School of Materials Science and Engineering, Harbin Institute of Technology , Harbin 150001, China.
MOE Key Laboratory of Micro-System and Micro-Structures Manufacturing, Harbin Institute of Technology , Harbin 150080, China.
ACS Appl Mater Interfaces. 2017 Jul 5;9(26):21933-21941. doi: 10.1021/acsami.7b03907. Epub 2017 Jun 21.
Ferromagnetic metal/alloy nanoparticles have attracted extensive interest for electromagnetic wave-absorbing applications. However, ferromagnetic nanoparticles are prone to oxidization and producing eddy currents, leading to the deterioration of electromagnetic properties. In this work, a simple and scalable liquid-phase reduction method was employed to synthesize uniform CoFe nanospheres with diameters ranging from 350 to 650 nm for high-performance microwave absorption application. CoFe@SiO core-shell nanospheres with SiO shell thicknesses of 30 nm were then fabricated via a modified Stöber method. When tested as microwave absorbers, bare CoFe nanospheres with a diameter of 350 nm have a maximum reflection loss (RL) of 78.4 dB and an effective absorption with RL > 10 dB from 10 to 16.7 GHz at a small thickness of 1.59 mm. CoFe@SiO nanospheres showed a significantly enhanced microwave absorption capability for an effective absorption bandwidth and a shift toward a lower frequency, which is ascribed to the protection of the SiO shell from direct contact among CoFe nanospheres, as well as improved crystallinity and decreased defects upon annealing. This work illustrates a simple and effective method to fabricate CoFe and CoFe@SiO nanospheres as promising microwave absorbers, and the design concept can also be extended to other ferromagnetic alloy particles.
铁磁金属/合金纳米颗粒因其在电磁波吸收应用方面的广泛应用而受到广泛关注。然而，铁磁纳米颗粒容易氧化并产生涡流，导致电磁性能恶化。在这项工作中，采用了一种简单且可扩展的液相还原法，合成了直径为 350 至 650nm 的均匀 CoFe 纳米球，用于高性能微波吸收应用。然后通过改进的 Stöber 法制备了具有 30nm SiO 壳厚的 CoFe@SiO 核壳纳米球。作为微波吸收剂进行测试时，直径为 350nm 的裸 CoFe 纳米球在 1.59mm 的小厚度下，在 10 至 16.7GHz 范围内具有最大反射损耗（RL）为 78.4dB 和 RL>10dB 的有效吸收。CoFe@SiO 纳米球表现出显著增强的微波吸收能力，具有有效的吸收带宽和向更低频率的偏移，这归因于 SiO 壳对 CoFe 纳米球之间直接接触的保护，以及退火后结晶度的提高和缺陷的减少。这项工作说明了一种简单有效的方法来制备 CoFe 和 CoFe@SiO 纳米球作为有前途的微波吸收剂，并且该设计概念也可以扩展到其他铁磁合金颗粒。
