Coating formulation and application of organic passivation layer onto iron-based rare earth powders

Abstract

The present disclosure relates to coating formulations for neodymium-iron-boron type magnetic powders manufactured from rapid solidification processes for the purpose, inter alia, of corrosion and oxidation resistance when exposed to aggressive environments. The coating formulation preferably contains an epoxy binder, curing agent, an accelerating agent, and a lubricant. By incorporating coupling agents and optionally, other specialty additives with the magnetic powder and the organic epoxy components, additional oxidation and corrosion prevention, enhanced adhesion and dispersion between the filler and matrix phases can be achieved. This disclosure relates to all such rare earth-transition metal-boron (RE-TM-B) powders produced by rapid solidification and encompasses both the bonded magnet products that include combinations of the materials mentioned and the application processes.

1 - 20 . (canceled) 
     
     
         21 . A process of liquid-coating a rapidly solidified rare earth-transition metal-boron magnet material, comprising:
 providing a homogeneous solution comprising a solvent, an organotitanate or organozirconate coupling agent, an epoxy resin, a hardener, an accelerator, and a lubricant, wherein said homogeneous solution is a homogeneous 8-25% solution;   combining a rare earth-transition metal-boron magnet powder with said homogeneous solution to form a slurry mixture;   stirring said slurry mixture periodically; and   maintaining said slurry mixture at a temperature between 40-60° C., such that said solvent evaporates.   
     
     
         22 . The process of  claim 21 , wherein the solvent is acetone. 
     
     
         23 . The process of  claim 22 , further comprising introducing an organoclay into the homogeneous 8-25% solution. 
     
     
         24 . The process of  claim 22 , further comprising introducing an antioxidant agent into to the homogeneous 8-25% solution. 
     
     
         25 . The process of  claim 22 , wherein both an organotitanate and an organozirconate coupling agent are added to the homogeneous 8-25% solution. 
     
     
         26 . The process of  claim 22 , wherein said slurry mixture is maintained at a temperature between 50-60° C. 
     
     
         27 . (canceled) 
     
     
         28 . The process of  claim 21 , wherein said solvent is tetrahydrofuran, and said process further comprises pre-treating the rare earth-transition metal-boron powder by dissolving a POSS additive in tetrahydrofuran to form a 50% solution; adding the rare earth-transition metal-boron powder into the 50% solution; and evaporating the tetrahydrofuran to produce a pre-treated rare earth-transition metal-boron powder. 
     
     
         29 - 48 . (canceled) 
     
     
         49 . A process of liquid-coating a rapidly solidified rare earth-transition metal-boron magnet material, comprising:
 providing a homogeneous solution consisting essentially of a solvent, an organotitanate or organozirconate coupling agent, an epoxy resin, a hardener, an accelerator, and a lubricant, wherein said homogeneous solution is a homogeneous 8-25% solution;   combining a rare earth-transition metal-boron magnet powder with said homogeneous solution to form a slurry mixture;   stirring said slurry mixture periodically; and   maintaining said slurry mixture at a temperature between 40-60° C., such that said solvent evaporates.   
     
     
         50 . A process of liquid-coating a rapidly solidified rare earth-transition metal-boron magnet material, comprising:
 providing a homogeneous solution comprising a solvent, an organotitanate or organozirconate coupling agent, an epoxy resin, a hardener, an accelerator, and a lubricant, wherein said homogeneous solution is a homogeneous 8-25% solution; and   combining a rare earth-transition metal-boron magnet powder with said homogeneous solution to form a slurry mixture.   
     
     
         51 . The process of  claim 50 , further comprising stirring said slurry mixture periodically. 
     
     
         52 . The process of  claim 50 , wherein the solvent is acetone. 
     
     
         53 . The process of  claim 52 , further comprising introducing an organoclay into the homogeneous 8-25% solution. 
     
     
         54 . The process of  claim 52 , further comprising introducing an antioxidant agent into to the homogeneous 8-25% solution. 
     
     
         55 . The process of  claim 52 , wherein both an organotitanate and an organozirconate coupling agent are added to the homogeneous 8-25% solution. 
     
     
         56 . The process of  claim 50 , wherein said solvent is tetrahydrofuran, and said process further comprises pre-treating the rare earth-transition metal-boron powder by dissolving a POSS additive in tetrahydrofuran to form a 50% solution; adding the rare earth-transition metal-boron powder into the 50% solution; and evaporating the tetrahydrofuran to produce a pre-treated rare earth-transition metal-boron powder.