POLYCRYSTALLINE FOAMS EXHIBITING GIANT MAGNETIC-FIELD-INDUCED DEFORMATION AND METHODS OF MAKING AND USING SAME
First Claim
12. A magnetic material comprising:
- a polycrystalline porous structure of the solid magnetic material;
said porous structure comprising polycrystalline struts connected at nodes;
at least some of said polycrystalline struts including grain boundaries that extend transversely across an entire strut;
wherein said porous structure comprises pores between said struts and in said nodes, said pores being of at least two ranges of pore size comprising a first pore-size-range, and a second, smaller pore-size-range.
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Accused Products
Abstract
Magnetic materials and methods exhibit large magnetic-field-induced deformation/strain (MFIS) through the magnetic-field-induced motion of crystallographic interfaces. The preferred materials are porous, polycrystalline composite structures of nodes connected by struts wherein the struts may be monocrystalline or polycrystalline. The materials are preferably made from magnetic shape memory alloy, including polycrystalline Ni—Mn—Ga, formed into an open-pore foam, for example, by space-holder technique. Removal of constraints that interfere with MFIS has been accomplished by introducing pores with sizes similar to grains, resulting in MFIS values of 0.12% in polycrystalline Ni—Mn—Ga foams, close to the best commercial magnetostrictive materials. Further removal of constraints has been accomplished by introducing pores smaller than the grain size, dramatically increasing MFIS to 2.0-8.7%. These strains, which remain stable over >200,000 cycles, are much larger than those of any polycrystalline, active material.
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Citations
26 Claims
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12. A magnetic material comprising:
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a polycrystalline porous structure of the solid magnetic material; said porous structure comprising polycrystalline struts connected at nodes; at least some of said polycrystalline struts including grain boundaries that extend transversely across an entire strut; wherein said porous structure comprises pores between said struts and in said nodes, said pores being of at least two ranges of pore size comprising a first pore-size-range, and a second, smaller pore-size-range. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23)
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24-1. The method of claim 24 wherein the space-holder is NaAlO2.
Specification