A research team led by Dr. Yeon Kyung-Pek and Dr. Jeong Gu Lee succeeded in developing the world’s first technology for the sequential production of epsilon iron oxide, which can absorb millimeter waves with a high coercive force equivalent to neodymium (Nd) magnets. The researchers work in the Magnetic Materials Division of the Powder Materials Division of the Korea Institute of Materials Science (KIMS), a government-funded research institute under the Ministry of Science and ICT.
The high-coercivity epsilon crystal phase iron oxide material is almost the only magnetic material that absorbs ultra-high frequencies, which is the potential 6G frequency range. So far, it has been formed only in nanoparticles of 50 nanometers or less. Japan has succeeded in producing pure epsilon iron oxide using a batch wet process, but it involves a time-consuming, multi-step process that results in low yields.
Image credit: Korea Institute of Materials Science (KIMS)
The research team used an aerosol process to solve the problem of low yield and succeeded in making a composite powder in which epsilon iron oxide nanoparticles are embedded in silica particles by spray-drying precursor solutions in a hot chamber. When the precursor material solution is continuously injected and the droplets dry instantaneously, the iron precursor is trapped in the silica xerogel particles and growth is limited during heat treatment. Epsilon-type iron oxide nanoparticles can be continuously produced using a micrometer-sized powder manufacturing process, which is important because it has shown the possibility of commercializing millimeter-wave absorbing materials.
While conventional metals that absorb electromagnetic waves have reduced absorption capacity in high frequency ranges or have limitations in controlling the frequency ranges, epsilon iron oxide has high potential as a material for future communication parts due to its ability to absorb in ultrahigh frequencies (30 -200 GHz). The continuous production technology of epsilon iron oxide with the ability to absorb millimeter waves can be used for 5G/6G millimeter-band wireless communication, radar sensors for unmanned vehicles, stealth components and low-orbit satellite communication components. Also, because it is a magnetic material with high coercive force, it can be used for electric motor parts for future mobility.
Image credit: Korea Institute of Materials Science (KIMS)
At present, no company commercially produces products with applied magnetic materials capable of absorbing millimeter waves. Only two or three companies in the US, Japan and Germany produce materials for absorption and shielding of the 5G range. The technology developed by KIMS researchers is expected to be localized and exported to the global market in the future.
Lead researcher Dr. Yeon-Kyong Baek said, “Epsilon iron oxide can selectively absorb ultrahigh frequencies over a wide range (30 to 200 GHz). The significance of the study is that it developed the first continuous process for the production of epsilon iron oxides. In the future, this technology is expected to accelerate the commercialization of millimeter-wave wireless communication devices, radars for self-driving cars, and absorption technology for space satellite communications.”
The research was carried out as a project on the development of magnetic composite materials with tunable magnetic characteristics KIMS and was funded by the Ministry of Science and ICT. In addition, the research was published in Chemical Communications, a well-known scientific journal in materials science, published by the Royal Society of Chemistry of Great Britain on September 23. The research team is currently discussing technology transfer with many companies to mass-produce iron oxide absorbing materials, and is conducting further research to improve the ability to absorb waves up to terahertz, which is 100 gigahertz (GHz) or higher.
certificate: “Facile Synthesis of Epsilon Iron Oxides by Spray Drying for Millimeter Wave Absorption” Gi Reon Jo, Min Byol Yoon, Yong Hoon Sung, Byungjin Park, Jeong-Gu Lee, Young-Guk Kim, Young-Guk Son, and Yoon-Kyoung Baek on September 23, 2022 Chemical Communications .
DOI: 10.1039/D2CC03168J
