APPLICATIONS CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. Provisional Patent Application No. 62/443,955 filed on January 9, 2017 entitled“Magnetocaloric Alloys Useful for Magnetic Refrigeration Applications”, and U.S. Provisional Patent Application No.62/481,385 filed on April 4, 2017 entitled “Magnetocaloric Alloys Useful for Magnetic Refrigeration Applications”, the contents of which are incorporated herein by reference in their entirety. BACKGROUND

Field

[0002] Embodiments of the present invention generally relate to magnetocaloric materials comprising ternary alloys useful for magnetic refrigeration applications. In some embodiments, the disclosed alloys exhibit only 2 ^nd order magnetic phase transitions, with no thermal or structural hysteresis losses. This makes them attractive candidates for use in magnetic refrigeration applications. Additionally, the disclosed compositions are lower cost and higher performance than prior art materials. Description of the Related Art

[0003] Magnetic Refrigeration utilizes the magnetocaloric effect (MCE), which is the temperature variation of a magnetic material after exposure to a magnetic field. A more detailed description of the magnetocaloric effect is described by Plaza and Campoy, J. of Magnetism and Magnetic Mat., 321, 446 (2009). A critical challenge of developing low cost magnetic refrigerators is the cost and availability of MCE materials, which are typically rare- earth and very expensive. The magnetocaloric effect (MCE) is an intrinsic property of a magnetic solid which has been successfully utilized for a variety of applications. The thermal response of the MCE material to the application or removal of a magnetic field is typically maximized when the material is near its magnetic ordering temperature. Thus, the materials considered for magnetic refrigeration devices must exhibit a magnetic phase transition temperature near the temperature region of interest, i.e. for hydrogen liquefaction ~20K, for nitrogen liquefaction ~80K, etc. Some of the most common MCE materials include RNi ₂ (R=Gd, Dy and Ho) and RAl ₂ (R=Er, Ho, Dy and Dy _0.5 Ho _0.5 , Dy _x Er _1-x and GdPd), all of which are rare-earth and expensive, according to B.G. Shen, J.R. Sun, F.X. Hu, H.W. Zhang, and Z.H. Cheng, Adv. Mater., 21, 4545 (2009). Kamiya et al., Cryocoolers, 14, 637 (2007), successfully demonstrated a small scale hydrogen liquefaction magnetic refrigerator with efficiency approaching 90% of the Carnot efficiency, however, 280g of the rare-earth MCE material, dysprosium (bulk price ~$350/kg for 99% purity) gadolinium (bulk price ~$55/kg for 99.9% purity) aluminum garnet, was needed to achieve a maximum cooling power of 14.6W. These starting materials must further undergo significant processing to obtain the desired MCE properties which can increase the materials cost by 10-100X. Clearly, the capital cost of a magnetic refrigeration system capable of >400W of cooling power using the traditional rare-earth based MCE materials would far exceed its economic feasibility.

[0004] One of the major hurdles inhibiting the development of magnetic refrigeration technologies is the lack of commercially available low cost magnetocaloric materials that will actually function, for a long period of time, in a magnetic refrigeration environment such as the active magnetic regenerator (AMR) which is in development by several entities. While there has been extensive research discovering new materials with magnetocaloric properties, the majority of these material compositions will require substantial engineering to be compatible with AMR technologies. Materials such as GdSiGe or LaFeSi based alloys have sparked interest due to their giant magnetocaloric effect, however, this effect is due to a first order phase transition which has significant magnetic and thermal hysteresis and also exhibits structural changes, as described by Shen, J.R Sun, F.X. Hu, H.W. Zhang, and Z.H. Cheng, Adv. Mater., 21, 4545, 2009 and V. Provenzano, A.J. Shapiro, and R.D. Shull, Nature, 429, 853, 2004. The hysteresis reduces the reversibility of the MCE such that during high frequency magnetization and demagnetization, which is required for high efficiency AMRs, the magnitude of the MCE is drastically reduced. Methods to suppress thermal and magnetic hysteresis are possible, but require additional materials and processing and also act to suppress the MCE. Additionally, the structural changes typically manifest as volume expansion and contraction of the material, causing cracking during the magnetization and demagnetization cycles which quickly reduces the MCE response and lowers the thermal conductivity, making these materials incompatible in AMRs. While methods to improve mechanical stability of MCE materials with first order transitions can be employed, this will also require significant additional materials and processing which will increase cost. Further, scalable manufacturing of many MCE materials has yet to be demonstrated.

[0005] Literature has also suggested the microstructure of MCE materials can significantly influence its MCE properties. Micro- or nano- sized material synthesis occurs in either a top-down approach, which involves the breaking down of the bulk material into nano-sized structures or particles, or a bottom-up approach which refers to the building up of a material atom-by-atom, or molecule-by-molecule. Yang et al., Journal of Alloys and Compounds, 555, 150 (2013), chemically synthesized (bottom-up approach) LaCaMnO nanoparticles and showed that variation in particle size shifted the MCE response temperature and also broadened the response temperature range compared to the bulk material. However, nanomaterial synthesis of the more common MCE alloys is extremely difficult. Using the top-down approach, surface oxidation which has minimal effect on bulk materials, is extremely rapid with the large surface area of nano-grains, and the MCE response of most alloys will be significantly reduced with even the slightest presence of oxygen. US Patent Application No. 2014/0290274 discloses LaFeSi based MCE materials with grain sizes of 15um-800um, where the micron sized grains were produced using ball milling techniques. The authors report an increase in magnetization response as the particle size decreases, with an optimal particle size in the range of 15um-200um. Particle sizes less than 10um showed drastically reduced MCE response which may be due to the surface oxidation of these smaller particles which is difficult to eliminate using traditional ball milling techniques. On the other hand, bottom-up approaches for metal alloys allow for enhanced control of particle size but are still under development, with oxidation, as well as obtaining the necessary crystalline structure presenting significant challenges. SUMMARY [0006] Some embodiments of the present invention provide a magnetocaloric material comprising (CexNd1-x)Si wherein x is in the range of about 0.1 to about 0.9. In some embodiments, the magnetocaloric material exhibits a 2 ^nd order magnetic phase transition in the temperature range of about 10K to about 42K. In some embodiments, the magnetocaloric material is Ce _0.1 Nd _0.9 Si _1.0 , Ce _0.2 Nd _0.8 Si _1.0 , Ce _0.3 Nd _0.7 Si _1.0 , Ce _0.4 Nd _0.6 Si _1.0 , Ce0.5Nd0.5Si1.0, Ce0.6Nd0.4Si1.0, Ce0.7Nd0.3Si1.0, Ce0.8Nd0.2Si1.0, Ce0.9Nd0.1Si1.0, or any combination thereof.

[0007] Some embodiments of the present invention provide a magnetocaloric material comprising RE (Siy A1-y) wherein RE is selected from the group consisting of Ce, Nd, or Gd, and wherein A is selected from the group consisting of Sn, Co, Al, Ni, Fe, Mn, Zn, or Cu, and wherein y is in the range of about 0.1 to about 0.9. In some embodiments the material is Ce _1.0 Si _0.9 Sn _0.1 , Ce _1.0 Si _0.8 Sn _0.8 , Ce _1.0 Si _0.7 Sn _0.3 , Ce _1.0 Si _0.6 Sn _0.4 , Ce _1.0 Si _0.5 Sn _0.5 , Ce1.0Si0.4Sn0.6, Ce1.0Si0.3Sn0.7, Ce1.0Si0.2Sn0.8, Ce1.0Si0.1Sn0.9, or any combination thereof. In some embodiments the material is Nd1.0Si0.9Mn0.1, Nd1.0Si0.8Mn0.8, Nd1.0Si0.7Mn0.3, Nd _1.0 Si _0.6 Mn _0.4 , Nd _1.0 Si _0.5 Mn _0.5 , Nd _1.0 Si _0.4 Mn _0.6 , Nd _1.0 Si _0.3 Mn _0.7 , Nd _1.0 Si _0.2 Mn _0.8 , Nd _1.0 Si _0.1 Mn _0.9 , or any combination thereof. In some embodiments the material is Gd1.0Si0.9Mn0.1, Gd1.0Si0.8Mn0.8, Gd1.0Si0.7Mn0.3, Gd1.0Si0.6Mn0.4, Gd1.0Si0.5Mn0.5, Gd1.0Si0.4Mn0.6, Gd1.0Si0.3Mn0.7, Gd1.0Si0.2Mn0.8, Gd1.0Si0.1Mn0.9, or any combination thereof. In some embodiments the material is Nd _1.0 Si _0.9 Fe _0.1 , Nd _1.0 Si _0.8 Fe _0.8 , Nd _1.0 Si _0.7 Fe _0.3 , Nd _1.0 Si _0.6 Fe _0.4 , Nd _1.0 Si _0.5 Fe _0.5 , Nd _1.0 Si _0.4 Fe _0.6 , Nd _1.0 Si _0.3 Fe _0.7 , Nd _1.0 Si _0.2 Fe _0.8 , Nd _1.0 Si _0.1 Fe _0.9 , or any combination thereof. In some embodiments the material is Gd1.0Si0.9Fe0.1, Gd1.0Si0.8Fe0.8, Gd1.0Si0.7Fe0.3, Gd1.0Si0.6Fe0.4, Gd1.0Si0.5Fe0.5, Gd1.0Si0.4Fe0.6, Gd1.0Si0.3Fe0.7, Gd1.0Si0.2Fe0.8, Gd _1.0 Si _0.1 Fe _0.9 , or any combination thereof. In some embodiments the material is Nd _1.0 Si _0.9 Zn _0.1 , Nd _1.0 Si _0.8 Zn _0.8 , Nd _1.0 Si _0.7 Zn _0.3 , Nd _1.0 Si _0.6 Zn _0.4 , Nd _1.0 Si _0.5 Zn _0.5 , Nd _1.0 Si _0.4 Zn _0.6 , Nd1.0Si0.3Zn0.7, Nd1.0Si0.2Zn0.8, Nd1.0Si0.1Zn0.9, or any combination thereof. In some embodiments the material is Nd1.0Si0.9Ni0.1, Nd1.0Si0.8Ni0.8, Nd1.0Si0.7Ni0.3, Nd1.0Si0.6Ni0.4, Nd1.0Si0.5Ni0.5, Nd1.0Si0.4Ni0.6, Nd1.0Si0.3Ni0.7, Nd1.0Si0.2Ni0.8, Nd1.0Si0.1Ni0.9, or any combination thereof. In some embodiments the material is Nd _1.0 Si _0.9 Co _0.1 , Nd _1.0 Si _0.8 Co _0.8 , ^Nd _1.0 ^Si _0.7 ^Co _0.3 ^{, Nd} _1.0 ^Si _0.6 ^Co _0.4 ^{, Nd} _1.0 ^Si _0.5C ^Co _0.5 ^{, Nd} _1.0 ^Si _0.4 ^Co _0.6 ^{, Nd} _1.0 ^Si _0.3 ^Co _0.7 ^, Nd1.0Si0.2Co0.8, Nd1.0Si0.1Co0.9, or any combination thereof. In some embodiments the material is Nd _1.0 Si _0.9 Cu _0.1 , Nd _1.0 Si _0.8 Cu _0.8 , Nd _1.0 Si _0.7 Cu _0.3 , Nd _1.0 Si _0.6 Cu _0.4 , Nd _1.0 Si _0.5C Cu _0.5 , Nd1.0Si0.4Cu0.6, Nd1.0Si0.3Cu0.7, Nd1.0Si0.2Cu0.8, Nd1.0Si0.1Cu0.9, or any combination thereof.

[0008] In some embodiments, the magnetocaloric material comprises nano-grains, wherein at least one dimension of the nano-grains is in the range of about 0.1 nm to about 1000 nm. In some embodiments of the magnetocaloric material, the at least one dimension of the nanograins is in the range of about 1nm to about 100nm. In some embodiments of the magnetocaloric material, the at least one dimension of the nanograins is in the range of about 1nm to about 50nm.

[0009] Another embodiment of the invention is a magnetic refrigerator comprising the magnetocaloric material. In some embodiments, a magnetic refrigerator comprises a magnetocaloric material, wherein the magnetocaloric material comprises (Ce _x Nd _1-x )Si wherein x is in the range of about 0.1 to about 0.9. In some embodiments, a magnetic refrigerator comprises a magnetocaloric material, wherein the magnetocaloric material comprises RE (Siy A1-y) wherein RE is selected from the group consisting of Ce, Nd, or Gd, and wherein A is selected from the group consisting of Sn, Co, Al, Ni, Fe, Mn, or Cu, and wherein y is in the range of about 0.1 to about 0.9. In some embodiments, a magnetic refrigerator comprises a magnetocaloric material, wherein the magnetocaloric material comprises Nd5.0 (Siz D3-z) wherein D is selected from the group consisting of Sn, Co, Al, Ni, Fe, Mn, or Cu, and wherein z is in the range of about 0.1 to about 2.9.

[0010] Another embodiment of the invention is a method of manufacturing a heat pump, comprising fabricating at least one part of the heat pump from a magnetocaloric material. In some embodiments, a method of manufacturing a heat pump comprises fabricating at least one part of the heat pump from a magnetocaloric material, wherein the magnetocaloric material comprises (CexNd1-x)Si wherein x is in the range of about 0.1 to about 0.9. In some embodiments, a method of manufacturing a heat pump comprises fabricating at least one part of the heat pump from a magnetocaloric material, wherein the magnetocaloric material comprises RE (Si _y A _1-y ) wherein RE is selected from the group consisting of Ce, Nd, or Gd, wherein A is selected from the group consisting of Sn, Co, Al, Ni, Fe, Mn, or Cu, and wherein y is in the range of about 0.1 to about 0.9. [0011] For purposes of summarizing aspects of the invention and the advantages achieved over the related art, certain objects and advantages of the invention are described in this disclosure. Of course, it is to be understood that not necessarily all such objects or advantages may be achieved in accordance with any particular embodiment of the invention. Thus, for example, those skilled in the art will recognize that the invention may be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other objects or advantages as may be taught or suggested herein.

Some embodiments relate to magnetocaloric materials comprising ternary alloys useful for magnetic refrigeration applications. The disclosed ternary alloys are Cerium, Neodymium, and/or Gadolinium based compositions that are fairly inexpensive, and in some cases exhibit only 2 ^nd order magnetic phase transitions near their curie temperature, thus there are no thermal and structural hysteresis losses. This makes these compositions attractive candidates for use in magnetic refrigeration applications. Surprisingly, the performance of the disclosed materials is similar or better to many of the known expensive rare-earth based magnetocaloric materials.

[0012] Further aspects, features and advantages of this invention will become apparent from the detailed description of the embodiments which follow.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 illustrates the change in entropy versus temperature for a Ce _0.5 Nd _0.5 Si alloy.

[0014] Figure 2 illustrates the magnetization versus temperature for several CeNdSi alloy’s.

[0015] Figure 3 illustrates the magnetization versus temperature for a Nd1.0Si0.9Zn0.1 alloy.

[0016] Figure 4 illustrates the magnetization versus temperature for a Nd _1.0 Si _0.9 Ni _0.1 alloy.

[0017] Figure 5 illustrates the magnetization versus temperature for a Nd1.0Si0.9Mn0.1 alloy. [0018] Figure 6 illustrates the magnetization versus temperature for a Nd1.0Si0.9Fe0.1 alloy.

[0019] Figure 7 illustrates the magnetization versus temperature for a Nd _1.0 Si _0.9 Al _0.1 alloy.

[0020] Figure 8 illustrates the magnetization versus temperature for a Nd _1.0 Si _0.9 Co _0.1 alloy.

[0021] Figure 9 illustrates the magnetization versus temperature for a Nd1.0Si0.9Cu0.1 alloy.

[0022] Figure 10 illustrates the magnetization versus temperature for a Nd1.0Si0.9Sn0.1 alloy. DETAILED DESCRIPTION

[0023] The magnetocaloric effect (MCE) is a phenomenon in which the temperature change of a suitable material is caused by exposing the material to a changing magnetic field. The magnetocaloric effect can be quantified with the equation below:

where T is the temperature, H is the applied magnetic field, C is the heat capacity of the working magnet (refrigerant) and M is the magnetization of the refrigerant. The temperature change in the material is caused by a change in the entropy of the material.

[0024] As used herein, the term “magnetocaloric effect” includes any phenomenon in which the temperature change of a material is caused by exposing the material to a changing magnetic field.

[0025] The magnetocaloric effect exhibited by most magnetocaloric materials is as follows: the temperature of the magnetocaloric material increases when the magnetic field is moved near or in contact with the magnetocaloric material, and wherein the temperature of the magnetocaloric material decreases when the magnetic field is moved away from the magnetocaloric material. Materials which undergo a magnetocaloric effect with application and removal of a magnetic field include, but are not limited to, Gadolinium based alloys. In some embodiments, the magnetocaloric material exhibits a magnetocaloric effect, wherein the temperature of the magnetocaloric material increases when the magnetic field is moved near or in contact with the magnetocaloric material, and wherein the temperature of the magnetocaloric material decreases when the magnetic field is moved away from the magnetocaloric material.

[0026] However, some magnetocaloric materials exhibit a inversed magnetocaloric effect, wherein the temperature of the magnetocaloric material decreases when the magnetic field is moved near or in contact with the magnetocaloric material, and wherein the temperature of the magnetocaloric material increases when the magnetic field is moved away from the magnetocaloric material. Materials which undergo an inverse magnetocaloric effect with application and removal of a magnetic field include, but are not limited to, Heusler alloys, which include, but are not limited to, NiMn based alloys. In some embodiments, the magnetocaloric material exhibits an inverse magnetocaloric effect, wherein the temperature of the magnetocaloric material decreases when the magnetic field is moved near or in contact with the magnetocaloric material, and wherein the temperature of the magnetocaloric material increases when the magnetic field is moved away from the magnetocaloric material.

[0027] Some embodiments of the present invention provide a magnetocaloric material comprising (CexNd1-x)Si wherein x is in the range of about 0.1 to about 0.9. In some embodiments, the magnetocaloric material exhibits a 2 ^nd order magnetic phase transition in the temperature range of about 10K to about 42K. In some embodiments, the magnetocaloric material is Ce0.1Nd0.9Si1.0, Ce0.2Nd0.8Si1.0, Ce0.3Nd0.7Si1.0, Ce0.4Nd0.6Si1.0, Ce0.5Nd0.5Si1.0, Ce0.6Nd0.4Si1.0, Ce0.7Nd0.3Si1.0, Ce0.8Nd0.2Si1.0, Ce0.9Nd0.1Si1.0, or any combination thereof.

[0028] Some embodiments of the present invention provide a magnetocaloric material comprising RE (Siy A1-y) wherein RE is selected from the group consisting of Ce, Nd, or Gd, and wherein A is selected from the group consisting of Sn, Co, Al, Ni, Fe, Mn, Zn, or Cu, and wherein y is in the range of about 0.1 to about 0.9. In some embodiments the ^{material is Ce} _1.0 ^Si _0.9 ^Sn _0.1 ^{, Ce} _1.0 ^Si _0.8 ^Sn _0.8 ^{, Ce} _1.0 ^Si _0.7 ^Sn _0.3 ^{, Ce} _1.0 ^Si _0.6 ^Sn _0.4 ^{, Ce} _1.0 ^Si _0.5 ^Sn _0.5 ^, Ce1.0Si0.4Sn0.6, Ce1.0Si0.3Sn0.7, Ce1.0Si0.2Sn0.8, Ce1.0Si0.1Sn0.9, or any combination thereof. In some embodiments the material is Nd1.0Si0.9Mn0.1, Nd1.0Si0.8Mn0.8, Nd1.0Si0.7Mn0.3, Nd _1.0 Si _0.6 Mn _0.4 , Nd _1.0 Si _0.5 Mn _0.5 , Nd _1.0 Si _0.4 Mn _0.6 , Nd _1.0 Si _0.3 Mn _0.7 , Nd _1.0 Si _0.2 Mn _0.8 , Nd1.0Si0.1Mn0.9, or any combination thereof. In some embodiments the material is Gd1.0Si0.9Mn0.1, Gd1.0Si0.8Mn0.8, Gd1.0Si0.7Mn0.3, Gd1.0Si0.6Mn0.4, Gd1.0Si0.5Mn0.5, Gd1.0Si0.4Mn0.6, Gd1.0Si0.3Mn0.7, Gd1.0Si0.2Mn0.8, Gd1.0Si0.1Mn0.9, or any combination thereof. In some embodiments the material is Nd _1.0 Si _0.9 Fe _0.1 , Nd _1.0 Si _0.8 Fe _0.8 , Nd _1.0 Si _0.7 Fe _0.3 , Nd _1.0 Si _0.6 Fe _0.4 , Nd _1.0 Si _0.5 Fe _0.5 , Nd _1.0 Si _0.4 Fe _0.6 , Nd _1.0 Si _0.3 Fe _0.7 , Nd _1.0 Si _0.2 Fe _0.8 , Nd _1.0 Si _0.1 Fe _0.9 , or any combination thereof. In some embodiments the material is Gd1.0Si0.9Fe0.1, Gd1.0Si0.8Fe0.8, Gd1.0Si0.7Fe0.3, Gd1.0Si0.6Fe0.4, Gd1.0Si0.5Fe0.5, Gd1.0Si0.4Fe0.6, Gd1.0Si0.3Fe0.7, Gd1.0Si0.2Fe0.8, Gd _1.0 Si _0.1 Fe _0.9 , or any combination thereof. In some embodiments the material is Nd _1.0 Si _0.9 Zn _0.1 , Nd _1.0 Si _0.8 Zn _0.8 , Nd _1.0 Si _0.7 Zn _0.3 , Nd _1.0 Si _0.6 Zn _0.4 , Nd _1.0 Si _0.5 Zn _0.5 , Nd _1.0 Si _0.4 Zn _0.6 , Nd1.0Si0.3Zn0.7, Nd1.0Si0.2Zn0.8, Nd1.0Si0.1Zn0.9, or any combination thereof. In some embodiments the material is Nd1.0Si0.9Ni0.1, Nd1.0Si0.8Ni0.8, Nd1.0Si0.7Ni0.3, Nd1.0Si0.6Ni0.4, Nd _1.0 Si _0.5 Ni _0.5 , Nd _1.0 Si _0.4 Ni _0.6 , Nd _1.0 Si _0.3 Ni _0.7 , Nd _1.0 Si _0.2 Ni _0.8 , Nd _1.0 Si _0.1 Ni _0.9 , or any combination thereof. In some embodiments the material is Nd _1.0 Si _0.9 Co _0.1 , Nd _1.0 Si _0.8 Co _0.8 , Nd1.0Si0.7Co0.3, Nd1.0Si0.6Co0.4, Nd1.0Si0.5CCo0.5, Nd1.0Si0.4Co0.6, Nd1.0Si0.3Co0.7, Nd1.0Si0.2Co0.8, Nd1.0Si0.1Co0.9, or any combination thereof. In some embodiments the material is Nd _1.0 Si _0.9 Cu _0.1 , Nd _1.0 Si _0.8 Cu _0.8 , Nd _1.0 Si _0.7 Cu _0.3 , Nd _1.0 Si _0.6 Cu _0.4 , Nd _1.0 Si _0.5C Cu _0.5 , Nd _1.0 Si _0.4 Cu _0.6 , Nd _1.0 Si _0.3 Cu _0.7 , Nd _1.0 Si _0.2 Cu _0.8 , Nd _1.0 Si _0.1 Cu _0.9 , or any combination thereof.

[0029] Some embodiments of the present invention provide a magnetocaloric material comprising (Ce _y Nd _5-y ) Si _3.0 wherein y is in the range of about 0.1 to about 4.9. In some embodiments, the magnetocaloric material exhibits a magnetic phase transition in the temperature range of about 40K to about 300K. In some embodiments, the magnetocaloric material is Ce0.1Nd4.9Si3.0, Ce0.2Nd4.8Si3.0, Ce0.3Nd4.7Si3.0, Ce0.4Nd4.6Si3.0, Ce0.5Nd4.5Si3.0, Ce _0.6 Nd _4.4 Si _3.0 , Ce _0.7 Nd _4.3 Si _3.0 , Ce _0.8 Nd _4.2 Si _3.0 , Ce _0.9 Nd _4.1 Si _3.0 , Ce _1.0 Nd _4.0 Si _3.0 , Ce _1.1 Nd _3.9 Si _3.0 , Ce _1.2 Nd _3.8 Si _3.0 , Ce _1.3 Nd _3.7 Si _3.0 , Ce _1.4 Nd _3.6 Si _3.0 , Ce _1.5 Nd _3.5 Si _3.0 , Ce _1.6 Nd _3.4 Si _3.0 , Ce _1.7 Nd _3.3 Si _3.0 , Ce1.8Nd3.2Si3.0, Ce1.9Nd3.1Si3.0, Ce2.0Nd3.0Si3.0, Ce2.1Nd2.9Si3.0, Ce2.2Nd2.8Si3.0, Ce2.3Nd2.7Si3.0, Ce2.4Nd2.6Si3.0, Ce2.5Nd2.5Si3.0, Ce2.6Nd2.4Si3.0, Ce2.7Nd2.3Si3.0, Ce2.8Nd2.2Si3.0, Ce2.9Nd2.1Si3.0, Ce3.0Nd2.0Si3.0, Ce3.1Nd1.9Si3.0, Ce3.2Nd1.8Si3.0, Ce3.3Nd1.7Si3.0, Ce3.4Nd1.6Si3.0, Ce3.5Nd1.5Si3.0, Ce _3.6 Nd _1.4 Si _3.0 , Ce _3.7 Nd _1.3 Si _3.0 , Ce _3.8 Nd _1.2 Si _3.0 , Ce _3.9 Nd _1.1 Si _3.0 , Ce _4.0 Nd _1.0 Si _3.0 , Ce _4.1 Nd _0.9 Si _3.0 , Ce _4.2 Nd _0.8 Si _3.0 , Ce _4.3 Nd _0.7 Si _3.0 , Ce _4.4 Nd _0.6 Si _3.0 , Ce _4.5 Nd _0.5 Si _3.0 , Ce _4.6 Nd _0.4 Si _3.0 , Ce _4.7 Nd _0.3 Si _3.0 , Ce4.8Nd0.2Si3.0, Ce4.9Nd0.1Si3.0, or any combination thereof.

[0030] Some embodiments of the present invention provide a magnetocaloric material comprising Nd (Si _y A _1-y ) wherein A is selected from the group consisting of Sn, Co, Al, Ni, Fe, Mn, Zn, or Cu, and wherein y is in the range of about 0.1 to about 0.9. In some embodiments, the magnetocaloric material is Nd1.0Si0.9Sn0.1, Nd1.0Si0.8Sn0.8, Nd1.0Si0.7Sn0.3, Nd1.0Si0.6Sn0.4, Nd1.0Si0.5Sn0.5, Nd1.0Si0.4Sn0.6, Nd1.0Si0.3Sn0.7, Nd1.0Si0.2Sn0.8, Nd1.0Si0.1Sn0.9, or any combination thereof. In some embodiments, the magnetocaloric material is Nd _1.0 Si _0.9 Co _0.1 , Nd _1.0 Si _0.8 Co _0.8 , Nd _1.0 Si _0.7 Co _0.3 , Nd _1.0 Si _0.6 Co _0.4 , Nd _1.0 Si _0.5C Co _0.5 , Nd1.0Si0.4Co0.6, Nd1.0Si0.3Co0.7, Nd1.0Si0.2Co0.8, Nd1.0Si0.1Co0.9, or any combination thereof. In some embodiments, the magnetocaloric material is Nd1.0Si0.9Cu0.1, Nd1.0Si0.8Cu0.8, Nd _1.0 Si _0.7 Cu _0.3 , Nd _1.0 Si _0.6 Cu _0.4 , Nd _1.0 Si _0.5C Cu _0.5 , Nd _1.0 Si _0.4 Cu _0.6 , Nd _1.0 Si _0.3 Cu _0.7 , Nd _1.0 Si _0.2 Cu _0.8 , Nd _1.0 Si _0.1 Cu _0.9 , or any combination thereof.

[0031] Some embodiments of the present invention provide a magnetocaloric material comprising Nd _5.0 (Si _z D _3-z ) wherein D is selected from the group consisting of Sn, Co, Al, Ni, Fe, Mn, Zn, or Cu, and wherein z is in the range of about 0.1 to about 2.9. In some embodiments, the magnetocaloric material exhibits a 2 ^nd order magnetic phase transition in the temperature range of about 40K to about 300K. In some embodiments, the magnetocaloric material comprises Nd _5.0 (Si _z Sn _3-z ) wherein z is in the range of about 0.1 to about 2.9. In some embodiments, the magnetocaloric material is Nd _5.0 Si _0.1 Sn _2.9 , Nd5.0Si0.2Sn2.8, Nd5.0Si0.3Sn2.7, Nd5.0Si0.4Sn2.6, Nd5.0Si0.5Sn2.5, Nd5.0Si0.6Sn2.4, Nd5.0Si0.7Sn2.3, Nd5.0Si0.8Sn2.2, Nd5.0Si0.9Sn2.1, Nd5.0Si1.0Sn2.0, Nd5.0Si1.1Sn1.9, Nd5.0Si1.2Sn1.8, Nd5.0Si1.3Sn1.7, Nd _5.0 Si _1.4 Sn _1.6 , Nd _5.0 Si _1.5 Sn _1.5 , Nd _5.0 Si _1.6 Sn _1.4 , Nd _5.0 Si _1.7 Sn _1.3 , Nd _5.0 Si _1.8 Sn _1.2 , Nd _5.0 Si _1.9 Sn _1.1 , Nd _5.0 Si _2.0 Sn _1.0 , Nd _5.0 Si _2.1 Sn _0.9 , Nd _5.0 Si _2.2 Sn _0.8 , Nd _5.0 Si _2.3 Sn _0.7 , Nd _5.0 Si _2.4 Sn _0.6 , Nd _5.0 Si _2.5 Sn _0.5 , Nd5.0Si2.6Sn0.4, Nd5.0Si2.7Sn0.3, Nd5.0Si2.8Sn0.2, Nd5.0Si2.9Sn0.1, or any combination thereof.

[0032] In some embodiments, the magnetocaloric material comprises nano-grains, wherein at least one dimension of the nano-grains is in the range of about 0.1 nm to about 1000 nm. In some embodiments of the magnetocaloric material, the at least one dimension of the nanograins is in the range of about 1nm to about 100nm. In some embodiments of the magnetocaloric material, the at least one dimension of the nanograins is in the range of about 1nm to about 50nm.

[0033] Another embodiment of the invention is a magnetic refrigerator comprising the magnetocaloric material. In some embodiments, a magnetic refrigerator comprises a magnetocaloric material, wherein the magnetocaloric material comprises (CexNd1-x)Si wherein x is in the range of about 0.1 to about 0.9. In some embodiments, a magnetic refrigerator comprises a magnetocaloric material, wherein the magnetocaloric material comprises (Ce _y Nd _5-y ) Si _3.0 wherein y is in the range of about 0.1 to about 4.9. In some embodiments, a magnetic refrigerator comprises a magnetocaloric material, wherein the magnetocaloric material comprises Nd (Siy A1-y) wherein A is selected from the group consisting of Sn, Co, Al, Ni, Fe, Mn, Zn, or Cu, and wherein x is in the range of about 0.1 to about 0.9. In some embodiments, a magnetic refrigerator comprises a magnetocaloric material, wherein the magnetocaloric material comprises Nd _5.0 (Si _z D _3-z ) wherein D is selected from the group consisting of Sn, Co, Al, Ni, Fe, Mn, Zn or Cu, and wherein z is in the range of about 0.1 to about 2.9.

[0034] Another embodiment of the invention is a method of manufacturing a heat pump, comprising fabricating at least one part of the heat pump from a magnetocaloric material. In some embodiments, a method of manufacturing a heat pump comprises fabricating at least one part of the heat pump from a magnetocaloric material, wherein the magnetocaloric material comprises (Ce _x Nd _1-x )Si wherein x is in the range of about 0.1 to about 0.9. In some embodiments, a method of manufacturing a heat pump comprises fabricating at least one part of the heat pump from a magnetocaloric material, wherein the magnetocaloric material comprises (Ce _y Nd _5-y ) Si _3.0 wherein y is in the range of about 0.1 to about 4.9. In some embodiments, a method of manufacturing a heat pump comprises fabricating at least one part of the heat pump from a magnetocaloric material, wherein the magnetocaloric material comprises Nd (Siy A1-y) wherein A is selected from the group consisting of Sn, Co, Al, Ni, Fe, Mn, or Cu, and wherein x is in the range of about 0.1 to about 0.9. In some embodiments, a method of manufacturing a heat pump comprises fabricating at least one part of the heat pump from a magnetocaloric material, wherein the magnetocaloric material comprises Nd5.0 (Siz D3-z) wherein D is selected from the group consisting of Sn, Co, Al, Ni, Fe, Mn, or Cu, and wherein z is in the range of about 0.1 to about 2.9.

[0035] In some embodiments, the nanograins of the magnetocaloric material are synthesized by methods known in the art, such as, but not limited to, spark erosion, ball milling, hydrothermal method, chemical precipitation synthesis, arc melting, chemical vapor deposition, physical vapor deposition, etc. In some embodiments, the nanograined manganese based magnetocaloric material is synthesized using a spark erosion technique.

[0036] In some embodiments, the nano-grained magnetocaloric material is formed into a pellet structure by various methods known in the art, such as sintering, hydraulic pressing, swaging, hot pressing, or any other method which effectively packs powder material into solid pellet form. In some embodiments, the magnetocaloric material may be formed into a porous structure.

[0037] R.D. McMichael, J.J. Ritter, and R.D. Shull, J. Appl. Phys., 73, (10) 6946 (1993), showed that the addition of iron nanoparticles to gadolinium-gallium composites increases the magnetocaloric response by a factor of 3-4, which may be due to a local field amplification effect. Therefore, incorporation of iron and/or its composites into the magnetocaloric material may act to locally amplify the magnetic field in the material, and further enhance the magnetocaloric response of the material. In some embodiments, the magnetocaloric material further comprises iron or any material, composite, or alloy comprising iron. In some embodiments the magnetocaloric material comprises nanoparticles of iron or nanoparticles of any material, composite, or alloy comprising iron. In some embodiments, the magnetocaloric pellets further comprise iron or any material, composite, or alloy comprising iron.

[0038] In some embodiments the magnetocaloric material comprises nanograins. In some embodiments, at least one dimension of the nanograins is in the range of about 0.1nm to about 1000nm. In some embodiments, at least one dimension of the nanograins is in the range of about 1nm to about 500nm. In some embodiments, at least one dimension of the nanograins is in the range of about 20nm to about 100nm. In some embodiments, at least one dimension of the nanograins is in the range of about 100nm to about 200nm. In some embodiments, at least one dimension of the nanograins is in the range of about 1nm to about 75nm. In some embodiments, at least one dimension of the nanograins is in the range of about 5nm to about 20nm. In some embodiments, at least one dimension of the nanograins is in the range of about 1nm to about 100nm. In some embodiments, the at least one dimension of the nanograins is in the range of about 1nm to about 50nm.

[0039] The response temperature of the magnetocaloric material may be adjusted with small changes in the composition of the material. In some embodiments, the response temperature of the magnetocaloric material is adjusted by changing the composition of the material. In some embodiments, the magnetocaloric material exhibits a magnetocaloric effect at any temperature in the range of about 1K to about 350K. In some embodiments, the magnetocaloric material exhibits a magnetocaloric effect at any temperature in the range of about 10K to about 50K. In some embodiments, the magnetocaloric material exhibits a magnetocaloric effect at any temperature in the range of about 50K to about 1000K. In some embodiments, the magnetocaloric material exhibits a magnetocaloric effect at any temperature in the range of about 100K to about 350K. In some embodiments, the magnetocaloric material exhibits a magnetocaloric effect at any temperature in the range of about 50K to about 200K. In some embodiments, the magnetocaloric nanomaterial exhibits a magnetocaloric effect at any temperature in the range of about 10K to about 80K.

[0040] For purposes of summarizing aspects of the invention and the advantages achieved over the related art, certain objects and advantages of the invention are described in this disclosure. Of course, it is to be understood that not necessarily all such objects or advantages may be achieved in accordance with any particular embodiment of the invention. Thus, for example, those skilled in the art will recognize that the invention may be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other objects or advantages as may be taught or suggested herein.

[0041] Further aspects, features and advantages of this invention will become apparent from the detailed example embodiments which follow.

EXAMPLES

[0042] The embodiments will be explained with respect to preferred embodiments which are not intended to limit the present invention. Further, in the present disclosure where conditions and/or structures are not specified, the skilled artisan in the art can readily provide such conditions and/or structures, in light of the teachings herein, as a matter of routine experimentation.

[0043] The object of this current invention is to provide magnetocaloric materials useful for magnetic refrigeration applications. Example 1

[0044] A Nd _0.5 Ce _0.5 Si _1.0 ingot was prepared by arc melting in an argon atmosphere. The ingot was sealed in a quartz tube furnace under argon and annealed at 950C for 2 weeks. Figure 1 shows the DS vs entropy and Figure 2 shows the magnetization versus temperature for the Nd _0.5 Ce _0.5 Si _1.0 alloy with 2 ^nd order phase transition occurring near 32K. Example 2

[0045] A Nd _0.2 Ce _0.8 Si _1.0 ingot was prepared by arc melting in an argon atmosphere. The ingot was sealed in a quartz tube furnace under argon and annealed at 950C for 2 weeks. Figure 2 shows the magnetization versus temperature for the Nd0.2Ce0.8Si1.0 alloy with 2 ^nd order phase transition occurring near 15K. Example 3

[0046] A Nd0.4Ce0.6Si1.0 ingot was prepared by arc melting in an argon atmosphere. The ingot was sealed in a quartz tube furnace under argon and annealed at 950C for 2 weeks. Figure 2 shows the magnetization versus temperature for the Nd _0.4 Ce _0.6 Si _1.0 alloy with 2 ^nd order phase transition occurring near 25K. Example 4

[ ^{0047] A Nd} _0.6 ^Ce _0.4 ^Si _1.0 ^{ingot was prepared by arc melting in an argon} atmosphere. The ingot was sealed in a quartz tube furnace under argon and annealed at 950C for 2 weeks. Figure 2 shows the magnetization versus temperature for the Nd0.6Ce0.4Si1.0 alloy with 2 ^nd order phase transition occurring near 36K. Example 5

[0048] A Nd0.8Ce0.2Si1.0 ingot was prepared by arc melting in an argon atmosphere. The ingot was sealed in a quartz tube furnace under argon and annealed at 950C for 2 weeks. Figure 2 shows the magnetization versus temperature for the Nd _0.8 Ce _0.2 Si _1.0 alloy with 2 ^nd order phase transition occurring near 42K. Example 6

[0049] A Nd _1.0 Si _0.9 Zn _0.1 ingot was prepared by arc melting in an argon atmosphere. Figure 3 shows the magnetization versus temperature for the Nd1.0Si0.9Zn0.1 alloy with 2 ^nd order phase transition occurring near 75K. Example 6

[0050] A Nd1.0Si0.9Ni0.1 ingot was prepared by arc melting in an argon atmosphere. Figure 4 shows the magnetization versus temperature for the Nd _1.0 Si _0.9 Ni _0.1 alloy with 2 ^nd order phase transition occurring near 75K. Example 7

[0051] A Nd _1.0 Si _0.9 Mn _0.1 ingot was prepared by arc melting in an argon atmosphere. Figure 5 shows the magnetization versus temperature for the Nd1.0Si0.9Mn0.1 alloy with 2 ^nd order phase transition occurring near 125K. Example 8

[0052] A Nd1.0Si0.9Fe0.1 ingot was prepared by arc melting in an argon atmosphere. Figure 6 shows the magnetization versus temperature for the Nd1.0Si0.9Fe0.1 alloy with 2 ^nd order phase transition occurring near 75K. Example 9

[0053] A Nd _1.0 Si _0.9 Al _0.1 ingot was prepared by arc melting in an argon atmosphere. Figure 7 shows the magnetization versus temperature for the Nd _1.0 Si _0.9 Al _0.1 alloy with 2 ^nd order phase transition occurring less than 50K. Example 10

[0054] A Nd1.0Si0.9Co0.1 ingot was prepared by arc melting in an argon atmosphere. Figure 8 shows the magnetization versus temperature for the Nd _1.0 Si _0.9 Co _0.1 alloy with 2 ^nd order phase transition occurring near 75K. Example 11

[0055] A Nd _1.0 Si _0.9 Cu _0.1 ingot was prepared by arc melting in an argon atmosphere. Figure 9 shows the magnetization versus temperature for the Nd1.0Si0.9Cu0.1 alloy with 2 ^nd order phase transition occurring near 75K. Example 12

[0056] A Nd1.0Si0.9Sn0.1 ingot was prepared by arc melting in an argon atmosphere. Figure 10 shows the magnetization versus temperature for the Nd _1.0 Si _0.9 Sn _0.1 alloy with 2 ^nd order phase transition occurring less than 50K. Example 13

[0057] An example magnetic refrigerator comprising the disclosed magnetocaloric material is made by the following steps 1) preparing the magnetocaloric material into thin plates or millimeter sized spherical balls, 2) placing the magnetocaloric material into a magnetic field, where the application of the magnetic field causes the material to heat up, 3) using a heat transfer fluid to remove the heat from the magnetocaloric material, 4) then removing the magnetic field causing the magnetocaloric material to cool down, 5) then exposing the cold magnetocaloric material to the desired refrigeration environment where heat from the refrigeration environment is transferred to the magnetocaloric material, 6) then repeating steps 1 to 5 to create a refrigeration cycle which maintains a desired cold temperature within the refrigeration environment. Example 14 [0058] An example magnetic refrigerator comprising the disclosed magnetocaloric material is made by the following similar steps as in Example 13, except that a heat transfer fluid is used in step 5 to expose the cold magnetocaloric material to the desired refrigeration environment, where the heat from the refrigeration environment is transferred to the heat transfer fluid. Example 15

[0059] An example heat pump comprising fabricating at least one part of the heat pump from a magnetocaloric material is made by incorporating at least one magnetocaloric material of the disclosed invention, at least one permanent magnet, and at least one mechanical movement system; wherein the magnetic field generated by the permanent magnet enables the magnetocaloric effect of the magnetocaloric material when at least one oscillation cycle is performed by the mechanical movement system, wherein a change in temperature of the magnetocaloric material occurs when the magnetocaloric material is moved into or out of a magnetic field; and wherein the mechanical movement system performs the at least one oscillation cycle by physically moving the permanent magnet, the magnetocaloric material, a magnet shielding material, or any combination thereof; and wherein the at least one oscillation cycle comprises exposing the magnetic field to the magnetocaloric material at a predefined magnetic field ramp-up speed, holding the magnetic field near or in contact with the magnetocaloric material for a specified contact holding time, removing the magnetic field from the magnetocaloric material at a predefined ramp-down speed, and holding the magnetic field away from the magnetocaloric material for a specified removed holding time; and wherein the at least one oscillation cycle is optimized to provide cooling on one side of the heat pump device.

[0060] For purposes of summarizing aspects of the invention and the advantages achieved over the related art, certain objects and advantages of the invention are described in this disclosure. Of course, it is to be understood that not necessarily all such objects or advantages may be achieved in accordance with any particular embodiment of the invention. Thus, for example, those skilled in the art will recognize that the invention may be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other objects or advantages as may be taught or suggested herein. It will be understood by those of skill in the art that numerous and various modifications can be made without departing from the spirit of the present invention. Therefore, it should be clearly understood that the forms of the present invention are illustrative only and are not intended to limit the scope of the present invention.