, a first object of the present invention is to provide new Ca-Mrn-Ni based alloys of the AB$ type, which axe capable of absorbing and desorbing hydrogen from a gas phase at ambient temperature with a relative flat plateau
Substitution of Ni by Mm and AI in the CaNiS type alloys can improve the cycling stability as disclosed in US 4,631,170 (see reference 8). However, the long term cycling stability of the alloys according to this patent is still not good enough. Typically more than 20% of the capacity is lost upon 200 times of hydrogen absorption/desorption cycling.
Further improvement has been achieved by concomitant substihition of Mm for Ca and Zn and A1 for Ni, as reported by the present inventors of record (see reference 9). The capacity loss after 500 cycles has proved to be less than 20% for Cao_BMmo.2Ni4,8Zno.~Alo,, and less than 10% for Cao~Mmo,3Ni4,8Alo.lZno,l, However, the maximum storage capacity is significantly reduced by substitution of Zn and Al for Ni.
Summary of the invention In accordance with the present invention, it- has now been found that substitution of Si, Ge and some other metalloid elements (also called "semi- _ metals") for Ni in a ternary Ca-Mm-Ni alloy of the ABS type can substantially improve the long term stability of such an alloy without causing much reduction of the storage capacity. Essentially, no capacity loss has been observed after 500 hydrogen absorption and desorption cycles.
Thus, a first object of the present invention is to provide new Ca-Mrn-Ni based alloys of the AB$ type, which axe capable of absorbing and desorbing hydrogen from a gas phase at ambient temperature with a relative flat plateau
3 pressure and a storage capacity larger than l:2wt.%. These new alloys are of the formula (I):
(CaxMl-x)c~l-yTY)s (I) where M is selected from the group consisting of: any mischmetal, any rare earth metal, and an homogeneous or an inhornogeneous combination of any of: (i) at least two mischrnetals, (ii) at least two rare earth metals, and (iii) at least one mischmetal and at least one rare earth metal.
T is selected from the group consisting of metalloids and an homogeneous or an inhomogeneous combination of at least two metalloids;
0<x< 1 0<y< 0.5 and 0.8 < t < 1.2.
Another object of the invention is to provide a process for the preparation of the above mentioned alloys of formula (I), which comprises the following steps:
a) preparing a powder by milling a mixture of elemental powders and/or pre-alloyed substances of the elemental ingredients of the alloy to be~prepared (such as, for example, Ca, Ni, Mm, CaNi2, CaNis, MmNis and so on) in adequate proportions to obtain the required alloy; and b) annealing and/or sintering the so prepared powder at elevated temperatures in a crucible for a short period of time in an inert or reactive atmosphere.
In use, step a) may consist of a ball milling or of a mechanical alloying and can be carried out at room temperature or at high temperatures with or without anti-sticking agents.
d Step b) is essential to the above process. This step must actually be carried out to achieve high reversible capacity and a flat plateau. In use, the annealing can be carried in a crucible made of stainless steel at a temperature higher than 600°C but not higher than 1100°C.
Alternatively, the new compounds according to the invention can be produced by conventional melt casting methods ar powder sintering methods.
The compounds according to the invention are useful for hydrogen storage in a gaseous form and such is a further object of the invention.
DETAILED DESCRIPTION OF THE INVENTION
As aforesaid, the invention is directed to new alloys of the ABs type, which are of the formula:
(CaXMi-X)t~l-yTy)s M can be mischmetal, or any rare earth metal. M can also be an homogeneous or an inhomogeneous combination of any of: (i) at least two mischmetals, (ii) at least two rare earth metals, and (iii) at least one mischmetal and at least one rare earth metal. In this respect, M is selected from the group consisting of any mischmetal, any rare earth metal, and an homogeneous or an inhomogeneous combination of any of: (i) at least two mischmetals, (ii) at least two rare earth metals, and (iii) at least one mischmetal and at least one rare earth metal T is selected from the group consisting of: metalloids, and an homogeneous or an inhomogeneous combination of at least two metalloids;
0<x< 1 (x$0); preferably 0.4<x<l;
0< y < 0.5 (y$0), preferably 0<y<0.3; and 0.8 < t < 1.2.
A suitable mischmetal is one of the composition 51 wt% Ce, 26.4 wt% La, 16.4 wt% Nd and 5.3 wt%Pr. A further suitable mischmetal is one of the 5 composition 62 wt% La, 21 wt°f°Ce; 3 wt% Pr, and 14 wt% Nd.
Many further compositions are suitable, and differ in the properties of the constituent elements La, Ce, Pr, and Nd.
Examples of rare earth metals are Y, La, Ce, Pr, Nd, Sm, Dy, Gd, Ho, Th, U, Pm, Tb, Er, and Lu. Preferably, the rare earth metal is any of La, Ce, Pr, Nd, Dy, Th, and Y.
Suitable metalloids include Si, Ge, and Ga.
As aforesaid, the invention is actLially based on the discovery that significant further improvements have been achieved by substituting Si, Ge and/or other metalloids for Ni in the above mentioned Ca-Mm-Ni alloy of the ABS type (see the definition of T in the formula given hereinabove). This substitution has significant effect of improving the long-term stability while keeping predominantly the ABS structure and hydrogen storage capacity according to the invention that are particularly useful.
The new Ca-Mm-Ni alloys of the AB5 type according to the invention with improved properties can be made by mechanical alloying of elemental powders (such as Ca, Mm, Nis) and/or mixW res of intermetallic compounds (such as CaNis, MmNis) corresponding to the required composition, followed by an thermal annealing treatment at temperatures higher than 600°C for short period of time, typically at ,.1000°C or slightly higher for O.Sh-lh in a steel crucible. Annealing at temperatures lower than 600C does not improve the hydrogen storage properties very much.
The invention and its advantages will be better understood upon reading the following description made with reference to the accompanying drawings.
Fig. 1 is a curve giving the hydrogen storage capacity of an alloy of formula lCa0.b4 Mm0.36~1.1 Nis as a function of the pressure after 3 cycles and 250 cycles;
Fig. 2 is a curve similar to the one of Fig. l, but with an alloy of formula (Cao,s4 ~o.3s)a.i Ni4.9 Sia.i;
Fig. 3 is a curve similar to the one of Fig. 1, but with an alloy of formula (Cao.sa Mmo.s6O.~ Nia.s Sio.2;
Fig. 4a is a X-ray analysis of the alloy of formula (Cao.~,~ Mrno,36)1.1 N~.s Sio.a mentioned hereinabove (see Fig. 3);
Fig. 4b is an X-ray analysis of the alloy of formula (Cat~,~4 Mmo,3~;),,~ Nis mentioned hereinabove (see Fig. 1); and Fig. 5 is a curve similar to the one of Fig. 1, but with an alloy of fornmla (Cao.s4 Mmo.36)~.i Ni4.es Geo.is.
EXAMPLE 1 (Preparation of a known compound by the process of the invention) (Cao,6aMmo.36)~.~Nis was synthesized by mechanical alloys in a SPEX high energy ball mill under argon. A MmNis powder (>99%, + 100mesh), Ca granules (>99.5, ~2mm in size) and Ni powders 099.9%,-325mesh) were used as starting materials.
After alloying, an isothermal annealing was performed in a tubular furnace under argon. The mechanically alloyed powder was sealed in a stainless steel crucible before annealing. The powder was heated to 1050°C at a heating rate .
of 30°C/min, and held at 1050°C for 1 hour, then cooled down to room temperature in the furnace. ~ __ The hydrogen absorptionldesorption properties were measured by using an automatic Sievert's type apparatus. The annealed powder normally needs mild activation treatment, such as heated to 200°C under vacuum and then cooled down. The activated (Cao.64Mmo.ss)i.i Nis alloy exhibits a relative flat plateau and a maximum storage capacity of 1.44 wt.% under 4.0MPa of charging pressure.
A hydrogen absorption/desorption cycling experiment Was performed at 30°C
under an absorption pressure of 3.SMPa and a desorption pressure of 0.01 MPa. The absorption and desorption time was 12 minutes respectively.
Under these conditions, the alloys could be fully hydrided and dehydrided.
The hydrogen purity was 99.999%. As shown in Fig. l, the maximum storage capacity was reduced to 1.23 wt. % after 250 cycles (20% loss). The reduction of the effective reversible storage capacity is even bigger.
EXAMPLE 2 (Compound according to the invention made by the process of the invention) (Cao.64Mmo.s6O.iNia..9Sio.~ was synthesized by mechanical alloying of elemental Ca, Si and MmNis powder blends. The alloy was annealed in the same manner as in Example 1. This alloy had a maximum hydrogen storage capacity of l.4wt.%. The maximum hydrogen storage capacity are slightly reduced by 8% after 250 cycles as shown in Fig.2 in contrast to the 20% loss in the (Cap,g4Mmp.3G)1.IN15~
EXAMPLE 3 (Compound according to the invention made by the process of the 30 invention) (Cao,~Mmo,36)i.iNia.BiSio.2 was synthesized by mechanical alloying of elemental Ca, Si and MmNis powder blends. The alloy was annealed in the same manner as in Example ~1. This alloy had a hydrogen storage capacity of l.3wt.%. The maximum and reversible hydrogen storage capacities are slightly improved upon hydrogen absorption and desorption cycling as shown in Fig.3. __.
X-ray analyses show that Si-substituted alloys have very high resistance to peak broadening upon cycling as shown in Fig.4a. While the (Cao,saMmo.36)~.~Nis alloy without Si substitution shown obvious peak broadening after cycling as shown in Fig. 4b. It was believed that hydrogen absorption/desorption cycling introduces defects, such as rnicrostrain, chemical disorders and grain boundaries (reduced grain size), therefore leads to reduced storage capacity. The peak broadening reflects the defects introduced during cycling experiments.
r5 EXAMPLE 4 (Compound according to the invention made by the process of the invention) Cao,~ Mmo,4Ni4,8sGeo.is was synthesized by mechanical alloying of elemental powder blends. The alloy was annealed in the same manner as in Example 1.
This alloy had a maximum hydrogen storage capacity of l.3wt.% in the as-synthesized state. Substantial improvement in the maximum and reversibly storage capacity is observed after 500 cycles as shown in Fig.S.
y REFERENCES
(1) "A new family of hydrogen storage alloys based on the system nickel-misch metal-calcium)" by G.D. Sandrock, proc. 12th intersociety energy conversion Engineering Conference, 12th IECEC, Am. Nuclear Society, 1 (1977) 951.
(2) "Stability of Rechargeable hydriding alloys during extended cycling" by P. D. Goodell, J Less-Common Met., 99 (1984) 1.
(3) "Systematic B-metal substitution in CaNiS" by J.O. Jensen and N.J. Bjerrum: J. of Alloys and Compounds 293-295 (1999) 185
(CaxMl-x)c~l-yTY)s (I) where M is selected from the group consisting of: any mischmetal, any rare earth metal, and an homogeneous or an inhornogeneous combination of any of: (i) at least two mischrnetals, (ii) at least two rare earth metals, and (iii) at least one mischmetal and at least one rare earth metal.
T is selected from the group consisting of metalloids and an homogeneous or an inhomogeneous combination of at least two metalloids;
0<x< 1 0<y< 0.5 and 0.8 < t < 1.2.
Another object of the invention is to provide a process for the preparation of the above mentioned alloys of formula (I), which comprises the following steps:
a) preparing a powder by milling a mixture of elemental powders and/or pre-alloyed substances of the elemental ingredients of the alloy to be~prepared (such as, for example, Ca, Ni, Mm, CaNi2, CaNis, MmNis and so on) in adequate proportions to obtain the required alloy; and b) annealing and/or sintering the so prepared powder at elevated temperatures in a crucible for a short period of time in an inert or reactive atmosphere.
In use, step a) may consist of a ball milling or of a mechanical alloying and can be carried out at room temperature or at high temperatures with or without anti-sticking agents.
d Step b) is essential to the above process. This step must actually be carried out to achieve high reversible capacity and a flat plateau. In use, the annealing can be carried in a crucible made of stainless steel at a temperature higher than 600°C but not higher than 1100°C.
Alternatively, the new compounds according to the invention can be produced by conventional melt casting methods ar powder sintering methods.
The compounds according to the invention are useful for hydrogen storage in a gaseous form and such is a further object of the invention.
DETAILED DESCRIPTION OF THE INVENTION
As aforesaid, the invention is directed to new alloys of the ABs type, which are of the formula:
(CaXMi-X)t~l-yTy)s M can be mischmetal, or any rare earth metal. M can also be an homogeneous or an inhomogeneous combination of any of: (i) at least two mischmetals, (ii) at least two rare earth metals, and (iii) at least one mischmetal and at least one rare earth metal. In this respect, M is selected from the group consisting of any mischmetal, any rare earth metal, and an homogeneous or an inhomogeneous combination of any of: (i) at least two mischmetals, (ii) at least two rare earth metals, and (iii) at least one mischmetal and at least one rare earth metal T is selected from the group consisting of: metalloids, and an homogeneous or an inhomogeneous combination of at least two metalloids;
0<x< 1 (x$0); preferably 0.4<x<l;
0< y < 0.5 (y$0), preferably 0<y<0.3; and 0.8 < t < 1.2.
A suitable mischmetal is one of the composition 51 wt% Ce, 26.4 wt% La, 16.4 wt% Nd and 5.3 wt%Pr. A further suitable mischmetal is one of the 5 composition 62 wt% La, 21 wt°f°Ce; 3 wt% Pr, and 14 wt% Nd.
Many further compositions are suitable, and differ in the properties of the constituent elements La, Ce, Pr, and Nd.
Examples of rare earth metals are Y, La, Ce, Pr, Nd, Sm, Dy, Gd, Ho, Th, U, Pm, Tb, Er, and Lu. Preferably, the rare earth metal is any of La, Ce, Pr, Nd, Dy, Th, and Y.
Suitable metalloids include Si, Ge, and Ga.
As aforesaid, the invention is actLially based on the discovery that significant further improvements have been achieved by substituting Si, Ge and/or other metalloids for Ni in the above mentioned Ca-Mm-Ni alloy of the ABS type (see the definition of T in the formula given hereinabove). This substitution has significant effect of improving the long-term stability while keeping predominantly the ABS structure and hydrogen storage capacity according to the invention that are particularly useful.
The new Ca-Mm-Ni alloys of the AB5 type according to the invention with improved properties can be made by mechanical alloying of elemental powders (such as Ca, Mm, Nis) and/or mixW res of intermetallic compounds (such as CaNis, MmNis) corresponding to the required composition, followed by an thermal annealing treatment at temperatures higher than 600°C for short period of time, typically at ,.1000°C or slightly higher for O.Sh-lh in a steel crucible. Annealing at temperatures lower than 600C does not improve the hydrogen storage properties very much.
The invention and its advantages will be better understood upon reading the following description made with reference to the accompanying drawings.
Fig. 1 is a curve giving the hydrogen storage capacity of an alloy of formula lCa0.b4 Mm0.36~1.1 Nis as a function of the pressure after 3 cycles and 250 cycles;
Fig. 2 is a curve similar to the one of Fig. l, but with an alloy of formula (Cao,s4 ~o.3s)a.i Ni4.9 Sia.i;
Fig. 3 is a curve similar to the one of Fig. 1, but with an alloy of formula (Cao.sa Mmo.s6O.~ Nia.s Sio.2;
Fig. 4a is a X-ray analysis of the alloy of formula (Cao.~,~ Mrno,36)1.1 N~.s Sio.a mentioned hereinabove (see Fig. 3);
Fig. 4b is an X-ray analysis of the alloy of formula (Cat~,~4 Mmo,3~;),,~ Nis mentioned hereinabove (see Fig. 1); and Fig. 5 is a curve similar to the one of Fig. 1, but with an alloy of fornmla (Cao.s4 Mmo.36)~.i Ni4.es Geo.is.
EXAMPLE 1 (Preparation of a known compound by the process of the invention) (Cao,6aMmo.36)~.~Nis was synthesized by mechanical alloys in a SPEX high energy ball mill under argon. A MmNis powder (>99%, + 100mesh), Ca granules (>99.5, ~2mm in size) and Ni powders 099.9%,-325mesh) were used as starting materials.
After alloying, an isothermal annealing was performed in a tubular furnace under argon. The mechanically alloyed powder was sealed in a stainless steel crucible before annealing. The powder was heated to 1050°C at a heating rate .
of 30°C/min, and held at 1050°C for 1 hour, then cooled down to room temperature in the furnace. ~ __ The hydrogen absorptionldesorption properties were measured by using an automatic Sievert's type apparatus. The annealed powder normally needs mild activation treatment, such as heated to 200°C under vacuum and then cooled down. The activated (Cao.64Mmo.ss)i.i Nis alloy exhibits a relative flat plateau and a maximum storage capacity of 1.44 wt.% under 4.0MPa of charging pressure.
A hydrogen absorption/desorption cycling experiment Was performed at 30°C
under an absorption pressure of 3.SMPa and a desorption pressure of 0.01 MPa. The absorption and desorption time was 12 minutes respectively.
Under these conditions, the alloys could be fully hydrided and dehydrided.
The hydrogen purity was 99.999%. As shown in Fig. l, the maximum storage capacity was reduced to 1.23 wt. % after 250 cycles (20% loss). The reduction of the effective reversible storage capacity is even bigger.
EXAMPLE 2 (Compound according to the invention made by the process of the invention) (Cao.64Mmo.s6O.iNia..9Sio.~ was synthesized by mechanical alloying of elemental Ca, Si and MmNis powder blends. The alloy was annealed in the same manner as in Example 1. This alloy had a maximum hydrogen storage capacity of l.4wt.%. The maximum hydrogen storage capacity are slightly reduced by 8% after 250 cycles as shown in Fig.2 in contrast to the 20% loss in the (Cap,g4Mmp.3G)1.IN15~
EXAMPLE 3 (Compound according to the invention made by the process of the 30 invention) (Cao,~Mmo,36)i.iNia.BiSio.2 was synthesized by mechanical alloying of elemental Ca, Si and MmNis powder blends. The alloy was annealed in the same manner as in Example ~1. This alloy had a hydrogen storage capacity of l.3wt.%. The maximum and reversible hydrogen storage capacities are slightly improved upon hydrogen absorption and desorption cycling as shown in Fig.3. __.
X-ray analyses show that Si-substituted alloys have very high resistance to peak broadening upon cycling as shown in Fig.4a. While the (Cao,saMmo.36)~.~Nis alloy without Si substitution shown obvious peak broadening after cycling as shown in Fig. 4b. It was believed that hydrogen absorption/desorption cycling introduces defects, such as rnicrostrain, chemical disorders and grain boundaries (reduced grain size), therefore leads to reduced storage capacity. The peak broadening reflects the defects introduced during cycling experiments.
r5 EXAMPLE 4 (Compound according to the invention made by the process of the invention) Cao,~ Mmo,4Ni4,8sGeo.is was synthesized by mechanical alloying of elemental powder blends. The alloy was annealed in the same manner as in Example 1.
This alloy had a maximum hydrogen storage capacity of l.3wt.% in the as-synthesized state. Substantial improvement in the maximum and reversibly storage capacity is observed after 500 cycles as shown in Fig.S.
y REFERENCES
(1) "A new family of hydrogen storage alloys based on the system nickel-misch metal-calcium)" by G.D. Sandrock, proc. 12th intersociety energy conversion Engineering Conference, 12th IECEC, Am. Nuclear Society, 1 (1977) 951.
(2) "Stability of Rechargeable hydriding alloys during extended cycling" by P. D. Goodell, J Less-Common Met., 99 (1984) 1.
(3) "Systematic B-metal substitution in CaNiS" by J.O. Jensen and N.J. Bjerrum: J. of Alloys and Compounds 293-295 (1999) 185
(4) "Hydriding behavior in Ca-Mg-Ni-B" by H. Oesterreicher, K.
Ensslen, A. Kerlin and E. Bucher": Mat. Res. Bull. 1 S (1980) 275.
Ensslen, A. Kerlin and E. Bucher": Mat. Res. Bull. 1 S (1980) 275.
(5} "Mechanical alloying and hydrogen storage properties of CaNiS-based alloys", by G. Liang, J. Huot and R. Schulz, J.
Alloys & Compounds, 321 (2001) 146.
Alloys & Compounds, 321 (2001) 146.
(6) "Nickel-misch metal-Calcium alloys for hydrogen storage" by G.D. Sandrock, US patent Nos. 4,096,639 and 4,161,402.
(7) "Synthesis ofHnanocrystalline CaNiS-based alloys and use for metal hydride electrode", by G. Liang, S. Ruggeri, C. Lenain, H. Alamdari; J. Huot, L. Roue and R. Schulz", J. Metastable and Nanocrystalline Materials-11 (2001~__7_l. _
(8) "Calcium-Nickel-misch metal-Aluminium quaternary alloy for hydrogen storage", by K. Ohnishi, T. Ogawa, US patent, 46311?0.
(9) "Synthesis of low cost metal hydrides by mechanical alloying"
by G. Liang and R. Schulz, Report for the CRADA project (CR-99-004),2001.
by G. Liang and R. Schulz, Report for the CRADA project (CR-99-004),2001.
Claims (9)
1. A Ca-Mm-Ni based alloy of the AB5 type, said alloy being of the formula:
(Ca x M1-x)t(Ni1-y)5 (I) where M is selected from the group consisting of: any mischmetal, any rare earth metal, and an homogeneous or an inhomogeneous combination of any of: (i) at least two mischmetals, (ii) at least two rare earth metals, and (iii) at least one mischmetal and at least one rare earth metal.
T is selected from the group consisting of: metalloids, and an homogeneous or an inhomogeneous combination of at least two metalloids;
0<x<=1;
0<y<= 0.5; and 0.8 <= t <= 1.2.
(Ca x M1-x)t(Ni1-y)5 (I) where M is selected from the group consisting of: any mischmetal, any rare earth metal, and an homogeneous or an inhomogeneous combination of any of: (i) at least two mischmetals, (ii) at least two rare earth metals, and (iii) at least one mischmetal and at least one rare earth metal.
T is selected from the group consisting of: metalloids, and an homogeneous or an inhomogeneous combination of at least two metalloids;
0<x<=1;
0<y<= 0.5; and 0.8 <= t <= 1.2.
2. The alloy of claim 1, wherein, in the formula I:
0.4<= x <=1;
0<y<= 0.3; and 0.85 t<= 1.2
0.4<= x <=1;
0<y<= 0.3; and 0.85 t<= 1.2
3. The alloy of claim 1 or 2, wherein:
M is a mischmetal; and T is any of Si, Ge and Ga.
M is a mischmetal; and T is any of Si, Ge and Ga.
4. The alloy of claim 1 or 2, wherein:
M is a mischmetal, and the metalloid of T is any of Si, Ge, and Ga.
M is a mischmetal, and the metalloid of T is any of Si, Ge, and Ga.
5. Use of the alloy of claim 1, 2, 3 or 4 for storing hydrogen.
6. A method of preparation of an alloy of being of this formula:
(Ca x M1-x)c(Ni1-y T y)5 (I) where M is selected from the group consisting of: any mischmetal, any rare earth metal, and an homogeneous or an inhomogeneous combination of any of: (i) at least two mischmetals, (ii) at least two rare earth metals, and (iii) at least one mischmetal and at least one rare earth metal.
T is selected from the group consisting of: metalloids, and an homogeneous or an inhomogeneous combination of at least two metalloids;
0<x<=1;
0<y<=0.5; and 0.8<=t<=1.2.
comprising the steps of:
a) preparing a powder by milling a mixture of elemental powders and/or pre-alloyed substances of the elemental ingredients of the alloy to be prepared in adequate proportions to obtain the required alloy; and b) annealing and/or sintering the so prepared powder at elevated temperatures in a crucible for a short period of time in an inert or reactive atmosphere.
(Ca x M1-x)c(Ni1-y T y)5 (I) where M is selected from the group consisting of: any mischmetal, any rare earth metal, and an homogeneous or an inhomogeneous combination of any of: (i) at least two mischmetals, (ii) at least two rare earth metals, and (iii) at least one mischmetal and at least one rare earth metal.
T is selected from the group consisting of: metalloids, and an homogeneous or an inhomogeneous combination of at least two metalloids;
0<x<=1;
0<y<=0.5; and 0.8<=t<=1.2.
comprising the steps of:
a) preparing a powder by milling a mixture of elemental powders and/or pre-alloyed substances of the elemental ingredients of the alloy to be prepared in adequate proportions to obtain the required alloy; and b) annealing and/or sintering the so prepared powder at elevated temperatures in a crucible for a short period of time in an inert or reactive atmosphere.
7. The process of claim 6, wherein the milling in step (a) consists of a ball milling or mechanical alloying.
8. The process of claim 7, wherein the milling in step (a) is carried out in the presence of at least one anti-sticking agent.
9. The process of any one of claims 6 to 8, wherein the annealing and/or sintering in step (b) is carried out at a temperature higher than 600°C
but not higher than 1100°C in a steel crucible.
but not higher than 1100°C in a steel crucible.
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|---|---|---|---|
| CA002456823A CA2456823A1 (en) | 2003-02-04 | 2004-02-04 | Ca-mm-ni based hydrogen storage alloys |
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| CA2,418,332 | 2003-02-04 | ||
| CA002418332A CA2418332A1 (en) | 2003-02-04 | 2003-02-04 | Ca-mm-ni based hydrogen storage alloys |
| CA002456823A CA2456823A1 (en) | 2003-02-04 | 2004-02-04 | Ca-mm-ni based hydrogen storage alloys |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1511099A1 (en) * | 2003-08-26 | 2005-03-02 | HERA, Hydrogen Storage Systems, Inc. | Ca, Mg and Ni containing alloys, method for preparing the same and use thereof for gas phase hydrogen storage |
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2004
- 2004-02-04 CA CA002456823A patent/CA2456823A1/en not_active Abandoned
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP1511099A1 (en) * | 2003-08-26 | 2005-03-02 | HERA, Hydrogen Storage Systems, Inc. | Ca, Mg and Ni containing alloys, method for preparing the same and use thereof for gas phase hydrogen storage |
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