This article employs a hydrothermal method combined with a calcination process to prepare CoO microsheets with varying Ni doping concentrations. Microstructural analysis reveals that the obtained samples are single-phase, free from other impurities, and exhibit a unique self-assembled porous micro-nanostructure. The micron-sized secondary aggregates consist of small nanometer-sized particles with many voids. The nanoscale pores between the nanoparticles contribute to the dissipation of incident microwaves. The dielectric and magnetic properties of CoO microplates can be effectively tuned by adjusting the Ni doping concentration. Comparative results indicate that the Ni-doped CoO microsheets with 0.03 mol% Ni exhibit the minimum reflection loss (RL) of −34.7 dB at 16.56 GHz, with a thickness of just 1.4 mm. Simultaneously, the effective absorption bandwidth (EAB) reaches 4.32 GHz within the frequency range of 13.68–18 GHz. With an absorber thickness of 1.5 mm, the EAB can reach 5.2 GHz from 12.8 to 18 GHz. By adjusting the matching thickness of the absorber in the range of 1.4–4.5 mm, the EAB of Ni-doped CoO can cover multiple frequency bands from 3.6 to 18 GHz. The outstanding microwave absorption performance primarily stems from the unique porous micro-nanostructure and enhanced dielectric and magnetic losses. The results provide an effective component regulating strategy to promote microwave absorption, meanwhile suggest that the low-cost Ni-doped CoO is a promising microwave absorption material.

中文翻译：

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微纳米多孔结构的Ni掺杂Co3O4作为高效微波吸收剂

本文采用水热法结合煅烧工艺制备了不同 Ni 掺杂浓度的 CoO 微片。微观结构分析表明，所得样品为单相，不含其他杂质，并表现出独特的自组装多孔微纳米结构。微米级二次聚集体由具有许多空隙的纳米级小颗粒组成。纳米颗粒之间的纳米级孔隙有助于消散入射微波。通过调整Ni掺杂浓度可以有效地调节CoO微板的介电和磁性特性。比较结果表明，含 0.03 mol% Ni 的 Ni 掺杂 CoO 微片在 16.56 GHz 时表现出最小反射损耗（RL）为 -34.7 dB，厚度仅为 1.4 mm。同时，有效吸收带宽（EAB）在13.68-18 GHz频率范围内达到4.32 GHz。吸收体厚度为 1.5 mm 时，EAB 可在 12.8 至 18 GHz 范围内达到 5.2 GHz。通过在1.4~4.5 mm范围内调整吸波体的匹配厚度，Ni掺杂CoO的EAB可以覆盖3.6~18 GHz的多个频段。优异的微波吸收性能主要源于独特的多孔微纳米结构以及增强的介电和磁损耗。研究结果为促进微波吸收提供了有效的成分调节策略，同时表明低成本的Ni掺杂CoO是一种有前途的微波吸收材料。