Magnet recycling to create Nd—Fe—B magnets with improved or restored magnetic performance

1. A recycled Nd—Fe—B sintered magnet comprising:

a composition of W a R b A c , where waste material W comprises material from a waste Nd—Fe—B sintered magnet, rare earth containing material R comprises Nd and Pr at a ratio of 75 wt. % Nd to 25 wt. % Pr and 0.1 to 1 at. % of the recycled Nd—Fe—B sintered magnet, and elemental additives A comprising a) Co, b) Cu, and c) Fe;

indices a, b, and c indicate atomic percentages of the corresponding compositions or elements;

a(t) is the atomic percent of element t in the waste material W relative to the composition of the recycled Nd—Fe—B sintered magnet;

b(t) is the atomic percent of element t in the rare earth containing material R relative to the composition of the recycled Nd—Fe—B sintered magnet;

c(t) is the atomic percent of element t in the elemental additives A relative to the composition of the recycled Nd—Fe—B sintered magnet; and

a, b, c, a(t), b(t), and c(t) have values satisfying:

81 at. %≦a≦99.9 at. %,

0.1 at. %≦b+c≦19 at. %,

3 at. %-99.9%*a(Co)≦c(Co)≦3 at.%-81%*a(Co), wherein a(Co)≦3.003003003 at. %,

0.3 at. %-99.9%*a(Cu)≦c(Cu)≦0.3 at. %-81%*a(Cu), wherein a(Cu)≦0.3003003 at. %,

77 at. %-99.9%*(a(Fe)+a(Co))≦c(Fe)≦77 at. %-81%*(a(Fe)+a(Co)), wherein (a(Fe)+a(Co))<77.07707708 at. %,

a(Nd)+b(Nd)+c(Nd)+a(Pr)+b(Pr)+c(Pr)>0 at. %,

a(Nd)+b(Nd)+c(Nd)+a(Pr)+b(Pr)+c(Pr)+a(Dy)+b(Dy)+c(Dy)≦18 at. %,

a(Co)+b(Co)+c(Co)≦3 at. %,

a(Cu)+b(Cu)+c(Cu)≦0.3 at. %,

a(Fe)+b(Fe)+c(Fe)+a(Co)+b(Co)+c(Co)≦77 at. %, and

b(Nd)+c(Nd)+b(Pr)+c(Pr)+b(Dy)+c(Dy)≧0 at. %.

2. The recycled Nd—Fe—B sintered magnet of claim 1 wherein the rare earth containing material R and the elemental additives A are distributed in the grain boundary homogeneously throughout the thickness of the recycled Nd—Fe—B sintered magnet such that a concentration of the rare earth containing material R and a concentration of the elemental additives A increases on average in a mixture of waste material W surrounding the primary Nd 2 Fe 14 B phase within the recycled Nd—Fe—B sintered magnet.

3. The recycled Nd—Fe—B sintered magnet of claim 1 comprising an average particle size less than 5 microns.

4. The recycled Nd—Fe—B sintered magnet of claim 1 comprising an average particle size less than 2.5 microns.

5. The recycled Nd—Fe—B sintered magnet of claim 1 comprising a density between about 7.56 g/cm 3 to about 7.6 g/cm 3 .

6. The recycled Nd—Fe—B sintered magnet of claim 1 comprising a remanence and a coercivity at least the same as the waste Nd—Fe—B sintered magnet.

7. The recycled Nd—Fe—B sintered magnet of claim 6 wherein the coercivity is between about 0 to about 20% greater than the coercivity of the waste Nd—Fe—B sintered magnet.

8. The recycled Nd—Fe—B sintered magnet of claim 1 comprising a remanence about 97% of another remanence of the waste Nd—Fe—B sintered magnet and a coercivity at least 30% greater than another coercivity of the waste Nd—Fe—B sintered magnet.

9. The recycled Nd—Fe—B sintered magnet of claim 1 comprising a remanence about 95% of another remanence of the waste Nd—Fe—B sintered magnet and a coercivity at least 80% greater than another coercivity of the waste Nd—Fe—B sintered magnet.

10. The recycled Nd—Fe—B sintered magnet of claim 1 comprising a remanence about 5% greater than another remanence of the waste Nd—Fe—B sintered magnet and a coercivity is at least the same as another coercivity of the waste Nd—Fe—B sintered magnet.

11. The recycled Nd—Fe—B sintered magnet of claim 1 wherein a combined atomic percentage of Nd, Pr, and Dy in the recycled Nd—Fe—B sintered magnetic is greater than or equal to a combined atomic percentage of Nd, Pr, and Dy in the waste Nd—Fe—B sintered magnet.

12. The recycled Nd—Fe—B sintered magnet of claim 1 comprising 1.98 at. % oxygen or less.

13. The recycled Nd—Fe—B sintered magnet of claim 1 comprising between 1.32 to 1.98 at. % oxygen.

14. The recycled Nd—Fe—B sintered magnet of claim 1 wherein the elemental additives A comprise Dy.

15. The recycled Nd—Fe—B sintered magnet of claim 1 wherein the elemental additives A comprise the rare earth containing material R.

16. A recycled Nd—Fe—B sintered magnet comprising a composition of W a R b A c , where waste material W comprises material from a waste Nd—Fe—B sintered magnet, rare earth containing material R comprises Nd and Pr at a ratio of 75 wt. % Nd to 25 wt. % Pr and 0.1 to 1 at. % of the recycled Nd—Fe—B sintered magnet, and elemental additives A comprises at least one of: a) Nd, b) Pr, c) Dy, d) Co, e) Cu, or f) Fe, and indices a, b, and c indicate atomic percentages of the corresponding compositions or elements and the rare earth containing material R and the elemental additives A have values satisfying:

Nd[0.1-19%*s(Nd), x],

Pr[0.1-19%*s(Pr), y],

Dy[0.1-19%*s(Dy), z],

Co[0 at. %, d],

Cu[0 at. %, e],

Fe[0 at. %, f],

wherein:

[m, n] means a range from a first value in a minimum interval m and a second value in a maximum interval n;

s(t) is the atomic percent of element t in starting composition;

x=18 at. %-[81, 99.9]%*(s(Nd)+s(Pr)+s(Dy)), wherein (s(Nd)+s(Pr)+s(Dy))<18.01801802 at. %;

y=18 at. %-[81, 99.9]%*(s(Nd)+s(Pr)+s(Dy));

z=18 at. %-[81, 99.9]%*(s(Nd)+s(Pr)+s(Dy));

d=3 at. %-[81, 99.9]%*s(Co), wherein s(Co)<3.003003003 at. %;

e=0.3 at. %-[81, 99.9]%*s(Cu), wherein s(Cu)<0.3003003 at. %; and

f=77 at.%-[81, 99.9]%*(s(Fe)+s(Co)), wherein (s(Fe)+s(Co))<77.07707708 at. %.

17. The recycled Nd—Fe—B sintered magnet of claim 16 wherein the rare earth containing material R and the elemental additives A are distributed in the grain boundary homogeneously throughout the thickness of the recycled Nd—Fe—B sintered magnet such that a concentration of the rare earth containing material R and a concentration of the elemental additives A increases on average in a mixture of waste material W surrounding the primary Nd 2 Fe 14 B phase within the recycled Nd—Fe—B sintered magnet.

18. The recycled Nd—Fe—B sintered magnet of claim 16 wherein a first atomic percentage of the waste material W in the recycled Nd—Fe—B sintered magnet is between about 99.9 at. % and about 81 at. % and a second atomic percentage of a combination of the rare earth containing material R and the elemental additives A in the recycled Nd—Fe—B sintered magnet is between about 0.1 at. % and about 19 at. %.

19. The recycled Nd—Fe—B sintered magnet of claim 16 comprising an average particle size less than 5 microns.

20. The recycled Nd—Fe—B sintered magnet of claim 16 comprising an average particle size less than 2.5 microns.

21. The recycled Nd—Fe—B sintered magnet of claim 16 comprising a density between about 7.56 g/cm 3 to about 7.6 g/cm 3 .

22. The recycled Nd—Fe—B sintered magnet of claim 16 comprising an atomic percentage of Co less than or equal to 3 at. %.

23. The recycled Nd—Fe—B sintered magnet of claim 16 comprising an atomic percentage of Cu less than or equal to 0.3 at. %.

24. The recycled Nd—Fe—B sintered magnet of claim 16 comprising a combined atomic percentage of Fe and Co less than or equal to 77 at. %.

25. The recycled Nd—Fe—B sintered magnet of claim 16 comprising a combined atomic percentage of Nd, Dy, and Pr less than or equal to 18 at. %.

26. The recycled Nd—Fe—B sintered magnet of claim 16 wherein the elemental additives A comprise the rare earth containing material R.

27. The recycled Nd—Fe—B sintered magnet of claim 16 wherein the elemental additives A comprise Dy.

28. The recycled Nd—Fe—B sintered magnet of claim 16 comprising 1.98 at. % oxygen or less.

29. The recycled Nd—Fe—B sintered magnet of claim 16 comprising between 1.32 to 1.98 at. % oxygen.