Freeze-cast magnetic flake composites

Abstract

In an embodiment, the present disclosure pertains to a method of making a composite. In some embodiments, the method includes applying an external magnetic field to a mixture composed of a plurality of magnetic materials in a container, in which the external magnetic field produces a homogenous and uniform magnetic flux in the container. In some embodiments, the method further includes solidifying the mixture to result in the growth of solvent crystals in the mixture, and subliming a solvent phase of the mixture in the container to thereby form a composite having uniformly aligned magnetic materials. In an additional embodiment, the present disclosure pertains to a composite having uniformly aligned magnetic materials. In some embodiments, a majority of the magnetic materials in the composite are aligned in the same direction.

What is claimed is: 
     
         1 . A method of making a composite, said method comprising:
 applying an external magnetic field to a mixture comprising a plurality of magnetic materials in a container,
 wherein the external magnetic field produces a homogenous and uniform magnetic flux in the container; 
   solidifying the mixture,
 wherein the solidifying results in the growth of solvent crystals in the mixture; and 
   subliming a solvent phase of the mixture in the container,
 wherein the method results in the formation of a composite comprising uniformly aligned magnetic materials. 
   
     
     
         2 . The method of  claim 1 , wherein the homogenous and uniform magnetic field is generated by a magnetic fixture associated with the container, wherein the magnetic fixture comprises:
 one or more soft magnetic materials in parallel arrangement,
 wherein the one or more soft magnetic materials further comprise one or more permanent magnets positioned therebetween, and 
 wherein the one or more soft magnetic materials facilitate the production of the homogenous and uniform magnetic flux in the container. 
   
     
     
         3 . The method of  claim 2 , wherein the one or more permanent magnets are coiled magnets. 
     
     
         4 . The method of  claim 1 , wherein the mixture further comprises at least one of a binder, an electrically insulating binder, a thermally conducting binder, a semiconducting binder, a particle, and a dispersant. 
     
     
         5 . The method of  claim 4 , wherein the binder comprises a polymer. 
     
     
         6 . The method of  claim 1 , wherein the magnetic materials are in the form of magnetic flakes. 
     
     
         7 . The method of  claim 1 , wherein the magnetic materials are in the form of particles comprising a surface and an internal core, wherein at least one of the surface and the internal core are magnetic. 
     
     
         8 . The method of  claim 1 , wherein the container comprises a square or rectangular shape. 
     
     
         9 . The method of  claim 1 , wherein the container comprises a bottom portion with an inclination angle greater than or equal to 0°. 
     
     
         10 . The method of  claim 1 , wherein the magnetic field rotates at least some of the magnetic particles without significantly translating (changing the position) of the magnetic particles. 
     
     
         11 . The method of  claim 1 , wherein the applying the external magnetic field results in alignment of the magnetic materials in a first direction and the solidifying step results in alignment in a second direction. 
     
     
         12 . The method of  claim 11 , wherein the first direction is parallel to a magnetic flux generated from the applied external magnetic field, wherein the second direction is parallel to a solidification direction, and wherein the second direction is perpendicular to the first direction. 
     
     
         13 . The method of  claim 11 , wherein the first direction is parallel to a magnetic flux generated from the applied external magnetic field, wherein the second direction is parallel to a solidification direction, and wherein the second direction is parallel to the first direction. 
     
     
         14 . The method of  claim 11 , wherein the first direction is at least one of parallel and perpendicular to the second direction. 
     
     
         15 . The method of  claim 1 , wherein the solidifying step comprises solidification by at least one of a bottom-up, top-down, bottom-up and top-down, and double-sided direction freezing method. 
     
     
         16 . The method of  claim 1 , further comprising a step of compressing the formed composite. 
     
     
         17 . The method of  claim 1 , wherein a majority of the magnetic materials in the composite are aligned in the same direction. 
     
     
         18 . A composite comprising uniformly aligned magnetic materials, wherein a majority of the magnetic materials in the composite are aligned in the same direction. 
     
     
         19 . The composite of  claim 18 , wherein the magnetic materials are in the form of magnetic flakes. 
     
     
         20 . The composite of  claim 19 , wherein the magnetic flakes are aligned in a head-to-tail chain and laterally spaced apart to thereby form a nacre-like packing. 
     
     
         21 . The composite of  claim 18 , further comprising at least one of a binder, an electrically it s g binder, a thermally conducting binder, a semiconducting binder, a particle, and a dispersant. 
     
     
         22 . The composite of  claim 21 , wherein the binder comprises a polymer. 
     
     
         23 . The composite of  claim 18 , wherein the magnetic materials are in the form of particles comprising a surface and an internal core, wherein at least one of the surface and the internal core are magnetic. 
     
     
         24 . The composite of  claim 18 , wherein the composite is in the form of a porous scaffold. 
     
     
         25 . A container for freeze-casting, wherein the container comprises a square or rectangular shape and a bottom portion, and wherein the container is associated with a magnetic field source for applying an external magnetic field to the container. 
     
     
         26 . The container of  claim 25 , further comprising a magnetic fixture comprising:
 one or more soft magnetic materials in parallel arrangement,
 wherein the one or more soft magnetic materials further comprise one or more permanent magnets positioned therebetween. 
   
     
     
         27 . The container of  claim 25 , wherein the bottom portion comprises copper. 
     
     
         28 . The container of  claim 25 , further comprising a plurality of mold guides for holding a sample in the container. 
     
     
         29 . The container of  claim 25 , further comprising at least one cooling mechanism. 
     
     
         30 . The container of  claim 29 , wherein the at least one cooling mechanism is positioned in a location selected from the group consisting of below the bottom portion, above a sample, in a double-sided arrangement, and combinations thereof.