POLYCRYSTALLINE FOAMS EXHIBITING GIANT MAGNETIC-FIELD-INDUCED DEFORMATION AND METHODS OF MAKING AND USING SAME

• US 20110064965A1
• Filed: 07/20/2010
• Published: 03/17/2011
• Est. Priority Date: 08/30/2007
• Status: Active Grant

• Current Assignee: Boise State University, Northwestern University
• Original Assignee: Boise State University
• Inventors: Witherspoon, Cassie, Dunand, David C., Mullner, Peter, Zhang, Xuexi, Boonyongmaneerat, Yuttanant, Chmielus, Markus
• Granted Patent: US 8,586,194 B2
• Time in Patent Office: Days
• US Class Current: 428/613
• CPC Class Codes: B22F 3/1115 comprising complex forms, e.g. honeycombs
• CPC Class Codes: B22F 3/1121 by using decomposable, meltable or sublimatable fillers
• CPC Class Codes: C22C 1/0433 Nickel- or cobalt-based alloys
• CPC Class Codes: C22C 19/00 Alloys based on nickel or cobalt
• CPC Class Codes: C22C 2202/02 Magnetic
• CPC Class Codes: C22C 38/00 Ferrous alloys, e.g. steel alloys cast-iron alloys C22C37/00
• CPC Class Codes: H01F 1/0308 with magnetic shape memory [MSM], i.e. with lattice transformations driven by a magnetic field, e.g. Heusler alloys
• CPC Class Codes: Y10T 428/12479 Porous [e.g., foamed, spongy, cracked, etc.]
• CPC Class Codes: Y10T 428/12681 Ga-, In-, Tl- or Group VA metal-base component
• CPC Class Codes: Y10T 428/12771 Transition metal-base component
• CPC Class Codes: Y10T 428/12861 Group VIII or IB metal-base component
• CPC Class Codes: Y10T 428/12931 Co-, Fe-, or Ni-base components, alternative to each other
• CPC Class Codes: Y10T 428/12951 Fe-base component

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.

Claims

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.

13. A material as in claim 12, wherein said struts are comprised of grains of magnetoplastic or magnetoelastic material and said pores of said first pore-size-range are generally the size of said grains.

14. A material as in claim 12, wherein said pores of said second pore-size-range are inside said nodes.

15. A material as in claim 14, wherein said struts are comprised of grains of magnetoplastic or magnetoelastic material and said pores of said second pore-size-range are smaller than said grains.

16. A material as in claim 12, wherein said second pore-size-range is an order of magnitude smaller than said second pore-size-range.

17. A material as in claim 12, wherein said second pore-size-range is 0.05-0.25 times said second pore-size-range.

18. A material as in claim 12, wherein said first pore-size-range is 500-600 μ

m and said second pore-size-range is 75-90 μ

m.

19. The material of claim 12 including alloys formed from the elements Ni—

Mn—

Ga.

20. The material of claim 12 including alloys formed from the elements Fe—

Pt.

21. The material of claim 12 including alloys formed from the elements Fe—

Pd.

22. The material of claim 12 including alloys formed from the elements Ni—

Co—

Ga.

23. The material of claim 12 which comprises at least 10 atomic percent each of Ni, Mn and Ga.

24-1. The method of claim 24 wherein the space-holder is NaAlO₂.