为解决传统球形颗粒制备的软磁复合材料在高频应用中面临的导磁性与损耗难以兼顾的问题，本工作以片状FeSiAl软磁颗粒为原料，提出了一种融合界面化学反应与磁场定向成型的FeSiAl/Al2O3软磁复合材料制备新策略。通过片状FeSiAl颗粒与NaOH体系的界面化学反应，原位生成致密均匀的Al2O3绝缘层；同时利用外加磁场引导颗粒沿易磁化方向定向排列，构建出具有层状结构的绝缘体系。研究表明，颗粒的宽厚比对绝缘层形貌、厚度分布及磁性能具有显著调控作用。当宽厚比为141时，样品形成致密连续的绝缘层，展现出优异的综合电磁性能：有效磁导率达126.3、总损耗低至108.0 kW/m3、电阻率高达331.1 Ω?m。基于密度泛函理论模拟，揭示了FeSiAl与Al2O3界面间的共价键合行为，及其对界面结合强度的增强作用。此外，通过三维损耗分离模型，定量分析了各类损耗机制在不同宽厚比下的贡献差异。本研究不仅揭示了片状颗粒宽厚比在微观结构调控与电磁性能优化中的关键作用，更为高频、低损耗软磁复合材料的设计提供了理论依据和可行工艺路径，具有重要的工程应用潜力。

To address the persistent challenge of balancing magnetic permeability and core loss in soft magnetic composites (SMCs) fabricated from conventional spherical particles for high-frequency applications, this study proposes an innovative strategy using flaky FeSiAl particles as the base material. A novel FeSiAl/Al2O3 composite is synthesized by integrating interfacial chemical reactions with magnetic field-assisted orientation. A dense and uniform Al2O3 insulation layer is formed in situ via the reaction between the FeSiAl particle surface and a NaOH-based system. Subsequently, the application of an external magnetic field facilitates the alignment of flaky particles along the easy magnetization axis, thereby constructing a layered insulating architecture. The results demonstrate that the particle aspect ratio plays a crucial role in determining the morphology, thickness uniformity, and adhesion quality of the Al2O3 layer, which in turn influences the magnetic properties of the composites. Particularly, the sample with an aspect ratio of 141 achieves a highly continuous insulation layer, exhibiting an excellent combination of effective permeability (126.3), low power loss (108.0 kW/m3), and high electrical resistivity (331.1 Ω?m). Density functional theory (DFT) simulations reveal that strong covalent bonding at the FeSiAl/Al2O3 interface significantly enhance interfacial stability and reduces charge carrier mobility. Furthermore, a three-dimensional separation model based on Bertotti's loss theory is applied to quantify hysteresis, eddy current, and excess losses under varying particle geometries. The study provides in-depth insights into the structure-property relationship by correlating particle shape with magnetic behavior, confirming that optimized aspect ratio engineering can effectively suppress magnetic dilution and enhance energy efficiency. This study not only reveals the critical influence of the aspect ratio of flaky particles on the regulation of microstructure and the optimization of electromagnetic performance, but also establishes a solid theoretical foundation and a feasible technological pathway for the design and fabrication of high-frequency, low-loss soft magnetic composites, demonstrating significant potential for practical engineering applications in advanced electromagnetic systems and energy-efficient devices.