A sintered R-T-B based magnet includes a main phase formed of an R.sub.2T.sub.14B compound and a grain boundary phase at grain boundaries of the main phase. The grain boundary phase contains an R-T-M compound (M is at least one selected from the group consisting of Ga, Cu, Zn, Al and Si) and an R-M compound. In any cross-section of the sintered R-T-B based magnet, a sum of an area ratio of the R-T-M compound and an area ratio of the R-M compound is not lower than 1.5% and not higher than 3.5%, the area ratio of the R-T-M compound is not lower than 0.4% and not higher than 2.5%, and the area ratio of the R-M compound is not lower than 0.4% and not higher than 2.5%.

This invention provides, by simple mechanical treatment, a metal powder that generates no smoke phenomenon when laminating and shaping a metal object even when decreasing a preheating temperature. In the metal powder, a solidification structure including a dendritic structure on the surface of the metal powder has been flattened. The solidification structure including the dendritic structure has been flattened by mechanical treatment including collision treatment of the metal powder. The mechanical treatment is performed by heating the metal powder to 100° C. to 300° C. The metal powder is a metal powder that is heated to a predetermined temperature and whose capacitance component of a measured impedance becomes zero. This metal powder is a powder of a metal alloy produced by an atomization process or a plasma rotation electrode process. The metal alloy includes a nickel-based alloy, a cobalt-chrome alloy, an iron-based alloy, an aluminum alloy, and a titanium alloy.

This invention provides, by simple mechanical treatment, a metal powder that generates no smoke phenomenon when laminating and shaping a metal object even when decreasing a preheating temperature. In the metal powder, a solidification structure including a dendritic structure on the surface of the metal powder has been flattened. The solidification structure including the dendritic structure has been flattened by mechanical treatment including collision treatment of the metal powder. The mechanical treatment is performed by heating the metal powder to 100° C. to 300° C. The metal powder is a metal powder that is heated to a predetermined temperature and whose capacitance component of a measured impedance becomes zero. This metal powder is a powder of a metal alloy produced by an atomization process or a plasma rotation electrode process. The metal alloy includes a nickel-based alloy, a cobalt-chrome alloy, an iron-based alloy, an aluminum alloy, and a titanium alloy.

A reactor for forming fully coated particles having a solid core, the reactor comprises a reactor vessel which is configured to receive particles, and a gas phase coating mechanism that is configured to selectively introduce pulses of gas phase materials that form a coating on the particles. The reactor also includes a sieve (16) that is located within the reactor vessel, and a forcing means that is configured to force the particles through the sieve (16) in use. The sieve is configured to deagglomerate any particle aggregates formed in the reactor vessel upon forcing of the particles by the forcing means through the sieve.

A permanent magnet is expressed by a composition formula: R.sub.pFe.sub.qMrCu.sub.5Co.sub.100-p-q-r-s. The magnet includes a crystal grain having a main phase including a TbCu.sub.7 crystal phase, and a volume ratio of the TbCu.sub.7 crystal phase to the main phase is 95% or more.

A permanent magnet is expressed by a composition formula: R.sub.pFe.sub.qMrCu.sub.5Co.sub.100-p-q-r-s. The magnet includes a crystal grain having a main phase including a TbCu.sub.7 crystal phase, and a volume ratio of the TbCu.sub.7 crystal phase to the main phase is 95% or more.

A sintered magnet body (R.sub.aT.sup.1.sub.bM.sub.cB.sub.d) coated with a powder mixture of an intermetallic compound (R.sup.1.sub.iM.sup.1.sub.j, R.sup.1.sub.xT.sup.2.sub.yM.sup.1.sub.z, R.sup.1.sub.iM.sup.1.sub.jH.sub.k), alloy (M.sup.1.sub.dM.sup.2.sub.e) or metal (M.sup.1) powder and a rare earth (R.sup.2) oxide is diffusion treated. The R.sup.2 oxide is partially reduced during the diffusion treatment, so a significant amount of R.sup.2 can be introduced near interfaces of primary phase grains within the magnet through the passages in the form of grain boundaries. The coercive force is increased while minimizing a decline of remanence.

The present disclosure relates to a method of preparing a nano-porous powder material. The method includes: firstly removing A in the alloy A.sub.xT.sub.y by using an ultrasonically-assisted de-alloying method to prepare a nano-porous T coarse powder, and then, allowing the nano-porous T coarse powder to perform M-ization reaction with a gas reactant containing M to obtain a nano-porous T-M coarse powder, and finally, further crushing the nano-porous T-M coarse powder using a jet mill to obtain a nano-porous T-M fine powder. The method can achieve low-cost mass production of the nano-porous T-M fine powder, bringing broad application prospects.

An R-T-B based permanent magnet in which R is a rare earth element, T is Fe or a combination of Fe and Co, B is boron, and further includes M. The R-T-B based permanent magnet includes main phase grains consisting of R.sub.2T.sub.14B phase. M at least includes Ga and Zr. The R-T-B based permanent magnet further includes C and O. R content is 29.0 mass % to 33.0 mass %, B content is 0.85 mass % to 1.05 mass %, Ga content is 0.30 mass % to 1.20 mass %, 0 content is 0.03 mass % to 0.20 mass %, and C content is 0.03 mass % to 0.30 mass %. Further, the R-T-B based permanent magnet satisfies 3.48m(B)−2.67≤m(Zr)≤3.48m(B)−1.87 in which m(B) (mass %) is B content and m(Zr) (mass %) is Zr content.

An R-T-B based permanent magnet in which R is a rare earth element, T is Fe or a combination of Fe and Co, B is boron, and further includes M. The R-T-B based permanent magnet includes main phase grains consisting of R.sub.2T.sub.14B phase. M at least includes Ga and Zr. The R-T-B based permanent magnet further includes C and O. R content is 29.0 mass % to 33.0 mass %, B content is 0.85 mass % to 1.05 mass %, Ga content is 0.30 mass % to 1.20 mass %, 0 content is 0.03 mass % to 0.20 mass %, and C content is 0.03 mass % to 0.30 mass %. Further, the R-T-B based permanent magnet satisfies 3.48m(B)−2.67≤m(Zr)≤3.48m(B)−1.87 in which m(B) (mass %) is B content and m(Zr) (mass %) is Zr content.