We describe an electrolytic process which successfully decrepitates (pulverizes) sintered Nd₂Fe₁₄B magnets in preparation for further recycling. Laboratory-scale measurements on magnets that had been removed from end-of-life hard disk drives demonstrate that cm-size magnet fragments, in electrical contact with a titanium cathode in a 2 M KOH solution, can undergo hydrogen decrepitation (HD) into powder with grain size < 50 μm. Electrolysis during 2 h at 4.7 V, 13–15 A, with nickel foil as the anode, was sufficient for complete material pulverization under ambient conditions. As a guide for understanding the reaction thermodynamics of each of the magnet components with hydrogen, the Gibbs energies for two groups of reactions in the temperature range 273–473 K were calculated: (1) reactions with atomic hydrogen radical (i.e., uncharged atom, unpaired electron); (2) reactions with hydrogen gas. As expected for small grain HD powders that have not been degassed at elevated temperatures, only weak remanent magnetic polarization and coercive field are detected in SQUID magnetometer measurements; demagnetization to facilitate powder handling is therefore not required. We expect that the financial cost, time, and safety of a scaled-up version of our electrolytic process should compare favorably with high pressure and/or high-temperature hydrogen gas decrepitation protocols currently in use.

Graphical Abstract

中文翻译：

---

环境条件下钕铁硼磁体的电解氢爆裂

我们描述了一种电解工艺，该工艺成功地破碎（粉碎）烧结的 Nd ₂ Fe ₁₄B 磁铁为进一步回收做准备。对从报废硬盘驱动器中取出的磁体进行的实验室规模测量表明，在 2 M KOH 溶液中与钛阴极电接触的厘米大小的磁体碎片可以经历氢爆裂 (HD) 成粉末晶粒尺寸 < 50 μm。在 4.7 V、13-15 A 下电解 2 小时，以镍箔为阳极，足以在环境条件下完全粉碎材料。作为了解每个磁体组件与氢的反应热力学的指南，计算了 273-473 K 温度范围内两组反应的吉布斯能量：（1）与原子氢自由基（即不带电原子，未配对电子）；(2)与氢气反应。正如预期的那样，对于未在高温下脱气的小颗粒 HD 粉末，在 SQUID 磁力计测量中仅检测到微弱的剩磁极化和矫顽场；因此不需要去磁以促进粉末处理。我们预计，我们的电解工艺的放大版本的财务成本、时间和安全性应该与目前使用的高压和/或高温氢气爆裂协议相媲美。

图形概要