Patent Application
20130038164
The present invention is directed to mechanically strong, sequentially laminated, rare earth, permanent magnets having dielectric layers separated from permanent magnet layers by transition and/or diffusion reaction layers, where the transition and/or diffusion reaction layers impart an unexpected improvement in mechanical strength to the sequentially laminated, rare earth, permanent magnets.
The present invention relates to sequentially laminated, rare earth, permanent magnets for use in high performance, rotating machines featuring dielectric layers reinforcing transition and/or diffusion reaction layers. The high electrical resistivity, rare earth, permanent magnets of the invention, with reinforced dielectric layers; are characterized by reduced eddy current losses combined with improved mechanical strength suitable for use in high performance, rotating machines. Rare earth, permanent magnets of the invention featuring dielectric layer(s) reinforced by transition and/or diffusion reaction layers exhibiting improved electrical resistivity, along with improved mechanical strength. They are particularly well suited for commercial use in high performance, rotating machines, such as motors and generators.
Addressing eddy current losses in permanent magnets is critical in the design of high performance motors and high speed generators. Reduction of these eddy current losses in permanent magnets used with rotating machines is preferably accomplished by increasing the electrical resistivity of the permanent magnets. For example, when rare earth permanent magnets are subjected to variable magnetic flux, and the electrical resistivity is low, excessive heat attributed to an eddy current is generated. This increased heat reduces the magnetic properties of the permanent magnet with corresponding reductions in the efficiency of rotating machines.
Adding layers of high resistivity, dielectric material to laminated, rare earth magnets, perpendicular to the plane of the eddy currents, generally results in a substantial decrease of eddy current losses. However, heretofore adding these layers of high resistivity material to laminated, permanent magnets were generally associated with shortcomings in mechanical strength. Specifically, these composite, laminated, permanent magnets with improved electrical resistivity failed in commercial use in high performance, rotating machines due to shortcomings in mechanical strength. Demands of high performance, rotating machines require improved mechanical strength beyond that traditionally available in laminates with suitable dielectric properties.
Rare earth, permanent magnets with improved electrical resistivity are described in U.S. Patent Publication No. US2006/0292395 A1 and U.S. Pat. Nos. 5,935,722; 7,488,395 B2; 5,300,317; 5,679,473; 5,763,085 and in U.S. Patent Application, “Rare Earth Laminated Composite Magnets with Increased Electrical Resistivity; and Ser. No. 12/707,227 filed Feb. 17, 2010.
U.S. Patent Publication No. 2006/0292395 A1 teaches fabrication of rare earth magnets with high strength and high electrical resistance. The structure includes R—Fe—B-based rare earth magnet particles which are enclosed with a high strength and high electrical resistance composite layer consisting of a glass phase or R oxide particles dispersed in a glass phase, and R oxide particle based mixture layers (R=rare earth elements).
U.S. Pat. No. 5,935,722 teaches the fabrication of laminated composite structures of alternating metal powder layers, and layers formed of an inorganic bonding media consisting of ceramic, glass, and glass-ceramic layers which are sintered together. The ceramic, glass, and glass-ceramic layers serve as an electrical insulation material used to minimized eddy current losses, as well as an agent that bonds the metal powder layers into a dimensionally-stable body.
U.S. Pat. No. 7,488,395 teaches fabrication of a functionally graded rare earth permanent magnets having a reduced eddy current loss. The magnets are based on R—Fe—B (R=rare earth elements) and the method consists in immersing the sintered magnet body into a slurry of powders containing fluorine and at least one element E selected from alkaline earth metal elements and rare earth elements, mixed with ethanol. Subsequent heat treatment of the magnets covered with the respective slurry allows for the absorption and infiltration of fluorine and element E from the surface into the body of the magnet. Thus, the magnet body includes a surface layer having a higher electric resistance than the interior.
U.S. application Ser. No. 12/707,227, teaches laminated, composite, rare earth magnets with improved electrical resistivity.
To date, there is no teaching implied nor suggested in the prior art of the critical elements of the present invention including:
A. “Intermediate” transition and/or diffusion reaction layers, combined with sequentially laminated layers of permanent magnets based on Sm—Co or Nd—Fe—B, where the transition and/or diffusion reaction layers surround and separate a dielectric layer(s) from permanent magnet layers. The sequentially laminated, rare earth, permanent magnets of the present invention comprise Sm—Co or Nd—Fe—B layers separated from dielectric layers by transition and/or diffusion reaction layers. All the layers in the sequentially laminated, rare earth, permanent magnet are consolidated simultaneously with the sequentially laminated, permanent magnet indicating acceptable magnetic properties with improved electrical resistivity and mechanical strength sufficient to support use with high performance, high speed rotating machines.
B. Monolithic, sequentially laminated structures consisting of sequential layers of rare earth based magnets and layers of dielectric materials or dielectric layers comprising mixtures of rare earth rich alloys with dielectric materials separated from the permanent magnet layers by transition and/or diffusion reaction layers. These dielectric layers provide unexpected advantages in electrical resistivity as the laminated, dielectric layers partly interact at the interface, creating a transition and/or diffusion reaction layer separating the dielectric layer from permanent magnet layers. The resultant sequentially laminated, rare earth, permanent magnet exhibits exceptional electrical resistivity combined with no compromise in magnetic properties and improved mechanical strength suitable for use in high speed motors.
There is no teaching in the prior art of “intermediate”, “transition”, and/or “diffusion reaction” layers separating laminated layers of rare earth, permanent magnet materials based on Sm—Co or Nd—Fe—B from layers of dielectric materials including dielectric semiconductor layers,
For purposes of the present invention, dielectric materials suitable for the magnets of the present invention include: Al2S3, Sb2S3, As2S3, BaS, BeS, Bi2S3, B2S3, CdS, CaS, CeS, Ce2S3, WS, Cr2S3, CoS, CoS2, Cu2S, CuS, Dy2S3, Er2S3, EuS, Gd2S3, Ga2S3, GeS, GeS2, HfS2, Ho2S3, In2S, InS, FeS, FeS2, La2S3, LaS2, La2O2S, PbS, Li2S, MgS, MnS, HgS, MoS2, Nd2S3, NiS, NdS, K2S, Pr2S3, Sm2S3, Sc2S3, SiS2, Ag2S, Na2S, SrS, Tb2S, Tl2S, ThS2, Tm2S3, SnS, SnS2, TiS2, WS2, US2, V2S3, Yb2S3, Y2S3, Y2S3, Y2O2S, ZnS and ZrS2 or a combination of any of these materials.
For purposes of the present invention the above referenced, sulfide-based, dielectric materials include the sulfide compounds described above and:
Oxysulfides,
Sulfides and oxyfluorides,
Mixtures of sulfides,
Mixtures of sulfides and fluorides,
Mixtures of sulfides, fluorides, oxysulfides and/or oxyfluorides, and/or
Each of the above mixed with rare earth alloys.
Other dielectric materials suitable as the source for increased electrical resistivity are summarized in Table 1 below.
A primary object of the invention is to produce mechanically strong, high electrical resistivity, Sm—Co and Nd—Fe—B, sequentially laminated, rare earth, permanent magnets with dielectric layers separated from rare earth, permanent magnet layers by transition and/or diffusion reaction layers that contribute to the improved strength of the sequentially laminated, rare earth, permanent magnets of the invention.
Another object of the invention is to produce the first sequentially laminated, Sm—Co and Nd—Fe—B magnets capable of delivering high electrical resistivity without sacrificing mechanical strength or magnetic properties, wherein the permanent magnet layers are separated from dielectric layers by transition and/or diffusion reaction layers.
An object of the present invention is to form sequentially laminated structures with increased electrical resistivity consisting of sequential layers of rare earth, permanent magnet and dielectric layers separated from the permanent magnet layers by transition and/or diffusion reaction layers, where the sequentially laminated magnets are suitable for reducing eddy current losses without sacrificing rare earth, permanent magnet properties and with mechanical strength suitable for use in high performance motors and generators.
Another object of the invention is to form sequentially laminated structures with increased electrical resistivity consisting of sequential layers of rare earth, permanent magnets separated from layers of mixtures dielectric materials and rare earth rich alloys separated from the permanent magnet layers by transition and/or diffusion reaction layers; where the sequential laminate is suitable for reducing eddy current losses when used in high performance motors and generators, while maintaining a mechanically strong laminate structure without sacrificing magnetic properties.
A further object of the invention is to form sequentially laminated structures with increased electrical resistivity consisting of sequential layers of: (1) dielectric layers, (2) transition and/or diffusion reaction, rare earth, rich alloy layers surrounding the dielectric layers, and (3) rare earth, permanent magnet layers, wherein the sequentially laminated, permanent magnets is suitable for reducing eddy current losses when used in high performance motors and generators, while indicating improved mechanical strength over traditional, sequentially laminated, rare earth, permanent magnets.
Still a further object of the invention is to form sequentially laminated structures with increased electrical resistivity consisting of: sequential layers of: dielectric materials; transition and/or diffusion reaction layers and rare earth, permanent magnet layers, where the transition and/or diffusion reaction layers separate the dielectric and permanent magnet layers; where the sequentially laminated, permanent magnet is suitable for reducing eddy current losses when used in high performance motors and generators.
Another object of the invention is to form mechanically strong, sequentially laminated structures with increased electrical resistivity consisting of layers of: dielectric materials surrounded by transition and/or diffusion reaction layers and layers of rare earth, permanent magnet materials sequentially laminated, suitable for reducing eddy current losses when used in high performance motors and generators.
Yet another object of the invention is to form sequentially laminated, rare earth, permanent magnet structures featuring transition and/or diffusion reaction layers separating dielectric layers with increased electrical resistivity from permanent magnet layers, resulting in sequentially laminated, permanent magnets with mechanical strength suitable for use in high performance, rotating machines.
The above and other objects, features and advantages of the present invention will be better understood from the following detailed description of the invention taken in conjunction with accompanying Tables 1 through 3, Examples 1 through 17, and
The following terms are defined as set out below, to insure a clear understanding of the invention and its unexpected increased resistivity and mechanical strength as detailed in the Examples, Drawings and Tables set forth below and in the claims:
“Rare earth permanent magnets” are defined as permanent magnets based on intermetallic compounds with rare earth elements, RE, such as Nd and Sm, transition metals, such as Fe and Co, and, optional, metalloids such as B. Other elements may be added to improve magnetic properties.
“Sequentially laminated structures” are defined as structures containing at least two permanent magnet layers separated from one dielectric layer by at least two transition and/or diffusion reaction layers of the invention.
“Eddy current” is defined as the vortex currents generated in electrically conductive materials when exposed to variable magnetic fields. Eddy currents result in building up heat which adversely affects the magnetic properties of permanent magnets.
“Electrical resistivity” is defined as a measure of the resistance strength by which a material opposes the flow of electric current.
“Dielectric” is defined as a material exhibiting high electrical resistivity exceeding 1MΩ.
“High electrical resistivity layer” is defined as a dielectric laminate layer of material with electrical resistivity greater than that of surrounding transition and/or diffusion reaction layers of the invention, which separate the high electrical resistivity layer from the rare earth, permanent magnet layers.
“Transition layers of the invention” is here defined as layers introduced into a sequentially laminated, permanent magnet where the transition layer properties compensate for alteration of the stoichiometry at the interface between two distinct crystallographic layers having diverse compositions and diverse functions (i.e., a dielectric function and a magnet function).
“Diffusion reaction layers of the invention” are defined as layers in sequentially laminated, permanent magnets that surround dielectric layers which physically separate the permanent magnet layers from dielectric layers.
“Rare earth rich alloy” is defined as an alloy containing one or more rare earth element(s) in an amount exceeding specific phase stoichiometries.
“Green compact” defines a permanent magnet composite which is consolidated by pressing the precursor powders at room temperature, resulting in a density less than that of the bulk (with no porosity) counterpart.
“Elemental diffusion” is defined as the diffusion or migration of atomic species in the transition and/or diffusion reaction layers of the invention, where the diffusion or migration of atomic species is due to thermal activation.
“Diffusion reaction interface layer of the invention” is here defined as that region between the permanent magnet layers and the dielectric layers, where the original stoichiometry is altered due to the diffusion of the atomic species and their eventual reaction.
“Sulfide-based dielectric material” is defined as sulfides, oxysulfides, sulfide and oxyfluoride mixtures, mixtures of sulfides and fluorides and mixtures of sulfides, fluorides, oxysulfides and/or oxyfluorides and where each of the above can be mixed with rare earth alloys.
“Sequentially laminated permanent magnets with dielectric layers” are defined as monolithic, sequentially laminated structures consisting of sequential layers of: rare earth-based magnets, transition and/or diffusion reaction layers of the invention surrounding dielectric layers.
“Mechanically strong, sequentially laminated, rare earth, permanent magnets with enhanced electrical resistivity” are defined as magnets of the invention which exhibit mechanical strength:
An accepted approach to minimizing eddy current losses that plague rare earth permanent magnets used in high performance, electric motors or other rotating machines is to machine rare earth permanent magnets into segments which are subsequently assembled into the desired configuration or to alternatively blend the magnet powder precursor with an electrical insulating material.
The present invention provides for improved rare earth, permanent magnets with minimum eddy current losses; comprising forming monolithic laminated structures consisting of sequential (1) layers of rare earth magnets, (2) layers of dielectrics and/or layers of mixtures of rare earth rich alloys and dielectric materials, separated by (3) transition and/or diffusion reaction layers of the present invention.
This sequential laminating process of the invention results in transition and/or diffusion reaction layers of the invention separating the dielectric layer from rare earth, permanent magnet layers as shown in
The function of the transition and/or diffusion reaction layers of the present invention is to compensate for an interaction that occurs between the dielectric layer material and the rare earth magnet layer. This interaction modifies the stoichiometry at the rare earth, permanent magnet/dielectric interface. The resulting transition and/or diffusion reaction layer of the present invention accommodates variances in diffusion reactions between the dielectric layer and the various permanent magnet layers or permanent magnet alloy layers comprising the rare earth, permanent magnet layers.
It is suggested that the transition and/or diffusion reaction layer of the present invention surrounding the dielectric layer plays a key role in the improved mechanical strength of the sequentially laminated, permanent magnets of the invention.
The laminated, permanent magnets of the present invention comprise sequential layers whose compositions interact at the interface with the dielectric layer. Laminated, permanent magnets of the invention, as detailed in Examples 1 through 8 and Table 2 and further illustrated in
In a preferred embodiment of the invention, substances for the dielectric layer are selected from the group consisting sulfide-based, dielectric/semiconductor materials, wherein sulfides refers to the group consisting of: Al2S3, Sb2S3, As2S3, BaS, BeS, Bi2S3, B2S3, CdS, CaS, CeS, Ce2S3, WS, Cr2S3, CoS, CoS2, Cu2S, CuS, Dy2S3, Er2S3, EuS, Gd2S3, Ga2S3, GeS, GeS2, HfS2, Ho2S3, In2S, InS, FeS, FeS2, La2S3, LaS2, La2O2S, PbS, Li2S, MgS, MnS, HgS, MoS2, Nd2S3, NiS, NdS, K2S, Pr2S3, Sm2S3, Sc2S3, SiS2, Ag2S, Na2S, SrS, Tb2S, Tl2S, ThS2, Tm2S3, SnS, SnS2, TiS2, WS2, US2, V2S3, Yb2S3, Y2S3, Y2S3, Y2O2S, ZnS, ZrS2 and combinations thereof, as well as combinations of any of these materials with: sulfides, oxysulfides, fluorides and oxyfluorides, mixtures of: sulfides; sulfides and fluorides; sulfides, fluorides, oxysulfides and oxyfluorides. In addition, mixtures of all of the above with rare earth alloys can be used as the dielectric layer.
In Table 1 below, physical properties are presented as examples for dielectric materials suitable for sequentially laminated, rare earth, permanent magnets where transition and/or diffusion reaction layers of the invention surround dielectric layers.
The preferred rare earth permanent magnet materials of the present invention include Sm—Co and Nd—Fe—B based intermetallic compounds, which are described in Examples 1 through 8, Table 2 and
The distinctive, magnetic properties of the present invention are based on the morphology of sequentially laminated, permanent magnet layers with dielectric layers where the dielectric layer is accompanied by transition and/or diffusion reaction layers of the invention separating dielectric layer(s) from rare earth, permanent magnet layers as shown in
In the sequentially laminated magnets of the present invention, the composition of the rare earth permanent magnet material, particularly the amount of the rare earth component in the laminate, is increased at the interface with the dielectric layer, i.e., at the transition and/or diffusion reaction layers of the present invention. This can be achieved by capitalizing on different morphologies: (a) by replacing pure dielectric substances with mixtures of dielectric substances with rare earth rich alloys, or (b) by using rare earth, rich alloy, transition and/or diffusion reaction layers of the invention between dielectric layers and magnet layers. This elemental diffusion feature of the magnets of the present invention is achieved during thermal processing of the laminate rare earth magnets of the invention, resulting in the transition and/or diffusion reaction layers of the invention forming at the interface between the Sm-rich magnet layer and the dielectric layer. This is shown, for example, in
The thickness of the dielectric layer in the sequentially laminated magnet is preferably adjusted between an upper limit determined by bonding strength and a lower limit controlled by continuity of the dielectric layer. In a preferred embodiment of the invention, the thickness of the dielectric layer is normally less than 500 μm. More preferably, the dielectric layer is less than 100 μm thick. The number of dielectric layers in the laminate magnets will be determined by the application of the sequentially laminated, permanent magnet. For example, in cases of high speed machines, more dielectric layers are preferred. The thickness of the rare earth, permanent magnet layers are also determined by the application, and are usually not less than 500 μm.
Consolidation methods of the present invention required to achieve full density of the sequentially laminated, permanent magnet include: sintering, hot pressing, die upsetting, spark plasma sintering, microwave sintering, infrared sintering, combustion driven compaction and combinations thereof. These are referenced in Examples 1 through 8 and in Examples 9 through 17 set forth in Table 3.
Delamination of the magnets of the present invention can be controlled by the thickness of the dielectric layer and the mechanical strength of the sequentially laminated, permanent magnet. The improved mechanical strength of the rare earth, permanent magnets of the invention is determined, in part, by the bonding strength between the transition and/or diffusion reaction layers of the invention and the permanent magnet layers. Breakage of the laminated structures during processing is controlled in the present invention by introducing different morphologies into the green compact, for example, into: (1) partial layers near one of the magnetic poles of the magnet, and (2) partial layers in the center of the magnet.
Thus, one embodiment of the invention is a laminated, rare earth, permanent magnet, having improved electrical resistivity, comprising sequential layers of: (1) rare earth, permanent magnets and (2) dielectrics layers where each dielectric layer is surrounded by transition and/or diffusion reaction layers of the present invention that interface with permanent magnet layers.
Another embodiment of the invention is a laminated, rare earth, permanent magnet having improved electrical resistivity, comprising sequential layers of rare earth permanent magnet and dielectric layers surrounded by transition and/or diffusion reaction layers of the present invention, wherein said rare earth, permanent magnet layers are selected from the group of intermetallic compounds consisting of:
RE(Co,Fe,Cu,Zr)z,
RE-TM-B,
RE2TM14B,
RE-Co
RE2Co17,
RECo5 and
combinations thereof;
wherein z=6 to 9; RE is selected from the group consisting of rare earth elements including yttrium and mixtures thereof, and TM is selected from a group of transition metals consisting but not limited to Fe, Co and other transition metal elements, and said laminated, rare earth, permanent magnet structure includes sequential layers dielectric surrounded by selected diffusion reaction interface layers, transition layers of the present invention and combinations thereof.
Yet another embodiment of the invention is a laminated, rare earth, permanent magnet, having improved electrical resistivity and improved mechanical strength without compromising magnetic properties comprising sequential layers of rare earth, permanent magnet and dielectric layers surrounded by transition and/or diffusion reaction layers of the present invention and combinations thereof; wherein said dielectric material comprising dielectric material selected from the dielectric materials set out in Table 1 or sulfide-based, dielectric materials selected from the group consisting of:
S or S/F-based dielectric/semiconductor materials, wherein sulfides refer to: Al2S3, Sb2S3, AS2S3, BaS, BeS, Bi2S3, B2S3, CdS, CaS, CeS, Ce2S3, WS, Cr2S3, CoS, CoS2, Cu2S, CuS, Dy2S3, Er2S3, EuS, Gd2S3, Ga2S3, GeS, GeS2, HfS2, Ho2S3, In2S, InS, FeS, FeS2, La2S3, LaS2, La2O2S, PbS, Li2S, MgS, MnS, HgS, MoS2, Nd2S3, NiS, NdS, K2S, Pr2S3, Sm2S3, Sc2S3, SiS2, Ag2S, Na2S, SrS, Tb2S, Tl2S, ThS2, Tm2S3, SnS, SnS2, TiS2, WS2, US2, V2S3, Yb2S3, Y2S3, Y2S3, Y2O2S, ZnS, ZrS2 and combinations thereof or a combination of any of the foregoing with sulfides, oxysulfides, mixtures of sulfides, mixtures of sulfides with oxyfluorides, mixtures of sulfides and fluorides, mixtures of sulfides, fluorides, oxysulfides and/or mixtures oxyfluorides, and/or combinations of the above with rare earth alloys.
In another embodiment of the invention, a sequentially laminated, rare earth, permanent magnet, as described herein, the thickness of said sulfide-based dielectric layer is less than about 2 mm and more preferably less than 500 μm.
Yet another embodiment of the invention calls for a sequentially laminated, rare earth, permanent magnet as described herein, wherein said rare earth permanent magnet material layer is represented by the chemical formula:
RE11.7+xTM88.3−x−yBy
where x=0 to 5, y=5 to 7; RE is selected from the group consisting of rare earth elements including Nd, Pr, Dy and Tb; and TM is selected from the group consisting of transition metal elements including Fe, Co, Cu, Ga and Al.
Another embodiment of the invention calls for a sequentially laminated, rare earth magnet as described herein, wherein said transition layer of the invention consists of rare earth rich alloys represented by the formula:
RE11.7+xTM88.3−x−yBy
where x is from 5 to 80, y is from 0 to 6; RE is selected from the group consisting of rare earth elements including Nd, Pr, Dy and Tb; and TM is selected from the group consisting of transition metal elements including Fe, Co, Cu, Ga and Al.
Yet another embodiment of the invention calls for a sequentially laminated, rare earth, permanent magnet, as described herein, wherein said rare earth, permanent magnet material is represented by the formula:
RE(CouFevCuwZrh)z
wherein u is from about 0.5 to 0.8, v is from about 0.1 to 0.35, w is from about 0.01 to 0.2, h is from about 0.01 to 0.05, and z is from about 6 to 9; and wherein RE is selected from the group consisting of Sm, Gd, Er, Tb, Pr, Dy and combinations thereof.
Another embodiment of the invention calls for a sequentially laminated, rare earth, permanent magnet, as described herein, wherein said rare earth magnet material is represented by the formula:
RECox
where x is from 4 to 6 and RE represents rare earth elements including Sm, Gd, Er, Tb, Pr, and Dy and mixtures thereof, while other metallic or non-metallic elements are optional and should not exceed 10 atomic %.
Yet another embodiment of the invention calls for a sequentially laminated, rare earth permanent magnet as described herein, wherein said transition layer of the invention is a rare earth rich alloy having the formula:
RE(CouFevCuwZrh)z
wherein u=0 to 0.8, v=0 to 0.35, w=0 to 0.20, h=0 to 0.05, z=1 to 7; and RE is selected from the group consisting of rare earth elements and mixtures thereof.
Another embodiment of the invention calls for a sequentially laminated, rare earth, permanent magnet as described herein, wherein said transition layer of the present invention is a rare earth rich alloy having the formula:
RECox
where x is from 1 to 4 and RE is selected from the group consisting of rare earth elements and mixtures thereof.
Yet another embodiment of the invention calls for a sequentially laminated, rare earth, permanent magnet as described herein, wherein said dielectric material is selected from the group of dielectrics consisting of those detailed in Table 1 and:
RE11.7+xTM88.3−x−yBy
where x=5 to 80, y=0 to 6: RE is selected from the group consisting of rare earth elements selected from the group consisting of Nd, Pr, Dy, and Tb; and TM is selected from the group consisting of transition metal elements Fe, Co, Cu, Ga, and Al.
Another embodiment of the invention calls for a sequentially laminated, rare earth, permanent magnet as described herein, wherein said dielectric layer contains at least 30 weight % of a dielectric material with the balance comprising a rare earth rich alloy having the formula:
RE(CouFevCuwZrh)z
wherein u=0 to 0.8, v=0 to 0.35, w=0 to 0.20, h=0 to 0.05, z=1 to 7; and RE is selected from the group consisting of rare earth elements consisting of Nd, Pr, Dy, and Tb.
Yet another embodiment of the invention calls for a sequentially laminated, rare earth, permanent magnet as described herein, wherein the dielectric layer comprises at least 30 weight % of a dielectric material with the balance comprising a rare earth rich alloy having the formula:
RECox
wherein x=1 to 4 and RE represents a rare earth element.
Another embodiment of the invention is directed to improvements in high performance, electric motors and generators having improved mechanical strength and electrical resistivity with no compromise in magnetic properties using rare earth magnets with transition and/or diffusion reaction layers of the invention with reduced eddy current losses comprising sequentially laminated, rare earth, permanent magnet layers and dielectric layers surrounded by transition and/or diffusion reaction layers of the invention.
Yet another embodiment of the invention is directed to improvements in high-performance, rotating machines by reducing eddy current losses with improved mechanical strength with no compromise in magnetic properties through the use of sequentially laminated, rare earth, permanent magnet layers, separated from dielectric layers by transition and/or diffusion reaction layers of the invention.
Another embodiment of the invention is a sequentially laminated, rare earth, permanent magnet as described herein, wherein the diffusion reaction layers of the invention are arranged as shown in
Yet another embodiment of the invention is a sequentially laminated, rare earth, permanent magnet as described herein, wherein said laminated layers are arranged as shown in
Another embodiment of the present invention calls for a sequentially laminated, rare earth, permanent magnet, as described herein, wherein said laminated layers are arranged as shown in
Yet another embodiment of the invention is a sequentially laminated, rare earth, permanent magnet, as described herein, wherein said laminated layers are arranged as shown in
The sequentially laminated, rare earth, permanent magnets of the invention with high electrical resistivity and improved mechanical strength with no compromise in magnetic properties can be produced according to one of the method of manufacture for the present invention by pressing sequential layers as illustrated in
The permanent magnet powder may be prepared by coarsely pulverizing the precursor ingots produced by melting and casting the starting material and pulverizing in a jet mill, ball mill, etc., to particles having an average particle size from 1 μm to 10 μm, preferably from 3 gm to 6 μm.
In one process for producing the sequentially laminated magnets of the present invention, submicron sized sulfide and fluoride particles used in the dielectric layers surrounded by transition and/or diffusion reaction layers of the invention are prepared using either top down or bottom up manufacturing. For example, top down approaches include: mechanical milling, ball milling, mechanical alloying, low energy ball milling and high energy ball milling, and combinations thereof. In contrast, bottom up approaches include various chemical approaches followed by annealing.
In the various processes used to manufacture magnets with transition and/or diffusion reaction layers of the present invention surrounding the dielectric laminate layers can be prepared by various methods, including:
1. Homogeneous gas phase reactions with volatile sulfur precursors
2. Gas—Solid reactions
3. Reactions with elemental sulfur
4. Solution Processes
5. Solvated Elemental Sulfur
6. Homogeneous Precipitation
7. Flux driven reactions
8. Reduction Process
9. Thermal decomposition of Dithiolato Complexes
10. Non-Aqueous Solvent Routes using metal alkyls and Sulfur precursors
11. Ceramic Method (High Temperature Solid State Synthesis)
12. Sulfidized Sol-Gel derived Precursors
Dielectric fluoride particles suitable for use in combination with sulfide-based dielectrics, of the present invention, can be prepared using the following methods:
Gas solid reactions
Solution processes
Co-precipitation processes
Ball milling processes
Particle sizes of referenced sulfide-based dielectric particles can be further reduced by a variety of milling techniques and ultrasonic processes.
In the processes used to manufacture the sequentially laminated magnets of the present invention, colloidal or submicron sized dielectric particles are mixed with polar or non-polar solvents at different concentrations based on the density of the dielectric material and the volume required to produce a particular dielectric layer thickness on the green compact pressed magnetic materials layer. The dielectric materials are introduced onto the surface of the pressed green, compact, thick magnetic layers using a semi-automatic, flow rate controlled, sprayer which controls the flow rate of the colloidal dielectric particles and as well as the as the area to be sprayed based on the different sizes of the nozzle used during spraying. Thickness of the dielectric layer is controlled by the concentration of the dielectric material in the solvent used during the spray process. The sprayed dielectric layers thickness on the pressed green magnets varies from about 1 μm to 1000 μm and preferably from about 1 μm to 500 μm and particularly preferred from from about 10 μm to 400 μm. Transition and/or diffusion reaction layers of the invention surround the dielectric layers. Subsequently Sm(Co,Fe, Cu,Zr)z magnetic particles are sprayed onto the coated magnet in thick layers which are pressed to make a green compact magnetic layer. Second and third dielectric layers with comparable or different thicknesses, each surrounded with transition and/or diffusion reaction layers can be added following the above procedure. The number of sulfide-based dielectric layers is determined by specific applications of the sequentially laminated, permanent magnet of the invention.
The green, compact, laminated magnets of the invention are formed by pressing the laminates under a pressure of from 500 to 3000 kgf/cm2 in a magnetic field of from 1 to 40 kOe. The green, compact, sequentially laminated, permanent magnet is then consolidated by sintering at from 1000° C. to 1250° C. for from 1 to 4 hours in vacuum or in an inert gas atmosphere such as an Ar atmosphere. The sintered product may be further homogenized and heat-treated to develop optimum magnetic properties.
In the present invention, the laminated, high electrical resistivity, rare earth, permanent magnets consist of sequential layers having different chemical compositions, each of which has a different function; namely:
(a) rare earth, permanent magnet layers,
(b) dielectric layers surrounded by
(c) transition and/or diffusion reaction layers of the invention.
Rare earth permanent magnet layers are preferably comprised of rare earth permanent magnets, including RE-Fe—B and RE-Co-based permanent magnets, wherein RE is at least one rare earth element including Y (yttrium). Other rare earth, permanent magnet compositions suitable for use in the present invention are discussed below.
In a preferred embodiment, the rare earth magnet layer is represented by RE-Fe(M)-B comprised of 10-40 weight % of RE and 0.5-5 weight % of B (boron) with the balance of Fe(M) comprising Nd, Pr, Dy and Tb, with Nd particularly preferred. Further, it is preferred to use Dy up to 50 weight %, preferably up to 30 weight % of the total amount of RE. In an effort to improve the coercive force, M represents other optional metallic elements, such as Nb, Al, Ga and Cu. The addition of Co improves the permanent magnet, corrosion resistance and thermal stability. Co may be added up to 25 weight % based on the total amount of the RE-Fe—B-based magnet, as a replacement for Fe. An additional amount exceeding 25 weight % of Co unfavorably reduces the residual magnetic flux density, as well as the intrinsic coercive force. Nb is effective for preventing the overgrowth of crystals during processing while enhancing thermal stability. Since an excess amount of Nb reduces the residual magnetic flux density, Nb is preferably limited to up to 5 weight % based on the total amount of the RE-Fe—B-based magnet.
As stated above, the rare earth magnet layer can also include RE2Cor-based magnets with 10-35 weight % of RE, 30 weight % or less of Fe, 1-10 weight % of Cu, 0.1-5 weight % of Zr, an optional small amount of other metallic elements such as Ti and Hf, with the balance comprising Co. The RE-Co-based, rare earth, permanent magnet is preferred based on its cellular microstructure consisting of cells with 2:17 rhombohedral type crystallographic structure and cell boundaries with 1:5 hexagonal crystallographic structure. In this magnet, the rare earth element is preferably Sm, along with optional other rare earth elements such as Ce, Er, Tb, Dy, Pr and Gd. When the amount of RE is lower than 10 weight %, the coercive force is low, and the residual magnetic flux density is reduced when RE exceeds 39 weight %. Although a high residual induction, Br, can be achieved by the addition of Fe, a sufficient coercive force can not be obtained when the amount exceeds 30 weight %. It is preferable to add Fe at least 5 weight % in order to improve Br. Copper, Cu, contributes to improving the coercive force. The addition of less than 1 weight % Cu shows improvement, while the residual magnetic flux density and coercive force are each reduced when the addition of Cu exceeds about 10 weight %.
The rare earth, permanent magnet, laminate layer can also comprise RECo5-based magnet with 25-45 weight % of RE, and the balance Co. RE is preferably Sm along with other rare earth elements.
Other metallic or non-metallic elements can be present in Nd—Fe—B and Sm—Co based sequentially laminated magnets of the present invention at preferably less than 10 weight %. It is understood that the RE-Fe—B-based magnets and RE-Co-based magnets used in the sequentially laminated magnets of the present invention may include inevitable impurities such as C, N, O, Al, Si, Mn, Cr and combinations thereof.
The dielectric layer consists of dielectric materials described in Table 1, as well as substances selected from the group consisting of sulfide-based dielectric/semiconductor materials; where the sulfide-base includes: Al2S3, Sb2S3, As2S3, BaS, BeS, Bi2S3, B2S3, CdS, CaS, CeS, Ce2S3, WS, Cr2S3, CoS, CoS2, Cu2S, CuS, Dy2S3, Er2S3, EuS, Gd2S3, Ga2S3, GeS, GeS2, HfS2, Ho2S3, In2S, InS, FeS, FeS2, La2S3, LaS2, La2O2S, PbS, Li2S, MgS, MnS, HgS, MoS2, Nd2S3, NiS, NdS, K2S, Pr2S3, Sm2S3, Sc2S3, SiS2, Ag2S, Na2S, SrS, Tb2S, Tl2S, ThS2, Tm2S3, SnS, SnS2, TiS2, WS2, US2, V2S3, Yb2S3, Y2S3, Y2S3, Y2O2S, ZnS and ZrS2 or combinations of any of these materials with sulfides, oxysulfides, sulfides and oxysulfides, mixtures of: sulfides, sulfides and fluorides, and mixtures of sulfides, fluorides, oxy sulfides and/or oxyfluorides, oxysulfides, fluorides, oxyfluorides, mixtures of sulfides and fluorides.
The high electrical resistivity, dielectric layers surrounded by transition and/or diffusion reaction layers of the present invention include mixtures with rare earth elements RE; wherein RE is selected from the group consisting of rare earth elements and mixtures thereof, and rare earth rich alloys. These rare earth rich alloys are different for different types of laminate layers. The following are some examples of the rare earth rich alloys suitable for inclusion in the dielectric layer:
The transition and/or diffusion reaction layers of the present invention are added or produced during the manufacturing process for the magnets of the invention to compensate for the reactions that takes place between the materials in the dielectric layers and the rare earth, permanent magnet layers. These transition and/or diffusion reaction layers of the present invention vary in composition depending on the types of magnet layers and dielectric layers present. The following are examples of rare earth, rich alloys suitable for transition and/or diffusion reaction layers of the present invention:
The unexpected enhanced electrical resistivity and improved mechanical strength properties combined with excellent magnetic properties of the sequentially laminated, rare earth, permanent magnets featuring transition and/or diffusion reaction layers of the present invention are further described in Examples 1 through 17, Tables 1 through 3 and
An anisotropic Sm(Co,Fe, Cu,Zr)z/Sm2S3 sequentially laminated magnet with increased electrical resistivity was synthesized by regular powder metallurgic processes consisting of sintering at from 1200° C. to 1220° C., solution treatment at from 1160° C. to 1180° C. and aging at from 830° C. to 890° C. This step was followed by a slow cooling to 400° C. The sequentially laminated, anisotropic magnet consisting of three sequential Sm(Co,Fe, Cu,Zr)z layers and three sequential Sm2S3 layers surrounded by diffusion reaction layers of the present invention, shown in
The photograph set out in
Residual induction: Br=10.516 kG
Intrinsic coercivity: Hci>24.5 kOe
Maximum energy product: (BH)max=25.5 MGOe
The electrical resistivity of this sequentially laminated, rare earth, permanent magnet of the invention was unexpectedly increased by approximately 32 times (about 3000%) compared to a standard permanent magnet. Improved mechanical strength was also observed and was attributed, at least in part, to the interface diffusion reaction layers of the present invention.
Residual induction: Br=10.73 kG
Intrinsic coercivity: Hci>24.5 kOe
Maximum energy product: (BH)max=25.5 MGOe
The electrical resistivity of this sequentially laminated, permanent magnet of the invention was unexpectedly increased by approximately 35 times (about 3000%) compared to a standard permanent magnet. The improved mechanical strength observed was attributed, at least in part, to the interface diffusion reaction layer of the present invention.
An anisotropic Sm(Co,Fe, Cu,Zr)z/Sm2S3 sequentially laminated, permanent magnet of the invention with increased electrical resistivity was produced according to a method of manufacturing of the invention; using regular powder metallurgical processes consisting of: sintering at 1195° C., solution treatment at 1180° C. and aging at 850° C. followed by a slow cooling to 400° C.
This anisotropic, sequentially laminated, permanent magnet consisting of sequential Sm(Co,Fe, Cu,Zr)z and Sm2S3 dielectric layers surrounded by diffusion reaction layers of the present invention was produced by a one-step sintering process. As shown in optical micrograph (unetched)
Compared to a conventional magnet matrix, the electrical resistivity of the sequentially laminated magnet of the invention as shown in
An anisotropic Sm(Co,Fe, Cu,Zr)z/Sm2S3 sequentially laminated, permanent magnet with increased electrical resistivity was produced by a method of manufacture which used a powder metallurgical process consisting of: (a) sintering at 1195° C., (b) solution treatment at 1180° C., (c) aging at 850° C., followed by (d) a slow cooling 400° C.
Sequentially laminated, anisotropic magnets consisting of sequential Sm(Co,Fe, Cu,Zr)z and Sm2S3 layers surrounded by diffusion reaction layers of the present invention were produced by a one-step sintering process. As shown in the optical micrograph set out in
The electrical resistivity of the sequentially laminated magnet of the present invention was unexpectedly increased approximately 12 times over the magnet matrix, i.e., by about 1190%. Improved mechanical strength observed was attributed, at least in part, to the diffusion reaction layer separating the dielectric layer from the permanent magnet layer.
An anisotropic Sm(Co,Fe, Cu,Zr)z/Sm2S3 sequentially laminated, rare earth, permanent magnet with increased electrical resistivity and improved mechanical strength was developed by powder metallurgical processes consisting of: (a) sintering at 1195° C., (b) solution treatment at 1180° C., (c) aging at 850° C., followed by (d) a slow cooling 400° C. Sequentially laminated, anisotropic magnets consisting of sequential Sm(Co,Fe, Cu,Zr)z and Sm2S3 layers surrounded by diffusion reaction layers of the present invention were produced by a one-step sintering process.
As shown in the optical micrograph set out in
The electrical resistivity of the magnet shown in
An anisotropic Sm(Co,Fe, Cu,Zr)z/(Sm2S3+CaF2) sequentially laminated, rare earth, permanent magnet with increased electrical resistivity and improved mechanical strength was produced by a powder metallurgical processes consisting of: (a) sintering at 1195° C., (b) solution treatment at 1180° C., (c) aging at 850° C., followed by (d) a slow cooling 400° C. A sequentially laminated, anisotropic magnet consisting of sequential Sm(Co,Fe, Cu,Zr)z magnetic layers and (Sm2S3+CaF2) dielectric layers surrounded by diffusion reaction layers of the present invention were produced by a one-step sintering process. As shown in
The electrical resistivity of this magnet shown in
An anisotropic Sm(Co,Fe, Cu,Zr)z/MnS sequentially laminated, rare earth, permanent magnet with increased electrical resistivity and improved mechanical strength was developed by a powder metallurgical processes consisting of: (a) sintering at 1195° C., (b) solution treatment at 1180° C., (c) aging at 850° C., followed by (d) a slow cooling to 400° C. Sequentially laminated, anisotropic magnets consisting of sequential Sm(Co,Fe, Cu,Zr)z and MnS layers surrounded by diffusion reaction layers of the present invention were produced by a one-step sintering process.
As shown in the optical micrograph in
The electrical resistivity of the magnet shown in
Magnetic Properties and Electrical Resistivity Properties of sequentially laminated, permanent magnets, as described in Examples 1 through 8; are summarized in Table 2 below:
The present invention is further described by illustrative Examples 9 through 17 set out in Table 3, which provides additional examples of typical morphologies of the sequentially laminated, rare earth, permanent magnets having sequential: permanent magnet layers and dielectric layers surrounded by transition and/or diffusion reaction layers of the present invention. The projected increase of the electrical resistivity of such sequentially laminated magnets of the invention which is substantially greater than the electrical resistivity of conventional magnets is achieved without loss in mechanical strength or in magnetic properties. Manufacturing methods of the present invention for the sequentially laminated, rare earth magnets are detailed in Table 3 include: sintering, hot pressing, die upsetting, spark plasma sintering, microwave sintering, infrared sintering and combustion driven compaction. In Table 3, x=1 to 6, unless otherwise specified.
The following conditions apply to each of Illustrative Examples 8 through 17 in Table 3 as indicated therein by the appropriate symbol (#, +, and *) wherein:
