白云鄂博共伴生原矿混合稀土永磁材料的制备及机理研究

Rare earth permanent magnetic materials play important roles in our national security and national economy. However, it costs mainly low-abundance rare earth elements to produce traditional rare earth permanent magnets, leading to the extreme unbalance in the resource utilization. The rare earth content in Bayan Obo ore ranks first in the world, which is associated commonly with iron and has the characteristic of barrenness, fineness and mixture. In addition, the distributions of Pr, Nd, La and Ce agree with each other in the ore. In this project, the commonly associated rare earth permanent magnets will be prepared first time using the mixed rare earth elements from Bayan Obo commonly associated green ore directly to save the resources. The new method avoids unnecessary separation process of rare earth elements, which can utilize the resources efficiently and protect the environment. The duay-alloy technique is employed to investigate the effect of the compositions on magnetic properties and microstructures in commonly associated permanent magnetic materials made from mixed rare earth elements in the green ore. The comparative analysis approach is adopted with the focus on the effect of the ore’s concomitance and natural formulation. The influences of the structure differences of the main phases including Ce2Fe14B, La2Fe14B, (LaCe)2Fe14B etc. as well as the chemical compositions, crystalline structures and morphology features of the rare earth rich phase on the magnetic properties of the permanent magnets from the mixed rare earth elements in the green ore will also be discussed in the project. In the meantime, hysteresis loops and domain structures are analyzed in combination with micromagnetics. The role of the rare earth rich phase in the processes of the magnetization and demagnetization will be discussed and the coercivity theory for the permanent magnets from mixed rare earth elements in the green ore will be constructed.

稀土永磁材料是国家安全和国民经济的重要材料，但传统稀土永磁体主要消耗低丰度稀土元素，资源利用极不均衡。白云鄂博矿稀土含量居世界首位，具有贫、细、杂且与铁共伴生的特点，其中镨、钕、镧、铈矿相分布一致。本项目首次直接利用白云鄂博共伴生原矿混合稀土制备资源节约型共伴生稀土永磁体，避免了不必要的稀土元素分离过程，达到资源高效综合利用和环境保护的目的。我们将通过对比分析的方法，采用双合金工艺研究原矿混合稀土永磁材料的成份特别是共伴生特点与天然配方属性对磁性能与微结构的影响。项目将充分考虑原矿混合稀土永磁体中的Ce2Fe14B、La2Fe14B、 (LaCe)2Fe14B等多主相结构差异，以及富稀土相的化学成份、晶体结构、形貌特征等因素对磁性能的影响。同时，我们结合微磁学方法分析磁滞回线和磁畴结构，探讨富稀土相在磁化和反磁化过程中的作用，建立原矿混合稀土永磁材料矫顽力的理论。

稀土永磁材料是国家安全和国民经济的重要材料，但传统稀土永磁体主要消耗低丰度稀土元素，资源利用极不均衡。白云鄂博矿稀土含量居世界首位，具有贫、细、杂且与铁共伴生的特点，其中镨、钕、镧、铈矿相分布一致。本项目首次直接利用白云鄂博共伴生原矿混合稀土制备资源节约型共伴生稀土永磁体，避免了不必要的稀土元素分离过程，达到资源高效综合利用和环境保护的目的。研究白云鄂博共伴生原矿混合稀土永磁材料的成份特别是共伴生特点与天然配方属性对磁性能与微结构的影响。研究白云鄂博共伴生原矿混合稀土永磁材料的双合金工艺对磁性能与相结构的影响。结合微磁学方法分析磁化与反磁化过程中的磁性能与磁畴结构变化特点，建立白云鄂博共伴生原矿混合稀土含量与磁体矫顽力变化规律的唯象关系。本项目分别利用简单掺杂（稀土取代）与双合金工艺制备RE2Fe14B（RE=Pr、Nd、MM）烧结磁体；提出了微磁学计算和分析模型。利用共伴生混合稀土与人工配制混合稀土分别制备RE2Fe14B（RE=Pr、Nd、MM）烧结磁体。研究发现烧结温度明显影响烧结MM-Fe-B永磁材料的组织和性能，随烧结温度升高，磁体的致密度升高，主相晶粒长大，富稀土相分布更加均匀。双主相法制备的磁体性能更好，当MM占稀土总量20wt.%，最优磁性能为Br=13.26 kGs，Hcj=8.368 kOe，(BH)max=41.49 MGOe，其磁性能与N40磁性产品相当，但生产每吨磁体原材料成本可降低2.4万元。MM占总稀土含量的50wt.%时，磁体性能为Br=12.25 kGs，Hcj=5.24 kOe，(BH)max=31.31 MGOe。添加PrNd粉末后，磁体矫顽力显著增加，但当纳米PrNd粉末添加过多时，磁体方形度有明显降低。双主相磁体的反磁化过程分析表明，磁体热激活尺寸约为纳米级，与磁畴壁尺寸相当。磁反转方式为磁畴壁的形核和位移。50公斤级中试生产线已全面建成，并正式运行，打通了从实验室实验到工业生产的中间环节。以上结果必为混合稀土永磁材料的生产提供指导意义。