Czasopismo | INŻYNIERIA MATERIAŁOWA | Rocznik 2016 - zeszyt 5

Pressure effect on hydrogen absorption by Nd-Fe-B magnets during HD and HDDR

10.15199/28.2016.5.9

nr katalogowy: 101856
10.15199/28.2016.5.9

Scrap, sintered Nd-Fe-B magnets were subjected to hydrogen treatments of Hydrogen Decrepitation (HD) and Hydrogenation-Disproportion-Desorption and Recombination (HDDR) route. In HD treatments, increasing hydrogen pressure from 100 kPa up to 200 kPa at room temperature, does not affect particles size distribution but accelerates the reaction by decreasing the incubation time. In this study a faster HD process is reported when fresh materials are provided compared to one week stored ones. As part of the exothermic nature of the HD process, the increment of temperature was registered. The temperature rise was slightly higher for the fresh material (close to 2°C) comparing with the one week stored material (around 1.5°C). Hydrogen absorption was analysed during the HDDR process carried out at 850°C under three hydrogen pressures: 30, 100 and 200 kPa. For 30 kPa, due to hydrogen consumption, additional refilling was necessary, while other tested pressures were high enough to avoid additional refilling during the HDDR. Key words: hydrogen decrepitation, hydrogenation-disproportionation-desorption and recombination, hydrogen absorption.1. INTRODUCTION Recovery of rare earth metals is forced by a huge demand for these critical materials strongly requested by the high-tech industry [1]. Electronic devices, modern medicine, automotive industry, as well as green energy sectors are the biggest receivers of these unique and precious metals. Some of the products, with high demand in these areas, are high performance magnets made of rare earth elements. Hydrogen-assisted recycling treatments are currently under investigation for such magnetic materials [2, 3]. As an example, Hydrogen Decrepitation (HD), discovered by Harris et al. [4], allows for crushing of bulk pieces of Nd-Fe-B ingots into hydride powder. This is caused by an increase of volume in the rare earth metal lattice due to absorption of hydrogen. In magnets, hydrogen is absorbed mostly b[...]

Bibliografia

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