High Entropy NiMn-based Magnetic Refrigerant Materials

Abstract

A magnetocaloric alloy composition consists essentially of 20-40 weight % Mn, 6-26 weight % In, 1-5 weight % Si, and 0.3-12 wt. % of at least one other element selected from the group consisting of: Ga, Ge, Ag, Gd, Co, Pd, Sm, V, and Sn, balance Ni.

Description

BACKGROUND OF THE INVENTION

Heating, ventilation, air conditioning and refrigeration, (HVACR) consume approximately 32% of all energy used in commercial buildings. Modern refrigerators/coolers still use greenhouse gases that affect global warming. Therefore, efficient technologies and systems for HVACR are of great importance for the Department of Energy (DOE).

The need for materials with enhanced magnetocaloric effect (MCE) is one of the challenges of modern high efficiency heating, ventilation, air conditioning and refrigeration (HVACR). Magnetic refrigeration (MR) technology presently is considered as the most promising alternative to conventional gas compression HVACR systems. MR is environmentally friendly. It does not use hazardous chemicals or greenhouse gases. It eliminates high consumption of electricity and high capital cost typical for conventional gas compression technology. In MR, the interest in increased MCE, and its sensitivity to magnetic fields, is combining to demand further development of alloys working in a larger temperature interval with higher efficiency. These objectives cannot be met without new high performance magnetic refrigerant materials.

BRIEF SUMMARY OF THE INVENTION

In accordance with one aspect of the present invention, the foregoing and other objects are achieved by a magnetocaloric alloy composition consisting essentially of 20-40 weight % Mn, 6-26 weight % In, 1-5 weight % Si, and 0.3-12 wt. % of at least one other element selected from the group consisting of: Ga, Ge, Ag, Gd, Co, Pd, Sm, V, and Sn, balance, Ni. Other elements may be present as impurities in quantities too small to have a significant effect on the beneficial properties of the composition.

In accordance with one aspect of the present invention, a magnetocaloric device includes at least one magnetocaloric material, at least one magnet, apparatus for moving the magnetocaloric material into and out of proximity with the magnet, and apparatus for transferring heat to and from the magnetocaloric material, the magnetocaloric material consisting essentially of 20-40 weight % Mn, 6-26 weight % In, 1-5 weight % Si, and 0.3-12 wt. % of at least one other element selected from the group consisting of: Ga, Ge, Ag, Gd, Co, Pd, Sm, V, and Sn, balance Ni. Other elements may be present as impurities in quantities too small to have a significant effect on the beneficial properties of the composition.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph showing raw heat flow curves for sample 1 measured by differential scanning calorimetry (DSC) directly during heating and cooling.

FIG. 2 is a graph showing specific heat capacity curves for sample 1 derived from the respective raw heat flow curves.

FIG. 3 is a graph showing raw heat flow curves for sample 2 measured by differential scanning calorimetry (DSC) during heating and cooling.

FIG. 4 is a graph showing specific heat capacity curves for sample 2 derived from the respective raw heat flow curves.

FIG. 5 is a graph showing raw heat flow curves for sample 3 measured by differential scanning calorimetry (DSC) during heating and cooling.

FIG. 6 is a graph showing specific heat capacity curves for sample 3 derived from the respective raw heat flow curves.

FIG. 7 is a graph showing raw heat flow curves for sample 4 measured by differential scanning calorimetry (DSC) during heating and cooling.

FIG. 8 is a graph showing specific heat capacity curves for sample 4 derived from the respective raw heat flow curves.

FIG. 9 is a graph showing raw heat flow curves for sample 5 measured by differential scanning calorimetry (DSC) during heating and cooling.

FIG. 10 is a graph showing specific heat capacity curves for sample 5 derived from the respective raw heat flow curves.

FIG. 11 is a graph showing raw heat flow curves for sample 6 measured by differential scanning calorimetry (DSC) during heating and cooling.

FIG. 12 is a graph showing specific heat capacity curves for sample 6 derived from the respective raw heat flow curves.

FIG. 13 is a graph showing raw heat flow curves for sample 7 measured by differential scanning calorimetry (DSC) during heating and cooling.

FIG. 14 is a graph showing specific heat capacity curves for sample 7 derived from the respective raw heat flow curves.

FIG. 15 is a graph showing variations in heat capacity curves for sample 7 measured under magnetic fields, H, of indicated strengths.

FIG. 16 is a graph showing the change in entropy AS(T) for sample 7 with a 5-Tesla magnetic field minus that without a magnetic field.

FIG. 17 is a graph showing raw heat flow curves for sample 8 measured by differential scanning calorimetry (DSC) during heating and cooling.

FIG. 18 is a graph showing specific heat capacity curves for sample 8 derived from the respective raw heat flow curves.

FIG. 19 is a graph showing variations in heat capacity curves for sample 8 measured under magnetic fields of indicated strengths.

FIG. 20 is a graph showing an enlarged section of FIG. 19.

FIG. 21 is a graph showing the change in entropy AS(T) for sample 8 with a 5-Tesla magnetic field minus that without a magnetic field.

FIG. 22 is a graph showing magnetization, M, as a function of magnetic field, H, at the temperatures near the critical temperature for sample 8.

FIG. 23 is a graph showing raw heat flow curves for sample 9 measured by differential scanning calorimetry (DSC) during heating and cooling.

FIG. 24 is a graph showing specific heat capacity curves for sample 9 derived from the respective raw heat flow curves.

FIG. 25 is a graph showing magnetization, M, as a function of magnetic field, H, at the temperatures near the critical temperature for sample 9.

FIG. 26 is a graph showing raw heat flow curves for sample 10 measured by differential scanning calorimetry (DSC) during heating and cooling.

FIG. 27 is a graph showing specific heat capacity curves for sample 10 derived from the respective raw heat flow curves.

FIG. 28 is a graph showing variations in heat capacity curves for respective sample 10 measured under magnetic fields of indicated strengths.

FIG. 29 is a graph showing the change in entropy AS(T) for sample 10 with a 5-Tesla magnetic field minus that without a magnetic field.

FIG. 30 is a graph showing variations in heat capacity curves for sample 12 measured under magnetic fields of indicated strengths.

FIG. 31 is a graph showing the change in entropy AS(T) for sample 12 with a 5-Tesla magnetic field minus that without a magnetic field.

FIG. 32 is a graph showing variations in heat capacity curves for sample 13 measured under magnetic fields of indicated strengths.

FIG. 33 is a graph showing an enlarged section of FIG. 32.

FIG. 34 is a graph showing the change in entropy AS(T) for sample 13 with a 5-Tesla magnetic field minus that without a magnetic field.

FIG. 35 is a graph showing variations in heat capacity curves for sample 14 measured under magnetic fields of indicated strengths.

FIG. 36 is a graph showing the change in entropy AS(T) for sample 14 with a 5-Tesla magnetic field minus that without a magnetic field.

FIG. 37 is a graph showing the adiabatic temperature change derived from magnetization measurements for sample 14.

FIG. 38 is a graph showing variations in heat capacity curves for sample 15 measured under magnetic fields of indicated strengths.

FIG. 39 is a graph showing the change in entropy AS(T) for sample 15 with a 5-Tesla magnetic field minus that without a magnetic field.

FIG. 40 is a graph showing specific heat capacity curves for sample 11 derived from the respective raw heat flow curves.

FIG. 41 is a graph showing specific heat capacity curves for sample 12 derived from the respective raw heat flow curves.

FIG. 42 is a graph showing specific heat capacity curves for sample 13 derived from the respective raw heat flow curves.

FIG. 43 is a graph showing specific heat capacity curves for sample 14 derived from the respective raw heat flow curves.

FIG. 44 is a graph showing specific heat capacity curves for sample 15 derived from the respective raw heat flow curves.

FIG. 45 is a 3-dimensional graph showing an array of X-ray diffraction (XRD) data for samples 1-15.

For a better understanding of the present invention, together with other and further objects, advantages and capabilities thereof, reference is made to the following disclosure and appended claims in connection with the above-described drawings.

DETAILED DESCRIPTION OF THE INVENTION

The invention relates to high-performance, multicomponent NiMn-based alloys with an enhanced near room temperature magnetocaloric effect. Quinary, senary, septenary, etc. magnetocaloric alloy compositions consist essentially of 20-40 weight % Mn, 6-26 weight % In, 1-5 weight % Si, and 0.5-12 wt. % of at least one other element selected from the group consisting of: Ga, Ge, Ag, Gd, Co, Pd, Sm, V, and Sn, balance, Ni. Other elements may be present as impurities in quantities too small to have a significant effect on the beneficial properties of the composition.

More particularly, examples of the new magnetocaloric alloy compositions described herein can contain at least one of the following: 2-3 weight % V, 4-5 weight % Co, 7-9 weight % Pd, 3-8 weight % Gd, 6-9 weight % Sm, 10-12 weight % Sn, 6-9 weight % Ga, 0.2-1% Ge, and 3-10 weight % Ag.

A method of preparing a multicomponent, magnetocaloric alloy can begin by preparing a heat (mixture) comprising an appropriate amount of each component. The mixture is heated slowly (generally over several hours, within a range of 8 to 18 hours, for example) in an inert atmosphere to a melting temperature and cooled to form a solid mixture. The protracted heating period is effective in achieving diffusion bonding between the elements and minimizing vaporization and loss of low-temperature melting elements. A re-melting step can be carried out in order to obtain a homogenous polycrystalline microstructure in the alloy.

A two-step annealing process can be used to homogenize the alloy. A first annealing step can be carried out at a temperature in a range of about 950 to about 1050° C., preferably about 980 to about 1020° C. for a period of time in a range of about 55 to about 90 hours, preferably about 62 to about 82 hours in an inert atmosphere of Ar. A second annealing step can be carried out at a temperature in a range of about 750 to about 850° C., preferably about 790 to about 810° C. for a period of time in a range of about 22 to 26 hours in an inert atmosphere of Ar.

A one-step annealing process at can be carried out at a temperature in a range of about 950 to about 1050° C., preferably about 980 to about 1020° C. for a period of time in a range of about 62 to about 82 hours in an inert atmosphere of Ar followed by a very slow cooling (about 10° C. per hour) to room temperature. Heat/mixture homogeneity may not be as complete as in the two-step annealing process.

EXAMPLE

Cylindrical, homogeneous polycrystalline specimens of various new, multi-component, magnetocaloric alloy compositions were made as described hereinabove. For each specimen, a 100 g heat comprising an appropriate amount of each component was heated for 12 hours in an inert atmosphere and cooled. The alloy was re-melted in order to obtain a homogenous polycrystalline microstructure in the alloy specimen. The alloy specimen was subsequently annealed by a two-step process, first at 1000° C. for 72 hours and second at 800° C. for 24 hours, both steps being carried out in an inert atmosphere of Ar.

Table 1 shows compositions of the specimens in terms of weight percent, not accounting for minor impurities that have no significant effect. Specimen 1 is a known composition; specimens 2-15 are new compositions. It is contemplated that constituent elements in the new magnetocaloric alloy compositions can be varied by about ±5%, as indicated by the values provided in Table 2.

Various magnetocaloric properties of samples described herein were tested and compared. FIGS. 1, 3, 5, 7, 9, 11, 13, 17, 23 and 26 show raw heat flow curves for samples 1-10, respectively, measured by differential scanning calorimetry (DSC) during heating and cooling. Dashed lines indicate change of heat flow during heating and the solid lines indicate change of heat flow during cooling. Positive heat flow is exothermic and negative heat flow is endothermic.

FIGS. 2, 4, 6, 8, 10, 12, 14, 18, 24, 27, 40, 41, 42, 43, and 44 show specific heat capacity curves for samples 1-15, respectively, derived from the respective raw heat flow curves. The Y-axis represents specific heat; square data points indicate specific heat capacity during cooling; circular data points indicate specific heat capacity during heating.

FIGS. 15, 19, 28, 30, 32, 35 and 38 show variations in heat capacity curves measured by heat pulse calorimetry (also known as relaxation calorimetry) for respective samples 7, 8, 10, 12, 13, 14, and 15, measured under magnetic fields of indicated strengths. FIGS. 20 and 33 are enlarged section of respective FIGS. 19, and 32, showing shifts in the curves. Square data points indicate change of heat flow during cooling; circular data points indicate change of heat flow during heating.

The data sets discussed above are helpful in determining the temperature of structural and magnetic transitions. Structural transition with cooling is generally the change from cubic phase to orthorhombic (sometimes it can be tetragonal or monoclinic) phase. The structure of the alloy at room temperature was additionally checked by X-ray analysis. The samples with transition temperatures lower than room temperature generally have cubic symmetry, which was also confirmed by X-ray analysis.

Many of the new compositions have transition temperatures bracketing room temperature. This temperature interval is of interest for possible applications of the magnetocaloric materials. Magnetocaloric effect is maximal within the temperature range of magnetic and structural transitions.

Other important parameters are the adiabatic change of entropy (delta S) and adiabatic change of temperature (delta T) during phase transition under magnetic field.

FIGS. 16, 21, 29, 31, 34, 36, and 39 show the change in entropy ΔS(T) for respective samples 7, 8, 10, 12, 13, 14, and 15 with a 5-Tesla magnetic field minus that without a magnetic field.

FIGS. 22 and 25 show magnetization M as a function of magnetic field H at the temperatures near the critical temperature for samples 8 and 9, respectively. Measurements of magnetic susceptibility were performed to determine the temperature of phase transition during heating and cooling more precisely and choose an appropriate temperature ranges for heat pulse calorimetry measurements.

FIG. 37 shows adiabatic temperature change near the critical temperature for sample 14. As sample 14 showed the hignest value of the adiabatic entropy change ΔS(T), the measurements of AT was performed for this sample.

FIG. 45 shows an array of XRD data for samples 1-15 for comparison. The sample numbers are identified to the left of each plot.

Among all the suggested new compositions of the alloys with the transition temperature at or slightly above the room temperature, sample 14 showed the best magnetocaloric properties with ΔS=11 Jkg⁻¹K⁻¹ and ΔT=3K, and the transition temperatures in the range 300-310K. These properties are comparable with the best As-containing magnetocaloric materials, which are hazardous. In contrast, the suggested alloy does not contain any hazard elements. Moreover it does not contain any light elements such as hydrogen. Therefore the properties of the suggested alloy are stable and will not change during exploitation as magnetic refrigerants. The properties are very sensitive to the composition variations.

The skilled artisan will recognize that the magnetocaloric compositions described hereinabove are useful materials for use in devices where magnetocaloric heat transfer is employed. A magnetocaloric device generally comprises a magnetocaloric material, at least one magnet, apparatus for moving the magnetocaloric material into and out of proximity with the magnet, and apparatus for transferring heat to and from the magnetocaloric material. Examples of magnetocaloric cooling devices include refrigerators, freezers, air conditioners, cryogenic apparatus, and cooling systems associated with mechanical devices, electrical devices, electronic devices, and the like. The same and other types of magnetocaloric devices can be used to provide magnetocaloric heating.

While there has been shown and described what are at present considered to be examples of the invention, it will be obvious to those skilled in the art that various changes and modifications can be prepared therein without departing from the scope of the inventions defined by the appended claims.

Tables 1 and 2 follow:

TABLE 1
Specimen	Ni	Mn	In	Si	Ga	Ge	Ag	Gd	Co	Pd	Sm	V	Sn
1	46.43	30.43	21.80	1.33	0	0	0	0	0	0	0	0	0
2	46.53	27.87	21.87	1.33	0	0	0	0	0	0	0	2.40	0
3	44.37	29.07	20.83	1.27	0	0	0	0	4.47	0	0	0	0
4	42.83	28.07	20.10	1.23	0	0	0	0	0	7.77	0	0	0
5	44.30	26.53	20.80	1.27	0	0	0	7.10	0	0	0	0	0
6	44.43	26.60	20.87	1.27	0	0	0	0	0	0	6.83	0	0
7	46.27	30.30	10.87	1.33	0	0	0	0	0	0	0	0	11.23
8	48.50	31.80	11.40	1.40	6.90	0	0	0	0	0	0	0	0
9	40.23	29.30	21.00	1.27	0	0	8.30	0	0	0	0	0	0
10	46.27	30.33	21.73	1.10	0	0.57	0	0	0	0	0	0	0
11	47.07	30.83	12.90	1.37	7.83	0	0	0	0	0	0	0	0
12	43.80	36.43	11.43	1.40	6.93	0	0	0	0	0	0	0	0
13	48.60	31.83	10.93	1.40	6.63	0.60	0	0	0	0	0	0	0
14	47.30	29.67	11.10	1.37	6.73	0	0	3.80	0	0	0	0	0
15	41.97	30.53	10.93	1.33	6.63	0	8.57	0	0	0	0	0	0

TABLE 2
Specimen	Ni	Mn	In	Si	Ga	Ge	Ag	Gd	Co	Pd	Sm	V	Sn
2	Balance	26.5-29.3	20.3-23.3	1.28-1.38	0	0	0	0	0	0	0	2.3-2.5	0
3	Balance	26.5-31.5	19.8-21.8	1.21-1.33	0	0	0	0	4.2-4.6	0	0	0	0
4	Balance	26.6-29.4	19.1-21.1	1.17-1.29	0	0	0	0	0	7.3-8.1	0	0	0
5	Balance	24.2-28.8	19.8-21.8	1.21-1.33	0	0	0	6.8-7.4	0	0	0	0	0
6	Balance	25.3-27.9	19.8-21.8	1.21-1.33	0	0	0	0	0	0	6.5-7.2	0	0
7	Balance	28.8-31.8	10.2-11.4	1.26-1.40	0	0	0	0	0	0	0	0	10.4-11.8
8	Balance	30.6-33.4	10.8-13.0	1.33-1.47	6.6-7.2	0	0	0	0	0	0	0	0
9	Balance	27.8-30.8	19.5-22.5	1.21-1.33	0	0	7.9-8.7	0	0	0	0	0	0
10	Balance	28.8-31.8	20.2-23.2	1.05-1.15	0	0.54-0.60	0	0	0	0	0	0	0
11	Balance	29.3-32.3	12.3-13.5	1.31-1.43	7.4-8.2	0	0	0	0	0	0	0	0
12	Balance	34.6-38.2	10.8-11.3	1.33-1.47	6.5-7.3	0	0	0	0	0	0	0	0
13	Balance	30.2-33.4	10.3-11.5	1.33-1.47	6.3-6.9	0.57-0.63	0	0	0	0	0	0	0
14	Balance	28.1-31.1	10.6-11.6	1.31-1.43	6.3-7.1	0	0	3.6-4.0	0	0	0	0	0
15	Balance	29.0-32.0	10.3-11.5	1.26-1.40	6.3-6.9	0	8.2-9.0	0	0	0	0	0	0

Claims

1. A magnetocaloric alloy composition consisting essentially of 20-40 weight % Mn, 6-26 weight % In, 1-5 weight % Si, and 0.3-12 wt. % of at least one other element selected from the group consisting of: Ga, Ge, Ag, Gd, Co, Pd, Sm, V, and Sn, balance Ni.

2. A magnetocaloric alloy composition in accordance with claim 1 wherein said at least one other element comprises 6 to 9 weight % Ga.

3. A magnetocaloric alloy composition in accordance with claim 1 wherein said at least one other element comprises 0.2 to 1 weight % Ge.

4. A magnetocaloric alloy composition in accordance with claim 1 wherein said at least one other element comprises 7 to 9 weight % Ag.

5. A magnetocaloric alloy composition in accordance with claim 1 wherein said at least one other element comprises 3 to 8 weight % Gd.

6. A magnetocaloric alloy composition in accordance with claim 1 wherein said at least one other element comprises 4 to 5 weight % Co.

7. A magnetocaloric alloy composition in accordance with claim 1 wherein said at least one other element comprises 7 to 9 weight % Pd.

8. A magnetocaloric alloy composition in accordance with claim 1 wherein said at least one other element comprises 6 to 9 weight % Sm.

9. A magnetocaloric alloy composition in accordance with claim 1 wherein said at least one other element comprises 2 to 3 weight % V.

10. A magnetocaloric alloy composition in accordance with claim 1 wherein said at least one other element comprises 10 to 12 weight % Sn.

11. A magnetocaloric device comprising at least one magnetocaloric material, at least one magnet, apparatus for moving said magnetocaloric material into and out of proximity with said magnet, and apparatus for transferring heat to and from said magnetocaloric material, said magnetocaloric material consisting essentially of 20-40 weight % Mn, 6-26 weight % In, 1-5 weight % Si, and 0.3-12 wt. % of at least one other element selected from the group consisting of: Ga, Ge, Ag, Gd, Co, Pd, Sm, V, and Sn, balance Ni.

12. A magnetocaloric device in accordance with claim 11 wherein said at least one other element comprises 6 to 9 weight % Ga.

13. A magnetocaloric device in accordance with claim 11 wherein said at least one other element comprises 0.2 to 1 weight % Ge.

14. A magnetocaloric device in accordance with claim 11 wherein said at least one other element comprises 7 to 9 weight % Ag.

15. A magnetocaloric device in accordance with claim 11 wherein said at least one other element comprises 3 to 8 weight % Gd.

16. A magnetocaloric device in accordance with claim 11 wherein said at least one other element comprises 4 to 5 weight % Co.

17. A magnetocaloric device in accordance with claim 11 wherein said at least one other element comprises 7 to 9 weight % Pd.

18. A magnetocaloric device in accordance with claim 11 wherein said at least one other element comprises 6 to 9 weight % Sm.

19. A magnetocaloric device in accordance with claim 11 wherein said at least one other element comprises 2 to 3 weight % V.

20. A magnetocaloric device in accordance with claim 11 wherein said at least one other element comprises 10 to 12 weight % Sn.