Magnetic nanoparticles, bulk nanocomposite magnets, and production thereof

Abstract

Provided herein are systems, methods, and compositions for magnetic nanoparticles and bulk nanocomposite magnets.

1 . A composition of magnetic nanoparticles comprising:
 a. a plurality of magnetic nanoparticles produced by surfactant-assisted ball milling, wherein the magnetic nanoparticles have an average size below about 100 nm; and   b. the magnetic nanoparticles comprise at least one of FeO, Fe 2 O 3 , Fe 3 O 4 , Co, Fe, Ni, CoFe, NiFe, CoO, NiO and ferrites including MFe 2 O 3  where M comprises one of the transition metallic elements including Co and Ni; and FePt, CoPt, SmCo-based alloys, including SmCO 5 , Sm 2 CO 17 , Sm 2 CO 7 , and SmCO 7 , and rare earth-FeB-based alloys, including R 2 Fe 14 B, where R comprises one of Nd and Pr.   
     
     
         2 . The magnetic nanoparticles of  claim 1 , wherein the Sm—Co based alloys include an average size of 23 nm, a coercivity of equal or larger than 3.1 kOe, and an elongated rod-shape. 
     
     
         3 . The magnetic nanoparticles of  claim 1 , wherein the Fe—Co based alloys include an average size of at least about 1.7 to 4.0 nm and an ultrafine spherical shape. 
     
     
         4 . The magnetic nanoparticles of  claim 1 , wherein the Sm—Co, NdFeB, and Co magnetic nanoparticles include an elongated rod-like shape. 
     
     
         5 . A bulk magnetic nanocomposite comprising:
 a. a soft phase material with particle size from at least about 2 nanometers to 100 micrometers comprising at least one of FeO, Fe 2 O 3 , Fe 3 O 4 , Co, Fe, Ni, CoFe, NiFe, CoO, NiO and ferrites including MFe 2 O 3  where M comprises one of Co and Ni;   b. a hard phase material with particle size from 2 nanometers to 100 micrometers comprises at least one of FePt, CoPt, SmCo-based alloys, including SmCO 5 , Sm 2 CO 7 , Sm 2 CO 17 , and SmCO 7 , and rare earth-FeB-based alloys, including R 2 Fe 14 B, where R comprises one of Nd and Pr;   c. wherein the hard phase material and the soft phase material is warm compacted to form a bulk nanocomposite.   
     
     
         6 . The bulk magnetic nanocomposite of  claim 5 , wherein the soft phase material and the hard phase material comprise interphase exchange coupling and the hard phase material is aligned. 
     
     
         7 . The bulk magnetic nanocomposite of  claim 6 , wherein the soft phase material and the hard phase material includes a grain size in the nanoscale. 
     
     
         8 . The bulk magnetic nanocomposite of  claim 7 , wherein the density of the nanocomposite is between at least about 50% to 100% of the theoretical density. 
     
     
         9 . The bulk magnetic nanocomposite of  claim 8 , wherein the hard phase material and the soft phase material comprise magnetic nanoparticles. 
     
     
         10 . A process of forming a plurality of magnetic nanoparticles comprising:
 a. providing a powder with particles of first size in an inert environment;   b. dissolving the powder in a first solvent with a surfactant;   c. ball milling the powder into a plurality of nanoparticles having a second size;   d. dispersing the nanoparticles into a second solvent; and   e. separating the nanoparticles by a size selection process.   
     
     
         11 . The process of  claim 10 , wherein the powder is selected from one of FeO, Fe 2 O 3 , Fe 3 O 4 , Co, Fe, Ni, CoFe, NiFe, CoO, NiO and ferrites including MFe 2 O 3  where M comprises one of Co and Ni, FePt, CoPt, SmCo-based alloys, including SmCO 5 , Sm 2 CO 17 , Sm 2 CO 7 , and SmCO 7 , and rare earth-FeB-based alloys, including R 2 Fe 14 B, where R comprises one of Nd and Pr. 
     
     
         12 . The process of  claim 11 , wherein the powder is a SmCo-based alloy and the ball milling step includes a weight ratio of the powder to the ball mill comprises about 1:10. 
     
     
         13 . The process of  claim 10 , wherein the separating step comprises a spinning step of about 1600 g of relative centrifugal force for a period of time and separating a first supernatant from a first slurry to obtain a plurality of nanoparticles with an average size distribution of about 4 to about 10 nm. 
     
     
         14 . The process of  claim 13 , further comprising
 a. washing the first slurry with a solvent;   b. dispersing the first slurry in a surfactant-coated centrifugal tube by ultrasonic vibration;   c. settling down the dispersed solution for about 2 to about 5 hours;   d. spinning the settled down solution at about 45 g of relative centrifugal force; and   e. separating a second supernatant from a second slurry to obtain a plurality of nanoparticles with an average size distribution of about 10 to about 15 nm.   
     
     
         15 . The process of  claim 13 , further comprising:
 a. washing the first slurry with a solvent;   b. dispersing the first slurry in a surfactant-coated centrifugal tube by ultrasonic vibration;   c. settling down the dispersed solution for about 20 to about 30 minutes;   d. spinning the settled down solution at about 45 g relative centrifugal force; and   e. separating a second supernatant from a second slurry to obtain a plurality of nanoparticles with an average size of about 23 nm.   
     
     
         16 . A process of forming a bulk nanocomposite magnet, comprising:
 a. mixing at least one hard phase magnetic material and at least one soft phase magnetic material in a solution with original particle size from at least about 2 nanometers to 100 micrometers;   b. spinning the solution and drying the solution;   c. heating the dried hard and soft phase material under an inert atmosphere at a first temperature for a first period of time to form a second powder; and   d. compacting the second powder under a first pressure at a second temperature for a second period of time to produce a bulk nanocomposite magnet having a bulk dimension.   
     
     
         17 . The process of  claim 16 , where the soft phase material comprises at least one magnetic nanoparticle of FeO, Fe 2 O 3 , Fe 3 O 4 , Co, Fe, Ni, CoFe, NiFe, CoO, NiO and ferrites including MFe 2 O 3  where M comprises one of Co and Ni; and the hard phase material comprises at least one magnetic nanoparticle of FePt, CoPt, SmCo-based alloys, including SmCO 5 , Sm 2 CO 17 , Sm 2 CO 7 , and SmCO 7 , and rare earth-FeB-based alloys, including R 2 Fe 14 B, where R comprises one of Nd and Pr. 
     
     
         18 . The process of  claim 17 , wherein the hard phase material comprises the magnetic nanoparticle FePt with fcc structure and the soft phase material comprises the magnetic nanoparticle Fe 3 O 4 , wherein the compacting step compacts the magnetic nanoparticle FePt from the fcc structure to the Ll 0  structure. 
     
     
         19 . The process of  claim 16 , wherein the mixing step further comprises ball milling the hard and soft phase magnetic nanoparticles under a gas or a liquid in a vibrating vial, wherein the milling time and vibrating strength are adjusted to form a nanocomposite morphology. 
     
     
         20 . The process of  claim 17 , wherein the first pressure comprises at least about 1.0 GPa, the second period of time comprises at least 10 minutes, and the second temperature includes a range of about 20° C. to about 800° C. 
     
     
         21 . The process of  claim 20 , further comprising annealing the bulk nanocomposite magnet under a forming gas for a third period of time and at a third temperature of about 20° C. to about 800° C.