Control of the Crystal Phase Composition of FexOy Nanopowders Prepared by CO2 Laser Vaporization
Control of the Crystal Phase Composition of FexOy Nanopowders Prepared by CO2 Laser Vaporization
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DOI：
10.1021/cg4010533
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发表时间：
2013-09
影响因子：
3.8
通讯作者：
C. Stötzel;Heinz-Dieter Kurland;J. Grabow;S. Dutz;E. Müller;M. Sierka;F. Müller
中科院分区：
文献类型：
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作者：
C. Stötzel;Heinz-Dieter Kurland;J. Grabow;S. Dutz;E. Müller;M. Sierka;F. Müller
以赤铁矿(α-Fe_2O_3)为原料，采用CO_2激光蒸发法制备了晶态磁性纳米氧化铁粉末。常压冷凝导致纳米粉末中的主相为磁铁矿(γ-Fe_2O_3)。随着冷凝区氧分压的增加，Fe_2O_3晶型e-Fe_2O_3的含量增加。用X射线衍射仪、透射电子显微镜和化学分析等手段对熔岩法制备的纳米Fe_2O_3进行了表征，并对其磁性进行了研究。提出了一种初始成核机制，解释了e-Fe_2O_3在冷凝气氛中随氧含量的增加而形成的原因。该模型是基于富氧凝结大气中存在臭氧的证据。密度泛函理论计算表明，臭氧促进了6重氧配位铁离子的形成，在纳米粒子的固化过程中，铁离子作为新出现的晶体结构的构建单元。这种对...的洞察。
Crystalline magnetic iron oxide nanopowders are prepared by CO2 laser vaporization (LAVA) of a hematite (α-Fe2O3) raw powder. Condensation at normal pressure leads to maghemite (γ-Fe2O3) as the main phase in the nanopowders. With an increasing oxygen partial pressure in the zone of condensation, an increasing amount of Fe2O3 polymorph e-Fe2O3 is found. The LAVA-prepared Fe2O3 nanopowders are characterized by X-ray diffraction, transmission electron microscopy, and chemical analysis and with respect to their magnetic properties. A mechanism for the initial nucleation is proposed to explain the formation of e-Fe2O3 with an increasing oxygen content in the condensation atmosphere. The model is based on the evidence of ozone in oxygen-rich condensation atmospheres. Density functional theory calculations indicate that ozone facilitates the formation of 6-fold oxygen-coordinated Fe ions acting as building units for the emerging crystal structure during the solidification of the nanoparticles. This insight into ...