Nd-Fe-B PERMANENT MAGNETIC MATERIAL AND PREPARATION METHOD THEREOF

Abstract

The present disclosure discloses a permanent magnetic material comprising an Nd—Fe—B alloy and an additive including at least a cobalt ferrite, and a method for preparing a permanent magnetic material. The method comprises steps of mixing an Nd—Fe—B alloy and an additive including at least a cobalt ferrite to obtain a mixture; magnetically orienting and pressing the mixture in a magnetic filed; and sintering and tempering the mixture under the protection of vacuum or an inert gas.

1 . A permanent magnetic material, comprising: an Nd—Fe—B alloy; and an additive including at least a cobalt ferrite. 
     
     
         2 . The permanent magnetic material of  claim 1 , wherein the cobalt ferrite is about 0.5 wt % to about 10 wt % of the Nd—Fe—B alloy. 
     
     
         3 . The permanent magnetic material of  claim 1 , wherein an average particle diameter of the cobalt ferrite is in a range of about 10 nanometers to about 150 nanometers. 
     
     
         4 . The permanent magnetic material of  claim 1 , wherein the cobalt ferrite is represented by a general formula of Co n Fe 3−n O 4 , where n is in a range of about 0.1<n<2.0. 
     
     
         5 . The permanent magnetic material of  claim 1 , wherein the Nd—Fe—B alloy is represented by a general formula of Nd a Re b Fe (100-a-b-c-d) B c M d , where:
 Re is at least one element selected from a group consisting of Pr, Dy, Tb, Ho, Gd, La, Ce and Y; M is at least one element selected from a group consisting of Co, Al, Cu, Zr, Ga, Nb and Mo; and a, b, c, and d are atomic weight ratios, in which a is in a range of about 1≦a≦10, b is in a range of about 5≦b≦12, c is in a range of about 5≦c≦8, and d is in a range of about 0≦d≦15. 
 
     
     
         6 . A method for preparing a permanent magnetic material, comprising steps of: mixing an Nd—Fe—B alloy and an additive including at least a cobalt ferrite to obtain a mixture; magnetically orienting and pressing the mixture in a magnetic filed; and sintering and tempering the mixture under the protection of vacuum or an inert gas. 
     
     
         7 . The method of  claim 6 , wherein the cobalt ferrite is about 0.5 wt % to about 10 wt % of the Nd—FeB alloy. 
     
     
         8 . The method of  claim 6 , wherein the cobalt ferrite is represented by a general formula of Co n Fe 3−n O 4 , where n is in a range of about 0.1≦n≦2.0. 
     
     
         9 . The method of  claim 6 , wherein the mixing step comprises mixing the Nd—Fe—B alloy and the additive in the presence of an antioxidant, and the amount of the antioxidant is about 0.1 wt % to about 5 wt % based on the weight of the Nd—Fe—B alloy. 
     
     
         10 . The method of  claim 6 , wherein the Nd—Fe—B alloy is represented by a general formula of Nd a Re b Fe (100-a-b-c-d) B c M d , where:
 Re is at least one element selected from a group consisting of Pr, Dy, Tb, Ho, Gd, La, Ce and Y; M is at least one element selected from a group consisting of Co, Al, Cu, Zr, Ga, Nb and Mo; and a, b, c, and d are atomic weight ratios, in which a is in a range of about 1≦a≦10, b is in a range of about 5≦b≦12, c is in a range of about 5≦c≦8, and d is in a range of about 0≦d≦15. 
 
     
     
         11 . The method of  claim 6 , wherein an average particle diameter of the cobalt ferrite is in a range of about 10 nanometers to about 150 nanometers. 
     
     
         12 . The method of  claim 6 , wherein the magnetically orienting and pressing is performed under a magnetic filed intensity of about 1.2 T to about 3.0 T and a pressure of about 10 MPa to about 200 MPa for a period of about 10 seconds to about 60 seconds; the sintering is performed at a temperature of about 1030° C. to about 1120° C. for a period of about 2 hours to about 8 hours; and wherein the tempering steps comprising a first tempering step and a second tempering step, in which the first tempering step is performed at a temperature of about 800° C. to about 920° C. for a period of about 1 hour to about 3 hours, and the second tempering step is performed at a temperature of about 500° C. to about 650° C. for a period of about 2 hours to about 4 hours. 
     
     
         13 . The method of  claim 6 , wherein the mixing step comprises mixing the Nd—Fe—B alloy and the additive in the presence of an antioxidant and a lubricant in which based on the weight on the Nd—Fe—B alloy, the amount of the antioxidant is about 0.1 wt % to about 5 wt %, and the amount of the lubricant is about 0 wt % to about 5 wt %. 
     
     
         14 . The method of  claim 6 , wherein an average particle diameter of the Nd—Fe—B alloy is in a range of about 2 microns to about 5 microns.