Patent ID: 8535634

Claim:
A method of making iron nitride powder, the method comprising the steps in the following sequential order: a) providing FeOOH starting bulk material in a reactor; b) separating the FeOOH starting bulk material into a plurality of individual particles such that an individual particle of the plurality of particles is suspended in the reactor by flowing a reducing agent in the reactor, wherein an entire surface of the individual particle is exposed to gas flowing in the reactor; c) maintaining an elevated temperature in the reactor of between about 350° C. and 500° C. in the presence of the reducing agent to reduce the individual particle to form a reduced individual particle; d) cooling down the elevated temperature in the reactor to a constant temperature of between 110° C. and 180° C. in the presence of the reducing agent; e) stopping flow of the reducing agent after reaching the constant temperature; f) flowing a nitrogenation gas with an ammonia gas and a nitrogen gas to suspend the reduced individual particle in a fluidized environment and maintaining the constant temperature in the fluidized environment from about 1 hour up to about 48 hours to nitride the reduced individual particle to form an iron nitride particle of the iron nitride powder; g) cooling down the constant temperature in the reactor between room temperature and 50° C. to define a passivating temperature; h) stopping flow of ammonia gas after reaching the passivating temperature; and i) exposing an entire surface of the iron nitride particle of the iron nitride powder to an air and nitrogen gas mixture to passivate the entire surface of the iron nitride particle to prevent oxidation, whereby the iron nitride powder having (i) a saturation magnetization of between 230 and 250 emu/g as determined by plotting a magnetization curve as a function of an inverse of magnetizing field and extrapolating a linear part of the magnetization curve from 10 kOe to 16 kOe toward an inverse of an infinite magnetizing field, (ii) 4 to 90 wt % Fe16N2, (iii) 0 wt % Fe4N, and (iv) remaining balance of the iron nitride powder being body centered cubic (bcc) iron.