“三维外延形核”系统中高硅钢复合铁芯内核壳异质结构调控机制研究

The high silicon steel has excellent soft magnetic properties, and is a sort of ideal material for iron core of high frequency electromotor. Due to such problems as high brittleness at room temperature and difficulty in rolling, the production and application of the high silicon steel is limited. Meanwhile, the high silicon steel will develop towards the low total core-loss to meet the high frequency demands for the electromagnetic conversion equipment in the near future. The eddy current loss gradually becomes the major component of the total core-loss with an increasing application frequency. Therefore, it is of great importance to reduce the eddy current loss effectively. Based on this situation, the free-rolling high silicon steel soft magnetic composites will be prepared using the three-dimensional heteroepitaxial nucleation system adopted through the fluidization vapor in-situ deposition and the following resistance pressing sintering process in this project. The eddy current loss of high silicon steel can be decreased by introducing a core-shell heterostructure. First, the strongly correlated factors on the core-shell heterostructure in the three-dimensional heteroepitaxial nucleation system will be investigated. The growth and control mechanisms of core-shell heterostructure will be analyzed. Then, the evolution laws of core-shell heterostructure under the high temperature during the resistance pressing sintering process will be revealed. Finally, in order to take full advantage of the core-shell heterostructure in reducing the eddy current loss, the influence rules of the microscopic features of core-shell heterostructure on the magnetic properties of the high silicon steel will be mastered. The results of this project will not only enrich and develop the method and theory of the advanced preparation of high-performance materials, but also promote the large-scale industrial production and application of the high silicon steel in China.

高硅钢具有优异的软磁性能，是高频电机铁芯的理想材料。但室温脆性大、轧制成型困难等问题限制了其生产与应用。同时，为满足未来电磁转换装置高频化的应用需求，高硅钢的研发必将向降低铁损的方向发展；随铁芯使用频率升高，涡流损耗成为铁损的主要部分，如何有效降低高硅钢涡流损耗显得至关重要。针对上述问题，项目采用流态化气相原位沉积构建“三维外延形核”系统，结合通电加压烧结制备高硅钢软磁复合铁芯，避开难以轧制的技术瓶颈，引入核壳异质结构新理念，降低铁芯涡流损耗。拟阐明“三维外延形核”系统中影响核壳异质结构的强关联因素，解析核壳异质结构的生长机理和调控机制。研究通电加压烧结过程，揭示核壳异质结构在高温环境下演化机理。掌握核壳异质结构显微特征对材料电-磁性能的影响规律，充分发挥核壳异质结构降低高硅钢铁芯涡流损耗的作用。研究成果能丰富和发展高性能材料先进制备理论和方法，还将推动我国高硅钢的大规模工业化生产和应用。

高硅钢具备优异的软磁性能，是航空航天、交通运输和电子信息等领域高效发展不可或缺的共性关键材料，但其室温脆性大、轧制成型困难限制了它的生产与应用。同时，为满足未来电磁转换装备高频化的应用需求，高硅钢的研发必将向高导磁和低铁损的方向发展。本项目研究了1) 探究了异质界面和SiO2包覆层的形成物理化学条件和形成机理；结合热力学、动力学以及分子动力学，解析了Fe-6.5wt.%Si/SiO2核壳异质结构的精确调控机制；研究结果表明“三维外延形核”系统中完整Fe-6.5wt.%Si/SiO2核壳异质结构的Fe-6.5wt.%Si/SiO2复合粉末的最低温度为920K，最少时间为960s，最低前驱体浓度为3vol.%，最佳稀释气体流量为200～300 sccm 。2) 高温环境下高硅钢软磁复合铁芯内Fe-6.5wt.%Si/SiO2核壳异质结构的演化机理以及对高硅钢基体的影响规律；研究结果表明，在烧结成型过程中高硅钢软磁复合铁芯内核壳异质结构中SiO2绝缘层会发生结晶，但不影响高硅钢基体的晶体结构。3) 定量地解析了流态化气相原位沉积工艺参数对制备的高硅钢软磁复合铁芯电磁性能的影响规律，包括饱和磁感应强度、电阻率、磁导率、涡流损耗、以及总损耗，建立的相关的工艺参数-性能控制模型，开发了一套具有自主学习功能的高硅钢软磁复合铁芯智能化生产系统。本项目采用流态化气相原位沉积与通电加压烧结的综合手段，成功制备免轧制的高硅钢软磁复合铁芯，通过引入核壳异质结构，降低铁芯的铁损，是我国在高硅钢合金领域实现从“依赖进口”到“自主创造”的重大突破，研究结果经王运敏院士等专家鉴定达到国际先进水平。通过本项目的研究，共发表论文14篇，其中SCI论文9篇，中文核心期刊论文5篇；授权国际专利3项，授权国家发明专利2项，软件著作权1项，另申请国家发明专利3项；已培养毕业硕士生4名、毕业博士生1名，在读博士生1名、硕士生1名；获安徽省科技进步奖二等奖1项、中国发明协会发明创新奖二等奖1项。