富Co基耐高温无稀土硬磁纳米结构的可控生长与自组装

To meet the high-temperature application demand of permanent magnets for the emerging industries such as wind power and electric vehicles, and reduce the permanent magnet dependence on rare-earth elements, we will choose Co-rich rare-earth-free hard magnetic Zr2Co11 and HfCo7 systems with high Curie temperature (Tc) and high magnetocrystalline anisotropy (Ku) as the research object in this project. Controllable growth and self-assembly of hard magnetic and soft/hard exchange coupled nanostructures are investigated in the present proposal. The following issues will be focused:. (1) High-temperature organic solvent reaction is employed to realize the nanostructures regulation on the magnetic properties, and thus obtain the optimal preparation conditions for Co-rich rare-earth-free hard magnetic nanostructures with high magnetic energy product. The controllable growth rule of hard magnetic and soft/hard nanostructures can be obtained. (2) Based on the experiment results, we will explore the Ku enhancement mechanism of hard magnetic phase by the first-principles calculations on Ku value and electronic structure. The magnetization reversal mechanism of soft/hard nanostructures can be revealed using the micromagnetic simulations on magnetization process. (3) We will also assemble these nanostructures into ordered arrays using magnetic field induced method, and illustrate the magnetic field induced self-assembly mechanism for hard magnetic nanostructures, which will promote their practical applications. . These research achievements can relieve effectively resource crisis caused by Nd2Fe14B and SmCo5 rare-earth permanent magnets, enrich and develop the magnetization reversal mechanism and assembly technology of soft/hard nanocomposite permanent magnets.

为满足风力发电与电动汽车等新兴产业对耐高温永磁体的需求和减少永磁对稀土的依赖，本项目以高居里温度(Tc)和高磁晶各向异性能(Ku)的富Co基无稀土硬磁Zr2Co11和HfCo7为研究对象，开展硬磁单相与软磁/硬磁交换耦合纳米结构的可控生长与自组装研究。主要包括：(1)采用高温有机溶剂反应法实现纳米微观结构对磁学性质的调控，优化高磁能积硬磁纳米结构的最佳制备条件，获得硬磁纳米结构的可控生长规律；(2)在实验基础上采用第一性原理对晶体结构Ku值和电子结构的计算，揭示硬磁结构的Ku增强原理，通过对异质结构磁化过程的微磁模拟揭示其磁化反转机制；(3)通过磁场诱导实现硬磁纳米结构的长程有序排列，阐明高性能纳米硬磁的磁场诱导自组装机理，推动无稀土硬磁的实际应用。研究成果可以缓解Nd2Fe14B和SmCo5等稀土永磁带来的资源危机，丰富和发展软磁/硬磁纳米复合永磁体的磁化反转机制和应用组装技术。

本项目采用高温有机溶剂法和固相反应法制备出Co基和Cr基等硬磁及相关磁性纳米材料，并对其结构可控生长机理和磁化反转机制进行了系统研究。采用高温有机溶剂法和固相反应法制备出CoZr合金，研究了Co:Zr比例及工艺参数对磁学性能的影响。基于3d过渡金属与重金属或重非金属元素形成高各向异性的原则，我们还开展了Cr基和Fe基无稀土永磁与稀土永磁材料的制备。首次采用高温有机溶剂法获得高矫顽力Cr2Te3无稀土永磁纳米材料，并采用第一性原理揭示了其矫顽力增强原理，通过Co和Se共掺杂可使Cr2Te3矫顽力最高达到14.6kOe；以Cr2Te3无稀土永磁纳米材料为模板制备出CrGeTe3二维材料，实现了非范德华硬磁材料到范德华软磁二维材料的转变；类似方法还制备出MnTe/Cr2Te3纳米棒异质结，实现了反铁磁到铁磁的调控；通过微磁模拟方法揭示了Nd2Fe14B/α″-Fe(Co)16N2双层膜的磁化反转机制，优化出最佳磁学性能的结构模型。以上研究成果为新型无稀土永磁及稀土永磁材料的研发及应用奠定了重要实验与理论基础，也同时开辟了新颖磁性纳米材料的合成策略。