采用熔盐法制备α-Al₂O₃，采用硅烷偶联剂γ-氨丙基三乙氧基硅烷（KH550）对α-Al₂O₃进行表面改性，得到KH-α-Al₂O₃。以低密度聚乙烯（LDPE）为基体、不同的α-Al₂O₃为添加剂，制备α-Al₂O₃/XLPE和KH-α-Al₂O₃/XLPE接地线绝缘材料。对α-Al₂O₃和KH-α-Al₂O₃的晶体结构、微观结构以及基团进行分析，考察不同α-Al₂O₃含量对α-Al₂O₃/XLPE接地线绝缘材料电学性能和热学性能的影响。结果表明：熔盐法制备的α-Al₂O₃是具有六方结构、结晶度高、直径5~10 μm的不规则圆片，KH550的改性不会造成α-Al₂O₃结晶度的变化。KH-α-Al₂O₃在KH-α-Al₂O₃/XLPE接地线绝缘材料中沿材料厚度方向排列，且分散更为均匀，有利于抑制电荷在基体中的传输。KH-α-Al₂O₃有利于提高XLPE的直流击穿场强和直流电导率。当KH-α-Al₂O₃的添加质量分数为1.5%时，KH-α-Al₂O₃/XLPE的直流击穿场强达到320 kV/mm，电导率为1.043×10^-13 S/m。KH-α-Al₂O₃的引入使XLPE基体和KH-α-Al₂O₃之间的界面产生一定数量的陷阱，有效实现了对注入电荷的抑制。KH-α-Al₂O₃可以明显降低XLPE的热失重速率，提高KH-α-Al₂O₃/XLPE接地线绝缘材料热稳定性。当KH-α-Al₂O₃的质量分数达到1.5%时，分解温度升高至475.44 ℃，90 ℃条件下的导热系数从0.390 W/（m·K）增加到0.545 W/（m·K）。

α-Al₂O₃ was prepared using the molten salt method, and its surface was modified with the silane coupling agent γ-aminopropyltriethoxysilane (KH550), resulting in KH-α-Al₂O₃. Using low-density polyethylene (LDPE) as the matrix and different α-Al₂O₃ as additives, grounding wire insulation materials of α-Al₂O₃/XLPE and KH-α-Al₂O₃/XLPE were prepared. The crystal structure, microstructure, and functional groups of α-Al₂O₃ and KH-α-Al₂O₃ were analyzed, and the effects of different α-Al₂O₃ contents on the electrical and thermal properties of α-Al₂O₃/XLPE grounding wire insulation materials were investigated. The results show that the α-Al₂O₃ prepared by the molten salt method has a hexagonal structure, high crystallinity, and is an irregular disc with a diameter of 5~10 μm. The modification with KH550 does not alter the crystallinity of α-Al₂O₃. In the KH-α-Al₂O₃/XLPE grounding wire insulation material, KH-α-Al₂O₃ is aligned along the thickness direction of the material and is more uniformly dispersed, which is beneficial for suppressing charge transport within the matrix. KH-α-Al₂O₃ enhances the DC breakdown strength and DC conductivity of XLPE. When the mass fraction of KH-α-Al₂O₃ is 1.5%, the DC breakdown strength of KH-α-Al₂O₃/XLPE reaches 320 kV/mm, and the conductivity is 1.043×10⁻¹³ S/m. The introduction of KH-α-Al₂O₃ creates a certain number of traps at the interface between the XLPE matrix and KH-α-Al₂O₃, and effectively suppresses the injection of charges. KH-α-Al₂O₃ significantly reduces the thermal degradation rate of XLPE and improves the thermal stability of the KH-α-Al₂O₃/XLPE grounding wire insulation material. When the mass fraction of KH-α-Al₂O₃ reaches 1.5%, the decomposition temperature increases to 475.44 ℃, and the thermal conductivity under 90 ℃ conditions increases from 0.390 W/(m·K) to 0.545 W/(m·K).