Department of Chemical Engineering, National Chung Cheng University, 168 University Road, Min-Hsiung, Chia-Yi 621, Taiwan.
ACS Appl Mater Interfaces. 2011 Aug;3(8):3084-90. doi: 10.1021/am200602n. Epub 2011 Aug 5.
A three-dimensional urchin-like α-Fe(2)O(3) microstructure is formed via a simple, template-free, and one-step thermal oxidation of Fe spheres in an air atmosphere at temperatures in the range of 300-450 °C. The urchin-like α-Fe(2)O(3) microstructure consists of crystalline α-Fe(2)O(3) nanoflakes grown perpendicularly on the surface of the sphere, a shell layer of α-Fe(2)O(3)/Fe(3)O(4), and an Fe core. During the oxidation process, the nanoflakes germinate and grow from cracks in the oxidation layer on the surface. The length of the nanoflakes increases with oxidation time. The tip diameters of the nanoflakes are in ranges of 10-20 nm at 300 °C, 20-30 nm at 350 °C, and 40-60 nm at 400 °C; the length can reach up to a few micrometers. The field-emission characteristics of the samples are experimentally studied and simulated. The results show that the urchin-like emitter has a low turn-on field of 2.8 V/μm, high field-enhancement factor of 4313, excellent emission uniformity of over 4 cm(2), and good emission stability during a 24 h test.
通过在 300-450°C 的温度范围内，在空气气氛中对 Fe 球进行简单、无模板和一步热氧化，形成了三维刺猬状 α-Fe(2)O(3) 微结构。这种刺猬状 α-Fe(2)O(3) 微结构由垂直生长在球体表面的结晶 α-Fe(2)O(3) 纳米片、α-Fe(2)O(3)/Fe(3)O(4) 的壳层和 Fe 核组成。在氧化过程中，纳米片从表面氧化层的裂缝中发芽和生长。纳米片的长度随氧化时间的增加而增加。在 300°C 时，纳米片的尖端直径范围为 10-20nm，在 350°C 时为 20-30nm，在 400°C 时为 40-60nm；长度可达数微米。实验研究和模拟了样品的场发射特性。结果表明，这种刺猬状发射器具有低开启电场 2.8 V/μm、高场增强因子 4313、超过 4cm(2)的优异发射均匀性以及在 24 小时测试期间的良好发射稳定性。
