Abstract
An Nd 16Fe 76B 8 sintered magnet was powdered and sieved to different particle sizes in the 0–100 μm range. The powders were heated at 300, 340, 360 and 650°C for different times, and observed by optical and high-resolution electron microscopy. The kinetic curves at 300°C, obtained by Mössbauer spectrometry, were fitted according to a single-particle analysis model, whose assumptions were validated by the microstructural observations. The results were interpreted consistently by considering the effects of intergranular and intragranular diffusion of oxygen. It was confirmed that the determination of the kinetic parameters of the dissociation of the Nd 2Fe 14B phase is possible with small particles (with size less than 40 μm) when the intergranular diffusion process dominates, and for bigger particles when the intragranular diffusion process dominates. The temperature from which the intragranular diffusion dominates the intergranular diffusion was estimated to be 350°C.
Published Version
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