The present disclosure relates generally to a method for improving the performance of sintered NdFeB magnet. A method of preparing a sintered NdFeB magnet therefore comprises the steps of: a) preparing alloy flakes from a raw material of the NdFeB magnet by a strip casting process; and b) preparing a coarse alloy powder from the alloy flakes by a hydrogen decrepitation process, the hydrogen decrepitation process including treatment of the alloy flakes under a hydrogen pressure of 0.10 MPa to 0.25 MPa for a duration of 1 to 3.5 hours, then degassing the hydrogen at a predetermined temperature between 300° C. to 400° C. for a duration time of 0.5 to 5 hours, and then mixing the resulting coarse alloy powder with a lubricant.

An R-T-B-based sintered magnet and a preparation method therefor. The R-T-B-based sintered magnet comprises: R, B, Ti, Ga, Al, Cu, and T. The contents thereof are as follows: R is 29.0-33%; the content of B is 0.86-0.93%; the content of Ti is 0.05-0.25%; the content of Ga is 0.3-0.5%, but not 0.5%; the content of Al is 0.6-1%, but not 0.6%; the content of Cu is 0.36-0.55%. The percentage is the mass percentage. Under the condition that no heavy rare earth is added or a small amount of heavy rare earth is added, by using a low B technology, not only the remanence performance of the R-T-B-based sintered magnet is improved, but also the coercivity and the squareness of the magnet are ensured.

A neodymium-iron-boron permanent magnet, a preparation method and use thereof are disclosed. The neodymium-iron-boron permanent magnet has a composition represented by formula I: [mHR(1−m) (Pr.sub.25Nd.sub.75)].sub.x(Fe.sub.100-a-b-c-dM.sub.aGa.sub.bIn.sub.cSn.sub.d).sub.100-x-yB.sub.y formula I; where a is 0.995-3.493, b is 0.114-0.375, c is 0.028-0.125, d is 0.022-0.100; x is 29.05-30.94, y is 0.866-1.000; m is 0.02-0.05; HR is Dy and/or Tb; M is at least one selected from the group consisting of Co, Cu, Ti, Al, Nb, Zr, Ni, W and Mo.

A waste magnet regeneration method includes the following steps. First, waste magnets and auxiliary alloys are provided, pre-treat the waste magnets, hydrogen decrepitating and sieving the waste magnets and the auxiliary alloys to form main alloy powders and auxiliary alloy powders. The main alloy powders and the auxiliary alloy powders are mixed in a predetermined ratio to form a mixture, and then the mixture is subjected to the jet mill pulverization, magnetic field alignment compacting, sintering and aging treatment to obtain a regenerated magnet.

A zirconium nitride powder having a volume resistivity of 107 Ω.Math.cm or more in the state of the pressurized powder body hardened at a pressure of 5 MPa, and a particle size distribution D90 of 10 μm or less when ultrasonically dispersed for 5 minutes in a state of being diluted with water or an alcohol having a carbon number of which is in a range of 2 to 5. Also, the zirconium nitride powder is dispersed in an acrylic monomer or an epoxy monomer to prepare a monomer dispersion. Further, the zirconium nitride powder is dispersed in a dispersing medium as a black pigment and further a resin is mixed to prepare a black composition.

Provided is an R—Fe—B-based sintered magnet which has a composition comprising R (wherein R represents at least one element selected from rare earth elements, and essentially contains Nd), B, M (wherein M represents at least one element selected from Si, Al, Mn, Ni, Co, Cu, Zn, Ga, Ge, Pd, Ag, Cd, In, Sn, Sb, Pt, Au, Hg, Pb and Bi), X (wherein X represents at least one element selected from Ti, Zr, Hf, Nb, V and Ta) and C, with a remainder comprising Fe, O and unavoidable impurities, and has a main phase comprising R.sub.2Fe.sub.14B and a grain boundary phase comprising an R—C phase having a higher R concentration and a higher C concentration than those in the main phase, the R—Fe—B-based sintered magnet being characterized in that the area ratio of the R—C phase in a cross section of the magnet is more than 0% and 0.5% or less.

Provided is an R—Fe—B-based sintered magnet which has a composition comprising R (wherein R represents at least one element selected from rare earth elements, and essentially contains Nd), B, M (wherein M represents at least one element selected from Si, Al, Mn, Ni, Co, Cu, Zn, Ga, Ge, Pd, Ag, Cd, In, Sn, Sb, Pt, Au, Hg, Pb and Bi), X (wherein X represents at least one element selected from Ti, Zr, Hf, Nb, V and Ta) and C, with a remainder comprising Fe, O and unavoidable impurities, and has a main phase comprising R.sub.2Fe.sub.14B and a grain boundary phase comprising an R—C phase having a higher R concentration and a higher C concentration than those in the main phase, the R—Fe—B-based sintered magnet being characterized in that the area ratio of the R—C phase in a cross section of the magnet is more than 0% and 0.5% or less.

The purpose of the present invention is to achieve both high residual flux density and high coercivity, which are conventionally mutually exclusive characteristics, in an R—Fe—B sintered magnet. The present invention provides an R—Fe—B sintered magnet characterized by having a composition which contains R (R is one or more elements selected from among the rare-earth elements but must be Nd), B. X (X is one or more elements selected from among Ti, Zr, Hf, Nb, V, and Ta), and C, with the remainder comprising Fe, O, other arbitrary elements, and unavoidable impurities. The R—Fe—B sintered magnet is also characterized by satisfying relational expression (1), where [B], [C], [X], and [O] are the atomic percentages of B, C, X, and O, respectively.

0.86×([B]+[C]−2×[X])−4.9<[O]<0.86×([B]+[C]−2×[X])−4.6   (1).

The purpose of the present invention is to achieve both high residual flux density and high coercivity, which are conventionally mutually exclusive characteristics, in an R—Fe—B sintered magnet. The present invention provides an R—Fe—B sintered magnet characterized by having a composition which contains R (R is one or more elements selected from among the rare-earth elements but must be Nd), B. X (X is one or more elements selected from among Ti, Zr, Hf, Nb, V, and Ta), and C, with the remainder comprising Fe, O, other arbitrary elements, and unavoidable impurities. The R—Fe—B sintered magnet is also characterized by satisfying relational expression (1), where [B], [C], [X], and [O] are the atomic percentages of B, C, X, and O, respectively.

0.86×([B]+[C]−2×[X])−4.9<[O]<0.86×([B]+[C]−2×[X])−4.6   (1).

A neodymium-iron-boron permanent magnet, a preparation method and use thereof are disclosed. The neodymium-iron-boron permanent magnet has a composition represented by formula I: [mHR(1-m) (Pr.sub.25Nd.sub.75)].sub.x(Fe.sub.100-a-b-c-dM.sub.aGa.sub.bIn.sub.cSn.sub.d).sub.100-x-yB.sub.y formula I; where a is 0.995-3.493, b is 0.114-0.375, c is 0.028-0.125, d is 0.022-0.100; x is 29.05-30.94, y is 0.866-1.000; m is 0.02-0.05; HR is Dy and/or Tb; M is at least one selected from the group consisting of Co, Cu, Ti, Al, Nb, Zr, Ni, W and Mo.