ε-iron oxide (ε-Fe₂O₃) has drawn attention from the viewpoints of high-density magnetic recording and high-frequency millimeter wave absorption. To date, chemical conversion from Fe₃O₄ (magnetite) to ε-Fe₂O₃ under wet process conditions have been difficult. Herein, we report that ε-Fe₂O₃ could be obtained from Fe₃O₄ using a nanosize wet process. In the present method, 10 or 16 nm sized Fe₃O₄ nanocrystals are used as the precursor. Fe₃O₄ nanocrystals are embedded in a silica matrix and subsequently sintered around 1000 °C in air, resulting in the chemical conversion from Fe₃O₄ to ε-Fe₂O₃ being confirmed. In the case of 10 nm sized Fe₃O₄ precursors, the sample consists of 16% ε-Fe₂O₃ and 84% γ-Fe₂O₃, whereas in the case of 16 nm sized Fe₃O₄ precursors, the sample consists of 24% ε-Fe₂O₃ and 76% γ-Fe₂O₃. The magnetic hysteresis loops of the samples are theoretically predicted using the large hysteresis loop of ε-Fe₂O₃ and the magnetization curve of super-paramagnetic γ-Fe₂O₃. The experimental and predicted hysteresis loops agree well. First-principles calculations suggest that Fe₃O₄ nanocrystals between 8 and 43 nm transform directly to ε-Fe₂O₃. Due to the strict size condition, the chemical conversion from Fe₃O₄ to ε-Fe₂O₃ is the first to be observed by a wet process. The nanosize wet process from Fe₃O₄ to ε-Fe₂O₃ should accelerate the development of highly functional hard magnetic ferrite ε-Fe₂O₃.

中文翻译：

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选自Fe化学转化的直接观察₃ Ò ₄的ε-的Fe ₂ ö ₃由纳米尺寸湿法

ε -铁氧化物（ε-的Fe ₂ ö ₃）已引起关注由高密度磁记录和高频毫米波吸收的观点来看。到目前为止，化学转化选自Fe ₃ ø ₄（磁铁矿）的ε-的Fe ₂ ö ₃湿的工艺条件下已经很难。在本文中，我们报道了ε-的Fe ₂ ö ₃可以选自Fe获得₃ ö ₄使用纳米尺寸的湿法工艺。在本方法中，将10或16nm尺寸的Fe ₃ O ₄纳米晶体用作前体。铁₃ O ₄纳米晶体嵌入在二氧化硅基质，并随后在空气中烧结1000℃左右，从而在化学转化选自Fe ₃ Ò ₄的ε-的Fe ₂ ö ₃被确认。在10nm大小的铁的情况下₃ Ò _4个前体，将样品由16％的ε -铁₂ ö ₃和84％γ-的Fe ₂ ö ₃，而在为16nm的情况下的尺寸的Fe ₃ ö _4个前体，将样品由24％的ε -铁₂ ö ₃和76％γ-的Fe ₂ ö ₃。样品的磁滞回线正在使用ε-Fe的大的滞后环理论上预言₂ ö ₃和超顺磁性γ -铁的磁化曲线₂ ö ₃。实验和预测的磁滞回线非常吻合。第一原理计算表明，铁₃ ö _4层8和43之间的纳米晶体纳米直接变换到ε -铁₂ ö ₃。由于严格的尺寸条件，选自Fe化学转化₃ Ò ₄的ε-的Fe ₂ ö ₃是通过湿法工艺中观察到的第一个。Fe ₃的纳米湿法工艺Ò ₄到ε -铁₂ ö ₃应该加速的高功能的硬磁铁氧体ε -铁发展₂ Ó ₃。