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The world's first method to repeatedly produce epsilon iron oxide, which can absorb millimetre waves with a powerful coercive force comparable to that of neodymium (Nd) magnets, was created by a research team under the direction of Drs Youn-kyoung Baek and Jung-goo Lee. The researchers are at the Korea Institute of Materials Science (KIMS), a government-funded research facility run by the Ministry of Science and ICT, in the Powder Materials Division's Department of Magnetic Materials.
Most magnetic materials that absorb ultra-high frequencies, a potential 6G frequency range, have high coercive epsilon crystal phases, such as iron oxide. It has only ever been generated in nanoparticles that are 50 nanometers or smaller up until this point. Japan succeeded to produce pure epsilon iron oxide through a batch-type wet process, but it involves a time-consuming multi-stage process, resulting in a low yield. The research team adopted the aerosol process to solve the low-yield problem and succeeded in producing 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 are instantly dried, the iron precursor is trapped in the silica xerogel particles and limited to growth during heat treatment. Epsilon iron oxide nanoparticles could be continuously produced through a micrometre-sized powder manufacturing process, which is significant as it showed the possibility of commercialization of millimetre wave-absorbing materials. While conventional metals that absorb electromagnetic waves have reduced absorption capacity in high-frequency bands or have limitations in controlling frequency bands, epsilon iron oxide has high potential as a material for future communication parts due to its absorption capacity in the ultra-high frequency (30-200GHz) band. Continuous manufacturing technology of epsilon iron oxide with millimetre wave absorption capability can be used for mm-wave 5G/6G wireless communication, radar sensors for driverless cars, and stealth and low-orbit satellite communication components. In addition, as it is a high-coercivity magnetic material, it can be used for electric motor parts for future mobility. Currently, no companies commercially produce products with applied magnetic materials capable of absorbing mm waves. Only two or three companies in the US, Japan, and Germany produce 5G band absorbing and shielding materials. The technology developed by researchers at KIMS is expected to be localized and exported to the global market in the future. Principal investigator Dr Youn-kyoung Baek said, "The epsilon iron oxide can selectively absorb ultra-high frequencies in a wide band (30 to 200 GHz). The significance of the study is that it developed the first continuous manufacturing process of epsilon iron oxides. The technology is expected to accelerate the commercialization of wireless communication devices using millimetre waves, self-driving car radars, and absorber technology for space satellite communication in the future." (ANI)
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