Patent Publication Number: US-8524107-B2

Title: Magnetocaloric structure

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This is a non-provisional application that claims priority to U.S. Provisional Patent Application No. 61/243,390 filed Sep. 17, 2009, herein incorporated by reference in its entirety. 
    
    
     BACKGROUND 
     The present invention relates to a magnetocaloric structure. 
     Lately, a superconductive technology was developed rapidly. As the application field of the superconductive technology was expanded, the natural trend of a freezer is miniaturization and high performance. It is required that the miniature freezer be lighter weight, smaller and higher thermal efficiency, and the miniature freezer is being applied to various application fields. 
     The miniature freezer has many conventional magnetocaloric structures and a working fluid. The problems associated with the conventional magnetocaloric structures include being breakable, easy to block the flowing way of the working fluid, lower stabilization, lower heat conductive rate and easy to oxidize. Thus, the conventional freezer with the magnetocaloric structure has many limitations in use and is vulnerable. 
     SUMMARY 
     The present invention provides a magnetocaloric structure to increase stabilization and lifetime. 
     The present invention provides a magnetocaloric structure, which comprises a magnetocaloric material and at least one protective layer. The magnetocaloric material has bar type or plank type. The protective layer is disposed on the magnetocaloric material. 
     The present invention provides a magnetocaloric structure. The magnetocaloric structure comprises a magnetocaloric material and at least one protective layer. The protective layer is disposed on the magnetocaloric material. The protective layer is a physically-resistant material or a chemically-resistant material. The magnetocaloric material has bar type, plank type or particle type. 
     The material of the protective layer includes a metal, an organic metal composite, inorganic metal composite, a carbonaceous compound, or a higher heat conductive, lower permeable material. The protective layer can be a film or a flake. 
     The magnetocaloric structure further comprises at least one concave-convex structure disposed on the magnetocaloric material and the protective layer. The concave-convex structure has a polygonal shape, a curved shape or an irregular shape. The number of the concave-convex structure is more than two, and the concave-convex structures are irregularly arranged, regularly arranged, bar-shaped arranged, or matrix arranged. The protective layer is formed by chemical vapor deposition or physical vapor deposition. The size of the protective layer is less than 3 μm or 1 μm. 
     In the magnetocaloric structure, the magnetocaloric material comprises manganese (Mn), iron (Fe), phosphorus (P), or arsenic (As). The general formula of the magnetocaloric material is MnFeP 1-y As y , where 0.1≦y≦0.9, 0.2≦y≦0.8, 0.275≦y≦0.725, 0.3≦y≦0.7, or y=0.5. 
     Because the magnetocaloric structure of the present invention is in a special shape or has a protective layer, the magnetocaloric structure has higher resistance to impact force, larger endothermic area, higher anti-oxidation, higher stabilization, and longer lifetime. The magnetocaloric structure of the present invention does not block the flowing way of working fluid. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       The present invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein: 
         FIG. 1  is a partial schematic sectional view of a magnetocaloric structure according to one embodiment of the present invention. 
         FIG. 2  is a partial schematic sectional view of a magnetocaloric structure according to another embodiment of the present invention. 
         FIG. 3  is a partial schematic sectional view of a magnetocaloric structure according to still another embodiment of the present invention. 
         FIG. 4  is a partial schematic sectional view of a magnetocaloric structure according to yet another embodiment of the present invention. 
         FIG. 5  is a partial schematic sectional view of a magnetocaloric structure according to still yet another embodiment of the present invention. 
         FIG. 6  is a partial schematic sectional view of a magnetocaloric structure according to yet still another embodiment of the present invention. 
         FIG. 7  is a partial schematic sectional view of a magnetocaloric structure according to still yet another embodiment of the present invention. 
         FIG. 8  is a partial schematic sectional view of a magnetocaloric structure according to yet still another embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     The magnetocaloric structure of the present invention comprises a magnetocaloric material and at least one protective layer. 
     The magnetocaloric material may have non-sphere type, bar type, plank type or particle type. When the magnetocaloric material is bar type or plank type, the magnetocaloric material has better resistance to impact force and higher stabilization. 
     Besides, the magnetocaloric structure can have one or more concave-convex structures. For example, the concave-convex structure is disposed on the magnetocaloric material or the protective layer. When the number of the concave-convex structure is more than two or three, each concave-convex structure can only be disposed on a single surface or different surfaces of the magnetocaloric structure. When the number of the concave-convex structure is more than two, the concave-convex structures are irregularly arranged, regularly arranged, bar shaped arranged or matrix arranged. Preferably, the concave-convex structure has a polygonal shape, a curved shape, or an irregular shape. The polygonal shape can be a triangle shape or a quadrangle shape. The curved shape can be an arc shape, an oval-shape or a curved shape. The concave-convex structure can be used to increase the contact surface area (or endothermic area), the impact strength or the heat-transmission efficacy ratio of the magnetocaloric structure. 
     In the magnetocaloric structure, the magnetocaloric material comprises manganese (Mn), iron (Fe), phosphorus (P), or arsenic (As). The formula of the magnetocaloric material is P 1-y As y . For example, the magnetocaloric material is MnFeP 1-y As y , where 0.1≦y≦0.9, 0.2≦y≦0.8, 0.275≦y≦0.725, 0.3≦y≦0.7 or y=0.5. When the y value is within the above range, the magnetocaloric material has a better magnetic entropy change (MEC) to get a better magnetocaloric effect. 
     The protective layer can be disposed on the magnetocaloric material or cover the magnetocaloric material, such that the protective layer increases the physical resistance and/or chemical resistance of the magnetocaloric material without decreasing hot-transmission efficacy. The material of the protective layer can be a physically-resistant material or a chemically-resistant material. For example, the material of the protective layer can be a metal, an organic metal composite, inorganic metal composite, a carbonaceous compound, or a material having higher heat Conductivity and lower permeability. The protective layer can be a film or a flake, which is formed by chemical vapor deposition or physical vapor deposition. The physical vapor deposition can be electroplating or sputtering. The size of the protective layer is less than 3 μm or 1 μm. The shapes of the protective layer and the magnetocaloric material can be the same or different. The protective layer can enhance the magnetocaloric material by providing a physically-resistant function, a chemically-resistant function, or longer lifetime. The physically-resistant function may be a heat conduction function or an anti-impact force function. The chemically-resistant function may be an anti-corrosion function. 
     Because the magnetocaloric structure of the present invention has a special shape or includes the protective layer, the magnetocaloric structure has higher resistant to impact force, a larger endothermic area, higher anti-oxidation, higher stabilization, and longer lifetime. Therefore, the magnetocaloric structure of the present invention does not block the flowing way of working fluid. 
     Referring to  FIG. 1 , the magnetocaloric structure  100  has a magnetocaloric material  102  and a protective layer  104 . The magnetocaloric material  102  can be a block type or bar type with a circular cross-section or oval-shaped cross-section. The protective layer  104  is disposed on the surface of the magnetocaloric material  102 . 
     Referring to  FIG. 2 , the magnetocaloric structure  200  has a magnetocaloric material  202  and a protective layer  204 . The magnetocaloric material  202  can be a block type or bar type with a polygonal shaped cross-section. The protective layer  204  is disposed on the surface of the magnetocaloric material  202 . 
     Referring to  FIG. 3 , the magnetocaloric structure  300  has a magnetocaloric material  302  and a protective layer  304 . The magnetocaloric material  302  has a block type or bar type with an irregular shaped cross-section. The protective layer  304  is disposed on the surface of the magnetocaloric material  302 . 
     Referring to  FIG. 6 , the magnetocaloric structure  600  has a magnetocaloric material  602  and a protective layer  604 . The magnetocaloric material  602  has a plank type. The protective layer  604  is disposed on the surface of the magnetocaloric material  602 . 
     Referring to  FIG. 4 , the magnetocaloric structure  400  has a magnetocaloric material  402  and a protective layer  404 . The magnetocaloric material  402  has a block type or bar type. The protective layer  404  is disposed on the surface of the magnetocaloric material  402 . A concave-convex structure  406  is formed by the protective layer  404  and the magnetocaloric material  402 . 
     Referring to  FIG. 5 , the magnetocaloric structure  500  has a magnetocaloric material  502  and a protective layer  504 . The magnetocaloric material  502  has a block type or bar type. The protective layer  504  is disposed on the surface of the magnetocaloric material  502 . A concave-convex structure  506  is formed only by the protective layer  504  or the magnetocaloric material  502 . 
     Referring to  FIG. 7 , the magnetocaloric structure  700  has a magnetocaloric material  702  and a protective layer  704 . The protective layer  704  is disposed on the surface of the magnetocaloric material  702 . A concave-convex structure  706  is formed on one surface of the protective layer  704  and the magnetocaloric material  702 . 
     Referring to  FIG. 8 , the magnetocaloric structure  800  has a magnetocaloric material  802  and a protective layer  804 . The protective layer  804  is disposed on the surface of the magnetocaloric material  802 . A concave-convex structure  806  is formed on two or more surfaces of the protective layer  804  and the magnetocaloric material  802 . 
     Because the shape of the magnetocaloric structure or the concave-convex structure has above variation, the magnetocaloric structure can have better anti-impact force function or heat-transmission efficacy ratio. 
     While the present invention has been described with respect to preferred embodiments, it is to be understood that the present invention is not limited thereto, but is intended to accommodate various modifications and equivalent arrangements made by those skilled in the art without departing from the spirit of the present invention.