Abstract Given the increasing concern regarding the global decline in rare earth reserves and the environmental burden from current wet-process recycling techniques, it is urgent to develop an efficient recycling technique for leftover sludge from the manufacturing process of neodymium–iron–boron (Nd–Fe–B) sintered magnets. In the present study, centerless grinding sludge from the Nd–Fe–B sintered magnet machining process was selected as the starting material. The sludge was subjected to a reduction–diffusion (RD) process in order to synthesize recycled neodymium magnet (Nd2Fe14B) powder; during this process, most of the valuable elements, including neodymium (Nd), praseodymium (Pr), gadolinium (Gd), dysprosium (Dy), holmium (Ho), and cobalt (Co), were recovered simultaneously. Calcium chloride (CaCl2) powder with a lower melting point was introduced into the RD process to reduce recycling cost and improve recycling efficiency. The mechanism of the reactions was investigated systematically by adjusting the reaction temperature and calcium/sludge weight ratio. It was found that single-phase Nd2Fe14B particles with good crystallinity were obtained when the calcium weight ratio (calcium/sludge) and reaction temperature were 40 wt% and 1050 °C, respectively. The recovered Nd2Fe14B particles were blended with 37.7 wt% Nd4Fe14B powder to fabricate Nd–Fe–B sintered magnets with a remanence of 12.1 kG (1 G = 1 × 10−4 T), and a coercivity of 14.6 kOe (1 Oe = 79.6 A·m−1), resulting in an energy product of 34.5 MGOe. This recycling route promises a great advantage in recycling efficiency as well as in cost.

中文翻译：

---

一种将 Nd-Fe-B 污泥回收为高性能烧结磁铁的有效工艺

摘要 鉴于全球稀土储量下降和当前湿法回收技术对环境造成的负担日益受到关注，迫切需要开发一种高效的钕-铁-硼（Nd- Fe-B) 烧结磁铁。在本研究中，来自 Nd-Fe-B 烧结磁体加工过程的无心研磨污泥被选为起始材料。对污泥进行还原-扩散（RD）工艺以合成再生钕磁铁（Nd2Fe14B）粉末；在此过程中，同时回收了大部分有价值元素，包括钕 (Nd)、镨 (Pr)、钆 (Gd)、镝 (Dy)、钬 (Ho) 和钴 (Co)。RD过程中引入了熔点较低的氯化钙（CaCl2）粉末，以降低回收成本，提高回收效率。通过调节反应温度和钙/污泥重量比，系统地研究了反应机理。结果表明，当钙的重量比（钙/污泥）和反应温度分别为 40 wt% 和 1050 ℃ 时，可以获得具有良好结晶度的单相 Nd2Fe14B 颗粒。回收的 Nd2Fe14B 颗粒与 37.7 wt% 的 Nd4Fe14B 粉末混合，以制造剩磁为 12.1 kG（1 G = 1 × 10-4 T）和矫顽力为 14.6 kOe（1 Oe = 79）的 Nd-Fe-B 烧结磁体。 A·m-1)，产生 34.5 MGOe 的能量积。这种回收路线在回收效率和成本方面具有很大优势。