Reduction expansion synthesis for magnetic alloy powders

Abstract

In this work submicron scale ferromagnetic and magnetic rare-earth alloys were produced using Reduction Expansion Synthesis (RES), a technique in which metal particles are the product of the rapid heating to approximately 800 degrees Celsius, in inert atmosphere, of physical mixtures of urea, or similar molecules, and metal oxide, hydroxide or nitrates. As shown by scanning electron microscopy and x-ray diffraction, RES produced submicron magnetic particles. Essential to both 3D printing and metal injection molding (MIM) is the availability of fine powders to manufacture small, complex, metal parts. There are technological limits to the minimum particle size that can be produced using available low cost techniques, which is approximately 10 microns. This minimum particle size in turn limits the size of features on MIM and 3D printed metal parts. The demonstrated ability of RES to produce sub-micron particle sizes indicates this technology could enable the manufacture of finer features using either 3D printing or MIM.