Wang Xiang, He Yang, Liu Lili, Song Duo, Kovarik Libor, Bowden Mark E, Engelhard Mark, Li Xiaoxu, Du Yingge, Miller Quin Rs, Wang Chongmin, De Yoreo James J, Rosso Kevin M, Zhang Xin
Physical & Computational Science Directorate, Pacific Northwest National Laboratory, Richland, Washington, 99354, United States.
Environmental Molecular Sciences Laboratory, Pacific Northwest National Laboratory, Richland, Washington, 99354, United States.
Small. 2024 Nov;20(46):e2402717. doi: 10.1002/smll.202402717. Epub 2024 Aug 15.
Investigating the structural evolution and phase transformation of iron oxides is crucial for gaining a deeper understanding of geological changes on diverse planets and preparing oxide materials suitable for industrial applications. In this study, in-situ heating techniques are employed in conjunction with transmission electron microscopy (TEM) observations and ex-situ characterization to thoroughly analyze the thermal solid-phase transformation of akaganéite 1D nanostructures with varying diameters. These findings offer compelling evidence for a size-dependent morphology evolution in akaganéite 1D nanostructures, which can be attributed to the transformation from akaganéite to maghemite (γ-FeO) and subsequent crystal growth. Specifically, it is observed that akaganéite nanorods with a diameter of ∼50 nm transformed into hollow polycrystalline maghemite nanorods, which demonstrated remarkable stability without arresting crystal growth under continuous heating. In contrast, smaller akaganéite nanoneedles or nanowires with a diameter ranging from 20 to 8 nm displayed a propensity for forming single-crystal nanoneedles or nanowires through phase transformation and densification. By manipulating the size of the precursors, a straightforward method is developed for the synthesis of single-crystal and polycrystalline maghemite nanowires through solid-phase transformation. These significant findings provide new insights into the size-dependent structural evolution and phase transformation of iron oxides at the nanoscale.
研究氧化铁的结构演变和相变对于深入了解不同行星上的地质变化以及制备适用于工业应用的氧化物材料至关重要。在本研究中，采用原位加热技术结合透射电子显微镜（TEM）观察和非原位表征，以全面分析不同直径的赤铁矿一维纳米结构的热固相转变。这些发现为赤铁矿一维纳米结构中尺寸依赖性的形态演变提供了有力证据，这可归因于从赤铁矿到磁赤铁矿（γ-FeO）的转变以及随后的晶体生长。具体而言，观察到直径约为50nm的赤铁矿纳米棒转变为中空的多晶磁赤铁矿纳米棒，在持续加热下，这些纳米棒表现出显著的稳定性，且晶体生长未停止。相比之下，直径在20至8nm之间的较小赤铁矿纳米针或纳米线倾向于通过相变和致密化形成单晶纳米针或纳米线。通过控制前驱体的尺寸，开发了一种通过固相转变合成单晶和多晶磁赤铁矿纳米线的简便方法。这些重要发现为纳米尺度下氧化铁的尺寸依赖性结构演变和相变提供了新的见解。
