氮掺杂对铁基非晶合金的软磁性能及其腐蚀行为的影响研究

Iron-based amorphous alloys are widely used in electric power, electronic information, intelligent sensing and other industries, which are the green energy-saving materials for national key promotion. However, there are still some problems such as limited glass-forming ability (GFA), low saturation magnetization and weak corrosion resistance in the application process. In this project, nitrogen (N) is selected as the doping element, and the kinetics and crystallization behavior of the nitrogen doped alloys are studied by optimizing the N solubility of the typical iron-based amorphous alloy system. Combined with the first-principles molecular dynamics simulation, the influence mechanism of N on the GFA of the alloys is discussed. Besides, the spin and orbit magnetic moments of the iron atoms, as well as the magnetic moments, valence states, bonding characteristics and electron cloud symmetry of the iron nucleus are studied. The effects of N doping on the soft magnetic properties are revealed from the viewpoint of electron-atomic exchange coupling. Moreover, the composition of the passivation film on the surface of the alloys and the distribution of the core-level binding energy, the density of the valence electrons (weight), the binding energy shift and the work function are studied. The effects of N doping on the corrosion properties are analyzed from the perspective of electronic and ion transport characteristics, and then to establish its correlation with the soft magnetic properties. Our project is expected to provide theoretical basis and technical reserve for the development of new nitrogen-containing iron-based bulk amorphous alloys with high saturation magnetization and high corrosion resistance.

铁基非晶合金广泛应用于电力电气、电子信息、智能传感等行业，是国家重点推广的绿色节能材料。但目前在应用过程中仍存在非晶形成能力小、饱和磁感应强度低、耐腐蚀性能弱等问题。本项目拟选择氮作为掺杂元素，通过优化典型铁基非晶合金体系的氮溶解度，研究合金的动力学行为和晶化行为，并结合第一性原理分子动力学模拟，揭示氮掺杂对非晶形成能力的影响机制。研究铁原子的自旋磁矩和轨道磁矩，以及铁原子核的磁矩、价态、成键性质和电子云对称性，从电子-原子核交换耦合作用的角度揭示氮掺杂对软磁性能的影响机制。研究合金表面钝化膜在纵向分布上的成分和芯能级位移、价电子态密度分布(权重)、结合能位移和功函数等，从电子/离子输运特征的角度揭示氮掺杂对腐蚀性能的影响机制，并建立其与软磁性能之间的关联。为发展新型高饱和磁感应强度、高耐蚀性的含氮铁基块体非晶合金提供理论基础和技术储备。

氮作为大气中资源最丰富的元素，与金属复合后呈现出许多独特的物理和化学性质。但是在本领域尚缺乏一种综合性能较好的高氮铁基非晶/纳米晶合金以及有效的制备方法。本项目通过等离子渗氮、氮化物掺杂和反应溅射氮掺杂系统研究了氮掺杂对铁基非晶/纳米晶合金磁学和腐蚀性能的影响。主要结果如下：. （1）等离子渗氮之后Fe90Zr7B3纳米晶合金的耐蚀性得到改善，热力学稳定性提高，而磁性性能未发生明显变化。等离子渗氮合金退火之后析出了更细小的α-Fe晶粒(10~15nm)以及少量的纳米尺度的Fe3N及ZrN相。等离子渗氮引起的相析出可以在溶液中诱发产生NH4+、NO3-(NO2-)离子，进而调控溶液的pH并抑制金属的阳极反应。另外，等离子渗氮促进了锆元素在金属钝化膜中的富集并形成致密的氧化物膜，从而合金的耐蚀性得到提高。. （2）通过ZrN掺杂使Fe90Zr7B3合金的饱和磁感应强度提高0.1T，热处理温度区间增大。第一性原理计算表明掺氮之后锆原子的电子能量提高，且氮元素均匀分布于合金内部，对耐蚀性的贡献不大，但会使Fe3d轨道与N2s轨道之间发生电荷转移，进而引起电子自旋态密度的改变。此外，由于氮原子与铁原子之间的耦合，会导致其周围局部铁原子的磁矩发生改变，因此合金的饱和磁感应强度Bs可以得到一定程度的提高。. （3）研究了不同流量比下，FeCoHf-N软磁薄膜的结构、形貌、静态磁性能的变化关系。随着氮元素的添加，粗大且分布不均匀的柱状晶转变为细小的纳米晶，说明氮元素有效提高了薄膜的非晶形成能力。薄膜的矫顽力随氮掺杂量不断降低，其难轴矫顽力从未掺氮前的140Oe降低到R(N2)=12%的10Oe，而电阻率从500μΩcm增加到1000μΩcm以上。沉积的FeCoHfN 薄膜表现出 16.2KGs的高饱和磁化强度、GHz下高达293的大初始磁导率和2.97GHz的高铁磁共振频率，在千兆赫兹高频电磁设备中有大的应用潜力。